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Sub-Antarctic Marion Island has had a permanent research station for 50 years and the islands Wandering Albatrosses have been intensively studied for 20 years. The reactions of breeding birds to approaches by a human on foot were recorded. Three response variables were calculated: intensity of vocal reaction (IVR), intensity of non-vocal reaction (INR) and overall response index (ORI). At 5 m from the nest, twice as many birds stood and/or vocalised as at 15 m. Nearest neighbour distance, age and gender did not explain individual variability of responses. Study colony birds had higher IVR scores than non-study colony birds; birds at colonies closest to the station had the highest ORI scores. A better breeding record was associated with lower IVR and ORI scores, but a causative relationship remains to be demonstrated. A minimum viewing distance of 25 m is recommended for breeding Wandering Albatrosses.
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Marienne S. de VilliersEmail: Fax: +27-21-6503434 |
John CooperEmail: |
Peter G. RyanEmail: |
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A key point in the analysis of dynamical models of biological systems is to handle systems of relatively high dimensions.
In the present paper we propose a method to hierarchically organize a certain type of piecewise affine (PWA) differential
systems. This specific class of systems has been extensively studied for the past few years, as it provides a good framework
to model gene regulatory networks. The method, shown on several examples, allows a qualitative analysis of the asymptotic
behavior of a PWA system, decomposing it into several smaller subsystems. This technique, based on the well-known strongly
connected components decomposition, is not new. However, its adaptation to the non-smooth PWA differential equations turns
out to be quite relevant because of the strong discrete structure underlying these equations. Its biological relevance is
shown on a 7-dimensional PWA system modeling the gene network responsible for the carbon starvation response in Escherichia coli.
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Laurent Tournier (Corresponding author)Email: |
Jean-Luc GouzéEmail: |
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Methanogens growing on C-1 substrates synthesize 2-carbon acetyl groups in the form of acetyl-CoA for carbon assimilation
using the multienzyme complex acetyl-CoA decarbonylase/synthase (ACDS) which contains five different subunits encoded within
an operon. In species growing on acetate ACDS also functions to cleave the acetate C-C bond for energy production by methanogenesis.
A number of species of Methanosarcina that are capable of growth on either C-1 compounds or acetate contain two separate ACDS operons, and questions have been
raised about whether or not these operons play separate roles in acetate synthesis and cleavage. Methanosarcina thermophila genomic DNA was analyzed for the presence of two ACDS operons by PCR amplifications with different primer pairs, restriction
enzyme analyses, DNA sequencing and Southern blot analyses. A single ACDS operon was identified and characterized, with no
evidence for more than one. MALDI mass spectrometric analyses were carried out on ACDS preparations from methanol- and acetate-grown
cells. Peptide fragmentation patterns showed that the same ACDS subunits were present regardless of growth conditions. The
evidence indicates that a single form of ACDS is used both for acetate cleavage during growth on acetate and for acetate synthesis
during growth on C-1 substrates.
Electronic Supplementary Material Supplementary material is available for this article at
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David A. Grahame (Corresponding author)Email: |
Edward DeMoll (Corresponding author)Email: |
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To our knowledge, this paper is the first record/report of a juvenile light-coloured Weddell seal (Leptonychotes weddellii) at Cape Shirreff, Livingston Island in January 1998, determining that it was an albino individual. Based on available literature,
three cases of albino seals have been reported exclusively for Harbour seal pups, and no albino has been reported for Antarctic
pagophilic true seals. Therefore, this is the first confirmed case of albinism in Antarctic pagophilic true seals species,
indicating that this phenomenon is indeed of a rare occurrence.
相似文献
Daniel TorresEmail: |
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Causal Explanation of Indonesian Forest Fires: Concepts, Applications, and Research Priorities 总被引:1,自引:0,他引:1
Andrew P. Vayda 《Human ecology: an interdisciplinary journal》2006,34(5):615-635
Problems with studies, claims, and assumptions that have been made about the causes of fires in Indonesia's tropical moist forests are identified, and the kinds of concepts, methods, prioritizing, and data needed to resolve the problems are discussed. Separate sections are devoted to studying ignitions, studying fire susceptibility and fire behavior, and using the goal of causal explanation to guide interdisciplinary research.
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Andrew P. VaydaEmail: |
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The recent contribution by Jarmila Kukalová-Peck on Hennigian phylogenetics and hexapod limb evolution is critically evaluated.
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Michael S. Engel (Corresponding author)Email: |
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Antibodies are very often used as specific cell and/or tissue markers. An example of this is anti-horseradish peroxidase (HRP),
an antibody raised against a plant glycoprotein, which was shown some twenty-five years ago to specifically stain neural tissue
in an animal, Drosophila melanogaster. This peculiar finding was later expanded to other invertebrate species including Caenorhabditis elegans, which were also shown to bear anti-HRP epitopes. Initial experiments indicated that the epitopes recognised by anti-HRP
in invertebrates are of carbohydrate nature. Indeed, more recent experiments have characterised relevant core α1-3-fucosylated
N-glycan structures that act as epitopes in various model and parasitic organisms. Moreover, a number of enzymes required
for the synthesis of such structures have been identified. Over the years, medically-relevant roles of these structures have
become apparent as regards allergenicity and immunoregulation. Although major advances have been made in understanding of
the underlying mechanisms and structures related to the anti-HRP epitope, the in vivo role of the relevant epitopes in neural and other tissues is yet to be resolved. Current understanding of the anti-HRP epitopes
synthesis and their relevance is discussed and elaborated.
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Katharina PaschingerEmail: |
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Robert Sparrow 《Journal of bioethical inquiry》2009,6(1):13-23
This paper attempts some predictions about the social consequences of nanotechnology and the ethical issues they raise. I
set out four features of nanotechnology that are likely to be important in determining its impact and argue that nanotechnology
will have significant social impacts in—at least—the areas of health and medicine, the balance of power between citizens and
governments, and the balance of power between citizens and corporations. More importantly, responding to the challenge of
nanotechnology will require confronting “philosophical” questions about the sort of society we wish to create and the role
that technology might play in creating it. This in turn will require developing institutions and processes that allow the
public to wield real power in relation to technological trajectories. My ultimate contention is that the immediate task established
by the likely social impacts of nanotechnology is not so much to develop an ethics of nanotechnology as to facilitate an ethical
conversation about nanotechnology.
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Robert SparrowEmail: |
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Douglas Medin Norbert Ross Douglas Cox Scott Atran 《Human ecology: an interdisciplinary journal》2007,35(3):315-329
There is a continuing controversy over Native American fishing and hunting rights. We show that Native American (Menominee)
and European American fish experts have a common knowledge base and share values and attitudes associated with fishing practices
(though organized around different ethical principles). Nonetheless, perceived group differences are dramatic (especially European American perceptions of Native Americans). Cultural differences in models
of nature and associated inference processes appear to mediate these stereotypes and may hold the key to reducing intergroup
conflict over resources.
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Douglas MedinEmail: |
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Peter Olofsson 《Biology & philosophy》2008,23(4):545-553
The explanatory filter is a proposed method to detect design in nature with the aim of refuting Darwinian evolution. The explanatory filter borrows
its logical structure from the theory of statistical hypothesis testing but we argue that, when viewed within this context,
the filter runs into serious trouble in any interesting biological application. Although the explanatory filter has been extensively
criticized from many angles, we present the first rigorous criticism based on the theory of mathematical statistics.
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Peter OlofssonEmail: |
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A surface plasmon resonance-based solution affinity assay is described for measuring the K
d of binding of heparin/heparan sulfate-binding proteins with a variety of ligands. The assay involves the passage of a pre-equilibrated
solution of protein and ligand over a sensor chip onto which heparin has been immobilised. Heparin sensor chips prepared by
four different methods, including biotin–streptavidin affinity capture and direct covalent attachment to the chip surface,
were successfully used in the assay and gave similar K
d values. The assay is applicable to a wide variety of heparin/HS-binding proteins of diverse structure and function (e.g.,
FGF-1, FGF-2, VEGF, IL-8, MCP-2, ATIII, PF4) and to ligands of varying molecular weight and degree of sulfation (e.g., heparin,
PI-88, sucrose octasulfate, naphthalene trisulfonate) and is thus well suited for the rapid screening of ligands in drug discovery
applications.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
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Vito FerroEmail: |
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Kevin J. Emerson Sabrina J. Dake William E. Bradshaw Christina M. Holzapfel 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2009,195(4):385-391
For over 70 years, researchers have debated whether the ability to use day length as a cue for the timing of seasonal events
(photoperiodism) is related to the endogenous circadian clock that regulates the timing of daily events. Models of photoperiodism
include two components: (1) a photoperiodic timer that measures the length of the day, and (2) a photoperiodic counter that
elicits the downstream photoperiodic response after a threshold number of days has been counted. Herein, we show that there
is no geographical pattern of genetic association between the expression of the circadian clock and the photoperiodic timer
or counter. We conclude that the photoperiodic timer and counter have evolved independently of the circadian clock in the
pitcher-plant mosquito Wyeomyia smithii and hence, the evolutionary modification of photoperiodism throughout the range of W. smithii has not been causally mediated by a corresponding evolution of the circadian clock.
相似文献
Kevin J. EmersonEmail: |
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The interconnection network is one of the key architectural components in any parallel computer. The distribution of the traffic
injected into the network is among the factors that greatly influences network performance. The uniform traffic pattern has
been adopted in many existing network performance evaluation studies due to the tractability of the resulting analytical modelling
approach. However, many real applications exhibit non-uniform traffic patterns such as hot-spot traffic. K-ary n-cubes have been the mostly widely used in the implementation of practical parallel systems. Extensive research studies have
been conducted on the performance modelling and evaluation of these networks. Nonetheless, most of these studies have been
confined to uniform traffic distributions and have been based on software simulation. The present paper proposes a new stochastic
model to predict message latency in k-ary
n-cubes with deterministic routing in the presence of hot-spot traffic. The model has been validated through simulation experiments
and has shown a close agreement with simulation results.
相似文献
Geyong MinEmail: |
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Andrei V. Astashkin Arnold M. Raitsimring F. Ann. Walker Christopher Rensing Megan M. McEvoy 《Journal of biological inorganic chemistry》2005,10(3):221-230
Electron paramagnetic resonance (EPR) spectroscopy has been used to structurally characterize the copper-binding site in CusF protein from Escherichia coli. The EPR spectra indicate a single type II copper center with parameters typical for nitrogen and oxygen ligands (A~200 G, g~2.186, g~2.051). The pulsed EPR data show that one of the ligands to Cu2+ is an imidazole ring of a histidine residue. The remote amino nitrogen of this imidazole ring is readily observed by electron spin-echo envelope modulation spectroscopy, while the imino nitrogen that is directly coordinated to the Cu2+ ion is observed by pulsed electron–nuclear double resonance (ENDOR). In addition, the ENDOR spectra reveal the presence of one more nitrogen ligand that was assigned to be a deprotonated peptide nitrogen. Apart from the two nitrogen ligands, it has been established that there are two nearby hydroxyl protons, although whether these belong to a single equatorial water ligand or two equatorial hydroxide ligands is not known.
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Megan M. McEvoyEmail: Phone: +1-520-6213489Fax: +1-520-6211697 |