127 research outputs found
Clay Shale Foundation Slide at Waco Dam, Texas
A major slide occurred during construction of the dam in 1961. It was caused by a combination of unusually high pore pressures in the clay shale foundation and a low residual shear strength. The dam was completed with wide berms to provide stability. Since completion there has been a very slow decrease in foundation pore pressure
Kerrville Ponding Dam, Guadalupe River, Texas
Kerrville Ponding Dam is a relatively small channel dam in the Guadalupe River in Kerrville, Texas. The dam is 22 feet (6.7M) high and 600 feet (183M) long and provides a water supply for the City of Kerrville. The dam was constructed during 1979-1980. Seepage problems in the abutments were observed during the initial filling of the reservoir. Some minor corrections to the problems were made at that time. In June 1981, after a moderate flood flow passed over the dam, additional seepage problems occurred. The downstream slope protection was displaced to the extent that cracks appeared in the concrete. This damage lead to a more significant amount of repair. On December 31, 1984 the dam was overtopped by a flood to a depth of 10.5 feet (3.2M) above the spillway elevation. The dam suffered severe damage including loss of a portion of the concrete cap and significant erosion of the clay core over approximately one-third of the length of the dam, and seepage related damage at both the abutment areas. Figure 1 shows the conditions of the structure in January 1985. The dam suffered a “Type 1 Accident” as defined according to International Commission on Large Dams (ICOLD)
Fusion of radioactive Sn with Ni
Evaporation residue and fission cross sections of radioactive Sn on
Ni were measured near the Coulomb barrier. A large sub-barrier fusion
enhancement was observed. Coupled-channel calculations including inelastic
excitation of the projectile and target, and neutron transfer are in good
agreement with the measured fusion excitation function. When the change in
nuclear size and shift in barrier height are accounted for, there is no extra
fusion enhancement in Sn+Ni with respect to stable Sn+Ni.
A systematic comparison of evaporation residue cross sections for the fusion of
even Sn and Sn with Ni is presented.Comment: 9 pages, 11 figure
The Detection of Ionizing Radiation by Plasma Panel Sensors: Cosmic Muons, Ion Beams and Cancer Therapy
The plasma panel sensor is an ionizing photon and particle radiation detector
derived from PDP technology with high gain and nanosecond response.
Experimental results in detecting cosmic ray muons and beta particles from
radioactive sources are described along with applications including high energy
and nuclear physics, homeland security and cancer therapeuticsComment: Presented at SID Symposium, June 201
Plasma Panel Sensors for Particle and Beam Detection
The plasma panel sensor (PPS) is an inherently digital, high gain, novel
variant of micropattern gas detectors inspired by many operational and
fabrication principles common to plasma display panels (PDPs). The PPS is
comprised of a dense array of small, plasma discharge, gas cells within a
hermetically-sealed glass panel, and is assembled from non-reactive,
intrinsically radiation-hard materials such as glass substrates, metal
electrodes and mostly inert gas mixtures. We are developing the technology to
fabricate these devices with very low mass and small thickness, using gas gaps
of at least a few hundred micrometers. Our tests with these devices demonstrate
a spatial resolution of about 1 mm. We intend to make PPS devices with much
smaller cells and the potential for much finer position resolutions. Our PPS
tests also show response times of several nanoseconds. We report here our
results in detecting betas, cosmic-ray muons, and our first proton beam tests.Comment: 2012 IEEE NS
Development of a plasma panel radiation detector: recent progress and key issues
A radiation detector based on plasma display panel technology, which is the
principal component of plasma television displays is presented. Plasma Panel
Sensor (PPS) technology is a variant of micropattern gas radiation detectors.
The PPS is conceived as an array of sealed plasma discharge gas cells which can
be used for fast response (O(5ns) per pixel), high spatial resolution detection
(pixel pitch can be less than 100 micrometer) of ionizing and minimum ionizing
particles. The PPS is assembled from non-reactive, intrinsically radiation-hard
materials: glass substrates, metal electrodes and inert gas mixtures. We report
on the PPS development program, including simulations and design and the first
laboratory studies which demonstrate the usage of plasma display panels in
measurements of cosmic ray muons, as well as the expansion of experimental
results on the detection of betas from radioactive sources.Comment: presented at IEEE NSS 2011 (Barcelona
Cis–trans isomerization at a proline opens the pore of a neurotransmitter-gated ion channel
5-Hydroxytryptamine type 3 (5-HT_3) receptors are members of the Cys-loop receptor superfamily. Neurotransmitter binding in these proteins triggers the opening (gating) of an ion channel by means of an as-yet-uncharacterized conformational change. Here we show that a specific proline (Pro 8*), located at the apex of the loop between the second and third transmembrane helices (M2–M3), can link binding to gating through a cis–trans isomerization of the protein backbone. Using unnatural amino acid mutagenesis, a series of proline analogues with varying preference for the cis conformer was incorporated at the 8* position. Proline analogues that strongly favour the trans conformer produced non-functional channels. Among the functional mutants there was a strong correlation between the intrinsic cis–trans energy gap of the proline analogue and the activation of the channel, suggesting that cis–trans isomerization of this single proline provides the switch that interconverts the open and closed states of the channel. Consistent with this proposal, nuclear magnetic resonance studies on an M2–M3 loop peptide reveal two distinct, structured forms. Our results thus confirm the structure of the M2–M3 loop and the critical role of Pro 8* in the 5-HT_3 receptor. In addition, they suggest that a molecular rearrangement at Pro 8* is the structural mechanism that opens the receptor pore
Elastic scattering and breakup of 17^F at 10 MeV/nucleon
Angular distributions of fluorine and oxygen produced from 170 MeV 17^F
incident on 208^Pb were measured. The elastic scattering data are in good
agreement with optical model calculations using a double-folding potential and
parameters similar to those obtained from 16^O+208^Pb. A large yield of oxygen
was observed near \theta_lab=36 deg. It is reproduced fairly well by a
calculation of the (17^F,16^O) breakup, which is dominated by one-proton
stripping reactions. The discrepancy between our previous coincidence
measurement and theoretical predictions was resolved by including core
absorption in the present calculation.Comment: 9 pages, 5 figure
Measurements of (p,p) and (p,p'γ) Observables for 1+ States in 12-C at 200 MeV
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
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Entry State Distributions of Discrete Yrast Transitions in Heavy Ion Induced Fusion Reactions
Gamma rays emitted during yrast transitions from compound nuclei are detected with a 4..pi.. multielement gamma ray detector system. Both total pulse height (H) and coincidence fold data (k) are obtained for each event. Results presented include entry state distribution states, k and H projections for some of these distributions, and k and H as a function of spin of the yrast transition. 5 figs. (DWL
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