Only One Path in the Looking Glass

Question: I understand that only the best path is advertised to eBGP neighbors, but is this true of iBGP? If I peer with two providers, I was under the impression that anyone else peering with both of my providers would have two paths to me. After inspecting a number of looking glasses, it appears this isn't so.
Answer: BGP always only advertises the best path onward to its peers.  This is true for eBGP, iBGP, route reflection (which is merely a special case of iBGP), and any other way you might use BGP.
But, yes, you are correct, if you are sending advertisements to providers A and B, and I have connections and BGP sessions also with providers A and B, then I should see both paths in my BGP tables.  I may not see multiple routes created in my routing tables...that's a question of the configuration of my devices and whether I allow multiple routes of equal AS Path lengths to be inserted into the routing table...typically BGP will only install a single route.  The BGP tables, though, should show advertisements from both providers.
Actually...even if I'm peering with providers B and C, or even C and D, I should still see multiple paths in my BGP tables as long as you are reachable through B, C, and D.  All other things being equal, my devices should pick B because that should be the shortest AS PATH, but I would still see the paths with the longer AS PATHs from C and D.  Now, perhaps C and D have both decided that the path through A is better than the path through B, then the paths that I would see would have AS PATHs of "A C" and "A D", so it would appear as if you weren't connected to B at all, but if the path through A went away, then the path through B would get propagated onward through C and D.
If you can give some specifics...maybe even your blocks that you're advertising if you're willing to share that....others can take a look at what we're seeing and perhaps give some more specific guidance.
Answer: One aspect not yet covered by these answers is BGP "add-path" which lets a BGP peer send not only their best route, but some or all of their alternates as well.
This is most useful (as well as likely to work) on iBGP, and gives better ECMP.
For EBGP if you have multiple sessions to the same peer on a single router you should be using BGP "multipath" to allow ECMP. Depending on how and where route reflection is done in an SP network this can result in using all sessions quite evenly.
Here's a presentation from Dave Ward (then at Juniper, now at Cisco) about add-path:
http://www.nanog.org/meetings/nanog48/presentations/Tuesday/Ward_AddPath_N48.pdf
Answer: Typically, BGP peers can only send a single path to eachother, with any updates for that path replacing the existing one.
However, there is an extension to BGP, typically known as additional-paths which puts an identifier on each route sent to a peer and thus enables BGP peers to exchange multiple routes to a path, thereby giving you not only a greater scope for traffic engineering, but also a reduced convergence time in the event of path withdrawal since the non-bestpath prefix(es) can be installed in the FIB as a backup route(s) that will be used the moment the bestpath gets withdrawn - this is particularly significant if you're running full internet tables as the BGP scanner on a Cisco router will run every 30 seconds at best and walking over 300,000 routes takes its toll.
Note that BGP additional-paths has nothing to do with ECMP since obviously, we're talking about receiving multiple prefixes with the same next-hop - with the only exception being cases where you're running iBGP and not using next-hop-self (or doing dirty things with eBGP where the nexthop is preserved)
Since it is an extension, both routers must support it and negotiate the feature at connection time (or alternatively, have negotiated dynamic capability). It is usable with both eBGP and iBGP.
Answer: Trying to look for your own routes in looking glasses does not always work the way you expect, particularly if you buy from someone who purchases a lot of transit. For example, Internap buys transit from many other large ISPs. If you buy from Internap and then someone else, there is a good chance that your route on the other provider would be hidden by virtue of not being best. Most ISPs prefer their own customer routes. Seeing or not seeing your own routes in a looking glass has very little to do with if your route is propagating correctly or not.
Answer: Your question touches not BGP itself, but ISP policies. Not always - either by policy or by mistake - your providers will announce your space to upstreams. Are you using PI or PA by the way?
Answer: There's so much filtering between you and the LG (looking glass) that can get your prefix removed from on path or another.  What's the length of your advertised prefix?  Do you have PI or PA space?  Since the bestpath is advertised to peers, you two paths can be competing with one another upstream and only one is making it to the LG.  If you shutdown one of your paths, does it then show up in the LG after convergence?  That will tell you you're losing one to bestpath.  Try LG's with your providers to confirm your prefix is there first, then try to work your way up to the next SP.
For your iBGP bestpath question, default is to only advertise one.
Answer: The answer is not a simple "yes" or "no", but I think essentially your observation is indeed true that "this isn't so."
For more detail, see here.
For the sake of curation, SE prefers against answers that are purely links to other pages, however, so I'll reproduce some of that here in case the source someday disappears or changes.

How the Best Path Algorithm Works
BGP assigns the first valid path as the current best path. BGP then
  compares the best path with the next path in the list, until BGP
  reaches the end of the list of valid paths. This list provides the
  rules that are used to determine the best path:
1) Prefer the path with the highest WEIGHT.
Note:  WEIGHT is a Cisco-specific parameter. It is local to the router
  on which it is configured.
2) Prefer the path with the highest LOCAL_PREF.
Note: A path without LOCAL_PREF is considered to have had the value
  set with the bgp default local-preference command, or to have a value
  of 100 by default.
3) Prefer the path that was locally originated via a network or
  aggregate BGP subcommand or through redistribution from an IGP.
Local paths that are sourced by the network or redistribute commands
  are preferred over local aggregates that are sourced by the
  aggregate-address command.
4) Prefer the path with the shortest AS_PATH.
Note: Be aware of these items:
This step is skipped if you have configured the bgp bestpath as-path
  ignore command.
An AS_SET counts as 1, no matter how many ASs are in the set.
The AS_CONFED_SEQUENCE and AS_CONFED_SET are not included in the
  AS_PATH length.
5) Prefer the path with the lowest origin type.
Note: IGP is lower than Exterior Gateway Protocol (EGP), and EGP is
  lower than INCOMPLETE.
6) Prefer the path with the lowest multi-exit discriminator (MED).
Note: Be aware of these items:
This comparison only occurs if the first (the neighboring) AS is the
  same in the two paths. Any confederation sub-ASs are ignored.
In other words, MEDs are compared only if the first AS in the
  AS_SEQUENCE is the same for multiple paths. Any preceding
  AS_CONFED_SEQUENCE is ignored.
If bgp always-compare-med is enabled, MEDs are compared for all paths.
You must disable this option over the entire AS. Otherwise, routing
  loops can occur.
If bgp bestpath med-confed is enabled, MEDs are compared for all paths
  that consist only of AS_CONFED_SEQUENCE.
These paths originated within the local confederation.
THE MED of paths that are received from a neighbor with a MED of
  4,294,967,295 is changed before insertion into the BGP table. The MED
  changes to to 4,294,967,294.
Paths received with no MED are assigned a MED of 0, unless you have
  enabled bgp bestpath med missing-as-worst .
If you have enabled bgp bestpath med missing-as-worst , the paths are
  assigned a MED of 4,294,967,294.
The bgp deterministic-med command can also influence this step.
Refer to How BGP Routers Use the Multi-Exit Discriminator for Best
  Path Selection for a demonstration.
7) Prefer eBGP over iBGP paths.
If bestpath is selected, go to Step 9 (multipath).
Note: Paths that contain AS_CONFED_SEQUENCE and AS_CONFED_SET are
  local to the confederation. Therefore, these paths are treated as
  internal paths. There is no distinction between Confederation External
  and Confederation Internal.
8) Prefer the path with the lowest IGP metric to the BGP next hop.
Continue, even if bestpath is already selected.
9) Determine if multiple paths require installation in the routing
  table for BGP Multipath.
Continue, if bestpath is not yet selected.
10) When both paths are external, prefer the path that was received
  first (the oldest one).
This step minimizes route-flap because a newer path does not displace
  an older one, even if the newer path would be the preferred route
  based on the next decision criteria (Steps 11, 12, and 13).
Skip this step if any of these items is true:
You have enabled the bgp best path compare-routerid command.
Note: Cisco IOS Software Releases 12.0.11S, 12.0.11SC, 12.0.11S3,
  12.1.3, 12.1.3AA, 12.1.3.T, and 12.1.3.E introduced this command.
The router ID is the same for multiple paths because the routes were
  received from the same router.
There is no current best path.
The current best path can be lost when, for example, the neighbor that
  offers the path goes down.
11) Prefer the route that comes from the BGP router with the lowest
  router ID.
The router ID is the highest IP address on the router, with preference
  given to loopback addresses. Also, you can use the bgp router-id
  command to manually set the router ID.
Note: If a path contains route reflector (RR) attributes, the
  originator ID is substituted for the router ID in the path selection
  process.
12) If the originator or router ID is the same for multiple paths,
  prefer the path with the minimum cluster list length.
This is only present in BGP RR environments. It allows clients to peer
  with RRs or clients in other clusters. In this scenario, the client
  must be aware of the RR-specific BGP attribute.
13) Prefer the path that comes from the lowest neighbor address.
This address is the IP address that is used in the BGP neighbor
  configuration. The address corresponds to the remote peer that is used
  in the TCP connection with the local router.

That said, however, I could be wrong. I'm rather a novice in this field.
Comment: While the BGP decision algorithm is definitely useful and something one should know fairly well, I don't think it particularly answers the OPs question (unless I've misread it)
Comment: SOHO networking, enterprise networking, provider networking... it's all based on the same fundamentals.

Only One Path in the Looking Glass


Is a gasless MIG welder a contradiction in terms?

Question: There are lots of very low cost "MIG" welders such as this one for under $100. It claims it's gasless. But the girth of the torch and its lead look like it could feed gas. No gas inlet barb or hose is visible. But calling it MIG if it can't use gas seems like complete misrepresentation?
Comment: I'm voting to close this question as off-topic because it is not a DIY question at all. I decided to vote instead of closing it outright to see what others say.  There are plenty of not allowed question that are "allowed"  will this be one of those ?
Comment: You might have just edited your question.  You know about the reputation system, there's a parallel channel of "quasi?" reputation the system uses.  You get a demerit in that system for deleting a question with answers.  As your score worsens you lose rights, ultimately the right to ask questions.  For instance my ???rep is such that I can close questions as dupes on my vote alone. It's a little unsettling at times...
Comment: Sorry I deleted and rewrote the comment to make more sense.  Meanwhile you answered lol.  Anyway that one *did* have an answer -- oh hold on, now I remember, it was deleted... nevermind...
Comment: @Harper - thanks - I didn't think I'd get penalised unless it had been answered - I noticed a warning but stupidly ignored it, I was sure it didn't do that before!
Comment: If a *not allowed* non-DIY question on a DIY stack is  *allowed* is it a contradiction ?
Comment: This is fun! If a non-DIY question is not allowed, that does not say anything about whether DIY questions are allowed. But I get a hint - and these are DIY machines, so... this question should be allowed?
Comment: @CL22 The title is a quasi philosophical question and the question itself asks nothing about **Doing It Yourself**. There is no *how to* at all in there.  I may have to close my first question.
Comment: Hobbyist welders are common. I started looking at this yesterday. Professional ones are 20 times the price. But I got my answer, so do as you please :)
Answer: It is a "MIG" (Metal-Inert-Gas) welder in the sense that it does have a shielding gas for the weld - but the shielding gas comes form the flux core in the wire being vaporized during the welding process and not from a separate gas supply.
You'll note in the product listing "Requires flux cored wire " - because without the flux core there's no shielding gas.
Comment: As a side-note, I first learned to weld with my dad's 'stick' welder back in the 80's - back when anything other than a stick welder was esoteric & expensive, and most of my early attempts came out looking like a line of bird-cr@p. I recently bought a decent-ish multi-process welder which came with a roll of flux-cored wire, fully expecting to have to re-learn how to weld with this new-fangled thing, and very pleasantly surprised myself when my 1st few test welds came out looking half-way decent. Unless I find a need to weld aluminum I'll probably not bother hooking up the gas to it.
Answer: shocked Deadpool face
Misrepresentation!? From Chinese junk on Amazon Marketplace!!??
The crux of the matter may be about Amazon
Jeff Bezos made the fanciful decision to open his business infrastructure to all comers.  This created the Amazon Marketplace which has become a "junk shoppe" like eBay and AliExpress.  You know it's the Amazon Marketplace flea market when it says anything other than "Sold from and ships by Amazon.com" under the "buy" button.
Amazon also allows anyone to use their warehousing/shipping infrastructure, so these Marketplace items often ship with Prime.  Regardless, they count legally as not having entered the EU yet for purposes of safety and fitness certifications.
Better manufacturers have their equipment tested by a proper testing lab such as BSI, TUV, ETL, CSA, and UL, where they do a Big Clive tear-down (and then some).  However, there are "voluntary" marks like CE and RoHS, where they merely promise they self-tested. These marks only bear on manufacturers are importers who are inside the EU, everyone else is free to stick the mark on anything.  I call it "counterfeit", but that only applies if it's brought into the EU.  And sitting in an Amazon warehouse inside the EU doesn't count for some reason.
Suffice it to say, when you buy off Amazon Marketplace, you're the importer.  Making you responsible for assuring the CE stamp is valid.  Obviously that does not happen, so this becomes a loophole for selling you substandard junk.
Unfortunately it also sets your expectation for prices, so you become biologically unable to pay 500 quid for a competent welding setup.
MIG means inert gas
The whole idea of MIG is to cloud the work in an inert gas - because the hot molten weld is extremely vulnerable to reacting with oxygen in the air. With steel, you can get by with exhaust gases from a gas welder or vaporization from flux from a coated stick.  But aluminum is so sensitive it must be an inert gas.
Now with flux-core wire, they put flux on the inside of the wire instead of the outside of a welding stick.  Whatev's.  But this flux is certainly no more effective than on an electric stick welder, and that is wholly inadequate for aluminum.
How you would make this one work?  If you're welding easy stuff like steel, the flux-core wire is simply the equivalent of the flux-covered welding stick, and the upgrade is that it is continuous.  For challenging material like aluminum, I suppose you'd need to work in a glove box which you have filled with inert gas.
Novice user + cheap tools = path to failure
Welding is a skilled craft.  One does not just pick up a welder and start making competent welds.  An experienced craftsman can often work around the shortcomings of cheap tools. For a novice, to fight both the lack of experience and the tool itself is often too much.  When you stack on the difficulty/impracticability of welding aluminum, forget it.
My suggestion would be get a membership in a maker space and do your work using their (hopefully competent) tools with their advisors on-hand.


Why is mass proportional to the strength of a dipole-dipole attraction? meaning more mass more strength

Question: I don't understand why the mass of a molecule make it attract more to other polar molecules.
Comment: Hi, take a look to the question posted by Philipp if this doesn't clear your doubts make one more specific or clarify what you mean! :-)
Answer: Increasing mass increases the availability for molecules to attract through London dispersion forces (induced dipole-dipole). A longer chain has more atoms and hence more electrons and therefore experiences stronger bonding.
When you say 'polar' I assume you mean permenant dipole-dipole and hydrogen bonding which is actually not affected by the 'mass' or length of a carbon chain in a molecule. However if you take ethanol and pentanol as an example they both have hydrogen intermolecular bonding on account of the -OH group but pentanol also experiences greater London dispersion forces than ethanol which results in its significantly higher melting and boiling points.
So to recap increase mass is not a direct causal link to charge. It is in fact more mass meaning more atoms meaning more electrons meaning induced dipoles leading to greater intermolecular forces. I hope that's clear (:


Failure to install mysql on macOS Mojave

Question: I've moved to a new machine and installing MySQL is turning out to be quite an issue (the last time I installed it on a mac it was quite seamless).
I used two approaches to install MySQL: brew and the offical installer
Brew:
I started with brew install mysql. This installed the latest version of MySQL. It initially worked and I could log into the root user without a password. When I tried to set the password for the root account I ended up being locked out of the root account. I proceeded to uninstall that version of MySQL and tried a different version (5.7). When I installed that I got the following error: ERROR 2061 (HY000): Authentication plugin 'sha256_password' reported error: Authentication requires SSL encryption. I ended up uninstalling that version of MySQL as well.
Native Package:
Tried the latest version was asked for a password but could not login to the root user with the password. Received this error: ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock'. Additionally I could not run mysql.server start, received the following error: command not found: mysql.server. I did not add anything to my PATH, should I have done that?
Additionally, this is how the MySQL widget in the System Information looks like. I tried pressing Start MySQL Server a bunch of times, it would start and almost immediately stop.
Can anyone suggest a clean way in which I can remove all these defunct installations and have a clean MySQL install?
Answer: MySQL 8 makes big changes compared with previous version 5.7. Downgrading directly to the lower version 5.7 from 8.x won't work.
Solution:

Uninstall all MySQLs you've installed.
Since you're setting up a new machine, there's no existing database. Just clean up the broken database.
# brew-installed mysql
rm -rf /usr/local/var/mysql

# db from the official installed
# should be located at /usr/local/mysql (I'm not very sure)
ls -ald /usr/local/*mysql*
# then delete any folders listed by ls

You'd better remove the conf file /usr/local/etc/my.cnf as well.
Reinstall MySQL.


Explanation behind the 'human' reaction to 'terrorism'

Question: My question is essentially, what are the philosophical reasons behind the way in which societies as a whole react to terrorism. Taking the recent Manchester attacks as an example, 22 people were killed in a bomb explosion. On average about 1400 people die a day in the UK. Now what is it about terrorism that attracts the outcry/policy changes and general disproportionate impact upon society relative to the absolute damage caused?
Comment: I think this may be more of a cognaitve science question, or psychology. Myself, I perceive the answer to be a consequence of our division of things into conscious and unconscious.  If something is unconscious, like heart disease or even a DUI driver who we feel is unaware of their actions, we put them in a bin of things that are predictable.  We can do statistics on them.  If we feel like something conscious is attacking us, we put it in a different bin because we're terrified of the idea of an attack that has some intelligence behind it.  We don't know what comes next.
Comment: What does this have to do with your study of philosophy?
Comment: @JosephWeissman Well I was wondering what the philosophical reasons might be, for people having a stronger reaction to terrorism, than to other things which cause a much larger loss of life.
Comment: We feel that we can control the unconscious things if we want, but we know we cannot control another conscious entity.
Comment: @CorrAmmon you have some interesting thoughts on the matter, I would love to read more about what you think the cause is.
Comment: somehow my comment is gone. if mrnovice wants to know about the ethics of war and how it relates to terrorism, I might be able to help (I had to teach that in "ethics and society" course.
Comment: @NanheeByrnesPhD Please do, I'd be interested in reading any answer which has some relation to my question.
Comment: Is there a way to move this to the [Politics.SE](https://politics.stackexchange.com/)?
Answer: Terrorism is classified as war and thus understood in the context of war ethics. Traditionally, the ethics is divided into two considerations: when to go to war or who has the moral right to start a war (called jus ad bellum), and what should be morally permissible ways of acting during the war (called jus in bello).
Under jus in bello, citizens are viewed as non-combatants, and thus as being innocent. Thus argued is that terrorism whose nature is the attack of citizens is morally impermissible. Viewed in this light, terror acts attract public outcry for the acts' moral impressibility.
Now the story does not end here. Many terrorists regard themselves as freedom-fighters, and regard their cause as being just. This means that they can appeal to jus ad bellum. That is, in a way they believe that they have the right to start a war. They then argue that in a democracy, all the citizens are morally, collectively culpable when their leaders engage in unjust wars. After all, it is the citizens who chose their leaders.
There are articles that concede this point, yet try to show why attacking democratic citizens is nonetheless morally impermissible (.e.g, terrorism makes people live in constant fear, which is despotic. Meeting injustice with another injustice thus cannot be justified.)
Comment: An interesting counterargument - Rousseau would argue that "Terrorism" cannot be classified as "war". In "On The Social Contract" he defines war as "a relationship between one state and another", and explicitly excludes other aggressions. The term "war" has taken on other contexts - e.g. "the war on drugs" - but this seems more a literary use, and therefore I am not sure if military doctrine applies to it. Perhaps it's a historical distinction without a difference in terms of terrorism, but I'm not sure.
Comment: But surely American civil war is defined as 'war', despite the fact that it occurred within one nation. An organized entity that asserts the right to self-determination  can be loosely viewed as a sovereign.
Comment: But in the American civil war there was a clear state and Confederate government. This was also demonstrated by the distinction between the IRA and Sinn Féin. Without a true Caliphate with a distinct government, ISIS and other terrorist organizations are not organized in the traditional sense. Instead the "war" is against radicalism (an ideology) and not a sovereign nation. *I am just exploring the concept, I found your original answer interesting and reasonable.
Answer: First and foremost, this is a tragedy for all those directly affected as well as so many people in the wider society. I hope that the focus in the response is not offensive or callous towards this or any other event like this.
I would argue that the OP reference to a "disproportionate impact" is not appropriately contextualizing the event. The "absolute damage" the OP describes is quantified by the human casualties of the attack. However, the purpose and damage of a terrorist attack is wider than the tangible impact. The damage extends to the creation of fear and disruption. Demonstrated when attacks do not include any military or political target, the intent is to strip any sense of security which is foundational to society and to chip away on the morale of a population. This demoralization is a historically significant mechanism of attacking an enemy in many forms of competition; psychological warfare, ideological conflicts, politics, etc.
It is important to counteract these effects and reinforce the collective unity. To do this, we share in the pain and loss. We demonstrate strength through support. If we are undeterred to live our lives together and not dissolve into hate, it is a triumph over terror.
Answer: I assume that is because, in our view, the victims' deaths were unfair and unjustifiable while we do not care about the thousands deaths that occur naturally a day because it's the natural course of events.
Then again, media make money out of news like these. News spread and we start thinking "what if we were in that situation?". The fear of death/the sorrow for our relatives' death makes us feel horrified about what happened.


Dark Matter Detection

Question: A paper appeared at the arXiv.org (in April or May) claimed that the writers have found the gamma rays emitted by annihilation of dark matter in a satellite galaxy of the Milky Way by examining the Fermi data.  I cannot find this article anymore.  (It is possible that the writers withdrew the article.) Has someone actually detected gamma rays emitted by neutralino (or any other dark matter) annihilation?
Comment: Perhaps http://arxiv.org/abs/1503.02320 ?
Comment: By this question, I was hoping to get an expert opinion on the status of the DM detection even-though I accepted the given answer.  What is the reason for the down vote?  It would be helpful to know why one would think this is a bad question.  I stayed away from groups which down vote questions with no apparent reason.  I hope I do not have to stay away from this group, especially when it is in the beta mode.
Answer: Is it the paper David H pointed out, by Geringer-Sameth et al. (2015)? If so, then I should point out that they're not the first. Just using Wikipedia, I came across Weniger (2012) and Albert et al. (2008).
Geringer-Sameth et al.'s abstract reads (in part)

We present a search for gamma-ray emission from the direction of the newly discovered dwarf galaxy Reticulum 2. . . . Reticulum 2 has the most significant gamma-ray signal of any known dwarf galaxy. If Reticulum 2 has a dark matter halo that is similar to those inferred for other nearby dwarfs, the signal is consistent with the s-wave relic abundance cross section for annihilation.

Albert et al. also studied a dwarf galaxy:

The nearby dwarf spheroidal galaxy Draco, with its high mass to light ratio, is one of the most auspicious targets for indirect dark matter (DM) searches. Annihilation of hypothetical DM particles can result in high-energy γ-rays, e.g., from neutralino annihilation in the supersymmetric framework. A search for a possible DM signal originating from Draco was performed with the MAGIC telescope during 2007.

The point is, this has been done before. These folks aren't the first.

Has someone actually detected gamma rays emitted by neutralino (or any other dark matter) annihilation?

More analysis is probably needed. I'll quote the paper itself:

While Ret2's X-ray signal is tantalizing, it would be premature to conclude it has a dark matter origin. Among alternative explanations, perhaps the most
  mundane is the possibility that an extragalactic source lies in the same direction. Searching the BZCAT [54] and CRATES [55] catalogs reveals a CRATES quasar (J033553-543026) that is 0:46 from Ret2. Further work must be done to determine whether this particular source contributes to the emission, though we note that at spectrum radio quasars rarely have a spectral index less than 2 [56]. One of the much-discussed astrophysical explanations for the apparent Galactic Center excess is millisecond pulsars [24, 26, 57{61]. In the case of Ret2, it is the high-energy behavior which disfavors a pulsar model, as millisecond pulsars exhibit an exponential cut-offat around 2.5 to 4 GeV [26, 30, 61{64]. Alternatively, high-energy cosmic ray production could potentially arise in the vicinity of young massive stars. Upcoming photo-metric and spectroscopic analysis of Ret2 will check this possibility.

Don't jump to conclusions. They didn't. It stinks, but the answer to your question is, "Nobody's sure."

Dark Matter Detection


Tactics for filtering out fake hotel reviews

Question: There is a popular question on how to spot fake reviews on TripAdvisor How to spot fake reviews on TripAdvisor? My question is if there are any tactics on how to leverage multiple review website to eliminate the noise or any other tools outside of the TripAdvisor itself. For example, I speak in three languages (Russian and Ukrainian) and read reviews in my native languages to check for reviews. My assumption is that hotel will not bother with hiring a company or an interpreter to boost their rating (you can exclude Spanish for Caribbean hotels as well). I also check multiple English websites hoping that if a hotel hired a company to boost their rating it will do it only for a couple of most popular websites. I apply this tactic only when I have a list of 5-6 hotels chosen based on price and TripAdvisor rating. I understand that assumption I make may be wrong, but after visiting two hotels with 4.5 TripAdvisor ratings that ruined my vacation, I would rather spend an extra hour or two to choose a proper hotel.
Comment: Personally, I don't go by overall rating, but I read the most negative reviews and try to decide if they give a poor rating because of something that would ruin my vacation (club in the basement, music can be heard inside the rooms) or something I don't care about (no breakfast available at the hotel). Then I go for a hotel that falls into the latter group,
Comment: My view is that a few reviews are always fake, so if there are only a few than you know which they are!
Comment: Check the number of reviews a reviewer has posted. If a user has posted multiple reviews check the other reviews, should give you a good idea.
Comment: Of course, all answers would be equally helpful as tactics to better write fake reviews.
Comment: The two answers so far do not attempt to answer your question and instead belong on your linked question.
Answer: It is usually pretty easy to spot fake reviews. Those have some of these (if not all) symptoms :

they include typos
they are only positive or only negative, very rarely balanced
they contain fake details (for instance "great pool" while there is no pool at the hotel)
they usually don't refer to any specific employee that did a great job
they look generic and don't offer added value insight (like "we had room XX and it has a great view over XX")
if you look at the profile of the user that submitted the review, either it doesn't have many reviews, either all its reviews are too positive
Answer:
you should not look for hotel reviews on TripAdvisor. You would better look for reviews on Booking.com, as they allow reviews only from people who has booked the hotel and lived there. The fake reviews will be very expensive as the property owner pays 20% of price to the Booking.com.
do not read reviews from people, which are from the same country the hotel is located in.
read bad reviews, not good ones. The bad always include issues in the hotel. If people tell it is noisy, in reality it is.
pay attention to the rating. If the hotel has more than 20 reviews in Booking.com and rating more than 9.0, it is good. If the rating is lower, this means the hotel has some issues.
the rating is not connected with price. I was staying in extremely cheap hotels with great comfort and in expensive ones with poor experience.
read reviews in different languages. I have noticed that Russian people notice less issues in hotel, than people from USA.


How can i get apps on my phone from ONLY my other phone, and not my tablet?

Question: I am going to get a replacement phone and i only want apps from my old phone to be downloaded to the new one, and not my tablets apps. i know there is "google play-my apps-all", but that includes my tablets apps too. they are all on the same account. (the reason for this is my phone has very little storage and i dont want my tablets 3GB apps taking up my phone.) my phones are both on android 4.0.4 (sony xperia tipo) (ICS). i do not want to root but i will download any app (no apks please, sorry). thanks in advance!! :D
Answer: Use the Helium app to backup your phone and then do a restore on the new one.
I am not affiliated with developers of Helium in any way, only a regular user.
Helium is just a (sophisticated) frontend to adb backup, so if you feel adventurous, you can achieve similar results using just adb.
Answer: What if u change the account on the tablet first, then try to transfer apps from old phone? Not certain ofd that will work, but It should. If Apple can do it android can.


Why can't I use cortana?

Question: I'm using a Nokia 928 on Verizon. I have the most available updates so window 8.1 is the operating system. I have confirmed this so please don't ask. My region is United States. My language is English (United States). When I try to turn on Cortana it says Cortana is not available with my selected region and language. Any idea why my phone would think I have chose a region and language other what I described. I am also physically in the United States. Central Texas specifically.
Answer: Try changing the speech and everything to En-Us.
Comment: also change the location to ON

Why can't I use cortana?


Do I need an appostile when providing documents for a Danish short-term visa?

Question: Hi I am an Indian citizen and I would like to visit Aarhus University, Denmark for a month in this summer. I have an invitation letter from them saying that they are providing me travel and local hospitality during my stay. I would like to take my family (my wife and a year old daughter). For my wife we will apply for a dependant visa. I have sufficient financial proof to support their travel and stay. My passport has my wife's name endorsed but in her passport my name is not endorsed. We have a marriage certificate but its not appostiled by the Ministry of External Affairs. Again my daughter's passport has our names endorsed but her birth certificate is not appostiled. Will these documents be enough to get our visas? Also, does my one year old daughter need a ticket to travel ?
Comment: What was the question? Are you asking if documents need an apostille?
Comment: ya, you are right. Is apostille is necessary in this case or my wife's name in my passport is enough to get a visa.
Comment: Based upon what you wrote you should get the marriage certificate and the birth certificate apostilled.
Answer: According to the Ministry of Foreign Affairs of Denmark, India is a party to the Apostille convention. You would therefore need to receive an apostille at the Indian Ministry of Foreign Affairs before submitting your documents.


Is a deceased obligated to pay financial debts

Question: Say someone becomes niftar and owes a petty sum (under 100 currency units) is his next-of-kin chayav to pay his debts under halachah?
Comment: To the best of my (limited) knowledge, I don't know if there's ever a halachic difference based on the value of an object, as long as it's at least a Shaveh Prutah, a very [minute amount](http://judaism.stackexchange.com/questions/5685/cash-value-of-perutah).
Answer: These things can get complicated, but generally speaking the children are obligated to pay off the father's debts from either land or chattel IF the father left them an inheritance of at least that size. If the father did not leave any inheritance, the children are not obligated to pay anything. (Shulchan Arukh CM 107:1)
If the debt is from a loan which was made orally and without documentation (milveh 'al peh), the children are only obligated if it can be ascertained with certainty that the father never paid. (ibid 108:1)


GeoEvent streaming service labeling in ArcGIS Online or Portal

Question: Is it possible to label streaming services within AGOL or Portal?  There is not a create label option available after adding a streaming service to AGOL or portal.
Answer: As of 10.3.1 it is not possible as per this documentation:

You can create labels for features in hosted feature layers, ArcGIS Server feature service layers, individual layers from ArcGIS Server map service layers, CSV on the web, and layers from files.

Strangely there is a streamLayer label class in the JS API but it's not available in AGOL.
Confirmed this with tech support which sparked the debate "was this oversight or purposely designed this way"
Comment: Thanks for sharing the outcome.  I imagine if the capability is there, it will make it into a subsequent release of AGO.  Pending which template your using, might not be too much work to host your template externally and modify to include labelling.  Im doing the same right now with the map journal but tweaking some styling.


What is difference between High quality and low quality proteins

Question: I have seen in news that some bodybuilder died of taking steroids; when I went through details I learned that  "low quality proteins" contributed to their death. I have studied about linkages in proteins but I don't understand what makes them stronger or weaker. So what is the difference between high quality proteins or low quality proteins? How does low quality protein affect muscular activity or growth?
Comment: I'm voting to close this question as off-topic because it belongs to [fitness.SE](http://fitness.stackexchange.com) not biology.SE.
Comment: @Remi.b I tried to save this question for the OP - I think there is an on-topic question contained there once the personal health component is removed. There might be an additional question to send to fitness.SE about how/whether to use protein supplements that wouldn't be appropriate here.
Comment: Without a link to the news story, and subsequently the investigation into this individual's death, it's impossible to know what exactly "low-quality" means in this context. It *could* be what @BryanKrause talks about in his answer, or it could mean "low-quality" as in it was procured from a disreputable source that didn't take adequate care to verify the protein's purity, or adulterated the product somehow like the melamine [scandal regarding milk powder in China](https://en.wikipedia.org/wiki/2008_Chinese_milk_scandal) beginning in 2008.
Answer: "Low quality" vs. "high quality" protein does not refer to anything about the linkages between amino acids in proteins. Instead, these terms are used in a nutritional context to refer to whether an individual protein source is sufficient as a sole source of protein in someones' diet.
Essential amino acids are the amino acids that humans cannot synthesize; other amino acids can be synthesized from these, but they do not need to be part of the diet. Not all sources of protein have sufficient quantities of all of the essential amino acids. Low-quality protein sources are also referred to as "incomplete" and high-quality sources as "complete."
Meat products are typically "high quality" because they contain all of the essential amino acids together. Therefore, if you subsisted on various foods but only got your protein from one animal source, you would be okay.
Some plant products do not have all the essential amino acids in large concentrations. However, if you combine protein sources from different "low quality" plant sources that together cover these deficiencies, there is no disadvantage compared to a single "high quality" source.
In the digestive process, all you take out of the proteins you eat is the individual amino acids (generally): that means that only the amino acid composition matters, not the strength or quality of the bonds between amino acids. If someone tries to tell you otherwise, they are probably just trying to sell you something.
Here is a paper that talks about some of these issues, and addresses some of the myths about balancing proteins. The quick summary is that problems develop if you get your sole protein from a source that is low in a particular essential amino acids over a long time period, but there is no need to ensure every meal contain all the amino acids.
It is possible for people on unusual protein diets, either because they are avoiding animal products or using incomplete protein supplements, to develop a particular amino acid deficiency. Otherwise, as long as all amino acids are supplied, there is no difference on health or muscles to consuming "low quality" vs "high quality" proteins.

References:
Young, V. R., & Pellett, P. L. (1994). Plant proteins in relation to human protein and amino acid nutrition. The American journal of clinical nutrition, 59(5), 1203S-1212S.
Comment: My understanding is that amino acids are not generally stored. Say you eat just corn which is first-limiting in lysine. Once you've built what proteins you can before the lysine is exhausted, the remaining amino acids are further metabolized, mostly for energy, as opposed to being incorporated into proteins. My source dates to my Biochem degree in the '70s, and textbooks from the '90s. Maybe something new has been discovered about storage of amino acids? (Still, +1 on your post.)
Comment: @bpedit Thanks, I think that's a good point, to my understanding you are correct that amino acids aren't "stored" the way fats are (at least not in humans) - and I didn't say anything about storage in my answer. However, you have a huge storage of amino acids in the form of all the proteins in your body. When proteins are degraded they aren't just junked, you can reuse a lot of the amino acids. The lysine you take in from a single meal is just a fraction of your total body lysine. So, it takes awhile for the shortage to catch up and cause problems.
Comment: @bpedit ...From the source I linked and just a general survey of "advice on the internet" it seems like a general guideline for vegetarians is to try to get a complete protein intake within the timeframe of a day, rather than worrying about being complete at each and every meal. I'm sure there is no immediate problem missing a day or two at a time, either, because fasting on those timescales isn't harmful (to my knowledge).
Comment: @bpedit You mention "many" but only gave one example. Many cultures have also suffered from things like rickets and scurvy at various points. I'm not sure what your perspective is, but I'd caution against the logical fallacies that people in the modern "paleo" movements employ, assuming that cultures they are less familiar with must have it all "figured out." Surely there are good evolutionary/anthropological reasons why there aren't extant cultures that subsist solely on corn with no other protein source, but I wouldn't read much further than that.


What is the best free automation tool for Windows applications

Question: What is the best free automation tool for Windows application using object ID's. So NOT with keystrokes and x,y coordinates.
Comment: The duplicate also contains some frameworks that use objects instead of images and coordinates, like TestStack White: http://sqa.stackexchange.com/a/9201/3201
Answer: I do not think it is possible to automate generic Windows apps without sending keystrokes and mouseclicks. (But if I am wrong, I am looking forward to learn something)
Only the method on how you find the position for the click makes the difference:

via x/y (any tool can do this)
via objectID/Windows titles/... (e.g. AHK, TestStack White,...)
via images (e. g. Sikuli or Kantu)


Creating views or facets search with multiple flags

Question: So I'm categorising with flags and I will have over 20 per node so that multiple people can flag a node with their opinion... Searching for the past two weeks I have found it hard to work out how I put these flagged results on to the front end, in search, making multiple flag recipes (to show to searchers), with views?
My first question is, do I have to make a view for every single flag I have on the front end? There are over 20 of them, I don't mind doing this but can't this be put in to an exposed view or something so I can have one view with all outputs covered?
How can I mix up certain flags together/make recipes so that if I wanted three certain flags together so that people can search through that output I could, can I do this in views with flags?
My final question is, how do I put the output of a search or a view I make and make it sortable by how many times that node has been flagged with that flag or combination of different flags? If someone wants to see the nodes all flagged with 'river' and that the nodes that come to the top of the search/output/view has had it's 'river' flag flagged by more users than those below it. This will show that that node is definately more 'river' than the other ones.
Answer: I found out that if I add all of the flags (each one individually) as a relationship, so I end up with 20+ relationships, I can expose each one in a field to visitors and that way they can click through what type of flags they want to see and don't.
It's not pretty, you will end up with 20+ true/false select boxes but its working.


How did the wrong dog get in the cage?

Question: In Isle of Dogs, Atari finds a dog in the locked cage which he initially assumes is his dog Spots. Later we discover that it's actually a different dog called "Sport", whereas Spots was carried to the animal testing facility while still in his cage. This begs the question of how did Spots' cage manage to get back to the western part of Trash Island, get locked again and contain a different dog? Unless I missed something, this was not addressed in the film?
Answer: It's not the same cage. I don't believe there's anything more complicated here than the pack being mistaken about which cage they brought Atari to. It appears that many dogs were deposited on the island in cages, and at least one found himself unable to get out. The pack concluded it was Spots, but they were simply wrong.
Two dogs. Two tags. Two cages. Simple mix-up.
Comment: Still the question remains that how did the cage even got unlocked with Atari's key. The cage of Spots was opened using a master key, whereas the cage that Atari opened got opened using the key for Spot's cage.
Answer: Well, I think they went all wrong with this. Because it was the same place where Spot landed, also the cage was opened with Atari's key with the secure lock sign plus this was the same dog Spot chatted with, right? They messed up I think.

How did the wrong dog get in the cage?


Is it just coincidence that the Moon follows the ecliptic?

Question: Or has it been gravitationally steered that way because of how it was formed?
Answer: No, this is not entirely a coincidence, though perhaps not in the way you expect (and other answers have indicated): it may have been coincidal at formation, but is required for long-term stability of the Moon-Earth system itself and, possibly, Earth climate.
The formation mechanism of the Moon (or the Moon-Earth system) is still debated. The favoured model involves a collision (between a pre-Earth and a Mars-sized object), when the resulting orientation of the Moon-Earth orbit depends critically on the impact parameters, which are essentially random, i.e. coincidal. Conversely, if the Moon-Earth system formed by some form of capture (possibly involving some surrounding gas to absorb the excess energy), a orientation in the eccliptic is more likely.
Howerver, the formation mechanism is not all there is to this. It is also required that the Moon-Earth system remains stable over 4.5 Gyr. This excludes any orbit initially circular and inclined by more than $i=\arccos\sqrt{3/5}\approx39.2^\circ$, when the Kozai mechanism would result in a collision of the Moon with Earth within a few years. The critical incliniation for a non-circular orbit is even smaller.
Even an inclination $i\approx30^\circ$ may not be viable, since it may imply that the Earth's spin axis (which is after all tidally coupled to the Moon's orbit) would be/have been tilted considerably stronger than by merely $\approx23^\circ$. A strong tilt of the Earth spin axis would have significant consequences for the Earth's climate and may well have prevented the formation of higher live forms. This is essentially a weak form of the antropic principle.
Comment: @LocalFluff **No**, only the total angular momentum is conserved, i.e. the inclination of the combined Moon-Earth system is about the same as that of the (mass-weighted) mean inclination of the pre-Earth and Theia. But the orientation of the resulting Moon-Earth orbit is not contrained by angular momentum conservation (the angular momentum in the relative orbit is tiny compared to the orbit of the Earth-Moon system around the Sun).
Comment: Shouldn't the inclination of the Moon at formation be roughly the inclination of Theia? The highest inclination planets today is Mercury's 7 degrees, even Pluto i only 17 degrees. The rest are at less than 2.5 degrees, half that of the Moon. Isn't it unlikely that Theia had higher inclination than that?
Answer: From what I can find out on-line (Wikipedia, etc.) most natural moons tend to be in the equatorial plane of the planet (formed in a circumplanetary disc). The Earth's moon is commonly thought to have formed in a collision with a Mars size object. It probably settled initially into an orbit inclined about 10 degrees to the equatorial plane of the Earth due to accretion disc processes. Since then, tidal forces from the sun (due to Earth's proximity) have brought the Moon more inline with the ecliptic.
Comment: I don't think that tides with the Sun will necessarily bring an inclined moon into the ecliptic. Do you have any reference/evidence for this?
Comment: @Walter I may have been mistaken here. I read that "tidal evolution calculations" show that the moon's inclination changed from 10 deg. from the equatorial plane to it's current 5 deg. from the ecliptic. I couldn't find my original source, but hou.usra.edu (3041.pdf) "The Lunar Inclination as a  Monitor of Late Stage Terrestrial Accretion" by K. Pahlevan et al. (2015) says the same thing. I think this may be referring to planetary tidal forces as the moon changed from 10 R(e) to 60 R(e). Coincidence that it lined up with the ecliptic??
Answer: The Earth and Moon are rather better thought of as a two planetoid system both orbiting the Sun, than a planet and a satellite (the Moon does indeed orbit the Sun as well as the Earth). The Moon orbits Earth at a point where Earth's gravitational pull is of the same order as the Sun's.
We also believe that the Moon was formed as a result of a catastrophic event involving the proto-Earth - ie one planet split into two.
As such it is not a surprise that it has an orbit close to the plane of the ecliptic.
Other planets' satellites are not the same - the gas giants dominate their satellites and in Mars's case it seems likely that Phobos and Demos are captured planetoids from the asteroid belt rather than anything much to do with Mars as such.
Answer: It is not a coincidence at all! (There was, however, some statistical chances involved.) A key question to answer before answering your question, though, is Why is there an ecliptic at all? It is fair to see all the planets and a majority of the smaller bodies existing in a nice flat plane (the ecliptic) and think that it didn't have to be that way. Why not have different planets orbiting in different planes, or even backwards? To get the answer, we have to go back to the origins of the Solar System, when it was still a collapsing cloud of interstellar gas and dust. As gravity collapsed the cloud, the small amount of angular momentum it had became more significant, much as an ice skater pulling her arms in while spinning will make her spin faster. So, with the help of friction, the early Solar System flattened and had a 'spin' in a preferential direction.
As the Solar System evolved, planets formed, and all of them had ingrained in them this spin. Today, we see that in not only the existence of the ecliptic and the fact that planets orbit in the same direction, but in the fact that most planets rotate in the same direction as the sun does (Uranus and Venus being notable exceptions) and most large moons orbit their planets in the same direction (Triton around Neptune being a notable exception).
What about the moon? A leading theory for its formation is that it formed from the debris that resulted in a collision between a still-forming Earth and another planet-sized object. Statistically, both these objects would be most likely to have similar angular momenta to that of the overall Solar System (though it was by no means guaranteed), so their resulting debris would have it as well. When that debris coalesced into our moon, it too would also keep the original angular momentum 'signature,' and its orbit would thus be comparable to that of the ecliptic.
Of course, this is all a very chaotic and statistical process. While angular momentum is always conserved, there are ways of exchanging it between bodies (via gravitational interactions & collisions). Consequently, there are variations away from the ecliptic: the moon is inclined 5 degrees from the ecliptic; Earth's rotation is inclined 23 degrees from it; smaller bodies like comets will sometimes orbit well outside the ecliptic; etc. But the general trend holds, and is a marker you can see present throughout the solar system.
As an interesting aside, while all major planets in our Solar System lie roughly along the ecliptic, that is not always the case for other planets in other star systems. Wasp 17-b, for example, is observed to have a retrograde orbit around its host star, while others have been observed to orbit outside of their own system's ecliptics entirely.


Can I move "Pages" of apps in iOS 5?

Question: I have an iOS 5 iPad 2 and my homescreen is a bit confused. My apps are stored in pages of like content but the pages aren't logically ordered. Is there a way I can move a whole page of apps/reorder them (not just one app at a time)?
Comment: iOS 11 users: you should be looking at this answer instead: https://apple.stackexchange.com/questions/304521/is-there-a-way-to-rearrange-home-screens-on-ios
Answer: You can move it by pages in the iTunes interface but (so far as I know) not on the iPad itself.

Connect to your computer
open iTunes
select the iPad in the left column
select the apps tab along the top

At this point at the upper right is a view of the apps on the iPad.  You can drag and drop apps to move them around.  You can grab a page and drag it up and down the list to rearrange the pages.
Comment: I assume I have to be plugged in via USB to do this? I'll have to try this at home.
Comment: Just tested it. As long as the device is connected to iTunes and visible in the sidebar it works, even over wifi.
Answer: Yes you can.
Just simply hold the icon first with your finger so that they all start to jiggle.
After that, simply take one of the app icons under your finger and move it towards either end in your screen.  Just keep it going for either direction for about 2 seconds.
After that it will move to another page.
Hope the answer helped :)
EDIT and now I noticed I didn't read the original question with enough accuracy.
Comment: You should delete incorrect answers. Don't just edit them to indicate their incorrect'ness.

Can I move "Pages" of apps in iOS 5?


When an enzyme is diluted with water, what is slowing down the rate of reaction?

Question: I'm specifically talking about the decomposition of hydrogen peroxide by bovine catalase. The number of catalase molecule obviously doesn't change, so there's the same number of catalase molecule within an undiluted and a diluted solution. Also, seeing as water is not an enzyme inhibitor, and doesn't change the pH or temperature, then shouldn't the rate of reaction remain the same regardless of concentration, since every environmental conditions & the number of catalase molecule in the solution before dilution is the same after it is diluted?
Answer:
[…] there's the same number of catalase molecule within an undiluted and a diluted solution. Also, seeing as water is not an enzyme inhibitor, […]

Q: Why is dating between a fixed number of guys and girls more difficult on a large square packed with nuns than in a small club (without the nuns)? ;)
A: It's more difficult to bump into each other since the girls a more far away and there are legions of nuns in between!
You are right in that the absolute amount of catalase molecules does not change upon dilution, but the concentration does!
Reactions are about collisions of the reactants and in the case of dilutions, there are more collisions with innocent bystanders than with an other reactant.
Comment: @LtotheV **Exactly!** Although the role of water molecules isn't necessarily an active preventing by blocking the active site (there will always be some water molecules there, e.g.  due to hydrogen bonding), It really is more about finding less catalase and $\ce{H2O2}$ molecules in the same volume element. Assuming a constant movement of molecules in solution, **it just takes longer** for the reactants to form a collision complex while making their way through the water. And since rate is conversion **over time**...
Comment: I've only got rudimentary of chemistry knowledge, so I'm paraphrasing your idea into terms I can understand. What's happening is the water molecule is interfering with the active site of the enzyme, preventing it from working at full capacity, thus lowering the rate of reaction. Therefore, more diluted solution means more water molecules means more interference, and an overall lower rate of reaction. Is this a correct understanding?
Answer: If you diluted the catalase, while keeping the peroxide concentration fixed (by adding both water and peroxide to the solution), then you're right, the total reaction rate (measured in reactions catalyzed per second, within the whole solution) would not change.
However, by adding just water to the solution, you're diluting both the enzyme and the peroxide.  The lower the peroxide concentration is, the longer it takes for each catalase enzyme unit to bump into another peroxide molecule after reacting with the previous one.


Write cycles material node output to image file

Question: How can I write output of a Node/Node Group in Cycles Render to the file (PNG or something else)? I saw a special File Output Node, but I can't find in Search ShiftA).
Answer: The File Output node is a compositor node, not a Cycles material node - so it will only output the results of the actual render, not that particular material.
To output the shader results to an image you need to look into unwrapping your mesh and baking the material to an image.


Orthogonal Procrustes problem with Absolute Values

Question: Given a non-negative matrix $T$, how to find a orthogonal matrix $O$ minimising
$$ \left\lVert \, |O| - T \right\lVert_F,$$
where $\lVert \cdot \lVert_F$ denotes the Frobenius norm, and $| \cdot |$ denotes the entry wise absolute value.
If $|O|$ is replaced with $O$, then this is the classic Orthogonal Procrustes Problem. I don't expect a closed form solution, but rather a way to reduce the dimensionality of the problem and tackle the problem numerically.
Answer: Let $A, B \in \mathbb{R}^{n \times m}$ be positive matrices. Consider the problem,
$ \underset{A, B}{\arg\min} || A + B - T ||_F $ subject to $A > 0, B > 0$, and $(A - B) = O$ is orthogonal and $A_{ij}B_{ij} = 0\ \forall i \in n, j \in m$
It is obvious that a solution to this would lead to a solution of the original problem.
Now, the objective is quadratic in terms of $A, B$ and $A > 0, B > 0$ are linear constraints so those are easy. The first tricky part is ensuring that $A-B$ is orthogonal. Depending on whether we need only the columns to be orthogonal or both the rows and columns to be orthogonal we can add constraints. Let's say we only want the columns of $O = A-B$ to be orthogonal. We can add the constraints that off-diagonals entries of $(A - B)^T(A-B)$ are zero. There are going to be $m(m-1)$ such equalities where $m$ is the number of columns. Each of these equalities is again a quadratic constraint.
The constraints that $A_{ij}B_{ij} = 0 \forall i \in n, j \in m$ can also be encoded as a quadratic equality constraint by considering an indicator matrix $M \in \mathbb{R}^{2mn}$ with a single unit entry at the appropriate location such that the quadratic form results in $A_{ij}B_{ij}$. By adding $2mn$ such inequalities we can encode all these equality constraints as well.
So at least a QCQP solver can solve this problem.
Comment: Thanks for the fix. However, I was hoping that there would be somehow a way to exploit more the structure of orthogonal matrices and separate the magnitude matrix and sign pattern matrix. Namely, orthogonal matrices can't be purely positive, and certain sign pattern matrices may be associated with orthogonal matrices. Although, I've got to admit that this is pure speculation.
Comment: You're saying that $A+B = |O|$ and $A-B = O$, but don't you need an extra constraint like $A_{ij} B_{ij} = 0$ for all $i$ and $j$?
Comment: @SebastianSchlecht : Ah, yes . otherwise $A + B \ne |O|$. Thanks for catching that. I think the technique can still be applied though.
Comment: fixed the solution.
Answer: Here are alternate encodings based on Sebastian's comments on my previous answer.
Comment: If you want to constrain the solutions found to a particular sign pattern matrix then an additional $mn$ linear inequalities added to the above formulation can do the job.
Encoding 1: Here is another encoding of the problem that reifies the absolute value matrix. This one is efficient.
Let $ |O| = \tilde{O}$

The objective becomes $||\tilde{O} - T||_F$, a order 2 polynomial in $\tilde{O}$.
$O$ is orthogonal, i.e. $O^TO$ is diagonal. Quadratic constraints again.
$\tilde{O} = |O|$ which means either $\tilde{O}_{ij} = O_{ij} \text{ if } O_{ij} > 0$, or $\tilde{O}_{ij} = -O_{ij} \text{ if } O_{ij} \le 0$. This can be coded as $\tilde{O}_{ij} \ge 0$ and $\tilde{O}_{ij}^2 = O_{ij}^2$, which is a linear and a quadratic constraint.

Encoding 2: Here is another encoding of the problem that uses sign pattern matrices. But its really inefficient.
We can use the kronecker product to express $ |O| = O \odot sign(O) $,
So let $O, \tilde{O}$ be the orthogonal matrix and its signed counterpart respectively. Now,

The objective becomes $||O \odot \tilde{O} - T||_F$, a order 4 polynomial in $\tilde{O}, O$.
$O$ is orthogonal, i.e. $O^TO$ is diagonal,
$\tilde{O} = sign(O)$ which means $\tilde{O}_{ij} O_{ij} > 0\ \forall i,j$, and  $\tilde{O}_{ij} \in \{0, 1\}$

This encoding of the problem is not practical because it's now an IP with a fourth order polynomial. There might be ways to improve this encoding but that's future work :)


My two-way trust with selective auth seems to behave opposite to a one-way trust

Question: I'm not sure why I'm the only one running into this, I think it's a larger problem with Server 2012 and RDS protocols...  With 2008 machines, you can use utilize a one way trust to authenticate across domains with the TSGateway service, but with 2012 it breaks when running across a one way trust.  I'm trying to implement a two way trust that acts like a one way trust for everything but kerberos auth for things like TSGateway and RDS services...

A little backstory, I've currently got two domains (A and B) with a one way, external trust.  (Outgoing trust on A, users in B can access devices in A)
At the moment, I can log into a computer in domain A, and add a user from domain B with the GUI.  (I can also do it from the CLI, but that's not relevant here)
When I build my test domain, I can recreate this behavior.  If I create the test domain with a two-way trust, domain-wide authentication in both directions this behavior doesn't change, though it does allow me to auth in the reverse direction (duh) which I don't want.
When I change Domain B to 'selective authentication' for some reason the Users and Computers GUI stops working as expected.

For Domain B computers, I can still browse the GUI like normal, and
even add Domain A users, though they're not allowed to log in, due to
the selective Auth setup.
For Domain A computers, browsing the GUI doesn't allow the selection of users or groups, and the advanced search turns up an error that says: "The following error prevented the display of any items: Unspecified error"
For Domain A computers, if I know the username from Domain B, I can add the account using the 'net localgroup' commands and everything works just fine, but the GUI is broken, and this won't likely be a usable solution for the majority of our users...

My question (Sorry to take so long to get to it) is why does selective auth change the behavior of the trust so that it behaves differently than a one-way trust, and is there some simple thing I'm missing?
When I get the 'unspecified' error from the GUI, I get an error on the DC for Domain B:

A Kerberos service ticket was requested.
Account Information:  Account Name:       bob@DOMAINA     Account
  Domain:       DOMAINA     Logon GUID:     {00000000-0000-0000-0000-000000000000}
Service Information:  Service Name:       ldap/DC.DOMAINB/DOMAINB
    Service ID:     NULL SID
Network Information:  Client Address:     ::ffff:192.168.18.70    Client
  Port:     62103
Additional Information:   Ticket Options:     0x40800000  Ticket
  Encryption Type:  0xFFFFFFFF  Failure Code:       0xC     Transited Services: -
This event is generated every time access is requested to a resource
  such as a computer or a Windows service.  The service name indicates
  the resource to which access was requested.
This event can be correlated with Windows logon events by comparing
  the Logon GUID fields in each event.  The logon event occurs on the
  machine that was accessed, which is often a different machine than the
  domain controller which issued the service ticket.
Ticket options, encryption types, and failure codes are defined in RFC
  4120.

I don't understand why it tries to authenticate against DomainB using 'bob' from DomainA, when I provided DomainB credentials...
Thanks for any help you can provide, I've been banging on this for 3 days straight and haven't found anything useful yet.
Comment: due to shadowing accounts maybe?
Answer: You have to allow authentication on the computer objects you want to allow logins from the external domain.
You can do it computer by computer, or you can set the permission in the OU that contains the computer objects.
What I would suggest is the following. In domain A create a local group, in domain B create a global group.
Make the global group in domain B a member of the local group in domain A.
Right-click on the ou containing the systems you want to allow and select properties. In the security tab, click advanced.
Add the domain local group and select Allowed to authenticate checkbox.
This will allow any users from domain b who are members of the global group, rights to sign into the systems you've designated.


Who were the people who loaded the data into his brain?

Question: In the beginning of Johnny Mnemonic, who were the people who loaded the information into his brain? Were they from Pharmokon? And if they were, who broke in and shot up the place? I thought they were from Pharmokon. Can anybody clear this up?
Comment: Those tags are not appropriate here.
Comment: Somebody tag this with william-gibson and keanu-reeves.
Comment: @leeand00 Yeah...no, please don't.
Answer: Wikipedia has most of the answers,
The intended recipients of the data:

Jane takes Johnny to meet her friend and street doctor Spider who had installed Jane's implants. In discussions, Spider reveals he and his allies at a local clinic were to be the recipients of Johnny's data.

Who attacked and shot up the place:

After uploading their data, the group is massacred by Yakuza, but Johnny manages to escape with a portion of the encryption password.

Why?

Johnny returns to Newark and soon finds that two groups are after the data he carries. One is the international pharmacological company, Pharmakom, led by its United States executive, Takahashi, who believes the data to be critical to the company's interests. The other is the Yakuza guided by Shinji, who wishes to deny this information to Takahashi and claim it for themselves.

What is the data:

Supposedly Pharmakom's unpublished cure for "nerve attenuation syndrome", a plague ravaging mankind, due to the over-reliance on technology, and causing political strife.


Where are new accounts stored?

Question: Today, I found out how EOS creates and saves new accounts. But I am still not sure whether EOS saves new accounts on RAM or on disk?
Answer: The new account is stored on RAM, nothing is stored on disk with EOS.
Comment: Well, so when I created 1.000.000 accounts on my computer(1GB RAM , 512 GB SSD) but EOS still run? Why? (with 4KB for an account)
Comment: If you are on testnet or mainnet then your RAM will not be occupied i am amazed that you managed to run eos on 1gb RAM.
Comment: @Mr.Y, I am on testnet, I am not clear with your answer, because I just want to test my knowledge when I read code of EOS. Why my RAM not occupied? I think when i create new account, it will be store on account_object table (in function apply_eosio_newaccount) and it consumes RAM. But when I test it that its not true.
Answer: New accounts will consume RAM. The data of your new accounts will be saved in the state which is in the RAM. However, if your machine running nodeos does not have enough memory for the whole state, swapping will happen, which means your nodeos instance will have to access your virtual memory on hard drive and read/write disk frequently. This will drastically slow down your nodeos performance.
In addition, the transactions/actions that create your new accounts will be saved in block data. You could think of this as saved on disk (mostly).
Comment: Thank you for your comment, so How can I calculate how many RAM can be swapped? Where I can read it? Please give me some advice, thanks.
Comment: @Onotoko Swap is a linux/unix system concept, https://www.linux.com/news/all-about-linux-swap-space
Answer: Here is some description of RAM. i.e,
RAM is used for permanent storage. One example is how account keys and balances needs to be stored in RAM and accessed very quickly every time they are called upon. So while it may not be the traditional definition of "permanent", on the EOS blockchain RAM provides a permanent means of storage.
When you created account on testnet it means it occupied some RAM which is bp's RAM not your local machine's RAM.To check your ram usage you can either go on testnet site and go on account info tab or you can check by the command cleos get account "ACCOUNT_Name" it will show you your account information.
Comment: Thank @Mr.Y, I got it, but my answer is why 1 million accounts can run on computer which has only 1GB RAM :)
Comment: As i said it is not based on your machine's RAM.It is based on your accoun's RAM which is a part of Block Producer's RAM.
Comment: Well, maybe I am wrong when understand this machine is a Block Producer that mean when I run EOS on local, it is a Block Producer. Am I wrong? If I wrong so if I set 'chain-state-db-size-mb'  equal 512, EOS will be broken?
Comment: If you run eos on local and make account on that(means by accessing on127.0.0.1:8888 or your nodeos port) it will consume your RAM but as you said you are on testnet means you are accessing block producer's machine resources.
Comment: Thank @Mr.Y, I think I need to change value of  'chain-state-db-size-mb' and test again. I hope after that I can understand more about this problem.

Where are new accounts stored?


What currency do the antminer pools generate?

Question: Sorry to be a newbie, But I'm pretty lost. I just set up my first Antminer and don't understand very much. There are three pools suggested as the default. What am I generating as far as currency?
Answer: Antminer is good a a certain type of cryptographic hash: SHA256. So while you can technically hash any cryptocurrency that uses SHA256 (ie. http://www.coinwarz.com/miningprofitability/sha-256) most pools will be focused around Bitcoin and even those that don't mine Bitcoin directly, will give you the option to trade whatever they're mining, directly to Bitcoin.
Some pools can hash several similar cryptocurrencies at the same time but considering their relative values they are hardly worth the bother and admin taken to trade them and you can probably find a pool that does all of this automatically. Go ahead and visit the pools' websites and read their FAQ pages and ask for help on their forums!
Beware though - many, if not most, pools and Bitcoin services are run by Crooks out to steal your money or use your hashing power for their own gain. Look for pools that have been around for several years, and with lots of users and a friendly community!
Also beware! If you are paying for electricity, you are probably going to mine less Bitcoin than the cost of the electricity - so you might as well not mine at all and just spend the money that you would have spent on electricity, directly on buying Bitcoin at an exchange. For older hardware this holds true, even if Bitcoin should reach $3000 each.
Comment: Thank you for your courteous reply. I trying a S5 and if that can be profitable, I'll look at the S7's.


Rocket vs aeroplane? Difference in take off?

Question: Although both aeroplane and rocket burn fule and eject smoke but
Why aeroplane moves and runs horizontally before take off ?why does not it takes off at its original/initial place just like rocket?
Answer: A plane relies on aerodynamic lift to stay airborn. This is much more efficient than using raw vertical thrust like a rocket does. The downside is that planes always need to be moving perpendicular to the direction of gravity.
Pretty much all planes except for fighter jets do not have enough thrust to take off vertically.
For traveling from point A to B on land that's fine, since the path is perpendicular to gravity anyway. If you wanted to go straight up though, a plane would be forced to fly in a large spiral.
So the short answer is: Planes take off horizontally because they have to. Rockets can take off in any direction, but they're not efficient.
Answer: Vertical-takeoff aircraft do exist. A lot of research has gone into this (mainly in the 1960s), but it all led to one conclusion: there's no commercial case for vertical-takeoff jet aircraft.
Only 4 VTOL (vertical takeoff and landing) aircraft have gone into production: the Harrier, the F-35 (B version only), the V-22 Osprey and the Yak-38. These are all military aircraft created for a specific niche: the need to operate from small bases either on land or on a ship.
This is an example of a civilian VTOL design:

as you can see, there's a massive increase in the number of engines compared to a normal airliner. All of these engines are used for only a few minutes per flight, they are dead weight and drag the rest of the time, making operation of a VTOL airliner much more expensive than a conventional aircraft.
VTOL operation is also very loud, so the only advantage of a VTOL aircraft (doesn't need a large airfield so it could land closer to its destination city) falls foul of noise regulations.
Rockets are the other way round: they need massive thrust to get up to the speed required for orbit. This also turns out to be enough thrust to take off vertically.
A rocket only spends a few minutes inside the atmosphere. So while it is possible to add wings to a rocket to take off horizontally, those wings would be dead weight for most of the flight. Rockets operate close to the edge of what's physically possible, and dead weight is the last thing you want.
Answer: Rockets are carrying their own oxygen. Airplanes rely on the oxygen in the atmosphere.
Also as has been mentioned in @drew's answer airplane engines have been optimized for flying in the atmosphere with continuous power on but very small relative thrust, a range of between 20% to 30% of the weight of the airplane. While rockets must provide 100+% thrust for the lift off.
There are new technologies that are breaking this mold like solar wind rockets or vertical take off planes with rotating wings or military jets which have hovering capabilities.
But the two major differences in majority of the cases is rockets do not need air either for developing lift or for oxygen, while planes need air to generate lift and use it's oxygen to burn their fuel.


Duration vs Work...Resource Overallocation Errors

Question: I am fairly new to project so apologies up front...I have several tasks in my project plan which have a set duration; i.e. start and end dates/due dates, but the actual amount of time required for each task is not the entire duration. For example, one task has the duration of 1 day but only requires 1 hour of work. I have set each task to Fixed Duration, input the Work column to calculate hours but still have errors regarding resource overallocation. Logically, these resources are not overallocated because they have not even been assigned more than a few hours of work each day. Like I said I am new to project so I know I'm missing something just not sure what. Any insight or help would be much appreciated! Thank you!
Comment: Which software are you using; then we can explain to you how to split tasks.
Comment: When you say "I am fairly new to project", do you mean "Microsoft Project"?
Comment: If you mean Microsoft Project, then yes it is a pain. It makes you specify things that are not important to you.
Answer: How many Tasks are there in schedule and what is the calendar defined at project Level. Have you defined any resource calendar ?
can you check in Leveling option, whether it is Day by day, week over week or month over month.
if one resource is defined in project and one Task is defined in Project.
work = 8 hrs ( assume resource is full time).. 4 hrs ( Resource is part time)
another scenario, 2 Tasks are defined and each assigned with Resource X, on first task with resource assignment ( 50%) and other task with resource assignment ( 60%) and Leveling options defined as Day by day, then system will show Resource Overallocation. incase of other settings, overallocation will not come into visibility.


Pressing charges for domestic assault

Question: My husband (now ex husband) was arrested for domestic assault after pushing me so hard my head hit and broke a table. I didn't press charges at the time because I was afraid of him and under duress from his constant threats, emotional, verbal, and psychological abuse. Years later I was diagnosed with severe and complex PTSD. I've been in treatment and now finally have a voice. Can I press charges now even though it happened 6 years ago?
Comment: Deadlines for filing vary greatly between countries and states. Some have no statute of limitations at all, while many would have a statute of limitations of less than six years for this offense. Duress or fear of a victim are irrelevant to criminal statutes of limitations, and unlikely to receive much consideration even in a contemplated action for civil damages. In practice, it is unlikely that a prosecutor would be willing to prosecute such a stale case, even if the statute of limitations has not run in the relevant jurisdiction.
Answer: Given the state you are in most states limit (domestic) assault filings between 18 months and 5 years.   Also unless your husband admitted guilt there really isn't much the police or prosecutor can do without hard video evidence, even if you were within statute.
As for civil matters PTSD caused by another person is a really serious accusation.   There are cases where people have won judgments but these were people brutally abused for years and kidnapped and so on.   It sounds that your husband had a temper and there was some abuse but you are relying on one incident that you didn't even press charges on.   You could certainly consult a lawyer and if a lawyer took your case on contingency then maybe you move forward.
I would not advise you to start paying a lawyer though as a means of extracting money from   your husband based on what he did to you in marriage.   There are two things here.   First most civil courts understand that most family courts are still more apt to side with women on custody and separation agreements.   And second the fact is this should have been brought up during your divorce proceedings and used to discuss splitting of assets and possible future alimony.   The fact that you bring this up in addition to your divorce hearings is kind of double dipping in the courts.
Answer: You can make a complaint to the police: they will decide if they want to investigate the matter.
Depending on which country/state you are in there may be a statute of limitations that means they cannot take action. Notwithstanding, unless there were witnesses apart from him and you this would be an extremely difficult case to get a conviction as there is unlikely to be any physical evidence or contemporaneous records - for this reason, the police may choose not to investigate.
Comment: @blankip and if there were 312 witnesses? Notwithstanding, there are plenty of people in jail on 30+ year old testimony from a single witness the jury believed.
Comment: If the attacker was arrested, there will probably be records of that (but not necessarily medical records etc) - but I agree that a conviction may be difficult.
Comment: @Dale M - I doubt witnesses matter at this point.   This doesn't seem to be a "huge" incident - a push and no medical report?  Any witness to this, given the timeline wouldn't be deemed as impartial by a good police officer or prosecutor.   Not sure what the point is here other than revenge.   I have had some abusive ex's... I would rather not see them again.

Pressing charges for domestic assault


Can I exchange Bitcoins to get Dollars?

Question: Can I exchange Bitcoins to get Dollars? If I get some Bitcoins, Is it possible to sell it and get Dollars?
Comment: @DavidPerry It is not similar, it is quite opposite. And changing bitcoins to fiat currency can bring problems at some sites (unreasonably much time or high fee).
Comment: Please search before you post. While it's not an exact duplicate because you're asking about selling coins rather than buying them, the answer is the same as this particularly ancient question: http://bitcoin.stackexchange.com/q/91/
Answer: Yes, Bitcoins are exchanged for a variety of different currencies and goods, definitely including US Dollar, Canadian Dollar, New Zealand Dollar, probably also Hong Kong Dollar, Namibian Dollar, Singaporean Dollar, Taiwanese Dollar, maybe even Brunei Dollar, Belize Dollar, and Namibia Dollar.
In general it is expected behavior for currencies to be exchanged for one-another. There exists at least one exchange course for each currency pair. Here is one example for Bitcoin and US Dollar: CoinDesk Bitcoin Price Index
As to where and how you can exchange Bitcoin for Dollar and vice versa, you can find many questions here discussing that. See for example How do you obtain Bitcoin?, What's the best place to sell bitcoin in Australia?, What are the options available to convert Bitcoin ot Paypal-USD?. You can find a better fit by using the search function with the appropriate input terms, e.g. sell bitcoin usd.

Can I exchange Bitcoins to get Dollars?


Star Trek episode where an alien race enters the body upon death

Question: Can anyone remember what episode of Star Trek it was that an alien species entered the body upon death and drew on the person of the deceased, on their memories, their personality, until it gradually took over? I remember furrowed brow, gray complexion, and that the starship doctor gave the woman an injection that returned her to normal, or so it seemed
Comment: Which series was that? TOS, TNG?
Comment: [Conspiracy](http://memory-alpha.wikia.com/wiki/Conspiracy_(episode)), perhaps? [The Lights of Zetar](http://memory-alpha.wikia.com/wiki/The_Lights_of_Zetar_(episode))?
Comment: _Buffy the Vampire Slayer_?  The parasite inhabits a human corpse, inherits its memories, gives it a paler complexion and sometimes furrows the brow … —Okay okay, I'm kidding.
Answer: You're thinking of Lindsay Ballard in Voyager's "Ashes to Ashes".

A long-presumed-dead crewmate returns to Voyager, pursued by the aliens who revived her

The aliens are the Kobali:

Their method of reproduction was unique and their most distinguishing characteristic: they added to their population by reanimating the deceased corpses of other species, altering their DNA to transform them into fellow Kobali.

And their appearance matches your memory:
Comment: Minor comment, but this conflicts with the OP's comment that "an alien species entered the body upon death", as the  Kobali just reanimated corpses, ie they didn't enter the body which hints towards something parasitic in nature.
Comment: Was there supposed to be some kind of message in this episode?
Comment: @Loki, it's not minor.  I believe OP simply misremembered a detail.   And *entering* could be interpreted different ways.  This is one of the more figurative ones.
Answer: I'm going to guess you're misremembering an Andromeda episode as Star Trek.
Episode 2x15, Dance of the Mayflies, involves an infectious parasite that first kills, then reanimates corpses.  The parasites are sentient, and partway through the episode they communicate through Trance's body after infecting her.  She's a pale purple for most of the season - the far left in this image of the crew from that season (maybe you'll recognize the rest of them?):

By the time this episode comes around, she's exchanged places with her adult self, pale with a golden sheen:

Eventually they figure out a strong electric shock will destroy the parasites, and start using their main handheld weapon, Force Lances, at full power on the corpses but can only fire 3 shots on each before it runs out of power.  However, in order to kill the parasites in anyone still living, they inject nanobots modified to deliver the shocks directly to the parasites without harming the host.
Andromeda doesn't have a ships doctor, but Trance often acted as one.  From what I remember and a small part of the linked summary, Trance was freed by the parasites by the lethal shock, but didn't die.  She was the one that then modified the nanobots.
(Aside:  Trance's body did not react the same as anyone else's when she came into contact with the parasites.  She didn't die, they took over her completely when she was first infected; that's how she was able to be rescued despite the parasites having control over her body, when they needed to kill everyone else to get control.  This was one of the major clues that there's something seriously different about her species, before we started getting answers.)
Comment: thanks, everyone! I am amazed to get your answers. It was definitely Star Trek, though -- I remember that quite clearly. I'm going to look into that Kobali episode -- it could well be it, thank you!
Comment: The key thing I remember is that the starship doctor gave her shots to suppress her external alien characteristics -- that there was hope for some time that she'd remain human. I don't think it worked out, though.
Comment: OK, guys, this is definitely it: http://memory-alpha.wikia.com/wiki/Jhet%27leya
Answer: The episode is called "Coda" (1997) from Star Trek: Voyager.
From IMDb:

Chakotay and Janeway crash on a planet and are stuck in a time loop where Janeway dies.

I found the exact episode because I was searching for the same one.  The idea that an alien parasitic race recycles souls by pretending to be the newly deceased relatives who lure them into the light where they will be eaten is frightening, because what if it's true?
Comment: the episode you seek is called "coda" from the star trek voyager series
Comment: Hi, welcome to SF&F.  You should [edit] your answer to put the details from your comment into the answer; please read [answer] for more information on writing a good answer.


Why does the Sudarshana Chakra resemble a tantric yantra in this image?

Question:
In the above image, the Sudarshana Chakra looks like a tantric yantra. Is there any scriptural reason behind this?
Answer: We get the following invocation Mantra for Sudarshana from this PDF:

śaṅkhaṁ cakraṁ ca cāpaṁ paraśuṁ asimiśuṁ śūla pāśāṁ kuśāṁśca |
  bibhrānam vajra keṭaṁ hala musula gadā kuṇṭaṁ atyugra daṁṣṭraṁ ||
  jvālā keśaṁ trinetraṁ jvaladānala nibhaṁ hāra keyūra bhūṣam |
  dhyāyet śaṭkona saṁsthaṁ sakala ripu-kula prāṇa saṁhāra cakram ||
I visualize   Sudarshana
  the   eliminator  of  all hostile forces, located within  the six-cornered  star,
  bearing    the    conch,  discus, bow,    axe, sword,
  trident,  noose,  goad,   the diamond-shield, plough, cudgel, mace, spear,
  with  aweful  sharp   fangs,  with    blazing halo,   three   eyes,
  the   intensity   of a    raging  inferno,    adorned with     garlands and   anklets.

This Shatkona is also found in the Sudarshana Yantra, which is worshipped as the Sudarshana Chakra.
In the image given in the question too, we can see a Shatkona (six-pointed star). So, they have drawn it roughly as per the Dhyana Sloka.
Answer: Actually, sudarshan chakra is a manifestation of Narayan's Ida and Pingala naadi. Shiva, the Adiyogi, taught Narayan the way to use power of these Naadis as a weapon, in the form of boon to His Tapasyaa. And as we know that these Naadis are used to enlighten the 7 chakras in body. So, one can use power of Chakras and Naadis(in Sanskrit, this thing is mentioned as Yogshakti) in such a way(like a weapon), if learned from any Siddh yogi(Here, Shiva Himself). Henceforth, sudarshan chakra is represented as Tantric Chakra because both the systems are conveying similar messages, i.e., using Chakras and Naadis efficiently.
Comment: A verse would be useful if you can quote
Comment: Thanks very much for your answer.As Akshay S said, quoting a verse or citing some scriptural source woould be appreciated.


Fielder tosses the ball after legitimate catch. What's the minimum time a fielder needs to hold the ball after the catch is taken?

Question: Sometimes in cricket a fielder immediately tosses the ball after legitimately catching it. Batsmen generally are out in such cases and I haven't yet seen anyone objecting to it. Is there a min requirement of time for the fielder to keep it in his/her hands? Also, What happens if the ball reaches/crosses boundary on such random throw ups in the air?
Answer: Quoting relevant clause from the official discussion of Law 32 (Caught), Law 32 in Action:

A Fair Catch A catch shall be considered to have been fairly made if:-

(a) The Fieldsman is within the field of play throughout the act of
  making the catch.
(i) The act of making the catch shall start from the time when the
  Fieldsman first handles the ball and shall end when he both retains
  complete control over the further disposal of the ball and remains
  within the field of play.

There is no time limit for how long the fielder should hold on to the ball, but the umpire should be convinced that he was in complete control of the disposal of the ball after completing the catch.
For the add-on question of what happens if the random toss up lands the ball beyond the boundary, as Spinner pointed out in the comments, once dismissal is complete, the ball becomes dead, and where it goes after that is irrelevant.
Trivia: Perhaps the most famous instance when this came into prominence was when Herschelle Gibbs caught Steve Waugh during a Super Six match of the 1999 ODI World Cup. In his haste to celebrate, he threw the ball away without being in complete control of it. Steve Waugh was declared not out, and went on to win the game for Australia. The result of this match came back to haunt South Africa later as their semi-final game ended in a tie, and Australia qualified for final having beaten South Africa in the Super Six game.
Comment: @Spinner Thanks for the edit. Also, I didn't notice there was an "add-on" question, thanks for pointing that out. I will edit the answer to include it. PS: It is mildly annoying (to me, anyway) when the question has a bunch of these "Also, what happens if ..." type add-on questions.
Comment: Correct. As regards the question of what happens if it subsequently crosses the boundary: once the umpire considers the to ball be under control, the dismissal takes place, which renders the ball dead under [23.1(iii)](http://www.lords.org/mcc/laws-of-cricket/laws/law-23-dead-ball/). Once it's dead, what happens to the ball becomes irrelevant; the fielder could, in theory, throw it into the crowd (although I haven't seen that happen).
Answer: There's no minimum number of seconds in law - the general rule of thumb is that the fielder needs to be in control of the ball and control of his own movements. There have been occasions when a fielder tries to celebrate too early and drops the ball (Hershelle Gibbs in the World Cup a few years back, for instance).
The boundary only comes into play if the ball touches the ground, so a clean catch is not possible then.


I'm confused about the sentence 「何も悪い事は聞いた事がありません」

Question: To my understanding the sentence 「何も悪い事は聞いた事がありません」means something along the lines of "I have'nt heard any bad things". What I'm confused about though are these words: 「何も悪い事は聞いた事がありません」As far as I now all three of these mean "thing". So why is this word used three times in this sentence, what use does each one serve?
Answer: ことがある is a set phrase that when combined with the past tense (た form) of a verb, means "have had the experience of doing V". The word こと here doesn't have any meaning in and of itself; it's a nominalizer that turns the verb phrase into a noun so that you can talk about it as a concept:

悪いことは聞かなかった。

I didn't hear a bad thing.

悪いことは聞いたことがありません。

I haven't heard a bad thing. (Lit.: the act of hearing a bad thing doesn't exist)
The first こと in this sentence literally means (intangible) "thing."
Finally, 何も means "not any" or "nothing." Without it, the sentence could be construed to mean "I haven't heard the bad thing." With it, it becomes "I haven't heard any bad things." 何も doesn't mean "thing."
Answer:
何も

This modifies 悪い事 and means "any/all"

悪い事

You said it yourself "bad things" so 事 here can be translated as "thing"

聞いた事がありません

This is part of the [past tense verb]+ことがある construction meaning that there was a time where the action occurred or that the speaker is expressing their experiences. This manifests itself in your translation "I haven't heard any bad things" which contrasts something else like "I didn't hear any bad things"
Putting it all together makes something like "I haven't heard any bad things" or "I've never heard anything bad"

I’m confused about the sentence 「何も悪い事は聞いた事がありません」


Identify the adverb phrase in the sentence

Question:
The cracks spanned over the screen's upper surface like tendrils, white and glossy in appearance.

Does the phrase white and glossy in appearance modify the word 'tendrils', or the word 'cracks' and 'spanned'?
Answer: It does not seem to be a very well written sentence. "Spanned over" should be "spanned." Technically, "white and glossy" should modify "tendrils," but I suspect that it is intended to modify "screen."
Here is what I am guessing was intended.
The screen, spanned by tendrils of cracks, looked white and glossy.
LATE EDIT DUE TO OP's COMMENT & JASON BASSFORD'S EXCELLENT ANSWER
If what was intended was to modify "tendrils," the common positioning of the adjectives would be before the noun modified. It is permitted in certain circumstances to put adjectives after the noun modified, especially when the adjective itself is modified by a prepostional phrase. For example, it is not good English grammar to say "He picked up a sheet red," but it is good grammar to say "He picked up a sheet red with blood."
Now this is opinion about prose style, but I think your original sentence was hard to interpret because "in appearance" does not really modify "white" or "glossy," terms which are by definition about appearance. So your intended meaning could easily have been rendered as "glossy, white tendrils." By changing to a grammatically questionable word order with a redundant prepositional phrase, the reader stops to decipher what is really being said and then wonders whether the intended meaning is the same as the grammatically correct meaning. It is why I like a spare style.
Comment: Thanks for replying :)..  I actually tried  to target 'tendrils', and describe them as 'white and glossy'. And it looked odd, the way I had written it. So my question is does 'white and glossy' modify tendrils, in spite of having  that comma in between. And how can I rewrite it, so it only modifies the tendrils?
Answer: To paraphrase a comment (note that the existing answer is a perfectly correct interpretation in terms of what was actually asked):
How can I rewrite the sentence in my question so that white and glossy (unambiguously) modifies tendrils?
You could try something like this:

The cracks spanned the screen's upper surface like white and glossy tendrils.