A dam-breach erosion model: II. Application

In Part I, the earthen dam breach erosion was analyzed. To this end, the BEED (breach erosion of earthfill dams) model was modified and extended. In this paper, Part II of the series, the extended BEED model is applied to three historical cases: South Fork Dam, Buffalo Creek Dam, and Teton Dam. The testing before it can be used for forecast purposes. A sensitivity analysis of the model to its parameters shows that the model is very sensitive to friction factors; Chenzy's for breach erosion, and Manning's for flood routing.     

Propagation Characteristics of an Elliptically-cored Highly Birefringent Fiber using an Analytical Method

By using the method of separation of variables in the elliptical coordinate system, a representative formula in terms of Mathieu and modified Mathieu functions is derived and longitudinal field components for the even and odd modes are presented for the proposed fiber. The eigen value equation for the fiber to be considered is obtained by solving the fourth order determinantal equation under weak guidance condition and is given in this paper. The cutoff frequency of several lower orders modes for different eccentricities have been obtained and their propagation characteristics have been plotted. The effect of the eccentricity on the modal cutoff values and mode transmissions is discussed. Finally, the modal birefringence in the proposed fiber is also estimated.     

Identifying axial load patterns using space frame FEMs and measured vibration data

The axial loading of a space frame may need to be quantified, perhaps for improvement of a finite element model (FEM) to better represent the structural dynamics or to ascertain how close the structure is to buckling. The coexistence of compressive and tensile forces in a space frame causes certain frequencies to increase with respect to load while others decrease. This intricate behaviour has been modelled in the FEM of a bi-tetrahedral space frame through consideration of the geometric stiffness, which accounts for stiffness changes in the loaded members. Updating the load pattern in the FEM using Newton's method (traditional sensitivity-based model updating) brings the model frequencies closer to those physically measured from the real bi-tetrahedral frame and thus provides identification of the axial loads. This load pattern is a predetermined set of frame axial forces in equilibrium. Such a constraint means that the extent of loading can be described by just one scalar updating parameter, an improvement upon former methods that updated member forces as independent parameters. When compared to the loads measured using strain gauges, the loads identified by model updating are seen to offer approximations of the actual loading. Difficulties such as modelling joint behaviour are discussed. The present work extends a series of numerical studies on load updating published by the authors by offering a demonstration of load pattern identification using physically measured vibration data from a real space frame.     

Electrochemical evaluation of the synergistic effect of molybdate tungstate inhibitor mixtures in chloride ion medium and effect of Cl− ion on inhibition efficiency of molybdate

It is well known to corrosion community about chromates and nitrates which are widely used as corrosion inhibitors. However, it is also well known that these inhibitors are oxidizing inhibitors of which chromates are carcinogenic also. Therefore, use of non toxic inhibitors such as molybdate and tungstate are gaining importance. AC impedance analysis of mild steel panels exposed to 3% NaCl containing 6000 ppm molybdate, 5000 ppm molybdate + 1000 ppm tungstate, 3000 ppm molybdate + 3000 ppm tungstate, 1000 ppm molybdate + 5000 ppm tungstate, 6000 ppm tungstate were evaluated. The impedance studies were carried out for different durations viz. 1 hour, 1 day and 7 days. From impedance analysis, it is clear that molybdate and tungstate are not forming any promising synergistic mixtures. The effect of chloride ion concentration viz. 0.01M, 0.05M, 0.1M, 0.3M and 0.6M on inhibition efficiency of molybdate has been discussed. Addition of small amount of tungstate along with molybdate enhances long term film stability on mild steel. It has been found that the inhibition effect is decreasing with increase in concentration up to 0.1M and on further increase in concentration viz. 0.3M and 0.6M, an increase in inhibition efficiency was observed. It has been found that deaeration negatively affected the film properties and did not form a stable film. The corrosion products formed were analyzed using Mössbauer spectroscopy and FT-IR spectroscopy, which showed the presence of oxyhydroxides.     

CSCC for the mean and standard deviation of non-normally distributed life test data

In this paper Cumulative Sum Control Charts (CSCC) have been constructed for the mean and standard deviation of non-normally distributed life test data. The parameters of the V-mask have been determined and finally the expression for the Average Run Length is derived.     

镀锌焊接钢丝网水泥在一种模拟海洋环境中的疲劳特性

使正常养护２８ｄ的７０个镀锌焊接钢丝网水泥试件持续受弯，最外层钢丝的计算应力达到腐蚀下容许值２０７Ｎ／ｍｍ＾２，再放入自制的以７０℃干燥６０ｍｉｎ和４３℃，３．５％ＮａＣｌ溶液浸渍３０ｍｉｎ为一周期的忆速模拟海洋环境实验系统中，分别承受荷载－腐蚀共同作用１、３、７和１８个月（４８０￣８６４０个周期），再对这些试件进行弯曲疲劳－腐蚀试验。分析评估了影响钢丝网水泥抗荷载－腐蚀性能的因素，给出了破坏概率     

The effect of surface recombination on the frequency-dependentcharacteristics of an ion-implanted GaAs OPFET

The effect of modulation frequency and surface recombination on the characteristics of an ion-implanted GaAs OPFET is determined analytically. The drain-source current is found to decrease with the increase in both modulation frequency and trap center density. The current changes significantly with the trap center density only when the latter is greater than 10²⁰/m². The threshold voltage does not change appreciably with the modulation frequency as in a silicon OPFET. However, the increased in the trap center density causes V_T to increase in the enhancement device and decrease in the depletion device. Further, V_T increases under the normally ON condition and decreases under the normally OFF condition with an increase in the photon absorption coefficient in GaAs. Some anomalous behavior is observed for higher values of the absorption coefficient     

High-resolution crystal structures of delta5-3-ketosteroid isomerase with and without a reaction intermediate analogue

Bacterial Delta5-3-ketosteroid isomerase (KSI) catalyzes a stereospecific isomerization of steroid substrates at an extremely fast rate, overcoming a large disparity of pKa values between a catalytic residue and its target. The crystal structures of KSI from Pseudomonas putida and of the enzyme in complex with equilenin, an analogue of the reaction intermediate, have been determined at 1.9 and 2.5 A resolution, respectively. The structures reveal that the side chains of Tyr14 and Asp99 (a newly identified catalytic residue) form hydrogen bonds directly with the oxyanion of the bound inhibitor in a completely apolar milieu of the active site. No water molecule is found at the active site, and the access of bulk solvent is blocked by a layer of apolar residues. Asp99 is surrounded by six apolar residues, and consequently, its pKa appears to be elevated as high as 9.5 to be consistent with early studies. No interaction was found between the bound inhibitor and the residue 101 (phenylalanine in Pseudomonas testosteroni and methionine in P. putida KSI) which was suggested to contribute significantly to the rate enhancement based on mutational analysis. This observation excludes the residue 101 as a potential catalytic residue and requires that the rate enhancement should be explained solely by Tyr14 and Asp99. Kinetic analyses of Y14F and D99L mutant enzymes demonstrate that Tyr14 contributes much more significantly to the rate enhancement than Asp99. Previous studies and the structural analysis strongly suggest that the low-barrier hydrogen bond of Tyr14 (>7.1 kcal/mol), along with a moderate strength hydrogen bond of Asp99 ( approximately 4 kcal/mol), accounts for the required energy of 11 kcal/mol for the transition-state stabilization.     

Brain abscess in solid organ transplant recipients receiving cyclosporine-based immunosuppression

There is currently a stark therapeutic void in the treatment of evolving stroke. Although P-selectin is rapidly expressed by hypoxic endothelial cells in vitro, the functional significance of P-selectin expression in stroke remains unexplored. In order to identify the pathophysiological consequences of P-selectin expression and to identify P-selectin blockade as a potential new approach for the treatment of stroke, experiments were performed using a murine model of focal cerebral ischemia and reperfusion. Early P-selectin expression in the postischemic cerebral cortex was demonstrated by the specific accumulation of radiolabeled anti-murine P-selectin IgG, with the increased P-selectin expression localized to the ipsilateral cerebral microvascular endothelial cells by immunohistochemistry. In experiments designed to test the functional significance of increased P-selectin expression in stroke, neutrophil accumulation in the ischemic cortex of mice expressing the P-selectin gene (PS +/+) was demonstrated to be significantly greater than that in homozygous P-selectin-null mice (PS -/-). Reduced neutrophil influx was accompanied by greater postischemic cerebral reflow (measured by laser Doppler) in the PS -/- mice. In addition, PS -/- mice demonstrated smaller infarct volumes (5-fold reduction, P<.05) and improved survival compared with PS +/+ mice (88% versus 44%, P<.05). Functional blockade of P-selectin in PS +/+ mice using a monoclonal antibody directed against murine P-selectin also improved early reflow and stroke outcome compared with control mice, with reduced cerebral infarction volumes noted even when the blocking antibody was administered after occlusion of the middle cerebral artery. These data are the first to demonstrate a pathophysiological role for P-selectin in stroke and suggest that P-selectin blockade may represent a new therapeutic target in the treatment of stroke.