北京市自然保护区空间布局与三区二带理念

研究的主要目标是北京市自然保护区的空间布局,通过Arcgis软件,矢量化北京市保护区边界,使得自然保护区成为研究底图中的斑块,参照位置的不同,利用Fragstats软件计算聚集度指数（AI）从而提出三区划分的假设,将北京市分成3个大的保护区体系,在此基础之上,计算各个保护区之间的几何最近邻距离（ENN）,证明三区划分的合理性。然后,通过小班数据,分析连接三区廊道之间的土地利用结构,为北京市划分出连接保护区体系的西部山脉廊道和东部水域廊道。最终形成北京市自然保护区分布格局三区二带规划理念。     

Fine structure of abscission zones

Summary The fine structure of the abscission zones of Lycopersicon esculentum and Nicotiana tabacum flower pedicels was studied, with special reference to structural changes in the walls of cells during the abscission process. The separation of cells appeared to be initiated primarily in the middle-lamella region of the cell walls. Disintegration of the primary wall, which usually followed breakdown of the middlelamella region, also occurred concurrently with the lysis of the middle-lamella region. During cell-wall degradation, the walls appeared to swell and became highly flexible. The walls of at least some cells in the zone of separation invaginated during the advanced stages of cell-wall disintegration, and ultimately collapsed. Cell-wall changes in abscising pedicels are almost identical to those which occur in abscising cotton and Coleus leaves, as described by Bornman (1967).     

Fine structure of abscission zones

Summary The effect of ethylene on abscission of flower pedicels of tobacco plants has been investigated. For the first 2 h of exposure to C₂H₄, the pedicels bend rather than break in response to applied force, but after 2.5 h exposure they break at the abscission zone under an applied force of 40 g. The break strength of the abscission zone decreases exponentially with time to 5 g at 5 h after beginning of the C₂H₄ treatment. An examination of the tissue at the fine structural level 2 h after exposure to C₂H₄ reveals the accumulation of rough endoplasmic reticulum (RER) in the abscission cells. Rough ER becomes increasingly abundant by 3–5 h exposure of the tissue to C₂H₄. There is approximately a 30 fold increase in RER by 5 h of exposure, as compared to untreated tissue.Loss in the integrity of the membranes of microbodies occurs by 5 h exposure of the tissue to C₂H₄. As cell wall degradation proceeds, fibrous material, vesicular structures, and electron dense bodies—the latter often appearing striated—develop in the disintegrating wall. Little change is seen in the structure of nuclei, mitochondria, chloroplasts and in the crystalloid cores of microbodies during the first 5 h of exposure of the tissue to C₂H₄. However, disorganization of cytoplasmic components does occur in cells where cell wall breakdown is at an advanced stage.     

Fossil plankton depth zones

Varied evidence from the known depth correlated distribution of benthic shelly facies communities in the Ordovician and Silurian clearly shows that graptolite taxonomic diversity increased from the nearshore regions to the shelf margin regions, as well as into the deeper portions of epicontinental basinal areas. We then consider a method for determining the depth distribution of individual graptolite taxa. This method depends on correlating the first appearance of graptolite taxa as one departs from shoreline in terms of the underlying benthos, arrayed in benthic assemblages. The first appearance departing from shoreline corresponds with the upper depth limits of each taxon in terms of the underlying depth indicated by the underlying, associated benthos. The depth of maximum abundance for each taxon should correspond to that point in the increasing relative abundance of that taxon where relative increase in abundance ceases. The lower depth limit of each taxon should correspond to that point on the relative abundance curve where increase in total relative abundance ceases.Using information about the stratigraphic ages indicated by the graptolite faunas, zone-by-zone, combined with that provided by the communities present within the associated and formerly underlying benthic assemblages should provide a more refined stratigraphic zonation than that obtained without combining both.     

Fine structure of abscission zones

Summary Electron micrographs of the zone of separation in flower pedicels of Lycopersicon esculentum and Nicotiana tabacum are presented with particular reference to the indentation of epidermal tissue in the abscission zone, subcellular organelles, and the cell wall. The indentation or groove which delineates the abscission zone extends some distance into the pedicel with branchings off the main groove. These branches are approximately 20 m in width while the main groove averages approximately 200 m in width. Invaginations of the plasmalemma are observed with considerable frequency. within these invaginations one observes a material of about the same density as the cell wall except that it is more fibrillar. Plasmodesmata are also observed, with considerable branching into middle lamellae of cells comprising the abscission zones. Microbodies with crystalloid cores appear with considerable frequency in cells of the abscission zone. The crystalloids appear to be cubical in shape and are composed of parallel sheets of osmiophilic material. The sheets average about 6 m in thickness and are spaced at 4 m intervals. The microbodies with crystalloid cores are observed to be characteristically of two size groupings. In tobacco the microbodies average 900 m and 1,500 m in profile. In tomato they average 300 m and 500 m. Chloroplasts contain a granular component which is membrane-enclosed. The component is large in comparison with the plastid in which it occurs, averaging 1.2–1.4 in diameter in chloroplasts ranging from 1.6 to 2.2 in diameter. The inner membrane of the chloroplast is highly invaginated, and DNA- and phytoferritin-like materials are observed within the plastids. Microtubules with an average diameter of 20 m are observed adjacent and parallel to the plasmalemma, primarily in the corners of the cells. Micrographs of other normally occurring cytoplasmic inclusions are also presented.     

Clustering of contact zones, hybrid zones, and phylogeographic breaks in North America

A recent test for the existence of suture zones in North America, based on hybrid zones studied since 1970, found support for only two of the 13 suture zones identified by Remington in 1968 (Swenson and Howard 2004). One limitation of that recent study was the relatively small number of hybrid zones available for mapping. In this study, we search for evidence of clustering of contact zones between closely related taxa using data not only from hybrid zones but from species range maps of trees, birds, and mammals and from the position of phylogeographic breaks within species. Digital geographic range maps and a geographic information system approach allowed for accurate and rapid mapping of distributional data. Areas of contact between closely related species and phylogeographic breaks within species clustered into areas characterized by common physiographic features or predicted by previously hypothesized glacial refugia. The results underscore the general importance of geographic barriers to dispersal (mountain chains) and climate change (periods of cooling alternating with periods of warming, which lead to the contraction and expansion of species ranges) in species evolution.     

Molecular determinants of presynaptic active zones

The presynaptic cytoskeletal matrix (cytomatrix) assembled at active zones has been implicated in defining neurotransmitter release sites. Munc13, Rim, Bassoon and Piccolo/Aczonin are recently identified presynaptic cytomatrix proteins. These multidomain proteins are thought to organize the exocytotic and endocytotic machinery precisely at active zones.     

Evaluation of the immunogenic and reactogenic properties of vaccine "Euvax B" in persons aged 16-18 years in different geographical zones of Russia

The comparative evaluation of the reactogenic and immunogenic properties of vaccine "Euvax B" in adolescents aged 16-18 years was carried out in factory housing estate Lvovsky, the Podolsk district, the Moscow region, and in the Yamalo-Nenets Autonomous District (AD): in towns Salekhard, Noyabrsk, Muravlenko, in housing estate Tarko-Sale. The evaluation demonstrated that the use of this vaccine in a dose of 20 mg/ml produced no postvaccinal complications and the frequency of postvaccinal reactions was insignificant. Postvaccinal anti-HBs were detected, on the average, in protective concentrations in 98.4 +/- 1.8% of the vaccines (99.0 +/- 1.9% in the Moscow region, 97.7 +/- 3.2% in the Yamalo-Nenets AD). In most of the vaccinated adolescents high concentrations of postvacinal anti-HBs were detected: in 51.4 +/- 9.7% of the vaccinees in the Moscow region and in 89.7 +/- 6.4% in the Yamalo-Nenets AD they exceeded 1,000 I.U./lit. The conclusion was made that in the territories located in subarctic latitudes vaccinal prophylaxis against hepatitis B was safe and highly effective and have no limitations connected with the conditions of the Far North.