87 resultados para BLACK HOLES


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One of the most endangered populations of Black-necked Cranes (Grus nigricollis), the central population, is declining due to habitat loss and degradation, but little is known about their space use patterns and habitat preferences. We examined the space use and habitat preferences of Black-necked Cranes during the winter of 2007-2008 at the Napahai wetland in northwest Yunnan, China, where approximately 300 Black-necked Cranes (>90% of the total central population) spent the winter. Euclidean distance analysis was employed to determine the habitat preferences of Black-necked Cranes, and a local nearest-neighbor, convex-hull construction method was used to examine space use. Our results indicate that Black-necked Cranes preferred shallow marsh and wet meadow habitats and avoided farmland and dry grassland. Core-use areas (50% isopleths) and total-use areas (100% isopleths) accounted for only 1.2% and 28.2% of the study area, respectively. We recommend that habitat protection efforts focus on shallow marsh and wet meadow habitats to maintain preferred foraging sites. Core-use areas, such as the primary foraging areas of Black-necked Cranes, should be designated as part of the core zone of the nature reserve. Monthly shifts in the core-use areas of the cranes also indicate that the reserve should be large enough to permit changes in space use. In addition to preserving habitat, government officials should also take measures to decrease human activity in areas used by foraging Black-necked Cranes.

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介绍了应用过夜地粪便来估计白马雪山黑白仰鼻猴群大小和组成的一种方法。该物种以单雄多雌单 元和全雄组的形式在树上过夜。粪粒根据其大小可分为3种类型:成年雄性的(最大)、成年雌性的(中等大小)和 未成年个体的(最小)。2000一2001年,搜集了滇西北白马雪山国家级自然保护区北部南任村(99。04 7E,28。34 7N) 附近黑白仰鼻猴群每个季节2个过夜地的粪粒。根据2001年11月猴群通过开阔地的数据来确定猴群组成。每个 季节,由于单雄多雌单元的成年个体数与其粪粒数正相关,所以二者回归直线的斜率可以看作是每个个体每晚 的平均排便量。由于该物种的栖息地主要为高山峡谷,而且能见度较低,因此,利用过夜地粪便比以前通过猴群 活动痕迹来估计猴群大小和组成相对准确、可靠。从估计成年雌性个体数的角度看,利用粪粒来估计种群大约有 9.4%的偏差。导致偏差的可能原因有杂草和灌丛对粪粒准确计数的影响、个体排粪率的差异以及成年雄性最小 粪粒与成年雌性最大粪粒的混淆等。该方法适应于栖息地和主要食物与本文研究种群相似的其他种群。

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The black-crested gibbon, Hylobates concolor, is one of the few species of gibbons that has not yet been the subject of a long term field study. Field observations in the Ai Lao and Wu Liang Mountains of Yunnan Province, China indicate that in this area the habitat and ecology of this species differ markedly from those of other gibbons that have been studied to date. These differences are correlated with some behavioral differences. In particular, these gibbons apparently have greater day ranges than other gibbons. It has also been suggested that this species lives in polygynous groups. To demonstrate this requires observation of groups with two or more females with young. Our own observations and those from other recent studies suggest that there are alternative explanations consistent with available data.

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Feeding and vocal behaviours of wild black gibbons (Hylobates concolor) were observed from 1987 to 1989 in south-western Yunnan, notably H. concolor jingdongensis at Mt. Wuliang (24-degrees 18-42'N, 100-degrees 30-50'E) in the early spring of 1989. 12 plant species were observed to have been eaten by the gibbons; these included tree species, lianas and epiphytes. Approximately 21 % of feeding time was devoted to eating fruits, 61 % to leaf buds and shoots, 7 % to flowers and 11 % to leaves. The gibbons preferred fruits to leaves even though they commonly ate leaves. In this study, the morning songs (duet and solo), reponsive (territorial) songs, alarm calls and communication calls were recorded. The gibbons sang their morning songs mainly in the early morning, with a single bout lasting more than 10 min on average. The singing of a group would trigger other groups, and all groups in an area tended to sing sequentially. The morning duet song bout was dominated by an adult male. The male emitted booms, aa notes, early multimodulated figures, intermediate multimodulated figures and codas, the latter occurring only in duets following the female's great call. The female uttered great calls and abortive great calls. The subadults or juveniles also took part in the morning songs. Lone males were heard to utter solos which lasted longer than the duets of the pairs.

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Data on sleeping sites of a group of black-and-white snub-nosed monkeys Rhinopithecus bieti (Colobinae, Primates) were collected between April-July and September-December 2001 to try to determine the factors affecting site selection at Nanren (99 degrees

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Data on social organization of two bands of black-and-white snub-nosed monkeys (Rhinopithecus bieti) 14 were collected when the monkeys were crossing an open spot at Nanren and Bamei (northwest of Yunnan, China) using a sampling rule where individuals wit

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Data on mating and birth seasonality were recorded in wild black-and-white snub-nosed monkeys (Rhinopithecus bieti) at Xiaochangdu in the Honglaxueshan National Nature Reserve, Tibet. This represents one of the harshest habitats utilized by any nonhuman p

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A growth trial was conducted to estimate the optimum requirement of dietary available phosphorus (P) for black seabream (Sparus macrocephalus) in indoor net cages (1.5x1.0x1.0 m). Triplicate groups of black seabream (11.45 +/- 0.02 g) were fed diets containing graded levels (0.18, 0.36, 0.54, 0.72, 0.89 and 1.07%) of available P to satiation for 8 weeks. The basal diet (diet 1), containing 0.18% available P, was supplemented with graded levels of monosodium phosphate (NaH2PO4 2H(2)O) to formulate five experimental diets. The fish were fed twice daily (08:00 h and 16:00 h) and reared in seawater (salinity, 26-29 g l(-1)) at a temperature of 28 +/- 1 degrees C. Dissolved oxygen during the experiment was above 5 mg l(-1). The specific growth rate (SGR), weight gain (WG), feed efficiency (FE) and protein efficiency ratio (PER) were all significantly improved by dietary phosphorus up to 0.54% (P<0.05) and then leveled off beyond this level. Hepatosomatic index (HSI) was inversely correlated with dietary phosphorus levels (P< 0.05). Efficiency of P utilization stabled in fish fed diets containing 0.18%-0.54% available P and then decreased dramatically with further supplementation of dietary phosphorus. Body composition analysis showed that the whole-body lipid, ash, calcium and phosphorus contents were all significantly affected by dietary available P concentration (P<0.05), however, no significance were found in whole-body calcium/phosphorus (Ca/P) ratios among all the treatments (P>0.05). Dietary phosphorus levels also affected the mineralization of vertebrae, skin and scale (P<0.05). Ca/P ratios in vertebrae and scale were not influenced by dietary P supplementation, while skin Ca/P ratio increased statistically with dietary available P levels (quadratic effect, P<0.001). The blood chemistry analysis showed that dietary available P had distinct effects on enzyme activities of alkaline phosphatase (ALP) and plasma lysozyme (LSZ), as well as contents of triacyglycerol (TG) and total cholesterol (T-CHO) (P<0.05). Broken-line analysis showed maximum weight gain (WG) was obtained at dietary available P concentrations of 0.55%. Quadratic analysis based on P contents in whole fish, vertebrae or scale indicated that the requirements were 0.81, 0.87 and 0.88%, respectively. Signs of phosphorus deficiency were characterized by poor growth, slightly reduced mineralization and an increase in body lipid content. (C) 2008 Published by Elsevier B.V.

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Immunostimulants are the substances, which enhance the non-specific defence mechanism and provide resistance against the invading pathogenic micro-organism. In order to increase the immunity of shrimps against the WSSV, the methanolic extracts of five different herbal medicinal plants like Cyanodon dactylon, Aegle marmelos, Tinospora cordifolia, Picrorhiza kurooa and Eclipta alba were selected and mixed thoroughly in equal proportion. The mixed extract was supplemented with various concentrations viz. 100 (A), 200 (B), 400 (C), and 800 (D) mg kg(-1) through artificial diets individually. The prepared diets (A-D) were fed individually to WSSV free healthy shrimp Penaeus monodon with an average weight of 8.0 +/- 0.5 g for 25 days. Control diet (E), devoid of herbal extract was also fed to shrimps simultaneously. After 25 days of feeding experiment, the shrimps were challenged with WSSV, which were isolated and propagated from the infected crustaceans. The shrimps succumbed to death within 7 days when fed on no herbal immunostimulant diet (E). Among the different concentrations of herbal immunostimulant supplemented diets, the shrimps fed on diet D (800 mg kg(-1)) significantly (P < 0.0001) had more survival (74%) and reduction in the viral load. Also the better performance of haematological, biochemical and immunological parameters was found in the immunostimulant incorporated diets fed shrimps. The present work revealed that the application of herbal immunostimulants will be effective against shrimp viral pathogenesis and they can be recommended for shrimp culture. (c) 2006 Published by Elsevier Ltd.

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The natural reproduction of grass carp, black carp, silver carp, and bighead will be affected adversely by the Three Gorges Project in the Yangtze River. One of the methods to save the fish is to regulate the water levels, keeping them suited for the species to spawn. Nine factors associated with the scale of larvae-flood of the four species are classified into five levels, and the ranges of these factors producing larvae-floods are given by using the "factor-criteria system reconstruction analysis" method. Moderate beginning water levels and flow, with high daily increases in the rate of water level and flow, and a long duration of water level rising are important for the production of a large larvae-flood.

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We propose an ultracompact triplexer based on a shift of the cutoff frequency of the fundamental mode in a planar photonic crystal waveguide (PCW) with a triangular lattice of air holes. The shift is realized by modifying the radii of the border holes adjacent to the PCW core. Some defect holes are introduced to control the beam propagation. The numerical results obtained by the finite-difference time-domain method show that the presented triplexer can separate three specific wavelengths, i.e. 1310, 1490 and 1550 nm with the extinction ratios higher than - 18 dB. The designed device with a size as compact as 12 mu m x 6.5 mu m is feasible for the practical application, and can be utilized in the system of fiber to the home.

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Electron spin relaxation of charged excitons X+ and X2+ are investigated by time-resolved and polarization-resolved photoluminescence spectroscopy. For X+ configuration, the electron spin relaxation shows a typical decay curve induced by hyperfine interaction with nuclei, whereas for X2+ state the electron spin relaxation is affected not only by nuclei but also by electron-hole exchange interaction, leading to a power-law time dependence.

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The magnetisation of heavy holes in III-V semiconductor quantum wells with Rashba spin-orbit coupling (SOC) in an external perpendicular magnetic field is studied theoretically. We concentrate on the effects on the magnetisation induced by the system boundary, the Rashba SOC and the temperature. It is found that the sawtooth-like de Haas-van Alphen (dHvA) oscillations of the magnetisation will change dramatically in the presence of such three factors. Especially, the effects of the edge states and Rashba SOC on the magnetisation are more evident when the magnetic field is smaller. The oscillation center will shift when the boundary effect is considered and the Rashba SOC will bring beating patterns to the dHvA oscillations. These effects on the dHvA oscillations are preferably observed at low temperatures. With increasing temperature, the dHvA oscillations turn to be blurred and eventually disappear.

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By integrating a resonant tunneling diode with a 1.2 mu m-thick slightly doped n-type GaAs layer in a three-barrier, two-well resonant tunneling structure, the resonant tunneling of photo-excited holes exhibits a value of peak-to-valley current ratio (PVCR) as high as 36. A vast number of photo-excited holes generated in this 1.2 mu m-thick slightly doped n-type GaAs layer, and the quantization of hole levels in a 23nm-thick quantum well on the outgoing side of hole tunneling out off the resonant tunneling diode which greatly depressed the valley current of the holes, are thought to be responsible for such greatly enhanced PVCR.