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Auswahl der wissenschaftlichen Literatur zum Thema „Low density populations of koalas“
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Zeitschriftenartikel zum Thema "Low density populations of koalas"
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Sullivan, B. J., W. M. Norris und G. S. Baxter. „Low-density koala (Phascolarctos cinereus) populations in the mulgalands of south-west Queensland. II. Distribution and diet“. Wildlife Research 30, Nr. 4 (2003): 331. http://dx.doi.org/10.1071/wr00032.
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This study used faecal pellets to investigate the broadscale distribution and diet of koalas in the mulgalands biogeographic region of south-west Queensland. Koala distribution was determined by conducting faecal pellet searches within a 30-cm radius of the base of eucalypts on 149 belt transects, located using a multi-scaled stratified sampling design. Cuticular analysis of pellets collected from 22 of these sites was conducted to identify the dietary composition of koalas within the region. Our data suggest that koala distribution is concentrated in the northern and more easterly regions of the study area, and appears to be strongly linked with annual rainfall. Over 50% of our koala records were obtained from non-riverine communities, indicating that koalas in the study area are not primarily restricted to riverine communities, as has frequently been suggested. Cuticular analysis indicates that more than 90% of koala diet within the region consists of five eucalypt species. Our data highlights the importance of residual Tertiary landforms to koala conservation in the region.
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Law, B., L. Gonsalves, R. Bilney, J. Peterie, R. Pietsch, P. Roe und A. Truskinger. „Using Passive Acoustic Recording and Automated Call Identification to Survey Koalas in the Southern Forests of New South Wales“. Australian Zoologist 40, Nr. 3 (Januar 2020): 477–86. http://dx.doi.org/10.7882/az.2019.033.
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Cost-effective surveys of low density koala populations are challenging, but technological developments in the acoustics field offer great potential for landscape-scale surveys and monitoring. We assessed passive acoustic recording coupled with automated call identification as a survey method for koalas Phascolarctos cinereus . Surveys targeted areas of previously known koala activity based on scat surveys in southern forests of New South Wales where a low density of koalas is suspected. We set 24 Song Meters to record at night over a two week period (~3,696 hours) in the koala breeding season (October/November) in Murrah Flora Reserve. Recordings were scanned by a koala call recogniser and “matches” were manually verified. Across the 24 sites, 522 validated koala bellows were recorded at 21 sites (87.5 % detection rate). Three environmental variables had most influence on detection probability of koalas, including nightly rainfall (-ve), nightly temperature (-ve) and topographic position (lower on ridges). Calling activity peaked at midnight. Sustained site occupancy, at least in the short-term, was apparent as under optimal conditions (no rain) koalas were recorded, on average, for > 50 % of survey nights rather than for just a few nights. We suggest that only a modest survey effort (4–5 nights) in the breeding season, on nights with < 3 mm of rain, is required to achieve 90–95 % probability of koala call detection in an area of low koala density. Comparison with scat surveys at the same sites revealed that detection rates were more than three times greater with acoustic surveys. Technological advances will continue to provide improvements for wildlife survey, and perhaps most importantly, for collecting much needed long-term data to assess trends in occupancy or other population attributes over time.
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Menkhorst, Peter, David Ramsey, Tim O'Brien, Emily Hynes und Desley Whisson. „Survival and movements of koalas translocated from an over-abundant population“. Wildlife Research 46, Nr. 7 (2019): 557. http://dx.doi.org/10.1071/wr19090.
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Abstract Context At some sites in southern Victoria, browsing pressure caused by high-density koala populations can result in defoliation of preferred browse trees. In extreme cases, this over-browsing can lead to widespread tree death and starvation of koalas. To reduce the potential for mortality of trees and koalas, a management strategy that includes fertility control of females and translocation of healthy individuals (male and female) has been adopted. AimsTo compare the short- to medium-term survival and body condition of koalas translocated from over-browsed habitat and released into unoccupied (or nearly so) habitat with that of koalas left in situ in compromised habitat. Methods We monitored survival and body condition of 36 translocated koalas for 4–5 months after translocation relative to that of a control group (24 animals) left in situ. Koalas were recaptured and body condition measured (as a scaled body-mass index) ~40 and 137 days after translocation. Additionally, GPS loggers were used to investigate patterns of koala movement. Key resultsSurvival rates of translocated koalas were not different from those of controls and females in both groups showed slightly higher survival rates than did males. After 137 days, control animals had lower scaled body mass, whereas translocated animals, after an initial reduction, had mostly regained, or increased their scaled body mass. Translocated females regained their original scaled body mass faster than did translocated males. Male koalas in both control and translocated groups had higher rates of movement than did females, and translocated koalas had slightly higher rates of movement than did control koalas. Translocated koalas moved farther from their release location than control koalas. ConclusionsOn the basis of the scaled body-mass index, translocated koalas fared better than those left in situ in compromised habitat, even though the density of koalas in the over-browsed habitat had been reduced by a wider salvage translocation program. The process used to identify potential release sites, including a spatial koala-habitat index, accurately predicted suitable koala habitat. ImplicationsThe current management strategy of translocating koalas out of over-browsed habitat is supported and could be more widely applied.
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Masters, Pip, Toni Duka, Steve Berris und Graeme Moss. „Koalas on Kangaroo Island: from introduction to pest status in less than a century“. Wildlife Research 31, Nr. 3 (2004): 267. http://dx.doi.org/10.1071/wr03007.
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In less than a century the ecological profile of koalas on Kangaroo Island has shifted from that of a species introduced for conservation purposes to one of pest status. Between 1923 and 1925, 18 koalas were released on Kangaroo Island. Their numbers increased rapidly and in 1997 a population-control program was implemented based on a population estimate of 5000 koalas. During the course of this program, it became clear that the koala population on Kangaroo Island was much greater and more widely distributed than previously thought, hence a more comprehensive population survey was carried out.In 2000–01 the koala population size was calculated using a stratified sampling approach based on five 'catchment units' and three habitat classifications that were known to support koalas. The koala population was estimated to be ~27 000 koalas in 2001. There were substantial differences in koala density in the low-, medium- and high-quality habitat within each catchment unit, and therefore large differences in the spatial distribution of koalas across Kangaroo Island. This revised population estimate has substantial ramifications for the Kangaroo Island Koala Management Program that was set in place in 1997.
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Sullivan, B. J., G. S. Baxter, A. T. Lisle, L. Pahl und W. M. Norris. „Low-density koala (Phascolarctos cinereus) populations in the mulgalands of south-west Queensland. IV. Abundance and conservation status“. Wildlife Research 31, Nr. 1 (2004): 19. http://dx.doi.org/10.1071/wr02037.
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Urban encroachment on dense, coastal koala populations has ensured that their management has received increasing government and public attention. The recently developed National Koala Conservation Strategy calls for maintenance of viable populations in the wild. Yet the success of this, and other, conservation initiatives is hampered by lack of reliable and generally accepted national and regional population estimates. In this paper we address this problem in a potentially large, but poorly studied, regional population in the State that is likely to have the largest wild populations. We draw on findings from previous reports in this series and apply the faecal standing-crop method (FSCM) to derive a regional estimate of more than 59 000 individuals. Validation trials in riverine communities showed that estimates of animal density obtained from the FSCM and direct observation were in close agreement. Bootstrapping and Monte Carlo simulations were used to obtain variance estimates for our population estimates in different vegetation associations across the region. The most favoured habitat was riverine vegetation, which covered only 0.9% of the region but supported 45% of the koalas. We also estimated that between 1969 and 1995 ~30% of the native vegetation associations that are considered as potential koala habitat were cleared, leading to a decline of perhaps 10% in koala numbers. Management of this large regional population has significant implications for the national conservation of the species: the continued viability of this population is critically dependent on the retention and management of riverine and residual vegetation communities, and future vegetation-management guidelines should be cognisant of the potential impacts of clearing even small areas of critical habitat. We also highlight eight management implications.
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Hynes, E. F., K. A. Handasyde, Geoff Shaw und Marilyn B. Renfree. „Levonorgestrel, not etonogestrel, provides contraception in free-ranging koalas“. Reproduction, Fertility and Development 22, Nr. 6 (2010): 913. http://dx.doi.org/10.1071/rd09253.
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Management of high-density koala (Phascolarctos cinereus) populations is essential because of the browsing damage they inflict on their habitat. We have tested two types of gestagen implant, namely levonorgestrel and etonogestrel, as contraceptives for koalas. Free-ranging female koalas were given either a control, levonorgestrel (70 mg) or etonogestrel (34 or 68 mg) implant before the breeding season. Koalas were monitored every 4–12 weeks for births. Plasma progesterone was measured and a cytological smear of the urogenital sinus was taken. Fertility was high in the control group and the two etonogestrel-treated groups, with approximately 90% of females giving birth. In contrast, no levonorgestrel-treated female produced young during the study. Removal of levonorgestrel implants from six females reversed the contraceptive effect in the next breeding season, whereas the eight females in which the levonorgestrel implants were left in remained infertile for six breeding seasons. Vaginal cytology showed evidence of oestrous cycles during the breeding season in all females from all groups and there was no difference seen in the prevalence of cornified epithelial cells in the oestrous smears. This indirectly suggests that levonorgestrel does not prevent follicular development and oestrous cycling. Plasma progesterone in levonorgestrel-treated females remained low all year, but rose in controls concurrent with the onset of the breeding season. This suggests that levonorgestrel prevents pregnancy by blocking ovulation. Etonogestrel had absolutely no contraceptive effect at the two doses delivered and so is not suitable for controlling koala populations. In contrast, levonorgestrel was effective as a long-term, reversible contraceptive in wild koalas.
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Seabrook, Leonie, Clive McAlpine, Greg Baxter, Jonathan Rhodes, Adrian Bradley und Daniel Lunney. „Drought-driven change in wildlife distribution and numbers: a case study of koalas in south west Queensland“. Wildlife Research 38, Nr. 6 (2011): 509. http://dx.doi.org/10.1071/wr11064.
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Context Global climate change will lead to increased climate variability, including more frequent drought and heatwaves, in many areas of the world. This will affect the distribution and numbers of wildlife populations. In south-west Queensland, anecdotal reports indicated that a low density but significant koala population had been impacted by drought from 2001–2009, in accord with the predicted effects of climate change. Aims The study aimed to compare koala distribution and numbers in south-west Queensland in 2009 with pre-drought estimates from 1995–1997. Methods Community surveys and faecal pellet surveys were used to assess koala distribution. Population densities were estimated using the Faecal Standing Crop Method. From these densities, koala abundance in 10 habitat units was interpolated across the study region. Bootstrapping was used to estimate standard error. Climate data and land clearing were examined as possible explanations for changes in koala distribution and numbers between the two time periods. Key results Although there was only a minor change in distribution, there was an 80% decline in koala numbers across the study region, from a mean population of 59 000 in 1995 to 11 600 in 2009. Most summers between 2002 and 2007 were hotter and drier than average. Vegetation clearance was greatest in the eastern third of the study region, with the majority of clearing being in mixed eucalypt/acacia ecosystems and vegetation on elevated residuals. Conclusions Changes in the area of occupancy and numbers of koalas allowed us to conclude that drought significantly reduced koala populations and that they contracted to critical riparian habitats. Land clearing in the eastern part of the region may reduce the ability of koalas to move between habitats. Implications The increase in hotter and drier conditions expected with climate change will adversely affect koala populations in south-west Queensland and may be similar in other wildlife species in arid and semiarid regions. The effect of climate change on trailing edge populations may interact with habitat loss and fragmentation to increase extinction risks. Monitoring wildlife population dynamics at the margins of their geographic ranges will help to manage the impacts of climate change.
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Graham, C., L. Woolford, L. Johnson und K. N. Speight. „Age-dependent changes in gross and histological morphology of the thyroid gland in South Australian koalas (Phascolarctos cinereus)“. Australian Journal of Zoology 62, Nr. 5 (2014): 360. http://dx.doi.org/10.1071/zo14011.
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Studies characterising the thyroid gland structure of koalas are limited and have not previously been undertaken in South Australian populations. Hence, this study aimed to describe the thyroid gland morphology of koalas from the Mount Lofty region, South Australia. Results showed that thyroid gland morphology was highly variable between individual koalas (n = 36), ranging from that considered typical for healthy mammals, in which small colloid-filled follicles were lined by cuboidal epithelium, to that consistent with colloidal goitre, in which macrofollicles distended with colloid were lined by flattened epithelium. Juvenile koalas more frequently showed typical thyroid gland morphology than adults, with significantly higher thyroid follicle density (P < 0.05) and a higher proportion of follicles lined by cuboidal epithelium compared with flattened epithelium (P < 0.05). Thyroid glands of most adult koalas were characterised by colloidal macrofollicles (P < 0.01), and classified as colloidal goitre. There were no significant differences in thyroid gland morphology based on health status or sex of koalas. These findings suggest that an age-dependent colloidal goitre occurs in adult koalas, which is unlikely to have ill effects and may be associated with the low metabolic rate of this species, or exposure to a dietary goitrogen.
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Martin, R. W. „Overbrowsing, and decline of a population of the koala, Phascolarctos cinereus, in Victoria. III. Population dynamics“. Wildlife Research 12, Nr. 3 (1985): 377. http://dx.doi.org/10.1071/wr9850377.
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The demography of a population of koalas at Walkerville, Victoria, which was severely defoliating its preferred food trees was monitored for 3 yr from Aug. 1977. Population density declined from 3.0 animals/ha in winter 1978 to 0.7/ha in winter 1980. Population density also fluctuated seasonally, with a max. in autumn/winter and a min. in spring. Fertility rate was low compared with that of other populations and declined over the period of the study. This was due to depressed fertility among the younger females and substantial infertility among the older females. Mortality was heaviest in the winter, and the majority of carcasses found were of old females. A sharp decline in population density, caused by the dispersal of many of the residents, occurred in winter 1980 when the defoliation of the preferred food species, Eucalyptus ovata, was most advanced.
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Lunney, Daniel, Mathew S. Crowther, Ian Shannon und Jessica V. Bryant. „Combining a map-based public survey with an estimation of site occupancy to determine the recent and changing distribution of the koala in New South Wales“. Wildlife Research 36, Nr. 3 (2009): 262. http://dx.doi.org/10.1071/wr08079.
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The present study demonstrates one solution to a problem faced by managers of species of conservation concern – how to develop broad-scale maps of populations, within known general distribution limits, for the purpose of targeted management action. We aimed to map the current populations of the koala, Phascolarctos cinereus, in New South Wales, Australia. This cryptic animal is widespread, although patchily distributed. It principally occurs on private property, and it can be hard to detect. We combined a map-based mail survey of rural and outer-urban New South Wales with recent developments in estimating site occupancy and species-detection parameters to determine the current (2006) distribution of the koala throughout New South Wales. We were able to define the distribution of koalas in New South Wales at a level commensurate with previous community and field surveys. Comparison with a 1986 survey provided an indication of changes in relative koala density across the state. The 2006 distribution map allows for local and state plans, including the 2008 New South Wales Koala Recovery Plan, to be more effectively implemented. The application of this combined technique can now be extended to a suite of other iconic species or species that are easily recognised by the public.
Dissertationen zum Thema "Low density populations of koalas"
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Ward, Steven J., University of Western Sydney, of Science Technology and Environment College und of Science Food and Horticulture School. „Koalas and the community : a study of low density populations in Southern Sydney“. THESIS_CSTE_SFH_Ward_S.xml, 2002. http://handle.uws.edu.au:8081/1959.7/265.
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The aim of this study was to investigate the distribution, density, health, condition, fertility, causes of mortality, home range size and tree preferences, of koalas in low density populations in the south of Sydney. This information was then used to make management recommendations; good management is needed because there is rapid human population growth and pressure for development of koala habitat in the Sydney region. State Environment Planning Policy 44(SEPP44) is New South Wales legislation that relates to developments affecting koala habitat. Problems in the application of SEPP44 in the Sydney region were found to exist, such as Sutherland Local Government Area (LGA) not being covered, and changes to this legislation are also recommended.Doctor of Philosophy (PhD)
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Ward, Steven John. „Koalas and the community : a study of low density populations in southern Sydney /“. View thesis View thesis, 2002. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030331.112329/index.html.
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Thesis (Ph.D.) -- University of Western Sydney, 2002."A thesis submitted to the University of Western Sydney in partial fulfillment of the requirements for the degree of Doctor of Philosophy" Bibliography: leaves 200-215.
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Tcheslavskaia, Ksenia Sergeyevna. „Mating Success in Low-Density Gypsy Moth Populations“. Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/27859.
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Field studies were conducted to evaluate the effect of mating disruption on the mating
success of the gypsy moth, Lymantria dispar (L), in low-density populations. The gypsy moth is
an insect pest of hardwood forests in many regions of the world. The discovery of the sex
pheromone disparlure (cis-7,8-epoxy-2-methyloctadecane) produced by females marked the start
of a new era in the control and management of gypsy moth populations. Sex pheromones, like
disparlure, have been used for detecting new populations, monitoring the spread of populations
and for population control based on the disruption of mating communication. Although mating
disruption has been used against populations of insect pests in agricultural and forest systems,
considerable information about the use of this method for managing gypsy moths is still lacking.
Studies, therefore, were designed and carried out specifically to improve current understanding
of the mechanism of mating success, to evaluate existing techniques for mating disruption, and to
develop methods that would improve the application of pheromone used for mating disruption so
as to reduce the costs associated with the use of this management tactic.
The first study was conducted to compare the mating success and mortality of gypsy
moth females in low-density populations in Virginia and Wisconsin because of differences,
which have been observed in the population dynamics and the impact of management strategies
between these two states. The results suggested that the higher rate of population spread in
Wisconsin might be due to the increased mating success of females compared with Virginia,
which may be due in part to increased long-distance dispersal of males and increased longevity
of females.
The effect of artificial pheromone applied at various doses and formulations on mating
success in low-density gypsy moth populations also was studied. Dose-response relationships
were obtained for pheromone doses ranging from 0.15 to 75 g a.i./ha. The doses of 37.5 and 15 g
a.i./ha of pheromone were shown to effectively disrupt mating and, therefore, have been
recommended for operational use. The results also showed that the disruption of mating and
attraction of males to pheromone-baited traps as a result of application of pheromone formulated
in plastic flakes (Disrupt® II, Hercon Environmental, Emigsville, PA) was stronger and lasted
longer than for the pheromone formulated as microcapsule (3M Canada Co., London, Ontario,
Canada) and in liquid (Shin-Etsu Chemical Co. Ltd, Tokyo, Japan).
Another study was carried out to improve the use and efficacy of the pheromone for
mating disruption by reducing the amount of pheromone that was sprayed and the flight distance
during aerial application. This study showed that in mountainous landscapes the effect of
disparlure along the valley between mountains could be observed at a larger distance (633 ± 63
m) from the treated area than across the valley (104 ± 22m). In a relatively flat area, the effective
distance for mating disruption was similar to the effective distance across the valley in a
mountainous area (67 ± 17m). These dispersal characteristics of the pheromone provided further
evidence that it could be used effectively in mating disruption treatments.
Finally, a portable Electroantennogram (EAG) device was evaluated for its ability to
detect disparlure sprayed for mating disruption in gypsy moth populations. The study found no
relationship between the dose of artificial airborne pheromone and response of gypsy moth
antenna as measured by the voltage ratio. The inability to detect differences between airborne
pheromone concentrations in the plots treated for mating disruption might have been due to high
variability among antennae and also by the inability of the EAG device to detect the low
concentration of airborne pheromone used operationally for mating disruption. Further studies
are required to improve the sensitivity of the portable EAG device before it can be recommended
for use in the field.Ph. D.
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Etienne, Freed. „Urban Growth and Segregation in the Roanoke, Virginia, Metropolis: The Effects of Low-Density Development on Low-Income Populations and Racial Minorities“. VCU Scholars Compass, 2006. http://scholarscompass.vcu.edu/etd/1393.
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This dissertation examines urban growth patterns in the Roanoke, Virginia, metropolis. It draws on the literature of contemporary human ecology and social area analysis to examine the effects of low-density development on low-income populations and racial minorities. The continuous spread of residential development beyond the boundaries of the central city and older suburbs into more distant, once rural areas is segregating the metropolitan area by race and income. Since the prominence of the so-called "Chicago School" of urban sociology (1913-1940), contemporary urban sociologists have outlined theories and methods to examine how American urban areas have changed and why. This dissertation is not about urban problems and solutions. It is about familiarizing readers with the theories of human ecology and social area analysis and their utility for explaining contemporary urban spatial patterns. If we are to get better and more equitable metropolitan areas, we must find out what really creates our urban areas, physically, economically, and socially. We must reach a deeper understanding of the forces and processes that have shaped them. Finally, we must understand the social consequences to urban life, relative to concentration of poverty and racial minorities in central cities. Toward that end, this study uses the statistical techniques called Social Area Analysis and Factorial Ecology to examine and describe the social-spatial patterns of the Roanoke, Virginia, metropolis, focusing on poverty and race. Specifically, the study uses 1980, 1990 and 2000 census data and the U.S. Geologic Survey of Land Use Cover to compute the factor analysis, construct the Socio-Economic Status (SES) index, rank the metropolis' census tracts based on the SES factors and develop the ecological growth model for the Roanoke metropolis. The analyses of the SES areas reveal that the metropolis' growth model is a combination of Ernest Burgess' concentric zone theory and Harris and Ullman's multiple nuclei model. Ultimately, the significance of this study lies not in the creation of an alternative theory of urban spatial patterns, but as an opportunity to amend more traditional approaches of human ecology so as to include racial segregation and income polarization as influences on metropolitan spatial patterns, and to produce a more integrated and accurate theoretical framework. This dissertation is organized as follows: Chapter 1 provides a brief introduction to the study. In Chapter 2, relevant literature regarding urban spatial patterns and contemporary human ecology is reviewed. Chapter 3 provides a thorough explanation of the research methodology. In Chapter 4, the results of the social area analysis and factor analysis are presented. GIS maps are also used to show the SES areas or multiple spatial patterns in the metropolis, especially the areas of concentrated poverty and race. In Chapter 5, the evolution of the metropolis' growth pattern is reviewed, and a contemporary ecological growth model is developed for the Roanoke metropolis. This model is then compared against the traditional human ecology growth models, including concentric zone theory, sector model theory and multiple nuclei theory. Chapter 6 concludes with a brief discussion of the consequences of the metropolis' growth pattern and the utility of the human ecological perspective for explaining contemporary urban spatial patterns, and suggestions for further research.
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van, Geel Catherina Francisca (Nienke). „Predator movements in complex geography : spatial distribution and temporal occurrence of low-density bottlenose dolphin communities off western Scotland“. Thesis, University of the Highlands and Islands, 2016. https://pure.uhi.ac.uk/portal/en/studentthesis/predator-movements-in-complex-geography(f898982a-6509-4e73-9340-b0ad7463ae6d).html.
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The coastal waters off western Scotland are inhabited by two small under-studied common bottlenose dolphin (Tursiops truncatus) communities: the Inner Hebrides and the Sound of Barra (SoB) community. The region is considered for future developments for the marine renewables industry, which have the potential to negatively impact these communities; however the assessment of impacts and the development of plans to minimise these are currently hampered by a lack of knowledge about the dolphin's distribution and residency patterns, and spatial and temporal mobility. Using a variety of research methods (dedicated cetacean surveys and targeted photo-ID trips, acoustic monitoring and the collection of opportunistic photo-ID and sightings data from the general public) the current study examined local dolphin spatial and temporal mobility patterns by investigation of their spatial distribution and temporal occurrence. Collectively, the results revealed the presence of two socially and geographically separated (at least 2006-2013) resident communities which both demonstrated year-round presence and long-term site-fidelity, but maintained different ranging patterns. Long-term presence of individuals from the Inner Hebrides community dated back to 2001 and dolphins from this community ranged widely in nearshore waters throughout the entire currently known communal range, and practically used the entire range throughout the year. The SoB community, on the other hand, appeared to have a more restricted distribution, and appeared female-dominated. Summer censuses of the SoB community revealed annual estimates of ≤15 dolphins, with four individuals first identified in 1995, and at least eight calves born since 2005. Acoustic presence of dolphins in the SoB varied through the year, and in relation to the tidal and diel cycles. This study demonstrated that the integration of complementary methodological approaches is useful in investigating mobility patterns of low-density populations, and given the indications for social and spatial isolation, these communities should be managed independently.
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Louis, Marceau. „Collective foraging is an efficient strategy for low density population of the bark beetle Ips typographus (Coleoptera, Curculionidae) in need for scarce, unpredictable and ephemeral resources“. Doctoral thesis, Universite Libre de Bruxelles, 2016. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/222963.
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Ips typographus est le principal ravageur de l'épicéa en Europe, s’attaquant en masse aux arbres vivants en période d’épidémie, par le biais d’une communication chimique. Comme de nombreuses autres espèces de scolytes « agressives », le typographe se reproduit uniquement sur des arbres affaiblis ou des chablis en périodes d’endémie, quand les densités de population ne sont pas suffisantes pour surmonter les défenses des arbres vivants. Ces ressources sont en général présentées dans la littérature comme étant dispersées et imprédictibles dans le temps et l’espace. De plus, ces ressources affaiblies sont sans doute disponibles pour de nombreuses espèces compétitrices. Ces caractéristiques imposent des contraintes importantes sur la dynamique de population et l’écologie du typographe et principalement sur sa stratégie de prospection. Cela dit, cette espèce et ces questions sont très peu étudiées en période d’endémie.Durant ma thèse de doctorat, je me suis attelé à tout d’abord caractériser les facteurs déterminant la distribution spatio-temporelle des chablis, qui va influencer l’évolution des stratégies de dispersion. Cet aspect s’est prolongé par l’étude de la « durée de vie » des chablis, c’est-à-dire la période durant laquelle ils sont colonisables par les scolytes après déracinement. Cet aspect a été mis en parallèle avec les capacités de défenses de ces mêmes arbres et leurs effets sur la sélection de l’hôte et le succès des scolytes. Enfin, les données obtenues par ces études ont été intégrées à un modèle spatialement explicite visant à valider les hypothèses comportementales relatives à la prospection pour les ressources chez le typographe, à savoir une dispersion aléatoire à grande distance suivie d’un recrutement au niveau des ressources nouvellement trouvées.Les résultats obtenus au cours de cette thèse confirment l’importance de la prospection sociale et de l’agrégation dans la découverte et l’exploitation de ressources dispersées, dont la dégradation intrinsèque représente une faible contrainte temporelle. Ces comportements ont sans doute été développés chez des insectes saproxyliques en raison de l’avantage qu’ils apportent en termes de découverte de ressources. Dans un second temps, ces comportements auraient pu permettre l'attaque d‘arbres vivants, notamment en réponse à une pression de compétition inter-spécifique importante sur des ressources peu défendues.Option Biologie des organismes du Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Etienne, Freed G. „Urban growth and segregation in the Roanoke, Virginia, metropolis : the effects of low-density development on low-income populations and racial minorities /“. 2006. http://hdl.handle.net/10156/2053.
Der volle Inhalt der QuelleBücher zum Thema "Low density populations of koalas"
1
Parkinson, Eric A. Impaired school formation at low density: A mechanism for depensatory mortality in sockeye salmon. Vancouver, B.C: Ministry of Environment, Lands, and Parks, Fisheries Branch, Fisheries Research and Development Section, 1990.
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2
Parkinson, Eric A. Impaired school formation at low density: A mechanism for depensatory mortality in sockeye salmon (Fisheries management report). Ministry of Environment, Lands, and Parks, Fisheries Branch, Fisheries Research and Development Section, 1991.
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Estes, James A., und M. Tim Tinker. Rehabilitating sea otters. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198808978.003.0020.
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This chapter examines the complexities of assessing the merits and drawbacks of wildlife rehabilitation. Wildlife rehabilitation is often costly, and the resulting benefits differ depending on whether one’s interest is in the welfare of individual animals or conserving populations. Two examples of this dilemma include the rehabilitation of oiled sea otters following the Exxon Valdez spill in Prince William Sound, Alaska, and the rehabilitation of stranded sea otter pups in central California. In the first example, substantial financial investment resulted in little or no benefits for population conservation. In the second example, the potential for population-level benefits is context dependent: in populations near carrying capacity the conservation impacts are negligible, whereas in isolated, low-density populations rehabilitation and release can be an effective conservation tool. Wildlife rehabilitation is valued by people for various reasons, but recognizing and acknowledging the difference between individual and population welfare is an important step toward effective wildlife conservation.
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Jacobsen, Dean, und Olivier Dangles. Ecology of High Altitude Waters. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198736868.001.0001.
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This book brings together current knowledge on patterns and processes in the ecology of streams, lakes, and wetlands situated at more than 3000 m above sea level. The alpine headwaters of the large Asian rivers and Lake Titicaca are both well-known and iconic examples. High altitude waters include more than these systems—they are both numerous and cover many habitat types, organisms, and specializations. The book provides an overview of the variety of aquatic ecosystems and habitats, their environmental features, prominent species, and their functional adaptations to the harsh aquatic environmental conditions through to global diversity patterns along altitudinal gradients, community dynamics, species interactions and dispersal, trophic relations, and energy flows. High altitude waters are ideal systems to address a broad range of topical themes in ecology because patterns and processes are both diverse and singular. The book highlights how key concepts in ecology (e.g. the stress gradient hypothesis, the biodiversity–ecosystem functioning relationship) could find relevant study models in high altitude waters. The usual perception of pristine mountain waters is far from true, particularly in the case of high altitude waters at low latitudes where human population density is often high, and local communities live in intimate contact with, utilize, influence, and exploit these aquatic systems. Climate change effects, extinction risks of mountain populations due to vanishing glaciers, multiple human impacts, management, and conservation are also treated thoroughly. The book is richly illustrated with diagrams and numerous pictures of these poorly known systems and species.
Buchteile zum Thema "Low density populations of koalas"
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Van Der Hulst, J. M., E. D. Skillman, G. D. Bothun und T. R. Smith. „The HI Surface Density in Low Surface Brightness Galaxies“. In The Stellar Populations of Galaxies, 499. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2434-8_166.
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Gulyaev, S. A. „Review of the Populations of Highly-Excited States of Atoms in Low-Density Plasmas“. In Radio Recombination Lines: 25 Years of Investigation, 37–49. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-0625-9_3.
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Botsford, Louis W., J. Wilson White und Alan Hastings. „Age-structured models with density-dependent recruitment“. In Population Dynamics for Conservation, 166–93. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198758365.003.0007.
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This chapter examines age-structured models with density-dependent recruitment. In particular, it focuses on populations with over-compensatory density dependence, such as may occur due to cannibalism or some types of space competition. When the slope (at the equilibrium point) of the relationship between egg production and subsequent recruitment is declining in an over-compensatory way, the population may exhibit unstable limit cycles with period twice the generation time (2T). These cycles occur when that slope is steeply negative and the spawning age distribution has a high mean and low width. These results are applied to study the behavior of cycles in the U.S. west coast Dungeness crab fishery, variability in populations of an intertidal barnacle, and cycles in populations of a pest, the flour beetle. Additionally, it is shown how single-sex harvesting and compensatory growth affect population cycles and equilibria.
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Rubio-Méndez, Gabriel, Alberto Prado, Jacqueline C. Bede, José Arturo De-Nova, Joel Flores, Juan Antonio Reyes-Agüero und Laura Yáñez-Espinosa. „The Endangered Species Dioon edule in the Sierra Madre Oriental in San Luis Potosí: Demography and Genetic Diversity“. In Natural History and Ecology of Mexico and Central America. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96372.
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The distribution of the endangered species Dioon edule is in populations scattered throughout the Sierra Madre Oriental in San Luis Potosí, Mexico. Its habitat is tropical dry forests at lower elevations and oak forests at higher elevations, mainly disturbed by anthropic activities. We determined and analyzed nine populations’ demographic structure and explored the genetic diversity of five using SSR markers. The population density averaged 2050 individuals ha-1 and have an aggregated distribution pattern. Differences in the plants’ size among localities are due to site quality, based on their adaptation capacity and response to climate and soil traits. Most populations have the highest mortality in the early stages of life, with a low mortality rate for those who survive this bottleneck. Two populations have a relatively constant mortality rate, attributed to disturbance of the habitat. The populations show low genetic diversity and an excess of homozygotes. Their similarity is probably related to the formation of natural corridors favoring connectivity between populations. The deterioration and fragmentation of the habitat have severe effects on the populations’ viability, like reducing gene flow, which has led to inbreeding and genetic drift.
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Tanhuanpää, Miia, und Kai Ruohomäki. „Population Cycles of the Autumnal Moth in Fennoscandia“. In Population Cycles. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195140989.003.0012.
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Most species of insect herbivores are restricted to low densities, but some display large-scale density fluctuations, including periodic outbreaks (Faeth 1987, Mason 1987, Hanski 1990, Hunter 1995). The tendency to reach high densities has been related to certain life history traits (Hunter 1991, 1995, Tammaru and Haukioja 1996). However, all populations of a given outbreaking species do not necessarily display high densities. In those cases, outbreaks are frequently more pronounced in populations in physically severe and marginal habitats (Wallner 1987, Myers and Rothman 1995). The autumnal moth, Epirrita autumnata (Borkhausen) (Lepidoptera: Geometridae) is an example of a species with both outbreaking and nonoutbreaking populations. In mountain birch [Betula pubescens ssp. czerepanovii (Orlova) Hämet-Ahti] forests of northern and mountainous Fennoscandia (hereafter northern populations), E. autumnata displays fluctuations with a statistically significant periodicity of 9-10 years (Tenow 1972, Haukioja et al. 1988, Bylund 1995). During outbreaks, forests may be totally defoliated and trees may even die over large areas (Tenow 1972, Lehtonen and Heikkinen 1995). In more southern parts of the species' Holarctic distribution (hereafter southern populations), outbreaks are absent and populations remain at low densities. Cycles of northern E. autumnata populations vary in their amplitude (Tenow 1972). Outbreak densities that produce conspicuous defoliation are typically reached in only some areas, and often in different areas during successive peaks (Tenow and Bylund 1989). Empirical data indicate a fairly regular pattern of fluctuations, that is synchronous on a regional scale, also in populations with moderate or low peak densities (Bylund 1997). Thus, there are two main questions regarding population regulation of northern and mountainous E. autumnata—what causes the cycles, and what causes spatial variations in outbreak severity? In southern populations, the main question is what prevents outbreaks? Larvae of E. autumnata hatch early in spring at the time of birch bud break. Birches (Betula spp.) are the main host plants, although larvae are able to feed on many deciduous trees and shrubs (Seppänen 1970).
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„Burbot: Ecology, Management, and Culture“. In Burbot: Ecology, Management, and Culture, herausgegeben von Martin A. Stapanian, Charles P. Madenjian, Charles R. Bronte, Mark P. Ebener, Brian F. Lantry und Jason D. Stockwell. American Fisheries Society, 2008. http://dx.doi.org/10.47886/9781888569988.ch7.
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Abstract.—Burbot <em>Lota lota </em>populations collapsed in four of the five Laurentian Great Lakes between 1930 and the early 1960s. Collapses in Lakes Michigan, Huron, and Ontario were associated with sea lamprey <em>Petromyzon marinus </em>predation, whereas the collapse in Lake Erie was likely due to a combination of overexploitation, decreased water quality, and habitat degradation. We examined time series for burbot population density in all five lakes extending as far back as the early 1970s to present time and characterized the long-term trends after the initial collapses. Burbot population density in Lake Superior has remained relatively low and stable since 1978. Recovery of the burbot populations occurred in Lakes Michigan and Huron during the 1980s and in Lake Erie during the 1990s. Control of sea lampreys was a requirement for recovery of burbot populations in these three lakes. Declines in alewife <em>Alosa pseudoharengus </em>abundance appeared to be a second requirement for burbot recovery in Lakes Michigan and Huron. Alewives have been implicated in the decline of certain Great Lakes fish stocks that have pelagic larvae (e.g., burbot) by consuming the pelagic fry and possibly by outcompeting the fry for food. Relatively high populations of adult lake trout <em>Salvelinus namaycush </em>compared to burbot served as a buffer against predation by sea lampreys in Lakes Huron and Erie, which facilitated recovery of the burbot populations there. Although sea lampreys have been controlled in Lake Ontario, alewives are probably still too abundant to permit burbot recovery.
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Botsford, Louis W., J. Wilson White und Alan Hastings. „Linear, age-structured models and their long-term dynamics“. In Population Dynamics for Conservation, 54–86. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198758365.003.0003.
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The chapter describes age-structured models that are linear (i.e. without density dependence). Like simple (non-age-structured) linear models they eventually either increase to infinity or decrease to zero. They are only appropriate when density dependence is not an important factor, such as recently introduced populations or those that have declined to low abundance. The chapter steps through several different ways of formulating such models. First are Lotka’s renewal equation and the M’Kendrick/von Foerster equation, both continuous time, continuous age models. Next is the Leslie matrix, which operates in discrete age and time. Solutions to linear matrix equations, such as the Leslie matrix, can be written in a general way in terms of eigenvalues and eigenvectors. These form the basis of analyses of dynamic stability throughout the book. Practically speaking, the Leslie matrix approach is the primary model used in modern ecology.
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„Conservation, Ecology, and Management of Catfish: The Second International Symposium“. In Conservation, Ecology, and Management of Catfish: The Second International Symposium, herausgegeben von ROBERT S. GREENLEE und CATHERINE N. LIM. American Fisheries Society, 2011. http://dx.doi.org/10.47886/9781934874257.ch30.
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<em>Abstract</em>.—Introduced blue catfish <em>Ictalurus furcatus</em> populations in tidal rivers of the Atlantic slope support important recreational and commercial fisheries, with the James River trophy fishery being nationally recognized. During the period 2001–2008, low-frequency (15 pulses/s) pulsed DC electrofishing was used to sample blue catfish in tidal fresh-oligohaline sections of the James, Mattaponi, Pamunkey, and Rappahannock River systems; 54,174 blue catfish were collected, and 4,660 of these were aged using otoliths. Mean catch per unit effort (CPUE) was generally high (ranging from 223 to 6,106 fish per hour). Trends of increasing CPUE through time occurred in the James (839–4,449 fish per hour) and Rappahannock (1,400–6,106 fish per hour) rivers, and differences in CPUE were detected among rivers. Temporal shifts in growth (mean length at age) were observed, with growth slowing for all ages in the Pamunkey River and slowing for older ages in the Mattaponi (ages 9–13) and Rappahannock (ages 8–12 and age 14) rivers. In the Pamunkey and Rappahannock rivers, a negative relationship existed between growth (mean length at age 10) and density (CPUE). Although density increased dramatically in the James River, growth remained stable. Growth varied among rivers; by the end of the study, mean total length at age 10 ranged from 416 mm in the Rappahannock River to 675 mm in the James River. Growth through age 15 fi t linear models, as opposed to the von Bertalanffy nonlinear curve. In three of the four populations, the maximum age sampled increased in each succeeding survey year, and the maturing of all four populations was reflected in concurrent increases in size distributions. Recruitment was variable, with coincident strong and weak year-classes occurring in all four populations—an implication that landscape-level environmental variables play a role in determining recruitment success. In three of the four populations, patterns in year-class strength persisted, with correlation of catch-curve residuals from surveys separated by time. Approximately 35 years poststocking in the James and Rappahannock rivers and 25 years poststocking in the Mattaponi River, these populations had not yet reached equilibrium. It is unknown what the dynamics of blue catfish abundance, growth, and survival will be in the long-term in these rivers, leaving uncertainty regarding the future of the fisheries the populations support, as well as unanswered questions related to potential effects on other species.
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„Conservation, Ecology, and Management of Catfish: The Second International Symposium“. In Conservation, Ecology, and Management of Catfish: The Second International Symposium, herausgegeben von MARK T. PORATH, LARRY D. PAPE, LINDSEY K. RICHTERS, KEVIN L. POPE und MARK A. PEGG. American Fisheries Society, 2011. http://dx.doi.org/10.47886/9781934874257.ch47.
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<em>Abstract</em>.—In recent years, several state agencies have adopted the use of baited, tandem-set hoop nets to assess lentic channel catfish <em>Ictalurus punctatus</em> populations. Some level of escapement from the net is expected because an opening exists in each throat of the net, although factors influencing rates of escapement from hoop nets have not been quantified. We conducted experiments to quantify rates of escapement and to determine the influence of throat configuration and fish density within the net on escapement rates. An initial experiment to determine the rate of escapement from each net compartment utilized individually tagged channel catfish placed within the entrance (between the two throats) and cod (within the second throat) compartments of a single hoop net for overnight sets. From this experiment, the mean rate (SE) of channel catfish escaping was 4.2% (±1.5) from the cod (cod throat was additionally restricted from the traditionally manufactured product), and 74% (±4.2) from the entrance compartments. In a subsequent experiment, channel catfish were placed only in the cod compartment with different throat configurations (restricted or unrestricted) and at two densities (low [6 fish per net] and high [60 fish per net]) for overnight sets to determine the influence of fish density and throat configuration on escapement rates. Escapement rates between throat configurations were doubled at low fish density (13.3 ± 5.4% restricted versus 26.7 ± 5.6% unrestricted) and tripled at high fish density (14.3 ± 4.9% restricted versus 51.9 ± 5.0% unrestricted). These results suggest that retention efficiency is high from cod compartments with restricted throat entrances. However, managers and researchers need to be aware that modification to the cod throats (restrictions) is needed for hoop nets ordered from manufacturers. Managers need to be consistent in their use and reporting of cod end throat configurations when using this gear.
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Saely, Christoph H. „Metabolic syndrome and diabetes“. In The ESC Handbook on Cardiovascular Pharmacotherapy, herausgegeben von Heinz Drexel und Massimo Francesco Piepoli, 49–58. Oxford University Press, 2019. http://dx.doi.org/10.1093/med/9780198759935.003.0003.
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The metabolic syndrome (MetS) and even more so diabetes confer a significantly increased risk of cardiovascular disease. A multifactorial approach is required to improve the prognosis of patients with the MetS or diabetes. Glucose control is essential to reduce microvascular diabetes complications and, over long periods of time, may also lower the risk of cardiovascular events in patients with diabetes. As in other patient populations, lowering low-density lipoprotein (LDL) cholesterol and treating arterial hypertension are paramount interventions to reduce cardiovascular event risk in patients with the MetS and diabetes. Most patients with diabetes must be considered at a very high risk of cardiovascular events, which qualifies them for low LDL cholesterol targets. An-tiplatelet therapy is recommended for patients with the MetS or diabetes who already have established cardiovascular disease. Because the MetS or diabetes confers an extremely high risk of cardiovascular events once cardiovascular disease is established, it is extremely important to intervene early to prevent these patients from developing cardiovascular disease.
Konferenzberichte zum Thema "Low density populations of koalas"
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Amar, Haddad, Redjaimia L. ilia, Kadi Zahia, Rached-Kanouni Malika und Kara Karima. „ASSESSING THE HEALTH OF THE CHETTABA FOREST (ALGERIA)“. In GEOLINKS Conference Proceedings. Saima Consult Ltd, 2021. http://dx.doi.org/10.32008/geolinks2021/b2/v3/01.
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The establishment and interpretation of diameter and height structures are essential for forest management decisions. This study aims to describe the diameter structure and spatial distribution of Pinus halpensis populations in the Chettaba state forest (Constantine, Algeria). The knowledge of these parameters is an essential step for their sustainable management. The diameter at 1.30 m from the ground and the total height of P. halpensis individuals were measured on 6 plots along an altitudinal gradient. The height structure shows that trees in the height classes between 5 and 10m have a very high density, indicating low natural regeneration. The total structure indicates that smaller trees are more abundant than larger trees (17.5<d≤27.5cm). These results contribute to the improvement of knowledge on current condition indicators of natural Pinus halpensis stands that can be used as a basis in the management of Chettaba forest
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Pereira, J., C. Cretney und R. H. Aster. „VARIABLE EXPRESSION OF ALLOANTIGENS IN PLATELET COHORTS OF DIFFERENT MEAN DENSITY:AN EFFECT OF AGING IN VIVO“. In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644158.
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Platelets differ widely in size and density, but the relationship of this heterogeneity to platelet age and function is not established. Published evidence suggests that platelet alloantigens of the HLA and PlA systems may be acquired by or releasedfrom platelets in the circulation. We therefore studied expression of HLA, PlAl, and other markers in platelet cohorts of high density (HD) and low density (LD) separated on a linear, isoosmotic arabinogalactan gradient. HD and LD cohorts contained 11-14% of total platelets and did not differ significantly in mean cell volume. Alloantibodies reactive with antigens P1A1, Baka, and HLA-A2 were used to saturate alloantigen sites. Surface markers were quantified (Human Immunol. 15:251, 1986) with radiolabeled monoclonalprobes specific for HLA A, B, C antigens (W6/32), the Fc fragment of IgG (Hb-43) and the glycoprotein IIb/IIIa complex (AP-2).As shown in the Table, HD platelets carry significantly more PlAl (located on GPIIIa) and significantly less HLA than LD platelets. However, HD and LD cohorts express the same number of GPIIb/IIIa and Baka (located on GPIIb) molecules. These findings are consistent with preferential loss of HLA molecules from HD- platelets in the circulation or acquisition by LD platelets. The variable expression of P1A1 in HD and LD cohorts is apparently due to a conformational change in GPIIIa, rather than acquisition or loss of the GPIIIa molecule, because total GPIIb/IIIa was thesame in the two platelet populations. Whether antigen differences in HD and LD platelets are determined at the time of platelet production or result from aging of platelets in the circulation is under investigation.
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Lambrecht, Marlies, und Abderrahim Almazouzi. „The Influence Irradiation-Induced Microstructure on the Hardening of RPV Steels“. In 17th International Conference on Nuclear Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/icone17-75109.
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The hardening and embrittlement of reactor pressure vessel steels has been investigated for many years. Nowadays, a consensus is reached assuming a two-component hardening model of copper-enriched clusters and matrix damage. Nevertheless, despite being the subject of significant research efforts, it is still a debatable question, whether a linear or quadratic superposition law is appropriate. The inaccuracy of either choice might be the effect of the existence of different populations of defects, such as loops, decorated interstitial and vacancy clusters, as every defect contributes to the hardening in a particular way. In this work, a correlation on model alloys is attempted between experimental results on microstructure found by different complementary techniques and a theoretical prediction of the hardening, where each defect is defined by a specific pinning strength. It is found that loops are very strong defects, but due to their low concentration, they only play a minor role in the hardening itself. For the precipitates, the contrary is found, although they are quite soft (due to their very low sizes), they still play the dominant role in the hardening due to their high density. Vacancy clusters are important for the formation of the former two defects, but they will play almost no role in the hardening by themselves.
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Mohr, S., Y. H. Zhang, A. Macaskill, P. J. R. Day, R. W. Barber, N. J. Goddard, D. R. Emerson und P. R. Fielden. „Optimal Design and Operation for a Droplet-Based PCR Chip“. In ASME 4th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2006. http://dx.doi.org/10.1115/icnmm2006-96131.
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A two-temperature continuous-flow PCR polymer chip has been constructed that takes advantage of droplet technology to avoid sample contamination and adsorption at the surface. Samples contained in aqueous droplets are continuously moved by an oil carrier-fluid through various temperature zones, introducing the possibility of real-time quantitative PCR. The use of droplet technology also makes it possible to perform high throughput analyses of single cells allowing the study of populations of cells and facilitating a more comprehensive understanding of biological variance with relation to disease. In the present device, the thermal cycling time is significantly reduced and the PCR samples are exposed to more uniform temperatures. This paper investigates many of the factors affecting droplet-based PCR chip design, including specific heat capacity, density, flow rate, and thermal resistance. The study focuses particularly on the fluid and substrate temperature distribution within the PCR chip and the droplet residence times in critical temperature zones. The results show that, in general, the carrier-fluid should have a low thermal mass to ensure minimal heating and cooling times. It was found that the predicted temperature distribution in the chip arises from a subtle thermal interaction between the substrate and the carrier-fluid. The simulations demonstrate that the flow rate strongly affects the carrier-fluid’s temperature field. Above a critical flow rate, the carrier-fluid fails to achieve the temperatures required for DNA amplification. Moreover, the thermal resistance of the different layers is shown to have a major impact on the temperature profile in the channel.