#六度分割#说你最多通过6人就能认识世界上任一陌生人。而巴拉巴西教授的复杂网络进阶版：任一网页最多需要经过19次点击，就可以与任意的另一个网页相连。人们相信产品购买建议的概率：自己好友或小圈子 = 3~4倍 x 没交往的博主专家或微博大V。所以微信导向比微博有效！周六日一广深京Webplus.com沙龙见
Six Degrees of Separation can help cure Cancer?
The documentary film, Connected: The Power of Six Degrees offers a very powerful explanation of why natural systems tend to organize themselves into networks. It gives both mathematical and practical insights into a variety of physical and biological phenomena, from pandemics, to terrorist attacks, to financial breakdowns and spread of diseases. The bottom line is that you are separated from me by only six handshakes. Thus if you know Bob, Bob knows Kevin, Kevin knows Raj, Raj knows Sarah and Sarah knows me, then theoretically, you are connected to me by exactly six degrees. And thus, as a bioengineering researcher, i was quite intrigued by the implications that this simple theory can have on curing some of the most dreadful diseases like cancer.So, i had a look at this BBC documentary movie.Very eye-opening indeed.
"Imagine if we try to understand traffic in a city without having any map, without having any idea of how interconnected the different roads are. Analogies are never perfect but its one way that i can imagine how things occur in the cell." explains Marc Vidal, a geneticist at Harvard Medical School.
Cells contain thousands of little proteins that interact with each other, constantly on the move and communicating with one another just like people communicating with each other in a city. If you start with a protein and start analyzing its interaction behavior with another protein, you come to the wonderful concept of six degrees of separation "Who is connected to whom?". Vidal believes that if he could produce a map of the inter connectivity between genes, then he can probably locate the breakdowns in the system that cause diseases like cancer.
But all of these started with two individuals, named Steven Strogatz, currently the Jacob Gould Schurman Professor of Applied Mathematics at Cornell University, and Duncan Watts, currently the principle researcher at Yahoo Research, and then a PhD student under Strogatz at Cornell. Together they explained such synchronization phenomenon as observed in nature, like how the snowy tree crickets chirp and fireflies flash lights in unison. That actually let them to think about patterns of connections or the six degrees of separation concept in a network. And thus guys like them and others including Albert-László Barabási (UNotre Dame/Northeastern/Harvard) and Alessandro Vespignani at Indiana University, started looking into the man-made and natural networks including the U.S. electric power grid, the Internet, and even the nervous system of worms.Here is the Steven Strogatz's video from the TED where he shows how flocks of creatures (like birds, fireflies and fish) manage to synchronize and act as a unit -- when no one's giving orders. The powerful tendency extends into the realm of objects, too.
Nevertheless it was Hollywood, that actually offered them a pathway to test their ideas. More than a million actors have worked in Hollywood in half a million films. And it is an enormous network of connections. In the mid 90's a computer science student at the University of Virginia, Brett Tjaden designed a game called The Oracle of Bacon after Kevin Bacon, to connect actors or actresses to Kevin Bacon in the smallest number of links possible. It turned Kevin Bacon into a cult figure and became the major inspiration for a breakthrough. And the Hollywood network too conformed precisely to the theory. A few random links shrunk the distance between a million actors. Nevertheless it was until Albert-László Barabási, the former Emil T. Hofmann professor at the University of Notre Dame and current Distinguished Professor and Director of Northeastern University's Center for Complex Network Research (CCNR) and an associate member of the Center of Cancer Systems Biology (CCSB) at the Dana Farber Cancer Institute, Harvard University who actually made the major breakthrough.
Barabási published a seminal paper in Nature in 2000 titled Error and attach tolerance of complex networks that demonstrated that error tolerance is not shared by all redundant systems: it is displayed only by a class of inhomogeneously wired networks, called scale-free networks, which include the World-Wide Web, the Internet, social networks and cells. That such networks display an unexpected degree of robustness, the ability of their nodes to communicate being unaffected even by unrealistically high failure rates. Or, in layman terms, naturally occurring networks self organize into a hub-based network. In a hub based network, a few nodes will have many connections while the majority of nodes will have only a few links. Hub based networks have a high degree of inter connectivity, especially near the hub nodes. This contributes to the small world effect (this term comes from the feeling that it is a small world when we meet someone new who knows another person we know).
The conventional theory states than most of the characteristic fall into a "bell curve", for example, height and weight of animals, grades in your college exams etc. Since so many characteristics fall into a bell curve, it might be naively expected that the distribution of links in a naturally occurring network follow this pattern as well. But that's not the case. The distribution of links in a variety of networks follows a power law. And Barabási came up with his seminal equation P(k)~k^(-gamma).
The Human Disease Network (Barabási and Vidal et al., 2007, Nature, 25:1119-1126)
It was this work that Marc Vidal stumbled upon for applying the similar model to explain diseases. And Vidal with Barabási published a seminal paper in Nature in 2007, where they developed a bipartite graph (see the figure above) composed of US Food and Drug Administration–approved drugs and proteins linked by drug–target binary associations. This can have amazing implications in drug discovery and research.
A decade on, Kevin Bacon has decided that he might as well accept his cult status. And now he has put the power of social networking to good use by launching a charity website named Sixdegrees.org, through which you can support favorite charities by donating or creating fund raising badges.
Sometime back TVNZ explained the secret behind NZ's degrees of separation along with Mike Steele from the University of Canterbury. The bottom line is that strangers in New Zealand are parted by only two degrees of separation.
After all, Six degrees in not an urban myth.
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