Stability and natural frequencies of functionally graded stringer-reinforced panels

The paper presents an analysis of stability and free vibrations of rectangular functionally graded panels reinforced by a system of parallel stringers. The exact solution of the problem is illustrated for large aspect ratio panels with simply supported long edges and arbitrary boundary conditions along the short edges (hereafter the reference to an “exact solution” implies a closed-form solution in the content of the theory of plates). The spacing between the stringers and the cross sections of individual stringers can be arbitrary. In the particular case where identical stringers are equally spaced, the solution is simplified using the smeared stiffeners technique. The optimization problem concerned with the choice of stringers and their spacing in the situations where the buckling loads or fundamental frequencies are prescribed is also considered. The closed-form solution of the optimization problem is shown in the case of blade stringers.     

Biculturalism and perceived competence of Latino immigrant adolescents

The present study investigated acculturation to the Hispanic and American cultures and self-perceptions of competence among 123 Latino immigrant adolescents. The study tested a contextual model of biculturalism by examining whether different acculturation styles predicted perceived competence in life spheres with different cultural demands. Perceived competence was assessed using Harter's (1988). Self-Perceptions of Competence Profile for Adolescents for the life spheres of school, peers (both Latino and non-Latino), and global self-worth. In addition, an analogous scale to assess perceptions of competence in the family was constructed for that sphere. The study found some support for a contextual model of acculturation. Acculturation to American culture predicted positive self-perceptions of competence with American peers, while acculturation to Hispanic culture predicted positive self-perceptions of competence with Latino peers. Perceived family competence, however, was predicted by acculturation to American rather than Hispanic culture. Results with respect to biculturalism are tentative, with a trend relating biculturalism to positive self-perceptions of global self-worth. However, because many of the conditions stipulated by the model were not met, results with respect to biculturalism raise questions about current approaches to operationalizing the construct.     

Active control of composite plates using piezoelectric stiffeners

The governing equations for geometrically nonlinear, arbitrarily laminated rectangular plates reinforced by stiffeners which include piezoelectric and composite layers are presented. General equations obtained in the paper are reduced to a single equation of motion for piezoelectrically reinforced, geometrically linear, specially orthotropic plates. A criterion for an effective control of forced vibrations of such plates using piezoelectric stiffeners and a static electric field is illustrated. Active control of dynamic stability using a dynamic electric field with a frequency equal to that of the in-plane load is also considered.In addition, an approach to the analysis of piezoelectrically stiffened nonlinear plates whose motion is represented by single-term functions of the coordinates is discussed.Numerous active control problems can be addressed using the theory outlined in the paper.     

Parametric vibrations of long cylindrical shells subject to transverse static load

The problem of parametric vibrations of long circular cylindrical shells prestressed by a uniformly distributed transverse static load has been considered. The static equilibrium position is found as a result of the solution of a nonlinear problem, where the factors contributing to nonlinearity include flattening of circular cross sections during deformation, stretching of elastic axis and hardening elastic foundation. Small amplitude forced parametric vibrations about the static position are then studied. The solution of the nonlinear parametric vibration problem in the absence of the static load is also shown.     

Rare-earth, 2d-generation image enhancement screens and their use in x-ray study of the gastrointestinal tract

It is technically feasible to examine human urothelial biopsy specimens by light microscopy after the same specimen has been examined by scanning electron microscopy. This combined microscopic procedure demonstrates that surface microfeatures of human urothelial cells, including pleomorphic microvilli, are variably present in atypical and in malignant vesical tissues. Scanning electron microscopy of a urothelial specimen requires direct light microscopic correlation of the pathologic disorder which is present in a particular area of the specimen which has been examined by scanning electron microscopy.     

A Dynamic Light-Weight Group Service

The virtual synchrony model for group communication is a powerful paradigm for building distributed applications. Implementations of virtual synchrony usually use failure detectors and failure recovery protocols. In applications that require a large number of groups, significant performance gains can be attained if these groups share the resources required to provide virtual synchrony. A service that maps multiple user groups onto a small number of instances of a virtually synchronous implementation is called a light-weight group service. This paper describes a new design for the light-weight group protocols that enables such service to function transparently. We discuss how these protocols can be applied in dynamic environments, where group mappings cannot be defined a priori and may change over time. We show that it is possible to establish mappings that promote resource sharing and, at the same time, minimize interference. These mappings can be established in an automated manner, using heuristics applied locally at each node. Experiments using an implementation in the Horus system show that significant performance improvements can be achieved with this approach.     

Identification and structural characterization of two genes encoding glutamate transporter homologues differently expressed in the nervous system of Drosophila melanogaster

The aim of the present investigation was to study the effect of neurotoxic ibotenic acid lesion of the retrochiasmatic area on the daily profile of pineal N-acetylserotonin and melatonin synthesis and on the pineal metabolic reactivity to nocturnal short-term retinal photostimulation. Groups of rats were killed 6 h after lights off either in the dark of immediately after being photostimulated for 1 or 15 min. Additionally, groups of rats were sacrificed at six different time points throughout the 24-hour light-dark cycle. The results suggested the presence of two functionally distinct territories in the retrochiasmatic area. The basal retrochiasmatic area, an area situated immediately ventral to the third ventricle, behind the suprachiasmatic nuclei and in front of the arcuate nucleus, is implicated in the nocturnal inhibitory process induced by short-term retinal photostimulation. The lateral retrochiasmatic area, which is situated immediately lateral to the anterior periventricular nucleus, below the anterior hypothalamic nucleus and in front of the ventromedial hypothalamic nucleus, is importantly involved in the control of the peak amplitude of the daily production of N-acetylserotonin and melatonin by the pineal gland.