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Atmospheric pollen was collected with a Burkard sporetrap in Ankara, Turkey from January 1993 to January1994. The sum of the annual totals of the dailyconcentration of pollen, belonging to 44 taxa, was57,735. A relatively high pollen concentration wasrecorded in June which could be caused by higher windspeed and lower rainfall. Pinaceae,Cupressaceae/Taxaceae, Gramineae, Platanus, Populus,Moraceae, Chenopodiaceae/Amaranthaceae, Acer, Quercus,Betula, Salix, Rumex and Plantago are found tobe the dominant pollen types in the atmosphere inAnkara.  相似文献   

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Astrocytes represent an abundant type of glial cell involved in nearly every aspect of central nervous system (CNS) function, including synapse formation and maturation, ion and neurotransmitter homeostasis, blood–brain barrier maintenance, as well as neuronal metabolic support. These various functions are enabled by the morphological complexity that astrocytes adopt. Recent experimental advances in genetic and viral labeling, lineage tracing, and live- and ultrastructural imaging of miniscule astrocytic sub-compartments reveal a complex morphological heterogeneity that is based on the origin, local function, and environmental context in which astrocytes reside. In this minireview, we highlight recent findings that reveal the plastic nature of astrocytes in the healthy brain, particularly at the synapse, and emerging technologies that have advanced our understanding of these morphologically complex cells.  相似文献   

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Loch Leven is a large, shallow lake in lowland Scotland, UK. Scientific research began here almost 200 years ago. Early research characterised the biodiversity and physical characteristics of the loch, providing an important historical background for future research. In the mid-1960s, this ad hoc approach was superseded by a more structured research programme under the umbrella of the International Biological Programme. This was the beginning of the Loch Leven long-term monitoring programme. Today, the results of these studies form one of the longest and most comprehensive limnological datasets for shallow freshwater lakes in the world, comprising more than 500 physical, chemical and biological variables collected at two-weekly intervals. To celebrate the 40th anniversary of the start of the long term monitoring programme, and to highlight the scientific investigations still being conducted at Loch Leven, the NERC Centre for Ecology & Hydrology (CEH) organised a symposium entitled “Loch Leven: 40 years of scientific research” in Kinross, Scotland, UK, on 11 December 2008. This examined the role of long-term monitoring in developing our understanding of the links between pollution, climate change and ecological responses in shallow lakes. This article introduces a series of papers summarising the scientific results presented at this meeting.  相似文献   

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The niche provides a specialised microenvironment necessary for maintenance of stem cells in a non differentiated state. While the hematopoietic stem cell (HSC) niche in vertebrates was the first to be recognized, Drosophila niches supporting germline stem cells were characterised first. Recent evidence for the existence of a niche maintaining hematopoietic precursors in Drosophila opens the way to study in vivo the niche/hematopoietic precursors interactions. The availability of a large collection of cell markers, mutants and sophisticated genetic tools makes Drosophila an attractive model for investigating the cellular and molecular mechanisms that are involved in these interactions.  相似文献   

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A preliminary list of all the plant and animal foods for wild chimpanzees at Bossou, south-east of the Republic of Guinea, is presented for comparison with that of other study areas and as the basic data for the further studies. Altogether 205 food items (species × part eaten) from 156 species in 106 genera of plant food are recorded (Table 1). On the other hand little of animal food has been recorded (Table 2). Thus only one species of mammal (tree pangolin) and bird (wood owl) are represented in the diet along with only a few types of other animals. As calculated from number of food items fruits and seeds (nuts) occupy more than half of the diet; and leaves, shoots, and twigs (stems) constitute about one third.  相似文献   

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HDP1 is an archaeological and faunal site located on the Hoedjiespunt peninsula at Saldanha Bay, South Africa, that has recently yielded fossil human remains. Artefacts from the associated archaeological deposits are identified as being Middle Stone Age. U series analysis of capping calcretes and analysis of the foraminifera and fauna associated with the human fossils indicate an age for the deposit in excess of 74,000 years before present, and it most probably dates to around 300,000 years before present. The fossil human teeth from in situ deposits at Hoedjiespunt are described and found to be large by comparison with modern humans but smaller than the known upper dentitions of southern African “archaic” Homo sapiens. The Hoedjiespunt molars are found to be morphologically within the range of variation observed in the teeth of modern Homo sapiens. © 1995 Wiley-Liss, Inc.  相似文献   

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Data from an urban sample of American women of reproductive ages demonstrate that age at menarche is correlated with age at first intercourse, that age at first intercourse is correlated with age at first pregnancy, and that menarche is therefore correlated with age at first pregnancy. This applied to both blacks and whites when examined for the early years of the reproductive cycle. Girls with early menarche, compared to those with late menarche, are more than twice as likely to have had intercourse by age 16, and almost twice as likely to have given birth or had a pregnancy terminated by age 18. It is therefore useful to think of the timing of menarche as an indicator of the probability of early intercourse and early childbearing.  相似文献   

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Investigation was carried out from 1976 to 1979 to establish a new control system against the houseflies, Musca domestica, at a sea-filling waste disposal site in Osaka Bay, Japan. Field surveys showed that the garbage was favorble for the fly breeding for 20–30 days after being disposed, while the sewage sludge and the ash from incinerated refuse were unfavorable. Comparing the fly density at the site to the reported cases of the public complaints in the urban area near to the site, a complaint threshold density of the flies at the site was estimated. Then, a control threshold density was assumed from the complaint threshold density and the reproductive rate of the housefly population. Several insecticides, as well as a surface active agent, polyoxyethylene lauryl ether (PEL), were found effective for the temporary suppression of the fly density. Based on the results obtained, the following control system was worked out. 1) Refuse is disposed onto the same area as other inorganic wastes to deteriorate the capacity of breeding sources. 2) The fly density is examined on newly disposed refuse almost everyday by landfill operators. 3) PEL is sprayed when the density slightly exceeds the control threshold density. If the density increases rather higher, insecticide should be used. 4) The disposed refuse is covered with soil or other inorganic wastes on every weekend or every other weekend by 15 cm thickness. Success in both fly control and reduction of the amounts of insecticides sprayed was achieved by a field application of this new control system.  相似文献   

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Summary Microbial reefs, together with stromatolitic mounds and ooid shoals, constitute massive limestones in Famennian platform marginal strata in Guilin, in sharp contrast to the well-known coral-stromatoporoid reefs in the Givetian and Frasnian. Microbes played a significant and important role as stabilizers in the Famennian carbonate deposits of Guilin. A reef at Zhaijiang was constructed byEpiphyton andRenalcis, and is representative of such carbonate buildups. The reef is situated 10 km west of Guilin and corresponds to a microbe-dominated platform margin carbonate complex. Organisms in the Zhaijiang microbial reef are low diversity and dominated by ostracods and two genera of microbes,Epiphyton andRenalcis. Other microbial genera such asSphaerocodium andWetheredella occur in most of reef facies in Guilin, but their role as reef builder is doubtful because they occur only in minor amounts. The same four genera occur in volumetrically significant amounts in the upper Devonian carbonate complexes of Alberta. Canada and Western Australia. However.Epiphyton is more abundant in the Guilin reefs. The Zhaijiang microbial reef developed above Famennian proximal slope faices, as suggested by reef architecture and paleogeographic setting. The facies sequence of the microbial reef can be divided into three parts. The lower part is composed of medium-bedded bioclastic grainstones with a few microbial framestone lithoclasts, representing a proximal slope facies. The middle part consists of thin-bedded mudstone and shale with limestone lenses that are thought to be low stand deposits. In some cross sections, mudstone and shale infilled tidal channels that developed in the bioclastic grainstones.Renalcis-Epiphyton framestone constitutes the upper part with massive stacking patterns. The reef is 35 m thick and over 50 m in width. Nine litho- and biofacies are recognized. Zhaijiang reef provides an example of a binder guild-dominated buildup in the almost vacant reef ecosystem of the Famennian and represents a characteristic kind of reef after the Frasnian/Famennian extinction.  相似文献   

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