Naučni radovi zanimljivi za siru javnost
Posted 23 March 2012 - 06:43:20
Posted 28 March 2012 - 15:19:18
Ovo je smisao zivota.
Solving Sudoku puzzles is one of the most popular pastimes in the world. Puzzles range in difficulty from easy to very challenging; the hardest puzzles tend to have the most empty cells. The current paper compares the performance of three computer algorithms in solving puzzles. Backtracking, simulated annealing, and alternating projections are generic methods for attacking combinatorial optimization problems. Our results favor backtracking. It infallibly solves Sudoku puzzles or deduces that a unique solution does not exist. However, backtracking does not scale well in high-dimensional combinatorial optimization. Hence, it is useful to expose statistics students to the other two solution techniques in a concrete setting. Simulated annealing shares a common structure with MCMC (Markov chain Monte Carlo) and enjoys wide applicability. The method of alternating projections solves the feasibility problem in convex programming. Converting a discrete optimization problem into a continuous optimization problem opens up the possibility of handling combinatorial problems of much higher dimensionality.
Posted 11 April 2012 - 09:30:46
Posted 11 April 2012 - 13:19:13
Posted 23 May 2012 - 14:18:17
ukratko, pronadjene su genetske razlike izmedju jednojajcanih blizanaca.
krenulo se od ispitivanja faktora adhd-a, i cinjenice da se jednojajcani blizanci nekad razlikuju po tome koliko su u stanju da odrzavaju paznju. do sada se smatralo da to po defaultu znaci da i okolina utice na formiranje ovog problema. ovi istrazivaci su, medjutim, nasli suptilnu razliku u genima, koja se tice broja kopija odredjenih (inace identicnih) sekvenci. a ta razlika je povezana sa prisustvom adhd-a. heh.
Posted 09 June 2012 - 19:09:55
Worse was to come, however. Levick spent the Antarctic summer of 1911-12 observing the colony of Adélies at Cape Adare, making him the only scientist to this day to have studied an entire breeding cycle there. During that time, he witnessed males having sex with other males and also with dead females, including several that had died the previous year. He also saw them sexually coerce females and chicks and occasionally kill them.
Levick blamed this "astonishing depravity" on "hooligan males" and wrote down his observations in Greek so that only an educated gentleman would understand the horrors he had witnessed. Back in Britain he produced a paper (in English), titled Natural History of the Adélie Penguin. However, the section about the animal's sexual proclivities was deemed to be so shocking it was removed to preserve decency. Levick then used this material as the basis for a separate short paper, Sexual Habits of the Adélie Penguin, which was privately circulated among a handful of experts.
In fact, Levick's observations turned out to be well ahead of their time. Scientists had to wait another 50 years before the remarkable sexual antics of the Adélie were revealed. By this time his pamphlet and its detailed records of Adélie shenanigans had been lost to science .
But now a copy of Sexual Habits of the Adélie Penguin has been unearthed, thanks to sleuthing by Douglas Russell, curator of birds at the Natural History Museum, who discovered a copy among records of the work of Scott's expeditions and has had it published in the journal Polar Record, with an accompanying analysis of Levick's work.
"The pamphlet, declined for publication with the official Scott expedition reports, commented on the frequency of sexual activity, auto-erotic behaviour, and seemingly aberrant behaviour of young unpaired males and females, including necrophilia, sexual coercion, sexual and physical abuse of chicks and homosexual behaviour," states the analysis written by Russell and colleagues William Sladen and David Ainley. "His observations were, however, accurate, valid and, with the benefit of hindsight, deserving of publication."
Levick's lost masterpiece certainly has its eye-watering moments with its descriptions of male Adélies who gather in "little hooligan bands of half a dozen or more and hang about the outskirts of the knolls, whose inhabitants they annoy by their constant acts of depravity". Injured females are mounted by members of these "gangs", others have their chicks "misused before the very eyes of its parents". Some chicks are crushed and injured, others are killed.
It is startling stuff, though Russell told the Observer that recent studies have helped understand the behaviour of these "hooligan" penguins. "Adélies gather at their colonies in October to start to breed. They have only a few weeks to do that and young adults simply have no experience of how to behave. Many respond to inappropriate cues. Hence the seeming depravity of their behaviour. For example, a dead penguin, lying with its eyes half-open, is very similar in appearance to a compliant female. The result is the so-called necrophilia that Levick witnessed and which so disgusted him."
In addition, the penguin is the most humanlike of all birds in its appearance and its behaviour is most often interpreted in anthropomorphic terms, added Russell. For this reason, Adélie behaviour, when it was observed for the first time in detail, seemed especially shocking. "Levick was also a gentleman, travelling with a group of men in very difficult circumstances, witnessing behaviour he neither expected nor understood," said Russell. "It is not surprising that he was shocked by his findings."
The discovery ofLevick's paper is important because its helps shed new knowledge on a species that has been called the bellwether of climate change. "The Adélie needs pack ice from which to dive to get fish. When that ice disappears, numbers may crash – and we will have a clear warning that things are getting bad," said Russell.
Levick's experiences with the Adélie penguins were not the only root of his suffering in the Antarctic. In February 1912, he and five other members of Scott's team were waiting to be picked up by the expedition ship, Terra Nova, but found that pack ice had blocked its route. The men had to spend an entire Antarctic winter huddled in an ice cave with no provisions and only an occasional seal or penguin to eat. "They ate blubber, cooked with blubber, had blubber lamps," recalled one expedition member. "Their clothes and gear were soaked with blubber, and the soot blackened them, their sleeping bags, cookers, walls and roof, choked their throats and inflamed their eyes."
Remarkably, the men all survived and Levick returned to England in 1913 – in time to sign up for the first world war. He served in the Grand Fleet and at Gallipoli, and after the war founded the British Schools Exploring Society in 1932, of which he was president until his death in June 1956. An obituary described him as "a truly great English gentleman".
Posted 20 June 2012 - 13:43:45
Posted 28 July 2012 - 14:49:54
spas od pipetiranjem izazvanog tendonitisa i dosadnih protokola
posebno zanimljivo je treniranje u virtuelnom okruzenju, tj. cinjenica da robot nije specijalista i moci ce da se prilagodi labovima koji rade na razlicitim organizmima/model sistemima.
edit: ironija je samo sto ce verovatno moci da ga priuste samo oni labovi koji se bave poljima za koje je ionako vec skoro sve mehanizovano
Edited by estel, 28 July 2012 - 14:54:59.
Posted 16 August 2012 - 09:27:38
Language offers a clue to countries' economic behavior.
BY JOSHUA E. KEATING | SEPT/OCT 2012
Why do Germans revere austerity and fiscal discipline, while Greeks spend like there's no tomorrow? Why can't the United States convince China to consume more and save less? Yale University economist Keith Chen thinks part of the answer may be in language -- particularly in how different languages treat time.
Languages differ in the degree to which they distinguish future events from the present. For example, in what linguists call strong future-time reference (FTR) languages like English, a speaker says, "It will rain tomorrow." In a weak-FTR language like German, one simply says "Morgen regnet es"-- literally, "Tomorrow, it rains." Mandarin Chinese has similarly weak time construction. Strong-FTR speakers have to do a little more verbal work to make it clear they're talking about the future. Chen, who grew up in a Chinese-speaking household in the United States, thinks this subtle difference actually changes the way speakers of different languages conceive of time -- which affects how people act in the present.
Extensive psychological research shows that linguistic differences actually do affect the perception of external phenomena. A 2007 study in the National Academy of Sciences journal noted that Russian speakers, who have separate words for "blue" (siniy) and "light blue" (goluboy), have a better ability to distinguish between similar shades of the color than English speakers. When it comes to gauging time, Chen's hypothesis is that weak-FTR speakers see the future as less distant and therefore engage in fewer behaviors with negative future consequences."Every time your language forces you to specify that you're talking about the future, it's a little nudge that this is something different than the present," Chen says. "It's something that you do to yourself thousands of times a day."
Weak-FTR languages include German, Mandarin, Japanese, and the Scandinavian languages, while English, Greek, Russian, and Spanish are strong-FTR. In a recent paper, Chen compared European families of similar education, income, and religion and found that speakers of weak-FTR languages on average save more for retirement, smoke less, and are less likely to be obese. "Every one of the countries that we think of as an outlier in terms of savings is also an outlier in terms of how they speak about the future," Chen says.
So it's not just that the Chinese and Northern Europeans are better at planning for the future: They're already living -- or at least speaking -- in it.
Edited by buffalo bill, 16 August 2012 - 09:28:19.