THE PROBLEM OF MEASURING THE ABSOLUTE YIELD OF 14-Mev NEUTRONS BY MEANS OF AN ALPHA COUNTER

The assumptions used to derive the total neutron yield per detected alpha particle (from the D-T reaction) which were derived in an earlier report are reexamined in the light of additional experimental information. It is concluded that for an alpha counter at 90 deg to the incident beam direction the assumptions introduce practically no difficulties. Therefore, for precise monitoring in the absence of certain target information it is recommended that this configuration be used. For counters at angles different from 90 deg , nonuniformity of target loading contributes the most serious error to the computed yield. (auth

High-field magnetoresistance of Fe/GaAs/Fe tunnel junctions

We investigate transport through 6 to 10 nm thin epitaxial GaAs(001) barriers sandwiched between polycrystalline iron films. Apart from a pronounced tunneling magnetoresistance effect (TMR) at low magnetic fields we observe a distinct negative magnetoresistance (MR) at low and a positive MR at higher temperatures. We show that the negative MR contribution is only observed for the ferromagnetic iron contacts but is absent if iron is replaced by copper or gold electrodes. Possible explanations of the negative MR involve suppression of spin-flip scattering or Zeeman splitting of the tunneling barrier.Comment: 12 pages, 4 figures, submitted to Appl. Phys. Let

Cylindrical, periodic surface lattice — theory, dispersion analysis, and experiment

A two-dimensional surface lattice of cylindrical topology obtained via perturbing the inner surface of a cylinder is considered. Periodic perturbations of the surface lead to observation of high-impedance, dielectric-like media and resonant coupling of surface and non-propagating volume fields. This allows synthesis of tailored-for-purpose "coating" material with dispersion suitable, for instance, to mediate a Cherenkov type interaction. An analytical model of the lattice is discussed and coupled-wave equations are derived. Variations of the lattice dispersive properties with variation of parameters are shown, illustrating the tailoring of the structure's electromagnetic properties. Experimental results are presented showing agreement with the theoretical model

Conservation genomics reveals fine-scale population structuring and recent declines in the Critically Endangered Australian Kuranda Treefrog

The Kuranda Treefrog occurs in tropical north-east Australia and is listed as Critically Endangered due to its small distribution and population size, with observed declines due to drought and human-associated impacts to habitat. Field surveys identified marked population declines in the mid-2000s, culminating in very low abundance at most sites in 2005 and 2006, followed by limited recovery. Here, samples from before (2001–2004) and after (2007–2009) this decline were analysed using 7132 neutral genome-wide SNPs to assess genetic connectivity among breeding sites, genetic erosion, and effective population size. We found a high level of genetic connectivity among breeding sites, but also structuring between the population at the eastern end of the distribution (Jumrum Creek) versus all other sites. Despite finding no detectable sign of genetic erosion between the two times periods, we observed a marked decrease in effective population size (Ne), from 1720 individuals pre-decline to 818 post-decline. This mirrors the decline detected in the field census data, but the magnitude of the decline suggested by the genetic data is greater. We conclude that the current effective population size for the Kuranda Treefrog remains around 800 adults, split equally between Jumrum Creek and all other sites combined. The Jumrum Creek habitat requires formal protection. Connectivity among all other sites must be maintained and improved through continued replanting of rainforest, and it is imperative that impacts to stream flow and water quality are carefully managed to maintain or increase population sizes and prevent genetic erosion

U.S. SPACE FORCE (USSF) ACQUISITION OCCUPATIONAL COMPETENCY INTEGRATION INTO A TALENT OPERATIONS PLATFORM

The idea of using competencies as a vehicle for effective talent management has been an idea explored by many organizations. Recently all service components across the Department of Defense (DOD) have begun a revolution within talent management, particularly with job placement. The DOD’s newest component, the United States Space Force (USSF), actively seeks to implement a competency-based process as dictated by the Guardian Ideal. This capstone report provides USSF with recommendations on effectively integrating a scalable competency-driven system into a talent operations platform that manages Guardian talent during assignment placement. The team evaluated civilian and governmental talent operations systems and processes through interviews with relevant talent management personnel within the DOD and industry. This qualitative analysis fueled the team’s development of a simulation model to identify the effects of competency integration on the system and its interaction with external variables. Throughout the research, the team confirmed that all services desire the effective integration of competencies but lack the implementation of accountable competencies by a validation method. The team recommends Space Force develop a way to validate and input competency assessments by implementing the competency framework within a software system in terms of a scoring algorithm to provide a clear picture for Guardians and Commanders to determine the best fit for vacant billets.Space Force Talent Management Office (ETMO)Major, United States ArmyCaptain, United States ArmyCaptain, United States ArmyCaptain, United States ArmyCaptain, United States ArmyApproved for public release. Distribution is unlimited

Infection dynamics, dispersal, and adaptation: understanding the lack of recovery in a remnant frog population following a disease outbreak

Emerging infectious diseases can cause dramatic declines in wildlife populations. Sometimes, these declines are followed by recovery, but many populations do not recover. Studying differential recovery patterns may yield important information for managing disease-afflicted populations and facilitating population recoveries. In the late 1980s, a chytridiomycosis outbreak caused multiple frog species in Australia's Wet Tropics to decline. Populations of some species (e.g., Litoria nannotis) subsequently recovered, while others (e.g., Litoria dayi) did not. We examined the population genetics and current infection status of L. dayi, to test several hypotheses regarding the failure of its populations to recover: (1) a lack of individual dispersal abilities has prevented recolonization of previously occupied locations, (2) a loss of genetic variation has resulted in limited adaptive potential, and (3) L. dayi is currently adapting to chytridiomycosis. We found moderate-to-high levels of gene flow and diversity (Fst range: <0.01-0.15; minor allele frequency (MAF): 0.192-0.245), which were similar to previously published levels for recovered L. nannotis populations. This suggests that dispersal ability and genetic diversity do not limit the ability of L. dayi to recolonize upland sites. Further, infection intensity and prevalence increased with elevation, suggesting that chytridiomycosis is still limiting the elevational range of L. dayi. Outlier tests comparing infected and uninfected individuals consistently identified 18 markers as putatively under selection, and several of those markers matched genes that were previously implicated in infection. This suggests that L. dayi has genetic variation for genes that affect infection dynamics and may be undergoing adaptation

Classification Strategy to Identify and Classify Common Cracks in Green-State Powdered Metallurgy Compacts

The presence of and/or the potential for cracks in powder metallurgy components is an industry recognized quality concern. In an industry wide survey, eliminating or controlling of cracks was found to be the second most important research priority identified [1]. The general improvement of mechanical properties was the number one issue identified. It should be noted, however, that the benefits of material properties gains only slightly exceeded that of the cracking issue in importance to the industry respondents of the surveys

Efficient cosmological parameter sampling using sparse grids

We present a novel method to significantly speed up cosmological parameter sampling. The method relies on constructing an interpolation of the CMB-log-likelihood based on sparse grids, which is used as a shortcut for the likelihood-evaluation. We obtain excellent results over a large region in parameter space, comprising about 25 log-likelihoods around the peak, and we reproduce the one-dimensional projections of the likelihood almost perfectly. In speed and accuracy, our technique is competitive to existing approaches to accelerate parameter estimation based on polynomial interpolation or neural networks, while having some advantages over them. In our method, there is no danger of creating unphysical wiggles as it can be the case for polynomial fits of a high degree. Furthermore, we do not require a long training time as for neural networks, but the construction of the interpolation is determined by the time it takes to evaluate the likelihood at the sampling points, which can be parallelised to an arbitrary degree. Our approach is completely general, and it can adaptively exploit the properties of the underlying function. We can thus apply it to any problem where an accurate interpolation of a function is needed.Comment: Submitted to MNRAS, 13 pages, 13 figure

Standing out from the crowd:Dedicated institutional investors and strategy uniqueness

This paper examines the effect of dedicated institutional investors on firms' strategy uniqueness. We build on the uniqueness paradox where unique strategies are important drivers of economic rent, yet create an information problem whereby CEOs face discounts from the capital market, thus discouraging them from selecting unique strategies. We propose dedicated institutional investors as a partial remedy to the uniqueness paradox. Dedicated institutional investors invest in gaining private information about their investments, devote effort to understanding firms' strategies, and reduce capital market pressure. Thus, dedicated institutional investors can encourage CEOs to pursue more unique strategies. Our empirical results show the positive influence of dedicated institutional investors on strategic uniqueness, which is even stronger when firms operate in industries that are hard to value

A Research Agenda

For decades, the literatures on firm capabilities and organizational economics have been at odds with each other, specifically relative to explaining organizational boundaries and heterogeneity. We briefly trace the history of the relationship between the capabilities literature and organizational economics and point to the dominance of a “capabilities first” logic in this relationship. We argue that capabilities considerations are inherently intertwined with questions about organizational boundaries and internal organization, and use this point to respond to the prevalent “capabilities first” logic. We offer an integrative research agenda that focuses, first, on the governance of capabilities and, second, on the capability of governance