Monthly Archives: July 2009

Efficient Nanopillar Solar Cells….and Cheap Too…..!!

Nanopillar Solar CellResearchers at the University of California, Berkeley, have made a new kind of solar cell by growing an array of upright nanoscale pillars on aluminum foil. They make bendable solar cells by encapsulating the entire cell inside a transparent, rubbery polymer. The design, the researchers suggest, could lead to solar cells that cost less than conventional silicon photovoltaics.

The nanopillars allow the researchers to use cheaper, lower-quality materials than those used in conventional silicon and thin-film technologies.

So the cost would decrease 10 folds when it will be made on a big scale.

The solar cells are made of uniform 500-nanometer-high pillars of cadmium sulfide embedded in a thin film of cadmium telluride. Both materials are semiconductors used in thin-film solar cells.

In an online Nature Materials paper, it was shown that the cells have an efficiency of about 6 percent in transforming sunlight into electricity as compared to other nano pillars grown with expensive materials which have an efficiency of 2%.

In conventional cells, silicon absorbs light and creates free electrons, which need to get to the electrical circuit before they get trapped at defects or impurities in the material. This requires extremely pure, expensive crystalline silicon to achieve the most efficient photovoltaic devices.

The nanopillar design splits up silicon’s duties: the material surrounding the pillars absorbs light and creates electrons, and the pillars transport them to the electrical circuit. This increases efficiency in two ways. The closely packed pillars trap light between them, helping the surrounding material absorb more. The electrons also have a very short distance to travel through the pillars, so there are fewer chances of their getting trapped at defects. That means you can use low-quality, less expensive materials.

The researchers also intend to try other semiconductor materials for the pillars and surrounding material. The fabrication process is compatible with a wide range of semiconductors, and other combinations could increase the efficiency.

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Firefox 3.5 Launched..What Next…!? Firefox Aims to Unplug Scripting Attacks

The latest version of Firefox(3.5) is here with so many features……namely User Experience, Performance, Security, Customization…..!!

Still there is so much Firefox is looking ahead to……..Here is the most significant one which is up the sleeve…..

The matter of concern is how websites can block code from unknown sources. Here, firefox wants to Unplug Scripting Attacks.

IllustrationSites that rely on user-created content can unwittingly be employed to attack their own users via JavaScript and other common forms of Web code. This security issue, known as cross-site scripting (XSS), can, for example, allow an attacker to access a victim’s account and steal personal data.

Now the makers of the Firefox Web browser plan to adopt a strategy to help block the attacks. The technology, called Content Security Policy (CSP), will let a website’s owner specify what Internet domains are allowed to host the scripts that run on its pages.

XSS attacks have caused numerous headaches, particularly for social networks and Web 2.0 companies, allowing attackers to hijack eBay auctions, for example, and create a worm that caused MySpace users to automatically befriend a user named “Samy.” The core problem is that many sites allow untrusted users to add their own content to pages while Web browsers treat all content returned by a website as coming from the same entity. If the website is trusted, the content created by an unknown user is trusted as well. The issue has been counted as one of the 25 most serious coding problems by the SANS Institute, a training organization for system administrators and programmers.

In many cases, Web companies can hunt down and restrict dangerous user-created content. But because many sites are so big, finding and fixing all vulnerabilities is a time-consuming and difficult task. Moreover, many sites, notably social-networking ones, want to allow their users some leeway to create interesting content.

Mozilla’s CSP will break with Web browsers’ tradition of treating all scripts the same way. Instead, it will require that participating websites put their scripts in separate files and explicitly state which domains are allowed to run the scripts.

An engineer at the Mozilla Foundation, Gervase Markham, championed the idea within the Firefox team and further developed the technology, and noted Web security researcher Jeremiah Grossman publicly called for adoption of the technique. Four years later, Mozilla has committed to implementing the technology.

The new Firefox security feature could help block another form of attack, known as clickjacking, which allows an attacker to trick a user into clicking an unsafe button–for example, initiating a bank transfer when she believes that she is sending an e-mail. However, clickjacking is a problem so pervasive that an opt-in model really doesn’t work, says Hansen.

Source

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