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71.
KARI BJØRNERAAS BRAM VAN MOORTER CHRISTER MOE ROLANDSEN IVAR HERFINDAL 《The Journal of wildlife management》2010,74(6):1361-1366
Abstract: Animal locations estimated by Global Positioning System (GPS) inherently contain errors. Screening procedures used to remove large positional errors often trade data accuracy for data loss. We developed a simple screening method that identifies locations arising from unrealistic movement patterns. When applied to a large data set of moose (Alces alces) locations, our method identified virtually all known errors with minimal loss of data. Thus, our method for screening GPS data improves the quality of data sets and increases the value of such data for research and management. 相似文献
72.
In this profile article, we report what we consider to be a rich learning experience which intertwines pedagogy and research:
a process of community-based action research which has initiated a transition towards the sustainability of the University
of British Columbia’s (UBC) food system. We call this initiative the UBC Food System Project (UBCFSP). The UBCFSP is a jointly
initiated project between the Faculty of Land and Food Systems and the UBC Sustainability Office, and includes nine UBC organizational
partners and one collaborator. The project emerged out of the recognition that our global, national, regional, and local food
systems are increasingly characterized as socially, ecologically, and economically insecure and unsustainable. As a result,
these food systems are experiencing an array of vulnerabilities, particularly those that are demonstrated by profound disruptions
in our ecosystem and in a worldwide epidemic of malnutrition. The overall objective of the project is to conduct a campus-wide
UBC food system sustainability assessment, where barriers that hinder and opportunities to make transitions towards food system
sustainability are being collaboratively identified and implemented. This article is part of a series intending to share the
experiences gathered so far through the project. The purpose of this profile is to provide a brief overview of the UBC Food
System Project, including the context and significance, both the pedagogical approach and research methods, and some accomplishments
to date. 相似文献
73.
74.
1. Regional distribution, frequency of occurrence and relative abundance were scored in 2467 Norwegian lakes for all the recorded 130 species of crustacean zooplankton. The majority of species were rare in the sense that 65% of species were recorded in fewer than 10% of localities. Only six species were recorded in more than 50% of localities, and the median number of species in a given locality was 14 (i.e. 10% of the total species pool). 2. Abundances of all species were scored according to the fraction of lakes in which they were recorded, their geographical range of distribution, and their numerical abundance. Typically the most rare species were rare by all three criteria, and vice versa for the common species, pointing to rarity as an inherent property of some species. For some species this rarity reflects being on the edge of their distributional range, while for others rarity seems to be a consequence of their life cycle strategies. 3. Some of the truly rare species have high dispersal rates and high colonization abilities, but are rapidly replaced by other species. Others are confined to specific habitats, often highly eutrophic, pointing to highly specialized niche adaptations. 4. A major cause for the few truly common species seems to be the limited number of species that are able to coexist within a given locality, reflecting ‘the ghost of competition past’ and predation pressure. 5. While species composition and species richness may reflect colonization abilities and stochastic events, the presence or absence of species is not only a random lottery but also a consequence of species‐specific attributes. 相似文献
75.
JARI ILMONEN PETER H. ADLER BJÖRN MALMQVIST ALINA CYWINSKA 《Zoological Journal of the Linnean Society》2009,156(4):847-863
The value of using characters from multiple sources – chromosomes, ecology, gene sequences, and morphology – to evaluate the species status of closely related black flies is demonstrated for three European members of the Simulium vernum group: Simulium crenobium (Knoz, 1961), Simulium juxtacrenobium Bass & Brockhouse, 1990, and Simulium vernum s.s. Macquart, 1826. Simulium juxtacrenobium is a chromosomally, molecularly, and morphologically distinct species that diverged from S. crenobium and S. vernum s.s. about 2 Mya. It is specialized for intermittent streams, is univoltine, and is recorded for the first time from northern Europe, based on collections from Finland and Sweden, representing a range extension of about 1800 km. In contrast, S. crenobium, although confirmed as a distinct species, differs from S. vernum s.s. by only a few larval and chromosomal characters, and by a breeding habitat restricted to mountain spring brooks. Whereas all four character sets independently support the specific distinctness of S. juxtacrenobium and S. vernum s.s., multiple character sets are required to establish the specific validity of S. crenobium. 相似文献
76.
Jirsová Z Kucera T Martínek J Liska F Krenová D Kren V 《Biomedical papers of the Medical Faculty of the University Palacky, Olomouc, Czechoslovakia》2004,148(2):213-215
Germinal epithelium of seminiferous tubules in adult, infertile hypodactylous males displays significant reduction in the number of germ-line cells. Detection of apoptosis in the germ-line cells during postnatal differentiation was performed to elucidate the mechanism of the decreased number of germ cells in the testes of adult rats. Evaluation of DNA fragmentation and expression of activated caspase-3 in germ cells did not confirm marked germ cell death during the onset of spermatogenesis as a main cause of significant reduction of germ cells in Hd/Hd testes of adult males. The primary cause of spermatogenesis defect seems to be rather associated with a disorder in the cell cycle regulation and interrelation of germ-line cells with Sertoli cells. 相似文献
77.
We describe the upper portion of the bill sheath (rhinotheca) of the kākāpō (Strigops habroptilus) from three adult female specimens. The external buccal surface of the rhinotheca is deeply concave with a prominent palatal stop and hardened chevrons creating a ‘milling apparatus’ that the kākāpō uses to grind food. The palatal stop presents a working face of 40–50?mm2. The internal surface of the rhinotheca mirrors the overlying premaxilla and provides a distinct thickened abutment consistent with resistance against the increased workload of the mandibles (gnathotheca) due to the kākāpō’s fibrous diet and chewing style. Along the midline, the rhinotheca at the abutment is up to 5.6?mm thick, compared with as thin as 2.1?mm elsewhere on the midline. The closely related Nestor parrots have less developed palatal stops, chevrons and abutments on their rhinothecas consistent with their lower preference for fibrous plant material. The form of the rhinotheca agrees with the kākāpō’s feeding ecology as a generalist herbivore that grinds locally available fibrous material to assist digestion. 相似文献
78.
79.
The fractal doubly stochastic Poisson process (FDSPP) model of molecular
evolution, like other doubly stochastic Poisson models, agrees with the
high estimates for the index of dispersion found from sequence comparisons.
Unlike certain previous models, the FDSPP also predicts a positive
geometric correlation between the index of dispersion and the mean number
of substitutions. Such a relationship is statistically proven herein using
comparisons between 49 mammalian genes. There is no characteristic rate
associated with molecular evolution according to this model, but there is a
scaling relationship in rates according to a fractal dimension of
evolution. The FDSPP is a suitable replacement for the homogeneous Poisson
process in tests of the lineage dependence of rates and in estimating
confidence intervals for divergence times. As opposed to other fractal
models, this model can be interpreted in terms of Darwinian selection and
drift.
相似文献
80.
Postnatal Passive Immunization of Neonatal Macaques with a Triple Combination of Human Monoclonal Antibodies against Oral Simian-Human Immunodeficiency Virus Challenge 总被引:6,自引:0,他引:6 下载免费PDF全文
Regina Hofmann-Lehmann Josef Vlasak Robert A. Rasmussen Beverly A. Smith Timothy W. Baba Vladimir Liska Flavia Ferrantelli David C. Montefiori Harold M. McClure Daniel C. Anderson Bruce J. Bernacky Tahir A. Rizvi Russell Schmidt Lori R. Hill Michale E. Keeling Hermann Katinger Gabriela Stiegler Lisa A. Cavacini Marshall R. Posner Ting-Chao Chou Janet Andersen Ruth M. Ruprecht 《Journal of virology》2001,75(16):7470-7480
To develop prophylaxis against mother-to-child human immunodeficiency virus (HIV) transmission, we established a simian-human immunodeficiency virus (SHIV) infection model in neonatal macaques that mimics intrapartum mucosal virus exposure (T. W. Baba et al., AIDS Res. Hum. Retroviruses 10:351-357, 1994). Using this model, neonates were protected from mucosal SHIV-vpu(+) challenge by pre- and postnatal treatment with a combination of three human neutralizing monoclonal antibodies (MAbs), F105, 2G12, and 2F5 (Baba et al., Nat. Med. 6:200-206, 2000). In the present study, we used this MAb combination only postnatally, thereby significantly reducing the quantity of antibodies necessary and rendering their potential use in humans more practical. We protected two neonates with this regimen against oral SHIV-vpu(+) challenge, while four untreated control animals became persistently infected. Thus, synergistic MAbs protect when used as immunoprophylaxis without the prenatal dose. We then determined in vitro the optimal MAb combination against the more pathogenic SHIV89.6P, a chimeric virus encoding env of the primary HIV89.6. Remarkably, the most potent combination included IgG1b12, which alone does not neutralize SHIV89.6P. We administered the combination of MAbs IgG1b12, 2F5, and 2G12 postnatally to four neonates. One of the four infants remained uninfected after oral challenge with SHIV89.6P, and two infants had no or a delayed CD4(+) T-cell decline. In contrast, all control animals had dramatic drops in their CD4(+) T cells by 2 weeks postexposure. We conclude that our triple MAb combination partially protected against mucosal challenge with the highly pathogenic SHIV89.6P. Thus, combination immunoprophylaxis with passively administered synergistic human MAbs may play a role in the clinical prevention of mother-to-infant transmission of HIV type 1. 相似文献