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Livermore National Laboratory (livermore + national_laboratory)

Distribution by Scientific Domains
Medical Sciences60%

Kinds of Livermore National Laboratory

  • lawrence livermore national laboratory
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    Selected Abstracts

    Evaluating high-performance computers,

    CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 10 2005
    Jeffrey S. Vetter
    Abstract Comparisons of high-performance computers based on their peak floating point performance are common but seldom useful when comparing performance on real workloads. Factors that influence sustained performance extend beyond a system's floating-point units, and real applications exercise machines in complex and diverse ways. Even when it is possible to compare systems based on their performance, other considerations affect which machine is best for a given organization. These include the cost, the facilities requirements (power, floorspace, etc.), the programming model, the existing code base, and so on. This paper describes some of the important measures for evaluating high-performance computers. We present data for many of these metrics based on our experience at Lawrence Livermore National Laboratory (LLNL), and we compare them with published information on the Earth Simulator. We argue that evaluating systems involves far more than comparing benchmarks and acquisition costs. We show that evaluating systems often involves complex choices among a variety of factors that influence the value of a supercomputer to an organization, and that the high-end computing community should view cost/performance comparisons of different architectures with skepticism. Published in 2005 by John Wiley & Sons, Ltd. [source]

    Superresolution planar diffraction tomography through evanescent fields,

    INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 1 2002
    Sean K. Lehman
    We consider the problem of noninvasively locating objects buried in a layered medium such as land mines in the ground or objects concealed in a wall. In such environments, the transmitter(s) and receiver(s) are frequently within the near-field region of the illuminating radiation. In these cases, the scattered evanescent field carries useful information on the scattering object. Conventional diffraction tomography techniques neglect, by their design, the evanescent field. Under near-field conditions, they treat it as noise as opposed to valid data. If correctly incorporated into a reconstruction algorithm, the evanescent field, which carries high spatial frequency information, can be used to achieve resolution beyond the classical limit of ,/2, or "superresolution." We build on the generalized holography theory presented by Langenberg to develop a planar diffraction tomography algorithm that incorporates evanescent field information to achieve superresolution. Our theory is based on a generalization of the Fourier transform, which allows for complex spatial frequencies in a manner similar to the Laplace transform. We specialize our model to the case of a two-dimensional multimonostatic, wideband imaging system, and derive an extended resolution reconstruction procedure. We implement and apply our reconstruction to two data sets collected using the Lawrence Livermore National Laboratory (LLNL) Micropower Impulse Radar (MIR). © 2002 John Wiley & Sons, Inc. Int J Imaging Syst Technol 12, 16,26, 2002 [source]

    Extrem dichtes Plasma im Festkörper

    PHYSIK IN UNSERER ZEIT (PHIUZ), Issue 5 2003
    Siegfried Glenzer
    Am Lawrence Livermore National Laboratory (LLNL), USA, ist es gelungen, für kurze Zeit im Innern eines Festkörpers ein extrem dichtes Plasma zu erzeugen. Mit Hilfe von Röntgenstreuung konnten zudem Temperatur und Dichte mit guter Genauigkeit gemessen werden [1]. [source]

    Cancer incidence rates among Lawrence Livermore National Laboratory (LLNL) employees: 1974,1997,

    AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 1 2004
    M. Donald Whorton MD
    Abstract Background In the mid-1970's an excess of malignant melanoma of the skin was noted among employees at the Lawrence Livermore National Laboratory (LLNL). A 1984 cancer incidence study showed a non-significant excess of total cancers among female employees with significant excesses for melanoma, rectum and anus, and salivary gland cancers. For male employees, there was a non-significant deficit of total cancer with significant excesses in melanoma and non-brain nervous system cancers. This paper reports the results of a surveillance effort to update our understanding of the patterns of cancer incidence in this population. Methods We used California Cancer Registry (CCR) data to ascertain employees who had worked for six or more consecutive months at LLNL during the 24-year period of 1974 through 1997 who were diagnosed weith cancer during that time frame. We used the Standardized Incidence Ratio (SIR) in our analyses. Results There were 17,785 employees who provided 186,558 person-years of observation: 145,203 were from males and 41,355 were from females. The CCR, through its linkage techniques, identified 541 individuals with invasive cancer and 96 with in situ cancer. A total of 404 males had invasive cancer and 33 had in situ cancer whereas there were 137 females with invasive cancer and 63 with in situ cancer. The SIR for invasive cancer in males was 69 (95% CI 62,76). The overall cancer SIR for males was unaffected by calendar time. There were only two invasive cancer sites with significant excess: melanoma and cancer of the testes. For eight categories or cancer sites, we found a statistical deficit in cancer incidence. The most striking deficit occurred in cancer of the lungs and bronchus with a SIR of 36 (95% CI 26,50). The SIR for invasive cancer in females was 80 (95% CI 67,94). The overall cancer SIR for females decreased over calendar time. There was a statistically significant deficit for cancers of the female genital organs. There were 84 cases of invasive and in situ melanoma in both genders. Time-trend analyses for melanoma showed a significant excess during the years 1974,1985 but a reduction to community rates from 1986 through 1997. There were 21 individuals with testicular cancer with a SIR of 207 (95% CI 129,317). There were no differences in age at diagnosis or cell type with the comparison population. We analyzed the data using the same radiosensitive cancer categories used in the 1984 study. There were no increases in SIRs in any of these categories. Conclusions We found that the LLNL employees had less cancer than expected with males having relatively fewer cancers than females. The lung cancer rate for males was remarkably low. Since 1986 the melanoma rates resemble the community rates. Testicular cancer rates are modestly elevated and appear to have been so for the past 20 years. Lifestyle patterns, including smoking, and cancer screening activities are probably important contributors to the observed low cancer rates. Am. J. Ind. Med. 45:24,33, 2004. © 2003 Wiley-Liss, Inc. [source]