Biomechanical testing of the spine. Load-controlled versus displacement-controlled analysis

Mechanical testing of the spine can be carried out in either a load-controlled or a displacement-controlled manner. Each method requires certain assumptions and offers different advantages. Dr. W. Thomas Edwards believes that displacement-controlled testing most accurately reflects the in vivo environment, while Drs. Vijay Goel, David Wilder, and Malcolm Pope support the use of the load-controlled method as most logical and easily standardized.     

Pharmacological actions of Pongamia pinnata seeds--a preliminary study

Direct ethanolic and sequential petroleum ether, chloroform, acetone and ethanolic extracts (50-100 mg/kg, i.p.) of P. pinnata seeds given 30-60 min before revealed anti-inflammatory, analgesic and anti-ulcerogenic activities in rats. The activities were present maximum in petroleum ether and chloroform extracts. However, the extracts also showed shortening of pentobarbitone induced 'sleep time' in rats.     

Visual search for natural grains in pigeons (Columba livia): Search images and selective attention.

The experiments reported here were designed to test the suggestion of many researchers that selective attention to visual features of a prey can account for search-image effects. In 3 experiments pigeons ate wheat and vetch grains presented on multicolored and gray gravel trays. In Experiment 1 search-image effects were evident when grains were cryptic but not when they were conspicuous. Experiment 2 demonstrated that search images can be activated when the grains encountered are either cryptic or conspicuous but that search images affect search performance only when the grains are cryptic. Experiment 3 demonstrated that search images are short-term in nature: A 3-min delay between successive encounters with a type of grain disrupted an activated search image. The discussion addresses how these results further develop a model in which search images are viewed as selective attention to visual features of a prey. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Models for Hardware-Software System Operational-Performance Evaluation

Stochastic models for hardware-software systems are developed and used to study their performance as a function of hardware-software failure and maintenance rates. Expressions are derived for the distribution of time to a specified number of software errors, system occupancy probabilities, system reliability, availability, and average availability. The behavior of these measures is investigated via numerical examples.     

Diopside – Mg orthosilicate and diopside – Ba disilicate glass–ceramics for sealing applications in SOFC: Sintering and chemical interactions studies

Diopside (CaMgSi₂O₆) based glasses compositions containing magnesium orthosilicate or barium aluminosilicates phases have been appraised for sealing applications in solid oxide fuel cells (SOFCs) and other solid-electrolyte devices. The sintering behavior and crystalline phase evolution of glass powders has been investigated under isothermal and non-isothermal conditions in the SOFC operating temperature range (800–900 °C). All the glass compositions exhibited two-stage shrinkage behavior resulting in well sintered and mechanically strong glass–ceramics with Augite as the primary crystalline phase. The appropriate coefficient of thermal expansion (CTE), long term thermal stability (300 h at 900 °C), high electrical resistivity, good adhesion and minimal reactivity with SOFC components makes the investigated glass–ceramics potential candidates for further experimentation as SOFC sealants.     

Study of Crystallization Kinetics in Glasses along the Diopside–Ca-Tschermak Join

We report on the thermal stability and crystallization kinetics of the glasses in the diopside (CaMgSi₂O₆)–Ca-Tschermak (CaAl₂SiO₆) system. Four glasses with compositions corresponding to different diopside/Ca-Tschermak ratio were studied. Structural investigations on the glasses have been made by employing Infrared spectroscopy (FTIR). Activation energies for structural relaxation and viscous flow have been calculated using the data obtained from differential thermal analysis. The existence of glass-in-glass phase separation was observed in all the glasses. Kinetic fragility of the glasses along with other thermal parameters have also been calculated. Nonisothermal crystallization kinetic studies have been employed to study the mechanism of crystallization in all the four glasses. The Avrami parameter for the glass powders is ∼2, indicating the existence of intermediate mechanism of crystallization. Crystallization sequence in the glasses has been followed by X-ray diffraction analysis, scanning electron microscopy, and FTIR.     

Analysis of Dirichlet, Generalized Hamming and Triangular window functions in the linear canonical transform domain

Linear canonical transform is a four-parameter class of integral transform that plays an important role in many fields of optics and signal processing. Well-known transforms such as the Fourier transform, the fractional Fourier transform, and the Fresnel transform can be seen as the special cases of the linear canonical transform. This paper presents a new mathematical model for obtaining the linear canonical transforms of Dirichlet, Generalized “Hamming”, and Triangular window functions. The different window function parameters are also obtained from the simulations. By changing the value of four parameters and then changing the adjustable parameter, the main-lobe width, ?3 dB bandwidth, ?6 dB bandwidth and correspondingly, the minimum stop-band attenuation of the resulting window functions can be controlled. It has been shown that by using linear canonical transform, we are able to obtain all window parameters successfully as compared to fractional Fourier transform.     

Evaluating the development of elastic anisotropy with plastic flow

It has been observed that many initially isotropic materials show the development of anisotropic elastic response after plastic flow. It is desirable to be able to model this change in the elastic properties as a function of the extent of plastic flow. This is particularly important when considering the traveling of waves in some glassy polymers that exhibit large differences in the wave moduli along the different directions resulting from unequal plastic flow in these directions. A thermodynamically based model of plasticity is developed and used to evaluate the elastic moduli associated with infinitesimal elastic deformations around the unloaded configuration. It is shown that for this model there are at least four independent material functions describing the elastic moduli of an initially isotropic material. These moduli are functions of the isotropic invariants of the right plastic Cauchy stretch tensor.