What best explains why the United States intervened militarily in former Yugoslavia and not in Rwanda in the 1990s?

Cold war strategies, of course. Yugoslavia was an independent state, with no strong Soviet Union ties, nor connections with the West.

As long as the Soviet Union was in place, the war in Yugoslavia would not have occured as the Soviets would have backed the Serbs - their ally up until the rise of Tito's Yugoslavia  - and the situation would've gotten far too risky.

But the Soviet Union DID collapse in the early 90's and NATO knew that the newly formed Russia didn't have the power to react.

Thus, NATO countries (most prominently Germany, of which Croatia was an ally in WW II and beloved country for vacations) began to support and fuel Croatia's and Slovenia's rise to independence, so that they could become under NATO's sphere of influence.

Serbians in Croatia opposed the idea of an independent Croatia, since they didn't want to lose their nationality. They, instead, wanted the areas in which they lived to become Serbian. As for Slovenia, not many Serbs lived here so there was no war, although the Yugoslavian army did try to invade Slovenia, but was stopped in its tracks.

Now, the NATO planned on "seizing" Croatia and Slovenia, since Croatia has a widely stretching coastline, both interesting strategically and for tourists, and Slovenia was the most developed state of Yugoslavia, plus an easy target (because of its homogenity).

HOWEVER, Bosnia, of which the majority of citizens are muslim Bosniaks, but a population of 30% are Bosnian Serbs, and a remainder of 15% Bosnian Croats, was still left. The Bosniaks either didn't want to live in the remains of a Yugoslavia dominated by Serbs, or were attracted to the promises that NATO made to Croatia and Slovenia (maybe a combination of both). The problem is that NATO either completely forgot about Bosnia, or simply let the Bosniaks drive into war with Serbia, knowing that it would get crushed by the latter. This would of course cause for bad publicity for the Serbs, and a stronger case for Croatia who at this time lost several areas of its territory to Croat Serbs.

The rest is history. Bosnia called for independence, which the Bosnian Serbs AND Bosnian Croats neglected, after which both parties started attacking the Bosniaks - it's just that you'll never hear about the Bosnian Croats in Western media. Moreover, Bosniaks under the knowledge of NATO and the US allowed thousands of Mujahideen from the Middle East(the same rebels that fight for Al-Qaeda now) to come to Bosnia and fight against the Serbs.

All parties committed atrocities, of which Serbs the most. However, in the media only Serbs were accused, a similar thing of what happened in Syria with Assad. The difference is that now we know the rebels real face, through the internet. If it were not for those ISIS videos, I believe that we would still be believing that the latter is "a friendly rebellion fighting for a good cause".

ANYWAY, the horrible massacre of Srebrenica happened, which Serbs claim to be a killing of terrorist Mujahideen (since only men were killed) that operated in Serbian villages around Srebrenica for several years, killing and decapitating victims.

The Srebrenica massacre and other atrocities committed by the Serbs in term "justified" NATO intervention in Croatia, which caused an estimated 200.000 Croatian Serbs to flee. Most of their houses were burnt down and to this day they have still not returned.

After this, peace talks ended the war, and Yugoslavia was no more, all its former states except for Serbia now under NATO sphere of influence. To this day all of the former states, except for Slovenia, are poorer than they were before the war.

All sides committed horrible atrocities, of which Serbs the most, but only the Serbs got convicted.Tens of Serbian officers have been charged to a life in prison, while Bosnian rebel leader Naser Oric and Croatian general Ante Gotovina, who was sentenced to 30 years, but was released due to lack of evidence, still walk around freely.

I'm going to Siem Reap, Cambodia. Should I book tourist activities before I go or when I get there.?

We have a lower medium type budget. Also, is it worth the extra money to hire an English speaking tour guide? What are the average tipping prices there? Can you bargain with tourist services. My husband is Chinese and he isn't used to paying for things at the same American tourist rate.

Yoshua Bengio: What is the most exciting machine learning research paper you read in 2015?

No single paper stands out, and I realize talking to people that different researchers are impressed by different contributions, so the choice of the advances below is very subjective:

* the Batch Normalization paper is exciting because of the impact it already had in training numerous architectures, and it has been adopted as a standard

* the Ladder Networks paper is exciting because it is bringing back unsupervised learning ideas (here some particularly interesting stack of denoising autoencoders) into the competition with straight supervised learning, especially in a semi-supervised context

* this year's papers on generative adversarial networks (GAN), the LAPGAN and DCGAN, have really raised the bar on generative modelling of images in impressive ways, suddenly making this approach the leader and contributing to the spirit of rapid progress in unsupervised learning over the last year; they compete with another big advance in deep generative modelling based on variational autoencoders, including the very impressive DRAW paper from early last year.

* the papers that use content-based attention mechanisms have been numerous over the past year; I saw it start with our neural machine translation with attention, followed by the neural Turing machine (and later the end-to-end memory networks), and many exciting uses of this type of processing for things like caption generation and manipulating data structures (I liked in particular the Pointer Networks and the other papers on differentiable data structure operations with stacks, queues, Teaching Machines to Read and Comprehend, etc.). So this architectural device is here to stay...

Was Volkswagen actually the brainchild of Adolf Hitler, or is that a modern myth?

That's actually true. He wanted a car produced that had 4 seats, could hold a traveling speed of 100 km/h, was economical in its fuel needs and should cost no more than 1000 Reichsmark. Since the existing car companies did not think that this could be done, he tasked Ferdinand Porsche to design such a car and the Deutsche Arbeiterfront (German Workers Front) to build a factory to produce the car.

The result was the KdF-Wagen (KdF="Kraft durch Freude"="Power through joy"), a predecessor of the Volkswagen Beetle.
Fun fact: Wolfsburg, the city the Volkswagen company has its headquarters in, did not exist at that time. It developed around the new car factory and was first called "Stadt des Kdf-Wagens nahe Fallersleben" (City of the KdF-Wagen near Fallersleben).
There were plans to rename the city to Adolf-Hitler-Stadt (Adolf Hitler City), but this did not take place due to WW II. After the war the city was renamed to the name of a medieval castle nearby, called Wolfsburg (Wolf's Stronghold).

What is it like to work for the United Nations?

First of all, it was quite an honor. I was very young and had recently gotten out of the US Army and no US government agency wanted to hire me untiil after they'd seen that I'd qualified myself by getting hired at the UN first. Then the offers came but I rejected them because I was already at the UN. =)

Seriously, the vote of confidence I got from the premier international organization after learning German and Russian in the US armed forces was much better than the vote of zero confidence I got from US government agencies after having applied to them as well (they hadn't sent rejection letters; they just hadn't bothered to show interest).

The UN give a morning aptitude exam near the Manhattan compound to all those aspiring to work there. Rather than try to commute to midtown from my parents place in the suburbs (Rockland County), I arrived the day before the exam (which was given at least once a week) and stayed at a really cheap run-down hotel in Hell's Kitchen...before the rejuvenation of that area. I was determined to try to make it on my own and had refused to let my parents pay for a decent hotel. I still remember the dried blood on the hotel room walls that had been sprayed by heroin addicts; this signified the financial low point of my life in the moments before I took that UN exam.

I believe the results of the exam were immediate (my memory may have forgotten if there was an extra day's wait) and I went to the main recruiting office to formally present myself for a job with the test results in my hand.

Waiting for the job interview, I remember sitting with a recent American citizen graduate of John Hopkins who had majored in International Relations, undergrad or grad, I forget. As we talked, it was clear that he felt himself to be far more qualified than I was because he had such a low opinion of those who would serve in the US military. To him, it didn't matter that the Army had taught me Russian and German, fluently and that I'd served all over Europe and been all over the US and Hawaii. He assumed he was from a higher socio-economic class (even though I also had an undergraduate degree) and that he would get any job that was currently open.

He went into his interview first. When he came out 15 minutes later, he was ashen-faced and mortified. He had studied so many years at John Hopkins only to be told to go jump in the lake by the interviewer. He looked at me and said "Listen, if I couldn't get in, you might as well not even bother interviewing. There are no jobs available". Then he limped out as if his life were over.

That spooked me. When I heard my name called for my interview, I walked into the office, handed over my papers and said to the woman "I just heard from the John Hopkins grad that there are no jobs available, but I want you to know that, with my languages and military background, I'm highlly qualified to be a guard at the gates and will gladly accept $2K per month to be one."

She looked at me and laughed. She said "You mean that arrogant little fool that thought he was God's gift to the UN?" Of course there are jobs open. We just tell people whom we don't like that there aren't any."

Then she said "You've got the highest aptitude score I've ever seen. Now you could work as one of our brave and honored guards but I was thinking you might like a choice position that just opened as the archives manager for the Security Council Division on the 35th Floor of the Secretariat [ which of course is the tall building that symbolizes the organization at the corner of 1st Avenue and 42nd Street]. Let me make a phone call. Hold on." She then made a call and spoke in French to a woman who said I should come right over to be interviewed. I went over to the Secretariat and took an elevator to the 35th floor. The interview there went extremely well and my about-to-be-new-boss made a quick call to the Russian deputy to the Undersecretary General of that department. He was busy and said he trusted her opinion of the new potential hire and so I was hired. In retrospect, if this man had interviewed me and understood I'd just served with the US Army, he'd probably have said no out of fear that I was a CIA plant, which in fact I was not. The CIA hadn't been competent enough to even keep an eye on people getting out of the Army with skills they might want to exploit.

As it happened, I got along extremely well with all my Russian colleagues at the UN and they were glad, in retrospect, that I'd been hired even though the initial reaction on the 35th floor to having an ex-US miltary colleague was that of shock and acute discomfort (because they basically ran the 35th floor). I made good friendships with them and with political appointees from some very interesting countries and every moment at the Secretariat was fascinating.

Work started at 09:00 and ended at 17:00 for almost everyone at the Secretariat. The food and company in the cafeteria was fantastic at lunch-time and the place was packed. The view was of the East River right outside the glass wall and I remember the big neon Pepsi sign on the building in Queens across the river. It was used when filming "The Highlander".

Even better food was to be had when a top official invited me to eat in the ambassadorial dining room on an upper floor. That was posh.

The main cafeteria was open until 19:00 but 99.9% of UN employees refused to not go home when the bell rang at 17:00. There was never anyone to eat with in the vast dark cafeteria in the evenings. I never understood this because the food was great and low-cost. Why not eat before going home after work?

When the book "The Satanic Verses" was under attack at the UN, I played a not-insignificant role by accident. Just about every ambassador who was asked by their home government to condemn the book, was not allowed to read it himself. They all knew that their speeches were going to appear "uninformed". But, through the grapevine, a number of them learned that I had bought the book for myself at lunchtime the day before in a store on Second Avenue and that I had read the entire book overnight. So I had a parade of ambassadors coming to my office one afternoon (one after another) where we stood behind the filing cabinets and I pointed out the passages that I believed were rather controversial. They composed their speeches around my opinion of what was shocking.

Ironically, while I'm really into free speech, I'm proud that I was able to contribute to an informed discussion of the matter. Those speeches were accurate as to what Salmon Rushdie had written.

I also got on television receiving letters from protestors outside the buiding.

Sometimes in the late afternoon I'd be invited to parties being hosted by various embassies. The most interesting of these was that of Saddam Hussein's Iraq. While socializing, I witnessed an American who was obviously with the CIA who kept passing his business card to Iraqi embassy staff members. Following him was an eagle eyed Iraqi secret service member who made sure he re-collected every last card that had been given out. You could cut the tension with a knife there. I still had fun. I was there for the food.

I organized a big Christmas party that was canceled at the last second because of a plane crash. When UN employees are killed, everyone feels it. =(

By the way, the average UN secretariat employee was a woman from the Philippines because they were considered the least ideologically oriented and, thus, the most likely to be loyal to the UN itself.  

Now here's the kicker: The biggest perquisite for working at the UN was that I got invited to black tie balls on Park Avenue by people who were not related to the UN but respected people like me who worked there, regardless of their politcal opinion on whether taxpayer money was being wasted there. I'd be the first to admit that there were a lot of slackers sleeping on the job at the Secretariat. It still carried a ton of cachet to have a job there. The party invitations never stopped.

If my goal was to marry an heiress and be rich without having to work the rest of my life, I could have easily pulled that off in the year I was at the UN, because of all the cocktail parties and black tie parties. I could have quit the UN to be a Park Avenue house-husband or manage a wife's money.

But, one year later, I accepted a scholarship to take an MBA at the University of Toronto. I've been in business since then.

Part of the decision to leave the UN was that there was no real career path upwards because the top jobs, the boss spots such as ambassador or undersecretary, were all given by governments to political appointees assigned to the UN. If I want to be the US Ambassador to the UN, I will have to be personal friends with a future US President (which is entirely possible despite my reluctance so far to publicly discuss any political views in writing).

How to learn Machine Learning as a medical student?

It really depends on your background and how much mathematics can you understand. I will give a list of steps that you need to do to understand machine learning. Any comments are welcome to improve my answer as I am not the best machine learning scientist out there so far and I will improve my answer in the future. Please read the disclaimer in the end.

I assume that you have a basic understanding of mathematics to a college level*. I am also going to focus on the most basic things that you need to know; otherwise the background material might be overwhelming for you. I believe that learning comes from the experience, therefore you need to start with machine learning applications as soon as possible and learn the mathematics that you do not have studies on the first pass later.

First you need the mathematical background and you need to study at least the basics from the following topics.

Linear algebra.

• You need to understand matrices and vectors, inverse matrices and matrix derivatives (see number 2).
• You can study this topic from various sources and it is fairly easy. I have seen the following referenced:

1. Linear algebra
2. Linear Algebra Done Right, Sheldon Axler
3. The Matrix Cookbook

Calculus (single- and multi-variable calculus).

• The most important topic from calculus is the derivative and the way to find the maximum (or the minimum) of a function. This is because machine learning defines a functions and tries to go to its maximum (or minimum - depending on the problem) by using its derivatives. You should also understand integrals but you need only to have an idea of what an integral is at first and you can study more if you need it later (you need integrals for probability distributions). You do not care about the more theoretical concepts here (as if the function is continuous, etc.) so focus mostly on derivatives and optimization (e.g. finding the max or min) if there is available material on that.
• Can't give you a reference here because I have only studied from textbooks written in my native language. Maybe Thomas' Calculus ?

Probability and statistics.

• This is the most important requirement that you need to understand. Statistics is the basis of machine learning and this field is huge so don't get lost here. The concept of the probability and that of the uncertainty are the most important and you need to study to a point where you can understand probability distribution functions such as the Normal distribution , the Bernoulli distribution , etc.
• Many excellent books here from where you can learn probability and statistics. Any of the following will help you to understand the topic really good:

1. Introduction to Probability, Bertsekas and Tsiklis
2. Probability Theory: The Logic Of Science, Jaynes
3. Introduction to Probability and Statistics from a Bayesian Viewpoint, Part 1, Probability, Lindley
4. Other Probability on-line free courses (such as Introduction to Probability - The Science of Uncertainty ) and textbooks might be good as well

• Remember that if you find some topics hard enough you can skip them and come back later.

I am proposing a way to get you started. As you try to deal with more complex topics and ideas you might need to go back and study more that's the process of learning. At this point you do not need to focus on optimization methods as this will be overwhelming. If you want to study later then the Convex Optimization, Boyd and Vandenberghe is the way to go here. But you can start with basic machine learning text books and then find what you need to study next by yourself or by asking other people who know.

Second, the best sources to study machine learning (this is not an extensive list, many other excellent books are missing).

Machine learning.

• Many great text books out there and I am only going to focus on those that provide a mathematical way to present thing and not on the cookbooks.

1. The Stanford's Machine Learning  course is one of the best courses out there and the material taught in the class is freely available in the course's website. Check out the lecture notes (exceptionally good) and the Lecture videos from Andrew Ng.
2. Information Theory, Inference, and Learning Algorithms, David MacKey , a free online textbook which provides many different ways that you can study it from page iv and on.
3. Machine learning textbook, Kevin Murphy is the book that I am currently studying. It is excellent so far and most figure (maybe all?) have the accompanying MATLAB source code that you can download. I would recommend it to everyone.
4. Christopher M. Bishop | PRML I have heard that it is a bit more of an advanced book and it will be my next stop after I finish the two previous books.

Machine learning applications

• There are many tools out there and libraries/frameworks which you can use to do your job and you need to get familiar with those because they provide a good interface to the algorithms use.

1. Python Data Analysis Library
2. scikit-learn: machine learning in Python
3. R for Machine Learning  
4. And many more.....

*Different educational systems in different countries have different requirements so my answer tries to be as general as it can be.

Disclaimer: There are many different sources to learn the material you need. There are also many other GREAT books that I am not aware off yet. Please search other questions and answers and also visit a library to take a look at those books as they might not fit your needs. This is just a guideline on what you need to study and not from where to study it.