What is the "delta" option quoting convention about?

At my work I often see option prices or vols quoted against deltas rather than against strikes. For example for March 2013 Zinc options I might see 5 quotes available for deltas as follows: ZINC MARCH 2013 OPTION DELTA -10 POINTS ZINC MARCH 2013 OPTION DELTA -25 POINTS ZINC MARCH 2013 OPTION DELTA +10 POINTS ZINC MARCH 2013 OPTION DELTA +25 POINTS ZINC MARCH 2013 OPTION DELTA +50 POINTS The same 5 values -10, -25, +10, +25, + 50 are always used. What are these deltas? What are the units? Why are those 5 values chosen?

Delta is the partial derivative of the value of the option with respect to the value of the underlying asset. An option with a delta of 0.5 (here listed as +50 points) goes up \$0.50 if the underlying asset goes up \$1.00. Or goes down \$0.50 if the underlying asset goes down \$1.00. Keep in mind that delta is an instantaneous derivative, so the value will change both in time (charm is the change in delta with time) and with changes in value of the underlying asset (gamma is the change in delta with the underlying asset, which is also...

Scott Mixon argues in What Does Implied Volatility Skew Measure that among all measures of implied volatility skew, the (25 delta put volatility - 25 delta call volatility)/50 delta volatility is the most descriptive and least redundant (volatility is Black-Scholes implied volatility). His paper, recently published in the Journal of Derivatives , gives a number of both theoretical and empirical arguments in favor of this measure. He distinguishes between "skew", which is a measure of the slope of the implied volatility curve for a given expiration date, and "skewness", which is the skewness of an option implied, risk neutral probability...

The volatiltiy surface is just a representation of European option prices as a function of strike and maturity in a different "unit" - namely implied volatility (while the term implied volatility has to be made precise by the model used to convert prices (quotes) into implied volatilities - for example: we may consider log-normal vols and normal vols). Volatility is often preferred over prices, e.g., when considering interpolations of European option prices (although this may introduce difficulties like arbitrage violations, see, e.g., http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1964634 ). A local volatility model can generate a perfect fit to the implied volatility surface via Dupire's...

VIX is a measure of implied volatility , specifically, model-free implied volatility , a concept originally developed by Demeterfi et. al. at Goldman Sachs in the 1990s . One of my recent questions, How to extrapolate implied volatility for out of the money options? , addressed some aspects of MFIV, and the papers mentioned in the question and answers will give you some more background on the concept. Also check out this JPMorgan research piece . The VIX is the square root of the market-implied variance swap rate, calculated based on the exchange-traded options portfolio typically used to hedge an...


Does a roadway bridge experience more load when vehicles are parked or when they are moving?

Bridges are designed for the loads that come from the vehicles that are expected to cross them. This includes the weight the vehicle and any dynamic loads that may be introduced from movement of the vehicle. Dynamic loads may be from "bouncing" or from hitting a joint or pothole. Initially it would seem obvious that more load is applied to a bridge while the vehicles are in motion (weight of vehicle plus dynamic load). The dynamic loads are proportional to the travelling speed of the vehicles, but as vehicles go faster, they typically are spaced farther apart. When vehicles are stopped, they typically are much more closely spaced than when they are moving. Can there be a situation where more load is on a bridge because of closely spaced parked vehicles than from moving vehicles that are farther apart? Are these two situations covered in bridge design?

Electricity production optimization is a very complex subject. It is also affected by many parameters , which I will try to outline below. TL;DR: Demand is constantly monitored and supply is constantly adjusted TL;DR 2: Lshaver's excellent post is a suggested reading after reading this, because it expands and explains what happens at timescales ranging from the micro-second to minutes timescales. Changes in energy demand during the day First of all, the energy demand during the day, week, month of year can change quite a lot. Below is a typical day in New England. Fluctuation in power energy consumption a...

This is to make sure they know what the foundation is made of. For all they knew there may have been an old tunnel underneath that would have collapsed when the new building is put on top. London is built on top of an old marsh, this type of soil is very prone to sinking and uneven settling, digging down and reinforcing the foundation alleviates that. It also ensures the foundation is uniform under the building to avoid a new tower of Pisa. Given the age of the city it may have been to scour the land for potential archaeological...

The loops are known as expansion loops. They need to be placed in pipelines to enable the pipelines to contend with thermal expansion and contraction and other forces that can affect the pipeline. They are typically placed in gas pipelines, irrespective of when the gas is hot or cold - natural gas or steam. The following quote is from Pipeline Design . It's near the end of the page under Pipe Expansion and Supports Steel piping systems are subject to movement because of thermal expansion/contraction and mechanical forces. Piping systems subjected to temperature changes greater than 50°F or temperature changes...

Parked vehicles vs moving vehicles Closely spaced parked (or slow moving) vehicles are definitely more onerous, as stated on page 89, Appendix 2.A, Clause 2.A.1 of the South African bridge design code TMH7 : It is generally accepted and can readily be shown that except in the very small span range, the worst loading condition occurs under congested (bumper to bumper) conditions caused by a traffic blockage and that the dispersion of traffic at speed caused by increased vehicular inter-spacing, more than off-sets the effects of impact. However, this is only true by inspection for an unlimited number of vehicles...


My wife and I have found a vacant lot (this is in Utah, BTW) where we would like to build a house. However, the HOA that the lot belongs to does not allow more than four occupants, regardless of the size of the home. The CCR actually says (community name) is designed and intended to be for a specific lifestyle. Neither the Units nor the common areas are designed to accommodate large families. Permanent residents of (community name) shall be restricted and limited to families with no more than four person's related by blood, marriage, or adoption. Does the HOA actually have authority to enforce this? What happens if we build a house (with plenty of room), move in with our two kids, and then have another baby?

Your question is the subject of longstanding and ongoing debate that has generated countless articles and books and dissertations, so you're probably not going to get a fully satisfactory answer here. But here's the short version: Different systems operate on different assumptions. Your question suggests you are not a retributivist, i.e., someone who views sentencing as a means for taking retribution for the criminal's offenses. Some systems (most, I imagine) are built around that idea, but some view criminal sentencing primarily as a means of preventing recidivism, or as a means for achieving rehabilitation, the interests you indicated you see...

Trump was an officer of the government, and Twitter wasn't. The First Amendment forbids the government and its agents from viewpoint discrimination, but private companies are not bound by it and can discriminate as much as they please. (There was a question as to whether such discrimination might affect whether the company enjoys a shield from liability under 47 USC 230 , but even so they have the right to block and censor as they wish if they are willing to risk that liability.)

There is a history of "giving away patents", which allows the original grantor to foster innovation instead of stifle it. Here are some examples: Sealand Industries - ISO Shipping Container Patented the standard shipping container, then gave away the patent royalty free, allowing a revolution in ocean going shipping. Annually it is estimated that $440 billion are shipped through these containers. Tesla - 200+ patents Elon Musk announced that the company "will not initiate patent lawsuits against anyone who, in good faith, wants to use our technology." . Toyota - Hydrogen Fuel Cell Patents Released 5,680 patents related to hydrogen...

As stated, this is not a reasonable restriction and runs afoul of the Fair Housing Act . You cannot discriminate based on family status, with an exemption for " housing for older persons ", and the act "does not limit the applicability of reasonable local, state, or federal restrictions regarding the maximum number of occupants permitted to occupy a dwelling" (let's leave aside HOA restrictions for a moment). The number of occupants can legally be restricted in terms of a reasonable relation to a legitimate interest such as parking availability, safety, noise or securing the property. A restriction based on...


How are correlation and cointegration related?

In what ways (and under what circumstances) are correlation and cointegration related, if at all? One difference is that one usually thinks of correlation in terms of returns and cointegration in terms of price. Another issue is the different measures of correlation (Pearson, Spearman, distance/Brownian) and cointegration (Engle/Granger and Phillips/Ouliaris).

time-series statistics correlation cointegration

This isn't really an answer, but it's too long to add as a comment. I've always had a real problem with the correlation/covariance of price . To me, it means nothing. I realize that it gets used (abused) in many contexts, but I just don't get anything out of it (over time, price has to generally go up, go down, or go sideways, so aren't all prices "correlated"?). On the flip side, correlation/covariance of returns makes sense. You're dealing with random series, not integrated random series. For example, below is the code required to generate two price series that have...

The term has a different meaning to different people. to econometricians, microstructure noise is a disturbance that makes high frequency estimates of some parameters (e.g. realized volatility) very unstable. Generally this strand of the literature professes agnosticism as to the its origin; to market microstructure researchers, microstructure noise is a deviation from fundamental value that is induced by the characteristics of the market under consideration, e.g. bid-ask bounce, the discreteness of price change, latency, and asymmetric information of traders. The last example is frequently cited but I don't think it is accurate. Asymmetric information does not have to be a...

Just to be painfully clear, it only seems to make sense to consider the logarithm of returns, i.e. $X=\log (1+\frac r{100})$ for a simple return of $r\%$ in an arbitrary period because this is what sums when returns are temporally aggregated. A basic property of cumulants is that cumulants of all orders are additive under convolution, for which a proof can be found here here . So if $X_1$, $X_2$, ... $X_n$ are i.i.d. , then all the cumulants of $$Y_n = \sum_{i=1}^nX_i$$ scale linearly with $n$, i.e. $$\kappa_k(Y_n)=n\kappa_k(Y_1).$$ However, I suspect that you are normalizing this sum so that...

In general there are two basic ways to make money out of your option pricing models: Sell side (market maker, risk neutral): You use these models to calculate your greeks to hedge your portfolio, so that you live on the spread. Buy side (market/risk taker): You use your model to find mispriced options in the market and buy/sell accordingly. (A third possibility would be to write fancy books and papers about these models and get rich and/or tenure this way ;-)


If a SARS-CoV-2 asymptomatic infected individual is exposed to a high viral load, could they develop COVID-19 disease?

I would add my own research if I could to respect site rules, but I can't. There are no studies on SARS-CoV-2, all I can find is for SARS-CoV-1 and some Chinese information based studies. My government is planning to do massive testing (when tests are available) and transfer and isolate every asymptomatic person in buildings such as hotels. The right is in arms saying this is like gulags and saying now they don't want to do the test. My question, I hope generically, is: if someone is infected but asymptomatic, could the exposure to a high virus load lead to COVID-19 disease? Or conversely: if your immune system is already coping well with the virus, the addition of more virus load can't worsen your diagnosis.

What your government is proposing is a lot less than what was actually done in China. There, and perhaps that is still the case, large numbers of asymptomatic infected people were housed together in halls with only social separation between them, and masks to prevent others from infecting others. Your government is proposing to house the asymptomatic infected in hotels, presumably in separate rooms. We know that people who are infected because they have virus identified using PCR swabs of their upper airways. CT scans can show pulmonary lesions present even without cough or fever. And even speaking can aerosolize...

Because leprosy and multiple myeloma are conditions for which other treatment options are limited. All treatments have side effects, some more debilitating than others. The trick with pharmacology is to balance the benefit of treatment with the hazards of the side effects. Take cancer chemotherapy. The drugs we use for cancer chemotherapy are horrible poisons. We literally use derivatives of chemical weapons to treat cancer. Why do we deliberately poison cancer patients with what amounts to a weapon of mass destruction? Because if we don't, the cancer will kill them. In pharmacology there's a concept of a therapeutic window ....

Short answer: Sophie Trudeau's positive test may still mean 3 : 1 odds of not having contracted Covid-19, but the odds could also be far more towards having Covid-19. Justin Trudeau's negative test almost certainly means he was negative when tested. Of course, should Sophie be positive, that may have changed by now. Update: I found a web page of the FDA listing tests that have this Emergency Use Approval . Each of them has manufacturer instuctions that list their test results towards the end. Some of the submitted test results use ≈100 negative samples in the clinical evaluation. But...

Ear tubes do many things to help ear infections. The most important things they do are draining the ear of fluid and ventilating the ear. Overall, this will help your child hear better. The tubes also stop fluid from building up behind the ear drum, which should help prevent the ear infections. Stuff to watch out for There is always the possibility of ear infections coming back after the 6-12 months that the tubes will be in. There is also a minor chance of hearing loss because of scarring of the ear drum. The tube can become blocked, stopping it...


Is it a crime to take my own package from a delivery truck before it has reached my home?

Not that I would ever do this, but I'm curious: if I were to go into a stopped delivery truck and remove from it an item that is addressed to me, would this be a crime? If so what crime would it be? It seems to me that I would not be stealing anything since it's my own property that I'm taking. I might even have a reason to suspect that if I did not take the package from the truck, then the driver would leave it sitting out in the open where it would likely be stolen (or that the driver himself might steal it), in which case I'd actually be preventing a crime by taking it from the truck directly. I don't think this would be burglary either, since that would tend to require that I was breaking into a restricted area with the intent to commit a crime. Especially if the delivery truck had no doors or I acted while they'd been left open, then I wouldn't even be "breaking and entering." I can't see this as being "trespass" if the truck was on a public street, unless trespass applies to the interior of vehicles. Even then, as long as I'd leave before anyone noticed me, I could just say I only went in to retrieve what's mine and prevent it from being damaged or stolen. So I'm guessing there must be some kind of arcane laws that only the US Postal Marshalls deal with. Yes, there are special guys called "US Postal Marshalls," who investigate mail-related crimes. So I'm curious what crime this would be? Note: I did review this post about "stealing your own property back" but it does not really seem to apply here.

There is a history of "giving away patents", which allows the original grantor to foster innovation instead of stifle it. Here are some examples: Sealand Industries - ISO Shipping Container Patented the standard shipping container, then gave away the patent royalty free, allowing a revolution in ocean going shipping. Annually it is estimated that $440 billion are shipped through these containers. Tesla - 200+ patents Elon Musk announced that the company "will not initiate patent lawsuits against anyone who, in good faith, wants to use our technology." . Toyota - Hydrogen Fuel Cell Patents Released 5,680 patents related to hydrogen...

Yes, it's illegal You are missing something terribly important: The package might not be your property [yet]. In any way, it is not in your possession, while it is in the hands of the postal service! The contents of the package started fully owned by the sender and were entrusted to the postal service to deliver it. This entrustment is (contractually) defined as the time it is handed to the postal service, but the postal service does not gain any ownership. They do however have insurance on the parcel (to some degree), as they are liable for the loss of...

Virginia employer terminated employee and wants signing bonus returned Can the employer legally keep his last check and send the employee a bill for the remainder ? No, unless (1) the employee resigned and (2) his resignation does not amount to constructive termination . The employer may withhold the remaining $7,000 only if the employee did not meet the condition of " 30 days of employment with xxxxx ". Absent any language to the contrary, the requirement of " 1-year commitment " is to be construed as the consideration expected from the employee (namely, " not to quit ") in...

It is legal, at least in the US, for a store (or other entity) to refuse to sell any item to any individual for any non-prohibited reason (prohibited reasons are typically things like race or religion). More over, in various US jurisdictions, it is prohibited to "furnish" alcohol to a "minor" (for example, under California's ABC law), which can be interpreted as prohibiting to an adult if they reasonably suspect that adult will pass the alcohol onto the "minor". This is to prevent "straw" sales. Additionally, larger chains generally prefer to have harmonized policies across branches, and where practical, across...


Legality of penalising Russian Oligarchs

What is the legal basis for penalising individual Russian Oligarchs? Having ill-gotten wealth and dubious friends is hardly unique to Russia, and whilst I can understand with the desire of the Western / European powers to been seen to be doing something I can't see the legal basis of confiscating their assets. If they really are just a bunch of crooks why have they been swanning around the free-world for the last 25 years? What have they done in the last nine-days which suddenly justifies personal sanctions against them? As far as I know most of them don't hold any current positions of power/authority in Russia (not officially anyhow). Whilst I broadly accept the consensus that they're Putin's cronies who owe much of their current success to their past associations with him, and whilst I'd personally be delighted to see their money go to support Ukrainian refugees I can't actually see a good legal argument for sanctions other than 'guilt by association' - which probably wouldn't stand up in court.

In the UK Armed Forces, conscientious objection is grounds for a refusal at the admission stage and has been since the end of conscription in 1963. Where a person develops an objection to military service during their term of service, they have the option to appeal for a discharge. Interestingly there's no primary legislation to manage this process but there are established military procedures to take care of this when it happens. Mostly the process seems to be managed informally , with the objector simply being shuffled into a non-combatant role within their regiment and just left there for the...

In the united-kingdom , the legal basis flows from the Sanctions and Anti-Money Laundering Act 2018 . This allows regulations to be made for particular sanctions regimes, in this case The Russia (Sanctions) (EU Exit) Regulations 2019 and its several amendments, including three revisions this year. Under those regulations, the Secretary of State may designate individuals who are then subject to particular sanctions. A consolidated list is available for all individuals and organizations who have been named under any of the regulations, not just the Russia one. Working backwards from the list, we see such names as Vladimir Putin, who...

Technically anyone can sit on a jury. Lawyers are not automatically excluded from juries anymore, as being called for jury duty is a right and a duty that the law abhors automatically excluding people from. That is the official line on this. However, in reality, lawyers will always be stricken from serving by one of the lawyers trying the case. Each lawyer has a certain number of preemptory strikes (the ability to get rid of a juror for any reason, aside from those protected by law, such as race, religion, etc). They also have unlimited "for cause strikes," which are...

This aspect (and many others) of contract law is applicable in the US and various countries of the EU. can they renege after the candidate has begun their journey, thus saddling the candidate with the travel cost? No. The company would incur breach of contract. There is no need for a formal contract. The candidate only needs to prove that the company agreed (in writing, orally or clearly through its conduct) to cover or reimburse those expenses and that this elicited a meeting of the minds . The agreement would be void if the candidate incurred the expenses despite knowing...


Is it possible that someone made an attack (DoS or something else) to my Wi-Fi router (without knowing of the password) and make my router's signal unavailable? 1) How it can be done? 2) What are remedies?

No, Docker containers are not more secure than a VM. Quoting Daniel Shapira : In 2017 alone, 434 linux kernel exploits were found , and as you have seen in this post, kernel exploits can be devastating for containerized environments. This is because containers share the same kernel as the host, thus trusting the built-in protection mechanisms alone isn’t sufficient. 1. Kernel exploits from a container If someone exploits a kernel bug inside a container, they exploited it on the host OS. If this exploit allows for code execution, it will be executed on the host OS, not inside the...

There's a lot of ways you can attack a WiFi without knowing any passwords: Physical layer attacks: Simply jam the frequency spectrum with your own signal. That signal might just be noise, but it might also be a WiFi of your own under heavy load, with the nodes in that WiFi being configured not to play nice with others. (depending on the WiFi chipset, that can be extremely easy) Spectrum can only be used once! Tool : noise source (e.g. Gunn Diode, SDR device ), or normal AP Electromagnetic sledgehammer: EMI gun. Take microwave oven oscillator, attach directive antenna, pray...

You are touching a sore point… Historically , computers were mainframes where a lot of distinct users launched sessions and process on the same physical machine. Unix-like systems (e.g. Linux), but also VMS and its relatives (and this family includes all Windows of the NT line, hence 2000, XP, Vista, 7, 8...), have been structured in order to support the mainframe model. Thus, the hardware provides privilege levels . A central piece of the operating system is the kernel which runs at the highest privilege level (yes, I know there are subtleties with regards to virtualization) and manages the privilege...

/** Dave's Home-brew Hash */ // user data $user = ''; $password = ''; // timestamp, "random" # $time = date('mdYHis'); // known to attackers - totally pointless // ^ also, as jdm pointed out in the comments, this changes daily. looks broken! // different hashes for different days? huh? or is this stored as a salt? $rand = mt_rand().'\n'; // mt_rand is not secure as a random number generator // ^ it's even less secure if you only ask for a single 31-bit number. and why the \n? // crypt is good if configured/salted correctly // ... except you've...


Why did this US prosecutor keep asking whether documents would refresh a witness's memory?

Background I served on a jury during a criminal trial in the United States several years ago. There was a strangely formal interaction that repeated itself a few times during the trial. The prosecutor, while holding some document, would ask a question which required the witness to recall some specific detail. The witness would reply "I don't remember." The prosecutor would then ask "Would looking at [some document] refresh your memory?", to which the witness would answer "Yes." The prosecutor would then hand the document to the witness, who would look at it and then answer the question. It's obvious that the prosecutor already knew the question wouldn't be answerable without reference to the report or document - that's why they were holding it. But then why perform the dance of "do you recall" / "no" / "would this refresh your memory" / "yes"? The Question It's clear the witness needs the document to answer the prosecutor's question, so what's the value in the prosecutor asking the witness the question the first time without the document? Disclaimer ( it may be that this was simply this prosecutor's way of phrasing questions, rather than a feature of the United States criminal judicial system. If that's the case this question won't be answerable, since it calls for knowing the mindset of a specific individual. If so, let me know and I'll delete it ) Further information In the real-life situation I found myself in, the witness was for the prosecution. However, I'm equally interested in answers ( such as hszmv's ) that explain why the adversarial lawyer might also use this technique, if relevant.

Maybe, Hence the Lawsuits In the absence of clear statute law these all circle around tort law. For the scooter companies, trespass to chattels , and for the affected landowners (who hire the removalists) trespass to land and nuisance seem applicable. In essence, I can’t take your stuff (trespass to chattels) but you can’t leave your stuff on my property (trespass to land) or impeding access to it (nuisance). If you do, I am entitled to the reasonable costs of dealing with it. Note that, as owner, you remain responsible for you stuff even if you rented it to someone...

united-states Witnesses are generally confined to giving testimony from their own personal memory; most of the time, they can't read a statement into the record or just tell the jury to go look at some other piece of evidence. But this creates problems when a witness knows an important fact but doesn't remember it when she takes the stand. Maybe she counted exactly how much money she stuffed in the robber's bag as she was doing it, and she wrote it down as soon as he fled, but a year later, she can't remember that it was $93,736.45. But the...

While there is an act that President Trump and his supporters are citing, titled the Presidential Records Act (PRA) , to accuse House Speaker Pelosi of breaking federal law, it is important to understand what actions the law accounts for. The act mandates that the President of the United States preserve records and other laws governing the federal government. This serves as a form of checks and balances to prevent the president and his advisers from shielding documentary information from public view. The act is fairly new, as it was passed in 1981. It is important to realize that this...


What are the popular methodologies to minimize data snooping?

Are there common procedures prior or posterior backtesting to ensure that a quantitative trading strategy has real predictive power and is not just one of the thing that has worked in the past by pure luck? Surely if we search long enough for working strategies we will end up finding one. Even in a walk forward approach that doesn't tell us anything about the strategy in itself. Some people talk about white's reality check but there are no consensus in that matter.

The minimum variance solution loads up on securities that have low variances and co-variances. Theoretically you are correct that this should have a low expected return profile. However, it turns out - in contradiction to modern portfolio theory - that securities that have low-volatility or low-beta experience higher returns than high-volatility or high-beta stocks. This is well-documented in the literature as the low-volatility anomaly . As a result, many funds and ETFs have been launched in recent years to exploit this phenomenon. There are a couple arguments as to why the anomaly exists. The paper I cite above argues that...

1. Determine Factors Economically, the use of factor models can be either motivated using the ICAPM or the APT . Although there are some theoretical differences between the model, for empirical and practical work these differences are irrelevant. In the end, both models stipulate that returns and expected returns are linear functions of the factors: $$ r_{i,t} = \alpha_i + \sum_j \beta_{i,j} F_{j,t} + \epsilon_{i,t} \quad (1)$$ $$ \mathbb{E}[ r_{i,t}] = \lambda_o + \sum_j \beta_{i,j} \lambda_j \quad\quad\quad(2)$$ where $F_{j,t}$ is the factor surprise of factor $j$ at time $t$ and $\lambda_j $ is the factor risk premium of factor $j$....

Strictly speaking, data snooping is not the same as in-sample vs out-of-sample model selection and testing, but has to deal with sequential or multiple tests of hypothesis based on the same data set. To quote Halbert White: Data snooping occurs when a given set of data is used more than once for purposes of inference or model selection. When such data reuse occurs, there is always the possibility that any satisfactory results obtained may simply be due to chance rather than to any merit inherent in the methody yielding the results. Let me provide an example. Suppose that you have...

The volatiltiy surface is just a representation of European option prices as a function of strike and maturity in a different "unit" - namely implied volatility (while the term implied volatility has to be made precise by the model used to convert prices (quotes) into implied volatilities - for example: we may consider log-normal vols and normal vols). Volatility is often preferred over prices, e.g., when considering interpolations of European option prices (although this may introduce difficulties like arbitrage violations, see, e.g., http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1964634 ). A local volatility model can generate a perfect fit to the implied volatility surface via Dupire's...


Recently I was weighting stuff with my dad and as I was playing with one of the old 2 kg weights I felt with my fingers number "5". After cleaning and upon further inspection it turned out the writing on the weight says "5Φ". We checked and it indeed weights 2 kg as my dad remembered. It was done with a simple balance scale by comparing with another weight of similar age that is properly marked as "2 kg". There are no other marks on that weight. On the opposite side is a bulge but it's an irregular blob - I think it's remainder of sprue. So, question that arised in my head is - what does that Φ mean? Is it some rare unit of mass? Some sort of preferred series or standard for weights? I was looking for answers and found nothing. I ruled out pounds that was first thing that came to my mind because the difference was to big (5 pounds is approx. 2.26 kg) - though there are some signs of wear and corrosion it's in rather good shape and I don't believe it weighted 0.26 kg more originally. Also, considering I'm from Poland and the weight is really old it probably was made during the soviet era (maybe even in USSR) - so that phi could be actually cyrilic fe - but that also gave me no results. As a last resort I decided to ask here - maybe some member of that community will know the answer. Below is a photo of the weight in question.

As other have pointed out, the main utility is to allow easier cleaning of the tank cars from sediment (solid precipitates). Usually, there is a drain in the lowest point. The reason that it is in the middle is that in this way, you can allow double the incline compared to if you had the drain at one of the ends for the same height. For example, if the allowed height difference is about 15 cm, and about 15 m length, then if you had the drain in: the edge, the angle would be $\arctan\left(\frac{0.15}{15}\right)=0.57^\circ$ or 1%. the middle ,...

You are probably right (it being of Russian origin). The weight seems to be 5 funt. 1 funt is the Russian equivalent of a pound. It is written as Фунт, funt, and around 1900 it was the basic unit of weight measurement in Russia (so it survived in the USSR days), but now its obsolete. 1 Φ is about 409.5 grams.

Biggest advantage is that when connecting to trailers, there are no bleeding issues. Imagine having to connect hydraulic pipes and remove the air bubbles... As for the amount of air - the compressor and receiving tanks are designed for normal use. However if you wish to accompany AC/DC with the air brakes you will run out. Disc brakes already exist in an airbrake version for trucks - came out over 10 years ago IIRC. But one big difference is that if you lose hydraulics on a car braking system then you lose stopping power (except for handbrake etc) but with...

It is more efficient to transmit DC using about the same infrastructure. This is because of several effects: Skin effect experienced with AC. There is no skin effect with DC. Higher voltage allowed with DC for the same transmission lines. The lines have to withstand the peak voltage. With AC, that is 1.4 times higher than the RMS. With DC, the RMS and peak voltages are the same. However, the power transmitted is the current times the RMS, not peak, voltage. No radiation loss with DC. Long transmission lines act as antennas and do radiate some power. That can only...


How to interpret the eigenmatrix from a Johansen cointegration test?

I ran a Johansen cointegration test on 3 instruments, A B and C. The results that I got are: R 36.7 18.9 21.1 25.8 r=1 --> 8.4 12.29 14.26 18.52 r=2 --> 0.21 2.7 3.8 6.6 EigenValues EigenMatrix 0.03 --> 0.25 | 0.512 |-0.79 0.007 --> -0.96 | -0.618 | 0.14 0.00017 --> 0.05 | 0.59 | 0.59 My question is how I interpret these results? How do I know there is a cointegration for the these instruments. How to build a portfolio using the eigen vector? Which eigen vector should I choose to build my portfolio?

I can only talk about quantitative trading. As a rule of thumb, the lower frequency you work in, the more econometrics is important, whereas for a higher frequency, the more econometrics becomes useless . (I would still recommend a top econometrician for HFT since they have what it takes to succeed, it's just the models aren't out-of-the-box applicable.) But if I was interviewing someone who was educated in econometrics for a quantitative research position, I would hope for (given the relevance to financial time-series): I have tried to put in a legend, ^ is something you should learn later and...

There seems to be a basic fallacy that someone can come along and learn some machine learning or AI algorithms, set them up as a black box, hit go, and sit back while they retire. My advice to you: Learn statistics and machine learning first, then worry about how to apply them to a given problem. There is no free lunch here. Data analysis is hard work . Read "The Elements of Statistical Learning" (the pdf is available for free on the website), and don't start trying to build a model until you understand at least the first 8 chapters....

From remote memory, The first question is Yes/No question. Is there any stationary, i.e. I(0), time series for different levels of combination r? This question is answered by your first table. For example, if [r=2]'s test stat is say 7 while the critical value of 99% confidence is 6.6 like your example, then I have over 99% confidence to say that all instruments A, B, and C are stationary by themselves. You don't even need to build a co-integrated portfolio/combination. They are ready for mean-reversion strategy already. Obviously, in your example, your [r=2] stat is way much lower than even...


How do I graphically represent the evolution of a covariance matrix over time?

I am working with a set of covariance matrices evaluated at various points in time over some history. Each covariance matrix is $N\times N$ for $N$ financial time-series over $T$ periods. I would like to explore some of the properties of this matrix's evolution over time, particularly whether correlation as a whole is increasing or decreasing, and whether certain series become more or less correlated with the whole. I am looking for suggestions as to the kinds of analysis to perform on this data-set, and particularly graphical/pictorial analysis. Ideally, I would like to avoid having to look in depth into each series as $N$ is rather large. Update The following graphs were generated based on the accepted answer from @Quant-Guy. PC = principal component = eigenvector. The analysis was done on correlations rather than covariances in order to account for vastly different variances of the $N$ series.

Representing time series (esp. tick data) using elaborate data structures may be not the best idea. You may want to try to use two arrays of the same length to store your time series. The first array stores values (e.g. price) and the second array stores time. Note that the second series is monotonically increasing (or at least non-decreasing), i.e. it's sorted. This property enables you to search it using the binary search algorithm. Once you get an index of a time of interest in the second array you also have the index of the relevant entry in the first...

It is hard to find a stable non-trivial dependence structure in financial data. Usually when such is found it is hard to rationalize. One of my favorite (although I am sure there are others) is the so called "Presidential Puzzle". This is an old finding by Santa-Clara and Valkanov (2003) They find that " Excess return in the stock market is higher under Democratic than Republican presidencies: 9 percent for the value‐weighted and 16 percent for the equal‐weighted portfolio. At the time the finding was very robust and did not seem to be explained by anything else. What is more...

The minimum variance solution loads up on securities that have low variances and co-variances. Theoretically you are correct that this should have a low expected return profile. However, it turns out - in contradiction to modern portfolio theory - that securities that have low-volatility or low-beta experience higher returns than high-volatility or high-beta stocks. This is well-documented in the literature as the low-volatility anomaly . As a result, many funds and ETFs have been launched in recent years to exploit this phenomenon. There are a couple arguments as to why the anomaly exists. The paper I cite above argues that...

I would consider a motion chart that plots the eigenvalues of the covariance matrix over time. For a static view you can create a table: rows represent dates, and columns represent eigenvectors. The entries of the table represent changes in the angle of the eigenvector from the previous row. This will show how stable your covariance structure is. You can also create a second table this time with eigenvalues as the columns sorted from high to low (and the corresponding values below for each date). This shows the variance described by each eigenvector so you can see whether correlation as...


Should SSL be terminated at a load balancer?

When hosting a cluster of web application servers it’s common to have a reverse proxy (HAProxy, Nginx, F5, etc.) in between the cluster and the public internet to load balance traffic among app servers. In order to perform deep packet inspection, SSL must be terminated at the load balancer (or earlier), but traffic between the load balancer and the app servers would be unencrypted. Wouldn't early termination of SSL leave the app servers vulnerable to packet sniffing or ARP poisoning? Should SSL be offloaded? If so, how can it be done without compromising the integrity of the data being served? My main concern is for a web application where message layer encryption isn't an option.

OpenSSL s_client To check if you have disabled the SSLv3 support, then run the following openssl s_client -connect example.com:443 -ssl3 which should produce something like 3073927320:error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure:s3_pkt.c:1258:SSL alert number 40 3073927320:error:1409E0E5:SSL routines:SSL3_WRITE_BYTES:ssl handshake failure:s3_pkt.c:596: meaning SSLv3 is disabled on the server. Otherwise the connection will established successfully. Nmap Alternatively, you can use nmap to scan server for supported version: # nmap --script ssl-enum-ciphers example.com Starting Nmap 6.47 ( http://nmap.org ) at 2014-10-15 03:19 PDT Nmap scan report for example.com (203.0.113.100) Host is up (0.090s latency). rDNS record for 203.0.113.100: edge.example.com Not shown: 997 filtered ports PORT STATE...

You are touching a sore point… Historically , computers were mainframes where a lot of distinct users launched sessions and process on the same physical machine. Unix-like systems (e.g. Linux), but also VMS and its relatives (and this family includes all Windows of the NT line, hence 2000, XP, Vista, 7, 8...), have been structured in order to support the mainframe model. Thus, the hardware provides privilege levels . A central piece of the operating system is the kernel which runs at the highest privilege level (yes, I know there are subtleties with regards to virtualization) and manages the privilege...

Here is a dramatization of how the communication goes, when a mail is received anywhere. Context: an e-mail server, alone in a bay, somewhere in Moscow. The server just sits there idly, with an expression of expectancy. Server: Ah, long are the days of my servitude, That shall be spent in ever solitude, 'Ere comes hailing from the outer rings The swift bearer of external tidings. A connection is opened. Server: An incoming client ! Perchance a mail To my guardianship shall be entrusted That I may convey as the fairest steed And to the recipient bring the full tale....

It seems to me the question is "do you trust your own datacenter". In other words, it seems like you're trying to finely draw the line where the untrusted networks lie, and the trust begins. In my opinion, SSL/TLS trust should terminate at the SSL offloading device since the department that manages that device often also manages the networking and infrastructure. There is a certain amount of contractual trust there. There is no point of encrypting data at a downstream server since the same people who are supporting the network usually have access to this as well. (with the possible...


Why is the OS obfuscation defense against "It's a Unix system!" not widely implemented?

The Jurassic Park scene referenced in the title is infamous for how ludicrous it sounds to those who are tech literate. But it also illustrates what seems to me to be a glaringly huge hole in web security, particularly IoT devices--as soon as attackers find out a server or camera or baby monitor is running linux, they instantly know volumes about how it works. They know that commands like sudo are big juicy targets and they know that shell access will bring with it gobs of useful tools like ls and cat . So why isn't OS obfuscation more of a thing? I'm not talking about just hiding the version in web headers. Similar to JavaScript minification or obfuscation, I'm talking about changing the names of binaries and filepaths in the OS itself. Wouldn't entire classes of attacks be practically useless if the OS had ha7TrUO and RRI6e29 commands instead of sudo and ls ? Imagine a hacker that somehow gained remote root access--what are they even going to do if they don't know any commands? Implementation would be fairly easy for compilers. Take the simplest case of "rename this function and all calls to it." You could give an OS compiler and an application compiler the same randomized names and they'd be able to talk to each other. But even if the application has poor security and is vulnerable to bash injection, such attacks would be fruitless. Obviously this technique can't be used in all scenarios. Setting aside scenarios like servers maintained by human sysadmins, it seems to me that any device or server managed by automation is a prime candidate for this defense. I guess the question(s) needs to be a bit more concrete: Is OS obfuscation as described used widely and I just haven't encountered it? If not used widely, what are the practical or technical barriers to usage?

There are a few issues with HTTP Basic Auth: The password is sent over the wire in base64 encoding (which can be easily converted to plaintext). The password is sent repeatedly, for each request. (Larger attack window) The password is cached by the webbrowser, at a minimum for the length of the window / process. (Can be silently reused by any other request to the server, e.g. CSRF). The password may be stored permanently in the browser, if the user requests. (Same as previous point, in addition might be stolen by another user on a shared machine). Of those, using...

Before I tear your idea apart, let me say that it's a really interesting idea and it was super fun to think about. Please continue to think outside the box and ask interesting questions! Alright, let's do this! Let's take a step back and ask why that baby monitor is running Linux in the first place? What if there was no operating system and the application was written in bare microcontroller code (think arduino code)? Then there would be no sudo or ls or even a shell for the attacker to use, right? I'm not an expert here, but I...

No, Docker containers are not more secure than a VM. Quoting Daniel Shapira : In 2017 alone, 434 linux kernel exploits were found , and as you have seen in this post, kernel exploits can be devastating for containerized environments. This is because containers share the same kernel as the host, thus trusting the built-in protection mechanisms alone isn’t sufficient. 1. Kernel exploits from a container If someone exploits a kernel bug inside a container, they exploited it on the host OS. If this exploit allows for code execution, it will be executed on the host OS, not inside the...

Rainbow Tables are commonly confused with another, simpler technique that leverages a compute time-storage tradeoff in password recover: hash tables. Hash tables are constructed by hashing each word in a password dictionary. The password-hash pairs are stored in a table, sorted by hash value. To use a hash table, simple take the hash and perform a binary search in the table to find the original password, if it's present. Rainbow Tables are more complex. Constructing a rainbow table requires two things: a hashing function and a reduction function. The hashing function for a given set of Rainbow Tables must match...


What are the engineering principles for a train to get electricity from the railway

How many general methods are there for transferring electricity from the railway to a train? I could see that some trains are connected by a pantograph and some have a third rail. Are there any other methods? What is the general engineering principle behind each? What are the basic differences (pros and cons) of each method? I was looking for these questions but could not find a good review. If anyone has a reference or could answer them kindly do. Also, is it possible to build a small model of such a system and scale it up? I am not talking about a commercial model train. I am aiming at self-designing the same engineering principals and demonstrating them on a scalable small model. If so, I would be happy to have a nice tutorial reference. I am focusing on Electric multiple units (EMU) .

Please note : I'm not a building designer by trade, but I have had to investigate related questions for other reasons. I'll let you in on a dirty secret about sanitation lines within buildings - The biggest concern is not about how fast things are flying, it's about maintaining air pressure and providing adequate ventilation. This guide presents a bit of a historical background to tall building design with respect to sanitation system design. This presentation provides some more recent perspective and goes into some of the research that is refining current building standards. The traditional viewpoint is that waste...

The current limit specification for a wire is limited by the heat that current will produce, and how much heat the wire can dissipate before getting too hot. "Too hot" depends on the circumstances. You will see higher current ratings for the same type of wire in chassis wiring applications than the electrical code allows for home installations, for example. This is mostly due to how hot too hot is. The ultimate limit for extreme applications is that the conductor not melt. Temperatures anywhere near that would be unsafe running along wooden supports inside a wall in a house. As...

Pantograph and third rail are pretty much it. Engineering principles: both have a conducting surface on the train (moving) in contact with the stationary rail/wire, in both cases you need a material that's resilient and conductive. The contact strip is a wear material . Differences: overhead catenary wires are flexible and will move around when a train drives underneath them. At high speeds, the pantograph can set up waves in the catenary wire, if these waves aren't damped sufficiently, the pantograph will start bouncing. third rail is limited to low voltages to reduce the risk of arcing between the rails....

If the receiver does not detect the sub-carrier for the "colour burst" signal which is transmitted during the horizontal blanking period the receiver switches on the "colour-killer" circuit so the set reverts to black and white mode. The colour-burst signal - 8 to 10 cycles of 3.85 MHz - is unlikely to be generated by random noise. Figure 1. The colorburst signal is transmitted on the "back porch" between the horizontal blanking pulse and the start of that line's luminance signal. The colorburst signal is used to synchronise the QAM (quadrature amplitude modulation) oscillator which can hold its frequency accurately...


Can being cold or wet be a significant influence in getting the common cold?

As most people know, it's a common thing to say something like "better wear a sweater, otherwise I'll get the cold tomorrow." In my limited understanding, the common cold is caused by a virus. How does being cold affect this? Can being cold and/or wet be a significant influence in your chances of 'catching' the common cold?

Overall, there has been inconsistent data on the effects of using zinc lozenges to treat the common cold. Most studies have also been done on children, which may lead to more uncertainty about its effects on adults, but some of the studies I will mention have been tested on adults. One study showed the effects of using zinc to prevent the common cold in schoolchildren. They found that between the two groups they studied (one took zinc sulfate tablets, the other placebos) that the zinc-supplemented group had less of a chance of getting the cold. They concluded that zinc supplements...

TLDR: The pathogenesis of eczema is multifactorial, but broadly follows a process of genetic (or epigenetic, in the case of the early gut microbiome) dysregulation relating to barrier integrity proteins like filaggrin with corresponding changes in the skin microenvironment's ceramide content. Following these changes in protein structure and function and lipid quantity, the compromised barrier is predisposed to irritation and infection, which leads to an abnormal immunological response as Th2 cells work to resolve inflammatory processes in the skin (it's not clear how B cells participate in the pathogenesis of eczema at this time). Treatment options for mild-moderate eczema are...

Great question! I think it's answerable as an overview, but please know this is only the tip of the iceberg.* Summary : Yes, we have deficits of certain blood products in certain locations at certain times that affect patient care. However, a small percentage of blood product does expire unused (because it wasn't the right product [see background] in the right place at the right time). A little background Donated blood is not usually transfused into a patient as whole blood. Instead, it's broken down into several components which are transfused in different clinical scenarios. The issues of storage and...

This is a pretty old old-wives tale, taking many forms: don't go out into the cold while it's raining, or without a hat, with wet hair, without a warm coat or scarf, without boots, etc., "or you'll catch your death of cold." The old wive's tale was immortalized by Jane Austin in her book, Pride and Prejudice , when the heroine's sister Jane falls ill after getting a soaking in the rain. This has been studied extensively. A New York Times article describes one such uncomfortable-sounding study: In the 1950's, Chicago researchers repeated the experiment on a larger scale with...


How can I tell if I got counterfeit aluminum?

I recently received an order of extruded aluminum strip 3/32" thick that supposed to be 6061 hardened to specification ASTM B221. However, when we tried to bend it, it broke and the interior looked like cast zinc coated with aluminum. Is 6061 supposed to look that way and be unable to bend 90-degrees? How can I verify that I have solid aluminum and not some fake alloy with zinc in it?

I figured out a simple test. Since the density of 6061 is 2.5 g/cm3 and the density of zinc is over 7 g/cm3, all I had to do was measure the density of the material. This showed that indeed it was aluminum. So, its brittleness is probably just because it was hardened.

The picture, below, of the exaggerated long section of the Channel Tunnel was taken from Wikipedia . Full-sized image here . Some of the limiting factors for the Channel Tunnel are: Railways don't like steep gradients The tunnels comprising the Channel Tunnel were excavated using tunnel boring machines (TBMs). Like railways, they cannot tolerate steep gradients. The tunnel was excavated in chalk marl (green coloured material in the picture). This was due to its depth (not being too shallow and not being too deep) and its ability to be easily dug but also it would cause major support issues for...

Please note : I'm not a building designer by trade, but I have had to investigate related questions for other reasons. I'll let you in on a dirty secret about sanitation lines within buildings - The biggest concern is not about how fast things are flying, it's about maintaining air pressure and providing adequate ventilation. This guide presents a bit of a historical background to tall building design with respect to sanitation system design. This presentation provides some more recent perspective and goes into some of the research that is refining current building standards. The traditional viewpoint is that waste...


Is it legal to have an abortion in another state or abroad?

Alabama passed new laws recently, making abortion a very limited option. In that context is it legal for a US national who lives in Alabama to have an abortion in another state where it is legal in the circumstances she in in? have an abortion abroad, in circumstances which are illegal in the US? Does the "US national" above matter? In other words: is the specific act of abortion illegal on itself in Alabama (or another state if it matters), just because of the geographic constraints - or is it related to the fact that someone lives in Alabama or, more broadly, is a US citizen (second bullet of my question)? Or, yet phaserly differently: can someone who lives in Alabama just travel to another state and get an abortion, then come back safely (= Alabama law enforcement does not care) or is it still a felony to have an abortion outside of Alabama? Note: Alabama is taken as an example following the recent law changes and their wide broadcasting in France. Any other state with a similar law will do.

This aspect (and many others) of contract law is applicable in the US and various countries of the EU. can they renege after the candidate has begun their journey, thus saddling the candidate with the travel cost? No. The company would incur breach of contract. There is no need for a formal contract. The candidate only needs to prove that the company agreed (in writing, orally or clearly through its conduct) to cover or reimburse those expenses and that this elicited a meeting of the minds . The agreement would be void if the candidate incurred the expenses despite knowing...

Does the "US national" above matter? The nationality of the person is not relevant. Like most criminal statutes, the law applies to acts within the jurisdiction of Alabama, which basically means within the state's territory. The only foreign people who would be immune from that jurisdiction would be diplomats and the like, but such people would not be licensed to practice medicine in Alabama. This brings us to the point in the next paragraph. is it still a felony to have an abortion outside of Alabama? No. It is not even a felony to have an abortion inside Alabama. The...

As stated, this is not a reasonable restriction and runs afoul of the Fair Housing Act . You cannot discriminate based on family status, with an exemption for " housing for older persons ", and the act "does not limit the applicability of reasonable local, state, or federal restrictions regarding the maximum number of occupants permitted to occupy a dwelling" (let's leave aside HOA restrictions for a moment). The number of occupants can legally be restricted in terms of a reasonable relation to a legitimate interest such as parking availability, safety, noise or securing the property. A restriction based on...

Legally speaking, very many nations grant asylum, and religious persecution is one of the most basic grounds for granting asylum, following the 1951 Refugee Convention . This newspaper article compares asylum statistics in Ireland versus other parts of Europe. The Irish immigration authorities spell out the details for an asylum application. Note that you must already be in Ireland, to apply for asylum in Ireland (you should apply when you enter the country). One could also apply to Norway (almost an English-speaking country), but again you have to be in Norway to do so. There is a generic solution to...


Why is thalidomide a current drug on the market?

Given the thalidomide birth defect disaster of the 1960s, why was it later approved by the U.S. FDA for treatment of leprosy (1996) and of multiple myeloma (2006)? Presumably, the teratogenic issues and problems with permanent nerve damage didn't go away, as the liver can convert the "good" enantiomer to the "bad." Thalidomide affects even non-pregnant women, so why approve a drug with known severe complications?

The MSDS linked to is for a product sold as a solution of 10% SM-102 in 90% chloroform. It's listed as "SM-102" because that's the interesting/useful thing that the company is selling. It's common for chemicals to be sold packaged with solvents to make a solution. Sometimes that solvent is just water, but if the product is not water-soluble in sufficient concentrations then other solvents may be necessary. Alcohol solutions are quite common, but for more hydrophobic chemicals it may be necessary to use more "exotic" solvents. Because chloroform is quite a dangerous chemical for people to be exposed to...

It is not possible. The regulation of human body temperature (thermoregulation) is very subtle. Wikipedia article about thermoregulation contains a very nice graph about that mechanism. The labels are not described in the text in detail and the reference in the caption does not include this picture. Picture is a work by one JW Dietrich and I also searched PubMed for this guy, but he has no works on this topic. Another more pragmatic picture is here. Fever or increased body temperature is almost solely caused by to the production prostaglandin E2 (PGE2) . PGE2 acts on the hypothalamus or...

Your question contains a lot of misconceptions. A cure is definitely possible A cure could be found, proved, and proved safe, more quickly than a vaccine People and firms that could be working on cures are choosing to work on vaccines None of these are correct. Most virus-caused diseases have no cure: colds, Zika, Dengue, and so on. A tiny handful have treatments that can ease the course of the disease: you've heard of Tamiflu and so on. And some can be actually cured with medication. So the first assumption, that a cure exists to be found, is not a...


Is there any reason to not show users incorrectly entered passwords after a successful login?

Our client has come up with the requirement that in case the username in question has had multiple failed login attempts, the incorrectly entered password(s) must be shown once a successful login is performed. Correctly entered information, including previous passwords, will not be shown in any case. Our lead dev has told us it is technically possible by not hashing incorrect entries, but she is extremely uncomfortable with the feature and thus it has been put on hold while we brainstorm it out. The website in question is a broad mapping/GIS application that does not feature any monetary transactions whatsoever. Other login/authentication options include Google/LinkedIn/Twitter/facebook, so obviously no passwords to be stored there and handling that is primarily a UX issue. What security vulnerabilities come with implementing such a feature? Our client is not entirely without technical knowledge so a general explanation is enough. My apologies if the question is too broad or the answer very obvious.

Yes, it is a security feature, and the purpose of the delay is to prevent attacks based around tricking the user into entering input to skip past the dialog by popping it up unexpectedly when the user is in the middle of inputting multiple key presses or mouse clicks in quick succession. The two examples that are given in this blog post explaining the feature are: A CAPTCHA that asks the user to type the word only . When they press n , a save dialog is popped up, and then the user will immediately press l and then y...

As a starting point, we will consider that each elementary operation implies a minimal expense of energy; Landauer's principle sets that limit at 0.0178 eV, which is 2.85×10 -21 J. On the other hand, the total mass of the Solar system, if converted in its entirety to energy, would yield about 1.8×10 47 J (actually that's what you would get from the mass of the Sun, according to this page , but the Sun takes the Lion's share of the total mass of the Solar system). This implies a hard limit of about 6.32×10 68 elementary computations, which is about...

The primary issue is that incorrect passwords have to be stored in a way that allows them to be later displayed to users. Which, as your dev pointed out, means they can't be cryptographically hashed first. The result is that you store them either as plaintext (bad) or encrypted (better but not normally recommended). The biggest risk is if this database of invalid passwords becomes accessible to attackers. Either they compromise the server, perform SQL injection, or retrieve it in some other way. Rather than cracking the primary passwords, which hopefully are strongly hashed and therefore tougher targets, they could...


Is it bad practice to use your real name online?

On some accounts I use my real name on-line (Google+/Facebook/Wikipedia/personal blog), others (Q&A/Gaming) I use an alias. My question is: Security and privacy wise, what can people do with my real name? What are the dangers of using your real name on-line.

This is actually an interesting new field in infosec— reputation management . Employers, Law Enforcement and other government agencies, legal professionals, the press, criminals and others with an interest in your reputation will be observing all online activity associated with your real name. These "interested parties" (snoops) are usually terrible at separating professional and personal life, so you could be made to suffer for unpopular opinions, political or religious convictions, associates or group affiliations they consider "unsavory", and any behavior that can be interpreted in the most uncharitable light. (Teachers have been forced to resign for drinking wine responsibly while...

Needing to install things is kind of the point of needing the laptop, so it makes perfect sense that they want to install Office, AV, and certificates. There are no surprises there. To do that, they need admin access, but I would want to revoke that access once they were done. I would want to know the list of everything they want to install, and if they have central control over the AV (and if they do, why they want that). If your worry is that they might install malware, then download a Live CD of an anti-malware program and...

The reason password expiration policies exist, is to mitigate the problems that would occur if an attacker acquired the password hashes of your system and were to break them. These policies also help minimize some of the risk associated with losing older backups to an attacker. For example, if an attacker were to break in and acquire your shadow password file, they could then start brute forcing the passwords without further accessing the system. Once they know your password, they can access the system and install whatever back doors they want unless you happen to have changed your password in...

Loading that page loads https://www.googleadservices.com/pagead/conversion.js https://www.googletagmanager.com/gtm.js?id=GTM-WPPRGM https://stats.g.doubleclick.net/dc.js The reason Google can track you is that the website shares details of your visit with them - in this case via loading Google JavaScript code for their ads service. *To expand on this - The Google ad code will use a cookie to track you. But even if it didn't there are browser fingerprinting mechanisms which in most cases can correctly identify a user's machine even after a full browser cache / history clear. When you visit a site with ads a request is made to the ad providers server. This sends...


If someone's record has been expunged, can they legally say that they have not been arrested?

If someone applies for a job and the application asks whether they've ever been arrested, can they legally say on the application that they have not been arrested before? Note: Case was dismissed with no finding of fact.

Public nudity is illegal in New York as it is in almost every U.S. jurisdiction. And, if the police had arrested the nude protesters, the arrests probably would have been upheld in court, because a ban on nudity in public would probably be viewed as a time, place and manner restriction on the freedom of speech which is constitutionally valid. For example, the Ninth U.S. Circuit Court of Appeals recently upheld San Francisco’s public nudity ordinance in Taub v. City and County of San Francisco (2017). As the court in that case explains in a factually very similar case: Public...

In the case of United States vs Wong Kim Ark 169 U.S. 649 (1898) (a 6-2 decision), the Supreme Court wrote: [T]he real object of the Fourteenth Amendment of the Constitution, in qualifying the words, "All persons born in the United States" by the addition "and subject to the jurisdiction thereof," would appear to have been to exclude, by the fewest and fittest words (besides children of members of the Indian tribes, standing in a peculiar relation to the National Government, unknown to the common law), the two classes of cases -- children born of alien enemies in hostile occupation...

New York Criminal Procedure - Article 160.6 states, Upon the termination of a criminal action or proceeding against a person in favor of such person, as defined in subdivision two of section 160.5 of this chapter, the arrest and prosecution shall be deemed a nullity and the accused shall be restored, in contemplation of law, to the status he occupied before the arrest and prosecution. The arrest or prosecution shall not operate as a disqualification of any person so accused to pursue or engage in any lawful activity, occupation, profession, or calling. Except where specifically required or permitted by statute...

Think through the logical combinations of two questions: The government is tyrannical or just, the revolution is successful or not. Tyrannical government, revolution successful: The revolutionaries will congratulate each other, and of course they are not persecuted by the new government they install . Just government, revolution successful: The revolutionaries will congratulate each other, and of course they are not persecuted by the new government they install . Tyrannical government, revolution not successful: The legal system will find the justified attempt illegal (because they are the legal system defending a tyrannical government), the would-be revolutionaries are persecuted. Just government, revolution...


Why do wooden gate designs recommend a brace under compression instead of tension?

Looking at guides for building wooden frame gates I almost always find the following design recommendation: The idea is that the cross brace will distribute load from the top outside corner into the bottom of the hinge bracket. I understand this logic and am sure it works but wouldn't it be preferred to use a tension brace rather than a compression brace in this application? For example virtually every recommendation for a wire rope support shows the opposite: In this case the wire rope supports the far end under tension, but is there a reason a 2x4 couldn't also be used under tension rather than compression? Is the former design more effective for some reason? I realize that using the 2x4 for tension would require stronger joinery but it's certainly possible to secure it more than well enough to take the load. Additionally a common theme here seems to be that the load on the gate is too trivial to really care either way but I strongly disagree with that statement. Wooden gates almost never hold up to time, and we aren't talking decades here...most wooden gates will sag within 1-2 years. Wood is certainly a troublesome material but plenty of critical structures have been made from wood with proper engineering and have held up much longer than this. So maybe we should consider complicating things more? It's certainly cheaper and easier to use more complicated joinery/a 99 cent steel bracket and 2x4s than it is to fabricate an all steel gate frame. Are 2x4s just undersized to support a load like this or is it possible the bracing can make a difference?

The current limit specification for a wire is limited by the heat that current will produce, and how much heat the wire can dissipate before getting too hot. "Too hot" depends on the circumstances. You will see higher current ratings for the same type of wire in chassis wiring applications than the electrical code allows for home installations, for example. This is mostly due to how hot too hot is. The ultimate limit for extreme applications is that the conductor not melt. Temperatures anywhere near that would be unsafe running along wooden supports inside a wall in a house. As...

It is more efficient to transmit DC using about the same infrastructure. This is because of several effects: Skin effect experienced with AC. There is no skin effect with DC. Higher voltage allowed with DC for the same transmission lines. The lines have to withstand the peak voltage. With AC, that is 1.4 times higher than the RMS. With DC, the RMS and peak voltages are the same. However, the power transmitted is the current times the RMS, not peak, voltage. No radiation loss with DC. Long transmission lines act as antennas and do radiate some power. That can only...

The reason is simple: the load applied on the gate is pretty trivial, and the brace (be it a 2x4 or a wire) is mostly added for rigidity. Indeed, you could put that 2x4 in tension and it would work just as well (since the load is usually trivial, a 2x4 is probably 10x stronger than necessary in both tension and compression). However, as you mentioned, that would require more complex joinery, so... why bother? Obviously, when using a wire, it must be in tension, so you don't even have the choice. But with a 2x4, you can choose, so...

If you consider only the static forces then indeed the thickness might seem over-engineered. However, engine blocks are not statically loaded. They operate in the range of a few hundred to a few thousand rpm (Revolution Per Minute), so there are dynamic considerations here. Fatigue When materials are subjected to cyclic loading they exhibit a reduction in the allowable stresses. See below for an example: In general, BCC (body-centered cubic) materials (like steel) show a marked drop in strength (close to 50% or more depending on the steel). For these material there is stress (called the endurance limit), for which...


How can we reverse engineer a market-making algorithm (HFT)?

Consider a market participant $A$ who is mechanically following an automated liquidity providing algorithm (HFT) in a number of large cap stocks on a specific exchange. Assume furthermore that we are able to observe all orders placed by $A$ and that we know that the algorithm used by $A$ takes only public market data as input. $A$ starts and ends all trading days with zero inventory. We want to reverse engineer the algorithm used by $A$. Let's call this algorithm $f(...)$. The first step in reverse engineering the algorithm $f(...)$ would be to collect potential input variables to the algorithm that can later be used to infer the exact form of $f(...)$. The first problem we face is which input variables we should collect in order to be able to reverse engineer $f(...)$. To have a starting point we can consider the input variables used in Avellaneda & Stoikov (2008) . In Avellaneda & Stoikov (2008) the authors derive how a rational market maker (non-specialist) should set his bid and ask quotes in a limit order book market. The results are obviously contingent on the assumptions and model choices made in the paper. The optimal bid (or ask) in Avellaneda & Stoikov (2008) is a function of the following inputs: The trader's reservation price, which is a function of the security price ($S$), the market maker's current inventory ($q$) and time left until terminal holding time ($T-t$) The relative risk aversion of the trader ($\gamma$) (obviously hard to observe!) The frequency of new bid and ask quotes ($\lambda_{bid}$ and $\lambda_{ask}$) The latest change in frequency of new bid and ask quotes ($\delta\lambda_{bid}$ and $\delta\lambda_{ask}$) What potential input variables should we collect in order to be able to reverse engineer $f(...)$?

trading algorithmic-trading high-frequency market-microstructure

I'll take a stab at it, but this is a really broad question. A direct answer: Bayesian models often use "probability that the counter-party is informed." Indirect answers: I think your assumption is that the algorithm operates on each stock individually, and has no knowledge of what it's doing in any other stock. But, it is likely that the algorithm is doing some hedging that you don't see yet. You should look at similar products (or build synthetic baskets) and see if your algorithm is changing it's quote sizes/prices when other products' quote sizes/prices change. (It is also possible that...

The risk-neutral measure $\mathbb{Q}$ is a mathematical construct which stems from the law of one price , also known as the principle of no riskless arbitrage and which you may already have heard of in the following terms: "there is no free lunch in financial markets". This law is at the heart of securities' relative valuation , see this very nice paper by Emmanuel Derman ("Metaphors, Models & Theories", 2011) and some part of this discussion. In what follows, assume for the sake of simplicity existence of a risk-free asset ; deterministic and constant rates, with risk-free rate $r$ ;...

The lead paper in the January 2011 Journal of Finance ( Hendershott, Jones, and Menkveld ) addresses algorithmic trading (AT). In short, they find that AT improves liquidity as measured by bid-offer spreads. Taking the econometrics as correct (it is in the Journal of Finance) the next question is if bid-offer spreads are a sufficient statistic for measuring liquidity (or any other benefits). It is a difficult question to answer because, given current market structure, AT may improve liquidity (as measured by bid-offer spreads), but without data on other market structures, it is hard to say that we wouldn't better...


If you have a look at the car's wheels, you'll notice that they have holes which can be of different forms (mostly circular or rectangular). Why do they have such holes? Doesn't that reduce the stiffness of the wheels?

The turbulence model can make a big difference in your simulation . There are many turbulence models around. It becomes a tough job to select one out of them. There is no perfect turbulence model. It all depends on several parameters like Reynold's number, whether the flow is separated, pressure gradients, boundary layer thikness and so on. In this answer, brief information about a few popular models is given along with pros and cons and potential applications. However, interested users can see this excellent NASA website and references therein to know more about turbulence modeling. A) ONE EQUATION MODEL: 1....

At the beginning of my career (1979) as a design engineer at HP, the mechanical engineer created the part design and then rendered it in pencil on paper, and then transferred it onto sheets of vellum paper held onto a huge flat tilting table called a drafting board which had a precision sliding arm on it with which parallel and right angle lines could be drawn anywhere on the sheet. Clever graphical rules were applied to the resulting drawings which permitted auxiliary views of the part to be generated so it could be viewed from any desired angle, as an...

Car wheels have holes mostly due to weight and cost considerations. Each hole is a chunk of material that you aren't wasting and weighing down the wheel with. As another bonus, the holes help with cooling the brakes by allowing airflow between the inside and outside. The shape and size of the holes are calculated to have a minimal impact on the structural integrity of the wheel.

As with all good things, it depends. If you can assume that your supports are totally stiff and that the loading on the shelf will be approximately uniform, then you basically have the following structure: A rectangular cross-section (such as a plank) will behave equally under positive or negative bending moment, so your objective should be to balance both. To do so, you want your main span to be $2\sqrt2 \approx 2.83$ times the cantilevers. This is found by calculating the cantilever required to offset half of the bending moment due to a uniform load along a simply supported beam:...


Can I forbid the government from using my patented invention?

(this is a purely hypothetical situation, for literary research) I've filed a patent on a certain technology for facial recognition/analysis, and as the patent holder I want to use my exclusivity to ensure it's not used to harm anyone. Unfortunately, the nature of the invented technique can be easily misused for what I believe are evil purposes. Military, then law enforcement agencies, have begun connecting me with manufacturers who want to incorporate my technique into their software suites, to which I am firmly opposed. Mind, the patent is still in review, so getting inquiries this soon strikes me as odd. My question is, can I deny the military use of my invention should the patent be approved, and if not, are there any ways in which I can sabotage or otherwise render it difficult for them? Perhaps by requesting an impractically large royalty or purposely presenting a subtly faulty implementation to their manufacturing firm?

Think through the logical combinations of two questions: The government is tyrannical or just, the revolution is successful or not. Tyrannical government, revolution successful: The revolutionaries will congratulate each other, and of course they are not persecuted by the new government they install . Just government, revolution successful: The revolutionaries will congratulate each other, and of course they are not persecuted by the new government they install . Tyrannical government, revolution not successful: The legal system will find the justified attempt illegal (because they are the legal system defending a tyrannical government), the would-be revolutionaries are persecuted. Just government, revolution...

If you are not a member of the Bar of Maryland, you may not "practice, attempt to practice, or offer to practice law in the State unless admitted to the Bar." Maryland Business Occupations and Professions § 10-601 . "Practicing law" includes "representing another person before a unit of the State government or of a political subdivision." Maryland Business Occupations and Professions § 10-101 . "[A] person who violates § 10-601 of this subtitle is guilty of a misdemeanor and on conviction is subject to a fine not exceeding $5,000 or imprisonment not exceeding 1 year or both." Maryland Business...

You cannot deny the federal government the right to use your patent, but you can sue them for "recovery of [your] reasonable and entire compensation for such use and manufacture", see 28 USC 1498 . Note that the statute refers to such use as being "without license of the owner thereof or lawful right to use or manufacture the same", that is, there is no lawful right to infringe on a patent, but recourse for infringement is highly limited. A suit against the government under §1498 is (see the summary in Airborne Data v. US , 702 F.2d 1350) on...

The third Geneva convention says in its second article (emphasis added): the present Convention shall apply to all cases of declared war or of any other armed conflict which may arise between two or more of the High Contracting Parties, even if the state of war is not recognized by one of them. The Convention shall also apply to all cases of partial or total occupation of the territory of a High Contracting Party, even if the said occupation meets with no armed resistance. The violence in Ukraine qualifies for at least two reasons: it is an armed conflict between...


What is the difference between the Polar Moment of Inertia, $ I_P $ and the torsional constant, $ J_T $ of a cross section?

This question is so fundamentally basic that I am almost embarrassed to ask but it came up at work the other day and and nearly no one in the office could give me a good answer. I was calculating the shear stress in a member using the equation, $\frac{Tr}{J_T}$ and noticed, that for a shaft with a circular cross section, $J_T = I_P$. Both $I_P$ and $J_T$ are used to describe an object's ability to resist torsion. $I_P$ is defined as, $ \int_{A} \rho^2 dA $ where $\rho$ = the radial distance to the axis about which $I_P$ is being calculated. But $J_T$ has no exact analytical equations and is calculated largely with approximate equations that no reference I looked at really elaborated on. So my question is, what is the difference between the Polar Moment of Inertia, $ I_P $, and the torsional constant, $ J_T $? Not only mathematically, but practically. What physical or geometric property is each a representation of? Why is $J_T$ so hard to calculate?

mechanical-engineering structural-engineering applied-mechanics stresses

This is to make sure they know what the foundation is made of. For all they knew there may have been an old tunnel underneath that would have collapsed when the new building is put on top. London is built on top of an old marsh, this type of soil is very prone to sinking and uneven settling, digging down and reinforcing the foundation alleviates that. It also ensures the foundation is uniform under the building to avoid a new tower of Pisa. Given the age of the city it may have been to scour the land for potential archaeological...

The torsion constant $J_T$ relates the angle of twist to applied torque via the equation: $$ \phi = \frac{TL}{J_T G} $$ where $T$ is the applied torque, $L$ is the length of the member, $G$ is modulus of elasticity in shear, and $J_T$ is the torsional constant. The polar moment of inertia on the other hand, is a measure of the resistance of a cross section to torsion with invariant cross section and no significant warping . The case of a circular rod under torsion is special because of circular symmetry, which means that it does not warp and it's...

As with all good things, it depends. If you can assume that your supports are totally stiff and that the loading on the shelf will be approximately uniform, then you basically have the following structure: A rectangular cross-section (such as a plank) will behave equally under positive or negative bending moment, so your objective should be to balance both. To do so, you want your main span to be $2\sqrt2 \approx 2.83$ times the cantilevers. This is found by calculating the cantilever required to offset half of the bending moment due to a uniform load along a simply supported beam:...

Some ideas: Wheel Load Distribution : The load is greater on the rear wheels providing the power; more force on the front ones bring no benefit and would provide less traction. Better manoeuvrability from having a shorter wheelbase. Better Ground Clearance in some conditions, especially for bumps and or up a increasing slope for instance. Better Driving : The front wheels now turn around a point closer to the C.G. than with the rear wheels. Not good with vehicle dynamics but this appears better than the rear end 'trailing' behind. Structural : As some people have pointed out, it's better...


From an engineering standpoint, what is the purpose of the indent in a coffee lid?

I've see the same lids every day but I never really thought about their construction. There is an indent in a "Solo Travel Lid" for coffee cups that is just above the hole that you drink the coffee from. You can see the crescent shaped indent in the image. What is it for? Does it somehow increase fluid flow? Is it just a good spot for your upper lip? If so, why is there not a matching one for the nose? I tried googling this but I got no answer.

If the receiver does not detect the sub-carrier for the "colour burst" signal which is transmitted during the horizontal blanking period the receiver switches on the "colour-killer" circuit so the set reverts to black and white mode. The colour-burst signal - 8 to 10 cycles of 3.85 MHz - is unlikely to be generated by random noise. Figure 1. The colorburst signal is transmitted on the "back porch" between the horizontal blanking pulse and the start of that line's luminance signal. The colorburst signal is used to synchronise the QAM (quadrature amplitude modulation) oscillator which can hold its frequency accurately...

I'm going to set aside the potential legal liability aspects of your question. In part because you didn't ask about them, but also because liability will vary based upon jurisdiction. Obviously, consult an attorney familiar with the relevant law. Ethically, I think you've done everything that you're obligated to do. You have contacted the customer and notified them of an unsafe situation or configuration of the product. And you have (strongly) advised them that they need to discontinue using the older product in the unsafe configuration. If the customer remains insistent about using the product in an unsafe manner, you...

From the "Solo Traveler" patent : A more specific object of the present invention is to provide a lid having an opening formed therethrough to enable drinking, and having a recess formed in the lid adjacent the opening to accommodate the upper lip of one drinking from the cup This is also illustrated in the patent diagrams. I came across this interesting article on the history, use, design, and styles of disposable lids. The Solo Traveler is prominently featured for its excellent aesthetics and design . The article reiterates that: the Solo Traveler lid was designed to accommodate the nose...


I fancy myself an amateur lawyer. Can I represent someone in court, in the state of Maryland?

I live in Montgomery County Maryland. I am not a lawyer. But I have significant legal experience. I have successfully sued people, watched many trials, I have successfully won dozens of trials for my own traffic violations. And I'm a former state legislator. So I have read and argued about lots of legislation. Sometimes I feel like an amateur lawyer myself. And a pretty darn good one at that. My father recently received a ticket from an automated-traffic-enforcement system because he made a right turn without coming to a full stop. The fine is $75. But he doesn't want to pay it and I don't want him to pay it. It's more the principle of the matter than the fine amount. Because of my extensive experience litigating traffic trials, I want to represent my father in his trial. But as I mentioned above, I am not a licensed attorney. Can I represent him nonetheless? When the judge goes through the docket and calls his case, can I stand up and say, "Your Honor, I'm here representing Mr. Ali in this case?" Or will I get in trouble for doing so? This case is in the District Court of Maryland in Montgomery County.

united-states maryland unlicensed-practice legal-representation

Yes, it's illegal You are missing something terribly important: The package might not be your property [yet]. In any way, it is not in your possession, while it is in the hands of the postal service! The contents of the package started fully owned by the sender and were entrusted to the postal service to deliver it. This entrustment is (contractually) defined as the time it is handed to the postal service, but the postal service does not gain any ownership. They do however have insurance on the parcel (to some degree), as they are liable for the loss of...

Yes. Let's assume this anecdote takes place while Gates was CEO. Bill Gates doesn't own all of Microsoft, and as an officer of the company, he owes a fiduciary duty to act in the best interests of the company and its shareholders as a whole. Taking the company's property for personal use breaches that fiduciary duty . Now, in this particular hypothetical, Gates might have a decent argument that, as a public figure who can afford any piece of technology he desires, him being seen using a Microsoft Surface actually is acting in the company's best interests. But that wouldn't...

An essential component of your contract with them is that they will provide you with food free of animal stuff (the exact nature of "vegan approved" may be up for debate, but actual meat should not be included). So they breached their contract with you, and you might sue them for breach of contract. The case of Gupta v. Asha (orders were mixed up) could be useful in this matter. In this case, Hindus were served samosas containing beef, despite repeated assertions that they were vegetarian. Plaintiffs sued, the case was dismissed, and the appeals court deemed that the lower...

If you are not a member of the Bar of Maryland, you may not "practice, attempt to practice, or offer to practice law in the State unless admitted to the Bar." Maryland Business Occupations and Professions § 10-601 . "Practicing law" includes "representing another person before a unit of the State government or of a political subdivision." Maryland Business Occupations and Professions § 10-101 . "[A] person who violates § 10-601 of this subtitle is guilty of a misdemeanor and on conviction is subject to a fine not exceeding $5,000 or imprisonment not exceeding 1 year or both." Maryland Business...


How hard is it to intercept SMS (two-factor authentication)?

A lot of two-factor authentication mechanisms use SMS to deliver single-use passphrase to the user. So how secure is it? Is it hard to intercept the SMS message containing the passphrase? Do mobile networks use any kind of encryption on SMS? I found an interesting article regarding two-factor authentication and the ways it could be attacked.

authentication mobile multi-factor phone sms

GSM includes some protection through cryptography. The mobile phone and the provider (i.e. the base station which is part of the provider's network) authenticate each other relatively to a shared secret, which is known to the provider and stored in the user's SIM card. Some algorithms known under the code names "A3" and "A8" are involved in the authentication. Then the data (as sent through the radio link) is encrypted with an algorithm called "A5" and a key derived from A3/A8 and the shared secret. There are several actual algorithms which hide under the name "A5". Which algorithm is used...

General SSL (and its successor, TLS ) is a protocol that operates directly on top of TCP (although there are also implementations for datagram based protocols such as UDP). This way, protocols on higher layers (such as HTTP) can be left unchanged while still providing a secure connection. Underneath the SSL layer, HTTP is identical to HTTPS. When using SSL/TLS correctly, all an attacker can see on the cable is Which IP and port you are connected to Roughly how much data you are sending What encryption and compression are used In SSLv3 through TLS version 1.2 : the current...

This is an exact description of the panic feature built into phones as Peter Harmann already said. Anecdotally I can tell you on my previous Samsung smartphone, I could trigger this exact feature by pressing the power button 3 times in a quick succession. My phone would then take a couple pictures record a short clip of audio and then text those along with my current gps location to a list of contacts I had set up previously. This could actually be incredibly useful as a panic feature to get help when you are in so much danger that you...

You are touching a sore point… Historically , computers were mainframes where a lot of distinct users launched sessions and process on the same physical machine. Unix-like systems (e.g. Linux), but also VMS and its relatives (and this family includes all Windows of the NT line, hence 2000, XP, Vista, 7, 8...), have been structured in order to support the mainframe model. Thus, the hardware provides privilege levels . A central piece of the operating system is the kernel which runs at the highest privilege level (yes, I know there are subtleties with regards to virtualization) and manages the privilege...


A Virginia employee was terminated within 1 year of hiring because the on-site customer felt he was "too negative". Offer Letter: Along with this offer, you are receiving a $10,000.00 signing bonus, which includes $3,000.00 to be paid directly to you in your first company paycheck and the remaining $7,000.00 to be paid to you at 30 days of employment with xxxxx. A 1−year commitment required or the bonus will be repaid in full to xxxxx. Can the employer legally keep the employee's last check and send the employee a bill for the remainder ?

Virginia employer terminated employee and wants signing bonus returned Can the employer legally keep his last check and send the employee a bill for the remainder ? No, unless (1) the employee resigned and (2) his resignation does not amount to constructive termination . The employer may withhold the remaining $7,000 only if the employee did not meet the condition of " 30 days of employment with xxxxx ". Absent any language to the contrary, the requirement of " 1-year commitment " is to be construed as the consideration expected from the employee (namely, " not to quit ") in...

Most leases have a provision allowing a landlord to make entry without notice in an emergency, but the better course of action, as noted in a comment by @BlueDogRanch, is to call the police and ask them to make a "welfare check." You would ordinarily be permitted to cooperate with police by unlocking doors in furtherance of their welfare check. The police are trained to do this properly in a way that properly balances the need to aid someone who is sick or ill, the need to preserve evidence if there was a death or crime that needs to be...

There isn't any indication in that news story that the disabled son was anywhere nearby. I agree the situation you describe sounds like a legitimate use of the placard, but it seems in this situation, the placard was being used in a manner totally unrelated to the transport of a disabled person. My guess is that the cops cited her because the son wasn't in the car, and was not inside the establishment at which she parked. California code has this to say: A person to whom a disabled person placard has been issued may permit another person to use...