用于千兆以太网基带铜缆接收器均衡的甚高频自适应 连续时间Gm-C 二阶带通滤波器的研究和设计

本文设计了用于千兆以太网基带铜缆接收器均衡的甚高频自适应连续时间Gm-C二阶带通滤波器。基于最陡梯度下降算法，带通滤波器的零点在57－340MHz的频率范围内可以自适应地调节，中心频率为1.278GHz。通过外接电阻伺服环路，滤波器中跨导转换器的跨导值不受工艺偏差和温度变化的影响，采用CSMC－HJ0.6μm CMOS工艺器件模型，用Cadence Spectres仿真器仿真了设计的自适应滤波器电路，仿真结果验证了设计原理和设计的电路。系统的最长学习时间为880个参考时钟周期。     

Hybridization of acoustic waves in piezoelectric plates

The conditions for hybridization of the zero-order and high-order acoustic waves propagating in a piezoelectric crystal plate have been studied. The dependence of the phase velocity of the hybrid waves on the parameter hf (h is the plate thickness and f is the wave frequency) is established for the potassium niobate and lithium niobate plates possessing various crystallographic orientations and conductivities. It is found that hybridization takes place when the conductivity of a thin surface layer exceeds a certain critical value, which can vary within broad limits depending on the plate material and orientation. The degree of dispersive repulsion of the coupled modes grows with increasing electromechanical coupling coefficient.     

Shock-induced phase transitions of C70 fullerite

Shock-induced phase transitions of C₇₀ fullerite were studied at the pressure range up to 52 GPa with use of recovery assemblies of planar geometry. The starting material consists of two crystalline phases: phase with hexagonal close-packed (HCP) and phase with rhombohedral structure. We have found that C₇₀ fullerite undergoes a series of polymorphic phase transitions in conditions of step-like shock-wave compression. In the specimens, recovered from 9, 14 and 19 GPa, a dominant phase was fullerite C₇₀ with cubic structure. Also, some amount of C₇₀ with HCP structure was observed. The quantity of HCP phase was decreasing with increasing of intensity of shock loading. With further growth of shock pressure, destruction of C₇₀ molecules occurs. In the samples, recovered after shock loading, the main phase was graphite with a low degree of three-dimensional regularity.     

The hemostatic system function of patients with severe forms of diphtheria

Hemostasis of 100 patients with severe diphtheria infection was studied throughout the disease. The patients were found to have marked procoagulant, anticoagulant and fibrinolytic disorders. Antithrombogenic activity of the vascular wall was also abnormal. The above impairments correlated with the symptoms severity and are interpreted as DIC syndrome which ran subclinically or as hemorrhagic syndrome. The majority of the patients underwent a hyperhypocoagulant phase of DIC syndrome.     

Effect of freezing rate on the denaturation of myofibrillar proteins

Freezing of bovine muscle has a denaturating effect on myofibrillar proteins, Differ-ential Scanning Calorimetry (DSC) studies of fresh and frozen muscle at different freezing rates show a decrease on denaturation enthalpies; the lower the freezing rate the greater the loss. When measuring the specific areas (ratio between each partial area in cm', and the dry weight of the sample, in mg) of the DSC thermograms, it can be observed that the area ascribed to myosin decreases with freezing, while the area corresponding to actin is not affected. These results are in agreement with the ATPase activity decreases as a consequence of freezing observing higher losses at lower freezing rates. The denaturation observed could be a result of a partial unfolding of the myosin head being more pronounced at low freezing rate.     

0412-1961

TAN Yanchang; HE Bin; ZHAO Yuhua (Northeast Institute of Technology, Shenyang)     

Biogenesis of cellulolytic enzymes by Trichoderma ligorum on media with "inductor"

Identical distribution of C2- and Cx-cellulase activities of enzyme complexes produced by Trichoderma lignorum on a medium with lactose, a soluble "inductor", and on a medium with cellulose was found by means of disc elestrophoresis in polyacrylamide gel. The maximum rate of synthesis of cellulases on the medium with lactose was registered during the highest deceleration, and even complete cessation, of the fungal growth. During this phase, only one electrophoretically homogeneous cellulase component with Rf of 0.44 possessing all types of the cellulase activity is present in the cultural broth. In the course of growth of the fungus on cellulose after 48 hours, also only one electrophoretically homogeneous component with Rf of 0.44 was found in the cultural broth when the rate of the substrate degradation was highest. The appearance of minor protein components with the activity of cellulase at later stages of cultivation after cessation of the fungal growth is supposed to be caused by modification of the main cellulase component with Rf of 0.44 by the growth medium.     

Preparation and bactericidal properties of silver nanoparticles in aqueous tea leaf extract

Ag nanoparticles 10 to 60 nm in size have been prepared by reducing silver ions in aqueous tea leaf extract. The properties of the nanoparticles have been studied by ultraviolet spectroscopy, atomic absorption, surface-enhanced Raman spectroscopy, and atomic force microscopy. According to the Raman spectroscopy results, the equilibrium of the redox reaction is displaced to an antioxidant form of flavonoids. The presence of silver nanoparticles enhances the antioxidant and bactericidal properties of tea.