Minimum weight design of a rectangular panel subject to a flutter speed constraint

The thickness distribution for a simply supported rectangular panel is determined for minimum panel weight and a specified aeroelastic eigenvalue. Finite difference equations are used for derivatives with respect to the spanwise variable so that the partial differential constraint equations are approximated by sets of ordinary differential equations. Numerical solutions are obtained for the resulting optimal control problem using a gradient projection algorithm.     

Down's Syndrome (mongolism): The heritable aspects.

Striking technological advances in the study of human chromosomes have revealed an excess of genetic material in the cells of patients with Down's syndrome. Both the trisomic and translation forms of mongolism are discussed, as is the assessment of morbidity risks in relatives of a given patient. The origin of the chromosomal abnormalities, and the mechanisms by which they generate the clinical picture of Down's syndrome, constitute questions for further research. When this etiological enigma is resolved optional management of patients and their relatives will depend, even more than at present, upon the active collaboration of psychologists and psychiatrists with human geneticists. (100 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cross-country sailplane flight as a dynamic optimization problem

A minimum?time, thermal?to?thermal sailplane trajectory optimization problem is formulated as a non?linear optimal control problem. Numerical solutions are obtained using a gradiaent projection algorithm which incorporates conjugate directions of search. Further insight into the nature of the solutions and the computational process is ontained through an analysis of the linearized sailplane dynamics and the necessary conditions for optimality. Numerical results are presented for two sailplane types and various values of thermal strength and distance between thermals. An additional problem is formulated and solved for the case of bounded control rate.     

Embolic pulmonary aneurysms in yearling feedlot cattle

Throughout all of 1974, we surveyed, for illnesses and deaths, about 407,000 yearling feedlot cattle. Of 1,988 cattle necropsied, 25 (1.3%) had ruptured pulmonary aneurysms and an additional 4 had gross pulmonary emboli without rupture. The emboli originated from thrombi in the caudal vena cava where that vessel closely applies to the left border of the liver and where parenchymal abscesses had developed. The emboli had lodged in the pulmonary artery, weakened its wall, and led to saccular aneurysms. Infection weakened and blood pressure ruptured the saccule and opened the adjacent bronchi. Extravasated blood dissected the tunica adventitia, formed hematomas, poured into the bronchus, and was expelled from the larynx. A portion was swallowed into the rumen, and some was coughed and blown from the nose and mouth. Deaths were attributed to exsanguination and pulmonary incapacitation.     

Time resolved characterization of diesel particulate emissions. 1. Instruments for particle mass measurements

The measurement of diesel vehicle exhaust particulate mass is currently accomplished using filter collection methods according to the Code of Federal Regulations (CFR). Such filter methods limit time resolution to a minimum of several minutes, making it impossible to study emissions during transient operating conditions. Extensive testing of five different measurement methods has demonstrated that fast response measurements of diesel exhaust particulate mass concentrations, consistent with CFR filter measurements, are feasible using existing technology. The measurement principles of choice are the real time weighing of exhaust samples as implemented in the tapered element oscillating microbalance (TEOM) and the measurement of light scattering from exhaust particles as implemented in the DustTrak nephelometer. Each of these two instruments has distinctive strengths. The TEOM excels in the area of constant calibration, independent of vehicle. For the DustTrak, this calibration varies by vehicle. On the other hand, the DustTrak has an excellent signal-to-noise ratio, freedom from interference due to other exhaust sample properties, good time resolution, and simplicity. The strengths of the two measurement methods are complimentary, so an obvious suggestion is to integrate them. The nephelometer would obtain a fast response signal, with near real time calibration provided by the microbalance.     

FETI‐DP: a dual–primal unified FETI method—part I: A faster alternative to the two‐level FETI method

The FETI method and its two‐level extension (FETI‐2) are two numerically scalable domain decomposition methods with Lagrange multipliers for the iterative solution of second‐order solid mechanics and fourth‐order beam, plate and shell structural problems, respectively.The FETI‐2 method distinguishes itself from the basic or one‐level FETI method by a second set of Lagrange multipliers that are introduced at the subdomain cross‐points to enforce at each iteration the exact continuity of a subset of the displacement field at these specific locations. In this paper, we present a dual–primal formulation of the FETI‐2 concept that eliminates the need for that second set of Lagrange multipliers, and unifies all previously developed one‐level and two‐level FETI algorithms into a single dual–primal FETI‐DP method. We show that this new FETI‐DP method is numerically scalable for both second‐order and fourth‐order problems. We also show that it is more robust and more computationally efficient than existing FETI solvers, particularly when the number of subdomains and/or processors is very large. Copyright © 2001 John Wiley & Sons, Ltd.     

Fate and effect of quaternary ammonium compounds on a mixed methanogenic culture

The potential inhibitory effect of four quaternary ammonium compounds (QACs) and Vigilquat, a commercial sanitizer which is a mixture of the four QACs, was investigated at concentrations up to 100 mg/L using a mixed, mesophilic (35 degrees C) methanogenic culture. Dextrin and peptone were used as the carbon and energy sources. A batch assay conducted at a range of QAC concentrations showed that QACs were inhibitory to methanogens at and above 25 mg/L. Methanogenesis was more susceptible to QAC inhibition than acidogenesis. Adsorption of QACs on biomass was successfully simulated with the Freundlich isotherm equation. The inhibitory effect of Vigilquat on the mixed methanogenic culture was also investigated in a batch reactor fed with dextrin and peptone. Methanogens were inhibited when the total QAC concentration reached 30 mg/L and volatile fatty acids (VFAs) accumulated. However, methane production recovered in 57 days of incubation, and all VFAs were consumed, suggesting that a prolonged incubation period is necessary for the methanogens to overcome the transient inhibition at a relatively low QAC concentration. None of the QACs tested in this study was biodegraded under methanogenic conditions.     

Comparative analysis of Cr-B coatings deposited by magnetron sputtering in DC and HIPIMS modes

Surface coatings of the Cr-B system have been obtained by magnetron sputtering in the DC and high-power impulse (HIPIMS) regimes. It is established that the passage from the DC regime to HIPIMS leads to suppression of the columnar grain growth and a twofold increase in the resistance of coatings to plastic deformation, while the plasticity index and hardness of coatings increase by 29 and 18%, respectively.     

Perspectives on electron cryo-tomography of vitreous cryo-sections

A major objective of modern structural biology is to appreciate the cellular organization by elucidating the spatial arrangement of macromolecular complexes within a cell. Cryogenic sample preparation, combined with cryo-ultramicrotomy, enables large cells and pieces of biological tissues to be thinned for electron cryo-tomography, which provides a three-dimensional view of the biological sample. There are, however, limitations associated with the technique that must be realized, addressed and overcome for the procedure to become mainstream. Here, we provide perspectives on the continued advancements in cryogenic sample preparation for vitreous cryo-sectioning, image collection and post-image processing that have expanded the attainable information limit within the three-dimensional reconstructions of cells and pieces of biological tissues.