Is the Mind (Citta) the Self? If not, what is it?

Question: It's been discussed in all perspectives that the Buddha was teaching about not-Self (Anatta) in this forum. However, it taught that one should empty the Mind (Citta) to realize Anatta, or Sunyata, in Dhyana (Jhana). If this mind is already not-Self, why it needs to be emptied and what is to be emptied? If this mind is also not-Self, how does it have the autonomy/independence to realize/discern Emptiness? If this mind is Self, how can it realize not-Self? If this mind is not-Self, who controls/owns the Five Aggregations and intellect? Who/what is this mind?
Comment: It is like saying I have this 'bucket'. What is in the bucket is not mind, so I empty it. Once empty, I can clearly see that the bucket is not mind either. At that point, I have a choice: I can go on seeking the mind under every rock and rainbow, or I can get on with helping others and enjoying what life gives me with no asking or seeking necessary.
Comment: @nocomprende *seeking the mind*... from Lotus Sutra there a metaphor about a rich turned poor man wandering for making a living but didn't realize he has a precious wishing-gem sewn inside his worn-out jacket ~
Comment: I wish I had one of those, and I wish I would realize it before it is too late!
Comment: me too! @nocomprende
Answer:
1. If this mind is already not-Self, why it needs to be emptied and what is to be emptied?

The mind is only 'not-self' from the viewpoint of enlightenment & truth. But for the unenlightened mind, the mind is 'self' because of ignorance ('blindness').
The mind is ideally 'emptied' so it can see clearly, similar to cleaning a window or mirror. It is emptied of the pollutants that obscure clear seeing, similar to a window or mirror cleaned from dust.
The Pali scriptures describe this in the Sangaravo Sutta.

Imagine, Brahman, a bowl of water mixed with lac, turmeric, dark green or crimson dye. If a man with good eyesight were to look at the
  reflection of his own face in it, he would not know or see it as it
  really was. In the same way, Brahman, when a man dwells with his heart
  possessed and overwhelmed by sense-desires... then he cannot know or
  see, as it really is, what is to his own profit, to the profit of
  others, to the profit of both. Then even sacred words he has long
  studied are not clear to him, not to mention those he has not
  studied. Sangaravo Sutta

2. If this mind is also not-Self, how does it have the autonomy/independence to realize/discern Emptiness?

The mind has a wisdom faculty to discern emptiness. It is not possible to explain how or why this can occur. The Pali suttas simply say:

Discernment (wisdom/panna) & consciousness are conjoined, not disjoined. It's not possible, having separated them one from the
  other, to delineate the difference between them. For what one
  discerns, that one cognizes. What one cognizes, that one discerns.
  Mahavedalla Sutta

Jesus Christ said:

If the flesh came into being because of spirit (consciousness), that is a wonder. But if spirit came into being because of the body, that is the wonder of
  wonders. Yet I marvel at how this great wealth has come to dwell in
  this poverty.
Gospel of Thomas

3. If this mind is Self, how can it realize not-Self?

The citta is not a self. It is impermanent. It is not-self. To quote:

"All things are not-self". Dhammapada 279.

It would be better for the uninstructed run-of-the-mill person to hold to the body composed of the four great elements, rather than the
  mind, as the self. Why is that? Because this body composed of the four
  great elements is seen standing for a year, two years, three, four,
  five, ten, twenty, thirty, forty, fifty, a hundred years or more. But
  what's called 'mind (citta),' 'intellect (mano)' or 'consciousness' (vinanna) by day and by
  night arises as one thing and ceases as another. Assutavā Sutta

4. If this mind is not-Self, who controls/owns the Five Aggregations and intellect? Who/what is this mind?

Nothing owns or ultimately controls the five aggregates, as was explained at the start of the Buddha's 2nd sermon. However, the mind itself, via enlightenment, can control its mental formations (sankhara) while the mind is alive.
SN 12.12 states there is no "who" that is conscious. The idea of "who" arises later at clinging & "becoming":

"Who, O Lord, has a sense-impression?"
"The question is not correct," said the Exalted One.
"I do not say that 'he has a sense-impression.'...the correct way to ask the question will be 'What is the condition of sense-impression?'
  And to that the correct reply is: 'The sixfold sense-base is a
  condition of sense-impression, and sense-impression is the condition
  of feeling.'"
"Who, O Lord, feels?"
"The question is not correct," said the Exalted One....the correct way to ask the question will be 'What is the condition of feeling?'
  And to that the correct reply is: 'sense-impression is the condition
  of feeling; and feeling is the condition of craving.'"
"Who, O Lord, craves?"
"The question is not correct," said the Exalted One. "I do not say that 'he craves.'...the correct way to ask the question will be 'What
  is the condition of craving?' And to that the correct reply is:
  'Feeling is the condition of craving, and craving is the condition of
  clinging.'"
"Who, O Lord, clings?"
"The question is not correct," said the Exalted One, "I do not say that 'he clings.' Had I said so, then the question 'Who clings?' would
  be appropriate. But since I did not speak thus, the correct way to ask
  the question will be 'What is the condition of clinging?' And to that
  the correct reply is: 'Craving is the condition of clinging; and
  clinging is the condition of the process of becoming.' Such is the
  origin of this entire mass of suffering.

As previously said, the mental faculties are named according to their functions:

And why, bhikkhus, do you call it feeling? 'It feels,' bhikkhus, therefore it is called feeling.
And why, bhikkhus, do you call it perception? 'It perceives,' bhikkhus,therefore it is called perception.
And why, bhikkhus, do you call it formation/construct? 'They construct the constructions,' bhikkhus, therefore they are called
  formations.
And why, bhikkhus, do you call it consciousness? 'It cognizes, ' bhikkhus, therefore it is called consciousness.
SN 22.79
Comment: Comments are not for extended discussion; this conversation has been [moved to chat](http://chat.stackexchange.com/rooms/66041/discussion-on-answer-by-dhammadhatu-is-the-mind-citta-the-self-if-not-what-i).
Answer:  Is the Mind the Self? If not, what is it?

It's a delusion of mind.
why it needs to be emptied

Because it's the cause of suffering.
How does it(Mind) have the autonomy/independence to realize/discern Emptiness?

By developing a new faculty called wisdom to realize Anatta or Sunyata, but not emptying the mind.
Who controls/owns the Five Aggregations and intellect?

Craving ( delusion/moha/avijja) takes five aggregates as a self.
Who/what is this mind?

Not Me(or i), but it arises from six-sense faculty, when ignorance is.

Story:
While crossing the stream on a plank over it, a dog looks down into the
water. Seeing a dog there, it either wags its tail in a friendly way
or  growls  angrily.  Or  else  out  of  curiosity  it  keeps  on  looking
down  again  and  again.  Due  to  wrong  attention  it  doesn't understand what really happens.
The dog thinks that it is looking because it sees. But the truth  of the matter  is that it sees because it looks. Every time it looks it sees a dog.   Consciousness has such a delusive magical quality about it. This is because consciousness has  the  property  of  reflecting  something.
Comment: wow, almost the best answer so far, thank you; except not sure with the last 3. i like the story, i do get something out of it, esp. "consciousness has the property of reflecting something".
Comment: @Bhumishu米殊 welcome!. the story is equate from [Ven. K.Gannananda](http://seeingthroughthenet.net/wp-content/.../The-Law-of-Dependent-Arising_Vol_1.pdf)
Comment: At night, the mirror does not reflect anything.
Comment: @Shrawaka I don't understand this story very much.  seeing is reflecting?  contact at the sense-base is the cause of reflection?  consciousness reflects on the mind (brain)?
Comment: Feedback property of brain. The output proses.
Answer:
And going further, he reviews bones covered with skin, flesh and blood, and he knows the unbroken stream of consciousness as established in this world and established in the next.
...

Sampasadanīya Sutta (Quoted from Piya Tan's Translation of DN 28)
In intermediate stages of meditation is seems like consciousness is continuous and you will feel there is a permanent observer. If it is continuous then it can be considered self by some meditations. This maybe a mistake quite a few meditators would fall into hence the explicit mention. But as your meditation deepens this you realise that consciousness is also not unbroken, i.e., it is broken, hence it is not / non self1:

And going further, he reviews bones covered with skin, flesh and blood, and he knows the unbroken
stream of consciousness as both unestablished in this world and unestablished in the next.

Sampasadanīya Sutta
Though the above deals with viññāṇa it is applicable to Citta also. That is, if Citta is discontinuous in this life than it is not self. It not self that if you mind is in a pleasant mental state you cannot prolong it. It comes to an end what when that happens it deals to unpleasantness. When pleasantness changes it is unpleasant. [Cūla Vedalla Sutta] Whatever, unsatisfactory is not self.
The mind partly controls the body. This is not absolute. By thinking I will transform back you my x year body you cannot. By thinking I will not age any more you cannot stop it. There are a lot of areas the mind has no control on what it can do hence it is not self.
Also following might be of interest for additional references: Sutta references which Discuss Self and Not Self under Different Contexts

1 Out of the 5 aggregates Consciousness is the last of what you see as the Three marks of existence

Craving arises at any of the six viññāṇas of the sense doors. As a description of mind, the four aggregates of viññāṇa, saññā, vedanā, and saṅkhāra generally suffice. Deeper Vipassana separates them. Before that stage is reached however, philosophies start because, despite the experience of arising and passing, the observer—which is viññāṇa—seems to remain and it is not divided or dissected. It is viewed as eternal soul: je viññāya te āya ye āya te viññāya (Whatever is viññāṇa is soul and whatever is soul is viññāṇa). However at a deeper level it does become separated: eye viññāṇa cannot hear, ear viññāṇa cannot see, any or all of these viññāṇas can stop, and when mind viññāṇa also stops, nibbāna comes.

Source: Discourses on Satipatthana Sutta - S. N. Goenka

1) "unbroken/broken consciousness", is the consciousness the mind, the observer, or both are minds?

While you cannot see impermanence in consciousness you feel there is a soul as the observer. Until you see consciousness as impermanent you feel there is a soul.
The easiest part to see impermanence is the body as it is subjected to: pain disease, aging, etc.
It is harder to see arising and passing of the mind. Though as you progress you see parts of the 5 Aggregates making up the mind also as arising as passing. In my opinion the 1st would be sensation and the as the suttas last would be consciousness. Perception and Fabrication it will be difficult to say what order. As far as I know, sutta source only mention consciousness is last, it does not say about body is 1st, but this is something I inferred. But nevertheless when you see consciousness arising and passing you see there no part of the mind which is permanent.
In another way you might see selfhood in external (mine, god controlling soul), body and mind. As our understanding expands the sphere of selfhood contracts to body and mind (corporeal body), the mind only, parts of the mind final residue being consciousness, and finally there is no self conceiving at all. This is gradual.

2) "The mind partly controls the body..." then what is the other part also controlled the body, how do their co-ordinations be achieved? In experimental world we can't control age, not necessarily the mind is incapable, but the mind is partially in function?

Mind has some control: you can lift you hand and foot if you want (provided they are functional)
Mind has no control: can you stop aging

Above statements together: The mind partly controls the body.

3) "eye viññāṇa cannot hear..." Arahats or "X-man" can have their faculties switched, experiment by one Taiwan Uni. principal, children could be trained to "read" with ears!

It could be very well that this research miss infereded reading with the eye faculty as ear. Sometimes there is fake news on the net. It could be such a instance.
Also if abhiññā is developed then is not the physical eye you see from by and extension of this faculty. You might be able to read something head to the side or back of your head perhaps. This does not mean you are reading from your ears.

modern medicine has developed devices to enable blind patients to see

People are not meant to fly but aeroplanes people do. Likewise you can use a device to achieve something which is not possible. If you use medical technique this is repairing the faculty. To see there should be contact (attention, external contact, working faculty, consciousness). Medical techniques repair the faculty. Even perhaps a blind person may have latent, the eye consciousness. what is missing is the faculty.
Comment: This is found in one place in the suttas, it is not spoken  by the Buddha and the meaning is questionable. Also, the proper translation is "other world" rather than "next world". The "other world" is generally a heavenly world of jhana.
Comment: @Suminda Thanks the info. Many of the above sayings are incomplete. 1) "unbroken/broken consciousness", is the consciousness the mind, the observer, or both are minds? 2) "The mind partly controls the body..." then what is the other part also controlled the body, how do their co-ordinations be achieved? In experimental world we can't control age, not necessarily the mind is incapable, but the mind is partially in function? 3) "eye viññāṇa cannot hear..." Arahats or "X-man" can have their faculties switched, experiment by one Taiwan Uni. principal, children could be trained to "read" with ears!
Comment: @Suminda Thanks the edits. I put into skeptics of S. N. Goenka, having not really studying his works, I keep silent. But point to emphasize, "Sometimes there is fake news on the net..." without wrestling this "news" its authenticity, modern medicine has developed devices to enable blind patients to see with ears[link]http://www.rebuildyourvision.com/blog/vision-news/new-sound-device-teaches-blind-people-to-see/, and more on BBC which I forget where, watched long ago.
Comment: Wonderful, comprehensive answer! Thank you for this effort.
Answer: Mind is a non living thing same as any object like a book or stone, it does not have its own existence, it is getting pran from soul.
For example these trees and plants does not have soul, but there is one mind in earth.
As Buddha says "Experience it, don't believe anything".
So we are supposed to observe pran and chitta and then they are supposed to be mixed and become one.
Comment: Sanskrit is vast, in fact English language produces least type of sounds, that is why native English speaker faces lot of trouble pronouncing Sanskrit or other vast language.
Comment: It all f**ks up for English has one term for all Citta, Vijnana... etc. - called Mind


Pull up/ Pull down resistor

Question: I am using an external pullup resistor on my input pin, and a switch connected to GND. It is like in the picture below. In the below picture, when the switch is open, the MCU input pin will see a logical high. I want to reverse this condition and see a logical high when the switch is closed. Should I use an internal pull up or pull down resistor to accomplish this? Also, what will happen if I use a pull-up? What will happen if Vcc is connected to Vcc or GND is connected to GND. I am really confused.
Regards,
Karan.
Answer: To reverse your logic you just need to reverse the pull up and make it a pull down.

simulate this circuit – Schematic created using CircuitLab
Answer: For almost all applications there should be no reason to need to change the way the switch connection works in the initial posted schematic. The sense of the input signal can be simply inverted in MCU software.
If you think you need to have the "activate high on switch press" behavior because some internal interrupt or enable to an I/O function on the MCU requires a a high level then you should definitely be thinking about an alternate solution. The reason is that simple switch connections will require debouncing. That process can easily be done with any MCU using a periodic time interrupt to sample the input. Once the sampled input is debounced and qualified by the software the high / low sense of the input can also be managed easily.

Pull up/ Pull down resistor


Can I stop a WhatsApp message from being delivered?

Question: If I delete a message with a single tick, does that just get deleted from my local device ( Android) or does it no longer get delivered to the recipient?
Answer: Whatsapp marks messages that have been delivered from the sender to the Whatsapp servers with a single tick, and messages delivered from the Whatsapp servers to the recipient with two ticks. After the single tick has appeared, the message is already on the server and can't be removed/aborted.
If your data connection is slow/unavailable, you can cancel the message by deleting it before the tick appears.
Comment: Here's confirmation of this on the [WhatsApp FAQ for check marks](http://www.whatsapp.com/faq/en/general/20951546).
Answer: If you wish to stop a whatapp message from being delivered to a recipient, I have found that after you have sent this (✅) and before this is delivered (✅✅) you add the person temporarily to your block list until they come on line next as you can still see there date stamp. The message then doesn't get delivered. You can then reinstate them and the message will never get delivered and stays in the status of ✅. Hope that helps.
Comment: This did not work. I tried this above thing. But, it dint work. My messages to the blocked person were delivered.
Comment: This does not work and this answer should not be marked as accepted.
Answer: I tried deleting a single ticked message which I sent to another WhatsApp account of mine, but it got delivered even after that as soon as I logged into the other account. So it looks like deleting a message with a single tick only erases your local copy.
Comment: @asgs No - if it's got a single tick, it has already reached the WhatsApp servers.
Comment: Unless there is a connectivity issue on yiur phone which prevents it from getting sent to the Whatsapp servers?
Comment: @Neo yes, that's the point I made too.
Answer: If you had internet / mobile data when the message was sent, then there is high possibility that the other person has already received it. So, deleting it from your phone doesn't matter.
More or less, it works the same way as SMS.
Source.
Comment: My understanding is that a single tick next to a message indicates that your message has been delivered to the WhatsApp server. A double tick indicates it has been subsequently delivered to the recipients device. I was wondering whether a local deletion at that first stage also prevents the second stage from occurring.
Comment: @Rob If it's already in the WhatsApp server, then it's going to get sent to the user. It's probably just waiting for a batch job / trigger from their servers to send it.
Answer: Single tick denotes message delivered at WhatsApp server. Double tick denotes message delivered to destination, i.e., to whom it was addressed.
At single tick status, the message was delivered but not yet delivered to receiver, block the receiver.
Keep him blocked till he opens WhatsApp. Of course you don't know when he will open WhatsApp. So don't unblock immediately.
If he opens WhatsApp while blocked by you then your message will never will be sent to him even if you unblock him.
Try it and confirm.
Comment: An anonymous user edited this in attempting to reply "WELL, IT DOES NOT WORK. I TRIED IT BUT ONCE THE BLOCK IS REMOVED, THE RECEPIENT RECEIVES THE MESSAGE. THANKS."


In this scenario could gamma be higher for OTM options?

Question: Let's say there is a $1 stock, with say 1 day to expiration. The 1.5 strike call, is probably a 0 delta at this point; however, a 1 point increase would mean the stock would be at trading at 2 dollars; thus the 1.5 strike call would now almost be guaranteed to finish in the money right, and would seemingly now have close to a 100 delta. It seems then, that it's gamma was 100 in this scenario, making it higher than an ATM option. Where am I wrong?
Answer: under the black scholes assumptions it is nearly impossible to move 50% in 1 day. A 1day move will be of size $\sigma \sqrt{1/252}$ (assuming 252 trading days). So you are talking about something that is about a 40 stdev move (assuming $\sigma$ = 0.2).
that's why your gamma is 0.


How to improve my English from Academic papers?

Question: I'm not a native speaker. However, I'm doing my PhD in an English country and I read Academic papers which are in English. How can I improve my English from those papers? Any ideas? Although sometimes those papers are not written by native English speakers and may still have problems.
Comment: @Barun: Better than your supervisor might be a fellow student (with good English) who you can bribe with a case of beer :) Correcting someone's writing is kind of a tedious task, and kind of a lot to ask of an advisor who's more interested in the research itself.  (Besides, the advisor's English might not be so great, either!)
Comment: If you also want to improve your *spoken* communication skills, take a look at Toastmasters (http://www.toastmasters.org/).  There may even be a club in your school already.
Comment: One of the best ways to master the writing skill is to write a paper yourself, have you supervisor correct it, and then, thoroughly go through the review. If this process is repeated over 2-3 papers, you would have a strong hold in the style. But the key is to understand the corrections made to your draft.
Answer: The old adage is: "the language of science is bad English" (and at least in computer science it is 100% true). That being said, I have known PhD students who have failed mainly because of their lacking English language skills – they had ideas, but they could not communicate them to anybody, and they could not write them down in a paper for the life of them. You need decent English to write any paper, and you need pretty good English to write papers at top venues.
You ask how to improve your language skills from reading papers. I would say, you can't do that effectively at all. Clearly, reading anything written in English will help you to some extent, but if you feel like you need to improve your English, taking one or more (good) courses in technical English will help you more than reading through a few dozen papers.
However, there is one language-related skill that reading papers for is really useful – if you are setting out to write the first or one of your first papers of your own, nothing beats analyzing existing papers (at the same conference, in the same journal) to find out how papers in these venues are usually structured. This gets you started much faster than drafting something only for your advisor to tear it apart.
Comment: Wish I could +2, over the said opinion point: `you can't do that effectively at all`
Comment: Perhaps it's worth adding that many universities offer English language courses geared towards PhD students, which focus on academic writing.
Answer: While I understand that there's a big difference between scientific and day-to-day language, I actually think you need both to succeed in academia.
While you do need to excel in research (e.g. publish papers, communicate ideas), only the "top level" will be done in pure scientific and formal language: writing papers and scientific presentations. A lot comes from communicating your ideas, either in formal and informal settings. The "level" of English varies from setting to setting: at some point, you would not want to host a prominent researcher in your country, and take him to lunch only to realize you do not know how to translate the menu.
That said, I think you need to improve your English overall, and the best way to do it is to expose yourself to the language as much as you find comfortable:

if you usually read (non-scientific literature), switch from your native language to English
when watching movies/TV shows, don't go for the dubbed versions: go for the original language, first with the subtitles in your language, then in English, and then no subtitles at all
try and find yourself in social situations where English is the main spoken language. Listen to people and talk to them. I saw a big change in a lot of people in just a few months from this.
take a course, possibly in technical English
specific terminology and style of writing will come in time, with immersion in your field, but it is okay to use a dictionary for rare terms
in addition to just using a dictionary (translations are not always stellar), use Thesaurus to find synonyms and antonyms. It is also useful when you know the correct word, but you feel your writing is too repetitive
have some kind of spell checker activated when you type (not only your papers, but also your posts, chats and e-mails), use it whenever it tells you that you misspelled the word, and try to remember your mistakes
start using an English-English dictionary, as often as you can when you come across an unknown word. For me, just typing "define:whatever" in Google works just fine.
Answer: In addition to other good observations... : the idiosyncrasies of English are not easily codified in "rules", so considerable familiarity with many good examples of standard use, to allow faithful mimicry, (in addition to more formal study and hearing-experience) is surely helpful.
That is, rather than "composing" in a vacuum (worst of all translating into English...), it is very convenient to be able to recall already-vetted phrases and wording-choices and simply re-use them.
This is especially true with regard to "articles" "a", "an", "the", or their absence, and related seemingly-innocent modifiers. Also, verb tenses.
Thus: imitation from good models.
Answer: Reading good papers from your field would improve to some extend your technical language specifically the style and structure in your field. I recommend you to read a few good books about writing science and manuscripts.
Answer: The exercise is to learn English by writing. Take a few paragraphs from Academic paper. Print the text and then write it by hand. Check if you have any errors? No errors? Then take another piece of paper and hide the side of printed text so that you can't see two letters at the end of each line. Write the whole text again. Check for errors? No errors? Move the sheet further and repeat. Have an error? Start from the beginning. Write the text looking at a printed one. Then add a sheet of paper on a side and write again and re-check for errors. No errors - move paper further. If you experience a mistake you need to start from very beginning! Eventually you should be able to write the text by looking at one letter of each line only and then the whole text by memory without any mistakes. Congrats! Do the same for second time next day. Once you complete second text, re-write first one too. Check for mistakes in both. Got a mistake? Start from text 1! Now you do that for 10 text and you will be shocked!
Another thing you need to do is to practice writing sentences. Take any phrase that has a new structure to you (e.g. from the academic paper) and write it down. Then write again. Repeat this 10 times. Then change one word using a thesaurus. And write 10 times again. Change the same word again and write re-phrased sentence 10 times. Repeat this task for each word. This practice will allow to learn the limited range of rules that are used in English sentences.
Surely you may check English grammar from time to time if you really want to know why something is like that, however don't spend too much time doing it. You will become bored and overloaded with information very soon.
Happy learning!
Answer:
Participate in discussions strictly related to academic papers.
Don't read only - be active in your discussions and write as much as you can (you can make errors but you will self-eliminate them with more practice).
Comment: Please do not use this site for astroturfing; such practice is [against site policy](http://academia.stackexchange.com/help/behavior).


If the Canaanites occupied the land in Moses' day, why would Moses write that they were in the land then?

Question: What does the Torah imply when it notes 'the Cannannites were then in the land' (Gen. 12:6)? It seems to suggest they were in the land then (when the tale took place) but not now (when the book was written). As there were Cannannites in the land during the entire lifetime of Moses, who wrote the Pentateuch, why does the text seemingly speak in the past tense?
Comment: [Josh Waxman](http://judaism.stackexchange.com/users/458/josh-waxman) has a nice blog post discussing this, [here](http://parsha.blogspot.com/2004/10/lech-lecha-and-canaanites-were-then-in.html). It is a very old question, certainly, discussed by ibn Ezra, and possibly earlier.
Answer: Rashi on the verse (Bereshit 12:6) tells us that Israel was part of the portion of Shem. At that time, the Canaanites (descendants of Cham) were conquering the land from them.
However, Rashi in Bamidbar 13:22 (and Devarim 11:10) says that Cham built Chevron for his son Canaan, which would seem to indicate that the land of Canaan was part of Cham's portion.
The Chumas Shai LaMorah brings a Chizkuni (to both the verses from Bereshit and Devarim cited above) that explains the southern part of Israel was given to Cham, while the nothern part was given to Shem. Apparently these northern lands were now being conquered by the Canaanites.
Two other answers are brought here:

Rav Eliyahu Mizrachi (in his commentary to Rashi in Parashat Lekh-Lekha) concludes that we have no choice but to view these two Midrashim as conflicting with one another. It should not surprise us, Rav Mizrachi adds, that Rashi adopts both views in his commentary; in any given context he adopts the explanation that he feels best explains the local text, even if it contradicts a claim made to explain the text in a different context.
Levush ha-Ora (in Bereshit). When Rashi writes in Sefer Bereishit that Canaan captured the territory from Shem, he did not mean that Canaan launched an independent campaign. Rather, his father, Cham, assigned him the task of conquering the unsettled areas of the land for him, Cham. After Canaan completed the conquest, Cham rewarded him with the land and built the city of Chevron. We can thus reconcile the two comments of Rashi. On the one hand, the land originally belonged to Shem and was seized by Canaan; however, Canaan acted not independently, but on behalf of his father, who then built for him the city of Chevron.

I'm not sure I'm understanding it correctly, but the Chizkuni (Bereshit 12:6) also brings another explanation (seemingly not according to Rashi). He says that the word "Az" is future tense, telling us that not only were there Canaanim in the land during the time of Avraham, but there will also be Canaanim in the land when it comes time for the Jews to conquer it.
Answer: R. Avraham ibn Ezra seems to have been bothered by this question. He gives two possible answers in his commentary to this verse:

יתכן שארץ כנען תפשה כנען מיד אחר ואם איננו כן יש לו סוד והמשכיל ידום.
It is possible that Canaan took the land of Canaan from someone else. And if not, then it has a secret, and the intelligent one will remain silent.

So his first answer, similar to Rashi quoted in Menachem's answer, is that the word 'then' is saying that Canaan had already, by then, conquered the land. It is not discussing the status of the land at the time the verse was written.
His second, cryptic explanation is understood by R. Yoseph Tuv Elem II in his super-commentary Tzofnat Pa'anei'ach as follows:

נראה שלא כתב משה זאת המילה בכאן רק יהושע או אחד משאר הנביאים כתבוה
It appears that Moshe did not write this word here, rather Yehoshua or one of the other prophets wrote it.
Comment: It occurs to me that in writing this answer I have confirmed that I am not a משכיל (at least as defined by ibn Ezra).

If the Canaanites occupied the land in Moses’ day, why would Moses write that they were in the land then?


Making a "Gears turning" Effect, and then grinding to a halt

Question: What would be a way to acquire this sound without actually building or finding metal gears that turn?
Answer: You need two components - metal clangs for gear hitting gear and grinding sound for the shaft rotating. Record lots of metal clangs - you need many variations and often finding the sound that matches perfectly takes some time. Experiment with samplerate of existing sounds. Grinding sound should match to material shaft is connected to, but if it's unknown just use some metal grinding sound.
Play metal clangs in a sequence and adjust the gap between each clang according to gear rotation speed. With low speeds decreasing volume is usually a good idea too and you could try lowpass filtering the clangs too. With grinding sound adjusting only volume according to rotation speed is often enough, but sometimes minor samplerate modulation can be used.
Optimal would be building an instrument with sampler that supports playing a sequence of sounds and modulating trigger rate. Can't recommend any, since I use game audio middleware for that kind of purposes.
I've done lots of gear sounds and this is how I usually do it.
Answer: Sauli's way sounds spot on! I've never done a gear sound effect before myself but if you had to record it yourself, maybe space some bricks out and use a shovel and drag it along so it hits each brick in succession. Random idea I just thought of and may or may not work at all.
Answer: I would add, for grinding to a halt: the shaft component of the sound might screech, groan, shudder, go down in pitch, or otherwise respond to the changing force, while the clanks of the teeth will slow down and stop.
Are the gears visible on stage? This is something you'll want to set aside tech time to practice the sync if so.
Good luck, sounds like fun!
Answer: There is one possibility for a field recording that, if successful, would be very easy. Most overhead roll-up garage doors (on commercial warehouses, not residential) have a manual override mechanism: a chain that runs through several gears and pulleys. Affix a contact mic (or two) to the chain and hoist away. Easy to control rate, and the door panel itself usually squeaks and grinds as it lowers. Very complex and rich soundscape.


How to track and manage project progress & opportunities?

Question: I am trying to manage project progress; what is the best way to track and manage project progress? As the project progresses, how does one recognize, anticipate and track alternative possibilities?
Comment: This site does not recommend tools.  But the manner in which you asked this question suggests you're missing something even more fundamental: project management know how.  All tools come with pluses and minuses and everyone has an opinion of which is better, but in reality the tool is quite inconsequential when compared to the basics of PM knowledge.  I think you need to ask questions around that.
Comment: Can you add more specifics to your question? What is it you want to know about your project and what kinds of alternative possibilities are you on the lookout for?
Answer: And while I wouldn't recommend using Traditional Development (Waterfall), if you do then you want to pull on the Project Management Body of Knowledge (PMBoK). Chapter 6 of the PMBoK covers Project Time Management.
Earned Value is a common one used in old style projects.
Comment: You can used EV with agile.
Comment: True, you can, I wouldn't typically. There are better measures for agile projects.
Answer: I would add:

The important thing is to have a way to track all the details you need, in order to get to completion.
Make sure to update your tracking frequently (could be every day, if not every few hours, depending on your type of project). Having a tracking system doesn't help if it's not up-to-date.

Once you have all the details tracked and up-to-date you should be able to see if you're heading towards your expected result or if you want to change anything.
If you're not technical enough, then have periodic meetings with key players to review the project status.
Don't use a tool/methodology you don't understand. You cannot "practice" and manage at the same time. At the very least, run in parallel; use the new tool but also a system you understand, so that you can understand what is happening at any time.
Comment: To be more specific, "track all the details you need, and nothing more".
Useless data takes work to be gather and are increase the risk of the team giving up progress tracking.
Answer: The tools you will use depends on the level of granularity you want to track.
For short periods (1-4 weeks (sprint in Scrum)), you can use Burndown and Burnup charts. The first one measures your progress against a planned scope; the second one measures your progress against the current scope in a given time.
For longer times, in order to measure how well and smoothly a team is going, you can use Cycle Time and Velocity. For forcasting project completion and addition work added during the project impact, you can use Cumulative Flow Diagram.


Best way to hide tile edge *and* hardie board edge?

Question: My googlefu may be off, but I cannot find what I'm looking for...  I'm installing a backsplash using 3/8 inch thick marble.  The tile will be set on 1/4 inch backer board (didn't want to demo to the studs, and the wall surface is not suitable).
The total thickness of backer->thinset->tile is about 3/4 inch.  There are a couple of spots where I need to hide the edges of the backer+thinset+tile assembly.  I would like to use a brushed aluminum trim piece to accomplish this, but cannot find anything suitable.  All the Schluter trim pieces seem to be L-shaped which works fine for hiding only the tile edge or the backer (depending on which way your orient the L) because they do not appear to make 3/4 inch wide L-shaped trim that I'd need to hide everything.  I suppose what I need is a T-shaped trim with a 1/4 inch hide on one side, and 1/2 inch on the other.  Anyone know a source for such a thing?
I'm toying with the idea of just using the trim that is available to hide just the backer board.  Then maybe just use white caulk along the sides of the tile to hide the thinset layer...  Anyone ever do that and how does it look?  Would it be difficult to achieve something decent looking?
(Please note: bullnose for this particular tile is not available and I don't want to fabricate my own.  Also, we don't care for the look of quarter round finish.)
Answer: I think you are asking for "Reno-T"  Schluter.

However, you might want to consider looking for 'bull-nosed' versions of your current tile:

or matching some v-cap, deco mold, granada shaped 'chair rail' as trim:


Roland TR-808 TO Roland Boutique JU-06

Question: Just to reinterate the last question as to using the 808 with the Ju-06. What kind of lead jacks would i use to connect them ? I take it, it would be a 1/4" stereo jack from 808 output to 3.5mm stereo jack to input of JU-06 ? Or mono jacks ? Slightly confused !!
Answer: The 808 is mono, so just a regular TS 1/4" plug will then go to what I will assume is a mono, TS 3.5mm plug for the input of the JU-06.  If it sounds funky (comb-filtering) or no sound but works if you pull the 3.5mm out halfway then use a TRS 3.5mm (stereo).  There are premade 1/4" to 3.5mm readily available.  Too bad RadioShack doesn't exist anymore so you could string 5 adapters together!

Roland TR-808 TO Roland Boutique JU-06


Showing a singular integral operator takes Hölder continuous functions to Hölder continuous functions of the same order

Question: I would like to show the following function is $\gamma$-Hölder continuous. Said function $F:\mathbb{R}^n \rightarrow \mathbb{R}$ is defined by a singular integral operator of convolution type as follows (for some fixed $i$ and $j$)
$$
F(x)= \lim_{\epsilon \rightarrow 0} \int_{|x-y| \geq \epsilon}  \partial_k \partial_j k_i(x-y) \left(Y_k(x)- Y_k(y) \right)f(y)dy
$$
where $f \in C_c^{\gamma}(\mathbb{R}^n)$ (ie a compactly supported $\gamma$-Hölder continuous function) and the integral kernel $k:\mathbb{R}^n\backslash \lbrace \vec{0} \rbrace \rightarrow \mathbb{R}^n$ is defined as
\begin{equation}
k_i(x) =\frac{x_i}{|x|^n}
\end{equation}
Note $k$ is the derivative of the Newtonian kernel up to a constant factor. In addition, we have $Y: \mathbb{R}^n \rightarrow \mathbb{R}^n$ such that
$$
\| \nabla Y \|_{1, \gamma} = |Y(0)|+\|\nabla Y\|_0 + |\nabla Y|_{1,\gamma} < \infty
$$
where
$$
|W|_{\gamma} = \sup_{x \neq y} \frac{|W(x)-W(y)|}{|x-y|^{\gamma}}
$$
is the $\gamma$-Hölder seminorm. Note $Y$ has bounded $\gamma$-Hölder continuous derivatives.
-----------------------------Attempt at Solution -------------------------------------
In attempting to prove the $\gamma$-Holder continuity of $F$, my strategy thus far has involved expanding $Y$ as a first order Taylor polynomial as follows
$$
Y_k(y)=Y_k(x) + \partial_l Y_k(x)(y_l-x_l) +(y_l-x_l)\int_0^1 \left( \partial_l Y_k(x+t(y-x)) -\partial_l Y_k(x) \right)dt
$$
I'll denote the remainder term as $R_x(y)$. Note $|R_{x}(y)| \leq C|y-x|^{1+\gamma}$.
So I write
\begin{eqnarray}
&& F(x+h)-F(x)=\lim_{\epsilon \rightarrow 0} \bigg( \int_{|x+h-y|\geq \epsilon} \partial_k \partial_j k_i(x+h-y)\partial_lY(x+h)(x_l+h_l-y_l)f(y)dy \\
&&- \ \int_{|x-y|\geq \epsilon} \partial_k \partial_j k_i(x-y)\partial_lY(x)(x_l+h_l-y_l)f(y)dy -\int_{|x+h-y|\geq \epsilon} \partial_k \partial_j k_i(x+h-y)\partial_lR_{x+h}(y)f(y)dy \\
&& + \int_{|x-y|\geq \epsilon} \partial_k \partial_j k_i(x-y)\partial_lR_{x}(y)f(y)dy \bigg)
\end{eqnarray}
I can show the absolute value of the difference of the first two terms is bounded by $C|h|^{\gamma}$. This is done by first observing that $\partial_j k_i$ is the integral kernel of a singular integral operator (ie it is smooth everywhere but $\vec{0}$, is homogeneous of degree $-n$, and has mean value on the unit sphere). In fact, this mean-value property extends as follows:
\begin{equation}
\int_{|x|=1}x^{\beta}D^{\alpha}k_i(x)dS=0 \quad \Rightarrow \int_{r \leq |x|\leq R} x^{\beta}D^{\alpha}k_i(x) dx = 0
\end{equation}
for any multi-indices $\alpha$ and $\beta$ such that $|\alpha|=|\beta|+1$. In particular terms of the form
\begin{equation}
C\int_{r \leq |x|\leq R} x_l \partial_k\partial_jk_i(x) dx = 0
\end{equation}
for C constant can be added freely.
The first two terms can be dealt with (roughly, this is jut a sketch) in two steps. The first is
\begin{eqnarray}
&& \int_{ |h|>|x+h-y|\geq \epsilon} \partial_k \partial_j k_i(x+h-y)\partial_lY(x+h)(x_l+h_l-y_l)f(y)dy \\
&& = \int_{ |h|>|x+h-y|\geq \epsilon} \partial_k \partial_j k_i(x+h-y)\partial_lY(x+h)(x_l+h_l-y_l)\left(f(y)-f(x) \right) dy \leq c|f|_{\gamma}|h|^{\gamma}
\end{eqnarray}
where we made use of the $\gamma$-Holder continuity of $f$ and the mean-value property of the kernel by adding a zero term. The second is
\begin{eqnarray}
&&  \int_{ |x+h-y|\geq|h|,|x-y|\geq 2|h|} \Big( \partial_k \partial_j k_i(x+h-y)(x_l+h_l-y_l) - \partial_k \partial_j k_i(x-y)(x_l-y_l) \Big)\left(f(y)-f(x+h) \right) dy \\
&& \leq c|f|_{\gamma}|h|^{\gamma}
\end{eqnarray}
through the use of the mean-value theorem on the integral kernel $\partial_k \partial_j k_i$ and the further addition of zero terms.
--------------- Remaining Problems -----------------
I have trouble bounding the difference of the remainder terms by $C|h|^{\gamma}$. Following a similar method as above I can bound them by $C|h|^{\xi}$ for $\xi < \gamma$. But perhaps there is a more general theorem I could use? I'd also be interested in textbook recommendations covering similar subject matter.
Answer: This is covered in Gilbarg-Trudinger, and I think it can be put under the heading "potential theory approach to Schauder estimates". "Kellog's theorem" might reveal something too. It is closely related to the Calderon-Zygmund theory of singular integral operators, although the latter is typically concerned with $L^p$ spaces.


Why is beta thalassemia major not lethal while alpha thalassemia with loss of all 4 genes lethal?

Question: So why is beta thalassemia major with two B0 alleles not fatal in utero (despite the hemoglobin not having any B chains), while alpha thalassemia with deletion of all 4 genes encoding for the alpha chain fatal? Is the alpha chain more important than the beta chain?
Answer: This has to do with the fact that fetal hemoglobin (HbF) isn't made of the same chains as adult hemoglobin. The latter comes with 2 alpha chains and 2 beta chains while the main fetal hemoglobin is made of 2 alpha chains and 2 gamma chains. Hence any disease affecting the quality or quantity of beta chains won't have nearly as much impact on a fetus as it does on an adult.
Reference: https://www.uptodate.com/contents/fetal-hemoglobin-hemoglobin-f-in-health-and-disease
Answer: In essence, yes, the alpha chain is more important than the beta chain, because there are alternative forms of hemoglobin that can deliver oxygen without beta chains, but the hemoglobin forms without alpha chains cannot.
Hemoglobin has a bunch of different forms, depending on which four globin chains make up the protein. While there are even more, here's an overview of the most important forms:

Hemoglobin A is α2β2, this is the normal form, and in adults this makes up 95% of our hemoglobin.
Hemoglobin A2 is α2δ2, with 2 delta chains instead of beta chains. It normally makes up about 2-3% of hemoglobin, and its properties are nearly identical to HbA.
Hemoglobin F is α2γ2, with 2 gamma chains instead of beta chains. This is the primary form in utero, because it has a higher affinity for oxygen, and thus can extract oxygen from the maternal circulation. It normally decreases after birth, and makes up <1% of adult hemoglobin.
Hemoglobin H (β4) and Hemoglobin Bart's (γ4) are defective forms of hemoglobin that occur without alpha chains. Both of these are unstable molecules, and are poor at delivering oxygen because their affinity for oxygen is too high (not allowing it to be released in the tissues).

What you'll notice from the above is that there are functional hemoglobin variants that don't have beta chains, but no functional variants without alpha chains.
If someone has beta thalassemia major, with loss of both β alleles, the body compensates by ramping up production of HbA2 (with delta chains) and HbF (with gamma chains), which compensate for not having HbA. That's not to say that everything is okay... it's still a very serious condition, and usually progresses to death before age 20 if untreated. But, the hemoglobin variants are sufficient enough to allow people to live.
If someone loses all 4 alpha alleles, the only hemoglobin they produce is Hb Bart's, which isn't functional. There are no alternatives to the alpha chain like there are with beta thalassemia, so there's no mechanism to compensate for this loss. Because forming HbF isn't possible without alpha alleles, this condition is fatal in utero.


How do I remove the top sash of a medium size new double glazed window?

Question: How do I remove the top sash of my new double glazed window to wash the outside (while remaining inside the house). I was able to lift the bottom and lean it inside the room and thoroughly clean it then push it back into place. I can not see how to pull the top section inside to wash it. (not possible to wash it outside, prickly bushes and I wouldn't know how to remove the tall screen).
Comment: call the manufacture
Answer: Find the Mechanism
There is usually a release mechanism along the top edge or the bottom edge of the upper sash that allows it to tilt in.
Get the Lower Sash out of the Way
The trick is moving the inner, lower sash out of the way.  That is done by releasing the mechanism on the lower sash, tilting it inward and lowering it toward the sill.
Tilt the Upper Sash in
You then slightly lower the top sash, which is no longer blocked by the lower sash.  You can then release the mechanism on the top sash and tilt it inward, either up or down depending on the position of the mechanism.


Gaps in an 'Eiruv

Question: Under what circumstances may there be gaps in an 'Eiruv enclosure: how many can there be, and how large can they be?
Answer: An opening is not considered a breach if it is either

less or equal to 10 amos or (SA OC 362:9)
is set up as an opening with (minimally) 2 posts and a crossbar or as a gated structure (OC 362:11)

However, the entire enclosure must not be mostly open (OC 362:9) (with the exception of eiruvei tzuras hapesach, see below) and the walls must be defined (you cannot have an entire wall missing just because it's less than 10).
According to the Rosh, if the enclosure is surrounding multiple living quarters where many openings are common, the community may surround their area with posts and crossbars even if the area will be mostly open.  The Rambam only allows posts and crossbars if the area is mostly closed (OC 362:10).
I had lived in a gated community which had an electronic gate at the enterance, but the opening was larger than 10 and it had no crossbar.  My Rav told me that the gate is a tzuras hapesach.  The crossbar just makes it a tzuras hapesach even without a gate.
Comment: Is the gate closed sometimes or is it always open?
Comment: The gate automatically closes unless electronically opened.  My Rav considered it unbreached even at the time that the gate was open.
Comment: You should know, I didn't mention the Rambam in my answer because Igrot Moshe OC II 83 seems to say that minhag haolam is not like him.
Comment: I f the less than 10 amah break is on a CORNER it can still invalidate (be considered a breach in) the eruv
Answer: If the majority of the enclosure is gaps, it is invalid unless each gap is less than 3 tefachim wide. (OC 362:8)
If the total amount of wall is greater than or equal to the total amount of gaps, it is kosher provided that there is no gap of more than 10 amot which is not closed using a tzurat hapetach (lit: form of an opening, it is two vertical posts with a horizontal one across representing a doorway). If the area enclosed is not residential but is rural, then a tzurat hapetach is only effective (to consider it closed for calculations of the majority) for gaps below 10 amot. (OC 362:9-10)

Gaps in an 'Eiruv


Why do we take antibiotics if our immune system already produces them?

Question: Why do we take antibiotics if our immune system already produces them? Is it because our body doesnt make enough or the specific complementary antibody to fit with the antigen?
Comment: Perhaps you could respond to the answers — or this comment — to clarify whether you were really confusing antibiotics and antibodies, or whether you were interested in "innate immunity".
Answer: Since people and animals routinely get sick, it is obvious that our immune system (which includes but isn't limited to antibodies) doesn't always protect against pathogens.  There are many reasons for this, far too many to summarize here, but one common reason is that it takes several days for the adaptive part of the immune system (which includes antibodies, among other things) to gear up and control an infection. Therefore, early treatment with antibiotics can help limit an infection before the immune system is fully engaged.
Pathogenic bacteria are often resistant to immunity in many ways as well; that's one of the adaptations that makes them pathogenic. That means that even later in an infection, antibiotics can supplement the immune response and help eliminate bacteria.  Note that many antibiotics require a functional immune system to be completely effective.
Answer: I assume from your question (and your pseudonym) that you are confused by terminology. Our adaptive immune system does not make antibiotics, it makes antibodies. Antibiotics are small molecules that interfere with bacterial metabolism. Antibodies are proteins that recognise foreign macromolecules. (You could regard both as "anti-bacterials" — perhaps this is what you were thinking of — but the immune system is not restricted to recognizing bacteria.)
We take antibiotics when we have an infection from bacteria that have evaded the immune system.
Comment: So sulfonamides were not initially called antibiotics, but antibacterial agents because they were synthetic.
Comment: This isn't true. We do make antimicrobial peptides, which are essentially antibiotics.
Comment: @MattDMo The immune system makes antibiotics? I answered the question at the level it was asked. We are dealing with a first poster who is unfamiliar with scientific terms. We do not help him or anyone else by muddying our answers with esotericism.
Comment: Questions are simply a vehicle for producing answers. Remember, the point of Stack Exchange is not to answer an OP's specific question *just* for the OP, it is to produce a lasting repository of knowledge. If you're going to make an answer, make it an *accurate, complete* answer. Besides, antimicrobial peptides (AMPs) are not "esoteric" - they're a vital part of the innate immune system.
Comment: @mattdmo To be strictly fair, David is correct since the original definition of an antibiotic was that it was s substance made by bacteria and fungi. But the internet and non scientific use, progress, and synthetic antibacterial agents has invalidated the original definition.
Comment: Methinks thou dost protest too much. But if I am wrong, retitle the question  something like immunity and antibiotics, rewrite it, and supply your answer. Because if you don't nobody will benefit from your contribution as they'll assume that it's a naive question that really should be pulled.
Comment: The op isn't involved in the discussion
Comment: @GrahamChiu  Op?
Comment: I give a short straightforward answer to an obvious misunderstanding and someone marks it down. OK.I'll make it less comprehensible by qualifying it, then will that person mark me up again. In my dreams! What's wrong with you guys?
Answer: We take antibiotics when our own immune system is insufficient to control infections. We do make antibiotics as localized defence systems

Defensins and cathelicidins belong to antimicrobial peptides (AMP), called also the natural antibiotics. They are found in Prokaryotes and Eukaryotes, also are synthesized in plants. These molecules were described in bacteria, invertebrates, vertebrates, also in mammals including humans.

But clearly these  can be overwhelmed by bacteria resistant to their action, or by overwhelming rates of reproduction of invading bacteria
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3487008/
Our mammalian physiology has further evolved the innate immune system, and the adaptive immune system to cope with invasions that bypass these simple non-adaptive molecular defenses.
Comment: Please provide a citation for your quote.


How do I diagnose weak water flow from tub faucet and shower?

Question: I have a shower that has very low flow from the hot and cold water and also from the shower when you turn the valve to switch it to the shower.  All of the other fixtures in the house have strong flow including the sink in the same bathroom.  Unfortunately there isn't an easy way to get access behind the shower (tile on both sides of the wall).  Does this sound like something that could be caused by bad cartridges?  What about some kind of corrosion built up in the pipes?  How can I go about diagnosing this without ripping open the walls?
Comment: Has the flow always been low, or has it gotten worse over time? Where are you from? Some places have water saving plans in place, so there could be pressure reducing devices in place (that cannot be removed).
Comment: What kind of fixture is it? Many fixtures have components that are serviceable from in front, after removing a handle and faceplate. If that applies to you, you might try taking out the valve cartridge and soaking it in vinegar to dissolve any mineral build-up.
Comment: It is a spare bath so doesn't get much use.  It has been slow at least for the last 10 years.  The fixture is probably 30 years old (same age as the other bath that isn't slow) so I wouldn't expect a water saving device to be to blame.
Comment: Do you have hard water (lots of minerals in the water)? Over time, the minerals can build and block pipes and valves, especially hot water pipes.
Answer: Sometimes there is a screen in the shower head that can collect mineral deposits over time. They look kind of like white beads. Try removing the shower head and see if any more water comes out.
Comment: I am careful replacing shower heads, because some of the new ones have severe water saver washers that are hard or impossible to remove, and I end up with a dribbly shower. (I live where there is plenty of fresh water.)
Comment: Or just replace the entire shower head.  They are quite cheap and sometimes it's more than the mesh that clogs.  Alternatively soak the entire shower head in a bucket with 20% CLR.
Answer: Remove the shower head, then try the shower.  If you get full flow, replace the shower head.  If you get low flow, probably there is a buildup of corrosion inside the pipes.  We have replaced pipes recently and the amount of crud that can build up is unbelievable (sorry I did not take photos).
Comment: The faucet in the tub does the same thing.  Do you think the shower portion could be affecting the faucet part as well?
Comment: @Dougman: if you have a single set of faucet valves with a diverter, you could get lucky and be suffering from buildup in the valves.  But the buildup is probably in the pipes.  I'd start hunting for some kind of hidden plumbing access, possibly from the hall outside the bathroom, because you're going to have to replace something inaccessible.
Answer: If you have a shutoff valve feeding that bath or that shower, I would check:

Is it on all the way?
If it is, you can sometimes disassemble it in place (of course turn the house water off first).  The typical valves for this application are gate valves, which can get a lot of gunk in them.  Disassembly will also let you see if the problem is before or after the valve (with valve disassembled, turn on house water for a second; Did you get good flow or not?).
If you disassemble a gate valve don't be surprised if you need a new stem seal (the seal that keeps it from leaking around the shaft).


Why do we say "Qué hora es" instead of "Qué hora está"?

Question: I was taught that está is used in certain contexts meaning a temporary state (like emotion). Isn't "time" always temporary in that it is constantly changing? If so, why don't we use está instead of es?
Comment: That rule is not always true, I'd say. For instance *está bien bonita* or  *estás bien idiota* both are not really  'temporary states'. And I wouldn't close the question, it's a good one.
Comment: Why is "está bien bonita" not a temporary state? I understand "está bien bonita" as "she looks good now" (in that dress, with that make-up, etc). If I want to say that she is  beautiful (all the time, regardless of clothes and make-up), I'd say "es bien hermosa".
Answer: This answer has grown enough to require an outline. Here it is:

"¿Qué hora es?" versus "¿Qué hora está?"*
"estar" versus "ser"
"a state" versus "an attribute"
"¿Qué hora es?" versus "¿Qué horas son?"

1. "¿Qué hora es?" versus "¿Qué hora está?"*
I feel tempted, like others, to write that Spanish uses the verb "ser" to ask the time, simply, because that's the standard usage. One could imagine, like you have, that the "estar" verb should be used instead. Here, I'm going to propose an explanation based on the usage of verbs "ser" and "estar".
In Sections 2 and 3, I've described the difference in usage between "ser" and "estar". The main idea in that description is that "estar" is used to talk about a state that has changed or that it is expected to change in the future. If you think of "time" as being a clock, as in "What is the time displayed on the clock?", then you could argue that the use of "estar" is more appropriate.
However, when we ask for the time, we are only interested in knowing what the time is. We are not interested in clarifying that we know that the answer is for a specific time. Doing so would feel redundant.
If we ask:

¿Qué hora es?

we are simply saying we want to know the time. But if it were correct to ask:

¿Qué hora está?

we would be saying not only that we want to know the time, but also that the answer is going to change in the future. Since we don't do these mental acrobatics, that's why we use the verb "ser".

2. "estar" versus "ser"
I reckon "temporary" isn't the best word to describe the usage of verb "estar". I would rephrase this rule of thumb as:

"estar" is used to express a state of someone or something. For example:

Eva está mala (Eva is sick)
El aceite ya está caliente (The oil is already hot)

"ser" is used to express an attribute of someone or something. For example:

Eva es mala (Eva is bad)
Estas guindillas son muy picantes (These chilis are very hot)

3. "a state" versus "an attribute"
One of the comments to this answer has made realise that distinguishing "state" and "attribute" in the context of this answer is as difficult as distinguising "ser" and "estar".
In the section above, "attribute" is simply used to mean a quality of someone or a property of something. (Note that I'm being careful here and I'm avoiding to say whether this quality or property is permanent or not).
On the other hand, "state" is a quality of someone or a property of something at a specific time. Thus, when we choose to use the verb "estar", we are making the point that we are talking about a state that has changed or that it would be expected to change in the future.

4. "¿Qué hora es?" versus "¿Qué horas son?"
The diccionario panhispánico de dudas explains that, in the educated general register, the question "what time is it?" is asked as "¿Qué hora es?". In this form, "hora" does not mean "hour" but "the time of the day".
This dictionary also explains that the form "¿Qué horas son?", although less recommendable, is also admissible. It is found in some American countries, specially in the popular register.
Another common use of "¿Qué horas son?", cited in this dictionary, is to express disapproval. For example:

¿Qué horas son estas de llegar a casa? (What time is this to come back home?)
Comment: seems almost necesary to add this: "¿A qué hora estamos?"
Comment: @BrianH. *"¿A qué hora estamos?"* means *"At what time are we in?"*. This is an example of a truncated phrase. Depending on the context, the question could be completed as: *"¿A qué hora estamos trabajando?"*, *"¿A qué hora estamos atendiendo al público?"*, ... See other examples of phrases with *"estar"* [here](http://lema.rae.es/dpd/?key=estar).
Answer: The verbs ser and estar, one of the most complex things to explain, since in english estar = to be and ser = to be
SER: to be, as in "To be or not to be", to have an intrinsic quality.
Examples: be a good boy/sé un buen chico. she is a good girl/es una chica buena
ESTAR: to be someplace, to feel some way, to have some relative/external quality.
Examples: she is good looking/está buena. He is busy/está ocupado. He is in Europe. Está en Europa.
Since the time of the day is an intrinsic property of the day, and not some state, place or external/relative property, then you ask
¿Qué hora es?
And please, never, and I mean never, use ¿Qué horas son? or worst yet ¿Qué hora son? unless you want to sound like an uneducated/ignorant person.
The time of the day at any given infinitesimal instant is only one for the exact point where you are standing, so you ask for the time in singular, not in plural, no matter what time of the day it is, 10, 12 or 1.
The only acceptable instance where you can use "que horas son" is when you are generalizing about a certain time period of the day and complaining/asking about people doing certain things:
¿Qué horas son estas de llegar? Literally: What hours are these to arrive?
Comment: -1 I don't know why "Qué horas son?" should sound ignorant or uneducated. I think it's a regional difference. We say "Son las 3", so why not "Qué horas son?"
Comment: I have always known it to be `Qué horas son`.  When I was learning Spanish in primary school, the teacher would teach us `Qué hora es`, while my Native Mexican friends would continue to ask `Qué horas son`, which would also be slurred into a 3-syllable word.  `Kio-rah-son`
Answer: Ser is always used for temporal clauses, phrases about the time.
It's actually more accurate to ask Que horas son (in plural form) instead, because you have an 11 out of 12 chance of it being grammatically correct.  Que hora es carries a bit of hope with it I suppose you could say.  It would be like asking someone It's not past 1 yet is it?
Regardless, ser goes with time always, because one point in time and space cannot continue, or else we could travel into the future.
It didn't used to be 5 o'clock yesterday, it was 5 o'clock yesterday for a whole minute.
There very first rule of ser on this page
http://spanishobsessed.com/spanish-grammar/ser-vs-estar/
says that Ser is used for time.
Comment: http://spanish.stackexchange.com/questions/694/is-que-hora-es-or-que-horas-son-preferred


Why are engines mounted so that torque goes sideways?

Question: When I see someone rev the engine on their car, it is typical for one side to drop a little in relation to the other.  I understand that this is due to the torque of the engine.  Why isn't the engine positioned so that the torque pushes down on the wheels that are providing the pull, as that would seem to result in better traction?
Answer: If you think about it, the torque actually does help. The reason for this is since the engine (in most cases) spins clockwise  (looking from the grill backwards), the affected torque is transmitted CCW making the vehicle "roll" opposite of the engine spin. The driveshaft will (in the forward gears) also spin CW. As it spins, the torque will naturally lift the right side of the axle (as realized from the driver's seat) yet the torque will be pushing the body of the vehicle down on the same side. This behavior counteracts the torque and helps plant the rear wheel which is being lifted.
It doesn't mean much in a front wheel drive car, as the engine is transverse instead of longitudinal with most RWD vehicles. There's not much body torque which will occur there.
Comment: @Paulster: "horizontal"? Don't you mean transverse?
Comment: @Paulster2 your last sentence is what I pointed out : "They are in most front wheel drive cars - started with the mini designed by Sir Alec Issigonis."  however, I think you didn't meant to use "horizontal"... Also my answer has not been appreciated or, probably, understood so deleted...
Comment: @tlhlngan "horizonal" works for me.  I had to look up what was meant by "transverse".
Answer: Huh?  That's your question, really?  The engine has a spinning crankshaft. You can design the system to spin clockwise or counterclockwise. Pick one.
You can mount an engine with its crankshaft oriented in alignment with vehicle centerline or transverse. Pick one.
Note that the majority of screw fasteners are designed to tighten when turned clockwise (and that tooling is very expensive). Re-evaluate the two decisions you made above analyzing the fasteners in your system.
Now you tell me what happens when you apply engine power to your system.  It's very predictable.
Note there are some interesting design alternatives here. An example is a dual engine, dual propellor shaft boat.  One engine spins clockwise (CW) the other spins counter clockwise (CCW). You have to be careful with the CCW engine as some of the fasteners used need to be left hand threads.
Comment: There is one more engine orientation you didn't mention ... *vertical*. Since you mention boats, most outboard boat motors are vertically oriented with the crankshaft pointing up and down.
Answer: It is as Paulster wrote, the torque usually is canceled out, though I'm not sure if he got it correctly.
When a motor spins clockwise, it applies clockwise torque to the shaft and, as Newton said, encounters a counter-clockwise torque which it applies to the frame.
The interesting point is, that the shaft applies the exactly same clockwise torque to the body of the next gearbox, which in turn puts this torque on the frame, canceling out the torque of the motor body. Yet, this might twist the frame a little, but since there is no net torque, this will not cause the car to roll.
Of course, the gearbox will apply a second torque to the frame contrary to the rotation direction of the output shaft, but then, there is the differential, which again behaves like the gearbox. Finally, the torque is applied to the street by the wheels, and since the car is not tied to the street, this is the point where torque is converted into movement of the frame.
Now, this is not absolutely correct. If the car accelerates, the rotating speed of all the rotating parts accelerates, too, and this of course "consumes" some torque. This definitely puts toque on the frame which is not canceled out, and could let the car roll. But most of the torque is lead to the wheels, and only a small fraction is needed to accelerate the rotating parts.
This is a little different when the clutch is not engaged and the motor can rev up quite fast, and then, you can notice that the car might to a roll movement.
Further more: Most rear and 4wd driven cars have the motors built in laterally, while most front driven cars have the motor built in transversally. Otherwise, another gear to change the direction of the output shaft by 90° would be needed, which means additional losses.
On front driven cars, the motor sits about over the front axles, which means any torque applied to the frame by the motor would not cause an increase or decrease of "weight" on the front wheels, only on the rear wheels. And then, well, lets assume a torque of 200Nm and 2m distance to the rear wheels, this gives a "weight" of 10kg, which is about nothing (and doesn't matter, since that wheels are not driven)

A little off-topic:
Torque applied to the frame is a topic for propeller-driven aircraft, since they put the air into a swirling motion, i.e. apply torque to the air. Plus, the motors can make up a large fraction of the entire aircraft weight. On many two-engine aircraft, the one motor spins clockwise, while the other spins counter-clockwise. For example, see this PA-42, where the mirrored propellers indicate a different direction of rotation for both motors.


If the IRS asks for a proof for a medical expenditure, can we provide a scan, or do we have to provide the original receipts?

Question: In the United States, one can deduct part of the expenses a taxpayer paid for medical and dental care for themselves, their spouse, and their dependents. In case the IRS asks for a proof, are scans of receipts valid? Or does one have to provide the original receipt?
Comment: Oh goodness, I thought you were referring to scans like X-rays.
Comment: @quid and blood samples :)
Comment: The IRS cares about receipts.
Comment: @quid so are scans of receipt are not valid proofs?
Answer: A scan of receipt is more than acceptable. Keep in mind that all of society has gone digital. Many of my receipts never existed in hard copy form.
The computer in the doctors office is used to send the information to the insurance company, who then generates the Explanation of Benefits. The EOB is then posted to the insurance company website where I can view it or download it. Then I send the money from my Health Savings Account website to the doctor's office computer.
There never was an original bill. In the rare case where the workflow doesn't follow that pattern, I don't send original receipts to the insurance company I send them electronically.
Comment: The question is not about what is logical or obvious, but what the *IRS* accepts. That's not necessarily the same.
Comment: @Aganju - the IRS has accepted digital copies of receipts for expense reports for most of the 21st century, at least. And they prefer digital copies of most other documents, too (every return, for example, is efile processed - even the paper ones (they're entered by seasonal employees and processed electronically afterwards)).


Ubuntu 12.10 not rebooting after hard shutdown. Cannot access BIOS

Question: Ubuntu 12.10 not rebooting after hard shutdown.
After I suspended my laptop, I tried to wake it up but it did not, when I pressed any of its keys. So I did a forced shutdown. Now I am not able to reboot it after pressing the power button.
Only the numlock and capslock lights blink.
Not able to access BIOS also.
Tried to boot through LiveCD, but I think it is not at the top of the Boot device order.
Also, my laptop heats up normally. When I remove/insert DVD in the DVD-drive, it makes a normal sound after inserting the CD, which means system is working. But there is no display on the screen.
Please help.
System Details: hp pavilion dv6 2005ax
AMD Processor, ATI RADEON graphics card, 4gb RAM (link below for complete specifications)
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01869762&tmp_task=prodinfoCategory&cc=us&dlc=en&lc=en&product=4039727
Answer: That sounds like a hardware problem to me.  Check this out: HP forums


Relationship between default risk and value of bond

Question: In particular Mortgage-backed securities. I've read from a book that underestimating the risk of default is tantamount to overestimating the value of the bond, giving rise to a bubble in MBS. I'm unclear of how that works.
My guess is that since the probability of default risk is low, thus banks give out lower coupon rates. Investors buy MBS up because they are safer, demand for MBS increase, price of these MBS pushed up.
Answer:
[...] underestimating the risk of default is tantamount to overestimating the value of the bond.

The reason behind this is simply due to how bonds are priced.
$$
P = \sum_{n=1}^N \frac{C + M[{I_{n=N}}]}{(1+i)^n}
$$
Where $i$ is the contractual interest rate, $C$ is the coupon payment, $N$ is the number of payments, $I_{n=N}$ is an indicator function taking the value of $1$ when $n=N$ is $true$ or $0$ otherwise, $P$ is the market price of the bond, $M$ is the value of the bond at maturity.
When $i$ goes up, $P$ goes down and vice versa, see

$\rightarrow$ if $i$ is underestimated, $P$ will be overestimated. Indeed, it is $i$ which, via a premium, internalizes the default risk consideration and is an increasing quantity of it.
Answer: I like @keepAlive's answer, but I thought it might be more accessible to discuss this question in a simpler setting.
Imagine that a \$100 face amount bond that lasts for one period. If the bond does not default than at the end of the period then it pays a coupon $c$ and returns the face amount. The bond defaults with probability $P_{d}$ and then returns zero. Assume the appropriate discount rate is $r$. What is this bond worth?
$$ P_{bond} = \frac{0}{(1+r)^0} + (1- P_{d})\cdot \frac{100+c}{(1+r)^1} + (P_{d})\cdot \frac{0}{(1+r)^1} $$
$$ = (1- P_{d})\cdot \frac{100+c}{(1+r)} $$
But assume that you are mistaken, and you estimate a default rate that is too small (that is $\hat{P}_{d} <  P_{d}$). You should infer the bond is worth:
$$ \hat{P}_{bond} = (1- \hat{P}_{d})\cdot \frac{100+c}{(1+r)}$$
Which implies the difference in price is:
$$ \hat{P}_{bond} - P_{bond} = (1- \hat{P}_{d})\cdot \frac{100+c}{(1+r)} - (1- P_{d})\cdot \frac{100+c}{(1+r)}$$
$$ = (P_{d} - \hat{P}_{d})\cdot \frac{100+c}{(1+r)}$$, which by construction is positive. Therefore, assuming that the default rate is too low implies that you will overestimate the value of the bond all other things equal (even if you get the other parameters correct).


Are the stars in all galaxies orbitting around a middle?

Question: In our Milkyway all the stars are orbitting around the black hole in the center. But what is the cause it this rotation and are there galaxies where the stars aren't orbitting a center?
Answer: Stars aren't really orbiting the center of a galaxy, as much as they're orbiting the gravitational potential of the galaxy. The galaxy doesn't need to have a black hole in the center for the stars to orbit, and even if it does (which in fact it does most of the time), the black hole does not dominate the gravitational potential, except in the most central part (see sphere of influence of a black hole).
All matter in the galaxy contributes to the gravitational potential, but since dark matter comprises 5/6 of the mass, this is the most important contributor. Only in the hypothetical case of a perfectly symmetrical distribution of masses, would the black hole and the center of rotation coincide. And since the paths of the stars are ellipses and not perfect circles, the center of the potential will not lie in the center of their orbits, but in one of the focal points. Furthermore, galaxies are dynamical and the potential continually changes, in turn changing the exact orbit of a star.
Galaxies form due to the collapse of a dark matter halo, and the gas that follows  along. Such a halo will in general have a non-zero angular momentum, which is partially conserved during the collapse (they do lose a significant amount, for instance through minor and major merging; see e.g. D'Onghia et al. 2006).
As in the case of a forming star, a forming planet, an ice skater, or you on an office chair, reducing the radius means increasing orbital speed. This is the origin of the rotation.
Comment: @WayfaringStranger: Yes, just as we orbit the place where the Sun was 8 minutes ago. To a high degree of precision, however, that effect can usually be safely ignored, as the dynamical timescale of a galaxy ($\sim\sqrt{R^3/GM}$) is much larger than the light crossing time ($\sim R/c$).
Comment: At 100,000 LY across, stars are not going to be orbiting the exact center of mass of the milky way. They'll be orbiting around some weird time average of where the center of mass *was*. Gravity is still thought to travel at speed of light, and galaxy is *big* relative to that.
Comment: The stars in the galaxy NGC 1132 are rotating in all directions how is this possible? Is this also due to the dark matter?
Comment: @Marijn: In general, galaxies can be dynamically either rotation-dominated (like spiral galaxies), or dispersion-dominated (like elliptical galaxies). The latter are probably formed through a major merger of two galaxies, which disturb the system so much as to "destroy" the orbits and let the stars have random orbits. NGC 1131 is an elliptical galaxy. (major mergers don't necessarily result in ellipticals; it depends on a number of factors, including the relative direction of their individual angular momenta).
Comment: @Marijn, if you're not satisfied with the answer, let me know what could make it better.
Answer: The cause of the rotation is that the hydrogen cloud that the galaxy condensed out of had some angular momentum which was conserved as the cloud collapsed into a galaxy.
The stars in a galaxy have to be in orbit around something. (Even if it's just the center of mass of the galaxy.) If they were at rest with respect to the center of mass, they'd fall into it!


Rewrite issues in going from apache to nginx

Question: We have a custom WP site that we are having to migrate from Apache to nginx and while most things are working ok, some big things are not.
For example on our custom plugin our url structure looks like this: domain.com/causes-details/PERMALINK ; PERMALINK is the field we use in the db to populate the cause information. In wordpress that is just a page with no content and a special theme page.
It works fine in apache, it doesn't work at all in nginx. We get a null page.
In the root directory on the apache site there is an .htaccess file that looks like this:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

So I tossed it into a converter http://www.anilcetin.com/convert-apache-htaccess-to-nginx/ and I get
if (-e $request_filename){
    set $rule_0 1;
}
if ($request_filename ~ "-l"){
    set $rule_0 1;
}
if (-d $request_filename){
    set $rule_0 1;
}
if ($rule_0 = "1"){
    #ignored: "-" thing used or unknown variable in regex/rew
}
rewrite ^/.*$ /index.php last;

But that doesn't really fix anything on the site. So without that in there, this is what my nginx config looks like:
server {
    listen 80;
    root /usr/share/nginx/html/domain.com;
    index index.php index.html index.htm;
    server_name domain.com www.domain.com;
    location / {
        try_files $uri $uri/ /index.php?args;
    }
    location ~ /\. { access_log off; log_not_found off; deny all; }
    location ~ ~$ { access_log off; log_not_found off; deny all; }
    location ~ \.php$ {
        try_files $uri $uri/ /index.php?args;
        include fastcgi_params;
        fastcgi_pass php5-fpm-sock;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_intercept_errors on;
    }
}

Answer: Your try_files directives aren't passing arguments through correctly (you're missing the $ for $args. You also shouldn't need a try_files inside the .php block.
location / {
    try_files $uri $uri/ /index.php?$args;
}


Managing duplicate questions

Question: Lately I have been answering a lot of questions about karma.  I have noticed that some of the questions and answers are closely related to each other.  For example, someone gets a different error than somebody else, but the root of the problem is the same, so the answer will be the same.  How can I manage these "duplicate" questions to reduce the amount of repetitious answers on SO without coming across as rude?
Comment: If the error is different, can we really say that it's a duplicate question?
Comment: I've always taken it as duplicate *questions* need to be closed. If the same root issue can present with multiple symptoms, it's not a problem to have multiple questions with the same answer; that lets others with the range of symptoms have a google target. Generally a good answer will speak to the particulars of the question anyway (explaining how the common root cause leads to *this* presentation); I don't know that I've actually seen many "different questions with duplicate answers" on the site.
Comment: @DidierL That's a good point.  However, for something like a karma configuration file, there can be a wide number of errors for the same problem.  For instance, if you leave out library dependencies, it will incrementally throw an error for each library; it complains about one, you add it, and then it complains about another one.  They are the same type of error, but are "different".  I've just seen a lot of questions posed differently for the same problem.  Most of the time it's developers that are new to using Karma in the first place.  I'm happy to help, but just want to reduce duplication.
Answer: Wait until you'll have the Cast Close And Reopen Votes Privilege:

Awarded At: 3,000 Reputation

that enables you to vote-to-close questions for many reasons - one of them is a duplication.
Until then, you can write a comment and link the user to the duplicate question, and you can flag for closure.
Comment: Below 3k rep you can actually flag the question as a duplicate. This automatically posts a "Possible duplicate" comment with the link to the other question. The comment is automatically removed if the question is indeed closed as a duplicate.
Comment: Also, flagging (and I think VTC) as duplicate creates the auto comment linking to the other question.  So the user doesn't have to write the comment on their own.  They can always just edit the auto comment.
Answer: If one doesn't exist yet, and you know enough about the problem domain, you can write (or find and polish) a good canonical, self-answered Q&A.
Then you can flag to close newer (and older) questions as duplicate of that canonical one.
Answer: Perhaps its time for SO to build a Watson / Cognitive / NLP front end and trap these types of problems at source. It could learn by watching the negative comments.
This would assist both the OP in getting a quicker answer and owner from managing duplicates.

Managing duplicate questions


How can I make inline images bigger by default?

Question: I'm a new emacs user (spacemacs, really, switched from Vim), and I'm having difficulty configuring emacs on my HiDPI display. Basically, I'm suffering from this bug. The problem is that, while I can scale the font size on emacs fine, graphics and images don't scale. That's most apparent in inline images, say, in org mode, EIN, or anything that displays an image. Is there a way to just make all images twice as big, by default?
Answer: I'm far from being an expert on this, but would setting this variable help?
<code>(setq org-image-actual-width SIZE_IN_PIXELS)
</code>
Comment: The variable is org-image-actual-width, not org-mode-actual-width. I submitted an edit.
Comment: My version of org-mode doesn't have this variable, what does it do? Regardless, this wouldn't help outside Org mode.
Comment: Setting that variable doesn't seem to have any effect.
Comment: I'd suggest trying this with emacs-26, which has a number of improvements in scaling support (although inline images might not be one of them).


Facebook pages merge

Question: I decided to merge two pages. They have same name, both pages have same admins, belongs to same business account. But when I tried to merge pages it says that "The merge request is rejected". So what is the problem?
Comment: _The merge request is rejected_ is it full error message or you are getting anything else in error message?
Answer: I believe your request got rejected because your both pages have same name. I would say, change the second page name first, but keep the page name similar to other page name with which you want to merge and then try to merge. Also, if you pages have physical address, then it should be same.
From Facebook Help Centre:

If you have 2 Facebook Pages for the same thing, you may be able to merge them if:

You're an admin of both Pages.
Your Pages have similar names and represent the same thing.
Your Pages have the same address, if they have physical locations.

Before you request a Page merge, please make sure that any campaigns you're running aren't pointing to the Page that will be deleted.

Before merging check that all these conditions are satisfied, otherwise your page merging request get rejected.
You may also check the Pages-Specific Policies.
If still you face the issue, you can report a problem to Facebook technical team.

Facebook pages merge


How can a child be blood type AB, if both of the parents are blood type A?

Question: Basically, both of my parents are blood type A (both are confirmed and it's also certain both of them are my biological parents). I recently found out my blood type is AB. How is this possible? I tried reading about different mutations in blood type, but I couldn't find anything that was similar to my case.
Answer: Blood type A has a variety of subtypes, which have different features in terms of their antigens. This leads to people with different A subtypes having somewhat different kinds of antibodies in their blood (for a technical article, see here). I don't know the population prevalences well, but I read somewhere (can't find it now) that as many as 20% of blood type A people actually have one of the subtypes. And these are themselves going through their own mutations. It is possible that you have an A subtype of some kind.
Testing blood types usually consists of testing which antigens and antibodies are present in your blood (see e.g. here). So if you have some kind of A subtype that didn't fit well into the blood test's expectations, you might have shown up as AB. I'm not a hematologist or physician, so I'm not sure how plausible that is.
But if you are really interested, you might consider getting a DNA test that will identify which type/sub-type you have, as this will add a different source of information on top of the standard blood test. In the jargon, the standard blood test is for "phenotype" (what are your blood cells actually doing), whereas DNA tests are for "genotype" (what is your DNA sequence). Often genotype and phenotype have less to do with each other than you might expect, or they don't fit in all that well with the cut-and-dried tests. In particular, a lot of medically underserved populations have variation that isn't really accounted for by standard medical typology.
Hope that helps.
Comment: Of course this, while possible, overlooks the most obvious cause.  As Homer put it '"My mother," answered Telemachus, "tells me I am son to Ulysses, but it is a wise child that knows his own father."'
Comment: @jamesqf : Well, we have to trust OP: "Basically, both of my parents are blood type A (both are confirmed and it's also __certain both of them are my biological parents__)". (my emphasis).


What tool should I use to cut memory foam?

Question: I need to cut 2x2 ft square pieces from a sheet of memory foam. Not sure what tool is best for this. Any ideas? In the future I'd like to cut circles and eventually sculpt irregular shapes, I don't know what tool can be used for this sort of job.
Answer: For thicker pieces you might find you get better results by compressing the foam before cutting it. You could make a simple straight-line clamp out of a couple of 2x4s linked with a door hinge -- just put your foam in between, clamp the open end shut with a C-clamp, and use one edge of the wood as a guide for your cut. For your curved cuts it might make more sense to make a plywood die to match the final shape and press it down by hand or with something heavy before cutting around it.
Comment: Compressing first makes a ton of sense.  I used to run a blinds franchise and had to cut honeycomb shades occasionally.  Compressing then cutting resulted in near factory edges.
Comment: Thanks -- using this trick for honeycomb shades is an awesome idea too!
Comment: It is hard to visualize, could some one post a picture of how the setup looks like?
Answer: I used a sharp razor knife on my memory foam.  You can make a line and just make long cuts.  Do not try to cut through it all at once.  Start by making your first cut deep enough that you can follow it through and make a straight cut.  Just keep cutting down your line until you are through.  Take your time and be careful and you will have a clean cut.  Don't use a saw or hot knife you will just ruin your topper.
A razor knife is your best tool for this.
Comment: I was afraid this was the answer.  It's what I do too, but it requires a steady hand and a ton of patience.  I've yet to make a cut I was remotely pleased with.
Comment: If you wanted, you could make you a mark with a chalkline or some straight edge to go by. Mine was not perfect either. But the sheets will cover it :). If you do not want to sell it the future, dont worry about it being too messy. It will still work the same.
Comment: Sharp Chef's knife works as well: https://en.wikipedia.org/wiki/Chef's_knife The added width of the knife helps keep the cut from wandering as you get deeper into the foam.
Answer: An electric fillet knife does great at cutting this stuff. Seriously. Give it a try if you have one.
Comment: Agreed (and I'm guessing so does Yitchak, who might not've realized they go by more than one name).  It's that strange electrical appliance that you'd see in the 1970s for carving turkeys or roast.
Comment: I've used an electric carving knife for cutting memory foam and it worked very very well.
Answer: If this were styrofoam, I'd recommend a hot knife (basically a wire stretched taut on a frame similar to a jigsaw, and electrified to heat it). However, visco-elastic foam will behave differently and you probably don't want to be breathing in the fumes produces by melting it.
In this white paper from the Polyurethane Foam Association regarding visco-elastic ("memory") foam, the PFA states that most conventional tools including saws can be used to cut VEF. However, care must be taken to go slowly and not deform the foam too much with the cutting action, because the slower recovery of VEF to its original shape will cause defects in the kerf line and possibly cause the saw to bind more easily.
Answer: I use an electric carving knife. It works great.
Answer: If you don't have an electric carving knife, which is the best tool, use a serrated bread knife.  Same action on both.
Comment: This worked for me as well, its quite controllable if you use a l right sawing motion
Answer: a really sharp knife should do the trick.
Answer: I strongly recommend you let the mattress chill outside on a flat surface that maintains its original shape. The mattress becomes very hard when cold, in the same way warmth causes it to soften.
I would then follow the PFA recommendation; "that most conventional tools including saws can be used to cut VEF".
P.S. I do not know what the PFA thinks about having soft or hard memory foam, but I know which of these I prefer.
Comment: Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably [take our tour](//diy.stackexchange.com/tour) so you'll know how best to contribute here.
Answer: I used a pair of Cutco scissors. They worked great. The foam I cut was about 3" thick. I tried some other scissors first but they didn't even think about cutting it. I think the reason the Cutco scissors worked so well is the serrated edge they have. This made them bite into it instead of pushing back out like the other scissors I tried to use.
Answer: Well the best option is to clamp the memory foam between the 2 x 4' s.mentioned before.on top off a sharpy marked line, which is a marker.adjustable wood working clamps would work great for this. no matter how thick, which will decide the length of your knife. a good brand new razor utility knife preferably one that is disposable the kind that when you extend it you can break off the used dull portion. By using this kind of . razor knife when new you can extend it long enough to make a deep good clean cut through the thickness. without having to buy or use one of your wife's or husbands kitchen knives or just something that just won't do a good job Wright off the bat, and wind up with something that looks like A person having a nervous break down did it . the cost of a new razor knife like this is at the most $5 bucks at the dollar General store.


How can I play Dominion by myself (like solitaire)?

Question: Is there any suggested way to modify the rules to play Dominion on your own, like a Dominion Solitaire? It seems possible given that you're mostly just building your own deck and collecting victory points, but I'm not sure how to replicate the scarcity aspect that makes the game competitive and challenging.
Comment: See [this thread](https://boardgamegeek.com/thread/357795/solitaire-easy-rules) for a discussion of one possible game structure.
Comment: Did you find this one on BGG? It's linked through a question much like yours on their forum. https://boardgamegeek.com/thread/415837/soloplay-variant-dominion-now-available
Answer: Probably the best way to make a bot to play against is to not make it have a deck at all, just every other turn make it take a duchy and on the other turns make it randomly take an attack card and do it's effect (only bother with the effect that effects you for the bot doesn't have a deck)
You should check out the game Ascension, it is a deck building game like dominion, but with a viable built in solitaire variant.
Answer: Copied from https://boardgamegeek.com/thread/428919/dominion-solitaire

I was bored today so I came up with a sort of "Dominion Solitaire".
The way you do it is you set up a standard two player game with you being one player. You simulate the other player's turns in a purely mechanical way, as follows:
Purchase a Province or, if unable to do so, purchase the highest valued treasure you can.
Apart from the randomness in card drawing, you'll be playing a deterministic opponent.
Then see how many points you can beat this "computer" player by.
Comment: Did you copy this from BGG in the sense that you originally wrote it, or are you quoting someone else's idea? Make sure you mark the respective parts as such, and if possible, provide a source link.
Comment: While this would work, the method seems lacking in a few ways. It's uninteresting because in some Kingdoms, Big Money (the strategy described) is the best way to go, while in others, it is hopelessly ineffective. It's uninformative because the point total isn't good way to judge success. It's possible to have a definitive win locked down with only a point or two of margin, but also possible to barely squeak out a win even with a large point margin. It's unnecessary because BM, on average, takes 17 turns to buy 4 Provinces. There's no need to simulate, just use that as a benchmark.
Comment: @NuclearWang "BM on average takes 17 turns to buy 4 Provinces" - only if the opponent(s) never play any attack cards. As soon as you introduce cards like Militia, simulation is necessary.
Comment: @user2390246 If attack cards are in play, BM is almost certainly going to lose to any strategy that employs them. That puts this scenario under the "uninteresting" category. I don't really see the point in simulating a game when you have an >80% chance of winning.
Answer: I think one way you could do it is as a strategy test - eg: What's the shortest number of rounds you can reach a pre-determined condition, or highest number of points you can earn in x rounds.
Answer: On Dominion Online, you can play a one-player game. It allows you to do all sorts of solitaire challenges.