Ionoluminescence decay measured with single ions

A new ion beam analysis-based, single ion technique called the time to first photon has been developed to measure the decay of the luminescence signal of phosphors. Such measurements are currently needed to study luminescence decay mechanisms following high-density excitations and to identify strongly luminescent phosphor coatings with short lifetimes for ion photon emission microscopy (IPEM). The samples for this technique consist of thin phosphor layers placed or coated on the surface of PIN diodes. Single ions from an accelerator strike this sample and simultaneously create ion beam induced luminescence (IBIL) from the phosphor that is measured by a single-photon-detector, and an ion beam induced charge collection (IBICC) signal in the PIN diode. In this case, the IBICC signal provides the start pulse and the IBIL signal the stop pulse to a time to amplitude converter. It is straightforward to show that this approach also measures a signal proportional to activity versus time with an accuracy of 5% as long as the number of detected photons per ion is less than 0.1, which usually requires the use of absorbers for the IBIL detector or electronic discrimination for the IBIL signals. Details of the new analysis are given together with examples of luminescence decay measurements of several ceramic phosphors being considered to coat IPEM samples. IPEM is currently being developed at Sandia National Laboratory (SNL), the University of North Texas in Denton, and the Universities and INFN of Padova and Torino.     

The revised URGAP model to describe the gap conductance between fuel and cladding

The URGAP gap conductance model has been extended and revised generally. An enlarged data base consisting of approximately 1000 data has been constructed and was used to calibrate the revised URGAP model. With this model the gap conductance for very different conditions such as material pairing, gas and contact pressure, surface roughness of fuel and cladding, gap width, gas temperature and composition are very satisfactorily described. URGAP may be used in any code describing the fuel rod behaviour of any reactor type.     

Overview of LIMEX'87 ice observations

Ice observations, results, and conclusions are summarized for the March 1987 Labrador Ice Margin Experiment (LIMEX'87), an international oceanographic study conducted in the pack ice of the Grand Banks area off the coast of Newfoundland. Included are the ice extent, flow size and thickness, ice kinematics and rheology, ice microwave properties, oceanic properties under the ice, and penetration of swell into the ice     

Neurovisceral integration in cardiac and emotional regulation

The utility of heart-rate variability (HRV) to index important aspects of neural control of the heart has made it one of the most valuable tools for researchers interested in health and behavior. However, most of the literature and extant data on the central origins of HRV have been derived from animal models. As yet little is known about the central nervous system (CNS) origins and concomitants in humans. In the following we will briefly detail a set of neural structures that have been associated with important CNS functions including cardiac regulation and emotional regulation. We will briefly summarize recent data using pharmacological, neuroimaging, and psychophysiological techniques that have examined CNS concomitants of HRV especially during emotion. Based on these and other data will we report the results of a computational model that examined the interactions of several neural structures and their effect on emotion-related HRV.     

Comments on anisotropic yield criteria

Limitations of several anisotropic yield criteria are discussed. Hill's 1948 criterion overestimates the variation of yield strength with direction, while the specializations of Hill's 1979 theory assume planar isotropy. Shear stress terms cannot simply be included in either the author's 1979 criterion or in Hill's 1979 general criteria.It is suggested that the author's criterion be modified so that it is expressed in terms of principal stresses rather than referring stresses to the symmetry axes.     

An accurate analysis of scalar quantization-based data hiding

This paper comes to fill a gap in watermarking theory, analyzing the exact performance of the scalar Costa scheme (SCS) facing additive Gaussian attacks when the usual approximation of high-resolution quantization is not valid, thus taking into account the host statistics. The analysis is focused on the assessment of the probability of error, showing new results, an although it is valid in a general scenario, its practical interest is increased when SCS is used in conjunction with the so-called spread-transform. The accomplished reformulation of the problem also permits to show that the achievable rate of SCS is never worse than that of classical spread-spectrum-based methods, as it was thought so far, and allows to establish interesting links with spread spectrum and the Improved Spread Spectrum method.