How feasible is it that aliens would use a number field other than the standard real numbers?

Question: I will begin this with a disclaimer that I barely understand the p-adic analysis beyond very general ideas of what the p-adic numbers are and how they are constructed. But this is a question I've been pondering for a while now; is there something special about the real and complex numbers that make them a natural first attempt at creating algebraic closures of integers? Might an alternate chain of human development stumble upon a p-adic field prior to the reals? If this is possible how significant would this be for scientific development? Are the p-adic numbers in anyway better for approaching question in specific disciplines?
Comment: [This](https://arxiv.org/pdf/0904.4205) and [this](https://www.nature.com/articles/s41598-020-79507-4) might be helpful. I also saw the phrase "adelic physics" when I searched "p-adic numbers and science."
Comment: [Here](http://empslocal.ex.ac.uk/people/staff/mrwatkin/zeta/physics7.htm) is some more on that.
Comment: wow. I did not understand the question, so I went a-surfing and studied up on this field.. and.... Now I do no undertand the question, *and* I have a headache.
Comment: Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/122826/discussion-on-question-by-tox123-how-feasible-is-it-that-aliens-would-use-a-numb).
Answer: It is quite possible - after all, we (for certain definition of "we") are using other fields. It happens $\mathbb{R}$ seems most intuitive, simple and "natural" to a layman (though it isn't, in fact), so that it is the first stop (as something that has a direct interpretation in geometry). The second stop is $\mathbb{C}$, less intuitive, but still somewhat explainable without heavy math, and very useful in physics. (Then there are vectors and matrices, but usually we do not call them "numbers").
What is however very feasible and somewhat surprising it did not happen on Earth is a widespread adoption of hyperreals. They also form a closed field, have almost all the properties of reals, tackle infinitesimals and infinities in a somewhat intuitive way, and make grasping calculus much easier.
Comment: Interesting. On reflection, I do agree that it's surprising that a hyperreal field wasn't more widely accepted. Perhaps the sheer amount of work to make the hyperreals rigorous creates a boundary? While the transfer principle makes sense intuitively, it takes some leg work to do all of the model theory and such to construct a satisfactory field.
Answer: Taking a different approach to the problem, lets posit the question as 'What would our math system be without fractions?'
If we had never 'invented' the fraction, the only numbers we would have would be 'counting numbers'. There would be no 'real number system', methinks, because all of the issues with real numbers begins and ends with fractions (decimals are just an extension of fractions).
Consider if the entire evolved math system and the concept of 'unity' had been totally different? Would we even have a need for anything past 'counting numbers' and 'integers'?
Take for instance the process of taking a 'whole' pizza and divided it up into 8 pieces. Our 'math' creates a concept of a fraction of a whole - each piece is one-eighth of the whole, or 0.125 of the whole. But suppose this concept had never been created or even entertained by humans? Suppose, instead, we stopped at 'there are now eight 'wholes'? Without the concept of fractions, there would be no one-third fractions to become 0.333333333.... and thus no 'real' numbers.
Consider the digitization of our accounting system. We have the concept of the 'dollar', and of 'pennies'. One hundred pennies make a dollar. So we use the 'fraction' (decimal) annotation of $3.20 to represent three dollars and twenty pennies. The British, with pounds and shillings and pence, could not ascribe to such notation. Every transaction was done with 'whole numbers' of counting individual pounds, shillings, and pence, not 'fractions of a pound' and 'decimals of a dollar'. Imagine if the concept had ended there?
When the computer was invented, and thanks to a road trip to some quaint country-side pub, we use binary instead of decimal as the numerical representation in computer accounting, and the problem with digital notation of money soon became evident. In our accounting systems (spreadsheets and such) decimals - cents -  were converted, in the computer circuitry, to bicemals. The problem is, amounts such as 13 cents, or 0.13, created an infinite bicemal when converted to binary. The digital computer could not handle it properly. Rounding occurred. Over thousands of transactions per day, the small differences added up. It is rumored that one bank almost went under, when their 'daily interest' calculations on the computer did not match with daily interest calculations computed manually. The books done manually did not balance with he computer numbers. The balance sheet was out by thousands of dollars. Fraud was suspected. It was a very common problem with early spreadsheets. The solution was to enter $8.13 as 813 pennies, not dollars, and revert back to using only counting numbers, not fractions and decimals.
So, imagine a society that had never gotten their heads around fractions (like so many students in the early grades) and used only whole numbers (or, eventually, integers). This society would never have fractions, and thus decimals, and thus real numbers.
Consider our concept of time. Sixty seconds form a minute. Each second is a unitary concept, and then we create a new unitary concept 'minute' out of the sum of the parts. But somewhere along the line, humans went in reverse. They thought only of the minute as being the primary unitary concept (instead of a 'bunch' of unitary concepts 'seconds') and created the system of 'A second is 1/60th of a minute'. Given the absolute chaotic confusion this presents when primary school teachers attempt to get it across to their students, it is definitely not a 'natural' concept, but a very 'contrived' concept. Suppose a society had never even conceived of fractions? Suppose they had developed a system of mathematical notation where the 'second' was always considered a 'unitary concept', not a 'fraction of the whole'? And 'one minute 30 seconds' was always referred to as 'one minute thirty seconds', not as 'one and a half minutes'?
For division, 7 divided by 3 is 2 with one remainder, and it stops there. No 'one-third remainder'. That last remaining animal is not cut up into 'thirds', it remains a 'whole'.
That is, this society wold END at integers, not develop any alternative system of representing fractions. No p-adic necessary.
Elementary students would love it. It certainly makes their life easier. But that is the issue. We would not HAVE science as we now know it. Instead of dollars and cents, we might still be using the British system of pounds shillings, and pence.
What would our science and math look like? Perhaps this answer could come from children who have never experienced the horror of 'fractions'. Methinks it would be far more based on biology and the environment, rather than physics and engineering. Whatever it looked like, it would be very different from our world. A true 'world-building' exercise.
But one thing for sure, pies would always be round, and cake are square.
Answer: The difference between real and $p$-adic numbers is in how they measure size
In the reals, a number becomes big when you add it to itself many times. For instance,
$$1 + 1 + 1 + \cdots (\text{many times}) \cdots + 1 = \text{big number}$$
For $p$-adics, a number never grows beyond a fixed size no matter how many times you add it to itself. More importantly, it becomes small if $p$ divides it a lot.
For instance (taking $p = 2$), let's call:
an even number something like $10$,
a "very even number" something like $24$ (i.e. divisible by $8$ rather than just $2$)
an "extremely even number" something like $1024$ (divisible by $2^{10}$),
and so on.
The more even a number is, the smaller it is. So $1024$ is very small. But $1025 = 1024 + 1$ is not that small at all; it has the same size at $1$.
So what?
Why might a $p$-adic number system be invented? Well, it pinpoints numbers that are highly divisible by $p$.
So if you had some alien culture with, say, a religious obsession with a particular prime $p = 7$, then they might have a strong motivation to devise a way to systematically keep track of which integers are divisible by lots and lots of $7$s. This is what the $p$-adic integers do.
Answer: Mathematics is the science1 of developing formal models and applying them to get insights into the real world.
Some of those models are more useful than others. Consider euclidean and non-euclidean geometry. Euclidean geometry is taught in most schools because it is applicable to the real world at human-sized scales. Non-euclidean geometry is taught later, mostly because thinking about in comparison with euclidean geometry teaches thinking about models.
When it comes to real numbers, studying them gives insight in some real-world physical processes and also teaches thinking about models. The former is a reason why sufficiently advanced aliens would probably know real numbers. To the core of your question, decades ago I went through the traditional human progression of mathematical education, and it seems natural to progress from integers to real numbers. That could be the bias I picked up from my teachers.

1 It isn't exactly like other hard sciences, but close enough for me to apply that label.
Comment: the science of developing formal models and applying them to get insights into the real world is called physics. Mathematics "doesn't care" of the applicability into real world of its models and theories.
Comment: @L.Dutch-ReinstateMonica, I disagree. There is applied mathematics, there is non-applied mathematics funded in the hope that it will some day benefit applied mathematics (if only by teaching well-rounded students), and there is non-applied mathematics which "doesn't care." The last often has to struggle for funding, so jobs go into the first two.
Comment: Mathematics is the science of figuring out answers to questions we won't realize are actual problems for another 500 years.
Comment: @JohnO, nice quip, but people like Black and Scholes would disagree, and so do the bankers who use their work.
Comment: This answer not only ignores the facts that a lot of early math was in fact motivated by mysticism and that other fields and rings are very useful in describing real-world phenomena but also ignores the meat of the question. "It seems natural to progress from integers to real numbers." Why?
Comment: @tox123, those mystics believed that astrology and fortune-telling **was** the real world. Their belief was wrong, but it prompted the science. And fields and rings are useful, but not all are equally useful. We teach children first to add integers, and later as a special case to add hours on the clock, where 10 (a.m.) + 5 (hours) = 3 (p.m.).


Is a ccH, ccX and ccH equivalent to a cH, ccX and cH sequence?

Question: It appears to me that a ccH, ccX and ccH sequence is exactly equivalent to a cH, ccX and cH gate sequence. Is there any quick way to see/verify this?
Answer: Start

No control equals each control $\forall U : U = C(U) \cdot \bar{C}(U)$

Opposite controls commute $\forall U, V : [C(U), \bar{C}(V)] = 0$

No control equals each control $\forall U : U = C(U) \cdot \bar{C}(U)$

Self-inverse operations self-cancel

Done
More generally, for any "V conjugated by U" operation of the form $U_a \cdot C_b(V_a) \cdot  U_a^{-1}$, the $U$ operation can gain or lose any controls that $V$ has without changing the circuit's effect.
Answer: There is a way to simplify it down slightly - for some controlled unitary $C\left(U\right)=I\oplus U$ and some arbitrary unitary $V$ (of the same dimension as $U$), $$\left(I\otimes V\right).C\left(U\right).\left(I\otimes V^\dagger\right) = \begin{pmatrix}V&0\\0&V\end{pmatrix}\begin{pmatrix}I&0\\0&U\end{pmatrix}\begin{pmatrix}V^\dagger&0\\0&V^\dagger\end{pmatrix} = C\left(VUV^\dagger\right),$$ so it's now clear that $\left[I\otimes C\left(H\right)\right].C\left(C\left(X\right)\right).\left[I\otimes C\left(H\right)\right] = C\left(C\left(H\right).C\left(X\right).C\left(H\right)\right)$.
Funnily enough, if instead of using $I\otimes V$ in the above and instead used $C\left(V\right)$, we'd find that $$C\left(V\right).C\left(U\right).C\left(V^\dagger\right) = \begin{pmatrix}I&0\\0&V\end{pmatrix}\begin{pmatrix}I&0\\0&U\end{pmatrix}\begin{pmatrix}I&0\\0&V^\dagger\end{pmatrix} = C\left(VUV^\dagger\right)$$ and so it's not just clear that \begin{align*}C\left(C\left(H\right)\right).C\left(C\left(X\right)\right).C\left(C\left(H\right)\right) &= C\left(C\left(H\right).C\left(X\right).C\left(H\right)\right) \\ &=\left[I\otimes C\left(H\right)\right].C\left(C\left(X\right)\right).\left[I\otimes C\left(H\right)\right]\end{align*} but the more general version $$\left(I\otimes V\right).C\left(U\right).\left(I\otimes V^\dagger\right) = C\left(V\right).C\left(U\right).C\left(V^\dagger\right)$$ is also true, for any unitaries $U$ and $V$

My use of brackets in the control operation is maybe slightly more unusual, but hopefully it makes it more obvious what the operation is


What does it mean for transitive closure to be minimal?

Question: I don't understand what that word "minimal" has to do with anything. Can anyone explain and give an example?
Comment: I assume you are talking about relations?
Comment: If the relation is on a set $X$, then $X^2$ is transitive. Usually, you don't want this to be the transitive closure. In fact, there may be a lot of relations inbetween $R$ and $X^2$ that are transitive as well.
Answer: I assume you are talking about relations.
Some basics:

A relation $R$ on a set $A$ is, as you know, a subset of $A\times A$, so $R\subset A\times A$. Instead of $(a,b)\in R$, we often write $aRb$
A relation is transitive if, for any three elements $a,b,c\in A$ for which $aRb, bRc$, we also have $aRc$.

Now, a transitive closue (let's call it $T_R$) of $R$ is the, as you say, minimal transitive relation that includes $R$. By include, I mean literally that $R$ is its subset, or in other words, $Q$ includes $R$ if, for all $a,b$ for which $aRb$, we also have $aQb$.
This means that among all of the transitive relations that include $R$, $T_R$ is the one that is the smallest set.
For example, $A\times A$ is a transitive relation that includes $R$, but there may be some smaller relations that also are transitive and include $R$.

For example, let $A=\{a,b,c\}$ be a two element set, and let $R=\{(a,b), (b,c)\}$.
$R$ is clearly not transitive, but the following relations (all of which include $R$) are all transitive:

$R_1=\{(a,b), (b,c), (a,c)\}$
$R_2=\{(a,b), (b,c), (a,c), (a,a)\}$
$R_3=\{(a,b), (b,c), (a,c), (b,b)\}$
$R_4=\{(a,b), (b,c), (a,c), (c,a), (c,b), (a,a), (c,c), (b,b)\}$

All of these (and some others) are transitive relations that include $R$, but only $R_1$ is the minimal transitive relation that includes $R$. In fact, any transitive relation that includes $R$ has the following properties:

It contains $(a,b)$ (because $R$ includes $(a,b)$)
It contains $(b,c)$ (because $R$ includes $(b,c)$)
It is transitive (by definition)
It contains $(a,c)$ (follows from 1,2,3)
It contains $R_1$ (follows from 1,2,4).
Comment: Thanks, but I already know all this. I just don't understand why it is that if I have a transitive relation R, I can't just take away one element and have an even smaller one. I still don't understand what minimal means here, that's why I asked for an example, so someone could show that a certain relation can't be any smaller or something.
Comment: @paulpaul1076 I gave an example. The point is if you have a transitive relation $R$, and you take away one element, the resulting relation may not be transitive any more. In fact, that's the whole point of transitive closures: It's such a relation from which nothing can be taken away.


How does the sonic screwdriver eliminate the Cybermen in The Age of Steel

Question: The sonic screwdriver is known to do many things (well, as long as it's not to wood). But at the beginning of The Age Of Steel, the Doctor destroys a good few Cybermen by blasting something out of the screwdriver. Any idea how to justify that? Any other examples of the screwdriver having a bit more power than expected?
Answer: It's not the Sonic Screwdriver. A minute later in the episode, Rickey asks what that thing was. That thing being ... nothing. It's tiny. One of those insignificant little power cells that no one ever bothers about, and it's clinging onto life, with one little ounce of reality tucked away inside.
It's a Tardis Power Cell that the Doctor and Mickey find half way through the 1st part of the Two-Part Cyberman series, Rise of the Cybermen. After the Doctor finds it, he charges it with some of his life force (I just gave away ten years of my life. Worth every second.).
Comment: @EtiennePellegrini it's a power cell, it can be charged, then discharge, then charge itself again. Only needed 4 hours the second time around.
Comment: Oh I didn't get that he used the power cell. But wouldn't that use up some of the energy that they were patiently waiting for?
Comment: @cde Just hope there's no memory effect. :)


Pass parameters to RelayCommand in code behind

Question: I know that there are multiple posts with similar titles all over SOF and Google, but please bear with me for a minute.
I am following this article to create a context menu for my gridview: http://www.koaxkoaxkoax.com/ribbit/2010/09/creating-dynamic-menus-in-wpf.html
I create the HierarchicalDataTemplate in UserControl.Resources, I have an empty menu in the resources of the gridview, which I then reference in the actual context menu. The XAML (first part of the gridview) looks like this:
        <DataGrid.Resources>
            <Views:ViewMenuItemCollection x:Key="Menu">
                <Views:ViewMenuItem Text="foo"/>
                <Views:ViewMenuItem Text="bar"/>
            </Views:ViewMenuItemCollection>
        </DataGrid.Resources>
        <DataGrid.ContextMenu>
            <ContextMenu ItemsSource="{DynamicResource Menu}"/>
        </DataGrid.ContextMenu>

In the code behind I use FindResource to get a reference to the menu and create one ViewMenuItem-object that is on the same level as foo and bar. Then I iterate through a list and create one ViewMenuItem-object per list item and attach them as child objects. That looks just as I want to have it. But I can't get the actual functionality to work.
The inner part of the foreach-loop (where I create the child objects) looks like this:
ViewMenuItem seriesItem = new ViewMenuItem();
seriesItem.Text = series.ForcedName;
seriesItem.Command = new RelayCommand<Series>(p=>_view.SetSeriesExecute(p));
_setSeriesMenuItem.Children.Add(seriesItem);

Especially the line containing p=>_view.SetSeriesExecute(p) is confusing me. I have found many many examples that look exactly like it. When I run my program and click on one of the child elements, the SetSeriesExecute method is properly called - but the paramter is always null. Not too surprising, because at no point I actually supply an object of type Series as parameter. I have tried to provide the parameter in the RelayCommand constructor like this: p=>_view.SetSeriesExecute(mySeriesObject). It compiles, but SetSeriesExecute is never called.
My goal is very simple (at least I think it is): When the program reacts to a click on an element in the context menu, the method (SetSeriesExecute) needs to know which item has actually been selected (=clicked on) by the user. Unfortunately I was not able to figure out where and how I can supply the parameters to SetSeriesExecute, despite 4 hours of serious research. And the fact that everyone else seems to understand the available examples doesn't make me feel particularly good about myself and I offer lifelong gratitude for every hint.
Best
Peter
Answer: What you're missing is the CommandParameter.
Try setting seriesItem.CommandParameter to whatever you would like to pass to the SetSeriesExecute method.  p in p=>_view.SetSeriesExecute(mySeriesObject) will be that parameter.
Comment: +1, or apply a binding to the `CommandParameter`. In fact, both should be bound.
Comment: I have added `Series CommandParameter` to my `ViewMenuItem`-class. But the parameter in `SetSeriesExecute` is still null. How would SetSeriesExecute know to look for this Property anyway?
Comment: What is `series.ForcedName` ?
Comment: `ForcedName` is a string property and is used as the text of the menu item
Comment: I thought text is set here: ``
Comment: Yes, those are different items. In my example I create 2 items in XAML and one item with many child items at runtime. My question is how I can pass parameters at runtime without XAML databinding.
Comment: @sixlettervariables: Can you give me a short example of what I have to do?


Can mage hand block magic missile?

Question: This question asks if the spell mage hand can catch thrown objects. But if you managed to place the mage hand in the way of a spell, such as fire bolt or magic missile, would the spell be blocked by the mage hand?
Answer: Magic Missile: no
This is the simple one; magic missile has no attack roll or saving throw, so nothing can stop it short of something that specifically calls out that it is capable of doing so (such as the Shield spell, for example).
Note how it just says:

Each dart hits a creature of your choice that you can see within range.

Firebolt: not really, but flavor, sure
Mage Hand does not specifically have any interaction with any attack spells, but there is a simple option available to everyone that lets you "block" Firebolt, which would be taking the Dodge action.
If you tell me "I'm taking the Dodge action and I'm going to try and block any incoming attacks with my Mage Hand" then sure, I'd let you do that. Of course, you could also take that action with an active Mage Hand and the result would be the same, but it's cooler this way.
Mechanics
The basic reason why the question has no real answer other than the above is that you ask "If you place it in the way of the spell", but the Mage Hand does not give any of its own mechanics for doing that, so mechanically you can't do it. At best, you can use some other mechanic to do roughly the same.
Note that if you want a giant hand that blocks attacks and enemies coming for you, you want Bigby's Hand, but that's a 5th level spell, not a cantrip, and it gives you an idea of how powerful something like that is.
Comment: @Erik *Bigby's hand* granted that paragraph partial cover and Ryan missed it.
Comment: @RyanC.Thompson isn't that what I say in the last paragraph? :P
Comment: Another good spell to contrast would be Bigby's Hand, which is a hand-shaped spell that *can* provide partial cover against attacks.
Comment: @Erik Sorry, I was reading on mobile and I guess I scrolled too far on my tiny phone screen.
Comment: It is kind of strange that nothing can stop a magic missile within range though even if line of effect is unavailable. For example, you could cast magic missile at an enemy wizard at the end of a corridor and it will hit even if the wizard cast invisibilty on a gelataneous cube which is between you and the wizard and entirly filling the corridor.
Answer: Blocking magic missile is a function of the spell shield.
Shield says:

An invisible barrier of magical force appears and protects you. Until the start of your next turn, you have a +5 bonus to AC, including against the triggering attack, and you take no damage from magic missile.

There is a spell that can block magic missile, and it costs a 1st level spell slot and your reaction.
In general, since mage hand doesn't say it can block spells, it cannot block spells.
5th Edition has a "specific beats general" rule, which states:

If a specific rule contradicts a general rule, the specific rule wins.

Since magic missile states:

Each dart hits a creature of your choice,

each dart just hits the creature. To block magic missile a feature has to explicitly call out magic missile, as we see in the spell description of shield.
This applies in general as well, since mage hand doesn't say it can block spells as you describe, it cannot block spells as you describe - the spell description is the effect of the spell:

Each spell description in Chapter 11 begins with a block of information, including the spell's name, level, school of magic, casting time, range, components, and duration. The rest of a spell entry describes the spell's effect.

Since the spell description of mage hand does not include blocking spells, blocking spells is not an effect of mage hand.

Can mage hand block magic missile?


How to Handle Radio Complaint in Supply Center

Question: An employee (complainant) claims to have sensitive hearing has complained about a co-worker (defendant) that his radio is too loud.  The defendant says it helps him concentrate and therefore, more productive.  The complainant disagrees arguing that the co-worker turns it up louder on purpose, to which the defendant disagrees stating that the complainant talks loud and he can barely hear his music.  They are in an area where earbuds or headphones are not allowed.  What should the manager do? Remove the radio? Relocate the complainant to another area away from the radio?  Tell the two co-workers to sort it out themselves?  What would you do?
Comment: Why are earbuds and headphones not allowed? I'm having difficulty thinking of a scenario where that would make sense **and** playing a radio is permitted.
Comment: @Keith. Doesn't have to make sense to be enforced by higher management. I've worked under a similar scenario, which was simply because higher managers believed that earbuds and headphones work like they do in Hollywood movies (e.g. plane crashes into a building and the janitors obliviously mopping up listening to his ipod). So they banned them (and not radios) so employees were still aware of things such as the fire alarm.
Comment: Sorry, remove 'Office Cubical', as it is not an office cubical, but a supply center where employees work in the back and serve customers up front. A radio in the back is ok when it is kept at a level that shouldn't bother/distract others (but this level varies by individual); ear buds are not allowed when serving customers (looks unprofessional) and block out all sound, which could be a safety concern.
Comment: @NewManager - You should really add that information to the question.
Answer: I sympathize.  Cube farms are incubators for clashes in environmental preferences -- sound, light, temperature, and others.
I'm going to assume that if there were a volume at which the one could enjoy it while the other wouldn't be bothered, then they'd already be doing that.  This answer addresses the case where they can't agree.
Unless listening to the radio is part of the job or something to be expected in that particular workplace (like, maybe you work at a radio station), the radio-using coworker should defer to the coworker who is bothered by it.  (Presumably it hurts his concentration, just as the other says it helps his.)  If you allow him to say that it helps him concentrate so the other person should just suck it up, then you open the door for other things that help people concentrate.  I know people who extol the virtues of burning incense, for example, but I don't think you want them to do so in your workplace.
If you can separate the two without causing other problems, it's worth doing so -- avoiding easily-avoided friction is a win for everybody.  If doing so would give one of them a benefit, though (like a better workplace), you should factor in concerns about fairness.  I had a coworker once who admitted that he was deliberately loud and annoying because he hoped this would get him out of the cube farm and into a private office.  Don't reward that sort of thing.
From your description it sounds like this problem has already escalated; the one is turning his radio up louder to annoy the other, who is responding by talking louder.  If that is going on then they both need to grow up, and that's best accomplished by their manager(s) sitting each of them down privately and talking to them about professionalism.
Answer: Since you are a new manager, this is how I would proceed. First I would determine for myself if the music is too loud and/or if the other person talks loudly. You need to know if one or both or neither complaints are valid. Go spend some time casually in their work space and make note of how it seems to be to you Don't be obviously looking at this. Go by for other reasons, but pay attention when you are there. Further, observe how these people work with each other. There is a strong likelihood that neither the loud talking or the radio is the real issue. These kinds of things tend to come up when two people don't like or respect each other. So watch their interactions for a couple of days.
Next evaluate which of the two people is your better employee. It is likely that you may have to take an action that makes one of these two unhappy; know in advance which person is the one you most want to support especially if the both complaints have some validity. This does not mean the better employee gets a free pass on his behavior if he is in the wrong. It is one factor of many that you can consider. It really only comes into play when someone is significantly better, the job is critical, and especially if the position is hard to fill at that level of performance.
Next discuss the whole issue with HR.  As a new manager, you may not be used to consulting with HR about personnel issues. However, they can help you a good bit in knowing what the options are and what process you need to follow. Don't start out telling them the actual issue and people involved. First talk to them abuot what the copmany policies for conflict resolution are.  Once you know how much freedom you have to decide what happens, then you have a better idea of what you can do.
I am suspecting you will find that both people are contributing to the problem.  You will have to watch whatever solution you have to make sure these two don't escalate into new issues espcially if one person feels he has won over the other.
Of the options avaiable, if it is possible to move these people so they don't interfere with each other, that is probably the best move. It is the least likely to generate further complaints. Neither person will feel as if he is the winner as long as one does not end up with a significantly better location than the other. It will seem the most fair solution to most people.
But it may not be possible. I don't know how closely these two people need to work. Or if they both need to work with the same equipment.
If you have to come down on one side or the other, consider other people who work in the same area.  When I worked in an office where the radio was played, majority ruled on whether it was played and what station it was on. Taking this route makes it a group decsion. Of course this doesn't help if the group consists of only these two people.
Whichever side you come down is bound to make someone unhappy. Consider in your solution if you can find some other thing to give the person who loses this discussion as a sweetener and to show that you are not just favoring one person.
Answer: Here's a compromise you might suggest.  Personally, I like to listen to music, but I also need to have an ear out in case someone calls my name.  So I put in just one earbud (in the ear that is turned away from my coworkers).  Suggest that he find one of those really small ones which is essentially just a long wire with a tiny earbud; the worker should be able to hide the fact that he is wearing it from customers, and it will be inaudible to the coworker.
Here's an example: http://www.amazon.com/Panasonic-RPHJE120K-In-Ear-Headphone-Black/dp/B003EM8008/ref=sr_1_1/185-0282560-2991306?s=electronics&ie=UTF8&qid=1433963760&sr=1-1&keywords=ear+earbuds


Is it possible to reset FileVault password in recovery mode?

Question: I have problems with my startup volume, and it's encrypted with FileVault. I don't remember the pasword, but have the recovery key. Is it possible to reset the password?
Answer: If you have the recovery key (assuming it's the alphanumeric kind), you can reset your account password in the following way:

Boot your Mac to the FileVault 2 login window.
Enter your password incorrectly three times
It should prompt you for your recovery key. Enter it and hit return.

Your Mac should boot and stop at the OS's login window.

When prompted, reset your account's password.

If your Mac isn't able to boot from its regular boot drive and you can only start from the recovery drive, you should unlock and then decrypt your Mac prior to trying to fix your Mac. I have a post available here showing how to unlock and decrypt your Mac using your recovery key:
Unlock or decrypt your FileVault 2-encrypted boot drive from the command line


How to disable Apple Wireless Trackpad from recovery mode?

Question: I booted into recovery mode / macOS Utilities and erased my hard drive anticipating to reinstall the OS. Unfortunately my computer is paired to an Apple Wireless Trackpad that I can't find. I believe this trackpad's button is permanently pressed, preventing me from left-clicking, so I can't get all the way through the installer. This trackpad is listed as paired and connected when I go into Terminal and run system_profiler. However recovery mode has no System Preferences so I don't know how to disable this trackpad. Is there any way I can disable the trackpad from recovery mode, such as from Terminal?
Comment: If the trackpad is definitely the culprit, move out of possible Bluetooth range for the device, which is 10 metres (or 32 feet.)
Comment: @IconDaemon Thanks, that's probably the most practical solution. Maybe post that as an answer.
Comment: OK. I made it an answer, but don't accept it unless it proves to be correct!
Answer: Try moving the computer to another location a good distance away from where the trackpad may be located. The theoretical maximum distance for Bluetooth is actually far larger than what I thought. See this page, and this one for more info about Bluetooth ranges.
Comment: This is what I did and it worked.


On which basis Adi Shankaracharya was considered shivavtar?

Question: What is the reference of consider bhagwatpad Adi Shankaracharya to be an incarnation of shiva ? Did he proclaimed himself to be so anywhere ?
Answer: Well, many Puranas mention Adi Shankara to be an incarnation of Shiva.
Lord Shiva in the Padma Purana, Uttara Khanda, Chapter 236 states:

mayavadam asac chastram pracchannam bauddham uchyate mayaiva kalpitam devi kalau brahmana rupina (Padma Purana 6.236.7)
Translation: "Mayavada or Advaita philosophy is an impious, wicked belief and against all the conclusions of the Vedas. It is only covered Buddhism. My dear Parvati, in Kali-Yoga I assume the form of a brahmana (Adi Shankara) and teach this imagined philosophy.

In the 30th chapter of the Kurma Purana too, Adi Shankaracharya is mentioned an incarnation of Shiva:

तदेव साधयेन्नृणां देवतानां च दैवतम्। करिष्यत्यवताराणि शंकरो नीललोहितः॥३३॥
श्रीतस्मार्तप्रतिष्ठार्थ भक्तानां हितकाम्यया। उपदेक्ष्यंति
  तज्ज्ञानं शिष्याणां ब्रह्मसंज्ञितम्॥ ३४॥
सर्ववेदान्तसारं हि
  धर्मान्वेदनिदर्शितान्। सर्ववर्णान् समुद्दिश्य स्वधर्मा ये निदर्शिताः।।३५।।
Translation: The people should adore Lord Mahadeva, who happens to be the god of
  gods. The brown complexioned Shiva, for the establishment of Srauta
(Vedic) and Smarta dharmas (belonging to the Smritis), and for the
welfare of the devotees shall incarnate on earth. He will enlighten
his devotees on the subjects of the gist of Vedantas, the knowledge
relating to the Brahman, and all the dharmas enshrined in the Vedas,
  which have been narrated earlier.
Comment: Hi, thanks but these are indirect references. How can anyone conclude that this is about Adi Shankaracharya only ?
Comment: It talks explicitly about a preacher of Advaita philosophy or Smarta Dharma which points to Adi Shankaracharya. @user19357
Comment: @Surya Kanta Bose Chowdhury First reference talks of mAyavAda. Now whether this is a reference to advaita, how do we know? Second reference is generic. Who knows whom it refers to? By the way, I think both references are post-Shankaran, but trying to argue from an insider perspective.


Where do I focus ? On the outer nose or outer nose with upper lip?

Question: My question is that where do I focus ? The outer nose or outer nose with upper lip
Comment: Where ever touch is sensed, good householder.
Comment: the context for your question is way too vague to give any kind of reasonable answer without clarification. What meditation are you practicing, and what style/tradition/lineage of that meditation are you trying to accomplish?
Comment: I practice goenkas retreat
Answer: The instruction is: sati-parimukkham, or parimukkham-sati.
This means: mind-around-mouth
It also means: mind-around-face
It also means: mind around the front
It also means: mind around the interface [between the personal and the external]
It also has been interpreted as meaning: mind the business at which you are about (that is minding).
This instruction is found in cases where a formula for meditation is being set forth, not exclusive to minding the in and out breaths.
There is no instruction that reads: 'focus where the breath is felt' or 'at the nose' or at any specific place. Try to focus on the point where the breath passes the nostrils you will quickly see that you cannot find that place. It moves around at light-speed!
That is why the instruction reads "around" (pari). The point is the focus, not the locus. This is also important as a preventive measure: our job here is not to maintain a state of concentration on any object. We are trying to develop concentration (or better, focus) as a skill with a tool to be used in understanding other things. You are not going to Nibbana with your mind focused on your nose!
Follow the instructions without trying to pick it apart and you will see the advantages of minding around the mouth as a starting point, minding the face as a matter of minding the sense-reactions, minding the front as minding the whole body, minding the interface as minding the inter-relations of the body and the external world, and minding your business as keeping you focused on the task. Round and round, up and down, back and forth. A spectrum.
Answer: A correct translation of agama passage EA 17.1 is "pervade the entire body" -- here is the excerpt from my translation at
http://lucid24.org/agama/ea/ea17/ea17-01/index.html

From the agama school, the dhayna samadhi sutra is an excellent representation of how most of the Agama schools understand breath meditation -- i.e. that awareness pervades the entire anatomical physical body) -- in radical contrast to Visuddhimagga's outlier (wrong) view that one should focus only at the nostrils and ignore the entire physical body.
Excerpt from
http://lucid24.org/sted/16aps/index.html

409 CE Dhyāna Samādhi Sutra
This is not from the EBT period, but is fully EBT compliant in describing step 3 of 16aps and capturing what is so peaceful, sublime, ambrosia, a brahma dwelling, and the Buddha's preferred meditation of choice on his retreats.
  Dhyāna Samādhi Sutra (corresponds with Ānāpānā step 3, sabba kāya patisamvedi)
  Dhyāna Samādhi Sutra (chinese to english trans. By Dr. William Chu)
T15n0614_p0275b25(08)║念諸息遍身。亦念息出入。
  "One is mindfully aware of various breaths suffusing the whole body, as one attends to the exhalation and inhalation of the breath.
T15n0614_p0275b26(05)║悉觀身中諸出息入息。
  As one pervasively observes the various kinds of inhalation and exhalation inside the body,
T15n0614_p0275b27(14)║覺知遍至身中乃至足指遍諸毛孔如水入沙。
  one becomes aware and comprehends what is happening throughout the body, up to and including one's toes and pores—[awareness] pervades as if water seeps into sands.
T15n0614_p0275b28(13)║息出覺知從足至髮遍諸毛孔亦如水入沙。譬如[夢-夕+棐]囊入出皆滿。
  In the same way, with [each] out-breath, awareness and understanding pervade—from the toes to the hairs, permeating all the pores—as if water seeps into sands. Just like a sack that is completely filled from its bottom to its opening,
T15n0614_p0275b29(05)║口鼻風入出亦爾。觀身周遍見風行處。
  so too should one experience the body being saturated this way with [each] in-breath coming in from mouth [and/or] nose.
T15n0614_p0275c01(07)║如藕根孔亦如魚網。復心非獨口鼻觀息入出。
  One should perceive that throughout the body, where 'wind' traverses, it is as if it traverses through the holes of a lotus root; it is as if it traverses through the eyes of a fish net.
T15n0614_p0275c02(06)║一切毛孔及九孔中。亦見息入息出。
  Furthermore, one should not just perceive the breath as going in and out of one's mouth [and/or] nose; one should also see that the breath comes in and out from all the pores and from the nine orifices of the body.
T15n0614_p0275c03(09)║是故知息遍諸身
  For this reason, one should understand that the breath pervades throughout the body."

In SN 54, the Anapana Samyutta, prior to this sutta in the first 9 suttas, the 16 steps of 16 APS have not been associated with the 4 tetrads of 4sp (satipatthana, right mindfulness). So the first thing to understand about this context is that the Buddha is trying to explain how the breath is related to each of the 4 tetrads. One might question, how is the breath related to the anatomical body (kāya)? So the Buddha explains that the breath is also a type of body. One might question, how is vedana (feeling) a breath? And the Buddha explains the breath is a certain type of feeling. One might question how is the breath related to the tetrad of citta-anupassana, and so on. So in saying that the breath is one type of body, the context here is trying to justify how the breath ties in to 4sp (satipatthana) practice in general, how it ties in to kāya anupassana (body contemplation). He's not trying to redefine the default definition of body understood as physical.
The second thing to notice is that the Buddha is saying the breath is a type of kāya (body), is ONE type of body, among the already established understanding of body as being composed of 4 elements. He is not overriding the definition of kāya here, he is not saying breath is the only type of body, and he certainly didn't say in this context breath is the whole body and the anatomical body should be discarded from meditative awareness.
The third thing to notice, even if we want to practice 16 APS taking the breath to be the only part of the physical body that we're contemplating, ignoring the remaining 3 of the 4 elements, this body of breath has shape, dimension, occupying the same physical space as our anatomical body.

detailed comprehensive analysis on term 'pari mukha'
http://lucid24.org/tped/p/parimukha/book/index.html
Comment: Quite interesting method and controversy. The main piece of evidence is Buddha saying that breath is a body among bodies in satipatthana sutta, so many would split on this.
Comment: @116PУC Perhaps there's also empirical evidence, and whether it accords with preconceived doctrine i.e. what people might already/previously know to be true.
Comment: My guess is that it works similarly, one more or less contemplates the air element and stops thinking in the second jhana. Probably a very old controversy
Comment: see reedited post for response to comment. Vism. interpretation of step 3 of 16 steps meditation is completely unfounded. There really shouldn't be a controversy. But like anything, buddhism is political. the ruling political party dictates the 'correct' interpretation, when careful examination of evidence is incontrovertibly clear their interpretation is wrong.
Answer: Focus on where you feel the in and out breath. The location varies with each individual so there is no 1 place to focus on.
Answer: I don't want to answer the down voting answers. But If you can read the below quote's from the cannon, you may re-think about what you are doing as a meditation with external world instead of the dependent core-arising.
Below is about the uninstructed run-of-the-mill person from Assutava Sutta

Monks, an uninstructed run-of-the-mill person might grow disenchanted
  with this body composed of the four great elements, might grow
  dispassionate toward it, might gain release from it. Why is that?
  Because the growth & decline, the taking up & putting down of this
  body composed of the four great elements are apparent. Thus the
  uninstructed run-of-the-mill person might grow disenchanted, might
  grow dispassionate, might gain release there.

And below is about instructed disciple of the noble ones from same Assutava Sutta

"The instructed disciple of the noble ones, [however,] attends
  carefully & appropriately right there at the dependent co-arising
Answer: In this guide, Thanissaro Bhikkhu wrote that you can focus on any place where the breath can be sensed, whether it is the nose, chest, abdomen or any other place:

Only when you have cleared the mind in this way, and set outside
  matters aside, are you ready to focus on the breath. Bring your
  attention to the sensation of breathing. Breathe in long and out long
  for a couple of times, focusing on any spot in the body where the
  breathing is easy to notice, and your mind feels comfortable focusing.
  This could be at the nose, at the chest, at the abdomen, or any spot
  at all. Stay with that spot, noticing how it feels as you breathe in
  and out. Don't force the breath, or bear down too heavily with your
  focus. Let the breath flow naturally, and simply keep track of how it
  feels. Savor it, as if it were an exquisite sensation you wanted to
  prolong. If your mind wanders off, simply bring it back. Don't get
  discouraged. If it wanders 100 times, bring it back 100 times. Show it
  that you mean business, and eventually it will listen to you.

According to Chapter 2 "Sitting Meditation" of the book "How To Meditate" by Yuttadhammo Bhikkhu, you can also try to observe movements of the abdomen, instead of nasal sensations:

The purpose of formal meditation is to limit our experience to the
  fewest number of objects in order to allow for easy observation
  without becoming overwhelmed or distracted. When sitting still, the
  whole body is tranquil and the only movement is when the breath enters
  and leaves the body. When the breath enters the body, there should be
  a rising motion in the abdomen. When the breath leaves the body, there
  should likewise be a falling motion. If the movement is not readily
  apparent, you can put your hand on your abdomen until it becomes
  clear.
If it is difficult to perceive the motion of the abdomen even with
  your hand, you can try lying down on your back until you are able to
  perceive it. Difficulty in finding the rising and falling motion of
  the abdomen when sitting is generally due to mental tension and
  stress; if one is patient and persistent in the practice, one's mind
  and body will begin to relax until one is able to breathe as naturally
  sitting up as when lying down.
The most important thing to remember is that we are trying to observe
  the breath in its natural state, rather than forcing or controlling it
  in any way. In the beginning, the breath may be shallow or
  uncomfortable, but once the mind begins to let go and stops trying to
  control the breath, the rise and fall of the abdomen will become more
  clear and allow for comfortable observation.
It is this rising and falling motion that we will use as our first
  object of meditation. Once we are able to observe the motion of the
  abdomen without difficulty, it will serve as a default object of
  meditation for us to return to at any time.
Comment: Thk u all respected sir and masters for giving me guidance .I could feel the rise and fall of abdomen with and without placing hands in sitting position.Once again I thk u all If it is possible for you to send a video of watching breath at abdomen.
Answer: Just breathe.  You are overthinking it too much.


Within-group and between-group variation in real life processes?

Question: In the context of Statistical Process Control (SPC), control charts are used to monitor a process over time and detect shifts in the mean or variation. The traditional Shewhart $\bar{X}$ charts makes use of (rational) group means to monitor the process mean over time. However, one of the assumptions is that there is no between-group variation. While this is the ideal scenario for a process, it does not seem to be realistic in the real world. To be precise, the underlying model that is used in traditional charts is
$$X_{ij} = \mu + \varepsilon_{ij} \tag{M1},$$
where $\mu$ is the process mean and $\varepsilon_{ij} \sim N(0,\sigma^2)$ is a random variable. This model fails to account for between-group variation.
The article Statistical process control with several components of common cause variability (Woodall and Thomas, 1995) discusses this topic, along with an example.  They propose the model
$$X_{ij} = \mu + \beta_{i}+\varepsilon_{ij} \tag{M2},$$
where now $\beta_i \sim N(0,\sigma_{B}^2)$ is a random variable that accounts for the between-group variation.They also refer to other specific examples presented by other authors.
However, I was wondering whether there have been larger and/or more recent studies regarding this topic. Ideally, studies that use data from the industry to show that between-group variation is usually present. I would greatly appreciate any references or ideas!
Answer: These models are referred to as linear mixed effect or random effects models in general.
A search for articles in this area yield a couple of potential references:

Monitoring of Linear Profiles Using Linear Mixed Model in the Presence of Measurement Errors
Statistical Process Control Charts as a Tool for Analyzing Big Data
Nonparametric Profile Monitoring by Mixed Effects Modeling
Statistical Process Control Methods for Network Monitoring Using Generalized Linear Mixed Models
Statistical process control methods for network monitoring using generalized linear mixed models

Another method is to look at papers that cite the paper you reference:

Daewon Yang, Jinsu Park, Hayang Park, Sungki Hong, Jongmin Kim, Seonghui Huh, Eunkyung Kim, Jaeyong Jeong & Yeonseung Chung. (2023) Robust control chart based on mixed-effects modeling framework: A case study in NAND flash memory industry. Quality Engineering 0:0, pages 1-11.
Rob Goedhart & William H. Woodall. (2022) Monitoring proportions with two components of common cause variation. Journal of Quality Technology 54:3, pages 324-337.
T. C. Chang & F. F. Gan. (2004) Shewhart Charts for Monitoring the Variance Components. Journal of Quality Technology 36:3, pages 293-308.
Stephen M. Scariano & Jaimie L. Hebert. (2003) Adapting EWMA Control Charts for Batch-Correlated Data. Quality Engineering 15:4, pages 545-556.
Thomas C. Maness, Robert A. Kozak & Christina Staudhammer. (2003) Applying Real-Time Statistical Process Control to Manufacturing Processes Exhibiting Between and Within Part Size Variability in the Wood Products Industry. Quality Engineering 16:1, pages 113-125.


Why are Horcruxes associated with Dark Magic?

Question: In the Harry Potter universe, Horcruxes are described as dark objects in both the movies and the books. Could these objects be classified as "good or neutral" magic if a  "good" wizard had created them (without murdering)?
Comment: The horcruxes are dark magic because one has to split own soul to create one. There's a single method known in the books: murder.
Comment: There is no concept of "white magic" in Harry Potter.
Comment: @Gallifreyan Thank you for this comment, I just edited the question. :)
Comment: @TheDarkLord , Thanks for your advise. I'll remove it for a clear question.
Answer: Horcruxes are dark magic first because, in order to create one, you must commit murder. You must tear your soul apart. Accidental death and just war and so on don't seem to count, it's murder that damages the soul, that violates nature, and that is exploited.

'How do you split your soul?'
'Well,' said Slughorn uncomfortably, 'you must understand that the soul is supposed to remain intact and whole. Splitting it is an act of violation, it is against nature.'
'But how do you do it?'
'By an act of evil - the supreme act of evil. By committing murder. Killing rips the soul apart. The wizard intent upon creating a Horcrux would use the damage to his advantage: he would encase the torn portion -'
Harry Potter and the Half-Blood Prince - p.465 - Bloomsbury - Chapter 23, Horcruxes

There is no good way of splitting off a part of the soul and it certainly isn't the producer that makes a Horcrux evil. It is killing another to save yourself.
Secondly, although this isn't shown on-screen:

'Encase? But how -?'
'There is a spell, do not ask me, I don't know!' said Slughorn, shaking his head like an old elephant bothered by mosquitoes. 'Do I look as though I have tried it - do I look like a killer?'
Harry Potter and the Half-Blood Prince - p.465 - Bloomsbury - Chapter 23, Horcruxes

Off-screen we see that encasing the torn portion itself requires an especially vile act too gruesome even to make it into the books:

MA: What is the process? Do you-- Is there a spell? Is there a-- What do you have to do?
JKR: I see it as a series of things you would have to do. So you would have to perform a spell. But you would also-- I don't even know if I want to say it out loud, I know that sounds funny. But I did really think it through. There are two things that I think are too horrible, actually, to go into detail about. One of them is how Pettigrew brought Voldemort back into a rudimentary body. 'Cause I told my editor what I thought happened there, and she looked as though she was gonna vomit. And then-- and the other thing is, how you make a Horcrux. And I don't even like-- I don't know. Will it be in the Encyclopedia? I don't know if I can bring myself to, ummm... I don't know.
(Source)

There's absolutely no question that, in-universe, Horcruxes are considered evil and utterly beyond the pale even by Dark wizards.

'I haven't found one single explanation of what Horcruxes do!' she told him. 'Not a single one! I've been right through the restricted section and even in the most horrible books, where they tell you how to brew the most gruesome potions - nothing! All I could find was this, in the introduction to Magick Moste Evile - listen - "of the Horcrux, wickedest of magical inventions, we shall not speak nor give direction" ... I mean, why mention it, then?' she said impatiently, slamming the old book shut; it let out a ghostly wail.
Harry Potter and the Half-Blood Prince - p.357 - Bloomsbury - Chapter 18, Birthday Surprises
Comment: It's a popular theory that the creation of a Horcrux involves cannibalism, which is why JKR was so reluctant to say.
Comment: @Mithrandir I think with all such things it's better when you don't know and it's left to the imagination
Answer: It's Dark magic because it involves murder, then splitting the soul.
There are two main reasons why creating a Horcrux is considered Dark magic. The first is that they're created with murder, which is a 'dark' act of itself.

"By an act of evil – the supreme act of evil. By committing murder. Killing rips the soul apart. The wizard intent upon creating a Horcrux would use the damage to his advantage: he would encase the torn portion –" - Harry Potter and the Half-Blood Prince, Chapter 23 (Horcruxes)

This adds to, but isn't the sole reason that, Horcruxes are considered Dark.
Splitting the soul is considered a Dark act, even without murder.
Then, after the murder has been done, the wizard creating the Horcrux must intentionally split their soul to encase a part of it in their chosen object. This is considered an extremely Dark act - it's likely considered Darker than simply murdering.

"Well,' said Slughorn uncomfortably, 'you must understand that the soul is supposed to remain intact and whole. Splitting it is an act of violation, it is against nature." - Harry Potter and the Half-Blood Prince, Chapter 23 (Horcruxes)

Dumbledore explains in his notes that "tampering with the deepest mysteries" is something that should not be attempted. This shows that the splitting, not just the murder, is considered Dark.

"The resemblance of this action to the creation of a Horcrux has been noted by many writers. Although Beedle's hero is not seeking to avoid death, he is dividing what was clearly not meant to be divided — body and heart, rather than soul — and in doing so, he is falling foul of the first of Adalbert Waffling's Fundamental Laws of Magic:
Tamper with the deepest mysteries — the source of life, the essence of self — only if prepared for consequences of the most extreme and dangerous kind." - The Tales of Beedle the Bard

Though it's not possible, Dumbledore describes what the warlock in "The Warlock's Hairy Heart" as being Dark magic, though the warlock didn't harm anyone to do it.

"He wants to remain forever uninfected by what he regards as a kind of sickness, and therefore performs a piece of Dark Magic that would not be possible outside of a storybook: He locks away his own heart." - The Tales of Beedle the Bard

So, splitting the soul would similarly be considered Dark, whatever the method used.
Answer: Horace Slughorn said to Tom Riddle:

"Well, you must understand that the soul is supposed to remain intact and whole. Splitting it is an act of violation, it is against nature."

... so even if there were some way of creating a Horcrux without committing murder and other crimes (which, as Au101's well-researched answer explains, there isn't) it would still be considered a Dark Art simply because the end goal is considered inherently wrong.  The end doesn't justify the means, but the means don't justify the end either.
Fiendfyre is another example of the general principle: so far as we can tell, it does not require a murder or any other crime to cast, but it is still a Dark Art.


What is "Out-of-band Remote Access"?

Question: DMIDECODE:
<code>Handle 0x001E, DMI type 30, 6 bytes
Out-of-band Remote Access
  Manufacturer Name: Intel
  Inbound Connection: Disabled
  Outbound Connection: Enabled
</code>
LSHW:
<code>*-remoteaccess UNCLAIMED
       vendor: Intel
       physical id: 2
       capabilities: outbound
</code>
LSHW GUI:
Image Link
Answer: What is "Out-of-band Remote Access"?
This allows remote monitoring of networks.

Out-of-Band
Out-of-Band Network Access Control appliances watch traffic from
  outside of the network. They make a copy of any traffic that goes
  through, and they review it. They report on the harmful things that
  have come through, and make changes so that they can't happen again.
  By copying every piece of traffic, and then sending code through for
  remediation, they essentially double the amount of traffic coming
  through, slowing down your network. Out-of-Band NACs also have to be
  compatible with your specific network equipment.
Out-of-band Network Access Control solutions offer some of the policy
  smarts for NAC but leave the enforcement elements to Ethernet
  switches, VPN concentrators and wireless access points. They also
  require endpoint agents, which can be removed from the devices,
  especially if they are personal or BYOD devices.
These solutions rely on Layer-3 ACLs and Layer-2 VLANs for some
  traffic segmentation, but offer no enforcement, and are extremely weak
  at identity-based access control, the cornerstone of NAC.
These solutions are also very dependent on the types of switches,
  access points and VPN concentrators, and on the software versions
  running on these devices.
They have so many moving parts and management issues as to make their
  deployment, beyond an interesting lab demonstration, a costly
  proposition.
Inline
Inline Network Access Controls, sit right on your network. They're
  able to stop threats as they emerge, instead of having to remediate
  them later. It's a common misconception that having an inline NAC will
  slow down your network. The reality is that while it looks at every
  piece of data coming through, it only needs to do it once. As you can
  see above, Out-of-Band not only makes copies, doubling the traffic,
  but it sends through more traffic when making repairs.
Inline doesn't need to talk with the switches, routers, or other
  networking equipment, and is therefore agnostic. It can be used with
  any type of network.
Inline solutions offer the most effective NAC functionality, including
  traffic inspection, and when deployed in a standard network require
  almost no changes to existing network equipment.
These solutions offer a complete NAC lifecycle without the integration
  costs, moving parts, switch upgrades to the latest and greatest
  software patches, and changes in configuration required on the
  network.

Source Inline vs. Out-of-Band :: MiltonSecurity.com

What is "Out-of-band Remote Access"?


How to make stock quantity of another product decrease, when another product is bought?

Question: I am having trouble in finding ways of making other products quantity decrease, when a person buys a different item. This is because the item they buy will use quantities of other items listed.
Comment: please elaborate your question by putting an example or demo in your question. This way you can improve your question and thus will get help from community
Comment: If you are using for example a configurable product that will happen immediately
Comment: Also have a look at bundle or grouped products.
Answer: You can use the event checkout_submit_all_after. That is dispatched when the order is placed.
Check all the products that are bought and decrease the qty for matching products.
public function checkoutSubmitAllAfter($observer) {
    $items = $observer->getQuote()->getAllItems();
    foreach ($items as $item) {
        $product = $item->getProduct();
        $matching = ...insert your logic here for finding the products that need qty decresing...
        foreach ($matching as $match) {
            $stockItem = $match->getStockItem();
            $stockItem->setQty($stockItem()->getQty() - $item->getQty());
            $stockItem->save();
        }
    }
}

I know that using save in a loop is not the best idea. But it's better than nothing. You can make it work first and work on performance after that.
Answer: Checkout the methods in this observer: Mage_CatalogInventory_Model_Observer
You should be able to use some of the events that this observer hooks into to accomplish what you want to with updating quantity of other products.


when some of your coefficients in multivariate logistic regression model is negative

Question: when some of your coefficients in multivariate logistic regression model is negative while i know  these variable have positive sign in univariate model, What should I do؟
Comment: Welcome to the site! Could you describe what you mean by "univariate model"? And maybe describe the results you're getting in a little more detail.
Comment: This question is also answered at http://stats.stackexchange.com/questions/41633 (for general regression).
Answer: This is a general phenomena caused by correlation between your independent variables.  Here's a small example I constructed for you to experiment with.  I demonstrated with a linear regression as the phenomena is easier to see pictorially in this case, but it also happens with any generalized linear model, including logistic regressions.
First, let's create a vector of random uniform values
x_1 <- runif(200, 0, 1)

and then construct another vector that is explicitly correlated with x_1
x_2 <- .5*x_1 + rnorm(200, 0, .25)

Since I forced a statstical dependency between x_1 and x_2, these random variables are correlated
cor(matrix(c(x_1, x_2), ncol=2))
          [,1]      [,2]
[1,] 1.0000000 0.5059403
[2,] 0.5059403 1.0000000

You can see this geometrically with a scatterplot

Now let's make a dependent variable that depends on both
y <- 3*x_1 - x_2 + rnorm(200, 0, .1)

This collection of three variables show the behavior that you are witnessing.  Putting x_2 in a univariate model shows a positive coefficient
df <- data.frame(x_1=x_1, x_2=x_2, y=y)

# Univariate model
lm(y~x_2, data=df)

Call:
lm(formula = y ~ x_2, data = df)

Coefficients:
(Intercept)          x_2
     1.1152       0.5061

In fact, you can see that both x_1 and x_2 are positively correlated with y in a picture

But if I put them all together, I get recover the true negative coefficient for x_2!
# Multivariate model
lm(y ~ x_1 + x_2, data=df)

Call:
lm(formula = y ~ x_1 + x_2, data = df)

Coefficients:
(Intercept)          x_1          x_2
   -0.01096      3.00800     -1.00790

Comment: Thanks for taking the time to provide this detailed example!
Answer: The most common reason is that the remaining variables of the fitted model influence the changing of the sign!


Multinomial regression with categorical choice and predictos and factor analysis

Question: I have a non-ordinal categorical dependent variable with 3 choice outcomes and 20 ordinal categorical predictors and want to do a multinomial logistic regression. However, I want to reduce the predictors to just a few variables with factor analysis. SPSS gives regression factor scores as variables for each of my cases. Do I replace my original 20 predictors with these 5 regression factor score variables, or do the factors need to be on another format before using them as predictors?
Answer: Provided that the factor analysis is itself valid, then you can replace your 20 predictors with the 5 factor score variables.  That is, there is no special relationship between multinomial logistic regression and factor analysis that makes the application of factor analysis as a way of pre-processing the data invalid.
In terms of the validity of the factor analysis, you may want to use dimension reduction technique that are designed for categorical data.  From memory, SPSS has one or two (HOMALS and Categorical Principal Components Analysis).
The other practical challenge is that it is possible that the best predictor variable may end up with relatively little weight in the factor analysis, so it may be useful to only do the factor analysis with variables that are known to have some predictive relationship with your dependent variable.
Comment: Thank you! But given that the factor scores used as predictors are "composite"' how one one properly interpret mlogit reg output?
Comment: This is what I was alluding to when I said "Provide that the factor analysis is valid".  If all you are doing is factor analyzing a lot of variables without having a specific theoretic rationale for doing so there is no real way of interpreting the coefficients.  Typically, when people use factor analysis in this context they either have a good reason to do so based on theory (e.g., a reason to believe that there are some underlying dimensions, as is often the case with survey ratings, as an example), or, they are just trying to predict and do not need to interpret the coefficients.


Sql server database restore vs index rebuilds

Question: In SQL Server, if Database Restore Time takes less time compare to Index Rebuilds OR Reorganize  . Can we  Choose Restore as a option for DE-fragmentation.
If its not a 24/7 database.
Answer: That doesn't make much sense.  If you restore a database from a time earlier, you won't be capturing data that has changed since the backup. (but I'm assuming you mean a backup directly followed by a restore)
If you're talking about taking a full backup and then immediately a restore, then you will persist the fragmentation in the restored database as it was when it was backed up.
So either way I will say no that is not advisable.  Prudent index rebuilds/reorganization based on the fragmentation is best practice.
See this blog post that on database restoration and index fragmentation that debunks that myth.  Restoring a database also restores the fragmentation at the time of the backup.
Comment: That link is dead now. :(
Answer: No, it doesn't work that way.
There are two layers at work here that you should be concerned with (there are more if you consider the underlying storage subsystem, but I'll ignore this here):

Internal database data file layout: this is how data pages are located within each data file. When SQL Server needs to allocate some space, it does so by grabbing an available space within the data file. This can causes fragmentation within the data file, as these new allocations may be physically out of order to the logical structure of which they're a part. When SQL Server restores a backup, it reconstitutes the exact layout of pages within the data file as when they were backed up: therefore, this does not eliminate index fragmentation.
Physical storage layout: this is how parts of the database data files are located on the storage device. SQL Server assumes that database data files themselves are perfectly defragmented on disk (because it would be ridiculous performance-wise to assume otherwise). Windows is free to make allocations wherever there is free space on disk. This is why it's recommended to not rely on file auto-growth: if you have many databases with auto-growth happening, the physical allocations can be all over the disk (i.e., fragmented).

Given these two factors, it's recommended to (a) run index maintenance procedures to eliminate the internal database data file layout fragmentation, and also (b) run Defrag at the Windows level to eliminate physical storage layout fragmentation*. Doing only one of the two does not eliminate the need for the storage device to do random I/Os.
Doing a restore as you suggest may eliminate the physical storage fragmentation, but it won't eliminate the internal data file fragmentation.
* Physical-level (and lower) defragmentation is not recommended for SSD-based storage.
Answer: In general no, the restore, at least in "modern" sql servers, is optimized to read and write data quickly. The indexes are left as they were at the time of backup.
Answer: The DB restore may de-fragment (physically) at the disk level, but there will still be the same internal fragmentation at the page level. Hence you will still need to do your index maintenance.
Comment: I don't think I can agree with this answer. Can you show some references or documentation defending your stance?


How to measure classification accuracy in object detection task?

Question: Object detection uses mAP as the metrics. But if we are only interested in classification once the object in a bounding box is extracted, what metrics should we use? Thanks!
Answer: For classification problems, using crossentropy and bce is always my go-to option. It usually performs best for these types of problems. However, using MSE or its variants is also common in some cases. Hinge loss is another one that you might want to look at if the previous options didn't work.
Comment: Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer).
Answer: You could use top-n accuracy with a couple different n values like is normally done in simple classification tasks.
For a given class prediction, you score it as 1 if the ground truth label is in the top $n$ prediction probabilities, and 0 if it isn't in the top $n$. Then you average all these values over all your relevant predictions. (see https://stats.stackexchange.com/questions/95391/what-is-the-definition-of-top-n-accuracy for more on this)
For object detection specifically you could only count boxes towards your accuracy score that have sufficient IOU with a ground truth box so that it is only evaluating class accuracy on accurate bounding boxes.
You can also make a confusion matrix (https://en.wikipedia.org/wiki/Confusion_matrix) to see which classes are being commonly confused.
The problem with using class loss as your metric, as suggested in one of the other answers, is that it's one of the parameters you'd want to play with while aiming for a better accuracy so you wouldn't have a consistent way to score your experiments.


Does Java 8 support multiple inheritance?

Question: I have come across this topic while reading interface in Java 8, there are scenarios where we define method in interface using default or static keyword, allowing the next child to either re-define the same method or implement it. Does that means multiple inheritance? There's one more issue that I found is that, return type must be co-variant type else compile issue, that means it still doesn't support multiple inheritance? Can we say that java supports multiple inheritance? Let me know more details in regard to this topic.
Comment: @Draken I don't think that other question is really answering his question - as that question is not talking about Java 8 and default implementations within interfaces at all.
Comment: The confusion is in the usage of the word inheritance, inheritance technically only should be used for extending classes, not for interfaces. So we can't do multiple inheritance, but can do multiple implementation. I feel further reading on the subject would help a lot more
Comment: Yeah you are right @Jägermeister
Comment: The other problem is that we're dealing with static methods in interfaces to make a faux inheritance, I would still avoid using that word as it brings more confusion to the table than it's worth. It's better to stick with more common terminology like overriding than saying it's inheritance.
Answer:
Does that means multiple inheritance?

For interfaces, yes, but not classes. It is usually classes people think of as only classes can have fields and constructors.  This is no different to Java 1.0

return type must be co-variant type else compile issue, that means it still doesn't support multiple inheritance?

The need for covariant returns type is not related to whether you have multiple inheritance or not.

Can we say that java supports multiple inheritance?

For interfaces, yes.
Comment: @ShaikhNizamuddin if you have two methods which return incompatible types, it may be confusing for the developer to give the methods the same name.  I would suggest giving different names so it is clear for the developer using it what result they should expect to get.
Comment: @ShaikhNizamuddin Type inference is new in Java, however it could use type inference to determine which overloaded method should be called. NOTE: The JVM includes the return type in the method signature so it supports methods with the same name with different return types (and there was a bug in the Java 6 compiler which allowed you to use it)
Comment: If we are writing 2 different interface having same default method but with different return type then Java expects the return type to be co-variant type in the implementing class. Without co-variant type, Java throws compiler error. But to make it support multiple inheritance, return type may be different. We can use of static method to make our Java support multiple inheritance. Still there's a problem, we actually have to append Parent interface to use its static methods...
Comment: Yeah its good to use different names for the methods having different return type. Maybe in the upcoming Java versions(bit of assumption, being optimistic) we can see this co-variant type to be non-ambiguous. :)


Calculating W4 after Marriage

Question: I recently got married and am updating my W4. I looked at my last pay stub to see what is currently being withheld in taxes and it's about $700 (local + state + federal). After I completed my W4 form, I ended up with a number of $565 for "additional withholding." If I submit this, does that mean I will have $700 + $565 (so $1265) withheld from my future paychecks? Or only $565? I guess I am confused by the term "additional." I just assumed I'd be withholding less now that I'm married, not more. Thanks!
Comment: It's still not clear what you mean by "ended up with a number of $565 for 'additional withholding.'" The W-4 instructions tell you how many allowances to claim, and allows you request an additional dollar amount but doing so would be at your own discretion. Could you clarify what instructions you were following to get an "additional withholding" amount?
Comment: Where are you seeing "additional withholding"?  Also, is this the US?  What did you change on the form?  It's quite possible that you'd pay more tax after marriage, particularly if your spouse makes more than you.  Half the married deduction is less than the old single deduction, especially if you use to file as head of household.  In addition, you may have moved to a different tax bracket.
Comment: Yes, it's additional. To know if that makes sense or not would depend on you and your spouses income levels.
Answer: Yes.  Additional means "additional" as in "in addition to what is withheld based on the number of claimed allowances".
I recently adjusted my withholding, and used IRS Pub15 to figure out how my employer was figuring out how much to withhold.  Then I figured out how many allowances to claim to get the amount I want withheld reached by last paycheck of 2017.  We'll see how good my computations were next week when I get my next paycheck.
my recommendation, Nicole, is that you simply change your filing status and nothing else -- wait and see how your paycheck changes.  THEN see what to do.
Remember that the US income tax system is progressive -- that is the tax rate progresses (goes up) as your income goes up.  On the other hand, deductions reduce the amount of your income subject to tax.
Lets assume that both your and your spouse pay tax on 90,000, after deductions and all that other jazz.  For 2017, 90,000 filing as single, your tax rate is 5226.25 plus 25% of (90,000-37,950) = 5226.25 + 18238.75.  So together you and your sweetie would've payed 36,477.50.  However, the brackets don't scale the same married filing jointly.  Instead, 180,000 joint taxable income is taxed as 29752.50 plus 28% of (180,000 - 153,100), or 37,284.50.  It seems, looking at the tax brackets I found at https://taxfoundation.org/2017-tax-brackets/, that as income rises, there are subtle differences in how the brackets are constructed between Single and "Married Filing Jointly".
In other words, don't count on your taxes going down.
Comment: +1 for the third paragraph but the math in the fifth paragraph does not make sense. How  does 5226.25+18238.75 paid separately by two people add up to 36,477.50 for "you and your sweetie"?

Calculating W4 after Marriage


Prove that all the numbers in the table are even.

Question: In each cell of a 20 x 20 table an integer is written , such that for every 7 rows and 7 columns that we consider the sum of these 49 cells (the cells where the rows and columns intersect) is an even number. Prove that all the numbers in the table are even.
Comment: Where does this problem come from? [I hope not a contest...]
Comment: It is from my homework I've been thinking about :) I need some hints.
Answer: HINT to an alternate solution, partly inspired by @JaapScherphuis and partly inpsired by linear algebra (modulo $2$, i.e. in $\mathbb{F}_2$).
Let $A$ denote the original $20\times 20$ table, $R$ denote a subset of rows, $C$ denote a subset of columns, and
$$S(R,C) = \sum_{r \in R \\ c \in C} A_{r,c}$$
be the sum of numbers in the intersection of those rows and those columns.
(1) You are given that: $S(R,C)$ is even whenever $|R|=|C|=7$, i.e. there are $7$ rows and $7$ columns.
(2) Prove, by repeated applications of (1), that $S(R,C)$ is even whenever $|R|=7, |C|=2$.
(3) Prove, from (1) & (2) together, that $S(R,C)$ is even whenever $|R|=7, |C|=1$, i.e.  for the single column case.
Now you go through the analogous process to shrink the number of rows:
(4) Prove, from (3), that $S(R,C)$ is even whenever $|R|=2, |C|=1$.
(5) Prove, from (3) & (4) together, that $S(R,C)$ is even whenever $|R|=|C|=1$, i.e. every cell is even.  QED
BTW: this method also clearly shows that the result works only because $7$ itself is odd.  If the initial condition were $S(R,C)$ is even whenever $|R|=|C|=6$, then (step 3) breaks down, and indeed there are many counter-examples, e.g. the all-odd grid, checkerboard of odds and evens, etc.
Answer: Here is one way to do it.
First prove that the sum of any 4 cells in a rectangle (the intersection of two rows and two column) is even. This is done by carefully selecting various sets of 7 rows by 7 columns, and subtracting them from each other.
Next you have to see that you are free to rearrange the rows or rearrange the columns of the large table, without changing the fact that it satisfies the conditions of the problem.
Assuming there is an odd entry somewhere in the table, you can rearrange the rows/columns so that that number is in the top-left corner. Then rearrange the remaining columns so that the first row has all the odd numbers first, followed by the even numbers (if any). Also rearrange the remaining rows so that the first column has its odd numbers at the top, followed by any even numbers underneath.
If you have this top row and left column starting with odd numbers, work out where the odd and even numbers must be in the rest of the table. Finally show that there is some 7x7 section that fails the conditions. This means that the assumption that there was an odd entry in the table must have been wrong, so there can only be even numbers in the table.


Fields of Steady Currents Using Electrostatics

Question: Suppose you have a uniform ring charge rotating at constant angular velocity so that you also have a uniform ring of steady current, and thus you can use the Biot-Savart Law to compute the magnetic field. But I also remember from college that to good approximation you can use electrostatics to compute the electric field due to the charge if the current is steady, in spite of the fact that charges are moving. I never understood how this works. Can someone offer insight?
Answer: In the stationary situation all partial derivatives with respect to time vanish (this is in a sense the definition of a stationary state). Looking at the Maxwell equation relevant to determine the electric field, you note that they are given by
$$\nabla \cdot \mathbf E = \rho, \qquad \text{and} \qquad \nabla\times\mathbf{E} = -\frac1c\partial_t\mathbf B=0,$$
i.e., the same equations as in the steady state, so you can introduce a potential and reduce the set of equation to Poisson's equation.
Comment: That's crystal clear. I was anticipating some complex cancellation of first order contributions. It would also seem I was somewhat mistaken in that given ideal sources, the reliability of electrostatics is in fact exact, not just an approximation. That's good to know.


Custom Search functionality based on Account lookup in a VF Page

Question: I have a Custom Object in which a lookup field(Acclook)  is related to account has been created. On a VF page We have an Inputfield which is a lookup(Acclook) for account. Once we click the Search button, based on the lookup field(Acclook) the related data(custom Object data) should be retrieved and displayed in a table. kindly guide me with any sample code or links if any.
Answer: You will want to create a command button to perform the search and use the reRender to rerender the results section.  The following is a basic framework, but is definitely not the completed working version.  That's up to you to do. :)
Your Visualforce will have some code like the following:
<apex:pageBlock>

  <apex:pageBlockSection title="Search Input" id="searchInput">
    <apex:inputField value="{!yourObj.AccountLookup__c}" />
    <apex:pageBlockSectionItem >
      <apex:outputText value=""/>
      <apex:commandButton
            action="{!search}"
            value="search"
            reRender="searchResults"/>
     </apex:PageBlockSectionItem>
   </apex:pageBlockSection>

  <apex:outputPanel id="searchResults">
    <apex:pageBlockSection title="Search Results" rendered="{!yourResults.size > 0}">

    </apex:pageBlockSection>
  </apex:outputPanel>
</apex:pageBlock>

Your Apex Controller will have need to have a search method that returns a PageReference. In this case you can just return null to stay on the same page and only have the partial refresh of the sections you indicated should be reRendered.  Here is some of the body of the controller.
YourObject__c yourObj;

public YourController() {
   yourObj = new YourObject__c(); // or get it from DB, somehow.
}

public PageReference search() {
  // Do your search based on the input value of

  if (yourObj.AccountLookup__c == null) {
    ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR, 'Account is required to search'));
  } else {
    // query the DB
    // set the yourResults list to have the results
    // alternatively, you might just have some
    // fields that you are setting and displaying
  }
  return null;
}


Does adding two hash values generate a valid hash?

Question: Does adding 2 hash values generate another valid hash value? In other words will this hash(a) + hash(b) != hash(c) + hash(d) always be true? I don't think it will but does it matter? Are the essential properties of the hash function preserved under addition?
Answer: Since several values can have the same hash, it could be that hash(a) = hash(b) = hash(c) = hash(d), so also hash(a) + hash(b) = hash(c) + hash(d).
Comment: for mathematical/entropy reasons it is recommended to use XOR to "merge" the hashes rather than summing them up.
Answer: A hash, by the pidgeonhole theorem, can't be collision free.  So hash(a)+hash(b) == hash(c)+hash(d) for some values of a, b, c, and d.  Adding hash functions still gets you the good qualities of the hashes that you added together, but it won't make the result any better than the better of the two.  (You're not increasing your hash table space.)On second thought, the result will be only as good as the worse hash that you added.
Answer: This depends on your hashing algorithm, and in general it will not be true. Given a finite hash table, any two hash keys near the end of the table when added together will clearly give you a hash key off past the limit of your legal hash values.
Answer: I'm working under the assumption that when you say "hash" you're refering to a cryptographic one like MD5 or SHA1, if you're talking about something else... ignore me.
Adding hashes together would be kind of a weird process, XORing them might make more sense... ish.
It's possible for hash(a) + hash(b) == hash(c) + hash(d), but incredibly unlikely. By merging the two hashes you're creating the possibility (though there's the possibility that hash(a) == hash(c) off the boat, it's just slim). Hashing identical items would clearly result in equality.
Answer: Your question expressed in English doesn't match the expression you give. Do you want to know if:
<code>  hash(a) + hash(b) != hash(c)
</code>
will always be true?
The answer is no. Any value might be a valid hash value.


Acceptable in Bilbao: is it better to speak Spanish or English?

Question: I will be visiting Bilbao next week and I would like to know whether I should speak English or Spanish. I don't know Basque. What is acceptable for tourists? And are there any "don'ts" I should be aware of?
Comment: @fkraiem this isn't just an open ended "what to know before visiting X" though, the question body is much more specific and makes it clear it's about language and related sensibilities which can be a big deal in a region with a history like that of the Basque country
Comment: Not worthy of an answer, but I lived in the Basque country for ten years and never learned any Basque beyond ordering a beer or counting up to twenty. If you know a little Spanish, that will be better than most Spaniards' English.
Comment: My edit was to remove the request of what to see/do, as that is not part of TSE format and could result in your question being closed as off topic.
Comment: I've never been to any Basque areas, but I've been to touristy areas in Catalonia, and I'd be surprised if speaking either language as a tourist would cause you trouble.  You can always ask people if they prefer one language or the other.  This shows that you want to be careful not to offend, which already goes a long way to avoiding offense.
Comment: We get a lot of "what to know before visiting X" questions; IMO they are both too broad and opinion-based; what's important for one person need not be for another.
Comment: @user568458 The question has been edited in the meantime.
Answer: I was there last year. The locals do speak Euskarian and Spanish. There is a clear bias to Euskarian similar to how Canadians in Quebec or Montreal speak English: They all can do it quite well, but they will speak French by default.
English is touch and go: you can certainly do simple transaction like ordering food, buying stuff, etc but we didn't meet a lot of people that could engage in a deep conversion.
I'd recommend: If you are proficient in Spanish, use that. Otherwise, use English as it sets a clear context and some mishaps or miscommunication are expected and perfectly okay.
Great town & people to visit! Have fun !
EDIT: one tip: around 6pm or so most bars start serving Pintxos which is small sandwhiches and finger foods. It's very good (and affordable) and very popular, so the places are packed. In Spanish it would be called pinchos or maybe tapas, but it's always Pintxos in Bilbao
Answer: I have been four times to the Basque Country (and twice specifically to Bilbao) and I never had any problem speaking Spanish to Basque people.
Bilbao locals are usually native to both languages and sometimes they simply use a few words from one language when speaking the other one. For instance, some Basque words that I got used to hear because they are often used among Spanish dialogues are: "aita" (dad), "ama" (mom), "agur" (bye), "ez" (no), "bai" (yes), "zorionak" (congrats), "ongi etorri" (welcome) and "eskerrik asko" (thanks).
So, if you can speak fluent Spanish, just use it.
Regarding the "don'ts":

Don't speak about politics (this is extensible to any country in the whole world).
Don't miss the opportunity to have some "pintxos" and drink some "zuritos".
Answer: It is Preferable that you use Spanish to communicate, even if you only know a little, since most Basques (not to mention almost all) do not speak English or are not fluent in the language, although there are some places and people who can assist you in English, it will be very little, since English is not a very popular or well-known language in the country. The most Spoken Languages are Euskera, the mother tongue of half of the Basque population with 40%, and used daily. French which is spoken by 20% to 35% in some regions, and Spanish which is spoken by 95% of the Basque population and used in all parts of the Basque Country, being the lingua franca of the Country. So you could refine your Spanish a little before going on a trip to the Basque Country, the use of Spanish will help you a lot to get in touch with the culture like the people of the Basque Country, I hope you enjoy your trip a lot :)


How to address a formal letter to a group of women

Question: How do you address a formal letter to a group of women - i.e. the equivalent of Dear Sirs, for women?
Comment: I shudder at 'Dear Ladies' or 'Dear Madams',  but if I had to choose to be included in one it would be the former. If I was one of the people to be included in the address I would prefer, as @Brillig suggests, the use of the group name or descriptor and failing that, 'Dear all'.
Comment: *Ladies* comes to mind; *Dear Ladies* or *My Dear Ladies* if you prefer.  Traditional writing often used *Dear Sir or Madam* so *Dear Madams* is correct although I think people avoid it today after that famous speech from the play *I am not a Madam!* which played on the occasional usage of this word for a woman who runs a house of prostitution.  You can address one specifically the rest as a group like *Dear Mrs. Smith and your fellow sewing group members*  You can address the group:  *Dear Daughters of the American Revolution members*.  In what way are these women a group?
Comment: I think it is traditional even in Anglophone contexts to resort to French on the rather rare occasions when pluralizing such ordinary courtesy titles becomes necessary; at least it is an option. The masculine plural *Messieurs* can be abbreviated *Messrs.*--an uncommon but available plural for the abbreviated English courtesy title *Mr.*--but I confess I know no such abbreviation for the feminine plural *Mesdames* (which carries no discernible implication of bawdry).
Comment: @BrianDonovan: though you are right, and you might write a letter to Mesdames Smith, Jones and Green, *Dear Mesdames* is not workable.
Comment: @YosefBaskin - I don't like "Attention."  It gives me the same feeling as an email message in all caps.  Normally, "Attention: Mary Sue" would go on a fax or an envelope, if you are sending a letter to an office or department, and you want the letter to land directly on Mary Sue's desk.
Comment: @YosefBaskin - So now we don't provide feedback on each other's contributions?
Answer: If the group has a function or better yet a name, use it.  Such as Dear league of women voters or Dear members of {name of group}.
Comment: I don't think "Dear League of Women Voters" works well in a formal letter.
Answer: I see no reason to specify gender, and would suggest, in the case that you don't know the people you are writing to:

Dear friends:

In the U.S. I don't think it would feel too informal to address letters this way, unless it were a legal matter or there were a contentious, adversarial tone to the communication.
However, if "Dear friends" does feel too informal for you, here are some alternatives:

Mesdames:

or

Good morning [afternoon],

This is a nice trick with a formal group email, and I don't see why it wouldn't work in a business letter format.
Now, since Dear sir or madam is technically addressed to a single person, but it works for a group, you could follow that pattern, and address your letter to a single female person:

Dear madam:

Which follows the old-fashioned pattern of

Dear sir:

These would only be used if you don't have a name to address the letter to.
If you need to address a letter to a clearly defined group, there are already Q&As about that here; let me know if you want me to hunt one down.
Comment: @Mari-LouA - I expanded the answer. // My personal opinion about "Dear all" is that it's acceptable but more informal a style.
Comment: Friends for a formal letter? And if you didn't know them personally? Dear All, is neutral and less intimate in my opinion.
Answer: I think "Dear Madams" is still fine (it's akin to "sirs").  If they are colleagues of yours, I've seen people begin with "Dear colleagues," or "Colleagues,".