Refined Mindlin-Reissner theory of forced vibrations of shear deformable plates

Two theories of shear deformable plate vibrations that account for the influence of the transverse normal stress component are derived. The first is a slightly modified Mindlin theory, including a shear correction factor, while in the second the use of the shear correction factor is replaced by stress components that exactly satisfy elasticity motion equations and plate face boundary conditions. A comparison with the exact 3D solution for a sinusoidally loaded rectangular plate and infinite strip is made. It is found that the refined theories significantly increase the accuracy of results compared to the original Mindlin theory.     

New model of screening kinetics

An understanding of screening requires a knowledge of screening kinetics. The new model of screening kinetics presented in this paper is theoretically described and experimentally proven. Samples of different raw materials, different in their density, bulk density, particle size distribution and particle shape, were used.The conducted experiments confirmed that the new model of screening kinetics successfully describes the process of screening of various raw materials even when they are exposed to a range of factors that most influence the screening process (dimensions of the screen, particle size distribution of raw materials, particle shape, and thickness of the bed on the screen).The advantage of this model of screening kinetics lies in its simplicity as it is characterized by the fact that it has only one parameter, i.e., (k) - the screening rate constant, which is experimentally measured. This constant can be measured on the basis of a single screening experiment. This fact is very significant for practical applications of the model to an industrial screen.     

Crosslinking of atactic polypropylene by the system peroxide-pentaerythritol tetraallyl ether

The influence of the concentration of peroxide (mainly dicumyl peroxide) and pentaerythritol tetraallyl ether as coagent and the effect of temperature on the crosslinking of atactic polypropylene (a-PP) with molar mass 12 000g/mol were investigated. Using this system, crosslinking of 40mass% of a-PP at 160°C was obtained. The problems associated with the mechanism for crosslinking of a-PP are discussed.     

Ciliary neurotrophic factor increases the survival of magnocellular vasopressin and oxytocin neurons in rat supraoptic nucleus in organotypic cultures.

Organotypic cultures of the rat hypothalamus are very useful models for the long-term study of parvocellular vasopressin (VP) neurons in the paraventricular (PVN) and suprachiasmatic (SCN) nuclei. However, they do not preserve significant numbers of VP magnocellular neurons (VP-MCNs) in either the PVN or the supraoptic nucleus (SON). Vutskits et al. [(1998) Neuroscience 87:571-582] reported that ciliary neurotrophic factor (CNTF) was a selective survival factor for rat VP-MCNs in organotypic cultures of the rat hypothalamic paraventricular nucleus (PVN). We examined the effects of CNTF on the survival of these neurons in rat and mouse SONs. CNTF (10 ng/ml) in the culture media increased the survival of VP-MCNs by 6-fold and OT-MCNs by 3-fold. In the mouse, both OT- and VP-MCNs survive very well in organotypic cultures under standard culture conditions and the addition of CNTF had no further effect. Consistent with these results, in situ hybridization showed substantially higher levels of VP- and OT-mRNA in rat PVNs and SONs in the presence of CNTF, but produced no changes in these nuclei in the mouse. The optimum period for the survival effect of CNTF on MCNs in the rat hypothalamic cultures was in the first 7-10 days of culture and this effect is maintained for at least 5 additional days if CNTF is then removed from the medium. Therefore, using CNTF in the culture media can provide an opportunity for long-term studies of rat VP- and OT-MCNs in SONs in organotypic cultures.     

Exploiting the Hessian matrix for content-based retrieval of volume-data features

Published online: 14 May 2002     

Tunable self-assembly of one-dimensional nanostructures with orthogonal directions

High-temperature exposure of a Mo(110) surface to borazine (HBNH)₃ leads to the formation of two distinctly different self-assembling nanostructures. Depending on the substrate temperature during preparation, either well-aligned, ultra-thin boron nanowires or a single-layer stripe structure of hexagonal boron nitride forms. Both structures show one-dimensional (1D) characteristics, but in directions perpendicular to each other. It is also possible to grow the two phases in coexistence. The relative weights are controlled by the sample temperature during preparation.     

Is 1-hexene epoxidation in TS-1 diffusion limited in different solvents?

PFG NMR diffusion measurements were carried out to determine the effect of solvent on intracrystalline reactant diffusivities and on 1-hexene epoxidation rates in TS-1 catalyst. Using n-hexane in silicalite as a mimic for the TS-1 system, the self-diffusivity of n-hexane in silicalite was found to be 24% higher in methanol solvent than in acetonitrile solvent and 45% higher than in acetone solvent. The presence of trace Al did not affect n-hexane diffusivity. Based on analysis of the Weisz modulus for a slab morphology, the 1-hexene epoxidation reaction in TS-1 was found to be diffusion limited only if the crystal size is at least 38 μm in the methanol system.     

Pitch discrimination in field- and isolation-reared black-capped chickadees (Parus atricapillus).

Prior research has shown that male black-capped chickadees (Parus atricapillus) raised in the field produce constant relative pitch cues (frequency ratios) in their songs, whereas males reared in isolation from adult song do not. In this study, the authors found that field-reared male chickadees needed fewer than half as many sessions to learn an operant (go/no-go) auditory discrimination that linked S+ note pairs with a constant-frequency ratio than a discrimination that varied the frequency ratio of S+ pairs randomly. Most important, isolation-reared males needed over 5 times as many sessions to learn the constant-ratio discrimination compared with field-reared males. This is, to the authors' knowledge, the first report of impaired pitch discrimination in isolate songbirds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A new inductive displacement transducer

Injection system is the main unit of diesel engines having a major impact on proper operation of the engines. Delivery valve as an important element of the injection system assures its smooth functioning. In order to learn as much as possible about the movement of the delivery valve during the operation of the injection system an inductive displacement transducer has been designed. The results of the measurements clearly indicate that the movements of the delivery valve are in agreement with the other measured parameters of the injection and that the proposed method for measuring the delivery valve lift can be successfully used with certain types of delivery valves.