From set membership to group membership: a separation of concerns

We revisit the well-known group membership problem and show how it can be considered a special case of a simple problem, the set membership problem. In the set membership problem, processes maintain a set whose elements are drawn from an arbitrary universe: They can request the addition or removal of elements to/from that set, and they agree on the current value of the set. Group membership corresponds to the special case where the elements of the set happen to be processes. We exploit this new way of looking at group membership to give a simple and succinct specification of this problem and to outline a simple implementation approach based on the state machine paradigm. This treatment of group membership separates several issues that are often mixed in existing specifications and/or implementations of group membership. We believe that this separation of concerns greatly simplifies the understanding of this problem.     

Risk factors associated with recidivism among extrafamilial child molesters.

This study examined the predictive efficacy of 10 rationally derived, archivally coded variables for assessing reoffense risk among extrafamilial child molesters. Follow-up data on 111 child molesters who were discharged from the Massachusetts Treatment Center between 1960 and 1984 were used. Degree of sexual preoccupation with children, paraphilias, and number of prior sexual offenses predicted sexual recidivism. Juvenile and adult antisocial behavior, paraphilias, and low amount of contact with children predicted nonsexual victim-involved and violent recidivism. Area under the receiver-operating characteristic curves in all three analyses indicated discrimination that was substantially better than chance, ranging from .73 to .79. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the mechanisms of adenosine induced pulmonary vasoconstriction in rats

The effect of adenosine on pulmonary vessels was studied in isolated perfused rat lungs. Drugs were administered intra-arterially in a fixed volume of 0.1 ml Krebs solution as bolus injections. Adenosine responses were obtained before and 10 min after drug injections. When applied in logarithmically increasing doses (1-100 micrograms/ml), adenosine caused dose-dependent increases in pulmonary perfusion pressure (e.g. pulmonary vasoconstriction) which were readily reversible. Challenging adenosine with quinidine, dihydroergocristine and cyproheptadine (2 micrograms/ml each) did not significantly alter adenosine responses. Pretreatment of lungs with 0.5 mM theophylline, 10 micrograms/ml indomethacin, 30 micrograms/ml tebokan (a PAF antagonist) or 1 microgram/ml methylene blue for 10 min, however, antagonized the vasoconstrictor effect of the drug significantly. From these experiments, it was concluded that the mechanisms underlying the pulmonary vasoconstrictor action of adenosine are complex, and that both types of purinoceptors, prostaglandins, PAF and other vascular endothelial hormones might be involved.     

Organizational computer security policy: the reality

Computer security issues are normally addressed from a technical perspective. Increasingly, however, organizations and computer specialists are coming to realise that applying more technology as the basis of an answer to a problem that derives from technology cannot, in the long term, be a viable solution. This paper shows how it is important that other considerations are taken into account, such as business and management requirements, and practical user issues. In order for this approach to make any progress, we must first establish the current situation in ordinary organizations. This paper describes key results from research carried out to determine the status of computer security in organizations today.     

Simplified characterization of uniaxial and biaxial nonlinearoptical crystals: a plea for standardization of nomenclature andconventions

Standards which eliminate ambiguity in reporting nonlinear phenomena, especially in the increasingly complex realm of biaxial crystals, are proposed. In order to restore uniformity to the designation of crystallographic axes and crystal tensor properties, adoption of IEEE/ANSI Std. 176, with a small but much needed modification for crystal class mm2, is recommended. For the reporting of nonlinear interaction characteristics, other frames are proposed which result in simpler rules than heretofore given for categorizing phase-matching loci, and for characterizing eigenmode polarizations, double refraction, effective nonlinear coupling, and first- and second-order acceptance bandwidths (angular, spectral, thermal) along these loci. Similarities as well as differences between biaxial and uniaxial crystals are emphasized     

Buck converter small-signal models and dynamics: comparison ofquasi-resonant and pulsewidth modulated switches

The generalized canonical model obtained from extended state-space averaging is used as a design tool for the evaluation of the buck converter dynamics in different switching schemes. Designs are given at a specified constant conversion ratio and load for the pulse width modulated, zero current, zero voltage, and nonlinear resonant switch full- and half-wave converters. The small signal equivalent circuit model is discussed, and the feedback effects introduced by resonant switching on line and control transfer functions are evaluated. The small signal transfer functions of half-wave converters are heavily load-current dependent, and exhibit significant damping at light loads, which can result in two real poles in the converter response instead of a complex conjugate pair. This damping effect is evaluated over the entire normalized load current range for the linear and nonlinear zero-current switching converters. Simple approximate expressions are given for the real poles. Experimental verification of the half-wave analysis is presented, and the effects of converter efficiency on model accuracy are discussed     

Physical and chemical characterization of thermosoftened bases for molten filled hard gelatin capsule formulations

Dynafill, Dynasan-114, Lutrol-F68, PEG-10000 and PEG-20000 have been examined as potential bases for the preparation of fusion formed solid dispersions for molten filling into hard gelatin capsules. Investigations included, an examination of thermal effects on crystal structure by DSC and XRD, a theological study to evaluate capsule filling characteristics, dissolution studies on drug/base formulations, chemical analysis for free fatty acid impurities in Dynafill and Dynasan-114, and detailed studies on selected drug/base formulations. PEG-20000 and Dynasan-114 were not examined in detail, after preliminary investigations had shown high viscosity and poor filling characteristics for PEG-20000 and poor dissolution characteristics for Dynasan-114. Dynafill provided good release profiles when formulated with a variety of model drugs (Acetohexamide, Ibuprofen, Indomethacin, Quinidine sulphate and Theophylline). Results from hot stage photomicrography supported by DSC and XRD were used to construct a phase diagram of the Ibuprofen/Lutrol-F68 system. The evidence from the phase diagram indicated the formulation of a simple eutectic system with no solid solubility and a eutectic composition at approximately 35% w/w Ibuprofen.     

Effects of internal scattering on X-ray microtomography imagereconstruction

A computer simulation is used to study the problem of internal scattering for targets that are imaged using X-ray microtomography. A strategy is outlined for selecting X-ray energy and image resolution based on properties of the material being imaged. The X-ray scanning process is simulated by applying a Monte Carlo technique to a modeled target that emulates the material properties of a microelectronic device. The X-ray photons are subject to photoelectric absorption, Rayleigh scattering, and Compton scattering. The simulation applies a method of high-resolution image reconstruction based on discrete Fourier transforms. Examples of reconstructed images that have 0.5-μm spatial resolution are shown for images of simulated lead and aluminum targets     

Duality transformations for general bi-isotropic (nonreciprocalchiral) media

The transformation is defined to leave a given bi-isotropic medium invariant, whence it is self-dual in this transformation. It is shown that duality transformations always exist in pairs, labeled as left-hand and right-hand transformations. Self-dual fields are seen to be generalizations of the wave fields E± applied in the analysis of reciprocal chiral media. It is demonstrated that plane wave propagation and reflection problems in bi-isotropic media can be solved easily in terms of self-dual field decompositions. Nonreciprocity is seen to give rise to effects like polarization rotation in reflection, which cannot be interpreted in terms of reciprocal chiral media