shabbat - Kriyah at time of death when it occurs on Shabbos

When somone is there at Yitzias Neshomah (time of death) there is a requirement to rip Kriyah what happens if this situation occurs on Shabbos? Do you rip Kriyah or do the laws of Shabbos prevent you from doing so?

Answer

As far as I can tell, definitely not - both on Shabbos and Yom Tov.

The Mishna and Gemara in Shabbos are discussing whether the one did it is exempt from bringing a Korbon (after the fact). The Gemara ends up saying that it depends on whether there's an obligation to tear for that relative. If there's an obligation, then the one who tore is חייב, if not the one who tore is פטור.

However, one should definitely not do it Lechatchilah. (confirmed source: here page 9)

Interesting aside: you specifically asked about death. But the same would also apply to tearing for the Kosel. Which is one of the ways to avoid having to tear for the Kosel (i.e. by having the first visit done on Shabbos or Friday Afternoon) [see here for source].

Two things I'm not sure of though, which I would hope someone could cover in the comments:

• If the death is on Friday afternoon or Rosh Chodesh, should kriyah be performed?


• If Kriyah should be performed later, if it wasn't performed because of one of the above cases

halacha - Loshon hara vs. Honor code

Note: This question is in fact hypothetical--but any suggestions for edits that could make it a less ostensibly CYLOR-type question would be welcome.

Let's say I attend a university which requires all incoming students to sign an honor code which states that they will report any incidents of cheating/unethical behavior that they observe other students committing.

1) Would reporting these incidents be a violation of halacha* if I told on a Jewish student?

2) If yes to #1: May I sign this honor code, with the knowledge that following through with the code could in some cases be a violation of halacha?

3) If I do sign, and then I do, ch"v, observe a Jewish student cheating, what must I do? Would there be any possible halachic leniencies to report the cheating?

4) Would any of the above change in consideration of the fact that I myself may be punished (i.e., expelled) for not reporting the cheating?

*The potential issues I have in mind are loshon hara and mesira. In light of the latter possibility, it might be appropriate to consider two (three?) separate cases here: one in which one is reporting to academic authorities who are Jews in a Jewish academic institution (such as YU or possibly an actual kollel/yeshiva); one in which one is reporting to academic authorities who are goyim in a secular institution; and (maybe) one in which one is reporting to Jewish authorities, or a mix of Jewish authorities and goyim, in a secular institution.

syntax - what is the meaning of a た形の動詞 ＋ とする

The sentence is 例えば外食時、定食屋さんでとても美味しいご飯をたべたとする。

I've looked at some other answered questions which explain how とする, when appended to a verb expresses quitting an old action and starting a new one. However I can't understand it in this case, because it seems odd that it would be used in the past tense.

Does it take on a different meaning if the verb is in the past tense?

Answer

clause + とする can mean "assume ～", "suppose ～", "regard ～", "let ～", etc. So the sentence means "Suppose you eat ..."

Examples and explanations are found on the following sites:

The ta-form is used in combination of many hypothetical or conditional expressions. I think this ta-form is for denoting the perfect aspect, not the past tense. 定食屋さんでご飯をたべるとする refers to what you would think/plan/do before eating a meal (e.g., choosing a good restaurant). 定食屋さんでご飯をたべたとする refers to what you would think/do at a mealtime or after the meal (e.g., paying with a credit card).

halacha theory - What are the sources of Jewish law?

What are the sources for the Jewish law or "Halacha"? Is there any priority among these sources? In common practice, when a law is described, is the citation given form the main sources or derived codified books? (Please consider explaining any Jewish/Hebrew terms.)

Answer

G-d gave all the laws to Moses, and he passed it on to his students orally until the time of R' Yehudah, who wrote everything down in the mishnah in a concise way (Gitin 60a). We accept everything written there, since it came from G-d Himself. However, by that time, disputes had already risen over things that had to do with logic (which we are expected to apply to other cases when relevant), but not over the tradition itself (Tosafos Yom Tov, Avos 1:4). At around the same time, baraysos (laws not included in the mishnah) were written by contemporaries of R' Yehudah (e.g. Tosefta by R' Chiya). (See also this.)

R' Yehudah had three students, Rav, Shmuel, and R' Yochanan (Introduction to Mishneh Torah). Rav and Shmuel moved to Babylonia, and are therefore major authorities in the Talmud Bavli, while R' Yochanan moved to Israel, and became an authority for the Talmud Yerushalmi (these are both commentaries on the mishnah). However, they didn't actually write these Talmuds, but rather their students did. It turned out that the Yerushalmi was completed before the Bavli. Therefore, we assume that the ones who put everything in the Bavli saw everything in the Yerushalmi, so if the Bavli disagrees, we assume the Bavli disagrees even though it saw the Yerushalmi, so it must have had a good reason for disagreeing. However, if the Yerushalmi is not in doubt and the Bavli is in doubt, we follow the Yerushalmi. This is the explanation that I heard. See also Sdei Chemed Klalei HaPoskim 2:1.

Also, there was the Zohar, written by R' Shimon bar Yochai, but we follow the Bavli over Zohar (Mishnah Brurah 25:42 in the name of the Kneses HaGedolah; see also these sources). We also follow Yerushalmi over Zohar (see this answer). We follow Tosefta over Yerushalmi as well (see Sdei Chemed Klalei HaPoskim 2:5; the Pri Chadash quoted there disagrees). There were other works (e.g. Sifra, Sifri, etc.), but I won't cover them all.

Afterwards, disputes arose in the intent of those Talmuds themselves. There rose up many works of law in order to clarify which opinions in the Talmuds we follow, etc. There were many works (e.g. Bahag), but the Rif's commentary was the first most accepted original work to explain the law. After him rose the Rambam, who most of the time followed the Rif (Migdal Oz in many places). The Rosh also wrote a commentary. These three works were the ones that formed the basis for most of the laws of the Tur (the son of the Rosh).

The two people who wrote the first commentary on the Tur were the Beis Yosef (R' Yosef Karo) and the Darkei Moshe (R' Moshe Isserless), who explained (and sometimes disputed) the decisions of the Tur. But after all their comments, it ended up being that it took a lot of work to find the practical halachah. Therefore, the Beis Yosef wrote the Shulchan Aruch ("set table"), arranged like the order of the Tur, which only contained the practical halachah, its source being the corresponding chapter in the Tur, from which anyone could see how the law developed.

After the Shulchan Aruch, new commentaries came up to explain it and dispute it, so now the most common work to find the halachah is the Shulchan Aruch and its commentaries.

(As a side note, these commentaries which disputed their predecessors didn't dispute the authority of the Talmuds; they either found a case in the Talmuds which they brought as proof against a different case, or made rulings based on logic.)

halacha - Can you drink a beer (such as Miller or Budweiser) at a bar?

Can you buy and drink a beer (such as Miller or Budweiser) at a bar owned by non-Jews?

Answer

According to the Shulchan Aruch (YD 114:1) it is forbidden to drink beer in the same place as non-Jews do, i.e. bars. This is not a kashrus concern, but rather is forbidden out of concern that Jews will come to socialize overly much with non-Jews and come to eat with them. The Rama there writes that the custom in ashkenaz was to be lenient on honey and wheat based alcoholic drinks. However, barley based alcoholic drinks (such as beer) remain forbidden. (The Shach understands the Rama to be permitting barley as well. The Gra and the Peri Chadash there both reject the Rama's leniency.)

With regards to other hard liquor, there is a difference of opinion. Some achronim (Aruch Hashulchan 114:11 among others) say that drinks like rum and cognac are permitted to drink at bars because they are very expensive and were not a part of the original decree not to drink. However, in our times this might be a difficult case to make considering that these drinks are very commonly consumed in bars (see SHU"T shevet halevi 2:43).

Some authorities (chochmas adam, pischei teshuva ibid.) actually assume that this decree includes drinking tea and coffee in coffee shops with non-Jews because the same issue of socialization is a concern. There are some poskim today that actually reccommend not drinking in Starbucks because of this. However, many are lenient on this point (particularly if the leniency is utilized occasionally).

However, it should be noted that all of the issues above are not applicable if you take the beer out of the bar and drink it elsewhere (see Shulchan Aruch ibid).

organic chemistry - Number of resonance structures of nitrobenzene

I was studying about the resonance and here's my doubt:

How many resonating structures are there in nitrobenzene? Is it 5 (as drawn) or is it 4 because first and the last structures are same or is it 3 because second and fourth structures are also same?

In short, do we count fifth structure when we take the number of resonating structures?

Answer

We never really need to know the number of resonance structures. The whole concept is qualitative, so we can't draw any quantitative conclusions from it. But if you want to do it anyway, then of course 1 and 5 are the same, while 2 and 4 are not (they have positive charges on different atoms).

Also, both oxygens are in fact equivalent, so you might want to add the structures with their roles reversed.

word choice - What's the meaning of ですね in here?

I know that ですね is a form of saying right? but in this sentence これビデオですね what does that means? I understand that means "it's a video" but I don't understand the ね. A friend was recording a video and some people thought it was a photo and they posed but then she said it ain't was a photo.

• focusing in some friends


• they pose


• これ、ビデオですね。



• ビデオですか？


• laughs

Answer

As @l'électeur asked, what is the context?

• It could mean This is a Video, isn't it?


• It could also mean This is a video as if introducing some long lost technology.



• It could also show some kind of small astonishment like having found a video where they were expecting something else Oh! A video!


• When addressing something you are confident is a video, without wanting to offend another person's interpretation of the object This, as you may already know, is a video


• Realisation that you are being recorded rather than photographed You are taking a video right?


• From the view of the person taking the video I'm recording! (implying that a video rather than a photo is being taken - as with the photo/video element of digital cameras and phone camera/video recorders)

The ね is either implying a question where agreement is expected (as in the first example). Implying solid understanding of the subject (That is definitely a video) as in the second example. Indicating a small amount of astonishment (as in the third example). Without intending to cause offense at stating an obvious fact (fourth example). Questioning the state of something and expecting an answer (fifth example). Softly stating a fact that others may have not been aware of (sixth example).

EDIT to include @Michael and @user224579's comments

Once again, without more background it could mean anyone of these things and/or more.

rabbis - Smicha from R' Zalman Nechemia Goldberg?

One often sees that individuals' have smicha from R' Zalman Nechemia Goldberg. The smicha exams are typically considered more theoretical than that of the Israeli rabbinate, which requires more memorization. Nonetheless, it would appear from this discussion that individuals from the States can take and pass his exam on issur v'heter by paper exam alone.

Is this the case? Is a formal learning program (e.g., in yeshiva) required for this smicha? Also, does that discussion list his correct exam? It's the only such source I could find online of the exam... it appears from this prep book advertisement that R' Goldberg also gives smicha for Niddah as well as Issur v'Heter? How about Shabbat? Are there available exams for these?

organic chemistry - What is metamerism

According to metamerism in polyvalent functional groups, if both alkyl groups' around functional group are different then they are considered as metamers but in few books it is given that if one of the alkyl group is different then it is a metamer.

In my opinion, for e.g. diethyl ether and methyl propyl ether are metamers. But methyl propyl ether and methyl isopropyl ether should be position isomers and not metamers.

Which is true?

kinetics - Can a multi-species system oscillate around equilibrium?

In reading about chemical oscillations such as those that occur in the Belousov–Zhabotinsky reaction (BZ), it's often reported that these reactions were initially not taken seriously, because of a result that a homogeneous system cannot oscillate around its equilibrium point. It is usually claimed that the assumption of detailed balance guarantees this. I want to understand this result, but I can't find any specific references to it.

I understand very well why this argument doesn't apply to the BZ reaction, since the latter doesn't oscillate around its equilibrium point. However, I'm interested in understanding what this argument is, and whether it does really apply to all oscillations around the equilibrium point.

Kondepudi and Prigogine (2002) imply that the argument is as follows: for a single reaction, one cannot move from one side of the equilibrium to the other without passing through the equilibrium. Once the system reaches equilibrium it can't then keep on reacting, as this would contradict the second law, and therefore an oscillatory approach to equilibrium is impossible in such a system.

This of course makes sense for a system that only involves one reaction. However, for a system in which multiple reactions can take place it doesn't seem to be enough. For example, let's imagine that I have reactions $\ce{A <=> B}$, $\ce{B <=> C}$ and $\ce{A <=> C}$, whose kinetics are determined by some complicated set of catalytic effects. Let's also suppose that the Gibbs energies of A, B and C are the same, so that the equilibrium contains all three reagents in a 1:1:1 ratio.

Now it doesn't seem impossible that I could start off with a high concentration of A and watch the following sequence of events:

1. 
   

   most of the A is converted into B, leaving a little bit of A unconverted;

   
   


2. 
   

   most of the B is converted into C, leaving a little bit of B unconverted;

   
   


3. 
   

   most of the C is converted into A, leaving a little bit of C unconverted;

   
   
   


4. 
   

   this cycle repeats, with the unconverted material building up over time until the system converges to its equilibrium concentrations.

   
   

If I were to plot the concentration of the three reagents against one another as a 3D plot, it would look something like this (with apologies for my shaky drawing)

The black dot is the equilibrium point to which the concentrations eventually converge. The path is confined to a plane, because the total concentration of A+B+C cannot change. The free energy decreases as the path approaches the equilibrium point, so the second law by itself doesn't seem to rule out this behaviour.

If a system behaved this way, it would be an example of oscillations around equilibrium in a multi-reaction system. My question is, is there a result that says this cannot happen, if we assume the kinetics obey detailed balance at the equilibrium point?

If so, what is it called, how is it derived, and where can I read about it? If not, is there a known example of a chemical system that does approach equilibrium through oscillations in this way? (A 'toy' system will do, as long as the kinetics obey detailed balance.) Note that the BZ reaction is again not an example of this, since its oscillations do not take place around the equilibrium point.

Perhaps part of the argument is that the reasoning described by Kondepudi and Prigogine must hold for each reaction, independently. For the three-reagent system I described, this seems to be enough to rule out oscillations around equilibrium: the $\ce{A <=> B}$ reaction cannot pass through its equilibrium point, regardless of what happens to the concentration of C. But for a four-species system this no longer seems true: then the $\ce{A <=> B}$ reaction can move away from its equilibrium, as long as it's coupled to the $\ce{C <=> D}$ reaction. If oscillations around equilibrium really are impossible in every conceivable system this seems quite non-trivial, and it would be nice to see a proof.

_{Reference: Dilip Kondepudi and Ilya Prigogine (2002) Modern Thermodynamics: From Heat Engines to Dissipative Structures. Wiley. 2nd edition.}

translation - Figurative language ひどく下品な上に

Reading 幽霊塔 by 江戸川乱歩, I have come across a rather long sentence:

第一、栄子は女学校は辛うじて卒業したけれど、私の眼からは、低能児同様の無教養に見えるし、素姓の知れぬ乳母の連れ子だけあって、ひどく下品な上に、意地悪なことは人一倍だ。

Here is my interpretation:

First of all, even though Eiko barely managed to pass high school, from my perspective she seemed like an unrefined feeble minded child who was just the daughter of some ill-bred divorced wet nurse, and to the upper that is extremely vulgar, was malicious more so than others.

I'm not sure how 上 is functioning in the phrase ひどく下品な上に. Is it correct to interpret it as meaning "upper"? I would like to read some other perspectives on this phrase and how it fits into the sentence.

Answer

上に in this sentence means " in addition". Your sentence is translated as " In addition that She is extremely vulgar, is malicious more so than others."

grammar - When to use Dono or Nan?

I am learning Japanese using "learn Japanese in the car". It has the following sentences:

Which seat is it? / Dono seki desu ka. 

Which train car is it? / Nan gosha desu ka.

Why does one use Dono and the other use Nan. What is the rule to know when to use each one?

Answer

席{せき} is a good example. Please look at examples as follows.

A. どの席{せき}ですか。
B. 何{なん}席{せき}ですか。
C. 何{なに}席{せき}ですか。

All of these are grammatically, and each sentence is different question from the others.

A. どの席ですか。

You would say A when you don't know which seat it is.
どの is used when you want to know which of the three or more.
どちらの is used if you don't know which of the two.

B. なん席ですか。

I dare to write in hiragana, なん, to make clear the pronunciation, although people usually write it in Kanji, 何.
B means ''How many seats?''

なん is used when you speak about the number, order, or the amount of something.

The answer will be a word with the number, or the ordinal.
''席'' in this sentence is a counter suffix. なん is followed by a counter suffix, as ''なん号車{ごうしゃ}'', ''なん人{にん}'', ''なん枚{まい}'', ''なん回{かい}'', ''なんメートル'', ''なんか国{こく}'', ''なん歳{さい}'', ''なん年{ねん}'', ''なん月{がつ}'', etc.

However, 曜日{ようび} is also asked with なん.
So if you forgot whether it is Wednesday or Thursday, you would ask someone ''今日はなん曜日ですか。''.

C. なに席ですか。

Perhaps this usage of なに isn't listed in dictionaries.
You can use ''なに席'' when you want to know what kind of the seat.
You can use it for many aspects of kind, so you and someone you talk to have to know what you guys are speaking about.
C can be a question about various features.

指定席{していせき} reserved seats／自由席{じゆうせき} non-reserved seats

禁煙席{きんえんせき} non-smoking seats／喫煙席{きつえんせき} smoking-allowed seats
テーブル席 seats at the table in a restaurant／カウンター席 seats at the counter
These of ''○○席'' can be asked by using ''なに席''.

---

My kindergarten had three classes, ばら{rose}組{ぐみ}, もも{peach}組,　ゆり{lily}組. If I asked my friend what class had you been in, I would say ''幼稚園{ようちえん}の時{とき}、なに組だった？'' .
While, my elementary school and high school had several classes too, they ware named as 1組{くみ}, 2組, 3組, 4組, then, I would ask ''なん組だった？'' to my friend.
Furthermore, the university I graduated from has a large, extensive campus, so tourists who visit there may wonder that ''なん学部あるんだろう'', ''How many faculties are there in this campus''.
When you say なに学部, it means what kind of faculty as ''あなたはなに学部の学生ですか。''

halacha - What happens to the family of a Kohen today if his wife is a victim of rape?

What happens to the family of a Kohen today if his wife is a victim of rape?

What are the steps taken and how does this come to be resolved according to halachah and in the most constructive way for them to deal with such a tragedy as human beings?

Also, can a divorce be avoided?

Some background: What differentiates the wife of a Kohen who is raped from any other victim, is that Jewish law prohibits the Kohen from being married to a woman who had intercourse with ANY other man while she is married. Harsh as it is it seems in the case of a rape the marriage must end.

magnetism - Could a magnet pull oxygen out of the air?

I read that the $\ce{O2}$ molecule is paramagnetic, so I'm wondering: could a strong magnet pull the $\ce{O2}$ to one part of a room – enough to cause breathing problems for the organisms in the room?

(I'm not a professional chemist, though I took some college chemistry.)

Answer

I'm a physicist, so apologies if the answer below is in a foreign language; but this was too interesting of a problem to pass up. I'm going to focus on a particular question: If we have oxygen and nothing else in a box, how strong does the magnetic field need to be to concentrate the gas in a region? The TL;DR is that thermal effects are going to make this idea basically impossible.

The force on a magnetic dipole $\vec{m}$ is $\vec{F} = \vec{\nabla}(\vec{m} \cdot \vec{B})$, where $\vec{B}$ is the magnetic field. Let us assume that the dipole moment of the oxygen molecule is proportional to the magnetic field at that point: $\vec{m} = \alpha \vec{B}$, where $\alpha$ is what we might call the "molecular magnetic susceptibility." Then we have $\vec{F} = \vec{\nabla}(\alpha \vec{B} \cdot \vec{B})$. But potential energy is given by $\vec{F} = - \vec{\nabla} U$; which implies that an oxygen molecule moving in a magnetic field acts as though it has a potential energy $U(\vec{r}) = - \alpha B^2$.

Now, if we're talking about a sample of gas at a temperature $T$, then the density of the oxygen molecules in equilibrium will be proportional to the Boltzmann factor: $$ \rho(\vec{r}) \propto \mathrm e^{-U(\vec{r})/kT} = \mathrm e^{-\alpha B^2/kT} $$ In the limit where $kT \gg \alpha B^2$, this exponent will be close to zero, and the density will not vary significantly from point to point in the sample. To get a significant difference in the density of oxygen from point to point, we have to have $\alpha B^2 \gtrsim kT$; in other words, the magnetic potential energy must comparable to (or greater than) the thermal energy of the molecules, or otherwise random thermal motions will cause the oxygen to diffuse out of the region of higher magnetic field.

So how high does this have to be? The $\alpha$ we have defined above is approximately related to the molar magnetic susceptibility by $\chi_\text{mol} \approx \mu_0 N_\mathrm A \alpha$; and so we have¹ $$ \chi_\text{mol} B^2 \gtrsim \mu_0 RT $$ and so we must have $$ B \gtrsim \sqrt{\frac{\mu_0 R T}{\chi_\text{mol}}}. $$ If you believe Wikipedia, the molar susceptibility of oxygen gas is $4.3 \times 10^{-8}\ \text{m}^3/\text{mol}$; and plugging in the numbers, we get a requirement for a magnetic field of $$ B \gtrsim \pu{258 T}. $$ This is over five times stronger than the strongest continuous magnetic fields ever produced, and 25–100 times stronger than most MRI machines. Even at $\pu{91 Kelvin}$ (just above the boiling point of oxygen), you would need a magnetic field of almost $\pu{150 T}$; still well out of range.

---

¹ I'm making an assumption here that the gas is sufficiently diffuse that we can ignore the magnetic interactions between the molecules. A better approximation could be found by using a magnetic analog of the Clausius-Mossotti relation; and if the gas gets sufficiently dense, then all bets are off.

water - What is the pH of ice?

The pH of pure liquid water depends on temperature. It is about pH = 7.0 at room temperature, pH = 6.1 at 100 °C, and pH = 7.5 at 0 °C. What happens to the pH (or to the ion product) of pure water when it freezes?

I assume that the proton transfer reactions $$\ce{2H2O <=> H3O+ + OH-}$$ $$\ce{H3O+ + H2O <=> H2O + H3O+}$$ $$\ce{H2O + OH- <=> OH- + H2O}$$ are too fast, so that any present $\ce{H3O+}$ and $\ce{OH-}$ cannot be easily trapped in the solid ice crystal when it grows. Does that mean that pure ice crystals are free of $\ce{H3O+}$ and $\ce{OH-}$ ions?

halacha - Kitnyot and hatarat nedarim

Can a Ashkenazi do hatarat nedarim on kitnyot? According to Halachipedia the Rosh holds that one can do hatarat nedarim (annuling of a Neder) on a meritorious personal minhag. The pri chadash says that a minhag of your parents isn't binding upon you until you've observed it once. Therefore it sounds like it's considered a personal minhag since you're the one hiding it upon yourself. Additionally in America there aren't really any communal minhagim as we're basically a mishmash of everyone. Therefore aren't all ashkenazi minhagim (like kitnyot) now personal minhagim and subject to hatarat nedarim? Am I missing any information? Any one know any discussions about this?

Source of non-verse in Selichot

In Ashkenazi Selichot, the following set of verses from Tanach (patterned around the opening verb ז.כ.ר.‏ to remember) appears towards the end of the Selichot service (there may be some slight variations depending on the particular Nusach):

1. זכור רחמיך יי וחסדיך כי מעולם המה


2. זכריני יי ברצון עמך פקדיני בישועתיך


3. זכור עדתך קנית קדם גאלת שבט נחלתך הר ציון זה שכנת בו


4. זכור יי חיבת ירושלם אהבת ציון אל תשכח לנצח


5. זכור יי לבני אדום את יום ירושלם האומרים ערו ערו עד היסוד בה


6. זכד לאברהם ליצחק ולישראל עבדיך אשר נשבעת להם בך ותדבר אליהם ארבה את זרעכם ככוכבי השמים וכל הארץ הזאת אשר אמרתי אתן לזרעכם ונחלו לעולם


7. זכור לעבדיך לאברהם ליצחק וליעקב אל תפן אל קשי העם זה ואל רשעו ואל חטאתו

The things is, verse 4 is not actually a verse in Tanach. What is the origin of this 'verse' and why was it placed here in Selichot?

audio - Wav To Spectrogram, Back To Wav

Currently, I'm writing a Python script, which should do the following:

• read an audio file respectively a wav file via scipy.io.wavfile.read().


• calculate the spectrogram of given wav file.


• write the data from spectrogram back into a wav file.

Here's a bit of Code:

# Define FFT params:-------------------------------------------------------
windowSize = 512

shiftSize = 160
nFFT = 1024
window_py = signal.hamming(windowSize)
nOverlap_py = windowSize-shiftSize

# Load wav file into memory:------------------------------------------------
fs_rate,s_orig = wav.read('demo.wav')

# Type Casting:-------------------------------------------------------------
s_orig_py = np.asarray(s_orig,dtype=np.float64)


# Spectrogram:--------------------------------------------------------------
Fpy,Tpy,Spy=signal.spectrogram(s_orig_py,fs=fs_rate,window=window_py,
noverlap=nOverlap_py,nfft=nFFT,detrend='constant',return_onesided=True,
scaling='spectrum',mode='complex')

#---------------------------------------------------------------------------
P_py = np.angle(Spy)                    # Phase extraction:
X = np.absolute(Spy)                    # Needed for neural network!
X1 = X*np.cos(P_py)+1j*X*np.sin(P_py)   # "orig." spectrum. Needed for resyn


# Resynthesize to wav:------------------------------------------------------
X1 = np.append(X1,np.conjugate(X1[-1:1:-1,:]),axis=0)
x_opt_py = synthSpectrogram(X1,shiftSize,nFFT,window_py,nOverlap_py)
wav.write('demo.wav',fs_rate,x_opt_py)

But there's is a huge problem: The data in "Spy" is not useable. When I try to write the data back in a wav file, the result is noisy respectively there's nothing at all. Furthermore, I have a Matlab file, which does the same as the code above and it works just fine and in both cases the parameters are the same.

The values in of S in Python and Matlab are not even close and I don't understand why. I get that they can't be identical due the fact that both functions use a different algorithm to compute the FFT but as I mentioned before they are not even close.

Matlab-Values

Python-Values

history - What is the explanation for the discrepancy between Seder Olam's chronology and that of historical scholarship?

Rabbi Harav Yaakov Medan (etzion.org.il/en/chapter-12b-daniels-prayer-continued) states: 'According to historical scholarship, the second year of the Persian Darius, when the rebuilding of the Second Temple commenced, was the year 521 B.C.E., and the Second Temple was destroyed in 70 C.E. Thus, according to this system, the Temple stood for 591 years. However, according to a beraita in Seder Olam [which places Creation at 3760 BCE] and the gemara in Bava Batra 4a, the Second Temple stood for only 420 years. Its construction began in the year 3408 and it was destroyed in 3828.' How is this year discrepancy to be explained--an important question for the elucidation of the seventy weeks prophecy of Daniel 9:24-27?*

*'The accepted interpretation in the Talmud (Nazir 32b) and all the commentators is that the "seventy weeks" allude to the 490 years between the destruction of the First Temple and the destruction of the Second Temple. This period includes within it the seventy years of desolation from the destruction of the First Temple until the second year of the reign of Darius (the Persian), when the building of the Second Temple commenced, and the 420 years that the Second Temple stood.' (Medan) In a footnote to this, he says, 'The discrepancy between these two calculations [that of historical scholarship and Seder Olam] is discussed at length in our article and that of C. Chefetz in Megadim 14 on the period of the kings of Persia and Media.' This journal is not accessible to me.

Answer

This excellent source sheet produced by R. Anthony Manning, lists a number of different approaches to resolving the discrepancy:

1. Seder Olam is correct and the conventional chronology is incorrect.

Conventional chronology is incorrect due to Christian manipulation (R. Sa'adia Gaon) or Greek manipulation (R. Alexander Hool).

2. Conventional chronology is correct and Seder Olam is incorrect.

To quote directly from footnote 1 in R. Manning's source sheet:

Mitchel First’s book gives a comprehensive account of over 100 different Jewish responses on this issue! He lists a number of respected orthodox thinkers who take different positions. These include: (i) some who follow the C.C. [conventional chronology] without even mentioning S.O. [Seder Olam], such as R. Hertz in his Chumash, R. Shlomo Riskin, and R. Emmanuel Rackman; (ii) some who quote both systems, without deciding in either direction, such as R. Aryeh Kaplan and R. Ya’akov Meidan; (iii) some who consider that S.O. is not to be taken literally, such as R. Mordechai Breuer ... It is interesting to note that the Da’at Mikrah Tanach published by Mossad HaRav adopts C.C.

_{Mitchell First's book mentioned above is the one listed here on amazon.com.}

3. Conventional chronology is correct and Seder Olam was intentionally adjusted.

Seder Olam was adjusted in order to obscure the date of the Messiah's arrival (R. Shimon Schwab), to line up the '2000 years of Torah' with the production of the Mishnah (Epstein / Dickman / Wilamowsky), to connect the Jewish year count with the 'minyan shtarot' system (R. Menachem Leibtag), or to hide the failures of the Jews to return to Zion at the start of the Second Temple period (R. Menachem Leibtag).

calendar - When do sefardim begin reciting selihot?

Since rosh hodesh Elul is a mini-holiday do you need to wait till the day after rosh hodesh or do sefardim begin saying selihot on the first of Elul?

halacha - Is it permitted to learn in kollel without earning a living?

Based on this post which states in part:

Ramoh in Yoreh Deah, 246:21 “A person should hire himself out for alien work rather than requiring assistance from others”; “The man who is self-sufficient is greater than the one who fears Heaven”; etc.

...Here Ramoh drives home this point even further, noting that someone who decides to busy themselves with Torah and live off charity rather than working has desecrated God's Name and brought the Torah into disrepute. He adds that Torah which is not accompanied by work leads to sin and theft (presumably because the Torah scholar/student is incapable of making a living via honest means). Similarly, the Rosh, discussing someone whose Torah is his profession, such that he is exempt from paying various taxes, defines this person as someone who only takes time away from his studies in order to earn a livelihood, “which is his obligation, for the study of Torah with derech eretz is beautiful, and if the Torah is not accompanied by work, it will end in neglect and will cause sin." This reflects the normative position amongst the Rishonim in Ashkenaz, where financing Torah study was unheard of; virtually all Torah scholars were self-supporting, and even financing Torah teaching was only reluctantly permitted by some.

...after stating the primary view, that it is forbidden and wrong for Torah scholars to receive funding, then noting a "yesh omrim," an alternate lenient view that it is permissible for rabbis to receive funding, we finally have a further lenient view that even students may receive funding. However, Ramoh notes that it is still preferable for Torah students to be self-supportive, if possible:

it would seem that it is problematic for a student to be supported full time in kollel without making any sort of income himself, especially in today's age when there are thousands of people already learning in kollel.

What then is the halachic basis for someone today to choose to learn in kollel full time without working and rely solely on someone else's support?

organic chemistry - Isomer Identification Using Condensed Structural Formulae

Which of the following pairs are isomers?

a) $\ce{C5H10}$ and $\ce{C10H20}$
b) $\ce{CH3(CH2)4CH3}$ and $\ce{CH3(CH2)3CH3}$
c) $\ce{CH3CH(CH3)(CH2)2CH3}$ and $\ce{CH3(CH2)2CH(CH3)2}$
d) $\ce{(CH3)3CH}$ and $\ce{CH3CH2CH2CH3}$

My textbook says the answer is C). I beg to differ. I think it is D). C) is just a different way of writing 2-methylpentane.

Answer

isomer

One of several species (or molecular entities ) that have the same atomic composition (molecular formula) but different line formulae or different stereochemical formulae and hence different physical and/or chemical properties.

Source:
Pure and Applied Chemistry, 1994, 66, 1077 (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
Pure and Applied Chemistry, 1996, 68, 2193 (Basic terminology of stereochemistry (IUPAC Recommendations 1996))

a)
C₅H₁₀
and
C₁₀H₂₀

different chemical formula → not isomeric

b)
CH₃(CH₂)₄CH₃ = hexane (C₆H₁₄)
and
CH₃(CH₂)₃CH₃ = pentane (C₅H₁₂)

different chemical formula → not isomeric

c)
CH₃CH(CH₃)(CH₂)₂CH₃ = 2-methylpentane (C₆H₁₄)
and
CH₃(CH₂)₂CH(CH₃)₂ = 2-methylpentane (C₆H₁₄)

same chemical formula and same structural formula → identical, not isomeric

d)
(CH₃)₃CH = isobutane (C₄H₁₀)
and
CH₃CH₂CH₂CH₃ = butane (C₄H₁₀)

same chemical formula and different structural formula → isomeric

symbols symbology - Meaning of dreams with some kinds of animals

The gemara in berachot says: "All kinds of beasts are a good sign in a dream, except the elephant, the monkey and the long-tailed ape" (57b). Why is a dream with an elephant, a monkey or a long-tailed ape not a good sign? Does this sentence of the gemara mean that a dream with one of those animals is a bad sign?

theoretical chemistry - Is s-p mixing referring to hybridization or is it the mixing of one atoms s orbital with the other's p orbital?

According to molecular orbital theory s and p orbitals can mix if they are close enough in energy to each other. For period 2 diatomics, this occurs for $\ce{Li}$, $\ce{Be}$, $\ce{B}$, $\ce{C}$ and $\ce{N}$ - in the case of oxygen and fluorine the s and p orbitals are two far apart in energy. The effect can be seen by realizing that s-p mixing causes the $2\sigma_\mathrm{g}$ orbital to be higher in energy than the $1\pi_\mathrm{u}$ orbital.

My question is: Does the mixing of the s and p orbitals occur between the orbitals of one atom (basically hybridization right?) or does the s orbital of one atom mix with the p orbital of the other (and vice versa)?

This has confused me because I realize that concept of hybridization is widely used and functions well so I initially believed that the mixing should occur in one atom - forming hybrid atomic orbitals - and then bonding. However, after I thought about it some more I began to doubt that this is the case. Firstly, the s and p orbitals on one atom do not have the correct symmetry to mix effectively (the s orbital would simultaneously constructively interference with one lobe of the p orbital and destructively interfere with the other). Also, the molecular orbital diagram of carbon monoxide reveals that s-p mixing must be occurring since the $3\sigma$ orbital is higher in energy than the $1\pi$ orbital.

This also seems to contradict the idea that the s and p orbitals mix on the same atom because in $\ce{O_2}$ there is no s-p mixing so why would oxygen mix its s and p orbitals when it's bonding with carbon.

Answer

According to molecular orbital theory s and p orbitals can mix if they are close enough in energy to each other.

We can make that statement a bit more general so that we can apply it to all orbitals, atomic and molecular, by saying,

According to molecular orbital theory orbitals can mix if they are

• close enough in energy to each other, and


• have the same symmetry

Does the mixing of the s and p orbitals occur between the orbitals of one atom (basically hybridization right?) or does the s orbital of one atom mix with the p orbital of the other (and vice versa)?

Good question, you are really thinking about this! First off, yes, mixing of the s and p orbitals occurring between the orbitals of one atom is called hybridization.

When I think of these problems I

• first, hybridize the atomic orbitals (s and p) on an atom to generate hybrid atomic orbitals



• second, mix these hybrid atomic orbitals that exist on separate atoms to form a bond, a molecular orbital

But that's not how it really happens. It is important to realize that hybridization only occurs in response to some type of interaction between two atoms. In other words, only when atoms begin to approach and interact with one another does hybridization start to occur. When hybridization starts to occur, bonding between the atoms starts to occur at the same time. To first hybridize and then bond (like I think of it in my mind) is an artificial construct that allows me to sort things out. Hybridization on an atom and bonding between two atoms both occur simultaneously.

the s and p orbitals on one atom do not have the correct symmetry to mix effectively (the s orbital would simultaneously constructively interference with one lobe of the p orbital and destructively interfere with the other).

Yes they do. As this picture shows we can add and subtract an s and a p atomic orbital to form two $\ce{sp}$ hybridized atomic orbitals.

picture source

in $\ce{O2}$ there is no s-p mixing so why would oxygen mix its s and p orbitals when it's bonding with Carbon.

I think they are leaving oxygen unhybridized. So, for example, they are mixing (adding and subtracting) a carbon $\ce{sp}$ orbital with an oxygen s orbital to form the $\ce{1\sigma}$ and $\ce{2\sigma}$ molecular orbitals in your MO diagram.

Edit: Response to OP's comment

Do you know why s-p mixing raises the energy of the $\ce{2σ_{g}}$ orbital? (it lowers the $\ce{1σ_{g}}$)

Nice diagrams and a helpful explanation can be found here. Basically, It has to do with the symmetry of the orbitals, like I mentioned above. Look at your $\ce{1σ}$ orbital, when you add or subtract it with the $\ce{3σ}$ orbital, the symmetry is such that there is no constructive or destructive overlap. Therefore there is no interaction and there energies will not change. On the other hand, the symmetries of the $\ce{2σ}$ and $\ce{3σ}$ orbitals are such that they can constructively and destructively overlap. As a result they interact and their energies change, one is pushed up and one is pushed down.

minhag - Must EMTs and others rend Kriyah each time they see a patient die?

I was looking at Yoreh De'ah 340:5 (יו"ד סימן ש"מ ס"ק ה) and Moed Katan 25b (כה עמוד ב), which require Kriyah (garment-rending) for all who are there at the time of death. It would seem to me that an EMT, EMS member, doctor, nurse, or any other emergency first responder who is there at the time of death must rip Kriyah for all the places they respond to when a death of a Jewish patient occurs. Also a doctor who regularly see patients die must tear Kriyah every time, as he can lose many patients in a single day (oncology, cardiology). What is the approach with ripping Kriyah in these cases?

thermodynamics - Why do we use external pressure to find force exerted by gas on a piston in a closed vessel during its expansion?

I was reading a book in which i got confused due to this. A gas is in a vessel covered by a friction-less piston. Gas pressure is more than outer atmospheric pressure (which is constant) due to which it expands. Since it expands and move the piston outward, it does work on it which is calculated by force times displacement. In finding force we use Force = Pressure times Cross section area of piston. In finding this force to calculate work why are we using Pressure on piston by atmosphere and its weight and not pressure exerted by gas. Why? Can you also tell how the correct work done by gas can be calculated. Thanks.

organic chemistry - Does resonance overrule hyper conjugation in terms of stability in alkenes?

Which of the following is more stable ?

1. 
   

   $\ce{CH2=C(CH3)-CH=CH2}$

   
   


2. 
   

   $\ce{CH3-CH=CH-CH3}$

   
   

I was going for answer 2 because it has 6 hyper conjugative effects. I found the answer given to be 1, which has 3 hyper conjugations but more resonance structures. Will the R-effect meet the deficit of 3 hyper conjugations and make 1 more stable than 2?

Answer

We can hydrogenate unsaturated compounds and measure the heat given off, this is called the heat of hydrogenation. As the following figure illustrates, if we hydrogenate the various butene isomers they all wind up producing the same molecule, butane.

image source

By comparing their heats of hydrogenation we can see which butene was lowest in energy to begin with, that is, which butene is the most stable. The heats of hydrogenation reported in the figure tell us that trans-2-butene is more stable than 1-butene by about 2.3 kcal/mol. This extra stability can be attributed to the additional hyperconjugative resonance structures involving hydrogen present in trans-2-butene (6) compared to 1-butene (2).

Next let’s consider 1,3-butadiene. Here when we hydrogenate it, butane is again produced and we might estimate that it will have a heat of hydrogenation equal to twice that reported for 1-butene (1-butene is the best model because its double bond has the same substitution pattern as found in 1,3-butadiene) or 60.6 kcal/mol of heat given off. When we actually run the experiment we find that only 57.1 kcal/mol of heat is given off, 3.5 kcal/mol less than we estimated. In other words 1,3-butadiene is about 3.5 kcal/mol more stable than isolated double bonds and this is due to the resonance interaction between the two double bonds in 1,3-butadiene.

The resonance stabilization in 1,3-butadiene (3.5 kcal/mol) is larger than the hyperconjugative stabilization in trans-2-butene (2.3 kcal/mol).

Your question actually asked about 2-methyl-1,3-butadiene. In this case we have the resonance stabilization found in 1,3-butadiene plus some hyperconjugative stabilization from the additional methyl group. It will be even more stable than 1,3-butadiene. Further, 2-methyl-1,3-butadiene is more stable than any butene, so answer #1 is correct. Resonance stabilization is larger than hyperconjugative stabilization in this series of compounds.

product recommendation - Lectures on "Shemiras Einayim"

Would anyone know of any online lectures on the inyan of Shemiras Einayim in English ( preferably lectures that I could download. )

parshanut torah comment - Was Rachav A Harlot (Prostitute)?

It specifically says several times in Yehoshua chapter 2 and chapter 6 that Rachav was a Harlot " וְאֶת רָחָב הַזּוֹנָה". Why is it that it is accepted that she wasn't a harlot but an innkeeper and someone who sold mezonot (wheat). Some opinions that I read say because she made herself available to everyone as she sold many provisions and because she was an innkeeper (" הַזּוֹנָה").

I just want to know why we cannot take this literally? It says it quite a few times. Why couldn't the Torah just say that she was a provisioner or an innkeeper?

And I know not everything is made to be taken literally in the Torah, like 'an eye for an eye'.

tanach - Where is the city of Ninveh?

Ninveh is mentioned in the book of Yona that is read on Yom Kippur. Where is Ninveh?

Answer

From http://en.wikipedia.org/wiki/Nineveh:

Nineveh was an ancient Assyrian city on the eastern bank of the Tigris River, and capital of the Neo-Assyrian Empire. Its ruins are across the river from the modern-day major city of Mosul, in the Ninawa Governorate of Iraq.

hebrew - Which pronunciation-permutation of "yod, hay vav, hay" is forbidden to pronounce?

@AvrohomYitzchok said that I should post this question as a new question. (He did not know the answer).

I was responding to a comment he made, which read

@Sarah When Rambam says "pronounces the name [of God] with its letters, yod, hay vav, hay" he means to articulate the name as it is written and not with the letters Alef Daleth Nun Yod (as we pronounce it). – Avrohom Yitzchok Jul 10 '16 at 20:18

And here is my question:

Does the pronunciation of "the name [of God] with its letters, yod, hay vav, hay" refer to the pronunciation as in the masoretic pointing of "yod, hay vav, hay" or to any pronunciation-permutation of "yod, hay vav, hay"?

I kindly request for a source for any answer. Thank you.

halacha - English translation of Sefer Machaneh Yisrael

Is there an English translation (preferably online) of the Chofetz Chaim's sefer Machaneh Yisrael (a guide for Jewish army conscripts), or other English works on the same topic?

Answer

There's a translation of Machane Yisrael into English published as English-only (the original Hebrew is not included). It's Machaneh Yisrael (I mean, that's how they spell the title) and the copyright page reads:

Authored by
Rav Yisrael Meir HaKohen Zt"l
The Chofetz Chaim

Translated by
Machon MEMEY
413 Ashley Ave. • Lakewood, NJ 08701
(732) 364-4003

© Copyright 2010
Printed in Israel

Published by

Machon Sofrim
(732) 942-7307

purim torah in jest - How big did Mordechai get, and was it only in the king's palace?

According to the Megillah (9:4), Mordechai grew to a very large size whenever he was in the king's palace (כִּי־גָדוֹל מָרְדֳּכַי בְּבֵית הַמֶּלֶךְ ... כִּי־הָאִישׁ מָרְדֳּכַי, הוֹלֵךְ וְגָדוֹל).

How large did Mordechai grow, and did he return to normal size upon venturing outside?

---

Answer

It is known that מרדכי's other name was "פתחיה". The names are related as follows: If you double the g'matriya of the first three letters of "מרדכי", you get the first three of "פתחיה"; and if you halve the last two of "מרדכי", you get the last two of "פתחיה".

• מ doubled is פ;


• ר doubled is ת;



• ד doubled is ח;


• כ halved is י;


• י halved is ה.

Continuing the trend, let's multiply the letters of "מרדכי" by other powers of two:

• מ eighthed is ה;


• ר quadrupled is תת;


• ד quartered is א;


• כ doubled is מ;



• י halved is ה.

Thus, מרדכי was ה׳תת אמה‎, 5800 amos tall. As mentioned in the pasuk, of course, this was only in the royal palace. The palace must have had very high ceilings, which is why the beginning of Ester, which describes the palace floors and other furnishings, doesn't describe the ceilings: anything more than twenty amos up is not noticed, as we see in hilchos Chanuka.

halacha - So you ate dairy after meat. Now what?

Whatever your tradition for waiting between meat and milk, let's say you forgot you were fleishig, and now realize that you have just eaten milk within your traditional waiting period. What are you supposed to do?

Do you continue to wait until the end of the initial waiting period?

Do you start over (I see this as unlikely, but had to ask)?

If one of the above, do you have to wash out the dairy taste from your mouth/brush your teeth, lest you continue to get Hanaah (enjoyment/benefit) from the potential mixture of meat and milk in your mouth?

Or does the waiting period come to an abrupt end, such that you can now eat as much milk as you want? (This would be especially convenient in some instances, such as if you've prepared a large dairy meal and realized after the first bite or two that you still have 'X' amount of time to wait until your traditional waiting period ends, after which you will be exceedingly hungry, and/or your meal will no longer be fresh.)

---

EDIT:

I'm also curious if you can go back to eating meat immediately (assuming you normally wait some period after milk before eating meat, or even if the milk product you ate requires you normally to wait the same length of time you wait after meat).

Answer

If you last ate meat at 1PM, and you normally wait 6 hours, then you can eat dairy at 7PM. It makes no difference what you've done in between. If you ate something you shouldn't have earlier, we don't penalize, but neither do we say you can eat whatever you want.

Rinsing your mouth would probably be advisable, but not required -- nothing about "prohibited benefit" here. Benefit is only prohibited if the meat and milk are Biblically prohibited, which requires that they be cooked together.

The reasons for the waiting period are either a blanket rule out of concern that there may be some traces around in your mouth, or that there's still some of the taste lingering as you digest. Either way, I see no reason why there should be any of these funny ideas you're throwing out there. Wait your normal hours from your last consumption of meat, and move on.

A more interesting question is how to deal, religiously, with your lapse.

halacha - To what grains do the laws of yoshon apply?

For which species must we wait until after pesach to eat the previous crop? Are there different cut-off dates for different species?

inorganic chemistry - Melting and boiling points of transition elements

The melting and boiling points of transition elements increases from scandium ($1530~\mathrm{^\circ C}$) to vanadium ($1917~\mathrm{^\circ C}$). They increase because as we go across the group, we have more unpaired (free) electrons.

But at chromium ($1890~\mathrm{^\circ C}$) however, the melting point decreases even though it has more unpaired electrons than the previous atoms. Why does this happen?

everyday chemistry - What gives fresh milk a yellow tinge?

Every now and then, when I pop over to my grandparents' house, they make sure to give me a glass (or two) full of fresh milk (or "whole milk" if you will) and then proceed to pamper me for the rest of the day.

Now, it suddenly struck me that the fresh milk I get over there actually has this really faint yellow tinge, as opposed to the skimmed milk I get at the store which is almost pure white.

I did try Googling this up, but I can't seem to find anything on what imparts the yellow tinge to fresh milk.

So,

What substance/pigment is responsible for the yellow tinge associated with fresh milk?

Answer

The main substances that cause the yellowish color of the milk are carotenoids [1]. The main carotene involved is the beta-carotene coming from the feed that cows eat.

Some studies have been carried on and it has been noticed that the milk with a more yellow tinge was collected during late spring and early summer when carotene levels are at a maximum [2] unfortunately for this reason in many products as mozzarella they add titanium oxide. The amount of Riboflavin is too little compared to that of beta-carotene and generally gives a slightly green-ish tinge to the milk as reported here and here [3].

1. P. F. Fox, Fundamentals of Cheese Science,p. 13


2. Kosikowski, Frank V., and David P. Brown. "Application of titanium dioxide to whiten mozzarella cheese." Journal of Dairy Science 52.7 (1969): 968-970.



3. Marion Eugene Ensminger,Audrey H. Ensminger,Foods & Nutrition Encyclopedia, 2nd Edition, Volume 1,p. 798

infinite impulse response - complementary IIR filters

I would like a pair of complementary IIR filters (lowpass/highpass). By complementary, I mean, when the output from the two filters is summed, the original signal is recovered. I thought I could build such pairs with butterworth filters but using a little math, I discovered only 1st order filters were complementary. I thought I'd done this before, but I'm forgetting how.

Is something wrong with my math? Is there an easy solution I'm forgetting about?

Thanks!

Answer

Juancho's answer is sort of right, however there is one problem: The complimentary filter of a low pass is generally NOT a high pass filter, at least not in the sense that you are looking for. For example the one's compliment of a 4th order Butterworth low pass does not look like a 4th order high pass filter at all. It has about only half the steepness, reaches a maximum gain of ca. +6 dB below the crossover frequency and than slowly approaches unity gain above the cross over frequency.

The only matching high and low pass filters that sum to unity are first order filters. You can however find matching higher order filters that sum to unity gain so that the overall transfer function of the sum is an all pass filter. These are odd order Butterworth filters and even order Linkwitz Riley filters.

organic chemistry - Does aniline react with diazonium ions at C or N?

In the azo coupling of aniline with benzenediazonium cation, I thought of two possible products 1 and 2 that could be formed. However, I can't work out which will be preferred. What would be the major product and why?

Answer

This is a really interesting question and the answer is that the reaction of benzenediazonium chloride with aniline is a bit different to most of the reactions of benzenediazonium salts in that the initial product is compound 1, diazoaminobenzene. It is possible to run the reaction to isolate diazoaminobenzene prep here.

These diazoaminobenzene compounds are unstable with respect to reversion to a diazonium salt + nucleophile, and so many references suggest that compound 2, 4-aminoazobenzene, is directly produced. The procedure for the transformation of diazoaminobenzene 1 to 4-aminoazobenzene 2 is by heating to 50 °C with aniline (prep here).

Pronunciation of しゃ, し, しゅ, しぇ, and しょ

Now I understand that although all the morae mentioned in the title are written in Hepburn as "sha shi shu she sho", they are actually palatalized and sound quite different (the little や makes it clear). In fact since I speak Mandarin Chinese natively, they sound completely different since in Mandarin the Hepburn "sh" and English "sh" are two distinct phonemes.

Now in my Japanese class, the TAs are native English speakers though the instructor is from Japan. When the TAs are asked to read passages, the teacher occasionally corrects them for pitch accent, the う vowels, and らりるれろ, but never for the (to my ears) totally Englishified pronunciation of し. In fact しゃ is pronounced exactly the same as the English word "shah" - it isn't even pronounced "shyah".

I also notice some Japanese singers randomly pronounce しゃ as "shah" with no consistency at all. Then again, song Japanese seems to be weird (を retaining the "wo" sound, らりるれろ often using an "l" sound). My question is, are the two sh's completely indistinguishable to Japanese ears? Even when correcting the students the Japanese teacher picks up on tons of small mistakes (mispronouncing the "u" as "oo", Korean people failing to pronounce the voiced stops, wrong pitch accent) but never picks out the clearly wrong "sh" that happens quite a lot.

Answer

(Warning: I do not know phonetics in general, and I do not speak Mandarin. I am writing this answer while consulting Wikipedia. Although I am trying my best to write an accurate answer, you should take it with a grain of salt, especially with my use of technical terms and with statements about Mandarin.)

My question is, are the two sh's completely indistinguishable to Japanese ears?

Completely? Probably no. But they are almost indistinguishable to most native speakers of Japanese.

In both English and Japanese, there is only one phoneme realized by voiceless postalveolar fricatives (the same holds for voiced postalveolar fricatives):

(The primary difference between these two consonants is the shape of the tongue.)

Therefore, most native speakers of English are not trained to distinguish different postalveolar fricatives, and they pronounce the consonant of しゃ, しゅ, しぇ, しょ as [ʃ] when they speak Japanese. This does not cause a problem for comprehension because we (native speakers of Japanese) are also not trained to distinguish different postalveolar fricatives. We probably notice something different in their pronunciation and recognize it as “Japanese with English accents,” but that’s all. Probably the same thing happens when native speakers of Japanese speak English.

(I wrote “しゃ, しゅ, しぇ, しょ” above. What happens when a native speaker of English pronounces し in Japanese? I cannot tell from my experience, but if he/she gets the vowel [i] in Japanese right, probably he/she will necessarily pronounce [ʃ] in a more palatalized way, resulting in [ɕ], even if he/she is not aware of it.)

This situation may look strange to you if [ʃ] and [ɕ] belong to distinct phonemes in your native tongue: how can anyone be unaware of the obvious difference between [ʃ] and [ɕ]? But the notion of “similar sounds” is surprisingly different from one language to another. For example, many native speakers of Japanese have trouble distinguishing [s] and [θ] when we speak English, and native speakers of English might wonder how anyone can be unaware of the obvious difference between [s] and [θ]. (I guess the same example applies to native speakers of Mandarin.) As another example, many native speakers of English have trouble distinguishing きょう (今日) and きよう (器用) when they speak Japanese, and native speakers of Japanese might wonder how anyone can be unaware of the obvious difference between them.

By the way, “sh” in Mandarin is not [ʃ] (“sh” in English), either. According to Wikipedia, it is retroflex fricative [ʂ], and therefore it has yet another tongue shape. If you do not notice the difference between Mandarin [ʂ] and English [ʃ], that is probably because of the same reason why native speakers of English and native speakers of Japanese do not notice the difference between English [ʃ] and Japanese [ɕ].

history - Which masechtot don't really have Rashi?

I often hear that the printed "Rashi" commentary in certain masechtot of the Talmud Bavli (first that come to mind are Moed Katan and Nedarim) is not actually written by Rashi. Does anyone have a full list of which of the commentaries were actually written by Rabbi Shlomo Yitzchaki and which were written by others in his style? How would one tell the difference?

history - When was 歴史的仮名遣い standardized?

Enno Shioji's answer to my question about 直音表記 says (emphasis added) that:

Historically there were multiple way to write a word, and this wasn't standardized. For example, some very old documents contain both 直音表記 and ヤ行表記.

This was subsequently standardized as 歴史的仮名遣い and then 現代仮名遣い.

When did this happen, and how? I imagine that at the time (whenever that was), there was no body analogous to the various ones that have been involved in the standardization of the modern language (e.g. the switch from 旧字体 to 新字体; the promulgation of the 常用漢字 list; standardization of 現代仮名遣い, etc.), so this must have been a more organic process.

Answer

The first phonetic spelling of Japanese was using kanji. This system was called man'yōgana, named after the Man'yōshū, an anthology of poems from the Nara period written in this manner. Hiragana and katakana developed as abbreviated forms of these kanji.

Although spelling wasn't entirely consistent, and multiple characters were used for individual sounds, Japanese spelling reflected the phonology of the time fairly well, and by looking at changes in spelling over time, we can observe sound changes such as the merger of kō-otsu.

At this point, I'd like to quote some passages from Frellesvig's A History of the Japanese Language (2010). Although I've tried to pare the quotes down to a minimum, they're still quite long, so I've bolded the key sections in case you'd like to skim.

The Japanese alphabet was, in part, standardized by the Iroha-uta. From page 165:

[T]he establishment and awareness of distinct orthographic categories is evident from three mnemonic word lists or poems from the first half of the Heian period in which each distinct letter category occurs only once: the Ame-tsuchi no kotoba (or Ame-tsuchi no uta), Taini-uta, and Iroha-uta … These lists/poems functioned as a kind of ABC to remember the distinct letter categories …

The three lists concur in not having distinct letters or representation for sei'on and daku'on. Chronologically, they all reflect a stage of the language after the merger of the kō-otsu distinctions (as there is no representation of these distinctions), but before the merger of non-initial /-p-/ with /-w-/ (950-1000, …

And from page 168:

It is difficult to exaggerate the importance of the establishment and dissemination of the Iroha-uta. It is a defining event in the history of Japanese script and writing, and more generally in Japanese culture, linguistic and otherwise, … The Iroha-uta finally defined the forty-seven kana letter categories which, with the sole addition of ん/ン for the moraic nasal, still are in use today, enshrined the principle of not having separate letters for sei'on and daku'on, and fixed the sequence of letters in a list. …

The Iroha continued to function as the Japanese alphabet, as a linguistic and meta-linguistic organizing principle until it eventually was replaced by the gojūonzu in the middle of the Meiji period…

However, Japanese sounds continued to change after the kana became well-established, and spelling didn't always change with it. From page 173:

[F]or the kana categories おをほ, いゐひ, えゑへ, うふ, わは, the mapping between sound and writing became much less straightforward than it had been …, and as may be expected, this led to efforts to regularize the use of these kana letters. Rather than reforming the inventory and use of kana letters along simple phonographic lines, … an etymological spelling principle gained ground from around the beginning of the thirteenth century, eventually resulting in the so-called rekishi-teki kana-zukai (歴史的仮名遣い) ‘historical kana-usage, historical spelling’ … The simple principle is that any word is to be spelled the way it was, or would have been, spelled within the kana categories of the Iroha, before the sound changes outlined [earlier in this chapter] took place. Thus kai ‘shellfish’ (< OJ kapi) is spelled かひ, ai ‘indigo’ (< awi) is あゐ, and kai ‘rudder’ (< ka.i) is かい. …

On pages 174-175, Frellesvig goes into more detail about who established the spelling principles and when. This section, I think, answers the core of your question:

The etymological spelling principle was first explicitly proposed by the poet and scholar Fujiwara no Teika (1162-1241) as part of his recommendations of the spelling of individual words … His primary concern was the production of faithful editions of earlier texts, preserving their original shape, and he based his spelling proposals on inspection of earlier manuscripts and text versions in order to establish original, ‘correct’ spellings. It seems there was some consensus about the spelling of individual words before Teika, at least to some extent on an etymological basis, … but it was Teika who explicitly established the etymological spelling principle which, together with his specific spellings of individual words, came to be known as Teika kana-zukai … and soon acquired the status of a spelling norm, … Thus, from Kamakura to early Edo most literary writing was spelling according to the Teika kana-zukai. …

There are inevitably not a few mistakes in Teika's etymological spellings … first of all because the copies of texts he had access to and worked from already contained errors … Therefore later scholars elaborated on and amplified Teika's work. The Kanamoji-zukai (completed after 1363) by the monk Gyōa … is the first large-scale application of Teika's principles. It lists spellings for more than a thousand words and for a long time served as the major normative spelling reference. … Mention must also be made of the kokugaku scholar Keichū (1640-1701) who provided the basis for the rekishi-teki kana-zukai in use today. In his Waji shōranshō (1695) he set the etymological spelling principle on a firm philological footing with systematic citation for specific spellings of sources which even by today's standards are mostly reliable.

And this system lasted for quite a long time, with some small changes. Modern sound changes were largely ignored, and so over time the system became further and further divorced from modern pronunciation. From page 173:

At the beginning of the NJ [Modern Japanese] period further sound changes took place which resulted in phonographic equivalence before the high vowels /i, u/ … rendering the kana pairs じ/ぢ and ず/づ phonographically equivalent. By then the etymological principle had long been established and so the principle for which kana to use was fairly clear, although usages which can be thought of as ‘spelling mistakes’ (for example writing mizu ‘water’ < midu as みず rather than the etymologically correct みづ) are frequent in Edo period NJ texts.

Although historical kana spelling started out largely ignoring the voiced-voiceless distinction, the voicing marks were occasionally used when it was necessary to indicate pronunciation more precisely, and eventually, the voicing marks became common. From pages 163-164:

The earliest attested use of diacritics to mark sei or daku on man'yōgana is from the late ninth century, and on kana from the eleventh century … [S]ei-daku … remained un-noted in general writing in the [Early Middle Japanese] period. … [I]t was not until … the beginning of the Edo period … that the dakuten we know today became established and widespread in general writing.

The dakuten was originally a voicing mark, distinguishing the voiced /g z d b/ from the voiceless /k s t p/ respectively. However, due to the sound changes in the /p/ row, the phrase "voicing mark" is no longer entirely accurate—the /p/ row is now the /h/ row, and /b/ is of course not a voiced version of /h/!

Since /p/ was retained in some contexts, this row now represented three phonemes, and the handakuten developed as a way to distinguish /p/ from the other two. From page 165:

However, towards the end of the [Late Middle Japanese] period Portuguese Jesuit missionaries instituted the use of a circle on the top right corner of a kana … in order to write unambiguously pV, e.g. は (fa/ha), ぱ (pa). This was first used in Rakuyōshū, a kanji dictionary published … in 1598. Since then this practice gradually spread and is, of course, today a fully integrated feature of Japanese writing.

And less than a hundred years ago, the system was finally replaced. From page 173:

The rekishi-teki kana-zukai was only abolished as the norm with the orthographic reforms in 1946 when the gendai kana-zukai … was adopted, in which the etymological principle largely has been abandoned, with a few well-known exceptions.

So as you can see, the development of Japanese spelling over more than a millennium was rather complicated. It started out as a relatively faithful rendition of speech, but pronunciation changed over time, and historical or etymological spellings took hold relatively early on. There was some variation in convention and there were some errors made, and there were several revisions of the system, and finally the addition of the dakuten and handakuten diacritics; but ultimately it was replaced in 1946 with modern spelling conventions, which were then revised again in 1986.

halacha - Attaching Conditions to a Sale

If I sell someone an item (e.g. an orange), and I attach a condition (e.g. "you may not make orange juice"), is it successfully binding? What happens if that someone does violate the condition (e.g. makes orange juice)?

Answer

The concept is the subject of interesting debate between the authorities, particularly nowadays in the realm of intellectual property. There's a good writeup of some important sources on pages 19-24 of this YU Shavuot-To-Go packet by R' Josh Flug.

kohen priest - Riddle: when do 10 Kohanim equal 1 Yisrael?

Pretty much what the title says. Where in the Torah do we find something for which we need 10 Kohanim or 1 Yisrael?

Answer

In a minyan with 11 Jews, if they are all Kohanim, one goes up to duchan and 10 stay behind and answer Amen. If one of them is a Yisrael, all the Kohanim can duchan and the one Yisrael answers Amen (he is significant on his own since the main mitzva is to bless the Yisraelim. (SA OC 128:2,5 MB 101)

sources mekorot - Hashem and Arabs

Someone quoted to me a Gemara in Sukkah which said that Hashem had charata that He created arabs. What daf in Sukkah is that on?

inorganic chemistry - Why is fluorine the best oxidising agent, but also the most basic?

(Please note that all comparisons I have made below are with respect to halide ions only.)

According to what I have learnt, the fluoride ion is the most basic ion, because it has the smallest size and thus the highest electron density. This implies that it has the highest tendency of sharing/giving away its electron density.

Why isn't the same logic applicable when reducing strength is compared? Fluorine should have the highest tendency to lose electrons, and hence should be the best reducing agent.

tzitzis - Front tzitzit in back?

I have noticed that sometimes people will be wearing their tallit as in the below image, with one of the front tzitziot thrown back. Why is this?

discrete signals - $mathcal{Z}$-transform of $frac{1}{n^2}$

This is a Question asked in IISC ( Indian Institute of Science,Bangalore,India) interview for MS admission.

What is the $\mathcal{Z}$-transform of $\dfrac 1{n^2}$ ?

Answer

The problem is not sufficiently specified, because the range of admissible values of $n$ is missing. Here I make the assumption that we consider $n>0$. With this assumption we have

$$X(z)=\sum_{n=1}^{\infty}x[n]z^{-n}=\sum_{n=1}^{\infty}\frac{z^{-n}}{n^2}\tag{1}$$

And that's the point where we might get stuck, if we didn't have a list of mathematical series, or if we didn't know about the polylogarithm, which is defined by

$$\text{Li}_{s}(z)=\sum_{n=1}^{\infty}\frac{z^n}{n^s},\qquad |z|<1\tag{2}$$

where $s$ is an arbitrary complex number.

In your case, $s=2$ and the corresponding function is called the dilogarithm or Spence's function.

Comparing $(1)$ and $(2)$ we get for the $\mathcal{Z}$-transform of $1/n^2$ for $n>0$

$$X(z)=\text{Li}_2\left(\frac{1}{z}\right),\qquad |z|>1\tag{3}$$

Another way to arrive at the solution is to use the differentiation property of the $\mathcal{Z}$-transform:

$$nx[n]\Longleftrightarrow -z\frac{dX(z)}{dz}\tag{4}$$

Applying $(4)$ twice will give you the result. You need the correspondence

$$u[n-1]\Longleftrightarrow \frac{1}{z-1},\qquad |z|>1\tag{5}$$

In a first step you'll arrive at the transform of $1/n$, $n>0$, and in a second step you'll arrive at the transform of $1/n^2$, $n>0$.

In this case you will be using the integral representation of the dilogarithm:

$$\text{Li}_2(z)=-\int_0^z\frac{\ln(1-u)}{u}du\tag{6}$$

parshanut torah comment - Was the whole earth covered during The Flood?

Are there commentaries that suggest that the flood during the time of Noach was localised to one geographic area, as opposed to the whole Earth. In Bereishit 8:9 when the dove was sent out it says:

וְלֹֽא־מָצְאָה֩ הַיּוֹנָ֨ה מָנ֜וֹחַ לְכַף־רַגְלָ֗הּ וַתָּ֤שָׁב אֵלָיו֙ אֶל־הַתֵּבָ֔ה כִּי־מַ֖יִם עַל־פְּנֵ֣י כָל־הָאָ֑רֶץ וַיִּשְׁלַ֤ח יָדוֹ֙ וַיִּקָּחֶ֔הָ וַיָּבֵ֥א אֹתָ֛הּ אֵלָ֖יו אֶל־הַתֵּבָֽה׃

Furthermore, the following passuk says that everything 'under all of shamayim' was covered (7:19):

וְהַמַּ֗יִם גָּ֥בְר֛וּ מְאֹ֥ד מְאֹ֖ד עַל־הָאָ֑רֶץ וַיְכֻסּ֗וּ כָּל־הֶֽהָרִים֙ הַגְּבֹהִ֔ים אֲשֶׁר־תַּ֖חַת כָּל־הַשָּׁמָֽיִם׃

However, throughout the flood story this is the only time the phrase "אֲשֶׁר-תַּחַת, כָּל-הַשָּׁמָיִם" is used. The only instance that the more all encompassing term of "עַל-פְּנֵי כָל-הָאָרֶץ" is used is when the the dove is sent out, otherwise its not used.

It seems, from the pesukim, that its not clear as to whether the whole earth was indeed covered. Since the plain meaning of the pesukim does not make it abundantly clear that the whole earth was covered do any commentaries address this issue by saying that only specific localities were affected by the flood?

hechsher certification - Claims on food labels: says who?

Sometimes a food item under rabbinical supervision claims on its package label not only to be under that supervision but also to contain only yashan grain, or to not contain sh'ruya, or to contain only chalav Yisrael, or to be m'vushal (if wine). I've always assumed that the agency whose certification mark appears on the package is also attesting to the other claim; but is that true, or does the certification mark only signify kashrus, with the other claims being only the manufacturer's?

grammar - What exactly is this でね construction?

The following dialogue is from the video game Final Fantasy VI:

宿屋{やどや}の[親父]{おやじ}は、[余所者]{よそもの}が[嫌]{きら}いでね。

I think I understand this sentence. It means something like "the old man at the inn doesn't like outsiders". But I'm not sure why it ends with でね (as opposed to, say, だよ). I can tell that it's the -te form of the copula だ plus the particle ね, but I'm not sure exactly when this combination is used.

I couldn't find discussion of ending sentences with で in dictionaries, or any explanation of the combination でね. So I decided to look for examples online. I found these on ALC and in the Tanaka corpus:

「それは私が知っているある海賊の名前でね。」
"It's the name of a buccaneer of my acquaintance"

「ああ、ただの黙想でね」
"O, it's just a retreat, you know"

「いやぁ、昨日は入れ食いでねえ。」
"They were biting like crazy yesterday."

Based on these four examples, it seems like でね is used to present new information. I feel like I'm missing some nuance or implication, though. (I tried looking for similar combinations with other particles instead of ね, but I couldn't find any.)

What exactly does でね mean in sentences like these?

EDIT: After posting this, I found てね in 大辞林, but I don't think the meaning fits what I'm seeing here... It says 「相手に対するやや甘えた依頼や希望を表す。てよ。」, but these sentences don't look like they express 依頼 or 希望.

Answer

でね is the continuative form of だ plus the "interjectory particle" (間投助詞) ね. (Works just as well with the continuative of any other verb.)

で is usually used to connect to phrases, but when the speaker is too excited about the first part already, s/he wants to affirm it with ね. In fact, でね can be used at the beginning, in the middle, or at the end of a sentence.

At the beginning, it could be interpreted as 「それで、…」.

In the middle, it really just is ascertaining the versatility of ね, which is used as interjection (and is expected to be confirmed with うん).

At the end the use is the same again, just the rest of the sentence is being omitted.

Only in the last case, the listener has to read into the speaker's mind of what the conclusion of the 「…で」 part should have been. E.g.

俺のこと嫌いって言ってね、本当にムカつくんだよ。

She told me she hated me, that old windbag.

becomes

俺のこと嫌いて言ってね。まぁ、とにかく、結婚するか今のとこは分からない。
She told me she hated me, but... In any case, I'm not sure we will actually get married.

hebrew - Is it "Vay-SHA-vucha" or "Va-YASH-vucha" in Anim Zemiros?

Is it "Vay-SHA-vucha" or "Va-YASH-vucha" in Anim Zemiros? I've heard both, and seen both in different siddurim. Any insight?

filters - Deconvolution by Convolution

This is now a second time I am attempting to ask this very important but simple question here. What I want to know is can you do deconvolution by convolving a signal. It is often stated that, for example by cutting and boosting the same frequency on an equalizer the result is the original signal. Is that the case? Can convolution be removed by convolving? That would certainly brake the identity that the convolved signal must be n+m-1 in length. I tried this with an equalizer and the results seem to be close to perfect, just some quantization distortion.

If the above can be done, I can not arrive at this conclusion. For example If I convolve (1) with (1, 1) the result is (1, 1). I can not find any impulse response that if convolved with (1, 1) would result in (1).

So what is the truth here?

grammar - 〜ものだから 〜もの ～もん What are the differences?

What is the connotation when using 〜ものだから　and 〜もの in a sentence? In my text, they state these examples:

The first set is 〜ものだから：

上着を脱いでもいいですか。　暑いものですから。

Can I take my jacket off? I'm feeling a bit hot.

遅くなってごめん。　道路が混んでいたもんだから。

I'm sorry I'm late. I got caught in a traffic jam.

The second set is 〜もの:

パーティーには行かなかったよ。　知らなかったんだもの。

I didn't go to the party, because I didn't know it was on.

しょうがないよ。　子供なんだもん。

It can't be helped. He's just a kid.

I was told that one is used more often to assert a reason or excuse for something being done, and the other for expressing feeling. Is this true? Other than that, is there any defining line between the two examples?

EDIT: I removed the question about whether a form was meant for subjectivity or objectivity.

Answer

I think ものですから/もんですから/もんだから/ものだから/だもの/だもん can all be used to state a reason or excuse. (暑い)ものですから sounds very polite and a bit feminine (and maybe elegant too). (暑い)ものですから sounds more polite than (暑い)もんですから. (暑い)もんですから doesn't sound feminine or masculine to me. (道が混んでいた)もんだから sounds more casual than (道が混んでいた)ものですから/もんですから. Hmm maybe ものだから sounds a bit more feminine than もんだから in casual conversation. I think ものだから is not used so often as もんだから.
So... you can rephrase them as 「上着(を)脱いでもいい？暑いもん(orの)だから。」(more casual than your example)「遅くなってすみません。道が混んでいたもの(orん)ですから。」(more polite than your example)

I think (知らなかったん)だもの sounds a bit more feminine than (知らなかったん)だもん.

You can also say;
知らなかったもん(sounds more casual and maybe a bit more blunt than 知らなかったんだもん)/
知らなかったもの(sounds a bit more feminine than 知らなかったもん)/
子どもなんだもの(sounds more feminine than 子どもなんだもん)/
子どもだもん(sounds a bit more blunt and maybe more childish than 子どもなんだもん).　

(BTW if you want to sound more elegant and feminine, you can say 「パーティには行きませんでしたわ。知らなかったんですもの。」「しかたありませんわ。子どもなんですもの。」)

Edit: Wait... now I think you're asking if the first set (~ものだから) and the second set (~だもの) are interchangeable, and how these two differ from each other...?

1「上着、脱いでもいい？暑いんだもの/暑いんだもん」
2「遅くなってごめん。道が混んでいたんだもん」
3-a「パーティーには行かなかったよ。知らなかったもんだから。」
b「パーティーには行きませんでした。知らなかったものですから。」
4-a「しょうがありません。子供なものですから。」
b「しょうがないよ。子どもなもんだから」

1 sounds fine to me, but I would rather say 「上着、脱ぐわ。(だって)暑いんだもん。」2 also sounds fine but I think it sounds like someone's blaming you for being late and you're stating an excuse. 3 sounds fine too. 4 sounds a bit awkward to me... I think you'd say 子どもなものですから/子どもなもんだから when you apologize to someone for something your kid has done. e.g. 「申し訳ありません、子どもなものですから」「ごめんね、子どもなもんだから」.

So... I think the first set (~ものだから/もんだから) are more used to just express a reason, while the second set (~だもの/だもん) might have a nuance of complaint or dissatisfaction, a grumbling tone or maybe a criticizing tone... so the second set might sound like 'I didn't go to the party, and it wasn't my fault, because I wasn't invited/nobody told me about it.'/'It can't be helped, and you shouldn't complain, because he's just a kid.'