Calculation of photogenerated carrier escape rates from GaAs/AlGa1-xAs quantum wells

We present a new theory for photogenerated carrier escape rates from single quantum wells, as a function of an applied electric field, that includes thermionic emission, direct tunneling, and tunneling via thermal occupation of upper subbands, and compare the results for GaAs/Al_xGa_1-xAs quantum wells with recent experiments. We account for the two dimensional (2D) density of states below the barrier, assume thermal equilibrium of carriers within the well, allow for the possibility of strain in the well and/or barrier, and include the contribution to electron thermionic emission from indirect conduction band minima. Our expressions for thermionic emission reduce, in the limit of large well width, to those derived by assuming a three-dimensional (3D) density of states. The results for electron emission from GaAs/Al_xGa_1-xAs quantum wells with x=0.2 and x=0.4 barriers at room temperature agree well with experiment. For wells with x=0.2 barriers, thermally assisted tunneling overtakes thermionic emission around 40 kV/cm, while for wells with x=0.4 barriers thermionic emission from the L valley conduction band minima dominates for fields less than 70 kV/cm. For holes we show that the escape rates are very sensitive to the in-plane effective masses, and results using simple expressions for the in-plane masses that do not include light/heavy-hole mixing agree poorly with experiment. The agreement with experiment is improved using in-plane masses that include light/heavy-hole mixing, particularly for wells with high barriers. We suggest that agreement with experiment would be improved by using more accurate in-plane hole masses for all of the subbands     

Antihypertensive Effect of Salt-Free Soy Sauce,a New Fermented Seasoning,in Spontaneously Hypertensive Rats

ABSTRACT: In this study, we focused on the antihypertensive effect of newly fermented salt-free soy sauce (SFS) in spontaneously hypertensive rats (SHRs). A 13-wk oral administration of SFS was performed daily in 8- to 21-wk-old SHRs with a dose of 200 mg/kg of body weight/d. The systolic (SBP) and diastolic (DBP) blood pressures were measured for each week during the experimental period. As a result, a significant (P < 0.01) BP lowering effect was observed from the 5th d to the end of the experiment in the SFS group compared with the control group (ΔSBP_21-wk: 27 mmHg, ΔDBP_21-wk: 20 mmHg). In contrast to such substantial effect by SFS intake, angiotensin I-converting enzyme activities in blood and local organs as well as pharmaceutical parameters such as serum Na⁺ or K⁺ level did not show any significant difference between in both SFS and control groups. Vasoconstriction experiment using thoracic aorta rings from 21-wk SHRs provided an interesting result that the rings from the SFS group evoked a >2-fold higher increase in the angiotensin II-stimulated constrictive response compared with the rings from the control group (P = 0.012), which suggested that the SFS-intake would be effective in possessing a higher vessel tone. Practical Application: In this study, we investigated the antihypertensive effect of newly fermented SFS in SHRs. As a result of 13-wk SFS-administration, we found a significant antihypertensive effect of the SFS. This finding strongly demonstrates that the developed SFS would be greatly beneficial for health and useful for health-related industries.     

Channel Models for Medical Implant Communication

Information regarding the propagation media is typically gathered by conducting physical experiments, measuring and processing the corresponding data to obtain channel characteristics. When this propagation media is human body, for example in case of medical implants, then this approach might not be practical. In this paper, an immersive visualization environment is presented, which is used as a scientific instrument that gives us the ability to observe RF propagation from medical implants inside a human body. This virtual environment allows for more natural interaction between experts with different backgrounds, such as engineering and medical sciences. Here, we show how this platform has been used to determine channel models for medical implant communication systems.     

Numerical simulation of critical current performance in Nb3Sn strand subjected to periodic bending deformation

In the ITER Engineering Design Activity (EDA), four NB₃Sn model coils were developed and successfully tested. However, it was revealed that the critical current of the conductor degraded with the increase of electromagnetic force. One of the explanations of this phenomenon is a strand bending caused by enormous electromagnetic force. The authors therefore developed a simulation code using the distributed circuit model to investigate dependency of the critical current performance on the periodic bending deformation. The simulation results were in good agreement with the experiments. The dependence of the critical current on the periodic transverse load, temperature, periodic load pitch, thickness of Ta barrier which prevents Cu stabilizer from being contaminated by Sn, twist pitch of the strand, and RRR of the bronze matrix was investigated using the developed code. The results showed that the critical current degraded less with decreasing the pitch of the transverse load and increasing the Ta barrier thickness. It suggests that the shorter cabling pitch and the larger bending stiffness prevent the critical current degradation. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(3): 7–15, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20923     

Estimation of Small Reservoir Storage Capacities with Remote Sensing in the Brazilian Savannah Region

Small reservoirs play an important role in supporting the local economy in the savannah areas of Brazil and are primarily used for the provision of water for irrigation and watering livestock. Hundreds of small reservoirs have been built in the last few decades in the Preto River Basin, but efficient water management and sound planning are hindered by inadequate knowledge of the number, storage capacity and spatial distribution of reservoirs in the basin. The main reason for the lack of this information is that current methodologies for quantifying the physical parameters of reservoirs are laborious, time consuming and costly. To address this lack of data, a simple method to estimate reservoir storage volumes based on remotely sensed reservoir surface area measured with LANDSAT was developed. The method was validated with a subset of reservoirs in the Preto River Basin for which surface areas, shapes and depths were determined with ground-based survey measurements. The agreement between measured and the remotely sensed reservoir volumes was satisfactory, indicating that remotely-sensed images can be used for improved management of water in the Brazilian Savannah region. With the newly developed methods we found that the Preto River Basin’s 147 small reservoirs can store 19 × 10⁶ m³ of water at full capacity.     

Hybrid Counterfactual Logics

The purpose of this paper is to argue that the hybrid formalism fits naturally in the context of David Lewis’s counterfactual logic and that its introduction into this framework is desirable. This hybridization enables us to regard the inference “The pig is Mary; Mary is pregnant; therefore the pig is pregnant” as a process of updating local information (which depends on the given situation) by using global information (independent of the situation). Our hybridization also has the following technical advantages: (i) it preserves the completeness and decidability of Lewis’s logic; (ii) it allows us to characterize the Limit Assumption as a proof-rule with some side-conditions; and (iii) it enables us to establish a general Kripke completeness result by using the proof-rule corresponding to the Limit Assumption.     

Contribution of different bitter-sensitive taste cells to feeding inhibition in a caterpillar (Manduca sexta).

Many compounds that taste bitter to humans also inhibit feeding in insects. Caterpillars (e.g., Manduca sexta) detect these compounds with a few bitter-sensitive taste cells. This study examined the role of these taste cells in feeding inhibition. Behavioral studies demonstrated that 3 bitter compounds (caffeine, salicin, and aristolochic acid) all inhibited feeding rapidly in Manduca sena. Electrophysiological studies revealed that each pair of bitter-sensitive taste cell differs in responsiveness to the bitter compounds. Ablation studies indicated that (a) those pairs of bitter-sensitive taste cells that responded vigorously to a particular bitter compound were sufficient to inhibit feeding on diets containing the same compound, but that (b) no pair of bitter-sensitive taste cells was necessary for inhibiting feeding. Thus, the different pairs of bitter-sensitive taste cells appear to make partially redundant contributions to feeding inhibition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

MOSBY: a molecular structure viewer program with portability and extensibility

A molecular structure viewer program, MOSBY has been developed for studies that use atomic coordinates to understand the structures of protein molecules. The program is designed to be portable with a comprehensive user interface by our high-throughput graphics library. In addition, it cooperates with extension modules customized for individual research topics and analysis. For example, an electron density module loads and displays electron density maps derived in X-ray crystallographic analysis superimposed to an atomic model. A molecular dynamics module reads a trajectory file of the results of molecular dynamics calculations and animates the structure. These plug-in modules are devised to function without modification to the MOSBY program. For variations of analysis and calculations with atomic coordinates, the portability and extensibility illustrated by MOSBY play an important rule in scientific computational tools with active software development.     

An investigation of the pH-activity relationships of Cex, a family 10 xylanase from Cellulomonas fimi: xylan inhibition and the influence of nitro-substituted aryl-beta-D-xylobiosides on xylanase activity

The kinetic parameters of Cex, a family 10 xylanase from Cellulomonas fimi, were determined at various pH levels using soluble birchwood xylan (BWX) as a natural polymeric substrate along with three other synthetic aryl-beta-D-xylobioside substrates. Using BWX, a high level of substrate inhibition was observed which increased with decreasing pH. In contrast, typical Michaelis-Menten-type profiles were obtained using the three aryl-beta-D-xylobiosides as substrates. The k(cat) values determined using o-nitrophenyl-beta-D-xylobioside did not change as the pH increased, whereas the k(cat) values obtained with BWX, phenyl-beta-D-xylobioside and p-nitrophenyl-beta-D-xylobioside decreased, suggesting that the presence of an ortho nitro group affects the activity displayed by Cex. These differences were not observed with XynB from Clostridium stercorarium F9, a member of the same family of xylanases as Cex. These results indicate that a careful evaluation is required when employing substituted aryl-beta-D-xylobiosides in the characterization of xylanases.