新型高效冷风机翅片管紧固效果的试验研究

采用网格法测量了冷风机翅片冲压加工的变形量，确定了翅片材料的成形极限。用塑性大应变计测试了不同工况下冷风机翅片管胀管变形的全过程，建立了分析冷风机翅片管紧固效果的特征曲线方法，提出了用宽裕度作为胀头过盈量设计取值的概念，综合评价了不同翅片管的紧固效果。     

自动选择重发方案的改进

在自动请求重发（ＡＲＱ）方案中，选择重发（ＳＲ）比等待重发（ＳＷ）和重返Ｎ－ＧＢＮ具有更高的传输效率，该效率是信道误码率、帧长及往返延时的函数。在任一给定的误码率情况下，可求得一种最佳帧长使传输效率达到最高。     

Uptake of3H-noradrenaline and3H-5-hydroxytryptamine in cultured rat brainstem

Zusammenfassung Die zelluläre Lokalisation der Aufnahme von³H-NA und³H-5HT in den Hirnstamm von Ratten wurde am Modell der Nervengewebskultur untersucht. Im Gegensatz zu den Aminosäure-Transmittern, welche in Neurone und Gliazellen aufgenommen werden, zeigen Monoamine nur eine Aufnahme in Zellkörper und Fortsätze von Neuronen, nicht jedoch in Gliazellen. Es besteht eine Korrelation zwischen den Ergebnissen von fluoreszenzmikroskopischen Versuchen und unseren autoradiographischen Untersuchungen.     

Free energy perturbation calculations on binding and catalysis after mutating Asn 155 in subtilisin

Site-directed mutagenesis is a very powerful approach to altering the biological functions of proteins, the structural stability of proteins and the interactions of proteins with other molecules. Several experimental studies in recent years have been directed at estimating the changes in catalytic properties, (rates of binding and catalysis) in site-directed mutants of enzymes compared to the native enzymes. Simulation approaches to the study of complex molecules have also become more powerful, in no small measure owing to the increase in computer power. These simulations have often allowed results of experiments to be rationalized and understood mechanistically. A new approach called the free-energy pertubation method, which uses statistical mechanics and molecular dynamics can often be used for quantitative calculation of free energy differences. We have applied such a technique to calculate the differential free energy of binding and free energy of activation for catalysis of a tripeptide substrate by native subtilisin and a subtilisin mutant (Asn 155----Ala 155). Our studies lead to a calculated difference in free energy of binding which is relatively small, but a calculated change in free energy of catalysis which is substantial. These energies are very close to those determined experimentally (J. A. Wells and D. A. Estell, personal communication), which were not known to us until the simulations were completed. This demonstrates the predictive power and utility of theoretical simulation methods in studies of the effects of site-specific mutagenesis on both enzyme binding and catalysis.     

Preferential cytotoxicity on tumor cells by caffeic acid phenethyl ester isolated from propolis

The honeybee hive product, propolis, is a folk medicine employed for treating various ailments. Many important pharmaceutical properties have been ascribed to propolis, including anti-inflammatory, antiviral, immunostimulatory and carcinostatic activities. Propolis extracts have provided an active component identified as caffeic acid phenethyl ester (CAPE), which was readily prepared in one step. Differential cytotoxicity has been observed in normal rat/human versus transformed rat/human melanoma and breast carcinoma cell lines in the presence of CAPE.     

Changes in the tooth enamel of early Paleocene mammals allowing increased diet diversity

Hunter-Schreger bands (HSB) are seen in teeth that are composed of crossed sets of enamel prisms. They are present in the teeth of man and many other mammals, but absent in most insectivores and multituberculates. It has been suggested that the presence of HSB makes the tooth enamel less likely to split and is associated with chewing ability. We have traced the occurrence of HSB back to the arctonic condylarths of the early Palaeocene (Puercan) age; this must be close to the first appearance of the bands in placental mammals. Our data indicate that the teeth of almost all large mammals since the early Palaeocene have contained these bands, in an orientation that is optimal for limiting the propagation of vertical fractures. The appearance of the bands is associated with the differentiation of herbivores and carnivores from insectivores and our data indicate that their development was critical to the diversification of mammals because it allowed the use of new types of foods.     

斯匹茨卑尔根群岛伯顺岬地区海克拉霍克岩系变质岩小构造特征

本文讨论了伯顺岬地区海克拉霍克岩系的变质岩小构造特征。主要的线理有窗棂构造、布丁构造、小褶皱怄纽线理、褶纹线理、拉伸线理、交线线理和剪切线理等;主要面理除原生层理外,还有早期次生面理S_1与晚期次生面理S_2。新生线理和面理与不同形变期的主褶皱有密切的伴生、组合关系。变质岩小构造的研究为恢复区域构造形变历史提供了丰富的证据。