Berkeley Lab Sheds Light on Improving Solar Cell Efficiency

Typical manufacturing methods produce solar cells with an efficiency of 12-15%; and 14% efficiency is the bare minimum for achieving a profit. In work performed at the Ernest Orlando Lawrence Berkeley National Laboratory (Berkeley, CA, 5 10-486-577 1)--a US Department of Energy national laboratory that conducts unclassified scientific research and is managed by the University of California--scientist Scott McHugo has obtained keen insights into the impaired performance of solar cells manufactured from polycrystalline silicon. The solar cell market is potentially vast, according to Berkeley Lab. Lightweight solar panels are highly beneficial for providing electrical power to remote locations in developing nations, since there is no need to build transmission lines or truck-in generator fuel. Moreover, industrial nations confronted with diminishing resources have active programs aimed at producing improved, less expensive solar cells. 'In a solar cell, there is a junction between p-type silicon and an n-type layer, such as diffused-in phosphorous', explained McHugo, who is now with Berkeley Lab's Accelerator and Fusion Research Division. 'When sunlight is absorbed, it frees electrons, which start migrating in a random-walk fashion toward that junction. If the electrons make it to the junction; they contribute to the cell's output of electric current. Often, however, before they reach the junction, they recombine at specific sites in the crystal' (and, therefore, cannot contribute to current output). McHugo scrutinized a map of a silicon wafer in which sites of high recombination appeared as dark regions. Previously, researchers had shown that such phenomena occurred not primarily at grain boundaries in the polycrystalline material, as might be expected, but more often at dislocations in the crystal. However, the dislocations themselves were not the problem. Using a unique heat treatment technique, McHugo performed electrical measurements to investigate the material at the dislocations. He was purportedly the first to show that they were 'decorated' with iron

Hunting the Scalar Glueball: Prospects for BES III

The search for the ground state scalar glueball G_0 is reviewed. Spin zero glueballs will have unique dynamical properties if the amplitude is suppressed by chiral symmetry, as it is to all orders in perturbation theory: for instance, mixing of G_0 with \bar qq mesons would be suppressed, radiative J/psi decay would be a filter for new physics in the spin zero channel, and the decay G_0 \to \bar KK could be enhanced relative to G_0 \to \pi \pi. These properties are consistent with the identification of f_0(1710) as the largely unmixed ground state scalar glueball, while recent BES data implies that f_0(1500) does not contain the dominant glueball admixture. Three hypotheses are discussed: that G_0 is 1) predominantly f_0(1500) or 2) predominantly f_0(1710) or 3) is strongly mixed between f_0(1500) and f_0(1710).Comment: 10 pages, talk presented at CHARM 2006, Beijing IHEP, June 5-7, 2006, to be published in the proceeding

Guidelines to improve airport preparedness against chemical and biological terrorism.

Guidelines to Improve Airport Preparedness Against Chemical and Biological Terrorism is a 100-page document that makes concrete recommendations on improving security and assessing vulnerable areas and helps its readers understand the nature of chemical and biological attacks. The report has been turned over to Airports Council International (ACI) and the American Association of Airport Executives (AAAE), two organizations that together represent the interests of thousands of airport personnel and facilities in the U.S. and around the world

The Role of Chinese Cities in Greenhouse Gas Emission Reduction

Currently, 3.9 billion people live in cities, representing 54% of the world’s population.1 Cities, as hubs of fossil fuel-based economic activity, emit over 70% of global energy-related greenhouse gas (GHG) emissions. The world’s 50 largest cities are collectively the third largest emitter of energy-related GHGs, after China and the U.S.2 In many North American cities, transportation accounts for the largest share of emissions, while industry and buildings are major sources in many Asian cities. The rate of urbanization is accelerating in the world\u27s most populous countries, with associated rapid and high-volume production of energy- and carbon-intensive building materials to construct urban infrastructure. Impacts of climate change are already being experienced in cities, from severe storms damaging infrastructure, to droughts and floods, intensified heat waves, worsening smog, and other ecological and human health impacts.3 Nearly 80 million Chinese city dwellers live in coastal zones at risk for sea-level rise, compared to 30 million in India and 20 million in the U.S.4 Both as drivers of climate change and sites vulnerable to climate impacts, cities are at the forefront of pursuing energy-efficient and low carbon development