Grain-Boundary Migration in Nonstoichiometric Solid Solutions of Magnesium Aluminate Spinel: II, Effects of Grain-Boundary Nonstoichiometry

The grain-boundary chemistry of magnesium aluminate spinel solid solutions MgO· n Al₂O₃ in which grain growth measurements were reported in part I has been investigated in order to understand the mechanism of grain-boundary migration. It is found that although segregation of impurity Ca and Si is common, much larger deviations in grain-boundary stoichiometry are present. There is an excess of Al and O relative to Mg at grain boundaries in all compositions. Grain-boundary migration appears to be rate-limited by solute drag from intrinsic defects accommodating lattice nonstoichiometry, rather than by extrinsic solutes, consistent with the observed impurity tolerance of grain-boundary mobility. Different rate-limiting defects are proposed for magnesia-rich and alumina-rich spinels.     

Using multithreshold quadratic sigmoidal neurons to improveclassification capability of multilayer perceptrons

This letter proposes a new type of neurons called multithreshold quadratic sigmoidal neurons to improve the classification capability of multilayer neural networks. In cooperation with single-threshold quadratic sigmoidal neurons, the multithreshold quadratic sigmoidal neurons can be used to improve the classification capability of multilayer neural networks by a factor of four compared to committee machines and by a factor of two compared to the conventional sigmoidal multilayer perceptrons.     

Subpubic sinus: a remnant of cloaca

A 14-month-old girl had purulent discharge from a sinus over the subpubic region for 2 weeks. Radiography and voiding cystourethrography revealed a 4.5 cm. long fistula extending to the retropubic region without any connection to the lower urinary tract. The fistula was excised. Histological findings revealed that the fistula had 3 different types of epithelium: stratified squamous, transitional and columnar. Clinical and pathological findings indicated that the sinus was most likely a remnant of the cloaca.     

Use of polymerase chain reaction to assess efficacy of leprosy chemotherapy

The assessment of chemotherapy efficacy in leprosy is difficult, since the only reliable method for determining whether the causative organism, Mycobacterium leprae, is viable depends on its growth in mouse foot pads. In an attempt to replace this expensive, time-consuming test, methods based on the polymerase chain reaction (PCR) have been developed. These methods depend on detection of DNA, which is more susceptible to degradation on cell death than are other cell components, so should be a more accurate indicator of viability. We have used a specific PCR assay to detect M leprae DNA in skin biopsy samples from leprosy patients. By use of limiting dilution PCR (LD-PCR), the concentration of M leprae DNA in the original sample could be measured. The DNA concentration was more closely correlated with the morphological index (derived from a staining technique that distinguishes morphologically intact and damaged bacteria) than with the number of bacteria visible (bacterial index, BI, which counts both alive and dead bacteria). In a longitudinal study of multibacillary patients on multi-drug therapy, skin biopsy samples were collected before treatment and 3, 6, 12, and 24 months after the start of therapy. While the BI showed little or no change during treatment, the number of genomes detected by PCR fell sharply, in parallel with the MI. We propose that PCR can be used as a rapid measure of M leprae viability and that this approach can be used for monitoring individual leprosy patients and for assessment of existing and new regimens. The method may be applicable to other infectious diseases in which culture of the causative organism is slow or impossible.     

嵌入设计--可编程逻辑的焦点

把可编程逻辑同预设计的标准嵌入处理器内核、片内存储器和外设结合到复杂的单芯片系统中的新产品正在涌现,这在以前是根本不可思议的。集成了快速SDRAM控制器、UART、记时器和片内双口存储器等外设的高性能嵌入处理器和可编程逻辑的单芯片系统,比采用分立部件具有更高的系统性能,相对ASIC具有更短的设计周期。     

Effects of pressurized cooking on the relationship between the chemical compositions and texture changes of lotus root (Nelumbo nucifera Gaertn.)

The texture of lotus root is hard and crispy, and the root can maintain its appearance and mouth feel after cooking at 100 °C for over 60 min. This study tried to elucidate relationships between pressurized cooking treatments (at 100 °C for 1, 3, 5, 10, 20, 30, 60 min and at 110 °C, 121 °C and 132 °C for 1, 3, 5, 10, 20, 30 min, respectively) and changes in its chemical composition and texture. Results showed that the contents of hemi-cellulose and cellulose of lotus root decreased with increasing pressurized cooking temperature/duration during heat treatment while lignin content remained almost the same. The NDF contents decreased more than did the ADF contents. Relative hardness of lotus root decreased with increasing pressurized cooking temperature/duration while solid loss increased (P < 0.05). These results could be used as references for the lotus root industry, as well as an academic basis for future development.     

Synthesis of C60 Fullerene-Silica Hybrid Nano Structures

We have recently demonstrated a procedure for the synthesis of silica nanometer and micrometer particles under modest conditions. Here we report the synthesis of C₆₀ fullerene-silica hybrid nanometer sized materials via sol-gel processing at neutral pH and under ambient conditions. The C₆₀ fullerene, when functionalized, was water-soluble and also able to facilitate the formation of silica structures from an aqueous silica precursor. This C₆₀ fullerene had similar functionality to the cationically charged polymers, which have been reported earlier to act as catalysts/templates for silicification. The resulting organic-inorganic hybrid was studied using SEM, EDS and UV/Vis spectroscopy. These hybrid materials may have applications in areas such as optical devices, semiconductors, chemical sensors, catalysis and in the medical field. The results presented in this study may be useful in developing a process for the synthesis of novel organic-inorganic nanometer sized materials and for the biomimetic synthesis of silica.     

HYDROGEN MASS TRANSFER IN HYDROGEN- METHANE-TETRALIN AND HYDROGEN-ETHANE-TETRALIN SYSTEMS AT ELEVATED TEMPERATURES AND PRESSURES

The volumetric mass transfer coefficient of hydrogen for the systems of hydrogen-methane-tetralin and hydrogen-ethane-tetralin at temperatures up to 650  K and pressures to 7 MPa were studied. Experiments were carried out using an automated hydrogen probe. The volumetric mass transfer coefficient of hydrogen decreased as the methane and ethane partial pressures increased as a consequence of the multicomponent transfer caused by the presence of the hydrocarbon gases. The presence of a second solute has a large effect on the hydrogen mass transfer rates at lower temperatures and lower initial hydrogen partial pressures than at higher values. These results indicate that light hydrocarbon production during coal liquefaction operations could adversely affect the overall liquefaction operation.     

CAMAC-CPIB接口电路

本文介绍CAMAC-GPIB接口电路,它允许任何满足GPIB标准的仪器联接到CAMAC系统中。该插件在CAMAC系统中是一个从设备,而在GPIB系统中则是主设备,使GPIB系统成为CAMAC系统的子系统。