共查询到20条相似文献,搜索用时 15 毫秒
1.
This paper reports results from monitoring atmospheric pollen in Salitral de la Vidriera, an area of natural vegetation near Bahía Blanca city (East Central Argentina). Sampling was carried out weekly during January
to December 2003 and May 2005 to April 2006 using a volumetric impact sampler. Observations of flowering in the field were
carried out at the same time as the aerial sampling. During this period, 43 pollen types were identified; most of these correspond
to pollen grains from either herbaceous or shrubby vegetation typical of the study area, for example Amaranthus, Brassicaceae, Centaurea, Poaceae, Chenopodiaceae, Urticaceae, some Asteraceae, and Condalia microphylla. This study on the atmosphere of Salitral de la Vidriera allowed us to identify the components of the vegetation type dominant in the area, namely a shrubby halophytic steppe. A
well represented family, for example Chenopodiaceae, could, under appropriate weather conditions, be an important contributor
of pollen to Bahía Blanca.
相似文献
María Gabriela MurrayEmail: |
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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.
相似文献
Marienne S. de VilliersEmail: Fax: +27-21-6503434 |
John CooperEmail: |
Peter G. RyanEmail: |
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The recent contribution by Jarmila Kukalová-Peck on Hennigian phylogenetics and hexapod limb evolution is critically evaluated.
相似文献
Michael S. Engel (Corresponding author)Email: |
7.
Threatened species and the spatial concentration of humans 总被引:1,自引:1,他引:0
Public policies that encourage high-density human living arrangements have been predicated explicitly on the assumption that
certain spatial distributions of a fixed-size human population are less environmentally damaging than others. We examine the
empirical validity of this assumption across 127 countries by analyzing whether the concentration of human presence in each
country is related statistically to the percentage of species that were on the IUCN Red List in 2004. Our findings indicate
that concentration of the human population is associated with reduced imperilment among amphibians but increased imperilment
among reptiles, and birds.
相似文献
Ram PanditEmail: |
8.
Peter Godfrey-Smith 《Biology & philosophy》2007,22(3):429-437
Jablonka and Lamb's claim that evolutionary biology is undergoing a ‘revolution’ is queried. But the very concept of revolutionary
change has uncertain application to a field organized in the manner of contemporary biology. The explanatory primacy of sequence
properties is also discussed.
相似文献
Peter Godfrey-SmithEmail: |
9.
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.
相似文献
Laurent Tournier (Corresponding author)Email: |
Jean-Luc GouzéEmail: |
10.
Terry Harmer 《Cluster computing》2007,10(3):277-285
Gridcast is an R&D project investigating grid ideas and technologies in the broadcasting technical infrastructure. In this
paper I discuss the business and technical issues in building infrastructures to support broadcasters and outline the structure
of the Gridcast grid-based service oriented architecture for broadcasting playout support.
相似文献
Terry HarmerEmail: |
11.
Andres Quiroz Nathan Gnanasambandam Manish Parashar Naveen Sharma 《Cluster computing》2009,12(1):73-85
We present a decentralized algorithm for online clustering analysis used for anomaly detection in self-monitoring distributed
systems. In particular, we demonstrate the monitoring of a network of printing devices that can perform the analysis without
the use of external computing resources (i.e. in-network analysis). We also show how to ensure the robustness of the algorithm,
in terms of anomaly detection accuracy, in the face of failures of the network infrastructure on which the algorithm runs.
Further, we evaluate the tradeoff in terms of overhead necessary for ensuring this robustness and present a method to reduce
this overhead while maintaining the detection accuracy of the algorithm.
相似文献
Naveen SharmaEmail: |
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Roger Sansom 《Biology & philosophy》2008,23(4):475-491
I show that gene regulation networks are qualitatively consistent and therefore sufficiently similar to linearly seperable
connectionist networks to warrant that the connectionist framework be applied to gene regulation. On this view, natural selection
designs gene regulation networks to overcome the difficulty of development. I offer some general lessons about their evolvability
that can be learned by examining the generic features of connectionist networks.
相似文献
Roger SansomEmail: |
14.
Event-related brain potentials (ERP) are important neural correlates of cognitive processes. In the domain of language processing,
the N400 and P600 reflect lexical-semantic integration and syntactic processing problems, respectively. We suggest an interpretation
of these markers in terms of dynamical system theory and present two nonlinear dynamical models for syntactic computations
where different processing strategies correspond to functionally different regions in the system’s phase space.
相似文献
Peter beim GrabenEmail: |
15.
Tanya Marie Hayes 《Human ecology: an interdisciplinary journal》2007,35(6):733-747
This article compares how public protection of forests and common-property forest institutions serve to control outside encroachment
into frontier forests in Honduras and Nicaragua. The article combines institutional analysis with ethnographically based fieldwork
and analysis of land-cover images to evaluate how property-rights arrangements influence monitoring, enforcement, and compliance
with rules to restrict agricultural expansion in two biosphere reserves in the Mosquitia Corridor. Findings show that territorial
demarcation and common-property rights are important components for frontier forest conservation. In areas with weak enforcement
mechanisms and heavy reliance on social norms over official regulatory measures, the findings suggest that the perceived legitimacy
of tenure arrangements and their respective land-use rules are fundamental to controlling the agricultural frontier.
相似文献
Tanya Marie HayesEmail: |
16.
Harold Levrel Christian Kerbiriou Denis Couvet Jacques Weber 《Biodiversity and Conservation》2009,18(7):1719-1732
Sustainability is said to be the science of integration, be it integration of scale, discipline or of stakeholders’ interests.
One way to integrate such diverse elements is to develop sustainable development indicators. Numerous national and international
organizations have attempted to develop such indicators, among which interaction indicators are of critical importance because
they enable us to link up human activities, ecological dynamics, and social goals. Among the various ways to develop such
indicators, the most common ones are the pressure–state–response (PSR) indicators, as well as others coming from this framework.
With realistic methodology one shall observe how PSR indicators might appear as an operational tool to face rapid social and
ecological changes within a French biosphere reserve in Brittany. Results suggest that such a framework is insufficient to
describe, understand and manage social and ecological interactions.
相似文献
Harold LevrelEmail: |
17.
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.
相似文献
Andrew P. VaydaEmail: |
18.
The influences of the operating system and system-specific effects on application performance are increasingly important considerations
in high performance computing. OS kernel measurement is key to understanding the performance influences and the interrelationship
of system and user-level performance factors. The KTAU (Kernel TAU) methodology and Linux-based framework provides parallel
kernel performance measurement from both a kernel-wide and process-centric perspective. The first characterizes overall aggregate kernel performance for the entire system. The second characterizes
kernel performance when it runs in the context of a particular process. KTAU extends the TAU performance system with kernel-level
monitoring, while leveraging TAU’s measurement and analysis capabilities. We explain the rational and motivations behind our
approach, describe the KTAU design and implementation, and show working examples on multiple platforms demonstrating the versatility
of KTAU in integrated system/application monitoring.
相似文献
Alan MorrisEmail: |
19.
Robin E. Snyder 《Theoretical Ecology》2008,1(3):129-139
The ability of environmental variation to affect species coexistence is much studied, yet environmental variation is not always
important. I present an approximate calculation for the long-run growth rate of a species in the presence of spatially and
temporally correlated environmental variation. I then perform a factorial numerical experiment, varying the mean seed dispersal
distances, competition radii, and overwinter seed survival probabilities for two competing species for an array of variational
regimes, noting the effects on their long-run growth rates. I find, first, that purely spatial variation has a greater capacity
for influence than variation with a temporal component. Second, spatiotemporal variation can promote coexistence as strongly
as purely temporal variation or more so, given the right species traits. Third, if the environmental variation has a spatial
component, traits which enable species to become spatially segregated promote coexistence most strongly. That is, it is the
possibility of spatial segregation which gives spatial variation its large potential to promote coexistence.
相似文献
Robin E. SnyderEmail: |
20.
Javier Plaza Rosa Pérez Antonio Plaza Pablo Martínez David Valencia 《Cluster computing》2008,11(1):17-32
The wealth spatial and spectral information available from last-generation Earth observation instruments has introduced extremely
high computational requirements in many applications. Most currently available parallel techniques treat remotely sensed data
not as images, but as unordered listings of spectral measurements with no spatial arrangement. In thematic classification
applications, however, the integration of spatial and spectral information can be greatly beneficial. Although such integrated
approaches can be efficiently mapped in homogeneous commodity clusters, low-cost heterogeneous networks of computers (HNOCs)
have soon become a standard tool of choice for dealing with the massive amount of image data produced by Earth observation
missions. In this paper, we develop a new morphological/neural algorithm for parallel classification of high-dimensional (hyperspectral)
remotely sensed image data sets. The algorithm’s accuracy and parallel performance is tested in a variety of homogeneous and
heterogeneous computing platforms, using two networks of workstations distributed among different locations, and also a massively
parallel Beowulf cluster at NASA’s Goddard Space Flight Center in Maryland.
相似文献
Javier PlazaEmail: |