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 132^{132}Sn with 64^{64}Ni

Evaporation residue and fission cross sections of radioactive $^{132}$Sn on $^{64}$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 $^{132}$Sn+$^{64}$Ni with respect to stable Sn+$^{64}$Ni. A systematic comparison of evaporation residue cross sections for the fusion of even $^{112-124}$Sn and $^{132}$Sn with $^{64}$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

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