Electrical Resistivity Studies Related to the Proposed Low Level Radioactive Waste Repository, Hudspeth County, Texas

As part of the site characterization effort for the proposed low-level nuclear waste disposal site north of Fort Hancock, Texas, the University of Texas at El Paso conducted an electrical resistivity survey of the area. This survey was contracted by the Texas Low-Level Radioactive Waste Authority. The intent is to repeat this survey annually if the site is licensed in order to monitor leachate migration. A series of soundings were made, and profile readings were taken around the entire perimeter of the proposed site. The locations of these measurements are shown in Figure 1. The procedures outlined in Draft Regulatory Guide 6.7 of the Texas Department of Health were followed. A Price array configuration was used to make the measurements, and the Barnes layer method (Barnes, 1953) was used to calculate apparent subsurface resistivities. The voltage readings were generally the average of 4 measurements, but in a few cases, 16 measurements were averaged. Repeatability was excellent (1 or 2%) for a specific placement of the electrodes. However, movement of any electrode by 1 m created variations in readings of up to 100%, and variations of 50% were common. These results are to be expected considering the near-surface variability in terms of soil composition and water saturation, but they must be kept in mind if the survey is repeated in the future.Bureau of Economic Geolog

A Compton telescope for remote location and identification of radioactive material

The spare detectors from NASA Compton Gamma-Ray Observatory COMPTEL instrument have been reconfigured to demonstrate the capability at ground level to remotely locate and identify sources of g radiation or the movement of material that might shield γ-ray sources. The Gamma-Ray Experimental Telescope Assembly (GRETA) employs two 28 cm diameter scintillation detectors separated by 81 cm: one 8.5 cm thick liquid scintillator detector and one 7.5 cm thick NaI(Tl) detector. The assembly electronics and real-time data acquisition system measures the energy deposits and time-of- flight for each coincident detection and compiles histograms of total energy and incident angle as computed using the kinematics of Compton scattering. The GRETA field of view is a cone with full angle approximately 120°. The sensitive energy range is 0.3 to 2.6 MeV. Energy resolution is ~10% FWHM. The angular resolution, ~19° in the simplified configuration tested, will improve to better than 5° with well-defined enhancements to the data acquisition hardware and data analysis routines. When operated in the mode that was used in space, the instrument is capable of measuring and imaging up to 30 MeV with an angular resolution of 1.5°. The response of the instrument was mapped in the laboratory with 14 Ci 22Na source 3 m from the instrument. Later, we conducted demonstrations under two measurement scenarios. In one, the remotely located instrument observed an increase of background radiation counts at 1.4 MeV when a large amount of lead was removed from a building and a corresponding decrease when the lead was replaced. In the other scenario, the location and isotope-identifying energy spectrum of a 500 μCi137Cs source 3-5 m from the instrument with two intervening walls was determined in less than one minute. We report details of the instrument design and these measurements

Position Resolution in LaBr3 and LaCl3 Scintillators Using Position-Sensitive Photomultiplier Tubes

Advanced scintillator materials such as LaBr3:Ce and LaCl3:Ce hold great promise for future hard X-ray and gamma-ray astrophysics missions due to their high density, high light output, good linearity, and fast decay times. Of particular importance for future space-based imaging instruments, such as coded-aperture telescopes, is the precise spatial location of individual gamma-ray interactions. We have investigated the position and energy resolution achievable within monolithic (5 cm × 5 cm × 1 cm) LaBr3:Ce and LaCl3:Ce crystals using position-sensitive light readout devices, including a position-sensitive photomultiplier tube and a multi-anode photomultiplier tube. We present the results of these tests and discuss the applicability of such advanced scintillators to future high-energy imaging astrophysics missions

Reactive oxygen species in spermatozoa: methods for monitoring and significance for the origins of genetic disease and infertility

Human spermatozoa generate low levels of reactive oxygen species in order to stimulate key events, such as tyrosine phosphorylation, associated with sperm capacitation. However, if the generation of these potentially pernicious oxygen metabolites becomes elevated for any reason, spermatozoa possess a limited capacity to protect themselves from oxidative stress. As a consequence, exposure of human spermatozoa to intrinsically- or extrinsically- generated reactive oxygen intermediates can result in a state of oxidative stress characterized by peroxidative damage to the sperm plasma membrane and DNA damage to the mitochondrial and nuclear genomes. Oxidative stress in the male germ line is associated with poor fertilization rates, impaired embryonic development, high levels of abortion and increased morbidity in the offspring, including childhood cancer. In this review, we consider the possible origins of oxidative damage to human spermatozoa and reflect on the important contribution such stress might make to the origins of genetic disease in our species

Complex Adaptive Systems: Adapting and Managing Teams and Team Conflict

Complexity comes from dramatic structural changes to organizations and governments such as globalization, global competition, workforce diversity, and continual innovations. Complex adaptive systems (CAS) are organizations that are a composite of the interconnected whole. Teams must manage and operate in emerging ecosystems, understand factors that lead to team effectiveness when managing and facilitating teams and team conflict, and understand the development of conflict models. This chapter provides an overview of teams, CAS, conflict stages, and conflict models. This chapter presents adaptive leadership as one leadership style that offers organizations with the capabilities of reacting to changing environments quickly. Adaptive leadership offers a prescriptive approach for managers and leaders to follow when dealing with organizational conflict while operating in today’s complex and global environment

Blunted Cystine–Glutamate Antiporter Function in the Nucleus Accumbens Promotes Cocaine-induced Drug Seeking

Repeated cocaine alters glutamate neurotransmission, in part, by reducing cystine–glutamate exchange via system xc−, which maintains glutamate levels and receptor stimulation in the extrasynaptic compartment. In the present study, we undertook two approaches to determine the significance of plasticity involving system xc−. First, we examined whether the cysteine prodrug N-acetylcysteine attenuates cocaine-primed reinstatement by targeting system xc−. Rats were trained to self-administer cocaine (1 mg/kg/200 μl, i.v.) under extended access conditions (6 h/day). After extinction training, cocaine (10 mg/kg, i.p.) primed reinstatement was assessed in rats pretreated with N-acetylcysteine (0–60 mg/kg, i.p.) in the presence or absence of the system xc− inhibitor (S)-4-carboxyphenylglycine (CPG; 0.5 μM; infused into the nucleus accumbens). N-acetylcysteine attenuated cocaine-primed reinstatement, and this effect was reversed by co-administration of CPG. Secondly, we examined whether reduced system xc− activity is necessary for cocaine-primed reinstatement. To do this, we administered N-acetylcysteine (0 or 90 mg/kg, i.p.) prior to 12 daily self-administration sessions (1 mg/kg/200 μl, i.v.; 6 h/day) since this procedure has previously been shown to prevent reduced activity of system xc−. On the reinstatement test day, we then acutely impaired system xc− in some of the rats by infusing CPG (0.5 μM) into the nucleus accumbens. Rats that had received N-acetylcysteine prior to daily self-administration sessions exhibited diminished cocaine-primed reinstatement; this effect was reversed by infusing the cystine–glutamate exchange inhibitor CPG into the nucleus accumbens. Collectively these data establish system xc− in the nucleus accumbens as a key mechanism contributing to cocaine-primed reinstatement

Geophysical Studies Related to the Proposed Low Level Readioactive Waste Repository Hudspeth County, Texas

Geologic characterization of sites for low-level radioactive waste repositories generally requires qualitative and quantitative estimates of variations in rock properties between test wells. Seismic reflection surveys are an accepted technique for providing a qualitative picture of structural and/or stratigraphic variation when tied closely to control information from wells. Reflection surveys also are useful in identifying areas where additional well control may be needed to adequately characterize geologic variations. Ten miles (16 km) of reconnaissance seismic data were collected and interpreted by Phillips et al. (1986) in the vicinity of the proposed repository site near Fort Hancock, Hudspeth County, Texas. Three lines were collected perpendicular to the major structural trends, and a fourth line tied these three together. These data typically resolve variations in stratigraphic thickness that are more than 20 ft (6 m) thick, one-fourth the dominant time wavelength, and that are more than 90 ft (27 m) deep. These data can image horizontal variations greater than 110 ft (34 m), with 8 common depth point samples per wavenumber.Bureau of Economic Geolog

Repeated \u3cem\u3eN\u3c/em\u3e-Acetylcysteine Administration Alters Plasticity-Dependent Effects of Cocaine

Cocaine produces a persistent reduction in cystine–glutamate exchange via system xc− in the nucleus accumbens that may contribute to pathological glutamate signaling linked to addiction. System xc− influences glutamate neurotransmission by maintaining basal, extracellular glutamate in the nucleus accumbens, which, in turn, shapes synaptic activity by stimulating group II metabotropic glutamate autoreceptors. In the present study, we tested the hypothesis that a long-term reduction in system xc− activity is part of the plasticity produced by repeated cocaine that results in the establishment of compulsive drug seeking. To test this, the cysteine prodrug N-acetylcysteine was administered before daily cocaine to determine the impact of increased cystine–glutamate exchange on the development of plasticity-dependent cocaine seeking. Although N-acetylcysteine administered before cocaine did not alter the acute effects of cocaine on self-administration or locomotor activity, it prevented behaviors produced by repeated cocaine including escalation of drug intake, behavioral sensitization, and cocaine-primed reinstatement. Because sensitization or reinstatement was not evident even 2–3 weeks after the last injection of N-acetylcysteine, we examined whether N-acetylcysteine administered before daily cocaine also prevented the persistent reduction in system xc− activity produced by repeated cocaine. Interestingly, N-acetylcysteine pretreatment prevented cocaine-induced changes in [35S]cystine transport via system xc−, basal glutamate, and cocaine-evoked glutamate in the nucleus accumbens when assessed at least 3 weeks after the last N-acetylcysteine pretreatment. These findings indicate that N-acetylcysteine selectively alters plasticity-dependent behaviors and that normal system xc− activity prevents pathological changes in extracellular glutamate that may be necessary for compulsive drug seeking