Timing of precedent setting: when exactly do precedents take "effect"?

Question: When a high court rules on a matter, when does the precedent take effect?  Say a case is in progress in a lower court which asks the same question as what was just decided on the same day in the high court.  I know most cases span months sometimes.  Do whole cases start right over from scratch when the high court sets a new precedent?  Do cases pause to wait for an answer?  What if two cases simultaneously ask the same question?
Answer: tl;dr: Precedent takes effect on the decision date.
You didn't list a jurisdiction, so I'll give a U.S. example.  In Citizens United v. FEC (U.S. 2010), there are three dates listed in the header:

Argued March 24, 2009
Reargued September 9, 2009
Decided January 21, 2010

Precedent attaches to a decision date.  That's also why we see 2010 in the case citation above.  However, it's important to note that not all precedent is binding.  A decision made in the 7th Circuit isn't binding on a district court in the 2d Circuit, and vice versa.
As to the impact on cases in progress, the party that is more favorably impacted by the change can bring it to the judge's attention.  The outcome will depend on the a) whether the decision is relevant, b) whether the decision is binding, and c) how far along the case at bar happens to be.  Note: most U.S. cases never go to trial.  It is (relatively) lower stakes to incorporate new legal theories in the pleading or discovery stage.
Comment: Sometimes the courts will also decide their precedent is retroactive and will make it effective for all cases. Usually the precedent becomes effective for all cases pending on or after the date of the decision.
Comment: Well, the decision of the precedent takes effect whenever the acts that were in dispute did - judicial decisions are necessarily retrospective. Judges are said to find the law as it always was - even when they overturn earlier decisions, they generally say that the previous ruling erred in some way, unless the change is due to some kind of legislative act.


Upload multiple files with the same file name into the library

Question: Probably this is a bit of a noob question, but... Is there any way to upload multiple files with the same name into the same library without use of folders (which are evil in SP :) )? My understanding is that this is not possible, but maybe I can do it if I somehow leverage some other unique column which SP will take into account along with file name so that name match won't present an issue?
Answer: Short answer, no.
If you have versioning disabled in the document library, the new file will replace the old.
If you have versioning enabled in the document library, the new file will be added as a version of the old.
You could develop an item adding event receiver that checks the file name and changes it if duplicates are found, but I don't think this is what you're looking for.
Comment: Yes, one file in each folder. You have to remember files in a document library all have a URL to them. If you had two files with the same name in the same folder you couldn't have unique URLs for files in document libraries. Document sets are just glorified folders.
Comment: But with folders I can have duplicate names, right? (one per folder and one in root) Could be the same achieved with use of Document Sets instead of folders?


I upgraded an app on my iPhone 4, but this new version doesn't work. How do I replace for the older version?

Question: I did the stupidity of upgrading the newest version of AM 880 KIXI radio, a retro radio station in Seattle. The version I had was the previous one, the 2.8 and I held off upgrading for a long time, but in a moment of insanity, decided to do it and deleted the app and downloaded again on the AppStore, thus downloading the 3.6 version, the next one after the 2.8- i tried uploading directly, but I kept being redirectioned to the app itself, that's why I deleted before downloading again.
The thing is my internet connection isn't that good, but the app always worked fine, but now with this version it keeps buffering at lot and it doesn't even show the music that's playing anymore, even when my connection is speedy. Is there any way to undo this? I have an iPhone 4 that hasn't been backed up to a computer, so I don't have the previous version saved as a .ipa file. I have iOS 7.0.4.  Seriously, what do I do? I know I sound desperate, but I listen to this station very single day, specially during work(I'm a translator) and it's essential for me to help concentrate. Is there any way I can retrieve the previous version of the app I was using? I also tried clicking on app support, next to the reviews on the AppStore to try and get in touch with the developer, but I keep getting 404 error. Seriously, I really need the 2.8 version back on my phone- I beg for help.
If it's necessary, I will jailbrake my phone, but as long as it's guaranteed I can have the 2.8 version of that app and download it.
Answer: Do you have a backup? Time Machine or otherwise? If so you can restore the file from a backup.
The iPhone apps are located in ~/Music/iTunes/Mobile Applications and end with the ".ipa" extension.
It has been a while since I tried this but I think you just have to place the restored file in the proper folder and sync your phone.
Comment: Please note that this will only work, if the .ipa file was on your Mac/PC. If you're not syncing with iTunes you're probably lost here.
Comment: The laptop I had one backup was stolen, so that's why I don't have a copy. If I jailbrake my phone, is it possible to get the previous version of the app to download?


Antennas behavior in different dielectrics

Question: I tried to set the antenna in the dielectric, thinking that the minimum frequency of the S-parameter would move, but it began to behave very strangely. What shoudl happens to the operating frequency of the antenna in the dielectric? Should it move, or does the surrounding dielectric change the resistance of the antenna, making it unworkable?
Answer: The dimensions of the elements of an antenna are dependent on the wavelength (frequency) of the incident waves to be received.
The wavelength of the waves will depend on the refractive index of the medium though which they are travelling.
Thus if the wave is travelling in a dielectric that might mean that the wavelength for which the antenna was designed is not the wavelength of the incoming wave.
You may also have a problem if the dielectric is "lossy" - absorbs the incoming waves.
Answer: In a dielectric the propagating wavelength gets shorter in ratio with the refractive index so you would expect that the formerly otherwise properly tuned antenna in air would be electrically large and now would tune to a lower frequency but if you did nothing else but placed the antenna in some dielectric then the antenna S parameters will surely behave funny ways because your external matching circuits will not be affected by the dielectric.
Reality is even more complicated because the radiation behavior will also depend on the size of the dielectric block relative to the antenna dimensions and also on the refractive index. Unless the linear dimension of the dielectric in the direction of the main lobe is at least as large as the Fraunhofer (Rayleigh) distance the reflections from the boundary will interact with the antenna itself distorting the beam shape.
Note too that the presence of the dielectric reduces the bandwidth of the antenna  (ie., increases its "Q") as well.
Another funny thing is that if you place a phased array in a dielectric then grating lobes may show up because for the same frequency the element spacing is too large now electrically.


Why tomato is too small?

Question:
I bought it a month ago then moved it to a bigger pot and the tomato started to be red but still too small, it is cherry tomato but still too small and not tasty sweet at all.
Answer: Tomatoes, and most soft fruits, need good sunlight to sweeten up as they  ripen. If you're growing indoors, whilst they will ripen, they won't be as tasty and sweet as they would if grown outdoors in warm/hot sunlight. This is why tomatoes harvested in summer are sweeter than those grown in greenhouses under artificial light/heat conditions in winter - the latter are certainly edible, but not so tasty. if your plant is not a small tomato like a cherry variety, they haven't reached full size because they're being grown indoors under ordinary house conditions, though lack of tomato fertiliser on a regular basis may also partially account for it - you haven't said what your care routine is.
Comment: Its  not freezing here (UK) but there's no question of growing tomatoes outdoors here yet,not before end  of May unless you  have a sunny greenhouse, so  I know the problem. Its pretty good you're getting tomatoes that ripen at all, whether they taste good or not... you can buy specialist  feeds specifically for tomatoes, one  of those would help with the size of the fruits, but not necessarily the flavour...
Comment: Thanks so much! actually I am just a beginner in gardening :), I don't fertilize it, just water it and I keep it inside because it is cold outside especially in winter it is freezing.

Why tomato is too small?


tried to allocate 4096 bytes) in /var/www/vhosts/rede.ca/httpdocs/wp-includes/

Question: I upgraded from WordPress 4.9.6 to 6.3 and initially everything seemed fine.
I installed the latest version of the X theme (by Themeco) with no issue.
But when I applied my old X child theme the site has crashed. The admin panel will not load, even Recovery Mode doesn't work.
I have subsequently removed all plugins and themes (except for twentytwentythree).
Nevertheless, I keep getting variations of this error in my Apache logs:

mod_fcgid: stderr: PHP Fatal error: Allowed memory size of 1073741824
bytes exhausted (tried to allocate 4096 bytes)

Out of desperation I have successfully increased the amount of memory available to 256M, then 512M and finally 1024M.
But no matter how much memory I allocate, the "tried to allocate" amount is always tiny: either 4096, 8192, or 20480 bytes.
Added to wp-config:
define( 'WP_MEMORY_LIMIT', '1024M' );

And php.ini:
memory_limit = 1024M

I have tried different versions of PHP from 7.4.33 to 8.1.23, and switching between FastCGI and FPM.
I found this comment on StackOverflow that seems to describe my situation, but I have no idea what the next step should be.

My guess is infinite recursion tried to allocate 8192 bytes typically
when this is a low value that is the reason. If you up the memory
above that amount and it still happens, then that's another marker for
it.

PHP 8.0.30  |  WordPress 6.3  |  CentOS 7.9.2009
Answer: Maybe this will help someone one day.
I turned out my theme was somehow still active, even though I had renamed its directory.
Now that I am actually running the default WP theme I can log into the admin panel.


How to Create a Dropdown menu in Thesis Sidebar?

Question: I have an issue with Thesis Wordpress theme. I want to create a dropdown menu for my categories and archives in the sidebar, not the navigation menu.
If anyone knows how or can point me to a website where this is explained I will be grateful.
Answer: I dont't have the thesis theme but showing a dropdown for categories or archives is a standard WordPress Plugin. Just select them from the widgets page within your backend.
Comment: Wow, not that I'm not grateful, but this was asked 45 days ago, and I found the solution 44 days and 22 hours ago :)


Is there any update to fix the warning 'ViewPager Android has been extracted from react-native core'?

Question: When I use react-navigation to implement the createMaterialTopTabNavigator it works fine for iOS but for Android it throws a warning stating that ViewPager Android will be removed in future release and asking me to use imported from "@react-native-community/viewpager' instead of react-native. Im sure this warning is from the react-navigation package and changes need to be done in react-navigation package to fix it.
But I don't see any open issue in their GitHub page regarding this or  is this a common update issue? Do I have to wait for their update in their next release?
Answer: Here's the issue thread about this in react-navigation which has unfortunately been closed without a resolution yet. Here's the suggested workaround to suppress that particular warning from: https://github.com/react-navigation/react-navigation/issues/5730#issuecomment-518372933
You can hide the yellow box for this warning in the meantime by doing this at the root level of your app:
import { YellowBox } from "react-native"

YellowBox.ignoreWarnings([
  "Warning: ViewPagerAndroid has been extracted",
])

Comment: Hardly an ideal solution


Is yoga a religion?

Question: Is Yoga a form of religious Hinduism? Are beliefs such karma, reincarnation or gods needed to practice it? Is appropriate to practice yoga if you are agnostic, atheist or believer in other religions such us Buddhism, Islam, Christianity etc?
Comment: Religion is a word from west wrongly used in place of word Dharma and sometimes truth associated with spirituality.  Yoga means union. Union of individual consciousness with universal consciousness. Yoga is Parama Dharma. Not religion. Only qualification for Yoga is purity of mind. Nothing else. There's no religion word ot religion in India.
Comment: @YDS you are counting Yoga as a philosophy some authors don't. Remember that Yoga predates perhaps even Samkhya. This later philosophy just like Buddhism is part philosophy part religion. eg. "Karma, reincarnation, etc". Please feel free to post that as an answer adding some relevant references. Namasté
Comment: No, but they are linked. Purusha-Prakriti of Samkhya Yoga (Patanjali Yoga Sutras) are worshipped as Shiva-Shakti in Hinduism while Brahma,Vishnu and Mahesha are 3 gunas of Prakriti. To practice Yoga one needs only a human body and a desire to understand the subtle science of consciousness, the seer.
Comment: @ManuKumar agreed again. Post some references to back up your comment please.
Comment: what do mean by religion? yoga is one of the six philosophies (ṣaḍdarśana): Sankhya, Yoga, Nyaya, Vaisheshika, Purva Mimamsa and Utara Mimamsa (Vedanta)...
Answer: Religion is a social-cultural system of designated behaviors and practices, morals, worldviews, texts, sanctified places, prophecies, ethics, or organizations, that relates humanity to supernatural, transcendental, or spiritual elements.
So Christianity, Islam, Buddhism, Jainism, etc, are religions.
Vaishnavism, Shaivism, Saakteism, etc, being in vogue under the name of Hinduism are religions.
However, Yoga is basically a pure SPIRITUAL CONCEPT.

The Sanskrit noun योग yoga is derived from the root yuj "to attach, join, harness, yoke".
Rig veda 5.81.1

युञ्जते मन उत युञ्जते धियो विप्रा विप्रस्य बर्हतो विपश्चितः | वि होत्रा दधे वयुनाविद एक इन मही देवस्य सवितुः परिष्टुतिः ||
The illumined yoke their mind and they yoke their thoughts to the
  illuminating godhead, to the vast, to the luminous in consciousness;

So Yoga means joining the mind with the God, ie., it indicates pure SPIRITUALITY.
Asanas, Pranayama, etc, which are part of Asthanga Yoga, will aid in joining the mind with the God.
A human can be irreligious/agnostic/religious, but can be SPIRITUAL.
Dr. Paul Brunton, a sceptic, approached Sri Ramana Maharshi and got spiritually elevated.
Answer: One has to understand the term religion to answer this question. What is a religion? A religion as understood in the western world consists of a belief in a God completely external to the universe and belief in certain doctrines and dogmas.
Hinduism or Sanatana Dharma is not religion by the definition given above.

What is the spirit of Hinduism? What are the essential principles? The
  spirit of science is not dogmatic certainty but the disinterested
  pursuit of truth, and Hinduism is infused by the same spirit. Fixed
  intellectual beliefs mark off one religion from another, but Hinduism
  sets itself no such limits. It is comprehensive and synthetic, seeking
  unity not in a common creed but in a common quest for truth. Hinduism
  is more a way of life than a form of thought. It insists not on
  religious conformity but on a spiritual and ethical outlook in life.
  It is fellowship of all who accept the law of right and earnestly seek
  for the truth.

History of Bengal, Bihar and Orissa under British rule by L.S.S. O'Malley quoted in British Paramountcy and Indian Renaissance Part II edited by R. C. Majumdar
Since Hinduism involves seeking for the Truth and is not a mere belief system, it needs a method for seeking. Yoga is such a method. So the answer to the question is Yoga is not a religion but a method used by followers of Sanatana Dharma to search for truth.
Answer: No, it's not.
According to a wikipedia article on Hinduism ref here:

In whatever way a Hindu defines the goal of life, there are several
  methods (yogas) that sages have taught for reaching that goal...

Yoga is defined as a method not as a religion which as four paths:  Bhakti Yoga (the path of love and devotion), Karma Yoga (the path of right action), Rāja Yoga (the path of meditation), Jñāna Yoga (the path of wisdom). Another method of Yoga is the one explained by Patanjali in the Yoga Sutras which could be considered a form of Raja Yoga. "Yogas chitta vritti nirodha" is Patanjali's definition of yoga which means that yoga is the removing of the fluctuations of the mind.
Hinduism is in fact a form of Bhakti Yoga, just like Christianity or any other devotional religion.
According to wikipedia:
Hinduism

This "Hindu synthesis" started to develop between 500 BCE and 300 CE...

Yoga

There is no consensus on its chronology or specific origin other than
  that yoga developed in ancient India. Suggested origins are the Indus
  Valley Civilization (3300–1900 BCE)[44] and pre-Vedic Eastern states
  of India,[45] the Vedic period (1500–500 BCE)

Apparently Yoga is way older than Hinduism itself. Meditative practices in India seem predate any dogma and it's harder to identify when those practices were firstly called Yoga being Sanskrit a 3500 year old language:

The meaning of the word "Yoga" is "union". It is derived from the
  Sanskrit root "yuj," (pron. "yug") meaning "to join"

Some teachers of Yoga in the Western world:
Paramahansa Yogananda
He was a pioneer in introducing Yoga in the western world in the 1920's-1930's.

...he claimed was the complete harmony and basic oneness of original
  Christianity as taught by Jesus Christ and original Yoga as taught by
  Bhagavan Krishna... ref here

Swami Vishnudevananda
He was a Sivananda's disciple ref here and founder of the International Sivananda Yoga Vedanta Centres and Ashrams. At those centres chants are dedicated to all deities (Allah, Mosses, Buddha etc) and they teach a universal mantra. ref here ref here and ref here
Acharya Rajneesh (Osho)
He was a very controversial yoga teacher in India and the Western World during the 1980's. ref here

Technology comes from the mind and religious technology also comes
  from the mind –  Yoga, mantra, yantra. Yoga means body postures, which
  can help you to  go deep inside yourself; they are created by the
  mind. That is religious  technology. That's why Yoga is not part of
  any particular religion.  There can be Christian yoga, there can be
  Hindu yoga, there is certainly  Buddhist yoga, Jaina yoga – there can
  be as many yogas as there are  religions.Yoga is just a technology. No
  machine is Hindu; no machine is Mohammedan. ref here

Conclusion
Yoga as taught in the Western world is a physical, ethical, mental, existential, spiritual, etc. method for personal development. This method can or cannot include Hinduism as base.
Answer: we all are speaking this in context of mind, Yoga, religion, spirit, oneness. We can name it anything... it is other dimension beyond this physical entity and can only be experienced and known ! what ever we name it, it is just words that be interpreted in our brain. what if we don,t understand and just admire something of no meaning / immense knowledge  .. that might what yoga meant to be..just my thought !!!
Comment: agreed. Then again a religion implies an organization, a system of believes and ultimately cultural indoctrination. Truth is not a discovery when you think you already know the truth.

Is yoga a religion?


Conservation of momentum when a shell is fired from a cannon

Question: When a shell is fired from a cannon free to move on a horizontal surface and inclined at an angle say 45 degree with horizontal. Does relative velocity of shell with respect to cannon depends on whether cannon is moving or not.That is, will the shell will have same velocity relative to cannon irrespective of the initial state of motion of cannon or not
Comment: yes, the speed of the shell relative to the cannon will remain the same
Answer: Let $\vec{p}_i$ and $\vec{p}_f$ denote the initial and final momenta of the cannon-shell system, respectively. Suppose we shoot the cannon horizontally (shooting at an angle will not change the argument) so that we can consider scalar quantities (or, equivalently, the components of the vectors in the horizontal direction).
Since no external forces are present, we may use conservation of momentum, which says that $\vec{p}_i = \vec{p}_f$, i.e., $p_i = p_f$ for our 1-dimensional problem.
Initially we imagine the system to be at rest, so $p_i = 0 = p_f$. On the other hand, we know that $p_f = m_\text{shell} v_\text{shell} - m_\text{cannon} v_\text{cannon}$. Equating the two expressions for the final momentum $p_f$ and solving for $v_\text{cannon}$, we conclude that
$v_\text{cannon} = \frac{m_\text{shell}}{m_\text{cannon}} v_\text{shell}$.
Therefore, the relative speed between the two objects is
$v_\text{relative} = v_\text{shell} - v_\text{cannon} = \left( 1 - \frac{m_\text{shell}}{m_\text{cannon}} \right) v_\text{shell} $.
Case 1:
If the cannon is "held fixed," we are imagining a situation in which the cannon is affixed firmly to the earth, so that the mass of the cannon can be taken to be very large. In this limit, $m_\text{shell}/m_\text{cannon}$ becomes very small, can $v_\text{relative} \sim v_\text{shell}$.
Case 2:
If the cannon is "free to move" or "recoil" we immediately see that $v_\text{relative} < v_\text{shell}$.
Case 3:
If we imagine a situation in which the cannon's speed is held at some fixed quantity (be it 0 or some value like, say, 100 m/s), we are really in Case 1 again, and the previous anaswer (of hiddenharmonizer) is valid.
Answer: You are correct. If the cannon was not moving and a shell was fired moving away from the cannon at 300m/s, it would still move away from the cannon at 300 m/s if the cannon itself was initially moving at 100 m/s.
In the perspective of the first cannon, the shell from the second cannon would be moving away at 400 m/s.
This would be the same as throwing a baseball out the window of your car in the direction you are driving. You already have an initial velocity relative to the earth and you are adding to the baseball additional energy when you throw it.


Are there other reasons than "the world is an illusion" that the radical skeptics use to doubt almost everything?

Question: Are there other reasons than "the world is an illusion or a simulation" that the radical skeptics use to doubt almost everything? I don't think there's a better reason than it, but maybe there are other reasons to doubt a lot of things, what are some of them? In my knowledge there aren't other reason, but I might be wrong.
Comment: Who exactly are those radical skeptics? If we can't identify who you are referring to we can't discuss their argument.
Comment: Pyrrho is the stereotype 'radical skeptic', and he did not bother with 'the world is an illusion', he just systematically undermined the assumptions we have about the well-foundedness of our reasons for things.  The Eleatics were more of the 'the world is all an illusion' bent, and they were not radical skeptics they followed their chosen foundations into the conclusion that you should not trust reality as do most 'perennial philosophies'.  So at least in their oldest forms, you are ascribing things wrong here.  Most people who think the world is all illusion do so from a very strong dogma.
Comment: "The world is an illusion or a simulation" is a skeptical claim, it is not a reason for it. Two typical reasons given are "we can't prove or disprove it with certainty" and pessimistic induction. The latter looks at history and surmises that many major claims widely believed in the past (stationary Earth at the center of cosmos, classical mechanics, phlogiston, ether, universal time, determinism, etc.) ended up overthrown by later developments, so why should it be any different with the rest.
Answer: Bertrand Russell has a famous quote according to here and here:

The fundamental argument for freedom of opinion is the doubtfulness of all our belief.

The fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt.

So if you don't want to be a radical skeptic, there's at least some philosophers' quote to argue for some skepticism in general. In deductive reasoning like logic and math realms, most common knowledge status quo may be hard to doubt under their corresponding applicable contexts or axiomatic systems. However, in inductive reasoning realm the confirmation of an argumentative conclusion in the form of hypothesis is very susceptible for doubt due to its limited background assumption and knowledge. For example, I. J. Good gives an example of the observation of a black raven actually decreases the probability of the to be confirmed hypothesis "All ravens are black" according to here:

Suppose that we know we are in one or other of two worlds, and the hypothesis, H, under consideration is that all the ravens in our world are black. We know in advance that in one world there are a hundred black ravens, no non-black ravens, and a million other birds; and that in the other world there are a thousand black ravens, one white raven, and a million other birds. A bird is selected equiprobably at random from all the birds in our world. It turns out to be a black raven. This is strong evidence ... that we are in the second world, wherein not all ravens are black...

So even you did some effort and empirically confirmed a hypothesis per your specific limited observations, you cannot claim such confirmation is strong enough or even relevant at all to inductively infer the intended hypothesis in some cases without knowing all other background assumptions, hypotheses and knowledges which may be never knowable as above example exemplifies...
Answer: Famously, Descartes assumed that a claim was false if it "falls prey to even the slightest doubt". He reasoned that if he did this, than any conclusions that he reaches must be undeniably true. Very few people claim that he was incorrect in this idea. Instead, people who reject his philosophy tend to claim that his notion of 'doubt' was not strict enough or that he made errors in his formal logic.


Breaking 2 blocks with each click?

Question: I break 2 blocks with just one click in creative mode. Why is this happening? I checked my touchpad and my mouse, and I found no problems at all with them.
Comment: Although I can't find an authoritative answer a few suggestions are given in [this form thread](http://www.minecraftforum.net/topic/828917-how-to-fix-double-block-single-click-issue/) that might work for you, including installing optifine and trying modifying the arguments used to launch Minecraft.
Answer: This is because breaking blocks in creative mode is instant, so you have to click VERY lightly or else the game reads the input as a 'hold' and will continue down the line instantly breaking blocks.
Comment: If your laptop is old, it may just not be fast enough to handle Minecraft, hence the game getting confused between 'click' and 'hold'.
Answer: It is a lag, and the game registers the one click as a double click. Therefore, two of the blocks are destroyed. It is the same issue as placing two blocks instead of one.
Answer: I got the same problem some months ago - though i got the problem in both modes.
Destroing 2 Blocks at a time means that your game registers two hits instead of one.
The first possibilty are corrupted mod files (or a wrong configured fast click mod)
-> check your mods
The second and more propable one would be a changed driver behaviour of you mouse - most likely caused by an installation of another game or software.
-> switch the usb port you are using with your mouse and try again
    (i dont think this will be a solution for you, as you got the error on your mouse and touchpad both, but its worth a try)
At last it may be a minecraft caused error.
These occur pretty often if your game crashed anytime before.
It's a little annoying but then you have to delete the folder ".minecraft/versions" in your Appdata folder.
As you wrote a very short question without that much information, i just guess your game is running on a windows machine.
In order to get to your .minecraft folder follow these steps:

press [Windows]+[R] (a small window should appear on your bottom left screen)
enter "%appdata%" (without the " and a folder should open, called appdata/roaming)
scroll this folder until you see another folder called ".minecraft"
open it and find the "versions" folder in it
delete the "versions" folder NOT the .minecraft folder
this does not affect your minecraft maps but your lastlogin file - so just don't mind if you have to enter your password afterwords.
at last just start minecraft and log in - you should be done.

please write a more detailed question next time :)
Comment: The entire "bin" folder thing of your question is horribly outdated. The last version where that was still valid was 1.5 IIRC.
Comment: Im sorry youre absolutely right i forgot this -.-'
I edited this.

Breaking 2 blocks with each click?


Commutator of $X$ and $P$ in quantum mechanics

Question: So, this is my first contact with Quantum Mechanics and I'm having trouble with this exercise. One of the steps involves calculating $[X,P]$, and I stuck there. Can anyone give me some help?
Comment: You need to tell us what assumptions you want to start with. Usually this is a starting assumption, though.
Comment: My answer at https://physics.stackexchange.com/a/261151/4993 might help.  (Though @EmilioPisanty 's answer below is great.)
Answer: "Calculating" $[X,P]$ is a hard thing to ask because the answer depends completely on where you start from.
If this is your first time studying QM, then odds are that you have been given $P=-i\hbar \frac{d}{dx}$ as a definition set in stone. In this case, calculating $[X,P]$ is just a matter of putting that operator in front of a wavefunction and seeing what happens:
$$
[X,P]\psi(x) = x(-i\hbar)\frac{d}{dx}\psi(x)-(-i\hbar)\frac{d}{dx}\left[x\psi(x)\right].
$$
Working through the product rule &c (with the details left to you) it's easy to see that $[X,P]\psi(x)=i\hbar \psi(x)$, so therefore $[X,P]=i\hbar$.
On the other hand, starting with a definition like that can often be pretty jarring to someone that's starting out in QM, and with good reason, and it's not particularly clear what the physical content of this relationship is. This comes down to two essential ingredients:

One is de Broglie's relationship: matter is (associated in some manner with) a wave, and matter of momentum $p$ is associated with a wavelength $\lambda = h/p$. In our wave mechanics, a wave with well-defined wavelength $\lambda$ must have a wavefunction $\psi_\lambda(x)= e^{2\pi i x/\lambda}$, and the definition $P=-i\hbar \frac{d}{dx}$ ensures that
$$P\psi_\lambda(x)=-i\hbar\frac{d}{dx}e^{2\pi i x/\lambda} = \frac{h}{\lambda}\psi_\lambda(x)=p\,\psi_\lambda(x).$$
The second is linearity: the above relationship holds only for wavefunctions with a well-defined wavelength, but we can express any wavefunction (through a Fourier transform) as a linear combination of those. There is only a single linear operator that coincides with $P$ on that basis (i.e. with $P\psi_\lambda(x)=\frac h\lambda \psi_\lambda(x)$ for all $\psi_\lambda(x)$), and it is $P=-i\hbar\frac d{dx}$.

On the other hand, it's important to say that once you go deeper into QM, the assignment $P=-i\hbar \frac{d}{dx}$ loses some of its prominence, giving way to the ('canonical') commutation relation $[X,P]=i\hbar$ as the central object.
This is partly because the two turn out to be just about equivalent, through a result known as the Stone-von Neumann theorem: in the same way that $P=-i\hbar \frac{d}{dx}$ implies that $[X,P]=i\hbar$, as calculated above, you can also do the converse and derive $P=-i\hbar \frac{d}{dx}$ from $[X,P]=i\hbar$. Neither is more fundamental than the other, but in abstract treatments of QM it is most often best to treat the canonical commutation relation $[X,P]=i\hbar$ as the foundational object; it is therefore most often treated as a postulate, and as such it cannot be "proved".
However, even when you make it that far, it is still important to keep an eye on the essential physics that it encodes, which is still just de Broglie's relation between momentum and wavelength.
Comment: @tparker That's a trivial gauge change away, so in the absence of external requirements on the relationship between the canonical and kinematic momentum I stand by that as a general statement (with more mathematical refinement possible if required). In any case, I did my best to get a handle on the OP's starting position, which to be honest I feel your answer just blows straight past.
Comment: I disagree that you can "derive $P = -i\hbar\ d/dx$ from $[X, P] = i \hbar$".  There are infinitely many other representations of the CCR that result in different wavefunctions but equivalent physics, as discussed in Shankar - e.g. $P = f(x) - i\hbar\ d/dx$ for an arbitrary function $f(x)$.
Answer: $[X, P] = i \hbar$ (times the identity operator) is a basic postulate of quantum mechanics called the canonical commutation relation, which cannot be derived.  (Well, whether or not it can be derived depends on what you choose the starting postulates to be.  Some people like to  start from Dirac's quantization rule that classical Poisson brackets are replaced by $1/(i \hbar)$ times quantum commutators.)


What are the core differences between DevOps and Agile ? And Is both two different approach to solve the similar problem?

Question: I read some articles related to DevOps and Agile and found both are two different methodologies for software development.
My questions is, If both methodology is solution for same problem then what is advantages of one over another.
Answer: Agile is a methodology to organize (or group) a set of changes to software components in a give period (= sprint), so think about it as a planning tool or so. Whereas the stake holders are the scrum master, the PO, the actual developers, etc.
DevOps is (mostly) about shipping modified components from one environment (e.g. unit testing) to another one (e.g. acceptance testing), and for which things like CI and CD can be used. Whereas the stake holders are the developers, the testers, operations control people (or SREs if you prefer), etc.
Answer: Agile is really a simple manifesto about how software should be developed by people working collaboratively with customers. It assumes change will happen (rather than trying to lock down requirements early) and uses demonstrable working software to track progress.
The manifesto was a response to heavyweight software delivery models.
Since 2001 (when the manifesto was written), we have learned a great deal using an agile style of software development. Lots of different methods (XP, Scrum, Disciplined Agile Delivery, and so on) were created under the Agile umbrella.
DevOps was originally a very simple idea about getting development teams and operations teams to collaborate. One of the main ideas here was to align their goals to remove an almost universal conflict between Dev and Ops that was caused by asking:

Developers to delivery more stuff, more often
Operations to keep everything stable

Over the past decade, DevOps has grown to include Lean, Agile, and Continuous Delivery (the modern version of XP) - thanks to a great deal of research by the folks at DORA (DevOps Research and Assessment).
If you look at the DevOps model, it includes culture, product development, technical practices, Lean management, and lots of other very specific ways of improving your performance. It doesn't require you to do all of them, it's like a list of ideas that can help solve problems. There's a predictive relationship that links the capabilities together with business outcomes.


How do I debug singletons in Objective-C

Question: My app contains several singletons (following from this tutorial). I've noticed however, when the app crashes because of a singleton, it becomes nearly impossible to figure out where it came from. The app breakpoints at the main function giving an EXEC_BAD_ACCESS even though the problem lies in one of the Singleton objects. Is there a guide to how would I debug my singleton objects if they were problematic?
Comment: Singletons aren't special objects. You should be able to debug them like any other object. Put a breakpoint in the methods you think are suspect, or in the accessor for the shared instance (though you won't be able to get that easily if you followed that page's tutorial).
Comment: (However, I just remembered that you're using those hokey macros.  They make debugging difficult because the lines of code they incorporate can't have breakpoints put in them.  Deep six macros, if nothing else.)
Answer: if you don't want to change your design (as recommended in my other post), then consider the usual debugging facilities: assertions, unit tests, zombie tests, memory tests (GuardMalloc, scribbling), etc. this should identify the vast majority of issues one would encounter.
of course, you will have some restrictions regarding what you can and cannot do - notably regarding what cannot be tested independently using unit tests.
as well, reproducibility may be more difficult in some contexts when/if you are dealing with a complex global state because you have created several enforced singletons. when the global state is quite large and complex - testing these types independently may not be fruitful in all cases since the bug may appear only in a complex global state found in your app (when 4 singletons interact in a specific manner). if you have isolated the issue to interactions of multiple singleton instances (e.g. MONAudioFileCache and MONVideoCache), placing these objects in a container class will allow you to introduce coupling, which will help diagnose this. although increasing coupling is normally considered a bad thing; this does't really increase coupling (it already exists as components of the global state) but simply concentrates existing global state dependencies -- you're really not increasing it as much as you are concentrating it when the state of these singletons affect other components of the mutable global state.
if you still insist on using singletons, these may help:

either make them thread safe or add some assertions to verify mutations happen only on the main thread (for example). too many people assume an object with atomic properties implies the object is thread safe. that is false.
encapsulate your data better, particularly that which mutates. for example: rather than passing out an array your class holds for the client to mutate, have the singleton class add the object to the array it holds. if you truly must expose the array to the client, then return a copy. ths is just basic ood, but many objc devs expose the majority of their ivars disregarding the importance of encapsualtion.
if it's not thread safe and the class is used in a mutithreaded context, make the class (not the client) implement proper thread safety.
design singletons' error checking to be particularly robust. if the programmer passes an invalid argument or misuses the interface - just assert (with a nice message about the problem/resolution).
do write unit tests.
detach state (e.g. if you can remove an ivar easily, do it)
reduce complexity of state.
if something is still impossible to debug after writing/testing with thorough assertions, unit tests, zombie tests, memory tests (GuardMalloc, scribbling), etc,, you are writing programs which are too complex (e.g. divide the complexity among multiple classes), or the requirements do not match the actual usage. if you're at that point, you should definitely refer to my other post. the more complex the global variable state, the more time it will take to debug, and the less you can reuse and test your programs when things do go wrong.

good luck
Answer: I scanned the article, and while it had some good ideas it also had some bad advice, and it should not be taken as gospel.
And, as others have suggested, if you have a lot of singleton objects it may mean that you're simply keeping too much state global/persistent.  Normally only one or two of your own should be needed (in addition to those that other "packages" of one sort or another may implement).
As to debugging singletons, I don't understand why you say it's hard -- no worse than anything else, for the most part.  If you're getting EXEC_BAD_ACCESS it's because you've got some sort of addressing bug, and that's nothing specific to singleton schemes (unless you're using a very bad one).
Macros make debugging difficult because the lines of code they incorporate can't have breakpoints put in them. Deep six macros, if nothing else. In particular, the SYNTHESIZE_SINGLETON_FOR_CLASS macro from the article is interfering with debugging. Replace the call to this macro function with the code it generates for your singleton class.
Comment: Primarily, the advice to essentially never use the app delegate was bad advice.  There's basically nothing you can do with a singleton that you can't do with an app delegate, and, if properly structured, the app delegate provides better clarity.  An app delegate is appropriate for a "portable" facility, but is unnecessary for the "body" of the app.  And the guy spent essentially zero time discussing how to avoid needing globals at all, a topic that merited more discussion.
Comment: For an example for EXEC_BAD_ACCESS: I'm accessing an object that hasn't been initialized. Normally without singletons, the debugger would point exactly where I screwed up in the code. But when I access an uninitialized object in a singleton, Xcode simply points to "main". That's why I'm wondering if there's anyway to figure out where my singleton isn't doing something properly.
Comment: The debugger has no idea that it's a singleton.  Something else is going on.
Comment: @Ninja -- seem my comment above.  Using those hokey macros makes debugging harder because the lines generated by the macros aren't debuggable.
Comment: Would you like to elaborate on what in the article constitutes "bad advice"? It would be helpful to those of us who didn't pick up on it. :)
Comment: Ah, that maybe it. I'll add the singletons manually and see how that works.
Answer: ugh - don't enforce singletons. just create normal classes. if your app needs just one instance, add them to something which is created once, such as your app delegate.
most cocoa singleton implementations i've seen should not have been singletons.
then you will be able to debug, test, create, mutate and destroy these objects as usual.
the good part is course that the majority of your global variable pains will disappear when you implement these classes as normal objects.
Comment: Though I appreciate the viewpoint, this doesn't address the OP's question, and should be a comment instead.
Comment: @quixoto 7 minutes before your comment, i added "then you will be able to debug, test, create, mutate and destroy these objects as usual. the good part is course that the majority of your global variable pains will disappear when you implement these classes as normal objects.". imo, this addresses the problem. I admit, the answer may not necessarily be the shortest possible route but (imo) the preferred long term solution in the majority of cases.
Comment: I've been scolded for doing this before (in a professional work environment). Now I'm being scolded for not doing this. Not sure what to do. Either way, this answer isn't exactly helpful. If there's no way to debug these singletons, please say so.
Comment: @Ninja not trying to 'scold' - just writing what i do to avoid these problems (professionally). it's helpful (imo) because a large mutable global state adds a lot of unnecessary complexities which can become very difficult to debug/reproduce. using a singleton is usually done with the intent to reduce complexity - often, it just moves the complexity. anyways, of course you can debug singletons - see my second answer. good luck.


What happens if my passport expires while I am in a different country?

Question: I'm an American. If I travel to the UK for the first time as a tourist and my passport expires while i am still visiting, what would happen?
Answer: The US State Department and the UK Government say that your passport should be valid for the entire duration of your stay. Before you fly to the UK, your airline will check your travel documents and will see a message saying that "- Passports and other documents accepted for entry must be valid for the period of intended stay."
As such, you might not get to have this problem, because you run a high risk of the airline denying you boarding. If you do make it to the UK border, you run a risk of being refused entry or having your authorized period of stay limited to the validity duration of your passport. These are all good ways to ruin your vacation.
If none of that happens and you do find yourself in the UK while your passport expires, you'd want to contact the US Embassy or Consulate so that they can get you new travel documents; airlines generally won't let you fly home with an expired passport.
If there's any doubt that your passport could expire during your trip, renew it before you leave (this can be done quite quickly if your trip is imminent). Note that many countries require your passport be valid for 3-6 months beyond the period of your intended stay, so there are a lot of places you could be denied entry if your passport expires soon.
Comment: There are standard ways to renew passports abroad for expats, who have long term visa or some such.
Comment: To add to my previous comment, what can be done is an emergency travel document from American Embassy, which will let you get back to the USA. This is not a passport, of course.
Comment: @Willeke I'm an American citizen permanently living in the UK. I renewed my US passport only a couple of month ago at the embassy in London.  While the process was painless, the earliest appointment at the Embassy was about 2 weeks from the date I enquired. I then I had to surrender my old passport - and received a new one after about 3 more weeks. Yes, you could renew by post, but you're still looking at minimum 3 weeks without passport.
Comment: It is a bit unfortunate that the last of the links presents an incorrect "six months after departure" rule for, say, the Schengen countries, where the actual requirement is only _three_ months after the intended departure.
Comment: @HenningMakholm Good point. I threw that in as an afterthought at the end. Replaced with a slightly better link, at least one that takes the time to provide the correct requirement there.


Knapsack problem formulation

Question: I would like to use a knapsack problem formulation based on Lucas paper. Namely, I try to implement the following math formula for Hamiltonian $H =H_A + H_B$, where
$$H_{B} = -B\sum_{i=1}^{n}v_{i}x_{i};
H_{A} = A(1-\sum_{j=0}^{M-1}2^{j}y_{j}+(c+1-2^{M})y_{M}-\sum_{i=1}^{n}w_{i}x_{i})^{2}\,.$$
I implemented it using sympy (imported as sp):

    def knapsack(values, weights, capacity, A, B):

    n = len(values)
    M = math.ceil(math.log2(capacity))

    # Define the variables
    x = [sp.Symbol(f'x{i}') for i in range(n)]
    y = [sp.Symbol(f'y{i}') for i in range(M+1)]

    # Define the objective function
    HB = -B * sum(values[i] * x[i] for i in range(n))
    HA = A * (1 - sum(2**j * y[j] for j in range(M)) + (capacity+1-2**M)*y[M] - sum(weights[i] * x[i] for i in range(n)))**2
    H = HA + HB

    # Expand the objective function
    expanded_H = H.expand()

    # Extract linear, quadratic, and constant terms from the expanded objective function
    linear_terms = {str(symbol): coeff for symbol, coeff in expanded_H.as_coefficients_dict().items() if symbol.is_symbol}

    # Extract quadratic terms
    quadratic_terms = {}
    for term, coeff in expanded_H.as_coefficients_dict().items():
        if isinstance(term, sp.Mul) and len(term.args) == 2:
            v1, v2 = sorted([str(a) for a in term.args])
            if (v1, v2) not in quadratic_terms:
                quadratic_terms[(v1, v2)] = coeff
            else:
                quadratic_terms[(v1, v2)] += coeff

    constant = expanded_H.as_coefficients_dict().get(1, 0)

    # Create a QuadraticProgram
    qp = QuadraticProgram()

    # Add binary variables to the QuadraticProgram
    for var in x + y:
        qp.binary_var(name=str(var))

    # Set the objective in QuadraticProgram
    qp.minimize(linear=linear_terms, quadratic=quadratic_terms, constant=constant)

    return qp

Next, I convert it to the Ising model to get an operator to pass to VQE. Next, I set up VQE to compute the minimum eigenvalue. My question is if the above formulation of the knapsack is correct. When running VQE (on statevector_simulator), I get solutions that are more or less random, sometimes suboptimal, sometimes incorrect (breaking capacity constraint). I suppose I missed something in the formulation of the problem.
Answer: It seems I mixed 2 formulations. It solves the problem with algorithm. Regarding randomness it is connected to backend set up on IBM Q.

Knapsack problem formulation


How can I install a grounding rod with bedrock four feet down?

Question: I have an 8 foot ground that hits solid rock at 4 feet. How can I meet the safety requirements for the 8 foot into the ground rule? Can it be cut in half and have two 4 foot rods driven into the ground?
Comment: Talk to your local authority.  8' is a national rule, local jurisdictions are meant to tune it for local conditions, they've seen the problem before and will have an answer.
Comment: Have you considered another type of electrode?
Answer: You can drive at an angle. If I remember correctly, you can dig a trench and lay the 8 foot rod(s) flat in the bottom of it (Personally, I'd never go with one rod anyway.) If you wanted a really good ground, you simply excavate your foundation to bedrock and use an UFER ground in the foundation concrete (it's a concrete encased ground electrode formed by electrically connecting the reinforcing steel in your concrete foundation - or a section of copper cable, but the steel is there and serves multiple purposes.) 20 foot minimum, but common sense is to tie all the steel together for the best possible result.
Note on re-reading - A CCE/Ufer ground does not require excavating to bedrock, but if bedrock is 4 feet down, you might was well put your foundation on the bedrock...
Responding to erroneous comment below:

Exception 1 to 250.68 indicates that buried electrode connections and
  concrete-encased connections to electrodes shall not be required to
  be accessible. Exception 2 indicates that exothermic welded
  connections and irreversible connections to grounding electrodes that
  are encapsulated in fireproofing material are not required to be
  accessible. The exception applies not only to the connection but also
  the mechanical fastening means, such as a nut or bolt, that
  establishes the connection to the metal framing member.

From EC Mag article. But you can also look it up in the code, that was just faster to find.
Comment: FYI - The first 2 feet of a ground rod are considered to be ineffective due to the variation of moisture in topsoil. That's why the code requires a minimum of a 6' rod. The deeper the rod the better the ground. Also the code requires all mechanical connections to the grounding electrode to be accessible for maintenance. Also in this state if a ground rod is used as the only means of grounding in a dwelling unit. It requires a least two be used, driven a minimum of 6' apart.
Answer: I'm having the same problem. My plan is to rent a roto-hammer (big one) with a grounded rod driver attachment, apparently this is a common problem. If what I've seen on Youtube is real, this tool will pound it through anything with ease. Alternatively, you get a well driller to sink you two 10-12 foot holes, and then grout your rods in. I'd leave the laying them horizontal as the last resort, some AHJ's might ask "So what's the phone # of the guy you asked to drill this for you".
Comment: Drilling a rod into bedrock may not get you the results you want, even with two widely spaced rods.  I'd be much more hip to a concrete-encased electrode, myself.
Answer: Try calling your local electrical supply and see if they have advanced driven rods.  These are grounding rods with carbide tips to be driven in with a hammer drill, just like drilling for oil☺.  Or you could use grounding plates that are buried 2x2 plates of copper. Oh and personally I have  a ground rod at each corner of the house all tied into the electrical supply.
Answer: I know this post is old, but for future reference, in the state of TN, a ground rod can be in ground horizontal, but has to be 30" or deeper. Or at an angle as well. Not sure on about other states, so I would check your local or state code guidelines.


How does one lift a heavy box up from the ground?

Question: Here are some pictures I found on how to lift a heavy box.
Is this correct technique? Mainly I am trying not to hurt my lower back.
Comment: The key is to hinge at the hip and not round your back
Comment: @DaveLiepmann True; in the case of atlas stones for example, you have to curve your back around them to get a good hold, but you don't straighten your back to pick it up; you still use the hips to provide force, and then straighten the back once the stone is sitting on your thighs.
Comment: "The back should be straight troughout the lift." -- disagree. There are plenty of things that must be lifted that cannot be lifted with a straight back. Do I prefer a straight back? Sure, it's safer and less tiring. Can I always achieve it while carrying a couch down 6 flights of stairs, or a mattress up those stairs, or lifting a baby's car seat out of the back? LOL
Answer: This idea that the "correct" way to lift involve getting your hips as low to the ground as possible is something that has historically been taught, but has no evidence behind it. It's more of a dogma than a correct technique.
Martimo, K.-P., Verbeek, J., Karppinen, J., Furlan, A. D., Takala, E.-P., Kuijer, P. P. F. M., Jauhiainen, M., & Viikari-Juntura, E. (2008). Effect of training and lifting equipment for preventing back pain in lifting and handling: systematic review. BMJ, 336(7641), 429–431. https://doi.org/10.1136/bmj.39463.418380.be
"There is no evidence to support use of advice or training in working techniques with or without lifting equipment for preventing back pain or consequent disability. The findings challenge current widespread practice of advising workers on correct lifting technique."
Regarding the deadlift addition that was added in a later edit, the statement "[arms perpendicular to the back] means that all the weight of the package is converted to dangerous shear forces on the back" is not true. There's nothing special about a situation in which the arms are parallel to the back, and shear forces are present in almost all loadings of the back and are not inherently harmful.
Comment: Your equation is wrong because it assumes that the arms hang from the shoulders in pure tension, and that the only force they impart on the torso is a downward tensile one. This is incorrect, as in a deadlift the lats are used to apply torque through the shoulders, meaning the arms do not hang vertically. The paper you cite describes models used for setting limits for manual handling activities in an industrial setting and isn't at all relevant to strength training. There is no indication that the forces on the spine in any part of a deadlift are inherently harmful and need to be avoided.
Comment: From mechanics we know that shear equals the normal component, Fn, of the force, F, applied to the spine trough the arms. Fn = F * sin(a), where a is the angle between the back and the arms. Fn is clearly maximized when a = 90 degrees. It is generally considered that the spine can tolerate more than 3 x more compression than shear: https://www.researchgate.net/publication/273068040_Revised_NIOSH_Lifting_Equation_May_generate_spine_loads_exceeding_recommended_limits
Comment: It could be that the ones who did not receive training experienced lower back pain from accumulative injuries months or years after the studies finished.
It could also be that most people intuitively lift correctly. I think there may be many confounding variables here.
Comment: Yes you were correct :-); there's nothing special about a situation in which the arms are parallel to the back. What matters is to minimize the horizontal distance from the hips to the center of mass of the object being lifted.
Comment: "It could be that the ones who did not receive training experienced lower back pain from accumulative injuries months or years after the studies finished." This is just speculation though, and the available evidence does not support it. The longest RCT in that systematic review (Daltroy et al, 1997) was 5.5 years, and in that time observed 360 back injuries among 4000 workers, finding no correlation between lifting technique education and injury risk. I really doubt the 2000 workers that didn't receive lifting technique education all then injured themselves right after the 5.5 year study ended
Answer: "The neutral back lifting posture has been found to be better overall than a rounded (opposite of arched) back in minimizing L5/s1
compressive forces and ligament strain.
Therefore, a normal lordotic lumbar spine position is superior to a rounded back for avoiding injury to vertebra, disks, facet joints, ligaments, and muscles of the back.
In addition, the low back muscles are capable of exerting considerably higher forces when the back arched rather than rounded." (1)
Further:
"It has been observed that 85% to 90% of all intervertebral disk herniations occur at the disk between the lowest two lumbar vertebrae (L4 and L5) or between
the lowest lumbar and the top sacral vertebra (L5 and S1)." (1)
From this we can conclude that we should lift with a "straight" back if possible.
And in order to keep a straight back we must hinge at the hips.
But why do the herniations occur at the bottom of the back and not further up the spine?
Let us model the spine as a rod flexing from the force from the weight transmitted trough our arms and shoulder.
This is similar to the cantilever beam problem in static analysis:

In our case the sacrum is the fixed end and our shoulders are the free end where the force is applied.
From the figure it can be seen that the bending moment at a position x where x=0 is fixed end and x=L is free end is:
M=(L - x)W
This moment is clearly largest near the fixed end.
Likewise the bending moment from lifting a weight is largest in the lower vertebraes (L4 and L5).
This bending moment is opposed by the erector spinae muscles. However:
"The back muscles operate at an extremely low mechanical advantage because the perpendicular distance from the line of action of the spinal erector muscles to the intervertebral disc are much shorter (about 5 cm) than the horizontal distance from
weights to the disks. As a result, the muscles must excert forces that frequently exceeed 10 times the weight lifted". (1)
This is illustrated here (from Physics in Biology and Medicine, Paul Davidovits):

In order to save our backs we should therefore outside the gym seek to minimize the torque from the lifted weight at the sacrum in case our erector spinae should not be strong enough. Inside the controlled environment of the gym we should strengthen our erector spinae by stressing it (deadlifts).
In another question I have found that we should try to lift as upright as possible and with shoulders as far as possible in front of weight.
However it seems these criteria oppose each others. The first leads to a squat and the second to a deadlift.
How do we do this in practice?
We use a lift somewhere between a squat and a (sumo) deadlift.
A sumo stance causes a more upright back position. And we try to get our hips as horizontally close to the center of mass of the box as possible.
It is important to notice that the height of the hips does not matter (2):

Regarding the first person in the original question:
the feet must be firmly planted in the ground in order to be stable. He is clearly limited by his ankle mobility and need to take a wider stance and turn his feet more out.
The second person has a good lift.
(1) Essentials of Strength Training and Conditioning, Biomechanics chapter, NSCA
(2) Towards Real-time Ergonomics Feedback and Educational Content with the use of Co-Robots


"Chance/Reason" to complain

Question: Do these sentences sound natural and likely:

I'll never give you a chance to complain.
I'll never give you a reason to complain.

Do these sound fine?
Comment: They both sound fine but mean very different things. If your question is only about grammar checking and not about anything else there's a good chance this will get closed - you could have researched this yourself.
Comment: This question is easily found online but I think you are really asking about the "I'll" so why not edit your question. [We say: X sounds fine. We don't usually say: Does x sound fine?]
Answer: Both sound correct, but they both mean different things. There may be more natural ways of saying them, but you haven't provided any context.

I'll never give you a chance to complain.

This means that you won't allow someone the opportunity to make a complaint, so they may have cause for complaint, but you won't allow it to be heard.

I'll never give you a reason to complain.

This means that you won't give someone any cause for complaint. In other words, you are promising to behave in such a way that they won't need to complain.
Answer: If someone has a chance [to do X], the strong implication is that they want to do X (so if it's possible, they probably will at least try to do it). That's to say, doing X is desirable (in some contexts, desirable from the speaker's perspective, but not necessarily from the subject's).
Having a reason to do something is often quite neutral as regards the desirability of that course of action - it's usually about necessity / compulsion.
In certain specific contexts (such as OP's cited example), having a reason to do it may carry the sense of justification (where the subject wants to do it, but cannot proceed unless and until certain preconditions are met, or certain arguments are presented). But this sense doesn't always apply, and won't normally be intended or understood unless there are other contextual factors supporting it.

Simply put, I'll never give you a chance to complain ALWAYS strongly implies that the speaker believes the other person would like to find fault with his performance - so it's effectively a "hostile / defiant" form, which you should probably avoid when talking to a "suspicious, pessimistic" new employer.
It's important to note that the speaker's "defiance / determination" in the chance version is effectively focused on thwarting the other person's implied desire to find fault. On the other hand, in I'll never give you a reason to complain, the speaker's defiance is implicitly focused on doing nothing that the other person disapproves of - which would normally be the desired implication.

DEFAULT INTERPRETATIONS:

I never had a chance to vote
   - I wanted to vote, but was unable to do so
I never had a reason to vote
   - I didn't care about voting anyway, regardless of whether I could (or even did) vote
Answer: A reason is a motivation to do something.
A chance is an opportunity to do something that you already have a reason for doing (we are assuming that you don't do things for no reason!)
Thus, these are not interchangeable words.  Your first sentence, using "chance", actually sounds rude (or unintentionally funny, as it's so unlikely to ever be said), while your second ("reason") is commonly used.
"No chance to complain" = you will be unsatisfied and you will be ignored
If you say "I will give you no chance to complain", you are saying that you are not going to give any opportunity for the other person to make their complaint to you.
You don't care if someone is unhappy with you, because you will simply ignore them.
"No reason to complain" = you will be satisfied
Here, you're saying something completely different.  You are promising that your behaviour or the quality of the work you are about to do will leave the other person so satisfied that they will have no motivation to make a complaint.

"Chance/Reason" to complain


What good are all the golden swords looted from zombie pigmen?

Question: I have a bunch of golden swords from the pigmen. What good are they? Can I change them into gold bars or nuggets or something else useful?
Answer: You can:

Enchant them with lvl-30 enchants and use them against the zombie pigmen!
Drop them all one at a time into a pit of lava!
Put them in a chest!
Combine them all together into one uber-sword!
Throw them at zombies!
Make a giant wall of item frames of golden swords, and rotate them to make a maze!
Use hoppers, dispensers and item lifters to make a continuous golden sword waterfall!
Make a gold sword sorting system and try to collect one of every enchantment!
Mine diamonds with them!
Throw them at endermen!

The sky is the limit really, just up to your imagination and creativity.  After all, isn't that what MineCraft is all about? :)
Comment: I disagree
Comment: I might make the waterfall. That sounds neat and useful.
Answer: No, the swords that Pigmen drop are useless, unless you want some things to enchant lvl 1 when so you can change the enchantments in the enchantment table. If you are playing modded you may be able to turn the swords into ingots but if you are playing vanilla the first option is the only option I am aware of.
Comment: Am I mistaken in believing that golden swords are easier to enchant? And by "easier" I mean have a higher chance of getting higher level enchants like "looting" or "fire aspect"?
Comment: @Ben That's right but it's still useless because of very short lifetime of golden tools (33 uses)
Comment: Just rack up the Unbreaking haha
Comment: Using them as enchantment sinks is a great idea. That gives a use to the piles of bows that our skeleton grinder produces, too.
Answer: They provide a good source of, well, golden swords.
You can craft 2 partially broken golden swords together to get a repaired one.
Other then that, as Dark Afterburn said, there's no use of golden swords in unmodded Minecraft.
Answer: If you're doing a pigmen farm (to gather XP and some other of their drops), you can use these to kill them without damaging your personal sword. But they don't have a better use.
Answer: As of Minecraft 1.15.2, you can use the dropped gold swords to get additional gold ingots. Here is how:

Collect the gold swords
      a. If they have enchantments on them, put them into a grindstone to salvage XP from them.
Put the sword(s) into a furnace, and smelt them. It is preferred that you use an automated smelting system, as loading each sword into the furnace may be rather tedious.
Each sword smelted will output 1 gold nugget.

I hope this helps.
Answer: I would use them at the Enchantment Table to reset the enchantment list, to get your desired enchant. (For this purpose, use the lowest level enchantments) If you still haven't got what you desired, you can combine them at a Crafting Table to lose the enchantments put on them and then give it another shot. Repeat this until done. (Note that sometimes it may still not work)
Otherwise, I haven't found any other good use for them. You can't make gold out of them, and they are poor at slashing(attacking) and have a horrible durability.
Comment: Sorry that this answer is a bit similar to Dark Afterburn's one.
Comment: Note that this answer is for Vanilla Minecraft.
Answer: I'm building a huge afk gold farm on the roof of the nether and collecting the gold in hoppers that put all the items through a filter. Gold nuggets go in one chest, rotten flesh in another, and gold ingots in the last one. The gold swords just go on through, and a dropper shoots them down to the bedrock to despawn cause I don't think there's any use in building some huge storage area for them at the farm. It's not worth it. They're practically worthless when I have a diamond sword with max enchants, and plenty of options to get Xp to repair it with. So if you ask me, don't even bother trying to get all of them, just trash them.
Answer: I find that random golden swords are useful for resetting enchantment table enchantments by getting the cheapest one and letting them refresh. You can use them as non-stackable items in an item sorter, but that is pretty pointless. Best thing in my opinion is just smelt them in an auto smelter as part of an afk farm.
Answer: You can use Gold Swords to quickly cut down cobwebs found in underground mineshafts.
Comment: Very doubtful advice. Considering that you can only cut 17 cobwebs with a fully-repaired Gold Sword, you will need to carry your whole inventory of them into the mine. But, at least, they will make something happen.


How to make alkaline iodide azide

Question: I'm an IB Chemistry student and I'm doing the Winkler's titration for my Internally Assesed Investigation. However, my school doesn't have alkaline iodide azide, so I need to make that myself first. How do you do that?
Comment: See: "A Laboratory Manual for Environmental Chemistry" and" Introduction to Environmental Sciences"

They are both in google books. As well as their procedure.
Make sure that you are doing this under supervision. A quick look to the MSDS of sodium azide shows that it can explode.
Comment: You might need a blast shield to do this. It's not recommended at the IB level...
Answer: I'm quite sure you meant alkaline iodide sodium azide solution. The preaparation of this reagent is given here:

To prepare this reagent, take 700 g of potassium hydroxide/500 g of
  sodium hydroxide and add 150 g of potassium iodide/ 135 g of sodium
  iodide and dissolve in freshly boiled and cooled water and make up tp
  1000 ml.
Dissolve 10 g of sodium azide in 40 ml distilled water and add this
  solution with continuous stirring to the cool alkaline iodide prepared
  previously.
Comment: The link you sent in your answer sometimes uses alkaline iodide azide and sometimes alkaline iodide sodium azide. I can't tell if they're using them interchangeably or if they are referring to two different things.
Comment: @ILoveJesus There is nothing called alkaline iodide azide. It is  alkaline iodide sodium azide.
Comment: the cool alkaline(NaOH/KOH) iodide(NaI/KI) solution they are referring is the 1 litre solution prepared previously.
Comment: @NilayGosh  I calculated that the molar ratio between the Iodide and the Hydroxide is 1:1. And then I calculated that the ratio of the masses between NaI and NaOH should be 3.75:1. However, in the thing you sent me and in other labs, they always take more NaOH than NaI, and it's actually with the same ratio, just inverted. Could you explain this to me please?

How to make alkaline iodide azide


Terracotta Disabling L2 cache and object serialization

Question: I'm quite new to Terracotta and I've installed and made it work properly with EHcache for distribute caching, but what I'm getting now is not what I really want.
In my application I would like to have several client caches (L1) with ehcache, and "propagate" the invalidation of a removed key from a client to all the other clients. I don't want that my cache will reside also on the terracotta server, so I'd like to simply disable L2 caching, so that my objects don't need to be serializable (the only actions done on cache are PUT and REMOVE).
I know this could be done using simply ehcache, but i have no multicasting support in my environment (Amazon EC2) and my clients will be automatically created with autoscaling features, so I cannot know their IPs.
So basically, I need a Terracotta Server only to propagate the invalidation request to all the clients. Is there any way to accomplish this?
Thanks a lot!
Answer: When you use EhCache backed by Terracotta and in your cache configuration you specify to use terracotta, e.g.:
<cache name="com.xyz.MyPOJO"
  <terracotta/>
</cache>

then your class must be serializable (since Terracotta will attempt to store it on the cache server instance.
However, in your configuration you can specify not to use Terracotta for some caches, e.g.
<cache name="com.xyz.MyPOJO"
  <terracotta/>
</cache>

<cache name="com.xyz.NotServerStoredPOJO"
</cache>

Then your "NotServerStoredPOJO" from the example above will not be stored on the terracotta cache server...instead it will live only in your local EhCache... but by doing that you will not be able to propagate it to other instances if your EhCache in diff JVMs.
So, perhaps you will need to keep something on the terracotta server (some sort of flags/ids) that will indicate what to invalidate. Then in your application code have a common class/functionality that will check that flag before getting value from the local EhCache...if it finds flag/id to be deleted, then it will delete it from local cache and will not return back anything to the requester.
On on the other hand, your use case kind of defeats the purpose of having central cache server. If you want to coordinate multiple cache instances without central location, you can use JGroups http://www.jgroups.org (instead of Terracotta)...its free of commercial license also. But then you'll need to implement your own mechanism over JGroups of how to invalidate certain entries in your local EhCache instances...


what is the difference between systemd's service and service and daemon and systemd files and systemd unit files?

Question: I am new to systemd fundamentals. I read sth about systemd units and unit files and services. Would someone please define these three terms for me clearly ? I'm mixed up .Also what is a daemon ? is daemon a service or unit or is it sth else? Does units are objects or handles to manage services by systemd or units are equivalent to services? Also for example when you type the command "systemctl list-units " or "systemctl list-units-files" ,do these commands print units and unit files or services? Thank you in advance.
Comment: Have you read `man systemd.service` and `man systemd.unit`? Or any other related documentation?
Comment: Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.
Answer: man systemd.unit, man systemd, and man systemd.service should answer most of your questions.

I read sth about systemd units and unit files and services. Would someone please define these three terms for me clearly ?

systemd units:

systemd provides a dependency system between various entities called "units" of 11 different types. Units encapsulate various objects that are relevant for system boot-up and maintenance.

systemd unit files:

A unit file is a plain text ini-style file that encodes information about a service, a socket, a device, a mount point, an automount point, a swap file or partition, a start-up target, a watched file system path, a timer controlled and supervised by systemd(1), a resource management slice or a group of externally created processes.

systemd services

A unit configuration file whose name ends in ".service" encodes information about a process controlled and supervised by systemd.

So in short,  a systemd service is one of several types of systemd units.  Specifically, it usually runs a process.  A service configuration file contains rules on how to run/restart/exit that process in the [Service] section of the file.  Service-specific options are detailed in man systemd.service, man systemd.exec and man systemd.kill.
Other types of units are things like mount points, sockets, or paths which have their own types of configurations.
But all units have a common set of behaviours, including relationships between them and how they are triggered.  You can see what options are available in their [Unit] or [Install] sections.

Also what is a daemon ?

Just think of a daemon as a background process.  It's what is managed by a systemd service.  There's probably a better definition, but it's not quite as relevent in systemd.

do these commands print units and unit files or services?

When you type systemctl list-units, units are listed (including services, but not only services).  You can see things like *.device, .mount in addition to the .service items listed.
Comment: Wikipedia has a nice [section regarding the "daemon" terminology.](https://en.wikipedia.org/wiki/Daemon_(computing)#Terminology) It originates from "Maxwells Demon", a physics thought experiment.


How to encrypt Google Drive on local machine

Question: I'm a Google Apps customer and one of the things I'm using is the Google drive service to sync my files from my work PC to my home. This works fantastic but I have a concern about theft of the machine locally.
Google likes to pride themselves with how secure there cloud based services are using multiple arrays, multiple locations and data encryption. However it's my understanding that all files are stored locally and are not encrypted which to me means that your data can be stolen, read, copied and modified.
I have tried using EFS on the Google drive on my desktop but Windows 7 reports an error. I've looked through all settings of Google drive and can't find an option! this seems a major flaw... unless I'm missing something.
Question
How can I encrypt the files locally when using Google Drive?
Answer: Trust nobody looks like boxcrypter is your best bet .. https://www.google.com/search?q=Google+Drive+encrypted+drive
you can do it cheaper with something like Amazon clouddrive  etc


Why is a UDP port scan more complex than TCP port scan?

Question: When I scour SO, I saw that it's a bit complex to port scan a UDP port than a TCP port, why?
Answer: Actually, you cannot really do a UDP port scan. While an open TCP port generally replies to a simple SYN probe, UDP has no concept for a socket connection. Simply put, there's no single probe message to see if a UDP port is listening.
Accordingly, you might not get any reply from an open UDP port unless you guess the right application protocol behind it and it chooses to reply (a DNS server replies to a DNS request, an SNTP server to an SNTP request, etc). Without a reply, you won't know whether a certain port is closed, whether the firewall has filtered the packet, or whether the application just chose to ignore your request.
Basically, you can only probe UDP ports that you know or guess the application-layer protocol of, and you can talk it into replying. That is a lot more complicated than sending a generic TCP SYN.
Of course, you could try to simply check for ICMP destination port unreachable messages for closed ports, but these are usually filtered (or not sent at all) on the open Internet and in many other scenarios.
Comment: Well, a DNS server will only reply to a valid DNS request, for instance.
Comment: sorry, what does "hit the right application protocol behind it and it chooses to reply" mean?
Comment: Thank you! I know it's an off topic, can you give me a sample DNS request?
Comment: Just run a lookup (`nslookup` or `dig`) and capture the packet. Or check out [RFC 1034](https://tools.ietf.org/html/rfc1034) for the header format.
Answer: With TCP there is a standardized connection setup process that is implemented by the operating system and applies regardless of what application protocol is being used. So you can send a "syn" packet as a probe and based on the response you can determine if the port is "open" (the server proceeds with the next step in the connection setup process, sending the "syn-ack"), "closed" (the connection is rejected with an ICMP error) or "filtered" (there is no response at all, which likely indicates the traffic is blocked by a firewall).
With UDP on the other hand "closed" ports will trigger a response from the operating system, but for open ports the operating system will simply pass the packet to the server application without generating any response of it's own. UDP server applications will normally not send a response to packets they do not understand.
So when you send a UDP probe packet and get no response you have no way of knowing whether your packet was filtered by a firewall or whether it was delivered successfully to an application that did not respond (either because it could not interpret the packet or because of it's own internal policies).
Answer: To further illustrate the challenge of scanning for UDP here are some details about how the functionality is implemented in nmap which is still probably the most popular port scanner nowadays:

UDP scan works by sending a UDP packet to every targeted port. For
some common ports such as 53 and 161, a protocol-specific payload is
sent to increase response rate, but for most ports the packet is empty
unless the --data, --data-string, or --data-length options are
specified. If an ICMP port unreachable error (type 3, code 3) is
returned, the port is closed. Other ICMP unreachable errors (type 3,
codes 0, 1, 2, 9, 10, or 13) mark the port as filtered. Occasionally,
a service will respond with a UDP packet, proving that it is open. If
no response is received after retransmissions, the port is classified
as open|filtered. This means that the port could be open, or perhaps
packet filters are blocking the communication. Version detection (-sV)
can be used to help differentiate the truly open ports from the
filtered ones.

And:

A big challenge with UDP scanning is doing it quickly. Open and
filtered ports rarely send any response, leaving Nmap to time out and
then conduct retransmissions just in case the probe or response were
lost. Closed ports are often an even bigger problem. They usually send
back an ICMP port unreachable error. But unlike the RST packets sent
by closed TCP ports in response to a SYN or connect scan, many hosts
rate limit ICMP port unreachable messages by default. Linux and
Solaris are particularly strict about this. For example, the Linux
2.4.20 kernel limits destination unreachable messages to one per second (in net/ipv4/icmp.c).

The last paragraph must be outdated, not sure about current implementations.

Nmap detects rate limiting and slows down accordingly to avoid
flooding the network with useless packets that the target machine will
drop. Unfortunately, a Linux-style limit of one packet per second
makes a 65,536-port scan take more than 18 hours. Ideas for speeding
your UDP scans up include scanning more hosts in parallel, doing a
quick scan of just the popular ports first, scanning from behind the
firewall, and using --host-timeout to skip slow hosts.

Source: nmap - Port Scanning Techniques
I seem to remember from a long time ago that the Unicorn scanner has its own way of scanning UDP but can't find the details right now. Since each port scanner has its own way of telling an open port from a closed port it can guess wrong, and results may vary. The best way would be to use a tool like Scapy to craft your own packets and interprets the responses for yourself.


Non-existent zip code but still get shipping methods

Question: Can someone explain to me why for a non-existent zip I still get shipping methods. Let's say I choose US, Florida and 32005. Using a service I get that zip code is not found but in Magento I can get an estimation shipping cost. Is it wrong to just tell that zip is wrong or should I leave it like it is now?
Comment: This highly depends on the shipping method. Many shipping methods doesn't check the ZIP and only calculate the costs depending on the state. What shipping method do you use?
Comment: There is no check. If you want a check you need a intelligent and learning implementation, like asking the API of dhl, ups, TNT etc. every time
Comment: @Fabian - Table rates
Comment: @FabianBlechschmidt - I am not sure I understand. What can DHL tell me about a zip (like in my example) which doesn't exist in US?
Comment: DHL has a WebAPI you can request shipping costs from and I'm sure (but don't know) they check the address before calculating the costs
Answer: Not all shipping methods validate the address when fetching rate quotes.  For example, FedEx has an Address Validation Service (AVS) which is separate from the Rate Service.  AVS catches the invalid addresses, but the Rate Service does not.
If you want to ensure the address and ZIP code are valid, you can run the address through AVS first.


Unknown USB Device (Device Descriptor Request Failed)

Question: I'm on Windows 8.1 Pro and my SD card slot on my Toshiba Satellite (L505D-S5965) doesn't work anymore. It suddenly stopped the day before yesterday and I know it's not internal damage because when I did a system restore it worked for about 3-5 Minutes before not working again. Is it a registery problem or is it something else?
Comment: Try to boot a live cd (e.g. ubuntu) and see if you can access it there. This would help rule out a software issue (registry or otherwise)
Comment: Have you tried with more than one card?
Comment: @harrymc Yes. I tried 2 microSD cards and 1 regular sized.
Comment: For an intermittent problem, have you considered a possible hardware failure? The suggestion of trying a live linux cd is a possible test.
Comment: This is a driver problem. I faced the same problem when connected my Lumia to my PC with USB. It always says USB device not recognised. I simply restarted both my PC and phone and tried connecting five times. Finally, installing device appeared and now it's working fine.
Answer: It could be a problem with the driver. You should go to Device Manager under Control Panel and uninstall the driver, then download the driver from the Toshiba website and reinstall again.
Comment: I tried this with a x64 driver, but It's telling me that this driver isn't. I right clicked the info and it said it successfully installed but it didn't show up and it still didn't work.
Comment: You should download the driver from the Toshiba website for your specific model and OS and install that using the installer, or if that doesn't work then manually. You may have to remove the existing driver first from inside device manager. So first, find your device in device manager, uninstall the driver and then try to install the one from the Toshiba website.
Answer: For an intermittent problem, have you considered a possible hardware failure?
A good test is to boot a live Linux CD to see if the problem still happens.
This can show whether the problem is hardware or software/driver
(although why would the driver fail so suddenly?).


How can I find my phone without an app

Question: I just lost my phone today and I dont have any Find Me app but I am logged in with all of my information. Like my email, facebook, and such things. How can I possibly find it?? I also know that my GPS is set on On.
Answer: You could log into to your Google account and check your location history...assuming you've turned on Latitude:  https://latitude.google.com/latitude/b/0/

How can I find my phone without an app


How can I get everything to use the same load balancer on DigitalOcean?

Question: I have a LoadBalancer service, and an Ingress that routes to various ClusterIP services. I've given both of them the following annotation:
annotations:
  kubernetes.digitalocean.com/load-balancer-id: 'myproject-dev-lb'

A new load balancer was created, although I see no reference to myproject-dev-lb on it. The LoadBalancer service (a Pulsar server) works fine, but my ingresses have stopped working. When I kubectl get my ingress, I get what looks like a previous IP address (might just be similar). When I describe it, it says it's not found. If I delete it and recreate it, it gets the same IP address. The address is pingable, but not listening on port 80. The created load balancer only has a rule for port 6650 (Pulsar).
I'm not really familiar with the relationship between Ingress, load balancers and services.
Answer: A service is a way to route traffic to an internal IP. By internal I mean inside Kubernetes. I mean you don't really point it to an IP, you point it to a deployment or w/e and Kubernetes takes care of the IP and routing traffic for you to the pods that make up that deployment.
Now not all services work the same. ClusterIP will create an internal hostname and then route traffic to the Pods's IP. This make the service only reachable from other pods inside the cluster.
Then you have NodePort, which opens a port on all worker nodes and routes the traffic to the deployment/pods or w/e. This exposes the service externally. So now it's reachable by a worker nodes IP and whatever port was selected by the service. You can also hard code a port but I wouldn't recommend it.
But who wants to deal with IP's and port numbers? Thats lame. We want hostnames. you know like myapp.dev.coolcompany.com or w/e.
That is where a Loadbalancer comes in. If you have a cluster running on a cloud provider then your cluster is likely already setup to use a LoadBalancer service. This service does two things. First it creates a nodePort service and then it configured a load balancer on your cloud provider to point traffic to all worker nodes and the NodePort for your service.
When your LoadBalncer is created it likely came with a public DNS name to reach it by. Now you can just create a DNS record to point from myapp.dev.coolcompany.com -> my.lb.dns.cloudprovider.com. Now your app is reachable externally and without knowing about IP's and ports.
Everything I just explained is explained even better and more accurately by the Kubernetes Service documentation. You should probably give it a read.
So what's an Ingress? Well an Ingress is like creating a "LoadBalancer" but inside the cluster. We call this the Ingress Controler and there are a ton of options like Nginx, Apache and Traeffik to name a few. This likely does not come included by default on your cluster. You will need to create and configure an ingress controller before you can use the "ingress" API object.
An ingress controller works like any other deployment running on your cluster. You will need to expose this application externally. Most often using a "LoadBalancer" Service. Confused yet? It will look like this: ExternalLB --> IngressLBService(NodePort) --> IngressController
Once your Ingress Controller is configured you can then expose your deployments externally without using a "LoadBalancer" service. You can instead use a "ClusterIP" service + an "ingresss" object configured to point at the service. It will look like this: ExternalLB --> IngressLBService(NodePort) --> IngressController --> DeploymentService(ClusterIP) --> DeploymentPods
As you can see the "LoadBalancer" service and IngressController work very similarly. So why do you need an IngressController?
Well if your application stack is simple then you probably don't. Some of the cloud providers "LoadBalancers" are pretty feature rich. Like on AWS. But some of these Ingress Controllers offer some pretty nice features. Like path bases routing, integrating with Authentication providers, Automatic TLS certificate provisioning and tracing+montioring etc. Basically, if you need these features and your cloud provider's Loadbalancer doesn't have these things then an Ingress Controller is the best way to get them.
Another tiny advantage is that an Ingress can help abstract away the cloud provider. Meaning less vendor lockin. If I have an application that is exposed externally via an Ingress controller then I can re-deploy that application on any cluster on any cloud provider as long as that cluster has an ingress controller.
If I'm depending on a "LoadBalancer" service then its likely that service is configured with a bunch of Annotations and that is often not compatible with other clouds. Meaning I cant just redeploy that application to another cloud provider. This use case isn't very important to many people and it wouldn't be a big deal to fix a service to use a different cloud LB but it is something to consider.
You can find a lot more in the Kubernetes Ingress documentation.


Recording all broker transactions in ActiveMQ

Question: I would like to record all transactions that happen in ActiveMQ. When someone writes to a queue or reads from it, I would like to log that. Is there a way to turn on this kind of logging, or is there a data store somewhere which I can parse and read?
Answer: You need to enable DEBUG level logging in the .properties file for log4j.  You can find more details about how to change it here:
http://activemq.apache.org/how-do-i-change-the-logging.html


How to help seedlings recover from tip burn

Question: I germinated some seeds and I had the seedlings under a two new 40w LED grow light for a few weeks. I'm used to keeping florescent lights very close to the plants, but apparently this LED light is more powerful. The tips of the leaves got yellow and crispy I turned off one of the lights and raised it up to 8+ inches above the leaves. It seems like it may be too late for some of my unfortunate toasted plants, but is there anything else I can do to help the others recover? I'm watering weekly with a mild organic kelp fertilizer.
Answer: Back off the fertilizer. Adding a fertilizer to plant that is not in a strong growth state will also cause leaf burn. Reduce the amount of water. If the plants not growing, the water just stays in the pot and the rots will rot. Secondly, it seems like the plants are indoors? Definitely place it in a location with a little more circulation. Or place it near a window where it gets filtered sunlight.


Can Ghosts Interact With Each Other?

Question: Can the ghosts in Harry Potter interact with each other?  I think I remember some games they played that indicated they were able to have physical contact.  Is that right?  Can they interact with each other on a physical level?  Or would they just pass through each other?
Answer: http://harrypotter.wikia.com/wiki/Category:Headless_Hunt_games lists 4 games from the Headless Hunt in CoS:
<code>Head Hockey
Head Polo
Horseback Head-Juggling
Headless Bowling
</code>
While the first 3 have no details of them, sounds like to make the game work you HAVE to have inter-ghost contacts. As for Bowling, even mortals can play, presumably (it's 100% true in a computer game, but can only be inferred from a book):

Sir Patrick: "So, Harry me lad, care for a little headless bowling?"
Harry: "I'm not sure. What is it?"
Sir Patrick: "Just take your head off... not yours, we'll find one for you to borrow... roll it down the alley, and knock over the pins."
Comment: I'm writing this from the present, where we all acknowledge the worthlessness of the Harry Potter wiki. Any chance you could quote from more trustworthy sources?
Comment: I'm writing this from the future, where the Harry Potter wiki is no longer accessible.  Any chance you could include a little more detail so we know what you're referring to?
Comment: @ibid - what, and lose my hypocrisy points? :)
Comment: @Tango - what's this, hassle DVK mid-writing-answer day today? This is the THIRD time people criticize my answer before reading the finalized version!
Comment: Only the third time?  We really were hoping to do more than that - but now that you're on to us, there's no point to it!
Comment: @TangoOversway - Conspiratio Obliviato!
Comment: Are these from the video games or something?
Answer: Ghosts likely are able to physically interact.
Ghosts likely can physically interact with each other, since they waltz at Nearly Headless Nick's
Deathday party.

"It was an incredible sight. The dungeon was full of hundreds of pearly-white, translucent people, mostly drifting around a crowded dance floor, waltzing to the dreadful, quavering sound of thirty musical saws, played by an orchestra on a black-draped platform." - Harry Potter and the Chamber of Secrets, Chapter 8 (The Deathday Party)

Waltzing typically requires a certain amount of physical contact, so presumably ghosts can indeed physically interact with each other.
Comment: I don't know why I'm only seeing this answer now. Speaking as a well experienced ballroom dancer, yes, waltzing does typically require physical contact, but it's not hard to find ways to waltz without contact. I have used no-contact ballroom dances in showcase routines I have done myself.

Can Ghosts Interact With Each Other?