Lethality of sounds and extreme "loudness"

Question: In theory, could pure sound be lethal? How loud would it have to be? Also, which events are the loudest in the universe, and how loud are they? I'm confining attention to events which occur regularly, e.g. starquakes.
Comment: You need to define what you mean by "loud" when it comes to astronomical phenomena.  Starquakes don't make any sound since there isn't an atmosphere to transmit the pressure wave.
Comment: Impact of sound/shock waves on human health is probabilistic. The first damage mechanism is ear drum rupture; next are the lungs (through hemorrage and edema), then the abdomen. There are all kinds of medical and not-so-medical handbooks with curves, including dependence on age.
Answer: Well, we've classified a whole range of scales for the human hearing (which includes pure tone too). For lethal, we don't use how loud it should be, but instead - we say "how intense it should be" so that it can affect our ears. A quote from Wiki...

Loudness, a subjective measure, is often confused with objective measures of sound strength such as sound pressure, sound pressure level (in decibels), sound intensity or sound power.

So, we don't say that the sound's frequency affects our ears (same as light to eyes). The same way we don't see IR or UV, we don't hear <20 Hz and >20 kHz sounds. As for light, we say the flux impinging on the retina. In case of ears, we say the power transmitted to our ears. And, we measure this on a logarithmic scale called decibel.
So, the intensity of sound should be around or above 130 dBs for hearing impairment.

Currently, I don't have a list of the events that are loudest. But, I can point out many - such as a MiG at shock-waving speeds, a TNT, a meteor crash, an 8-richter earthquake, etc...
By star quakes - if you're mentioning the real star-quakes, then I'd say - Yes, we can. Well, we can hear a blackhole. Why can't we do the same for NS?
All these sounds are indirect observations (i.e) we observe these pressure waves traveling through the medium around thereby producing X-rays and gamma ray flares. We haven't and we can't observe sounds directly from events in the universe because of the diffuse matter in space.
On the other hand, if you're thinking of supernovae, we can't hear those. First, the sounds would dampen out as they travel through the highly diffused space. But, SNs can create their own medium (from the explosion) which can allow these pressure waves. Still, you'd have to be near the medium (which seems quite unconventional to me...)
Answer: Your question in poorly defined because the concept of sound doesn't extend very nicely to non-atmospheric settings.  Are gravity waves sounds?  Are the pressure / shock waves in nebula?  I don't think there is a unambiguously correct interpretation of sound for your question.
Regarding lethal sound here on Earth, the answer depends on what you consider sound.  For example the spherical shock wave on this explosion is deadly:

You'd be dead before any debris or fire got to you.  I'd certainly call that shock wave a very loud sound.  Others may argue that it doesn't count because it isn't a continuous tone.
Beyond a planetary atmosphere, there are incredibly powerful acoustic pressure waves in stars.
Answer: Sound as we know it is a disturbance of our atmosphere, transmitted as a wave to our ears - and yes, it can absolutely be lethal - shockwaves can hurt people very badly, as anyone who's been to the scene of a large explosion can attest. We typically measure "loudness" on a log scale of the pressure of the sound wave - I admit I'm unsure of how much pressure it would take to kill a human, as it probably varies quite a bit.
Cosmic events do not make sounds. While they produce a lot of energy, we would not "hear" them, as there is no medium through which that energy can be transferred to our atmosphere and then to our ears. The most energetic cosmic events are supernovae and quasar/pulsars - a better measure of how "loud" something like that is how bright they are, in terms of the radiation they emit, and in those terms, they are very, very loud. Wikipedia cites that a quasar produces 10^40 watts of radiant energy.


Solve error too much

Question: this is the first time I have started learning camera tracking. I know there's an easy way to track but I'm doing it the manual way; by placing trackers. After giving all the camera details and stuff, when I start solving the camera tracks, the error comes out to be 10 and I can't seem to reduce it no matter what I do.  Please help me!
Answer: Start by trying to gain as much tracks over the whole framerange as possible. Short tracks living only for a few frames are very inefficient and can be removed in the "Clean up" Panel. Also you might want to check out the "Graph" section of the Movie Clip Editor, where you can easily see and delete misbehaving tracks. Other tricks might be changing the keyframes in the "Solve" Panel or letting Blender guess the best keyframes itself. You can also try the "Refine" options beneath it. Good luck!
Answer: The problem is that your footage does not seem to have much contrast points. For example, the grass is just one color and has no sharp edges, so it can't be really used for tracking. In general, edges are also not very good to track because the trackers will start to slide along them.
So, when filming footage for motion tracking, always try to have some "markers" (contrast points) in there. This can be natural things or printed markers which can give better results (you might want to remove them in post though)
The best thing for this footage is to use the "Clean up" panel to delete all the trackers with high error values. Should not be greater than something like 2.0

Solve error too much


Characterization of Asymptotic Stability via KL-class functions

Question: Let us adopt the following definition of stability and asymptotic stability of a dynamical system of the form:
$$
\dot{x}=f(x)
$$
The trajectory of this system starting from the initial point $x_0$ at $t_0=0$ will be hereinafter denoted by $\varphi(t,x_0)$.
Definition 1 (Stability). Let $x^\star$ be an equilibrium point for $\dot{x}=f(x)$, i.e. $f(x^\star)=0$. This point is said to be stable if for every $\varepsilon>0$ there is a $\delta=\delta(\varepsilon)>0$ such that
$$
\|x-x^\star\|<\delta \implies \|\varphi(t,x_0)-x^\star\|<\varepsilon
$$
for all $t\geq 0$.
Definition 2 (Asymptotic Stability). Let $x^\star$ be an equilibrium point for $\dot{x}=f(x)$, i.e. $f(x^\star)=0$. This point is said to be asymptotically stable if it is stable and additionally there is an $\alpha>0$ such that
$$\lim_{t\to\infty}\|\varphi(t,x_0)-x^\star\|=0$$
for all $x$ with $\|x-x^\star\|<\alpha$.
Definition 3 (Classes of functions). We define the following four classes of functions:
A function $\alpha:\mathbb{R}^+\to\mathbb{R}^+$ is said to be

$\mathcal{K}$-class and we denote $\alpha\in\mathcal{K}$ if it is continuous, strictly increasing and $\alpha(0)=0$.
A function $\beta:\mathbb{R}^+\to\mathbb{R}^+$ is said to be $\mathcal{K}_\infty$-class and we denote $\beta\in\mathcal{K}_\infty$ if $\beta\in\mathcal{K}$ and it is unbounded.
A $\mu:\mathbb{R}^+\to\mathbb{R}^+$ is said to be $\mathcal{L}$-class and we denote $\mu\in\mathcal{L}$ if it is continuous, strictly decreasing and $\lim_{\tau\to\infty}\mu(\tau)=0$
A $\gamma:\mathbb{R}^+\times\mathbb{R}^+\to\mathbb{R}^+$ is said to be $\mathcal{KL}$-class and we denote $\gamma\in\mathcal{KL}$ if $\gamma(\cdot,t)\in\mathcal{K}$ for all $t\in\mathbb{R}^+$ and $\gamma(r,\cdot)\in\mathcal{L}$ for all $r\in\mathbb{R}^+$

Proposition 1. An equilibrium point $x^\star$ is asymptotically stable if and only if there is a $\gamma\in\mathcal{KL}$ and a constant $\kappa>0$ so that:
$$
 \|\varphi(t;x_0)-x^\star\|\leq \gamma(\|x_0-x_\star\|,t)
$$
for all $x_0$ such that $\|x_0-x^\star\|<\kappa$ and for all $t\geq 0$.
I have some problem with the proof!
Proof: 1. [The first part looks easy] Let us assume that $x^\star$ satisfies the inequality mentioned above. Let us choose an $\varepsilon>0$; $\gamma(\cdot,t)$ is $\mathcal{K}$-class, so we may choose a $\delta$ such that $0<\delta<\kappa$ and $\gamma(\delta,0)\leq \varepsilon$. Now for $\|x_0-x^\star\|<\delta$ we have:
$$
 \|\varphi(t;x_0)-x^\star\|\leq\gamma(\|x_0-x_\star\|,t)\leq\gamma(\|x_0-x_\star\|,0)\leq\gamma(\delta,0)\leq\varepsilon
$$
So if the inequality state above holds then $x^\star$ is stable and more:
$$
 0\leq\lim_{t\to\infty}\|\varphi(t;x_0)-x^\star\|\leq \lim_{t\to\infty}\gamma(\|x_0-x^\star\|,t)=0
$$
Therefore
$$
 \lim_{t\to\infty}\|\varphi(t;x_0)-x^\star\|=0\Leftrightarrow\lim_{t\to\infty}\varphi(t;x_0)=x^\star
$$
What about the converse? How can one prove it?
We need to prove that if $x^\star$ is a (locally) asymptotically stable equilibrium point, then there is a $\gamma\in\mathcal{KL}$ and a constant $\kappa>0$ so that:
$$
 \|\varphi(t;x_0)-x^\star\|\leq \gamma(\|x_0-x^\star\|,t)
$$
for all $x_0$ such that $\|x_0-x^\star\|<\kappa$ and for all $t\geq 0$.
I would appreciate a proof or at least a reference to some book or article where I can find it clearly explained.
Answer: A proof can be found in Khalil, Nonlinear Systems, 3rd edition, appendix C.6.
Comment: It would be nice if you can give the outline here


Qualitative Benefit of Longer Sits

Question: I have recently tried meditating for 15 min at a time, at least once per day. I'm wondering, however, if long sits have a qualitative benefit. In other words, I'm wondering whether longer sits have a benefit other than  more of those of shorter sits, perhaps uniquely different benefit/s? (Here, longer sits would mean about 1h-1h30).
Comment: See also [maximum-productive-time-for-a-meditation-sit](https://buddhism.stackexchange.com/questions/30950/maximum-productive-time-for-a-meditation-sit)  and [what-is-the-minimum-amount-of-time-needed-for-a-productive-meditation-sit](https://buddhism.stackexchange.com/questions/2431/what-is-the-minimum-amount-of-time-needed-for-a-productive-meditation-sit)
Answer: Let's phrase this a different way.  If you just worked out for 15 minutes, would it be as effective as if you worked out for an hour?  The answer should be obvious.  The more time you dedicate to anything, the better you'll be at it and the more benefit you'll receive.  The mind is a muscle; same as your biceps.  If you only train it halfheartedly, you'll only get halfhearted results.
But it goes deeper than this.  Sitting is like baking a cake.  You can throw in all of the ingredients - the breath, the cushion, the concentration - but if you take the cake out of the oven before it's done baking, you don't pull out a cake, you pull out a hot mess.  The mind requires time to settle.  It has to remain secluded for an extended period of time before those ingredients can undergo the alchemy of practice and begin to phase change into true samadhi.
And it goes still deeper.  There are states that are only available when one sits for extended periods of time.  No matter how long you have been practicing, you probably will never reach access concentration until you've sat for at least an hour.  The day to day mind is just too scattered to reach it much sooner.  You will only begin to touch the outskirts of jhana after you've sat for an hour and a half.  Full jhana is only available to those who sit for hours a day and even then usually only on retreats of multiple days.
There are no shortcuts.  You get out what you put in.
Answer: Ideally, Buddhist Meditation practices quiets the effects of living in Samsara, and transforms the mind with the power of sunyata, Emptiness. This gives us a lightness of being, and diminishes those experiences where life becomes unmanagable. The length of time spent on the cushion is based on this, for beginners around 20-45 minutes. This is once or twice a day.

Qualitative Benefit of Longer Sits


What is the single most influential book every statistician should read?

Question: If you could go back in time and tell yourself to read a specific book at the beginning of your career as a statistician, which book would it be?
Comment: [This question](http://stats.stackexchange.com/questions/23841/what-factors-make-for-a-great-stats-book/23844) is another way of looking at this question. I hope that it will provide a good complement, once it gets some good answers.
Comment: There are really three separate questions here! 1) What is the single most influential book in statistics; 2) What book should every statistician read; 3) What book have you read that you most wish you'd read much earlier. (2) and (3) probably have considerable overlap; (1) may be quite distinct.
Answer: Here are two to put on the list:
Tufte. The visual display of quantitative information
Tukey. Exploratory data analysis
Comment: Both are worth a periodic re-reading, maybe once a decade, just to refresh the ideas.  Concerning Tukey: it's great to sit down just with pencil and paper once in a while and do a deep analysis of an interesting dataset.
Comment: For graphics for a statistician, I prefer William Cleveland's books to Tufte's.
Comment: I have a feeling these books were meant to analyze non-linear data when non-linear methods weren't as available?
Answer: The Elements of Statistical Learning from Hastie, Tibshirani and Friedman http://www-stat.stanford.edu/~tibs/ElemStatLearn/ should be in any statistician's library !
Comment: I disagree - that one is closely related to machine learning, not statistics *per se*!
Comment: Apparently I'm in the minority in thinking this book is overrated.  It seems to be written for a graduate-level student, but one who doesn't care about the details of how anything works.
Comment: @aL3xa: it is certainly focussed on machine learning...which is why I think statisticians should be exposed to it early on.
Comment: @TheLaconic you are not alone, i think the same. E.g. Bishop's PRML, while assuming much fewer prerequisites than ESL, goes into the theory of ML much deeper, giving more derivations.

ESL's broad following is ONLY because of the stellar authors (Tibshirani, Hastie, Friedman), as a pedagogic material it is so-so. Good as a reference though.
Answer: I am no statistician, and I haven't read that much on the topic, but perhaps
Lady Tasting Tea: How Statistics Revolutionized Science in the Twentieth Century
should be mentioned? It is no textbook, but still worth reading.
Comment: Many people have reported this as entertaining, but it's full of extraordinary errors. If you can find it, my review in _Biometrics_ 57: 1273-1274 (2001) gives a far from complete list. (Salsburg gets various Bernoullis mixed up, which is easier to do.)
Comment: I second this. Also, there is quite a lot of suggestions for further reading which I think are useful in the book.
Comment: I think this book speaks to those who knew nothing at the beginning but the obtuseness of the language and the cultural baggage associated with the field.  This book gave the mind wings - it says that statistics is about finding useful truth in a sea of noise and misunderstanding.
Answer: Darrell Huff -- How to Lie with Statistics
Comment: Back when this was a \$3.95 and then a \$4.95 paperback, I bought copies by the dozen and gave them away to friends, clients, and anyone else who might be interested.
Comment: It's deservedly remembered. But the non-statistical content dates it unfortunately, not least an extraordinarily large fraction of cartoons featuring people (and even babies) smoking.  60+ years on, that's not amusing any more. (Some reprints e.g. one in the UK updated the cartoons.)
Answer: Probability Theory: The Logic of Science
Comment: It is also a bit sad that some of the later chapters are missing and/or under developed - for example there is no chapter on regression, but a draft unpublished manuscript was available with some fascinating insights into "measurement error" regressions.  Some very cool stuff on time series though.
Comment: This book is tough. It is about the foundations of probability, and even in that part of Statistics, I don't think it is a reference text. I do believe there can be 14 people on planet Earth who read and understood its full message, but I would probably classify this as a must read for probabilists, for the sake of the thousands of others that are deep in stuff like GLMs, GAMs, Bayesian models and other things.
Answer: Not a book, but I recently discovered an article by Jacob Cohen in American Psychologist entitled "Things I have learned (so far)."  It's available as a pdf here.
Comment: Thats a wonderful article, written in Cohen's lucid and conversational style.
Answer: Long ago, Jack Kiefer's little monograph "Introduction to Statistical Inference" peeled away the mystery of a great deal of classical statistics and helped me get started with the rest of the literature.  I still refer to it and warmly recommend it to strong students in second-year stats courses.
Comment: Great recommendation, thank you -- I got a copy recently based on this and it really is quite good.
Comment: I'm glad to hear someone else appreciates this book!
Answer: William Cleveland's book "The Elements of Graphing Data"  or his book "Visualizing Data"
Comment: I agree. I think that, for statisticians, Cleveland is better than Tufte.
Comment: +1 to Robert Alberts, & +1 to Peter Flom (Cleveland's books are *definitely* better for statisticians, although Tufte's are beautiful as well, and I have read all of them). @AndyW, *Elements* is introductory, e.g., it has  guidelines for making an informative graphic. *Visualizing* demonstrates how to center your data exploration process around graphics; it starts with preliminary visualization of the data, talks about the issues at hand and walks all the way through to assessing the final model (e.g., residual analysis) via graphics. The latter is much more informative than the former.
Comment: I'm currently reading through The Elements (Visualizing Data is not in my current schools library). What is the difference between Elements & Visualizing Data? I haven't been able to find detailed enough descriptions to formulate what is exactly the difference between the two.
Comment: As @gung says, _Visualizing_ is a more advanced sequel to _Elements_. There is some overlap but it's helpful rather than irritating. Both strongly recommended. Last revision dates 1993 and 1994, but they are still fresh 20+ years later. Note that non-technical readers would get value from both: I can vouch personally that high school mathematics is sufficient background.
Comment: @AndyW One of them is a bit more technical than the other (I forget which is which though!)
Answer: I wouldn't argue that either of these should be considered "the most influential book... [for] statistician[s]", but for those who are just starting to learn about the topic, two helpful books are:

Robert Abelson, Statistics as Principled Argument
Paul Murrell, Introduction to Data Technologies
Comment: Abelson would be useful to many who re not just starting out, as well.
Answer: I think every statistician should read Stigler's The History of Statistics: The Measurement of Uncertainty before 1900
It is beautifully written, thorough and it isn't a historian's perspective but a mathematician's, hence it doesn't avoid the technical details.
Answer: I say the visual display of quantitative information by Tufte, and Freakonomics for something fun.
Answer: Andrew Gelman's interesting book recommendations are here:
http://thebrowser.com/interviews/andrew-gelman-on-statistics
Comment: That link rottened, maybe it is this one:  http://fivebooks.com/interviews/andrew-gelman-on-statistics
Answer: In addition to "The History of Statistics" suggested by Graham, another Stigler book worth reading is
Statistics on the Table: The History of Statistical Concepts and Methods
Answer: On the math/foundations side: Harald Cramér's Mathematical Methods of Statistics.
Comment: By the way, this is the earliest place I have found mention of Cramer's phi.  Amazing how a lovely little sidenote in that book became a well known method many decades later.
Answer: For a clear exposition of what should be in social science journal articles (assistance if you're writing or peer reviewing) I like The Reviewer's Guide to Quantitative Methods in the Social Sciences. In particular I like the table desideratra as a synopsis of the minimum that a paper (article, thesis, dissertation) should contain. The chapters are separated by analysis technique, which is nice. I think the book has wider applications than "just" the social sciences as the techniques covered are used across many fields.
Quite early on, so perhaps not covered by the question, I was introduced to Ott's Introduction to Statistical Methods and Data Analysis. It's quite expensive, but is a wonderful resource at showing the underlying statistical models for various GLM methods. I dream of the day that journals require articles to contain show the formula of the statistical model tested.
For checking test assumptions, looking at the effects of various options within a test, and so forth, this is the one book I wish I had when I was studying. I have the previous edition and it is one of the best general resources I have purchased because of the clear and consistent manner in which information about the tests is laid out. It contains nice examples illustrating the test(s), and does not require the reader to have a particular statistical package in order to follow the expositions.
Answer: I have read the above recommendations and was surprised to find that most of the people who answered the question were people who are not statisticians themselves. With 2 or 3 exceptions ...
As an industrial statistician who also happened to work with social scientists and health professionals I would say that if I could take only one book with me to a desert island it would be George E.P Box, Statistics for Experimenters (Wiley). In his inimitable humorous and lucid style he explains the essence and the philosophy of building mathematical models for real data. Rigorous thinking, no mathematical frivolities, no nonsense, teaches us to think statistically, plot and visualize whatever you can. A masterpiece of a competent applied scientist (chemical engineer turned statistician). Always fun to read again.
Comment: Good choice!  His coauthor the late William Hunter and J. Stuart Hunter also contributed to the book.
Comment: The first edition is cleaner and fresher than the second. Box was a great statistician but in later life a poor proof-reader.
Answer: Fooled By Randomness by Taleb
Taleb is a professor at Columbia and an options trader. He made about $800 million dollars in 2008 betting against the market. He also wrote Black Swan. He discusses the absurdity of using the normal distribution to model markets, and philosophizes on our ability to use induction.
Comment: A terrible book, written by someone who does not understand statistics...
Comment: Xi'an, care to expand, or provide links to some critiques?
Comment: There are a bunch of comments on The Black Swan (and Taleb more generally) [here](http://stats.stackexchange.com/questions/35956/taleb-and-the-black-swan)
Answer:
Michael Oakes' Statistical Inference:  A Commentary for the Social and Behavioral Sciences.
Elazar Pedhazur's Multiple Regression in Behavioral Research.  If you can stand the immense detail and the self-important tone.

In case you're interested, I've reviewed both on Amazon and at https://yellowbrickstats.com/favorites.htm
Answer: Rice: Mathematical Statistics and Data Analysis
Answer: Lots of good books already suggested. But here is another: Gerd Gigerenzer's "Reckoning With Risk" because understanding how statistics affect decisions is more important than getting all the theory right. In fact number one sin of statisticians is failing to communicate clearly. His book talks about the consequences of poor communication and how to avoid it.
Comment: _"understanding how statistics affect decisions is more important than getting all the theory right..."_  Ain't it the truth? I come from an architecture background, and I can tell you, sometimes theory just gets in the way...
Answer: I learned a great deal from the Bible of Bayesian statistics:
Jose Bernardo and Adrian Smith (2000) Bayesian Theory.
Answer: The Essential Guide to Effect Sizes: Statistical Power, Meta-Analysis, and the Interpretation of Research Results by Paul D. Ellis
This book if a "must have" for everyone conducting any scientific research, especially one that comes not from pure stats/maths. The book below extends the first one regarding confidence intervals.
Understanding The New Statistics: Effect Sizes, Confidence Intervals, and Meta-Analysis by Geoff Cumming
Answer: I am going to go ahead and propose a standard textbook in the field. I am talking about Probability and Statistics by DeGroot and Schervish, first published in 1975.
This book has served as a textbook for many students and is considered a classic, rightfully so in my opinion. It covers topics such as combinatorics, distributions, Bayesian statistics, likelihood inference and regression analysis. As far as I know no other textbook is so thorough so I believe it is a must-have.
Answer: It would probably be Bayesian Data Analysis by Gelman or Deep Learning with Python. But that's a bit like taking streptomycin to the middle ages. These were not written when I started my career and quite a few things from the books would have been big news back then. Some of the most influential things everyone should know are in no single source though (perhaps they should be, but...).
Answer: "Most influential" is a very different notion from "everyone should read". I am not qualified to answer the first - you'd need someone who is an historian of statistics - but for the second, here are some:

Statistics as Principled Argument by Robert Abelson should be read by anyone doing or using statistics in the pursuit of science, humanities, etc.

William S. Cleveland's two books on graphics: The elements of graphing data and Visualizing Data.  For statisticians, I'd put these ahead of even Tufte's work, not because Tufte isn't worthwhile but because a) Cleveland wrote with statisticians as his intended audience and b) Cleveland based his recommendations on experimental data about how people look at graphs, rather than intuition.

Exploratory Data Analysis by John Tukey.  It's dated but valuable - you can do a lot with a pencil and paper and  a brain (at least, if your brain is as good as Tukey's!)
Answer: Kennedy's A Guide to Econometrics contains a wealth of practical advice about a wide range of statistical analysis.  It's somehow both incredibly information-dense and easy to read, and I still learn something new every time I pick it up.
Wooldridge's Introductory Econometrics has a good amount of this kind of discussion too, but as an introductory textbook it is more self-contained.  I wish I'd had a course based around it.


Buying a web domain

Question: I am planning to redirect my blog at blogger to my own domain. But I am confused by various options available outside. I see options like domain registration, bundled site hosting, design templates and more in Yahoo. GoDaddy offers just domain name at a price. There is one local provider who provides 10 free email accounts along with domain registration. Now I am just wondering which option to choose? Can I buy one domain and use it as custom domain in Blogger?
Comment: Old question, but nowadays there are good alternatives like gandi.net or Google domains.
Answer: You can buy a domain from any place that sells them. Everyone will recommended some place to buy from because they have either used them or are affiliated with that company. I'm affiliated with a company but I won't push them or mention them unless you are curious.
The biggest domain seller is Go Daddy, I'm not a fan but they are pretty easy to buy from. Name Cheap is another one that is big. Then there is NetworkSolutions and Register.com, they are both big and old companies but they charge pretty high prices for domains.
You can also buy domains through Blogger. Here are the instructions on buying a domain from Blogger and just pointing a domain bought from someplace else: http://www.google.com/support/blogger/bin/static.py?page=ts.cs&ts=1233381
Answer: There are 3 separate things:

Buying a domain name
Buying a hosting service
Installing and configuring your blogging software

Many places will do more than one of these or even all of these for you to make more money. The advantage to you is that they take care of some details like pointing the domain name (DNS) to the hosting service.
My favorite place for hosting is Total Choice Hosting. They have reasonable price and the very best service I have experienced. I am not affiliated with them but I send many of my clients there. They also sell domain names and if you buy from them you do not have to configure the DNS.
Many hosting providers give you software pre-installed, but it is not you can do it yourself. Wordpress which is an excellent blogging platform has an ultra-easy install and even automated updates now.
For domain names, GoDaddy is cheap and many will tell you the service sucks. I do not have a bad experience with them and save money with their bulk domain name pricing since I buy lots of domains for clients. I do prefer Dotster for simplicity, so if you are a beginner I would go with them.
Answer: The short answer is YES, you can buy one domain, and use it as a "custom domain" in Blogger. (I'm assuming by "custom domain" that you mean the Blogger feature that lets point a domain to your blog, hosted at Blogger.)
Blogger's "custom domain" feature has one important requirement: the service that you buy your domain from must allow you to create a CNAME to your blog (hosted at Blogger). Also, the other big thing to watch out for is that Blogger doesn't allow you to redirect from a naked URL (in other words domain.com cannot be made to point to a Blogger-hosted blog). You must something like www.domain.com or blog.domain.com. See these URLs for more information:
http://www.google.com/support/blogger/bin/topic.py?hl=en&topic=12451
http://www.google.com/support/blogger/bin/answer.py?hl=en&answer=58317
As itai points out, there's a big difference between domains (the address), hosting (the actual physical "server" where your content lives), and the blogging software (the program that lets you type in content).
Good luck!

Buying a web domain


Gradient boosting algorithm example

Question: I'm trying to fully understand the gradient boosting (GB) method. I've read some wiki pages and papers about it, but it would really help me to see a full simple example carried out step-by-step. Can anyone provide one for me, or give me a link to such an example? Straightforward source code without tricky optimizations will also meet my needs.
Comment: https://medium.com/mlreview/gradient-boosting-from-scratch-1e317ae4587d Good article I came across to get overview about Gradient Boosting. Python implementation for the same using sklearn library
https://www.analyticsvidhya.com/blog/2015/11/quick-introduction-boosting-algorithms-machine-learning/
Answer: I tried to construct the following simple example (mostly for my self-understanding) which I hope could be useful for you. If someone else notices any mistake please let me know. This is somehow based on the following nice explanation of gradient boosting http://blog.kaggle.com/2017/01/23/a-kaggle-master-explains-gradient-boosting/
The example aims to predict salary per month (in dollars) based on whether or not the observation has own house, own car and own family/children. Suppose we have a dataset of three observations where the first variable is 'have own house', the second is 'have own car' and the third variable is 'have family/children', and target is 'salary per month'. The observations are
1.- (Yes,Yes, Yes, 10000)
2.-(No, No, No, 25)
3.-(Yes,No,No,5000)
Choose a number $M$ of boosting stages, say $M=1$. The first step of gradient boosting algorithm is to start with an initial model $F_{0}$. This model is a constant defined by $\mathrm{arg min}_{\gamma}\sum_{i=1}^3L(y_{i},\gamma)$ in our case, where $L$ is the loss function. Suppose that we are working with the usual loss function $L(y_{i},\gamma)=\frac{1}{2}(y_{i}-\gamma)^{2}$. When this is the case, this constant is equal to the mean of the outputs $y_{i}$, so in our case $\frac{10000+25+5000}{3}=5008.3$. So our initial model is $F_{0}(x)=5008.3$ (which maps every observation $x$ (e.g. (No,Yes,No)) to 5008.3.
Next we should create a new dataset, which is the previous dataset but instead of $y_{i}$ we take the residuals $r_{i0}=-\frac{\partial{L(y_{i},F_{0}(x_{i}))}}{\partial{F_{0}(x_{i})}}$. In our case, we have $r_{i0}=y_{i}-F_{0}(x_{i})=y_{i}-5008.3$. So our dataset becomes
1.- (Yes,Yes, Yes, 4991.6)
2.-(No, No, No, -4983.3)
3.-(Yes,No,No,-8.3)
The next step is to fit a base learner $h$ to this new dataset. Usually the base learner is a decision tree, so we use this.
Now assume that we constructed the following decision tree $h$. I constructed this tree using entropy and information gain formulas but probably I made some mistake, however for our purposes we can assume it's correct. For a more detailed example, please check
https://www.saedsayad.com/decision_tree.htm
The constructed tree is:

Let's call this decision tree $h_{0}$. The next step is to find a constant $\lambda_{0}=\mathrm{arg\;min}_{\lambda}\sum_{i=1}^{3}L(y_{i},F_{0}(x_{i})+\lambda{h_{0}(x_{i})})$. Therefore, we want a constant $\lambda$ minimizing
$C=\frac{1}{2}(10000-(5008.3+\lambda*{4991.6}))^{2}+\frac{1}{2}(25-(5008.3+\lambda(-4983.3)))^{2}+\frac{1}{2}(5000-(5008.3+\lambda(-8.3)))^{2}$.
This is where gradient descent comes in handy.
Suppose that we start at $P_{0}=0$. Choose the learning rate equal to $\eta=0.01$. We have
$\frac{\partial{C}}{\partial{\lambda}}=(10000-(5008.3+\lambda*4991.6))(-4991.6)+(25-(5008.3+\lambda(-4983.3)))*4983.3+(5000-(5008.3+\lambda(-8.3)))*8.3$.
Then our next value $P_{1}$ is given by $P_{1}=0-\eta{\frac{\partial{C}}{\partial{\lambda}}(0)}=0-.01(-4991.6*4991.7+4983.4*(-4983.3)+(-8.3)*8.3)$.
Repeat this step $N$ times, and suppose that the last value is $P_{N}$. If $N$ is sufficiently large and $\eta$ is sufficiently small then $\lambda:=P_{N}$ should be the value where $\sum_{i=1}^{3}L(y_{i},F_{0}(x_{i})+\lambda{h_{0}(x_{i})})$ is minimized. If this is the case, then our $\lambda_{0}$ will be equal to $P_{N}$. Just for the sake of it, suppose that $P_{N}=0.5$ (so that $\sum_{i=1}^{3}L(y_{i},F_{0}(x_{i})+\lambda{h_{0}(x_{i})})$ is minimized at $\lambda:=0.5$). Therefore, $\lambda_{0}=0.5$.
The next step is to update our initial model $F_{0}$ by $F_{1}(x):=F_{0}(x)+\lambda_{0}h_{0}(x)$. Since our number of boosting stages is just one, then this is our final model $F_{1}$.
Now suppose that I want to predict a new observation $x=$(Yes,Yes,No) (so this person does have own house and own car but no children). What is the salary per month of this person? We just compute $F_{1}(x)=F_{0}(x)+\lambda_{0}h_{0}(x)=5008.3+0.5*4991.6=7504.1$. So this person earns $7504.1 per month according to our model.
Answer: As it states, the following presentation is a 'gentle' introduction to Gradient Boosting, I found it quite helpful when figuring out Gradient Boosting; there is a fully explained example included.
http://www.ccs.neu.edu/home/vip/teach/MLcourse/4_boosting/slides/gradient_boosting.pdf
Answer: This is the repository where the xgboost package resides. That is from where the xgboost library for major languages like Julia, Java, R, etc are forked from.
This is the Python implementation.
Walking through the source code (as instructed in the "How to contribute") docs would help you understand the intuition behind it.
Comment: Thanks for your answer. I've read xgboost docs. But I meant a bit different thing. Not the code of using a framework. But the code of the algorithm of classifier itself.
Comment: Ohh.  Thanks for letting me know :)   I guess I've misunderstood your question.  And welcome to the site!
Comment: @shda I have edited the answer with the relevant links. Do let me know if you find it useful :)
Comment: Full xgboost source is rather complicated example) But i'll give it a try

Gradient boosting algorithm example


Removing surface rust from my Eggbeater pedals?

Question: So I did a couple of wet rides last month, and I guess I didn't dry the pedals as well as I should have.  I have Crank Brothers Eggbeater pedals, and I noticed a bit of surface rust on them that I'd like to remove.  What are my options, considering that I can't really disassemble the pedals, and they have a large number of surfaces that are hard to get to?
Comment: Where is the rust located?  I've had a Candy-SL pedal fail near the base of one of the clips so make sure that area isn't weakened from corrosion.
Answer: You're probably best with a metal brush the consistency of the items recommnded in the question below. Ultimately it's gonna happen though so all we can do is our best to dry up and clean up items. At some point they need replacing. A bit of light oil on the pedal the night before a wet ride might help keep of the rust by not letting water in. Of course it will attract dirt (hence the night before recommend so it dries).
Dealing with rust on a steel frame
Answer: I wouldn't worry about it too much, the rust will be worn away over time as you use them. For the future though, you could dry the pedals off after wet rides and periodically apply a small amount of light lubricant to the springs, etc.


Is the name Asma halal for baby girl?

Question: I really like that name Asma /Esma/, but as far as I know that is one of names of Allah - Asma-ul-Husna. So I would really like to know if it is halal to give that name to a baby girl?
Answer: "Asma" means "names" in Arabic; it's not one of the names of Allah (SWT). In fact Abu Bakr's (RA) daughter was named Asma.
"Asma-ul Husna" means "The Beautiful names"
Comment: when I checked the meaning of Asma it came as "supreme" so I thought if it is right to call a baby that way. Thank you so much
Answer: The name Asma' or اسماء  doesn't appear to be a haram name for humans. Besides, I can explain about its meaning that this name "Asma, Asmaa, Asmaa'" looks as the plural form of Esm اسم  which means name(s). as a result, I think it can be Okay and suitable and permissible for you in order to using such a name. you said it is a name of Allah? If I am not wrong, Asma'can be relevance with Asma'al-Hosna' ,  not as a direct name of Allah. Although I've heard that using Allah's names would be Okay in some conditions (if we observe them, may be intentions, and some other conditions that I am not aware about them at the moment). As a result, it is a permissible name as I have heard it before as the name of many Muslimahs too.

Is the name Asma halal for baby girl?


Why is the circuit board abreviation for transistor "Q"?

Question: On circuit boards, I see that transistors are "Q", but why Q? Shouldn't "TR" be transformer, so transistor can be "T" because transistors seem to be more common then transformers.
Comment: @hikeOnPast -- u = Greek Mu; uIC as in "Micro integrated circuit" (from the 50's)
Comment: And for that matter, why are ICs "U"?
Comment: Early in the transistor era, I occasionally saw schematics with transistors designated as TRnnn.
Comment: @HikeOnPast ICs are often called ICnn.
Comment: In the 1975 schematics for a Siemens Oscillar M07107 oscilloscope they use TsNNN.
Answer: There are claims that, after initial chaos, eventually the letter Q was chosen because of the popular TO18/TO39 case styles.

Just look at it from the bottom:

And of course, 'T' had been used for transformers since decades earlier.
Now, finding trustworthy sources available on the web... well, it hasn't been a lucky few minutes for me, but I know I read this somewhere in print years ago.
Comment: Ouch, that 2nd image came out bigger than intended!
Comment: Image Size: FTFY.
Answer: Here's the rumor I have read somewhere: When transistors were new, they were that strange part no one was really using yet. "T" was already taken (transformer), and the not-so-often used letter "Q" was (i) not used for anything else and (ii) seemed appropriate for a not-so-often used type of component.
I have stopped worrying about how to call parts. The letters are not used consistently in different parts of the world - "Q" for transistors, for instance, is an American tradition; Europeans often call transistors "T". Except for Germany, where discrete semiconductors (diodes, transistors) tend to be called "V" in some companies even though the standard DIN EN 60617 suggesting the letter "V" is not even valid any more, iirc. The current standard, DIN EN 61346, suggests the letter "K" for transistors, but I've met no one who is really hardcore enough to actually use it.
Oh, and I've just found out that DIN EN 61346 has been withdrawn and replaced by IEC 81346. The German wikipedia article has a complete list about all the suggested reference designators, and you can clearly see how the goal of finding one big classification, valid for everything and anything from board level design to industrial automation in large installations, has led to a big table that has FUBARed everything. Search for the term "transistor" in the wikipedia article, and you'll find that you're supposed to use "KF"!
Comment: There are enough tube ("valve") amplifiers still around, especially for guitar players, that Vnnn (for "valve") will be around for a long, long time yet.
Answer: TL;DR

The short answer is "because [someone] said so!" (Shockley? Moore?) and then it was codified
Might refer to the Q-point ("quiescent" point) as load-line analysis (Q-point analysis, or bias analysis) came of age around the same time as the advent of the transistor
FYI: "T" is transformer according to ANSI/IEEE

(My) Summary of the Codification History:
1950's Military defines standards for drafting to facilitate what we now call "lifecycle management"
1970's IEEE/ANSI tries to get in on the action and set a wide reaching commercial standard
1990's IEEE tries to update it, but realizes its pointless (e.g. good enough)
From Wikipedia (emphasis mine):

IEEE 200-1975 "Standard Reference Designations for Electrical and
  Electronics Parts and Equipments" is a standard that was used to
  define referencing naming systems for collections of electronic
  equipment. IEEE 200 was ratified in 1975. The IEEE renewed the
  standard in the 1990s, but withdrew it from active support shortly
  thereafter. This document also has an ANSI document number, ANSI Y32.16-1975. This standard codified information from, among other
  sources, a United States military standard MIL-STD-16 which dates back
  to at least the 1950s in American industry.
Comment: I would add another Wiki article with a great designators' table:
https://en.wikipedia.org/wiki/Reference_designator


Calculating dipole moments from atomic partial charges

Question: How can I calculate dipole moment of a complex molecule where the partial charges are available from density functional theory? I have the coordinates of each atom from atomistic simulations of an isolated molecule in a box along with the Bader charges. Will a simple charge times distance work in this case? The charges are not equal and opposite in many cases. What should the approach be to calculate the dipole in such cases?
Comment: We used to do this as a student exercise, albeit using Mulliken charges - it does not work well. The DFT calculation can provide the dipole moment (and higher ones) by using the appropriate operator.
Comment: @TAR86 Indeed. Mulliken charges can be very different. In case of stacked molecules, it's even worse. Sometimes totally opposite. DFT does provide dipole moment, but If I want contribution of just one part of a complex structure, then? Something like a local dipole.
Comment: Atoms and electrons are not point charges, therefore this approach will likely fail in many cases.
Comment: @user3840530 My point was not about Mulliken vs. some other charges - but pentavalentcarbon's answer partially covers that.
Comment: @TAR86 Ok. Anyway, sometimes I get really weird result using mulliken charges right from DFT output without any additional post processing, say a positive partial charge on an expected negatively charged species while the whole structure seems fully relaxed. That's why I pointed  it out.
Answer: From a theoretical standpoint, that approach is correct:
$$
\mu_i = \sum_{a}^{N_{\text{atoms}}} \sum_{i\in\{x,y,z\}} r_{ia}q_{a},
$$
where the set of atomic partial charges $\{q\}$ could come from partitioning the density in AO space (Mulliken, Lowdin), partitioning the density in real space (Bader, Voronoi, Hirshfeld), partitioning the electrostatic potential (ESP; Merz-Singh-Kollmann or ChElPG), or other methods I'm certainly forgetting. Another interesting method is based on atomic polar tensors [1], called GAPT or IR charges, which are a natural byproduct of harmonic vibrational frequency calculations.
This doesn't mean the results will be of good quality. Those based on partitioning the AO density seem to be the worst overall. Anecdotally, those based on ESP calculations are better, however if your system has a lot of "buried" atoms that aren't solvent surface-accessible, results may be questionable. Real-space partitioning is an attractive method since it is independent of direct basis set effects and surface accessibility. GAPT results also seem to be good, but they require a harmonic frequency calculation, which can be expensive.

Milani, A.; Castiglioni, C. Atomic charges from atomic polar tensors: A comparison of methods. Journal of Molecular Structure: THEOCHEM 2010, 995 (1-3), 158-164. DOI: 10.1016/j.theochem.2010.06.011
Comment: @pentavalentcarbon - one quick note is that you should remember to convert to Debye. Your formula will normally give e * Å if you don't convert: http://cccbdb.nist.gov/debye.asp
Comment: I am using the above mentioned formula for calculating the dipole. But it is also dependent on r. if you change your reference point for r, the simple multiplication will change the summation as well. How, then, we should calculate the dipole moment, let's say for a H2O molecule in a box (in the context of DFT) ? What should be the reference for the origin of distances (r) ? Can we  obtain the value of ~1.8D for H2O then?
Comment: For a neutral (sub)system, the dipole moment is origin-invariant. Otherwise, the center of nuclear charge is a reasonable choice. There is no guarantee you'll reproduce an experimental or analytic result by the partial charge approach.
Comment: I cannot test GAPT at the moment. I think the rest answers my question within the scope of the theory. Though the real problem of getting the dipole from partial charges remains, I will mark it as accepted. Thanks for the explanation and the link. Should be useful in the future.
Comment: If you want to try APT (there is a difference from GAPT that I don't remember), it should be available in DALTON under "Dipole-gradient based population analysis".
Comment: Another alternative that requires more manual labor is between the point charge approach and the fully analytic approach. Take your subsystem of interest as fully quantum mechanical, treat the rest of your system as point charges (calculated by your method of choice), and calculate the analytic dipole moment. This is something like an electrostatically-embedded QM/MM calculation.
Comment: Can you, please, provide a reference to your last suggestion? If possible, I will give it a shot.


Coriander: Seed vs Ground?

Question: I'm making a witbier this weekend that calls for 1 tsp of coriander added to the boil at 2 minutes. I'm wondering if I should purchase seeds and grind them myself, or just buy a jar of ground coriander off the spice rack.  Anyone have any experience they could share on which would be better?  Thanks in advance!
Comment: The easy way to to put them on a counter and use a pan to gently crack them.
Comment: I don't have any experience with buying coriander ground, but the coriander seeds from my garden smell great when I grind them.  It's not too hard to do, either, if you have a mortar and pestle.
Comment: Thanks Simon. I was considering using a coffee grinder with the seeds. But I think I've got a mortar/pestle buried somewhere in my kitchen if you think that'd be better.
Answer: You'll get the best flavor if you use whole, and coarsely crack it before adding.
Answer: I buy whole coriander and use a mortar and pestle to crack the shells before adding it to the boil. Whole coriander keeps longer and will give a fresher aroma than pre-ground.
To grind it at home, a coffee grinder would probably be overkill. You only need to break the shells. If you don't have a mortar and pestle, you can use a meat tenderizing hammer (or even a regular hammer). Just put the whole coriander in a plastic bag, wrap it in a towel and tap it evenly. You don't want to turn it to dust as that makes it more difficult to filter out.
Also it would be better to weigh the spices rather than use a teaspoon. A teaspoon of whole coriander versus a teaspoon of ground coriander can be very different by weight. 1 oz (28g) per 5 gallon batch is a common quantity.
Comment: Turned out I had neither a mortar/pestle nor a coffee grinder. So I placed the seeds on a plate and used the butt end of a pint glass to crack them. Worked great.
Answer: Also consider putting in a plastic zip lock or other and using a pastry roller.  It's also good for cracking small specialty grains that are too small for the setting on your mill.

Coriander: Seed vs Ground?


What's this plastic thing along my sidewalk pavers?

Question: I just moved into a new house and am unable to close my gate because there is something nailed to the ground at the threshold that is sticking up too high for the gate the close. Any idea what this thing is? I'm trying to decide if I just remove it to allow the gate to close or if I need to keep it there and bury it a little deeper.
Comment: Looks vaguely like a plastic drainage ditch but with no top-grate.
Answer: That is called Paver Edging. It is used to keep the pavers tight or to separate one section from the other. It's usually covered to the point that you only see a small strip of it. However, it looks like the installer didn't quite finish the job. I would probably do as you suggested and bury the edging deeper. You could also take up those few bricks that are outside the gate, level that area a little better and place those bricks closer to the edging for a more uniform look and to stabilize that immediate area.
Comment: While the ground is soft, you can probably pound it down with a mallet.  You might want to get a few more of those stakes if it doesn't want to stay in place.
Comment: I would suspect that the ground has heaved through a few freeze / thaw cycles.  As mentioned, you can either try to pound it down, or dig it out and secure it again.
Answer: Your particular brand, SnapEdge is simply too high.
You can find their various installation guides PDFs on the web-site.
But the clearest explanation comes from one of their drawings:

You need to remove the edge, and install it down below the gravel it's next to.
Or you can switch to another product where the edges to "under" the pavers; and are effectively hidden.
Answer: Can't upvote or comment at @alephzero's comment... but i'd say he's absolutely right: it was installed upside down. The part that is shown should be down in the dirt to keep a grip and not let the edging move with the seasons (frost heave or heavy rain runoff). The top surface won't be a collection of trip hazards as shown here.
Pull the spikes, turn it over, reinstall, and then finish by covering up the top layer with dirt or mulch or whatever matches.
Comment: not that Youtube is a reliable source, but this video seems to be by the company that makes these things and shows them in the orientation that mine are installed - thoughts? https://www.youtube.com/watch?v=uYSjHAAP-XQ
Comment: Interestingly this one shows the flat part UNDER the bricks: https://www.olyola.com/install-paver-edging/
Comment: @David Doria, in that first video, I don't think that is the same orientation: Where the spikes are getting driven in looks relatively flat and smooth... I'd assume the fins and built-up spike holes are actually underneath... but as you say, Youtube. :)

The second link shows both orientations. I've never seen the first... but I don't see any reason why it wouldn't work... other than needing to have your measurements perfect since you're not pushing it up against already lain bricks... you're leaving a void for the final course. Sounds way harder!
Comment: @DavidDoria What makes YouTube not a "reliable source"? It's simply a platform where anyone can upload videos. It has a *ton* of really high quality and more importantly, accurate content. I don't see why YouTube would be any more or less reliable than getting info from anywhere else. It's just... better because you get a video.
Comment: @only_pro Of course, I love it. But I figured I'd get flack from someone here if my argument was "yea but look how they did it in this youtube video" as if that were an authoritative source.
Answer: I suspect some klutz nailed it down back to front, and the raised edge is meant to be on the opposite side, along the edge of the bricks outside your property. If that would make your gate shut properly, just turn it round.
A slightly raised edge may be intentional, since it will stop rainwater runoff flowing downhill and ending up where you don't want it.
Comment: No, it's in the correct orientation. It's there to edge the bricks on the inside of the property, not the outside. The issue is that it's too high near the hinge side of the gate. It appears to have migrated upwards or inward (or just been installed wrong), probably due to being inadequately secured. The latch side of the gate has a clear cut-out so the gate's vertical support (the thicker portion of the gate) will not be obstructed.
Comment: It is not installed properly. It is there to finish the edge of the brick patio on the inside of the property. As is, it is currently sitting too high. Once installed under the bricks the edging will just come up to the brick surface, placing it low enough for the gate to swing over it.
Comment: I think you commented/voted on my answer [here](https://diy.stackexchange.com/a/178845/47125); I have edited to support my position conclusively.
Answer: The mentioned installation instructions say:

[...] our paver edgings may also be installed up against the paver, with the horizontal leg on the outside, if the installation requires it.


Meaning of the words "Ambition should be made of sterner stuff" from Julius Caesar

Question: What is the meaning of Antony's words "Ambition should be made of sterner stuff" in Act III of Shakespeare's Julius Caesar?
Answer: The origin of the expression is Shakespeare's Julius Caesar Act III, Scene V:

He was my friend, faithful and just to me:
But Brutus says he was ambitious;
And Brutus is an honourable man.
He hath brought many captives home to Rome
Whose ransoms did the general coffers fill:
Did this in Caesar seem ambitious?
When that the poor have cried, Caesar hath wept:
Ambition should be made of sterner stuff:
Yet Brutus says he was ambitious;
And Brutus is an honourable man.

the meaning here is to argue that Caesar was, in fact, not ambitious, that if he were, he would be more dedicated to his ambition, i.e., Ambition should be made of sterner stuff.
Answer: In present-day English, the term ambition is often used with a positive connotation; see the third meaning listed in Wiktionary:

A personal quality similar to motivation, not necessarily tied to a single goal.

Shakespeare used an older meaning of the term that corresponds with the first meaning listed in Wiktionary:

Eager or inordinate desire for some object that confers distinction, as preferment, honor, superiority, political power, or literary fame; desire to distinguish one's self from other people.

Caesar makes sure not to appear as ambitious. In Act 1, scene 2, Casca reports to Brutus and Cassius that Mark Antony had three times offered Caesar a crown and that Caesar had refused it each time. Still according to Casca, Caesar had noticed that "the common herd was glad he refused the crown", in other words, Casca sees the refusal as a trick to make Caesar more popular with the plebeians.
In Act 3, scene 2, Mark Antony, an opponent of the conspirators who killed Caesar, speaks the following words:

When that the poor have cried, Caesar hath wept:
Ambition should be made of sterner stuff

Stern has two meanings (Wiktionary):

Having a hardness and severity of nature or manner.
Grim and forbidding in appearance.

When Caesar wept, he did not appear as "hard or severe"; by claiming that Caesar did not possess "a hardness and severity of nature or manner", he denies Brutus's accusation that Caesar wanted to grab power ("ambition"). Of course, he conveniently ignores that the goal of Caesar's military campaign in Gaul was to gain command over a number of war-hardened legions that would be loyal to him and that his crossing of the Rubicon with the 13th legion, which was illegal, was nothing less than an act of insurrection against the Roman Senate. Caesar's ambition was definitely made of the "sterner stuff" that Mark Antony denies him.


Why did non prosecuted craftsmen go to the new world in the Roanoke era?

Question: I've just been reading The Rise & Fall Of The British Empire by Lawrence James. In this book, James said that craftsmen, who were not prosecuted for their religion, went to the New World because it was just what was done back then; It was quite normal for a blacksmith from Sussex village to travel from village to village across England. James seems to say that the reason for traveling to the New World despite its dangers was because of tradition. Does this explanation make any sense?
Comment: Not to my readings, many who came were endentured servants or who had a little money and no capability to establish trades in already saturated areas (such as large urban areas where they apprenticed).  So many made the journey to the New World which was in need of craftsmen, since the access to ships was "right there".  There probably were journeymen who did as James notes but my understanding of some trades like blacksmiths was that they put down roots and stayed.
Answer: There are people who want "adventure" or a "change of pace" in any event.
Persecution makes people more receptive to such a proposition (by making "what they have" less valuable), but wasn't always necessary to get people to want to go to the new world.


Are there differences in DNA between humans of today and humans from 2000 years ago?

Question: Are there any significant differences in our genome compared to the genes of our ancestors from 1000-2000 years ago?
And if there are significant differences, do they result in significant differences in phenotypic traits?
Comment: I don't understand the negative votes: there is some confusion in the DNA vs trait, but the question is still interesting
Comment: It's a huge leap from "differences in DNA" to "differences in traits."
Comment: Exactly, I wouldn't understand down votes either. "[D]ifferences in the genome" is a legitimate question. While one may at first think of sequence changes, and some mitochondrial and Y-chromosome haplogroups may have arisen within about 2000 yrs ago, changes at the level of methylation, acetylation and other levels fits the question.
Answer: The larger differences are most likely in epigenetic marks on the DNA. The environment is a lot different today than it was 2000 years ago and those differences are stronger determinants of epigenetic change than sequence change.
2000 years is only about 40 generations and that is not very much to see great differences in DNA sequence or allele frequencies - once founder populations are removed from the analysis.
Height is highly influenced by genetics, but can be masked by environment - notably diet. Diets higher in protein content are more likely to elicit the expression of the "height alleles" but only to a point as too much protein is also unhealthy.
Added in Edit 4 Apr 2012: I should add that my response is written from the perspective of frequency of alleles or epigenetic marks across a population.
Comment: Not all enviromental influences are inheritable through epigenetic marks. Have you any evidence of epigenetic changes in human population?
Comment: I did not imply that the epigenetic changes are heritable. The environment changed over the last 2000 yrs and some of those changes are constantly acting upon the genomes of successive generations. The question asked about a comparison of a current human genome with one from 2000 yrs ago. Because the environment is different, I expect that population-wide we would see differences in epigenetic marks.
Answer: In the literature, there are examples of DNA analysis from very old specimen. For instance, look at the analysis of both nuclear and mitochondrial DNA from 62 buried humans exhumed from a Mongolian cemetery dating from 2,000 years ago, as described by Keyser-Traqui et al. 2003, Am J Hum Genet 73(2): 247–260. Despite, the publication is open-access, the DNA sequences are not available, and no comparison with current mongolian DNA has been described in the study, but for sure your question should be answerable.
Answer: It depends on what you define as significant.
The mutation rate in human that I manage to find is given as about 140bp per genome per generation
http://sandwalk.blogspot.com/2015/04/human-mutation-rates-whats-right-number.html
2000 year ago is 40 generations. So that is about 5600 bp on average in a genome of 3200 million basepairs..... 0.000175% as calculate. Next to impossible to find.
Is that significant?
Functionally... most mutation that are inheritable though multiple generations are silent mutation.. which have neither negative or positive effects. (Negative mutations are weeded out relatively fast).
So are all these mutation silent? No, some actually do things... and these are mutations are usually related to the immune system... better able to survive disease like measles, black plague, smallpox, etc.
So they these changes significant? Well.. yes... in that if you don't have those DNA changes you would likely die. Yet those changes are minor structural changes to the proteins receptors that those pathogens use to get into a cell. So extremely minor. THe proteins are still able to do their natural function but are just different enough that pathogens do not have a free pass like smallpox had with the native americans.


how to avoid scatter confirmation message?

Question: I have built an dapp EOS blockchain. It's almost like twitter where the user can tweet and also use as a microblogging site in EOS blockchain.I have used scatter as transaction signer for using my dapp. The real problem arises when I write something in my twitter a press post button it will ask the scatter permission to sign the transaction. My question is whether is it possible to avoid the scatter confirmation to make it user-friendly. my dapp : www.tweetblocks.com
Answer: For the user, Scatter has "Enable Whitelist". You agree to the prompt, then check the boxes for the fields that are allowed to change. And then you are never asked again, unless you manually remove the whitelist entry.
Here is an article from Scatter author about whitelist permissions.
Answer: Both scatter extension and scatter desktop are client side applications. End user is the only authority to decide whether scatter automatically sign the transaction without asking every time. If the user trust your contract then he/she can set the contract in whitelist so that, all signing request from the same contract will be done automatically without asking again and again.


How to find infrequently visited confluence pages?

Question: How to find infrequently visited confluence pages?
Answer: I would say the best thing to do is set up Google Analytics on your Confluence installation (you can do this even if your installation is internal/intranet).
Simply register a new GA site profile, copy the GA script and paste it into the "At the end of Body" section of the Custom HTML Confluence admin backend function (you'll have to be a Confluence admin of course)
A more detailed explanation can be found here by David Simpson.
NOTE: Because our company's Confluence installation is internal, the domain name of a rendered Confluence page didn't match the site profile's, so I had to use this trick to get the GA script to track correctly.
If you are behind a corporate firewall and haven't configured Confluence to deal with issues relating to this, this page might be useful.
David's plugin will allow you to pull data from GA via the API and display it on pages in your own Confluence space (firewall issues notwithstanding) if you want.
After a period of time you should be able to use the data to find the quiet pages!
Answer: Install the Archiving Plugin for Confluence.
The plugin tracks the last view date of each page, and allows you to configure an automatic report to find the pages not viewed by anyone in the last N days. You can configure the feature and the value of N at space level.
Learn more


Throwing Out Bread

Question: What is the nature of the prohibition to destroy bread? Why is it commonly presented differently from other destruction (bal tashchit)?
Comment: @DoubleAA nonexistence is also a nature; i.e. if the answer is that there is no such prohibition, or that it is misrepresented, then that is the answer.
Comment: How do you know there is such a prohibition?
Comment: related: http://judaism.stackexchange.com/questions/3235/throwing-out-bread-or-challah
Answer: There appears to be an independent prohibition to throw out bread, and doing so could cause one to become poor (cf. Shabbos 143a, Tosfos to Brachos 52b) due to the respect and appreciation that we should have towards Hashem's sustenance that He has provided (cf. Aruch Hashulchan 180:4, Kaf HaHayyim 24:47-48). This rule-of not discarding bread with the rest of one's garbage-probably doesn't have to do with Val tashchis, because it applies only to pieces that are a kezayis or larger (Shulchan Aruch 180:4 though see Mishnah Berurah 180:10 for a stringency not to discard bread crumbs that would combine to be a kezayis).
Answer: from: http://thehalacha.com/wp-content/uploads/Vol3Issue6.pdf

Bread may be used for any purpose as long as it is not used in a disrespectful manner and the bread will not be
  ruined by what you are doing to it.7 One should not pass a cup of wine over a piece of bread because the wine
  may fall on the bread and make it uneatable. Similarly, one should not place raw meat onto a piece of bread.8
  One is allowed to use bread to cover food in a utensil, since this is not showing disrespect to the bread because
  it will be eaten as part of the food.9 Accordingly, it is common for caterers to use a bread-like food to cover the
  soup at weddings to retain the heat.10 When reciting kiddush one may place a siddur on top of the challah
  cover.11 Similarly, one who wants to lift up a sefer may place bread underneath the sefer in order to lift it.12
  When washing mayim achronim one should be careful not to let the water fall onto bread.13 Many caterers bake bread in a round shape, hollow the inside, and fill the space with soup (the bread is hard so no soup leaks
  through). It would seem that if the people eat the bread (bowl) afterwards this may be permitted.14
7 Mesechtas Berochos 50b, Tosfas "ein zurkin," Rosh 7:32, Shulchan
  Aruch 171:1, Mishnah Berurah 171:2. See Biur Halacha 171 "lo."
8 Refer
  to Rashi Mesechtas Berochos ibid "ein," Rabbeinu Yona, Rif page 37b,
  Shulchan Aruch 171:1, Pri Megadim M.Z. 1, Mishnah Berurah 171:2, 5,
  Kaf Ha'chaim 2.
9 Pri Megadim M.Z. 171:2, Mishnah Berurah 7.
10 Horav
  Yisroel Belsky Shlita. Refer to Torah L'shma 106.
11 Birchos Hashem
  3:17:footnote 62.
12 Eitz Hasadeh 17:footnote 8.
13 Kaf Ha'chaim
  171:4.
14 Refer to Shulchan Aruch 171:3.

It would seem however that whether bread really has a unique status might be subject to a dispute amongst the rishonim. From http://halachayomit.co.il/EnglishDefault.asp?HalachaID=2821 :

Regarding bread, however, the Rishonim disagree: According to the Tosafot, even if the bread will not become ruined as a result of throwing it, such as by throwing from side to side on a table, it is still forbidden to do so, for bread has a special significance and throwing is considered degrading towards it. The Rosh, Tur, and other great Rishonim rule likewise. (The commentary Tziyun Le'Nefesh Chaya, ibid, indeed infers this from the language of the Baraita.)
On the other hand, the Rashba and Rabbeinu Yonah (quoted by the Bet Yosef in Chapter 171) write that there is no distinction between bread and other foods and as long as the food is not ruined by throwing it, it is permissible to do so.

As far as why we would treat bread differently from other foods (assuming that is indeed the case) - I assume it has to do with the religious significance of bread in halacha (as seen in it's roles in the avodah e.g. in the menachot, lechem hapanim, shtei halechem, etc.) and the fact that it is representative of food in general (which is presumably why the hamotzi blessing exempts the brachot of all other items eaten as part of the meal, i.e.: with the bread). Also, I believe there may be midrashic/kabbalistic analogies between man and bread.
Comment: This would serve to prove that such a prohibition exists. But the OP wants an understanding to the nature of this prohibition. I.E. why it exist specifically for bread.
Comment: This discusses *throwing* bread. I asked about throwing *out* bread.
Comment: @mevaqesh I think that he is answering "Why is it presented differently from other destruction" under "bread really has a unique status". How else is bread different from other destruction? (If not respect)

Throwing Out Bread


Why is it preferable to use paths with slashes instead of query-string variables in a web page URL?

Question: Why is it preferable to use paths with slashes instead of query-string variables in a web page URL?
Answer: One reason for having this as a goal during initial development is that it forces you to think critically about your web site's link structure from the outset.  If the hierarchy is clear in the URL, then this clarity will naturally flow into the structure of the website and ease navigation for both your users and the search engines.
Depending on how you are developing your site, thinking about URL structure from the beginning may also help you with code design; what controllers you will need, how you are going to perform routing, etc.
Other reasons, such as URL readability and hackability have been touched on in other answers.
All of the search engines are doing a pretty good job with query string parameters these days, but if you're starting a new site, it is definitely worth using clean URLs.
Comment: Considering URL structure early on in a project *is* important.  For that reason, I'm selecting this one as best answer.
Answer: One of the primary reasons is for end-user readability. A slashed/re-written url is significantly easier to read and type than a long string of queries attached onto the end of a base url
Answer: You mean: example.com/Teams/Arsenal instead of example.com?team=arsenal
Will other than the fact they will be implemented differently the former is both cleaner and also hackable. So if you remove 'Arsenal' it could display a list of teams.
Answer: Some people claim that it has a positive SEO effect. By including keywords that people will search for within the URL, your search engine rankings can be higher.
Other reasons include a neat URL structure and URL "guessability" through removal of URL path components to get to higher levels of navigation.
If you are using an MVC framework of any kind, you are more-or-less made to work in this way by picking controller names etc. to be friendly to the URL routing.
Answer: The main reason I do it is for readability, specifically on search results. I've only heard this and don't have any hard numbers, but it's supposed to increase click through. In other words if you have 2 results with the exact same ranking, people are more likely to click on the clean and easy to read one. I don't think this always needs to be one with slashes, but I think this is easier than a query string.


How do you find a location to set up a photo exhibition?

Question: Where can you find a good place to set up a photo exhibition, and how do you go about getting accepted into that exhibition?
Comment: One obvious way are local coffeeshops. This may not be the style of exhibition you are looking for, but it is: easy to set up, easy to get accepted, and gives a fair amount of exposure. There are some downsides: the prices for prints should be lower to appeal to the market, the work is in danger(could be bumped, touched, espresso splatter), the environment is not dedicated to appreciation of your work, and the shop may restrict certain aspects of your display(subject, size, arrangement, number). These things considered, this is one option. Other varients are restaurants and small theaters.
Comment: @BBischof — that looks like it should be an answer, not just a comment.
Comment: @JayLancePhotography: Quite frankly, I'll take either. I'd just like to find a way to actually sell some of my prints at an exhibition of some sort. Even if it's simply a display at a local store, it's better than nothing.
Comment: Another easy one is local photo contests. Usually you can only hang a few, but at least in my area there are two or three contests per year that let you hang up to three shots in an actual photo museum for the term of the contest. This is far from ideal, but it is a way to get some exposure, and you may even win! I was even fortunate to have one shot selected for their permanent collection after the contest, so there are definitely some benefits!
Comment: I don't know, maybe. It seems a bit half baked and insufficient for such an important question. Of course I am not opposed to this being an answer. Just let me know.
Comment: I think I have an answer to your question but I wanted to clarify a bit first... Are you asking about how to go about getting accepted into *photographic exhibitions* (generally multi-artist shows of some variety, often with awards, but not always), or are you asking about how to get your work *exhibited*? Based on your second question it could go either way as to which of the two you're asking about...
Answer: The first thing to do is to think whether you want to do this as a commercial activity, or just for the joy of sharing your images.
If you're wanting to sell the images, then you need to think about marketing, which means having a pitch with a portfolio to show to prospective venues -- it's then a case of legwork of visiting your local friendly galleries, cafés, restaurants, etc. It's worth investigating each venue first to see if they share common goals (for example, do they prefer contemporary works, or do they prefer something more generic?). Be prepared and consider issues such as managing stock, and commission levels that you're willing to give to the venue.
If you're more interested in exhibiting for the fun of it, then it may be worth taking your portfolio along and approaching more cultural locations such as libraries or tourist information centres; If you group together with others in your area, there is the chance to hire a venue such as a town hall to run an exhibition yourself in the guise as a photography club (there was even the idea of there being an exhibition organised by this site at one point).
Answer: One aspect of exhibits that I don't really see represented in the current answers is the concept of exhibits used for advertising and marketing. This is the cornerstone of my retail business and so I wanted to mention it briefly (even though it appears that your gig is selling prints as opposed to selling sessions). Hopefully it will help someone whose bread and butter is more in the portrait space than the landscape art space...
At any one time in the city I live in I generally have between 5 and 10 displays set up at various locations around town. The displays consist of 3 or 4 pieces of my work, sized large (24x36 canvas wraps generally) framed and placed on easels... In addition I leave a stack of 'take away' brochures with all my information. The pieces aren't for sale at all, they're simply to attract attention, get people thinking about photography, and hopefully contacting me to set up a session (or at least ask more about what we do, which opens up the sales dialog...)
The size of the work is really important... The old adage of 'you sell what you show' is really true, but also it's a 'natural selection' move... If a person views my work and has no need (or can't afford) my large pieces they're less likely to call... Which means that a large chunk of my customers are 'pre-screened' before they even pick up the phone. Of course I also have a screening process during the initial call, but I get far fewer radically under-qualified solicitations this way.
Getting the first display placed was the hardest part for me... Once I had the first one I used that as a building point when pitching to the next location "I just placed a 1 month exhibit at XYZ Restaurant across town and they've been raving about it ever since." A surprisingly large number of establishments would love to have your work up... for a while. When I approach businesses I will often 'trade' a portrait session for the owner in exchange for one month of putting a few pictures in his/her entryway... These 'foot in the door' deals often lead to longer engagements for me because I rotate the work around so it's not always the same pictures for months on end, and because the work lends to the atmosphere. Getting into public spaces is even easier... Most locations have offices of public affairs, public relations departments, etc. They are often just itching to have works to show off...
Now in terms of who to approach, my strategy is to place it in upscale locations around town... Chamber of Commerce, City Hall, High end restaurants, hospitals (this was a huge find for me... You wouldn't believe how many doctors I have coming through my door because I set up displays in all 4 of my cities hospitals...), doctor's offices, libraries in 'upscale' neighborhoods... In fact, just about anything in upscale neighborhoods works. Again, this is a 'screening' action... I want as many people as possible who pick up the phone to be able to afford what I sell, and I want them to already be predisposed to purchase what I'm selling (because the last thing I want to do is sell 5x7s).
I can tell you that far and away this generates more business for me than anything else I do in the retail space... And at most it costs me a handful of portrait sessions given away to business owners every year. If I had to give up every form of marketing and advertising that I do except one, this would be the one I'd hold onto (yes, even above the internet).
Anyway, that's the 'nutshell' of my exhibit marketing strategy.
Comment: Great stuff here!
Answer: I would totally agree with Rowland Shaw (above), but I would also add to check out markets and the like also. For example, every month is an arts & craft markets in my town, and it makes a good 'springboard' as it lets you get a feel for setting up for an exhibition. Essentially, it is all identical but on a smaller and slightly more informal scale. A market stall is more about experience.
After starting there, I would then look into any small exhibiton space. Do you have a TAFE, university or arts colledge nearby? They often have small exhibition spaces that they use for their students' end-of-year works, but are often hired out. It's also often far cheaper than a specialised space.
Once you have tried both of those, by all means, jump into a full space! Bring a portfolio (actually, you probably should have for the TAFE/Uni etc. above, too) and let them know what you are capable of bringing to show. They want something that will send crowd away in a good mood talking good things both about you and their space. This is the important(ish) thing. Your exhibition will be a representation of their space. Don't do something controversial in a nun covenant's art exhibition hall. (If you were thinking of that :P)
Comment: Tractors and Farm Equipment?
Comment: What's a "TAFE"?
Comment: Ah, TAFE is "Technical And Further Education". It's tertiary education, but more focussed on trades and practical studies than a university. (My bad.)
Answer: Answer from Comments:
Local Business
One obvious way are local coffeeshops. This may not be the style of exhibition you are looking for, but it is:

Easy to set up
Easy to get accepted
Gives a fair amount of exposure
Flexible pricing.

for these reasons, I think a coffeeshop makes a good first exhibition. It gives you needed practice without too much stress.
That being said, there are some disadvantages:

Prices should be lower to appeal to the market
The work is in danger(could be bumped, touched, or splattered with espresso)
The environment is not ideal for viewing artwork, in particular because people's primary purpose for being there is not to view the art.
Sometimes they will want to restrict the display(subject matter, size, arrangement, number, etc.)

but if this sounds ok to you, I think its a good option. Also keep in mind restaurants and small theaters.
Local Photo Contests
Another easy one is local photo contests. Usually you can only hang a few, but at least in my area there are two or three contests per year that let you hang up to three shots in an actual photo museum for the term of the contest. This is far from ideal, but it is a way to get some exposure, and you may even win! I was even fortunate to have one shot selected for their permanent collection after the contest, so there are definitely some benefits to entering.
Good Luck with your potential exhibition.
Disclaimer People seemed to be pretty please with the comments, so I though I had might as well add it.
Answer: Rowland has some great points about things to consider before going into a potential venue, I just want to add another one to consider that I think a lot of people forget about: local furniture stores. Quite often they have large wall spaces in demo rooms setup with couches, chairs, tables, etc trying to make a faux living room or dinning room etc. Quite often they will have some tacky over priced bulk corporate "art" they bought site unseen from a catalog. They might well be very willing to either take some of your pieces on consignment, or just buy some prints outright for resale.


Solar luminosity proportional to $G^7$?

Question: A book I recently purchased describes Dirac's proposed variation of Newton's G, and why that specific proposal wouldn't work because the earth would have been too hot for the known history of life. A footnote explains that the luminosity of the sun is proportional to the seventh power of G, which seems incredible to me. I know that this has to be a simplification, since stellar dynamics are annoyingly complex, but if we put that aside, is this essentially correct, or is it a typo? What would be the theoretical justification for this in broad terms? (eg, "Gravitational pressure is proportional to this exponent of G, but since that also shrinks the size of the star, which increases the pressure, it's actually this exponent of G, and the rate of fusion is proportional to the gravitational pressure squared, so you end up with 7").
Comment: Can you clarify what you mean by "G"?
Comment: @Dean: Newton's universal gravitational constant.
Comment: It sounds like whatever you're talking about is a simple scaling law. Something akin to the stellar [mass-luminosity relation](https://en.wikipedia.org/wiki/Mass%E2%80%93luminosity_relation), $L\propto M^3$ or the stellar expected lifetime-mass relation, $T_{star} \propto M^{-2.5}$. Despite the complexity of a given physics scenario, there are often basic scaling laws one can boil the system down to with enough approximations.
Comment: Can you provide a small excerpt from the book of relevant material to this question?
Answer: I think the argument is the following. The central temperature can be estimated from a form of the virial theorem. At least dimensionally speaking,  total thermal energy $MkT/\mu$ (where $\mu$ is the average mass per particle) is proportional to gravitational potential energy $GM^2/R$. So $T \propto GM/R$.
But for a given mass, standard polytropic theory for a star, says that
$$M \propto \rho_c^{(3-n)/2n} G^{-3/2}$$
$$R  \propto \rho_c^{(1-n)/2n} G^{-1/2}$$
 where $n=3$ is an approximate polytropic index for the Sun and $\rho_c$ is the central density. See for example Does Eddington's variable polytropic index better fit data from the Standard Solar Model?
Putting this together we have
$$ T \propto GMR^{-1} \propto G^2 \rho_c^{-1/3}$$
The power generation in the solar core from the pp cycle goes approximately as $L \propto \rho_c^2 T^4$ and using the proportionality for $T$ derived above, we have $L \propto G^8 \rho_c^{2/3}$.
Finally, we note that for a $n=3$ polytrope, that $\rho _c$ and $M$ are independent, but that $\rho_c^{2/3} \propto G^{-1} R^{-2}$. So for a fixed solar radius we have $L \propto G^7$.

Solar luminosity proportional to $G^7$?


What material is a good alternative to neoprene?

Question: What material – such as polyester, polypropylene or wool – or combination thereof, both works to keep you warm when wet and dries quickly, as an alternative to neoprene? I'm looking for something cheaper and simpler than a dry suit but less restrictive than a wet suit, for paddling in cool but not very cold water. Something you can submerge in and still keep reasonably warm.
Comment: Works like neoprene, but is cheaper and more comfortable. I feel like if such a magic material existed it would be all the rage and you wouldn't have to ask if it was a thing.
Comment: I suggest you're looking for sightly the wrong thing. Better is a less restrive style of wetsuit (e.g. sleeveless) combined with wicking base layers and a dry cag that also protects you from the wind. A thin wetsuit is 3mm, and that thickness is important in the insulation. Layering fabric (close-fitting so no draughts) to 3mm would also be restrictive.
Comment: O, yeah, you definitely want sleeveless around 3mm for paddling. Honestly I wrote my answer assuming that is what was meant.
Comment: Are you simply looking for a way to keep the water from going up your sleeves and splashing down your collar? Or are you hoping to find something you can submerge in and still keep warm?
Comment: @ShemSeger - See added sentence.
Comment: See also https://outdoors.stackexchange.com/questions/8352/where-can-i-get-long-but-light-bottoms-for-water
Answer: I would say that it would depend more on the air temperature.
If you have cold water and rather warm temperatures, such as rafting on a cold river on a hot summer day, then synthetics like polyester or polypropylene would be the way to go since they will dry out quickly and not retain the water.
There are also  Polyolefin swimwear which are designed to provide insulation and warmth.
Where wool has an advantage is for fisherman/sailers who are spending time in much colder temperatures, since even if wool doesn't dry quickly, it retains its insulating properties even when wet. It looks like it was used for swimming suits but hasn't been used since the 1930s in the US.
Answer: Fleece dries fast, and fleece is relatively warm while wet. It's probably the best you're going to get in normal clothing materials. But it's not an alternative to a wetsuit or drysuit, more of a "I'm going hiking with a light jacket in autumn" option, or an addition for below a wetsuit. If that's what you're looking for in terms of how wet you'll get, how long you'll stay wet and how cold the weather will be, it's a good option. Add a dry top/anorak to keep the wind out, and you've got a decent flatwater kayak/canoe combination.
Thermal shirts (thanks for the correction Martin) sometimes called thermal underwear, often made from some combination of polyester and viscose or such, are a good option as well. They're a lot thinner than a good fleece sweater, but are form fitting and surprisingly warm for their thickness. A thermoshirt and an anorak works maybe just a bit worse than fleece and anorak, a thermoshirt alone can be nice of a warmer day if the water's not too cold. They can also be layered.
When doing even light whitewater, sea paddling or longer trips think about it a bit, try to build up some experience so you'll know your limits and those of your gear. Better safe than hypothermic.
Comment: I think  *thermoshirt* = *thermal shirt* in English?
Comment: I don't think anything with *viscose* in will be any good; it's made from plant fibre (just like cotton), isn't it?
Comment: *googles it* Apparently there's special insulating viscose with hollow fibers, and that's what they use for these shirts. So it looks like in general you're right: just any viscose doesn't help, but thermal shirts made from it do.
Answer: Rash vest/shorts
These are technically a baselayer for wearing under a wetsuit, but are often worn during the warmer months as the only layer for watersports. They're less restrictive, dry reasonably fast but designed to keep you warm when wet. Available in various weights from lightweight non-UV resistant to heavyweight thermals. Watch out for that UV resistance on cheap products.
Cost wise the cheapest would come in at slightly below the cheapest wetsuits, but expensive gear should only be about 3-5 times that base price.
This is probably the best option given your description.
Thermal baselayers
Again available as watersports specific, these are a step up from a rashie. More expensive but warmer, often valid as sole equipment down to quite low temperatures and liable to cause overheating if it's not cold enough.
Aquatherm
This is a fairly expensive option. It acts initially as a waterproof layer but once water gets inside it behaves much as neoprene does. Aquatherm gives you more freedom to move than wetsuits due to being a much thinner material. Competitive kayakers swear by this stuff for winter training. Expensive but cheaper than a high quality wetsuit.
Comment: Thanks. "Rash" is more of a purpose or function than a fabric type. I really wonder if polypropylene, being more hydrophobic, is slightly better than polyamide (nylon) or polyester, generally stated. Of course, how the material is spun and woven will also make a difference. Hence aquatherm, even though it is polyester, performs well.
Comment: @MartinF, "Rash vest" is also usually the product name, making them easier to find as off the shelf products rather than worrying about specific materials.


place quick smoke icosphere over video in video sequence editor

Question: I am new to blender and since i am unaware of the terminology i dont know what to search forI have a 'quick smoke' icosphere as a rendered mpeg file.
I have another video in which a man shows his hands as if he is holding the smoke ball.
But in Video Sequence Editor when i add both the clips and add the transform effect to the smoke clip with 'alpha over' and scale it,I get a black box (background) around the smoke.
I have tried to make it transparent as given here
Can Blender render pngs with the background transparent?
How should i display only the smoke without background?
Note:I have also tried changing the opacity of both the transform and smoke strips to no avail
Comment: As far as I know Mpeg format does not support alpha channel information. Try rendering the smoke as a png sequence.
Comment: @cegaton thank you for the quick answer.Does AVI support alpha channel transformation?Because i tried saving it as an avi raw file ,this also doesnt show the smoke properly
Comment: @cegaton thanks a lot for helping a newbie :)
I'd be glad to accept your answer if you post it,since it could help newbies like me
Comment: Note that it's a bad idea to render directly to a video anyway, as you cannot pause/stop the render without corrupting the video and losing all the progress you made.
Answer: Most video formats do not support alpha channels,at least not the ones built into blender. (there is one option if you are using OSX)
You have two options:
1.- Export your scene as an image sequence with in RBGA (in a format like PNG, Tiff, TGA, Jpeg2000 or OpenEXR) and then import it into the Video sequence editor to combine your shots
2.- Do the compositing directly in blender either by importing the smoke scene as a strip into the video editor or using the compositor located in the Node Editor


What's the difference between webapps and superuser?

Question: Reading the questions currently on webapps, it seems like a lot of them would fit equally well on superuser.  Are questions that focus on web apps being closed on superuser?  Have they always?  Even if you're drawing a distinction between local apps and web apps, don't these two appeal to exactly the same audience - advanced users?
Comment: Understood, and accepting an answer.  Perhaps my question should have been better phrased by focusing on the last part - is there really a difference (from the typical end-user's perspective) between a local app and web app, and will they think in terms of looking in different places for the answer?  (But I see now that that is just asking to change the off-topic definition in superuser, so I guess I'm too late with the thought.)
Answer:
Are questions that focus on web apps being closed on superuser? Have they always?

Not always but the prohibition against web-related question on Super User came long before Web Apps was created. It was felt that "web applications" was simply to big a subject to mix in with general desktop-related questions.
So, Web Apps was created to fill a void/need not fulfilled by Super User.
Answer: Questions about web applications are specifically mentioned as being off topic in the Super User FAQ

and it is not about …

videogames or consoles
websites or web services like Facebook, Twitter, and WordPress

So I don't see how a question here can "fit equally well on superuser[sic]".
If it fits here then it's off-topic for Super User, if fits on Super User then it's off topic for here.
There is a clear and definite distinction between local apps and web apps. It hasn't always been the case, so if you haven't been on Super User for a while you wouldn't necessarily have spotted it.
Can you post links to some examples.
Answer: Hmm. I'm not sure how you could get that impression. Here's the top 10 questions on Super User right now:

Simple email ticketing solution?
Kubuntu Monitor Out of Range
How can I make desktop.ini work on network locations?
Go straight back to currently active tag in my web browser?
How to customize Mac TextMate keyboard shortcuts with a "copy current line" command?
strange behaviour - dhclient needs to be run twice in order to connect to wireless
Good software for cleaning the computer?
Why does IE8 corrupt some zip files I download?
Thunderbird message panes
All network devices freezing when Airport Extreme Base Station is connected. Any ideas?

Do any of those strike you as being about "web apps"?
Super User is about traditional computer software and hardware, not websites or web apps.
(It can be about web browsers, in the sense that the web browser is software, but the focus is on the browser and not the website loaded in the browser.)