Active Damping of the E-P Instability at the LANL PSR

A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos National Laboratory Proton Storage Ring (PSR). This system was able to improve the instability threshold by approximately 30% (as measured by the change in RF buncher voltage at instability threshold). Evidence obtained from these tests suggests that further improvement in performance is limited by beam leakage into the gap at lower RF buncher voltage and the onset of instability in the horizontal plane, which had no feedback. Here we describe the present system configuration, system optimization, results of several recent experimental tests, and results from studies of factors limiting its performance

History of clinical transplantation

How transplantation came to be a clinical discipline can be pieced together by perusing two volumes of reminiscences collected by Paul I. Terasaki in 1991-1992 from many of the persons who were directly involved. One volume was devoted to the discovery of the major histocompatibility complex (MHC), with particular reference to the human leukocyte antigens (HLAs) that are widely used today for tissue matching.1 The other focused on milestones in the development of clinical transplantation.2 All the contributions described in both volumes can be traced back in one way or other to the demonstration in the mid-1940s by Peter Brian Medawar that the rejection of allografts is an immunological phenomenon.3,4 © 2008 Springer New York

Prevalence of antibodies to bovine paratuberculosis detected by a LAM-ELISA in Costa Rica

In Costa Rica the diagnosis of Johne's disease has been based on clinical, histopathological and bacteriological evidence and cutaneous testing; however, the prevalence of the disease at the national level is unknown. Since serum ELISA is a well accepted method of testing for antibody response to Mparatuberculosis (Collins and others 1991, Sockett and others 1992), a bovine serum bank collected in 1990 and a lipoarabinomannan antigen ELISA (LAM-ELISA) which included a preabsorption step with Mycobacteriumphlei (Sudgen and others 1987, 1989) was used.En Costa Rica el diagnóstico de la enfermedad de Johne se ha basado en pruebas clínicas, histopatológicas, bacteriológicas y pruebas cutáneas; sin embargo, se desconoce la prevalencia de la enfermedad a nivel nacional es desconocida. Dado que el ELISA en suero es un método bien aceptado de anticuerpos contra la Mparatuberculosis (Collins y otros, 1991). (Collins y otros 1991, Sockett y otros 1992), un banco de suero bovino suero bovino recogido en 1990 y un antígeno lipoarabinomanano ELISA (LAM-ELISA) que incluía un paso de preabsorción con Mycobacteriumphlei (Sudgen y otros 1987, 1989).Universidad Nacional, Costa RicaEscuela de Medicina Veterinari

Modeling of thermal hydraulic behavior and fission product releases in degraded cores

When core material reaches melting conditions severe degradation of the core geometry occurs. Data available on the core behavior in a severely degraded state suggest that extensive blockage of the flow channels would occur. If a sufficient bypass is available for the gas flow, such as in the LOFT LP-FP-2 test, severe retardation of the hydrogen and fission product sources from the degraded channel is suggested from the available data. This phenomena is expected to occur in an LWR core and should be considered by core models that are used for severe accident analysis. In the MAAP code it is done by preventing gas flow through molten core regions. Good agreement is obtained with all relevant data that are directly applicable to LWR accident conditions. A more mechanistic model for the freezing of core material and its effect on the coolant channel geometry is currently being investigated by the US Department of Energy Advanced Reactor Severe Accident Program (ARSAP). 8 refs., 2 figs

Difference in electron thermal diffusivity and profile between interior and exterior of TFTR L-mode plasmas

The local properties such as scale lengths of the electron density (L{sub n{sub e}}), temperature (L{sub T{sub e}}), and pressure (L{sub p{sub e}}), and the electron thermal diffusivity {chi}{sub e}(r) (m{sup 2}/s) for r/a > 0.3 have been studied for TFTR L-mode discharges under the assumption of {chi}{sub e} = {chi}{sub i}. The scale lengths and the electron thermal diffusivity in the interior 0.3 < r/a < 0.55 are significantly different from those on the exterior 0.55 < r/a < 0.8. following are some examples (temperatures in keV, other quantities in MKS units). In the interior (0.3 < r/a < 0.55), most of the scale lengths were constant or a weakly dependent on radius, and {chi}{sub e} can be expressed as (with correlation coefficient R = 0.61), {chi}{sub e}(r) = 1.44 {times} 10{sup 18}(r/a){sup 1.0}T{sub e}(r){sup 0.1}q(r){sup 0.1}/n{sub e}{sup 0.9}(r). In the exterior region (0.55 < r/a < 0.8), the scale lengths decrease monotonically, and {chi}{sub e} can be described as (with R = 0.68), {chi}{sub e}(r) = 2.3 {times} 10{sup 3}(r/a){sup 1.7}T{sub e}(r){sup 0.7}q(r){sup 0.8}/n{sub e}{sup 0.2}(r). It is interesting to note the negative n{sub e} dependence of {chi}{sub e} in the interior and the positive T{sub e} dependence of {chi}{sub e} in the exterior

Assessment and interpretation of cross- and down-hole seismograms at the Paducah Gaseous Diffusion Plant

This paper is an assessment and interpretation of cross-and down-hole seismograms recorded at four sites in the vicinity of the Paducah Gaseous Diffusion Plant (PGDP). Arrival times of shear (S-) and compressional (P-) waves are recorded on these seismograms in milliseconds. Together with known distances between energy sources and seismometers lowered into boreholes, these arrival times are used to calculate S- and P-wave velocities in unconsolidated soils and sediments that overlie bedrock approximately 320 ft beneath PGDP. The soil columns are modified after an earlier draft by ERC Environmental and Energy Services Company (ERCE), 1990. In addition to S- and P- wave velocity estimates from this paper, the soil columns contain ERCE's lithologic and other geotechnical data for unconsolidated soils and sediments from the surface to bedrock. Soil columns for Sites 1 through 4 and a site location map are in Plates 1 through 5 of Appendix 6. The velocities in the four columns are input parameters for the SHAKE computer program, a nationally recognized computer model that simulates ground response of unconsolidated materials to earthquake generated seismic waves. The results of the SHAKE simulation are combined with predicted ground responses on rock foundations (caused by a given design earthquake) to predict ground responses of facilities with foundations placed on unconsolidated materials. 3 refs