What is the proper response header when an address is not available but its parent is available and is displayed?

Question: My website addresses has a hierarchy structure. When one page is requested, and it is not a valid address, it tries to find its parent, and if the later exists, it will show it. Now, my question is that in this case, should I send a 200 header response or a 404 one? How differently do the search engines react to these headers?
Answer: Here is a run-down of some of the HTTP Status Codes.
If you want to know more about HTTP Status Codes, I suggest this page: http://en.wikipedia.org/wiki/List_of_HTTP_status_codes It explains things rather well.
A 202 status code is OK. This means that the request was successfully fulfilled.
A 301 status code Moved Permanently is a redirect.
A 303 status code See Other is similar to a 301 but rarely used.
A 404 status code is Not Found and the default returned by most if not all web servers.
A 410 is Gone is similar to 404 but not used enough.
Traditionally, the default that a web server returns if a page is not found is a 404 Not Found, however, this means that the page may return so search engines are likely to retry this page for a set number of times. A 410 is used when a page is removed and not expected to return but has to be issued explicitly. Technically, if a page is not expected to return, then a status code of 410 is best.
A 301 status code Moved Permanently is a redirect. However, a 303 status code See Other might be more accurate though not traditionally used. A 301 status code is more widely understood and traditional although you can easily try a 303 and I am reasonably sure it will work okay.
The same applies with a 404 status code. It is widely understood, however, the 410 should work too and seems correct for your scenario.
I would venture to guess that using a 301 and/or 404 are more browser friendly though I am sure most browsers handle 410 and 303 just fine.
Since you are trying to find and present another page, you will want to do 1 of 2 things conditionally whether you are successful in finding another page or not:
If a replacement page is found: Issue a 301 (or 303) redirect to the new page. This is easy enough to do in code.
--or--
If a replacement page is not found: Issue a 404 (or 410). This is easy enough to do in code.
Comment: The first half of your answer is a bit rambling and all over the place, might be simpler to have a short description of the status codes then a recommendation.
Comment: @DisgruntledGoat You may not have liked how my answer was written and you did the right thing to make an edit suggestion. However, the answer is technically correct. The down-vote was a bit excessive but your right to do of course. I made a comment to an answer that you made that is technically incorrect, but did not down-vote you. I gave you room to adjust what could be an excellent answer with the perfectly valid points you made with some room for what is another consideration for the OP. Perhaps I offended you which was not my intent.
Comment: The answer is badly written (no offence) so that makes it not a good answer in my opinion. I don't think that's "excessive". (I'm happy to up vote it later if it improves.)
Comment: @DisgruntledGoat Saying so is enough. It seemed retaliatory due to the timing of the remarks. No big deal. For what it is worth, I do like your answers and do not mean offense to you *at all*. There are two things going on here: I feel that there is too much inaccuracy in SEO advice on the web and it drives me nuts; and I was attacked here before and there was a time that retaliatory down-votes as a problem. I made a remark about giving the user time to adjust their answer and if this does not happen in time, then the down-vote makes sense. It is just polite (from a southerner's pov).
Answer: I strongly suggest you examine the status codes and their meanings. You did not explain why a client (which could be a human or a bot) might request a URL that does not exist but the URL might have a valid "parent" URL. The reasons for unusual situation will likely guide your choices of status codes.
The information provided by closetnoc is excellent, and I only have a few things to add.

203 might make sense depending on the relationship between the requested material and the served material.
Some status codes are largely for the benefit of humans (like 401), while others are largely for the benefit of bots (like 301). What is your target audience--human, bot, or both?
You might want to return different status codes based on the requesting client. For example, maybe you want search engines (bots) to completely remove the now-gone URL from their database, so you return 410, but you want to keep human users on your site, so you return 201, 301, 303, or 404.
You asked, "should I send a 200 header response[?]" Absolutely not.
"How differently do the search engines react to these headers?" See Google's answer.
Your fundamental issue seems to be link rot. If this is a common issue on your site, you might benefit from learning as much as you can about link rot.
Comment: One problem with at least part of your premise is that it takes a fair amount of data infrastructure and processing to know a bot from a human. There are some clues, however, it is **not** a snap to know bot from human anymore. I have about 25 or more criteria to know for sure and even then, that is not always possible. Due to the nature of the question, I thought it best to keep the answer simple and geared toward the main-stream without getting into too many nuances. I understand why he is doing this. Pages come and go but links do not match the effort. I still see links from 12+ years ago.
Comment: Oh I know. I just want to make sure that you knew I was not wearing my waffle stompers (hiking shoes- but fluffy white rabbit ear slippers). I like the answers you give and you are going to be one of the great ones for sure. I did not want to discourage but encourage you. ;-)
Comment: Excellent point, my bot list is so long that I don't even want to count how many are on it. I assume clients are human unless I know they are a bot. Since the majority of the bot traffic I care about comes from just a few sources, I don't cry to much about the scrapers. But you are right that people should keep in mind that it is more work to do it this way.
Comment: I was not trying to be critical. Trust me. I gauge the question based upon the OPs knowledge and experience. This was an odd one. Clearly the OP is not a noob, but asked a fundamental question. As well, a lot of people still try and use the agent name and other criteria that can be spoofed easily. I apply 7+ years of historical data and advanced network trust analysis to determine bots from humans and even then, sometimes a bot can have a human behind it that confuses the system slightly. Also keep in mind, that Google prefers certain status codes over others such as a 404 over a 301. Sheesh!
Comment: I did not interpret your comment as critical. I sincerely think it is a valid point and well worth considering. Very few people would benefit from my suggesting of trying to separate bots from humans, and since I did not make that clear, your comment did helps. In short, I agree with you.


Equivalence relation on set $\{0,1,2,3\}$

Question: I'm given a a relation on the set above as $R = \{(0,0), (1,1), (2,2), (3,3)\}$. I can see how this is reflexive. Since if $a = 0,1,2, 3$ then $(a,a)\in R$. However, how is it symmetric and transitive? For it to be symmetric $(a,b)$ and $(b,a)$ have to be in $R$ and for transitive, for $(a,b), (b,c), (a,c)$ has to be in $R$. But I don't see for which values of $a,b,c$ the relational set is symmetric and transitive.
Comment: You should make that an answer since it was a perfect response.
Comment: Symmetric means if $(a,b) \in R$, then $(b,a) \in R$. In your example, all elements are of the form $(a,a)$ so it is true. Transitivity is simple, because in this case, if $(a,b),(b,c) \in R$, then you must have $a=b=c$. Hence it is trivially transitive.
Comment: Took your suggestion, thanks!
Answer: Symmetric means if $(a,b) \in R$, then $(b,a) \in R$. In your example, all elements are of the form $(a,a)$ so it is true. Transitivity is simple, because in this case, if $(a,b),(b,c) \in R$, then you must have $a=b=c$. Hence it is trivially transitive.
Answer: Hint
Use $(a,b)\in R \Leftrightarrow a = b$ .
Answer:
For it to be symmetric (a,b) and (b,a) have to be in the set and for transitive, for (a,b) and (b,c), (a,c) has to be in the relational set.

No, you have a serious misunderstanding here. Symmetry of $R$ just says that whenever an ordered pair belongs to $R$, its reversal also belongs to $R$. It says nothing about specific labels $a$ and $b$, and it does not require the components of the ordered pair to be distinct. If a relation $R$ is symmetric, and the pair $\langle\text{thing}_1,\text{thing}_2\rangle$ happens to belong to $R$, then you know that the pair $\langle\text{thing}_2,\text{thing}_1\rangle$ must also belong to $R$. The components $\text{thing}_1$ and $\text{thing}_2$ can be $a$ and $b$, $x$ and $y$, $b$ and $a$, $u$ and $u$, $\xi$ and $\eta$, $3$ and $5$, $17$ and $17$, or anything else, depending on the underlying set of the relation.
In your case every pair in the relation is its own reversal, so the relation is automatically symmetric: it's automatically true that if a pair $\langle\text{thing}_1,\text{thing}_2\rangle$ is in $R$, the reversed pair $\langle\text{thing}_2,\text{thing}_1\rangle$ is also in $R$, because they're the same pair.
To put it another way, the only way to demonstrate that a relation $R$ is not symmetric is to find objects $\text{thing}_1$ and $\text{thing}_2$ in its underlying set (which in your case is the set $\{0,1,2,3\}$) such that
$$\langle\text{thing}_1,\text{thing}_2\rangle\in R$$ but
$$\langle\text{thing}_2,\text{thing}_1\rangle\notin R\;.$$
And in your case that's impossible.
You have a similar misunderstanding with respect to transitivity. Suppose that $R$ is a relation on a set $A$. Think of $A$ as a bunch of stepping-stones in a stream, and $R$ as a kind of list of the steps that are safe to take: if some pair $\langle x,y\rangle$ is in $R$, then you can step from $x$ to $y$. Transitivity of $R$ then says that if $x,y$, and $z$ are stepping-stones, not necessarily distinct, and if you can step from $x$ to $y$ and from $y$ to $z$, then you can step directly from $x$ to $z$. (No, it's not realistic, but it may help explain the idea.)
In the case of your relation, if you can step from $x$ to $y$ and from $y$ to $z$, then $x=y=z$, because the only 'steps' that your $R$ allows are stepping in place, from $0$ to $0$, $1$ to $1$, $2$ to $2$, or $3$ to $3$. Thus, if you can step $x$ to $y$ and from $y$ to $z$, you can certainly step directly from $x$ to $z$: $x=y=z$ and the steps from $x$ to $y$, from $y$ to $z$, and from $x$ to $z$ are in fact all just the same step under different names.
Answer: You have the set $X = \{0,1,2,3\}$. You define a relation by saying that for $x,y\in X$, $x\sim y$ if and only is $(x,y) \in R$. Now (as mentioned in another answer) this is the same as saying that $x \sim y$ if and only if $x = y$.
So it is symmetric because if $x\sim y$ then $x = y$ then $y =x$, and so $y\sim x$.
It is transitive because if $x\sim y$ and $y\sim z$ then $x = y$ and $y = z$ so $x = z$ and therefore $x \sim z$.


How do I get a Brother DCP-315CN printer working?

Question: I need detailed instructions for an absolute beginner to install my brother dcp-315cn under
ubuntu 11.10. I hope someone can help me with this problem.
Answer: If you are using 32bit, then click this link. Brother Printer Driver Download from their website. It recommends you to use the MFC-210C driver on the Brother support site, which I've given you the link to there. All you should have to do is click "Accept" for the license terms and then it will ask you to download it or open it in "Ubuntu Software Center". Open it in the Ubuntu Software Center and click install.
You might need to restart your computer afterwards but that should just work.


Finding the pH of the solution

Question: In this video, at 3:30 min professor solves two equations
$$\ce{H2O —> H+ + OH-}$$
and
$$ \ce{HCl —> H+ + Cl-}$$
and deduces $[\ce{H+}] = [\ce{Cl-}] +[\ce{OH-}]$. How come this happen from those two equations?
Can anyone elaborate and explain?
Comment: Left sides are neutral. If nothing else is going on, for every H+ made, either an OH- or a Cl- are made. It keeps the solution net neutral, which it should be.
Comment: For future reference, ChemSE benefits from mhchem's markup which eases input and display of chemistry-related content in questions, answers and comments -- just have a look at https://chemistry.meta.stackexchange.com/questions/86/how-can-i-format-math-chemistry-expressions-here.
Answer: Let's take the degree of dissociation of water be $\alpha$ and the $[\ce{H2O}] = c$, then at equilibrium the $[\ce{H^+}] = [\ce{OH^-}] = c\alpha$. And since $\ce{HCl}$ is a strong acid it will completely dissociate. So  $\ce{HCl}$ is a then the $[\ce{H^+}] = [\ce{Cl^-}] = a$. So $[\ce{H^+}]_{\textrm{net}} = a+ c\alpha$, which is equal to $[\ce{OH^-}] + [\ce{Cl^-}]$.
Comment: What is the meaning of the second alpha? And what is the concentration of water? Can you add subscripts to the two [H+] terms. They seem to have different values.
Answer: For a quick general answer, this equation represents the charge balance. In a solution, the charges of all ions should add up to zero. You charge balance reads:
$$\ce{[H+] = [Cl-] + [OH-]}$$
If you had divalent ions, you would have to correct for that, e.g. if the solution also contained magnesium ions:
$$\ce{[H+] + 2 [Mg^2+] = [Cl-] + [OH-]}$$

How come this happen from those two equations?

$$\ce{H2O —> H+ + OH- }\tag{1}$$
$$\ce{HCl —> H+ + Cl- }\tag{2}$$
Both equations are balanced, which includes charge balance. For every $\ce{H+}$ made by dissociation of water, an $\ce{OH-}$ is also made. For every $\ce{H+}$ made by dissociation of hydrogen chloride, an $\ce{Cl-}$ is also made. So the total $\ce{H+}$ concentration is equal to the sum of the $\ce{OH-}$ and $\ce{Cl-}$ concentrations.

[OP's comment] Won't it be HCl+H2O =2 [H+]+ [OH-] + [Cl-] ?

This is a bit a step in the wrong direction, but I'll explain it anyway.
It looks like you are trying to add the two reactions. This would be appropriate if they were coupled, i.e. if a nanomachine grabs one molecule of hydrogen chloride and one molecule of water, and spews out two protons, a hydroxid and a chloride. The overall equation of that would be:
$$\ce{HCl +H2O ->2 H+ + OH- + Cl-}$$
For example, one mole HCl and one mole water would make two moles $\ce{H+}$, one mole hydroxide and one mole chloride. This would maintain the charge balance.
However, these two reactions are typically not coupled but happen independently. In fact, usually when reaction (2) increases the concentration of $\ce{H+}$, reaction (1) would go in reverse, lowering the hydroxide concentration (and the $\ce{H+}$ concentration).
Deriving the charge balance from the two balanced equations
The two reactions are independent in the sense that there is no set stoichiometric factor linking them. So let's say reaction (1) makes a certain amount $x$ of $\ce{H+}$, and reaction (2) makes a certain amount $y$. If we start out with no ions at all, and ions are only produced by these two reactions, we can write down all the amounts:
$$n_{\ce{H+},\mathrm{total}} = x + y$$
$$n_\ce{OH-} = x$$
$$n_\ce{Cl-} = y$$
Adding up the anions:
$$  n_\ce{OH-} + n_\ce{Cl-} = x + y $$
So
$$n_{\ce{H+},\mathrm{total}} = n_\ce{OH-} + n_\ce{Cl-}$$
To turn this into a statement about concentrations, divide the amounts by the volume they are in. Because it is the same volume for all (they are all in the same solution), we get a similar equation for the concentrations:
$$[\ce{H+}]_\mathrm{total} = [\ce{OH-}] + [\ce{Cl-}]$$
Example with numbers
For example, if reaction (1) made $\pu{e-10 M}$ of $\ce{H+}$, and reaction (1) made $\pu{e-4 M}$ of $\ce{H+}$, there would also be  $\pu{e-10 M}$ of $\ce{OH-}$ and $\pu{e-4 M}$ of $\ce{Cl-}$.

Finding the pH of the solution


Why is "Encouragement of Climb" written in katakana instead of hiragana?

Question: I'm just a beginner in Japanese, but I know the difference between the use of katakana and hiragana in sentences. Katakana is used for transliteration of foreign words, onomatopoeia, technical or scientific terms, or from emphasizing words, but why is "Encouragement of Climb" written as ヤマノススメ and not やまのすすめ? It didn't pass any criteria for it to be written in katakana.
Comment: Try to avoid using Google Translate while learning a language.  You'll learn faster if you avoid it.
Comment: I really wish textbooks would stop oversimplifying things like this ... Think of it more like this. Those things are almost always katakana, but not the limit of it.
Comment: There's such a thing as _dictionary_, and Google Translate is not one. As for なつ, see for example [https://jisho.org/search/なつ](https://jisho.org/search/なつ), which indeed mentions both the translation "summer" and the kanji 夏.
Comment: When I translate it in google translate using やまのすすめ, the katakana ヤマノススメ is recommended by the google translate so I can't figure out why is that. I know that these rules are not the only limits and some certain words are exempted, but why specifically that phrase? even though it appears that there is nothing special about that phrase?
Comment: When I'm translating sentences from Japanese to English, some of the translations are wrong and I know for a fact that it is wrong since google translates word per word, the same for my own language. But, how do I figure out the meaning of each words if I don't know the translation? For example, I wouldn't know that なつ also means summer, and can be written in kanji as 夏, if not for google. I am familiar with it only as a name.
Comment: okay, thank you for that. I know that I am too reliant on google translate so I'll work it out.
Answer: There are a number of stylistic or aesthetic reasons to do so. Sometimes katakana is used for a native Japanese word because of the katakana's "international", "modern" or "high-tech" feeling:

Why is Toyota typically written in Katakana? (トヨタ)
ニッポン? Why Kana?

However, katakana is also associated with oldness and tradition because it was the standard script in formal or academic documents in the Meiji era:

Why is this written in katakana instead of hiragana?
Orthography at the turn of the previous century

(This may seem contradictory, but in reality, other design choices such as fonts also matter.)
In this specific case, I think the latter image is more relevant. This book title is a parody of 学問のすすめ, a very famous book written 150 years ago, and one of the earlier copies was full of katakana, like this. By using katakana, the author is signaling that this ヤマノススメ is like a climbing version of the nationally famous classic.
Also related:

Why are katakana preferred over hiragana or kanji sometimes?


Am I allowed to transmit on one repeater and receive on another?

Question: Lets say 2 people can receive on 2 repeaters equally, but one hits a repeater transmitting better and the other person hits the other repeater better. Am I allowed to transmit on one repeater, and receive on another and my buddy does opposite?
Answer: As long as you are both operating according to your license there is no technical or legal reason why you couldn't, but more on this at the end.  At minimum it may be very confusing to other users of the repeaters and repeaters are individually owned and operated - you should make sure your specific use of the repeaters in this manner is acceptable to the individuals or clubs that operate them.
As far as whether your license permits it, in the US the rule is "Each station licensee and each control operator must cooperate in selecting transmitting channels and in making the most effective use of the amateur service frequencies. (FCC Part 97.101(b))" and this is generally the same around the world.  The spectrum granted for your use is a shared medium, and using more than what is necessary for a communication may be breaking the spirit of this rule.
Keep in mind that when you're tying up a single repeater, you're actually using two channels.  Your friend is tying up two channels as well.  So effectively your conversation is eating up four channels, during which time no one else can use them.  Using two repeaters to hold a single conversation is very excessive, and should only be done when necessary.
Using two repeaters for rag chewing is likely to annoy other operators in the area also interested in using the repeaters.
Comment: I agree, I don't think there's a technical legal reason why not. But ethically, you would be occupying two repeaters for one QSO, and would probably annoy a lot of people.
Comment: I am curious as to how you would do that unless you used to individual VHF transceivers.  I just checked my VHF HT and base station and both do duplex the same way by using an offset from the receive frequency for transmit.  The receive frequency being the designated frequency of the repeater.  The offset is programmable but still just an offset.  No repeater assignment in a given area would allow RX/TX for a repeater to be the same as some other RX or TX frequency so the offset method would not work.  If your rig could TX and RX on VFO assigned frequencies like using split on HF then OK.
Comment: @DavidVK2VXK Good point, I've expanded on that thought.  Thanks!
Answer: No legal reason why not as long as your licence conditions allow it. It would be just like linking two or more repeaters together with Echolink or AllStar.
Answer: You can do it, but a repeater that hears well but doesn't transmit well is called a rabbit. A repeater that talks well but doesn't hear well is called an alligator. Repeater owners go to great lengths to tune their repeaters to be equal to both transmitting and receiving. Repeater owners that have a rabbit should increase the transmit power. Alligators should reduce power to properly balance the repeater.
Comment: Your post barely answers the question, and doesn't really add anything useful.


Is "es gibt" not used as often as the English "there is"?

Question: Do Germans use other verbs like befinden or existieren or totally different constructions to avoid using es gibt regularly?
Comment: How often do you use "there is"? – I don't think that there's objective analysis done.
Comment: Germans have a certain tendency to avoid repeating the same words or phrase again and again, instead looking for alternatives and other expressions. Apart from that, there's nothing wrong with _es gibt_.
Answer: I can only speak for myself – and I don't know how often you usually use "there is" – but I have the feeling, that "es gibt" is used constantly: it's simple, it can be informal and direct, it's rather neutral, and it's handy. I hear it (and use it) all the time: at work, in restaurants, when talking about the TV program, etc.
Just some quick samples:

"There is a problem." -> "Es gibt ein Problem"
"Today we'll have Pasta" –> "Es gibt Pasta."
"There's nothing on TV" –> "Es gibt nichts im Fernsehen"
"Don't be so nosy!" –> "Es gibt nichts zu sehen!" ( = "There's nothing to see here!")

Whereas befinden or existieren are way more formal – you wouldn't use either for any of the above cases. Instead, you would have to form a complete sentence - as probably is the case in English.
So I would say "es gibt" is actually very close to "there is".
Comment: I absolutely agree on the first part, however in the end it sounds like "es existiert" is more formal than "es gibt". In fact you would prefer "es gibt" in scientific work, as you want to write as simple as possible. "es existiert" will appear only if you have rly narrow defined mathematical phrases (thinking of the existince-quantor).
Comment: ok, thanks for the comment – and I agree. So "simple" instead of "informal" would probably better described what I mean.
Answer: Taking a rather very naïve approach:
Here is the Google-Ngram for there is/are in English:

And here is the same one for es gibt in German:

Assuming that the Ngrams reflect the actual speech, there is/are is used about three times as often at the very beginning of the sentence than es gibt. Something similar holds for cases where there is some introductory adverbial or similar as in:

In my opinion, there is nothing on TV.
  Meiner Meinung nach gibt es nichts im Fersehen.

So as long as we only look at there is/are and es gibt at the beginning of the sentence or similar, the former is used more often. (If we also want to take into account subclauses, it gets more complicated, because of sentences like "Ich bin der Meinung, dass es heute nichts im Fersehen gibt.")
Comment: did you account for number of speakers and indexed material?
Comment: @vectory: Yes, those are percentages.
Answer: The point is that es gibt, befinden und existieren are used differently with some intersections. Some examples.
Being somewhere:

Es gibt Kuchen in der Küche (There is cake in the kitchen (implies that you can have some)
  Es befindet sich Kuchen in der Küche (it is just there)
  Es existiert Kuchen in der Küche (correct, but no one would use it)

Existing:

Es existieren vier Naturkräfte (Four forces of nature exist)
  *Es befinden sich vier Naturkräfte (totally wrong)
  Es gibt vier Naturkräfte (there are four forces of nature)

Metaphorical:

Es gibt nichts im Fernsehen (There is nothing on TV (which I would like))
  *Es existiert nichts im Fernsehen (wrong)
  *Es befindet sich nichts im Fernsehen (wrong)

Being somewhere, interchangeable:

Es gibt Vulkane auf dem Mars (There are volcanoes on Mars)
  Es existieren Vulkane auf dem Mars (the context allows for the formal "existieren")
  Es befinden sich Vulkane auf dem Mars

As you cannot use one for the other in all situations, they cannot be used in general to avoid "es gibt".
Answer: My opinion as a German native speaker:
If you use "es gibt", then don't forget that you use a term, that is often used to replace other words. It is an expression that is used primarily in the vernacular.
For example:
"There is a problem." -> "Es gibt ein Problem" stands for "Es ist ein Problem aufgetreten" or "Wir haben ein Problem"
"There are volcanoes on Mars" -> "Es gibt Vulkane auf dem Mars" stands for "Es existieren Vulkane auf dem Mars"
"There's nothing on TV" –> "Es gibt nichts im Fernsehen" stands for "Es läuft nichts im Fernsehen"
Apart from that, I totally agree with Ingmar, that in the germans have a certain tendency to avoid repeating the same words or phrase again and again, instead looking for alternatives and other expressions.
If you want to write a paper or a scientific report, it is better use "es gibt" as seldom as possible.
Comment: Good remark. Maybe you can emphasize in your answer that it is primarily the "gibt" that is replaced and not the "es". It's possible to formulate the examples in active voice to get rid of the "es" : "Vulkane existieren auf dem Mars"
Comment: I think this is an important thing to keep in mind when comparing "there is" to "es gibt". "Es gibt" will often replace a more precise option of expressing your thoughts, thus making what you say/write sound less formal.
Answer: I know this is not exactly on topic, but it is a curious fact that in Yiddish the use of "es gibt" is considered a serious faus pas. A common acceptable alternative is:

es gefinnt sich a buch...

which of course roughly follows the German, but there are also:

'sis dâ a buch... (the â here indicates a vowel shift to o or u)
'sis dâ vorhan a buch...

or simply

vorhan a buch...

none of which seem to be reflected in Standard German. Maybe some dialects use these or similar forms?
Comment: ja, sicher, 's'is' kann sogar als einfaches 's' auftreten, *s'ne Antwort die nicht jedem gefällt*.

Is “es gibt” not used as often as the English “there is”?


My rats had a fight and one of them is injured - what can I do for him?

Question: My rats were fighting and one of them got bitten. It looks quite bad. What can I do for him?
Answer: With rats, wounds generally look worse than they really are. They very rarely require intervention - though their teeth are impressive, they also have thick fur and skin. Occasional fighting is normal for rats; if it gets more frequent, or it's a case of one rat picking on another, then you may have to investigate further.
Generally, you can leave a rat to deal with his own wounds, they are exceptionally fast healers. If he has an open wound, he needs to be kept away from others in a spotless cage until he heals (a day or two). Some rats, especially the more submissive ones, can get psychologically traumatized by a fight, so be sure to offer him comfort if he wants it, and be careful when putting him back with the other rats.
If it is an open wound, but not bleeding, you actually don't need to do anything, beyond check he is keeping it clean. If you think he's in pain (fur puffy, teeth chattering) you can give him some ibuprofen, as instructed here. "The dose is 15-60 mg/lb 2-4 times a day. Lower doses are for analgesia, higher for inflammation." Do not give ibuprofen if your rat is elderly, as it can interfere with kidney function, or if your rat is bleeding. More on this later.

from the ratfanclub.org
The feet, ears, tail and mouth all have a considerable blood supply, and injuries to these areas can cause profuse bleeding.  The first step to stop the bleeding is to apply direct pressure for two minutes.  If the bleeding continues, put some flour in a small container and press the bleeding area into the flour, or press some flour onto the wound. The flour will help the blood to clot.  Cornstarch can also be used, as well as a commercial product to stop bleeding.  Another thing to try is holding ice against the injury.  The cold will reduce the blood flow.
If the injury is a severed toe or tail tip, you may have to apply a tourniquet.  Tie string as close to the end of the extremity as possible.  Tighten the tourniquet until the bleeding slows to an ooze.  Do not tighten the tourniquet too much, or you could cause additional damage.  Remove the tourniquet after 20 minutes to see if the bleeding has stopped, or can now be stopped using the other methods.  If not, replace the tourniquet and take your rat to the vet. If a toenail is bleeding, the best way to stop it is to use styptic powder or a silver nitrate stick.  Flour or cornstarch can also be used like styptic powder.  Press some into the end of the nail.
After a wound to a toe, it's common for the toe to swell quite a bit and turn red.  It's not usually necessary to treat this condition and after a week or two, the toe will heal.  If you like, you can give the rat an anti-inflammatory such as ibuprofen to help bring down the swelling.
Ibuprofen interferes with blood clotting, so if your rat has a severe injury with profuse bleeding, you do not want to use ibuprofen that day.  For pain you can use acetaminophen (Tylenol) at 90-140 mg/lb every 4-12 hours.  Choose the dose according to the severity of the pain and possible length of use, with lower doses for repeated use.  Overdoses can damage the liver.
More here under the 'Wounds and Bleeding' section.

If the bleeding does not stop, contact a vet for more treatment.
Comment: Some people recommend putting some neosporin on it, FWIW.
Comment: @rogerdpack Ah yes, I forgot about that because it is not available here.
Answer: OK for me I had a rat who had a "wound" behind the right ear.  I assumed it was because of fighting.  In the end turns out it was because he had mites and so would scratch himself there, eventually drawing blood.  Fix for us was to wash them and apply some cream or other.  FWIW.
Comment: the op say the rats have been fighting,and asks what can i do for them.i am not sure what you are answering here,will washing and applying some cream stop them from fighting?
Comment: This is what ended up helping my rats when they were injured from what I presumed was fighting, FWIW (turn out in the end my hypothesis is that the rat lowest on the "pecking order" doesn't get grooming opportunities from the others, so he got more mitey and had to scratch a lot, so there was some rat contention going on there, FWIW).  Cheers!


Covariance Interest Rate Risk Time Series

Question: Apologies in advance if this question has been asked already.
I am estimating basis risk for different term points in the curve. Imagine i have three time series (1-month, 3-month, 1-year). I believe they are NOT independent of each other.  I have estimated the absolute daily change for each one of them (% change didn't work as some time series switch from negative to positive, or the other way around). I could generate a variance/covariance matrix of the absolute daily change in these three time series, and calculate some sort of a 'portfolio' standard deviation (assuming equal weights). This standard deviation would be in basis points, as mentioned above. For instance, 2 bps. I could also generate some sort of an expected value (average) for this portfolio, for instance 10 bps.
The question that I have is: how do I interpret the standard deviation in the context of each separate time series? If i want to estimate tail risk for this portfolio, is it accurate to (assuming normal distribution), to just estimate 2 standard deviations from the mean and analyze the tail risk from that data point? What would 4 basis points mean for each time series, i.e., how do I transform this portfolio tail risk to each time series, given that it is not proportional (%) change, but rather absolute change?
Answer: If $v$ is a vector of DV01 ezposures versus your various risk factors/buckets and $\Sigma$ is your covariance matrix tegen portfolio (delta-normal) Var is given by $$\alpha \sqrt{v^T \Sigma v }$$ where $\alpha$ is some point from the inverse cumulative normal.this gives you risk in cash (money) terms rather than % losses.
There are other ways to measure tail risks of course, both in metrics and methodology, but this looks like what you're after


Speed of Windows XP on external USB harddrive using VirtualBox on Mac

Question: I am considering installing Windows XP on an external hard drive in a VM with VirtualBox, but I am worried about it's speed? Would the slow transfer rate of USB slow down the performance of VirtualBox and Windows XP? Should I be worried about anything?
Answer: I/O will definitely take a penalty when working over a USB connection. If you have the option on your machine I would recommend an eSATA drive to give better performance.
What are your other options, really? Partition your installed HD? Create virtual disks? Depending upon your needs, an external drive is usually the most flexible option (especially when using a laptop). Depending upon what you're doing, it may actually be faster (overall) to have the virtual machine on a separate platter, as there will be no contention between the host and guest systems on the same hard drive.
YMMV, but external storage is a good solution.
Answer: I used to give a few presentations where I had virtual machines running from a USB disk.
Honestly, booting is slower and if you are running ~3+ at once, you do notice it is slower but if you have one or two doing standard tasks, it isn't very slow at all. It is only when you start doing intensive I/O based tasks that you notice it is slower.
If you disable the pagefile, you can also speed up the system (but you do need more memory) as it significantly reduces the amount of I/O operations that the system uses.
Answer: I run an XP Pro VirtualBox VM with Visual Studio 2008 for development use off an XP Pro host, the VM being on an external USB 2.0 HDD. It's perfectly fine and I can't see it being any different off a Mac host. Especially if it has lots of RAM.
Comment: i have 2 GB, what is your configuration?
Comment: 2GB also, 0.75GB allocated to the VM. It's perfectly usable although hardly earth-shattering performance-wise.


What's the difference between Radius and Kerberos?

Question: Is Radius just a better version of Kerberos? I can't find anything about this.
If you set up a Radius server in a modern network do you need Kerberos at all?
Answer: Kerberos will take verify your credentials and give you a "ticket" that you can use to prove to other systems/services that you are you. The ticket will expire, and doesn't contain your credentials. You have to be on the network for this to work. More information on Kerberos can be found here: MIT - Kerberos
RADIUS is a way to get on the network. You give your credentials, and they will be checked before you are allowed access to the network. More information on RADIUS can be found here: Wikipedia Entry
So when you are trying to access a network, you provide your credentials and RADIUS will check to see if you are allowed on the network. If you have wrong credentials, you don't get on.
After you are on the network, you will want to have access to other services, i.e. email. This is where Kerberos comes in. You authenticate to Kerberos, if you check out ok, Kerberos will give the ticket, (think of a pass) that you can use to access those other services without having to spread your actual credentials everywhere.
Comment: *Needs* is a strong word. You *could* use that set-up, or a completely different one. Newer tech is being developed all the time. You could look into OAuth or some others.
Comment: Yes, they serve different functions, but both deal with credentials. As far as installing, it depends on what you want in the network.
Comment: So they're completely different things? Should both be installed in a network?
Comment: So, a campus network needs both. It needs Radius to authenticate clients who want to log in to the network, and it needs Kerberos to authenticate clients who want to use specific services in that network?
Comment: @StephenSpencer, just wanted to suggest you replace the software-specific GNU Radius link in your answer above, with a more general description of RADIUS. For example, [the Wikipedia entry](https://en.wikipedia.org/wiki/RADIUS).
Comment: One is about giving you access to the network.  The other is about being able to give creditionals to join the network.
Comment: Sorry if this is late, does Kerberos still get used in modern networks or should something better be used?
Answer: Radius task/purpose is to authenticate you at the specific point, i.e. in a web interface or pptp dialup-like server. Every point that needs authentication does a query to a Radius server for your credentials like login and password.
Kerberos task/purpose is to distribute a trust to your session to all points connected/registered : you're performing your full authentication with your login and password only once, and in case of success you're granted a ticket that you will provide to all the points of authentication that trust that Kerberos server. And until the ticket is valid(it can be revoked and it has a lifetime timer) you're not authenticating at these points : you're just providing your ticket instead and they're assuming(not authenticating!) that it is you.


The thin line between winning and losing at the top level?

Question: At lower level, we often blunder many times and do not make the best moves, so there can be multiple ways to win.  But at the top level, for example, during the candidate matches going on now, the masters do not blunder often and they do not make very many mistakes, so I have noticed a theme which is not just in these games, but in others, and that is that the difference between winning and losing can come down to a single pawn for them and they will often fight to the death over one square.  I have noticed that for example if white attacks e4, black will immediately strive to defend it and they will battle over one square.  Is my assessment correct on this?  Are there other factors at the top level?
Comment: Whoever down-voted, care to explain why?
Answer: Note: I'm an average player, who learnt chess about 2 years ago, maybe I'm not the right guy to answer such question but I will try.
I wanted to ask a similar question, maybe I will today or tomorrow. As for your question.
Top level players do make mistakes, maybe they underestimate the opponent, maybe under time pressure, maybe they just don't see the moves, or maybe they are focusing on the attack.
To prove my point I'll show you 2 games and I"ll talk about the mistakes, you can click on the links to watch the videos
Levon Aronian vs Boris Gelfand Round 2 Candidates Tournament 2013
[FEN ""]
[White "Levon Aronian"]
[Black "Boris Gelfand"]
[Event "2013 Candidates Tournament"]
1. Nf3 c5 2. c4 Nc6 3. Nc3 g6 4. e3 Nf6 5. d4 cxd4 6. exd4 d5 7. cxd5 Nxd5 8. Qb3 Nxc3 9. Bc4 Nd5 10. Bxd5 e6 11. Bxc6 bxc6 12. O-O Be7 13. Be3 Qd5 14. Rfc1 Qxb3 15. axb3 Bb7 16. Ne5 O-O 17. Ra4 Rfd8 18. Nc4 Bf6 19. Na5 Rd7 20. Rb4 Ba6 21. Nxc6 Rb7 22. h3 Kg7 23. Rxb7 Bxb7 24. Ne5 Bd8 25. b4 Rc8 26. Bh6 Kg8 27. Rxc8 Bxc8 28. Nc6 Bf6 29. b5 Bd7 30. g4 g5 31. h4 gxh4 32. g5 Bxc6 33. bxc6 Bd8 34. Kg2 Bc7 35. Kh3

If you want a full analysis on that game you can watch the video, I"ll talk about 2 moves that changed the game.
16. Ne5 getting the knight involved, the more brilliant move is 18. Nc4 and 19. Na5 I didn't see that coming! putting pressure on the pawn, basically that knight destroyed black in my opinion.
Did Boris see it coming? Maybe he did, maybe he just ignored the knight, we all do ignore our opponent's moves, in the end of the middle game, especially if the opponent is attacking, we have to counter-attack, and we don't defend anymore, keep in mind that in this particular tournament, you get 2 hours for the first 40 moves, no time pressure, the game ended in 35 moves.
The next move is 26. Bh6 which finished Boris off. If the king takes, then eventually the knight will fork the black bishop. Didn't he see it? He should see that. The first thing I look at is the major minor pieces of my opponent. If black focused a bit he could've seen it, (Boris is a GM) so white has a knight, a rook and a bishop, it's obvious, has no where to go, if he didn't check the king, so Boris should have thought about what happens if the bishop attacks his king.
Bobby Fischer vs James Sherwin 1957 US Chess Championship
[FEN ""]
[White "Bobby Fischer"]
[Black "James Sherwin"]
[Event "1957 US Chess Championship"]
1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Bc4 e6 7. O-O b5 8. Bb3 b4 9. Nb1 Bd7 10. Be3 Nc6 11. f3 Be7 12. c3 bxc3 13. Nxc6 Bxc6 14. Nxc3 O-O 15. Rc1 Qb8 16. Nd5 exd5 17. Rxc6 dxe4 18. fxe4 Qb5 19. Rb6 Qe5 20. Bd4 Qg5 21. Qf3 Nd7 22. Rb7 Ne5 23. Qe2 Bf6 24. Kh1 a5 25. Bd5 Rac8 26. Bc3 a4 27. Ra7 Ng4 28. Rxa4 Bxc3 29. bxc3 Rxc3 30. Rxf7 Rc1 31. Qf1 h5 32. Qxc1 Qh4 33. Rxf8 Kh7 34. h3 Qg3 35. hxg4 h4 36. Be6

Let's focus on 30. Rxf7 Rc1 31. Qf1. Black didn't see Rxf7 and of course he didn't see Qf1. That's how you outsmart your opponent! I had to show a game played by Fischer. It answers your question perfectly. Let's say if
Rxf1+Rxf1+
Qxd5Rxf8+
Kxf8exd5
And white has a passed pawn.
All I want to say is that GMs do make mistakes, they do underestimate the opponent, ignore a move, or maybe they just don't see the game so well. But sometimes they are just outsmarted!
Answer: Almost by definition, the advantage needed to win gets smaller and smaller, the higher level the players get.
Between two rank beginners, the loss of a pawn or even a piece means very little, because such players will lose pawns and pieces to each other almost at random. One of them wins after the the other has made several mistakes, and gotten several pieces behind.
Among top level players, it takes very little "extra" to win. For instance, a board has 64 squares. I was once told that if a top player got control of five more squares than his "fair share" (e.g. 37 vs. 27), that was practically a winning advantage unless the other player had compensation in the form of an extra pawn or a kingside attack.
A "mistake" consists of giving the other player what he needs to be sure of winning. At the very top levels, these would consist of omissions that no one at say, the intermediate level would care about, because only a top player could exploit them. Conversely, for very bad players, the loss of a SINGLE pawn or even a piece that an "average" player would bemoan, might not make a difference.
Comment: I would not agree completely to your first statement. It is true that GM are very good at converting small advantages, but on the other hand they are also much stronger at defending worse positions. So there might be examples where a game ends in a draw between two top players, while the same position played between average 2000  players has a decisive result because they are not as good at defending.
Answer: Simply, at the top-level, a player has enough technique to exploit every little advantage. That's not always true at lower levels.
Thus, losing a pawn without compensation may be a little blunder in a match between two beginners, since the opponent could make a bigger blunder on the next moves, and lose the advantage.
In a match between 2 pros, a blunder like that will lead to a defeat (or to a tormented draw), because a top-level player will make very few mistakes (if none) and probably won't give away his advantage.
Of course even World Champions blunder spectacularly (Deep Fritz-Kramnik anyone?).
Answer: The goal of chess players is, ultimately, to create a threat that cannot be stopped.  But chess is a famously balanced game.  There is no way to create an unstoppable threat unless one of the players errs.  In the simple case, one player moves, the other counters, etc. No one makes any headway.
At the higher levels,  players drop material so rarely that it doesn't come into play.  And by drop material, I mean they don't just leave pieces hanging for the taking.
So how does a master win?  It comes down to efficiency.  A player must choose moves that provide more benefit than those chosen by the opponent.  Eventually, the sum of the efficiency gains build to the point that a dual threat can be created.  This generally results in the uncompensated loss of material.  Now the game is unbalanced and the player that is down will likely lose.
But this is not easy to do.  That's why there are so many draws at the master level. So what's a master to do?  Sometimes they sacrifice in order to create efficiencies that would not otherwise be possible.  Of course, they must jealously hoard the efficiencies gained and turn them into something tangible before their material disadvantage comes into play.  That is, a local advantage must be exploited before a global disadvantage asserts itself. Sometimes, they will simply work on building positions imcrementally such that their moves improve their positions more than their opponents' moves improve theirs.  Eventually the efficiencies can be converted to tangible gain.
One common way to talk about the accumulation of efficiencies is to use the common chess term "tempo."  This word works well when talking about maintaining the advantage after sacrificing a piece.  It works less well when talking about positional gains but the underlying efficiency is still there.  It's just harder to see.
Examples:
1. A player puts a knight on a great square.  The opponent needs to spend three moves to boot it out.  Those three moves can be used by the first player to make more mischief.

A player allows himself to have a backward pawn.  The position does not allow the pawn to be attacked.  No efficiencies are lost.
A player has a backward pawn on a half-open file.  The opponent piles rooks on that file.  The first player has to spend time defending a pawn while the opponent is building an attacking force that will not go away once the pawn is lost.  Meanwhile, the pieces defending the pawn can't be used elsewhere.
White allows Black to play a Posioned Pawn variant of the Sicilian reasoning that the loss of the b pawn is worth the resulting efficiencies gained while simultenously threatening the Black Q and developing half a box of pieces.


Is it possible to take over a Star Trek vessel by sabotaging its food replicators?

Question: I think it would be simpler to incapacitate a Star Fleet vessel by sabotaging its food replicators than fighting it out with shields and weapons. Are there safety mechanisms on replicators? If so, what are they? Can they be modified to include poison or other harmful substances in the foods they deliver?
Comment: Not technically a vessel I guess, but something similar to your idea happened in [the DS9 episode Civil Defense](http://en.memory-alpha.wikia.com/wiki/Civil_Defense_(episode).)
Comment: i mean, if you could get past the shields, to disable something like the food replicators, your already most the way their to just disabling vital things like life support... plus your assuming that they wont figure it out after the first few eat of it, and fix it.
Comment: A patient assassin could add a virus that takes weeks to incubate, and is triggered by a signal. Kill the crew and capture the ship without any fighting.
Comment: The safety interlocks can't be too stringent if tribbles can be dispensed instead of a chicken sandwich and a cup of coffee.
Answer: Yes, and no. Yes, you could do this, with enough access to the replicator systems, just like any computer system can be hacked and changed with the right access, electronic or physical. No, it won't be easy. The replicator, much like the transporter technology it partially uses, scans for viruses and hazardous particles. It has restrictions on replicating weapons, poisons, uniforms. Some things are not programmed in at all, while others need permission or access codes to produce the items. Finally, you would need to program in the new pattern and default programming, requiring familiarity with the system. And you have to get to them, through shields and an army of yellow shirts and civilian notice.
Answer: Given the sheer amount of difficulty that Counselor Troi had just to get a frigging chocolate sundae, this seems, while possible, ludicrously difficult.
Comment: This is Arthur Dent trying to get a cup of tea Level of difficulty we are talking about here.


Best practice for selecting a recurring event?

Question: I need to allow users to set the frequency with which they would like for a certain task to occur (example- every X days/week/month/year). So far, what I've come up with is an input box and a drop down to select either Days, weeks, months or years as options.
Could this be confusing and are there any better patterns for such cases?
Comment: Are there any limits, minima & maxima, on what they can set? Also what's the use case for this?
Comment: @DarrylGodden There are no limits as such. It's to automate file scraping from another location. The user gets to define if they'd like to scrape files every x interval of days/months (most common cases) or even years.
Answer: Planning of tasks tends to be more contextual than mathematical. What does that mean? It means that you

go to soccer practice every Tuesday,
pay your rent on the last work day of the month,
download that report on every 15th,
meet with Jeff on the first Monday of each month
check up on aunt Jeannie at least once in a quarter.

In the Gregorian calendar, only the first bullet point is a consistent interval. All other "tasks" depend upon the length of months, placement of calendar weeks, work week definitions, beginning of the week definitions.
What you need to do is to

Give a natural language context (for your locale)
Take away complexity in the beginning
Offer the most popular choices
Allow customization down the road

Microsoft, e.g., is doing a good job with this in their Outlook web app.  (Even if somewhat inconsistent cross-device)
1. Desktop

2. Mobile
Answer: I Think there should be hierarchy in layout and options should be daily, weekly, monthly as per the below example
Answer: Information hierarchy in your case is reversed

You will first have to take make the user select desired interval and
  then allow the user to input number of days/week/months.

We recently designed a similar control in our product. You can use it for inspiration.
Comment: Arguably, information hierarchy is just as reversed in natural speech (in English, at least; this must not hold true for all languages).
Comment: "Value" seems unclear to me here. Do you want "Every 30 days" or "the 30th day"?
Comment: @TimFitzGerald Yes Value in this case will not be clear. Maybe we can write "Enter number of days/weeks/years" in the input as placeholder
Answer: I would say that your approach should depend on the tasks your users need to perform. For example:

if I want to schedule a meeting which occurs every Monday morning I would want to set a start/end date and frequency
if I am a doctor and plan therapy for my patient I would probably prefer to choose the number of occurrences and don't bother about the start/end date.
I may want to use a combination of the above

Explore the user flow and what users need to achieve their goals and you will find the answer.


Optimizing Rectilinear Distance Traveled

Question: I have a simple pipe network like this (not to scale):

I can place a "valve" on any point on that pipe. What the valve does is it permits a certain viscous fluid to fill the pipes. However, because it is so viscous, it can only travel to a certain length $K_i$ along the pipe in any rectilinear direction, depending on the fluid I use.
Note: The valves need not be at vertices. They can be at any point in the network.
The less viscous the fluid, the larger the cost it incurs. So the farther the fluid can travel, the more expensive it is.
If I'm using a fluid that can travel only 5 units in any direction, and I place the valve at the top leftmost corner, the fluid (red) will travel like this:

Whereas if I used a fluid that could travel 10 units in any direction, it would look like this (blue):

If I used the first fluid but put the valve at the bottom right corner of the first square, the fluid will spread like this (red):

If I used the second fluid but put the valve at the bottom right corner of the first square again, the fluid spreads this way (blue):

Fluid 1 incurs a cost of 10 per valve where fluid 1 is used, whereas fluid 2 incurs a cost of 18 per valve (the fluids can mix). The goal is to fill the pipes with either fluid 1 or fluid 2 while incurring the least possible cost.
My question is, how can I optimize this situation mathematically? Does it require a linear program?
At first glance, it looks like there are many solutions. It doesn't look very convenient to do an LP. But, how else can it be approached with math?
Also, in the general case where the distances traveled are $K_i$, the costs incurred are $C_i$, and the pipe network is not as simple as the one I presented (all pipes still run up-down or left-right, but are more complex), how do I proceed about optimizing?
Comment: The valves need not be at vertices?
Comment: That's right, they don't need to be. I'm sorry, I should have noted that. Thanks!
Comment: Well, you said "any point", but I wanted to make sure
Answer: If you can discretize the problem (e.g., only look
for positions with integral coefficients),
it is a set cover problem:
consider a matrix with one column for each (integral) position in the network,
one row for each possible position of each fluid source,
and value 1 if the position (column) can be reached
by the fluid (row), 0 otherwise;
you are looking for a minimum-cost
set of rows with at least one 1 in each column.
The problem can be formulated as an integer linear program.


What is the difference between "vivre" and "habiter"?

Question: What is the difference between "vivre" and "habiter"? It seems that they both mean "to live"? But, when to use each?
Answer: "vivre" corresponds to the general abstract meaning of "to live". "Habiter" is the restricted sense of living at one particular place. As a rule of thumb, you can always use "vivre" instead of "habiter", but the reverse is not always true.
More precisely, you can only use "habiter" when you want to say "to live somewhere".
Some examples:

I live in this house

"Je vis dans cette maison" : OK
"J'habite dans cette maison" : OK (the meaning is the same)

I live a beautiful life

"Je vis une belle vie" : OK
"J'habite une belle vie" : makes no sense
"habiter" can also be used in a metaphorical sense, such as "Une passion m'habite" (Roughly translated "A passion is inside me"). This is still somehow related to the notion of living somewhere. Thanks to Stephane Gimenez for this remark.
Comment: Une certaine envie de downvoter m'habite. :-) Mais ce n'est surement qu'un détail.
Comment: J'ai édité une remarque, cela vaut effectivement le coup d'être mentionné. Je pense que la distinction de fond est tout de même bonne. Merci.
Comment: Habiter ne signifie pas seulement vivre à un endroit, car "habiter" suggère "y avoir ses habitudes", donc un certain attachement, une connaissance particulière, etc. Une  expression telle que "habiter le monde" n'est pas synonyme de "vivre dans le monde".
Answer: Vivre is the general translation of live, as in, what you go through until you die.
Habiter specifically refers to one's home. (The verb also has other, related, less common meanings.) Both vivre and habiter can be used in the sense of having one's home in a particular place. There is a nuance between them: habiter refers strictly to one's home, whereas vivre generally covers a larger area that includes the place where you work, shop, etc. Thus habiter tends to be used with more precise indications of locations, while vivre tends to be used with less precise indications.
Here are a few examples.

Je vis en France depuis trois ans.
I've been living in France for three years.
("J'habite …" is also possible, but gives a slight administrative vibe.)
Je vis à Paris.
I live in Paris. (Probably includes the suburbs, but could also mean just the municipality.)
J'habite à Paris.
I live in Paris. (Probably means the municipality, but could also mean the whole region.)
J'habite dans le cinquième arrondissement.
I live in the 5th arrondissement.
("Je vis …" would give the impression that you never get out of the arrondissement.)
J'habite au cinquième [étage].
I live on the fifth floor.
Answer: Vivre is related the fact of existing or being alive.
Habiter is related to a geographical location where you live or exist.
Even if people use them most of the time as the same they don't have the same meaning. Vivre has a larger one.
Answer: Vivre has the meaning of existing
Habiter is a location where someone or something can stay, live, or exist

What is the difference between “vivre” and “habiter”?


Intersymbol interference due to limited channel bandwidth

Question:
What is the difference between limited-bandwidth induced intersymbol interference (ISI) and ISI due to multipath propagation.
I noticed that the delay spread in indoor environment is in the range of nanoseconds, and is smaller than the symbol duration, yet ISI problem appears. Is this due to the limited bandwidth of the channel? Are there other causes for ISI?
Comment: Nice question, Welcome!
Comment: yes sir the problem of the ISI is limit of electronic Shannon's rules we need to design a wave not interference by the The Nyquist criterion this is the main option to avoid the ISI
Answer: Here is a graphic I have that demonstrates ISI due to multipath propogation:

Notice the eye diagram in the upper right hand corner showing what we should receive if there was no ISI, or other noise for that matter. (This eye diagram is showing the waveform vs time over 2 symbols again and again so that we can see the effects of ISI clearly. If you have any questions about eye diagrams in general, ask it as another question and we can go into further details on that).
This waveform reaches our receiver over multiple paths, each with their own delay and attenuation as shown by the multiple waveform vs time plots in the lower right hand corner of the figure. The eye diagram as received looks like the horrible mess due to this interference that is depicted in the lower left hand corner. (Luckily this can easily be undone through channel equalization in the receiver).
The variation in time of all the different propagation paths is known as the delay spread. Below is a plot I have shown in other posts showing the typical delay spreads for macro-cellular channels, as tabulated by Professor Paul Walter Baier of the University of Kaiserslautern, Germany (Vielen Dank, Herr Professor Baier!):

The significance of delay spread is whether we end up with Frequency Selective Fading (which means deep selective frequency nulls within the passband), or Flat Fading (which means the entire passband power level will vary, equally in frequency across the passband).  In the figure below this is demonstrated by two dominant paths with a Delay between the paths before summing together at the receiver. On the right is the resultant magnitude of the received signal versus frequency for two different delay conditions, the red plot is the result of a relatively long delay, while the blue plot is with a relatively short delay. The shaded region is our example channel at a particular frequency of interest. Notice for the red (long delay) given our channel bandwidth that we have the possibility of a deep null, selectively within our passband, while for the blue (short delay) the power level across the passband is generally much flatter. If you are familiar with the characteristics of an FIR comb filter then you know exactly what is going on; a fixed delay is a phase that varies linearly with frequency, so at some frequencies the phase will be $\pi$ radians so that the receive signals will cancel each other, while other frequencies the phase will $0$ (or equivalently multiples of $2\pi$) so that the signals will coherently add. Since the phase of a fixed delay varies linearly with frequency we see the repetition of this over frequency as the delayed path passes repeatably through $0$ and $\pi$ conditions as we vary the frequency of interest. A longer delay will increase more in phase for a given change in frequency, hence the tighter frequency response for that case.
Plot showing delay vs fading:
RED: Frequency response for a long delay.
BLUE: Frequency response for a relatively shorter delay.
SHADED AREA: Example frequency channel of interest.

Limited bandwidth induced ISI is easily understood in the time domain: A relatively tight filter in the frequency domain MUST have a long impulse response in the time domain (consider filtering as a low pass filter, and in order to really smooth the signal, you must average for a long time). So if you have a filter with a long impulse response, it goes to say that it's response to one symbol will extend into other symbols, causing Inter-Symbol-Interference. The trick is to provide relatively tight filtering while not causing ISI, and this is done with the class of Nyquist filters. They do this by having zero crossings in the impulse response at the symbol spacing. Thus the response from one symbol is always zero at the decision-sampling location of all other symbols. In fact the clean eye diagram in the first plot was created with such a Nyquist filter (the raised cosine filter specifically). All the deviations of the waveform are the result of trailing impulse responses of earlier symbols.
For further details on that see: Why root raised cosine filter can eliminate intersymbol interference (ISI) ?
Comment: Is there any fundamental thing that these two ISI have in common? Or they are totally different stuffs that only share the name?
Comment: Yes, quite similar: consider how FIR filter structures are the summation of different delays with different weights.
Answer: We know that signals with infinite-time support have a finite support in the frequency-domain, and viceversa. The only way to get a finite-time support is having an infinite bandwidth. Thus, if you have a band-limited channel, then the corresponding impulse response will be infinite in time. This means that no matter how spaced the symbols you send are, you will always have a "tail" of the previous symbol when sampling the current one. This is ISI caused by limited bandwidth.
Now, on top of it, you have to consider the fact that in real life electromagnetic waves are reflected and attenuated. For example, if I send a symbol at time $t_0$, maybe the wave follows two different paths to get to the receiver, each with delays $\delta_1$ and $\delta_2$. This means that, at the receiver, I will have the same symbol "twice": it will appear at $t_0+\delta_1$ and $t_0+\delta_2$. Depending on the symbol rate, this can be relevant or not. Imagine that I send the next symbol at some $t$ such that $t_0+\delta_1<t<t_0+\delta_2$. When I sample the signal to get it, how can I know that I'm getting information of the original new symbol, or of its combination with the delayed previous one? This is ISI cause by multipath propagation.
It's much more complicated actually, since there could be constructive and destructive interference, phase shifting, etc. However, those are the basic intuitive ideas behind the concepts. Apart from how they origin, the ISI has always the same effect on the receiver: it's just residual information from other symbols that we don't desire.
There are other causes for ISI. For example, bad synchronization. If I sample the received signal at non-optimum instants of time, I may be hitting the signal when it doesn't represent a pure symbol. The typical case is when using an ideal (infinite, non-causal) $\mathrm{sinc}$ pulse. If the symbol rate is $T$, and the width of the $\mathrm{sinc}$ is such that its zeros are located at $t=nT \ \forall n\neq0\in \mathbb{N}$ when it's centered at $0$, then if we sample the received signal every $T$ seconds, then we will only have information about the pure symbols, because every other pulse is null when the current symbol is at its maximum. If the sampling is not so tight, then we will be sampling linear combinations of all symbols previously sent and the current one. Thus, there will be ISI.
This last example is related to your second question. If the delay was constant, then you could take it into account and offest the receiver sampling for that amount. However, if the delay varies, then you can't do that. Hence, no matter how small the delay is, you will always have some amount of ISI.
Comment: This is a good answer and want to add the clarification for others to your first paragraph that we do not need to have an infinite impulse response for a band-limited channel using the typically used definitions for "band-limited". Consider that FIR filters introduce "band-limiting" but clearly have a finite impulse response. However what is true is that the narrower the response in frequency, the greater the response in time and vice versa. Also note how the weighted delays from multiple paths is similar to an FIR filter.


If you were in the middle of sinning but it's prayer time you must still pray?

Question: Suppose you were going to rob a bank and you heard the Adhaan so you stop to pray (it's Fardh) and then rob the bank - the prayer may well be worthless and "hypocritical" but you have obeyed Allah in fulfilling this Fardh act? Comment please?
Answer: It is evident from your question that prayer is fardh, so there is no need for further elaboration of the same.

If a Muslim performs his prayers, the prayers forbids him from sins and wrong-doings. Allah (JJ), says in the holy Quran,

Recite [O Muhammad] what has been revealed to you of the Book and establish prayer. Indeed, prayer prohibits immorality and wrongdoing, and the remembrance of Allah is Greater. And Allah knows that which you do.
          [Quran 29:45]

Now I am coming towards your question:-
Prayer according to Quran:-

Maintain with care the [obligatory] prayers and [in particular] the middle prayer and stand before Allah , devoutly obedient.
  -- al-Baqara 2:238

And establish prayer at the two ends of the day and at the approach of the night. Indeed, good deeds do away with misdeeds. That is a reminder for those who remember. -- Hud 11:114

The Hadith of the Prophet PBUH:

Adullah ibn Mas'ood  may  Allah  be  pleased  with  him said, "I asked the Prophet PBUH 'What is the best deed?' He (Prophet PBUH) said: 'Performing prayer in its due time.' I further asked, 'Then what?' He  replied: 'Dutifulness toward parents.' I further asked, 'Then what?' He  replied: 'Performing jihad in the Cause of Allah The Exalted.'"
  [Al-Bukhari and Muslim]

Fardh is an Islamic term which denotes a religious duty commanded by Allah (God) and its denial renders one to come out of the folds of Islam. Now, if somebody omits to perform any Fard without any valid shari'i reason, then such a person becomes a major sinner. So, there is no excuse for omission and missing of fard, whatsoever, anybody can't omit the salah (Fard). If somebody have faith in Allah, then prayers and righteous deeds will not let him to do the sin and evil.
إِنَّ الصَّلاةَ تَنْهَى عَنِ الْفَحْشَاءِ وَالْمُنْكَرِ
Comment: But how sincere is the prayer in such a mental state of robbing the bank or to commit adultery/kill a person? This a separate question.
Comment: But how sincere is the prayer in such a mental state of robbing the bank? Or use another example such as you are about to commit adultery or kill a person, it's prayer time you pray then continue with the sin.
Comment: @user26189 this is a different question which you should ask separately. Note that for praying after committing zina you need to take ghusl ...
Answer: İt is a little like trying to trick Allah, you pray thinking prayer is what saved you but you rape, kill and steal right after. Yes if you truly believe in Allah prayer will keep you away from sinning, but if you pray yet still do evil then are you not tricking Allah? This question isn't about just prayer, it is about what Allah thinks of sinners. Just an example, you go Infront of Allah; the almighty says you have committed these sins, then you reply saying "but I prayed before committing them and also after committing them". Does anyone really think Allah's justice is so worthless that you can trick him with only prayers?.. prayer is for us to show our appreciation not to save us from hell. First thing Allah demands us is to be good. İf you are evil then why pray? Only answer is that you think you can trick Allah.


Is death time predestined or can it be extended by supplication?

Question: Is it true that dua and keeping one's kin close could extend one's lifespan? Inversely, could severing one's relationships be a cause for someone's early demise? Ajal'ul qada' and ajal'ul qadar? For example, if a person commits suicide, does the person die earlier than the predestined time of death?
Answer: Nothing extends or reduces one's lifespan, regardless. This is the opinion that scholars mostly agree upon that when one's time is up, it will not be delayed, as Prophet Nūh ﷺ told his people:

يَغْفِرْ لَكُم مِّن ذُنُوبِكُمْ وَيُؤَخِّرْكُمْ إِلَىٰ أَجَلٍ مُّسَمًّى إِنَّ أَجَلَ اللَّهِ إِذَا جَاءَ لَا يُؤَخَّرُ لَوْ كُنتُمْ تَعْلَمُونَ
Allah will forgive you of your sins and delay you for a specified term. Indeed, the time [set by] Allah, when it comes, will not be delayed, if you only knew.
— Surat Nuh 71:4

Their good deeds would have only delayed them to a decreed time. When their time came, there was no postponement:

وَلَن يُؤَخِّرَ اللَّهُ نَفْسًا إِذَا جَاءَ أَجَلُهَا وَاللَّهُ خَبِيرٌ بِمَا تَعْمَلُونَ
But never will Allah delay a soul when its time has come. And Allah is Acquainted with what you do.
— Surat Al-Munafiqun 63:11

Potentially, there are two hadiths that may have caused you to ask your question.

First Hadith

عَنْ سَلْمَانَ قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم: لاَ يَرُدُّ الْقَضَاءَ إِلاَّ الدُّعَاءُ وَلاَ يَزِيدُ فِي الْعُمُرِ إِلاَّ الْبِرُّ
Salman narrated that the Messenger of Allah (ﷺ) said: "Nothing turns back the Decree except supplication, and nothing increases the life-span except righteousness."
— Jami' at-Tirmidhi, Vol. 4, Book 6, Hadith 2139

This hadith is graded da'īf (weak) due to Yahya ibn ad-Durais and Abu Mawdūd, but was graded hassan (good) or sahih (authentic) by others as there is another hadith with the same words narrated through Thawban, and was also documented in Al-Mustadrak by Al-Hākim an-Nisapūri.
Scholars, however, have explained that there are decrees in the manuscripts given to the angels with their orders to carry out. Such orders are the ones that may be changed by supplication. This opinion was expressed by Majmū' al-Fatāwa 15/492 by Ibn Taymiyyah, among other scholars.
This concept may be difficult to grasp, even among the companions. When the plague of Emmaus hit in Judea, 'Umar ibn al-Khattāb, who the Muslims' leader at the time, ordered everyone to supplicate to Allah, and that those who were in the land of the plague not to leave that land while the Muslims outside not to go in. Abu 'Ubaidah ibn al-Jarrāh, who was the leader of the Muslims in that land, asked 'Umar: "Are you escaping from Allah's Decree?" 'Umar reprimanded Abu 'Ubaidah and told him: "But we escape from Allah's Decree to Allah's Decree." Az-Zamakhshari mentioned in Al-Kashshāf 'an Haqā'iq at-Tanzīl that supplication would not make their lives any longer or shorter (see Musnad al-Fārūq 2/637-638 by Ibn Kathir).
Ramla bint Abi Sufyan, the wife of the Prophet ﷺ, also known as Umm Habība, had a similar concept to the one in your question. She supplicated that she would always benefit (i.e., keep alive) her husband, her father, and her brother. The Prophet ﷺ corrected her by saying that their lives' durations had already been set and would neither be brought forward not delayed:

قَالَتْ أُمُّ حَبِيبَةَ زَوْجُ النَّبِيِّ صلى الله عليه وسلم: اللَّهُمَّ أَمْتِعْنِي بِزَوْجِي رَسُولِ اللَّهِ صلى الله عليه وسلم وَبِأَبِي أَبِي سُفْيَانَ وَبِأَخِي مُعَاوِيَةَ. قَالَ فَقَالَ النَّبِيُّ صلى الله عليه وسلم: قَدْ سَأَلْتِ اللَّهَ لآجَالٍ مَضْرُوبَةٍ وَأَيَّامٍ مَعْدُودَةٍ وَأَرْزَاقٍ مَقْسُومَةٍ لَنْ يُعَجِّلَ شَيْئًا قَبْلَ حِلِّهِ أَوْ يُؤَخِّرَ شَيْئًا عَنْ حِلِّهِ وَلَوْ كُنْتِ سَأَلْتِ اللَّهَ أَنْ يُعِيذَكِ مِنْ عَذَابٍ فِي النَّارِ أَوْ عَذَابٍ فِي الْقَبْرِ كَانَ خَيْرًا وَأَفْضَلَ
Abdullah reported that Umm Habiba, the wife of Allah's Apostle (ﷺ), said: "0 Allah, enable me to derive benefit from my husband, the Messenger of Allah (ﷺ), and from my father Abu Sufyan and from my brother Mu'awiya." Allah's Apostle (ﷺ) said: "You have asked from Allah about durations of life already set, and the length of days already allotted and the sustenances the share of which has been fixed. Allah would not do anything earlier before its due time, or He would not delay anything beyond its due time. And if you were to ask Allah to provide you refuge from the torment of the HellFire, or from the torment of the grave, it would have good in store for you and better for you also."
— Sahih Muslim, Book 46, Hadith 49

In Sahih Muslim bi Sharh al-Nawawi 16/213 by Al-Nawawi, he explained that neither people's lifespans nor their provisions would be extended or reduced from what had already been decreed by Allah's knowledge in al-Lawh al-Mahfūdh (the preserved tablet, Arabic: اللوح المحفوظ).

Second Hadith

أَخْبَرَنِي أَنَسُ بْنُ مَالِكٍ، أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ: مَنْ أَحَبَّ أَنْ يُبْسَطَ لَهُ فِي رِزْقِهِ وَيُنْسَأَ لَهُ فِي أَثَرِهِ فَلْيَصِلْ رَحِمَه
Anas ibn Malik reported that Allah's Messenger (ﷺ) said: "He who likes that his sustenance should be expanded and his age may be lengthened should join the tie of kinship."
— Sahih Muslim, Book 45, Hadith 24

In Sahih Muslim bi Sharh al-Nawawi 16/114 by Al-Nawawi, he explained that the expansion in one's sustenance or one's provisions refers to its growth and its being blessed by Allah, and similarly the lengthening of one's age is by blessing one's time, guiding one to better utilization of time in what benefits one's afterlife, and protecting one from what is wasteful. It is not by increasing the number of years; rather, increasing what occupies the pre-ordained number of years, as Allah's Decree had already been determined:

وَمَا كَانَ لِنَفْسٍ أَن تَمُوتَ إِلَّا بِإِذْنِ اللَّهِ كِتَابًا مُّؤَجَّلًاَ
And it is not [possible] for one to die except by permission of Allah at a decree determined.
— Surat Al 'Imran 3:145


Extended Kalman filtering for IMU and Encoder

Question: I am trying to fuse IMU and encoder using extended Kalman sensor fusion technique. how do I fuse IMU pitch, roll with the orientation data I obtained from the encoder. Also, how do I use my position x and Y I got from the encoder which is the only position data i have because integrating IMu acceleration to obtained position is almost impossible due to errors.
I guess my state are position x, y, pitch, roll and control input are velocity of the right and left wheel.
Comment: Welcome to *Robotics* oluwayinka esan, but I'm afraid that it's not clear what you're asking. We prefer *[practical, answerable questions based on actual problems that you face](https://robotics.stackexchange.com/help/dont-ask)*, so it's a good idea to include details of what you want to understand, what you've researched, what you found & what you expected to find. Please take a look at [ask] & [about] for more information on how stack exchange works and work through the [*Robotics* question checklist](https://robotics.meta.stackexchange.com/q/1302/37) to edit your question to make it clearer
Answer: EKF sensor fusion is achieved simply by feeding data streams from different sensors to the filter. So all you need to do is setup your implementation to accept both encoder and IMU data. This is basically a matter of providing different versions of the observation model matrix $\mathbf{H}$ that converts states to sensor measurements, one for each sensor.
It's often the case that each sensor captures a different subset of the full state. In the case of a state as below:
$$
\mathbf{x} =
\begin{bmatrix}
x \\
y \\
roll \\
pitch \\
yaw
\end{bmatrix}
$$
Encoder readings reflect $[x \quad y \quad yaw]^T$, while IMU readings reflect $[roll \quad pitch \quad yaw]^T$. This is encoded in the $\mathbf{H}$ matrices by having the number of rows match the number of captured state components, the number of columns match the full state size, and the position of non-zero elements correspond to the position of the captured components in the state vector.
For example, the encoder observation model matrices $\mathbf{H}_{encoders}$ and  $\mathbf{H}_{IMU}$ would be defined as:
$$
\mathbf{H}_{encoders} =
\begin{bmatrix}
1 & 0 & 0 & 0 & 0 \\
0 & 1 & 0 & 0 & 0 \\
0 & 0 & 0 & 0 & 1 \\
\end{bmatrix}
$$
$$
\mathbf{H}_{IMU} =
\begin{bmatrix}
0 & 0 & 1 & 0 & 0 \\
0 & 0 & 0 & 1 & 0 \\
0 & 0 & 0 & 0 & 1 \\
\end{bmatrix}
$$
Notice how for the matrices above:
$$
\mathbf{H}_{encoders} \mathbf{x} =
\begin{bmatrix}
x \\
y \\
yaw
\end{bmatrix}
$$
$$
\mathbf{H}_{IMU} \mathbf{x} =
\begin{bmatrix}
roll \\
pitch \\
yaw
\end{bmatrix}
$$
All that said, I would counsel against having $(x, y)$ coordinates in a state estimated by a Kalman filter. The reason is that encoder drift error is not bounded, but grows endlessly with distance traveled — that's why we need SLAM after all. Instead I would recommend keeping track of linear and angular velocities, and integrate those over time outside of the filter to get a position estimate, if no better alternative is available. Velocity estimates can be trivially computed from encoder tick counts as below:
$$
v = \frac{c_L \alpha_L + c_R \alpha_R}{2 \Delta t}
$$
$$
\omega = \frac{c_R \alpha_R - c_L \alpha_L}{2 l \Delta t}
$$
Where $(v, \omega)$ are linear and angular velocity, $(c_L, c_R)$ the tick counts,  $(\alpha_L, \alpha_R)$ coefficients that convert tick count to traveled distance, $\Delta t$ the tick collection interval, and $l$ the lateral distance between wheels.
Comment: thanks for your quick responsexperroni .  I do not need the yaw from imu only interested in roll and pitch. how do I relate this IMU pitch, roll with the encoder x,y and theta.
Comment: It would be beneficial to get yaw from both encoders and IMU — that's half the point of sensor fusion — but if you must leave it out, you can just remove the bottom row from $H_{IMU}$:

$$
\mathbf{H}_{IMU} =
\begin{bmatrix}
0 & 0 & 1 & 0 & 0 \\
0 & 0 & 0 & 1 & 0 \\
\end{bmatrix}
$$


What are the main limitations on using the following setup to boost frames per second capturing?

Question: Suppose I have two identical cameras, a red camera and a blue camera, that can both shoot videos at 1000 frames per second. If I set them up in the following set up, using a half-silvered mirror to capture the object highlighted in green, could I not technically achieve 2000 frames per second by simply overlapping the two sets of data I get from the red and the blue cameras? (e.g., take the first frame from the red camera, the second frame from the blue camera, and so on?) In effect I could double the frames per second of any camera with correct timing with the following set-up, though I've personally never touched a camera so I don't know the limitations that cameras could impose on realizing this dream of mine. I'm not too sure if this is off-topic either, sorry if it is.
Comment: Sounds like a good idea. Triggering the cameras at the right interval might involve some custom electronics or software, and making the two images register perfectly might be tricky, but the rest would be relatively simple.
Answer: You could get twice the frame rate if (big if) the taking times of the cameras were shifted by 1/2 millisec. In other words, the frame R1 is time stamped 0.0010 sec and the frame B1 is time stamped 0.0015 sec, and so on. Sync would have to be centrally driven, and registration would have to be perfect.
That leads to the problem that the frames from camera B would be horizontally reversed WRT the frames from camera R. This could be overcome, just something to consider when trying to register the images.
Comment: @WineSoaked - Right, if the idea is to get better time resolution, interpolation wouldn't really help.
Comment: I think the biggest issue is the time sync. Cameras that operate at 1000 frames/second might have just enough jitter such that there wouldn't be a smooth blend between camera A & B footage.

Besides, at that rate, why not use interpolation software? Cheaper than a second camera, though of course you're not *actually* creating 2000 frames/second in camera.


Why don't Protestants engage in monasticism?

Question: One distinction between the vast majority of Protestant denominations and those of the Roman Catholic Church and Orthodox Church is the lack of monasteries and a monastic class. What is an overview of why Protestant denominations generally don't have monks?
Answer: Luther and Calvin
Protestant negativity toward monasticism can be traced back to the Reformers, particularly Martin Luther.  Luther was himself a monk, and after his conversion, he became progressively more opposed to the practice.  In 1537, he wrote that monastic vows "must be absolutely abolished."  He also frequently and enthusiastically attacked monasticism in his writings and sermons.
Other reformers, like John Calvin, followed him.  Calvin devotes a large portion of Book 4, Chapter 13 of his Institutes to the question.  He speaks somewhat favorably of Augustine's depictions of early monasticism, but he widely criticizes the 16th-century version, saying that "no order of men is more polluted by all sorts of foul vices" (4.13.15) and using words like "abominable" and "pestilential" to describe monasticism and its errors (4.13.12).
Doctrinal Criticisms
A concise criticism of monasticism can be found in the Augsburg Confession, the primary confession of the Lutherans.  Article 27, On Monastic Vows, admits that the monasteries were once "profitable to the church," but lists a number of evils that had been introduced by Luther's time, such as:

Propensity toward ensnaring the weak and ignorant (5-8)
Elevation of the monastic vows to being meritorious in themselves (11)
Elevation of monasticism above other vocations (13)
Rejection of the command to marry (18-21)
Holding people to vows perpetually, without recourse, especially those entered into too early (27-33)

Thus, the confession concludes:

So many wicked opinions are inherent in the vows, namely, that they justify, that they constitute Christian perfection, that they keep the counsels and commandments, that they have works of supererogation. All these things, since they are false and empty, make vows null and void.

Calvin and Luther's objections to the practice follow along these same lines, and also include denunciations of the "idleness" of monastics (Calvin, 4.13.10).  Given these objections, and the enthusiastic criticism of the practice by these and other early Protestant leaders, it's not surprising that monasticism has not generally existed among Protestants.
Early Reaction
An example of early Protestant reaction against suspected monasticism can be found in a 1641 Puritan pamphlet entitled The Arminian Nunnery, written in relation to a small religious community called Little Gidding. The author's initial concerns include women "watching and praying all night," their "canonical hours," and the decorations of their chapel, all of which "strongly savour of Superstition and Popery."
These concerns were not assuaged by the fact that two of the women, thirty and thirty-two years of age, were virgins who had given themselves to fasting and prayer.  The author attacks this as "a contemplative idle life" that insinuates that other callings are not service to God.  He admits the point that the women "had made no Vows," but finds many vestiges of Catholicism worthy of criticism.
The Arminian Nunnery thus mirrors several of the criticisms mentioned above, particularly those of rejection of marriage, the elevation of monasticism above other professions, the concern over vows, and the idleness of monastics.
Modern Day
Some modern Protestant "monastic" communities exist, among Anglicans and more generally within Protestantism.  Notably, other than in the most conservative Anglican orders,  even these tend to avoid at least some of the issues raised in Augsburg, by relaxing or not requiring vows of celibacy, poverty, or obedience.
Answer: Depending upon your usage of the word "monasticism" may render your question void. There are many Protestant groups who choose to 1) Live communally, 2) Bind themselves by communal rules, 3) Dedicate their community unto the service of the Lord and the help of the poor.
Consider this article: https://en.wikipedia.org/wiki/New_Monasticism#Protestant_forms_of_New_Monasticism
Comment: When I say monasticism I mean any form of practice that requires the taking of vows and ascetic lifestyles.
Answer: The last thing any one claiming to be Christian, be they Protestant, Catholic or whatever, is separate themselves from society for some idea that doing so is God ordained or even God pleasing. The command is to " Go into the world..." Mt.28:19,20, not cloister oneself on some mountain top.
When we read " Come out and be separate,"2 Cor.6:14-18, the context does not command us to pretend we are so pious as to look down our nose at the un-believers. This is a major fault of going into hiding on some mountain top. Besides that, if a psycho-evaluation were done on such who do these things, piety would not be found to be the justifying cause.
Denominations like to put rules of their own on their own which Christ condemns as in Mt.15.
See Col.2:20 to close.
Comment: A good point on the great commission. Two issues though: 1) if you provided a source or two that says the same thing we could be assured that it is more than your opinion, and 2) I don't think monasticism implies that they believe they are more pious than everyone else; your answer would be better without that kind of tone.


How do modern historians evaluate Sherman's "Total War"?

Question: A major element of Sherman's march to the sea was his army's burning southern farms and cities. The rationale for what Sherman called "Total War," approved by Grant and Lincoln, was that it would cause rebel troops to desert their units to check on family and home, and "break" the spirit of the Confederacy. Like the rationale for the atomic bomb, it was argued that the tactic would shorten the war and ultimately save lives? Do today's historians defend Sherman's tactic?  Wouldn't it today be a war crime and a crime against humanity notwithstaning?  An acceptable answer will describe what today's historians are saying about Sherman's march in light of 21st century attitudes about war. I DO NOT want opinion-based answers!
Comment: Such things are rarely *strictly necessary*, but rather more commonly justified on the basis of relative *costs sand benefits*. In any case, brutality was a normal fact of life in pre-Geneva armed conflicts. It hardly rises to the level of *crime against humanity* though.
Comment: Burning Atlanta, which was a crucial railroad hub linking Alabama and the Carolinas, had a tangible benefit in that it destroyed some of the infrastructure that the Confederacy used to support itself. The social consequences (reduced food supply, masses of slaves escaping) were real also and in the Union's interest. Surely no one doubts the effectiveness of these tactics, only their morals. I, for one, commend Sherman for doing the dirty work (that I could not personally do) that really unraveled Georgia's slave economy and brought the war to a Union victory sooner.
Comment: I doubt he was, y'know, burning homes while people were still in them.  That would have been considered a bit much for most of history.  I believe infrastructure is still a valid target - supplies and supply lines are a great way to take armies down several pegs.
Comment: @oldcat per my ancestor's diary, while serving in Cobb's Cavalry, in Johnson's Army, Sherman caused a great deal of worry and desertions. It broke the will of the CSA forces to win and put them in survival mode.
Comment: @BruceJames - as Sem. says. The main element that caused distress to the average farmer was the foraging. Imagine a farmstead having a visit from 60000 hungry mouths.  Even though they usually left some food for the farmers, suddenly all the reserves needed to feed the family well and to sell for other needs are gone.  The need to get the men back was dire, and naturally many soldiers had to respond.
Comment: My question asks what today's historians are saying about Sherman's march in light of 21st century attitudes about war. I DO NOT want opinion-based answers!
Comment: Well, technically speaking if a historian judges Sherman action in the light of 21st century morals/laws, then she/he is rather unprofessional.
Comment: -2 with two answers and no complaints in the comments?
Comment: Hard for me to vote up the mistaken premise that town burning was the dominant part of his strategy.
Comment: That says nothing about burning down towns per se. The rest of Sherman's actions would cause that understandable reaction.
Comment: I tried to add this source: http://www.ohiohistorycentral.org/w/Sherman's_March_to_the_Sea?rec=551#section_2. I'm on vacation using a Blackberry and can't tell if the source was inserted at "break".
Answer: Sherman burned parts of Atlanta - the military stores area and destroyed its railroads to prevent it being used as a base against him.  As the city was defended by an army, this is not improper by the rules of war.  He allowed civilians to leave to the South, or be carried by rail North.  Note that large parts of the city were burned by the retreating Southern Armies during the retreat, and the Union did not advance until the next day.
Note that uncontrolled fires as a Southern Army retreated before the US moved in also happened by Lee in Richmond.
During the march through Georgia, few structures were burned. Any government stores and railroads. I believe plantation cotton gins were usually burned, as this supported the government through the blockade.  I can't recall a town burned.
The March through South Carolina was much more free with the burning along the march, although the usual Civil War standard was that empty buildings were more likely to be looted or torched than if someone stayed home to watch the place.
The Burning of Colombia is the other incident and there again we have a similar situation to Atlanta - Wade Hampton's Cavalry burned some stores on the way out, there was a windstorm that blew up the flames, and deserters from both sides seem to have gotten into some liquor and possibly set some more fires too.  After a while, US troops secured the city and helped fight the fires and save some buildings.  While some say Sherman burned the town, knowing his character if he had ordered it burnt, he would have done so and crowed about it.  So I believe his story that it was an accidental act, with a bit of his blaming Wade Hampton for political effect.
When the army left South Carolina, they were back on good behavior for the rest of the campaign.
So, basically, I don't think that the idea that Sherman burnt towns during his marches stands scrutiny at all, much less as a tactic.  His tactic was to move freely, subsist for food and forage on the locals (allowable by the laws of war), and destroy government property.  The fact that he could not be stopped punctured the morale of the CSA.
Answer: As far as modern international law is concerned, things get interestingly complicated.
There is in fact a Geneva Convention protocol that was specifically written in 1977 to outlaw "scorched earth" strategies like (the popular view of) Sherman's March. However, the United States has not ratified that protocol. So current US policy seems to be that such actions are within bounds. Thus any southerner who wants to argue about modern international law being violated in Sherman's march probably needs to have a talk with their congressman first.
The effect of the march, if not decisive, was still a huge blow. Farms and industry in a wide swath of the state were destroyed, and railroads were ripped up to prevent nearly all movement of goods and men to support Lee's army. Since the Union already had the Confederate ports blockaded, the above two actions not only knocked Georgia completely out of the war, but also cut off any states west of Georgia. Effectively, thanks to Sherman's march, the Confederacy was now down to just the Carolinas and Virginia. (In the spring, he proceeded up through the Carolinas).
Comment: Can you answer the question by discussing how 21st century historians view Sherman in light of the new ethics of warfare?
Comment: @BruceJames - Not really, I can't. There is no universal agreement on what the "new ethics of warfare" are, and by the official US policy, "scorched earth" tactics are not off-limits. Oldcat's answer makes the argument that Sherman didn't employ them anyway, but even if he had, that's still acceptable warfare by US doctrine.
Answer: Sherman's March to the Sea (and "total war") was a logical extension of the so-called Anaconda Plan for beating the Confederacy. As the Anaconda Plan itself was "rehabilitated" by modern historians, so was Sherman's extension of it.
The original Anaconda Plan was seen as a "backup" plan to the main plan of capturing Richmond, and ultimately Virginia, one of the richest, most populous, and best-defended states in the Confederacy. The idea was to "break the enemy's strength."
The purpose of the Anaconda Plan was to "hit the enemy where he is weak," along the Mississippi River, where the South concentrated fewer, lower quality troops, and had no gunboats to speak of. The plan was to capture those parts of Tennessee and Mississippi, along the Mississippi River. If successful, the Union would occupy two out of eleven Confederate states, and isolate three more (Texas, Arkansas, and Louisiana), effectively cutting the main Confederacy in half.
The remaining six Confederate states were Virginia, North and South Carolina, Georgia, Florida, and Alabama. After Sherman captured Atlanta, he devised a daring plan to march east to the Savannah River (the border between Georgia and South Carolina), and downriver to Savannah itself. The idea was to "lop off" three more Confederate states (Georgia, Florida, and Alabama) from Virginia and the Carolinas. This was the infamous "March to the Sea."
It was a daring plan that required a form of "total war." 1) Because his supply lines back to the Mississippi River was menaced by Hood's defeated forces in Tennessee, Sherman had to "let them go" and live off the land (as Grant did in brief campaign against Jackson, Mississippi prior to Vicksburg), which is allowed by the rules of war. 2) As Sherman marched through Georgia, he systematically freed the slaves in his path, in line with the Emancipation Proclamation, which Southerners considered a form of "terrorism." (Many slaves marched behind Sherman's army, adding to the devastation.) 3) Sherman systematically destroyed Georgia's manufacturing capacity, making a point of removing and twisting rails from southern railroads, as far as his troops could march, to hinder the South's recovery.
Sherman did make a point of sparing civilians that were judged totally "innocent," but anyone who helped the South in any way (e.g. manufacturing or shipping supplies) was despoiled.
This probably shortened the war because the weak remaining Southern forces couldn't counteract Sherman. It might have lengthened the war if Hood had returned from Tennessee and caught Sherman in the campaign of mutual destruction that he began at Atlanta. But by the time of Appomatix, the South had lost Virginia to Grant, and South Carolina to Sherman, meaning that essentially, only North Carolina was left to Confederacy, even if Lee had managed to escape.