Archive for December 12th, 2010

December 12, 2010

Duelling Dipoles: In Search of a New Theory of Photosynthetic Energy Transfer

Chemists of Ludwig-Maximilians-Universität (LMU) in Munich have refuted a basic postulate of Förster theory, which describes energy transfers between pigment molecules, such as those that underlie photosynthesis. A revised version of the theory could have an impact on the design of optical computers and improve the efficiency of solar cells.
Photosynthesis, the formation of energy-rich chemical compounds with the aid of sunlight, is fundamental to life on Earth. In plants, sunlight is collected by so-called antennal complexes, consisting of proteins bound to the green pigment chlorophyll. The chlorophyll captures the light energy and relays it, virtually without loss, via several intermediate molecules, to the reaction centers, where it is converted into stable forms of chemical energy.

The intermolecular transfer process is described by Förster theory. This postulates that pigments act as oscillating dipoles to electrically excite adjacent molecules, in much the same way as the elements of a dipole antenna pick up and feed radio signals to a receiver. Measurements carried out in the laboratory of LMU chemist Professor Heinz Langhals, in collaboration with the Department of Physics at LMU Munich, have now refuted this model.
“Energy transfer between dipoles depends on their orientation,” says Langhals. “When dipoles are orthogonally disposed, no energy transfer should occur. We have now tested this assumption experimentally and, to our surprise, we found that energy is rapidly and very efficiently transferred under these conditions.” In collaboration with international partners, the LMU team now wants to establish a firm experimental basis for the formulation of a new theory of energy transfer. This may well have repercussions for the development of optical computers and might help to enhance the performance of solar cells.

Chlorophylls and other pigment molecules, often in association with specialized proteins, can form complexes which act as efficient antennas that collect light energy and pass it on to the photosynthetic reaction centers or to the conducting layer of a solar cell. The energy is captured and transiently stored in the bonds between specific groups of atoms in the pigments, which are therefore referred to as chromophores. Different chromophores absorb light of different wavelengths, so a complex containing various types can harvest light over a large segment of the spectrum. Indeed, the original goal of the LMU researchers led by Langhals was to synthesize such a broadband light collector.

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December 12, 2010

‘Logic Gates’ Made to Program Bacteria as Computers

A team of UCSF researchers has engineered E. coli with the key molecular circuitry that will enable genetic engineers to program cells to communicate and perform computations.The work builds into cells the same logic gates found in electronic computers and creates a method to create circuits by “rewiring” communications between cells. This system can be harnessed to turn cells into miniature computers, according to findings reported in the journal Nature.That, in turn, will enable cells to be programmed with more intricate functions for a variety of purposes, including agriculture and the production of pharmaceuticals, materials and industrial chemicals, according to Christopher A. Voigt, PhD, a synthetic biologist and associate professor in the UCSF School of Pharmacy’s Department of Pharmaceutical Chemistry who is senior author of the paper.

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December 12, 2010

Computer-Based Program May Help Relieve Some ADHD Symptoms in Children

An intensive, five-week working memory training program shows promise in relieving some of the symptoms of attention deficit hyperactivity disorder in children, a new study suggests.Researchers found significant changes for students who completed the program in areas such as attention, ADHD symptoms, planning and organization, initiating tasks, and working memory.
“This program really seemed to make a difference for many of the children with ADHD,” said Steven Beck, co-author of the study an associate professor of psychology at Ohio State University.
“It is not going to replace medication, but it could be a useful complementary therapy.”
December 12, 2010


DeTraS provides several tools to track development activities by registering applications that developers use on an X11 session. It also allows you to send collected data to a server and takes care about your privacy. The idea behind DeTraS is taken from Timeline, a shell script written by Nat Friedman.


December 12, 2010

Web Surfing History Is Accessible (Without Your Permission) Via JavaScript

The Web surfing history saved in your Web browser can be accessed without your permission. JavaScript code deployed by real websites and online advertising providers use browser vulnerabilities to determine which sites you have and have not visited, according to new research from computer scientists at the University of California, San Diego.
“JavaScript is a great thing, it allows things like Gmail and Google Maps and a whole bunch of Web 2.0 applications; but it also opens up a lot of security vulnerabilities. We want to let the broad public know that history sniffing is possible, it actually happens out there, and that there are a lot of people vulnerable to this attack,” said UC San Diego computer science professor Sorin Lerner.

The researchers documented JavaScript code secretly collecting browsing histories of Web users through “history sniffing” and sending that information across the network. While history sniffing and its potential implications for privacy violation have been discussed and demonstrated, the new work provides the first empirical analysis of history sniffing on the real Web.

“Nobody knew if anyone on the Internet was using history sniffing to get at users’ private browsing history. What we were able to show is that the answer is yes,” said UC San Diego computer science professor Hovav Shacham.

The computer scientists from the UC San Diego Jacobs School of Engineering presented this work in October at the 2010 ACM Conference on Computer and Communications Security (CCS 2010) in a paper entitled, “An Empirical Study of Privacy-Violating Information Flows in JavaScript Web Applications.”
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December 12, 2010

Air Defense: Greedy Algorithms Best for Multiple Targets

Thanks Science Daily for this nice information.
What algorithms should an air defense system work with? Particle swarm algorithms if there are ten targets to be hit. If there are more than ten targets, greedy algorithms work best. These findings are presented by researcher Fredrik Johansson at the Informatics Research Centre, University of Skövde, in Sweden.
So-called TEWA systems (Threat Evaluation & Weapon Allocation) are used to protect strategic targets from enemy attacks, such as an airfield that needs to be protected from incoming missiles.The systems discover threats, evaluates the threats, and aims the defender’s weapons system to be able to knock out the threat. The final decision to fire is then made by an operator.
Researcher Fredrik Johansson at the Informatics Research Centre, University of Skövde, in Sweden, recently defended his doctoral thesis on algorithms for TEWA systems.
“In the existing research literature there are proposals regarding what algorithms may be appropriate to use in TEWA systems. I have developed methods to test which algorithms work best in practice,” explains Fredrik Johansson.
Fredrik Johansson’s study shows that what determines the choice of algorithm is the number of weapons in the TEWA system and the number of targets the system has to deal with. “So-called particle swarm algorithms are effective if it’s a matter of up to about ten targets and ten weapons. If the TEWA system needs to keep track of more targets and weapons, we should use what are called greedy algorithms instead,” says Fredrik Johansson.
A greedy algorithm — simply put — is fast but not perfect. The algorithm works under broad guidelines and does not test all the alternatives necessary to obtain an optimal solution. The fact that it doesn’t need to test certain solutions makes it a rapid algorithm, a property that is crucial in a TEWA system.
“You can’t let it take many seconds between the system discovering a threat and the operator deciding whether or not to fire,” says Fredrik Johansson.
In previous studies TEWA systems have nearly always been treated as two parts: threat evaluation and weapon allocation separately. Fredrik Johansson’s study is one of the first to see the system as a unit. But to claim that you are the first to study something may be difficult when it comes to TEWA systems.
“Those conducting research in this field don’t always know what knowledge there is beneath the surface. There’s probably some research about TEWA systems that is secret and not available to us ordinary researchers,” concludes Fredrik Johansson.

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