Measurements of neutron energy using a recoil-proton telescope and a high-pressure ionization chamber

Two very different techniques for measuring the energy of neutrons in the energy range 0.1-10 MeV are presented and compared. A recoil-proton spectrometer is used to determine the energy spectra of neutrons produced by the d(4)-Be and p(4)-Be reactions down to the low-energy threshold of 0.7 MeV. The same radiation fields are also measured with a recently developed method using a high-pressure ionization chamber that can be used to determine the mean energy of the neutrons in a mixed neutron-gamma radiation field provided the gamma-ray absorbed dose fraction is determined independently. An intercomparison of the two methods shows that the high-pressure ionization chamber compares well and supplements the established recoil-proton spectrometer technique. The almost isotropic response of the chamber has enabled measurements to be made of the variation of mean neutron energy with depth in water for the two radiation fields.     

Derivation of sonograph quality parameters by the use of point spread function analysis

A measuring system evaluating a Point Spread Function generated in an ultrasonographic image by scanning a spherical target was developed. The target is moved in measuring bath filled by water over scanned volume via 3D computer controlled positioning system. A video signal obtained is converted to digital form and analyzed by original software to derive various objective parameters of the imager as follows: Focal areas in both the azimuth and the elevation directions, Ultrasound scanning lines visualisation, Manufacturer preloaded TGC, Width of the scanning plane, Side lobe levels and Amplification uniformity in the azimuth direction. The method was verified by testing 18 different equipments in 282 measurements. Samples of particular measurement results in form of graphical outputs are included. Medical and physiological impacts of this approach are discussed.     

Measuring quality of life in theory and in practice: a dialogue between philosophical and psychological approaches

Measuring quality of life is of concern to both philosophers and psychologists, yet the two disciplines typically approach the question in very different ways, ways so diverse that it may look as if they are engaged in such disparate activities that no dialogue between them is possible. In this paper we aim to construct the beginnings of a dialogue between the two disciplines which will show how they could serve each other and yet also show how, from the dialogue, difficult and previously unconsidered issues emerge for both sides.     

Determination of structural parameters from advanced molecular electronic spectroscopy: The double ionization of nitrous oxide by synchrotron radiation

The double photoionization of N₂O molecules, in the 30–50 eV energy range, has been studied by synchrotron radiation. In the whole energy range, dissociative ionization producing N⁺ + NO⁺ or N₂⁺ + O⁺ has been observed. These two processes appear to occur also below the vertical thresh-old of 35.8 eV, where the double ionization should be indirect. In the range between 35.8 and 38.5 eV. The two processes occur instead by direct coulomb explosion of the N₂O²⁺ dication. Above 38.5 eV, the dissociation leading to NO⁺ + N⁺ is also promoted by the formation of a dication metastable state, which decays by fluorescence to the ground state and then dissociates.      

Towards microbiological quality assurance in radiation sterilization processing: simulation of the radiation inactivation process

A method is developed for computer simulation of the inactivation of microorganisms on items by irradiation. It is shown that in a population of items subjected to increasing doses of radiation the proportion contaminated approaches the appropriate Limiting Case, outlined in a previous paper, as numbers of organisms are decreased by inactivation. The behaviour of populations of items having different proportions of 'spikes' (high bioburden levels) is considered.     

Quantitative analysis of molecular surfaces: areas, volumes, electrostatic potentials and average local ionization energies

We describe a procedure for performing quantitative analyses of fields f(r) on molecular surfaces, including statistical quantities and locating and evaluating their local extrema. Our approach avoids the need for explicit mathematical representation of the surface and can be implemented easily in existing graphical software, as it is based on the very popular representation of a surface as collection of polygons. We discuss applications involving the volumes, surface areas and molecular surface electrostatic potentials, and local ionization energies of a group of 11 molecules.

Variation in plant quality and the population dynamics of herbivores: there is nothing average about aphids

In the attempt to use results from small-scale studies to make large-scale predictions, it is critical that we take into account the greater spatial heterogeneity encountered at larger spatial scales. An important component of this heterogeneity is variation in plant quality, which can have a profound influence on herbivore population dynamics. This influence is particularly relevant when we consider that the strength of density dependence can vary among host plants and that the strength of density dependence determines the difference between exponential and density- dependent growth. Here, we present some simple models and analyses designed to examine the impact of variable plant quality on the dynamics of insect herbivore populations, and specifically the consequences of variation in the strength of density dependence among host plants. We show that average values of herbivore population growth parameters, calculated from plants that vary in quality, do not predict overall population growth. Furthermore, we illustrate that the quality of a few individual plants within a larger plant population can dominate herbivore population growth. Our results demonstrate that ignoring spatial heterogeneity that exists in herbivore population growth on plants that differ in quality can lead to a misunderstanding of the mechanisms that underlie population dynamics.     

Adaptive sex allocation in birds: the complexities of linking theory and practice

We review some recent theoretical and empirical developments in the study of sex allocation in birds. The advent of reliable molecular sexing techniques has led to a sharp increase in the number of studies that report biased offspring sex ratios in birds. However, compelling evidence for adaptive sex allocation in birds is still very scant. We argue that there are two reasons for this: (i) standard sex allocation models, very helpful in understanding sex allocation of invertebrates, do not sufficiently take the complexities of bird life histories and physiology into account. Recent theoretical work might bring us a step closer to more realistic models; (ii) experimental field and laboratory studies on sex allocation in birds are scarce. Recent experimental work both in the laboratory and in the field shows that this is a promising approach.     

Gender in bioethics: theory and practice -- an introduction

Does the care perspective make a difference? Can it reach as far as we would like? It is the goal of this special issue on Gender in Bioethics: Theory and Practice to begin to address some of these important questions. In the first article, Virginia Sharpe provides a comprehensive and thoughtful analysis of how the orientations of justice and care are played out in medical ethical theory. In the second article, James Nelson argues that the more traditional approach in Bioethics to maternal-fetal conflicts is not useful, and that a care perspective is more appropriate. Thoughtful commentary on Nelson's article is provided by Rosemarie Tong. For readers new to the justice-care debate in moral theory, the following articles will provide an informative introduction. For those who are more familiar, it is hoped that you will be challenged by the extension of the debate to the practical issue of maternal-fetal conflicts.     

rh_tsp_map 3.0: end-to-end radiation hybrid mapping with improved speed and quality control

rh_tsp_map is a software package for computing radiation hybrid (RH) maps and for integrating physical and genetic maps. It solves the central mapping instances by reducing them to the traveling salesman problem (TSP) and using a modification of the CONCORDE package to solve the TSP instances. We present some of the features added between the initial rh_tsp_map version 1.0 and the current version 3.0, emphasizing the automation of many steps and addition of various checks designed to find problems with the input data. Iterations of improved input data followed by fast re-computation of the maps improves the quality of the final maps. AVAILABILITY: rh_tsp_map source code and documentation including a tutorial is available at ftp://ftp.ncbi.nih.gov/pub/agarwala/rhmapping/rh_tsp_map.tar.gz. CONCORDE modified for RH mapping is available in the directory http://www.isye.gatech.edu/~wcook/rh/. The QSopt library needed for CONCORDE is available at http://www2.isye.gatech.edu/~wcook/qsopt/downloads/downloads.htm     

Modification of the theory of dual radiation action for attenuated fields. II. Application to the analysis of soft X-ray results

A formalism developed in the first paper in this series, based on the generalized Theory of Dual Radiation Action, is applied to survival data for cells exposed to soft X rays. It is shown that, in contrast to previous published analyses, this formalism--modified to account for the attenuation of dose across the sensitive matrix of the cell--is fully consistent with the experimental results. The reasons for previous disagreements are discussed.