Is there a word (or phrase) that describe a series of mishaps/misfortunes in one's life?

Question: I don't mean something like 'many hardships' or 'several tragedies'. I'm looking for a word or short phrase that would describe just a really rough spot or time frame in someone's life. For instance, [s]he was fired, lost a loved one and/or a friend, a pet died, [s]he wasn't getting much support from those around him/her. How can I describe such a cluster of emotional events in a simple way?
Comment: Lemony Snicket's ?
Comment: are you looking for a cliche? or for phrases generally? You might say something like "for a while her life was tragedy after tragedy".
Comment: "Life" is how I tend to describe it.
Answer: A bad patch. I've heard rough patch, too, but more commonly bad patch or rough time. I suppose sticky patch is chiefly British.
http://dictionary.cambridge.org/dictionary/british/go-through-a-bad-difficult-rough-sticky-patch
Comment: I've heard "bad/rough/stick patch" regularly applied to problems in relationships (e.g. "Their relation is going through a rough patch right now.") or other more specific instances (like problem at work, or problems with kids, etc.), but I can't say that I've ever heard it applied to life in general.
Comment: In Britain, the expression I think you are thinking of is 'sticky wicket', which is not applicable in this context. But we don't use the expression 'sticky patch' in this context, either. Despite what dictionary.Cambridge.org might say! It is too trivial in meaning to be a synonym for 'tragedy'.
Answer:
Trial and tribulation.
Ordeal.

i.e.: A period of trial and tribulation.
http://dictionary.reference.com/browse/trials+and+tribulations
Comment: just out of curiosity: any idea whether the phrase "trials and tribulations" is etymologically based on the story of Job in the Christian Bible?
Comment: Would fit Hercules just as well.
Answer: Adversity:

a state or instance of serious or continued difficulty or misfortune.

he had to cope with life's many adversities; she showed courage in the face of adversity.

also  vicissitudes  : (from M-W)

difficulties  or hardship attendants on a way of life, a career, or a course of action and usually beyond one's control.
Answer: "A string of bad luck" [1] is often used for a series of bad events in short order. Perhaps most commonly for a series of failures. (That is, the death of a pet is usually not a failure on your part, nor "bad luck", but a bad investment or denting your car is.)
For instance: "First I had a customer pull out of a project, but I had a lead on another sale until my contact in that company quit and then we didn't get funding for my third project because I was too busy firefighting. I'm telling you, I just had a string of bad luck this quarter!"
[1] http://idioms.thefreedictionary.com/a+string+of+bad+luck
Comment: A pet dying is not bad luck, and least of all is losing a loved one. The idiom is used when nothing seems to be going your way. When everything you try, fails, through sheer bad luck. As if destiny were dealing you rotten cards.
Comment: @Mari-Lou: You are right, a very good way of putting it
Comment: But one could indeed hear "a string of bad luck" used to describe a series of misfortunes that included something as serious as the death of a loved one. "She's had a string of bad luck, poor dear."  It would be a kind of understatement, bordering on euphemism.
Answer: If all the unfortunate events take place within the same year, then that year might be an 'Annus horribilis'. It's latin but it's widely understood in British English, since the Queen's usage of it in 1992.

Although the phrase is cited by the Oxford English Dictionary as being in use as early as 1985, it was brought to prominence by Queen Elizabeth II, in a speech to the Guildhall on 24 November 1992, marking the 40th anniversary of her accession, in which she described the closing of the year as an annus horribilis.
1992 is not a year on which I shall look back with undiluted pleasure. In the words of one of my more sympathetic correspondents, it has turned out to be an Annus Horribilis.
Comment: This may be well understood to a BrE speaker, but I can't say that I've ever heard used by a layperson in AmE.
Comment: Great suggestion; I think the antonym "annus mirabilis" is especially satisfying
Comment: I've heard it.  A bit "out there", though.
Comment: Yes. I've edited my answer to specify BrE.
Answer: The Oxford Dictionary of English Idioms suggests
a chapter of accidents

Definition: a series of unfortunate events
  This expression was apparently coined by Lord Chesterfield in a letter to Solomon Dayrolles in 1753: "The chapter of knowledge is a very short, but the chapter of accidents is a very long one"
Comment: When asked "What happened to her?" one might reply "There was a chapter of events..." The context defines it and tone usually requests that we *not get into it*. I have never heard 'chapter/series of *fortunate* events'.
Comment: I had to Ctrl-F or would of missed the cliched *series of unfortunate events*. I've never heard 'chapter of *accidents*'; *events*, maybe. +1 for the cliche that this question should be asking to avoid.
Comment: @Mazura   I agree with your observations, and  I feel "chapter of events" wouldn't necessarily express a run of unfortunate incidents. (Trying to avoid the clichè)
Answer: One common formulation is "a litany of troubles [or problems]," where litany has the sense of "a sizable series or set." The entry for litany in Merriam-Webster's Eleventh Collegiate Dictionary (2003) shows an interesting line of meanings:

litany n (13c) 1 : a prayer consisting of a series of invocations and supplications by the leader with alternate responses by the congregation 2 a : a resonant or repetitive chant {a litany of cheering phrases—Herman Wouk} b : a usu. lengthy recitation or enumeration {a familiar litany of complaints} c : a sizable series or set {a litany of problems}

All three of MW's nonliturgical definitions of litany have emerged within the past seventy years—definition 2a in the Seventh Collegiate (1963), definition 2b in the Ninth Collegiate (1983), and definition 2c in the Eleventh Collegiate (2003).
Merriam-Webster's unhurried recognition of meaning 2c notwithstanding, use of the word in that sense goes back almost a century. The first instance of "litany of troubles" that a Google Books search finds is in David Hamilton, Pale Warriors: A Novel (1929):

"There's no moon to-night," she said. "You ought to know that. Now, Thaddeus, dear, I am sure you will forgive me if I hurry away without reciting my litany of troubles to you, comforting and reassuring as you are.

More clearly relevant to the OP's question is this occurrence from Caryll Houselander, The Dry Wood (1947):

From house to house went Father O'Grady, listening to the same litany of troubles, the aches and pains of rheumatism, the damp seeping into the walls, the swarms of rats, the way the landlord wouldn't repair the roof (God have mercy on the black-hearted devil), the long wait at the Labour Exchange, the hardness of the Means Test, the children who had to be hidden when the inspectors came, the new flats with hot water laid on where you mayn't have children or dogs or cats, so no one can live in them.
Answer: I'm not sure if this fits what you're looking for but another option may be "A tragedy of errors"
Comment: Isn't that a play on the name of Shakespeare's "A comedy of errors"? I'd have assumed that it had a theatrical meaning rather than a life-stage one.
Answer: For those seeking a bit more artful phrasing, I propose:

(tempest-)tossed upon life's billows

Tempest-tost (also tempest-tossed), meaning "pounded or hit repeatedly by storms or adversities1" when used figuratively, has a long history, dating back to the late 16th century2.
The word has seen a fair bit of poetic use, perhaps most famously in the Emma Lazarus sonnet "The New Colossus":

Give me your tired, your poor,
  Your huddled masses yearning to breathe free,
  The wretched refuse of your teeming shore.
  Send these, the homeless, tempest-tost to me,
  I lift my lamp beside the golden door!

As for "upon life's billows," the phrase appears to have originated been popularized in the 1897 hymn "Count Your Blessings" by Johnson Oatman, Jr.:

When upon life's billows you are tempest tossed,
  When you are discouraged, thinking all is lost,
  Count your many blessings name them one by one,
  And it will surprise you what the Lord hath done.3

An Internet search will reveal that "(tempest)-tossed upon life's billows" has seen some use without becoming cliché.
An example of the phrase in use, from A Memoir of Eli Bickford: A Patriot of the Revolution by Charles Ira Bushnell, published in 1865:

Yet the freshness of youth still lingered around his heart, rendering him a fitting companion for every age, and children and youth, as they gazed upon him, felt that even age had its attractions. When a century had passed by, and left him still tossed upon life's billows, thought left the busy present, and wandered back to the bright scenes of the past, and the old man was a child again.

1 https://www.vocabulary.com/dictionary/tempest-tost
2 http://www.dictionary.com/browse/tempest-tossed
3 https://www.hymnal.net/en/hymn/h/707
Answer: If the series of unfortunate events inevitably lead to an undesirable outcome (such as going bankrupt, or having a nervous breakdown) you could use "perfect storm," a term popularized by the book and movie called "The Perfect Storm." by Sebastian Junger (1997, 2000). ("Perfect storm" predates Junger's work.)
"The losses were her perfect storm. We weren't surprised to hear that she spent some time in the care of a psychiatrist that summer."
Answer: Here's a different perspective : "Splintered by stress" (http://www.scientificamerican.com/article/splintered-by-stress/)
Answer: The Chinese phrase "May you live in interesting times". Means may you have lots of mishaps and events that cause your life to be interesting.... It means the same thing (as above) but in a veiled way that sounds like they are wishing a nice thing on you.


How do you increase the amount of pixels in the width of your photo?

Question: I have taken a photo in early November using my iPad mini when the weather was still really nivpce and warm. I would hate to not show it because for once, I'm pretty proud of my photos. I'm trying to enter it into a contest, and it keeps saying that The width of the image needs to be greater than 2000 pixels. Help plz!
Comment: Generally if the contest requires the image to be a certain size, they do not want smaller images that have been resized to be larger. In fact, that is exactly the type of thing they are trying to avoid.
Comment: Possible duplicate of [How can I upscale a low-res image to make it appear higher-res?](http://photo.stackexchange.com/questions/18468/how-can-i-upscale-a-low-res-image-to-make-it-appear-higher-res)
Comment: The iPad mini should take images at 2592×1936. That's either sufficient (landscape orientation) it just short (portrait orientation), unless you were using an app which reduces resolution — or using the front camera. Can you clarify?
Comment: I had a relative who was using some iProduct to send photos as email attachments, and persistently sent out very small (~320x240) image files, even though the full-size versions certainly existed somewhere in local or cloud storage. Whatever method they were using to access the photos was providing them with low-resolution copies. You may want to consider this angle, rather than attempting to enlarge a small copy.
Comment: On an iPad, PC, Mac, other? Please define.
Comment: @mattdm - That question assumes the OP has access to Photoshop.  Not sure that is the case.
Answer: In this case the answer is most likely "You don't".
This contest is apparently specifying a minimum width of 2000 pixels to weed out pictures from less serious cameras, like yours.  Having you submit a picture is exactly what they are trying to avoid.
Read the rules carefully.  They probably specify that the picture must have native size of 2000 pixels or more across.  While you can resize any picture to 2000 pixels across, that's not what they want, and is probably violating their rules.
Answer: I suggest using XnViewMP for that.

Open you photo in XnViewMP
Pick "Image->Canvas resize" from top menu
Add equal number of pixels to both width and height
Adjust background color for your preference

This way you will get a small border and won't loose image quality. Use "File->Format settings" to set JPEG quality.
You can also resize your image but I suggest that you add a small border instead because you will loose quality that way.
Comment: This is probably not what the contest wants, and possibly against the rules.  If you're going to give this kind of advice, the first thing should be to read the rules of the contest carefully.
Comment: We don't know the full contest rules in this case. If they ask for unmodified images, I agree that upscaling would be out of line. If they allow modifications, though, a 3% change might be okay — you might get similar that from lens distortion or perspective correction, for example. Does the restriction apply to the image as captured, or to the result?
Comment: @OlinLathrop: the question is not about dealing with contests, it is about compensating for slight shortage of resolution. I know it is critical for photographers to keep high economic entry barriers for photography but I do not think that it is critical enough to suggest that one cannot/shouldn't use 1936px wide image when 2000px is requested. If resolution is co critical why is it given with a multiple of power of ten? If they were so picky, why did not they say "2011px"? There is little insight in chosing multiples of power of ten with some rare exceptions.
Comment: No, this is exactly about how to cheat contest rules.  We don't know why they specified 2000 pixels minimum, but they did.  It is what it is.  Just because 1936 pixels is almost 2000, and in a genuine usage case they are effectively equivalent, doesn't make cheating right.  The contest has the right to set their rules as they like, whether you or I think they are sensible or not.  We have the right not to enter and to go somewhere else.  What we *don't* have the right to do is to deliberately violate the rules of something that was completely our choice to participate in.
Comment: @OlinLathrop: "What we don't have the right to do is to deliberately violate the rules" - is it backed up by some law? If not, it is protectionism. If authors cared about quality they would set the rule to accept no photos without EXIF and prohibit every mobile phone camera with small enough sensor (because, you know, 20mp tiny sensor is still usually worse than 6MP large one because of optics). Your answer implies some hidden restrictions, ethics and prohibition of borders (it is unrealistic, try to find contests which prohibits borders), my answer is about the question as it is asked.
Answer: If you have taken more than one picture of that scene then you can use the panorama stitcher Hugin to create a panorama. Whether or not this will work and yield a nice result, depends on whether there is enough overlap between the different pictures.
Answer: This isn't about quality, it's about quantity. I have seen marvellous smart phone photos (in fact, building-size). You can simply increase your image size in your favourite editor if it's merely more pixels that you want. This may not look too good for pixel-peepers, but viewed from a greater distance it may be just fine.


What is the function of のは in this question?

Question: きさまがこの時代に来てタマゴからそうなるまで3年間かかったのは...?
Comment: That is not a sentence.  It is only a very long topic + は.  The whole predicate is left unsaid and is represented by the '.....' at the end.
Comment: @MathieuBouville I think this way of using のは is clearly requesting for an explanation/reason, and it's not really interchangeable with こと(は) here.
Comment: Thank you, I changed the question. So the の and は are independent of each other?
Comment: 1. I see, thank you. 2. This is the full dialogue. The follow-up response is「いちどタマゴにもどってしまうとふたたび熟成するのに地中で3年...それだけ時間が必要なのだ 」3. So then the verb that is nominalized would be かかった, changing it from "take" to "taking"?
Comment: The の bit is nominalization (こと can also be used), you should find out about this first. Then read Naruto's answer below for は.
Answer: This is an "incomplete" cleft sentence, and that のは is part of the grammar of cleft sentences. Do you understand the following simpler example of cleft sentence used to emphasize the reason?

そこに山があるから、彼は山に登る。
  He climbs because a mountain is there.
彼が山に登るのは、そこに山があるからだ。
  It is because a mountain is there that he climbs.

And the sentence in question is an incomplete version of this grammar. The speaker left the latter half of the sentence (the reason part) unsaid, probably because he is expecting the other party will continue his sentence and explain the matter. In other words, it's like ending an English sentence with "because...".

彼が山に登るのは…
  He climbs, because...
きさまがこの時代に来てタマゴからそうなるまで3年間かかったのは...?
  So, after coming to this era, you spent three years to transform from the egg form to that form, and that's because...?


Cats peeing in potted plants. What to do?

Question: I have several big potted plants, and my cats are peeing on these plants. Needless to say, the plants aren't doing that great. The cat litters are always clean.
Is there anything I can do so that the cats stop peeing on the plants?
Comment: For whoever downvoted the question: Speak Up Child!
Answer: I think best thing to do would be making these plant pots unattractive as alternatives to litter box.
First thing to consider is replacing the old soil in all these pots, because cats will be attracted to urinate there as long as the soil has cat urine scent to it. I would advise against attempting to dilute the scent by doing washing-overwatering, as you could seriously damage your plants (I've drowned a few potted plants in the past by accident and it's easier than it seems). Next, you could cover up the soil in your pots with some larger rocks, or generally just a layer of some harmless blocky objects - it would impede with cat's natural instinct of covering up urinated places with soil and further discourage using pots as litterboxes.
Some research on the Internet I did also mentions placing rustling materials like aluminium foil ribbons into the pot to further spark a sense of unfamiliar environment being present and thus sending cats a subtle message that flower pots aren't really the best places to urinate into. I don't think it's a bad idea, but if you decide to take that advice please make sure these objects aren't in any way capable of hurting the cats or pose a choking hazard. Due to the latter, I would advise against using for example plastic bag ribbons in this context.
I would also not advise sprinkling cats with water if you see them urinating there, as they wouldn't get the message that urinating is prohibited there. At most, they would learn that it's just you who doesn't like them urinating there. Intended effect would not be achieved, as they will just begin behaving more sneaky and careful about it, causing unneeded stress for them as well as for you.
Also, please rule out that urinating outside of the litterbox is not caused by other factors. For example, I recall an issue someone had with their cat urinating in disagreeable places, and then it was discovered that the reason lied within the litterbox itself, as the texture of recently changed brand of litter was hurting cat's paws.


How does salt and pepper noise occurs in an image

Question: How does salt & pepper noise occur? And, what are some techniques to remove it?
Comment: One possible cause would be high-amplitude intermittent electrical interference, affecting either the analogue or digitised signal.  For example, arcing on electrical contacts.
Answer: Salt-and-pepper noise is a form of noise sometimes seen on images. It presents itself as sparsely occurring white and black pixels.
In another words ( in the sense of pixels), salt and pepper noise means that are high frequencies, so for salt noise the values of this noise type is high (255 ... 200), and for the pepper noise the values of this noise type is low (5 ... 0).
To salt noise there are good filters like harmonic mean filters
to salt and pepper noise.
$$
   \hat{f}(x,y) = \frac{mn}{\sum_{(s,t) \in S_{xy}}\frac{1}{g(s,t)} }
   $$
There are the contra harmonic filter that depends of a $Q$ argument, e.g., for salt noise $Q$ should be negative and for pepper Q should be positive.
$$
   \hat{f}(x,y) = \frac{\sum_{(s,t) \in S_{xy}}g(s,t)^{Q+1}}{{\tiny\sum_{(s,t) \in S_{xy}}}g(s,t)^{Q} }
   $$
Another aproach is the order statistics filters, e.g., $\operatorname{max}$
 filter are good for pepper noise, and $\operatorname{min}$ filter are good for salt noise.
$$ \hat{f}(x,y) = \operatorname{max}_{(s,t)\in S_{xy}}{g(s,t)}$$
$$ \hat{f}(x,y) = \operatorname{min}_{(s,t)\in S_{xy}}{g(s,t)} $$
And another one is alpha trimmed filter that also are a order statistics filter type.
$$ \hat{f}(x,y) = \frac{1}{mn-d}\sum_{(s,t) \in S_{x,y}} g_r(s,t)$$
Beside this there are Adaptive Mean Filter.
Comment: For completion sake, when both salt and pepper noise are present, median filter is good.
Answer: According to Wikipedia, salt-and-pepper noise is generated by errors during analog to digital conversion or data transfer. It can be corrected with median filtering.
Comment: A good answer should do more than quote a couple of sentences from Wikipedia...
Comment: A good question should ask for more than a couple of sentences from Wikipedia...
Comment: I agree; that's what the downvote button is for. Personally, I prefer to give links or pointers to the answer as a comment.


For my "switch on light with clap project " will sound sensors detect other sounds other than a clap and switch on the light?

Question: I am just a high school student who is trying to self-learn for my IoT home automation projects.Please excuse me if this question sound silly to you.This time I am working on this "clap to switch on the light" project.
I learnt that to detect the sound from the clap, I can use a sound sensor.In my case, the sensor will be connected to an Arduino UNO which will then be connected to a relay module that will control the lights.My question is: Will the light switch-on because of a loud sound other than a clap, because obviously it would be really annoying for the light to switch on and off when I don't want it to.
Comment: to differentiate between sounds, you will need to analyze the frequency spectrum of a detected sound as well as the attack and decay of the sound...... research `arduino fft` .............. https://www.norwegiancreations.com/2017/08/what-is-fft-and-how-can-you-implement-it-on-an-arduino/
Comment: more info here https://www.arduino.cc/en/Tutorial/ArduinoSoundClapDetector and here https://www.arduino.cc/en/Tutorial/ArduinoSoundWhistleDetector
Answer: Of course it will detect other sounds in the sense of noticing other sounds — that's what a sound sensor is for. Getting the trigger exact enough will probably be the most challenging part of the project — unless there is a library that detects the sound profile of claps.
That shouldn't deter you though. It's just about refining the detection bit by bit. Just know that you'll have misfires in the detection in the beginning. A lot.
The first Amazon Echos were quite bad at properly detecting the wake words. Nowadays they can detect it a few rooms away, while the tap is running, and the TV, and the Police drives by with sirens.


Customizing conditional email confirmations

Question: I would like to set for the confirmation e-mail item "Send when updated" by condition When: "Entry.Status is not Reviewed". I set up all correctly by my opinion, but that doesn't work.
Answer: I'm a developer with Cognito Forms.
I tried to set up the same 'When Updated' condition for my own Confirmation Email. In my testing I found that the confirmation email was sent out on submit, and when the status was changed to 'Complete'. I did not get an email when the entry transferred over to 'Reviewed'.
The 'When Updated' status I used is 'Entry.Status is not Reviewed' if you switch over to the Advanced Editor, you should see the following calculation.
<code>=(Entry.Status != "Reviewed")
</code>
If you're not seeing the correct interaction with your form please submit a Support Request so that we can take a closer look at the form your working with.


What is meant by the phrase "the mass is protected by a symmetry"?

Question: In a particle physics context I've heard this phrase used.  I guess it means that the mass of a particle is less than you'd naively expect from $E=mc^2$ after computing the momentum uncertainty corresponding to some appropriate length scale.  Assuming my interpretation of the phrase is right, how does a symmetry let you get away with a smaller mass ?
Answer: It means protection from radiative corrections.  If you integrate loop corrections to the mass, out to some virtual momentum scale $\Lambda$, for a generic Lagrangian you would get contributions of order that scale. So what if you observe $m<<\Lambda$? Well if there is a symmetry in the theory than guarantees that perturbative corrections to the mass will vanish, then you say the mass is protected by the symmetry, problem solved.  Otherwise you've got explaining to do why $m<<\Lambda$.
Answer: There are two ways in which this can happen. The trivial one is if the theory has some gauge invariance, in which case a mass term is simply not guage invariant and thus will never appear in any higher-order correction. There are complications if you break that symmetry and then combine it with some other field (e.g. electroweak or BCS transition).
The more complex possibility is via the Goldstone theorem. It states that if you break some continuous (global) symmetry then there will exist massless excitations. The broken symmetry version of that Lagrangian will often look very complex, and it will not be obvious that high-order diagrams will conspire to cancel and yield no radiative correction to the bare mass.
Concretely, consider a crystalline lattice. The lattice breaks translational invariance, and one obtains phonons as the Goldstone boson. In addition, these are guaranteed to have a dispersion relation which passes through zero. Intuitively, the reason is that one can apply a very long wavelength modulation to the atoms, and they will not exert a large potential on each other, so there will be very little restoring force.
A more interesting example is in QCD, where if the quarks were massless, then there would be an exact chiral symmetry. If that were so, then the $\pi$-mesons, which are the Goldstone bosons of breaking that symmetry, would be massless. However, the quarks are not quite massless (the bare quarks are on the order of a few tens of MeV) and thus the masslessness of $\pi$-mesons are not quite protected --- but they are still much less than the "natural" scale of confined QCD, which is on the order of a proton.
Answer: In addition to the cases which genneth has mentioned,

Goldstone bosons: whose zero mass is protected by the broken symmetry
Gauge invariance: where charged chiral fermions can't have a mass by gauge invariance (charge conservation)

I have to add the following cases, which make the complete list:

Supersymmetry: (user1631's answer) This is the statement that a scalar particle is related by supersymmetry to a necessarily massless charged fermion. The fermion must be massless, the scalar (absent supersymmetry) doesn't have to be, but in order to have supersymmetry, the scalar ends up massless.
Chiral symmetry enforcement: This is the only new one here.

The last one is a little confusing, because it isn't the same as the chiral symmetry breaking by the QCD quark-condensate that makes the pions light. The chiral symmetry breaking by the QCD quark-condensate is just an ordinary Goldstone thing, and the pions are Goldstone bosons.
The chiral symmetry enforcement is the statement that I require that the Lagrangian of a fermion be invariant under rotations of the left and right chiralities in opposite directions. The mass term of a Dirac equation is not invariant under this, because the mass term produces a left chirality from a right chirality with a definite phase (you fix this phase by making m real and positive).
So in order to make a Dirac equation (with two chiralities) massless, you impose chiral symmetry, which prevents the two chiralities from turning into each other. This symmetry can be a gauged symmetry, in which case this is an example of Gauge invariance--- charge conservation doesn't allow the two to flip into each other--- but it can also be a non-gauged symmetry, and then you are just forcing the mass to zero to impose a symmetry.
This is confusing because there is a tendency in high energy physics to write all fermions in Dirac form, because people often memorize Dirac matrix formulas, not Weyl formulas, and Dirac formulas generalize to higher dimension easier. Then any 2-component chiral fermion is represented as two components of a Dirac spinor, but with an extra chiral symmetry which decouples the other 2 components. The other 2 components are not physical--- they aren't there--- but the form of the Lagrangian makes the massless condition come from the chiral symmetry.
This is the sense in which the term "mass protected by a symmetry" comes up the most--- when mass terms for a (global or gauge) charge carrying Fermion are disallowed because of their 2-component nature. It's not a good way to say it, it is best to only have 2 components in your head, and consider it forbidden just by charge conservation, not by a chiral symmetry, but people unfortunately use the symmetry language in this case all the time anyway.
Comment: Having been interested (as I was several decades ago) more in the relativity side of things, spinors were 'always' two component $SL(2:\mathbb{C})$ objects.  It took some adjusting the other way to get used to the Dirac versions!
Comment: @twistor59: I agonized on this--- which is better notation? SL(2,C) is 4d specific, and in higher dimensions, you absolutely need Dirac, so Dirac is the most general. You need Majorana and Weyl conditions clearly separated in your head for 2d, 6d, 10d. But SL(2,C) is so much cleaner in 4d. I still don't have a good answer to the spinor notation problem--- you need both unfortunately. There will be a solution one day.
Answer: Nima gives a better explanation in this video I will be able to in written format here. Relevant portion starts at about 20 min in
http://streamer.perimeterinstitute.ca/Flash/c53bd5c4-4108-489c-b43b-941f06c601d1/viewer.html
along with some other interesting commentary.


Are the contents of ethereum storage private?

Question: I know that the code is public, but is the contents of storage private?
Comment: Possible duplicate of [Solidity functions - private visibility](https://ethereum.stackexchange.com/questions/6547/solidity-functions-private-visibility)
Answer: The contents are private only in the sense that other contracts can't read them if you set them private, but otherwise everything is public. All nodes need to be able to process the data so they also have access to all the data (including private variables).
More reading: Store secret data in contract (and its duplicate)
Comment: You should answer a question when it has been closed. Your answer should be removed.
Comment: Thanks for the input. Closing a questions does not make an answer invalid or wrong. If the question was closed when I opened it I couldn't have answered it anymore.
Comment: The question was closed and voted off the forum. That does make your answer invalid (obviously). A question is valid or invalid. It does not change its validity: if I say a brick is red, it was a red before I said it was a brick, my saying the colour does not change the colour. You answered an invalid question. You clearly think you can answer an invalid question but others cannot as if somehow your answer is better than others. As I said, your answer should be removed. If it is not removed, this forum is simply discriminating against other people.
Comment: You are entitled to your opinion. You can flag the answer for moderator attention if you feel that necessary.


Design and Fabricating My Own Lens

Question: I have a small business (just me) selling an inspection machine.  The camera and lens work well, but I've had to print my own camera mount to get the lens further away from the CCD to get a good focus.  The depth of field is extremely narrow, and I am interested in possibly making my own lens if I can buy the parts, and 3D print the barrel.  I believe it's simple, but I really don't know anything about this.  I downloaded software a year or two ago, I think called Synoptic.  I dabbled, but don't know what I'm doing.
The CCD is 1/3 inch, and it is placed six inches from the target, with the target being .7 inches diameter.  The target is not normal to the lens, and is at a 30 degree angle.  This angle causes problems with the top and bottom edges not being in focus.
Is there a tutorial somewhere for software that I can freely download?  Or, is there other reference material I should be reading?
Comment: You might rephrase the question title about how to photograph the CCD and not about how to design your own lens.  You have an XY problem otherwise: https://meta.stackexchange.com/questions/66377/what-is-the-xy-problem
Comment: Fingerprinting? I used to work in that space 20 years ago.
Comment: Ammunition brass.  www.hasgrok.com
Answer: You would likely be foolish to make your own lens. Likely Edmunds Scientific   http://www.edmundscientific.com/
will have everything you need. Make sure to be ready with the specifications of the lens you want when you contact them.
Answer: Sounds like what you need is to tilt your lens to get everything in focus.
Because the lens will be tilted, you'll probably need one with a larger image circle in order that it still covers your sensor when tilted, though you may find the existing lens has enough coverage.
Alternatively, try shifting the lens - that way, you can point the lens perpendicular to the target but not pointing straight at it - if you shift the
lens away from being inline with the target, the image of the target moves away from the center of the image - but you can compensate for that by moving the sensor so it's where the image ends up. Again, this will usually need a lens with a larger image circle, so the shifted image of the target is still inside the image circle.
Comment: He can also tilt the CCD. He can elevate the illumination, this will allow a tiny aperture to gain DOF.
Comment: Yes - shifting or tilting either the CCD or the lens will work. Good suggestion about stopping the lens down if the light is bright enough to get away with it.
Comment: This is an awesome idea.  Since I'm printing my own lens mount, I can easily make one that's offset or angled.  Is this a trial and error thing, or is there a calculation I can make related to the focal distance, size of target, and size of final cast image on the CCD?
Comment: Yes, there is a calculation, but I'm not sure I remember it.
Comment: For tilt, I think the subject plane, the lens plane, and your sensor plane need to intersect in the same line. For shift, if you know the reproduction ratio, you can probably just scale the distance from the center - so if the image on the sensor is half original size, then the sensor shift should be around half the offset of the subject from the lens position. If you can find a book that covers how view camera movements work (like Ansel Adams _The Camera_ ) that should explain it.... or just try a web search for "View camera movements" or "Large format techniques" which should find lots.
Answer: Depending on the subject you're photographing, you could try focus stacking:
https://digital-photography-school.com/an-introduction-to-focus-stacking/
Or Light field cameras such as the Lytro (may be discontinued?):
https://www.lytro.com/
https://www.bhphotovideo.com/c/product/801644830-USE/lytro_b5_0035_illum_light_field_digital.html
I would say it's cheaper and easier to find someone in China to help prototype a product for you.  Googling found this http://www.optics-online.com/Custom/prototype.asp
Also try Thor Labs for optical components: https://www.thorlabs.com/

Design and Fabricating My Own Lens


Generic Pairing Heap Performance

Question: I have made a generic pairing heap library in C.  Pairing heaps are one of the several heap variants with better asymptotic running times than standard binary heaps (others include Fibonacci heaps and binomial heaps).  However, pairing heaps are the only ones that really do better than binary heaps according to Wikipedia.
A pairing heap is either empty or consists of an element (the minimum) and a list of non empty pairing heaps.  (The name "pairing" is not derived from this definition whatsoever and actually refers to the normal implementation of the pop operation, which I have improved.)
I have a struct, pheap_ft, that holds function pointers and state data for allocating, comparing, and freeing nodes and so forth.  The pheap functions then support new, top, push, pop, meld, and delete.  It is often also useful to provide an update key operation for a heap, but since my nodes do not have parent pointers this is not practical (and anyway heaps do not support finding an element by value efficiently; an avl tree would probably suit such usage better).
new and top are trivial.  meld just adds the input heap with the larger root (minimum) element as the first child of the input heap with the smaller root.  push is just new then meld.  The only complicated operation is pop (typically, update key would be implemented as popping a non root node and then pushing it back onto the heap, but again I have omitted this because I do not think it is worth adding parent pointers).
pop removes the root (minimum) element and then merges its children.  The standard merge procedure pairs off the the child heaps and merges them in twos, creating a queue, the elements of which are then merged into each other iteratively.  I have instead used a variation of merge sort that does not need to know the input length.  I merge the first 2^0 elements, then 2^0, then 2^1, then 2^2, then 2^3, and so on, as long as there are elements.  Calls to merge 2^(n+1) will call merge 2^n twice, and merge 2^0 just splits off one child from the list (a single element is trivially sorted).  Once all of the child heaps have been merged, no more recursion will occur even if the 2^n is still not 2^0.  This could be further improved using natural merge sort which keeps monotonic runs that happen to occur.
I have made the pairing heap generic by using void pointers for parameter and return types, but the actual nodes use flexible length char arrays, which has a couple of problems I will discuss after the code.
Here is the main header file pheap.h
//pheap.h
//Pairing heap library by Hacatu
#ifndef __PHEAP_H__
#define __PHEAP_H__

#include <stddef.h>
#include "fla.h"

typedef struct pheap_node pheap_node;
struct pheap_node{
    pheap_node *first_child, *sibling;
    char data[];
};

typedef struct{//function table to hold function pointers and related data
    size_t size;
    int (*cmp)(const void *data, const void*, const void*);//some cmps are unsequenced so data really must not be modified here
    void *(*alloc)(void *data);
    void (*free)(void *data, void*);
    void *data;
} pheap_ft;

//Allocate a new pairing heap node using ft->alloc(ft->data), copy ft->size bytes from key to
//(return)->data, set (return)->first_child and (return)->sibling, and (return) the new node.
pheap_node *pheap_new(void *key, pheap_node *first_child, pheap_node *sibling, pheap_ft *ft);
//Return a pointer to the minimal data element of a pairing heap, or NULL if the heap is empty
void *pheap_top(pheap_node *r);
//Combine two pairing heaps.  The nodes of the existing heaps are reused and re-linked so no new
//allocations are done, but the original heaps are mutated.  Returns a pointer to the root element
//of the melded heap
pheap_node *pheap_meld(pheap_node *a, pheap_node *b, pheap_ft *ft);
//Insert an item into a pairing heap, returning the new root element on success or NULL on failure.
//Failure only occurs if allocation fails: items with duplicate keys are permitted with unspecified
//storage order
pheap_node *pheap_push(pheap_node *r, void *key, pheap_ft *ft);
//Remove the root (minimal) element from a pairing heap.  The input pointer is modified to indicate the
//new root.  The old root is returned, but its links may not be nulled.  If pop is called on an empty heap,
//nothing is done and NULL is returned.
pheap_node *pheap_pop(pheap_node **r, pheap_ft *ft);
void pheap_delete(pheap_node *r, pheap_ft *ft);

//macro for obtaining data field (without using a function like pheap_top) despite the strict aliasing
//rule.  The pairing heap nodes store data in a flexible length char array because there is no such
//thing as a flexible length void array.  This means that the data has a type of char and so to read it
//as another type without optimization messing it up (since pointers to different types "can't" refer
//to the same object) we have to use a union.  This macro does that, but it requires the __typeof__ extension.
#define PHEAP_DATA(T, n) FLA_CAST(T, (char*)((pheap_node*)(n))->data)

#endif

Here is the header file fla.h.  It contains a macro for working around a particular limitation of flexible length arrays:
//fla.h
#ifndef __FLA_H__
#define __FLA_H__

#include <stddef.h>

#define FLA_CAST(T, p) (((union{__typeof__(p) data; T a;})(p)).a)

#endif

And here is the source code (pheap.c):
//pheap.c
#include <stdlib.h>
#include <string.h>
#include "pheap.h"

void *pheap_top(pheap_node *r){
    return r ? r->data : NULL;
}

pheap_node *pheap_new(void *key, pheap_node *first_child, pheap_node *sibling, pheap_ft *ft){
    pheap_node *n = ft->alloc(ft->data);
    if(n){
        *n = (pheap_node){.first_child=first_child, .sibling=sibling};
        memcpy(n->data, key, ft->size);
    }
    return n;
}

pheap_node *pheap_meld(pheap_node *a, pheap_node *b, pheap_ft *ft){
    if(!a){
        return b;
    }else if(!b){
        return a;
    }else if(ft->cmp(ft->data, a->data, b->data) > 0){
        a->sibling = b->first_child;
        b->first_child = a;
        return b;
    }
    b->sibling = a->first_child;
    a->first_child = b;
    return a;
}

pheap_node *pheap_push(pheap_node *r, void *key, pheap_ft *ft){
    pheap_node *n = pheap_new(key, NULL, NULL, ft);
    return n ? pheap_meld(r, n, ft) : NULL;
}

//helper function for pheap_pop.  Uses mergesort to combine a pheap_node's children
//linked list into one pairing heap.  Since the length of the list of children is
//not stored, this function accepts a recursion depth and is called by another helper
//function (pheap_merge_exponential) with depth 0, 0, 1, 2, 3, 4, 5, 6, ... until all
//children are merged.  If the list is empty, nothing is done.  If the depth is 0,
//the first child in the remaining part of the list is removed and returned (1 node is sorted).
static pheap_node *pheap_merge_binary(pheap_node **n, size_t depth, pheap_ft *ft){
    pheap_node *a, *b;
    if(!*n){
        return NULL;
    }else if(!depth){
        a = *n;
        *n = (*n)->sibling;
        a->sibling = NULL;
        return a;
    }
    a = pheap_merge_binary(n, depth - 1, ft);
    b = pheap_merge_binary(n, depth - 1, ft);
    return pheap_meld(a, b, ft);
}

//helper function for pheap_pop.  Uses mergesort to combine a pheap_node's children
//linked list into one pairing heap.
static pheap_node *pheap_merge_exponential(pheap_node **n, pheap_ft *ft){
    pheap_node *a = pheap_merge_binary(n, 0, ft);
    for(size_t depth = 0; *n; ++depth){
        a = pheap_meld(a, pheap_merge_binary(n, depth, ft), ft);
    }
    return a;
}

pheap_node *pheap_pop(pheap_node **r, pheap_ft *ft){
    if(!*r){
        return NULL;
    }
    pheap_node *ret = *r;
    *r = pheap_merge_exponential(&(*r)->first_child, ft);
    return ret;
}

//attempts to be as iterative as possible but is still singly recursive.
void pheap_delete(pheap_node *r, pheap_ft *ft){
    for(pheap_node *t; r;){
        while(r->sibling){
            pheap_delete(r->sibling->first_child, ft);
            t = r->sibling;
            r->sibling = t->sibling;
            ft->free(ft->data, t);
        }
        t = r;
        r = r->first_child;
        ft->free(ft->data, t);
    }
}

I used a heap based sieve of Eratosthenes and Dijkstra's algorithm (specifically Project Euler 83) to test the library.  Both of these tests use a slab allocator and can be found in this gist.  The prime number sieve is actually 6% slower than one using a binary heap, but that is probably because it does not use any of the operations that are faster.
The problem with using flexible length char arrays to hold data is that C has the "strict aliasing rule" which says that an object of type a and one of type b cannot have the same address, so basically just casting the char[] to a struct foo* will be optimized to nonsense.  The workaround is to use a union since union members are exempt from the strict aliasing rule.  I cast through a union using a macro since I can't know the user's type.  However, the char[] is not very aligned and because of this there could be alignment issues on some platforms.  I am not sure if this is an important issue.  I do not want to use an inverted scheme and containerof because it requires extra type definitions.
There are a few aspects of pheap.h, pheap.c, and fla.h that I would like reviewed.  Is the approach that I used to make the heap generic good?  Are the flexible length char arrays a good idea and if not how should I replace them?  Can I make this faster?  Thank you.
Answer: The criteria I use for code reviews is:

Does the code compile without errors and warnings?
Does the code work as expected?
Is the code easy to maintain, especially by others?
Is the code portable (will it compile and run on multiple systems, Window, Linux and Unix)?
Does the code follow best practices? Usually this goes hand in hand with number 3.
How complex is the code? (Really also part of number 3)
Is the code extendable?

General Observations
Overall, nice job! The code in the question compiles without errors and warnings, this is not true of the test code (pheap_test_dijkstra.c and sla.c) in the GitHub link, but that code is outside scope of the question.
I am currently compiling using Visual Studio 2019 on Windows 10, since this code was written on Linux for Linux that makes the code portable.
The comments are meaningful and won't require a lot of maintenance.
The code in pheap.h could use some vertical spacing, I would put a blank line after every function prototype. The one thing I find troubling about the code for maintenance and readability reasons is the single character or two character variables names.

Generic Pairing Heap Performance


Suppress plots in R (mac)

Question: I am currently using R to generate some statistics for a couple hundred time-series from a simulation. I am employing something called the 'earlywarnings' package. The particular function I am using returns various statistics along with their respective plots. However, since I need to check hundreds of these things (in a loop), I'd like to know if there is a way to suppress this function from plotting every time.
I am new to R and I don't know how to see the contents of the package in order to change the code to achieve my goals.
Thank you for your help.
**** Edit *****
I have checked the package's documentation and there's is not mention of an option to stop the function from plotting.
Below is the code needed to run an example. Use any time-series:
<code>generic_ews(mytimeseries, winsize = 25, detrending = c("no", "gaussian",
                                            "loess", "linear", "first-diff"), bandwidth = NULL, span = NULL,
        degree = NULL, logtransform = FALSE, interpolate = FALSE,
        AR_n = FALSE, powerspectrum = FALSE)
</code>
Comment: does this work http://stackoverflow.com/questions/14725620/open-plots-in-a-null-device
Comment: [Please post an MCVE.](http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example/5963610#5963610)
Answer: Have a look at the documentation of the package. Search your function and look if there is an option to suppress plots.
Another possibility is to load the *tar.gz file from the CRAN server and open the file/function you use.

Suppress plots in R (mac)


PhD statistics with MS in CS?

Question: I have a MS in CS with couple extra courses in statistics at graduate level. I am interested in statistical machine learning, however the research can be carried out in Statistics and Computer science department both. I was wondering if anyone has an insight on how hard it would be to get into a statistics PhD with a Masters in CS, I do have some publications and currently working as a Statistical analyst.
Comment: Having a CS background won't prevent your from getting into a Statistics program or even necessarily hurt you, but it definitely does change your profile. Some departments/faculty might love the CS background and others might discount it.
Answer: There are plenty of PhD Statistics programs that would want you, just because of your background. Keep in mind that their are tons of PhD Statistics programs in the USA. You can apply to 10 relatively low ranked ones, and and 10 of your choice, and see from there, for example. One thing to reiterate, ranking is just a relative number. If you graduate and are seeking a Data Scientist position, and have a M.S. In Computer Science + A PhD in Stats, your good no matter where you went.
Answer: CS (in the theoretical track) and statistics both do considerably cover the mathematics! Actually, a robust background in mathematics could drive you to pursue the statistics program and many other interdisciplinary research fields, deservedly. With due attention to the fact that you have passed a couple of related courses in master level and taking your applied research in the target field, you have a noticeable chance to be successful in this way.

PhD statistics with MS in CS?


Basics of Reparametrization trick in Machine Learning

Question: I am trying to understand the reparameterization trick (RPT) used in the calculation of stochastic backpropagation. There are already some excellent answers here and here.
Under usual notation, we can represent the RPT $$\nabla_\theta \mathbb{E}_{p(x;\theta)}[f(x)] = \mathbb{E}_{p(\epsilon)}[\nabla_\theta f(g(\epsilon, \theta))]$$
The overarching objective of this equation is to show that both the gradients ( one with reparamterization and the other with out reparameterization) give rise to the same estimates.
My question:
So, I am trying to get my hands-dirty by calculating the gradients using the reparameterization trick.
Say, we observe a set of univariate random variables $x_1,\dots,x_n$. Some oracle has told us that these random variables come from a Normal distribution $N(\mu,\sigma^2)$.
This is a silly problem obviously, and we can get the estimate of $\mu$ and $\sigma$ from many techniques like MLE, MAP, so on. But, I just want to see how we go about using stochastic gradient descent and reparameterization trick.
Now, let's say we have a node that spits out random variables $x_1, \dots, x_n$. We cannot use the simple backpropagation as the output of the node - $y$ - is a stochastic one. Assume, our loss function $f(y)$ is squared error i.e. $(y-x_i)^2$. Using the LHS of RPT equation,
\begin{align}\nabla_\theta \mathbb{E}_{p(x;\theta)}[f(x)]  &= \nabla_\theta \int \sum_{i=1}^{n}(y-x_i)^2 p(y) dy \\
&= \nabla_\theta \int \sum_{i=1}^{n}(y^2+x_i^{2} - 2yx_i) p(y) dy \\
&= \nabla_\theta  \sum_{i=1}^{n}(\mu^2+\sigma^2 +x_i^2 -2*(\mu)*(x_i)) \\ \end{align}
Now, if we take the specific gradients with respect to $\mu$ and $\sigma^2$ and set to zero, we can see  the updates as $\mu = \frac{\sum_{i=1}^{n}x_i}{n}$ and I am unable to get the estimate of $\sigma^2$. Theoretically, I think the estimate of $\sigma^2 = (\frac{x_i^2}{n} - \mu^2)$
Now I am trying to get the same using the RHS of RPT equation,
\begin{align}\mathbb{E}_{p(\epsilon)}[\nabla_\theta f(g(\epsilon, \theta))]  &=  \int \nabla_\theta \sum_{i=1}^{n}(\mu+\sigma \epsilon-x_i)^2 p(\epsilon) d\epsilon \\
&=  \int \sum_{i=1}^{n} (2(\mu+\sigma \epsilon-x_i) \nabla_\theta (\mu+\sigma \epsilon-x_i)) p(\epsilon) d\epsilon \\
\end{align}
Again, if we take the gradient with respect to $\mu$ specifically, we will have
\begin{align}
\mathbb{E}_{p(\epsilon)}[\nabla_\mu f(g(\epsilon, \mu,\sigma))] =  \int \sum_{i=1}^{n} (2(\mu+\sigma \epsilon-x_i)  p(\epsilon) d\epsilon \\
\end{align}
Setting the above equation to zero, we can see that $$\mu = \frac{\sum_{i=1}^{n}x_i}{n}$$
This is the same as obtained from the LHS of RPT equation.
However, I try to show the same for the $\sigma^2$ estimate that both LHS and RHS of RPT equation give the same estimate but it isn't working out.
Can you please help me show the estimate for $\sigma^2$ using the Reparameterization trick for the simple Normal distribution case.
Edit:
Also, can we show from this simple case, that variance of the estimate obtained using RPT is lower than the one obtained without RPT?
Answer: To my knowledge, reparameterization trick is used to make the Monte-Carlo estimated ELBO have lower variance. In your formulation you seem to use it in other cases. Also, you shouldn't consider doing calculation by hand given very few machine learning problems can be solved analytically. Have you checked the VAE's code? $\mu$ and $\sigma$ are learnt in a nerual network.
To know more details about VAE, you can check my blog post.
Comment: @nbro Indeed.. Withour reparameterization, the estimator could be \begin{align}
\nabla_{\phi} E_{q_\phi(z)} \left [ f_{\theta, \phi}(z) \right]
&=\color{red } { E_{q_\phi(z|x)} [ (\log p_\theta(x,z) - \log q_\phi(z|x) )   \nabla_{\phi}\log{q_\phi(z|x) }   ] } \\

&\approx \color{blue}{\frac{1}{L} \sum_{l=1}^L f_{\theta, \phi}(z) \nabla_{\phi}   \log q_\phi(z^{(i)} |x)}

\end{align}, which the VAE paper claims have high variance.
Comment: @JPZhang: Great blog. Keep up the good work


How can I tell if a website is safe for conference registration?

Question: I am registering for a conference in Canada but the payment link has a weird name like yizhifubj and the website is Chinese.
Is that normal? Are there any guidelines for determining if a registration website is "safe"?
Comment: No. It is **not safe**.
Comment: @AndrésE.Caicedo Sorry, but making a payment for a Canadian conference on a Chinese website? This screams "scam" to me, in particular, since `.cn` might be easily confused for a Canadian domain.
Comment: @AndrésE.Caicedo Look, OP has some valid concerns. Saying "It seems safe." because the potential scammer was clever enough to at least give the impression that several conferences (which you apparently do not know) use this website is not helping anyone.
Comment: Have you asked the conference organizers?
Comment: @NateEldredge "Yizhifu" = prepaid. "bj" = probably Beijing. The website www.yizhifubj.com redirects to PayEase.
Comment: Naive question: does "yizhifubj" spell something in Chinese?
Comment: @AndrésE.Caicedo And have you checked if these are reputable conferences or even if they actually existed?
Comment: @Roland Hmm... You are right. Let me ask random people on the internet instead.
Comment: It seems safe. Why do you doubt it is? A quick google search reveals several conferences that use the site.
Comment: because its name and because google chrome marked the payment page as unsafe because of the https i think
Comment: The conference behind is called "International Conference on Mechanical Design and Engineering", Beijing, China. Surprisingly the conference itself is listed in the nature directory of academic event and the papers should get published in a journal with the ISSN 17426588. That means, the situation is a bit unclear.
Comment: you mean it is a scam? it is used for an ieee sponsored conference
Comment: So, no reasons really.
Comment: @Roland "A quick google search reveals several conferences that use the site."
Comment: [ICMV 2020](http://icmv.org/reg2.html) which is published by [SPIE](https://spie.org/Publications/Proceedings/Volume/11433) also uses this payment gateway.
Answer: You will not be able to get a definitive answer on this unless you contact the conference organisers.  Certainly the registration mechanism is - by modern western standards - backwards - and you are right to ring alarm bells and take extreme caution as it could well be a scam
That said, @GlenPierce answer is not the final word - and there are significant elements which indicate that the site itself is credible - these include

The actual payment IS done over HTTPS, and the certificate ties in with the domain name.  Of-course, this does not mean much, except that the domain has not been compromised.
The domain names associated with the site have been registered many years
The site purports to relate to academic.net - and, indeed, when you go to the academic.net website, the payment system does, indeed link to this domain name.   It is also relevant that most of conferences they have listed are held in China.
If you log onto the site, and change the meeting ID, it lists different headers for different ID's - that means that if the site has been hacked, its been hacked for a while, and there is a "non-trivial" amount of coding behind this - and yet Google have not flagged it as untrustworthy.

My inclination is to believe that this is more a case of incompetence then likely fraud (and this level of competency is not that uncommon in the parts of Asia I've been exposed to) - but I would still not register this site without confirmation from the organizer that it is legit.
Comment: It's definitively unsafe, it uses http, rather than https
Comment: Even if the actual payment is done over HTTPS, the pattern where an initial HTTP page redirects to a HTTPS one is still considered a questionable security practice by today's standards. The reason is that an attacker can rewrite the pages served over HTTP to point to a different malicious HTTPS page.
Answer: Not safe at all.

Http instead of https, never enter any information of any kind into an http site.
The mere fact that it's over http is such a huge flag that almost nothing else matters.
Wierd name. Weird names are evidence of unsafe sites. They probably keep getting blacklisted so need to create hundreds of sites to keep ahead of people writing reviews of their scams, blocking them from searches, etc.
Not a professional page. The layout and overall page design is poor. Real sites hire professional designers.

The payment gateway itself is over http. If your bank's ATM deposit drawer was a shelf that anyone could just walk up to and steal from, would you deposit your money via that ATM?
Even if these conference organizers are legit, they are not competent. This conference won't be good. People who are worth meeting won't attend simply because of this website problem. If they can't build a simple registration website, what else have they screwed up?
Comment: *Real sites hire professional designers* --- LOL I wish. It simply doesn't work that way in my part of academia, though. Small conferences and workshops have home-made sites and registration systems, ranging from home-made php, to Google forms or "send us an e-mail to confirm".
Comment: This is good advice in general, but none of it really resolves whether or not this is the real conference website.  Academic conference organizers rarely have the budget to hire professional designers and so things are often done by someone who just barely knows what they're doing.  Obviously the "safe" approach is to say "don't use it", but if it's real, then for OP that means not being able to go to the conference, which can have a career impact.  People don't always have the luxury of only being able to do that which is safe.
Comment: As to your last paragraph, I can say from experience that there is very little correlation between website design competence and scientific quality of the conference.  I don't know anything about this particular conference, but I certainly wouldn't make the judgment on that basis.  And there are many cases where a conference is important enough to me that I would gladly risk credit card fraud in order to attend (after all, the credit card company would typically eat any losses, not me).
Comment: Actually, the payment is made in another site through HTPS. Look: https://pay.yizhifubj.com/customer/i18n/i18n_input_card_new.jsp
Comment: I very much doubt that money sent through this website will actually result in actually attending a conference. The payment gateway itself isn't even over http. If this is not a scam, it's such a massive security vulnerability that everyone who goes though it will be compromised. Skip this conference.
Comment: That site is http, not https.
Comment: @NateEldredge what real conference website wants you to type in the name of the conference and the amount you need (want?) to pay in a form?
Comment: @GlenPierce https://ibb.co/m0B2DT
Answer: Well, I was trying to apply to a Chinese university and this portal showed up. Just like you, I got suspicious over the URL. The URL of the webpage where you require to enter your card details consisted of "https". This made it easier to go forward but I still had some doubts. I needed to apply for the university, whatever it was. The amount was 120USD. I processed and the payment was successful. The university received the amount and the application portal showed the status "Payment Successful". I was relieved. This is for all those people who encounter that weird-looking payment portal.


Using the diagonal in perpetual queen checks?

Question: There exists a heuristic that recommends checking from the diagonals (using a queen) in order to get a perpetual. This, I expect, is a rule that is meant for the worse player in queen and pawn endgames. My question is, why does checking from diagonals ensures, or at least raises the probability, for a draw?
Comment: I have never hard such a thing.
Comment: Never heard of such rule either. If anything, the opposite would make more sense to me, since checking horizontally/vertically (without support) two squares away from the king, you leave the king 4 escape squares while checking from a diagonal he has 6.
Comment: I don't think there is such a rule. I think rank and file checks are just too obvious for people so they just don't say how great they can be.
Answer: As you said, this is a very general guideline, but looking back it has served me well in practical play.
Note that by "checking from the diagonals", the pattern I have seen is that the queen maintains a stable circuit on a diagonal but the checks themselves are usually horizontal or vertical.
I think it's because the checks from a diagonal allow the queen to keep the king in a box with only minimal pawn support (a single nearby pawn for either side will usually do it). Checks from a file or rank each allow the king to run across the board in one direction unless there's a pawn directly blocking his path.
Comment: I don't understand what you mean. Could you post a concrete position to illustrate this method?
Answer: I first heard this from chess24.com's GM Jan Gustaffson during one of his commentary sessions. The explanation he gave was that it is harder for the opponent to block diagonal checks with the queen. In queen and pawn endgames it can be much harder to continue with checks once the opponent's queen has managed to come back and help.
Comment: Could you post a diagram illustrating this situation?
Comment: Don't see how it should be harder to block diagonal checks. Do you have a link to the video (and time)?
Answer: This personally makes no sense to me.  Gustafsson might have been referring to a specific situation with other pieces involved, but if you experiment with a lone queen versus the king on an open board, you'll see for yourself that it makes no difference. Perhaps in a situation such as with the white king on b1 and his pawn on b2, and the black queen checking from d1, then after the white king went to a2, the black queen could continue checking diagonally from a4 to d1 and back to a4 consecutively, with the white king rotating between a2 and b1, until the position had been repeated 3 times, but that's a specific situation.


Can someone who knows edit the "logic" tag wiki?

Question: A questioner asked why reason is mapped to logic.  Now I'm wondering the same thing.  I think the easiest way to clear up the confusion is if someone in the know would edit the tag wiki to clear things up.  (Thanks!)
Comment: I went ahead and removed the synonym; only 2 posts were affected. While looking at the list I also noticed killing > murder which I'm also not sure belongs, but that's a discussion for another thread. :P
Comment: Note that anyone can submit edits to the tag wikis. I am not exactly sure why this link is in place, and I agree it could be confusing
Answer: I see the point and agree with the removal of the tag synonym but I think any use of a "reason" tag will have to be used carefully. The problem is that "reason" can mean so many different things.
In a general sense, "reason" is what philosophy is all about, and in that way it'd be essentially as useless as a "philosophy" tag.

a basis or cause, as for some belief, action, fact, event, etc.: the reason for declaring war.
a statement presented in justification or explanation of a belief or action.

But in the sense the poster used it in the question you linked, "reason" is not referring to the justification of anything but rather the thing or process that reasons itself.

the mental powers concerned with forming conclusions, judgments, or inferences.

It can also refer to:

sound judgment; good sense.
normal or sound powers of mind; sanity.

So I'm all for delinking the "reason" tag with "logic", but for clarity we might consider figuring out ways in the long run to avoid confusion with the tag.
Comment: Creating the respective tag wikis would help.  (Yeah, in general `reason` could easily apply to all questions, hopefully.)
Comment: Yeah, tag wiki's for sure would help :)
Answer: Since nobody else has stepped in, I've suggested the following excerpt:

study of formal systems of reasoning—especially of the deductive variety.

(Only the — must be simulated with ---.)
This has been my approximate definition of logic for quite some time, but if anyone wants to use another, feel free.  I think the body needs to address the difference (or lack thereof) between logic and reason.  Since I haven't read Kant, I can't speak intelligently about it.  ;-)

I went ahead and asked a question about this on the main site.  I'm not sure if it's a good one since I've done very little research on the topic myself.


Question regarding $Z$ (Compressibility factor)

Question: Oh! This problem has been bugging me for a long time. According to Wikipedia, the Compressibility factor $Z$ is defined as the ratio of the volume occupied by a real gas to the volume occupied by an ideal gas at the same temperature and pressure.
$$Z=\frac{V_{real}}{V_{ideal}} \text{              ........(1)} $$
Now the Ideal Gas Equation is
$$P_{ideal}V_{ideal}=nRT   \text{        ....(2)}$$
Now from here we can substitute the value of $V_{ideal}$ into the above expression $(1 )$ to get
$Z=\frac{PV_m}{RT}$
Where $V_m$ is the molar volume of the gas and $P$ is the value of $P_{ideal}$ that was in the ideal gas equation $(2)$.
OK, So far so good!
Deriving the compressibility factor value from the van der Waals' gas equation:
We know for real gases the pressure exerted by them is always less than the pressure exerted by an ideal gas so we correct the pressure by the term $a\frac{n^{2}}{V^{2}}$, we get
$$P_{ideal}=P_{real}+a\frac{n^{2}}{V^{2}}$$
And the volume occupied by the gas molecules can be written as
$$V_{ideal}=V_{real}−nb$$
On substituting the above values of $P_{ideal}$ and $V_{ideal}$ in the ideal gas equation, we get our van der Waals' Gas Equation
$$(P+a\frac{n^{2}}{V^{2}})(V−nb)=nRT$$
Please note that in the above equation $P$ is $P_{real}$ and not $P_{ideal}$. Now I'm going a step further to calculate the value of Z from this equation by shifting the terms and I got this
$$Z=\frac{PV_m}{RT}=\frac{V_m}{V_m−b}−\frac{a}{RTV_m}$$
Now here's the problem that I'm facing: In the above expression the value of $P$ is not the $P_{ideal}$ but it is the value of $P_{real}$ that we had in the van der Waals' gas equation.
Doesn't that contradict the whole definition of Compressibility factor that we had learned in the first place? How this expression for $Z$ can be correct?
Thanks for reading.
Comment: related: https://chemistry.stackexchange.com/q/57909/102629
Comment: You may use \tag{N} for numbering equations, it would write right aligned  (N).
Answer: Forget about the ideal gas.  The definition of the compressibility factor is just $$Z=\frac{PV_m}{RT}$$


Can I wear this and pray and do other stuff

Question: Is it permissible to wear this hoodie
Answer: In terms of praying, the law is MAKRUH. Because the painting on the dress can disturb others like the picture on the back of the shirt, it will definitely disturb the person who is praying in the back.
Some scholars condemn it as HARAM. The Prophet S.A.W. curse those who paint pictures of creatures.
However, some scholars condemned it as MAKRUH. To avoid disturbing others in prayer, it is better if the shirt is turned over before prayer.
Despite that, your prayer remains valid.
Wallahualam.
Answer: The simple answer is, No
Wearing a garment (cloth, hoodie etc..) with any image of a being with a soul is not permissible, but to remove such image (by painting, cutting, etc...) and then wear it, this is permissible.
And Allah knows best.


Is Thai less tonal than Chinese or Vietnamese or Burmese?

Question: I'm curious about the comparative reliance on tonality in Asian languages.
By this I mean not the number of tones, but the frequency of tonal versus non-tonal words in communication. (When I say non-tonal here, I mean words that are neutral tone and have no other tonal homophones)
Among large tonal languages, Vietnamese sounds like the most extremely reliant on tonality, and Thai sounds the least. I imagine Vietnamese has much more words that would be indistinguishable if it wasn't for tonality than Thai.
Based on this, as a speaker of only non-tonal languages, I believe Vietnamese would be by far the most difficult for me to learn.
Roughly speaking, how often do tonal words appear in Thai? Would you say every 5th word is tonal, or every 20th word, or every other word? Thanks
Comment: In languages using tone, all words have tone. There is no such thing as a "non-tonal word", just like in English there is no such thing as a "non-syllabic word".
Comment: Jesus you guys are a bunch of skeptics, every question I ask someone comes to deny the existence of what I'm asking by purposely misinterpreting my question. But again, you are wrong, so why waste your and our time with comments like this? You are wrong, because many words even in tonal languages are base tone and don't have any other tonal variant that can be confused with. This is clearly what I meant, and it's easy to discern, unless you purposely want engage in petty argument. Thanks.
Comment: Asking how many words have tonal homophones is a very different question from asking how many tonal words there are. I'd recommend you [edit] your post taking into account the feedback you have received and to clarify any possibility of misunderstanding.
Comment: Thanks curiousdannii, I've added a sentence to clarify what I mean by non-tonal. I also think my first original sentence asking about the comparative reliance on tonality is pretty clear what I'm talking about.
Comment: @Florian Are you asking specifically about [neutral tones on weak syllables](http://en.wikipedia.org/wiki/Standard_Chinese_phonology#Neutral_tone)? Or are you asking about words without homophones? Because those are two very different things. It would be incorrect to call the second "neutral tone".
Comment: I'm not asking about syllables, I was asking about words and the frequency of words that could be described as neutral tone (whatever that happens to be in the given language) AND without any tonal homophones versus words that are not neutral tone AND/OR have other homophones with other tones. The first type is what I referred to as "non-tonal", which is apparently not a way I can refer to them without significant argument.
Answer: This may not be the type of answer you were hoping for.
You are correct in asserting that most tone languages can be analyzed from a phonological perspective as including words or syllables that lack a specification for tone. Some examples:

Mandarin can be analyzed as having "neutral" tone specified on things
like the sentence-final particle -le.
Many African languages can be analyzed as having single-tone systems,
with select syllables being marked for high tone and the rest being
unmarked.
"Standard" Japanese, which is usually analyzed as having a lexical
accent system (a subclass of tone systems), includes words in which one of the syllables is marked for a lexical pitch accent and the rest are not. Some words are
analyzed as completely "unaccented" (i.e., none of the syllables in
them are marked for accent).

However, in all such cases, there are "rules" that govern what pitch contours are given to the words and syllables that are analyzed as tonally "unmarked". They are analyzed by phonologists as "unmarked" only because their pitch contours are predictable. In other words, a language learner need not memorize any inherent tone shape associated with them, but the learner does need to be aware of the "rules" that govern their pronunciation, which is invariably dependent on the inherent tonal features of neighboring syllables that are marked for tone.
For example, in Mandarin, the fact that the particle -le is unmarked for tone doesn't mean that you can get away with pronouncing it with whatever pitch contour you feel like. What pitch contour is appropriate for the particle depends entirely on the tone of the syllable before it in the sentence. If that penultimate syllable is high or falling, the particle must be lower relative to the penultimate syllable. If the penultimate syllable is low or rising, the particle must be higher.
In African languages that are analyzed as marking select syllables as "high", usually all the rest of the syllables are pronounced with pitches that are lower compared to those that are tonally marked. Those other syllables could often just as easily be analyzed as being marked as "low", but to do so would be redundant.
In Japanese, the traditional analysis of its tonal system assumes that accented words include a syllable that is marked for a locus of a tonal shift from high to low. Syllables leading up to the marked syllable are given a relatively high pitch, and syllables following the marked syllable are given a relatively low pitch (it's a bit more complicated than that, but that's the basic system). In words that lack an accent-marked syllable, the pitch gradually rises through the end of the word.
I raise all these examples to illustrate the fact that getting the pitch of "unmarked" elements right is just as important as getting the pitch of marked elements right in tone languages. If anything, it can be even trickier for a non-native speaker to learn how to pronounce such unmarked elements. I've witnessed this firsthand watching American college students attempting to learn how to pronounce sentence-final particles in Mandarin--even after getting the basic four tones down, they often struggled with that elusive "neutral" tone.
So I know I didn't directly answer your question in terms of helping you find a tone language with a relatively large number of tonally "unmarked" words, but my point is that you may not want to use that criterion to predict which tone languages will be easier for you to learn.
EDIT in response to comments under the original question:
After reading some of the comments above, I think it's important to point out two things.
One--in the languages you mention, tone is contrastive at the level of the syllable, and while most "words" (in the morphological sense) are monosyllabic, many vocabulary items that you as an English speaker would consider to be "words" are compounds comprising multiple syllables. In these polysyllabic compounds, the tone of each syllable must be taken into consideration. I am not an expert in Thai or Vietnamese, and I know next to nothing about Burmese, but in Mandarin, there are almost no vocabulary items that lack tonal specifications. Either they are monosyllabic and the tone on that single syllable is specified, or they are compounds and just a subset (usually just one) of the syllables in the compound gets "stripped" of its underlying tone. The exception to this is monosyllabic particles, but they can't occur in isolation either. So the likelihood of encountering a standalone vocabulary item that is entirely unspecified for tone in Mandarin is pretty much nil. My limited understanding of Thai is that every syllable bears a tonal specification. In Thai orthography, which marks tones, some syllables don't bear a tonal marking, but (as in the examples above) there are rules that govern what tone such unmarked syllables bear. I found this Thai-language-learning website that lays out those rules.
Two--just because a word happens not to have any alternate-toned near-homophones (what linguists call minimal pairs), it does not mean that it's not important to be aware of its tonal specifications. There's not a perfect analogy in English, but think about a word like beige. I can't think of any other monosyllabic words in English that start with [b] and end with [ʒ]. But that doesn't mean that it doesn't matter how I pronounce the vowel in that word. A learner of English would have to learn how to pronounce the word with the correct vowel.
Comment: Okay thanks for your answer, I'm curious specifically about the Asian languages I listed, since I'm thinking about potentially learning them during my lifetime.
Comment: @Florian Sorry, I know a lot about Mandarin but little about those other languages. But I've added some points in my answer in response to comments (including your own) under your original question. My educated guess about Thai specifically as compared to the other languages is that the short answer is "no" (it is _not_ less tonal as you define it--i.e., every syllable bears a tone).


Add checkbox to Ubercart checkout

Question: It sounds quite easy, adding a checkbox to Ubercart's checkout form. The consultant I spoke to told be to use hooks, or try using the uc_extra_fields_pane module, which I also cannot get to work properly (it's config page is not showing up). I'm using Ubercart 2 and Drupal 7.22.
Answer: In your custom module use the hooks defined in the Ubercart terms and conditions module.
Comment: Thank you for pointing me in the right direction. I edited this module to fit my needs, thanks a lot!

Add checkbox to Ubercart checkout


Is there a way to resize multiple objects with different sizes, to the same dimensions?

Question: So I am very new to Blender and I am attempting to model a low poly P250, after a lot of struggle I had the wireframe outline, but when I looked at it in 3D view everything had different thicknesses, I've got no clue how to change all parts to the same dimensions. To an experienced user this must be painful to look at haha.
Comment: if those are different objects, you can go in the N panel > Item > Dimensions, and give them the same dimension on the chosen axis. If this is one object, you need to find an addon that will give you the dimensions of the selected mesh/edge, maybe check here: https://blender.stackexchange.com/questions/86829/edit-mode-dimensions
Answer: press TAB
select all by pressing "A"
press S to scale
now without touching anykey/mouse.. press X
and now move your mouse ... it will start scaling in X direction.


What kind of suspension do I have and how do I make it more soft? (I'm quite small)

Question: My suspension is very stiff, I would like to know why and how to make it better for my size. My bike is a 24" Muddy-Fox Impact hard tail. I went to a trail with friends and they were OK but I was not, please help!  I have tried putting oil on the outside even trying to breakdown the suspension by letting my big friend ride it but did not work.
Comment: The bike has a low end suspension fork, there is little if anything that can be done. Low level suspension is designed to give the appearance of suspension rather than act as an actual suspension.  You might get better results playing with tire pressure and/or tire size (i.e., larger and lower pressures).
Comment: New bike might help
Answer: I've googled and found this bike on Amazon.  Its also listed at a UK site.

Second site lists this at £160 so its firmly in low-spec price range.  Most likely the front fork is based on elastomer and/or a coil spring.
Some questions that discuss the internals of a fork:
What options do I have when replacing my fork's elastomers?
and this question states typical sag values which you should measure on your bike.
What maintenance does a front suspension fork need?
If you get on the bike and the suspension doesn't sag by 10-25% then you're simply too small and light for the suspension, and softening it could require removing some elastomer or replacing the springs with softer ones.
A more expensive option is to replace the fork with a better one, but this will cost significantly more than the rest of the bike.
As a pseudo-fix you could try adding weight to the front of your bike, with a handlebar bag, front drink bottle cage, or even just getting off the saddle and leaning forward more.
Comment: Some forks have springs in each side. Removing spring and/or elastomer from one side might help, but it might cause other problems.
Comment: @mattnz yes - you could mess about modifying springs, but that's generally going to make it worse.  The best thing is to replace the springs with new ones the same length and attachment but with a "lower" spring rate, means it takes less weight to compress/expand them.
Answer: I tried quite a few things with my hard-tailed bike. I put on a seat post with suspension. I got a big cushy seat with springs. I got soft cushy handle-bar grips. They all helped but nothing really did as much as getting another bike with full frame suspension. How much do you like this bike? Is it heirloom? Moderate to unpleasant vibration is kind of the nature of the beast. However, if you are not sentimentally attached to this bike and you want a more comfortable ride I would recommend a full suspension bike.
Comment: Hes got a £160 bike. Full suspension would be an upgrade only if you added a 0.


SSRS table populating data into a field that should be blank

Question: I am having trouble resolving an issue. I have a table on an SSRS report. The query for the table gets the definition, the total count of that definition and calculates the percentage of all the counts. However, as you can see in the image, one field is being populated with another fields data when it should be blank. Are there any SSRS experts out there who can lend a hand?
Here is the query:
<code>SELECT fundingyear
    , loan_type
    , COUNT() AS total_lntype
    , COUNT() * 1.0 / SUM(COUNT(*)) OVER (PARTITION BY fundingyear) as lntype_perc
FROM vw_LoanRpt
WHERE loan_type not in ('Line of Credit')
GROUP by fundingyear, loan_type
</code>
Comment: What is the query? And the formula?
Comment: Here is the query.

SELECT fundingyear, loan_type,
       COUNT(*) AS total_lntype,
       COUNT(*) * 1.0 / SUM(COUNT(*)) OVER (PARTITION BY fundingyear) as lntype_perc
FROM vw_LoanRpt
WHERE loan_type not in ('Line of Credit')
GROUP by fundingyear, loan_type
Answer: I found that using a Matrix instead of a table resolves the issue.


Basis expansion for regression using neural network?

Question: I am trying to approximate a nonlinear function using a neural network. There are 3-4 input units. The network is struggling a bit to generalize the function outside the vicinity of the training data set.
I asked someone and he suggested that basis expansion might help. Can someone please provide a reference for the same, I am not able to find any. Also, he suggested "basis expansion using kernel method".
Answer: I guess expanding basis is somehow looking at the problem using linear algebra perspective. For explaining it using a trivial example, in linear algebra, for the 3D space, there are three bases namely, $i$, $j$ and $k$. It means for referring to any vector in 3D space you just need a linear combination of these three vectors to construct any desired vectors. Each basis for each space has a number of properties like being orthogonal or not or maybe being linearly independent and some other important properties. By adding extra features, you increase the number of features if they are linearly independent.
In machine learning, there are situations that comparing each feature with the output directly may not lead to a good decision boundary while using some features alongside each other can make decision boundaries which can lead to a better decision boundary. All of that means that if you change the input space to space with more number of features which the features are extracted using the current feature space, you can find a space that the data can be separated better. Finding a feature space such with properties can be done using feature extraction methods. Kernel methods are some of them.
Kernel trick is a kind of mathematical approach for reducing the difficulties of transforming the data in the current feature space to the appropriate feature space. Suppose you have one million rows of raw data and the feature space belongs to $R^{3}$. Suppose you find out that a feature space that can have a good  generalisation belongs to the space which belongs to $R^{95}$. Trying to transform the data in hand to the desired feature space is a time-consuming task if possible. Instead of transforming the data directly, the kernel trick tries to calculate the outcome of the transformed data without transforming the data into the new space.


Navigation next, previous product for eshop

Question: Will visitors of eshop benefit from "Next product" and "Previous product" buttons on product detail page (just buttons, so they are basicaly getting random product from same category), even they can choose another product from "Similiar products" section close below? Client has it on his current eshop that I'm redesigning and wants to keep it and I'm just curious if it's good approach.
(I know the best way is to make usability test, but budget is kinda low and client himself doesn't have any analytics data).
Answer: The previous and next button could help preventing pogosticking.
Most guidelines against pogosticking are about making the result and category pages more accessible with more information while interacting.
Two great resources on this:
https://baymard.com/blog/ecommerce-quick-views
https://baymard.com/blog/secondary-hover-information
If the user is on a category page with products that are all potential products he or she wants to buy they would want to view the full product page of all products. The next and previous buttons could make this easier.
Keeping it not random would be wise. Just the next or previous in line as would be on the category page.
Too bad you don't have any analytics available. This would make it clear if the buttons are used by users.
I can't remember ever reading any data by NN Group or Baymard on this topic, nor can I easily find any other findings, so I can't enlighten you with any insights. So that leaves me with "no harm no foul". "If it doesn't hurt...". If you can think of no reason the buttons wouldn't fit into your design, I think you're left with doing what the client desires.
And do add analytics for your client this time! ;)
Answer: I think it depends on the products sold themselves a lot, as well as the User behaviour. Therefore, various strategies can be applied here.
Some products may be similar, and only have a difference in tiny details. Sometimes, products can be organised in a chain depending on the features (e.g. a NAS server with 256MB of RAM, 512MB of RAM, 1024MB of RAM etc.).
In those situations "next" means "better" or "of higher functional value", whereas "previous" means the opposite. In this situation, it does make sense.
Then, sometimes the offer may be really random, but as a user, you still need to dive into the details to decide. Like on Etsy, where searching for e.g. a wallet, you might want to go through either a list of thumbnails or navigate between them one-by-one. No "gradual" aspect of the offer applies here, you just look through a subset of your search criteria/category. Here, it also makes some sense, it's like Tinder for products then. But for that to work, I believe you need to focus on the technology part to support fast switching from one to another.
But, should the user be not interested in many of these products, they go through when going through the chain of previous/next, it is not a good idea to have it, as on every page they will just say "no, this is not something I am looking for". In those situations, it may be helpful to provide them with an excerpt from the list of the products available in the "next" and "previous" subsets, for example by displaying some thumbnail and the crucial features that would allow the user to decide. Then, they would be able to go to the e.g. 3rd next product, skipping the two that they could tell they would not be interested in at all just after seeing the thumbnail and the limited details.
No matter which approach you select, or come up with something even better, it's worth experimenting and collecting analytical data to make the proper decision. I know it is a limitation here, but anyway, listening to the users is the best way to design solutions that would work for them. If you are short on the budget, then maybe you could just do a corridor test with some of your friends, family etc.


What is the name of the bond between phosphate and the sugar in a nucleotide?

Question: I am slightly confused about what the name of the bond is between the phosphate and sugar within a nucleotide. All my research comes up with is a phosphodiester bond being the backbone of DNA. But within a single nucleotide, would we perhaps call it a phosphoester bond (all of my searches of phosphoester bond correct it to phosphodiester, so I don't think the term 'phosphoester' is in use...); or maybe it would be an O-glycosidic bond as it is a sugar molecule covalently bonded to another molecule via an O atom?
Comment: Please do not ask multiple questions.
Comment: @another 'Homo sapien' Glycosidic bonds certainly do not always involve an O atom (heard of N,C and S glycosidic bonds? Now THAT is something you can find out on Wikipedia). And I do not get your point- even if a glycosidic bond required an O atom, there is one between the sugar and the phosphate group.
Comment: @another'Homosapien' see above comment.
Answer: Phosophoester is a valid term. There are at least a 1000 peer-reviewed articles that use this term. IUPAC Goldbook defines nucleotides as:

Compounds formally obtained by esterification of the 3 or 5 hydroxy group of nucleosides with phosphoric acid. They are the monomers of nucleic acids and are formed from them by hydrolytic cleavage."

Phosphoester or phosphoric ester means an ester of phosphoric acid.
Answer: Expanding on WIYSIWG's correct answer:
Each nucleotide contains one phosphoester bond (between a phosphate O and sugar 5'-C). Additionally, two nucleotides are connected by one phosphoester bond (between a phosphate O and sugar 3'-C). So in a polymer of multiple nucleotides (DNA, RNA), the repeating monomer unit contains two phosphoester bonds, on "top" (5') and "below" (3') the sugar. Since the repeating unit contains two phosphoester bonds, and the phosphates alternate with the sugars in the sequence, we call this a sugar-phosphate backbone held together by phosphodiester bonds/linkages.
Schematic of single nucelotide  featuring vertical line as phosphoester bond (to 5' C):
$P \\
| \\
[sugar]-[base]\\
\\$
Two nucleotides, each with an internal phosphoester bond and with a new phosphoester bond connecting them (spanning 5' of one sugar to 3' of the next):
$P \\
| \\
[sugar]-[base]\\
|\\
P\\
| \\
[sugar]-[base]\\
\\$
Repeating unit in nucleotide polymer, with alternating sugar-phosphate backbone and one phosphodiester bond/linkage per unit/nucleotide residue (the ... ellipses indicate pattern continues for the entire nucleic acid polymer, with hydroxyls capping the very ends):
$...\\
P\\
| \\
[sugar]-[base]\\
|\\
...\\$
Comment: phosphomonoester is also a common term for the first case


Apple remove dir - user.sparsebundle

Question: The Sparse bundle directory in my Mac Snow Leopard is taking lot of space.
I don't have an option to disable FileVault on my Mac. Would like to know the after affects of removing the sparse bundle directory
Answer: You can disable filevault on your mac System Pref -> Security -> Turn off filevault. But it requires almost 2x disk space to decrypt all the data that your filevault contains !
It you delete the sparsebundle directory you will lost all the data contained in file vault !
If you can access to file vault, I recommend you to delete big files from it and usually on logout Mac OS x resize file vault allocated disk space. Then you can disable it !
Edit :
If you want to start from fresh :

Format your hard drive an reinstall Snow Leopard to have a clean system
Try to delete sparsebundle, you will lose your data and I don't tink SL will be so happy with it and let you start a new File Vault
Try to delete the user accounts associated with filevault (usually filevault contains user home folders) and recreate them afterwards
Comment: Somehow, the option is disabled, is there any other way to disable and enable this so that I can start fresh.
Answer: The sparsebundle for your user requires as much space as the data in your user directory, because these are its contents. Sometimes it gets larger, that's why it gets compacted during logout.
If you want to see what happens when you delete it: Create a new user and log in. That's an approximation of the data you will have left, of course Mac OS X might take issue with the file being gone as well.
Move all your data (contents Documents, iTunes, Movies, Pictures, etc.; NOT Library) to an external hard drive, log out, let it compact. Now it should be smaller. Turn off FileVault, and when it has finished, copy your data back to its original location.

Apple remove dir - user.sparsebundle


Is it possible to embed a PayPal donation button and still be GDPR compliant?

Question: I've read that PayPal embeds a pixel in its button which tracks every user that visits the website. Is that true?
More generally, is it possible to embed a PayPal donation button and still be GDPR compliant?
Answer: You can embed a third party button, but have to take care how and why you do this.
PayPal is not providing the button solely on your behalf, but for their own purposes. They are not your data processor, but another data controller. Thus, you need a legal basis (Art 6 GDPR) for sharing visitor data with PayPal. You do have a legitimate interest to accept "donations", but does this interest outweigh the privacy of people who are just visiting your website, without the intent to donate and without being aware of PayPal's data collection? Likely not. Common solutions:

You do not embed the button at all, but merely link to a PayPal page where the visitor can make a payment.

You show a placeholder for the embedded content, and only load the PayPal button when the user clicks on it.
Additionally, this placeholder could provide information about PayPal and their privacy policy. Then, your legal basis for embedding PayPal could be consent instead of legitimate interest (which may or may not be simpler compliance-wise).
An attractive aspect of explicit consent is that it can serve as a legal basis for international transfers, considering that US-based services are no longer covered by an adequacy decision following the Schrems II ruling in 2020.

Background: when you embed third party content on your page, you are jointly responsible for processing of personal data resulting from this. This applies to embedding buttons, scripts, iframes, and other content. There is good case-law on this through the Fashion ID case (ECJ C-40/17) that discussed the obligations of a site operator who embedded a Facebook "Like" button. They were held jointly responsible for the data collection of the button on the page (including merely disclosing the IP address for loading the button from Facebook), but not responsible for subsequent processing of this information on Facebook's servers. The site operator is the data controller even though the embedded button is actually loaded by the user's browser. The scenario is very similar to your question regarding PayPal.
Related questions:

Who is the data controller for embedded content? q/55925
Background on the "joint controller" concept, includes an example for embedding a Youtube video in a likely GDPR-compliant manner. q/55996