Why can All Might still do his buff form?

Question: All Might real form is very skinny and he was able to do his buff form because of One for All, supposedly. But now he no longer has One for All and he still can do his buff form. Is he supposed to still have some tiny remain of One for All , is his buff form made for comedy purposes or what?
Comment: I like the fan theory that his buff form was his quirk. He had to flex to do it and it was so tiring his quirk was useless. He wasn't really quirkless but he still empathized with Deku as he might as well be.  While alot of things support this theory, All Might's direct statements contradict this so it is non-canon drivel.  This is a comment as the answer is a non-canon fan theory.
Answer: Yes, it's mostly for comedic purposes. Some can argue that he still has a tiny bit of power but he used all of One for All. It's clearly stated in All Might vs All for One fight.
Answer: All Might's buff form has nothing to do with One for All. He mentions at the very start of the series that it's a conscious effort similar to flexing. Just because All Might lost One for All doesn't mean he also lost the ability to flex. He just can't keep it up for a long time on his base power.
Answer: If you are asking about latest episode then it's taking place before the events of 3rd season.
Answer: All wrong.
All might in his past was always a big buff guy thanks to his training. He never had a "skinny form" his muscle form is how he used to look always before AFO injured him. As all might said to deku, he wasted away from his surgeries and complications. When he uses his quirk his body transforms to its former prime to handle the power. As for why he can still do that form for brief moments may be for comedy purposes or maybe the quirk doesn't fully leave the host after passing it on. If so, hopefully all might will be able to utilize this in a way who knows.
Comment: Please include relevant sources/references.
Answer: I AGREE
ALL mights superior strength does not come from his quirk,it comes from his killer workought.This was shown when he fought wolfram.He has his quirk but in a drained form .He has it but he cant unleash it.


When freezing prepared meats, is it better to freeze the meat separate from the sauce/gravy?

Question: I am making a corned beef with a glaze to be eaten next week. Is it better for me to freeze the meat + gravy together, or to freeze the meat in one container and the gravy in another?
Answer: I use two containers when possible. The meat and the sauce usually thaw at different rates, so you end up w chunks of frozen meat embedded in thawed sauce. This can be messy to work with.
Once frozen, it's OK to combine meat and sauce in a single container. Just separate when thawing.
Comment: Separate containers also preserve the "option" to use the meat without the sauce/gravy/glaze for an alternate dish.
Answer: I find that when cooked meat is frozen separately it dries out quite a lot; it will still be moist after defrosting if it's submerged in its gravy as you freeze it.


Should 2FA be enabled on service accounts?

Question: See the title. I'm involved in a security audit right now, and am wondering whether 2FA should be enabled on not just human login accounts but also on service accounts (non-human accounts)? If so, how is this normally managed? Someone must still be at the other end to confirm the 2FA right? And would this be mainly a one time thing at setup or would they need to reconfirm the 2FA request periodically?
Comment: Assume for the moment the service you're authenticating against is 3rd party.  That means you'll have to automate 2FA for a service intended for a human, but now needs to be automated.  That sounds like something just waiting to break if the 3rd party changes the way the 2FA works where I human wouldn't care, but automation might rely on the old structure.
Comment: In some environments it's possible to set up service accounts where either interactive login is impossible, or the login can only be done by key credentials of some sort.
Answer: The trouble with requiring MFA on service accounts, is that it would have to be fully automated.  For instance, a time based OTP.
But as this OTP is based on a secret seed, it is effectively just another password stored in a config available to the service account.  And it therefore gives no real additional security above that of just a single factor such as a password.
Comment: Agree! A 2FA token is just another password. Make the service password a random, large password, and you are done. 2FA will not bring much security, and will be a moving part waiting to break.
Comment: The significant difference between a password and a TOTP token is that the OTP seed is never transmitted. So if there is a risk of interception and replay, an automated OTP would act as a kind of nonce, rendering intercepted traffic much less useful to an attacker. However, this would only be required if the system you're connecting doesn't implement a stronger authentication system anyway.
Comment: Definitely, if you have a choice of authentication mechanism don't go for password. The most practical choice would be to use some form of public key crypto.
Comment: There are of course password-based authentication systems that do not transmit the password itself, eg zero-knowledge proofs.
Answer: Multi-factor authentication is certainly possible without human intervention.
However, it requires a frame challenge.
When dealing with humans, the three typical factors for authentication are something you know (password), something you have (TOTP device/program, phone with SMS, access to an email account, etc.), and something you are (biometrics).  You can not combine different things from the same factor and call it multifactor authentication. I.e., a fingerprint and a retina scan is not 2FA, but a fingerprint and a password is 2FA.
Biometrics doesn't work over a network, whether you're scanning a human's fingerprints or you're "fingerprinting" a computer, since you can't verify that the client isn't lying unless you have a trusted agent standing by. "The client is in the hands of the enemy." -- Raph Koster (Game designer, not security expert, but the advice is well applied.)  Without that trusted agent, biometrics are only useful for identification, not for authentication(*).
The next authentication factor, something you have, is usually indistinguishable from something you know when you're a computer.  TOTP seeds, passwords, session tokens, RSA private keys, and so on are just bytes to a computer, and at some point will reside in RAM. Humans can get away with having TOTP seeds, session tokens, cryptographic keys, and the like be second factors, because humans are very unlikely to be able to memorize these, so they need access to separate hardware (or at least something written down).
However, there are things that a computer can't "know" ahead of time.  If you have a hardware device that performs cryptographic operations and stores the private key inside in a way that can't be copied (without obvious evidence of tampering), such as a U2F dongle, then this qualifies as something the computer has but doesn't know.  Similarly, information sent out-of-band can also be considered something the computer has, rather than something it knows.  For instance, a token can be emailed, FTPd, or sent through SMS.  Depending on your threat model, simply opening a connection on a different port may be good enough to fool automated surveillance tools, though I wouldn't trust it against an active eavesdropper.
Speaking of threat models, the current threat models against users using passwords isn't the fact that it's just one factor. The threat model is that most users reuse passwords, have low entropy passwords, and that nearly every human's data has been included in multiple data breaches, including many data breaches that have never been detected or reported.  Since computers don't have any problem memorizing very long and truly random passwords, and can memorize every password that's given to them, it is trivial to set up a unique, high entropy password for every service account.
Footnotes:
(*) Identification is different from authentication in that, I can identify myself as the queen of Mars, but I can't be authenticated as the queen of Mars.  A username is identification, but a username and password is authentication. A fingerprint is identification, but a fingerprint taken with a trusted agent overseeing the process is authentication.
Comment: @Jammin4CO, if that connection was completely unrelated to the connection that you're trying to authenticate through, was originated from the authentication server, and set up in order to send an out-of-band one-time-use token, then yes...  It's not _just_ a new connection, but the fact that it's out of band and out of control of the client that makes it a separate factor from just something you know.
Comment: Actually there are a number of schemes to use Biometrics for authentication over networks. Though, I think its really that the biometrics are used on device only and under the hood everything is really PKI. https://fidoalliance.org/how-fido-works/
Comment: There could probably be ways to create a non-reusable retina-scan with a single service. You could record a video of the retina and send it to the server for authentication and the server could use some (currently probably not available) hashing technique to check if the same video was reused or is an original new recording (the technique to verify this would need to be able to differentiate a true new recording from an old recording with some photo shopped changes)
Comment: So if I understand you correctly, allowing a connection from only a specific IP or computer name and using a service account/PW would be considered MFA?
Comment: @Falco How do you do a retina scan without a human being involved? If a human has to be involved, it's not automated, and therefore is not a [software] service account. (It's just a regular, human account, where a software service happens to provide the password (one of the factors).)
Answer: Network location as "something you are"
One way to improve the security of services that need automated connection to specific accounts is to augment secure authentication (e.g. a tls/ssh client certificate) with strict networking limits - if an automated service needs to connect twice a day from system A to system B, then system B should not only authenticate the request, but refuse any connections for that service/port/account that aren't coming from the IP address of system A.
Uncopyable credentials
Another way to approach the secrets of automated services is to have them be uncopyable, i.e. that the software running the business logic doesn't have full access to these credentials, but only a link to a 'signing system' on a HSM or "software-HSM", which generally don't allow extracting the secrets but only their usage in a restricted way. In that case if the main system is compromised, it still can't copy the secrets to be used at will later, they can only access them real-time without being able to circumvent logging, rate-limits, and other restrictions.
Comment: I was going to answer myself. You did it! Uncopyable credentials (i.e. certificates, TPM, hardware attestation) are the way. And I am actively working on that
Answer: 2FA for service accounts is not needed and it would be a pain if you would actually set it up.
Imagine you would potentially have like 100 service accounts, every time your system would shut down and you would have to re-authenticate, you would have to confirm the 2FA every time by yourself, if you wouldn't do this, the 2FA would be pointless.
Ways to secure a service account:

Rotate passwords frequently (there is no human that needs to remember the passwords, you could potentially rotate them every week)
Make password complexity high (you can potentially use like 24+ characters)
If it's a Windows environment use Windows service accounts, this option should provide you with enough security.
https://docs.microsoft.com/en-us/windows/security/identity-protection/access-control/service-accounts

I am really unsure what the auditors are after with requesting this, but if you provide them with enough proof that your service accounts are secured, you should be fine.
Answer: So the crux, certainly in the context of the question, is what level of protection is needed for such service accounts ? What are the risks ? And how can you mitigate these ? And, given the audit angle, can you show how you made that tradeoff ? And are you tracking any residual risks ?
I usually make a simple actor & threath model - paying specific attention to non-functional requirements such as uptime, access in exceptional cases, robustness, governance and organisational fluidity.
In general I find that service accounts then fall into three blocks 1) those which are widely used in the organisation and whose 'power' you can minimise to an extent where the risks of 2FA or other complexity start to outweight the risks of a `shared secret'. 2) Those who are routinely quite powerful as they are what service maintenance, upgrades and what not revolves around and 3) those who are really your ultimate/last resort exceptions - and, while rarely used, where you want to prevent inadvert loss - even when things are dire.
The first class is often shared secrets with good monitoring, governance and what not as mitigators. Or leads you to build a well secured bastion/webinterface on something with solid security - that only allows a few very specific routine operation to be triggered.
For the third class - analysis often finds the introduction of 2FA or similar very undesirable - as they need to work in extreme situations where fragility is an issue.  So one often resorts to offline passwords in sealed envelops in safes - to minimie disclosure & theft risk. And get robustness (and salted/hashes on the validation/server end) in return. You then pair this with your physical gouvernance and audit process.
But it is that middle class that is always the issue - very powerful, often used. And sometimes by multiple people. But you really do not want impostors or loss of that level  access. Even, or especially, when you are changing staff, learn of a security breach, and so on.
So here the tradeoff is between the `pain' of 2FA versus usability.
In my experience you often find that some sort of 2FA mitigation helps in your overall risk assessment - as it can bring non-clone-ability to the picture while removing the need to cycle things like passwords or the risk of disseminating acces too widely.
Common solutions are sets of x509 or SSH keys on USB tokens or chipcards (sometimes even without a PIN). As these anchor the authentication to a point in time and space.
Answer: No to 2FA, yes to Client Certificates
As per Geir Emblemsvag answer, 2FA is only another password. It's somewhat workaround for meat bags humans and their low entropy passwords.
But machines are fast, and could (or better, should) work with very high entropy in every access. No data should ever pass in plain text.
Client Certificate validation on server/service it's a way to guarantee that. It's ensure that data is always encrypted, and you get a service auth and identify for free.


What is the difference between concepts of Maya in Hinduism and Buddhism?

Question: How is the illusion in Buddhism and Hinduism different?An author writes <<The concepts of maya, avidya, vyayaharika-satya and paramarthika-satya, advaya, prajna, the unreality of the universe and time and the attributeless Brahman are all Buddhist contributions, without which there would be no Advaita philosophy>>Source : https://gosai.com/writings/mayavada-and-buddhism-are-they-one-and-the-same
Comment: As far as I know. Buddhism does not believe this world is fake. They think this is real. So, no Maya concept in Buddhism. Buddhism never talks about Maya too.
Comment: There's no 'illusion' in Buddhism ...
Answer: There are different schools and sub-schools within Hinduism and also different schools and sub-schools within Buddhism. So, for this answer, I will limit the scope. I choose to limit it to Advaita Vedanta in Hinduism as taught by Adi Shankaracharya in his own writings, and teachings from the Early Buddhist Texts (EBTs) in Buddhism, especially the Pali Canon.
Advaita Vedanta
From Adi Shankaracharya's Vivekachudamani:

This Atman is a self-cognised entity because It is cognised by Itself. Hence the individual soul is itself and directly the Supreme
Brahman, and nothing else.

That which clearly manifests Itself in the states of wakefulness, dream and profound sleep; which is inwardly perceived in the mind in
various forms as an unbroken series of egoistic impressions; which
witnesses the egoism, the Buddhi, etc., which are of diverse forms and
modifications; and which makes Itself felt as the
Existence-Knowledge-Bliss Absolute; know thou this Atman, thy own
Self, within thy heart.

Seeing the reflection of the sun mirrored in the water of a jar, the fool thinks it is the sun itself. Similarly the stupid man,
through delusion, identifies himself with the reflection of the Chit
caught in the Buddhi, which is Its superimposition.

Just as the wise man leaves aside the jar, the water and the reflection of the sun in it, and sees the self-luminous sun which
illumines these three and is independent of them;

All this universe which through ignorance appears as of diverse forms, is nothing else but Brahman which is absolutely free from all
the limitations of human thought.

If the universe be true, let it then be perceived in the state of deep sleep also. As it is not at all perceived, it must be unreal and
false, like dreams.

All modifications of clay, such as the jar, which are always accepted by the mind as real, are (in reality) nothing but clay.
Similarly, this entire universe which is produced from the real
Brahman, is Brahman Itself and nothing but That. Because there is
nothing else whatever but Brahman, and That is the only self-existent
Reality, our very Self, therefore art thou that serene, pure, Supreme
Brahman, the One without a second.

As the place, time, objects, knower, etc., called up in dream are all unreal, so is also the world experienced here in the waking state,
for it is all an effect of one's own ignorance. Because this body, the
organs, the Pranas, egoism, etc., are also thus unreal, therefore art
thou that serene, pure, supreme Brahman, the One without a second.

From Adi Shankaracharya's Aparokshanubhuti:

This world, though an object of our daily experience and serving all practical purposes, is, like the dream world, of the nature of
non-existence, inasmuch as it is contradicted the next moment.

The dream (experience) is unreal in waking, whereas the waking (experience) is absent in dream. Both, however, are non-existent in
deep sleep which, again, is not experienced in either.

Thus all the three states are unreal inasmuch as they are the creation of the three Gunas; but their witness (the reality behind
them) is, beyond all Gunas, eternal, one, and is Consciousness itself.

Just as (after the illusion has gone) one is no more deluded to see a jar in earth or silver in the nacre, so does one no more see
Jiva in Brahman when the latter is realized (as one's own self).

Just as earth is described as a jar, gold as an ear-ring, and a nacre as silver, so is Brahman described as Jiva.

Just as blueness in the sky, water in the mirage, and a human figure in a post (are but illusory), so is the universe in Atman.

Just as the appearance of a ghost in an empty place, of a castle in the air, and of a second moon in the sky (is illusory), so is the
appearance of the universe in Brahman.

So, according to the quoted verses, we see that the world that is perceived in a dream is unreal, after waking up. Similarly the world that you observe when you're awake does not exist in the dream or in deep sleep (turiya).
However, what is common in all three states, is Consciousness, the silent observer. And this Consciousness is Atman (the Self), which is the same as Brahman (the Ultimate Reality). This is a gist of Advaita to my understanding.
So, Advaita is very centered on Consciousness, the silent observer.
Although there are many living beings, there's only one Consciousness = Atman = Brahman. The perceived diversity of living beings and inanimate objects is a mirage or a dream or an illusion when Consciousness looks through the lens of maya, similar to living beings and inanimate objects perceived in a dream.
So, it is very clear that the universe is unreal and is an illusion in Advaita. The awake, dream and deep sleep states are all unreal (see Aparokshanubhuti 58). The only thing real, eternal and permanent is Consciousness = Atman = Brahman.
The enlightened person sees only Brahman, while the unenlightened person suffers because of the illusion of separation from Brahman and of diversity in forms.
Please see this excellent answer by Keshav Srinivasan for more details.
Buddhism
The Buddha's teachings from the Pali Canon is quite different. It does not use the word "maya" but it does have the concept of illusion or mirage.
By convention, a sentient being in Buddhism is one where the five aggregates of form, feeling, perception, consciousness and mental formations come together, just as when different parts of a chariot come together, you call it a chariot (SN 5.10).
Through dependent origination (pratityasamutpada), the mental idea of the self (atman) arises. Just as how different parts of a lute (vina) interact to create music, the five aggregates work together according to dependent origination to create the mental idea of the self. If you break down the five aggregates into their constituent parts, you will not be able to find the self anywhere, just as when you break the lute down, you cannot find music anywhere (SN 35.205).
Consciousness in Buddhism is not independent. It is dependent on the six sense media of eyes, ears, nose, tongue, body and mind or intellect (for thoughts). So, dependent on this, there is eye-consciousness, ear-consciousness, mind-consciousness etc. (MN 38)
The mind not just objectifies the mental idea of the self, but it also objectifies and classifies all that is perceived into non-self objects, relative to the mental idea of the self or based on its relationship to the mental idea of the self. This is also called reification or concept proliferation (papañca in Pali or prapañca in Sanskrit) (MN 18).
For e.g. a cooked meat dish is perceived by a meat lover as delicious food, by the vegan as something repulsive, and by the honey bee as dirt (because it is not its food). In this sense, the "delicious food" or "repulsive thing" doesn't exist, except as objectified and classified by the mind.
Another example is the sea. A fisherman looks at the sea as a source of fortune (like how a miner looks at a gold mine). A sailor looks at the sea as a place of adventure. A person who doesn't know how to swim and rarely spends time near large bodies of water looks at the sea as a dangerous place. Meanwhile, a fish may not perceive the sea as a body of liquid at all, since it is all around it. In this sense, the sea as a "source of fortune" or "source of adventure" or even "body of liquid" doesn't exist, except as objectified and classified by the mind.
So, in Buddhism, the universe itself is not a dream or a mirage or an illusion. But rather, how the mind objectifies and classifies what it perceives is what is unreal. Also, dreams are just thoughts in the mind based on what has been perceived before, observed by mind-consciousness.
An enlightened person will see things exactly as they are (MN 1). Meanwhile, reification (papañca) is a source of suffering for the unenlightened person, because craving is a habit of reification (MN 1, Snp 4.14), and craving (taṇhā or tṛ́ṣṇā) is the cause of suffering (dukkha) in Buddhism i.e. the second noble truth.
Through enlightenment, ignorance is uprooted, eliminating self-view and reification. This in turn will eliminate craving, which eliminates suffering.
Summary
In Advaita, according to Adi Shankaracharya, the universe is unreal and an illusion. Only Atman = Brahman is real. The illusion appears so when Consciousness looks through the lens of maya. Also see this answer.
Meanwhile in Buddhism according to the Pali Canon, which is an Early Buddhist Text (EBT), the universe itself is not explicitly considered unreal or an illusion. Rather, that which is reified in the mind is what is unreal and an illusion, and a cause of suffering.
Comment: Beautiful answer sir. Thanks a lot for answering my request. But I would request you to please read this article : https://gosai.com/writings/mayavada-and-buddhism-are-they-one-and-the-same
There is a Claim that Mahayana School inspired Shankaracharya or Vice Versa about concept of Maya and there's also lot of speculation that Upanishads are Buddhist Inspired. Your views please
Comment: @SethuSrivatsaKoduru  If you look at wikipedia's scholarly dates, the earliest Upanishads (Brhadaranyaka, Chandogya) came before the Buddha. A few other Upanishads (Taittiriya, Aitareya, and Kausitaki) developed around the same time as the Buddha. All Vedanta schools, Samkhya, Yogasutras of Patanjali, Purva Mimamsa school, the rest of the Upanishads (Kena, Katha, Isa, Svetasvatara, Mundaka, Prasna, Mandukya), Brahmasutras and Bhagavad Gita all came after the Buddha's time.
Comment: Sir do you think Vedanta borrows ideas from Madhyamika Buddhism as above article of Gosai claims??
Comment: @SethuSrivatsaKoduru The closest Buddhist school to Advaita appears to be [Yogācāra](https://plato.stanford.edu/entries/twotruths-india/#Yog), which according to [this wikipedia page](https://en.wikipedia.org/wiki/Yogachara), was founded by Asanga and Vasubandhu, who lived in the 4th to 5th century CE.  Meanwhile, Advaita founders Gaudapada and Adi Shankara lived in the 6th to 7th century CE and 8th century CE respectively.  Madhyamika founder Nagarjuna lived even one or two centuries before Asanga and Vasubandhu. So, it is likely that Advaita Vedanta was influenced by Mahayana schools.
Comment: Sir is Madhamika Buddhism authentic teachings of Buddha?Because you said earliest Buddhist teachings dont have anything to do with Illusion
Comment: @SethuSrivatsaKoduru Even Madhyamika school doesn't really say the universe is an illusion. Only the Yogacara school seems to say that the universe is an illusion and there is no real universe outside the mind. If you read [this page](https://plato.stanford.edu/entries/twotruths-india/), a lot of later Madhyamika philosophers like Candrakirti and Santideva criticized Yogacara for holding this view. That's why I have the personal opinion that Advaita Vedanta is similar to, and may have been influenced by Yogacara. The earliest teachings of the Buddha do not say the universe is an illusion.
Comment: @SethuSrivatsaKoduru I'm not sure whether Yogacara was influenced by Upanishads, but in Yogacara, there's no Atman or Brahman. It's all about mind and it's all in the mind like The Matrix.
Comment: @SethuSrivatsaKoduru I think this statement from [SN 7.9](https://suttacentral.net/sn7.9/en/sujato) should be clear enough: <>
Comment: Thanks a lot sir!
Comment: Sir can we say Yogacara school was influenced by Vedanta because few Upanishads were composed before Buddha??
Comment: Sir thanks a lot. Lastly does this Sutra mean Buddha rejected Caste System : https://suttacentral.net/mn98/en/sujato ??
Answer: There should be deeper study to understand the real usage of "Maya" in Vedanta.
Maya is used as a Upaya to turn the sadhaka inwards.
Please check this wonderful answer.
IshAvAsyaM idaM sarvaM - Isha Upanishad-1.
All this is enveloped by the Supreme Being.
Brahman is "satyam  jnanam  anantam  brahma" - Taittiriya  Upanishad 2.1.1.
Satyam is something whose existence cannot be negated.
From the above we can see what Upanishads are trying to Convey. Everything is Brahman and Brahman is real. Isn't world part of Everything ?
To understand the intricacies of Vedanta one should undertake at least some level of serious study of Upanishads with basic knowledge in Sanskrit under the guidance of a good Teacher.
Without this effort and relying on few texts and their translations doesn't help us much in grasping the true meaning of Vedanta.
Coming to the History of Vedanta, from discussion in comments i see a theme that Upanishads thought is mostly post Buddha period.I feel such a conclusion is harsh and there are disputes among scholars related to the dating of Upanishads.
Consider the example of Taittirīya Upanishad.Taittirīya Upanishad has come from Taittiriya Shakha (Sanskrit, loosely meaning 'Branch or School of the sage Tittiri'). Taittiriya Shakha  consists of the Taittiriya Samhita ('TS'), Taittiriya Brahmana ('TB'), Taittiriya Aranyaka ('TA'), and Taittiriya Pratisakhya ('TP').
Taittirīya Upanishad is part of Taittiriya Aranyaka.
Now check the Tevijja Sutta from Buddhist Palin Canon which clearly mentions about people who are already following the path of sage Tittiri.

"About the variety of paths, Master Gotama. Even though brahmins
describe different paths—the Addhariya brahmins, the Tittiriya
brahmins, the Chandoka brahmins, and the Bavhadija brahmins—all of
them lead someone who practices them to the company of Brahmā.
It's like a village or town that has many different roads nearby, yet
all of them meet at that village. In the same way, even though
brahmins describe different paths—the Addhariya brahmins, the
Tittiriya brahmins, the Chandoka brahmins, and the Bavhadija
brahmins—all of them lead someone who practices them to the company of
Brahmā."

Now can we say Taittiriya  Upanishad was Developed before Buddha ?
Placing Majority of Vedtantic development in post Buddha period is doing gross injustice to the history of Vedanta.

The history of the composition of the Upanishads is exactly the same
as the history of Vedanta School - Hajime Nakamura

If anyone wants to really understand how Buddhism & Vedanta influenced each other one should be well versed in Pali & Sanskrit as these are the languages used to convey their philosophical ideas. One should also consider the thinking process and social circumstances of people among which these ideas are developed.Last but not least one shouldn't be biased towards the school of her/his liking while undertaking this study.Otherwise any other study is incomplete and only confirms one's preconceived ideas.
I come across only one such Genuine scholar Hajime Nakamura.
I can't recommend enough His works on Buddhism & Vedanta especially this and this, one related to the life of Buddha and the other related to History of Vedanta.


Could Apple (OS X) wallpaper be licensed for commercial use?

Question: Does anyone know who owns the Zebra Wallpaper that comes with MBP Retina Display (and Mountain Lion)? Although this is my specific task (to hunt down who owns one specific likely copyrighted image), it would be nice to know if there is a way to read the image's metadata or otherwise track in general who owns what image that ships as part of Apple's OS.
Comment: @Thecafremo They are distinct questions.  Here, the OP may not *have* a license for his stated purpose (and likely recognizes that by asking this question) and so wishes to understand who owns the image, presumably to then seek a special license to use it.  The other question asks about what existing license is already in place.
Comment: @Thecafremo You are totally right. I intended to change it and explore the other side of the issue here. If the OP objects, we can regroup. Chris's answer is awesome. We already have a version of "where do I find the license?" - together they work very well to cover any conceivable need to learn about licensing Apple's content. One is "what can I do with the assets" - the other is "how can I seek added scope to use the image". I don't want to close this as too localized, since there is good knowledge being shared, so the question needed to either be closed or change…  I chose to change it.
Comment: possible duplicate of [What is the license on mac wallpapers?](http://apple.stackexchange.com/questions/61410/what-is-the-license-on-mac-wallpapers)
Comment: @ChrisW.Rea For the way the title is written, I wouldn't say the OP is trying to reach the actual owner of the image and ask for a license rather that just knowing if he could use that image for commercial purposes. If were like you say, it would make quite a difference, and, indeed, the question won't be a duplicate.
Comment: @bmike I think you've completely changed the question with your edit. I feel, too, that the OPs intention isn't clear enough for it.
Comment: @bmike Apparently I'm not having one of my best days here. You're completely right, as usual.
Comment: @Thecafremo I wish I were by the sea in Spain and we could sit and have a coffee (or stronger) and make your day better.
Comment: @Thecafremo Yes, the question title implied another possible interpretation of the question.  Absent the body, I'd tend to agree. Considering this is a legal question, I turned on my pedantic bit. :)
Answer: Apple and/or Apple's licensors own the images, as stated under Apple's Software License Agreement for Mountain Lion:

The Apple software (including Boot ROM code), any third party software, documentation, interfaces, content, fonts and any data accompanying this License whether preinstalled on Apple-branded hardware, on disk, in read only memory, on any other media or in any other form (collectively the "Apple Software") are licensed, not sold, to you by Apple Inc. ("Apple") for use only under the terms of this License. Apple and/or Apple's licensors retain ownership of the Apple Software itself and reserve all rights not expressly granted to you.
Comment: This answer would be much better on another question (or asked as a clarifying comment to the main post): http://apple.stackexchange.com/questions/61410/what-is-the-license-on-mac-wallpapers
Comment: Actually, your *"Apple owns the images"* inference is incorrect.  We don't know for certain from the above that Apple **owns** the image.  Apple may have licensed it (whether on a non-exclusive or exclusive basis) from someone else, much in the same way the OP is seeking to do.  Notice *"Apple's licensors"* in your quote above.  Those would be people that granted Apple a license for something Apple didn't itself own.  Apple likely knows who they are, if Apple doesn't own the image itself.
Comment: @ChrisW.Rea You are completely right. My answer was more focused on answering the commercial usage of the wallpapers, than the actual *Who owns them*. I'll update it to clarify my statement.
Comment: After your correction, I'm awarding +1.  This answer does highlight one important legal piece: **"[Apple etc.] reserve all rights not expressly granted to you."**  i.e. meaning if one wants the right to use the image in another context, one must expressly seek permission, and receive it ... hence, Apple Legal.
Answer: Yes.  Apple ought to know who owns the rights to that image.
To dereference your question one level further, I suggest the right people to ask or request permission from are Apple Legal.  You can contact Apple Legal through the Apple Legal Contact page.
Under "I have a question about", select "Copyright Information".  Then fill in the form.
Comment: This is great - Apple surely knows who owns each image they shipped, but they might not have their employees forward that information to anyone who comes along and asks for a referral to find a photographer or a single image. In fact, the contract between Apple and the photographer might be exclusive and have a clause whereby Apple or the Photographer is bound to not be identified or identifiable.
Comment: One will only know by asking.  You might be right, but that's conjecture.
Answer: I tried three methods of finding where to find this image.
The first is a useful site called TinEye.com. It allows you to upload an image and search the web for it. For the zebra image, I didn't find anything.
The second is to open the image in Preview and check the inspector to see if there are any useful info in there.  I didn't find any.
After that, you're stuck looking through stock image sites. I did find what appears to be the original on Fotolia, and Fotolia will allow you to license it for commercial use.
I noticed that there's a second, larger zebra in the backdrops.  TinEye was much, much more useful here.  The larger zebra seems to be from Steve Bloom and he's got a form on the site to enquire about a license.


As a bar owner, how can I block guest from using specific programs, like Spotify, over my free wifi?

Question: When guests log in to their Spotify account over the wifi, the bar gets thrown out. I would like to have in place a setup where I could still use Spotify, but have it blocked for our guests.
We use a standard wireless router from our telephone provider (Telefonica), the brand is "Comtrend" (Unfortunately I'm pretty blank when it comes to access hardware and such).
Suggestions?
Comment: All of this can be done yes but we'd need to know what existing router-type equipment you already have first.
Comment: @Hurragutt Whereabouts in Spain are you? I only ask, as I'm visiting Barcelona this week :)
Comment: Down south in Cadiz, but Barcelona rocks too!
Answer: To solve this problem as a bar owner:
Hire an IT professional
To solve this problem as an IT professional:
Set up your edge device to block traffic to certain domains and IP addresses.
Comment: +1 An answer befitting an of-topic question. @Hurragutt, last time I checked bar owners didn't fit the profile of an IT professional. Please read the FAQ.
Comment: I suspect it would have got a less favourable answer on SU.
Comment: Thanks WesleyDavid, that was really helpful. More quality answers like that and Joel Spolsky should have nothing to worry about.
Answer: How much control do you have over your WiFi / LAN settings?  Is it a combined WiFi router, or is it just an access point?
Some WiFi routers have built-in firewalling.  If you can block the great unwashed from accessing 18.104.22.168/22 then you'll block off Spotify's IP range.  You can exempt yourself from the block by giving your computers static IPs that aren't blocked by this rule.
Comment: @KJ-SRS: The vast majority of those random PCs are going to use the DNS servers they get from DHCP, so he/she does have control over those DNS settings.
Comment: Using OpenDNS will only work for PCs that are using OpenDNS for their DNS servers. Since you are dealing with random PCs connecting to your network and have no control of their DNS settings, OpenDNS will not help.
Comment: It's a simple Comtrends router, provided by Telefonica (I'm in Spain), but I should be able to block the range you mention. Thanks! Do you think OpenDNS.org could do the trick as well?
Comment: I have no experience with OpenDNS, but if they allow you to block lookups for Spotify, then that could work.
Answer: The cheapo comtrends that telefonica most probably supplies to its customers cannot do what you want.
If you are serious then pop down to your local tech store or browse amazon and get a new device. Most of the ones you have to buy have what you need which is basically filter the incoming and outgoing traffic.
Comment: I agree with this run Pfsense
Comment: I second pfSense.
Answer: I'm not too familiar with spotify but I'd venture to guess that it uses standard web-browsing ports to tunnel traffic. Unless you want to invest in a next-generation firewall that is application aware like a Palo Alto Networks or even the latest Sonicwall, there is usually a way around.
You could try other methods, blocking by DNS entry...
What kind of firewall is in place today?


How to extract views integration setting from the command line?

Question: Is there a way to output from the command line the views integration settings as listed in Administer > System Settings > CMS Database Integration? I need this as part of our upgrade script to automatically update settings.php (rewriting a php include file) every time a system upgrade is released.
Answer: It is possible, you can code it (and because you are a scripter I suppose you are a coder). In CiviCRM, the views settings are generated in the with file https://github.com/civicrm/civicrm-core/blob/master/CRM/Admin/Form/Setting/UF.php
I used this as inspiration to create the following script
<?php
$config = CRM_Core_Config::singleton();
$dsnArray = DB::parseDSN($config->dsn);
$tableNames = CRM_Core_DAO::getTableNames();
$tablePrefixes = '$databases[\'default\'][\'default\'][\'prefix\']= array(';
$tablePrefixes .= "\n  'default' => '$drupal_prefix',"; // add default prefix: the drupal database prefix
$prefix = "";
if ($config->dsn != $config->userFrameworkDSN) {
  $prefix = "`{$dsnArray['database']}`.";
}
foreach ($tableNames as $tableName) {
  $tablePrefixes .= "\n  '" . str_pad($tableName . "'", 41) . " => '{$prefix}',";
}
$tablePrefixes .= "\n);";

echo $tablePrefixes;

Run this script with the CiviCRM cv utility (see https://github.com/civicrm/cv) as follows.
cv scr


Development of the Idea of the Determinant

Question: While I basically understand what a determinant is, I wonder how this idea was developed?  What was the principal idea behind its origination?  I would like to know this so that I can have a better conceptualization of the determinant.
Comment: +1 good question. You're in for a wilder ride than you probably thought. Determinants were arguably the first linear algebra concept to be invented -- before abstract vector spaces, before even matrices. There were just these strange expressions that kept popping up when quite different problems were solved the hard way. Sometime along the way someone noticed that they were all structured similarly and gave them a name. I hope you get some good historical references in answers.
Comment: Non-duplicate: [where did determinant come from?](http://math.stackexchange.com/questions/62732/) which was closed as a duplicate of a _non-historical_ intuition-of-determinants question. One of the answers before it was closed links to an interesting historical wall-of-text, though.
Comment: If you are looking for something involving the history of determinants (and matrices) you might start here: http://www-history.mcs.st-and.ac.uk/history/HistTopics/Matrices_and_determinants.html#86
Comment: I know of two very interesting things; A chinese mathematician (B.C.) recorded the determinant of a 3x3 system; see http://books.google.co.uk/books/about/Basic_linear_algebra.html?id=40HnLsET7OEC and also Euler or Lagrange in a litter wrote down a system of equations in a letter as 11 + 12 + ... +17 = x (say) then 21 + 22 + ... + 27 = y and ... and ...81 + 82 + ... + 87 = z where 11 does not represent 11 but the first sum of the first equation - in matrix notation, if the system was represented by a matrix A cont.
Comment: 11 would be writte  a_1,1 and in general ij is a_ij. He wrote down a condition like 11.22.33 + ... - 12.34.25 = 0 for the system to have a solution that's non-trivial, that is the determinant.
Answer: Let me tell you what I know in general.
The determinant was primarily introduced as a gauge to measure the existence of unique solutions to linear equations. It's like a litmus paper (which is used to know about acids and bases, but in this case its the existence of unique solutions). If you doubt that one can measure the uniqueness of solutions, I have a pair of magic spectacles you may keep that enable you to visualize the determinant in a new geometric way (this in fact can be found in many standard books, but I wanted to write the quintessence here).
In response to your first question about origin, it dates back to the $3^{rd}$ century, when Chinese mathematicians used determinants in their book by name The Nine Chapters on the Mathematical Art (Chinese version and English version here ). At first, when the historians used the concept of determinants, they didn't refer to matrices but merely to the system of linear equations and treated the determinant as a property which tests for the existence of unique solutions for a system of linear equations. And later,  due to the discovery of matrix theory, determinants have been moved to the theory of matrices (in a new manner of evolution).
If you consider a matrix $$\begin{pmatrix} a&b\\c&d \end{pmatrix} $$ the determinant is given by $ad-bc$. You may wonder what information does $ad-bc$ may have within itself. All you need to do is to view things in geometric manner when you are unable to visualize things in algebraic way. Matrices are closely related to fields: in vectors and linear algebra, we representing vectors in terms of matrices. They can be seen as collections of vectors. The example that I have in mind is: consider a billiard table. Before hitting the balls, you take a thing which has a triangular frame and then arrange all the balls (present in an irregular manner) into a triangular shape.  It's like arranging things in an organised manner, as human beings always try to do.
Let me explain the topic in greater detail.
If you look at the above figure, you can clearly see the coordinates. You can think of the columns of the matrix as vectors and the entities in the column representing their Cartesian placement (the coordinate positions). So now if you take all the above things into consideration, you can clearly see that if $ad-bc=0$ then the rhombus suddenly became a straight line, and in generalized manner a parallelopiped suffers a decrement in dimension by one (making the volume zero, which indirectly implies that it has an area). So analogously one can see that if the determinant becomes zero, according to the Cramer's rule, it makes the denominator go $\infty$, which is a violation.

Some of the important alternative notions about determinants: (stress on second one)

Determinants in reality can be thought as a measure of multiplicative change in the volume of parallelopiped when it is subjected to linear transformation. It can be shown as :

And the main notion that answers the connection between the determinant and existence of solutions is that the determinant of a matrix is zero if and only if the column vectors of the matrix are linearly dependent. Thus, determinants can be used to characterize linearly dependent vectors. For example, given two vectors $v_1, v_2$ in $R^3$, a third vector $v_3$ lies in the plane spanned by the former two vectors exactly if the determinant of the $3$-by-$3$ matrix consisting of the three vectors is zero. So one needs to take the theory of multilinear forms into consideration. I can't express the entire theory, but to give you a short notion, the determinant is actually a multi-linear form in general. So in a deep sense it measures the manifestations of the things related to vectors.
And when determinants are negative, they have a role of orientation in geometric sense, which is another crucial point.

Some Beautiful References :
I have some suggestions for you. Apart from reading about matrix theory in Wikipedia page I suggest reading a very good article Making Determinants Less Weird by John Duggan. And I have come across another good article recently, which is here
P.S : I took much time to edit and post this, so users are kindly requested to post any suggestions, in case of down-votes.
Thank you.
Comment: Hello! I've noticed that your link to "Making Determinants Less Weird" has broken - do you know an alternate location this resource may be found?
Comment: Is it sufficient or I need to add something ?
Comment: "To your astonishment,..." seems rather presumptuous. You know how *you* felt, do you really feel the need to tell people how to feel about something which may or may not be a revelation to them?
Comment: @ArturoMagidin : Ok, sorry sir, I have fixed it. Thank you.
Comment: Sorry @Emrakul, I am not active on M.SE anymore. But a simple Google search, would have done. Anyway the link's here : https://dl.dropboxusercontent.com/u/17516137/RapidWeaverSite/resources/misc/determinants.pdf
Comment: I don't see how 'ad - bc' gives an area of a parallelogram. Intuitively I understand  that 'ad' part is an overestimate of an area as if it is a rectangle, but '-cb' feels non-intuitive.
Answer: The authoritative reference seems to be the books by Muir: Contributions to the history of determinants and A treatise on the theory of determinants. See also http://www-history.mcs.st-and.ac.uk/Extras/Muir_determinants.html.
There is also Miller,
On the History of Determinants.
Amer. Math. Monthly 37 (1930), no. 5, 216–219.


Dual GFCI/AFCI breaker to support regular TRR USB outlets on kitchen counter: to code?

Question: I would like to replace some outlets that run along my kitchen countertop because the TRR plugs are hard to plug in, and I would like to put ones that have USB jacks.  I know that GFCIs are required in this area, but if I install dual GFCI/AFCIs breaker to support this circuit and replace it with the non-CI USB outlets, would this be to code?  Is there any easy way I could have found out if this was to code myself (I assume reading NEC 20, is the start?), or is this a bad idea for a DIYer? Thanks!
Answer: You're not on NEC 2020 yet, unless your state just adopted it. (MA has so far).
Under NEC 2017, Code requires GFCI only in certain places (kitchen being one of those) and it generally does not require AFCI breakers in those places. The rationale being that providing both can be a technical challenge. So you probably do not require AFCI protection in the wiring to a kitchen, but it is a good idea if (in order of importance) roached wiring, aluminum wiring, old wiring, or wiring in non-metallic cabling or conduit. IMO.
Keep in mind despite the similar names, AFCI and GFCI do totally different things. AFCI protects wiring from burnup due to bad connections, and this mainly guards in-wall wiring, particularly backstab connections. Originally they were conceived to protect electric blankets, but "backstabs in plastic boxes" proved to be the main thing AFCIs defend from.  Whereas GFCI protects humans from shock, hence the requirement anywhere within reach of a sink.
AFCI is only constructive at the breaker.  GFCI can be anywhere, however. And at the breaker is just fine.  Your plan is perfectly fine.
Keep in mind that making an outlet USB does not erase any requirement for Tamper Resistance.  If TR is a requirement, then you need a recep that is TR and USB. There is a lot of junk on sale on Amazon Marketplace and other outlets of the Alibaba junkstream, which uses direct mail to circumvent the laws which assure the supply chain contains safe, UL-listed products.  Such things are best bought at a bricks-and-mortar retailer; if you don't like Home Depot's pricing, try a genuine electrical supply.
Do your level best to keep refrigerators, freezers, fire alarms, radon systems and other "needs power for safety" appliances away from both GFCI and AFCI.
Comment: thanks for the very detailed information.  Can you elaborate on "Do your level best to keep refrigerators, freezers, fire alarms, radon systems and other "needs power for safety" appliances away from both GFCI and AFCI."  I would classify fridge and freezer as for safety in my house,  radon i can see, and I assume if the fire alarms tripped then they would be permanently off. Is that the reason?  And if  my alarms have battery backups?
Comment: @Joe the ruling question is what happens if it trips and this goes unnoticed, and in particular, what if the circuit is reset *for other reasons* without realizing this appliance was affected?
Answer: You could swap out the breaker for a GFCI/AFCI breaker but then if it trips you have to go to the panel to reset it. You could use a dual function (GFCI and AFCI) outlet that are not tamper resistant, to replace the existing ones, but that isn't code now. TRR are required.  I don't know of a dual function outlet with USB, but you could put a non protected outlet with USB ports downstream of the GFCI/AFCI outlets.  Just be sure they are indeed protected  by the upstream outlets.  You can easily test this by pressing the test button on your existing outlets and see which other outlets no longer have power.
Comment: Clarifying one more thing:  Pressing the TEST button, tests the GFCI function of the outlet.   It will cut power to that outlet and any others "downstream" from it. You'll need to press the RESET button to restore power after you've tested other outlets with any plug in device. Just plug it in to various outlets and see if it works. You probably have multiple circuits to the kitchen (required) so you'll probably have more than one GFCI outlet and more downstream outlets connected to that one.   Just take your time, be methodical.
Comment: Tyler:  Wow, Great minds think alike!  We posted practically the same post at the same time!  Awesome.
Comment: Thanks for the reply.  I did see the 'downstream' suggestion mentioned in another answer. Going to the panel on a trip isn't a big deal to me, since these things very rarely trip for me.  But this would be my first time replacing a breaker and having the reset at the outlet is a slight benefit.  If I did decide to go that rout, as someone who is very amateur at this, how would I determine which outlet is 'downstream' of another?
Comment: Hi Joe.  I believe you have existing GFCI protected outlets in the kitchen, right?  They have been required for years.   Often one GFCI outlet will protect others in the kitchen. The downstream outlets are supposed to have stickers on them that indicated they are GFCI protected, unfortunately it doesn't get done very often.  Like I said in my answer, the easiest way to find out which outlets are protected is to press the TEST button on the GFCI outlet and determine which other outlets no longer have power.  Don't over-think this.  You don't need a meter, any plug in (IE: lamp) device will do.
Comment: @Joe like George said, if you have outlets on a countertop, press "TEST" on one of them and it will trip, cutting power to itself. Now, plug something in to the other outlets -- any of them that still have power are "upstream" of the GFCI that you TEST'ed, and any that don't have power are "downstream" of the GFCI that you TEST'ed. You can check if they're on by using a plug-in light, a blender, whatever.
Comment: I don't think going down to the panel to reset a GFCI should matter.  Because it shouldn't happen more than once or twice every couple of years.
Answer: According to National Electric Code 210.8(A)(6):

125-volt, single-phase, 15- and 20-ampere receptacles that serve countertop surfaces shall have ground-fault circuit-interrupter protection for personnel. [NEC 210.8(A)(6)]

What is ground-fault circuit-interrupter protection? It is either a GFCI outlet or a GFCI breaker:

GROUND-FAULT CIRCUIT-INTERRUPTER A device intended for the protection of personnel that functions to deenergize a circuit or portion thereof within an established period of time when a current to ground exceeds the value for a Class A device. [2017 Florida Building Code Ch. 35 ... NEC Citation needed]

So using a GFCI breaker is appropriate. Code does NOT state that an AFCI is required for the countertops, so using a dual GFCI/AFCI is just as acceptable as a regular GFCI breaker. Whatever receptacle outlets (your USB plugs) you decide to put in, well that's whatever you choose. As far as NEC code, you're compliant.


Lizmap add point to PostGIS layer - correct layer settings?

Question: Not able to add point to the layer using lizmap.
I'w been following this guidance
https://github.com/3liz/lizmap-documentation/blob/master/source/publish/advanced_lizmap_config.rst#id28
Point is not saved & lizmap page says:
"An error has been raised when saving the form!"
Lizmap error log says:
.... 2018-04-24 12:51:46    [2]   openlog() expects parameter 3 to be integer, string given ....
Lizmap messages log says:
2018-04-24 12:51:40 ::1 default   SQL =  INSERT INTO "public"."mytablename" ("geom", "Name", "description" ) VALUES (ST_GeomFromText('POINT(21.785181524973595 63.10872517176041)', 4326), 'blaablaa', 'blaaa' )  RETURNING "id";
My setup is Win10
Lizmap 3.2Beta + QGIS Server 2.18.18 + Postgres 10.2 & PostGis
plugin Lizmap 2.4.0
Layer "id" field i set to hidden using QGIS layer properties. + tick on WMS & WFS. And "id" type is integer and type name int4
By using PGAdmin i'm able to see that this id field has a Default value defined as nextval('mytablename_id_seq'::regclass). this field is a primary key.
On Lizmap plugin this layer is added to be edited with all the options +
Popup enbabled + qgis setting
Answer: Seems that my layer was 3D (PointZ) type.
And from pgAdmin i had to execute:
ALTER TABLE mytablename
ALTER COLUMN geom TYPE geometry(Point)
USING ST_Force2D(geom);
Comment: You can also accept your own answer: it is not frowned upon here, but welcomed.


When to avoid Random Forest?

Question: Random forests are well known to perform fairly well on a variety of tasks and have been referred to as the leatherman of learning methods. Are there any types of problems or specific conditions in which one should avoid using a random forest?
Comment: Hi. "PLS is the leatherman of ...", "Bootstrap is the leatherman of ...", "Random forest is the leatherman of ..." <- I advise you to be suspicious about such claims. It was just a comment :)
Answer: Thinking about the specific language of the quotation, a leatherman is a multi-tool: a single piece of hardware with lots of little gizmos tucked into it. It's a pair of pliers, and a knife, and a screwdriver and more! Rather than having to carry each of these tools individually, the leatherman is a single item that you can clip to your trousers so it's always at hand. This is convenient, but the trade-off is that each of the component tools is not the best at its job. The can opener is hard to use, the screwdriver bits are usually the wrong size, and the knife can accomplish little more than whittling. If doing any of these tasks is critical, you'd be better served with a specialized tool: an actual knife, an actual screwdriver, or an actual pair of pliers.
A random forest can be thought of in the same terms. Random forest yields strong results on a variety of data sets, and is not incredibly sensitive to tuning parameters. But it's not perfect. The more you know about the problem, the easier it is to build specialized models to accommodate your particular problem.
There are a couple of obvious cases where random forests will struggle:

Sparsity - When the data are very sparse, it's very plausible that for some node, the bootstrapped sample and the random subset of features will collaborate to produce an invariant feature space. There's no productive split to be had, so it's unlikely that the children of this node will be at all helpful. XGBoost can do better in this context.
Data are not axis-aligned - Suppose that there is a diagonal decision boundary in the space of two features, $x_1$ and $x_2$. Even if this is the only relevant dimension to your data, it will take an ordinary random forest model many splits to describe that diagonal boundary. This is because each split is oriented perpendicular to the axis of either $x_1$ or $x_2$. (This should be intuitive because an ordinary random forest model is making splits of the form $x_1>4$.) Rotation forest, which performs a PCA projection on the subset of features selected for each split, can be used to overcome this: the projections into an orthogonal basis will, in principle, reduce the influence of the axis-aligned property because the splits will no longer be axis-aligned in the original basis.
This image provides another example of how axis-aligned splits influence random forest decisions. The decision boundary is a circle at the origin, but note that this particular random forest model draws a box to approximate the circle. There are a number of things one could do to improve this boundary; the simplest include gathering more data and building more trees.

Random forests basically only work on tabular data, i.e. there is not a strong, qualitatively important relationship among the features in the sense of the data being an image, or the observations being networked together on a graph. These structures are typically not well-approximated by many rectangular partitions. If your data live in a time series, or are a series of images, or live on a graph, or have some other obvious structure, the random forest will have a very hard time recognizing that. I have no doubt that researchers have developed variations on the method to attempt to accommodate these situations, but a vanilla random forest won't necessarily pick up on these structures in a helpful way. The good news is that you typically know when this is the case, i.e. you know you have images, a time-series or a graph to work with, so you can immediately apply a method more appropriate to that type of data.
Comment: @AniruddhaAcharya I said "struggle," not fail. [My answer here](http://stats.stackexchange.com/questions/164048/can-random-forest-be-used-for-feature-selection-in-multiple-linear-regression/164068#164068) makes it clear that quadratic features are not an insurmountable problem. But diagonals or quadratics or other non-aligned types of splits will require the trees to split on those features again and again in a rectangular fashion to approximate a diagonal/curve. You can see that effect in the plot to this post: look at the sharp corners. RF is using a square to approximate a circle.
Comment: @AniruddhaAcharya If you know that square terms are the right model, you don't need random forest: just add square terms to a linear model. RF is a good way to approximate arbitrary functions, especially when they have axis-aligned decision functions.
Comment: @javadba In general, my attitude is that RF is a wonderful model, especially when you do not have a strong understanding of which features might be important or inter-related. But the more you know about the problem, the more readily you can build more specific models which directly incorporate that knowledge, and hedge against inclusion of spurious features and associations.
Comment: I think vanilla random forests have the potential to recognise non rectangular partitions. We can have quadratic features for example and recognise boundaries like x^2 < c.
Comment: I meant feeding the quadratic (and other higher order) features to RF would reduce the struggle in modelling non rectangular partitions. For example RFs can use 2 quadratics  to approximate the circle instead of using a square. Although I agree that its not as easy as models that incorporate interaction between variables, I feel its not that hard because RFs  are not restricted to using thresholds on the raw features.
Comment: Why is the (quadratic terms) feature engineering suggested by @AniruddhaAcharya not a useful step to use in conjunction with RF's?  Yes those features could be added to a linear model: but the latter does not provide the behavior of combining the contributions of many results that are individually optimized for differing subsets of the features.
Comment: @javadba Quadratic terms can be approximated by RF by repeated splits, but might require many such splits. Pre-computing the quadratic terms can be more efficient in a memory and compute if their number is small, or could be prohibitive if there are many features. You're correct that a rudimentary linear model with quadratic terms may not capture sub-sampling effects if such effects are present and important to your problem.
Comment: If you have strong learners - which follows from the "specific models" you mentioned then go ahead and use them: `RF` 's have a stronger sweet spot when there is less firm understanding of the interaction among terms.  The usage of polynomial terms is possible in both cases. It was not implied that quadratic terms would be generated off of *all* input features: instead the likely candidates would likely be chosen based on some knowledge of the datasets.  The developer/modeler  should apply the intuition/knowledge they have about the input data during the preprocessing and featurization steps.
Comment: We're saying the same things but with different emphases.
Comment: i'm glad to hear that: i'm v much a learner here ;)
Answer: Sharp corners.  Exactness.
They use diffusion methods.  They fit lumpy things well.  They do not fit elaborate and highly detailed things well when the sample size is low.  I would imagine that they do not do well on multivariate time-series data - when something over here depends on that one thing over there a distance.
Gradient boosted forests might fit or over-fit, but can get substantially lower error for the same data.
"Leathermen" do not exist.  There are no "silver bullets".  There are toolboxes.  Know your tools, and take good care of them so they can take care of you.  Be wary of "when you are a hammer, then every problem looks like a nail" especially when you do not have a dense library in your toolbox.
Until you know the problem well, it is easy to imagine anything might solve it, or your favorite tool might solve it.  Wisdom suggests getting deep in understanding the problem, and being very familiar with your tools.
Added:
If you have enough compute resources or time margin to use something else.  The RF is not only fast to train, but fast to execute.  A very deep boosted structure is less of that.  You have to have the overhead to support that.
Comment: To be the devil's advocate here: *Nothing* will "*fit elaborate and highly detailed things well when the sample size is low.*"
Comment: @usεr11852 - I strongly agree.  Nothing is good at it.  Some things are less bad than others.  I like where zero-sample learning is going there.
Answer: This is the first time I actually answer a question, so do not pin me down on it .. but I do think I can answer your question:
If you are indeed only interested in model performance and not in thing like interpretability, random forest is indeed often a very good learning algorithm, but does perform slightly worse in the following cases:
1.) When the dimensionality (number of features) is very high with respect to the number of training samples, in those cases a regularized linear regression or SVM would be better.
2.) In the case there are higher order representations/convolutional structures in the data, like e.g. in computer vision problems. In those computer vision cases a convolutional neural network will outperform a random forest (In general if there is knowledge one can incorporate into the learning that is a better thing).
That being said random forest are a very good starting point. One of the person I admire for his Machine Learning skills always starts with learning a random forest and a regularized linear regressor.
However, if you want the best possible performance I believe nowadays neural networks aka. Deep Learning is looking like a very attractive approach. More and more winners on data-challenge websites like Kaggle use Deep Learning models for the competition. Another pro of neural networks is that they can handle very large numbers of samples (>10^6 one can train them using stochastic gradient descend, feeding bits of data at a time).
Personally I find this a very attractive pro for Deep Learning.
Comment: What is the justification for (1)? You make a claim, but don't provide any supporting argument.
Comment: Nice answer, but your last point is not correct: mini-batch training can be implemented for all common machine learning algorithms, see for example [h2o](http://0xdata.com/).
Comment: I think random forest still should be good when the number of features is high - just don't use a lot of features at once when building a single tree, and at the end you'll have a forest of independent classifiers that collectively should (hopefully) do well.
Comment: Oke, interesting, I did not know that. Are you saying that using these methods one can train a (decision) tree using mini-batch/SGD learning and thus build a single tree based on a majority split of the training total data (say 65%)?
Comment: As far as I understand, h2o uses the map-reduce paradigm for minibatch-training. Single (CART) trees are not implemented as such in h2o (but I suppose an unpruned tree is a special case of random forest with just one tree and maximum choice of predictors?).
Answer: Random forest fits multi-dimensional staircase to your data. It produces sharp edges in predictions. If your data are of continuous nature, then probably there are better methods to fit them. That doesn't mean however that "you should avoid random forest to fit them" :-) I don't think there is any kind of data where you "should be worried" about using RF.
And, I wouldn't say RF is "leatherman", it's definitely not, in the sense that "it will do everything for you". It's just a basic universal method you can use on wide variety of data. I would say it's more like "first simple thing to try", or a "baseline" for benchmarking better methods. I also use it when I want to see which predictor variables are important; there is an excellent R package Boruta for this purpose.
Answer: There's already many good points by others e.g. about sparse feature spaces, when we know a step-function will not work well/when you don't have a good representation of the data (some of these may of course be a matter of creating better features first), as well as non-tabular data types where other approaches are known to work better especially for how to represent the input data (as mentioned by others: images, text, audio).
However, here are some additional situations that are non-ideal for RF (in approximately descending order of my strength of concern about using RF). Several of these are not specifically an issue with RF, but rather apply more broadly to many prediction modelling approaches.

When we know mechanistically what underlies the system we model. E.g. you can often define a set of biologically sensible differential equations that govern the blood levels of a drug in the human body. You are much better off to set-up a non-linear model based on these, while any modelling approach that ignores this understanding of the biology is going to be a lot less efficient - especially for small datasets -, and likely terrible at extrapolation (see below). I would not ever seriously consider basic RF (or other "default" prediction models like gradient boosted decision trees) here.
When you need to extrapolate beyond your training data. The fitted step-functions will remain constant outside the training feature value range, which will often be an implausible thing to assume. Extrapolation is generally a big challenge, but e.g. mechanistic models from the previous bullet point would be a much, much better bet for extrapolation than RF.
RF is also not so great for multivariate outputs. Even something as simple as many correlated multi-label binary classification tasks can be more efficient with neural networks. It becomes even clearer, when the desired outputs is e.g. an image, a series of values such as a sentence of words, or a variable number of bounding boxes with class assignments.
When you want to causally interpret the effect of a feature. This may be a really silly and obvious thing to point out, but I've seen too many people saying things like:"My RF predicts that being in a hospital is a predictor of a higher risk of death! Don't go to the hospital, if you get sick!" or similar other misinterpretations. Obviously, you need a different approach than the standard prediction set-up in order to try to approach a causal question (for which there are approaches that try to use RF).
When there are high cardinality categorical features. E.g. user ID when there's hundreds or thousands of users (in a sense see sparse inputs), products that are being sold etc. and so on. This is not necessarily a case where RF should not be used, but rather where other approaches (such as neural networks with embeddings) might outperform them (of course, you could use neural network embeddings as inputs).
When you need to win a data science competition on tabular data, RF is also not necessarily the first thing you'd try. Gradient boosting (xgboost, LightGBM, catboost etc.) tends to outperform RF once properly tuned. It's not necessarily by much and may not be of relevance for many applications unless every little improvement in prediction performance matters.
Answer: RF is a static model and when it comes to dealing with dynamical systems and online learning, the cost of adapting to the data drift is the same as reconstructing the entire structure again.
Comment: +1 cause I didn't expect anyone to make a decent point not already done but you have.
Answer: First of all, the Random Forest cannot be applied to the following data types:

images
audio
text (after preprocessing data will be sparse and RF doesn't work well with sparse data)

For tabular data type, it is always good to check Random Forest because:

it requires less data preparation and preprocessing than Neural Networks or SVMs. For example, you don't need to do feature scaling.
For Random Forest training you can just use default parameters and set the number of trees (the more trees in RF the better). When you compare Random Forest to Neural Networks, the training is very easy (don't need to define architecture, or tune training algorithm). Random Forest is easier to train than Neural Networks.
Comment: Please note that you must disclose your affiliation when you promote software in comments and answer. Otherwise, your comments and answers risk being removed as spam.
Answer: Random Forests are prone to exhausing memory and causing out-of-memory errors (as compared to an incremental / batch learning method that fixes memory usage.
Comment: Is there a sense in which exhausting memory is unique or particularly acute in random forests, but not a problem for other model types? Incremental/batch learning is only more memory efficient because it reduces the amount of the training data stored in main memory. In other words, the memory problem that batch learning solves is generic to any dataset that is too large, not a problem with random forest itself. You can also train random forests by subsetting the data and training 1 tree on a batch, only storing the batch in memory, so this claim isn't even true for random forests.
Comment: I don't agree, there are methods which consume much more memory. Never had memory problems with RF.

When to avoid Random Forest?


Is the realgg.nl exchange legit?

Question: I was on a site www.realgg.nl last night, they have some attractive funding options for me because I live in UK it's difficult to get coins. (Well a lot more difficult than US). Just wondering if anyone knows whether it's legit.
Answer: Absolutely not - terrible exhange for any type of (crypto) currency.
DO NOT BUY HERE - you will receive your coins late (I received mine after 3 days of placing my order) AND they used the exchange rate of the day and time of the processing of the order - in other words I lost 60% of my purchase because they were 'having problems with their system' and took 3 days to deliver.

Is the realgg.nl exchange legit?


Are there any cases that a minor triad can be a dominant chord?

Question: Okay so that is quite a weird question, but are there any possibilities? And in a natural minor key does a minor v count as a dominant?
Answer: A v chord is a chord built on the dominant scale degree (5th scale degree), but functionally is not a dominant chord.
To be a dominant chord, there must be a half step resolution to the root of the next chord via leading tone. For example, G or G7 going to C will have B resolve to C and this resolution is not in Gm or Gm7. This tension and resolution is the basis of functional harmony so it makes sense that a dominant chord must facilitate this kind of resolution to be recognized as such.
Answer: It depends on what you mean by "dominant."
In one sense, a "dominant" is just the chord built on the fifth scale degree. And just like tonic chords can be major or minor, just like mediant chords can be major or minor, a dominant chord can be major or minor (even if the minor version is more rare).
A corollary to this is the notion of the "altered dominant." For instance, sometimes composers will make the V triad augmented instead of major (G B D# in the key of C, for instance), smoothing out the voice leading into tonic (B goes by half step to C, D# goes by half step to E).
Other than altered dominants, chords can also be dominant substitutes. In doing so, these other chords have dominant function, though without being a chord built on scale-degree 5. In terms of minor chords, you'll sometimes find iii being used as a dominant substitute, and so in this sense of the word, there you have it: a minor triad that is a dominant (substitute).
Comment: I guess you'd include tritone subs as dominants?
Comment: I would consider that a dominant substitute, yeah.
Answer: Technically, no.   But it can be part of a 'cycle of 5ths' progression, where each chord is rooted a 5th above the next.  It would be ridiculous to say there wasn't an element of dominant of the dominant of the dominant...   in this, even if some of the triads were minor.
Em, Am, Dm, Gm, Cm...
add 7ths, the dominant function is stronger:
Em7, Am7, Dm7, Gm7, Cm7...
And if we make some of the basic triads major, stronger again:
Em7, A7, Dm7, G7, C.
But there's an element of dominant function in the first, minor triads, set, wouldn't you agree?
Answer: If you define the dominant as 1,3,5,b7, and the minor as 1,b3,5, you can lower the root by a step and a half to a minor chord (i.e. relative minor) which might be usable as a sub for a dominant 13. Depends on context.
C7 = C E G B
C13 = C E G A B
A minor = A C E
Comment: I think you mean C E G Bb?


Transaction still unconfirmed after 2 days

Question: Last time I tried sending a transaction with the minimum fee it was succesful after 1 day. 2 days ago i tried sending one with a higher fee and double the bitcoin amount but its still unconfirmed.
https://blockchain.info/tx-index/7e3e62569bb24f029ddce8730320bd2dbce10bc6893e4c117f5c49be18c96cf1
Answer: An unconfirmed transaction will eventually be accepted into a block by whichever mining pool mines the block, or the transaction will eventually be rejected by the bitcoin network after an estimated one to seven days. If it eventually is rejected, then the funds would remain at the bitcoin address they were sent from. The only thing you can do at this point is to wait and see if the transaction is accepted into a block. Like all wallet providers, Blockchain.info has absolutely no control over this, and cannot expedite transactions. This is always dependent upon the bitcoin network of miners, which we are not a part of.
Blockchain.info wallets utilize dynamic fees. The following link explains how this works - https://blog.blockchain.com/2016/03/16/introducing-dynamic-fees/.
Comment: Welcome to the site.  Many people have this same question, and we are trying to direct them to a single question where we can collect all answers and avoid people wasting their time saying what has already been said.  See the "Possible duplicate" comment above.  Also, in general you should only post one answer to a question.  If you have more information to add, use the "edit" button to update your existing answer.  I would suggest you edit one of your answers and delete the others.
Answer: The bitcoin mempool is currently backlogged, which is causing a delay with transaction confirmations. You can follow it live on this chart, which shows all pending bitcoin transactions on the bitcoin network - https://blockchain.info/charts/mempool-count. This is impacting the entire bitcoin network, not just Blockchain.info.


Will a USB powered fan cool my Pi 3 with a touchscreen attached and will it draw to much power?

Question: I have seen tutorials that show a fan plugged into the USB port to cool the Pi, would this overload the Pi? Is it necessary to use a fan at all?
Comment: Welcome to this Q&A - Please can you try and organise your question a little bit better. I am having difficulty understanding what you are asking. Please read it again as if somebody was trying to ask you this question. For example, you say running of the PINS.. which PINS? THere are 50 pins on the Pi. Why does the LCD drive CPU so high anyway? What is a 3.5v recharge? Are you concerned about damage due to overheat or are you asking how to wire the fan? Its very unclear.. Please just read over it again and explain better. Thanks +1 for joining and asking your first question!
Comment: I am trying to work this out on my own. Temperature doesnt seem to be as much of a problem as I thought. However the screen uses a ton of CPU, and occasionally I get a warning. I stopped using the screen for now while i gather more information
Answer: Generally speaking a cooling fan is not required for the safe operation of a Raspberry Pi.
The cooling fan would probably plug into the GPIO or USB, I've used a fan that is rated at 5V and 0.2A with my Pi 2. It reduced the temperature slightly but not significantly. Certainly not significant enough to warrant the noise the fan produced.
The Pi has a thermal limit of 85°C, when it reaches this temperature it will limit the performance of the CPU to reduce the temperature.
I think it is unlikely that you will ever reach this temperature unless you are either doing some serious overclocking or running the CPU at 100% for sustained periods of time.
If you do want to use a cooling fan make sure the Pi is adequately powered. You need to use a power supply that can reliably deliver 5V at 2A. Also to improve the cooling performance you could add a heatsink to the SoC and the Ethernet controller. Since these are the two chips on the board that tend to get the hottest.
Comment: I have  ordered the heat sinks already. I have the temp set on my panel already it is usually never running hotter than 80 max. I am not over clocked and keep an eye on my CPU. Thanks for adding your personal experience I never considered the noise factor.


Monolingual German learner's dictionaries with small defining vocabulary

Question: Most modern English learner's dictionaries use controlled defining vocabulary for defining lemmas. Which German learner's dictionaries incorporate controlled defining vocabulary?
Comment: Really useful question for all German learners. I have a hard time with Duden's definitions, which are often more complicated than needed. One example I have found today: https://www.duden.de/rechtschreibung/Feierabend , defined as "Freizeit im Anschluss an den Arbeitstag". Why not "Freizeit nach der Arbeitszeit", which is much simpler?
Comment: @AlanEvangelista While your alternative *Freizeit nach der Arbeitszeit* is probably easier to understand for learners, I'd assume the Duden chose its definition because it is stylistically more refined (as it avoids the doubling of *-zeit* plus emphasizes the opposition *Tag* – *Abend*) and more precise (as *im Anschluss* – 'following' – is more specific than *nach* – 'after').
Comment: @AlanEvangelista "Freizeit nach der Arbeit" would even be simpler. However, for a shift worker this could be at any time. The original meaning of "Feierabend" is in fact the free evening after a working day. In Middle High German the meaning was more precisely the evening before a (religious) holiday.
Answer: There are a few German dictionaries for learners that use a more restricted vocabulary than dictionaries for (adult) native speakers:

Duden - Basiswörterbuch Deutsch als Fremdsprache: according to the description on the Duden website, the definitions in this dictionary use only words that are defined in the dictionary, apparently 7.000 words. It contains the entire vocabulary for the Goethe-Zertifikat B1 (but not only those, I think).
The current edition dates from 2013.
Duden - Deutsch als Fremdsprache - Standardwörterbuch: this dictionary has 20.000 entries and is geared at learners on the levels B1 - C1. According to the publisher's description, the definitions are "easy to understand", but this is not defined in terms of controlled vocabulary.
The current edition dates from 2018.
Langenscheidt Großwörterbuch Deutsch als Fremdsprache is probably a "classic" in this field, as it has been around since the early 1990s. It is aimed at learners and contains 90.000 definitions, phrases and example sentences. Unfortunately, neither the publisher's website nor the dictionary's introduction mention the use of a controlled vocabulary (even though the definitions are simpler than what you find in dictionaries for native speakers).
PONS Großwörterbuch Deutsch als Fremdsprache contains 110.000 definitions, phrases and example sentences. However, neither the publisher's website nor the dictionary's introduction mention the use of a controlled vocabulary.

Based on this brief overview, the only learner's dictionary of which I can confidently say that it uses a controlled vocabulary for its definitions is Duden - Basiswörterbuch Deutsch als Fremdsprache. For the other dictionaries, I can only assume that they use a controlled vocabulary.

Update August 2020: Online, there is Online-Wörterbuch Deutsch als Fremdsprache von PONS, which is presumably based on the printed version (or the other way around).
Answer: I do not know if and to what extent "controlled defining vocabulary" is an issue in German monolingual dictionaries in terms of a concept that is explicitely defined as a policy, i.e. beyond the natural use of more simple and frequent words to describe the meaning of more complex or rare ones.
For yourself to assess, here is a page taken from "Duden Deutsches Universalwörterbuch", 8th edition. This dictionary is not intended explicitely for the use of learners with other first language, though, rather it is meant for universal use.

(I skimmed through the variuos prefaces of this 2000 pages dictionaries, but I did not find something like "controlled dictionary" mentioned there.)
One observation however: reading definitions like

Abfalleimer: Eimer für den Abfall

it seems to me that the concept of "controlled defining dictionary" is used here (although perhaps involuntarily), as you could argue that for a native speaker of German you do not need a simple-worded definition like "Eimer für den Abfall" for a word like "Abfalleimer" that a) everybody 3 years old knows and b) that is self-explanatory.
Comment: Nach dem, was ich bisher verglichen habe, entsprechen die Wortdefinitionen und Beispiele des Universalwörterbuchs so ziemlich denen des Online-Dudens, der Kauf des Ersteren dürfte daher in den meisten Fällen überflüssig sein. Beispiel: [abfangen](https://www.duden.de/rechtschreibung/abfangen)
Comment: @Pollitzer   Ich war immer davon ausgegangen, dass die Einträge gleich sind. Es wäre zu viel Aufwand, sie getrennt redaktionell zu betreuen. - Es gibt andere Gründe ein Buch zu kaufen oder auch die Desktop-Version für den Rechner, die beim Buch dabei ist, wie auch die Print-Version als Pdf. All dies funktioniert nämlich auch ohne Internet.
Comment: Ich sage ja: in den meisten Fällen. Und wenn schon kaufen, dann das da: [Das große Wörterbuch der deutschen Sprache](https://www.duden.de/Shop/Duden-Das-grosse-Worterbuch-der-deutschen-Sprache-0). Hat natürlich seinen Preis.
Comment: https://content.taylorfrancis.com/books/download?dac=C2009-0-19049-4&isbn=9781135182960&format=googlePreviewPdf
Comment: @Pollitzer.  Ja, bei 200 Euro kann man da nur auf das Christkind hoffen...
Answer: My recommendation is Pons Großwörterbuch Deutsch als Fremdsprache, see Pons Shop, which would exactly address, what you look for, but I'm unsure concerning the size of vocabulary used for explanations.
For Abfalleimer there is just a reference to Mülleimer, which in turn is defined as

Behälter für den Hausmüll

Abfall provides:

Stoffe, die nicht mehr verwendet und deshalb beseitigt werden
Answer: And one more:
Kempcke, Günter et al. Wörterbuch Deutsch als Fremdsprache (Berlin/New York, De Gruyter, 20xx)


How to enable Lightning Components in Developer edition?

Question: Documentation says that Lightning components can be enabled in Developer edition after registering a namespace. But Develop --> Lightning Components option is not available.
Please help.
Comment: Is your developer edition Winter '15?
Comment: @AlexTennant No. Winter 15 updates are not rolled out for my Org (ap1). I need to wait for that!!!
Answer: Sign up for a Winter '15 Pre-Release Org at
https://www.salesforce.com/form/signup/prerelease-winter15.jsp
Answer: Its not working for existing developer org. Need to register a new org after registering follow this steps.
<code>         - a.   Click Setup | Create | Packages and then click Edit.
           b.   Click Continue.
           c.   Type a namespace and then click Check Availability to see if it's unique.
           d.   Click Review My Selections and then Save
           e.   From Setup, click Develop | Lightning Components.
           f.   Select the Enable Lightning Components checkbox and click Save.
</code>
I followed this doc  which worked for me.
IRaj
Comment: I created a new Org but Setup --> Develop --> Lightning Components option is not available. I'm using AP1 instance - scheduled date for winter'15 roll out is Oct 18th 2014. I might need to wait till that!!! Thanks for your response
Comment: Hi Vignex, use this link for new dev org registration.  https://developer.salesforce.com/en/signup?d=70130000000lxK7
Answer: From Winter '16 on, Lightning Components is automatically enabled so you will not see an "Enable Lightning Components" checkbox in setup. However, Lightning App Builder will say that Lightning Components is disabled by default and will not show any custom components or AppExchange components in the org.
You need to create a custom domain under Settings | My Domain and deploy it to all users. Once this is deployed, you'll be able to see Lightning Components in the App Builder, navigate to standalone apps using components, or test them from Dev Console.
Answer: I have registered with the pre-release winter 16 link for developer and enterprise edition. But not able to find the link to switch to lightning experience.


need headphones for kids

Question: I need to get really tough over the ear headphones for my pre teen kids. I am not interested in Beats and want something that is over the ear and that will last. High bass is not a priority. They are strictly for listening and don't require a mike.
Answer: For a recent vacation, involving multiple connecting flights, rental cars, hotel rooms and hiking, I bought the relatively cheap JLab JBuddies headphones for my children for less than $20 each.

A couple notes:

The over the ear component is small. It definitely wouldn't feel comfortable on my ears. I'm not sure about pre-teen, but for young elementary school it works great.
They fold up and are compact, which was great for traveling and storage
They have a standard mini-jack and work great on the tablets
Built in maximum volume limiter
These survived being stuffed in backpacks by less than careful children, tossed around various hotel rooms, cars and airplane storage locations. The cords were not gently wrapped up after each usage and generally treated as I'd expect younger children to treat electronics when I don't glare at them to not break something. They survived all of that.

need headphones for kids