正弦稳态扫频信号的产生与输出

介绍用计算机软件产生正弦稳态扫频信号的编程方法。通过对Ｄ／Ａ变换与Ａ／Ｄ采集的同步输出可以获得不同频率量程和设定电压的扫频输出     

Endogenous retroviruses

The genomes of vertebrates contain sequences that are similar to present-day exogenous retroviruses. Such sequences, called endogenous retroviruses (ERVs), have resulted from ancestral germ line infections by exogenous retroviruses which have thereafter been transmitted in a Mendelian fashion. By analogy to exogenous tumorigenic retroviruses, ERVs have been implicated in the pathogenesis of cancer. Cumulative evidence from animal models indicates that ERVs may participate in the process of malignant transformation or promote tumor growth, e.g. through insertional mutagenesis or via counteracting tumor immunosurveillance. Here, we review the role of ERVs in tumorigenesis with focus on human ERVs (HERVs) in human cancer. Although available data suggest a potential role of HERVs in human cancers, in particular germ cell tumors, the contributions of HERVs to human tumorigenesis warrant further elucidation. (Part of a Multi-author Review)     

Electromagnetically induced transparency and slow light with optomechanics

Controlling the interaction between localized optical and mechanical excitations has recently become possible following advances in micro- and nanofabrication techniques. So far, most experimental studies of optomechanics have focused on measurement and control of the mechanical subsystem through its interaction with optics, and have led to the experimental demonstration of dynamical back-action cooling and optical rigidity of the mechanical system. Conversely, the optical response of these systems is also modified in the presence of mechanical interactions, leading to effects such as electromagnetically induced transparency (EIT) and parametric normal-mode splitting. In atomic systems, studies of slow and stopped light (applicable to modern optical networks and future quantum networks) have thrust EIT to the forefront of experimental study during the past two decades. Here we demonstrate EIT and tunable optical delays in a nanoscale optomechanical crystal, using the optomechanical nonlinearity to control the velocity of light by way of engineered photon-phonon interactions. Our device is fabricated by simply etching holes into a thin film of silicon. At low temperature (8.7 kelvin), we report an optically tunable delay of 50 nanoseconds with near-unity optical transparency, and superluminal light with a 1.4 microsecond signal advance. These results, while indicating significant progress towards an integrated quantum optomechanical memory, are also relevant to classical signal processing applications. Measurements at room temperature in the analogous regime of electromagnetically induced absorption show the utility of these chip-scale optomechanical systems for optical buffering, amplification, and filtering of microwave-over-optical signals.     

A novel viral oncogene with structural similarity to phospholipase C

Numerous oncogenes have been isolated from acutely transforming retroviruses. To date, the products of these viral oncogenes have been protein kinases, nuclear proteins, growth factors, or GTP-binding proteins. We have cloned the previously uncharacterized avian sarcoma virus CT10 and sequenced its genome. This virus encodes a protein, p47gag-crk, that has blocks of sequence similarity to the amino-terminal, non-catalytic region of the non-receptor class of tyrosine kinases. In addition, the structure of p47gag-crk has striking similarity to a 180-amino acid region of bovine brain phospholipase C. Biochemical data suggest that p47gag-crk activates one or several endogenous tyrosine kinases.     

Retinoids,a new class of compounds with prophylactic and therapeutic activities in oncology and dermatology

Summary A review of recent investigations in the retinoid field is presented. Retinoic acid exerts a prophylactic and a therapeutic effect on chemically induced benign and malignant epithelial tumors in mice. In clinical studies positive therapeutic results have been obtained in patients with preneoplastic and neoplastic epithelial lesions. However, treatment with retinoic acid is limited by serious side effects (hypervitaminosis A syndrome). Therefore, the synthesis of analogs of retinoic acid (retinoids) possessing a more favorable therapeutic ratio has been initiated. Among a large series of synthesized compounds, certain aromatic analogs proved to have a particularly favorable therapeutic ratio. The structure-activity relationship of the most active retinoids is discussed including some biological data concerning prophylaxis and therapy of epithelial tumors. The total synthesis of retinoids according to various building schemes is discussed in detail. Methods for the synthesis of the cyclic end group, of the polyene chain component, and of the full retinoid skeleton are described. Metabolic studies of retinoic acid and of the most active retinoid, as well as the synthesis of some isolated metabolites are outlined. Suggestions concerning the mechanism of action of retinoids are made. Some clinical results on the treatment of acne, psoriasis and precancerous conditions are reported.Based on a lecture presented at the Symposium on Horizons in Medicinal Chemistry, Centennial ACS Meeting, New York, 6 April, 1976.     

Effect of 2-Br-α-ergokryptine (CB 154) on lactation in the bitch

Zusammenfassung Es wurde gezeigt, dass bei Hündinnen die Lactation durch den Prolactin-Sekretionshemmer 2-Br--Ergokryptin-methanesulfonat (CB 154, Sandoz) gehemmt wird. Gemessen über 24 Stunden beträgt die ED₅₀ i.m. 6 g/kg.     

一类高阶非线性系统的零解稳定性

由Барбащин公式得到的四阶常系数线性系统的Ляпунов函数出发，通过类比法构造了一类四阶非线性系统的Ляпунов函数，并由此得到了这些系统零解的全局渐近稳定性的充分条件     

Glutamate receptors at atomic resolution

At synapses throughout the brain and spinal cord, the amino-acid glutamate is the major excitatory neurotransmitter. During evolution, a family of glutamate-receptor ion channels seems to have been assembled from a kit consisting of discrete ligand-binding, ion-channel, modulatory and cytoplasmic domains. Crystallographic studies that exploit this unique architecture have greatly aided structural analysis of the ligand-binding core, but the results also pose a formidable challenge, namely that of resolving the allosteric mechanisms by which individual domains communicate and function in an intact receptor.