Tests of a Gamma Spectrometer-Neutron Counter Relationship as a Neutron Alarm Metric in Mobile Radiation Search Systems

A mobile radiological search system (MRSS) is frequently used in nuclear security to interdict illicit nuclear material. One difficulty an MRSS faces is in characterizing its detectors’ background responses, particularly in its neutron counter(s). This difficulty adds complications to identifying the presence of neutron-emitting radiological materials during an operation. Fortunately, previous work has identified a power law relationship between muons registered by the MRSS’s gamma detectors and background neutrons. This relationship can be applied to estimate the MRSS’s background neutron count rate using that muon count rate. To test the usability of such an estimate, an MRSS was used to sweep a parking garage that had an 886 kBq 252Cf source present on various levels. A moving average of the MRSS’s muon count rate was used to estimate the background neutron count rate, and that dynamic estimate was compared against the observed neutron count rate to determine whether an alarm should occur. For a “control” method, a similar comparison was made between the observed neutron count rate and a constant estimate of the neutron background, where the latter came from a 6-minute measurement of the neutron background outside the parking garage. The results showed that the dynamic estimate of the neutron background performed as well as the constant estimate when identifying whether the 252Cf was present, particularly when the MRSS was on the same level as the material. In many cases, the dynamic estimate produced stronger evidence in favor of an alarm than the constant estimate, and the dynamic estimate was also more likely to produce an alarm when the MRSS was on a level adjacent to the 252Cf. In addition to these results, the dynamic method appeared to have similar performance as the constant method when outside the parking garage. All of these data indicates that applying the neutron–muon power law relationship improves an MRSS’s sensitivity to manmade neutron sources in extreme environments (such as a parking garage or urban center) while maintaining its sensitivity in more normal, open environments

Parking Garage Measurements Indicating a Gamma Spectrometer-Neutron Counter Background Correlation

Gamma spectroscopy and gross neutron counting systems are commonly employed together during nuclear security operations, particularly mobile searches. The data from these systems are typically analyzed independently; however, operational data suggest a relationship between the background signals from both systems. This relationship appears to occur between the neutron count rate and the high energy (greater than 3 MeV) gamma spectrometer count rate for background conditions. To verify the presence of this correlation, high energy gamma ray and neutron count rates were measured in five parking garages on the Texas A&M University campus. These measurements employed one 4” x 4” x 16” NaI detector with an Ortec digiBASE MCA, four moderated 1” x 18” 3He tubes (part of the Ortec NAI-SS system), and two unmoderated 2” x 15” 3He tubes (part of a Thermo PackEye system). The NaI detector was calibrated to a 50 MeV scale and ignored signals less than 4 MeV. Results show a decrease in the count rate of each detector as the systems were moved further below the roof of each garage. These decreases appear linear, but exponential relationships are plausible. More importantly, the data also show that the count rates from the two different detector types are linearly related. The linear relationships are strong, and the slopes vary depending on which neutron counter is considered against the gamma spectrometer. While it is possible that these relationships are the result of the NaI system detecting 4-50 MeV (or even higher energy) gamma rays, it is more likely that this system is detecting charged particles: muons generated by cosmic ray interactions with the atmosphere or protons produced by the decay of free neutrons. All three of these particles would be produced proportionally to the neutrons that the 3He tubes would detect, either from the decay of the neutrons themselves or by being produced from the same cosmic ray interactions that produce the neutrons

Injection of photoelectrons into dense argon gas

The injection of photoelectrons in a gaseous or liquid sample is a widespread technique to produce a cold plasma in a weakly--ionized system in order to study the transport properties of electrons in a dense gas or liquid. We report here the experimental results of photoelectron injection into dense argon gas at the temperatureT=142.6 K as a function of the externally applied electric field and gas density. We show that the experimental data can be interpreted in terms of the so called Young-Bradbury model only if multiple scattering effects due to the dense environment are taken into account when computing the scattering properties and the energetics of the electrons.Comment: 18 pages, 10 figures, figure nr. 10 has been redrawn, to be submitted to Plasma Sources Science and Technolog

Counterparts: Clothing, value and the sites of otherness in Panapompom ethnographic encounters

This is an Author's Accepted Manuscript of an article published in Anthropological Forum, 18(1), 17-35, 2008 [copyright Taylor & Francis], available online at: http://www.tandfonline.com/10.1080/00664670701858927.Panapompom people living in the western Louisiade Archipelago of Milne Bay Province, Papua New Guinea, see their clothes as indices of their perceived poverty. ‘Development’ as a valued form of social life appears as images that attach only loosely to the people employing them. They nevertheless hold Panapompom people to account as subjects to a voice and gaze that is located in the imagery they strive to present: their clothes. This predicament strains anthropological approaches to the study of Melanesia that subsist on strict alterity, because native self‐judgments are located ‘at home’ for the ethnographer. In this article, I develop the notion of the counterpart as a means to explore these forms of postcolonial oppression and their implications for the ethnographic encounter

Synthesis and reactivity of 4-oxo-5-trimethylsilanyl derived α-amino acids

A Lewis-acid promoted one-carbon homologation of an aspartic acid semialdehyde with trimethylsilyldiazomethane has led to the efficient synthesis of two silicon-containing α-amino acids. The use of trimethylaluminium or catalytic tin(II) chloride gave novel 4-oxo-5-trimethylsilanyl derived amino acids in yields of 71–88%. An investigation into the reactivity of these highly functional α-amino acids showed that selective cleavage of the C–Si bond could be achieved under mild basic conditions to give a protected derivative of the naturally occurring amino acid, 4-oxo-l-norvaline. Alternatively, Peterson olefination with aryl or alkyl aldehydes resulted in the formation of E-enone derived α-amino acids

Reporting on sustainability and HRM: a comparative study of sustainability reporting practices by the world’s largest companies

As a response to the growing public awareness on the importance of organisational contributions to sustainable development, there is an increased incentive for corporations to report on their sustainability activities. In parallel with this has been the development of ‘Sustainable HRM’ which embraces a growing body of practitioner and academic literature connecting the notions of corporate sustainability to HRM. The aim of this article is to analyse corporate sustainability reporting amongst the world’s largest companies and to assess the HRM aspects of sustainability within these reports in comparison to environmental aspects of sustainable management and whether organisational attributes – principally country-of-origin – influences the reporting of such practices. A focus in this article is the extent to which the reporting of various aspects of sustainability may reflect dominant models of corporate governance in the country in which a company is headquartered. The findings suggest, first and against expectations, that the overall disclosure on HRM-related performance is not lower than that on environmental performance. Second, companies report more on their internal workforce compared to their external workforce. Finally, international differences, in particular those between companies headquartered in liberal market economies and coordinated market economies, are not as apparent as expected

Evolutionary connectionism: algorithmic principles underlying the evolution of biological organisation in evo-devo, evo-eco and evolutionary transitions

The mechanisms of variation, selection and inheritance, on which evolution by natural selection depends, are not fixed over evolutionary time. Current evolutionary biology is increasingly focussed on understanding how the evolution of developmental organisations modifies the distribution of phenotypic variation, the evolution of ecological relationships modifies the selective environment, and the evolution of reproductive relationships modifies the heritability of the evolutionary unit. The major transitions in evolution, in particular, involve radical changes in developmental, ecological and reproductive organisations that instantiate variation, selection and inheritance at a higher level of biological organisation. However, current evolutionary theory is poorly equipped to describe how these organisations change over evolutionary time and especially how that results in adaptive complexes at successive scales of organisation (the key problem is that evolution is self-referential, i.e. the products of evolution change the parameters of the evolutionary process). Here we first reinterpret the central open questions in these domains from a perspective that emphasises the common underlying themes. We then synthesise the findings from a developing body of work that is building a new theoretical approach to these questions by converting well-understood theory and results from models of cognitive learning. Specifically, connectionist models of memory and learning demonstrate how simple incremental mechanisms, adjusting the relationships between individually-simple components, can produce organisations that exhibit complex system-level behaviours and improve the adaptive capabilities of the system. We use the term “evolutionary connectionism” to recognise that, by functionally equivalent processes, natural selection acting on the relationships within and between evolutionary entities can result in organisations that produce complex system-level behaviours in evolutionary systems and modify the adaptive capabilities of natural selection over time. We review the evidence supporting the functional equivalences between the domains of learning and of evolution, and discuss the potential for this to resolve conceptual problems in our understanding of the evolution of developmental, ecological and reproductive organisations and, in particular, the major evolutionary transitions

Dietary Docosahexaenoic Acid Prevents Silica-Induced Development of Pulmonary Ectopic Germinal Centers and Glomerulonephritis in the Lupus-Prone NZBWF1 Mouse

Ectopic lymphoid structures (ELS) consist of B-cell and T-cell aggregates that are initiated de novo in inflamed tissues outside of secondary lymphoid organs. When organized within follicular dendritic cell (FDC) networks, ELS contain functional germinal centers that can yield autoantibody-secreting plasma cells and promote autoimmune disease. Intranasal instillation of lupus-prone mice with crystalline silica (cSiO2), a respirable particle linked to human lupus, triggers ELS formation in the lung, systemic autoantibodies, and early onset of glomerulonephritis. Here we tested the hypothesis that consumption of docosahexaenoic acid (DHA), an ω-3 polyunsaturated fatty acid with anti-inflammatory properties, influences the temporal profile of cSiO2-induced pulmonary ectopic germinal center formation and development of glomerulonephritis. Female NZBWF1 mice (6-wk old) were fed purified isocaloric diets supplemented with 0, 4, or 10 g/kg DHA - calorically equivalent to 0, 2, or 5 g DHA per day consumption by humans, respectively. Beginning at age 8 wk, mice were intranasally instilled with 1 mg cSiO2, or saline vehicle alone, once per wk, for 4 wk. Cohorts were sacrificed 1, 5, 9, or 13 wk post-instillation (PI) of the last cSiO2 dose, and lung and kidney lesions were investigated by histopathology. Tissue fatty acid analyses confirmed uniform dose-dependent DHA incorporation across all cohorts. As early as 1 wk PI, inflammation comprising of B (CD45R+) and T (CD3+) cell accumulation was observed in lungs of cSiO2-treated mice compared to vehicle controls; these responses intensified over time. Marked follicular dendritic cell (FDC; CD21+/CD35+) networking appeared at 9 and 13 wk PI. IgG+ plasma cells suggestive of mature germinal centers were evident at 13 wk. DHA supplementation dramatically suppressed cSiO2-triggered B-cell, T-cell, FDC, and IgG+ plasma cell appearance in the lungs as well as anti-dsDNA IgG in bronchial lavage fluid and plasma over the course of the experiment. cSiO2 induced glomerulonephritis with concomitant B-cell accumulation in the renal cortex at 13 wk PI but this response was abrogated by DHA feeding. Taken together, realistic dietary DHA supplementation prevented initiation and/or progression of ectopic lymphoid neogenesis, germinal center development, systemic autoantibody elevation, and resultant glomerulonephritis in this unique preclinical model of environment-triggered lupus

Large non-Gaussian Halo Bias from Single Field Inflation

We calculate Large Scale Structure observables for non-Gaussianity arising from non-Bunch-Davies initial states in single field inflation. These scenarios can have substantial primordial non-Gaussianity from squeezed (but observable) momentum configurations. They generate a term in the halo bias that may be more strongly scale-dependent than the contribution from the local ansatz. We also discuss theoretical considerations required to generate an observable signature.Comment: 30 pages, 14 figures, typos corrected and minor changes to match published version JCAP09(2012)00