A modular approach for assessing the effect of radiation environments on man in operational systems. The radiobiological vulnerability of man during task performance

A modular approach for assessing the affects of radiation environments on man in operational systems has been developed. The feasibility of the model has been proved and the practicality has been assessed. It has been applied to one operational system to date and information obtained has been submitted to systems analysts and mission planners for the assessment of man's vulnerability and impact on systems survivability. In addition, the model has been developed so that the radiobiological data can be input to a sophisticated man-machine interface model to properly relate the radiobiological stress with other mission stresses including the effects of a degraded system

Water content and morphology of sodium chloride aerosol particles

This is the publisher's version, also available electronically from http://onlinelibrary.wiley.com/doi/10.1029/1999JD900286/abstract;jsessionid=41C36E183A6316F5D3C491131615BD7A.f01t04.Sodium chloride droplets with a median diameter of ∼0.4 μm were generated in the laboratory by atomizing an aqueous solution of NaCl under ambient conditions. Infrared extinction spectra of the aerosols under controlled relative humidity (RH) ranging from 15 to 95% were obtained. The extinction spectra contained both scattering and absorption components. In order to obtain an absorption spectrum of the condensed phase H2O associated with the particulates, it was necessary to subtract from the extinction spectra the absorption by H2O vapor and the scattering by the particulates. H2O vapor subtraction was accomplished by a standard technique. A procedure using Mie theory to subtract the scattering component of the extinction spectrum is described. The absorption spectra were used to determine the water content and structure of the particulates. Above ∼50% RH the aerosols contain aqueous droplets that have not reached equilibrium with the water vapor during the timescale of the experiments (∼10 s). There is a sharp transition in water content at around 50% RH which is consistent with other measures of the recrystallization point. Below 50% RH the NaCl particles contain an anomalously large amount of H2O. Several different particle models are considered to explain the H2O content. The model in which the NaCl particles contain pockets of aqueous NaCl solution was found to be most consistent with the spectroscopic observations. The relevance of salt particle morphology and water content to atmospheric aerosol chemistry is discussed

Intraduodenal sarcoma recurrence of retroperitoneal origin: an unusual cause for a duodenal obstruction.

Soft tissue sarcomas are uncommon tumors, and intraduodenal soft tissue sarcoma manifestation is even more rare. Only three cases of intraduodenal sarcomas have been reported in the literature thus far. Here, we report a case of an intraduodenal recurrence of a retroperitoneal sarcoma causing bowel obstruction. This unusual recurrence pattern likely relates to the patient's previous resection and radiation treatment, and highlights the benefits, limitations and follow-up strategies after multimodality treatment

Infrared spectroscopic signatures of (NH4)2SO4 aerosols

This is the publisher's version, also available electronically from http://onlinelibrary.wiley.com/doi/10.1029/96JD01543/abstract.Ammonium sulfate particles in air with average diameters ranging from 0.1 to 0.5-μm have been generated by atomizing aqueous solutions of (NH4)2SO4 of various concentrations at ambient temperatures and pressures. The infrared spectra from 4000 to 600 cm−1 of the resulting aerosols have been investigated. This spectral region has allowed us to study the four infrared-active vibrational modes of this salt: ν3(NH4+), ν4(NH4+), ν3(SO42−), and ν4(SO42−). The frequencies of these modes are similar to published results obtained from infrared studies of the single crystal but are displaced to higher wavenumbers. Depending on relative humidity, the aerosol particles are crystalline or supersaturated aqueous droplets. These phase identifications are possible because liquid water absorption features are found in the droplets but not in the crystals. Extensive Mie theory calculations have been performed for spheres of diameters ranging from 0.1-μm to 2.0-μm to explore frequency shifts and the relative contributions to extinction of scattering and absorption with particle size. We show that, for the smaller particles, the molecular cross section in the ν3(SO42−) region can be used to determine the number of (NH4)2SO4 molecules in an aerosol sample. The (small) frequency shifts in this region provide information on the aerosol particle size. A Mie theory calculation of extinction for a model polydisperse aerosol, believed to approximate that of an experimental aerosol, gives reasonable agreement with the observed spectrum. While calculated band centers of the four modes are within 1% of those observed, values of extinction can differ by as much as 50%. We discuss possible reasons for the discrepancies. Spectroscopic changes observed for an aerosol as the particles settle are discussed in terms of kinetic models and Mie theory. We discuss the potential of spectroscopic signatures of tropospheric (NH4)2SO4 aerosols for the characterization of their size, morphology, phase, and composition. Finally, we propose a field experiment to measure sulfate aerosol in the arctic troposphere

Dust from Mars-Analog Plains (Iceland): Physico-Compositional Properties as a Function of Grain-Size Fraction

Dust is a key component of the geological and climatic systems of Earth and Mars. On Mars, dust is ubiquitous. It coats rocks and soils, and, in the atmosphere, it interacts strongly with solar and thermal radiation. Yet, key questions remain about the genesis and fate of martian dust, as well as its sources, composition, and properties. We collected wind-blown dust from basaltic plains in SW Iceland at Skjaldbreiauhraun that represent a geologic Mars-analog environment. Icelandic dust differs from the typical continental sources (e.g. Sahara, Asia) because of its basaltic volcanogenic origin, which is similar to Mars. Dust collection took place in July of 2019 as a complementary project to the SAND-E: Semi-Autonomous Navigation for Detrital Environments project. Here we report preliminary analyses of this Mars-analog dust material, with the goal of understanding the processes that control the physico-chemical proper-ties of the different grain-size fractions

Qualitative study in Loop Quantum Cosmology

This work contains a detailed qualitative analysis, in General Relativity and in Loop Quantum Cosmology, of the dynamics in the associated phase space of a scalar field minimally coupled with gravity, whose potential mimics the dynamics of a perfect fluid with a linear Equation of State (EoS). Dealing with the orbits (solutions) of the system, we will see that there are analytic ones, which lead to the same dynamics as the perfect fluid, and our goal is to check their stability, depending on the value of the EoS parameter, i.e., to show whether the other orbits converge or diverge to these analytic solutions at early and late times.Comment: 12 pages, 7 figures. Version accepted for publication in CQ

Recovering the state sequence of hidden Markov models using mean-field approximations

Inferring the sequence of states from observations is one of the most fundamental problems in Hidden Markov Models. In statistical physics language, this problem is equivalent to computing the marginals of a one-dimensional model with a random external field. While this task can be accomplished through transfer matrix methods, it becomes quickly intractable when the underlying state space is large. This paper develops several low-complexity approximate algorithms to address this inference problem when the state space becomes large. The new algorithms are based on various mean-field approximations of the transfer matrix. Their performances are studied in detail on a simple realistic model for DNA pyrosequencing.Comment: 43 pages, 41 figure

Eddy‐driven sediment transport in the Argentine Basin: Is the height of the Zapiola Rise hydrodynamically controlled?

In this study, we address the question whether eddy‐driven transports in the Argentine Basin can be held responsible for enhanced sediment accumulation over the Zapiola Rise, hence accounting for the existence and growth of this sediment drift. To address this question, we perform a 6 year simulation with a strongly eddying ocean model. We release two passive tracers, with settling velocities that are consistent with silt and clay size particles. Our experiments show contrasting behavior between the silt fraction and the lighter clay. Due to its larger settling velocity, the silt fraction reaches a quasisteady state within a few years, with abyssal sedimentation rates that match net input. In contrast, clay settles only slowly, and its distribution is heavily stratified, being transported mainly along isopycnals. Yet, both size classes display a significant and persistent concentration minimum over the Zapiola Rise. We show that the Zapiola Anticyclone, a strong eddy‐driven vortex that circulates around the Zapiola Rise, is a barrier to sediment transport, and hence prevents significant accumulation of sediments on the Rise. We conclude that sediment transport by the turbulent circulation in the Argentine Basin alone cannot account for the preferred sediment accumulation over the Rise. We speculate that resuspension is a critical process in the formation and maintenance of the Zapiola Rise

Numerical loop quantum cosmology: an overview

A brief review of various numerical techniques used in loop quantum cosmology and results is presented. These include the way extensive numerical simulations shed insights on the resolution of classical singularities, resulting in the key prediction of the bounce at the Planck scale in different models, and the numerical methods used to analyze the properties of the quantum difference operator and the von Neumann stability issues. Using the quantization of a massless scalar field in an isotropic spacetime as a template, an attempt is made to highlight the complementarity of different methods to gain understanding of the new physics emerging from the quantum theory. Open directions which need to be explored with more refined numerical methods are discussed.Comment: 33 Pages, 4 figures. Invited contribution to appear in Classical and Quantum Gravity special issue on Non-Astrophysical Numerical Relativit