Many periodic tables place lanthanum and actinium in the f-block of elements, for example, this periodic table from Los Alamos National Laboratory.
However, this table from the Royal Society of Chemsitry places lanthanum and actinium in the d-block.
Which is the most appropriate placement of these two elements on the periodic table? What is the most recent scientific consensus regarding this matter?
I recall hearing the following story:
There was a non-observant Israeli Jew who kept having visions of his deceased father telling him he should do more religiously. Finally he was about to turn on the radio on Yom Kippur when he had a vision of his father telling him to shape up or else. The fellow went to Rabbi X, who asked if he had done anything especially meritorious; the fellow thought, then mentioned that in his youth, he and his father had been in a Nazi Ghetto and risked a great deal to give someone a proper Jewish burial. Rabbi X explained that generally if someone has decided to do something wrong, G-d doesn't interfere; only if the person is particularly meritorious.
If you've heard this story, can you remind me please who Rabbi X was? It would have been someone living in the second half of the 20th Century.
Can anyone recommend a source for the text of the Ketuba including nekudot, a transliteration, or a recording that could be used as a guide for pronunciation?
One can easily draw (pseudo-)random samples from a normal (Gaussian) distribution by using, say, NumPy:
import numpy as np
mu, sigma = 0, 0.1 # mean and standard deviation
s = np.random.normal(mu, sigma, 1000)
Now, consider the Fast Fourier transform of s:
from scipy.fftpack import fft
sHat = fft(s)
Considering "the Fourier transform of white noise is white noise":
Can we generate sHat directly without the Fourier-transform of s?
I have recently tried to discuss a practical implementation of such thought herein.
Answer
You can, but... you'll need to keep symmetry if your original time-domain signal is real-valued.
If a signal $x$ is real-valued, then its DFT $X$ will exhibit complex-conjugate symmetry: $$ X[k] = X^*[N-k]. $$
So you can generate $N$ Gaussian pseudo-random noise samples, $g[n]$, and place them in the frequency domain noise vector, $\epsilon$ as: $$ \epsilon[k] = g[k] + j g[k+N/2] $$ for $k \in \{ 0, 1, \ldots, N/2-1\}$ and $$ \epsilon[k] = \epsilon^*[N-k] $$ for $k \in \{ N/2, N/2+1, \ldots, N-1 \}$ where $\epsilon^*$ is the complex conjugate of $\epsilon$ and is equal to $\Re[{\epsilon}] - \Im[{\epsilon}]$ (i.e. the same real part and the negative of the imaginary part).
Organic compounds are typically defined as “molecules containing carbon”. Wikipedia states that there for some historical (read: non-logical) reasons,
a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the allotropes of carbon such as diamond and graphite, are considered inorganic.
I thus wonder: is activated charcoal (also known as activated carbon) typically classified as an organic or inorganic material?
If I follow the list of exceptions given by Wikipedia, it should be organic (it's not an allotrope of carbon, in particular), but I get the feeling that most people in the field of porous materials would classify it as inorganic. So, I'm looking for an authoritative reference on this question.
Answer
While nomenclature is of particular interest to organic chemists to specify an exact compound, the classification of X into broad category Y or Z isn't a precise science, and not really of practical use. The article cites a textbook by Seager to this effect, stating
The distinction between "organic" and "inorganic" carbon compounds, while "useful in organizing the vast subject of chemistry... is somewhat arbitrary"
Even if you find a source that says "charcoal is (in)organic", you may just as well find one stating the opposite. Just like the coal from which it may have been produced, it was once biomass and decidedly organic, but so was graphite and diamond, or CO2 and CO32−. I think it's overly pedantic and unproductive to try to come up with definitive judgements for these decidedly edge case scenarios.
After all, it's just a chemical on the shelf, what one does with it is far more relevant. I don't use it on a daily basis, but it seems more like a tool than a reagent. The fact it contains carbon seems beside the point; it's value isn't in the chemical composition but rather its extraordinary adsorptive properties.
I was reading JD Lee's Concise Inorganic Chemistry and it has given some values of mean radial distance which is increasing from s to p to d orbital. I had earlier read that the most probable radial distance of an orbital has the order s>p>d>f. This makes me wonder what is the difference between the mean radial distance and most probable radial distance. Also, why is the order of mean distance reverse from that of most probable radial distance? Also can you please explain why is the energy of an orbital proportional to mean radial distance as given in the book? 
Image Source: Concise Inorganic Chemistry by JD Lee
Some adjectives are used like this:
and others are used liked this: "Kawaī kuruma".
Though kiiro can also be used thus: "kiiroi kuruma".
When can I use an adjective with "no"? is it always or only in some special cases?
Answer
Grammatically, you can never use an adjective with の. You can only use の with nouns. You're confusion is arising because the parts of speech do not always correspond between English and Japanese: 次 is a noun, but "next" is an adjective.
Similarly, all colors in English are adjectives, but all colors in Japanese are nouns (except for six that have adjective counterparts, namely 赤い, 青い, 白い, 黒い, 黄色い, and 茶色い). You can't say 灰色い because it only exists as a noun, not an adjective (a fact you just have to memorize).
You can use nouns to modify other nouns in English, too (and probably most other languages). Health Department (or Department of Health) is an example in English: "health" is modifying "department" to describe what kind of department.
Is it Halachically appropriate to Daven in boots when in a Beis Kenesses?
A great answer should (in addition to being well-sourced) discuss details such as:
(I know that this is related to Is there a halachik problem with wearing shorts while davening?, but there are many differences between them.
My hands are cold in synagogue. May I put them in my pockets? May I wear gloves? likely has some content that would help answer this question, but still different, such as the fact that boots track dirt and leave puddles, and that question was asked because of the cold, this question is in general.)
Answer
This article says:
One should not stand in prayer wearing a raincoat, boots and gloves, because that is not the way to stand in front of important people (Mishnah Berurah 91:12). Yet, when it is very cold, it is permissible to pray in a raincoat and gloves, because this does not offend the respect due to prayer. Additionally, in a place where everyone regularly wears boots, one may wear them while praying.
One should not enter a shul when he has mud or dirt on his shoes or clothing. (See O.C. 151:8). So, at the least, it seems that if you have entered muddy or snowy terrain, you should at least remove the dirt or snow before entering the shul area and davening. (The shul is supposed to be treated BETTER than your own home in terms of cleanliness. If you wouldn't want this stuff in your own home, it's a given, that you don't want it in shul.)
The most stable resonating structure of 1-nitro-4-nitrosobenzene is:
In my view since in each case we have 4 charges and except in case 1 all have complete octets, so 1 is neglected. However, I am facing difficulty in eliminating other two in order to get the desired answer. I noticed that in case 3 it is in conjugation (alternating single and double bonds).
Answer
The answer is not that difficult. You should have a certain number of rules to follow in determining the most stable resonance (not "resonating") structure.
It probably starts with check all for octets (which you correctly did). 1 has ten electrons on the nitroso nitrogen, so that rules it out.
It probably then goes on to ask you to check for the least number of formal charges (which, judging by your description, you probably did).
The next step should probably say something about the negative charges being on the most electronegative elements. Electronegative atoms like O, F... (and N to a slightly lesser extent) are quite happy to take on a negative charge whereas carbon will not quite be so pleased.
Here, resonance forms 2 and 4 have the negative charge on carbon, whereas structure 3 has it on oxygen. 3 is therefore the most stable resonance structure.
Incidentally, all of the resonance forms 2 through 4 have complete conjugation throughout the molecule so that's not a factor. The $\mathrm{sp^2}$-hybridised anionic carbon can take part in conjugation equally well. Conjugation does not require alternating single and double bonds - it only requires an extended, continuous, $\pi$ system. Generally this means that all atoms along the chain must have unhybridised p orbitals parallel to each other.
Side note: "Most stable" resonance structure is a slightly sloppy description. None of these resonance structures actually exist and the true structure is a linear combination of all of these resonance structures. It should more properly be called the "greatest resonance contributor" or "greatest contributor to the resonance hybrid".
There are many days on which we don't say Tachanun, and much argument about whether we say it on any given day -- but is there any underlying reason why we wouldn't say it, a reason which might explain why we do or don't say it on a given day?
I looked in the Rambam and the M"B and all I saw was lists of when we do and don't say it -- no reasoning behind why. There were some explorations of why a specific day might be excluded, but no generalizable rule through which I could then predict whether on another day we would say Tachanun.
Is there a rule which determines saying or not saying Tachanun, or is the entire practice a series of individual cases with separate logic for each?
A similar question, but about Tu Bishvat specifically.
Different sources have given me different pronunciations.
I figured it must mean "Doujin aimed at males", but if that's the case, from what I know, it should be written [男性向け同人]{だんせいむけどうじん}。
Is 男性向 an abbreviation, and still pronounced だんせいむけ, despite the け not being there?
Answer
Yes, 男性向 is a valid abbreviation, and still pronounced だんせいむけ. Okurigana is often omitted, especially in longer compounds like 男性向同人.
Similar examples:
Omission of okurigana is largely customary and happens in limited number of words. Please don't try to omit okurigana freely.
In a boxing match, a trainer is telling a boxer to stay away from the opponent and wait the end of the round to recover, but he doesn't listen to him. Then the trainer says this sentence:
どんなハートしてんだよ、兵動【ひょうどう】！！
What is the meaning of this expression? Does ハート mean heart here, or is it the abbreviation of something else? Here is the page it is taken from. Thank you for your help!
Answer
する can often be translated into English as "to have". See: Meaning of 顔をする? and Use of する to describe one's colour
- 長い髪をした人
- 丸い形をしたコップ
- 複雑な構造をしたプログラム
- 緑色をした服
- 彼は戸惑った顔をしている。
So どんなハートしてんだよ is "What kind of heart do you have?" i.e., your behavior/mentality is unbelievable.
Sorry for the FAQ, but I really don't know where to find a full spreadsheet for element properties. I mean a table that has one row for each element, and the columns are its properties, such as name, atomic number, density, melting point, etc. I know that there are many sites or references for that, but I need it in tabular format, because I want to analyze data, make charts, etc.
Answer
Well, here's a CSV file that I parsed out of the JSON data provided by Paul Nathan's website, which in turn was produced from gPeriodic data in response to this question. gPeriodic is FOSS, so I can only assume that the element data contained within is good to share, though I have no idea of its provenance.
The parser uses the python json module to read the data, which I then wrote into comma separated values, which should be readable by any halfway competent spreadsheet program.
Here it is: Pastebin Link
save it as elementdata.csv and you're good to go.
Some gotchas:
Tried plotting Z versus covalent radius in R from this data - looks alright:
Some of the data points are missing, some are not read by R because they are wrapped in <> - pre-process to your heart's content.
When a person goes to Shul to say Yizkor they obligate themselves to give Tzedaka in memory of the deceased. Can this obligation be paid from Maaser or does it have to be paid from the persons personal funds? (sources please)
The Chumash in Shemot 23:14 begins describing the three regalim: Pesach, Shavuot, Sukkot, in that order. In Pasuk 17, the Chumash begins again with Pesach and Shavuot. Instead of listing sukkot again in that second list, the Pasuk mentions the prohibition of mixing meat and dairy (cooking a kid in its mother's milk.)
What happened to sukkot? What's the connection between meat and dairy and the regalim?
I am confused by the use of なんか, especially after the て-form of a verb. What do: あきらめてなんかない, 消えてなんかない mean? How do they differ from simply saying あきらめていない, 消えていない? What is the purpose of なんか？
Answer
Paul Richter's answer is partially right in the sense that なんか adds "emphasis against an assumption or statement by others and is used only in negative statements", but more accurately, なんか used here is not the same as 何か, and it means such thing as.
あきらめていない
'I have not given up.'あきらめて なんか (い)ない
'I haven't done such thing as giving up.'
In Numbers 31, God tells the Israelites to wipe out the Midianites (and incidentally, Balaam) by killing every male. But they spared certain women (v17-18):
Now therefore kill every male among the little ones, and kill every woman that hath known man by lying with him. But all the women children, that have not known man by lying with him, keep alive for yourselves.
Why did they spare these women (and not men who had not known women intimately)? And would this apply to women who may have been raped? How would they have told the difference, especially in a culture that may have been promiscuous?
Answer
In Chapter 25 we see that the Moabite women seduced some Israelites into temple prostitution. Therefore when God commanded Israel to raze the people of Midian he wanted the armies to kill the woman also and not take them as spoils of war. They did not do it at first but kept all the woman as booty. God was angry with them for that and then he makes it clear they can only spare virgins.
The idea seems to be that they can only take as plunder what had no threat of harm to Israel and no possibility of corruption from the Baal Peor worship.
Baal-peor.—Lascivious rites were widely spread and prevalent in Babylonia and Syria. See Knobel. [Also article Baal in Smith’s Bible Dictionary.—A. G.]. It was Baal, especially as he was worshipped at Peor, with lustful practice (hence Baal is sometimes called Peor). Beth-Peor, Deut. 3:29; 4:46. “He was a Moabitish Priapus, in honor of whom virgins and women prostituted themselves. As the god of war he was called Chemosh,” (Commentary on Numbers, Lange p167)
Naturally unless the woman were still virgins they may have already been involved in temple prostitution which was the original sin that they were being judged for.
According to the Purim timeline:
the 13th of Adar (of the next year) was set as the target day for wiping the Jews.
Mordechai became the vice in Nissan and the new decrees to fight Amolekites ware ruled and distributed on Sivan 23 of the current year.
Mordechai could command to exterminate all the supporters of Haman (or Amalekites or enemies in general) effective immediately, and not waiting for 8 months to see how the events would unfold.
He was still under the obligation of "הקם להרגך השכם להרגו" - to make a preventive fight.
Such an order would not contradict the first decrees that proposed that day for the extermination of the Jews. After all, whoever survives might fight the Jews on that day.
Why the commands to fights the Amalekites was postponed for Adar instead of immediately?
Does "vertical" travel require saying Tefillat haderech? Examples:
In all these cases, let's assume that the vertical distance is about 12,000 feet - close to 2 miles. (I don't know if there is a minimum horizontal distance requirement for this bracha, so I'm assuming an equivalent requirement for verticals.)
Answer
The Kitzur says in סימן סח - דין תפלת הדרך ושאר דברים שצריכין לזהר בדרך ובו י"ב סעיפים:
סעיף ב': אֵין לְהִתְפַּלֵּל אוֹתָהּ אֶלָּא אִם כֵּן יֵשׁ לוֹ לָלֶכֶת לְכָל הַפָּחוֹת פַּרְסָה.
As I elaborated here:
One does not say Tefilat HaDerech unless the trip is one Parsa (~4 Km / ~2.5 miles) long - outside the city.
There's a dispute amongst Posking if we're talking about actual distance, or the time it took to walk that distance. For example, the Kitzur-S.A.-Yalkut-Yosef (110:2) says that one only says it with Shem-uMalchut if one has to travel at least 72 minutes during that day.
ואמנם אינו חותם בשם ומלכות רק כשנוסע מעיר לעיר, ויש בנסיעתו כשיעור פרסה, שהוא שעה וחומש, [שבעים ושתים דקות], בין ברכבת ובין באוטובוס וברכב פרטי. ואף אם יש בדרך נקודות ישוב ומושבים, גם בזה מנהגינו לברך תפלת הדרך בשם ומלכות, אם נוסע בכביש בינעירוני במשך שעה וחומש. אבל אם נוסע מעיר לעיר פחות משיעור זה, לא יברך בשם ומלכות. ואם יש בהליכה וחזרה בו ביום שיעור פרסה, מברך בשם ומלכות, אף נסע מחצית שיעור פרסה בבוקר, ומחציתה בלילה. אבל אם נסע בלילה כחצי שעה, ולן בעיר אחרת, ולמחרת נסע עוד כשיעור שעה, אין הנסיעות מצטרפות, ויאמר תפלת הדרך בלא שם ומלכות. [ילקוט יוסף מהדורת תשס''ד, תפלה כרך ב, סימן קי הערה ב].
Either way, I don't believe it's an issue for your vertical activities.
For Hang Gliding you surely have the same halachot as an airplane - and if you glide more than 4 Km / for longer than 72 minutes outside the city - or over a body of water - then my guess would be that you have to say Tefilat HaDerech.
That said, the Aruch HaShulachan (as well as the B'er Heitev) in סימן קי - דיני תפילת ''הביננו'', ותפילת הדרך והפועלים says:
טו: אין לאמר תפילת הדרך אלא אם כן יש לו לילך פרסה, דפחות מפרסה לא נקרא ''דרך''. אלא אם כן הוא מקום סכנה, דאז גם בפחות מזה יש לאומרה.
"If one is in a dangerous area, then one says it even for less than a Parsa."
Note that he says dangerous place and not dangerous activity.
There is a famous question asked by the Beis Yosef (R' Yosef Karo): Why do we celebrate eight days of Chanukah if the miracle lasted only seven? The jug of oil contained enough to be lit for one day, so the first day was not a miracle.
Stolen directly from Grigory M's question in the definition phase:
http://area51.stackexchange.com/proposals/7526?phase=definition
Answer
They both mean "to fix"/"to repair"/"to correct", but 治す is used in the sense of "to heal or cure" ("to fix a disease"). "直す" is used for fixing, not healing.
EDIT: As per Tsuyoshi Ito's correction (confirmed with a bit of googling), I've removed a misleading bit about the object of these verbs.
What image analysis techniques can I use to extract the traffic signs from an image such as the one below?
Edit:
After Anisotropic diffusion: The background that i don't want gets cleared a little
After Dilation :
Thresholding after Diffusion : Not able to figure out the best thresholding for this purpose
However i am not able to figure out how to remove the background?
Edit : i just want these parts of my image
Taking another input image :
Applying median filtering and edge detection :
After Bottom hat filtering:
How do i isolate the road signs please help?
Answer
Did you try something simple like correlation?
(EDIT). The idea behind correlation is to use a template (in your case a trained road sign sample), and compare it to every position in the test image. The comparison operation I've used to generate the images below is called normalized cross-correlation. Roughly speaking, you standardize (mean=0, standard deviation=1) the pixels in the template and the image part you want to match, multiply them pixel by pixel, and calculate the mean value of the products. This way you get a "match score", i.e. a measure of similarity between the template and the test image at every position in the test image. The position with the best match (highest correlation) is the most probably candidate for the position of the road sign. (Actually, I've used the Mathematica function CorrelationDistance to generate the image below, which is 1 - (normalized correlation). So the darkest spot in the match image corresponds to the best match).
I don't have any other templates, so I simple cropped the sign from the second picture you posted:
Even though the template is rotated slightly, cross correlation still looks usable
and the best match is found at the right position:
(You'd need multiple scaled versions of each template to detect signs at any size, of course)
Consider the following reaction: $$\ce{Cu(H2O)_n^2+ + 4NH3 -> Cu(NH3)4^2+}$$
The amount of ammonium hydroxide added to your penny solution was not controlled (i.e. you did not add “stoichiometric” amounts). Discuss what would happen to its absorbance value, and explain why, if the amount added was too low and too high. (Assume the mark on the volumetric flask was not overshot in either scenario.)
I was hoping to get a second opinion on what happens to the absorption in the case where you add too much $\ce{NH3}$ and the case where you add too little.
I think that if I had added not enough $\ce{NH3}$ that some of the copper would not turn into $\ce{Cu(NH3)4^2+}$ and thus the absorption reading would be lower.
As for adding too much... I think it would be okay to add too much. I don't think it would affect the absorption.
Answer
Both your conclusions are absolutely correct.
I'll point out that you'll never get "all" the $\ce{Cu^{2+}}$ to the amine complex. You're trying to get greater than 99% of the $\ce{Cu^{2+}}$ to the amine complex. Because 99% and 99.9% and 99.99% would have virtually the same absorption reading.
To give even more detail, in mildly acid solution the copper will be in a octahedral complex $\ce{Cu(H2O)6^{2+}}$ which is a light blue. As you add ammonia at first $\ce{Cu(OH)2}$ forms, which is then dissolved as the various ammine complexes form.
$\ce{Cu(H2O)_6^2+ + NH3 <--> Cu(NH3)(H2O)5^2+}$ $\ce{Cu(NH3)(H2O)5^2+ + NH3 <--> Cu(NH3)2(H2O)4^2+}$ $\ce{Cu(NH3)2(H2O)4^2+ + NH3 <--> Cu(NH3)3(H2O)3^2+}$ $\ce{Cu(NH3)3(H2O)3^2+ + NH3 <--> Cu(NH3)4(H2O)2^2+}$
The tetraammine complex, $\ce{Cu(NH3)4(H2O)2^2+}$, is a much darker blue than the corresponding complex with water molecules alone. Thus colorimetry is much more sensitive measuring the tetraammine complex that the water complex.
The tetraammine complex has shorter Cu-N bonds than the C-O bonds. Thus the four ammine groups are one plane and the two water molecules at the apexes of the square bipyramidal complex.
Hopefully now the point about not converting all the copper to the tetraammine complex is clear. The various ammine complexes are in equilibrium with each other. Given that $\ce{[NH3] >> [Cu^{2+}]}$ then one can imagine the overall reaction as
$\ce{Cu(H2O)_6^2+ + 4NH3 <--> Cu(NH3)4(H2O)2^{2+}}$
In extremely concentrated solutions of ammonia the final two ammine groups will attach.
$\ce{Cu(NH3)4(H2O)2^{2+} + NH3 <--> Cu(NH3)5(H2O)^2+}$ $\ce{Cu(NH3)5(H2O)^{2+} + NH3 <--> Cu(NH3)6^2+}$
I found this in a phrase: 隠れていなくて. I can translate it simply as "aren't hiding" or "were hiding"? By the way, is it correct or is 隠れていません better?
By the way, the whole phrase is
お前はやはり私のような強いものの後ろに隠れていなくてはな。
A man and a woman who had undergone hardship together as children before being forced to part meet again and remember their last words to each other.
The woman says:
生きてて良かったって、心の底から思える瞬間って、どんな感じかしら？
I think the first part of the sentence
生きてて良かったって
means
“It’s good to keep on living”
the って here being a quotative particle since 生きてて良かった was the last thing the man said to the woman. (Please correct me if I’m mistaken).
The second part
心の底から思える瞬間って
confuses me. What is the function of the って here? It doesn’t seem like a quotative particle. I guess it translates to something like:
a moment that seemed to come from the bottom of your heart.
And I think the last part
どんな感じかしら？
translates as:
Was that your feeling, I wonder?
So, I think the meaning of the sentence (idiomatically) is something like:
You said, “It’s good to keep on living”, like you really believed it. Was that what you were feeling, I wonder?
Is this correct and what is the function of って in the second part of the sentence?
Answer
生きてて良かったって、心の底から思える瞬間って、どんな感じかしら？
These two って's are not the same.
The first って is a quotative particle. From デジタル大辞泉:
って 1⃣［格助］
１ 引用する語、または文の下に付いて、次に来る動作・作用の内容を表す。…と。「金を貸してくれって頼まれた」「読書しろって言われた」
The って is a quotative particle and means と. The two example sentences given in the dictionary can be rephrased as 「金を貸してくれと頼まれた」「読書しろと言われた」. って is more colloquial than と.
And the second is a binding particle (係助詞). From the same dictionary:
って 2⃣［係助］
１ ある事柄を話題として取り上げて示す意を表す。…は。…というのは。「あなたって親切な人ね」「彼ってだれのこと」
The って is used to introduce something as a topic. Means ～は or ～というのは. The examples can be rephrased 「あなたは親切な人ね」「彼というのはだれのこと」. って is more colloquial than は or というのは.
So your sentence can be rewritten as:
『生きてて良かった*』と、心の底から思える瞬間というのは、どんな感じかしら？
lit. Speaking of the moment when you can feel "I'm lucky to be alive" from the bottom of your heart, how would it feel? / what would it be like?
⇒ I wonder what the moment would be like when you can feel from the bottom of your heart "I feel lucky to be alive. / Thank God I'm alive."
*The た in ～～よかった here is the modal た, explained here: Usage of plain i-adjectives or た form (悪かったｖ悪い、良かったｖいい etc）
Breakdown:
生きてて -- lit. I'm alive (and) → to be alive
良かった -- (I find it) good.
って、-- quotative
心の底から -- from the bottom of your heart
思える瞬間 -- the moment you can feel
って、-- topical
どんな感じかしら？ -- What would it be like?
Please correct me if I’m wrong, but I’ve read that the reason why we use significant figures is to avoid making the result of a calculation more accurate than the starting values prior to the calculation. For example, if we were seeking the ratio of two weights, lets call them A and B, using a cheap scale and an expensive scale we could get the following varied results:
Cheap Scale $$A = 34 \space oz$$ $$B = 23 \space oz$$
Expensive Scale $$A = 34.0000 \space oz$$ $$B = 23.0000 \space oz$$
Computing the ratio $\frac{A}{B}$ using a calculator we get the following value: $$\frac{34}{23} = 1.47826$$ Now this is a correct ratio depending on the scale used (ie the cheap scale could not have produced such an accurate measurement given the starting values) This leads to the following question:
Why are the zeros behind a decimal point ignored if they are just place holders?
For example, the value 0.000023 oz only has two significant figures, but isn’t that value something only a very fine tuned scale could measure (keeping in line with the previous weight example). So why are these zeros ignored?
Answer
This is part of the reason I really don't like the way we teach significant figures. What's really important isn't the number of digits you have, but rather the uncertainty in your measurements. I think significant figures are taught as an approximation to the proper uncertainty analysis, but it really seems to be not worth the trouble.
What's really going on is this: when you say $A = 34$ oz, you're actually saying that $A$ is closer to 34 oz than it is to either 35 oz or to 33 oz. In other words, you mean $A = (34 \pm 1)$ oz. Likewise, when you say $A = 34.0$ oz, you're really saying $A = (34.0 \pm 0.1)$ oz. And in the final example you give, when you say $A = 0.000023$ oz $= 2.3 \times 10^{-5}$ oz, you're actually saying $A = (2.3 \pm 0.1)\times 10^{-5}$ oz.
The more precise way to do things is to use the uncertainty you have for each measurement, and use the rules for propagation of uncertainties to get the uncertainty in your final answer. One advantage of using the uncertainties is that your uncertainty won't always be 1 unit of your least significant digit, but the rules for propagating significant digits essentially imply that. Using sig figs usually gets close to the answer you would get from properly using uncertainties, but there are some cases where the result is really weird.
To answer your main question directly, you ignore those placeholder zeros because they don't affect the fractional uncertainty of the quantity you're looking at. Keeping them would give you an answer very different from the proper uncertainty analysis.
but isn’t that value something only a very fine tuned scale could measure?
Not necessarily. The cost of an instrument is much more closely related to the relative precision of its output, rather than the absolute precision. If all you're trying to do is weigh things with masses between $1 \times 10^{-5}$ and $1 \times 10^{-4}$ oz, then you don't care at all if your scale can measure 1 oz. But if you have objects that are 1 oz and $1 \times 10^{-5}$ oz, and you care about the difference, then you'll need a really precise scale.
Today in chemistry class we were discussing Organic Chemistry. We discussed what organic compounds basically are and then I asked the teacher whether $\ce{CO_2}$ is organic or not. She told that it is as it contains carbon and oxygen with a covalent bond. I told her it can't be as it is not found in animals (naturally). I am very confused about it.
I need some good reasons to agree with either explanation. (I have searched the internet already but found no great insights as of now).
Answer
It is entirely arbitrary whether you call it an organic compound or not, though most would not.
The distinction you make that organic compounds should be found in living things is not a useful criterion. Moreover you are wrong that carbon dioxide isn't: it is both made and used by living things. Animals make it when they metabolise sugars to release energy; plants consume it when they build more complex organic molecules through photosynthesis. In fact most organic molecules are, ultimately, derived from $\ce{CO2}$.
Even more importantly most molecules considered organic are neither made by nor are found in living things. Chemists make new carbon compounds all the time (tens of millions in the history of chemistry) and most have never been made by animals or plants.
The organic/inorganic terminology is mostly very simple: covalent compounds containing carbon are organic. The only fuzzy area is around very simple molecules like $\ce{CO2}$ where the distinction doesn't matter much. So we would not normally think of diamond or silicon carbide as organic. But we might (though many would not) call calcium carbide organic because it contains a $\ce{C2}$ unit with a carbon-carbon triple bond.
However since the terminology is mostly very obvious and also somewhat arbitrary, it isn't worth much argument to sort out those very simple but awkward edge cases.
Inspired by Dan's question , and requested by DoubleAA...
If one got a tattoo of G-d's name, either in ignorance or in spite of the prohibition against tattooing, may one have it removed? Would this be a violation of the prohibition on erasing G-d's name?
As a side point, would this differ if the tattoo-bearer wasn't Jewish?
As always, if this question is practically applicable to you, don't rely on what you read here. Consult a competent halachic decisor.
Answer
UPDATE:
Shalom pointed to the article "Medical and Cosmetic Tattooing" by J. David Bleich (Tradition 42:4), in which a pseudo-Kabbalist directed a woman to get a tattoo containing the Divine Name. The question of removing it was brought to Sephardic Chief Rabbi Eliyahu Bakshi-Doron and printed in Or ha-Torah Shevat 5762. R. Bleich's summarizes R. Bakshi-Doron's teshuvah that permitted such a removal:
Teshuvot Havvot Yair [no. 16] rules that a Divine Name written expressly for a mundane purpose may be erased...Rabbi Bakshi-Doron assumes that, in the case presented to him, the Divine Name was written for a mundane purpose [and can be removed].
[...] R. Moshe Sefer, Teshuvot Hatam Sofer, VI, no. 8, discusses the case of a properly written biblical verse that was subsequently pasted on the wall of a privy...in the event that a non-Jew is not available to do so, Hatam Sofer permits a Jew to scratch off the writing in order to prevent ongoing desecration of the Divine Name. Rabbi Bakshi-Doron regards removal of a tattoo containing the Divine Name to be comparable.
There may be additional operative consideration as well. Rambam Hilkhot Tefillin 1:13, followed by Shulchan Arukh 281:1, rules that a Torah scroll written by a Jewish "apikores" must be burned...Rambam, Hilkhot Yesodei ha-Torah 6:8, defines the term "apikores" as used in this context in the more general sense of "heretic" and comments that a Torah scroll written by an apikores "is to be burned together with its Divine Names because [the heretic] does not believe in the sanctity of the Name...Since such is his opinion the Name does not become sanctified and it is a mitzvah to burn it in order that there be left neither a name to the heretics nor to their deeds." Rabbi Bakshi-Doron concludes that, according to the Rambam, not only may a Divine Name tattooed by a heretic be destroyed but that it is a mitzvah to do so.
This is the only responsa I have found that deals with erasing a modern tattoo containing the Divine Name. This does not necessarily answer the original question, since
Furthermore, this teshuva was for a particular case with its own story, not a blanket statement allowing removal of the Divine Name on a tattoo.
--
As I wrote in Dan's question:
The Talmud (in Masekhet Shabbat 120b) directly discusses this issue:
דתניא: הרי שהיה שם כתוב לו על בשרו - הרי זה לא ירחוץ ולא יסוך ולא יעמוד במקום הטינופת. נזדמנה לו טבילה של מצוה - כורך עליה גמי ויורד וטובל. רבי יוסי אומר: לעולם יורד וטובל כדרכו, ובלבד שלא ישפשף
As it was taught in a baraita: If one had a sacred name of God written on his skin he may neither wash it in water lest it be erased, nor may he smear it with oil, nor may he stand in a place of filth because it is disrespectful of God's name. If an immersion of mitzvah happened to present itself, he wraps a reed over God's name and then descends and immerses. Rabbi Yosei says: Actually, he descends and immerses in his usual manner, even if it is not an immersion of mitzva, provided that he does not rub the spot and erase the name. Apparently, Rabbi Yosei's opinion is more lenient than that of the Sages with regard to indirectly causing a prohibited outcome. (Koren Talmud Bavli Steinsaltz translation - bolded words are the translated Hebrew text).
The law, as the Rambam in Yesodei HaTorah 6:6 records, is according to the Sages: that the person must wrap a reed around the name because one may not be naked before God's name. This is the starting point for a Jew who already has such a tattoo.
I don't know the halachot of a Gentile. What came to mind is the Rambam on cursing God's name (Melachim 9:3):
בן נח שבירך את השם. בין שבירך בשם המיוחד. בין שבירך בכינוי בכל לשון חייב. מה שאין כן בישראל
A gentile who curses God's Name, whether he uses God's unique name or one of His other names, in any language, is liable. This law does not apply with regard to Jews.
I don't know if a tattoo would be like cursing (desecration?), and this needs more research.
--
It has been suggested that perhaps a needle inserting dots (i.e., a tattoo) would not constitute writing and so perhaps permissible to remove. To argue against this, I refer to the Keset Hasofer, arguably the most authoritative legal code regarding the laws of safrut, written by R. Ganzfried (Kitzur Shulchan Aruch). In the chapter forbidding erasure of the tetragrammaton (11:2), he writes:
Even a name that was written by accident, that was written in a place where it shouldn't have been, or even if it wasn't written for a holy purpose, or even if it was formed through chok tochot [carving out a letter from a block of ink] and wasn't written for tefillin or a mezuzah, and even if it wasn't written in the Ashurit script but rather in a foreign script, and even if it was formed through sewing or weaving or with various colors: No matter how the Name was made, on anything or anywhere -- anything that was made with the intention that it is the Name, that he who wrote it or made knew that it was the Name of the Blessed Holy One - anyone who spoils one letter from it transgresses a prohibition and deserves lashes.
Thus, even if the letters of the Holy Name were comprised of connected dots made from a needle, since it was made knowing that it was the Name, it cannot be removed.
When I'm contacting a colleague for the first time and we're communicating online, I can use はじめまして as part of my greeting. Likewise, if I'm meeting someone for the first time and it is an in-person meeting, I can say はじめまして during my introduction.
However, if I talk with someone online and then we meet in person for the first time, is はじめまして still appropriate? Or is there some other typical greeting for this situation?
Answer
It doesn't matter. Feel it out based on your relationship with that person and whatever feels right. I have to imagine that if you had contact with someone before and you said 初めまして upon meeting them in person it would be accompanied by that kind of weak laugh of shared awkwardness like "what do I say in this situation?" In other words, meeting people from the internet is still a relatively new phenomenon, and while I'm sure there must have been people who had met by correspondence in the past, there is not some universally accepted cultural norm for what to do in this situation. I think you can compare it pretty directly to how the situation would play out in English.
So basically, I don't think there's a specifically Japanese way to do it. The meeting will probably be awkward and fumbling for the first few moments anyway. Personally I'd make a comment along the lines of "nice to finally meet you in person," as I would in English, but that's just me. Just go for what feels right.
Source: Paula Bruice Ed. 2017 Pg.877
From this excerpt, we infer that formyl chloride is unstable. But how does that affect the reaction in any way? Is it just mentioned as a point to note or does it have an effect on the reaction. And if acetyl chloride is unstable why is acyl chloride stable? 
Also note that I do realise that this is a duplicate of Stability of formyl chloride
But we’ve not used water in Gatterman Koch reaction as reasoned by @SimpliFire in the thread. So how does it remain unstable even when water is not involved.
Answer
The simplest stable acyl chloride is ethanoyl chloride or acetyl chloride; methanoyl chloride (formyl chloride) is not stable at room temperature, although it can be prepared at –60 °C or below. (Wikipedia)
The instability of $\ce{HCOCl}$ is caused by ease of elimination of HCl from its molecules. Cl is decent leaving group and after it's gone, remaining acylium cation has a very acidic hydrogen instead of alkyl present in other acyl halides. Thus easier breaking of C-H bond vs C-C bond causes drastic difference in thermal stability.
Note also the formyl chloride can be considered not only the derivate of formic acid, but also a derivate of formaldehyde.
Is there a Halachic problem with being in attendance to an intermarriage preformed in a regular hall meaning not a problematic location? What is the source in the Halachic literature if there is an Issur?
Answer
No. One cannot attend an intermarriage service.
See TorahWeb for a short hashkafic discussion of this.
When saying that someone or something is both this and that, is XもYもです appropriate?
彼は画家も教師もです。
I ask both for written and spoken. I feel like the copula is already a である so it should be something more akin to:
彼は画家(で)も教師でもあります。
Or something. But then that sounds formal or written-only.
As a non-beginner, this question is frankly a bit embarrassing to ask, as it's so fundamental, but I feel like it was never really specifically covered. Either that or getting used to reading more written form Japanese has messed with my expectations.
Answer
You have to use で and say 彼は画家でも教師でもあります or 彼は画家であり教師でもあります, both in written and spoken Japanese. If you want to make it shorter, you can say 彼は画家[兼]{けん}教師です.
彼は画家も教師もです is almost always ungrammatical, but in a rare unagi-sentence, it may make sense.
みんなの将来の夢について。私は将来看護師になりたいです。佐藤君はサッカー選手です。田中君は画家も教師もです。
Is Yirmiyahu 7:4 the source for the idea that there won't be a 4th Temple? If not, what is?
ד אַל-תִּבְטְחוּ לָכֶם, אֶל-דִּבְרֵי הַשֶּׁקֶר לֵאמֹר: הֵיכַל יְהוָה הֵיכַל יְהוָה, הֵיכַל יְהוָה הֵמָּה.
4. Trust ye not in lying words, saying: 'The temple of the LORD, the temple of the LORD, the temple of the LORD, are these.'
Edit: Rashi says this refers to the shalosh regalim, what is his source for that?
My question is about what it is - at the subatomic level - that determines the charge on atoms which participate in covalent bonding in reality. I understand that formal charge is just that - it's a formality, which gives human beings a very useful tool for modelling reality and making predictions. I, though, would like to know what is responsible for the charge we find in covalently bonded molecules.
Let me explain. If we picture an ionic bond as a highly polar covalent bond, we can see that in an atom like NaCl we have the state of affairs where the highly electronegative chlorine atom has "pulled away" an electron from the sodium atom.
(Orbitals omitted for ease of drawing)
Ultimately this means that Na, with its 11 protons has just 10 electrons, which gives it a positive charge, while Cl, with its 17 protons, now has 18 electrons, giving it a negative charge. Electrostatic forces between the two nuclei result in the bond.
Of course, it might be more accurate to say that the Na nucleus simply ceases to be significantly affected by its former 3s1 electron. As a result the 11 protons in the Na nucleus, which result in a +11 charge, are countered by only 10 electrons, giving a +1 charge overall. Meanwhile, the 17 protons of the Cl nucleus (+17 charge) experience the negative charge of 18 electrons (-18) giving a -1 charge overall.
Let's compare this with the situation we find in the carbonate ion. (Link) For the purposes of my question I won't worry too much about resonance, I don't mind too much whether we have the accurate -2/3 charge, but let's keep it simple and just look at one of the contributing structures.
(Orbitals again omitted for ease of drawing. Orange indicates an additional electron from some other source. Oxygen has only eight electrons ordinarily, but one will be gained when forming this ion)
In this case we have covalent bonding. In the case of the singly bonded oxygens, we have 8 protons and 10 electrons. This is two more negatively charged electrons than positively charged protons. This, though, is not ionic bonding, it is covalent bonding and the polarisation is not such that the electron contributed by carbon dissociates completely from the Carbon. Instead it is "shared" between the two. Nevertheless, the "sharing" is not equal and oxygen attracts the electrons more strongly than the carbon, so we have a -1 charge.
My question, though, is - why is it that the charge works out like this? Why is it that when you have oxygen (8 protons) (charge of +8) and a filled outer shell (8 electrons plus buried inner core gives -10 (charge of -1 on each electron)) you have a charge of -1 not -2, is it simply the covalent bond, is it simply the fact that the two electrons in the sigma bond are sufficiently far enough away in reality?
But then why should it be that the doubly bonded oxygen, which also has ten electrons surrounding it, has no charge at all? Meanwhile, the carbon atom in the middle is surrounded by 10 electrons also, whereas it has only 6 protons and yet carries no charge at all.
Naively the answer seems obvious. The bonds are covalent and the electrons are "shared." So, in the double bond (which, of course, has a different nature to the single bond) one must assume that the electrons are positioned in such away that they are balanced by the protons of the oxygen nuclei. There is therefore no charge on this atom.
In the case of the Carbon atom we surely again understand that the right balance of charges and distance from the nucleus is arrived at.
Overall we have 32 electrons and 30 protons so the overall -2 charge on the whole atom makes sense.
The ultimate question I've been trying to lead up to is what is it that dictates the distribution of charge. What is the difference - at the subatomic level - between two ionically bonded atoms, a covalently bonded molecule like the CO32- ion which carries a charge, and a covalently bonded molecule like H2O - which is also polar (hence we can have hydrogen bonding) but isn't usually assigned a charge. On what basis do we assign charge?
I have 3 signal sampled at 12 KHz frequency obtained from a motor rotating at constant 2000, 2020, and 2040 rpm. For 1 second signal recording I have 12,000 time samples. Depending on the frequency I can say (1/f) is the time period of oscillation.
But I am confused how to segment the signal with one time cycle from the whole signal, so that I can choose those many samples out of 12000 samples.
Is there any mathematical way to compute length of 1 cycle of signal when its sampling frequency and rpm are given, without observing the peak to peak in oscilloscope?
Answer
Although it is hardly related to DSP but here is a quick calculation:
$R$ Rotations per minute is $\frac{R}{60}$ Rotations per second which gives $12K$ samples per second. Hence, One rotation is proportional to $\frac{1}{\frac{R}{60}}\times 12000 = \frac{720,000}{R}$ samples. For instance, for $2000$ RPM there are $360$ samples per rotation.
My friend and I are reading 宝石泥棒 by Masaki Yamada. In the beginning of chapter five, there are a few paragraphs that discuss constellations and zodiac systems, but we can't figure out how to translate some of them. Here is the text (paragraphs are numbered):
- 今夜の〝宿〟は、斗宿{いて}だった。黄道{こうどう}星座の〝いて座〟が、今夜の宿星となっているのだ。斗、牛、女、虚、危、室、壁……など赤道帯を二十八に区分し、旅人に見たてられた月が、毎夜、それらの〝宿〟を移り歩いていく——いわゆる黄道二十八宿は、中国で生まれたものと考えられがちだが、似たようなものはインドやアラビアにも存在したという。
- 黄道二十八宿の本来の意味は、見失われて久しくなるが、夜空を二十八に区分し、星座の移り変わりを暦{こよみ}の基底に据{す}えるというその方法だけは、この時代の人間に引き継がれている。
- 本来の意味が失われるのも当然といえばいえる。参星{オリオン}、昴{すばる}などの宿星に変わりはないものの、星座そのものは大きく変化しているのだ。総じて、夜空は明かるさを増したようである。
- 美しいと形容するだけでは、言葉が充分ではない。たぎった星が、空を白く燃えあがらせている印象なのだ。
Our translation for paragraph 1 is:
"Tonight's 'mansion' was the Dipper. That is, the standard zodiac's Sagittarius constellation was the sign for this night. The equatorial belt is divided into 28 parts, The Dipper, The Ox, the Girl, The Emptiness, The Rooftop, The Wall etc., and the moon, which has been likened to a traveler, goes through those "mansions". The so-called 28 mansions of the ecliptic are thought to have been born in China, but similar systems exist in India and Arabia."
Paragraph 2:
"The proper meaning of the 28 mansion system has long since slipped into obscurity, but the division of the night's sky into 28 parts, and the method of basing calendars on the passage of constellations, those alone have been passed down to the people of the current age."
Now, the part that we are having issue with is paragraph 3. We are not sure how to break down this sentence. Is 当然といえばいえる a set phrase? If so, what does it mean? Or is it just 当然といえば and the second いえる belongs to the noun phrase that precedes 当然?
The sentence that follows seems to say
"Although Orion and Subaru have not changed, the constellation systems themselves have changed greatly. Generally, it seems the night's sky has increased in brightness".
We are not sure if this translation is right. I'm not sure how the fact that the constellation systems have changed relates to an increase in the night's brightness. Moreover, we don't know how to connect that to the sentence with the 当然. Is it the constellation systems as in "The Chinese system", "The western system" etc. that have changed, or the actual constellations in the sky, with the exception of Orion and Subaru, that have changed?
The final paragraph's translation seems to be:
"Words are insufficient even for describing it as beautiful. The impression is that overflowing stars are causing the sky to burn in white fire."
Although this seems straight-forward (in a poetic sort of way), we can't quite make out a coherent meaning for the entire passage.
So please help us with paragraph 3, and if possible, the overall meaning of paragraphs 2-4, as we seem to have lost the forest for the trees.
On the Skeptics stack exchange we have a question about burned toast being used as a treatment for poison, the idea being that burned toast acts as activated carbon.
We are skeptical due to the fact that gas activation requires heating to high temperature, but don't have the chemistry to rule out toast as a source of activated carbon.
My instinct tells me that:
Can someone answer those 2 questions?
I understand that molecular dipoles are electric dipoles. And electric dipole moment vectors point from the negative to the positive charge.
In class we learned to draw these special molecular dipole arrows (with a "plus" at the beginning) that point from the positive to the negative partial charge. I also see these arrows all over the internet, e.g.:
But for alpha-helices, the dipole moment points from the C to the N terminus. And the detail always shows the arrow pointing from the oxygen (negative) to the hydrogen (positive):
Should I just accept that even though an alpha-helix is a molecule like water, the "standard" way to draw its molecular dipole arrow is in the opposite direction than what people normally draw for water and other small molecules?
Edit: Another image, from a recent publication, but without macro-dipole arrow...:
Why is thionyl chloride ($\ce{SOCl2}$) preferred for preparing alkyl chlorides from alcohols, as opposed to say $\ce{PCl5}$ or $\ce{PCl3}$ ?
Answer
Thionyl chloride is preferred for preparing alkyl chlorides from alcohols because the by-products formed in the reaction are $\ce{SO2}$ and $\ce{HCl}$ which are in gaseous form and escape into the atmosphere leaving behind pure alkyl chlorides.
$$\ce{CH3CH2-OH + SOCl2 → CH3CH2-Cl + SO2 ↑ + HCl ↑}$$
I am a bit confused about what chemical shift value signifies in proton NMR spectroscopy. If the proton of the standard substance TMS absorbs X Joules of energy to go into resonance, than a substance with a chemical shift value of 2.5ppm means it absorbs:
energy absorbed= X- (2.5X/10^6)?
Could someone please tell me if this is what chemical shift value is mathematically. In my book, it says the substance absorbs "2.5 millionth less amount of energy than TMS to go into resonance"... but I don't really understand this.
I am new to chemistry and I find it fascinating. I am trying to learn about chemical reactions and I was wondering if there was an easy way to quickly tell if any combination of chemical substances would produce a reaction and what product(s) if any might be formed.
For example, if I pick any two random substances $\ce{A}$ and $\ce{B}$, can I determine if a reaction will occur and predict the products?
$$\ce{A + B -> \ ?}$$
More specifically, let's say I just learned that chlorine bleach (sodium hypochlorite) can be made by a reaction of sodium hydroxide and chlorine with sodium chloride as a byproduct:
$$\ce{NaOH(aq) + Cl2(g) -> NaOCl(aq) + NaCl(aq)}$$
Is there a way that I could have predicted this reaction (and any other) before I learned about it? I do not want to memorize the outcome of every combination o that I can answer questions about chemical reactions. I am hoping there is a short list of simple rules that govern all chemical reactions that I can commit to memory and then apply to any combination of substances. I might also like to be able to develop a simple computer program built around an algorithm for these reactivity rules that can sample databases of known substances and predict new reactions.
Answer
In theory, yes!
Every substance has characteristic reactivity behavior. Likewise pairs and sets of substances have characteristic behavior. For example, the following combinations of substances only have one likely outcome each:
$$ \ce{HCl + NaOH -> NaCl + H2O} \\[2ex] \ce{CH3CH2CH2OH->[$1.$ (COCl)2, (CH3)2SO][$2.$ Et3N] CH3CH2CHO} $$
However, it is not a problem suited to brute force or exhaustive approaches
There are millions or perhaps billions of known or possible substances. Let's take the lower estimate of 1 million substances. There are $999\,999\,000\,000$ possible pairwise combinations. Any brute force method (in other words a database that has an answer for all possible combinations) would be large and potentially resource prohibitive. Likewise you would not want to memorize the nearly 1 trillion combinations.
If more substances are given, the combination space gets bigger. In the second example reaction above, there are four substances combined: $\ce{CH3CH2CH2OH}$, $\ce{(COCl)2}$, $\ce{(CH3)2SO}$, and $\ce{Et3N}$. Pulling four substances at random from the substance space generates a reaction space on the order of $1\times 10^{24}$ possible combinations. And that does not factor in order of addition. In the second reaction above, there is an implied order of addition:
However, there are $4!=24$ different orders of addition for four substances, some of which might not generate the same result. Our reaction space is up to $24\times 10^{24}$, a bewildering number of combinations. And this space does not include other variables, like time, temperature, irradiation, agitation, concentration, pressure, control of environment, etc. If each reaction in the space could somehow be stored for as little as 100 kB of memory, then the whole space of combinations up to 4 substances would require $2.4 \times 10^{27}$ bytes of data, or $2.4\times 10^7$ ZB (zettabytes) or $2.4\times 10^4$ trillion terabytes. The total digital data generated by the human species was estimated recently (Nov. 2015) to be 4.4 ZB. We need $5.5\times 10^5$ times more data in the world to hold such a database. And that does not even count the program written to search it or the humans needed to populate it, the bandwidth required to access it, or the time investment of any of these steps.
In practice, it can be manageable!
Even though the reaction space is bewilderingly huge, chemistry is an orderly predictable business. Folks in the natural product total synthesis world do not resort to random combinations and alchemical mumbo jumbo. They can predict with some certainty what type of reactions do what to which substances and then act on that prediction.
When we learn chemistry, we are taught to recognize if a molecule belongs to a certain class with characteristic behavior. In the first example above, we can identify $\ce{HCl}$ as an acid and $\ce{NaOH}$ as a base, and then predict an outcome that is common to all acid-base reactions. In the second example above, we are taught to recognize $\ce{CH3CH2CH2OH}$ as a primary alcohol and the reagents given as an oxidant. The outcome is an aldehyde.
These examples are simple ones in which the molecules easily fit into one class predominantly. More complex molecules may belong to many categories. Organic chemistry calls these categories “Functional Groups”. The ability to predict synthetic outcomes then begins and ends with identifying functional groups within a compound's structure. For example, even though the following compound has a more complex structure, it contains a primary alcohol, which will be oxidized to an aldehyde using the same reagents presented above. We can also be reasonably confident that no unpleasant side reactions will occur.
If the reagents in the previous reaction had been $\ce{LiAlH4}$ followed by $\ce{H3O+}$, then more than one outcome is possible since more than one functional group in the starting compound will react. Controlling the reaction to give one of the possible outcomes is possible, but requires further careful thought.
There are rules, but they are not few in number. There are too many classes of compounds to list here. Likewise even one class, like primary alcohols (an hydroxyl group at the end of a hydrocarbon chain) has too many characteristic reactions to list here. If there are 30 classes of compounds (an underestimate) and 30 types of reactions (an underestimate), then there are 900 reaction types (an underestimate). The number of viable reaction types is more manageable than the total reaction space, but would still be difficult to commit to memory quickly. And new reaction types are being discovered all the time.
Folks who learn how to analyze combinations of compounds spend years taking courses and reading books and research articles to accumulate the knowledge and wisdom necessary. It can be done. Computer programs can be (and have been) designed to do the same analysis, but they were designed by people who learned all of the characteristic combinations. There is no shortcut.
I am doing a scan calculation using Gaussian09 and adding the Freq=Raman keyword to my input file. My objective is to obtain the Raman spectrum of each conformation in my compound. However, only the Raman spectrum of the last conformation in the scan is calculated. How can I solve this problem?
I understand that I will get negative frequencies, but these will be in a certain frequency range, so I can observe the variation in the signals.
I need to do these calculations, because I want to see the type of conformation that my compound adopts under heating.
From the MATLAB code below where do these theoretical equations for Rayleigh fading and white Gaussian noise come from? Or how are they derived?
h = 1/sqrt(2)*[randn(nrx,ntx,N/ntx) + 1i*randn(nrx,ntx,N/ntx)]; % Rayleigh channel
n = 1/sqrt(2)*[randn(nrx,N/ntx) + 1i*randn(nrx,N/ntx)]; % white gaussian noise, 0dB variance
I have two questions regarding the opening lines of a short story called 真夜中の王女(midnight princess)
ある王国でのこと。
うつくしい王女が十五歳でなくなって、そのなきがらをおさめたひつぎが、教会にはこびこまれた。
so my interpretation is, In a kingdom a 15 year old beautiful princess passed away and her corpse interned casket was carried to the church.
Answer
For your first question, 王国のこと would just refer to "something about a certain kingdom". Adding で to get "王国でのこと" means "something that happened in a certain kingdom".
To give a similar example "バスでの旅行" means "a trip via a bus". Removing the で here would mean just "a trip of a bus".
So yes, your interpretation of this point is generally correct.
Since this looks like a fairy tale, if you were doing a proper translation you might use a more appropriate English phrase, like "Once upon a time in a kingdom".
For your second question, I think Choco's comment confirms the usage of the verb おさめる in question here.
I would translate this part more as "the coffin carrying the princess's body..."
「……っしゃ！ ずらかるぞ！！ ……ん！？」
Is it a colloquial form of 「よっしゃ」?
Answer
It is just an abbreviation of 「よっしゃ」.
I'm not sure which way to say something like exit/leave/depart/get off/escape is most appropriate when the thing I want to get off is the system of expressways in Tokyo called the Shuto 首都高.
I'm not sure that any of these would be right:
Answer
You can use 降りる. User @Chocolate is also fond of 出る
高速を降りる
高速を出る
You can use these in the same way to express your idea of getting off of one form of expressway onto another.
首都高を降りて高速(or whatever)に入る・乗る
Just to address your original guesses:
出発する is to depart, as in the place of origin.
下車する is to get out of a car/vehicle.
残す is to leave something in the same way that you might leave food uneaten.
終了 is when something finishes.
and is it clear that he wrote it.
I'm simply curious.
I've heard a few different opinions on this. During longer prayer services, such as Shacharit on Shabbat, at least in Nusach Sefard, Pesukei D'Zimrah is quite long and there is a tendency for the chazzan where I daven to pray ridiculously fast. I'm fairly proficient at Hebrew, but there is literally no way that I could possibly enunciate every word clearly at that speed (and I have serious doubts that the chazan can either), let alone try to keep up.
I have heard from a friendly source that it's not completely necessary to say each and every word during certain parts of the prayer service, but I can't vouch for the correctness of this. I do know for sure that during specific parts of the service, extreme care must be taken to enunciate each and every word clearly and separately, namely the Shema.
Specifically, I have two questions:
I'm looking for specifics here, and a tertiary question I might offer is whether this all applies when one is praying alone. I know that whenever I end up praying alone and I'm not being rushed, I make my best effort to pray every single word in the siddur clearly.
I heard that Bava Basra is the longest masechta in blatt but Brochos is the longest mesechta in words. Did anyone else hear anything about that?
My understanding of I and Q channels is as follows (please correct me if I am wrong):
I = In-phase, or real componentQ = Quadrature (90° shift of real component)Where do these two channels come from in the first place? Is one the electric field and the other the magnetic field of a EM wave? I was under the impression that these channels are only present in digital waveforms; if this is true, and if so, why?
How can this be used to find the vector of on incoming signal, and would the signal modulation make a difference (assuming you can invoke the proper filtering necessary)?
Answer
The two channels exist only inside a transmitter or a receiver; the channels are physically combined in a single signal (or channel) in the physical medium (wire, coax cable, free space, etc). At the transmitter, two signals $s_I(t)$ and $s_Q(t)$ (called the I (or inphase) signal and Q (or quadrature) signal respectively) are combined into a single signal $s(t)$ that is transmitted over the physical medium in a frequency band centered at $\omega_c$ radians per second. Note that $$s(t) = s_I(t)\cos(\omega_c t) - s_Q(t)\sin(\omega_c t)$$ The receiver separates out the two signals $s_I(t)$ and $s_Q(t)$ from this by multiplying $s(t)$ by $2\cos(\omega_c t)$ and $-2\sin(\omega_c t)$ respectively, and low-pass filtering the two products. That is, $$\begin{align*} s_I(t) &= \text{result of low-pass filtering of}~ 2s(t)\cos(\omega_c t)\\ s_Q(t) &= \text{result of low-pass filtering of}~ -2s(t)\sin(\omega_c t) \end{align*}$$ Note that $$ \begin{align*} 2s(t)\cos(\omega_c t) &= 2s_I(t)\cos^2(\omega_c t) - 2s_Q(t)\sin(\omega_ct)\cos(\omega_c t)\\ &= s_I(t) + \bigr [s_I(t)\cos(2\omega_c t) - s_Q(t)\sin(2\omega_c t)\bigr]\\ -2s(t)\sin(\omega_c t) &= -2s_I(t)\cos(\omega_c t)\sin(\omega_c t) + 2s_Q(t)\sin^2(\omega_ct)\\ &= s_Q(t) + \bigr [-s_Q(t)\cos(2\omega_c t) - s_I(t)\sin(2\omega_c t)\bigr]\\ \end{align*}$$ where the quantities in square brackets are double-frequency terms that are eliminated by the low-pass filtering.
Are there any reactions with no activation energies? Our professor just told us there are no chemical cliffs. Is this true?
I read something about nuclear decay as being a reaction with no activation energies. Why is this so, and how does this work?
Answer
Marcus-Hush theory describes electron/charge transfer rates using conventional transition state theory, e.g.:
$\ce{A+ + B -> A + B+}$
Now one might naively assume that there's no activation barrier in a simple electron transfer, but that's not true. Since the geometry of $\ce{A+}$ and $\ce{A}$ as well as $\ce{B}$ and $\ce{B+}$ are not identical, there is a reorganization energy of both the molecular species and the solvent or environment. This reorganization energy ($\lambda$) serves as an activation barrier for the charge transfer.
Now the convenient thing about charge transfer reactions is that you can tune the $\Delta G$ of the reactants.
Marcus predicted that the maximum rate would occur when the $\Delta G^0 = -\lambda$ and thus the $\Delta G^\ddagger = 0$. If the reaction becomes more thermodynamically favorable, you enter the inverted region and the activation barrier goes up and the reaction rate goes down.
This is a long-winded answer to say there are some chemical reactions with no activation barrier, in addition to the other cases here. Usually the key phrase describing these in papers is "barrier-less reactions"
What is the practical difference between actions considered Pesik Reshe Delo Niha Le, Pesik Reshe Delo Ichpat Le, and Melecha She'en Sarich Legufa? What is an example that can demonstrate the difference between the three?
(Sources, of course [see the Rashash on Tosafot Ketuvot 6a])
Answer
In Hilchos Shabbos 1:7 of the Mishnah Torah, The Kesef Mishna brings HaRav Avraham Hachasid (Rambam's son) and explains psik reisha doesn't need the actual melacha, he brings the case of closing a door on a deer.By melacha shaina tzricha it is the melacha you want but not its purpose, ayin sham.
For example, while having lunch with your coworkers and you have to attend some matter soon, what would be a natural way to leave the table? I think that in this case saying お先に失礼します would be wrong.
Answer
I won't say お先に失礼します is completely out of place, but you should at least mention why you're leaving, so as to assure that you're not offended or anything:
すみません、片付けたい仕事がありますので、先に失礼します。
Abruptly announcing お先に失礼します is probably too closely tied to the idiomatic usage (when leaving work).
先に戻ります or 先に行きます can also work as a substitution for 先に失礼します.
すみません、やってしまいたいことがあるので、先に戻ります。
If you're unsure about which verb to use, just cut it short with a trailing ellipsis (see Axioplase's and Dave's answer):
すみません、ちょっと用事があるので...
If your colleagues already know you have something to attend to, or your KY radar is all clear, you can get as brief as:
じゃ、お先です。
Some people may think it's too informal for work, but you'll be ok as long as other people around you are using it.
ごちそうさまでした works best when you're eating your bentos together. See Dave's answer for a complete explanation.
What are the halakhoth regarding unglazed terra cotta flower pots? Does it absorb? Can it be kashered, and if so, how?
Sephardic rulings preferred, but will take any sources.
To me it is clear that if (G-d forbid) a person is sick to the point that it will kill them, or that (G-d forbid) they will get their wife sick, there's obviously no obligation to please their wife (fulfill the requirement of ona). If the doctor tells them not to, also it is clear to me that they are not obligated to (and maybe obligated not to).
So that raises the questions:
Answer
The Shulchan Aruch discusses this issue (Even HaEzer 76).
In Seif 3, he comments regarding the standard onot as fixed by profession:
בד"א, במי שגופו בריא ויכול לקיים העונה הקצובה לו, אבל מי שאינו בריא אינו חייב אלא לפי מה שאומדין אותו שיכול לקיים.
In what situation do [the above times] apply? For someone who's body is healthy and is able to perform his set onah. But for someone who is not healthy, he is only obligated according to what he is evaluated to be able to perform.
But note that in Seif 11 he writes:
ואם חלה או תשש כחו ואינו יכול לבעול, ימתין ששה חדשים עד שיבריא, שאין לך עונה גדולה מזו, אחר כך, או יטול ממנה רשות או יוציא ויתן כתובה
And if he became sick or weak and he is unable to perform his onah requiremnets, he can wait up to six months to get better, for that is the longest standard onah [that of a sailor]; then, he must either ask her permission to delay further [which is in general permissable] or he must divorce her and pay her ketubah.
So in summary, one may delay his onah requirements due to illness up to six months. If he still is too sick, then his wife may grant him more time or sue for divorce.
This post indicates that the earliest source for the story of Serach bas Asher and the harp, wherein she notified Yakov that Yosef was still alive in a very subtle musical fashion, is a very late midrash known as the sefer hayashar which the author dates to the 16th century. I would like to know: Are there are any earlier sources for the story?
Today I noticed this article about eating disorders in Japan, which I got to via the News on Japan site.
The first line jumps out at me. Supposedly, in an interview, a 25 year old Japanese woman named "Hachiko" says:
In Japanese there are no words for “I’m suffering” or “I’m sad”. I can’t share my feelings with anyone. Needing help is seen as failure, something to be ashamed of.
Maybe needing help is seen as failure, but I can think of a few ways to say "I'm suffering" or "I'm sad". Just off the top of my head:
私{わたし}は悲{かな}しい
あたしは苦{くる}しんでいます
自分{じぶん}の置{お}かれた状態{じょうたい}はきつい
So I'm wondering, is this just a reporter's ham-fisted attempt to inflate the human drama by painting a picture of a cruel and uncaring Japanese culture that exacerbates eating disorders?
Or is there any logical justification at all for claiming that the nuances of the Japanese language don't accurately convey the suffering someone with an eating disorder might feel?
Answer
So I'm wondering, is this just a reporter's ham-fisted attempt to inflate the human drama by painting a picture of a cruel and uncaring Japanese culture that exacerbates eating disorders?
There could be several reasons I can think of:
The Japanese woman who said this might of meant it "metaphorically" rather than "literally", in the sense that there is a tendency to not express ones inner feelings as much in Japan as in other cultures. However, anybody that has studied Japanese before should be able to realize that the sentence is false, so it's obvious the author is inept.
Somewhere along the lines, the actual meaning of the quote got botched, perhaps by the interpreter or someone else (this is very common and often leads to false information) (maybe due to reason #1).
The author exaggerated to get people's attention and sell magazines (the original article is from Marie Claire magazine). Unfortunately, the majority of the audience probably wouldn't realize this, which gives a false conception about Japanese to the general public (for example, as an extreme case of a false conception, in America, I met a person who asked me if people in Japan walk around with swords like "Samurai").
But the moral of the story is don't always believe what you read.
When an egg is kept in vinegar for one week, its hard calcium carbonate shell changes into a soft rubbery membrane. As vinegar is weak acetic acid, how does vinegar change calcium carbonate into a soft rubbery membrane? What is the reason for this?
I am analyzing a transient signal presumably consisting of superposed exponentials. Such a case is indicated for the Prony analysis, but my data aren't noiseless enough, so I have turned to the Kumaresan-Tufts (KT) algorithm.
After reading the original article (Estimating the Parameters of Exponentially Damped Sinusoids and Pole-Zero Modeling in Noise, 1982) and a bit of googling I made use of the Matlab package Complex Exponential Analysis and more or less things work
My concern is now an intuition on the process - or, better, on its input parameters (cause FFT-like thinking is of course out of question):
