May the prayer leader drink water (to lubricate his voice) during the weekday prayers?

I have seen the person leading the prayers taking a drink of water (to lubricate his voice) during the weekday prayers.

Assuming he made a blessing (for the water, as usual before eating or drinking anything) before he started the prayers, is there any problem with doing this?

IMHO there seems to be a certain lack of respect to drink while addressing the Creator.

Are there any parts of the prayers where it is forbidden?

Answer

R. Yitzchak Abadi has told me that it's no problem, at any point in the prayers.

There is also no need to make a shehakol if one is drinking the water for the sole purpose of lubricating one's throat. Shehakol is only recited on water when the drinking serves the purpose of quenching one's thirst (see Shulchan Aruch OC 204:7).

organic chemistry - Oxidation of fructose with conc. HNO3

I recently studied carbohydrates. I was taught that fructose on oxidation with strong oxidizing agents like concentrated $\ce{HNO3}$ yields glycolic acid and tartaric acid along with trihydroxy glutaric acid. Though I am confused why glycolic acid is formed instead of oxalic acid (since the terminal $\ce{-OH}$ should also have been oxidized) I am also satisfied that oxidation of the keto group in fructose breaks it off into 2 carboxylic acids and yields a 2 carbon(glycolic) and a 4 carbon(tartaric) containing acid.

But I am very much unable to figure out the formation of trihydroxy glutaric acid by oxidizing fructose since its a 5 membered carboxylic acid and in no reaction I know did I ever come across such breakage of ketones in 6=5+1. Some sources even cited the formation of trihydroxy butyric acid along with oxalic acid where I couldn't understand why tartaric acid wasn't formed by oxidation of the terminal $\ce{-OH}$ group.

Hence it will be very helpful if anyone can provide an insight into how do these products form.

Thank you.

Answer

Sir Arthur7: From your comments you appear to know how to liberate CO₂ and a proton by pushing arrows as illustrated by the blue arrows in generic α-oxoacid 1. You are correct in discrediting acyl anion 5 for two reasons. First, it is unstabilized and secondly, its protonation would provide an aldehyde, not a carboxylic acid. So why not push the red arrows in 1 to generate an acyl cation equivalent? The downside is that you don't want hydride as a leaving group. The solution is to replace the acidic hydrogen of 1 with a species that likes electrons, e.g., a high oxidation state metal or a hypervalent, non-metallic atom. Certainly, the nitrogen of HNO₃ fits the bill where M = NO₂ in structure 2. In this instance, nitrogen is n = 5 in structure 2 and 4. Bear in mind that for the purpose of electronic bookkeeping, transformation of the acyl anion 5 to a acyl cation 2 is a 2-electron oxidation while species M undergoes a 2-electron reduction. ---continued---

Moriarity, et. al.,¹ have effected this oxidative decarboxylation with the hypervalent iodine species, iodosobenzene 7. The path of the red arrows within the brackets provides a step-by-step version of their mechanism using α-oxoglutaric acid 6.² Notice that mixed "anhydride" 8 is the operational equivalent of species 2. The authors propose the formation of cyclic intermediate 9 that collapses to 12 with loss of CO₂ and a proton. [Note: Structure 10 is drawn for clarity. Collapse of 9 to succinic acid 12 is proposed as concerted.] The collapse of structure 8 might be thought to follow the course of the green arrows but because the reaction is conducted in anhydrous dioxane, it is unlikely that an acylium ion is formed directly because it is apt to form succinic anhydride. See examples studied in the chart below.

The Moriarity paper describes the iodosobenzene oxidation of mandelic acid to benzaldehyde and CO₂. See if you can now write a mechanism for this reaction.

1) R. M. Moriarty, S. C. Gupta, H. Hu, D. R. Berenschot, and K. B. White, J. Am. Chem. Soc., 1981, 103, 686. https://pubs.acs.org/doi/10.1021/ja00393a040

2) α-Oxoacid is preferred over α-ketoacid. The term keto (C=O) overcounts carbons. Oxo = (=O).

translation - How would you use the 'と思います' form to say what others are thinking?

'と思います' is usually used when saying what you think/your assumptions, that much I know, but is it possible to alter it so that you can say what others are thinking? For an example, how would you say, 'Mary thinks the stars are beautiful'?

Answer

Japanese is a language in which expressing others' feelings, thoughts, desires, etc. is done considerably more discreetly than expressing one's own.

It is 100% natural to say:

「私{わたし}は、星{ほし}はきれいだと思{おも}います。」

but it is not natural at all for a native speaker to say:

「田中{たなか}さんは、星はきれいだと思います。」

even if Tanaka has directly told the speaker that he (Tanaka) thinks that the stars are beautiful.

「思います」 is reserved for the speaker/writer; You cannot use it when the subject of the verb is another person. The same principle is applicable to other words like 「ほしい」、「したい」、「怖{こわ}い」, etc.

One could say instead:

「田中さんは、星はきれいだと思っています。」

If Tanaka has directly told you so. And you might say:

「田中さんは、星はきれいだと思っているようです。」

if the information has been obtained via a third person.

All this might sound strange to you, but you will need to get used to the idea. As a Japanese-speaker, I felt very strange, too, when encountering a sentence like "My father thinks I am crazy." in my English textbook a few years ago in junior high school and so did just about all of my classmates because that sentence made very little sense to us.

You might want to read:

When to use 欲しがる instead of 欲しい

Translation of 泳ぎたがっている

experimental chemistry - Are PTFE stir bars resistant to all lab solvents?

It seems like glass-coated stir bars are a specialty item. Standard stir bars are coated in PTFE. Is PTFE resistant to all typical lab solvents? Or is there a reference to check to ensure it is inert to the chemicals being stirred?

Answer

Labware manufacturers will often put out chemical compatibility charts for their products. A search on Google for the phrase ptfe chemical resistance yields a large number of hits, of varying thoroughness.

One fairly comprehensive one is this one from ThermoFisher Scientific.

Scanning it, PTFE has "Excellent" resistance listed for most solvents, except for pure 3-phenyl-2-propenal, which is "merely" "Good" ("Little or no damage after 30 days of constant exposure.") Lists from other sources have a different sets of compounds, some of which caution against conditions like "dry fluorine" or some rarer compounds. This one lists fluorine, gold monocyanide, and diethylamine as not recommended. (Though a number of other sources - including ThermoFisher - say diethylamine is perfectly fine.)

So PTFE is resistant to pretty much all lab solvents which a major manufacturer of lab equipment thinks it's relevant to mention - but if you have something that you think may be atypical or which you have particular concerns about, do a search for that particular compound or contact the manufacturer for their recommendations.

gentiles - The End of Prophecy amongst the Nations

There is a medrash that after the story with Bilaam attempting to curse the Jewish people and instigating the incident with the Midianites and Baal Peor, Moshe prayed that there never again be prophecy amongst the nations. Where is this medrash?

Answer

I'm not sure that this what you're looking for, but the Gmara in Baba Batra on daf 15 writes:

בתר דשכיב משה מי שריא שכינה על עובדי כוכבים והא אמר מר ביקש משה שלא תשרה שכינה על עובדי כוכבים וניתן לו, שנאמר: "ונפלינו אני ועמך".

Although it doesn't specify that this was a result of Bilaam but rather a request to make Israel more unique. This Gmara is more detailed in Brachot 7a:

וא"ר יוחנן משום ר' יוסי שלושה דברים ביקש משה מלפני הקב"ה ונתן לו, ביקש שתשרה שכינה על ישראל ונתן לו, שנאמר: "הלא בלכתך עמנו", ביקש שלא תשרה שכינה על עכו"ם ונתן לו, שנאמר: "ונפלינו אני ועמך", ביקש להודיעו דרכיו של הקב"ה ונתן לו, שנאמר: "הודיעני נא את דרכיך".

And in סדר עולם רבה (the end of chapter 21):

בלעם ואביו ואיוב מארץ עוץ ואליפז התימני ובלדד השוחי וצופר הנעמתי ואליהוא בן ברכאל הבוזי אלו הנביאים שנתנבאו לאומות עד שלא ניתנה התורה לישראל, אבל משניתנה תורה לישראל פסקה רוח הקודש מן האומות. וכן במשה הוא אומר: "ובמה יודע אפוא כי מצאתי חן בעיניך וגו' ". מנין שעשה הקב"ה רצונו? שנאמר: "הנה אנכי כורת ברית וגו' " - באותה שעה פסקה רוח הקודש מן האומות.

I hope this is what you were looking for.

art - What do Jews think angels look like?

I'm a Christian and I've seen and been constantly exposed to our common view of angels. That said I like Matisyahu who draws from a different culture based in Judaism rather than Christianity. In his music video Sunshine a little girl is featured as something spiritual perhaps an angel. Is this what you all think angels look like? Do you have any drawings or paintings?

politeness - How would I respectfully disagree with a superior?

If my manager says something that I know to be factually incorrect, how can I point that out without sounding disrespectful? (Is ~違います appropriate in this context or is that too strong?)

Is this a situation where I would use speech that is more formal than usual? For example, would I switch to a form of keigo for this even if I normally have a more informal relationship?

Answer

Not a bona fide answer, in that I am not confident enough to provide you with a reliable example of what you should be saying, but I can definitely tell you how you should not be saying it (despite some suggestions in the comments to your question):

• Any sentence that starts by a word expressing disagreement.


• Anything that hints at an actual error made by your boss: "間違っている", "間違い" or, Amaterasu forbid: "違う！" etc.

In fact, the two points above are probably good guidelines for any argumentative discussion with a Japanese person. I know the whole resolution by consensus thing is a bit of a tired cliché about Japanese society, but there is a reason it became one: you can safely expect Japanese in general, your business associates in particular, and your boss most definitely, to dislike direct confrontation even (particularly) when they are factually wrong.

The standard recommended way to handle both a personal or a business disagreement (there is no such thing as a factual error in Japanese, only differing viewpoints ;-) is:

• Start by agreeing wholeheartedly (そうですね etc).


• Introduce your correction/viewpoint, as if it was some last minute detail you just thought of, that was of no importance whatsoever, or as an improvement, rather than a correction.

Of course, I am drawing very broad strokes here and standard use-your-better-judgement disclaimer applies, but I think you can't really go wrong with this approach.

conjugations - Passive usage of 「済まされない」 in sentences

I cannot get my head around the verb 「済ます」／「済まされない」 in this sentence.

月10万円では済まされない。

I found this in the プログレッシブ和英中辞典 on goo dictionary's page for the verb 「済ます」. The page says that the sentence means I can't make do with 100,000 yen a month.

This is fine, I think I can understand the sentence and if I see something like this in the future I think I can recognize it.

However, as the goo dictionary page is about 「済ます」 and not 「済む」 I'm bound to think that [済まされない] is the passive conjugation of the former. But, if I translate this to English or to my native tongue (Hungarian) the sentence/expression/meaning doesn't sounds passive (to me) at all (forgive me if my translating skills are way off about this).

Can someone explain to me how the verb or verb conjugation can be interpreted "passively" in sentences? Thanks!

Answer

It's true that 〜(ら)れる is often referred to as a "passive" form because that's one of its main uses, but it has other uses as well. They can be divided into four categories:

• 受身 - passive (most common)


• 可能 - potential


• 尊敬 - honorific


• 自発 - spontaneous (least common)

This is an example of the potential use of 〜(ら)れる, here inflected to the negative 〜れない, meaning 〜することができない. You can see this reflected in the English translation in the word "can't":

月10万円では済まされない。
I can't make do with 100,000 yen a month.

Here, 済まされない means 済ますことができない.

hashkafah philosophy - How does "eilu v'eilu" work out with an absolute truth?

I'm under the impression that religious Judaism believes in absolute truths. That being the case, how does the concept of "eilu v'eilu divrei elokim chaim" (Eruvin 13b) work out? When two scholars argue, how can they both be right?

Answer

A simple parable for this idea is the idea of projection. If one looks at a cylinder, for example, it could be a square or a circle. In reality, it is both or neither.

Torah, in principle, is higher than human understanding. Therefore, as the Torah comes into human understanding it gets "filtered" through their brain (even two prophets would not use the same wording). Therefore, if someone applies the Torah approach to a problem and gets to one resolution, the result is true.

However, practically, as it comes into the world, there can be only one truth, which is known as "Halacha". Therefore, when one asks a shaila, he is expecting "what to do", not "there are two approaches" because this world, a physical world, is limited in the sense that one cannot do two opposite things at a time. Therefore, the halacha could go like either one or the other, and halachically, the other could be rejected completely, as if it wasn't there (Beis Shamai v Beis Hillel). In the source of Halacha, in the higher worlds, however, they are both true.

shabbat - 40 minutes offset for candle lighting?

Several Zmanim apps are giving a choice on my "candle lighting offset". The default here is 40 minutes instead of the usual 18 minutes I've heard.

Why 40? Why do I even have a choice?

Does the fact that I am in Jerusalem play a role?

Answer

The reason why we light candles a few minutes early (18 minutes) is in order to avoid any possibility of starting Shabbat late. Think of it as a train leaving the station. If you're one minute late, you missed it.

By the way, though most communities light Shabbat candles 18 minutes before sunset, local custom may vary. For instance in Jerusalem, the custom is to light 40 minutes before sunset.

http://www.aish.com/sh/ht/fn/48965051.html

Jerusalem lights candles 40 minutes before sunset. (Except for those who don’t follow that custom.) Which sunset? Important question. The standard practice is to count 40 minutes before “sunset of elevation”. Jerusalem is a little over 800m above sea level. If one could see the sun set over a horizon at sea level (which can be done from some parts of J’lem), it would set about 5 minutes later than someone watching from sea level, or seeing the sun set beyond mountains that are approx. the same height as Jerusalem is. Since the sunset on the same plane is 5 minutes earlier, and for Shabbat purposes is the sunset we would have to consider because of the strictness of Shabbat, then J’lem candle lighting time is really only 35 minutes before “the other” sunset.

All other places at some height above sea level have similar problems. Tzfat lights candles 30 minutes before sunset. Official candle lighting for Petach Tikva is 40 minutes before sunset, just like Jerusalem. Not everybody holds by that timing.

Some communities calculate Shabbat out at 33 minutes after sunset. Some use the angle of the sun below the horizon to “end Shabbat” (8.5 deg).

http://www.ou.org/torah/tt/5763/matmas63/zmanim.htm

here is the well known custom in Jerusalem to light Shabbat candles 40 minutes before sunset. This custom is derived from a view which requires one to add half of a "halachic hour" to one's Shabbat. This amount of time maximizes to be 40 minutes at the height of summer.[Shita Mekubetzet Beitza 30a] In order to avoid confusion and ensure consistency, this 40 minute period is adhered to all year long even when half a halachic hour would be less than that.

http://hirhurim.blogspot.com/2008/01/shabbat-candle-lighting-times.html

Sorry for the Quotes instead of a summary, but even though I don't start until 18 minutes before sundown Shabbat is coming!!:)

Would the mixture of vinegar and baking soda make a cleaning agent?

I've seen it suggested countless times that combining vinegar and baking soda is a great home cleaning solution, but this always seemed like nonsense to me.

I recognize that baking soda, a base, can eat away at certain kinds of grime and that vinegar, an acid, can operate similarly on different kinds of grime.

Mixed together, of course, the two create a neat foaming reaction and I think this is where the alleged myth would originate - people see the violent foaming and assume cleaning is occurring.

Isn't it true that the two are primarily reacting with each other and yielding only a relatively inert and neutralized sludge? That the mix reacts with any grime less than they would if both were applied in isolation against the grime? I assume that the only plausible benefit from this mix would be in any pockets of non-neutralized components floating on the foam and physically reaching new areas of grime that the individual volumes would not cover.

But I guess there could be more to cleaning effectiveness besides pH!

Am I right or are they?

Answer

Well, cleaning is a very broad subject. This is a question which could make a great Science Fair Project. Because vinegar is just a dilute solution of acetic acid (ignoring trace compounds present), and because both baking soda and sodium acetate are pretty soluble, it wouldn't probably be practical to try to make a saturated acidic solution of BS. That is, any precipitates will be made from alkaline solution, under normal circumstances.

There's two questions which would need to be answered:

1. 
   

   Does fresh V+BS slurry act the same way as old V+BS slurry?

   
   



2. 
   

   Are either better than water + BS?

   
   

Well, hmm. To be honest, IDK, but I'd guess "maybe" for both (which is why it would be interesting to see what happens). Let me explain:

Acetic acid dissolves soap scum (mostly K, & Ca salts of fatty acids) and dissolves water hardness (mostly Ca & Mg carbonates) So starting off getting rid of some or all of that junk could definitely be a good thing (and acetic acid is only going to be around for a very short time if BS is present in excess). But we know that acids attack metals, so leaving vinegar on metal isn't a good idea...and guess what? Once the BS fully reacts, the acid will be gone! I can't think of any other plausible reason that V+BS would be better than W+BS.

One other potential reason would be if the vinegar changed the abrasiveness of the BS, making it more effective (which is another thing you could test for), but I doubt it would. (possible but not quite plausible, if you know what I mean). Anyway, what you've got left is W+BS after the reaction, so what's the worst it can do?

I do know for sure that most cleaners (with the exception of many metal cleaners) are alkaline because higher pH tends to dissolve (and/or lift-off (which means form a colloid of or weaken the adhesion to the surface-to-be-cleaned of)) organics better than acidic solutions. Cleanser, which is usually just mostly silica, certainly is more abrasive than BS, but that also means it will tend to scratch (or fog) more surfaces. I don't know, but I'll bet most cleansers are alkaline for the reason mentioned above. (alkaline solutions are NOT more slippery, but they form soaps out of your skin, and those soaps are more slippery. So, the slipperiness you feel when you touch an alkaline (basic) solution is just your skin dissolving :)

song poetry - What is the source that singing and clapping sweetens judgment

I heard a song

"על ידי ניגונים ומחיאת כף מתמתקין כל הדינים".
Seeming to mean:
through singing (or songs) and clapping hands all the (negative) judgments (made in Heaven) get sweetened (less harsh)

Is this a right translation?
What is the source of these words?
What is the source of the source...?

Answer

It says in likutei moharan 10,1 (English audio 1, 2, 3): When there is G-d forbid judgements on the Jewish people, then through dancing and clapping the judgements are sweetened. (My translation). See the entire torah 10 for further elaboration.

history - Timeline of the 10 plagues in exodus?

Do we have a chronological timeline (with years) of the 10 plagues? I'm trying to recreate a full timeline of the הגדה של פסח for the upcoming holiday, going from the arrival of Jacob and his family to the splitting of the Yam Suf (red sea).

midrash - Coffee and the Source for Reason for Staying Up for Shavuos

In a fascinating article , Elliot Horowitz credits the introduction of coffee for the spread of the custom of staying awake at night. In the 15th century, the drinking of coffee originated in Yemenite Sufi circles in order that they could stay awake for their nocturnal rituals, and by the end of the 16th century coffee had spread throughout the Muslim world. Horowitz points out that both coffee and the custom of tikkun hazot spread westward from Sefat to Europe in the 17th and 18th centuries. ( qoute source: http://ou.org/holidays/shavuot/the-all-nighter. )

When did the rationale based off of the medrash which says that klal yisroel woke up late for kabalas hatorah first appear?

Answer

The Shulchan Aruch brings (תצ"ד, ג):

נוהגין הרבה להיות נעורים כל הלילה לעסוק בתורה

Quoting the Zohar (מ"א שם ד"ה איתא, בשם הזהר ח"א ח, א. ח"ג צח, רע"א. ח"י שם)

The Aruch HaShulchan (תצ"ד, ג) reinstates the connections to Mattan Torah and links it to a Zohar:

והחסידים הקדמונים היו נעורים כל הלילה כדאיתא בזוהר וגם עתה הרבה עושים כן... והכל זכר למתן תורה

In the introduction to the Zohar (ח ע"א), here is a hebrew translation, which makes reference to the 'marriage' of the Jewish people and Hashem at Har Sinai:

רַבִּי שִׁמְעוֹן הָיָה יוֹשֵׁב וְעוֹסֵק בַּתּוֹרָה בַּלַּיְלָה שֶׁהַכַּלָּה מִתְחַבֶּרֶת בְּבַעְלָהּ. שֶׁשָּׁנִינוּ, כָּל אוֹתָם הַחֲבֵרִים בְּנֵי הֵיכַל הַכַּלָּה, הִצְטָרְכוּ בְּאוֹתוֹ לַיְלָה שֶׁהַכַּלָּה עֲתִידָה לִהְיוֹת לַמָּחֳרָת בְּתוֹךְ הַחֻפָּה עִם בַּעְלָהּ לִהְיוֹת עִמָּהּ כָּל אוֹתוֹ הַלַּיְלָה, וְלִשְׂמֹחַ עִמָּהּ בְּתִקּוּנֶיהָ שֶׁהִיא מִתְתַּקֶּנֶת לַעֲסֹק בַּתּוֹרָה, מִתּוֹרָה לִנְבִיאִים, וּמִנְּבִיאִים לִכְתוּבִים, וּבִדְרָשׁוֹת הַפְּסוּקִים וּבְסוֹדוֹת הַחָכְמָה, בִּגְלַל שֶׁאֵלּוּ הֵם תִּקּוּנֶיהָ וְתַכְשִׁיטֶיהָ, וְהִיא וְעַלְמוֹתֶיהָ נִכְנֶסֶת וְעוֹמֶדֶת עַל רָאשֵׁיהֶם וּמִתְתַּקֶּנֶת בָּהֶם, וּשְׂמֵחָה בָהֶם כָּל אוֹתוֹ הַלַּיְלָה, וְלַמָּחֳרָת לֹא נִכְנֶסֶת לַחֻפָּה אֶלָּא יַחַד אִתָּם. וְאֵלֶּה נִקְרָאִים בְּנֵי הַחֻפָּה. וְכֵיוָן שֶׁנִּכְנֶסֶת לַחֻפָּה, הַקָּדוֹשׁ בָּרוּךְ הוּא שׁוֹאֵל עֲלֵיהֶם וּמְבָרֵךְ אוֹתָם, וּמְעַטֵּר אוֹתָם בַּעֲטֶרֶת הַכַּלָּה. אַשְׁרֵי חֶלְקָם.

I found this quote from the Zohar but the Aruch HaShulchan may be referring to another source related more specifically to the giving of the Torah. Either way, it is a mishnaic source which puts this at around 2000 years ago.

molecules - Identifying the number of bonding and lone pairs without a dot and cross diagram

I've just learned how to predict the shapes of molecules in class today using VSEPR theory. I would like to ask is there anyway to find the number of bond pairs and lone pairs without drawing a dot-and-cross diagram?

Answer

There is a simple, four-step calculation that you can perform:

1. 
   

   count the valence electrons the atoms you are bonding have.

   
   


2. 
   

   count the number of valence electrons the atoms would like to have for a noble gas’ valence shell. (i.e. eight for everything main group, two for hydrogen.)

   
   



3. 
   

   substract $2.-1.$, i.e. the first (existing) from the second (desired). This is your number of bonding electrons. Divide by two for bonding electron pairs.

   
   


4. 
   

   substract $1.-3.$, i.e. the third (bonding) from the first (existing). This is your number of free electrons. Divide by two for lone pairs.

   
   

Using a simple example such as sulphur dioxide:

1. 
   
   

   $6\ (\ce{S}) + 2 \cdot 6\ (\ce{2 O}) = 18$

   
   


2. 
   

   $8\ (\ce{S}) + 2 \cdot 8\ (\ce{2 O}) = 24$

   
   


3. 
   

   $24 - 18 = 6$, i.e. three bonding electron pairs.

   
   


4. 
   

   $18 - 6 = 12$ i.e. six lone pairs.

   
   
   

Unfortunately, that by itself does not allow you to write the structure; you need to know which element is in the centre and how they are connected. Here, we have a central sulphur bonded to two oxygens. The final result is:

$$\ce{O=S+-O-}$$

With two lone pairs on the left-hand oxygen, one on the sulphur and three on the right hand oxygen. The formal charges are important.

grammar - 安いらしい, 安いそうだ, and 高っぽい are incorrect?

I was reading up on the usage of げ, みたい, っぽい, らしい, そう, よう, and so on. Then, I came across a certain description on a website that ruined my day.

On this web page, the author states that 安いらしい, 安いそうだ, and 高っぽい are wrong. Now I am going to hazard my understanding below.

1. 
   

   安いらしい (*mainly?) has two usages. One is for hearsay, and the other is for how someone/something seems to have a certain typical property (but usually positively so). The author says that if らしい is attached to 安い (an adjective), the usage defaults to hearsay (伝聞), and therefore wrong in that the other usage (様態) is the focus in question. I assume this means that らしい when preceded by an adjective can only be about hearsay. In the same article, the author says that only when preceded by a noun can らしい express the meaning of 様態. In other words, I assume that な-adjectives or verbs succeeded by らしい only has the meaning of hearsay.

   
   

   Is this understanding correct?

   
   
   


2. 
   

   Similarly, 安いそう is about hearsay. This time there is no other possibility, for the grammatical structure dictates so (安いそう would be it). Again, I believe the author says it is wrong, because the hearsay usage is not the focus of the discussion in that part of the article. Does this mean that one simply needs to change the form into 安そう to fit the scope of the discussion?

   
   

   According to another website, not quite so. Here another author asserts that 安そう is unnatural:

   
   

   
   

   「安そうです」は不自然な感じがする。

   
   

   
   

   The author used two rather big terms, 言霊信仰, and 言語の経済学, to explain how 安そう is not ideal. I think I understand the point made, but do you agree with the author? Is **安そう** really not commonly used?

   
   


3. 
   
   

   The explanation given on another page on the first website says something to the effect that 高っぽい is incorrect due to っぽい's negative connotative nature. In other words, since one would usually view something factually 安い yet 高い appearance-wise as being positive, using 高っぽい to describe a cheap item would come across as strange. However, I feel that this is essentially more about context than prescriptive restriction. We all know 子供っぽい and 女っぽい are not necessarily negative. Do you agree with the author's view that **高っぽい** is illogical, and thus wrong?

   
   

*I feel like giving Japanese up already. Now the entirety of the question is based on what I could glean from the articles using my beginner-level Japanese. Please correct me if you find any misunderstanding of the text on my part. どうぞよろしくお願いいたします。

Answer

1. 
   

   Yes, your understanding seems correct. らしい cannot generally express the sense of having an appearance or property when attached to an adjective; only the hearsay meaning is applicable.

   
   


2. 
   
   

   Your initial understanding is accurate - at a basic level, 安いそう would express hearsay (that you heard something is cheap) whereas 安そう would express appearance (that something looks like it is cheap). Both are perfectly grammatical forms that will be easily understood.

   
   

   What the other page you linked is getting into a slightly more complex level, looking at the semantic subtleties of 安そう. In short, it can be used perfectly naturally in some contexts, but it is not nearly as common as 高そう when describing an object, mainly because 高い is perceived as a more inherent quality of an object than 安い.

   
   

   A 高い object has inherent value, and will fetch a high price no matter where it is sold, so it makes sense to talk about something being 高そう "looking expensive". However, being "cheap" is not an inherent quality of an object, but a decision of the seller - an object could have little inherent value but still be assigned a high price tag if the seller decides to price it as such. So it seems less natural to say that an item "looks" 安い. (This is quite different from English, where "cheap" has acquired an extended meaning of "low-quality" in addition to the literal "low price", and so we can quite freely say something "looks cheap".)

   
   


3. 
   

   I think it's worth noting that attaching っぽい to an adjective root is a very different process from attaching そう to that same root. そう is a productive suffix that can be added to the root of just about any adjective and produce the same basic meaning of "looks X".

   
   

   っぽい is also extremely productive in casual usage (in which it can attach to nouns, full adjectives or sometimes even full verbs to form the meaning "looks like X"), but it never attaches to adjective roots in this sense. It only attaches to adjective roots in its stricter, less casual and probably older sense as a very unproductive suffix that only applies to a handful of set words and produces quite specific meanings. It's better to think of these っぽい-suffixed adjectives as separate words in their own right, since their meaning can differ somewhat from the basic adjective they're derived from.

   
   

   For instance, あれは安いっぽい would be the casual, productive usage of っぽい meaning "It looks like that's cheap". However, あれは安っぽい is the unproductive usage of っぽい, and means "That is cheap-looking". Note that this is using "cheap" in the extended sense of "low-quality" which 安い doesn't usually possess in Japanese - this is a specific connotation that only applies to the word 安っぽい.

   
   

   As such, 高っぽい is unnatural on a whole different level from something like 安そう. 安そう is a perfectly reasonable construction that will always be understood but might not be very common due to its semantic subtleties. 高っぽい, on the other hand, simply doesn't exist as a word - it sounds plain wrong. (高いっぽい, meanwhile, can of course be used as a casual way of saying it "looks like" something's expensive. Note that this is quite different from saying something is 高そう - 高そう indicates you're looking at the object itself and saying it looks valuable, whereas 高いっぽい indicates you're deducing from surrounding information that something is actually being sold at a high price - eg. because it's on a shelf with other luxury items, or because you heard people talking in hushed whispers about how it's very sought-after.)

   
   

   The negative connotations of っぽい might be raised as one possible explanation for why 高っぽい doesn't exist while its corresponding 安っぽい does, but it's not a rule. Indeed, there are plenty of negative adjectives that don't have a っぽい form like this (Forms like つまらなっぽい and まずっぽい just sound plain meaningless). So no, I wouldn't agree that 高っぽい is wrong "because" it's illogical - it's wrong simply because the word doesn't exist.

   
   
   

usage - Difference between sentence final ものだ and ことだ

My understanding is that ものだ is used to assert things which are mostly known to everyone.

誰かの家に招待されたときは、何か手土産をもっていくものだ

'When invited to somebody's home it's customary to bring presents'.

On the other hand, ことだ is used to give someone advice.

A: どうすれば日本語が早く簡単に上達しますか。
B: 上手になりたいなら、真面目にコツコツ勉強することです。それ以外に方法はありません。

I can understand that B gives an advise to A, however B is not really saying anything that A couldn't already know. Moreover, when talking about what to do when going to somebody's home, "bring presents" is not necessarily something that everybody is aware of - could be that some cultures are used to bringing money.

So it seems to be that, in the examples above, ものだ and ことだ are can be freely exchanged. Note, that the examples are from my textbook so i guess they can't be exchanged.

Answer

I am not sure where your confusion comes from, but …するものだ means “it is customary to do …” and …することだ means “do ….” Their meanings are different, and they are not interchangeable.

bond - Fundamental forces behind covalent bonding

I understand that covalent bonding is an equilibrium state between attractive and repulsive forces, but which one of fundamental forces actually causes atoms to attract each other?

Also, am I right to think that "repulsion occurs when atoms are too close together" comes from electrostatic interaction?

Can a Japanese word combine both on'yomi and kun'yomi characters?

I would like to know whether a Japanese word combining at least two kanji can combine both on'yomi and kun'yomi characters, within the same word.

Thanks.

Is there a name for kanji with the same ON and KUN readings?

Is there a name for kanji with the same on and kun reading? I mean kanji like 労.

Answer

I'm not sure there are kanji that have the same on and kun reading and if there are, they would be extremely rare. For this to happen you would have to have a native Japanese word (at most two morae), which happens to be pronounced like a on reading (quite unlikely) and that word happens to be the on reading of the kanji that matches the meaning of the original Japanese word (extremely unlikely).

For example, か "mosquito" could be an on reading of a kanji. But it's not the on reading of the kanji that matches the meaning "mosquito", which would be 蚊【ブン】. So, we get 蚊 with kun reading か and on reading ブン.

---

It may happen that the on reading of a single kanji may be used as a word by itself (e.g. 駅). That doesn't make the reading a kun reading.

Also, sometimes the on reading of a kanji may be used in verbs (e.g. 愛す or 転じる). Even if the verb can be written in hiragana (as in あいす or てんじる), that doesn't make the reading (あい or てん) a kun reading. These verbs, that look like

[on reading] + す
[on reading] + じる
[on reading] + ずる

are fossilized versions of

[on reading] + する

as in 勉強する "to study" and you will agree that べんきょう isn't a kun reading of 勉強 just because it appears in べんきょうする.

matlab - How does resizing an image affect the intrinsic camera matrix?

I have a camera matrix (I know both intrinsic and extrinsic parameters) known for image of size HxW. (I use this matrix for some calculations I need).

I want to use a smaller image, say: $\frac{H}{2}\times \frac{W}{2}$ (half the original). What changes do I need to make to the matrix, in order to keep the same relation ?

I have, $K$ as the intrinsic parameters, ($R$,$T$ rotation and translation)

$$\text{cam} = K \cdot [R T]$$

$$K = \left( \begin{array}&a_x &0 &u_0\\0 &a_y &v_0 \\ 0 &0 &1\end{array} \right)$$

$K$ is 3*3, I thought on multiplying $a_x$, $a_y$, $u_0$, and $v_0$ by 0.5 (the factor the image was resized) , but I'm not sure.

Answer

Note: That depends on what coordinates you use in the resized image. I am assuming that you are using zero-based system (like C, unlike Matlab) and 0 is transformed to 0. Also, I am assuming that you have no skew between coordinates. If you do have a skew, it should be multiplied as well

Short answer: Assuming that you are using a coordinate system in which $u' = \frac{u}{2} , v' = \frac{v}{2}$, yes, you should multiply $a_x,a_y,u_0,v_0$ by 0.5.

Detailed answer The function that converts a point $P$ in world coordinates to camera coordinates $(x,y,z,1)->(u,v,S)$ is:

$$ \left( \begin{array}{ccc} a_x & 0 & u_0 \\ 0 & a_y & v_0 \\ 0 & 0 & 1 \end{array} \right) \left( \begin{array}{ccc} R_{11} & R_{12} & R_{13} & T_x \\ R_{21} & R_{22} & R_{23} & T_y \\ R_{31} & R_{32} & R_{33} & T_z \\ 0 & 0& 0 & 1 \end{array} \right) \left( \begin{array}{ccc} x \\ y \\ z \\ 1 \end{array} \right) $$

Where $(u,v,S)->(u/S,v/S,1)$, since the coordinates are homogenous.

In short this can be written as $ u= \frac{m_1 P}{m_3 P} , v = \frac{m_2 P}{m_3 P}$
where $M$ is the product of the two matrixes mentioned above, and $m_i$ is the i'th row of the matrix $M$. (The product is scalar product).

Re-sizing the image can be thought of:

$$ u'=u/2, v'=v/2 $$

Thus

$$ u' = (1/2) \frac {M_1 P} {M_3 P} \\ v' = (1/2) \frac {M_2 P} {M_3 P} $$

Converting back to matrix form gives us:

$$ \left( \begin{array}{ccc} 0.5 & 0 & 0 \\ 0 & 0.5 & 0 \\ 0 & 0 & 1 \end{array} \right) \left( \begin{array}{ccc} a_x & 0 & u_0 \\ 0 & a_y & v_0 \\ 0 & 0 & 1 \end{array} \right) \left( \begin{array}{ccc} R_{11} & R_{12} & R_{13} & T_x \\ R_{21} & R_{22} & R_{23} & T_y \\ R_{31} & R_{32} & R_{33} & T_z \\ 0 & 0& 0 & 1 \end{array} \right) \left( \begin{array}{ccc} x \\ y \\ z \\ 1 \end{array} \right) $$

Which is equal to

$$ \left( \begin{array}{ccc} 0.5 a_x & 0 & 0.5 u_0 \\ 0 & 0.5 a_y & 0.5 v_0 \\ 0 & 0 & 1 \end{array} \right) \left( \begin{array}{ccc} R_{11} & R_{12} & R_{13} & T_x \\ R_{21} & R_{22} & R_{23} & T_y \\ R_{31} & R_{32} & R_{33} & T_z \\ 0 & 0& 0 & 1 \end{array} \right) \left( \begin{array}{ccc} x \\ y \\ z \\ 1 \end{array} \right) $$

For additional information, refer to Forsyth, chapter 3 - Geometric camera calibration.

organic chemistry - Monobromination vs. Dibromination

My professor noted that bromination with light and methylene chloride gives you exclusively the monobromination product.

However, bromination without light will give you the multi-brominated product.

I have no found any reference to bromination in my textbook nor online. Is the second statement an accurate statement?

Answer

Bromination of alkanes with Br2 will not occur in a dark environment. In the presence of light, multiple halogenations can occur given enough time.

For more information, including the full mechanism, check out: https://en.wikipedia.org/wiki/Free-radical_halogenation

organic chemistry - Would C bond with H or D?

Is a C-D bond better than C-H bond? I mean if carbon has a chance to either for a bond with deuterium or hydrogen what would it choose and why? What if tritium competes too?

Answer

C-H would be the weakest bond, then C-D, then C-T would be the strongest.

This is due to the zero point energy of the bond and the fact the zero point energy is proportional to:

$$\sqrt{\frac{m_C + m_H}{m_C m_H}}$$

Zero point energy is the minimum energy the quantum harmonic oscillator can have.

Because the greatest mass isotope has the smallest zero point energy, the energy of the bond is greatest.

What is the difference between the titration of a strong acid with a strong base and that of the titration of a weak acid with a strong base?

Which of the following statements best characterizes the difference between the titration of a strong acid with a strong base and that of the titration of a weak acid with a strong base?

A) Both the strong acid and the strong base are completely dissociated in solution whereas the weak acid dissociation equilibrium constant is small enough that there is a measurable amount of the un-dissociated acid present in aqueous solution.

B) The equivalence point of a titration of a strong acid with a strong base may be observed with an indicator whereas the equivalence point of a titration of a weak acid with a strong base can only be observed with a pH meter.

C) The titration of a strong acid with a strong base is a fast reaction whereas the titration of a weak acid with a strong base is generally a very slow reaction.

This website seems to indicate that choice C is correct.

For B, all I know is that the pH at the equivalence point does not equal 7.00 (pH > 7.00) for the weak acid titration.

For A, I know the first part of that sentence is true. Strong acids and bases are characterized by completely dissociating whereas weak acids do not dissociate to the same extent. But is it true that there's a "measurable amount" of the un-dissociated acid present in aqueous solutions?

What constitutes eating on a fast day?

For example, does chewing on a stick or piece of plastic count as eating? grass? What about chewing sugar-free gum with no nutritional value? I imagine it must be "derech achila," but this certainly could be different for different people.

(am I making you hungry yet?)

Answer

When it comes to Yom Kippur, the halachah is that even chewing on something non-nutritional is prohibited. The example given is aromatic wood (Rema to Shulchan Aruch, Orach Chaim 612:6), and Mishnah Berurah (ibid. :18) explains that one does feel a sensation of flavor from doing so. So that would seem to cover your examples of a stick or sugar-free gum; I suppose you could argue that plastic is different, though.

As for grass - Rambam (Hil. Shevisas Asor 2:6) gives "bitter grasses" as an example of food not fit for human consumption, and says that someone who eats that on Yom Kippur is not subject to kares, but is punishable by makas mardus (lashes at the discretion of the beis din). Mishnah Berurah (Shaar Hatziyun 612, ד"ה אכל) explains that he means "bitter grasses" as opposed to edible herbs; I'd guess, though, that regular lawn grass would probably fall into the "bitter grasses" category (especially with all the pesticides usually applied to it...).

In connection with chewing something and spitting out the resulting saliva, Rema there references 567:3. There he says that this applies only to Yom Kippur, and that it would be permissible on other fast days. However, Mishnah Berurah (ibid. :13) says that this is correct only according to the Mordechai; according to the Mechaber (ibid. :1) this should be true of Tisha Be'Av as well, and according to the Rema (ibid.) it would be true of all public fast days.

solutions - Why does shampoo lather much more the second time it is applied?

When I shampoo my dirty hair, the first time it does not lather very much. The second time it lathers a lot. Why is this?

Answer

Quoting a reddit post from chemist nallen:

The short answer is that the dirt and oils from your hair compete for the surfactants making them less available to form lather, which is small bubbles.

To better understand the mode of action, you have to know a bit about the formulation of shampoos and the nature of dirt and oils.

Dirts and oils deposit on hair and fibers because they are at least partially hydrophobic (not soluble in water.) The surface of hair, skin, etc... is more hydrophobic than water (well of course!), so these dirts have greater adhesion for the surface than for water (the water actually pushes them out to minimize surface area.) This is why water is ineffective for removal, it won't pull the dirt off the surface by itself. Surfactants associate with the hydrophobic surfaces to make them more dispersible or soluble in water, allowing them to be rinsed off. So what happens when there is more surfactant than there is hydrophobic dirt surface?

The answer is that the surfactant orients to the surface of the water, because air is hydrophobic, and the water wants to push the hydrophobic portion of the surfactant out of the water molecule matrix. This orientation on the air-water interface is how skin of bubbles is formed. When the water/surfactant solution undergoes sufficient shear mixing, bubbles are formed, and that is lather. Lather typically forms when there is surfactant in excess of the hydrophobic surface. More dirt means less free surfactant, and therefore less lather.

Now, it's not purely that simple, because the amount of lather that a surfactant develops varies with the type of surfactant, some are better than others.

Lather does not mean that the shampoo is cleaning better, it's purely cosmetic. Typical shampoos are primarily SLES/Betaine, that is sodium laureth sulfate and cocamidopropyl betaine. The SLES is there for cleaning, and the betaine is there for lather, it's specifically added to produce lather because, well, people like it. There are some other benefits, but that's the primary one. If you used SLES by itself is would clean just as well, but people just don't like poor lather, so it would not sell.

organic chemistry - Why is it the middle ring of anthracene which reacts in a Diels–Alder?

I'm wondering why maleic anhydride adds to the middle cycle of anthracene, and not the outer two.

I would have expected that a Diels–Alder with the outer ring would be better, because I expected a naphtalene part to be lower in energy than two benzene parts (more resonance stabilisation).

I guess it has to do with reactant based arguments that the atomic coefficients for the two center carbon atoms (C-9 and C-10) are higher than from the outer cycle (C-1 and C-4). I ran a calculation using http://www.chem.ucalgary.ca/SHMO and the coefficients on C-9 and C-10 were 0.44, whereas those on C-1 and C-4 were only 0.31.

Answer

To provide a reason for the observed regioselectivity, it is helpful to draw anthracene's aromatic π-electron system in alternance of single and double bonds. In this instance, it is more beneficial than "the ring" symbolizing the delocalised electron system, as this helps you to account for the precise number of π-electrons before the reaction (starting materials), during the reaction (the mechanism), and after the reaction (the product).

For the Diels–Alder reaction, you may imagine two different pathways. I invite you to draw the mechanisms by yourself:

• A reaction that involves carbon atoms #1 and #4 (or #5 and #8). Possible, by mechanism. There are five double bonds remaining in conjugation, and you count one six-membered ring in the state of "a benzene ring" (the very left one). In the very right six-membered ring, there is only a single double bond, too.


• Alternatively, a Diels–Alder reaction with carbon atoms #9 and #10. This is more favourable then the former example, because both the very left as well as the very right ring of the product are in the state of "a benzene ring", each of these rings contain 6 π-electrons, the prerequisite of a Hückel aromatic compound. It is so much favourable to the former, that this is the reaction observed.

It may be helpful to add that benzene, naphthalene and anthracene are of course Hückel-aromatic compounds; with 6, 10 or 14 π-electrons they fit into the rule of $(4n + 2)$. Yet gradually, as experimentally found, in this group of three, benzene is the most, anthracene the least aromatic compound.

bond - Is this a valid structure for the nitrate ion?

Why is the below structure not considered a valid structure for the nitrate ion? Is it because adding a double bond reduces the formal charges present on the nitrogen? Does the above form exist anywhere?

Answer

Nitrate actually exists as a superposition of these three resonance forms:

(Source: Wikipedia)

Essentially, a lone pair from an oxygen with a negative formal change forms a double bond to nitrogen. However, as nitrogen is a period II element, and hence must obey the octet rule, it can not have 5 bonds to other atoms. The already-present double bond then turns into a single bond and the pair of electrons moves onto the oxygen. This "movement" can happen with all three of the oxygen atoms and all three of the bonds. This is called "resonance".

Due to resonance, the energy of the system is minimised making it more stable.

Your Lewis structure is not far off. The "true" structure of nitrate is:

(Source: Wikipedia)

Approximately, each oxygen atom contributes one third of a bond with the nitrogen, lowering the formal charge on each atom from what you have written, which does not exist in nature.

The true structure is sort of an average of the properties of each possibility for where the electrons could be located, including the three resonance forms above, your structure, and any other configuration. However, these other forms are of minuscule probability to be formed (perhaps read up on wavefunctions and electron distributions if you're interested), and so the main contributors to the "real" structure are the three resonance forms.

Note that none of these structures ever exist in isolation for more than the most infinitesimal of time periods.

nuances - What is the difference between 経験 and 体験?

I was wondering what the difference is between 経験 and 体験? I've come across both terms a couple of times, and I know they both mean 'experience', but what is the difference between the two?

Based on the kanji, I would guess that 体験 relates more to a personal experience? Maybe it's only used for your own experience?

Answer

This is no easy question and I do not claim to know all about it.

Informally, 「[経験]{けいけん}」 and 「[体験]{たいけん}」 are often used interchangeably when referring to a single incident that is a new experience for that person. Regarding whether or not doing so is appropriate, I will leave the judgement to the experts here. All I know for certain is that native speakers just use the two words interchangeably in many informal situations where no one really cares about precise word choices.

When we speak or write more formally about our experiences, however, we seem to become more careful about which word to use.

Formally, 「体験」 refers to any experience that one undergoes in life. If one does not reflect on the experience and learn something valuable from it, it remains a 「体験」. It is a one-time-only thing. However, if you reflect upon your 「体験」 and learn a lesson from it, it can turn into a 「経験」. Your life is that much richer because of it.

In another words,

「体験」 can often happen by sheer chance.

「経験」 often cannot just "happen" without one's active effort following the 「体験」.

Additionally, one could also say that 「経験」 is an accumulation of one's 「体験's」 in the sense that 「経験」 has a longer-lasting effect. If you have a 10-year experience in something, that "experience" should definitely be translated as 「経験」, not as「体験」.

MR Segmentation to draw marker over the MR Dicom Images

I am doing R&D over the MR Segmentation to draw marker over the Heart MR Dicom Images. My Question is that how I can draw a such marker over the dicom image that show in attach/link image. that Region of Interesr ROI read from the tag or its part of Pixel Processing.

kanji - Specific examples of tonal Chinese words rendered into Japanese

It is often said that Japanese contains a large number of homonyms because there was no way to render tonal Chinese words into Japanese. This makes complete sense. But I am looking for specific examples of Sino-Japanese words which are homonyms but where their original Chinese counterparts are not homonyms, i.e. the Chinese words have tonal differences, but the Japanese words do not.

rashi - Understanding "The Bruriah Incident"

Masecheth 'Avodah Zarah (18b) cryptically mentions "מעשה דברוריה" - "The Beruriah Incident" - as a reason R' Meir fled to Bavel. Rashi (ad loc) explains that R' Meir was teasing his wife (the noted scholar Beruriah) that she would one day admit that the rabbis were correct when they said "נשים דעתן קלות הן" - "Women's intellects are light" (my own translation, but its actual meaning is subject to dispute). To that end, he asked one of his students to "test her to a matter of sin" (presumably this means to seduce her sexually). After resisting for "many days", she succumbed, and when "she realized", she hanged herself and R' Meir fled out of shame.

According to the above-linked Wikipedia entry on Beruriah, Rashi is alone in his explanation of the incident, and there is a tradition among Orthodox rabbis to name their daughters after her to defy that story and reclaim her name as a righteous and scholarly woman of Israel.

My question:

a. If Rashi's explanation is correct, what was R' Meir thinking?? Even if it was to goad his wife to some non-sexual sin, what about Lifnei 'Iver? What happened to loving and honoring one's wife?

b. If Rashi's explanation is incorrect, where on earth did it come from, and what was he thinking??

inorganic chemistry - Why is dipositive dilithium more stable than neutral dilithium?

According to J.D Lee, compounds with fraction bond number are unstable. I calculated that the bond order of $\ce{Li2^2+}$ is 0.5 while that of $\ce{Li2}$ is 1. Hence, $\ce{Li2^2+}$ must be less stable than $\ce{Li2}$ due to half bond character.

But, in reality, $\ce{Li2}$ is more stable than $\ce{Li2^2+}$. Why is it so?

Answer

The comment asks "Why is Li2+ more stable than Li2". Li2 has a relatively low bond energy (gas phase) of 27 kcal/mol (Cotton and Wilkinson, Inorganic Chemistry). The energy cost to make one mole of Li gas is 37 kcal (CRC Handbook). The ionization energy of Li is 5.39 eV = 124 kcal/mol.

So, breaking a Li2 gas molecule into 2 Li (gas) costs 27 kcal/mol.

Breaking a Li2+ gas molecule into Li + Li+ involves not the separation of two uncharged atom, but the separation of a very small Li+ ion from a Li atom which provides some charge accomodation. The heat of formation of Li+ in water is 66 kcal/mol (presumably from aquation with 4 waters); the hydration bonding is worth about (124 + 37 + 66)/4 = 54 kcal/mole each. So I would estimate the bond between Li+ and Li to be perhaps 40 kcal/mol, at least a significant fraction of 54 kcal/mol, and probably more than 27 kcal/mol.

The important point is that the unusually small size of the Li+ ion makes it able to polarize a neutral atom to form a strong bond (and come in closer!), whereas the neutral atoms have only uncharged molecular orbitals to spread their electrons over. It is highly unlikely that larger atoms (Na, K) would show similar stability for an ion-molecule compared to a neutral molecule. Magnesium might be a similar exception, however, since both Li and Mg have small radii; it might be interesting to compare stabilities of Mg2 and Mg2+.

words - かかったためしない - how can this be translated?

I encountered the following sentence in a comic book which I could not make sense of.

The comic strip depicts a character using a simple bird trap and saying: 「長年やってるけどかかったためしないなあ」 The first part, 長年やってるけど, can be roughly translated as "I've been doing this for quite a while", and this is quite clear.

The second part, かかったためしない, is not clear.

My guess is that it means something like "Catching is not the reason I'm doing this." The dictionary shows that かかる can be translated as "to catch (prey)" and I know that ため can be an "intention" and する is "do". However, I feel I may be wrong here, especially since it's all written in hiragana.

Some help would be appreciated.

Answer

You are parsing the sentence incorrectly. It should be

長年やってるけど かかった ためし (は) ない なぁ

It then roughly means,

I have been doing this for quite some years, but it's not like I have ever caught anything.

ためし (written 試し) can mean "trial/test", but here it is used in the sense of "experience" (written 例 or 様; see Tsuyoshi Ito's comment below and the entry in Daijisen), as is often the case in the phrase ためし(は)ない, e.g.

部屋を綺麗に片付けたためしはないでしょ
You look like you have never had the experience of (or a taste of) what it is like to have cleaned a room.

The person from your sentence has been trying to catch birds for many years, but has never had the experience of having caught something.

physical chemistry - Distinguish between two possible configurations for angular momentum in carbon atom

Consider the possible values of $S$ and $L$ for carbon configuration $1s^2 2s^2 2p^2$ and the corresponding rapresentations with arrows indicating the spins (consider only $S=0,L=0$ and $S=0,L=2$, as for $S=1,L=1$ some are missing).

I can't understand which one of the two representations indicated in red belong to $S=0,L=0$ state and which one to the $S=0,L=2$ state (I took a guess making the picture).

The spin wavefunction is in all cases antysymmetric ($S=0$) and equal to $$\chi =\left(\, |\!\uparrow_1 \downarrow_2\rangle-|\!\downarrow_1 \uparrow_2\rangle\,\right)\div\sqrt 2$$

Therefore the spatial wavefunction $(L)$ must be symmetric for Pauli principle and in the second red configuration is

$$\Psi =p_0 (1) p_0 (2)$$ in the first one is

$$\Psi= \left[p_- (1) p_+ (2)+p_+ (1) p_- (2)\right]\div\sqrt2$$

The wavefunctions are different so there must be a difference between the two red configurations, but which of them should belong to $S=0,L=2$ and the other to $S=0,L=0$ and why?

halacha theory - Biblical versus rabbinic transgressions

Does the distinction between biblical versus rabbinic transgressions have implications or consequences today?

In the past, the punishment for them was different I believe.

kashrut kosher - Wine made/handled by Bnei Noach

Inspired by this question.

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Is wine made or handled by a Ben Noach, a righteous non-Jew, kosher? There should be no problem with the wine being used for avodah zarah, since the Ben Noach believe in Hashem, and his complete unity (unlike Christians).

Answer

This is debated by the Gemara (Avodah Zarah 64b). The Rambam rules that it is forbidden to drink the wine of a ger toshav, but it is permitted to derive benefit from it. This is the ruling of the Shulchan Aruch as well, regarding all non-idolatrous gentiles (Yoreh De'ah 124:6).

inorganic chemistry - Hydrates In Aqueous Solutions

Say you had copper(II) sulfate pentahydrate as a solid.

In an aqueous solution, is it still referred to by its hydrated form? Is it still called copper(II) sulfate pentahydrate (aqueous) or simply copper (II) sulfate (aqueous)?

I guess what I'm asking here is does the "hydrate" label apply exclusively to solids?

Answer

Yes, the ‘hydrate’ label applies exclusively to solids. Consider the following experiment: Dissolve both anhydrous $\ce{CuSO4}$ and $\ce{CuSO4 . 5 H2O}$ in water. You will get the same, blue solution.

What happened on a microscopic level is that the crystal lattice which once included the water atoms is broken up and the ions dissolve separately. What used to be copper(II) sulphate pentahydrate is now turned into a hexaaquacopper(II) complex.

$$\ce{CuSO4.5 H2O + H2O -> [Cu(H2O)6]^2+ + SO4^{2-}_{~(aq)}}$$

history - When will the period of Acharonim end?

What will mark the end of the period of Acharonim? What in general demarcates rabbinical eras? Are these halachic rules or conventions?

talmud gemara - How could the Temple have become tamei?

At Yoma 41a, there is a discussion regarding the appropriate offering for someone who causes the Temple to become Tamei (ritually impure)? But what are we talking about becoming tamei? The utinsels the metzora touched I can understand they would become tamei? But can a metzorah (or other tamei person) convey tumah to the stone floors or walls of the Temple or to any utensils he doesn't touch? How? If he can, what needs to be purified, and what is the method? Also, since the Holy-of-Holies and the altar are not under cover, could tumas mes (ritual impurity from a dead body) cause those areas to become tamei (if, for example, the Kohen Gadol dies while performing the avodah?

Answer

The phrase מטמא מקדש there does not mean one who causes the Temple to become impure, it means one who enters the temple in a state of impurity - see Rashi.

fourier transform - A query on Power spectral density (PSD)

Say a narrow band signal $n(t)$ has Power Spectral Density (PSD) $S(f)$.

If the signal $n(t)$ got multiplied by $\cos(2\pi Ft)$, then what will the PSD of resulting signal in terms of $S(f)$ be? Will this be $\frac{S(f+F) + S(f-F)}{2}$ ?

Answer

Almost, but let's start at the beginning. If the random process $N(t)$ has a power spectrum then it is at least wide-sense stationary (WSS), i.e., its mean and its autocorrelation function do not depend on time. However, the process

$$Z(t)=N(t)\cos(2\pi f_ct)\tag{1}$$

is not stationary, and, consequently, it has no power spectrum (the mean of the random process $Z(t)$ is given by $E[N(t)\cos(2\pi f_ct)] = E[N(t)]\cos(2\pi f_c t)$ which clearly depends on time even if $E[N(t)]$ does not, a similar reasoning can be made for the autocorrelation function).

Luckily, we're usually not interested in the power spectrum of the process $(1)$, but rather in the power spectrum of the process

$$Y(t)=N(t)\cos(2\pi f_ct+\theta)\tag{2}$$

where $\theta$ is a random phase which is independent of $N(t)$ and which is uniformly distributed on $[0,2\pi)$. This random phase reflects the uncertainty of the carrier phase with respect to the process $N(t)$. So adding a random phase is not only a "trick" that works well, but it actually reflects the nature of a modulated random process much better than the process $(1)$, which assumes a known relationship between the carrier phase and the signal.

The process given by $(2)$ is WSS, and its autocorrelation function can be computed as follows:

$$\begin{align}R_{YY}(\tau)&=E[Y(t)Y(t+\tau)]\\&=E[N(t)\cos(2\pi f_ct+\theta)N(t+\tau)\cos(2\pi f_c(t+\tau)+\theta)]\\&=\frac12 E[N(t)N(t+\tau)(\cos(2\pi f_c\tau)+\cos(2\pi f_c(2t+\tau)+2\theta))]\\&=\frac12R_{NN}(\tau)\cos(2\pi f_c\tau)+\frac12 R_{NN}(\tau)\underbrace{E[\cos(2\pi f_c(2t+\tau)+2\theta)]}_{=0}\\&=\frac12R_{NN}(\tau)\cos(2\pi f_c\tau)\tag{3}\end{align}$$

where I've used the independence of $N(t)$ and $\theta$, and where $R_{NN}(\tau)=E[N(t)N(t+\tau)]$.

Finally, the power spectrum of $Y(t)$ is given by the Fourier transform of $(3)$:

$$S_{YY}(f)=\frac14\left[S_{NN}(f-f_c)+S_{NN}(f+f_c)\right]\tag{4}$$

where $S_{NN}(f)$ is the power spectrum of $N(t)$.

In sum, if we add a random phase to the carrier then the modulated process is also WSS (if the baseband process is WSS), and its power spectrum is given by $(4)$.

tefilla - What to think about during each shofar sound

There are all kinds of meanings traditionally associated with the shofar blowing, as well as with each of its individual sounds. During the Rosh Hashana service, we have many sets of repetitions of the different sounds, associated with different parts of the service. It seems that it ought to therefore be possible to assign specific things to think about to each individual shofar call, based on which sound it is and where it is in the service and in its set of calls. That way, a person could be sure to cover all of the different meanings of the sounds and properly complement that awareness with awareness of the adjacent service.

Has anyone ever written a list of such assignments, so that I could look at it at each part of the service and have a good idea of what to think about right then? If not, are there general principles listed anywhere that we could use to generate such a list?

organic chemistry - Resonance structure of cyclobutadiene?

I studied cyclobutadiene as an anti-aromatic compound. But I am unable to draw the resonance structures for cyclobutadiene. Can anyone help me?

What is the driving force for the resonance to start?

Is it possible that a compound is having conjugate double bond system but not satisfying resonance structures?

Is a compound called as anti-aromatic if it is not undergoing resonance?

kanji - Can I use my Chinese name and if so, how do I say it?

My Chinese name in Kanji is 王元劭 (Wang Yuan Shao). I've heard there are many different readings I can use for each kanji, am I allowed to use whichever reading I like? Also, apparently the character 劭 is a hyogai Kanji, which means I can't use it.

audio - How to create a sine wave generator that can smoothly transition between frequencies

I am able to write a basic sine wave generator for audio, but I want it to be able to smoothly transition from one frequency to another. If I just stop generating one frequency and immediately switch to another there will be a discontinuity in the signal and a "click" will be heard.

My question is, what is a good algorithm to generate a wave that starts at, say 250Hz, and then transitions to 300Hz, without introducing any clicks. If the algorithm includes an optional glide/portamento time, then so much the better.

I can think of a few possible approaches such as oversampling followed by a low pass filter, or maybe using a wavetable, but I am sure this is a common enough problem that there is a standard way of tackling it.

Answer

One approach that I have used in the past is to maintain a phase accumulator which is used as an index into a waveform lookup table. A phase delta value is added to the accumulator at each sample interval:

phase_index += phase_delta

To change frequency you change the phase delta that is added to the phase accumulator at each sample, e.g.

phase_delta = N * f / Fs

where:

phase_delta is the number of LUT samples to increment
freq is the desired output frequency
Fs is the sample rate

This guarantees that the output waveform is continuous even if you change phase_delta dynamically, e.g. for frequency changes, FM, etc.

For smoother changes in frequency (portamento) you can ramp the phase_delta value between its old value and new value over a suitable number of samples intervals rather than just changing it instantaneously.

Note that phase_index and phase_delta both have an integer and a fractional component, i.e. they need to be floating point or fixed point. The integer part of phase_index (modulo table size) is used as an index into the waveform LUT, and the fractional part may optionally be used for interpolation between adjacent LUT values for higher quality output and/or smaller LUT size.

particles - How do you pronounce を after a subject?

For example :日本語を勉強します.

Do you pronounce ni hon go wo or ni hon go---

digital communications - Optimum matched filter without ISI

Given a filter used to shape the digital signal, $p(x)$, and given that we do not want the filter combination to cause any ISI, what "matched" filter, $q(x)$ will maximise the SNR?

Matched filters are used in digital communications to maximize the signal to noise ratio. Often a root-raised-cosine filter is used to shape the signal, since it is bounded in frequency space and the same filter can be applied to the received signal to improve the signal-to-noise ratio (SNR) without causing inter-symbol-interference (ISI).

However if a less optimum filter is used to shape the signal, then using the same filter at the receiver can introduce ISI. It is not immediately obvious what the best choice of filter at the receiving end is.

My understanding is that the SNR is maximized by maximizing $\int{p(x)q(x)dx}$, so I want to maximize this while satisfying the constraint that filters cause no ISI ($p(x)*q(x) = 0$ for $x=kT$, $k$ is an integer, $T$ is symbol width).

Presumably one could do this by solving a Euler-Lagrange equation with some lagrange multipliers for the constraints. Is there an easier way, or am I making a mistake, or going in the wrong direction?

Answer

For the case of linear modulation on the AWGN channel with equiprobable symbols (a very common case) the optimum approach is to truly use a filter that is matched to the symbol waveform, i.e.:

$$ q(x) = p(x) $$

Using a matched filter provides the optimum signal-to-noise ratio at the filter output at each decision instant. This is easy to see when you remember that a matched filter acts like a sliding cross-correlator between its input signal and the expected symbol waveform, correlating the two at all possible lags. At optimum decision instants, the filter's impulse response (typically scaled to have unit energy) lines up exactly with a transmitted symbol, analogous to a zero-lag condition on the cross-correlation operation. At this time value, the filter's output is equal to the amount of energy in the received symbol, scaled by a data-dependent factor (e.g. for BPSK, the matched filter would output $ E_s $ or $ -E_s $), plus a noise term.

The noise energy at the filter output during the sampling instant is not dependent upon the time-domain shape of the filter's impulse response, only the impulse response's total energy (as noted previously, typically unity). Therefore, the signal to noise ratio is maximized by maximizing the amount of signal energy in the filter output at the sampling instant. By choosing the receiver filter to be matched to the symbol shape, we have done so, as the symbol waveform has maximum correlation with a filter impulse response that has an identical shape. Thus, the matched filter provides maximum SNR, for the AWGN channel case.

With that bout of hand-waving out of the way (you can definitely get at it with more mathematical rigor, but I'm an engineer and this is a free service; if you want to dig into the details, check any digital communication theory text), you might be thinking that I forgot that you asked about the non-ideal, ISI case. Fear not, for I assert that if you know the transmitted pulse shape, the matched filter is still the optimum choice for the AWGN channel.

The key: if you know the responses of the pulse-shaping and receiver detection filters $p(x)$ and $q(x)$, and the last "few" transmitted symbols, you can calculate what the ISI induced by those previous symbols would be and account for it accordingly; it is a deterministic quantity. The amount of symbol history that you require is related to the amount of ISI you have, i.e. how many symbol periods the cascaded filter response smears across.

Of course, you typically don't know with certainty what the previous few symbols were; if you did, then you might be at a high enough SNR that your ISI can be neglected. In the more interesting case, you can't make that assumption. Instead, a maximum-likelihood sequence detection approach is employed using the Viterbi algorithm. This process is referred to as Viterbi equalization, because in this model you treat the ISI induced by the pulse shape like a soft-valued convolutional code that is applied to your transmit waveform. The time duration of the ISI in the Viterbi equalizer defines the required number of algorithm states, similar to the constraint length in a convolutional code.

This approach is often used in systems that have the non-optimum pulse shape that you noted; one notable example is GSM (which uses a Gaussian pulse shape that extends across multiple symbol intervals). One great reference on this topic was published by Sklar in 2003:

B. Sklar, “How I learned to love the trellis“, IEEE Signal Processing Magazine, pp. 87-102, May, 2003

halacha - Is it permitted to have a boy under barmitzvah age sing Anim Zemiros?

Is it permitted to have a boy under barmitzvah age sing the Shir Hakavod (or Anim Zemiros)? Why is it not like any other part of davenning where we use someone over barmitzvah?

Answer

According to the Rambam (Hilchot Tefilla chap. 9), only the following sections of davening (prayer services) require a Chazzan [over Bar Mitzvah]:

• Kaddish


• Birchot Kriat Shema


• Shemona Esrei, Chazart haShatz, and Kedusha


• Tachanun, Ashrei and Uva L'Tzion

In addition, if a part of davening doesn't require a minyan, it would make sense that a minor could lead it. Pseukei D'zimra and Anim Zemirot don't require a minyan, so it follows that a child could be chazzan.

christianity - Rav Chaim Volozhiner and Nittelnacht

In discussing the minhagim of Nittelnacht with a few people, I was told that Rav Chaim Volozhin "abolished" Nittelnacht. I don't know why Chaim Volozhiner would have any shaychis to Nittelnacht at all, that he would have to "abolish" it, but does anyone know of any sources that discuss Rav Chaim Volozhiner's dealing with Nittelnacht?

everyday chemistry - Which electrodes do not corrode at all?

I had used spare pieces of metal to perform electrolysis. They all had the disadvantage that they corrode when used as anode - and some of the oxides are toxic (copper, chromium).

I've found that carbon, which can be harvested from pencils and old batteries does not corrode contrary to my expectations (I'd expect it to produce $\ce{CO2}$). But soldering on carbon is completely impossible. Also, I need some bigger electrodes.

So are there any metals that do not corrode during electrolysis?

I'm using sodium carbonate as electrolyte.

Answer

This highly depends on what you are electrolyzing. When using solutions that are not very acidic, oxide-coated metals sometimes work, like lead-oxide electrodes, that can be harvested from old lead accumulators (attention, lead is toxic, wear lab coat and gloves when working with them. Lead accumulators contain ~20% sulfuric acid, so wear gloves as well and unassemble them in an acid-proof working space)

If you search the web for recipes of perchlorate preparation by electrolysis at home, you will find extensive discussions on the topic of anode materials and making oxidation-resistant electrodes.

Platinum is really hard to corrode, but even it corrodes in some cases.

words - Do all kana have a large and small reading?

Kana are written in large and small versions with different pronunciations in the composition of words but I am not able to determine if all kana can be used in this way. Thank you.

Answer

There are no such things as "lowercase" katakana in Japanese. If you mean ッ as opposed to ツ, and such, please call them small katakana. I assume you mean this.

Not all katakana have small versions. Here is the full list of small katakana characters defined in the Japanese character set.

ァ ィ ゥ ェ ォ
ヵ ㇰ ヶ ㇱ ㇲ ッ ㇳ
ㇴ ㇵ ㇶ ㇷ ㇷ゚ ㇸ ㇹ ㇺ
ャ ュ ョ ㇻ ㇼ ㇽ ㇾ ㇿ ヮ

Very common ones are ャ ュ ョ ッ. I think you already know how to use these. If not, consult the easiest textbook you have.

The character ヶ is also common but has a different usage from others (see this). ヵ is for the same purpose, but much rarer.

ァ ィ ゥ ェ ォ ヮ are relatively less common, but you will find them often used to approximate foreign sounds or old Japanese sounds (eg. ドゥ, フェ, グヮ).

The others are very rare special katakana used to write Ainu words (see: Special katakana for the Ainu language) and sometimes Korean words. You can safely forget them.

There are of course small hiragana, too. But the number is much smaller because we don't use hiragana to represent foreign words.

ぁ ぃ ぅ ぇ ぉ っ ゃ ゅ ょ ゎ

These small vowels are mainly used to represent long vowels in native Japanese words (see this).

grammar - why is it that some 形容動詞 accepts の after it while some only accepts な after it?

why is it that some 形容動詞 accepts の after it while some only accepts な after it?

Examples:

の only: 普通、大勢

な or の: 初心、特別、特殊

Is there a way for us to tell if a 形容動詞 needs a の or な particle after it.. or is it just by brute force memory?

Btw my second question is that if a 形容動詞 accepts both の and な after it, is it true that usually we will use the な, even though の is grammatically correct too?

Answer

I'm not sure if there's a real answer to that. At least not something that will help you learn which is which. Some 形容動詞 take な, some take の, and some take both. How did that happen? That's quite simple.

All 形容動詞 are in fact a special class of nouns. In academic English material, they are often called "adjectival nouns" or even "descriptive nouns", to emphasize the fact that they're nouns. So how do you use a noun to describe another noun? Since Classical Japanese we had two main methods of doing that:

1. Using the the copula (ADJであるNOUN)


2. Using the genitive relation particle (ADJのNOUN)

In Classical Japanese, the copula was なり, and for genitive relation we also had が besides の, but it probably worked more or less the same. In the modern language, the copula なり went out of use and was replaced by だ in all forms except for the positive present form, where な (which comes from なり) remains in use.

The inconsistency is mainly there, in the positive present form, since in other forms (past or negative), the copula is used always. That's because you just cannot use の in other forms, since it's not copula and therefore does not conjugate, so you have to replace it with forms of the modern copula だ. な, on the other hand, can be said to be a copula, but it conjugates like だ in all other forms, so in these forms all adjectival nouns behave the same.

But still, why is the choice of の, な or both in the present-positive form is so inconsistent? That's just how languages tend to work, chaotically. When you have two possible ways of forming an adjective (with a copula and with a genitive particle), people use both, and both forms come into what linguists call 'a competition'. There are several possible resolutions to a competition, such as one of the forms dying in favor of the other, or each form grabbing a different meaning. In this case, we have a complementary distribution, where some adjectival nouns settled take な, some settled for の, and for a good measure of irregularity some settled for both.

names - Which Amora is mentioned most often in the Gemara?

Which Amora is mentioned most often throughout Talmud Bavli?

Answer

I think there are different answers depending on the exact terms of the question; there are dozens of searches you could do on this one (e.g. "what value of X has the highest occurrences of amar rav X?").

As a first attempt, here are the most-common words in the Babylonian Talmud (using mechon-mamre's text as-is); I've highlighted the ones that may be a person's name. The problem is that "rava" could also mean "great"; "shmuel" could be the Amora or the Biblical prophet; and so on. I suspect Rav Ashi gets far more appearances than his colleague Ravina not necessarily by his own right, but because he also gets billing whenever his son, Mar bar Rav Ashi, appears.

From a quick glance, I'd give the most-unmistakable-occurrences prize to Abayei, except that there was more than one Abayei in the Gemara (if I'm not mistaken). Which means the most-unmistakable-occurrences prize would then go to Rav Huna (I don't think there was more than one Rav Huna? Anyone?)

Interesting that Rabba and his debate partner, Rabbi Nachman, appear almost exactly the same number of times.

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אמר 35633

לא 28819

רב 17630

ליה 16048

אלא 15040

רבי 13308

על 11589

את 10198

אין 9582

ולא 9550

אומר 9078

הוא 9067

מאי 9066

כל 8682

לו 8597

בר 8207

לה 7458

ר' 7446

של 7318

יהודה 7224

נמי 6820

הא 6709

דאמר 6154

אי 6099

בן 5989

אבל 5768

כי 5714

משום 5350

מה 5261

זה 5217

עד 4956

או 4875

יוחנן 4798

היא 4700

שלא 4687

א"ל 4499

מן 4475

לי 4408

אחד 4399

דלא 4323

הכי 4270

אם 4254

רבא 4108

להו 3988

בין 3777

אף 3750

לאו 3726

א"ר 3631

לך 3584

בו 3412

בה 3408

מי 3387

אינו 3382

יוסי 3287

שאין 3271

והא 3260

דכתיב 3208

שנאמר 3150

הכא 3047

(ויקרא 3009

אדם 2860

דרב 2828

קא 2802

הוה 2797

ואין 2759

אחת 2758

חייב 2730

ישראל 2722

הרי 2667

רבנן 2632

סבר 2621

שמעון 2589

אימא 2580

אביי 2571

ואמר 2558

עליו 2519

שמואל 2479

איכא 2473

אפילו 2421

התם 2410

זו 2353

דבר 2344

ואם 2336

אלעזר 2310

דתניא 2302

בית 2301

אמרו 2264

ואי 2251

האי 2239

דברי 2223

תנא 2202

כאן 2196

הונא 2196

היה 2137

ה' 2137

טעמא 2126

מפני 2118

שני 2092

כיון 2087

(דברים 2071

יש 2068

קרא 2057

אחר 2023

מר 1996

כוכבים> 1982

רבה 1971

נחמן 1965

אשי 1938

יום 1930

דמי 1912

עליה 1889

יוסף 1885

יהושע 1863

מהו 1862

קשיא 1855

אסור 1850

בני 1836

ביה 1830

קאמר 1784

כתיב 1764

אומרים 1763

אל 1752

פפא 1736

אליעזר 1721

ורבי 1718

תניא 1711

יצחק 1678

אבא 1654

אותו 1633

לעולם 1616

דרבי 1616

לרב 1613

אשר 1613

וכי 1604

(שמות 1565

אני 1564

ת"ל 1531

הוי 1526

אתה 1521

להם 1517

פטור 1508

בעי 1508

בהן 1497

אמרת 1488

רחמנא 1479

מותר 1476

לומר 1472

הן 1447

למה 1446

שנים 1444

יכול 1423

מעשה 1405

מאיר 1399

בריה 1395

היו 1394

תורה 1393

שמע 1392

חסדא 1392

היכי 1390

אמרי 1385

חייא 1384

(במדבר 1377

ההוא 1375

שהוא 1365

דלמא 1348

קתני 1340

ת"ר 1335

דאמרי 1332

כדי 1330

גבי 1329

אלו 1323

ואחד 1303

וכל 1302

חד 1297

בעל 1297

כך 1291

לפני 1282

מקום 1279

הלכה 1277

חנינא 1276

איש 1276

צריך 1264

אשה 1263

בשלמא 1258

מיניה 1245

שאני 1230

ישמעאל 1230