1000 resultados para northwest Mediterranean


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沙蜥属Phrynocephalus Kaup,1825隶属于爬行纲(Reptilia)有鳞目(Squamata)蜥蜴亚目(Lacertilia)鬣蜥科(Agamidae),是欧亚大陆荒漠和稀疏草原常见蜥蜴。沙蜥属的分类及系统演化关系、地理分布格局与新生代第三纪以来古地中海的变迁、青藏高原的抬升及亚洲内陆干旱荒漠化的过程有密切的关系,长期以来有关沙蜥属的研究一直受到中外学者们的关注。由于沙蜥属地理分布广、形态变异大、体色和斑纹变化复杂,虽然前人使用过许多形态性状来描述和分类沙蜥属物种,但是仍然存在许多问题。性状的分类学意义不明确是造成这些问题的主要原因之一,因此本研究针对沙蜥属常用的鉴别性状进行分类意义的分析,希望能对沙蜥属物种鉴定及分类学其它研究有所裨益。 中国沙蜥属物种主要分布于西北的干旱荒漠区域及青藏高原的大部分地区,大约为18种。 本文研究了中国境内12种沙蜥:青海沙蜥(Phrynocephalus vlangalii)、西藏沙蜥(P. theobaldi)、南疆沙蜥(P. forsythii)、变色沙蜥(P. versicolor)、旱地沙蜥(P. helioscopus)、荒漠沙蜥(P. przewalskii)、乌拉尔沙蜥(P. guttatus)、草原沙蜥(P. frontalis)、叶城沙蜥(P. axillaris)、白稍沙蜥(P. koslowi)、无斑沙蜥(P. immaculatus)和白条沙蜥(P. albolineatus),对它们的65项外部形态性状进行了观察和测量,其中数量性状29项、质量性状36项。评价了这些性状的序级性、间断性和代表性,结论如下: 1. 对于数量性状,得出了适合各级分类的数值区间; 2. 给出了在不同序级上适合分类的质量性状。 并利用各性状评价的结果,给出12种沙蜥的检索表,以及对中国沙蜥物种某些尚存在争议的问题进行了探讨。 详细记录了青海沙蜥红原亚种的骨骼系统,首次发现并命名了肘骨(elbow bone)和垫骨(stepping bone),为沙蜥属系统学研究补充了骨骼方面的证据;解剖了乌拉尔沙蜥、旱地沙蜥、荒漠沙蜥的雌体和雄体的骨骼系统,并在14项骨骼形态性状上对这3种沙蜥进行了比较。 Phrynocephalus (Squamata,Agamidae) is a familiar genus of lizards inhabited desert and sparse steppes in Eurasia. The taxonomics, phylogenetics and distribution pattern of Phrynocephalus are relative intensely to these events: the vicissitudes of the archaic Mediterranean sea since the Cainozoic, the uplift of Qingzang Plateau and the expending arid areas in the inland of Asia. Owing to the wide distribution, the large variability of the morphology and the different colors in Phrynocephalus, it is difficult to identify them. Tough many morphological characters are used to describe and discriminate them,a lot of questions still exist. One of the most important reasons is the confusion in the morphological characters. In this study, we demonstrate the validity and the invalidity of the familiar characters. There are about 18 species of the genus Phrynocephalus in China, which exist in arid desert in Northwest China and Qingzang Plateau. Twelve Chinese species was analyzed in this paper. They are P. vlangalii,P. theobaldi,P. forsythia,P. versicolor,P. helioscopus,P. przewalskii,P. guttatus,P. frontalis,P. axillaris,P. koslowi,P. immaculatus,P. albolineatus. We measure 29 quantitative characters and observe 36 qualitative characters in each individual. Through analyzing these characters, we made some conclusions as follows: 1. to every quantitative character, we get a clear numeric area to discriminate the different operational taxonomic units. 2. we chose the valid qualitative characters in these operational taxonomic units. This paper is the first to describe the “elbow bone”, which is a bone in pectoral appendage equivalent to patella,and “stepping bone”, which is a bone under carpal. A detailed description of the skeletal system of female Phrynocephalus vlangalii hongyuanensis was conducted. We also anatomise the skeletal systems of three species: P. guttatus,P. przewalskii,P. helioscopus, and compare or contrast 14 skeletal characters in them. What’s more,this paper offers some suggestions to the questions of Chinese Phrynocephalus species and keys to 12 species of Phrynocephalus basing on our conclusions on the evaluation of the morphological characters.

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Based on more than 4000 km 2D seismic data and seismic stratigraphic analysis, we discussed the extent and formation mechanism of the Qiongdongnan deep sea channel. The Qiongdongnan deep sea channel is a large incised channel which extends from the east boundary of the Yinggehai Basin, through the whole Qiongdongnan and the Xisha trough, and terminates in the western part of the northwest subbasin of South China Sea. It is more than 570 km long and 4-8 km wide. The chaotic (or continuous) middle (or high) amplitude, middle (or high) continuity seismic facies of the channel reflect the different lithological distribution of the channel. The channel formed as a complex result of global sea level drop during early Pliocene, large scale of sediment supply to the Yinggehai Basin, inversion event of the Red River strike-slip fault, and tilted direction of the Qiongdongnan Basin. The large scale of sediment supply from Red River caused the shelf break of the Yinggehai Basin to move torwards the S and SE direction and developed large scale of prograding wedge from the Miocene, and the inversion of the Red River strike-slip fault induced the sediment slump which formed the Qiongdongnan deep sea channel.

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Anti-cyclonic eddies northwest of Luzon of the Philippines in summer-fall are identified in the merged data products of satellite altimeters of Topex/Poseidon, Jason-1 and European Research Satellites. The generation and propagation of the anti-cyclonic eddies, which are confirmed by satellite ocean color data, are found to be a seasonal phenomenon that is phase-locked to the onset of the southwesterly monsoon and the relaxation of the cyclonic wind curl in the northeastern South China Sea. The eddies originate from northwest of Luzon in summer, move across the northeastern South China Sea to reach the China continental slope in fall, and propagate southwestward along the continental slope in fall-winter, inducing shelfbreak current variations in the western South China Sea in fall-winter. The anti-cyclonic eddy discovered by Li et al. (1998) in the northern South China Sea is found to originate from northwest of Luzon and carry primarily the South China Sea waters. It does not appear to be an eddy shed from the Kuroshio in the Luzon Strait area as alluded by Li et al. (1998) and others.

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Grain yields of over 14 Mg ha(-1) were reported in 1978 for spring wheat (Triticum aestivum L.) grown in Northwest China. Understanding the circumstances under which this record yield was achieved may be useful in defining the key factors that lead to high grain yields and in determining the limits to wheat yield. A relatively simple, mechanistic model was used in an effort to simulate the record yield. The model was used as a framework in which various crop traits could be adjusted to match the observed crop growth. The weather that was characterized by cool temperatures and high levels of solar radiation, proved to be especially important in allowing a full-season crop to achieve record yields. Variables defining plant development in the model also had to be set to describe the high yielding cultivar grown in China. Leaf development was defined by the length of a phyllochron, which was set equal to 78 TU (thermal units, base temperature equal to 0 degrees C) based on independent data. The description of grain fill had to be defined to match simulation results with the observations. Two variables, length of the grain-fill period and the grain growth rate, were set in response to the unique traits of this cultivar and the low temperatures during grain development. These simulations led to important suggestions for examining the interaction between cool temperature regimes and developmental traits of wheat cultivars. (C) 1997 Published by Elsevier Science Ltd.

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Integrating connectivity patterns into marine ecosystem management is a fundamental step, specially for stock subjected to the combined impacts of human activities (overfishing, habitat degradation, etc.) and climate changes. Thus, management of marine resources must incorporates the spatial scales over which the populations are connected. Notwithstanding, studying these dynamics remains a crucial and hard task and the predictions of the temporal and spatial patterns of these mechanisms are still particularly challenging. This thesis aims to puzzle over the red mullet Mullus barbatus population connectivity in the Western Mediterranean Sea, by implementing a multidisciplinary approach. Otolith sclerochronology, larval dispersal modelling and genetic techniques were gathered in this study. More particularly, this research project focused on early life history stages of red mullet and their role in the characterization of connectivity dynamics. The results show that M. barbatus larval dispersal distances can reach a range of 200 km. The differences in early life traits (i.e. PLD, spawning and settlement dates) observed between various areas of the Western Mediterranean Sea suggest a certain level of larval patchiness, likely due to the occurrence of different spawning pulses during the reproductive period. The dispersal of individuals across distant areas, even not significant in demographic terms, is accountable for the maintenance of the genetic flow among different demes. Fluctuations in the level of exchange among different areas, due to the variability of the source-sink dynamics, could have major implications in the population connectivity patterns. These findings highlight the reliability of combining several approaches and represent a benchmark for the definition of a proper resource management, with considerable engagements in effectively assuring the beneficial effects of the existent and future conservation strategies.

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Cryptococcus gattii causes life-threatening disease in otherwise healthy hosts and to a lesser extent in immunocompromised hosts. The highest incidence for this disease is on Vancouver Island, Canada, where an outbreak is expanding into neighboring regions including mainland British Columbia and the United States. This outbreak is caused predominantly by C. gattii molecular type VGII, specifically VGIIa/major. In addition, a novel genotype, VGIIc, has emerged in Oregon and is now a major source of illness in the region. Through molecular epidemiology and population analysis of MLST and VNTR markers, we show that the VGIIc group is clonal and hypothesize it arose recently. The VGIIa/IIc outbreak lineages are sexually fertile and studies support ongoing recombination in the global VGII population. This illustrates two hallmarks of emerging outbreaks: high clonality and the emergence of novel genotypes via recombination. In macrophage and murine infections, the novel VGIIc genotype and VGIIa/major isolates from the United States are highly virulent compared to similar non-outbreak VGIIa/major-related isolates. Combined MLST-VNTR analysis distinguishes clonal expansion of the VGIIa/major outbreak genotype from related but distinguishable less-virulent genotypes isolated from other geographic regions. Our evidence documents emerging hypervirulent genotypes in the United States that may expand further and provides insight into the possible molecular and geographic origins of the outbreak.

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The Sahara desert is a significant source of particulate pollution not only to the Mediterranean region, but also to the Atlantic and beyond. In this paper, PM 10 exceedences recorded in the UK and the island of Crete are studied and their source investigated, using Lagrangian Particle Dispersion (LPD) methods. Forward and inverse simulations identify Saharan dust storms as the primary source of these episodes. The methodology used allows comparison between this primary source and other possible candidates, for example large forest fires or volcanic eruptions. Two LPD models are used in the simulations, namely the open source code FLEXPART and the proprietary code HYSPLIT. Driven by the same meteorological fields (the ECMWF MARS archive and the PSU/NCAR Mesoscale model, known as MM5) the codes produce similar, but not identical predictions. This inter-model comparison enables a critical assessment of the physical modelling assumptions employed in each code, plus the influence of boundary conditions and solution grid density. The outputs, in the form of particle concentrations evolving in time, are compared against satellite images and receptor data from multiple ground-based sites. Quantitative comparisons are good, especially in predicting the time of arrival of the dust plume in a particular location.