halacha - When Adar Begins we increase our Joy-משנכנס אדר מרבים בשמחה

משנכנס אדר מרבים בשמחה- When Adar Begins we increase our Joy (I know it is not in Shulchan Aruch or the Rambam) What is the practical application of it?

Answer

Chasam Sofer says that it has little or no practical application, and indeed he says that this is why Rambam and Shulchan Aruch don't cite it as practical halachah.

However, the Minchas Elazar (Nimukei Orach Chaim 686:1) raises several objections against the Chasam Sofer's position. He writes (quoting his own statement in another of his sefarim):

אבל משנכנס אדר מרבין בשמחה נקט סתם כי מדה טובה מרובה, ובאיזה דבר שנוכל אז להרבות בשמחה מצוה איכא, וכל אחד ישער בלבבו ונפשו... מצוה בכל מה דאפשר להרבות בלבו ובעניניו בשמחה של מצוה ולקיים דברי חכמים

"But it just says 'when Adar begins we increase our joy' without further specification, because the good aspect is greater [than the "decrease in joy" during Av, for which specific areas are mentioned]. So whatever we can do to increase in joy - there is a mitzvah in doing so, and each person has to evaluate this according to his own heart and soul... It is a mitzvah, insofar as possible, to increase the mitzvah-related joy in his heart and in his affairs, and to fulfill the words of the Sages."

algorithms - How CDMA receiver extract it's corresponding data from the receiving modulated & superposition-ed signal?

I have difficulty understanding CDMA.

I have read all those PN/walsh code things, and understand orthogonality very well.

But none of the resources I found demonstrate how a receiver end extract data from modulated & superposition-ed signal.

Most of them just stop at the digital encoding & decoding part and skip the modulation part.

But in real implementation signals of different walsh code are modulated then superposition-ed.

I cannot figure out how it is done.

======================================================

P.S. I am confused that does the sender add the signals before or after modulation?

If before, take BPSK as an example, there is a chance there would be >2 different values in the added result vector, which can no longer be encoded in BPSK.

If after, then the signals are simply super-positioned, the receiver would often see both 0&1, with different amplitudes, at the same time, i.e. Acos(wt)+Bcos(wt+pi), which seems a bit hard to decode.

hashkafah philosophy - Hyperbole in the Gemara?

There are many times where the Gemara says that someone who does something is equivalent to one who is "kofer b'kol" or killing someone (for example regarding lashon harah in Erchin 15b

I have always been under the assumption that such language is hyperbolic.

Is that the case, or should such things be taken literally?

Answer

This is pretty explicit in Rambam Laws of Teshuva Ch. 3:

‏ [יד] כל אחד ואחד מארבעה ועשרים אנשים אלו שמנינו--אף על פי שהן ישראל, אין להן חלק לעולם הבא. ויש עבירות קלות מאלו, ואף על פי כן אמרו חכמים שהרגיל בהן אין לו חלק לעולם הבא, כדי להתרחק מהן ולהיזהר מהן.‏

כה ואלו הן: המכנה את חברו, והקורא לחברו בכינוי, והמלבין פני חברו ברבים, והמתכבד בקלון חברו, והמבזה תלמידי חכמים, והמבזה רבותיו, והמבזה את המועדות, והמחלל את הקודשים.‏

The above 24 matters [e.g. denying the existence of God] would preclude even a Jew from a share in the World to Come. Some sins are less bad than these [and therefore wouldn't], however the rabbis said "one who does these regularly will lose his share in the World to Come" in order to make a point and distance a person from them. They are: dubbing a friend with derogatory nicknames or using such nicknames, deeply shaming someone in public, putting oneself on a pedestal by taking advantage of someone else's shame, disgracing scholars or one's own teachers, disgracing the holidays or holy matters.

Similarly, there's a responsum from Rabbi Moshe Feinstein -- OC4:116 -- for someone overcome with sexual guilt. He says when the Zohar, and subsequently the Shulchan Aruch, say a certain sin is "as bad as all others combined", it's "lav davka" -- it doesn't really mean that.

talmud gemara - Did Rabbi Akiva Go To Africa?

The Gemara in Rosh Hashana 26a says:

ואמר רבי עקיבא כשהלכתי לאפריקי...

Rabbi Akiva said: when I went to Afriki

Is this referring to the continent of Africa?

Was Africa in this time period known by that name?

Are there any other Gemaras which talk about a trip to Africa that the Tanaim went on?

Answer

Yes! we definitely find this name in other Rabbinic literature. See Sanhedrin 94a. Yerushalmi Sheviis chapter 6.

Yitzchak Meitlis in the appendix to his book Excavating the Bible writes that this refers to Africa as the same story is found in the works of Procopius (Byzantine historian) where it is related that the Canaanites were afraid of Joshua Bin Nun (Girgashites according to Yerushalmi) and settled in Libya.

kibbud av veim honoring - Honor your Father and your Mother?

I heard a Rabbi at the Central Synagogue in New York say that honoring your parents was not just to agree with them but to understand them.

How does the halacha deal with parents who are very angry people who often say upsetting things or who are hard to understand. When and how are you allowed to answer them?

Not using くて in i-adjective Conjunctions

I've been reading 猿蟹 from this website.

I've come across a sentence that puzzles me grammatically:

まだ青い固い柿の実を、蟹に投げつけました。

Here, there is a conjunction of two i-adjectives, but the writer doesn't use くて to join them (to say 青くて固い）. I wonder why this is so?

Answer

In general, this pattern is found when the second adjective and the following noun are treated as one set phrase. (Compare "a kind old man" vs "a kind and old man" in English; "old man" is clearly treated as a set phrase in the former case.) In addition, くて is often avoided in lyrics or poems where people sometimes ignore formal grammar in favor of rhythm.

But this does not explain your example since this text is prose and 固い柿の実 is not a set phrase. I think this まだ modifies both 青い and 固い because a 柿 fruit gets softer as it ripens. So, in your case, I think まだ青くて固い柿の実 is better, and I don't see any good reason to prefer 青い固い here. It doesn't sound terribly bad, either, so I think you can regard this as a trivial mistake, and get moving.

minhag - Tu B'Shvat Seder: At night or day?

The Pri Etz Hadar, as incorporated in the Chemdas Yamim, tells us of the idea of making a Tu B'Shvat Seder. It seems that most people (such as here, here and here) assume the Seder is meant to take place at night. I conjecture that they take the parallel to the Pesach Seder as an indication of the time of day. However, the Chemdas Yamim does not say clearly when the Seder is indeed meant to occur. In fact, in a number of places (such as here in the first paragraph) he uses the term בעצם היום הזה, which I would take to mean that the Seder should be had at noontime or at least during the day, as that phrase usually means.

Does anyone know of a clear source text that states when the Seder should take place?

blessing - Bracha over Shelter

Question for a rainy day:

Every day we say Brochos to give thanks and praise over various pleasures and gifts that HaShem gives us. However not everything that would seem worthy of a bracha gets an explicit bracha, rather we say either that the action/pleasure in question is either not eligible for a bracha or meant to be included when we say a different bracha

For example, R' Eliezer HaGadol (and likely other rishonim such as the Rambam, depending on your interpretation) holds that the blessing on clothing in ברכות השחר is a ברכת הנהנין. For another example, R' Ya'akov Emden writes that hamapil exempts one from a theoretical obligation to recite a birkas hanehenin on tashmish hamita. – Fred Nov 17

My question is sleeping with a roof over ones head. Has anyone ever seen an opinion that states when one says bracha x that you can have in mind thanking HaShem that you slept with a roof over your head protected from the elements ?

Answer

The specific brochos in Birchas HaShachar are related to those things that are equally essential to all am yisroel. They are not personal brochos. Therefore one would make the brocha "sh'asah li kol tzarchi" on wearing shoes, even if they are not wearing shoes that day. On the other hand, on tisha b'av, when klal Yisrael is not wearing shoes, we dont make that bracha even if we ourselves have a heter to wear say, orthopedic leather shoes. The Gemara states that "one should even sell the beams of his house to buy shoes". From this we see that shoes are considered a more intrinsic necessity than a home. There are also those that may choose to sleep outside or are, G-d forbid, homeless. In Egypt our forefathers slept in the field.

It would also seem that since Shoes and clothing are both requirements for various mitzvas, we say a Brocha for them (chalitza, mourning, davening and learning, etc) while the mitzvahs tied to a home are either dependent on having a house (mezuza, chanukas habayis) or can be done without a traditional house (Hachnosos orchim, Bayis vaad l'chochomim).

Their are also other, much deeper, reasons why those specific Brochos were chosen for Birchas hashachar.

The appropriate time to Thank Hashem for having a home, would be as stated earlier, when buying the home (shehechyanu) or when placing a mezuzah. Some also have the custom of making a chanukas habayis on a rented home. We can also have it in mind when we say Birchas HaTorah if we learn in our home and any other bracho on a mitzvah done in the home.

physical chemistry - Why does oxygen not like to be a double anion?

The electron affinity of a neutral oxygen atom is −142 kJ (it releases this energy). The electron affinity for the now double anion $\ce{O^2-}$ is 710 kJ (work must be done on the atom).

My question is, why the large jump in electron affinity? We are taught that the electrons do not interact much with each other in the way of shielding. I think this to be incorrect, because otherwise, the effective nuclear charge on all of the valence electrons should be about the same, including the new ones added to ionize the atom. This would make the electron affinity about the same for each electron. Plus, doesn’t the oxygen atom want to complete its shell? So why is it putting up a fight?

parshanut torah comment - Black Magic by Pharaoh's Magicians

What are the various opinions regarding the efficacy of the magician's in the Exodus story?

halacha - Why do some prayers require you to stand?

Is there a significance of standing or sitting while reciting a prayer?

The following prayers require one to stand: baruch sheamar, yishtabakh, shemoneh esrei and aleinu (according to some minhagim).

This is more prevalent during the prayers of Rosh Hoshana and Yom Kippur where you are required to get up every 5 minutes when the ark is opened during hazaras hashatz.

organic chemistry - Why is the benzyne triple bond distorted?

In many places I've seen the "extra" bond in benzyne being labelled as $\ce{sp^2-sp^2}$ overlap or distorted (not parallel) $\ce{p\pi-p\pi}$ overlap. But I've failed to see why we can't have a normal, parallel $\ce{p\pi-p\pi}$ overlap.

Wikipedia says:

In benzyne, however, the p orbitals are distorted to accommodate the triple bond within the ring system, reducing their effective overlap.

That makes no sense to me — why can't a normal, parallel $\ce{p\pi-p\pi}$ overlap be "accommodated" within the system.

So, what is the reason for the distorted $\pi$ bond in benzyne?

I'm fine with answers involving a bit of QM/MO theory.

Answer

First, Wikipedia doesn't really say what is the extent of this change. Here are superimposed a benzene and a benzyne molecule (own HF calculation, don't ask for the details):

The carbon atoms involved in the triple bond are displaced by less than $\pu{0.2 Å}$. In benzene, we have with this level of calculation:

• $\ce{C–C}$ distance = $\pu{1.39 Å}$


• $\ce{C–H}$ distance = $\pu{1.08 Å}$


• $\ce{C–C–C}$ angle = $120^\circ$

while in benzyne, we have:

• $\ce{C–C}$ triple bond = $\pu{1.22 Å}$


• other $\ce{C–C}$ bonds = $\pu{1.38 Å}$ (almost all equal)

So, merely because the triple bond is stronger, the distance will be shorted and the benzyne structure is distorted.

Regarding orbitals, well, the p orbitals of the carbon atoms involved in the triple bond are “naturally” directed towards where the hydrogens would be. Slightly distortion of the system is possible, and indeed evidence above on the structure, but they will not be parallel, as that would disrupt the structure too much and diminish the $\sigma$ bond. So it's a competition between: making the new p orbitals “more parallel” increases overlap, but it weakens the $\sigma$ bonding pattern, which is much stronger. As such, while some distortion happens, you stay mostly close to the benzene-type orbitals.

image processing - Locating the outer boundary of the iris

I need help with iris localization. I have applied the imfincircle function to locate it, but it only locates the inner boundary of the pupil and does not find outer boundary.

How do I locate the outer boundary?

halacha - Until what time in the morning may you eat on a fast day?

On fast days that begin in the morning, (Asara B'Teves, Taanis Esther, Shiva Asar B'Tamuz, Tzom Gedalya) if you intend to eat when you awake, until what time may you eat in the morning? Does it depend on Shaos Zemanios?

grammar - Difference between 六歳にして and 六歳で

というわけで、僕は六歳にして、画家というすばらしい職業をめざすのをあきらめた。
For that reason, at six years old I abandoned my goal of having a wonderful occupation as a painter.

I don't really understand how にして works here. Literally I read "making into six years old". So might "having reached six years old" be a better translation than "at six years old"?

Answer

There is quite a big (and important) difference in meaning and nuance between 「六歳{ろくさい}で」 and 「六歳にして」.

「六歳で」 is just neutral and factual. "One did something at age six." There is no surprise or any other special feeling expressed regarding it happening at that age. For instance, if you moved to London with your family or started learning to play the piano when you were six, that would be 「六歳で」. No one would wonder "Why so early/late?", would he?

「六歳で」, therefore, is synonymous to 「六歳の時{とき}に」.

「六歳にして」 is much different in that it expresses the speaker's feeling that it was (a little) too early for something to occur at age six. Thus, it would mean "at as young as (six)", "at a rather young age of (six)", etc. One would normally expect that to happen at a later stage in life (if it happened).

"For that reason, at a rather young age of six, I abandoned my goal of having a wonderful occupation as a painter."

I am afraid neither "making into six years old" nor "having reached six years old" would capture the nuance of the phrase. The former does not even make much sense (to me at least).

home experiment - How explosive is hydrogen gas?

I want to electrolyze water to get oxygen and hydrogen. I want to mix them in a regular balloon and ignite it. How much hydrogen would you need in a 2:1 ratio with air for it to be dangerous? Is this generally a safe experiment?

Answer

First, let me say that I've enjoyed many times exploding soap bubbles of about one milliliter filled with hydrolysis gas. That is 1 cubic centimeter. That will give you a sound that rings in your ears in a decent sized living room. You may wish to use ear protection for the experiment.

50 ml will have an effect in a lecture hall that not only wakes up everyone, but also may make people complain.

Now while the explosive limits of hydrogen in air range from about 18 -- 60 % the flammable limits are from 4 -- 75 %, in oxygen the limit of flammability goes all the way from 4% to 95% read: for practical purposes, hydrogen in oxygen is always at least a flammable mixture.
For comparison, gasoline in air is flammable roughly between 1.5 - 7%.

However, you start with a stochiometric mixture which is ideal for explosion (after all, that's why you do it, right?), and it is in oxygen, not in air. So even if you "only" have a flammable mixture reaching an ignition source (e.g. electric switch), chances are quite high that as the ignition proceeds through the mixture, it can reach a zone where the gas/air mixture is explosive. Also, because hydrogen is so much lighter than air, it tends to accumulate under the ceiling, so even if there is enough air in the room that an ideal mixture would not be explosive, chances are that there is an explosive layer of gas. (Same with gasoline or, practially more relevant: solvent from glue for parquet floor tiles)

The safety relevant points are:

• the limits of explosion and flammability are, even in air, extremely wide.


• limits of flammability are important even if there happens to be no explosive mixture: hydrogen is a small and light molecule that diffuses fast. If the air you breathe happens to have a hydrogen concentration within the flammability limits, any ignition will burn deep into your throat on its way to the lungs.

number - Shisha Ushmonim?

Who knows eighty-six?

Please cite/link your sources, if possible. At some point in the next few days, I will:

• 
  

  Upvote all interesting answers.

  
  


• 
  

  Accept the best answer.

  
  


• 
  

  Go on to the next number.

  
  

Answer

86 is gym-atria for elokim, gd of all powers meaning one who has complete power over all worlds including nature. ---86

torah study - Is sign-language considered valid as "Targum"?

For fulfilling the mitvah of 2 Mikrah / 1 Targum, O.C. 285:2 says that if one cannot understand Targum, one may use Rash"i.

In viewing Mishnah Brurah commentary # 4, there's a suggestion on what to use if one doesn't understand Rash"i. The point appears to be that one needs to use something that he understands.

Later, in O.C. 285:5 he says that one who teaches babies is exempt from this mitzvah. Mishnah Berurah #16 explains that atthat time, the teachers would teach the babies the meaning of parsha and that counts as Targum. He doesn't explain which commentary he used, but, I'm inferring that it wasn't Targum and maybe it wasn't Rash"i, either. That's unclear. But, again, the point is that it was clear that he and the children had to understand what the Mikra was.

Thanks to @DoubleAA for pointing out (indirectly) this M.Y. answer that indicates that one must say "Targum" aloud. Most signers verbalize their signs. This may sound strange for readers that are thinking, "but they're deaf! What's the point?" There are various degrees of deafness. Many deaf people can hear something -- esp. cochlear implant wearers. But, they have trouble understanding what they hear. So, the sign language is a supplement. And, frequently, a signer is present at a mixed crowd. So, the purpose of the verbal is for the hearing people. In short, the signer IS saying things aloud.

So, with these ideas presented, would one be able to use sign language as a means of translation in place of Targum?

halacha - May one go by an alternate identity on the Internet?

On the Internet, nobody knows you're a dog. As much as I like dogs, I am not one myself. But the line does best explain the point I'm trying to make: you can be whomever you want to be on the Internet.

Is there a problem with pretending to be someone else on the Internet? For instance:

• Lying, or at least Geneivas Da'as - To a certain extent this would seem permissible as per the "preventing harm" permission, but how far can you stretch that?
  
  
  
  • Say a Jew pretends to be a non-Jew and is invited to a chat on Shabbos. Now what? If he wants to keep his identity intact he has to give some sort of a lie. Perhaps one shouldn't have a fake identity in the first place, lest it lead to a situation in which he ends up being stuck between pursuing his previous "white" lies with more serious transgressions or telling a bigger lie. Although the choice is obvious, to a person who's so caught up in this persona of his, it may not be so obvious, and he might c"v pick the former option.
  
  
  
  



• Beged ish/ishah - This is only somewhat facetious. If the problem is intermingling with the opposite gender (Nazir 59a), then would the same logic apply online?


• There are actually cases of people who in real life become their online personas, which could lead to them violating many mitzvos depending on the case. It's a real mental condition, though far from the halachic definition of a shoteh (they're still in full conscious control of their faculties). Like the sub-bullet point under "lying" above, perhaps one shouldn't be allowed to develop an online persona if there's a reasonable concern that he may become it. (This would, of course, not apply across the board.)
  
  
  
  • Or worse - there are also cases of people who try to keep this up long enough that they develop multiple personality disorder, which could very well devolve into a halachic shoteh.
  
  
  
  


• Anything else I didn't think of?

---

^{Now for the meta/clarification/avoiding-being-closed-as-dupe information. Basically, unless you're a mod or a close-vote-hunter, you can skip the rest of this post.}

This is not the case of one who creates accounts to boost his business. This is a person who has one account online who actively uses it to pretend to be someone else.

This is not the case where one pretends to be my elderly granny neighbor down the street. I am discussing a case where one makes up a new identity just for the fun of it, perhaps as an escape from reality.

This is also not the case of the 5-year-old indigenous New Zealander who wants to get more upvotes and answers by pretending to be a cute little kiwi. He's not trying to manipulate anyone. He's just wants to go by another persona just for the fun of it.

messiah - Who is Moshiach Ben Joseph and what does/did he do?

I am asking this as someone who has never heard of Moshiach Ben Joseph. I would appreciate detailed answers, or maybe links to places that explain it.

I have been interested in Judaism for a long time and have tried to study things here and there about it but never did I read anything about Moshiach Ben Joseph.

I am hoping I could get an answer here from those who practice Judaism or are well-versed in the Laws and traditions of Judaism.

Answer

Just to note, Rambam (Mishna Torah; Hil. Melachim 12:2) writes that one should not over-contemplate the events that are to come about with the redemption, for the prophecies are intentionally vague and no one will know for certain their meaning until they come to be realized. Even the Rabbis of the Talmud only said about the redemption and the Messiah what they could glean and derive from the verses of the Prophets, but did not have any sort of absolute knowledge or tradition as to what would happen.

That said, the Talmud (Succah 52a and 52b) does mention a figure known as "Mashiach ben Yosef", and does interpret a couple of verses in Zecharia in light of his existence. (In doing so, it is made clear that he will die in the apocalypse.) Who is this figure? It is not exactly clear.

R' Saadya Gaon (Emunot V'deot 8:6) seems to believe that his existence is only necessary if the Jews are not ready for the Messiah and need to do t'shuva to merit the redemption. [It is a common idea that the Messiah will come either if the Jews are meritorious, or if they are not, at a predetermined "deadline". R' Saadya is referring to if the Messiah must come at the "deadline", and the Jews need preparation to be redeemed.] In this case, the Mashiach ben Yosef will lead the Jews back to God's good graces allowing them to be worthy of redemption, and later he will die in battle (of Gog and Magog), allowing for the succession of the "real" Messiah, Mashiach ben David.

Abarbanel and Malbim, in their commentaries to the Prophets, treat the existence of Mashiach ben Yosef as a "kabbala" (tradition) known to Chazal from the prophets themselves. (See Abarbanel to Ezekiel 32 and Malbim to Ezekiel 37:19.) In their opinion, he will be (as indicated by his name) from the tribe of Yosef, or at least from one of the ten "lost tribes", who were exiled by Sancheriv. He will be instrumental in uniting the ten tribes with the rest of the Jews in exile, as well as uniting the Jews in exile themselves, and leading them in the final war leading to the Redemption, thereupon dying in battle.

According to some sources, Mashiach ben Yosef will be resurrected immediately after the war in the "Techiat Hameitim" (Resurrection of the Dead). Others maintain that he will remain dead so as not to detract from the monarchy of the Mashiach ben David.

number - Shisha Ve'arba'im?

Who knows forty six?

ששה וארבעים - מי יודע?‏

The traditional Passover song "Echad" implies a possible presupposition that there is a Jewish significance to be found for each natural number. Accordingly, there is an ongoing series on Mi Yodeya that is attempting to unearth significant Judaism facts about each number, in sequence.

What significant Judaism facts are there about the number 46? The more significant within Judaism and the more intrinsically dependent on the value 46, the stronger the answer. Please include sources for your information wherever possible, as with all other answers on this site.

And from lazy gematria, please don't try to base your entire answer.

Answer

46 are the chapters in each of the first two books of the Rambam's Mishneh Torah.

nucleophilic substitution - What are the partial charges in an SN2 transition state?

What are the partial charges of on the atoms in a SN2 reaction?

The nucleophile is normally negatively charged and has a lone pair of electrons. This would make you think the transition state would have a negative charge on the nucleophile. The leaving group also is taking the electrons from the molecule with it. So what is the charge separation?

Here are conflicting images.

First image

Second image

grammar - can あいだ / あいだに be used with non-past tenses

Last week I learned to use あいだ and あいだに to express things that happen at the same time (are parallel) or things that happen while other are occurring. But I noticed that all the examples on the book (みんなの日本語 - 中級１ - Lesson 8, pp. 82) as well as the exercises and their answers use past tense, like this:

電車に乗っているあいだ、本を読んでいた。

食事に出かけているあいだに、部屋にどろぼうが入った。

As I understand, in this grammatical pattern あいだ is used sort of like a "while". But can this be used to express things that are happening now or will happen in the future, while others occur? For example, is this correct:

あなたが映画を見ているあいだ、私は買い物に行きます。
(While you watch the movie I will go shopping)

みんなが遊んでいるあいだ、私は働いています。
(I'm working while everyone is having fun)

Answer

あなたが映画を見ているあいだ、私は買い物に行きます。
みんなが遊んでいるあいだ、私は働いています。

Both sentences are perfectly standard. The structure あいだ(に), is indeed not bound to being used with the past tense.

intermolecular forces - Why does silicon tetrafluoride have a higher melting point than sulfur tetrafluoride?

So looking at the Wikipedia pages of sulfur tetrafluoride and silicon tetrafluoride, the melting points are −121 °C and −90 °C respectively, and so $\ce{SiF4}$ has the higher melting point. However, their boiling points are −38 °C and −86 °C, respectively, giving $\ce{SF4}$ the higher boiling point.

I can justify that $\ce{SF4}$ has the higher boiling point because it is more polar since its Lewis structure has a lone pair on the sulfur atom, and so it experiences greater dipole-dipole forces. However, why does $\ce{SF4}$ have a lower melting point?

Answer

High symmetry molecules fit into crystal lattices especially well (higher m.p.), but are volatile for having fewer van der Waals interactions (lower b.p.).

$$\begin{array}{lrr} \hline \text{Compound} & \text{m.p.}/\pu{°C} & \text{b.p.}/\pu{°C} \\ \hline \text{pentane} & −130 & 36.1 \\ \text{isopentane} & −160 & 27.2 \\ \text{neopentane} & −18 & 9.5 \\ \hline \text{octane} & −57 & 125 \\ \text{2-methylheptane} & −110 & 117 \\ \text{2,2,4-trimethylpentane} & −107 & 99 \\ \text{2,2,3,3-tetramethylbutane} & 101 & 107 \\ \text{cubane} & 131 & 133 \\ & & \text{(sub. at r.t.)*} \\ \hline \text{decane} & −30  & 174 \\ \text{isodecane} & −75 & 167 \\ \text{adamantane} & 270 & \text{sub.} \\ \hline \end{array} $$

* sub. — sublimes; r.t. — room temperature.

number - How many words are there in Tanach?

How many letters are in the Torah?

How many words are in the Torah?

How many verses are in the Torah?

How many chapters are in the Torah?

How many letters, words, verses, and chapters are in every sefer of the Torah?

How many letters are in the Tanach?

How many words are in the Tanach?

How many verses are in the Tanach?

How many chapters are in the Tanach?

How many letters, words, verses, and chapters are in every sefer of the Tanach?

I just want to get a sense of how big it is. And to compare with other texts. Statistics.

purim torah in jest - PTIJ: Spontaneous Combustion on Erev Pesach

Mishnah Pesachim 1:5:

וְעוֹד אָמַר רַבִּי יְהוּדָה, שְׁתֵּי חַלּוֹת שֶׁל תּוֹדָה פְסוּלוֹת מֻנָּחוֹת עַל גַּג הָאִצְטַבָּא. כָּל זְמַן שֶׁמֻּנָּחוֹת, כָּל הָעָם אוֹכְלִים. נִטְּלָה אַחַת, תּוֹלִין, לֹא אוֹכְלִין וְלֹא שׂוֹרְפִין. נִטְּלוּ שְׁתֵּיהֶן, הִתְחִילוּ כָל הָעָם שׂוֹרְפִין. רַבָּן גַּמְלִיאֵל אוֹמֵר, חֻלִּין נֶאֱכָלִין כָּל אַרְבַּע, וּתְרוּמָה כָּל חָמֵשׁ, וְשׂוֹרְפִין בִּתְחִלַּת שֵׁשׁ:

Further did R' Yehudah say: There were two disqualified loaves of a Todah placed on the roof of the portico. Whenever they were placed, the entire people could eat. One was taken, they hang: they don't eat, and they don't burn. Both were taken: the entire people would begin to burn. R' Gamliel says: Chullin was eaten all the fourth hour, and Terumah all the fifth, and they would burn at the beginning of the sixth.

I assume the connection between eating and spontaneously combusting is that the people would begin to fast in preparation of their imminent demise. But why would they suddenly burn in the first place? Was there a way for them to protect themselves, so that they would survive the ordeal?

---

1D FFT algorithm elements explanation?

Can someone explain to me what each element of the 1D FFT algorithm are (i.e. N,x,n,j,k) ? From here, http://zone.ni.com/reference/en-XX/help/371361H-01/lvanls/fft/#details

(Can't post pictures on stackoverflow just yet.... but its the 1D FFT description)

Answer

Consider a MATLAB/OCTAVE implementation of 1D-DFT/FFT sum: $$X[k] = \sum_{n=0}^{N-1} {x[n]e^{-j \frac {2\pi}{N} k n} } $$ where $n=0,...,N-1$ and $k=0,...,N-1$

Those identifiers are used to denote the following:

$N$: is the FFT length as in $N$-point FFT.

$x[n]$: is the discrete-time signal whose DFT $X[k]$ is to be computed.

$X[k]$: is the complex-valued DFT of the signal $x[n]$

$n$: is the discrete-time index for the signal $x[n]$ in the range $n=0,...,N-1$.

$k$: is the frequency sample index of $X[k]$, in the range $k=0,...,N-1$.

$j$: is the imaginary unit $\sqrt {-1}$ in signal processing terminology.

Note if the signal $x[n]$'s length is shorter than the FFT length, then zero padding is applied on $x[n]$ to make its length $N$. Otherwise if it's longer than $N$, then the samples after $N-1$ are ignored according to MATLAB/OCTAVE implementation.

halacha - Is Exercise on Shabbos Allowed?

Is one allowed to do exercises on Shabbos?

Are any types allowed? Some examples of different types:

• Lifting weights or heavy items



• Jumping jacks


• Taking a walk (long, but without Techum issues)


• Doing sit-ups or push-ups


• Stretching


• Climbing steps

In all cases, assume that the user is doing such actions with intent to lose weight.

stability - Why is tin-112 stable, but indium-112 radioactive?

According to Wikipedia, tin-112 is a stable nuclide, but indium-112 is radioactive (half-life only 14 minutes). What is the explanation for this?

Answer

For isobars (i.e. nuclides with a constant mass number $A$), the binding energy $E$ as a function of the atomic number $Z$ describes a parabola, the so-called valley of β-stability (see also Weizsäcker’s formula or semi-empirical mass formula).

$$E = a \cdot Z^2 + b \cdot Z + c \pm d/A^{3/4}$$

The most stable nuclides lie at the bottom of the valley (but not necessarily exactly at the minimum of the parabola). Isobars with lower atomic numbers $Z$ are unstable to $\beta^-$ decay. Isobars with higher atomic numbers $Z$ are unstable to $\beta^+$ decay or electron capture. Therefore, at least one of two adjacent isobars must be radioactive (see Mattauch isobar rule).

Thus, since Sn-112 is stable, we expect In-112 to be radioactive.

The last term $(\pm d/A^{3/4})$ gives rise to three different parabola depending on whether the nuclides are even-$A$ (with even $Z$ and even $N$), even-$A$ (with odd $Z$ and odd $N$), or odd-$A$ (with even $Z$ and odd $N$, or with odd $Z$ and even $N$).
In the last case, in which the mass number $A$ is odd, the result is a single parabola with one stable nuclide at the bottom.
However, for even mass numbers $A$, we find two parabolas; the odd-odd-curve always lies above the even-even curve. Hence, it is possible that two or even three stable isobars exist.

The case with two parabolas also applies to your example. The stable nuclide Sn-112 has 50 protons and 62 neutrons (even-even). The radioactive nuclide In-112 has 49 protons and 63 neutrons (odd-odd). The next neighbour, Cd-112 has 48 protons and 64 neutrons (even-even) and is stable.

purim torah in jest - PTIJ: Using the Force on Shabbat

What halachic considerations must a Jewish Jedi take into account before using the Force on Shabbat?

word choice - Dismissing an expectation

What can be said when I need to dismiss an expectation?

Here are some examples of what I mean by "expectation":

• 
  

  I ask someone what time it is, then I remembered that I'm actually wearing a watch. The person expects to tell me what time it is but I no longer require help. (Expectation created by me)

  
  


• 
  

  I suspect I do not have enough coins to buy a drink from a coin-only vending machine. I ask someone for change. However I discover that I indeed have enough coins with me. The person still carries an expectation to help me although I no longer require help. (Expectation created by me)

  
  



• 
  

  A waiter offers to refill a glass. He is expected to serve me because of the nature of the job. I do not wish to have a refill. (Expectation not created by me)

  
  

I came up with もう要らない but I think saying that is unnecessarily direct in conveying "I no longer need (help)".

Answer

As Sawa said, やっぱりいいです works when the expectation is created by you. いいです works when the expectation was not created by you.

If you want to be more respectful, you can use (やはり)結構{けっこう}です.

There is also a variant (やっぱり)大丈夫{だいじょうぶ}です which is heard a lot, but some insist that this use of 大丈夫 is wrong or strange.

Just to warn you, もう要らない sounds quite rude. もう (anymore) could be taken as if you don't need the help anymore because the help wasn't given early enough. 要らない sounds a bit like "I don't need and I don't want".

The いい/結構 variants are really the best, similar to English "I'm fine, thanks".

halacha - Question about using the same bed after divorce

Let's suppose a married couple have relations in a specific bed, then divorce and one of then (let's suppose the man), keeps the bed in his house after the divorce.

Can that man have relations with his second wife in the same bed that he had relations with his previous wife, as his previous wife may be offended, or he might remember her, or his new wife may feel uncomfortable?

Answer

If the bed reminds the husband of his first wife and makes him think about her while with the 2nd wife, then he should not use that bed Nedarim 20b quoted in Shulchan Aruch Orach Chaim 240,2:

ולא תתורו אחרי לבבכם מכאן אמר רבי אל ישתה אדם בכוס זה ויתן עיניו בכוס אחר אמר רבינא לא נצרכא אלא דאפילו ב' נשיו
"And you shall not be swayed after your heart"(Bamidbar 15,39) Rebbi said one should not drink from this cup and think about another cup (euphamism for wife see Ran:שבשעה שנזקק עם אשתו לא יתן עיניו באשה אחרת אפי' היא אשתו) Ravina says even if they are both his wives.

If every bed looks the same to him (most people probably share this view), and its his bed (if it belongs to the first wife he should give it back), and his second wife does not care about using the same bed (if she did care she would make sure he gets a new bed nowadays cheaply purchased), then he can use his own bed for his second marriage (his first wife should not be coming to his house checking on him).

sources mekorot - Zoroastrianism v.s. Judaism

Does anybody think Zoroastrianism inflenuced Judaism, cause online people say Zoroastrianism was the first monotheistic religion http://avesta.org, and that Judaism copied it, also that Zoroastrianism was the first to have Angels, messiah, resurrection of the dead, etc http://www.cais-soas.com/CAIS/Religions/iranian/Zarathushtrian/zoroastrianism_influence.htm , and that Judaism copied that as well, Zoroastrianism is wrong because the Torah is true, enhance fourth Judaism was the first monotheistic religion., Also The Zoroastrian claim Ezra was a Zoroastrian priest, and that supposed the priests in the temple were Zoroastrian priest that pretended to be Cohens.

coordination compounds - Why are negatively charged ligands behind the neutral ligands in spectrochemical series?

I had doubt that shouldn't negatively charged ligands be better electron pair donors than neutral ligands like $\ce{CO}$ or $\ce{PPh3}$. But its not so. Why?

Answer

I think you are confused by what the spectrochemical series actually shows. It is not a rating of stronger or less strong ligands to mean they can bind more or less strongly to the metal. It is only a rating of which ligands induce a high crystal field split in the resulting complex.

The splitting derives from the metal $\mathrm{e_g}$ orbitals — $\mathrm{d}_{x^2 - y^2}$ and $\mathrm{d}_{z^2}$ — actually being antibonding to the metal-ligand interaction and thus higher in energy than the (unmodified in a complex with only σ type interactions) $\mathrm{t_{2g}}$ orbitals.

For systems more complex, i.e. including π interactions, the $\mathrm{t_{2g}}$ orbitals (the other three d-orbitals) interact in a π manner with ligand p-orbitals. If the ligand has populated p-orbitals such as halides have, the $\mathrm{t_{2g}}$ energy is raised as it is turned into a slightly antibonding interaction (the bonding one being on the ligands’ side). Since this brings $\mathrm{t_{2g}}$ closer to $\mathrm{e_g}$, the field split is reduced and the ligands are termed weak-field ligands. In simplified Lewis schemes, one could represent this by a double forwards bond from the ligands to the metal.

In the case of empty p-type orbitals such as in $\ce{CO}$, metal to ligand back-bonding can occur by populated metal orbitals interacting with unfilled ligand orbitals; now it is the metal’s side of things that is stabilised. Since this π backbonding stabilises the $\mathrm{t_{2g}}$ orbitals, their energy is lowered and the field split becomes greater. Hence they are termed strong-field ligands. In simplified Lewis structures one could represent that by drawing a donor-acceptor arrow from the ligand to the metal (σ forwards bond) and one the other way (π back bond).

This all has nothing to do with the overall strength of metal-ligand interaction, as I mentioned earlier. In fact, strong complexes are typically obtained for certain metal-ligand combinations and the same ligand can be very bad in interacting with other metals. Classic example: $\ce{CO}$ ligands are extremely good at stabilising low metal oxidation states such as in $\ce{[Fe(CO)4]^2-}$, while they are rather lousy in stabilising high ones: $\ce{[Fe(CO)6]^2+}$ can only be synthesised in the extreme absence of all other ligands, i.e. in $\ce{SbF5}$ from $\ce{FeF2}$ where the fluorides will be drawn towards antimony to generate the even more stable $\ce{[SbF6]-}$ complex.

halacha - Do you own chametz bought on credit?

On Hol Hamo'ed, someone purchases chametz on-line using a credit card. The order was processed during Hol Hamo'ed, but will arrive at the person's home after Pesach is over. The credit card payment is not due until after Pesach.

Has this person possessed chametz during Pesach? Is chametz owned only when it is physically present in your premises? Or, even if not, is the fact that you charged it and it is ready to be delivered mean that you own it even if you don't have it? Or do you not own it at all because the bill hasn't yet been paid or doesn't need to be paid until later?

What if prior to it being delivered you cancelled the order?

contractions - Meaning of わりィ in this sentence

わりィのはその関口って奴じゃねぇか。

I'm guessing that this って is という rather than は. So I get something like

It's that idiot Sekiguchi isn't it?

I can't even begin to guess at what the わりィ part is though.

Answer

It is just a phonetic reduction of 悪い{わるい}.

So we can translate the sentence as

わりィのはその関口って奴じゃねぇか。

The one who's in the wrong is that Sekiguchi guy, right.

shabbat - Veshameru in Chabad siddur

Why do Chabad siddurim always print Veshameru before the Shabbat Ma'ariv Amida, even while also noting that the Chabad custom is not to say it? Are there any groups that use the Chabad Nusach Ari siddur, and include Veshameru?

halacha - Torah prohibition of Shofar on Shabbos Rosh Hashanah?

The Torah says Rosh Hashanah is a יום תרועה, a day of shofar blasts, and זכרון תרועה, a remembrance of shofar blasts. This seems like a contradiction.

The Gemara (Rosh Hashanah 29b) suggests that the remembrance of shofar blasts refers to Rosh Hashanah that falls on Shabbos. The Gemara infers that this would be a Torah prohibition. There are questions on this suggestion, and it is subsequently rejected. Blowing the shofar on Shabbos RH is merely a rabbinic prohibition.

What was the hava amina, initial understanding, that it would be a Torah prohibition? Why would it be forbidden? What kind of prohibition would it have been? The Gemara states it's not a Melacha. Would it have been a new Melacha? Or a side prohibition, like having your animal rest?

I'm asking not just from the Hava Amina but from the Yerushalmi which makes the same suggestion as above to resolve the verse, and makes no mention of a rabbinic prohibition. The Damesek Eliezer (see below) says there's no mention in the entire Yerushalmi of a rabbinic prohibition. I heard the same fact in the name of Rav Meir Simcha. It sounds like the Yerushalmi sees it as a Torah prohibition.

I'm also wondering about the Biur HaGra. The Shulchan Aruch (OC 582:6), following the above Gemara that even though it's a rabbinic prohibition, the verse implies that there is no shofar on Shabbos, says to mention זכרון תרועה in the prayers. The Biur HaGra when writing the source of this halacha, says:

רא"ש סוף ר"ה וגמרא שם כט ב' ועי' בירושלמי שם

Rosh at the end of Rosh Hashanah, and the Gemara there 29b. And look at the Yerushalmi there.

Why is the Gra pointing to the Yerushalmi? He's letting you know it holds its a Torah prohibition? He holds its a Torah prohibition? Something else? Why mention it in a halacha about prayers. I looked at the Damesek Eliezer there and he wasn't so clear to me. Subsequently I saw Rav Shmuel Bornstein asks this in his sefer Shai LaMoreh.

If this last question isn't connected enough to the first one I can make it a separate question

particle に - The use of で and に with 座る

I came across this example in Genki I

.....まどの近くに座っています

And I was wondering about the use of に here and if we can replace it with で to make

......まどの近くで座っています

Is it correct? Please explain if possible. And thank you in advance.

parshanut torah comment - "Moshe cried out" - really?

In Parashat Va-eira, Pharaoh, plagued with frogs, asks Moshe and Aharon to "entreat" God to remove the plague and says that he'll respond by releasing the Israelites. Moshe agrees, and then we have (Exodus 8:8):

וַיֵּצֵא מֹשֶׁה וְאַהֲרֹן מֵעִם פַּרְעֹה וַיִּצְעַק מֹשֶׁה אֶל ה' עַל דְּבַר הַצְפַרְדְּעִים אֲשֶׁר שָׂם לְפַרְעֹה

And Moses and Aaron went away from Pharaoh, and Moses cried out to the Lord concerning the frogs that He had brought upon Pharaoh.

(emphasis mine)

I've always had a problem with the verb "cried out" here. It seems to me that people "cry out" about things that are really, really bothering them. In fact, this would seem to be the pattern the other times we have "וַיִּצְעַק" in the Torah:

• Esav, upon learning that Ya'akov had taken their father's blessing. (Genesis 27:34)


• Starving Egyptians, begging Pharaoh for food. (Genesis 41:55)


• The Israelites, when a wrathful fire from God was burning them for being whiners. (Numbers 11:2)


• Moshe, when his sister was afflicted with Tzara'at. (Numbers 12:13)

So, what was bothering Moshe so much here that he "cried out"? The frogs weren't plaguing him, and I assume that he didn't love Pharaoh like a sister. Why not just say to God "Pharaoh said he'd let us go if You take away the frogs. Could You please do that?" Why did Moshe have to get so emotional about his oppressors' frog problem?

halacha - Does the Torah prohibit leaving Earth?

I don't really know from where in the Torah or from which Rabbi this comes from, but I've heard that the Torah prohibits leaving the planet. Maybe it is because every mitzvah is made for Earth only, or because the Mitzvot that rely on time (like Shabbat and Tefilot) can't be done outside the planet.

Is this a real prohibition? Is there anything in judaism that actually discusses this?

inorganic chemistry - Confusion with Law of Equivalence

Law of equivalence states that

One equivalent of an element combines with one equivalent of the other.

Equivalent of $\ce{Na}$ is $22.99$ and that of $\ce{O}$ is $8$. By the law of equivalence, $1$ equivalent of $\ce{Na}$ combines with $1$ equivalent of $\ce{O}$. But in $\ce{Na2O2}$, $$ 23 \times 2 ~\text{parts by weight of sodium combines with } 16 \times 2~\text{parts by weight of oxygen} \\\implies 23~\text{parts by weight of sodium combines with } 16~\text{parts by weight of oxygen}$$ which means one equivalent of sodium combines with two equivalents of oxygen which is contradiction to law of equivalence. So why does this compound not follow the law of equivalence?

organic chemistry - Mechanism for chloromethylation of benzene with formaldehyde and HCl

What is the mechanism of the above reaction? I have thought of one possibility:

Would this work? How exactly is the chlorine installed on the alkyl chain?

Answer

This reaction is chloromethylation, similar to Blanc chloromethylation, but using $\ce{AlCl3}$ as co-catalyst instead of $\ce{ZnCl2}$. These are reactions belonging to a group related to Friedel-Crafts reactions, but characterized by usage of protonation instead of coordination with molecular Lewis acids

Mechanism of your reaction (not accounting for influence of co-catalyst) can be written as:

(source)

$\ce{AlCl3}$ coordinates to $\ce{HCl}$ creating adduct ($\ce{HAlCl4}$) which is much stronger acid.

halacha - Are seemingly hashkafik texts like Pirkei Avot and Rambam Hilchot Deot halachikly binding?

A surface read of Pirkei Avot and Hilchot De'ot would suggest that their contents appears to be primarily advice as to how one should proceed over and above the minimal halachik requirements. Nonetheless, these two respective works are codified among primarily halachik series, the Mishna and Mishna Torah respectively.

Do the instructions provided in these two volumes (and other volumes that fit my aforementioned criteria) contain halachik weight for anyone or everyone? Are they codes to teach us how to behave should we wish to go beyond the letter of the law? Are they simply there to enrich our lives?

Answer

Rambam Hilchos De'os is halachikally binding except where the Rambam specifically states that it is limited to a Talmid Chacham (e.g. chapter 5). Hilchos De'os contains the specification of no less than 11 Biblical mitzvos including the prohibitions against revenge and lashon hara and these commandments are certainly obligatory.

The portions that deal with treating others properly like greeting others pleasantly (sever panim yafos) are included in the mitzvah of emulating Hashem and are also binding. See 1:5 where this is explicitly stated by Rambam.

Similarly, Pirkei Avos, in general, applies to everyone; note that the Ein Mishpat (found in Vilna Shas end of Maseches Avodah Zara) has numerous footnotes citing the passages in Rambam and Shulachan Aruch that are based on the referenced mishna. In addition, in many Halachic contexts Tosfos on the Gemara (e.g. Rosh Hashana 4a s.v. Beshvil) raises questions from Avos (but also see Tosfos Yom Tov ibid and rambam end of hilchos teshuvah) who clearly maintain that this is not required but is certainly optimal). (Of course, some mishnayos in Avos were intended for Talmidei Chachamim e.g. 1:1 Shimon Hatazdik etc) Some mishnayos are intended as not required advice (). One has to see how the Poskim (e.g. Rambam, Shulchan Aruch, etc) understood those comments to determine if they are binding or simply advice.(e.g. Avos 1:5 "al tarbeh sichhah" and Rambam Hulchos De'os 5:4)

Your question is similar to the one raised by the Chofetz Chaim in his introduction to that sefer where he asks whether Rabenu Yonah's Shaarei Teshuva is halachically binding. Chofetz Chaim clearly understands that Rambam in Hilchos De'os is binding as he quotes from it extensively throughout his sefer. As a matter of fact, the issur for lashon hara is found in Hilchos De'os!

Can kanji compounds be formed arbitrarily?

I will take 客 as an example:

1. 
   

   Can 客 form a compound with 席, 娟, and all the other thousands of Japanese 漢字?

   
   


2. 
   

   If I put 席客, but not 客席, will the meaning be different? Or will it just have no meaning? Or is it only a grammar error? Even if it's a grammar error, can the meaning still be understood?

   
   

How flexible is the formation of kanji compounds?

Answer

Technically speaking, kanji don't compound. The Japanese language is not made of kanji. It's made of words and and parts of words, many (but not all) of which can be written with kanji. When you put these words or parts of words together, you can often (but not always) write the resulting compound using kanji.

Still, let's talk about "kanji compounds" for the time being. It's a convenient metaphor for how words are put together in Japanese because kanji so often correspond to the words or parts of words that can be compounded. Below, I'll reproduce a description from Habein and Mathias' Decoding Kanji pp.25-27, which I believe is now out of print. It catalogues several common types of compound:

1. 
   

   When two kanji are in a syntactic relationship:

   
   

   a. Subject-predicate

   
   

   地震（ジシン, earthquake): the "earth" (subject) "quakes" (predicate)

   
   

   b. Verb-object/locative

   
   

   造船（ゾウセン、shipbuilding): "make" (verb) "boat" (object)
   在日（ザイニチ、(someone) stays in Japan): "to be" (verb) "Japan" (locative)

   
   
   

   c. Adjective/noun-noun

   
   

   高級（コウキュウ, high class): "high" (adjective) "class" (noun)
   国宝（コクホウ, national treasure): "nation" (noun) "treasure" (noun)

   
   

   d. Adverbial first kanji

   
   

   不正（フセイ, injustice): "not" (adverb) "just" (adjective)
   未定（ミテイ, undecided): "not yet" (adverb) "decide" (verb)

   
   

   e. Auxiliary kanji

   
   

   私的（シテキ、private): "I/me" (noun) "-ic, -ous" (auxiliary)
   突然（トツゼン, suddenly): "sudden" (adjective) "state (of things)" (auxiliary)



2. 
   
   

   When two kanji are in a nonsyntactic relationship:

   
   

   a. Reduplication of kanji

   
   

   方々（ホウボウ、everywhere): two of "direction"
   月々（つきづき、every month): two of "month"

   
   

   b. Combination of two kanji of similar meaning

   
   

   平和（ヘイワ、peace): "calm" and "harmony"
   生活（セイカツ, living): "live" and "liveliness"

   
   

   c. Combination of two kanji with contrastive meanings

   
   

   子孫（シソン、descendants): "child" and "grandchild"
   左右（サユウ、left and right): "left" and "right"

Three-kanji compounds are usually made with a prefix and a two-kanji compound, e.g. 新時代（シン・ジダイ, new era): "new" and "age", or a two-kanji compound and a suffix, e.g. 仕事中（シゴト・チュウ, while working): "work" and "in the middle of". There are occasionally three-kanji compounds where all the kanji have contrasting meanings, such as 大中小（ダイ・チュウ・ショウ, large-medium-small): "large", "medium", and "small".

This description isn't exhaustive, and there are other ways to catalogue compounds, but it should give you at least an overview of how they're put together.

Still, although native speakers make new compounds fairly often, learners are generally taught not to make their own kanji compounds. Instead, we're taught that we should learn as many pre-existing Japanese compounds as possible. If you create your own without a good understanding of Japanese, you have a good chance of not being understood―and if you are understood, you have a good chance of sounding quite strange.

Think about it this way: if you didn't know the compound television, you probably wouldn't come up with it yourself by putting tele and vision together. That's a word you've got to learn, and coming up with your own compound for it simply won't work.

There are a couple ways you can put kanji together you'll need to be familiar with:

1. 
   

   What Habein and Mathias refer to above as "auxiliary" I would categorize under "prefixes and suffixes". There are a number of these you should know, such as their examples of 〜的 and 〜然.

   
   
   


2. 
   

   Japanese counters such as 〜人 or 〜枚 which attach to numerals to form words like 3人. (These could be considered a type of suffix as well.)

   
   

But putting 客 together with 席 or 娟 (what is this? I have no idea) is the wrong approach. Until you're comfortable with Japanese, you should try to use the words that are already part of the language rather than forming your own.

organic chemistry - Why is benzenediazonium fluoroborate water insoluble and stable at room temperature?

Benzenediazonium fluoroborate is water insoluble and stable at room temperature.

Why is this salt, water insoluble? Also I am told that benzenediazonium salts are stable only at low temperature(<5°C) and decompose at higher temperature, so what is the reason for such exceptional stability of Benzenediazonium fluoroborate?

words - How do 自他 triplets of related verbs work?

I thought this had been asked before (possibly by me), but I couldn't find it. I'm wondering why for certain verbs/words, instead of just a 自他 pair, there is a triplet (or possibly more) where two of the verbs are one type (自 or 他) and the third is the other type. Some examples:

• 他　→　縮【ちぢ】める　：　自　→　縮【ちぢ】まる　：　縮【ちぢ】む　→　both?
  
  
  
  • see @snailboat comment below - dictionary confirms. Exs.
    
    
    
    • 自　→　寿命が縮む　：　他　→　「ちぢめるの文語形」in dictionary def.
    
    
    
    
  
  
  
  
  


• 他　→　繋【つな】ぐ　・　繋【つな】げる　：　自　→　繋【つな】がる


• 他　→　緩【ゆる】める　：　自　→　緩【ゆる】まる　：　緩【ゆる】む　→　both? (same as above)


• 他　→　滅【ほろ】ぶ　・　滅【ほろ】びる　：　自　→　滅【ほろ】ぼす


• 他　→　含【ふく】む　・　含【ふく】める　：　自　→　含【ふく】まる

What's the deal with these triplets? Why are there two accepted verbs of one form for the same meaning? Are they somehow different? Is one of the two a classic/obsolete form like I talked about here? Does one of the two somehow rise to dominance over the other? I admit that I encounter 繋【つな】ぐ a lot less than 繋【つな】げる, but 縮【ちぢ】む seems just as frequent as 縮【ちぢ】まる to me.

Any other examples would be great to list too.

inorganic chemistry - How does the radial distribution function of Vanadium differ from that of Calcium and how does this affect the ionic electron configurations?

When Vanadium is ionised it loses the 4s electron first, meaning that it's 3+ ion has a different electron configuration to Calcium despite it being isoelectronic. Can it be explained in terms of radial distribution functions? Maybe the maxima of the 3d and 4s become further apart as the effective nuclear charge increases?

Answer

I think @NicolauSakerNeto mentioned a number of excellent points in his linked answer. Frankly, I think he deserves a bounty.

There are several effects occurring, which give different electron configurations to the transition metals. A very nice review article is available: "The Full Story of the Electron Configurations of the Transition Elements" J. Chem. Educ., 2010, 87 (4), pp 444–448

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  "d orbital collapse": Because of the difference in angular-momentum "centrifugal force" in quantum mechanics, incomplete shielding of core electrons, and nuclear attraction, the $Z_{eff}$ - effective nuclear charge - for 3d and 4s electrons are different. As a rule of thumb, electrons are typically lost from the 4s first,

  
  


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  electrostatic repulsion in 4s vs. 3d. It's interesting you mention V, since $\ce{V^0}$ is $[3d^3 4s^2]$ and $\ce{V+}$ is $[3d^4]$. The usual explanation is that while 3d is closer to the nucleus and energetically favorable, once you start filling the 3d electrons, the electrostatic repulsion is high, and for the neutral atoms, it's favorable to have one or two 4s electrons, which are more diffuse.

  
  

There are other things going on, particularly later in the periodic table, where relativistic and spin-orbit coupling effects occur. Also, many times the electron configuration can change in a free atom or ion compared to a complex.

names - What is a "Rabbi Meir Bal Hanes" tzedaka?

I have seen several Tzedaka organizations calling themselves something like "Colel Chabad (or Kupas Ha'Ir) Rabbi Meir Baal Haness Charity".

What does it mean that it is a "Rabbi Meir Baal Haness" charity and what does an organization have to do to get such a title?

minhag - Who is this (Haredi) Rabbi?

Who is this Rabbi?

This is a still taken from the beginning of a documentary on Haredi jews in Jerusalem: The Anti-zionist Jews of Jerusalem

I am curious to learn who this Rabbi is, why he is dressed this way and what kind of festivity we are witnessing here?

Answer

He is the Kaliver Rebbe.

[Rabbi] Menachem Mendel Taub (born 1923) is the Rebbe of the Kaliv Hasidic dynasty. Born in Transylvania in 1923, he is seventh in a direct paternal line to the founder of the dynasty, Rabbi Yitzchak Izak of Kaliv, a disciple of the Rebbe Reb Elimelech of Lizhensk.

An extremely talented Rabbi who recently moved his headquarters from Bnei Braq to Jerusalem. He speaks quite a few languages, and as a survivor of Auschwitz, he regularly speaks passionately about the Holocaust and Jewish unity. As a twin, Dr Mengele experimented on him and his sister (who didn't survive).

As a Chassidic Rebbe, he regularly conducts tischen where his Chassidim will join him for his meal. This particular picture is likely on Tu B'Shvat when Rebbes are known to distribute fruit.

And, video caption aside, he is NOT anti-Zionist!

UPDATE: The Kaliver Rebbe passed away in Jerusalem, on Nisan 23, 5779 [April 28, 2019] (aged 95–96).

phase - Signals cross-correlation

I am trying to measure phase difference between two received waves which are recorded by two separate PC's (microphones). The two PC's starts recording at the same time, then I make a sine wave sound with frequency of $1000\textrm{ Hz}$ using a sound speaker which is recorded by the two microphones.

For the purpose of measuring the phase difference between the two recordings, I do a cross-correlation between the two waves. Theoretically ... the distance between zero and the index of the peak value of the output graph (after cross-correlation) is the phase difference between the two waves.

For some reason I am getting a graph with more than one peak. I think this is because of the noise.

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  Does someone know if I can make a normalized cross-correlation to sound waves, does this solve my problem ?

  
  


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  If yes, how can I do this ?

  
  


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  If no, any suggestions to solve this problem ?

  
  

The waves and the correlation after plotting in MATLAB:

I know the two waves are not perfectly the same, they represent a sine wave with $1000\textrm{ Hz}$, which is recorded by two separate desktop PC's.

As you can see, there are 3 peaks in the cross-correlation graph. And this is just an example , some recordings gave me about 10 different peaks.

audio - inverse FFT when only a few time points are needed

I am developing C++ code to do some modeling that will take as input a parametric model of the complex frequency response (amplitude, phase) and produce as output an impulse response, e.g. using the iFFT. I would like to compare this to a "windowed" impulse response that I have measured for a loudspeaker in a room. The measured impulse can be characterized by an initial portion that corresponds to sound traveling directly through the air to the microphone that lasts a few millisecond, after which sounds that reflect off of the surfaces in the room (floor, walls, etc.) contaminates the signal. The uncontaminated portion is only 3% of the total measured impulse. For instance if I record 16k points at 96kHz, its only the first 470 points of the impulse. I want to compare the impulse response that the iFFT generates from the frequency response model to ONLY the uncontaminated portion of the measured impulse.

I could calculate the entire impulse response from the frequency response and then just throw away 97% of the result but this seems to be very inefficient. The iFFT will be calculated many, many times (thousands probably) while my model is being optimized so I want to make sure that I can make it as efficient as possible. At this point my only option seems to be using FFTW and then just throwing away the data that is not needed (for lack of a better idea).

Is there a fast way to calculate the inverse FFT only for those 470 time points of interest, e.g. not for the entire time span that the FFT can access? I am not intimately familiar with the computation of the FFT and iFFT, so I don't have insight on the answer to this question.

Answer

If your inverse FFT is producing a time series that is N times longer than you need, downsample your frequency domain signal by N and then take the IFFT. Try it!

Edit: As has been pointed out, this method will produce undesired time aliasing unless the content after the window of interest is very small or non-existent. This method may still be favorable in cases where the system response decays exponentially. However, if your window ends before the response has decayed by say, 20 or 30 dB, you should consider another method that will be free of aliasing. Either that, or scale your window down only to the point where you are not negatively affected by aliasing, and then throw out any un-needed samples from there.

halacha - Eating a fish underwater

Maseches Chullin 27b that fish do not need shechita but they do need asifa (gathering). Does that mean that it is assur to eat a fish underwater (it's dead -to exclude bal tishaktzu problem) without taking it out of water?

Is the gathering davka that one must take it out of water (meaning the gathering is the shechita) or it is just stating the norm for catching fish and there is no "shechita" concept by fish?

Answer

The Kesef Mishna (Shechita 1:3) writes:

וא"ת סוף סוף נימא דבעו אסיפה בעודם חיים. וי"ל שאילו היה אפשר לומר כן אה"נ אבל כיון דא"א לאכלם בלא אסיפה שאפילו קלטן בפיו ולא אספם בידו מ"מ בעת שהם בפיו נאספים הם אם כן אינו דבר מיוחד דמזהר עליה קרא
And if you want to say that in the end of the day we should say that it requires gathering while it is alive, one can answer the following: If it were possible to say such a thing then we would, but it is impossible to eat them without gathering. Even if one grabs them in one's mouth and didn't gather them with one's hands nevertheless while they are in one's mouth they are gathered. Therefore it isn't a distinct thing that the Torah would prohibit. (my translation)

There is more to say on the matter and you can find an extensive treatment in R Yerucham Fishel Perlow's commentary to Saadya Gaon's Sefer HaMitzvot, volume 3, Milu'im #8.

organic chemistry - Thermodynamic vs Kinetic Sulphonation of Naphthalene

The left hand isomer is clearly the kinetically favoured product and the right hand isomer is the thermodynamically favoured product. However, I have no idea why. Can you explain?

Answer

In contrast to many other electrophilic aromatic substitution reactions, aromatic sulfonation is reversible, in other words it is an equilibrium. If you use a large excess of $\ce{SO3}$ you push the reaction to the sulfonation side; if you heat the sulfonated product in the absence of $\ce{SO3}$ it will de-sulfonate. This makes sulfonation a nice method to 1) control where a second substituent will be introduced or 2) serve as a protecting group (block second substituent introduction) - and then when you are done, you simply de-sulfonate.

Now to your question

If we look at the intermediates leading to the 2 isomers we see that we can draw 2 resonance structures that preserve aromaticity in one ring for the transition state leading to naphthalene-1-sulfonic acid, but only one resonance structure where the other aromatic ring remains intact for the 2-isomer (draw the resonance structures to convince yourself).

(image source)

Therefore the transition state leading to the 1-isomer will be lower in energy and naphthalene-1-sulfonic acid will be formed fastest - it is the kinetically favored product.

However, naphthalene-2-sulfonic acid is a few kcal/mol more stable than its 1-isomer. This is due to an adverse 1,8 steric interaction present in the 1-isomer.

(image source)

Because the sulfonation reaction is reversible, if we run it long enough at high temperature (favoring reversibility), eventually we will wind up with the thermodynamically preferred (more stable) product, the 2-isomer.

organic chemistry - pKa differences and reactivity

I know a lot of chemists like to quote $\mathrm{p}K_\mathrm{a}$ values and subtract them to reinforce some notion about some acid-base reaction being highly favorable or highly unfavorable or whatnot.

For example, the $\mathrm{p}K_\mathrm{a}$ of acetic acid is about 5 and the $\mathrm{p}K_\mathrm{a}$ of LDA's conjugate acid is about 36. 36 minus 5 gives us 31 "zeros" of favorability.

However, $\mathrm{p}K_\mathrm{a}$ values themselves don't tell you what solvent you are using … can using this method blindly lead to problems when working across solvents? And as far as I know, a lot of $\mathrm{p}K_\mathrm{a}$ values are measured in water … but in organic chemistry we don't just use water as a solvent. So does this method even have general validity?

Answer

An important case of acidity constants changing with solvent, with consequences in organic chemistry, can be found for compounds with hydroxyls, especially water. It is possible to deduce that hydroxyl compounds are more acidic in protic solvents compared to aprotic solvents, which is attributed to an abnormally high stabilization of the resulting conjugate base via strong $\ce{O^{-}\ ^...\ H-O}$ hydrogen bonds.

The difference is most clear for water. Water molecules solvated by water itself have a $\mathrm{p}K_\mathrm{a}$ of 15.7 in ambient conditions, but if the unusual stabilization from hydrogen bonding were removed, they would have a $\mathrm{p}K_\mathrm{a}$ of around 28. In other words, $\ce{H2O}$ is a weaker acid by some 10 orders of magnitude in non-protic solvents compared to water, and correspondingly, its conjugate base $\ce{OH^{-}}$ is a stronger base by the same factor. This means hydroxide ions can effect quantitative deprotonation of even rather weak acids, including the hydrocarbons cyclopentadiene, indene and fluorene, in solvents such as 1,2-dimethoxyethane.

Unfortunately, compounds containing hydroxide ions have somewhat limited use as superbases in non-protic solvents because the solubility of common hydroxide bases such as $\ce{NaOH}$ or $\ce{KOH}$ is rather small. Other hydroxides such as quaternary ammonium hydroxides have appreciable solubility in non-protic solvents, but they are always found in the form of hydrates. Attempts to prepare anhydrous $\ce{R_4N^+OH^{-}}$ inevitably result in decomposition, because the crystallized water solvates the hydroxide ion and tames its reactivity; once the water is removed, the bare hydroxide ion immediately attacks the quaternary ammonium cation creating an alcohol and a tertiary amine.

As mentioned previously, other compounds containing hydroxyls also show changes in $\mathrm{p}K_\mathrm{a}$ comparing water and non-protic solvents, though the difference tends to be smaller. For ethanol, the difference is at most about 4 units of $\mathrm{p}K$.

sukkot - Why do we read Kohelet on Sukkos?

We read Kohelet either on the Shabbos Chol Hamoed of Sukkos or Shemini Atzeres.

Why do we specifically read this on Sukkos? What is the connection between Sukkos and Koheles?

pronunciation - How to refer to kana verbally

In the English alphabet, each letter has a pronunciation (or many) as well as a name (that is used when referring to the letter as an entity, when spelling, etc.). As far as I know, in Japanese, the kana have a pronunciation only and each kana's name is its pronunciation.

So my question is, "How do you verbally refer to a specific kana in Japanese?"

Specifically, I'm particularly interested in how to refer to ん (given that it represents a nasal sound and has no pronunciation by itself) and を (given that it sounds the same as お).

For example, how would one speak the following sentence:

「ん」と「を」の[読み方]{よみかた}は何{なん}ですか？

How do you read "ん" and "を"?

By the way, if the above sentence is not grammatical or unnatural, please correct me.

Answer

We usually call individual hiragana by its pronunciation. If it can be confusing, we can clarify that we're talking about hiraganas by saying, for example, "ひらがなの「あ」".

When we have to confirm that there is no mistake, we use words that include a certain hiragana. For example, we say "りんごの「り」". There is a standardized way to do this in radio communication. This is the same technique as we use to orally tell kanjis.

As you mentioned, 「を」 is special since it has same pronunciation as 「お」. There are various ways to refer to 「を」. I have heard "わ[行]{ぎょう}の「を」" and "くっつきの「を」". See Japanese Wikipedia article of を for more examples.

However, 「ん」 is not such a special hiragana, in that we can distinguish 「ん」 and others with pronunciation. Saying "ひらがなの「ん」" is enough.

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「ん」と「を」の[読み方]{よみかた}は[何]{なん}ですか？

How do you read "ん" and "を"?

I'd say:

ひらがなの、「ん」とわ行の「を」ってどう[読]{よ}めばいいんですか？

I used the techniques described above to refer to 「ん」 and 「を」.

"読み方は何ですか" is not wrong but it sounds like asking "What is the way to pronounce ...?". In this case asking "How ...?" is better, so I use the word どう that means "how."

Also, どう読めばいい（ん）ですか is more natural than どう読みますか. いい means "good" or "correct", so it sounds like "How to pronounce correctly ...?", which matches the context.

Does Rambam include the Oral Torah in his eighth principle?

When Rambam says that a principle of faith is that the entire Torah that we now have is that which was given to Moshe, does he include both written and oral Torah, or only the written Torah?

If the former, to what extent? Since he speaks of the Torah that we now have, it cannot mean the Oral Torah in an abstract sense, but, it seems to me, must include some redaction currently in our possession. Does he mean the entire Talmud? Only the Mishnah?

Answer

The Rambam, towards the end of his commentary to Sanhedrin 10:1, explicitly mentions the oral Torah.

... Similarly, the transmitted explanation of the Torah was also received from G-d. This is what we do nowadays with the forms of the sukah, lulav, shofar, tzitzis, tefilin, etc., which are the exact same forms that G-d gave to Mosheh. ...

messiah - Who is Armilus?

We are told (Ben Ish Chai year 2 miketz, and others...) that Mashiach ben Yosef will fall in the hands of Armilus HaRasha. Some poskim (see ילקוט יוסף תפילה ב הערות נוסחאות התפלה והברכות) who even say we need to pray in our Amidah that MBY will not die at the hands of Armilus. I even saw in a footnote (of מושגים תלמודיים גוג ומגוג) that Gog is Armilus.

Do we know anything else about this seemingly important (albeit evil) character? Please bring sources!

particles - 「X」と「Y」と - how does the second と affect the sentence?

I've seen some titles like this, for example an episode of an anime series that was called 敵{てき}と味方{みかた}と, or a manga that was called エルフと少年{しょうねん}と. I'm curious, how does the second と affect those sentences, what would change if they were removed? Would it make any sense to translate them as "X and Y and..." or would that be nonsensical?

Answer

I've seen this usage once in awhile, and haven't felt any difference in the meaning, but I did a search in Japanese to see what I could find.

This (you may need to set EUC encoding to view this properly) is a pretty long treatment on the subject in Japanese, but the summary is that originally this final と was used, but at present this is omitted most of the time. There are some situations where it can be natural to leave it in, and others where it is best to remove it.

Near the end of the post, it is mentioned that in some cases the final と may possibly be used to give a feeling of both parties doing something together or doing something mutually. Though it is acknowledged this is the opinion the author of that post.

Also, there is talk about how sometimes it is better to add と when it helps avoid confusion, as in the phrase "私とあなたの父との関係". Without the last と、technically that can be viewed as "私" and "あなたの父の関係” as opposed to the relationship of "私” and "あなたの父”.

I'd be curious to hear the opinion of native speakers, but my feeling is that for people learning Japanese as a second language it's usually best to just omit the final と.

Because of the above interpretation, I would generally translate the pattern as just "X and Y". "X and Y and" would be incorrect.

Edit: I apologize for originally including the improper link. I just fixed it. On my browser (Safari), I had to manually select "EUC" encoding to be able to view it.

grammar - How to know if ～たら is hypothetical or temporal

I encountered the following sentence in the chapter introducing conditionals from the online grammar guide Imabi.

休んだら、元気になった

When I rested, I got better.

Earlier, the article explained that たら can have either a hypothetical or a temporal meaning. When the verb in the main clause is in the non-past form, this is not an issue since the たら verb hasn't happened yet either way. To illustrate my meaning, take the following.

帰ったら、食べる。
When I go home, I'll eat. OR If I go home, I'll eat.

Regardless of which one is correct (most likely the first one), the action of "go home" has not yet happened.

However, in the case when the main verb is in the past (た形), I'm wondering if whether or not the conditional verb happened is clear or not. In other words, is the following translation possible?

休んだら、元気になった
If I had rested, I would have gotten better.

If not, how could the type of conditional above be translated?

And

If the main clause had a different subject than the conditional clause, would anything in the answer change? I'm only asking this because I have a feeling that a sentence like 「本を読んであげたら、弟が喜びました」where the speaker would be speculating about someone other than himself would change things (ignore this if it is too unclear).

Source: Imabi - 第109課: Conditionals I: The Particles と, なら(ば), たら, & ば

Answer

「休んだら、元気になった。」

「本を読んであげたら、弟が喜びました。」

I would interpret them as...

"When I rested, I got better."
"When I read a book for my little brother, he was delighted."

(In these examples, the たら verb happened and caused the main verb)

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If I wanted to say:

"If I had rested, I would have gotten better."
"If I had read a book for my little brother, he would have been delighted."

I would say like...

「休んだら(or休んでいたら)、元気になったのに / なっただろうに / なっただろう（なあ） / なっただろうけど。 etc...」
「本を読んであげたら(orあげていたら)、弟が喜んだのに / 喜んだでしょうに / 喜んだでしょう / 喜んだでしょうけど。 etc...」

(In these examples, the たら has a hypothetical meaning)

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_{In the examples below, the たら verb has not yet happened:}

_{「休んだら元気になるよ / 元気になるだろう。」
If you rest, you will get better.
「本を読んであげたら、弟が喜びますよ / 喜ぶでしょう。」
If you read a book for your little brother, he will be delighted.}

hashkafah philosophy - If voting doesn't do anything, should one vote?

All translations below are my own.

Shlomo HaMelech tells us (Mishlei 21:1):

פלגי מים לב מלך ביד יהוה על כל אשר יחפץ יטנו

[Like] streams of water is the heart of a king in the hand of Hashem: toward whatever He wants He turns it.

The commentators seem to understand this to mean that Hashem influences world policy through the leaders of the world. Take, for instance, the Ralbag:

כי פעולות המלך ומחשבותיו הם מוגבלות מהש''י והוא כמו שליח הש''י במה שיעשהו מדבר המלכות
...for the actions of the king and his thoughts originated from Hashem, blessed be He. He is like an agent of Hashem, blessed be He, in that which he does through his power of kingship...

You can debate all you want whether a president is considered a king. But it's completely irrelevant. If the statement is that it's ultimately Hashem dictating policy, then whichever candidate gets elected will do the same policies. Or, if you have a hard time swallowing that Trump will keep Obamacare or Hillary will build a wall, then perhaps you could say that Hashem will influence the election to elect His desired candidate with His desired policies. Either way, the effect is the same: Why should I be voting tomorrow if my vote doesn't matter? According to the first formulation, whoever wins the election will enact the same policies. According to the second formulation, you can't beat Hashem at rigging the elections. (Go tell that to Trump.)

According to Wikipedia, there were 235,248,000-odd eligible voters in the 2012 election, under 130,000,000 of which actually voted. No matter how you slice these facts, my individual vote is pointless. Even in a vote of 100,000 people my vote doesn't make such a big difference: certainly in a vote of over 1000% that size does it not make a difference.

Please don't tell me "If everyone followed that logic we wouldn't have anyone voting." That may very well be true. But until that point my vote doesn't matter. When the numbers change then we can knock this point off the list. Our country will probably be in deep trouble at that point as well.

So, then, if my vote doesn't count any more than a grain of sand on the beach, why should I bother doing my hishtadlus? It's not called hishtadlus if it doesn't matter what I choose. The choice, then, of whether to vote is the same as the choice of who to vote for. Regardless of my decision, the result will be the same.

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In summary, then, should I vote, if from a hashkafic perspective it seems pointless?

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Edit: There are several good points raised in the answers, but none of them satisfactorily answer the question. To clarify, I'm looking for an answer that not only satisfactorily explains why I have to vote but also why I have to vote for an actual candidate rather than Mickey Mouse.