Occurrence and Cesium-137 and Other Radionuclides in the Surface Layers of Soil in Ohio and Antarctica

Author Institution: Department of Geological Sciences, The Ohio State UniversityThe testing of nuclear weapons in the atmosphere in the 1960s and the accidental explosion of a nuclear reactor in 1986 near Chernobyl, Ukraine, caused large amounts of fission-product radionuclides to be deposited over most of the surface of the Earth. The present study was undertaken in order to compare the decay rates of l37Cs in the surface layer of soil in central Ohio at 40°N and in Antarctica at 77°S latitude. The measurements were made by means of gamma-ray spectrometry on 10 gram samples of bulk soil collected from the surface. The results indicate that the decay rate of l37Cs in the Ohio soil sample is (2.2 ± 0.8) x 10 ' pico Curies/g, whereas the rate of decay of this radionuclide in the antarctic soils is below the limit of detection (<1 x 102 pCi/g). In addition, roots in the Ohio soil do not contain detectable 137Cs, confirming that this radionuclide is not absorbed by plant roots because of its strong absorption on the surfaces of clay minerals. Soils in Ohio and Antarctica do contain long-lived unstable 40K, as well as short-lived unstable daughters of 238U (214Pb and 214Bi) and of 232Th (228Ac, 212Pb, 208Tl, and 228Th). The apparent absence of 137Cs in the surface layer of antarctic soils is most likely the result of nondeposition of radioactive fallout at the extreme southern latitudes of Antarctica

Impact of crystallite size on the performance of a beryllium reflector

Beryllium reflectors are used at spallation neutron sources in order to enhance the low-energy flux of neutrons emanating from the surface of a cold and thermal moderator. The design of such a moderator/reflector system is typically carried out using detailed Monte-Carlo simulations, where the beryllium reflector is assumed to behave as a poly-crystalline material. In reality, however, inhomogeneities in the beryllium could lead to discrepancies between the performance of the actual system when compared to the modeled system. The dependence of the total cross section in particular on crystallite size, in the Bragg scattering region, could influence the reflector performance, and if such effect is significant, it should be taken into account in the design of the moderator/reflector system. In this paper, we report on the preliminary results of using cross-section libraries, which include corrections for the crystallite size effect, in spallation source neutronics calculations.Comment: ICANS-XXII

Risk of respiratory depression with opioids and concomitant gabapentinoids.

Introduction:The combination of opioids and central nervous system depressants such as benzodiazepines and barbiturates has an additive effect on the frequency of oversedation and respiratory depression requiring naloxone use in hospitalized patients. Gabapentinoids (gabapentin and pregabalin) are frequently prescribed with opioids for their opioid-sparing and adjuvant analgesic effects. There is limited literature on the risk of respiratory depression due to the combination of opioids and gabapentinoids requiring naloxone administration. Methods:This retrospective study evaluated patients who were prescribed opioids and at least one dose of naloxone between March 1, 2014 and September 30, 2016. The primary objective of this study was to compare the frequency of respiratory depression among patients who received naloxone and opioids (non-gabapentinoid group) with those who received naloxone, opioids, and gabapentinoids (gabapentinoid group). Secondary objectives included comparing the association of oversedation, using the Pasero Opioid-induced Sedation Scale, and various risk factors with those in the gabapentinoid group. Results:A total of 153 patient episodes of naloxone administration (102 in the non-gabapentinoid and 51 in the gabapentinoid groups) in 125 unique patients were included in the study. For the primary objective, there were 33 episodes of respiratory depression associated with the non-gabapentinoid group (33/102=32.4%) versus 17 episodes of respiratory depression with the gabapentinoid group (17/51=33.3%) (p=0.128). Secondary objectives showed a significant association between respiratory depression and surgery in the previous 24 hours (p=0.036) as well as respiratory depression and age &gt;65 years (p=0.031) for patients in the non-gabapentinoid group compared to the gabapentinoid group. Conclusion:There was no significant association of respiratory depression in the gabapentinoid group versus the non-gabapentinoid group. There was an increased risk of respiratory depression in the gabapentinoid group, specifically in patients who had surgery within the previous 24 hours

Redefinition of salinity

Two definitions of salinity have been in use since the early part of the present century (Knudsen 1901, Forch et al. 1902). According to the procedural definition, salinity is the amount (in grams) of dissolved solid material in a kilogram of seawater after all the bromine has been replaced by an equivalent quantity of chlorine, after all the carbonate has been converted to oxide, and after all of the organic matter has been destroyed...

Design of a Horizontal Axis Open-Centre Tidal Stream Turbine using Computational Fluid Dynamics

Tidal energy is one of the most promising emerging renewable energy sources which remains largely untapped, due primarily to the challenges of submerged operation within sensitive marine environments. Extracting kinetic energy from dense and energetic flow streams which vary in height, reverse flow direction roughly twice a day and carry sediment as well as marine life requires a unique application of engineering knowledge. A variety of tidal turbine technologies have been developed in response, although as yet the industry is far from mature and there remains great potential for improvement. The research presented in this study introduces a new type of turbine design which has been developed specifically to address the issue of balancing marine friendly technology with efficient energy harvest. This is accomplished through the use of an open-centre concept which houses the blades between the hub and shroud, thus minimizing the risk of blade tip impact and providing free passage through the central aperture. In this study several iterations of the design are tested using the methods of computational fluid dynamics (CFD), each one featuring a different helical blade geometry of varying length and twist angle. A numerical model of the new design is presented in which the energy generation potential is assessed by measuring the amount of torque produced by a stationary blade placed in a steady flow. The torque is calculated by determining the pressure force acting on each blade surface and the resulting moment generated about the rotation axis of the turbine. This method allows for a great number of geometries to be tested under simulated turbine operating conditions, without requiring a prohibitive amount of computational resources. The initial assessment of this new type of turbine is promising, indicating that certain blade geometries produce a greater amount of torque than a model of the conventional open-centre turbine developed by OpenHydro

Strong and Weak Policy Relations

Access control and privacy policy relations tend to focus on decision outcomes and are very sensitive to defined terms and state. Small changes or updates to a policy language or vocabulary may make two similar policies incomparable. To address this we develop two flexible policy relations derived from bisimulation in process calculi. Strong licensing compares the outcome of two policies strictly, similar to strong bisimulation. Weak licensing compares the outcome of policies more flexibly by ignoring irrelevant (non-conflicting) differences between outcomes, similar to weak bisimulation. We illustrate the relations using examples from P3P

Simon-Ando decomposability and fitness landscapes

In this paper, we investigate fitness landscapes (under point mutation and recombination) from the standpoint of whether the induced evolutionary dynamics have a “fast-slow” time scale associated with the differences in relaxation time between local quasi-equilibria and the global equilibrium. This dynamical hevavior has been formally described in the econometrics literature in terms of the spectral properties of the appropriate operator matrices by Simon and Ando (Econometrica 29 (1961) 111), and we use the relations they derive to ask which fitness functions and mutation/recombination operators satisfy these properties. It turns out that quite a wide range of landscapes satisfy the condition (at least trivially) under point mutation given a sufficiently low mutation rate, while the property appears to be difficult to satisfy under genetic recombination. In spite of the fact that Simon-Ando decomposability can be realized over fairly wide range of parameters, it imposes a number of restriction on which landscape partitionings are possible. For these reasons, the Simon-Ando formalism does not appear to be applicable to other forms of decomposition and aggregation of variables that are important in evolutionary systems

Securing the Drop-Box Architecture for Assisted Living

Home medical devices enable individuals to monitor some of their own health information without the need for visits by nurses or trips to medical facilities. This enables more continuous information to be provided at lower cost and will lead to better healthcare outcomes. The technology depends on network communication of sensitive health data. Requirements for reliability and ease-of-use provide challenges for securing these communications. In this paper we look at protocols for the drop-box architecture, an approach to assisted living that relies on a partially-trusted Assisted Living Service Provider (ALSP). We sketch the requirements and architecture for assisted living based on this architecture and describe its communication protocols. In particular, we give a detailed description of its report and alarm transmission protocols and give an automated proof of correspondence theorems for them. Our formulation shows how to characterize the partial trust vested in the ALSP and use the existing tools to verify this partial trust