Second-harmonic generation from organic molecules incorporated in sol-gel matrices

Orientation of optically nonlinear organic molecules inside sol-gel matrices upon application of an external D.C. electrical field is demonstrated for the first time. The quadratic nonlinear response of silicon oxide or transition metal oxide based gels containing organic molecules has been determined from Electric Field Induced Second Harmonic (EFISH) measurements. Large concentrations of Optically Nonlinear Organic Molecules (ONOM) have been either incorporated inside the macromolecular network or chemically bonded to the oxide backbone of the gels. These results demonstrate the feasibility of permanently poled doped sol-gel matrices. Moreover, EFISH measurements performed on organic molecules appear to be a useful tool for monitoring the changes occurring during sol-gel transformations.     

广东省种子植物分布新资料

报道广东省种子植物分布新记录2属——甜茅属(Glyceria R. Br.)及锦鸡儿属(Caragana Fabr.)，2个新记录种——甜茅[Glyceria acutiflora subsp. japonica (Steud.) T. Koyama et Kawano]及锦鸡儿[Caragana sinica (Buc’hoz) Rehder]，均发现于丹霞山国家级自然保护区。新记录的发现对于研究丹霞山的区系发生具有一定指示意义。     

The recolonization of Europe by brown bears Ursus arctos Linnaeus, 1758 after the Last Glacial Maximum

1. At the end of the Last Glacial Maximum brown bears Ursus arctos recolonized the glacial landscape of Central and Northern Europe faster than all other carnivorous mammal species of the Holocene fauna. Ursus arctos was recorded in Northern Europe from the beginning of the Late-Glacial. The recolonization of northern Central Europe may have taken place directly after the maximum glaciation. The distribution of the brown bear was restricted to glacial refugia only during the Last Glacial Maximum, for probably no more than 10 000 years. 2. Genetic analyses have suggested three glacial refugia for the brown bear: the Iberian Peninsula, the Italian Peninsula and the Balkans. Subfossil records of Ursus arctos from north-western Moldova as well as reconstructed environmental conditions during the Last Glacial Maximum in this area suggest to us a fourth glacial refuge for the brown bear. Because of its connection to the Carpathians, we designate this as the ‘Carpathian refuge’. 3. Due to the low genetic distance between brown bears of northern Norway, Finland, Estonia, north-eastern Russia and the northern Carpathians (the so-called eastern lineage), the Carpathians were considered the geographical origin of the recolonization of these regions. During the recolonization of northern Europe the brown bear probably reached these areas rapidly from the putative Carpathian refuge.     

Role of inositol trisphosphate as a second messenger in signal transduction processes: An essay

This essay attempts to summarize some of the best evidence for the role of inositol trisphosphate as a second messenger in signal transduction processes. The following aspects are addressed in the essay: (a) The synthesis of inositol trisphosphate and other inositol lipids, (b) Receptor-phosphatidylinositol bisphosphate phospholipase C coupling and the N-ras protooncogene, (c) Inositol trisphosphate and intracellular calcium, (d) Cell growth and oncogenes, (e) Receptors linked to the phosphatidylinositol cycle, (f) Phototransduction and (g) Interactions between inositol trisphosphate and other second messengers.Abbreviations Cyclic AMP Adenosine 3,5-cyclic monophosphate - Cyclic GMP Guanosine 3,5-cyclic monophosphate - DG sn, 1,2-Diacylglycerol - EGF Epidermal growth factor - GDP Guanosine diphosphate - GTP Guanosine triphosphate - IP Inositol 1-monophosphate - IP₂ Inositol 1,4-diphosphate - IP₃ Inositol 1,4,5-trisphosphate - PA Phosphatidic acid - PDGF Platelet-derived growth factor - PI Phosphatidylinositol - PIP Phosphatidylinositol 4-monophosphate - PIP₂ Phosphatidylinositol 4,5-bisphosphate - PIP₃ Phosphatidylinositol 3,4,5-trisphosphate - PLC Phospholipase C     

Regulation of nicotinic acetylcholine receptors by protein phosphorylation

Neurotransmitter receptors and ion channels play a critical role in the transduction of signals at chemical synapses. The modulation of neurotransmitter receptor and ion channel function by protein phosphorylation is one of the major regulatory mechanisms in the control of synaptic transmission. The nicotinic acetylcholine receptor (nAcChR) has provided an excellent model system in which to study the modulation of neurotransmitter receptors and ion channels by protein phosphorylation since the structure and function of this receptor have been so extensively characterized. In this article, the structure of the nAcChR from the electric organ of electric fish, skeletal muscle, and the central and peripheral nervous system will be briefly reviewed. Emphasis will be placed on the regulation of the phosphorylation of nAcChR by second messengers and by neurotransmitters and hormones. In addition, recent studies on the functional modulation of nicotinic receptors by protein phosphorylation will be reviewed.     

云南省(虫齿)目二新种和灰背蛇(虫齿)的记述((虫齿)目:厚(虫齿)科、叉(虫齿)科、围(虫齿)科)

本文记述了云南省(虫齿)目二新种,Tapinella bannana sp.n.和Peripsocus plurimaculatus sp.n.及一新种记录种Ophiodopelma semicets Lee and Thornton,其雄虫为首次记载。     

Cooperative enhancement of reproductive success in white-winged choughs

Summary White-winged choughs are a cooperatively breeding species which provide parental care to their young over an entire year. I traced the reproductive success of groups of white-winged choughs from the start of one breeding season to the next over 3 years. I examined the effect of helper number on timing of breeding, the success of each effort, the number of efforts made in a season, and the final reproductive success at the end of each year. Timing of commencement of breeding varied between years but was not related to group size. Early broods were not more successful than late broods. Nest building (July–September) commenced earlier in years which had high rainfall in July; choughs rely on rainfall for supplies of mud for nest construction. Most nest failures occurred gradually and were attributed to starvation of nestlings, although some sudden failures were attributed to predation. Large groups have more young by the beginning of the following season; this is due to higher fledging success and a greater likelihood of having second broods. Disappearance of young after fledging and during the transition to independence was not dependent on group size. Only groups of seven and above produce more than one young on average over the entire year; choughs provide one of the most marked cases for helpers enhancing the reproductive success of breeders. Large groups are virtually guaranteed of reproductive success over the whole year and grow more quickly than small groups. These results highlight the need to consider the effect of helpers over the entire period of reproduction and care of young, rather than just at fledging.