What does the sentence ending particle や mean?

Out of all sentence ending particles, I cannot really pinpoint what や means. I don't meet it often (or maybe I don't have enough experience or exposure) and in situations which don't really explain themselves. Also, is it a real particle anyway?

Some examples I recently found (from books):

「くつろいでくれや」

「それが実はアイロンではないからや」

I hope those examples make sense without the context. I know that those kind of particles are hard to explain but any explanation is welcome.

Answer

We are actually discussing TWO different kinds of 「や」 here, which is probably why you are more confused than you should be.

In 「くつろいでくれや」, the 「や」 is a colloquial sentence-ending particle for 1) imperative, 2) invitation and 3) request. You are saying "(Please) make yourself at home."

In 「それが実はアイロンではないからや」, the 「や」 is a dialectal sentence-ender mostly for Kansai. It expresses affirmation and it is the equivalent of 「だ」 in Standard Japanese. "That is because it really is not an iron."

matlab - What is the difference between the PSD and the Power Spectrum?

Can any one explain the difference in the amplitude between the two and what does each one represents?

For example, when using the pwelch algorithm in MATLAB how do the two different options ('psd','power') affect the units of the output?

(I know the default is 'psd' and I can use 'power' to show something closer to the rms calculation, as stated here)

Answer

The power spectrum is a general term that describes the distribution of power contained in a signal as a function of frequency. From this perspective, we can have a power spectrum that is defined over a discrete set of frequencies (applicable for infinite length periodic signals) or we can have a power spectrum that is defined as a continuous function of frequency (applicable for infinite length aperiodic signals).

In the first case, each discrete component has units of power (W, mW, etc.). In the second case, each point in the continuous spectrum has units of power per frequency (W/Hz, mW/Hz, etc.). In the second case, one must integrate over a band of frequencies to obtain units of power. It is meaningless to talk about the amount of power at a frequency in the second case, one must talk about the amount of power contained in a spectral band (an interval of frequencies) or in several such bands. It is meaningful however to talk about the amount of power spectral density (PSD) at a particular frequency. This is an indicator of how much weight this frequency will contribute to the overall power if included in one of the spectral bands.

This allows us to compare the distribution of power at various frequencies in a signal (as opposed to comparing the power directly). This distribution is defined over a small delta of frequency (delta going to zero in the calculus sense). An alternative to PSD, would be to divide up the signal into chunks of a finite size (say 10 Hz) and compute the power for each bin (one way to obtain this would be to integrate the PSD over each bin). If another person performed a similar experiment and generated their own plot using a larger bin size (say 20 Hz), then the overall shape of both plots would be similar, but the latter plot would seem coarser and its numerical values would be greater. This would make it difficult to compare the two signals. Using power spectral density, the amplitude and bin size ambiguity is eliminated. This allows a fair comparison between the power distribution of two different signals.

For more information, here is a link to a related Wikipedia article.

homework - How to calculate the concentration of all relevant species in a buffer of a given pH?

You prepare $1.0~\mathrm{L}$ of a $0.25~\mathrm{M}$ acetic acid solution with a final $\ce{pH}$ of $6.0$. What are the molar concentrations of all relevant acetic acid species ($[\ce{HA}]$ and $[\ce{A-}]$) given that the $K_a$ for acetic acid is $1.74 \cdot 10^{-5}~\mathrm{M}$?

I am getting confused with this problem.

Since the $\ce{pH}$ is given, I know what the $[\ce{H^+}]$ is. So now when I try to do the ICE table

$$ \begin{array}{l|ccc} & \ce{HA} & \ce{H+} & \ce{A-} \\\hline \text{Initial} & 0.25 & 0 & 0 \\ \text{Change} & -x & +x & +x \\ \text{End} & 0.25 -x & +x & +x \\\hline \end{array}$$

And from here I begin to assume $[\ce{H^+}] = [\ce{A^-}]$, which I am not sure about. Then I set $x = 10^{-6.0} = 1\cdot 10^{-6}$ so I get $[\ce{A^-}] = 1\cdot 10^{-6}~\mathrm{M}$ and $[\ce{HA}] = 0.24999~\mathrm{M}$ which I think is incorrect, and to even further ensure my that it's incorrect, when I attempt to check the $K_a$ value with this, it does not match.

My second approach: $[\ce{HA}] = 0.25~\mathrm{M}$

In this I determine the $\mathrm{p}K_a$ from the $K_a$ which turns out to be $4.759$, which indicates that there should be more $[\ce{A-}]$ than $[\ce{HA}]$.

I now use the Henderson–Hasselbalch equation: \begin{align} 6.0 &= 4.759 + \log\left(\frac{[\ce{A-}]}{[\ce{HA}]}\right)\\ 17.40 &= \frac{[\ce{A-}]}{[\ce{HA}]}\\ 17.40 &= \frac{[\ce{A^-}]}{0.25~\mathrm{M}}\\ [\ce{A-}] &= 4.35~\mathrm{M}\\ \end{align}

I feel more confident about my second answer.

Can someone please help me out with this particular problem and perhaps tell me procedure I should use as well as what the correct answer should come out to be and why?

parshanut torah comment - What did the Jews do all day in the desert for 40 years?

They had food prepared for them.

Rashi says that during the first and last years they had a lot of journeys. But in the middle 38 years, there were only 20 journeys. Even though that doesn't tell us anything about how much time they were resting vs. traveling, Rashi does explain that they were not constantly traveling. There were a lot of resting periods.

What did they do all day? How did they spend their time?

organic chemistry - What is the hybridization state of the carbon atoms in [10]annulene?

I know that one of the more stable structures of [10]annulene or cyclodecapentaene is planar boat-shaped. But that means the hybridization state of the carbons must have changed to suit the geometry. What does it change to? And how are the hybridized orbitals distributed such that the double bonds remain intact?

Edit: I have encountered this molecule only once and am not familiar with the naming convention. For much the same reason, I don't know the exact structure of the most stable isomer of the compound. So even though I was more interested in the boat-shaped isomer of the compound, I think to do away with the ambiguity of the question, I should mainly ask for the most stable isomer of the molecule, viz., trans,cis,cis,cis,cis-isomer.

Colloquial contraction of だろう into ろ after past tense verb (e.g. 言 ったろ)

I noticed in many anime I watched that 「言っただろう」 is often contracted into 「言ったろ」 in conversations between friends and families. I'm guessing this contraction is both colloquial and standard (as in, everyone understands it).

But I'm wondering if this contraction of 「だろう」 is limited to the phrase 「言っただろう」 only. Is there any instance where 「だろう」 gets contracted before other past tense verbs than 「言った」, e.g. 来たろ?

Answer

I'm not sure that this is a contraction of 言っただろう, actually, I would interpret it as a contraction of 言ったろう -- which has the same meaning as 言っただろう, but is now archaic or at least very old-fashioned, I think (alas).

(Note: It is possible that the evolution was not direct, and 言っただろう/言っただろ were indeed intermediate steps. I don't have any evidence either way, just Occam's Razor.)

Anyway, the ろ ending can be applied to any verb in theory.　笑ったろ, 喰ったろ, etc. But be careful not to confuse it with the "-たろ" or "-たろう" that actually mean "-てやろう" -- totally different ending!

halacha - Are Jews permitted to work out?

Are Jews allowed to pump their muscles?

What if the intent is to make yourself look good?

translation - Explain how 向{む}く "to face" can take "上{うえ}" as a direct object using を?

There's a famous old song that's actually the only ever Japanese language song to reach #1 on the US pop charts: "上{うえ}を向{む}いて歩{ある}こう".

This is both the title of the song and a frequently repeated line in it.

向{む}いて is the -te form of 向{む}く, meaning "to face".

My understanding of 上{うえ} is that in Japanese it's a noun even though it's usually translated to another part of speech in English, such as "up".

It seems odd from the point of view of an English speaker that "to face", "to look toward" would be a transitive verb requiring a direct object.

Is that in fact what's happening or have I got it all wrong trying to parse this phrase due to my English speaker's intuition and my limited knowledge of Japanese?

Is what I'm seeing more of a quirk of the verb 向く or is there something about the particle を that I haven't learned yet? Or maybe it's all about the 上 in this case?

Answer

Although it is usually the transitive verb that takes a "Noun + を" in front of it, there is an important exception to this general rule.

Intransitive verbs such as 向く、[走]{はし}る (to run)、[飛]{と}ぶ (to fly)、[出]{で}る (to get out), etc. can take a "Noun + を" when it describes the place of an action or the direction of a movement.

上を向く = to look upward

[公園]{こうえん}を走る = to run in the park

[空]{そら}を飛ぶ = to fly in the sky

レストランを出る = to leave the restaurant

Other such intransitive verbs:

[曲]{ま}がる (to make a turn)、[降]{お}りる (to get off)、[通]{とお}る (to pass), etc.

grammar - Is 場合は considered a conditional form? (and how do you correctly use it?)

場合は、doesn't seem much of a conditional grammar structure to me but in class we learnt this form alongside たら、なら、と＆ば。　How does 場合は、compare to these structures and how do you correctly use it? (as in contextually not how to conjugate)

Thank you!

acid base - Will using vinegar harm car paint?

After having parked my car in a newly constructed airport parking garage, I came back to find something had dripped through a crack in the ceiling of the structure and left considerably thick film on my car. On a glass window surface, I tested soap and water, mineral spirits, two types of latex paint remover (i.e. goof off), and household chlorine bleach. None were effective. But plain white 5% vinegar dissolved the film if I let it soak or scrubbed on it with a cloth.

My question: is an acid of the strength of vinegar a risk to automotive "paint" (the top layer is probably "clear coat").

Answer

That is a valid question, because acid rain has been known to damage paints, particularly high-gloss, i.e. clear coat. Best would be to test the effect of vinegar on a hidden area, and double-check under bright light from different angles. Your idea to test on glass is good, because it shows how long a soak is needed.

• 
  

  If it appears unaffected, rinse afterwards with a weak solution of baking soda or ammonia, and then rinse again with plain water to remove any remaining acid.

  
  


• 
  

  If damage is slight, can car wax effect a good repair?

  
  
  


• 
  

  If vinegar does damage in the test spot, you might look at various car polishes or even cutting compounds, and then wax (or reapply a gloss coat, which may mean refinishing a large section of bodywork to get it to match).

  
  

Why does part of my image turn black when applying functions to a part of an image in Matlab?

When I select a part of an image and apply a negative function to it, it works 100%:

When trying to apply the same method using another function, the part of image becomes black:

What is the problem and how can I fix it?

halacha - How do I calculate the latest time to start the third Shabbos meal on erev Yom Tov?

From myzemanim.com for where I live, for this Shabbos, erev Shovuos, the “sho’o zemanis” (Proportional Hour) Gra & Baal Tanya is 1hr:22mins. Nightfall - 3 Stars is around 10:30 pm. Shkia is around 9:20 pm.

How do I calculate the latest time to start Sholosh seudas “sho’o asiris”?

Are there any leniencies bearing in mind the length of the sho’o zemanis?

continuous signals - Fourier Transform Identities

We know the below,

$$ \mathscr{F}\big\{x(t)\big\}=X(f) \tag{1} $$ $$ \mathscr{F}\big\{x(-t)\big\}=X(-f) \tag{2} $$ $$ \mathscr{F}\big\{x^*(t)\big\}=X^*(-f) \tag{3} $$

Now, if for some signal

$$ x(-t)=x^*(t) \tag{4} $$

Then, is it safe to assume the following?

$$ X(-f)=X^*(-f) \tag{5} $$

or does it depend on the type of signal?

tzitzis - Fake Techelet: invalidating the entire Tzitzit?

Let's say I use the pretty much disproven Techelet (Radzyner) : is my Tzitzit completely Pasul? I think according to the Arizal it isn't. Does anyone disagree?

Answer

If you honestly believe that you are wearing true tekhelet then you are not in violation of the Gemara (BM 61b). If your tekhelet turns out to be false tekhelet, then you will have only fulfilled the mitzvah of tzitzit but not the aspect of tekhelet, as the Gemara (Men. 40a) explains is the case for one who unwittingly wore kela ilan - see my article "False Tekhelet": http://tekhelet.com/pdf/false.pdf

moshe rabbeinu - If Moses wrote the Book of Job, was he Job's contemporary and writing history or is the Book an inspirational work of fiction?

The Talmud at Bava Basra 14b-15b teaches that Moses wrote the Book of Job before the Exodus. If so, was he a contemporary and a witness to Job's suffering, was he describing a historical figure he didn't know, or was it simply an inspirational fable?

Answer

There are many different opinions regarding when Iyov existed, if at all. Many are mentioned in the Talmud you cited in your question.

The Talmud (Sotah 11A) says that Iyov was one of Pharaoh's advisers along with Yisro and Bilaam. See the details translated here. They advised Pharaoh at the beginning of the Israelite's slavery.

The Talmud (Sotah 35A) brings an opinion that Iyov died shortly before the spied entered the land, a little more than a year after the Jews left Egypt.

The Talmud (Babba Batra 15A) (translation here) says that Moshe told the spies to see if Iyov was in the land.

The Talmud there also brings an opinion that 'The span of Job's life was from the time that Israel entered Egypt till they left it.'

According to Iyov 42:16, Iyov lived 140 years after his suffering. Since Moshe was only 80 at the time of the Exodus, he would not have seen Iyov's suffering.

halacha - Alarm clock in place of a shomer

There is an idea that one can an appoint a shomer (guard) to daven maariv (shma) and some achronim extend this idea to lighting the menorah. What this does is allows one to do work and eat something prior to performing the mitzvah and the shomer is there to ensure you don't forget about it.

A shomer is an actual person who reminds you. Is it acceptable to set an alarm clock which will remind you to perform the mitzvahs mentioned?

Answer

R' Sh'lomo Zalman Auerbach indicated that it would be acceptable to rely upon an alarm for eating if the alarm is functional, although it should not be relied upon to wake oneself from sleep (Halichos Sh'lomo, T'filla 2:12).

R' Bentzion Abba Sha'ul also indicated it would be acceptable to rely upon an alarm clock for eating, provided that the person intends to respond immediately when the alarm goes off and the person doesn't drink alcoholic beverages during the meal (Or L'Tziyon II, ch. 15, fn. 1).

organic chemistry - Why do we use ethanol in SN2 reaction?

Solomons and Fryhle has an example in which they have showed a very simple substitution reaction. The question was to synthesize methyl iodide. What they have done is taken methyl chloride and produced methyl iodide in the presence of $\ce{NaI}$ and ethanol through an $\mathrm{S_N2}$ mechanism.

Why did they use ethanol? I have read that $\mathrm{S_N2}$ reactions are favored under polar aprotic solvents and clearly ethanol is not that. Also, since it's a methyl and all substitution reactions on methyl go through $\mathrm{S_N2}$; so how would it affect my reaction if I would't use ethanol?

Answer

Usually, nucleophilic substitution reactions of anionic nucleophiles occur more rapidly in polar aprotic solvents. In such solvents (e.g. DMSO) the typical relative reactivity order is
$$ \ce{SCN-} < \ce{I-} < \ce{Br-} < \ce{Cl-} < \ce{F-}$$

In protic hydrogen-bonding solvents (e.g. ethanol), anions are solvated. Therefore, the reactivity of nucleophiles is decreased. Since hard nucleophiles are more strongly solvated than soft nucleophiles, the relative reactivity of soft anions is increased in such solvents. The typical relative reactivity order is
$$ \ce{F-} < \ce{Cl-} < \ce{Br-} < \ce{I-} < \ce{SCN-}$$

In the given example, $\ce{-Cl}$ shall be replaced by $\ce{-I}$; and in alcohols, the nucleophilicity of $\ce{I-}$ is higher than the nucleophilicity of $\ce{Cl-}$.

halacha - Laws regarding excessive conversation while dating

In speaking with a friend regarding conversation between men and women who are dating, this is what they said:

So I asked someone who knows about these things and she said that it originates from the gemara, and is in the shulchan aruch, that a couple should not speak too often; there are certain rules to that, and the [last Lubavitcher] rebbe said that a couple shouldn't talk too often. There are people who adopted seeing each other once a week in addition to speaking on the phone once a week. That is a common practice but not everyone talks so little – some talk more often – but there are guidelines to it.

The only source I could find for this was Mishna, Pirkei Avot 1:5, and that is more general. I've looked superficially in Shulchan Aruch, Even HaEezer; and Mishneh Torah, Issurei Biah. I can find nothing concrete.

Please provide specific sources for such an idea, if it indeed comes from traditional Torah sources.

expressions - What does 「ハイきた。」 mean?

Also seen as 「ハイきたぁ～！」.

Maybe it's used among young people.

It seems to express the idea that you have achieved your expectations, or something like that.

I hope someone can explain it better.

Yoroshiku.

transitivity - Is the verb 向く transitive or intransitive?

On jisho.org, 向ける is described as a transitive verb. Logically, 向く would be intransitive, but the entry just says:

Godan verb with ku ending

Wiktionary is exactly the same, listing 向ける as intransitive and nothing for 向く. But what really gets me is that jisho.org lists sentences using 向く that look both transitive and intransitive. E.g.

上を向きなさい。 "Look up"

この仕事は彼に向いている。 "He is well suited for this job"

In the first one, there is an object marker, and the second one, there isn't. I thought that transitive verbs always used the object marker を, the second sentence looks like an intransitive verb.

Could someone help me clear up this confusion?

Answer

From Samuel Martin's Reference Grammar of Japanese (1975), p.191:

The intransitive verb 向く【むく】 means 'faces, fronts on' or 'is suitable for, suits' with N に; but with N を it is a quasi-intransitive verb of motion meaning 'turn (one's face) toward)' [...]

He gives these examples:

横【よこ】を向いて【むいて】　turn to the side

前【まえ】を向いて【むいて】　turn to the front

This verb belongs to a class of verbs of motion which take を-arguments, which we nonetheless might want to consider intransitive. Martin uses the term "quasi-intransitive" to describe this sort of verb. You're probably familiar with examples like:

公園【こうえん】を散歩【さんぽ】する　take a walk in a park

橋【はし】を渡る【わたる】　cross a bridge

家【いえ】を出る【でる】　leave home

All of these are subtly different, and none is exactly like 向く, but I think that we can treat all four as examples of Martin's "quasi-intransitive verbs of motion".

If you consult monolingual dictionaries, you'll find that they disagree with one another on how to classify this use. For example, 明鏡国語辞典 calls 向く a transitive verb and treats the directional object as though it's a normal object. But other dictionaries like 広辞苑 call the verb intransitive.

You can find some previous answers discussing this use of を and the question of whether these verbs should be considered transitive if you search Japanese.SE. You can also find a description of some of these uses of を in A Dictionary of Basic Japanese Grammar by Makino and Tsutsui starting on page 349, though it doesn't cover 向く specifically.

I'm afraid this is one of the sticky points of Japanese grammar where descriptions differ, but hopefully you can look at how the verb is used and make sense of it one way or another :-)

hsab - Hardness and softness are terms used to describe which aspect of acidic behaviour?

What do hardness and softness mean?

Is it something to do with the polarisability.

electrochemistry - Is there any electronic component to water conductivity?

Answers to Decrease in temperature of a aqueous salt solution decreases conductivity indicate that the electrical conductivity of salt solutions arises from the mobility of ionic species and therefore the temperature dependence of conductivity is related to viscosity.

Question: Is there any measured or predicted electronic component to water conductivity as well, where the charge carriers are electrons rather than ions?

This could take place via charge exchange (migration of bound electrons) or even perhaps via solvated electrons, or some other mechanism.

In this case I'm interested in both pure water, and salt solutions.

Answer

I agree with the commenters that electrical conduction is very unlikely, but it's worth going through some possible mechanisms:

1. 
   

   actual solvated electrons: As others have noted, free electrons would be expected to react rapidly with protons, even in a basic solution, so this changes quickly to a scenario of sequential electron transfer between protons, so let's do that next.

   
   
   


2. 
   

   Sequential electron transfer between $\ce{H.}$ and $\ce{H+}$: Let's assume the solution is strongly acidic, so protons are abundant, and a proton gets reduced at the cathode to a hydrogen atom radical. Based on the bond dissociation energies, abstraction of $\ce{H.}$ from water to form $\ce{H2}$ and $\ce{HO.}$ is slightly unfavorable, the hydrogen radical would be preferred over the hydroxyl radical. (The H-H bond formed has a BDE of ~ $\pu{105 kcal/mol}$, while the $\ce{H-OH}$ bond broken has a BDE of ~$\pu{120 kcal/mol}$.) The problem is the rate of quenching by reaction of two hydrogen atom radicals to form $\ce{H2}$ (which is water electrolysis produces hydrogen gas). I couldn't find a rate constant for that, but there is a published rate constant for recombination of hydroxyl radicals in water that is around $\pu{10^10 M-1 s-1}$. As you might expect, that's essentially diffusion limited, so the rate constant of hydrogen atom recombination is going to be at least as high. If we optimistically assume that transfer of the electron from $\ce{H.}$ to $\ce{H+}$ has a comparable rate constant, you would still have to have a very low concentration of radical and very short path to travel in order for an electron to make it from a cathode to an anode, but it doesn't seem theoretically impossible.

   
   


3. 
   

   The third possibility would be sequential transfer of electrons from $\ce{HO-}$ to $\ce{HO.}$. In a strongly basic solution, this also seems like a theoretical possibility given a very short path and a very low concentration of radical, assuming there are no other molecules in solution that can quench the radical.

   
   

I'm not suggesting that either of these theoretical possibilities actually ever occurs, just that these are the mechanisms that seem most likely to me.

halacha - Becoming Bar Mitzva on Chanuka

A boy becomes Bar Mitzva on one of the nights of Chanuka. If he lights the Menorah at the preferred time (appx 15-20 minutes after Shkia to the best of my knowledge) it is not Tzeis HaKochavim yet. Would it be better to wait until Tzeis the night he becomes Bar Mitzva and lose out the Pirsumei Nisa of people still on the street or would it be better to wait and do the Mitzva till Tzeis HaKochavim when he is definite Bar Mitzva?

Answer

Quoting from נטעי גבריאל: הלכות והליכות בר מצוה והנחת תפילין,

פרק כו הלכה ב

נעשה בר מצוה בחנוכה רשאי להדליק נ"ח מבעו"י להנוהגים להדליק נ"ח תמיד לפני השקיעה, ונכון להדליק בבין השמשות

[One who] became a bar mitzva on Chanuka may light the candles during the day [if he is among] those who always light before sunset, but it is correct to light between sunset and nightfall.

In a footnote he refers to a more detailed explanation of the topic (where he presumably gives the reason for all this, taking into account your considerations) in נטעי גבריאל: חנוכה פרק ג' ס"כ.

experimental chemistry - Does a sulfuric acid/nitric acid mixture dissolve PTFE (ie. teflon)?

In our lab, we commonly use a mixture of sulfuric acid and nitric acid to clean borosilicate glassware. I'd like to clean some PTFE pieces in there, too, but not sure if they will dissolve or not.

Does anyone have any first-hand experience with this, and know whether or not a sulfuric acid/nitric acid mixture dissolve PTFE?

Answer

For having used "sulfonitric acid" (sulfuric and nitric acids mixture) for at least 2 decades, PTFE is definitely stable to such a mixture.

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Safety on the use of "sulfonitric acid"

I know it is off-topic but I think that safety should be learned as light touches, not as a-difficult-to-swallow course. (Please tell me if it is not in accordance with the site's rules).

You can safely use "sulfonitric acid" (i.e. usually a mixture of one volume of conc. sulfuric acid poured slowly into one volume of conc. nitric acid) to clean glassware and PTFE-ware if you follow some common sense rules. Explosions (or at least too vivid reactions) reported were the direct consequences of a poor understanding of what "sulfonitric acid" does.

1. Handle it under a fume hood (I told you it was common sense!!)


2. 
   
   

   NEVER pour sulfonitric acid on organic material as the latter will be oxidized in an explosive way! Every piece of glassware should first:

   
   
   
   
   • Be cleaned as much as possible with any solvent or manually removing solid substance which is stuck where it should not be,
   
   
   • Be thoroughly rinced with a solvent miscible with water (acetone, methanol, ethanol...),
   
   
   • Be thoroughly rinced with tap water, in order to eliminate most of any organic solvent,
   
   
   • Only then can you pour the sulfonitric acid onto your glassware and let it do its magick.
   
   
   
   


3. 
   

   Do not think that a plastic which can seemingly resist any solvent will actually resist exposure to sulfonitric acid! PTFE will resist but not common plastic materials.

   
   
   

If you follow these rules, there is no reason why you should experience any dangerous reaction in your lifetime. Be especially careful with sintered funnels.

word choice - What is the difference between 「はずがない」 and 「わけが ない」?

I know the following two sentences give implication that "not expecting me to understand (it)" but I have a feeling that they give different nuances that I just can't put my finger on:

それは分{わ}かるわけがないでしょう。 sore wa wakaru wake ga nai deshou.

それは分{わ}かるはずがないでしょう。 sore wa wakaru hazu ga nai deshou.

Would someone explain what is the difference of the two sentences, and also how to choose between using はず and わけ?

Answer

disclaimer: not a native speaker

I think 'wake' implies that things happened as expected, where as 'hazu' implies that what happened is not what was expected.

Or, 'wake' is a bit more neutral, a "matter of fact", where as 'hazu' is more of a personal opinion/subjective kind of thing.

This is how I would understand the difference:

それは分かるわけがないでしょう。 sore ha wakaru wake ga nai deshou.

You're not meant to understand this .. it's normal.

それは分かるはずがないでしょう。 sore ha wakaru hazu ga nai deshou.

I see no reason you could understand this .. so what's going on?

food - What Bracha do you make on (Kasha) buckwheat?

What Bracha Rishona and Bracha Achrona do you make on (Kasha) buckwheat?

Answer

This confuses everyone as it has the word "wheat" in its name, but it's not related to wheat!

It's not chametz on Passover, either (although it is considered by some to be kitniyot).

Assuming it hasn't been turned into mush (rendering it shehakol), ha'adama before, and borei nefashot afterwards. (Source: Brachos.com cites The Laws of B'rachos: A Comprehensive exposition of the background and laws of blessings by Rabbi Binyomin Forst with Rabbi Aaron D. Twerski. Artscroll, p. 361 ISBN: 0-89906-220-2 (hard cover) ISBN: 0-89906-221-0 (paperback))

usage - How would I say "Get well soon"?

Last summer my family hosted a Japanese exchange student for two weeks, and we've kept in touch with her a lot. Unfortunately, about 2 months ago I found out she had Leukemia. She said she'll recover...but it'll take a long time (6 months according to her)

I know Japanese at an intermediate level, so it strikes me as odd I've never picked up the phrase "Get well soon". We're sending her a bunch of gifts and a card (and my family knows I'm the only one with any knowledge of Japanese), so they put it on me to write what goes inside of it.

Please help me not screw this up =x She's 16 turning 17 soon if that makes a big difference.

Answer

There are a couple of ways to say this.

体に気をつけてください　→　Please look after yourself
体をお大事に　→　Take care of yourself

However, given the severity of her illness, these sound casual, a little "flaky", and somewhat insincere. Here are a few that are better.

ご自愛を祈ります　→　Please take good care of yourself / your health.
ご全快の一日も早いことをお祈りいたします　→　I hope you will get well soon. / I hope you will soon be restored to health.

minhag - Why read the hagadda on Shabbos Hagadol?

My family has a custom to read the hagadda on the Shabbos before Pesach, from עבדים היינו until לכפר על עוונותינו. This custom is mentioned in many hagaddos, and in the Ezras Torah Luach (although that last mentions that the Gra opposed this custom).

Double AA pointed me to the Rema (OC 430), who mentions this custom. I skimmed the nos'ei keilim on the page, but didn't see that anyone explained the reasoning behind the custom. The Gra there explains that this custom should not be followed because the hagadda should be reserved for the "שעה שיש מצה ומרור מונחים לפניך," the time when you have matzah and maror on the table, meaning the seder. (Based on Mechilta, at the end of Bo.)

None of the above sources mention why the hagadda should be read. I suspect that it is so that a person can familiarize themselves with the text ahead of the seder (my father shares this suspicion), but I'm looking for a source that explicitly explains the reasoning for this practice.

I checked the ספר טעמי המנהגים, which supplied reasons for calling the day "Shabbos Hagadol," the haftorah, and the Shabbos Hagadol derasha. None of the hagaddos I've seen explain the custom, but I will continue searching.

electrochemistry - Conducting current in electrolytes

I keep trying to figure out how current is conducted through an electrolyte but all I can find are BS half answers. They say the ions conduct, but the specifics are poorly explained or absent. I understand that if you, for example, put sodium chloride in water it will disassociate into positive sodium ions and negative chlorine ions, and that an electric field would cause the ions to move, allowing a current to flow. But what happens once the charges get to the electrodes? Obviously, they can't just stay there in elemental form stably. I would expect the sodium, once given an electron, to be looking for a way to give that electron back. Would it cause the water to split into hydrogen gas and hydroxide ions? On the chlorine side, would the chlorine atoms simply turn into chlorine gas. If this is all correct, it seems one would end up with sodium and hydroxide ions. Does it still conduct then? If so, how so? And don't you have a solution of sodium hydroxide? It seems this process necessitates that the water be split. Is there any salt or other compound which would act similarly but not result in electrolysis (just conducting)?

Answer

An approach using a classical model of electron flow

You can think of an electron flowing through a medium as analogous to a pinball bouncing around a pinball machine. The electric (potential) energy difference driving the displacement of the electron is analogous to the gravitational energy difference in the pinball machine. Now consider two pinball machines with differing numbers of obstacles to a falling pinball. The time it takes for a pinball to reach the bottom in each machine would be different by virtue of these obstacles (on average, taking more time with more obstacles). Similarly, the flow of electrons, I, in the presence of an electric potential, V, is higher for media with less resistance, R , to electron flow. We can use this model (Drude see below) to understand Ohm's law: $$I = \frac{V}{R}$$ The observation that electrons flow more readily through electrolyte solutions than non-electrolyte solutions indicates that solutions with charge carriers reduce the resistance of the media. A better understanding of why this is true at a molecular level will require a more in depth look. Notice, though, that we now have answers to your good questions!

"What happens once the charges get to the electrodes?"

The sodium stays in solution as an ion, but the hydrogen ion (from the hydrolysis of water) can be reduced to form hydrogen gas at the cathode, and the chlorine ion can be oxidized to form chlorine gas at the anode. Electrons can be passed through the solution as solvated electrons under some circumstances, but this is unlikely due to the larger energy barrier to this process (around 3 eV). With sufficient energy, these electrons (called solvated electrons) flow through metal and solutions. The resistance to electron flow in metals is much less than in electrolyte solutions, though.

"Would it cause the water to split into hydrogen gas and hydroxide ions?" and "I would expect the sodium, once given an electron, to be looking for a way to give that electron back."

Any additional redox reaction would require electric potential. You mentioned the splitting of water or the formation of sodium metal. This would not occur according to the standard electrode potential unless the electric potential provided is sufficiently high to overcome the "uphill" energy barrier and as you mention electrolysis would be involved.

The Drude Model

In 1900, Paul Drude used the following schematic of a lattice of metal ions sitting in a sea of electrons to derive a relationship between electron flow and electric potential applied.

Drude Model electrons (shown here in blue) constantly bounce between heavier, stationary crystal ions (shown in red). -From wikipedia entry on Drude model.

A metal's electrical resistance, R, (as seen in Ohm's law above) should take the form:

$$R = \left(\frac{m}{nq^2\tau}\right)$$

where, $m$ is mass of electron; $n$ is number density of electrons; $q$ is charge of electron and $\tau$ is the mean free path. While this classical model does not explain the resistances for all substances perfectly and quantum mechanics can be used to do a better job, it does suggest that if the mean free path for electron flow is increased and the assumptions of the model are valid, the electrical resistance of the media should be reduced.

One way to understand why there is lower electrical resistance (higher electrical conductance) in aqueous solutions of electrolytes is that there is less water in the way of the Drude ion lattice! In other words, in the limit that the solution is a molten salt, we approach a Drudian model. As you add more and more molecules of water to this model, you are reducing the mean free path of the electron and increasing the resistance of the solution.

Notes

1. 
   

   The fact that an electrolyte solution is comprised of positive and negative ions does not diminish the utility of Drude's model: electrons are equally attracted (and speed up) moving toward a (metal) cation as they are attracted (and slow down) moving away from a metal cation. The situation is reversed but the effect is the same for a nonmetal anion.

   
   


2. 
   

   For more evidence of the utility of note 1., read about the additive nature of the molar electrical conductance (inverse of resistance) of ions (cations and anions): Kohlrausch's Law of independent migration of ions. The additive nature suggests that both cations and anions improve the conductance of an electrolyte solution as the note above suggests.

   
   
   

organic chemistry - Anomalous Friedel–Crafts acylation with pivaloyl chloride

In class we were told of an anomalous Friedel–Crafts reaction with a tertiary acid chloride — $\ce{(CH3)3CCOCl}$, or pivaloyl chloride. When this reacts with benzene in the presence of $\ce{AlCl3}$, instead of effecting the normal acylation, it instead breaks down into the tert-butyl carbocation, which then alkylates benzene to form tert-butylbenzene.

I could find no satisfactory explanation for this, however, except for the fact that a tertiary carbocation is a very stable carbocation — and nor did I find any mention of this reaction on searching. Could anyone please detail this further?

Answer

You were on right path; tert-butyl carbocation is quite stable$\ldots$ so stable that the acylium cation, which normally reacts as an electrophile itself, instead decomposes via decarbonylation (loss of stable carbon monoxide molecule).

The t-butyl carbocation isn't as stable as the acylium cation (which is stabilised by resonance), but the difference is small enough that with the help of the non-reversibility of CO loss (which is removed from the mixture as a gas) and reduction of the steric strain (which is lower in t-butyl than in acylium), it is enough to make it the main reaction route instead of a side route.

halacha - Have to repeat shmoneh esrei on motze'i Shabbat. Say "ata chonantanu" again?

Suppose on a Saturday night, someone says shmoneh esrei with "ata chonantanu" but forgets another part that requires repeating shmoneh esrei (like ya'aleh v'yavo on chol hamoed). When he repeats shmoneh esrei, should he say "ata chonantanu" again?

image processing - what is $1/f$ property of the visual world?

I was watching a talk by Edward H. Adelson on the perception of materials and surfaces. He mentions a $1/f$ property of the visual world. He says:

low frequencies are prevalent than high frequencies.

Also,

the simplest model of the world is that it is random noise with a $1/f$ spectrum.

I didn't understand what he meant. Anyone willing to explain the concept he is talking about?

Answer

"Essentially, all models are wrong, but some are useful" (attributed to G. Box)

One of the simplest morphological model for 2D images decomposes objects into structure and texture. Both can be used to detect or understand objects. Even though image formation models are still complicated, objects often appear as smooth intensity gradient, filled with decoration, bounded by edges (some being false). Smooth intensity gradients are often the most energetic, thus low frequencies can be prominent. Edges, though energetic, are sparser and local, thus possibly less present in a spectrum.

So, a simple "low frequencies are prevalent than high frequencies" model is a decreasing spectrum. Now what would be the decreasing simplest model in terms of elementary functions? Possibly $1/f$. And yes, $\exp^{- |f`|}$ could seem better, especially with the singularity at $0$. More involved models involve $1/f^p$ or $\exp^{- p |f|}$ shapes. Indeed, such models are dependent of the transformations used to reshape the data, and Fourier is a very simple reshaping tool. More local tools like wavelets use Generalized Gaussian Distributions: $\exp^{-\alpha x^\beta}$ in the time/space domain.

Simpler can also be seen from a computational point of view, see Frequency Synthesis of Landscapes (and clouds):

Frequency synthesis is based upon the observation that many "natural" forms and signals have a 1/fp frequency spectra, that is, their spectra falls off as the inverse of some power of the frequency where the power is related to the fractal dimension.

This leads naturally to a method of generating such fractals:

• Generate a random (white noise) signal.


• Transform this into the frequency domain.


• Scale the resulting spectra by the desired $1 / f^p$ function.


• Inverse transform.

Such simple models can reproduce realistic shapes. From the frequency domain:

one gets:

organic chemistry - Mismatch of plane of symmetry vs Gold Book's definition for a pseudochiral carbon

Here is pentane-2,3,4-triol:

At first glance, without deciding the configurations at each chiral carbon, we can clearly see that this molecule has a plane of symmetry, perpendicular to the plane of paper and passing through the $\ce{-OH}$ and $\ce{-H}$ on the 3rd carbon atom.

However, if we then sit down to compute the R/S configuration at carbons 2 and 4, we find them to be R and S respectively. Thus, going by the definition of a pseudo-chiral carbon, given in Gold Book as:

a tetrahedrally coordinated carbon atom bonded to four different entities, two and only two of which have the same constitution but opposite chirality sense.

we would infer that the 3rd carbon is indeed pseudo-chiral. This is confirmed by ChemSketch which generates the name of the above compound as "(2R,3s,4S)-pentane-2,3,4-triol".

---

Thus, we have observed that using the plane of symmetry to check chirality, we end up declaring the 3rd carbon to be achiral, rendering the molecule optically inactive. However, if we use the Gold Book's definition, we end up declaring the 3rd carbon to be pseudo-chiral, rendering the molecule optically active.

Another fact confirming that the molecule is optically active is that there exist two isomers, of two opposite configurations of the central carbon atom - (2R,3s,4S)-pentane-2,3,4-triol and (2R,3r,4S)-pentane-2,3,4-triol. Here are their structures:

---

I have looked at several questions on pseudochirality here, yet I have been unable to resolve this conundrum. I believe I am using a wrong fact or a misguided inference, but whatever is it, I am unable to grasp it, and thus need help resolving the conundrum.

Answer

The Gold Book definition for a meso compound is

the achiral member(s) of a set of diastereoisomers which also includes one or more chiral members.

So, a meso compound has chiral subsets. Here we would have three such subsets:

1. Leftmost carbon (2R)



2. The centermost (pseudochiral 3S)


3. The rightmost (4S) carbon

Even though the centermost carbon is pseudo chiral, the plane of symmetry still exists. The compound remains meso, achiral.

Nomenclature is just for naming a compound.

---

The following two molecules are diastereomers, not enantiomers.

halacha - Learning w/o saying Birchas HaTorah

If someone,for whatever reason, cannot say Birchas HaTorah, would that person nevertheless be able to learn Torah that day?

halacha - stop benching at al-yichasiranu?

Can you stop benching (saying the grace after a meal) after al-yichasiranu (the end of the fourth blessing of the grace)?

halacha theory - "אלו ואלו דברי א' חיים" vs "נעשית תורה כשתי תורות" with examples

In numerous Halachic disputes I spotted two contradicting approaches:

1. 
   

   "אלו ואלו דברי א' חיים" - both approaches are legitimate and stem from the [one] living G-d. Each one is allowed to keep his way and his Halochos without forcing others to accept.

   
   


2. 
   

   "נעשית תורה כשתי תורות" - the two approaches appear as two different Torahs, therefore an obligating Halochoh must be issued for all.

   
   

How they can be reconciled?

(Understanding of this contradiction is especially useful for resolving my previous question about B"H and B"S wars: "what-happened-in-r-chananyas-penthouse-18-dvarim")

---

Examples (I'm not claiming "שתי תורות applies in every example, but it looks like it):

1. 
   

   B"H and B"S war: It was OK to have both schools side by side (as או"א) for some time, but [suddenly] it became "שתי תורות" and had to be [brutaly] resolved.

   
   


2. 
   

   R' Yehoshua and R' Gamliel on Kiddush Hachodesh: it was fine to have different schools until R"G decided to end it and rule himself.

   
   
   


3. 
   

   R' Eliezer and Chachamim in Tanuro Shel Achnai: R"E had his approach standing for decades alongside Chachamim's and all of sudden he finds himself boycotted.

   
   

software - Open Source tools to draw a set of 2d molecular graphs from sdf file

I have a sdf file for around 50 small-molecules for which I am doing structure-activity study. I would like to draw 2d graphs of all the molecules such that the image would fit into a single journal page. For example, in this paper, page number 3, they have listed 2d molecular structure. I have attached the image file from the same paper. I have software tools like MarvinSketch which give me 2d or 3d graph for a given sdf file. But I want the integrated image like shown below suitable for publication.

grammar - What is the function of と when it's not quoting, or doing exhaustive listing?

Consider these two sentences:

　(1) 母はついてくるようにアリスに合図した (Mother signaled to Alice to follow her)

　(2) 父は手で私に部屋を出ていくようにと合図した。 (Father gestured to me to go out of the room)

And another sentence which I suspect has the same use of と　as (2) but I cannot exactly say what it does:

(3) この本は子供を対象とした本です。(Unnatural: This book is a book that is done in order for children to be targets) (Natural: This is a book for children)

Now I deconstruct the use of AをBとC in (3) to mean "Do verb C to achieve state B in direct object A"

(Question) How would I understand the use of と in (2)? Since (1) does not require と yet has a similar structure involving ように. But XようにY means "to do Y so that X can happen". What happens when と is added to the mix as in (2)?

(Example sentences taken from WWWJDIC)

Answer

Francis Drohan's A handbook of Japanese usage has four whole pages on the usages of と, so I don't think a comprehensive answer is appropriate here. But a few key points:

• 
  

  There are two kinds of と: one is a case particle (格助詞), and another is a conjunctive particle (接続助詞). In both your examples, と is being used as a case particle.

  
  


• 
  

  According to Drohan, there are 7 main uses for the case particle と: Listing, accompaniment, target of comparison, result of change, adverbialisation, quotation, and simile.

  
  


• 
  

  と in your example (2) is being used to denote quotation. ‘Father signalled to me with his hand, “get out of the room.”’

  
  


• 
  
  

  と in your example (3) is being used to denote the result of change. (In fact, Drohan gives the following example: 学生を対象とする。 It is meant for students.) The construction 〜とする here has the connotation of a decision being made: the target audience was set to be students.

  
  

  Drohan gives some other examples of this usage:

  
  

  
  

  塵も積もれば山となる。 Many a little makes a mickle.

  
  

  夜となく昼となく働く。 They work morning, noon and night.

  
  

  
  


• 
  

  However, the collocation 〜とする also has other uses, e.g. 学生として ‘as a student’,　なかったとしたら ‘supposing there were none’, etc.

  
  

halacha - Can Holiness Be Retroactively Withdrawn?

Without getting into the debate of Ashurith (Modern Hebrew) vs K'thav Ivri (Paleo Hebrew), let's just say for the sake of argument that Paleo Hebrew was the original Hebrew. It is known that the Rabbis/Talmud legislates that Kthav Ashuri is to be considered the script that we now use and that the Tetragrammaton, when written in Ashuri has holiness. However, does that mean that the Tetragrammaton written in Paleo now has zero holiness?

If i print a piece of paper with the tetragrammaton written in Ashurith it has to go into a genizah, it cannot be thrown in the trash. But what if i printed the tetragrammaton in paleo hebrew, does it have any holiness according to halakha?

If one were to find an instrument of the Beit Hamikdash, lets say the Tzitz. If the original tzitz were discovered by archaeology, or found in the catacombs of the Vatican, would it be disqualified for use if it was written in Paleo Hebrew?

halacha - What to do when finding blood in eggs

When cooking something with eggs, I always check the eggs for bloodspots. But I wonder, if I find a blood spot, do I need to throw the whole egg away or can I take the blood out with a spoon and use the non bloody part?

sorcery magic kishuf - Hypnosis in Halacha

Is there a proplem in the Halachic literature with hypnosis? What, if anything, is the issue involved in either hypnotising people or being the subject of such an hypnosis?

organic chemistry - How this tricky Wagner-Meerwein rearrangement occurs?

In 1979, Karel Frantisek Wiesner performed a tremondous total synthesis in $59$ steps of the 13-desoxydelphonine. In one of those steps there is a very tricky Wagner-Meervien rearrangement. I tried to find something by myself, I also look on the net, I found this and you can see page $8$ they have the same problem than me.

What is the mechanism of this rearrangement ?

Just to be a bit more clear, the acetate which looks to appear magically obviously don't, it comes from the previous step because of the solvant, they just heat several days after so the solvant is still the same as you can see in the picture below.

If someone has an idea, I would be glad! Thank you in advance :)

Answer

My literal back of the envelope solution. Notable points:

1. I invoked a nonclassical carbocation in the first step of the rearrangement. This was the easiest way to explain the stereochemistry of the new acetate group.


2. This is a reaction from 1959-1960. It's almost certainly racemic. I think the product as drawn is actually the enantiomer of the one that you would expect from the reactant.

Is pure water very corrosive?

In other site, someone claimed that pure water is very corrosive.

Water distilled for some laboratory uses (like the Z-pinch reactor) is distilled to 0.00000009% purity, and is caustic enough to burn through most things.

Water, purified enough, cannot be distributed through stainless steel pipes. Instead, they use glass pipes to transport it within the plants where it's made.

For sure, caustic is not the correct word, since water is neutral.

But, is it that corrosive? Or is it even less than water with salt?

Answer

That quote had false statements all over it.

Type I ultra pure water (Milli-Q water, or others) are fairly common among all labs. They are not corrosive to stainless steel.

As @chipbuster said, purified water is never distributed through stainless steel partly because concern of contamination. Metal reacts not only with oxygen, but also many pollutants in the air. Overtime on metal surface will build up a layer that has all kind of compounds in them. When water flows through, ions get picked up.

However, the most major reason would be that glass is better in all respect. The reason glasswares are commonly used in the lab have little to do with pure water. Glasswares are relatively stable across wide range of pH and very hard to be oxidized or reduced. Plus, glasswares are cheap, extremely easy to manufacture, and transparent, so you can see through. You will really only need metal if extreme pressure or temperature is required.

As a matter of fact, it is also unwise to use glassware to distribute ultrapure water--you will get ion contaminations from glass as well. Purified water are actually almost always stored in plastic containers and distributed through plastic tubes.

grammar - Why たく isn't used in negative form in this sentence?

言いたくなりますが、見ていませんよ！

I have become a little confused about this sentence since it is not negative and still, in order to say want to instead of たい、たく is used.

Or maybe there was a misspelling when the author was writing the sentence, in which case it is 言いたくない＋ますが

Could it be that this is not, in fact, a negative sentence and たく is used in a positive sense to convey the meaning want to say?

Answer

「言いたくなります」＝「言う」+「たい」+「なる」+「ます」

There is no single "negative" element in this verb phrase.

Among the 4 words, I hope you know that all but the last one 「ます」 need to be conjugated into their 連用形{れんようけい} ("continuative form") in order to form the correct verb phrase. In that process:

「言う」 becomes 「言い」.

「たい」 becomes 「たく」.

「なる」 becomes 「なり」.

And 「ます」 stays the same.

Thus, 「言いたくなります」 is a 100% correct verb phrase meaning "I feel like saying", "(something) makes me want to say", "Every now and then, I want to say", depending on the context.

physical chemistry - During phase change in matter, why doesn't the temperature change?

I was working on something in school and came across the question:

Why does the temperature not change much during a phase change?

I'm really not sure why this happens in matter and I couldn't find an answer in my school resources. Does anyone here know?

Answer

From Changes of Phase (or State):

...

So, how could there be a change in heat during a state change without a change in temperature?

"During a change in state the heat energy is used to change the bonding between the molecules. In the case of melting, added energy is used to break the bonds between the molecules. In the case of freezing, energy is subtracted as the molecules bond to one another. These energy exchanges are not changes in kinetic energy. They are changes in bonding energy between the molecules.

"If heat is coming into a substance during a phase change, then this energy is used to break the bonds between the molecules of the substance. The example we will use here is ice melting into water. Immediately after the molecular bonds in the ice are broken the molecules are moving (vibrating) at the same average speed as before, so their average kinetic energy remains the same, and, thus, their Kelvin temperature remains the same."

hashkafah philosophy - Legal status of one sentenced to death until execution?

What's the legal status of one who's sentenced to death by a court (say smoked on Shabbos) from the moment of the verdict till the actual death:

• 
  

  What're his economical rights (his property, estate, debts, etc)?

  
  


• 
  

  What are his Mitzvas obligations - is he still commanded to keep all the Mitzvos till dead?

  
  

Why is "titkabel" not in Kaddish Yatom?

According to this write up of the development of the various forms of Kaddish, the Kaddish began in Second Temple times as what we now call the "half-Kaddish." Then a section was added for the Rabbis (kaddish Derobonon) and later,

By Talmudic times, it became customary to conclude the prayer service with the Kaddish. A sentence was added (the line beginning titkabel, "let be accepted") that replaces the passage for the rabbis and disciples and asks God to accept all prayers that were recited. This Kaddish is called Kaddish Shalem (Whole or Full Kaddish) and is still said by the chazzan at the end of the service. The full Kaddish includes two sentences, added to the Half Kaddish around the eighth century, that reflect the traditional yearning for peace (Yehei shlomo rabba and Oseh shalom).

Later there is record of the Orphan's Kaddish:

The first mention of mourners saying Kaddish at the end of the service is in a thirteenth century halakhic writing called the Or Zarua. The Kaddish at the end of the service became designated as Kaddish Yatom or Mourner's Kaddish (literally, "Orphan's Kaddish").

In the creation of this form, a line is removed -- the line beginning Titkabel.

What is it about this line that makes it inappropriate for the Orphan's Kaddish? Was the removal simply to differentiate the two forms?

Related.

Answer

See here

Citing from סדר טרוייש סימו ב:

After I explained that Tiskabel closes out Shemona Esrei, you now understand why the Kaddish recited by a child does not contain the line of Tiskabel and neither does the Kaddish that follows the recital of Megilos Shir Ha’AShirim, Rus, Koheles and why it is not included after reciting Tzidduk Ha’Din at a funeral and not after a lecture and not in any instance that is not the completion of Shemona Esrei. However, after reciting Selichos which are like Shemona Esrei we do recite Kaddish with the line of Tiskabel. There are those who do not consider Selichos to be the equivalent of Shemona Esrei so they do not recite Tiskabel after completing selichos. Concerning reciting Tiskabel before Selichos, everyone agrees that it is inappropriate to to do so. Not even regular Kaddish should be said unless you recited some verses because Kaddish was composed to be recited after verses as I explained.

There is other related items in this article, esp. some analysis from Ramba"m regarding whether this type of Kaddish is even considered a tefillah and how Kaddish Yatom was formed. Essentially, Kaddish Yatom seems to have formed from Kaddish Shalem and "Titkabel" was eliminated for the mourner, not the other way around (i.e. Titakbel was eliminated, not added.)

commentaries - Two roots applied to the same verses

I was looking up the word להורות on the pealim.com website, from the root ירה. And it gave all kinds of conjugations. But it also gave some related words one of those was: הוראה. Both seem to have to do with 'instruction', but one comes fom the root ירא while the other comes from the root ירה. I also noticed that some translators and root dictionaries refer to these two roots with regard to 2 Divrei Hayamim 26:15, Mishlei 11:25 and 2 Samuel 11:24 (וירו) [וירוא], but this time the root ירא seems to be some Aramaic-style-by-form of the verb ירה.

1.Are these roots indeed connected in some way? 2.Is it possible that both root words although different in meaning, apply to these verses?

history - How did the Star of David become iconic?

We all recognize the iconic symbol of the Star of David, do we know where it came from and where it got its name?

I always learned that the symbol appeared on King David's shield. True? How do we know?

(We gave seen in a previous question about Rabbinic Judaism in relationship to the Magen David, but I was not satisfied with the answer, so I thought I would restate it in a more historical fashion.)

EDIT: Please give sources from History.

Answer

My understanding of the Star of David is that it became iconic around the same time that Kabbalah and the Zohar began to gain acceptance as a input into Halacha. It is in the Merkavah literature and the Zohar that the 6 pointed star is given significance. The Star of David is seen as the star that connects the sephirah of Malchut to the 6 sefirot above it. Malchut is a sefira that is associated with King David.

An interesting note regarding the Star of David is that in Lurianic Kabbalah the seder plate is placed in such a way as to create two overlapping triangles. As per Gershom article where he tries to claim that it does not say such a thing. It seems that this practice, and the subsequent creation of Seder plates with this symbol is what spearheaded the Star of David into it's Iconic status.

It would make sense that a symbol used on Pesach would be able to overcome the traditional Jewish Symbol of the 7 branched Menorah.

There are many other numerlogical and structural signifcances of the symbol which give it a meaning of protection and a uniqueness to the Jewish people. (even though it's used by other cultures as well.)

The "shield of David" then grew to be understood as a literal symbol which King David bore upon his Shield (and the Maccabees) and became iconic as we know of it today.

grammar - What is the difference between しないで and しなくて?

I am still not so clear with the difference between '.....しないで.....’ and '....しなくて....' . Could you please explain them for me, and give me some examples?

hashkafah philosophy - How should a Rabbi resemble an angel?

The Gemmorah in Moed Katan 17 says:

א"ר יוחנן... אם דומה הרב למלאך ה' יבקשו תורה מפיו
ואם לאו אל יבקשו תורה מפיו

Rabbi Yoḥanan said as follows: ... If the teacher is similar to an angel [malakh] of the Lord, then seek Torah from his mouth, etc

How does (should) an angel of Hashem look/behave that a Rabbi must resemble him?

halacha - Is deodorant allowed on Yom Kippur?

May deodorant be applied on Yom Kippur, or is it a case of anointing which is forbidden?

ashkenazi - Retraining my davening pronunciation

I received a p'sak from my rav earlier today permitting me to revert my pronunciation from a modern Israeli-American pronunciation that I learned as a child to the old Yekkish Ashkenazis (with the חולם pronounced as as German au [aʊ] and ע as ng [ŋ], as well as the usual Ashkenazi features). However, while I was davening Minchoh, I noticed that some of my former liturgical pronunciation was slipping through.

Does anyone have any suggestions for how to drill oneself to successfully change the pronunciation for one's Hebrew? (although only partially, I want to maintain the Israeli accent for conversational purposes)

passive voice - Grammar of プレッシャーに晒される

不条理な暴力によるプレッシャーに晒される

after some searching, I also found these sentences:

絶え間ないプレッシャーにさらされる

来る日も来る日もプレッシャーにさらされる

プレッシャーに晒す, as far as i can tell, you a transitive verb can't take noun+に without a indirect object.

such as "X を/は Y に V-transitive" in general

what is going on in these instances? What is the agent of the passive verb? can pressure itself be the agent?

thank you

Answer

プレッシャーに晒す, as far as i can tell, you a transitive verb can't take noun+に without a indirect object.

In プレッシャーにさらす, プレッシャー is the indirect object. The direct object is left out.

［XXを］プレッシャーにさらす -- active voice
→［XXが］プレッシャーにさらされる -- passive voice

What is the agent of the passive verb? can pressure itself be the agent?

The agent of the さらす is not mentioned, either.　

［YYが］［XXを］プレッシャーにさらす -- active voice
→［XXが］［YYによって］プレッシャーにさらされる -- passive voice

bond - Why are some molecules unable to absorb infrared radiation?

Methane $\ce{CH4}$ is symmetrical and non polar, and so is oxygen $\ce{O2}$. But $\ce{O2}$ doesn't absorb IR. Why is that? People say that if a molecule can change its polarity then it will absorb IR, but I don't understand how a molecule changes its polarity while absorbing IR.

Please try to keep your answer simple — I don't have a strong background in infrared spectroscopy.

halacha - Does a fathers obligation to teach his sons a parnassah extend to his daughters too?

A father has an obligation to teach his sons Torah, a parnassah and to swim. To what extent do these obligations extend to his daughters too?

(edited to include my explanation from the comments)
As Ariel mentions in his answer, Gemara Kiddushin 29-30 discusses the 6 obligations a father has to his sons.

1 Bris, 2 Redeem the firstborn, 3 Teach him Torah, 4 find a wife for him, 5 teach him a parnassah, 6 (some say) to teach him to swim

1 and 2 necessarily apply only to sons not daughters. We learn from a pasuk that 3 applies only to sons not daughters. 4 applies to both sons and daughters (although in different ways). 6 is learned from the logic that his life may depend upon it, given that I don't see any reasonable way you could say that this shouldn't apply just as much to daughters as to sons. You can't really say that maybe at some future time your son might drown if he doesn't know how to swim, but if your daughter drowns that's OK.

The real question seems to me to be by Parnassah. The Gemara doesn't make clear whether or not this applies to daughters as well as sons.

The Gemara brings two reasons. In the first Chizkiyah shows a Pasuk that compares livelihood to getting married. So just as a Father has an obligation to see his son married, so to does he have an obligation to teach him a Parnassah. This would imply that this would apply to daughters too, since the Pasuk on marrying off your children explicitly includes daughters.

The second reason the Gemara gives for the requirement to teach your son a Parnassah is to compare it to the obligation to teach Torah. This would imply that the obligation would only extend to sons and not to daughters since the pasuk for teaching Torah excludes daughters.

Based only on my own reasoning, I would think that this obligation would mean that you should teach your children what they need to know to survive in the society that they are in. If they live in a society where women normally cook and sew and such then you should make sure that they learn this. If they live in a society where the wife will be expected to earn a living with a job outside the home then I would think that Rabbi Yehudah's rule that not teaching a trade is teaching to be a thief would apply. I want to make clear that I have no source for this.

colloquial language - How commonly are "あたし" or "[僕]{ぼく}" used?

My friend and I are learning Japanese. For a time, all we knew was 私, but after we learned more words, she started to use あたし when referring to herself, and I began using 僕. What I'm wondering is, how commonly are these used?

Related: Is it ok for non-japanese to refer to themselves as [僕]{ぼく} and if not why?

Answer

あたし is quite common for females, but 僕 is not that much. In my feeling, 僕 has some romantic sense, so using 僕 when you talk to girls should be no problem at all. (Note that I use romatic sense here is for non-family members, and non-closed friends)

Japanese use 俺 a lot recently, and here is a report about usage about 僕 and 俺

第１期　- 1895~1935, 第２期　- 1966-1991, 第３期　- 1991~1998

And this is the another report about 僕 vs 私 at business/work taken at 2011, results in around 20%~20% people using 僕.

ref:

grammar - Why でも is used rather than も in this sentence?

もし時間がないなら、明日でもいいよ。Why is the particle で used? With time expressions the で particle expresses time limit. So it's weird to see the で with 明日. 明日もいいよ seems better(?). でも here can be the "even though/even/but" meaning. But も sounds better(?).

Answer

One way to think of it, which I found in the Dictionary of Basic Japanese Grammar, is:

でも ＝ て-form of です/だ ＋ も

＝　verb meaning “to be”　＋　particle meaning “even”*

〜でもいい is the です/だ version of the grammatical pattern 〜てもいい, which we use when asking for permission to do things. By putting the verb です/だ in its て-form, we can then ask if the thing itself (a noun) is permissible.

• お手洗い行ってもいいですか？/ May I go to the bathroom? [literally: Is even going to the bathroom OK?]


• お手洗いでもいいですか？/ Is the bathroom OK? [literally: Is even it being the bathroom OK?] You’d say this if you’re doing something and asking if it’s OK to do it in the bathroom.

I recently wrote a blog post on this actually! Rescheduling appointments without sounding like a jerk… 〜でも…?

Is there a terminology contradiction about whether the conjugate of a strong acid is a "weak base"?

(Please note, I am not simply asking, "Is the conjugate of a strong acid a weak base?" I'm asking about the contradictory ways those terms seem to be used.)

I was revisiting strong/weak acids/bases to help some high school chemistry students and found a lot of apparent contradictions in the way that sources use the terms. One is whether the conjugate acid of a strong base is considered a "weak acid".

I understand that the strongER the base, the weakER the conjugate acid, and all sources use the relative terms consistently. The contradiction is in the use of the absolute terms "strong" and "weak".

There seem to be two conflicting conventions in use. In Convention I, the conjugate of a strong base is indeed called a weak acid (whereas weak bases and weak acids can also be conjugates), so you have these conjugate pairings:

\begin{array}{cc} \hline \text{acid} & \text{base} \\ \hline \text{strong} & \text{weak} \\ \text{weak} & \text{weak} \\ \text{weak} & \text{strong} \\ \hline \end{array}

In Convention II, the conjugate of a weak acid is a weak base, and vice versa; the conjugate of a strong base is too weak to be considered an acid, and the conjugate of a strong acid is too weak to be considered a base:

\begin{array}{cc} \hline \text{acid} & \text{base} \\ \hline \text{strong} & \text{not a base} \\ \text{weak} & \text{weak} \\ \text{not an acid} & \text{strong} \\ \hline \end{array}

You can find examples of both just by googling "conjugate of a strong acid", "conjugate of a weak base", etc. Many sources complete the sentence "conjugate of a strong acid [or base]" with "is a weak base [or acid]" (Convention I). On the other hand many sources complete "conjugate of a weak acid [or base]" with "is a weak base [or acid]" (Convention II).

I just want confirmation different sources really are using these terms in ways that contradict each other, so I can pass that on to my students and move on.

So, which of the following is true?

1. 
   

   There is no contradiction; I'm reading it wrong. (This seems unlikely since you can literally google "conjugate of a weak acid" and get what seem to be multiple contradictory answers.)

   
   
   


2. 
   

   One usage of these terms is correct, and the sources that say otherwise are using the terms incorrectly. (In particular, the more reliable sources seem to skew towards saying that the conjugate of a weak acid is a weak base, i.e. Convention II. Maybe the sources that say "the conjugate of a strong base is a weak acid" are wrong, and they're just garbling the (correct) statement that the strongER the base, the weakER the conjugate acid.)

   
   


3. 
   

   There is no agreed-upon definition of "weak acid" and different sources use it in contradictory ways, but real chemists don't care because they just use Ka values.

   
   

To avoid horrible confusion, please be clear in your answer if you're voting for #1, #2, or #3, or something else not listed here.

hashkafah philosophy - What is "emunas chachomim"?

My daughter came home from school with a textbook response for what "emunas chachomim" is. I disagreed strongly with what was written in the book, so I'm not even going to say what they said. Rather, I will ask the learned forum here if they have any good sources for what the origin is of this term, and what it means.

Answer

Emunat Chachamim צomes from Avot 6:6 where a list of 48 ways of achieving Torah wisdom are mentioned. There are many commentatries on Avot in general and this mishna in particular, all saying slightly different things. However..

Traditionally, this phrase is meant to mean that you must trust those people who are wiser than you to give over the tradition accurately.

A story is told in the Talmud (Shabbos 31a) where a convert asks Rabbi Hillel for the written Torah but not the Oral Torah. The first day the student is taught the aleph-bet properly. The second day, he is taught the Aleph Bet wrongly. The student asks what is going on, and Rabbi Hillel says something along the lines of: "Just as you trust me to teach you the written Torah, you must trust me with the Oral Torah."

This is the basis of Emunat Chachamim.

As a general rule, it is a good idea to trust your teachers and not question them every step of the way. This leads you to be able to gain more knowledge more quickly, and once you know more, you can then go back and question the things that were difficult or not very believable.

As they say, in design and literature, one must know the rules well before you can successfully break them.

Rabbi Aviner basically says the same thing I'm writing here, but with a very diferent tone, so it's worth reading and growing from it. (Also giving very different and extended sources)

Rabbi Rabinovitch has an article in Hakirah (translated from Hebrew) that goes through many sources explaining the term. (And also basically says what I wrote here, but in more detail)

quantum chemistry - How much energy does it cost to have electron configurations that are not in accordance with Hund's rules?

What is a ballpark figure for the difference in energy for an atom that follows Hund's rule vs one that has two electrons with opposite spins? I'd be interested to know carbon and nitrogen. Is there a bigger difference when there are two electrons with one spin and one electron with the opposite spin vs two electrons with opposite spins?

Answer

Each energy level of a given electron configuration is described by a Russell-Saunders term symbol, assuming LS coupling. The ground state term symbol is predicted by Hund's rules. Tables of atomic energy levels identified by their term symbols have been compiled by NIST. So, the only thing you have to do, is to compare the energies of the terms describing the electron configurations you are looking for with their respective ground states.

In the following pictures the notation $m_{S} = + \frac{1}{2} \overset{\scriptsize{\text{def}}}{=} \, \uparrow$ and $m_{S} = - \frac{1}{2} \overset{\scriptsize{\text{def}}}{=} \, \downarrow$ will be used for the spin quantum number $m_{S}$.

The data for carbon can be found here. The ground state for carbon is ${}^{3}\mathrm{P}_{0}$ - it is assigned the energy $0.00 \, \mathrm{cm}^{-1}$. From your question it's not 100 % clear what exact electron configuration you want. I assume it is either ${}^{3}\mathrm{P}_{2}$ or ${}^{1}\mathrm{S}_{0}$ therefore I will give the values for both of them (for comparison: the thermal energy at room temperature is about $200 \, \mathrm{cm}^{-1}$).

The data for nitrogen can be found here. The ground state for nitrogen is ${}^{4}\mathrm{S}_{3/2}$ - it is assigned the energy $0.00 \, \mathrm{cm}^{-1}$. From your question it's not 100 % clear what exact electron configuration you want. I assume it is either ${}^{2}\mathrm{D}_{5/2}$ or ${}^{2}\mathrm{P}_{3/2}$ therefore I will give the values for both of them.

calendar - "לְחֹדֶשׁ שְׁנֵים עָשָׂר" in the Megillah and Al Hanisim

As I was reading Al Hanisim this year, something odd struck me "לְחֹדֶשׁ שְׁנֵים עָשָׂר" - the 12th month. What struck me was that this year is a leap year so we actually celebrated Purim in the 13th month Adar Sheini (bet). What is the significance of mentioning לְחֹדֶשׁ שְׁנֵים עָשָׂר, it seems to imply Purim should be in the 12th month - which halachically is not so....?

Also, based on Why is Purim on Adar II during a leap year?, thanks @Yishai, I would like to add to my question -Why does the megillah emphasize "bi-Shloshah Asar le-Chodesh Shneim Asar" - that Purim was in the 12th month?

electronic configuration - sp² hybridized orbital

I do not understand why and how an atom with $\ce{sp^2}$ hybridization has only one p orbital??

For example in pyridine why is the lone pair of nitrogen not counted as a pi electron.

Answer

The picture below from the UC Davis ChemWiki summarizes why that lone pair is not available. It also explains how pyridine can function as a base.

The lone pair in the $sp^2$ orbital is perpendicular to the $p$ orbitals and $\pi$ bonds in the molecule. the electron pair from the nitrogen that participates in aromaticity is the one in the $\ce{C=N}$ bond.

To answer your first question about hybridization, we have a conservation law that guarantees that when orbitals mix (for any reason), we need to get the same number of orbitals out as we put in. The law is the Conservation of Angular Momentum, which does apply in quantum systems.

Nitrogen, in its valence shell, has four orbitals: $2s,2p_x,2p_y,2p_z$. The $sp^2$ hybridization is achieved by mixing two $p$ orbitals and one $s$ orbital. Because of the conversation of angular momentum, four orbitals in means four orbitals out. Thus, the $p$ orbital that was not mixed is still there (and is the only one still there).

$$[s,p,p],p\implies[sp^2,sp^,sp^2],p$$

We cannot have two $p$ orbitals at an $sp^2$ hybridized atom because then we would have 5 orbitals (or we would not have $sp^2$).

Now, let's create a general rule for aromatic heterocycles.

Look at pyrrole (also from ChemWiki);

In the structure of pyrrole, the $\ce{N-H}$ bond uses the $sp^2$ orbital and the lone pair is in the $p$ orbital. In general, if there is a double bond drawn to the nitrogen atom (like in pyridine), then the $\pi$ bond uses the $p$ orbital and the lone pair is in the $sp^2$ orbital and does not count toward aromaticity. If there is no double bond drawn to the nitrogen atom, usually there is a $\ce{N-H}$ bond (or some other bond to the nitrogen). This $\ce{N-H}$ bond uses the $sp^2$ orbital and the lone pair uses the $p$ orbital and counts toward aromaticity.

particles - Why can の and が both mark subjects in relative clauses?

夢のある人

and

夢がある人

I understand that both have obviously the same meaning, but why is it also correct to use の, which, as I learned, has the function of either a possessive particle or of a nominaliser. I heard this example in the first few seconds of following video (so you get the context):

ゴルゴ松本「少年院で漢字を使った魂の授業」

EDIT: As I read in the linked post in the comment now, I saw following: "In more precise terms: の can act like a subject (nominative) particle in descriptive (attirbutive/relative) clauses. " – user54609

To further my question now, is there historic context to this rule? How come の can take this role as well?

Answer

This is actually an interesting little story.

Old Japanese, as far as we can tell, didn't have a dedicated subject marker - if you wanted a subject that wasn't the topic also, you just left it unmarked. It had two genitive particles, though, *nə and *ŋga (modern の and が); which varied according to a kind of animacy hierarchy - *ŋga with personal pronouns and names IIRC (I've forgotten some of the details), *nə with the rest.

However, like several nearby languages that have this kind of relativisation-through-adnominalisation strategy (where relative clauses look like main clauses with different verbal morphology), the subjects of relative clauses could be marked as genitive. (Korean and Turkic both do/did this IIRC, Mongolic and/or Tungusic might.) This seems to be a reflection of the fact that noun clauses and verb clauses share some interesting structural similarities, especially crossover between subjects and possessors - compare English 'I don't like his having done that'.

Over time (starting around the Old > Middle Japanese transition IIRC), people reanalysed subject genitives inside relative clauses as just subject markers, and started using them within main clauses as well. The Ryuukyuuan languages have mostly stopped here, and maintain the dual use of reflexes of *nə and *ŋga in both subject and possessor functions. Mainland Japanese further reduced was now が to only marking subjects, and restricted what was now の to only marking possessors.

This case is the exception to that split. It's not clear whether it's a simple retention from earlier times or instead a further example of subjects and possessors patterning alike, and it's probably both.

(Yaeyama IIRC is an example of a Ryuukyuuan language that doesn't have an animacy hierarchy in subject markers, but it doesn't mark subject or object at all and leaves role marking to word order.)

organic chemistry - What is the role of pH in azo coupling reaction of diazonium with phenol and aniline?

Why is it so that azo coupling with phenol needs basic pH (9–10) and with aniline it needs acidic pH (4–5). How does pH participate in the mechanism? I have searched the internet for quite a while nowhere does it explain the actual ‘role’ of the pH. Any light on this matter would be helpful.

Answer

Deprotonation of the phenol and protonation of aniline result in species that easily react with a diazonium cation in the intended manner.

Let's have a look at the species involved. On the one hand, there is the diazonium cation:

Deprotonation of phenol yields phenolate, for which a resonance structure with a negative charge in para position to the substituent can be written:

We conclude: Deprotonation of the phenol means activation!

In the case of aniline, the lone pair on the nitrogen atom is the preferred centre for the reaction with the diazonium cation:

This isn't what we want! Protonation of aniline avoids this side reaction.

We conclude: Protonation of aniline means "masking" the wrong centre!