Showing posts with label TV's. Show all posts
Showing posts with label TV's. Show all posts

Friday, May 16, 2008

How to Escape From a Black Hole

Written by Nancy Atkinson

According to Einstein's theory of general relativity, black holes are regions of space where gravity is so strong that not even light can escape. And in the 1970's physicist Stephen Hawking asserted that any information sucked inside a black hole would be permanently lost. But now, researchers at Penn State have shown that information can be recovered from black holes.

A fundamental part of quantum physics is that information cannot be lost, so Hawking's claim has been debated. His idea was generally accepted by physicists until the late 1990s, when many began to doubt the assertion. Even Hawking himself renounced the idea in 2004. Yet no one, until now, has been able to provide a plausible mechanism for how information might escape from a black hole. A team of physicists led by Abhay Ashtekar, say their findings expand space-time beyond its assumed size, providing room for information to reappear.

Ashtekar used an analogy from Alice in Wonderland: "When the Cheshire cat disappears, his grin remains," he said. "We used to think it was the same way with black holes. Hawking's analysis suggested that at the end of a black hole's life, even after it has completely evaporated away, a singularity, or a final edge to space-time, is left behind, and this singularity serves as a sink for unrecoverable information."

But the Penn State team suggest that singularities do not exist in the real world. "Information only appears to be lost because we have been looking at a restricted part of the true quantum-mechanical space-time," said Ashtekar. "Once you consider quantum gravity, then space-time becomes much larger and there is room for information to reappear in the distant future on the other side of what was first thought to be the end of space-time."

According to Ashtekar, space-time is not a continuum as physicists once believed. Instead, it is made up of individual building blocks, just as a piece of fabric, though it appears to be continuous, is made up of individual threads. "Once we realized that the notion of space-time as a continuum is only an approximation of reality, it became clear to us that singularities are merely artifacts of our insistence that space-time should be described as a continuum."

To conduct their studies, the team used a two-dimensional model of black holes to investigate the quantum nature of real black holes, which exist in four dimensions. That's because two-dimensional systems are simpler to study mathematically. But because of the close similarities between two-dimensional black holes and spherical four-dimensional black holes, the team believes that this approach is a general mechanism that can be applied in four dimensions. The group now is pursuing methods for directly studying four-dimensional black holes.

Monday, January 28, 2008

Flat Panel TV's

Flat Panel Displays (FPD) in electronic products such as televisions and computer monitors have quickly grown in popularity. The most common FPDs are liquid crystal displays (LCD) and plasma displays. By 2008, devices that contain FPDs are projected to account for nearly 85 percent of the total U.S. demand for electronic products. By 2013, the demand is predicted to reach 94 percent.

While relatively few FPD devices have entered the waste stream so far, they represent a potentially large volume of material that will be recycled or discarded in the future. Because of this, we need to fully evaluate how to manage these materials and determine if there are any potential risks associated with the end-of-life handling of these products.

Taking a proactive approach to this issue, the King County Solid Waste Division in Washington State has conducted the first known comprehensive review of information regarding the end-of-life management issues associated with FPDs. The goal was to identify and quantify potential chemicals of concern, evaluate hazards associated with these chemicals and assess potential risks from recycling electronic products containing FPDs. The results are reported in “Flat Panel Displays: End of Life Management Report,” which was published earlier this year. The report serves as a resource for a broad group of players — from local governments to e-waste processors — who are determining how to manage products that contain FPDs.

The report includes available information on the various chemicals used in FPD devices. Researchers found a considerable amount of data about the use and toxicity of chemicals of potential concern, including heavy metals like lead, mercury, cadmium and chromium, as well as brominated flame-retardants. Some uncertainty remains, however, about the full spectrum of potentially hazardous FPD constituents and the toxicity of some components, such as liquid crystals. Moreover, no studies have specifically addressed the potential exposure risks to recycling workers and communities near electronics recycling facilities.

LCDs are the dominant technology used in FPD devices. An LCD is made up of a number of pixels arrayed in front of a light source or reflector. Approximately 300 different liquid crystal compounds are available for use in LCDs. Depending on its specific performance attributes, a typical LCD can contain as many as 25 different liquid crystal substances.

Manufacturers of liquid crystals have run several batteries of toxicity tests of individual liquid crystals and a variety of mixtures. Findings to date suggest low acute toxicity, minimal skin/eye irritant effects, low potential for cancer effects based largely on mutagenicity tests, as well as low bioaccumulation potential and aquatic toxicity. For proprietary reasons, much of the supporting scientific data behind these conclusions were not available for review but reportedly meet or exceed European Union and Japanese criteria for hazardous material production and handling.
While available data suggest a low potential for harmful effects, testing regimens are based on the premise that long-term exposure to large quantities of liquid crystals is not likely. As a result, no chronic animal studies have been conducted that look at cancer and other effects following prolonged exposure to liquid crystals. Data on the potential for liquid crystal release during end-of-life management of LCDs also is absent.

The U.S. Environmental Protection Agency (EPA) has evaluated the potential hazards and risks associated with the release of liquid crystals as part of the Toxic Substances Control Act (TSCA) New Chemicals Program. For several years, companies have been required to submit “premanufacturing notices” to the agency. Based on these reviews, EPA has concluded that there is not an unreasonable risk associated with the manufacture, processing and use of this large class of chemicals. However, this determination is based on theoretical modeling studies, not actual toxicity data. In addition, TSCA doesn't typically require a New Chemical Program review for chemicals that are contained within imported “articles.” Therefore, liquid crystals employed in an imported manufactured item — such as a panel or complete display unit — may not be reviewed by EPA under TSCA. King County's report therefore recommends further evaluation of liquid crystals before a definitive conclusion is drawn regarding potential risks associated with the end-of-life management of liquid crystal compounds.

Researchers also conducted interviews with selected recycling facilities regarding their operating procedures, seeking to gather information on the primary processes currently used to recycle FPD devices. Researchers found many different processing procedures and a wide range of standards for workers' protective gear. The report identifies a need for industry guidance for recycling FPD devices. Researchers found the most probable sources for exposures and releases to the environment were from e-waste dismantling and from activities at recycling facilities such as manual disassembly, shredding, grinding, burning and melting (to reclaim plastics), solder melting and metals processing. More information is needed to develop appropriate risk management guidance.

The report also found that the few state and federal regulations and guidelines addressing end-of-life management of electronic products have limitations or do not address the recycling of specific components.

Where Do We Go from Here?

King County sees this report as an opportunity to further the conversation about the proper management and recycling of devices that contain flat panel displays. This report is a starting place for building a combined industry effort to learn more about the substances contained in flat panel displays and best practices for managing these materials. Ultimately, proper management approaches should protect workers, surrounding communities and the environment.

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