905 resultados para Black skimmer


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The Korean black scraper, Thamnaconus modestus, is one of the most economically important maricultural fish species in Korea. However, the annual catch of this fish has been continuously declining over the past several decades. In this study, the genetic diversity and relationships among four wild populations and two hatchery stocks of Korean black scraper were assessed based on 16 microsatellite (MS) markers. A total of 319 different alleles were detected over all loci with an average of 19.94 alleles per locus. The hatchery stocks [mean number of alleles (N A) = 12, allelic richness (A R) = 12, expected heterozygosity (He) = 0.834] showed a slight reduction (P > 0.05) in genetic variability in comparison with wild populations (mean N A = 13.86, A R = 12.35, He = 0.844), suggesting a sufficient level of genetic variation in the hatchery populations. Similarly low levels of inbreeding and significant Hardy–Weinberg equilibrium deviations were detected in both wild and hatchery populations. The genetic subdivision among all six populations was low but significant (overall F ST = 0.008, P < 0.01). Pairwise F ST, a phylogenetic tree, and multidimensional scaling analysis suggested the existence of three geographically structured populations based on different sea basin origins, although the isolation-by-distance model was rejected. This result was corroborated by an analysis of molecular variance. This genetic differentiation may result from the co-effects of various factors, such as historical dispersal, local environment and ocean currents. These three geographical groups can be considered as independent management units. Our results show that MS markers may be suitable not only for the genetic monitoring of hatchery stocks but also for revealing the population structure of Korean black scraper populations. These results will provide critical information for breeding programs, the management of cultured stocks and the conservation of this species.

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The objective of this study was to examine the hydrothermal liquefaction of sugarcane bagasse using ethanol and black liquor (BL) in a pilot scale. Combinations of co-solvents (ethanol/ water, ethanol/BL) were studied at various concentrations and reaction conditions. The maximum oil yield of 61% was achieved with a reaction temperature of 300 °C for 30 min and using pure BL as a solvent, while the highest higher heating value (HHV) was obtained from a 50:50 ethanol-BL mixture. The oils contained alcohols, esters, phenolic compounds, aromatics, and heterocyclics. The O/C and H/C ratios of the oil were comparable with traditional biodiesel and commercial diesel. Although this study showed there are some improvements to be made to improve the chemical composition, the approach has potential for large-scale production of a substitute for fossil-fuel-based diesel.

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In this chapter, we explore the 'darker' faces of international business (IB). Over a decade ago, Eden and Len way (2001) raised the need for examining both the 'bright' and the 'dark' side of globalization in order to achieve a better understanding of the concept and of its impact on IB activities. In doing this, they posited the multinational enterprise (MNE) as the 'key agent' and 'f.1ee' of globalization and discussed, primarily, the relationship between MNEs and nation-states as the central interf.1ce of its impact. Additionally, they posited that, by and large, the community of IB scholars positioned themselves at the bright end of the globalization spectrum, seeing it as essentially positive, whilst most non-governmental organizations (NGOs) and international political economy (IPE) academics set themselves at the dark end. Whilst they acknowledged their own 'bright side' tendencies, they called for a more nuanced consideration of MNEs as what they referred to as the Janus bee' of globalization.

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Aerosol black carbon (BC) mass concentrations ([BC]), measured continuously during a multi-platform field experiment, Integrated Campaign for Aerosols gases and Radiation Budget (ICARB, March-May 2006), from a network of eight observatories spread over geographically distinct environments of India, (which included five mainland stations, one highland station, and two island stations (one each ill Arabian Sea and Bay of Bengal)) are examined for their spatio-temporal characteristics. During the period of study, [BC] showed large variations across the country, with values ranging from 27 mu g m(3) over industrial/urban locations to as low as 0.065 mu g m(-3) over the Arabian Sea. For all mainland stations, [BC] remained high compared to highland as well as island stations. Among the island stations, Port Blair (PBR) had higher concentration of BC, compared to Minicoy (MCY), implying more absorbing nature of Bay of Bengal aerosols than Arabian Sea. The highland station Nainital (NTL), in the central Himalayas, showed low values of [BC], comparable or even lower than that of the island station PBR, indicating the prevalence of cleaner environment over there. An examination of the changes in the mean temporal features, as the season advances from winter (December-February) to pre-monsoon (March-May), revealed that: (a) Diurnal variations were pronounced over all the mainland stations, with all afternoon low and a nighttime high: (b) At the islands, the diurnal variations, though resembled those over the mainlands, were less pronounced; and (c) In contrast to this, highland station showed an opposite pattern with an afternoon high and a late night or early morning low. The diurnal variations at all stations are mainly caused by the dynamics of local Atmospheric Boundary Layer (ABL), At the entire mainland as well as island stations (except HYD and DEL), [BC] showed a decreasing trend from January to May, This is attributed to the increased convective mixing and to the resulting enhanced vertical dispersal of species in the ABL. In addition, large short-period modulations were observed at DEL and HYD, which appeared to be episodic, An examination of this in the light of the MODIS-derived fire count data over India along with the back-trajectory analysis revealed that advection of BC from extensive forest fires and biomass-burning regions upwind were largely responsible for this episodic enhancement in BC at HYD and DEL.

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We propose a unified model to explain Quasi-Periodic Oscillation (QPO), particularly of high frequency, observed from black hole and neutron star systems globally. We consider accreting systems to be damped harmonic oscillators exhibiting epicyclic oscillations with higher-order nonlinear resonance to explain QPO. The resonance is expected to be driven by the disturbance from the compact object at its spin frequency. The model explains various properties parallelly for both types of the compact object. It describes QPOs successfully for ten different compact sources. Based on this, we predict the spin frequency of the neutron star Sco X-1 and specific angular momentum of black holes GRO J1655–40, XTE J1550–564, H1743–322, and GRS 1915+105.

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The LISA Parameter Estimation Taskforce was formed in September 2007 to provide the LISA Project with vetted codes, source distribution models and results related to parameter estimation. The Taskforce's goal is to be able to quickly calculate the impact of any mission design changes on LISA's science capabilities, based on reasonable estimates of the distribution of astrophysical sources in the universe. This paper describes our Taskforce's work on massive black-hole binaries (MBHBs). Given present uncertainties in the formation history of MBHBs, we adopt four different population models, based on (i) whether the initial black-hole seeds are small or large and (ii) whether accretion is efficient or inefficient at spinning up the holes. We compare four largely independent codes for calculating LISA's parameter-estimation capabilities. All codes are based on the Fisher-matrix approximation, but in the past they used somewhat different signal models, source parametrizations and noise curves. We show that once these differences are removed, the four codes give results in extremely close agreement with each other. Using a code that includes both spin precession and higher harmonics in the gravitational-wave signal, we carry out Monte Carlo simulations and determine the number of events that can be detected and accurately localized in our four population models.

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The distribution of black leaf nodes at each level of a linear quadtree is of significant interest in the context of estimation of time and space complexities of linear quadtree based algorithms. The maximum number of black nodes of a given level that can be fitted in a square grid of size 2n × 2n can readily be estimated from the ratio of areas. We show that the actual value of the maximum number of nodes of a level is much less than the maximum obtained from the ratio of the areas. This is due to the fact that the number of nodes possible at a level k, 0≤k≤n − 1, should consider the sum of areas occupied by the actual number of nodes present at levels k + 1, k + 2, …, n − 1.

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The purpose of this research is to extend an understanding of how Black and White South African consumers' causal attributions for major household appliance performance failures impact on their anger and subsequent complaint behaviour. A survey was administered to Black and White South African consumers who were dissatisfied with the performance of a major household appliance item. Respondents resided in a major metropolitan area. The findings showed that, compared to Whites, the Black South Africans felt a low but significantly higher external locus of causality and lower control, and experienced a higher level of anger regarding product failure. The level of anger determined the decision to take complaint action, but racial group determined the type of action taken. Blacks complained more actively to retailers and engaged more in private complaint action than Whites. These findings may show that Black South Africans are developing a more individualistic orientation as consumers. Therefore, researchers should consider the effect of cultural swapping when researching consumer behaviour in multi-cultural countries. Implications for retailers in terms of complaint handling are indicated.

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Seed production and soil seed hanks of H. contortus were studied in a subset of treatments within an extensive grazing study conducted in H. contortus pasture in southern Queensland between 1990 and 1996. Seed production of H. contortus in autumn ranged from 260 to 1800 seeds/m2 with much of this variation due to differences in rainfall between years. Seed production was generally higher in the silver-leaved ironbark than in the narrow-leaved ironbark land class and was also influenced by a consistent stocking rate x pasture type interaction. Inflorescence density was the main factor contributing to the variable seed production and was related to the rainfall received during February. The number of seeds per inflorescence was unaffected by seasonal rainfall, landscape position, stocking rate or legume oversowing. Seed viability was related to the rainfall received during March. Soil seed banks in spring varied from 130 to 520 seeds/m2 between 1990 and 1995 with generally more seed present in the silver-leaved ironbark than in the narrow-leaved ironbark land class. There were poor relationships between viable seed production and the size of the soil seed bank, and between the size of the soil seed bank and seedling recruitment. This study indicates that H. contortus has the potential to produce relatively large amounts of seed and showed that the seasonal pattern of rainfall plays a major role in achieving this potential

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The dynamics of Heteropogon contortus (black speargrass) populations were measured in a subset of treatments contained within an extensive grazing study conducted between 1990 and 1996 in H. contortus pasture in southern Queensland. This subset included 2 landscape positions and 3 stocking rates in both native pasture and legume-oversown native pasture. Severe drought conditions throughout much of the study necessitated ongoing adjustments to the original stocking rates and, as a result, drought was the major influence on the dynamics of H. contortus populations. Plant density and basal area in the silver-leaved ironbark landscape were consistently higher than those in the narrow-leaved ironbark landscape. There was limited evidence of any impact by either light or moderate stocking rate but there was evidence of an impact at the heaviest stocking rate. There was minimal impact of legume oversowing. Relatively large fluctuations in plant density occurred during this study resulting from the death of existing plants, due mainly to drought, and seedling recruitment. Similarly, there were relatively large fluctuations in basal area caused mainly by changes in plant size. Rates for turnover of plant numbers were relatively high whereas plant turnover rates of basal areas were relatively low. Regular seedling recruitment appeared necessary to ensure the persistence of this species. Despite the high turnover, populations were maintained at reasonable levels indicating the overall resilience of H. contortus.

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The dynamics of the unpalatable Aristida spp. (wiregrasses) were measured in a subset of treatments contained within an extensive grazing study conducted between 1990 and 1996 in H. contortus pasture in southern Queensland. This paper reports the results from these treatments which included 2 land classes (silver-leaved and narrowleaved ironbark), 3 stocking rates (0.3, 0.6 and 0.9 beasts/ha) in both native pasture and legumeoversown native pasture, all in the absence of fire. Changes in plant density and basal area of Aristida spp. reflected differences in both the survival and size of existing plants together with a large seedling recruitment in 1991. Two different taxa of Aristida spp. were distinguished; however, there were no clear differences in the response of these 2 taxa to the treatments. Grazing had the greatest impact on population dynamics through reducing basal area as stocking rate increased. Neither landscape position nor legume oversowing had a major impact on Aristida spp. The results suggest that populations of Aristida spp. will be highest under light grazing and that seedling recruitment may be episodic

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This paper reports an experiment undertaken to examine the impact of burning in spring together with reduced grazing pressure on the dynamics of H. contortus and Aristida spp. In H. contortus pasture in south-eastern Queensland. The overall results indicate that spring burning in combination with reduced grazing pressure had no marked effect on the density of either grass species. This was attributed to 2 factors. Firstly, extreme drought conditions restricted any increase in H. contortus seedling establishment despite the presence of an adequate soil seed bank prior to summer; and secondly, some differences occurred in the response to fire of the diverse taxonomic groupings in the species of Aristida spp. present at the study site. This study concluded that it is necessary to identify appropriate taxonomic units within the Aristida genus and that, where appropriate, burning in spring to manage pasture composition should be conducted under favorable rainfall conditions using seasonal forecasting indicators such as the Southern Oscillation Index

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The newly emerging Australian bat lyssavirus causes rabies like disease in bats and humans. A captive juvenile black flying fox exhibited progressive neurologic signs, including sudden aggression, vocalization, dysphagia, and paresis over 9 days and then died. At necropsy, lyssavirus infection was diagnosed by fluorescent antibody test, immunoperoxidase staining, polymerase chain reaction, and virus isolation. Eight human contacts received postexposure vaccination.

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Objective: To identify nematodes seen in histological sections of brains of flying foxes (fruit bats) and describe the associated clinical disease and pathology. Proceedures: Gross and histological examination of brains from 86 free-living flying foxes with neurological disease was done as part of an ongoing surveillance program for Australian bat lyssavirus. Worms were recovered, or if seen in histological sections, extracted by maceration of half the brain and identified by microscopic examination. Histological archives were also reviewed. Results: There was histological evidence of angiostrongylosis in 16 of 86 recently submitted flying foxes with neurological disease and in one archival case from 1992. In 10 flying foxes, worms were definitively identified as Angiostrongylus cantonensis fifth-stage larvae. A worm fragment and third stage larvae were identified as Angiostrongylus sp, presumably A cantonensis, in a further three cases. The clinical picture was dominated by paresis, particularly of the hindlimbs, and depression, with flying foxes surviving up to 22 days in the care of wildlife volunteers. Brains containing fifthstage larvae showed a moderate to severe eosinophilic and granulomatous meningoencephalitis (n = 14), whereas there was virtually no inflammation of the brains of bats which died when infected with only smaller, third-stage larvae (n = 3). There was no histological evidence of pulmonary involvement. Conclusion: This is the first report of the recovery and identification of A cantonensis from free-living Australian wildlife. While angiostrongylosis is a common cause of paresis in flying foxes, the initial clinical course cannot be differentiated from Australian bat lyssavirus infection, and wildlife carers should be urged not to attempt to rehabilitate flying foxes with neurological disease.