Can Photo- and Cathodoluminescence be Regarded as Complementary Techniques?

Photoluminescence (PL) usually provides macroscopic, high quality spectroscopic data. Cathodoluminescence (CL), on the other hand, offers the same information with microscopic imaging. However, replicating PL signatures in a CL system is not straightforward since matching experimental conditions, such as temperature and excitation density, is difficult. The matter is further exacerbated by inherent differences in the nature of excitation: electrons versus photons. Our work with high purity semiconductors suggests that CL is generally more sensitive to excitation circumstance than PL. For example, electrons can cause sample charging and contamination-related phenomena that dramatically affect CL. Changes in surface attributes (e.g., by chemical passivation) also affect PL and CL signals differently. Here, we extend previous work on GaAs by exploring the role of surface topography (by atomic force microscopy) and temperature (1.8K-100K) on excitonic lineshapes. We find that topographic subtleties strongly influence the character of exciton-polariton luminescence. We interpret these changes in terms of non-classical scattering phenomena derived from microscopic roughness. These microscopic changes also influence the temperature behaviour of excitons in crystals. Specifically, we find that passivated samples are brighter partly because there is a corresponding reduction in the (Arrhenius) activation energy for excitonic processes. In summary, the changes in surface topography and corresponding recombination physics seem well correlated

Seismic analysis of the acid liquid waste tanks at the Western New York State Nuclear Service Center, West Valley, New York

This report was prepared at the request of the Nuclear Regulatory Commission as part of a review of the nuclear fuel reprocessing plant operated by Nuclear Fuel Services, Inc., at West Valley, NY. The report discusses the seismic integrity evaluation by Lawrence Livermore Laboratory of two high-level, acid liquid-waste tanks, 8D-3 and 8D-4, adjacent to the plant. It describes the tanks and discusses the techniques used to model and analyze the structures and to combine the loads. Limiting criteria, results, and conclusions are presented

POPOVER Review Panel report

The POPOVER series of high explosive (HE) certification tests was conducted at the Big Explosives Experimental Facility (BEEF) in Area 4 of the Nevada Test Site (NTS). The two primary objectives of POPOVER were to certify that: (1) BEEF meets DOE requirements for explosives facilities and is safe for personnel-occupied operations during testing of large charges of conventional HE. (2) Facility structures and equipment will function as intended when subjected to the effects of these charges. After careful analysis of test results, the POPOVER Review Panel concludes that the POPOVER series met both objectives. Further details on the Review Panel`s conclusions are included in Section 7--Findings and Recommendations

A physical map of the chicken genome

Strategies for assembling large, complex genomes have evolved to include a combination of whole-genome shotgun sequencing and hierarchal map-assisted sequencing. Whole-genome maps of all types can aid genome assemblies, generally starting with low-resolution cytogenetic maps and ending with the highest resolution of sequence. Fingerprint clone maps are based upon complete restriction enzyme digests of clones representative of the target genome, and ultimately comprise a near-contiguous path of clones across the genome. Such clone-based maps are used to validate sequence assembly order, supply long-range linking information for assembled sequences, anchor sequences to the genetic map and provide templates for closing gaps. Fingerprint maps are also a critical resource for subsequent functional genomic studies, because they provide a redundant and ordered sampling of the genome with clones. In an accompanying paper we describe the draft genome sequence of the chicken, Gallus gallus, the first species sequenced that is both a model organism and a global food source. Here we present a clone-based physical map of the chicken genome at 20-fold coverage, containing 260 contigs of overlapping clones. This map represents approximately 91% of the chicken genome and enables identification of chicken clones aligned to positions in other sequenced genomes

Seismic evaluation of the U1a complex at the Nevada Test Site

As part of an overall safety evaluation of the Ula Complex, a seismic evaluation of structures, systems, and components (SSC) was conducted. A team of seismic, safety, and operation engineers from Los Alamos National Laboratory (LANL), Bechtel Nevada (BN) and Lawrence Livermore National Laboratory (LLNL) was chartered to perform the seismic evaluation. The UlA Complex is located in Area 1 of the Nevada Test Site (NTS) in Nevada. The complex is a test facility for physics experiments in support of the Science Based Stockpile Stewardship Program. The Ula Complex consists of surface and subsurface facilities. The subsurface facility is a tunnel complex located 963 feet below the surface. The seismic evaluation of U 1 a Complex is required to comply with the DOE Natural Phenomena Policy. This policy consists of an order, an implementing guide, and standards which provide guidance for design and evaluation of SSCs, categorization of SSCs, characterization of site, and hazard level definition

Genome Res.

As part of the effort to sequence the genome of Rattus norvegicus, we constructed a physical map comprised of fingerprinted bacterial artificial chromosome (BAC) clones from the CHORI-230 BAC library. These BAC clones provide 13-fold redundant coverage of the genome and have been assembled into 376 fingerprint contigs. A yeast artificial chromosome (YAC) map was also constructed and aligned with the BAC map via fingerprinted BAC and P1 artificial chromosome clones (PACs) sharing interspersed repetitive sequence markers with the YAC-based physical map. We have annotated 95% of the fingerprint map clones in contigs with coordinates on the version 3.1 rat genome sequence assembly, using BAC-end sequences and in silico mapping methods. These coordinates have allowed anchoring 358 of the 376 fingerprint map contigs onto the sequence assembly. Of these, 324 contigs are anchored to rat genome sequences localized to chromosomes, and 34 contigs are anchored to unlocalized portions of the rat sequence assembly. The remaining 18 contigs, containing 54 clones, still require placement. The fingerprint map is a high-resolution integrative data resource that provides genome-ordered associations among BAC, YAC, and PAC clones and the assembled sequence of the rat genome. [Supplemental material is available online at www.genome.org.

Genome Res

As part of the effort to sequence the genome of Rattus norvegicus, we constructed a physical map comprised of fingerprinted bacterial artificial chromosome (BAC) clones from the CHORI-230 BAC library. These BAC clones provide ~13-fold redundant coverage of the genome and have been assembled into 376 fingerprint contigs. A yeast artificial chromosome (YAC) map was also constructed and aligned with the BAC map via fingerprinted BAC and P1 artificial chromosome clones (PACs) sharing interspersed repetitive sequence markers with the YAC-based physical map. We have annotated 95% of the fingerprint map clones in contigs with coordinates on the version 3.1 rat genome sequence assembly, using BAC-end sequences and in silico mapping methods. These coordinates have allowed anchoring 358 of the 376 fingerprint map contigs onto the sequence assembly. Of these, 324 contigs are anchored to rat genome sequences localized to chromosomes, and 34 contigs are anchored to unlocalized portions of the rat sequence assembly. The remaining 18 contigs, containing 54 clones, still require placement. The fingerprint map is a high-resolution integrative data resource that provides genome-ordered associations among BAC, YAC, and PAC clones and the assembled sequence of the rat genome