halacha - Can I say the prayers of Birkot HaShachar and Tikkun Chatzot after Chatzot (Midnight), even if I don't sleep yet?

Can I say the prayers of Birkot HaShachar and Tikkun Chatzot after Chatzot (Midnight), even if I had not gone to sleep yet? How should I proceed with the Kriat Shema Al Hamitá if I will remain awake after midnight?

halacha - Women using tampons before marriage

Is there any issue with women using tampons before marriage? I would appreciate sourced answers discussing this either saying it's ok or not ok.

My thought is that since the use of a tampon requires inserting something through/past the hymen, the hymen could be stretched (or removed entirely, so to speak) and perhaps there as an issue with doing so before marriage. The only possible issues that I know of are:

1. She may become a mukat eitz which affect the value of her kesuba


2. There being no sign of the woman's virginity, which might have its own halachic implications.

(Even though the question could be boiled down to these 2 points in principle, I'm looking for a specific discussion about the use of tampons.)

minhag - What is the basis for the custom to stand or sit by Vayivarech Dovid?

What is the basis for the customs to either stand or to sit for Vayivarech Dovid?

Proof of one side or question on the other, talmud

A boy asked me today:

How does the gemora choose if to use something as a proof to one side or as a question on the other?

The example he brought was:

Of a question: Kiddushin 63b

תנן רצו אחד נותן גט ואחד כונס תיובתא דרב אמר לך רב שאני התם דכיון דאיכא אחר בהדיה אירתותי מירתת

Of a proof: Ibid

תניא כוותיה דרב אסי

Please help me find the answer

Decomposition of a signal to slow and fast components

I am currently recording biological responses which are triggered by different events. The figure below shows the original signal (black) and the occurrence of input events (colored dots). There is typically few seconds of a delay in response to different events, and only some of the events generate a response. These phasic responses occur simultaneously with slowly changing fluctuations (tonic component), which are also biologically important (rather than measurement noise). So it is important to come up with a model that can decompose these signals with few constraints that are biologically plausible: signal = tonic + phasic.

In this system, phasic responses can be well modeled with typical linear system characterization methods based on impulse response function. Also note that, these phasic responses are always positive, that is biologically speaking there is no inhibition. For this reason, if there were no slow fluctuations in the recordings, the recorded signal would never go below zero, except for measurement noise.

What is more problematic is to account for baseline shifts (the tonic component). I would like to come up with a method that can be used to model the tonic component and phasic responses simultaneously based on the following assumptions:

1/ tonic component changes slowly. 2/ phasic component changes fast. 3/ phasic component is always positive, that is: signal - tonic should contain as negative values as possible.

The problem boils down to extracting slow and fast components of a signal. I have already 4 methods in mind, and I would like to see what you think is best suited or come up with an alternative.

The first thing that comes to mind is to low-pass filter the signal to obtain an estimation of the tonic component (see blue line). The main problem here is that the estimated tonic component violates the above-mentionned constraint #3. According to this assumption, no points in the recorded signal should be below the tonic component. Instead the tonic component should pass through all the data points where the phasic response is close to zero (schematically shown with the red curve in the figure below).

Another approach would be to make an assumption about the duration of phasic response. In doing so, one could use recorded samples that are at least as far as the duration of phasic response as keypoints and interpolate using cubic splines for the remaining data points. This is actually how I have drawn the red curve, but I feel like the interpolation of data points between the key points is problematic, because there are not many key points.

A third approach would be to work on first or second derivative space and characterize the system in this domain, as it is supposed to be less sensitive to low-variations.

A fourth approach consists of extracting slow components. One could use rely more on the history, when the signal is changing fast, and update the history with new data when the signal changes slowly. I am not sure though how to mathematically tackle this one.

Answer

Your problem is pervasive in signal and image processing: being able to separate a trend (with some assumptions) from a signal (with some other assumptions) and potentially additional noise. This is an instance of (semi-)informed source separation: a sine from a drift, a texture from a cartoon image, a biological information from instrumental artifacts, etc, that requires a more involved modeling and optimization framework.

Your choices are related to fundamental questions related to the model you can build based on physical and mathematical assumptions, aside from the algorithmic tools you can program.

1) Low-pass filtering: Standard low-pass filtering is linear and time-invariant. Linearity is very consistent with "signal = tonic + phasic". But phasic could be (on theory) negative, as "$2+(-1) = 1$". As your graphic does not include x/y scales, "above" is clear, but i am not sure of what you can model with "no points in the recorded signal should be below the tonic component", since additional noise can be fluctuating too. But positivity is a property which can be taken into account, with some non-linearity caveats.

2) Duration: "that are at least as far as the duration of phasic response" : your assumption seems to me to related to a time-delay, yet i cannot interpret it precisely so far.

3) High-order derivatives: "A third approach would be to work on first or second derivative space and characterize the system in this domain, as it is supposed to be less sensitive to low-variations" Indeed, slow variations are expected to be with limited derivatives. This could result in a "sparsity" prior assumption.

4) Causality: "rely more on the history" there is some causality assumption behind that. This too is a tough stuff.

All your four approaches seem consistent to me, and may help you ponder and state your assumptions. They are otherwise termed as “morphological component analysis (MCA)”, “geometric separation” or “clustered sparsity”, adding positivity. Such topics are addressed for instance in "Blind source separation of positive and partially correlated data" http://dx.doi.org/10.1016/j.sigpro.2005.03.006.

You may find additional history for instance in the introduction of (mong other papers "Chromatogram baseline estimation and denoising using sparsity (BEADS)" http://dx.doi.org/10.1016/j.chemolab.2014.09.014 which also deals with positivity, low-pass-filtering and derivative sparisty, yet the causal approach is not considered. So you can specify your model in more precise terms (you did do talk about the noise yet), you may find some tracks to solve your questions

Why does a substance with an endothermic heat of solution dissolve?

How does a substance with an endothermic heat of solution dissolve?

Answer

Dissolution happens in three steps.

Solute-solute attractions must be broken (consumes energy, endotherm), solvent-solvent attractions must be broken (also endotherm), and finally solute-solvent attractions form. This results in a lower energy state and is exotherm.

Dissolution will be endotherm if it takes more energy to break the mentioned attractions, than is released in the last step. You are asking then, why is this reaction spontaneous? In other words, why does it occur? To find out we need chemical thermodynamics. $$\Delta G=\Delta H - T\Delta S$$

$\Delta G$ = Change in Gibb's free energy for a reaction. $\Delta G<0$ = reaction is spontaneous. Otherwise it is NOT spontaneous (ie. will not occur on its own).

$\Delta H$ = Change in enthalpy. $\Delta H <0$ = reaction is exotherm. If larger than 0, the reaction is endotherm. Already now we can see that an endotherm reaction will make $\Delta G$ for the reaction more positive, and thus the reaction is less likely to be spontaneous.

$T$ = temperature in K.

$\Delta S$ = Change in entropy. $\Delta S > 0$ = reaction leads to a state of higher entropy. Entropy describes disorder in a system. Dissolution of a solute in a solvent will always lead to a state of higher disorder, since we go from having all the solute concentrated in a cluster (more ordered) to being spread evenly throughout the solution (more disordered). We can see from the equation that if the reaction leads to higher entropy, then higher temperatures increase likeliness of $\Delta G < 0$, and the reaction will be spontaneous. On the other hand, if we're going to a more ordered state, lower temperatures increase likelihood for a spontaneous reaction.

So how do we apply this to dissolution? You know that the dissolution reaction is endotherm. That means that $\Delta H > 0$ for this particular reaction. Yet we know that the reaction is spontaneous, since you report that it does indeed occur! This means $\Delta G < 0$. The only way to make that happen is for $\Delta S$ to be positive. So the reaction must go to a more disordered state. Since it's a dissolution, we know that it does. The solute goes from being concentrated in a cluster (ordered) to being spread throughout the solvent (disordered). Pay attention to where temperature is in the equation. It is quite easy to see, that for a dissolution reaction where $\Delta S > 0$, you can increase the chance of the reaction being spontaneous by increasing temperature!

Bottom line Your dissolution reaction is endotherm, but because dissolution reactions lead to states of higher entropy, your particular reaction is spontaneous (it occurs) at your specific temperature nonetheless! If it wasn't, heating the system could make it so.

frequency response - How to design a variable slope highpass filter

I want to design some specific slope highpass filter to enhance speech; just like $1$ dB/octave, $2$ dB/octave and more. Is there a method to calculate the coefficients by specific slope?

halacha - Can a mother undress in front of her daughter?

Can a married woman with children undress in front of her daughter to try on clothes assuming she would be in undergarments?

grammar - Why is 「の」 used in 何十もの？

I was studying the words 何十/何百/何千, and I often see the particles「も」and「の」after.

For example,

彼は何十冊もの日本に関する本を持っている。

Or,

高速道路は何千もの車で渋滞した。

The「も」I think is used to emphasize that there's a large quantity, but what is the purpose of 「の」?

I also found some sentences with a similar pattern, but 「の」 is not used.

Example:

彼は何十冊も英語の本を持っている

Why is that the case?

Answer

It is all about grammar and nothing else.

「(Number) + も」 functions adverbially to modify a verb.

「(Number) + も + の」 functions adjectivally to modify a noun.

Let us look at your example sentences:

「彼{かれ}は何十冊{なんじゅっさつ}もの日本{にほん}に関{かん}する本{ほん}を持{も}っている。」

「何十冊もの」 modifies the noun 「本」.

「高速道路{こうそくどうろ}は何千{なんぜん}もの車{くるま}で渋滞{じゅうたい}した。」

「何千もの」 modifies the noun 「車」.

「彼は何十冊も英語{えいご}の本を持っている。」

In this sentence, 「何十冊も」 modifies the verb phrase 「持っている」.

What would happen if you inserted a 「の」 following the 「も」, then?

In the new sentence:

「彼は何十冊もの英語の本を持っている。」

「何十冊もの」 will simply modify the noun 「本」 instead. The meaning of the sentence will virtually stays the same. The new sentence will just have a different grammatical structure.

EDIT: I did not mention this, but this usage of 「も/もの」 always indicates that the speaker thinks the quantity in question is rather large as the questioner stated.

What is the bond angle of water?

I have been trying to find out the bond angle of $\ce{H2O}$, but every site I visit has a different answer.

So far, I have found the following angles listed:

• Site 1: 104.4º


• Site 2: 107.5º OR 104.5º, depending on where you are in the article.


• Site 3: 104.5º

Answer

In your comment, you say you are interested in "liquid water".

The values in your self-answer are for gas phase water, and the second source is citing the first source, so it is really just one source. The value is determined from gas phase rotation spectroscopy.

For liquid water, the value is not as precisely known:

105.5° (calculated) and 106° (experimental) as reported in Structural, electronic, and bonding properties of liquid water from first principles J. Chem. Phys. 111, 3572.

grammar - Meaning of 「生きるにしても死ぬにしても」

In the video game Mother 3, there is a group of beings called the Magypsy, who are rumored to be very old. While talking to humans, one of them says the following:

人間なんて生きるにしても死ぬにしても精々たった100年。

Note: The game's text is in almost all kana; kanji are mine. The original text is, 「にんげんなんて　いきるにしても　しぬにしても　せいぜい　たった１００ねん。」

While my guess is that this means something along the lines of, "A human life, from beginning to end, lasts at best a hundred years", I'm wondering about the exact meaning of the 「～にしても」construction. Jisho translates 「にしても」as "even if", but I can't find a way to phrase this sentence like that - "... even if they live, even if they die..." doesn't seem to make a lot of sense.

Is this some grammatical form I'm not familiar with, or is it perhaps my interpretation of the sentence that's the problem?

Answer

The sense of both verbs is active rather than passive sense. In that case "live or die as they might" could be a closer interpretation.

It may refer to the fact that humans barely live longer than a hundred years despite their best efforts, and nothing that they do lasts more than a century (thus the "die as they might" part).

As for 「～にしても」, it might make more sense if you interpreted it as "even if one (actively does an action)", rather than the simplistic "even if". It pertains to the consideration of the performance of some action, rather than referring to the action happening.

For considering the passive happening of some action, 「～としても」would be your ticket. For example, 「雨が降るとしても、天気が晴れるとしても、俺は傘を持っているから問題ない。」　would mean "Whether it may rain or it may be sunny, I've got my umbrella so there's no problem."

If we were to substitute 「～にしても」for 「～としても」, it would anthropomorphize the weather by giving it some sort of "will", as in "Whether the rain chooses to fall, or the weather decides to be sunny..."

purim torah in jest - Graciously accepting gifts

I delivered Shalach Manos today to a number of people. Much to my dismay, everyone accepted them graciously and gratefully, and not a single person expressed how disappointed they were with my gifts. It seems clear to me that you should hate every gift you receive, as the verse says (Mishlei 15:27):

שונא מתנות יחיה

One who hates gifts will live

and דברים שבלב אינם דברים - thoughts that are not expressed are not considered (Kiddushin 50b), so this hatred should be expressed and declared.

Is there any explanation for this practice?

---

Answer

On Purim, we have 2 separate rules which negate the recommendation of Mishlei:

1. 
   

   Vnahafoch hu -- the classic inversion rule, so we do the opposite. Now, you might think "how can we do the opposite of EVERYTHIING? Are we supposed to kill, eat treif etc, because it is opposite day? No -- the text tells us precisely when to invert:

   
   


2. 
   

   The people "kiymu v'kiblu" -- they fulfilled the obligation by receiving (the gifts).

   
   

hashkafah philosophy - Resources for learning about the foundations of Judaism

I recently met an intelligent Soviet immigrant interested in learning more about Judaism. He would like to start with understanding the basics. Such as:

How do we understand G-d?

What are the foundations of Judaism?

What is the purpose of mitzvos?

While I'm sure putting these questions out on j-se will elicit a number of excellent answers, a better option for him would be books or audio/video shiurim that have put effort into structuring the information in a palatable way.

Any ideas on specific materials or areas to look?

modulation - Why is a precoder necessary for DQPSK and what does it accomplish?

I've implemented a soft-decoder for DQPSK using the wonderful answers I received here:

How to soft decode DQPSK?

To get the soft-decoder working properly I needed to precode the data I was sending out. I implemented the precoder mentioned in this paper:

$I_k=\overline{u_k \oplus v_k}*(u_k \oplus I_{k-1})+(u_k \oplus v_k)*(v_k \oplus Q_{k-1})$ $Q_k=\overline{u_k \oplus v_k}*(v_k \oplus Q_{k-1})+(u_k \oplus v_k)*(u_k \oplus I_{k-1})$

I'd like to know why this precoder is necessary -- what does that complicated expression of XORs actually accomplish?

Here's a table showing what the equation yields. If "to_encode" is 00, the to_send symbol is the same as the previous ("prev") symbol. If the "to_encode" is 11, the to_send symbol is the previous symbol xor 11. What is the meaning in other cases?

to_encode prev  to send

[ 0 0 ] [ 0 0 ] [ 0 0 ]
[ 0 1 ] [ 0 0 ] [ 1 0 ]
[ 1 0 ] [ 0 0 ] [ 0 1 ]
[ 1 1 ] [ 0 0 ] [ 1 1 ]
[ 0 0 ] [ 0 1 ] [ 0 1 ]
[ 0 1 ] [ 0 1 ] [ 0 0 ]
[ 1 0 ] [ 0 1 ] [ 1 1 ]
[ 1 1 ] [ 0 1 ] [ 1 0 ]
[ 0 0 ] [ 1 0 ] [ 1 0 ]
[ 0 1 ] [ 1 0 ] [ 1 1 ]

[ 1 0 ] [ 1 0 ] [ 0 0 ]
[ 1 1 ] [ 1 0 ] [ 0 1 ]
[ 0 0 ] [ 1 1 ] [ 1 1 ]
[ 0 1 ] [ 1 1 ] [ 0 1 ]
[ 1 0 ] [ 1 1 ] [ 1 0 ]
[ 1 1 ] [ 1 1 ] [ 0 0 ]

Answer

Regard the dibits as Gray code representations of the integers $0,1,2,3$, more specifically,

$$[0, 0] \leftrightarrow 0, ~~ [0, 1] \leftrightarrow 1, ~~ [1, 1] \leftrightarrow 2, ~~ [1, 0] \leftrightarrow 3.$$

Then, the precoding scheme is nothing but differential encoding for QPSK with

to send = prev - to_encode modulo $4$.

For example the line [ 1 0 ] [ 0 1 ] [ 1 1 ] in the question says that to encode $3 = $ [1 0] when the previous symbol was $1 = $ [0 1], we send $1-3 = -2 \equiv 2 \bmod 4$ where $2 =$ [1 1].
As stated in the answers and comments on the previous question,

Differential encoding for QPSK is not the same as differential (binary) encoding of the I and Q bit streams separately.

So the precoding scheme is just differential encoding for QPSK. As to why it is included in the system, it must be that the channel characteristics and system requirements are such that coherent detection of the signal is not thought to be feasible, and so the receiver is being implemented is a differentially coherent detector for DQPSK (differentially encoded QPSK). Note that coherent detection requires that the receiver phase lock loop acquire (and track) the incoming carrier in both frequency and phase (including resolution of the four-fold phase ambiguity) while for differentially coherent detection, frequency acquisition and tracking suffices, so that the receiver is simpler and more robust, though of course for a given SNR, the BER of the differentially coherent receiver is higher than the BER of the coherent receiver.

history - Can a convert be a prophet?

I don't think there were any gerim amongst the nevi'im, but would it have been possible?

Answer

There is a tradition, recorded in various sources, that the prophet Ovadiah was an Edomite convert. This tradition is born of the fact that there is nothing within his short (one chapter) oracle that concerns Judeans or Israelites; the entire thing is an oracle about the Edomites instead.

Sources:

• Sanhedrin 39b;


• Tanchuma, Tazria 8.

See also Rashi and Radak on Ovadiah 1:1.

word choice - Multiple older siblings

I have 2 older sisters. When talking to other people about them, do i refer to them both as 姉 or do i refer to the younger one as 姉 and the older one as 姉上?

Thanks!

P.S I thought this question would have already been asked, but couldn't find any. Even Google didn't have much on it.

Answer

姉上【あねうえ】 is a very old-fashioned honorific word for 姉. You would hear someone respectfully addressing their older sister with 姉上 mostly in samurai dramas. But you can never use it to distinguish your two sisters.

To distinguish your two older sisters, you can use 上【うえ】の姉【あね】 (older) and 下【した】の姉【あね】 (younger). If you had three older sisters, you can say 一番上の姉, 真ん中の姉/2番目の姉, 一番下の姉/3番目の姉.

orbitals - How do I visualize an atom?

I have searched and searched, oh how I have searched.

I am looking for a 3-dimensional visualization of a whole atom, one that that includes all the orbital geometry. A proper "layered" view of the orbitals.

What I am not looking for:

• Individual orbital geometry.



• A "picture" of an atom (i.e. what looks like television static to me).


• Little spherical balls.


• Dot-and-cross diagrams.

I think I understand that this cannot be expressed in just one picture alone, so I look forward to discovering software, or a collection of pictures, that could help express this. Maybe something similar to an exploded view, for atoms?

Please. The universe is weird and I want to see.

Answer

I have searched and searched, oh how I have searched.

Do you know what I always tell my mom when she asks me to find something in the Internet she was not able to find herself? I ask her: "Are you sure that the thing you are looking for even exists?"

I am looking for a 3 dimensional visualization of a whole (moderately complex, hydrogen is just a ball) atom that includes 3 dimensional orbital geometry.

1. Hydrogen atom is not "just a ball".


2. There is no orbitals. In short, except for one-electron systems (such as the hydrogen atom) orbital description is just an approximate model of the reality.


3. Usually when one asks to visualize a physical object, he/she wants to visualize its physical "boundaries" with respect to some medium. The notion of such "boundary" simply looses its meaning in the microscopic world: atoms do not have "boundaries" like macroscopic objects do.

Please. The universe is weird and I want to see.

Sorry, but you can not do this: you can not visualize some things in the Universe, you can not even imagine them. Our visualization & imagination abilities (unlike an atom) has some boundaries, because they are based ultimately on our senses which in turn has their boundaries.

As Paul Dirac said on that matter:

[…] the main object of physical science is not the provision of pictures, but is the formulation of laws governing phenomena and the application of these laws to the discovery of new phenomena. If a picture exists, so much the better; but whether a picture exists or not is a matter of only secondary importance. In the case of atomic phenomena no picture can be expected to exist in the usual sense of the word 'picture', by which is meant a model functioning essentially on classical lines. One may, however, extend the meaning of the word 'picture' to include any way of looking at the fundamental laws which makes their self-consistency obvious. With this extension, one may gradually acquire a picture of atomic phenomena by becoming familiar with the laws of the quantum theory.

halacha - Israel News internet postings originated on Shabbos

On Friday afternoon in the U.S., am I permitted to click on a news site from Israel which I presume is maintained by Jews in Israel and continually updated by them, even on Shabbat (e.g., Jerusalem Post). Since it is already Shabbos for the Israel-based employees who are updating their website, am I inappropriately receiving benefit from a Jew’s work performed on Shabbos and thereby prohibited by “Maaseh Shabbos", benefitting from work that was done by a Jew on Shabbos if I read the articles which are newly posted after it is Shabbos in Israel? If this prohibition were to apply, then I can never look at those postings which originated on Shabbos.

grammar - たくさんの本を読んで versus 本をたくさん読んで

• 
  

  What is the difference between たくさんの本を読んで and 本をたくさん読んで?

  
  



• 
  

  Is たくさん an adverb in this case?

  
  

Another example, 多くの食料が輸入される and 食料が多く輸入される where 多く is an adverb here.

Answer

「たくさんの本を読んで」 and 「本をたくさん読んで」 have the same meaning which is "read many books then...", "because of reading many books, ..." or something like that, I think.

たくさん in 「たくさんの本を読んで」 is a noun.

たくさん in 「本をたくさん読んで」 is a noun originally, but it's working as an adverb here.

Which たくさん should be used in a sentence depends on the context or the other words in the sentence.

　

One of the purposes of using adverb-type たくさん is not to use too many の in a sentence. For example,

おばあちゃんの[家]{いえ}の[近所]{きんじょ}の[図書館]{としょかん}のたくさんの[本]{ほん}を[読]{よ}んで、[僕]{ぼく}は[天気]{てんき}と[気象]{きしょう}について[詳]{くわ}しくなった。

this sentence contains five のs and it sounds too many. In some situations, using many のs sounds childish or having a poorer writing/speaking skill. There is a Japanese picture book called 『これはのみのぴこ』 in which の is used again and again, and the sentence seems to keep growing forever. (This is the cover and last page of the book, if you are interested in it.) It's fun and I like it. But the way of using の like the book is not practical for most adults.

Using adverb-type たくさん helps polish the sentence.

おばあちゃんの家の近所の図書館の本をたくさん読んで、僕は天気と気象について詳しくなった。

And dividing a sequence of の is commonly preferred. The sentence above can be modified like this.

おばあちゃんの家の近所にある図書館の本をたくさん読んで、僕は天気と気象について詳しくなった。

This sentence looks better than the five-の version of it.

If there is no other の before 本を, 「たくさんの本を読んで」 is totally fine.

　

I think that 「多くの食料が輸入される」 and 「食料が多く輸入される」 also have the same meaning which is "Many foods are imported." or something like that.

In both cases of たくさん and 多く, it's common for Japanese people to select noun one or adverb one in order to make the meaning of a sentence clearer and to make a sentence sophisticated. I guess that the word balance in a sentence or sentences is the key. For example,

多くの食料が安全に輸入される。

in this case, 輸入される already has a modifier 安全に before it. So, if a speaker says 「食料が多く安全に輸入される。」, the listener might feel it's a little congested before 輸入される while there is no word before 食料が, and her/his understanding process might not go smoothly. 「多くの食料が安全に輸入される。」 sounds more balanced and natural.

家畜用の食料が多く輸入される。

In this case, 食料 has a modifier 家畜用の before it. So, putting 多く before 輸入される is a better idea than 「多くの家畜用の食料が輸入される。」, I think. 「多くの家畜用の食料が輸入される。」 is not wrong, though.

If I combine the two sentences above to form a new sentence, I would say

多くの家畜用の食料は、安全に輸入される。

This order of modifiers sounds natural to me. (By the way, I'm Japanese.)

　

Please note that there are other reasons people use noun-type one or adverb-type one. I can't explain all of them, sorry. I hope this answer is helpful.

kinetics - Multiplication of the reaction and Equilibrium constant

$$\begin{align}\ce{2A + 2B &-> 2C }\\ \ce{A + B &-> C}\end{align}$$

Why does the equilibrium constant change?

And why the rate of the first reaction square the rate of the second? I understand it mathematically, but logically and scientifically I can't understand it at all.

tanach - Is Rashi really pshat?

If Rashi on Tanach is a purely pshat oriented commentary, as professed several times, why do many of his comments originate from midrashim that most other "pshat" meforshim dismiss as "derech drash"? [For examples, see Ramban (Gen. 21:17), Ibn Ezra (Gen. 32:9), Radak (Gen. 21:7), Ralbag (Josh. 24:32), and Abarbanel (Gen. 23; first question).]

Did Rashi have a different definition of pshat and drash?

Answer

In view of the answers given, I would like to approach the answer to this question as did R' Herczeg (who translated for the Artscroll Rashi series) in his book "Patterns in Rashi", in which he takes an approach similar to Josh's answer.

To Rashi, the line between drash and pshat is vague. He viewed pshat as the simple meaning of the pasuk, but only insomuch as it adheres to it grammatically and contextually. Whenever Rashi could not find a pshat that fit with the grammar of the pasuk, he looked to Chazal's collection of aggados. He felt that if an explanation of chazal fits with the grammar and context of the pasuk, it falls into the category of pshat. You might say he felt that it was "pshat enough", even though it might not be the simplest explanation. Many times we will find Rashi bring the popular pshat explanation, then bring a medrash from chazal. This is because he saw some sort of flaw or redundancy in the pasuk that needed to be explained. To Rashi, that is included in pshat.

Besides for grammar, several other things caused Rashi to side with chazal, including juxtaposition of topics, unusually spelled words, and seemingly unnecessary information given by the Torah. Even though these topics are generally considered, even by Rashi, as needing only to be addressed with drash, and according to pshat they may be ignored, still in certain instances Rashi felt that for some specific reason they interfered with pshat on that occasion, and therefore he may, in such instances, use chazal's aggados to clear things up. He considered this to be consistent with the pshat approach.

Other later rishonim disagreed with Rashi. Meforshim like Ramban, Ibn Ezra, and Rashbam viewed pshat and drash as distinct categories, reserving the simplest explanation of the pasuk and that alone for pshat. What about the grammatical inconsistensies in the pesukim? We will have to explain them away continuing to use pshat. There is no need for the more fantastical explanations of chazal. Those are drash; they have another place, a separate place, in the interpretation of the pasuk.

This is what is meant by the famous argument Rashbam records that he had with Rashi. Rashbam felt that even the irregularities in the text can be addressed with pshat, without the need to resort to aggados chazal. He claims that Rashi conceded to him and admitted that if he had had more time, he would have included in his commentary the simpler explanations that were still consistent with the grammar of the pasuk, as they were "more pshat" than chazal's explanations.

For an extensive discussion on this topic, with an abundance of examples, I highly reccomend R' Herczeg's book.

choshen mishpat civil law - Can a book with ancient text really be copyright?

Pick up your local chumash, siddur or gemara. Open it to the front page. There it is, the dreaded ©.

But to me that seems quite odd. Can the text of the actual davening or talmud really be copyrighted? If anything it perhaps should be copyrighted by the original authors, and not by some modern day company that happened to reprint it.

But... I really don't know: So, do these copyrights only apply to the layout and typography, or is there any real basis to them? If I wanted to publish a siddur today, and pulled out an Artscroll siddur for reference, would that be wrong?

shaving - Where are the 5 corners of the beard?

In Vayikra 19:27, the Passuk says ולא תשחית את פאת זקנך - "and you shall not destroy the edge of your beard". I believe it says in Meseches Makkot (3:5) that this Passuk refers to 5 edges of the beard (or something to that effect).

• Do we know where these 5 edges are?


• Where are they?


• Are there any places on the face that we know can definitely be shaved by a razor?

covalent compounds - How to rationalise the increasing bond length order in the carbonate ion, carbon monoxide, and carbon dioxide?

I am unable to rationalise the order of increasing bond length in $\ce{CO3^2-}$, $\ce{CO}$ and $\ce{CO2}$. Having gone through the factors affecting bond length in two different books, my approach to the problem was:

• 
  

  $\ce{CO}$ has bond order 3 while carbonate and $\ce{CO2}$ have bond order 4 so $\ce{CO}$ should have longest bond length.

  
  

  $\ce{CO2}$ is sp hybridized while $\ce{CO3^2-}$ is sp² hybridized. Since carbonate has lesser s character and therefore it should have a greater bond length than $\ce{CO2}$

  
  
  

Thus, $$\ce{CO2 < CO3^2- < CO}$$

However, I am unsure about my method. What would be the best approach to determine the relative bond length order?

Answer

Actually, in regard to bond length, you should be looking at the bond order of a single bond within the molecule. The bond order is 2, not 4, for $\ce{CO2}$, and the bond order for the carbonate ion is somewhere between 1 and 2 due to resonance. Thus, the carbonate ion has the longest bond length, followed by carbon dioxide, and finally carbon monoxide.

shape analysis - Non-symmetrical lemniscate curve parameterization

I'm trying to fit a function to data points. The data generally resembles a butterfly/lemniscate shape, see drawing.

The problem is that the shape in my data can be rotated, skewed and/or non-symmetrical.

I've been looking at Bernoulli's, Devil's curve, Watt's curve, however, these are, as far as I can see, symmetrical.

Does anyone know of a plane curve that is able to represent the example shapes? Preferably in Cartesian coordinates.

Answer

There is a polar asymmetric modelling for the lemniscate:

which you can rotate and scale more easily that in Cartesian coordinates (but easy to convert). Such parameterizations are used very often as they can be less troublesome to fit.

Similar curves in astronomy are also called analemmas:

.

From an image processing fit point of view, you can consult: A Unified Scheme for Detecting Fundamental Curves in Binary Edge Images, Asano, Tetsuo et al., Computational Geometry, 2001

Validity of Houston Kabbalah centers?

For you Houstoners, there is a building on S Shepherd called "The Kabbalah Center" that uses a map of the 10 sefirot as it's logo. It looks like something that might exist in other cities. All the books inside are written by one man, Yehuda Berg. Is this place a genuine place to study Kabbalah? Is this man an accepted Kabbalistic scholar? Can anyone explain who this man is and what these places are?

Answer

Is this place a genuine place to study Kabbalah?

NO!

Sources:

http://culteducation.com/group/1008-kabbalah-centre/11830-kabbalah-center-visitor-comments.html

https://freedomofmind.com/Info/TheTruthAbouttheKabbalahCentre.php

At five years old a person should study the Scriptures, at ten years for the Mishnah, at thirteen for the commandments, at fifteen for the Talmud, at eighteen for the bridechamber, at twenty for one's life pursuit, at thirty for authority, at forty for discernment, at fifty for counsel, at sixty to be an elder, at seventy for gray hairs, at eighty for special strength (Psalm 90:10), at ninety for decrepitude, and at a hundred a man is as one who has already died and has ceased from the affairs of this world. (Pirkei Avos, 5:21)

The phrase "at forty for discernment" (wisdom) is traditionally understood to mean that a person needs to both reach the age of forty, AND complete all of the previous prerequisites (mastering Scriptures, Mishnah, Talmud, getting married, having a career, etc) before one can properly understand Kabbalah. (See the Shach, Yoreh Deah 246:6)

The Kabbalah Center is a dangerous cult, that uses some authentic Kabbalistic ideas from Rav Ashlag, just enough to impress spiritual seekers. Then, they squeeze every last dollar out of their victims, promising blessings for giving, and curses for not giving.

halacha - Fasting when Navi on Klaf falls on the floor

As is known, if a Sefer Torah falls on the floor (even if it's covered) there is a halacha that one must fast. (See this question and answer for many sources on this topic.) What about in a case when Navi or Kesuvim that was written on klaf fell on the floor (either when it was covered or not covered it -- if there is any difference in regards to Navi/Kesuvim)?

halacha - passive bal tashchis

is passive bal tashchis wrong?

i see jews eat things (sometimes even to the detriment of their health, (because of the amount or quality) so that they will not go to waste

is this a Jewish thing to do (obligation, recommendation...)? source, please

in general, do jews ever need to do something (active) to avoid bal tashchis, when the bal is happening from the inaction of the jew? (obligation, recommendation...)

halacha - Do you have a say in the order of the food you eat?

As a kid I learned that if you have foods with different brachos in front of you, you should make the bracha on the more important food first, like say mezonos over haetz. My question is how far do we extend this? If I know I'm going to be having dessert which will be mezonos, do I need to say a bracha and eat some of that before I have my scrambled egg? What if it's not on the table yet? What role does my personal preference for the order I'd like to eat things in play?

organic chemistry - Nitrosation of benzene

How does benzene react with $\ce{NaNO2/HCl}$? Will $\ce{PhNO}$ be obtained? I read that pyridine can be produced under special conditions, but what will happen in some less exotic conditions?

Answer

As you noted, the link you provided was to a reaction run under rather exotic conditions (low-temperature plasma). Under more everyday laboratory conditions, for example, in solution, activated aromatic rings can react with $\ce{NO^+}$ as shown below.

However if there is a ring-activating amino substituent present, then the $\ce{NO^+}$ will react with the nitrogen to produce the synthetically important diazonium ion.

conversion to judaism - What should a Jew do if encountered by ISIS?

Theoretically, if (Gd forbid) ISIS took over Israel, and the Jew in question was not immediately killed because he was Jewish and was not in the financial situation to pay the required taxes, should the Jew allow himself to be executed or become a practicing Muslim?

fft - What are best practices to compute an audio spectrogram?

The spectrogram if generally defined with the squared magnitude of the fft. However, in lots of implementation, it seems that people just use the magnitude without square.

Moreover an audio signal is by convention scale between -1 and 1. This scaling often needs a supplementary step in implementations, in python language for example, which is not always do.

Finally, what are best practices to compute an audio spectrogram? - square magnitude of the fft / magnitude of the fft ? - Integer audio values / scaling (-1 to 1) audio values

EDIT

As the comments tell, these are questions without consequences if the aim is to plot an image of the spectrogram.

However, I would like to use the matrix of the spectrogram as an entry point for sound analysis and recognition. In this case, the computation process matters and I find curious that the implementations differ so often.

Dropping particles in casual speech/songs

Hey i was listening to this song And it felt weird for me when one of these lines seemed to lack a particle, I am wondering if it is lacking one and it is ok to do so since it is a song, or if there was no need to a particle in there...

[君の前前前世から僕は君を探し始めたよ]

Why can I say 探し始めた without a particle, would it be ok to say 探しを始めた？

Is it perhaps like the difference between "I began to look for" vs "I began looking for" ?

When it's ok to drop a particle in casual speech? I know that if my sentence contains only one "が" particle it'd not be ok to drop it, but what about sentences with more particles?

Thanks in advance

Answer

No particle has been omitted in your example sentence. You can not say masu-stem + を始める in the first place (unless the "verb" is actually a lexicalized noun derived from some verb (eg 支払い = payment, 戦い = battle)).

Regardless of whether it's in speech or not, masu-stem + 始める is the right way of saying "start to [verb]", and there must not be any particle in between.

• 歩き始める start to walk


• 見始める start to watch


• 食べ始める start to eat

Don't ask me why. Japanese language has tons of 複合動詞 (compound verbs) which just look like this; 走り出す, 飛び立つ, 動き回る, 出払う, and so on.

Not to be confused with subsidiary verbs, which are small in number, and always follow the te-form of another verb.

word choice - Add English nuances to Japanese "いいえ"

Here are some natural ways to say "no" in English (please forgive the language):

• No


• God no


• Hell no


• F*** no

How to include the English nuances in Japanese?

---

Best attempts:

• No - いいえ or ううん


• God no - 絶対いや


• Hell no - ありえへん or ありえない


• F*** no - ??

Motivating examples:

• Wanna eat soba again tonight? No.


• Do you want to travel on Golden Week? God no.


• Should we run another 10 miles? Hell no.


• Want to go to a Justin Bieber concert? F*** no.

Answer

I will start by saying that Japanese-speakers do not say 「いいえ」 nearly as often as English-speakers say "No". 「いいえ」 is simply not an everyday word for many of us the same way "No" is for English-speakers.

As an average Japanese-speaker, the first time I ever used 「いいえ」 more than a couple times a week in my life was when I started learning English in junior high school and was "required" to translate "No" to 「いいえ」 every time we saw the word "No" as a reply in the textbook. It was painful as I was not accustomed to saying 「いいえ」 out loud.

In Japanese, we answer questions negatively mainly by negating the main verb, adjective or noun used in the question itself.

To the question "Wanna eat soba again tonight?", for instance, practically no Japanese-speakers will reply, 「いいえ」, believe it or not. That would be an incredibly firm denial if someone actually replied that way.

Mild-to-medium negation:

「（ううん）、あまり/イマイチ/そんなに(Verb)たくない/(Na-adjective)じゃない/(I-adjective)くない。」

「（それは and/or ちょっと）ないかも。」、「（それは and/or ちょっと）ありえないかも。」、「（それは and/or ちょっと）ムリかな。」

「それはちょっと・・・」← Kinda versatile, but do not overuse it!

Strong negation:

「いや/いやだ、[絶対]{ぜったい}(Verb)たくない/(Na-adjective)じゃない/(I-adjective)くない。」

「そんなわけねぇだろっ！」、「そんなわけないだろっ！」、 「なわけないっしょ！」、「ありえねえよ！」(そんな＝んな＝な)

「(Verb)はず（or わけ）ねぇだろっ！」、「(Verb)たいわけねぇだろっ！」

「絶対（or 100パー）ムリ！」、「絶対ダメ！」、「絶対ない」, etc.

「100パー～～（たく）ない！」

I count on your ability to conjugate verbs and adjective to fit into these expressions.

periodic table - How adding one more electron increases the ionization energy?

Elements of group 6A, compared to 5A, require less ionization energy due to the paired electrons of 6A.

But a question arises: why does group 7A, compared to group 6A, require more ionization energy in spite of the paired electrons in group 7a too.

Regardless of the general trend that the ionization energy increases as we go from left to right in periods, why didn't we apply the same procedure as the first comparison?

halacha - Is reading normal practical books about Judaism considered "Torah Studying"?

Aside from the Tanakh, Talmud, Shulchan Aruch, Mishne Torah and the likes..... Is reading normal books about practical laws in Judaism considered "Torah Study"? I mean books like "To Be a Jew" for example. It deals with several aspect of every day Jewish life from Blessings, to Kashering, to going to Synagogue, explaining how to slaughter the animal, how to behave, modesty, etc.

names - Hebrew document found in grandfather's attic—what does it state?

I found this document in my grandfather's attic and would be thankful if someone could tell me (a) what this document is, (b) whether there are any names written, and (c) which, if any, religious meanings or implications could arise.

Thank you all.

Answer

As Danny Schoemann says, it's a ketubah. A Ketubah is a Jewish marriage contract. The text in this form matches the standard text presented and translated on this Chabad.org page.

People

• Groom: Yehuda Leib, son of Avraham Noah. He is also a Levi


• Bride: Toiba Rachel, daughter of Yisrael Arye


• Witness: Aharon Leib, son of Moshe the Levi


• Witness: Abba David, son of Baruch

Date

It is dated Wednesday the 12th of Cheshvan 5670, which corresponds to October 27, 1909 on the Gregorian calendar, or after dark on Tuesday, October 26th. Since they were in Russia, which didn't adopt the Gregorian calendar until 1918, it would have been Oct. 14th (or 13th after dark) on the Russian (Julian) calendar.

Location

The city is given as אוטייאן which is the Yiddish name for the former shtetl which is now the Lithuanian city of Utena. At the time Lithuania was part of the Russian Empire.

The form

The form was printed in Vilna by the Katzenellenbogen family printers. Vilna was one of the few places in the Russian Empire where Jewish documents and books were allowed to be printed, so their documents were used at the time all around Russia (and it doesn't necessarily mean your ancestors were in Vilna themselves).

As Fred and Nikolai translate, the Russian text at the bottom says (in old orthography): "Sample marriage record for a maiden. Approved by the censor 7 January 1876 city of Vilna. Vilna to printer A.G. Katzenellenbogen on Nikolayev Alley to d. Dombrowski No. 64/18 1876 city."

Other facts

It was a first marriage for the bride as she is referred to as a virgin.

The specific choice of wording "מבי אבוה" ("from the house of her father," rather than "מבי נשא") that was filled in appears to indicate that the bride's father was alive at the time of her wedding.

Any chance this is your grandparents' marriage contract? Perhaps their parents?

image processing - How to measure distance between two 3d objects using cameras

I need some help regarding measuring distances between two balls and their position relative to surface(coordinates). Dimensions of balls and surface are known. Do i need just one camera to do this(measuring with ray diagrams and trigonometry)or more?

I hope this is the right thread,I tried on physics and photography before and it wasn't correct thread

Is it possible for one specific atom in a molecule to have a non-integer oxidation state?

I am wondering if fractional oxidation states of an atom are possible. I'm not referring to cases such as $\ce{Fe3O4}$ or $\ce{Mn3O4}$ where the average oxidation state is fractional, since these actually comprise a mixture of atoms which are individually in the +2 and +3 oxidation states. What I mean is, is it possible for an individual atom in some compound to have an oxidation state of (for example) 2.5?

To me it doesn't seem possible just because of the way oxidation states are defined. However I have seen some sources which state that fractional oxidation states are possible. I would be interested in knowing if there is some weird compound that has fractional oxidation states?

---

Note: This is not a duplicate of Are fractional oxidation states possible? I want to know if it is possible for an individual atom in some compound to have a fractional oxidation state, not its average fractional oxidation states.

Answer

It depends. Consider various radicals such as the superoxide anion $\ce{O2^{.-}}$ or $\ce{NO2^{.}}$. For both of these, we can draw simple Lewis representations:

In these structures, the oxygen atoms would have different oxidation states ($\mathrm{-I}$ and $\pm 0$ for superoxide, $\mathrm{-II}$ and $\mathrm{-I}$ for $\ce{NO2}$). That is the strict, theoretical IUPAC answer to the question.

However, we also see that the oxygens are symmetry-equivalent (homotopic) and should thus be identical. Different oxidation states violate the identity rule. For each compound, we can imagine an additional resonance structure that puts the radical on the other oxygen. (For $\ce{NO2}$, we can also draw resonance structures that locate a radical on both oxygens and another one that expands nitrogen’s octet and localises the radical there.) To better explain this physical reality theoretically, we can calculate a ‘resonance-derived average oxidation state’ which would be $-\frac{1}{2}$ for superoxide and $-\frac{3}{2}$ for $\ce{NO2}$. This is not in agreement with IUPAC’s formal definition but closer to the physical reality.

internet - Is unmasking an anonymous author addressed by Halacha?

If an individual writes a document for public consumption anonymously or pseudonymously and either explicitly or presumably desires to remain anonymous, is there a Halachic issue with publicly unmasking the author, or with publicly assembling information about the author toward the goal of unmasking them?

This activity ("doxing," in Internet slang) is practiced in various Internet forums, and the ethics thereof are a subject of controversy. It's potentially relevant on a forum like this one that values contributions from pseudonymous authors.

If sources address this activity, do they distinguish regarding the nature of the material that was anonymously authored - whether it was Torah, objectionable, controversial, etc.?

inorganic chemistry - Does nitric acid release hydrogen only when reacting with Mg and Mn?

$\ce{HNO3}$ always reduces its anion to give nitrogen containing compounds ( $\ce{NO2}$, $\ce{NO}$, and even $\ce{N2O}$) when reacting with metals, but with $\ce{Mg}$ and $\ce{Mn}$ it releases $\ce{H2}$. Is there a specific reason for this variation?

minhag - chassan/kallah signing the kesubah or tenaaim

I have seen bridegrooms and brides sign their names on their kesuba or tenaaim (prenup) before the chuppah (wedding ceremony). It seems maybe to be a chassidish custom, though I'm not sure.

Is there a source for this, and, if so, what's the reason?

Answer

I don't know that it is necessarily a Chassidish custom, but it is an Israeli one. Some sources include Orchas Mishpat 1. Yabia Omer 3 Even HaEzer 13, Trumas HaDeshen 2:232, Rashba on Bava Basra 175a and Nahar Mitzrayim 192b.

According to Rav Ovadiah Yosef who sums up most of these sources in his responsa in Yabia Omer the reason to to halakhically strengthen the grooms responsibility to pay his Ketubah including the added sum, as well as to make the contract legally binding in a civil court.

As far as the bride signing, I have not heard of that.

midrash - How do Rishonim argue on Drashos Chazal?

There is a known rule that Rishonim cannot argue on the Gemara when it comes to "Halachic" drashos. For example, a Rishon will never give a different answer to a question which the Gemara already answered (Tosfos may ask why the Gemara didn't give that other answer, but he will never give his own answer without more). This is true whether the Gemara's subject is practical Halacha or not.

However, when it comes to aggadic drashos on Tanach, we find Rishonim "disagreeing" with Midrashim and late Acharonim disagreeing on Rishonim. Why do Rishonim feel freer to disagree on an explanation of Chumash than to disagree with a Gemara?

halacha - Do you do a Tashlumin (make-up) on a Shemoneh 'Esreh if you later realize that you forgot a critical insert?

If you forgot to add a critical insert in the 'Amidah (one of the special additions to Shemoneh 'Esreh at certain times of the year, eg., HaMelech HaKadosh, Ya'aleh VeYavo, etc.), and you realize at the next service that you definitely forgot to say it earlier (eg., you got the date wrong and someone pointed it out to you, or you forgot the next time also but you heard the Sha"Tz say it), do you need to make up for it (Tashlumin, perhaps because it is as if your earlier prayer did not happen), or is Tashlumin not warranted (perhaps because it was a flawed, but fulfilled, prayer)?

halacha - Transferring discrete "kippah clips" between domains on Shabbat, if the clips are NOT sewn to the kippah

A) Imagine the following: It is Shabbat, and I am using spring-loaded hair clips or bobby pins to attach a kippah to my hair. The clips or pins are NOT sewn to the kippah: instead, they are discrete and separate. I don't live inside an eruv. May I walk from a private domain to a public domain on Shabbat? Or would this count as transferring between domains?

B) What if the clips or pins are clipped or pinned to the kippah, but not to my hair? (In this situation, instead of holding the yarmulke on my head, the clips really are doing nothing at all.)

Please cite sources.

Related: a question which assumes that the kippah clips are instead sewn to the kippah.

What types of chemicals/ionic liquid could perform this type of separation?

Ionic Liquids separation of oil and sand.

Answer

In the video from PennState, Aron Lupinsky tells that he is working in the group of Prof. Painter.

Combining these information, a cursory search furnishes the article

Recovery of Bitumen from Low-Grade Oil Sands Using Ionic Liquids by Phillip Williams, Aron Lupinsky and Paul Painter, published in Energy Fuels, 2010, 24, 2172–2173 (DOI).

On the first page of the article, it is mentioned that a mixture of toluene and 1-butyl-2,3-dimethylimidazolinium tetrafluoroborate, $\ce{[bmmim][BF4]}$, was used for the extraction.

halacha - Preparing kitniyot for Shabbat immediately after Pesach

In a year like this, where the last day of Pesach (for Israelis) is on Friday, can kitniyot be cooked on Pesach with an eruv tavshilin for use on Shabbat?

I know that eating kitniyot that don't need to be cooked is not a problem to eat on Shabbos, and many people in fact do this. If an eiruv tavshilin is made, it is permissible to prepare food for Shabbat on Yom Tov, but i don't really know all the laws of this. Here, the food is not fit for eating on Yom Tov, so it may be a problem to prepare.

words - How to understand チラツ

How to understand チラツ ?

My textbook gives "leaflet" as a translation. It's in katakana, though, so I'm looking for a corresponding English word, but what is it?

marriage - Tribe of the son of a Kohen and a convert

Kohanim are not allowed to marry a convert. However, if such a case happens (where there is a fully valid conversion), what is the status of the child? On one hand, they would be chalal, but would that offspring be able to inherit the Levite tribe of their father?

Related: Children of Converts and Specific halachos

Answer

Various shiurim and tapes have explained that a chalal is treated a a Yisroel and not a Levite. For example Rabbi Kaganoff gives the example of the son of a kohen who had married a divorcee had to perform a Pidyon Haben on his first born child.

The shiurim that I have seen explain the reasoning behind this, but I do not have the explicit citations right now.

Rambam does say

Yet if a chalal went ahead and offered a korban, his offerings are accepted after the fact (Maimonides, Bi'at Mikdash 6:10).

However, this is different and normally he is not allowed to even join the Leviim to sing or perform the Avodah of Levi in the Bais Hamikdash.

inorganic chemistry - Is there any way to refine Feldspar?

Feldspars are mostly composed of three compounds:

• 
  

  KAlSi$_3$O$_8$

  
  


• 
  

  NaAlSi$_3$O$_8$

  
  


• 
  

  CaAl$_2$Si$_2$O$_8$

  
  
  

I notice they each have Aluminum. Feldspar is far more common than Bauxite (the only Aluminum ore commercially mined). As it stands now, Feldspar is used in glass-making, but I'm wondering if there's some chemical refining process that can extract the Aluminum somehow?---especially that third one, since it has two Al's.

Note: I'm not looking for an economical method. That's proly asking too much. I'm not worried about aluminum reserves, because bauxite is still very plentiful. I'm simply interested in a chemical method to extract Aluminum, or at least Alumina (Al$_2$O$_3$), from Feldspar, purely for reasons of chemical curiosity.

The only thing I've researched is the Bayer Process, but I have no idea if it can be applied or modified for Feldspar.

Answer

Aluminium oxide can be isolated from feldspar by first acid digestion with a mixture of hydrofluoric acid and sulfuric acid (get rid of silicon by formation of silicon tetrafluoride), then digesting the residue with sodium-potassium carbonate, dissolving the obtained mass in dilute hydrochloric acid and then precipitating $\ce{Al(OH)3}$ by adding ammonia. The $\ce{Al(OH)3}$ can be calcined to aluminium oxide by heating to over 1100°C.

Note that the described procedure requires a suitably equipped laboratory .

grammar - Can we use negative form before ～てしまう : f.ex. なく+～てし まう？

Using the form ～てしまう we mean, that something happened in a way we did not expect. But what if we use a negative form before the ～てしまう ending? Will it be also grammatically right?

For example:

昨日メッセージを書いていなくてしまいました。

Answer

なくて doesn't connect to しまう but ないで does, in other words, you can say 昨日、メッセージを書かないでしまった.

(Technically, 書いていないでしまった is possible but that sounds very awkward. On the other hand, 書かないでいてしまった is fine though I still can't see the point to use it here.)

organic chemistry - Ester as a side product in the synthesis of bromoalkane from alcohol. Is it correct?

About 5 months ago, I answered a very interesting question albeit a very simple one.

Why do we need sulfuric acid in creating alkyl bromide and not in creating alkyl iodide from alcohol and hydrogen halide?

The question was why sulfuric acid is used to convert any alcohol to bromoalkane but not iodoalkane. Jan's answer quite pointed out the explanation:

• hydrogen iodide is sufficiently acidic to protonate the corresponding alcohol and drive the reaction. More acids are not needed.


• hydrogen bromide is not acidic enough to drive the reaction. Adding sulphuric acid protonates the alcohol partially and allows the
  reaction to proceed.


• in the case of weakly soluble alcohols and hydrogen iodide, phosphoric acid may be used instead since it does not oxidize iodide (while sulfuric acid does).

Though I am satisfied with Jan's excellent answer, I further pointed out that sulfuric acid may react with hydrobromic acid to form bromine(aq.) and sulfur dioxide. This bromine may oxidize alcohol to form aldehyde and carboxylic acid and they two will form ester. This was my proposed explanation but I couldn't find any experimental result to back my explanation and heavily relied on theory.

Now recently Nurdrage, a renowned chemist famous for his synthesis of pyrimethamine has uploaded a video on Youtube about the synthesis of bromoethane and bromohexane from ethanol and hexanol using sulfuric acid. He also explained the concern of forming bromine as side product from the reaction of hydrobromic acid and sulfuric acid. He showed a purification technique by adding sodium bicarbonate to react with bromine to form sodium hypobromide.

Now my question is:

Is my explanation of forming ester instead of bromoalkane correct enough? Is there any possibility of forming minute amounts of ester? The reaction may be slow but it can happen before any purification is done (reacting bromine with sodium bicarbonate). If so, what can be done to remove any ester or prevent the reaction of ester formation?

Also related: Why is alcohol boiled with HBr for preparing alkyl bromide?

bathroom - What are the parameters for washing after excusing one's self in the middle of the meal?

If I recall correctly from Chayei Adam and elsewhere, if you're in the middle of a bread-based meal and excuse yourself to defecate, first of all you should wash with soap and water for hygienic purposes, as you always should after using the restroom! But after that, you do a ritual washing and make "al netilas yadayim" as you usually would when starting to eat bread.

This halacha is the subject of some discussion, and not agreed-upon by everyone.

According to those who do require washing, however, what are the parameters of this washing? Can I talk afterwards? Do I say a new hamotzee if I'm having more bread? What if I wasn't in the mood for more bread, just cake? Just meat? Just water?

Answer

According to Rabbi Yosef Gavriel Bechhofer, if you want to eat more bread, you should wash, say al netilat yadayim and then not talk until you say hamotzee.

If you don't want to eat more bread, you don't have to wash.

digital communications - Loop bandwidth for symbol timing recovery

I am trying to design the Symbol timing recovery (STR) block of DVBS Receiver.

• How should I chose the loop bandwidth and damping ratio for determining the loop filter coefficients $k_1$ and $k_2$?

In some literature they are given as $B_nT_s= 0.005$, $\zeta = \frac{1}{\sqrt 2}$, while in others it is given as $B_nT_s= 0.05$, $\zeta = 1$.

• 
  

  How should I proceed for choosing the $B_n$ and $\zeta$?

  
  


• 
  

  Should $B_nT_s$ factor change as we change $T_s$ (say from $0.1$ to $10^{-5}$ sec)?

  
  

Answer

There is an optimum loop BW that maximizes the SNR, and this applies to both Symbol Timing Recovery as you inquire about as well as Carrier Recovery. The specific answer depends on the characteristics of the noise source involved in your system, such as clock jitter and phase noise, and the modulation you are using; specifically how the signal energy is distributed in frequency. Without knowing those an exact answer cannot be determined, but I can at least share some insights from my own experience with it.

To state generally, I have found that the optimum loop BW to usually be somewhere between R/100 and R/20, where R is the symbol clock rate being recovered. I start with a value in this range and then through simulation with a valid noise and waveform model (or lab measurement) determine the actual optimum using SNR metrics vs Loop BW setting.

As for damping factor, I also start with a damping factor of 0.5 and then through evaluation using a step or impulse response test adjust for possible ringing due to parasitic delays that may be present in the loop.

In addition to the SNR considerations given above, there are also acquisition time constraints or possible dynamic noise conditions that would also motivate you to have as fast of a timing loop as possible: The faster the loop, the faster the acquisition time, and recovery time from an interference event, or the ability to track a highly dynamic change if it exists. There may also be waveform specific constraints such as the duration of a header in a packet based waveform used to establish timing. However as the BW for the tracking loops increase beyond a significant fraction of the timing symbol clock rate (such as >R/20), tracking errors will start to dominate the noise in SNR, since the loop will start to track out the modulation of interest.

To explain further from the perspective of a trade of Loop BW and SNR, the Loop BW sets the boundary at which your recovery loop will track timing noise (jitter/phase noise) in your signal. Timing noise has components at all frequencies (such as that viewed with a phase noise spectral density), and the lower frequency components of the timing noise (the change in zero crossing locations that is moving very slowly) will be tracked by the timing loop, and therefore suppressed. However the higher frequency components will not be tracked by the timing loop and therefore remain and contribute to noise as part of SNR. The timing loop can be viewed as a high pass filter on the jitter/phase noise components, passing the higher frequency components (including the modulation signals) and supressing the lower frequencies at a rate depending on the order of the loop. Thus you see the motivation to make the timing loop as fast as possible in the interest of tracking out as much timing jitter as possible. However, some of the signal energy of interest will be part of the "noise" being supressed by the timing loop; and this can be quantified by understanding the spectral characteristics of the modulation used. As the loop BW increases, too much signal energy is also removed, and thus it is clear how there can be an optimum setting for the Loop BW that maximizes SNR.

This hopefully provides insight into the approach and what to look for in the development of the system. In conclusion, I set the Loop BW as fast as possible (typically in the range of R/100 to R/20 where R is the symbol rate) while monitoring through simulation with accurate noise and waveform models the SNR metric; and either choose the point of best SNR, or if other factors such as acquisition time or more stringent dynamic conditions are involved, maximize BW without going below a target SNR metric.

Is a sotah woman considered a suicide?

If a woman drinks the sotah water and dies is her death considered a suicide since she would have known that drinking would kill her?

energy - Can Rydberg constant be in joules?

In my textbook (Chemistry Part - I for Class XI published by NCERT), there is an equation for the energy of an electron in an energy state: $$E_n = -R_\mathrm H\left(\frac{1}{n^2}\right)$$ and there is a paragraph below it with the following text:

where $R_\mathrm H$ is called Rydberg constant and its value is $2.18\times10^{-18}\ \text{J}$.

There is another section with the expression for the wavenumber ($\overline{\nu}$): $$\overline{\nu}=109\,677 \left(\frac{1}{n_1^2} - \frac{1}{n_2^2}\right)\ \text{cm}^{-1}$$ with a paragraph with the following text:

The value $109\,677 \space\text{cm}^{-1}$ is called the Rydberg constant for hydrogen.

I checked online and found that in most (all) websites (incl. Wikipedia), the value of Rydberg constant is $109\,677 \space\text{cm}^{-1}$. But when I searched for its value in joules, I found this website with the value of Rydberg constant $= 2.18\times10^{-18}\ \text{J}$.

How can Rydberg constant be written in joules?

Answer

Authors may be sloppy about notation in this matter. I recommend considering $R_\ce{H} \approx \pu{10973 cm-1}$ and $Ry \approx \pu{2.18e-18 J}$, noting $Ry = hc \cdot R_\ce{H}$. Units of wavenumbers $(\pu{cm-1})$ and energy are often considered interchangeable in practice because they are proportional to each other by the constant value $hc$.

In my notes, I would always be sure to write $R_\ce{H}$ or $Ry$ to explicitly remind myself "which" Rydberg constant I was using (in fact I merged the R and y into a single symbol because I didn't like the suggestion of multiplication.)

Note also that there is a unit of energy known as a Rydberg, with $\pu{1 Ry} = Ry = hc \cdot R_\ce{H}$.

organic chemistry - Nomenclature of benzene derivatives with two functional groups

In several places, I have seen that while naming benzene derivatives, no priority for substituents is followed. For example, I've seen both 2-hydroxyaniline and 2-aminophenol being used.

Is there an order? Or is the order different from aliphatic compounds?

Answer

According to the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), the retained names “aniline” and “phenol” are preferred IUPAC names (PINs). Parent structures having retained names are called functional parent compounds.

    

For both retained names, substitution is permitted at any position. However, substitution of a functional parent compound is limited to substituent groups cited as prefixes in accordance with the seniority of the functional group that is explicitly expressed or implied in the functional parent compound name. (In systematic names, the presence of this characteristic group would normally be expressed as a suffix.)

P-15.1.8.2.1 Substitution rules for Type 2a retained names

Type 2a retained names include functional parent compounds whose name expresses or implies a characteristic group expressed as suffix in systematic names.

P-15.1.8.2.1.1 Substitution by substituent groups, expressed as prefixes, having a lower seniority than that denoted by the suffix is allowed.

(…)

P-15.1.8.2.1.2 The senior characteristic group or functional class name must be expressed in the name.

Therefore, the correct name for the compound given in the question is “2-aminophenol” (not “2-hydroxyaniline”) since hydroxy compounds are senior to amines.

frequency response - How to prove these two definitions of the minimum phase transfer function are same?

There are so many definitions of the minimum phase transfer function, and these are two of them.

1. The transfer function of the system which has no zeros or poles at right half plane.


2. The transfer function which has the minimum phase angle range among the systems which has the same magnitude characteristic.

And these two sentences are describing the same thing. So I want to prove that these statements are equivalent. How to prove it?

PS : Suppose that the system is continuous.

Answer

To your second definition it should be added that you only consider causal transfer functions, because it is not difficult to find a smaller phase lag with a non-causal system:

A minimum-phase system is a causal and stable system with a phase lag that is smaller than the phase lag of any other causal and stable system with the same magnitude response.

Note that a real-valued zero in the left half-plane contributes a phase change of $\pi/2$ to the total phase as we move along the frequency axis from $\omega=0$ to $\omega\rightarrow\infty$:

$$0\le\arg\{j\omega+a\}<\frac{\pi}{2},\qquad a>0,\quad\omega\in[0,\infty)\tag{1}$$

A complex conjugate pair of zeros contribute a phase change of $\pi$.

On the other hand, a real-valued zero in the right half-plane contributes a phase change of $-\pi/2$ as $\omega$ moves from zero to infinity:

$$-\frac{\pi}{2}<\arg\{a-j\omega\}\le 0,\qquad a>0,\quad\omega\in[0,\infty)\tag{2}$$

Note that I've chosen the sign of the term $s\pm a$ such that in both cases the phase is zero for $\omega=0$, which is necessary for a fair comparison between the two cases.

Consequently, exchanging a zero in the left half-plane for a zero in the right half-plane (without changing the magnitude of the frequency response) will always result in an additional phase lag of $\pi$ for $\omega\rightarrow\infty$.

As an example, consider two first-order transfer functions:

$$H_1(s)=\frac{s+2}{s+1}\quad\text{and}\quad H_2(s)=\frac{2-s}{s+1}\tag{3}$$

The signs of $H_1(s)$ and $H_2(s)$ were chosen such that their phases are both zero for $s=0$ (and not $\pm\pi$). The figure below shows the phase plots ($\arg\{H_1(j\omega)\}$ in blue, and $\arg\{H_2(j\omega)\}$ in green):

The pole contributes a phase change of $-\pi/2$ as $\omega$ moves from zero to infinity. The left half-plane zero of $H_1(s)$ contributes a phase change of $\pi/2$, resulting in a net phase change of zero, whereas the right half-plane zero of $H_2(s)$ contributes a phase change of $-\pi/2$, resulting in a total phase change of $-\pi$.

Another way to see the same thing is to note that any causal and stable transfer function can be written as the product of the minimum-phase transfer function with the same magnitude and a causal and stable allpass:

$$H(s)=H_m(s)H_a(s)\tag{4}$$

It can be shown that the phase of a causal and stable allpass is always non-positive for $\omega\in[0,\infty)$, and, consequently, the phase lag of the minimum-phase system is always less than or equal to the phase lag of any other causal and stable system with the same magnitude response.

everyday chemistry - Why ginger reacts with sparkling water?

I think that the ginger ale is born this way. Anyway, if you put the ginger in a glass and add sparkling water, small drops splash out of the glass, the water is fizzier, more effervescent. Why? what makes the two of them react?

commentaries - Beit Av v.s. Mishpechah

In Joshua 2:12-13(Mechon Mamre translation) the Torah reads:

12 Now therefore, I pray you, swear unto me by the LORD, since I have dealt kindly with you, that ye also will deal kindly with my father's house (Beit Av)--and give me a true token-- 13 and save alive my father, and my mother, and my brethren, and my sisters, and all that they have, and deliver our lives from death.'

And verse 18 reads:

Behold, when we come into the land, thou shalt bind this line of scarlet thread in the window which thou didst let us down by; and thou shalt gather unto thee into the house thy father, and thy mother, and thy brethren, and all thy father's household (Beit Av).

Joshua 6:23 and 25

23 And the young men the spies went in, and brought out Rahab, and her father, and her mother, and her brethren, and all that she had, all her kindred (Mishpachah) also they brought out; and they set them without the camp of Israel. 25 But Rahab the harlot, and her father's household, and all that she had, did Joshua save alive.

From these verses it seems that Mishpachah is part of Beit Av, while from Joshua 7:14-18 it seems that Mishpachah is part of a Shevet and a Beit Av is part of a Mishpachah:

14 In the morning therefore ye shall draw near by your tribes; and it shall be, that the tribe which the LORD taketh shall come near by families; and the family which the LORD shall take shall come near by households; and the household which the LORD shall take shall come near man by man. 15 And it shall be that he that is taken with the devoted thing shall be burnt with fire, he and all that he hath; because he hath transgressed the covenant of the LORD, and because he hath wrought a wanton deed in Israel.' 16 So Joshua rose up early in the morning, and brought Israel near by their tribes; and the tribe of Judah was taken. 17 And he brought near the family of Judah; and he took the family of the Zerahites. And he brought near the family of the Zerahites man by man; and Zabdi was taken. 18 And he brought near his household man by man; and Achan, the son of Carmi, the son of Zabdi, the son of Zerah, of the tribe of Judah, was taken.

Can anyone explain me which makes part of what?

hashkafah philosophy - What is the "good of marriage" in Jewish thought?

In Christian philosophy, many ancient philosophers such as Aquinas and Augustine speak about the "good of marriage." Marriage is "good", they argue, because it leads to offspring, chastity and permanence. See here for a lengthy article on the topic.

What is the "good of marriage" in Jewish thought?

Perhaps according to the Rosh, who doesn't view kiddushin as a Mitzvah, marriage has no inherent "good." The "good," rather, is external, since kiddushin is just one way to lead to the goal of having children. But, according to Rambam, who views kiddushin as an independent Mitzvah, what "good" does he believe exists in it?

kanji - Can I use my Chinese name as my Japanese name?

Im Chinese and my name is 陈依仁 (Chén Yī Rén). Can I use this as my Japanese name, and if so how do I read it in Japanese? Or would it be better to use the Katakana version of my English name which is タン・スジン?

Answer

Yes you can of course, as many have said. However, I am not sure why nobody mentioned that you can also pretty much use the kanji in your name and just associate to them a Japanese pronunciation as well.

In fact, I think it's important to notice that when it comes to pronunciation Japanese is quite flexible (especially with proper names) and it is not uncommon to find kanji in names associated to very peculiar readings.

If I check a name dictionary, I can actually find tens of possible readings for 陳. Most are similar to チェン. For example you have じん、しょう、ちいん、ちぇん　etc. However, I see also the more Japanese sounding のぼる (given name) or the kind of particular　くわおつく (last name).

And actually, I can even find 依仁 with the reading よりひと (a given name).

Given that these records exists you can very well write your name using exactly the original kanji (except for using the traditional version of 陈) and simply say that it is pronounced (last name-first name):

くわおつく-よりひと

Or play around and find any other combination you like. Maybe くわおつく sounds a bit odd, but if you pick a more standard じん for example, I feel that じん-よりひと or read it the other way around よりひと-じん is quite a cool sounding name. :D

sources mekorot - The Western wall (Kotel Hamaravi) forever

What is the source that the western wall of har habayis will never be destroyed?

I remember learning it somewhere and heard it numerous times but forgot the source.

theology - Do Jewish people believe in God?

This may sound like a simple question, but every time I speak with a Jewish person and ask them if they believe in God they talk about all kinds of things but they never give me a straight answer. They say that they don't believe in anything that is not in the Torah, and I ask them well then who do you pray to? And they say we pray to the Torah.

I don't understand do Jewish people pray to the book? Or do they worship the scrolls that the Rabbi's write, like the Rabbis are the descendants of God.

Answer

Yes.

Belief in God is axiomatic to Judaism.

Jewish prayer features, at least twice a day, every day, the Shema, a compact assertion of this belief from Deuteronomy 6:4:

Hear, O Israel: the LORD our God, the LORD is one.

Jews traditionally teach this prayer to our children almost starting at birth. I strongly suspect that almost any Jew with any knowledge of Jewish prayer knows this one.

According to the Sefer Hachinuch, this verse constitutes an actual commandment to believe in God.

---

Of course, there are plenty of individual Jews who believe all kinds of things, including atheism. I have never heard before of someone praying to the Torah.

hashkafah philosophy - Where does the sense of morality come from?

Where does our sense of morality which impels us to right conduct come from?

Is it something internal to us, or perhaps it is external to us? Is it physical or spiritual, etc.

For example, does our sense of right and wrong stem from thought, such as thinking about the distress of others (potential or actual) and feeling empathy thereby refraining from doing something which may harm them. Or perhaps it stems from some kind of spiritual sense in us.

Perhaps an explanation of what is the "yetzer tov" would answer this if that is the driving force.

organic chemistry - Relative stabilities of tropylium and cyclopropenyl carbocations

How can the stabilities of the tropylium and cyclopropenyl carbocations be compared?

Both are aromatic according to Hückel's rule. I think that to compare the stabilities, we must either count the number of resonance structures, or perhaps we could say that cyclopropenyl is less stable due to angle strain. Am I on the right track?

women - Dealing with an asexual wife

Inspired by this question

Many orthodox singles do not know about intimacy until right before the wedding. An asexual girl may of course choose not to get married, however, without prior experience she may find herself to be repulsed by intimacy, only after the wedding.

How should such a situation be dealt with? Do we force her to marital duties? Is there a base for divorce?

Answer

Well, here's Rambam Laws of Husbandhood Ch. 14:

יד,י [ח] האישה שמנעה בעלה מתשמיש המיטה--היא הנקראת מורדת, ושואלין אותה מפני מה מרדה: אם אמרה, מאסתיהו ואיני יכולה להיבעל לו מדעתי--כופין אותו להוציא לשעתו, לפי שאינה בשביה שתיבעל לשנוי לה; ותצא בלא כתובה כלל, ותיטול בליותיה הקיימין, בין מנכסים שהכניסה לבעלה ונתחייב באחריותן, בין מנכסים שלא נתחייב באחריותן. ואינה נוטלת משל בעל כלום; ואפילו מנעל שברגליה ומטפחת שבראשה שלקחן לה, פושטת ונותנת לו. וכן כל שנתן לה מתנה, מחזרת אותן, שלא נתן לה, על מנת שתיטול ותצא.

If a woman says: "my husband is a good man, doesn't beat me, practices perfect hygiene, all of that -- but physically I just find myself convulsing when I get close to him, for no particular reason", she can demand a divorce (though she wouldn't get her ketubah payment) -- we don't demand celibacy of those who didn't go into the marriage on those terms, and we can't ask her to do something on a regular basis that feels traumatic.

Obviously each couple is going to be different. In some situations, therapy may help. In some, they can determine some arrangement that works well enough for both of them. But if either side absolutely demanded out, a beit din would respect that. If they're asking their pastoral rabbi what to do, he'd assess the particulars of their situation before making a recommendation.

Keep in mind that when it comes to Jewish divorce law, sometimes there's "what is legal" and then there is "what would a good person do in this situation?" E.g. if she gets sick and her medical bills are high -- by the letter of the law he could figure out how much he would owe her upon divorce, pay that, and throw her to the curb. Ask any rabbi (or the Shulchan Aruch) what the right thing to do is? Don't be a savage. You take care of your wife.