Failure mode transition and energy dissipation in naturally occurring composites

The microstructural aspects of compressive inelastic deformation in balsa wood are investigated with emphasis on the failure mode transition and its effects on energy dissipation characteristics. The architectural features as well as the composite character of cell wall ultrastructure are discussed in a framework to understand the complex interrelationship between microstructure and macroscopic behavior in this extremely lightweight cellular biocomposite. Based on this discussion and experimental results, it is concluded that the biomimetic approach may prove to be a viable strategy in designing composite structures with high specific energy absorption capacity.     

Effect of enzymatic hydrolysis of proteins on growth of Bifidobacterium bifidus in milk

The effect of enzymatic hydrolysis of proteins in milk using neutrase on the growth of the probiotic strain Bifidobacterium bifidus was evaluated by estimation of microbial growth, acidity, viscosity and flavour production. A significant increase in the growth of B bifidus was observed in neutrase‐hydrolysed milk. The setting time of bifidus‐cultured milk was advanced by about 12 h at 5% degree of hydrolysis. Enzymatic hydrolysis of proteins prior to cultivation also significantly increased the viscosity of the product. An approximately 60% increase in viscosity of the product was observed in neutrase‐hydrolysed milk. Production of steam‐volatile monocarbonyls as an indication of development of flavour was also higher in neutrase‐hydrolysed milk. The concentration of steam‐volatile monocarbonyls was 2.47 µmol per 100 ml in neutrase‐hydrolysed milk but only 1.84 µmol per 100 ml in control milk at the setting point of the curd. © 2002 Society of Chemical Industry     

DEPOSITIONAL AND DIAGENETIC HISTORY OF THE KERENDAN CARBONATE PLATFORM, OLIGOCENE, CENTRAL KALIMANTAN, INDONESIA

The Kerendan carbonate platform (Oligocene Berai Limestone) covers a subsurface area measuring approximately 11 by 16 km in the westernmost Kutei Basin, Central Kalimantan. Aggradation of the Kerendan platform occurred during a major Oligocene transgression, and is contemporaneous with aggradation and backstepping of the Barito shelf margin which was located approximately 30 km to the south. The Kerendan platform is approximately 1,000 m thick, and comprises three aggrading seismic sequences identified by the downlap of basinal strata at the platform margin and downlap of transgressive strata within the platform. Carbonate deposition started in the Late Eocene, and ended when the upper limestone sequence drowned and was covered with shale in the Late Oligocene (approximately 28.6 Ma). Three depositional areas can be distinguished in seismic sections: (1) a platform interior (lagoon); (2) a slightly raised platform rim (1–2 km wide); and (3) a basinward‐dipping platform margin and slope. The margin of the platform is identified by inflections on the seismic profiles where the relatively flat platform top begins to slope basinward. Depositional models from outcrops combined with core from three Kerendan wells were used to extrapolate depositional facies onto the seismically‐defined platform. Platform‐interior (lagoon) facies consist largely of fossiliferous wackestones and packstones, and porosities are generally lower than 5%. The platform rim is characterized by interbedded bioclastic wackestones, packstones, grainstones and boundstones, with grainstones increasing toward the platform margin. Porosity preferentially occurs in packstones, grainstones and boundstones. The platform‐rim deposits have greater porosity (5–13%) than the platform interior because the platform run is more grainstone‐rich, and because acidic waters compacting out of basinal shales concentrated dissolution near the platform margin. Pore types include vuggy porosity, microporosity within grains, and intercrystalline porosity in dolomite in the upper part of the platform rim. Different pore types have resulted in variable but locally very high permeabilities (greater than 100 mD). Permeabilities decrease with depth as vuggy pores decrease, and microporosity becomes dominant.     

微波处理对离体黄瓜子叶生根和根活力的影响

用辐射功率200W微波（2450MHz）处理6～16，明显促进离体黄瓜子叶生根．根长和根鲜重增加。不同辐射强度和辐服时间对离体黄瓜子叶生根有不同影响。用TTC法测定，微波处理后与根活力相关的OD值比对照体增加了。用温箱模拟FISO微波炉功率为200W的温度，不同处理时间处理离体黄瓜子叶，没有发现促进生根。说明在一定条件下，微波辐射处理离体黄瓜子叶促进生根．主要是微波的辐射效应。     

A finite elastostatic analysis of bimaterial interface cracks

A numerical method is developed to study the bimaterial interface problem in Neo-Hookean materials under plane stress conditions. Comparison is made with the analytical predictions for the asymptotic field of the problem. The range of dominance of the asymptotic solution at different load levels is established and the amplitudes of the crack-tip asymptotic field are related to the far field loading. The numerical model is extended to analyze the experiments conducted on specimens with an edge crack at the interface between two dissimilar Solithane plates that are characterized by Mooney-Rivlin material behavior.

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Résumé On met au point une méthode numérique pour l'étude d'un problème d'interfaces entre deux matériaux néo-Hookiens sollicités en état plan de tension. On compare les résultats avec les prédictions analytiques étabiies pour un champ asymptotique. On établit la gamme dans laquelle la solution asymptotique est dominante, à différents niveaux de charge, et on met en relation l'ampleur du champ asymptotique à l'extrémité de la fissure avec celle du champ de contraintes à une certaine distance. Le modèle numérique est étendu à l'analyse d'essais sur éprouvettes comportant une fissure de bord à l'interface de deux tôles de Solithane caractérisée par un comportement de matériau de Mooney-Rivlin.

     

Conductivity study of polyethylene oxide (PEO) complexed with sodium bicarbonate

Ion conducting thin film polymer electrolytes based on polyethylene oxide (PEO) complexed with NaHCO₃ salt has been prepared using solution-cast technique. The complexation of NaHCO₃ salt with PEO is confirmed by XRD and IR studies. DC conductivity in the temperature range 303–368 K has been evaluated. The conductivity is found to increase in the PEO complex with the NaHCO₃ salt and also with an increase in temperature. Using this polymer electrolyte, an electrochemical cell with the configuration Na/(PEO + NaHCO₃)/(I₂ + C + electrolyte) has been fabricated and its discharge characteristics studied. Open Circuit Voltage (OCV) and Short Circuit Current (SCC) are found to be 2.69 V and 1.28 mA, respectively. Other parameters associated with the cell are evaluated and presented in this paper.     

Congenital adrenal hyperplasia presenting as massive adrenal incidentalomas in the sixth decade of life: report of two patients with 21-hydroxylase deficiency

Divergent recommendations exist regarding the evaluation of adrenal incidentalomas. Recent data have indicated a prevalence of adrenal tumors of 71% in nonclassical congenital adrenal hyperplasia (CAH) and unmasked heterozygotes. These data expand the differential diagnosis of such incidental tumors and substantially modify the approach to their evaluation. We present two patients, female pseudohermaphrodites with the simple virilizing form of CAH and 21-hydroxylase deficiency, who functioned successfully as married phenotypic males. Both came to medical attention in the sixth decade by virtue of massive adrenal incidentalomas encountered in the evaluation of recurrent urinary tract infections. Each had a 46, XX karyotype, no palpable testes, and markedly elevated baseline levels of 17-hydroxyprogesterone (17-OH Prog) of 6086 ng/dL and 6750 ng/dL. Both responded appropriately to dexamethasone suppression with reduction of 17-OH Prog, androgens and, in the second patient, ACTH to normal or near normal levels. Histologic and autopsy examination of the first patient's tumor and computed tomographic characteristics of the second revealed a benign adenoma and myelolipoma respectively. We extend and confirm previous recommendations that CAH be included in the differential diagnosis of adrenal incidentaloma and that baseline 17-OH Prog. levels be obtained, with ACTH stimulation if necessary, to diagnose the presence of nonclassical CAH.     

Artificial Intelligence System Approach for Optimization of Drilling Parameters of Glass-Carbon Fiber/Polymer Composites

Silicon - In recent times, the study on machining characteristics of combined (hybrid) fiber polymer composites has drawn a remarkable research attention because of its emerging industrial...