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1.
The interpretation of mass spectra (ms) of molecules containing poly-isotopic elements (e.g. Ge, Se, W, Os, Sn, Te, Zn, Yb)
can be difficult due to the occurrence of fragments resulting from isotopomeric composition. MS-clusters located in the range
lower than or equal to M/2 are very difficult to interpret. In this area many perturbations may be observed. The coincidence
of different fragmentation pathways, the existence of multiply charged ions, background levels, etc. can all contribute to
this problem. The present paper reports the application of multi-isotopomeric analysis methods for low-resolution ms. We present
a solution that may be useful for detection of the symmetrical decomposition of a molecule and for elucidation of cluster
ion genesis. The complex character of the cluster does not perturb determination of the contents of the investigated pattern.
In such cases the dominated component is applied in subsequent computations.
相似文献
Andrzej J. GorączkoEmail: |
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3.
High availability plays an important role in heterogeneous clusters, where processors operate at different speeds and are
not continuously available for processing. Existing scheduling algorithms designed for heterogeneous clusters do not factor
in availability. We address in this paper the stochastic scheduling problem for heterogeneous clusters with availability constraints.
Each node in a heterogeneous cluster is modeled by its speed and availability, and different classes of tasks submitted to
the cluster are characterized by their execution times and availability requirements. To incorporate availability and heterogeneity
into stochastic scheduling, we introduce metrics to quantify availability and heterogeneity in the context of multiclass tasks.
A stochastic scheduling algorithm SSAC (stochastic scheduling with availability constraints) is then proposed to improve availability of heterogeneous clusters while reducing average response time of tasks.
Experimental results show that our algorithm achieves a good trade-off between availability and responsiveness.
相似文献
Tao XieEmail: |
4.
Edward Walker Jeffrey P. Gardner Vladimir Litvin Evan L. Turner 《Cluster computing》2007,10(3):339-350
We describe a system for creating personal clusters in user-space to support the submission and management of thousands of
compute-intensive serial jobs to the network-connected compute resources on the NSF TeraGrid. The system implements a robust
infrastructure that submits and manages job proxies across a distributed computing environment. These job proxies contribute
resources to personal clusters created dynamically for a user on-demand. The personal clusters then adapt to the prevailing
job load conditions at the distributed sites by migrating job proxies to sites expected to provide resources more quickly.
Furthermore, the system allows multiple instances of these personal clusters to be created as containers for individual scientific
experiments, allowing the submission environment to be customized for each instance. The version of the system described in
this paper allows users to build large personal Condor and Sun Grid Engine clusters on the TeraGrid. Users then manage their
scientific jobs, within each personal cluster, with a single uniform interface using the feature-rich functionality found
in these job management environments.
相似文献
Evan L. TurnerEmail: |
5.
The quantum chemical cluster approach for modeling enzyme reactions is reviewed. Recent applications have used cluster models
much larger than before which have given new modeling insights. One important and rather surprising feature is the fast convergence
with cluster size of the energetics of the reactions. Even for reactions with significant charge separation it has in some
cases been possible to obtain full convergence in the sense that dielectric cavity effects from outside the cluster do not
contribute to any significant extent. Direct comparisons between quantum mechanics (QM)-only and QM/molecular mechanics (MM)
calculations for quite large clusters in a case where the results differ significantly have shown that care has to be taken
when using the QM/MM approach where there is strong charge polarization. Insights from the methods used, generally hybrid
density functional methods, have also led to possibilities to give reasonable error limits for the results. Examples are finally
given from the most extensive study using the cluster model, the one of oxygen formation at the oxygen-evolving complex in
photosystem II.
相似文献
Per E. M. SiegbahnEmail: |
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8.
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: |
9.
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
相似文献
David A. Grahame (Corresponding author)Email: |
Edward DeMoll (Corresponding author)Email: |
10.
11.
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: |
12.
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: |
13.
Motohiko Matsuda Tomohiro Kudoh Yuetsu Kodama Ryousei Takano Yutaka Ishikawa 《Cluster computing》2008,11(1):45-55
Several MPI systems for Grid environment, in which clusters are connected by wide-area networks, have been proposed. However,
the algorithms of collective communication in such MPI systems assume relatively low bandwidth wide-area networks, and they
are not designed for the fast wide-area networks that are becoming available. On the other hand, for cluster MPI systems,
a bcast algorithm by van de Geijn, et al. and an allreduce algorithm by Rabenseifner have been proposed, which are efficient
in a high bi-section bandwidth environment. We modify those algorithms so as to effectively utilize fast wide-area inter-cluster
networks and to control the number of nodes which can transfer data simultaneously through wide-area networks to avoid congestion.
We confirmed the effectiveness of the modified algorithms by experiments using a 10 Gbps emulated WAN environment. The environment
consists of two clusters, where each cluster consists of nodes with 1 Gbps Ethernet links and a switch with a 10 Gbps upper
link. The two clusters are connected through a 10 Gbps WAN emulator which can insert latency. In a 10 millisecond latency
environment, when the message size is 32 MB, the proposed bcast and allreduce are 1.6 and 3.2 times faster, respectively,
than the algorithms used in existing MPI systems for Grid environment.
相似文献
Motohiko MatsudaEmail: |
14.
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: |
15.
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: |
16.
Peter beim Graben Dimitris Pinotsis Douglas Saddy Roland Potthast 《Cognitive neurodynamics》2008,2(2):79-88
We construct a mapping from complex recursive linguistic data structures to spherical wave functions using Smolensky’s filler/role
bindings and tensor product representations. Syntactic language processing is then described by the transient evolution of
these spherical patterns whose amplitudes are governed by nonlinear order parameter equations. Implications of the model in
terms of brain wave dynamics are indicated.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.
相似文献
Peter beim GrabenEmail: |
17.
Leslie P. Francis Margaret P. Battin Jay Jacobson Charles Smith 《Journal of bioethical inquiry》2009,6(2):187-195
Syndromic surveillance uses new ways of gathering data to identify possible disease outbreaks. Because syndromic surveillance
can be implemented to detect patterns before diseases are even identified, it poses novel problems for informed consent, patient
privacy and confidentiality, and risks of stigmatization. This paper analyzes these ethical issues from the viewpoint of the
patient as victim and vector. It concludes by pointing out that the new International Health Regulations fail to take full
account of the ethical challenges raised by syndromic surveillance.
相似文献
Leslie P. FrancisEmail: |
18.
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: |
19.
Rapid prototyping of distributed systems can be achieved by integrating commercial off-the-shelf (COTS) components. With components
as the building blocks, it is important to predict the performance of the system based on the performance of individual components.
In this paper, performance prediction of a system consisting of a small number of components is investigated under different
inter-component communication patterns, and the number of threads provided by components. Based on the experimental results,
it can be inferred that the proposed composition rules provide a reasonably accurate prediction of the performance of a system
made out of these components.
相似文献
Barrett R. BryantEmail: |
20.
This study is dedicated to the development of manufacturing principles of food emulsions for food functionalization and formulation. In the experiments presented, the emulsions are generated using the effects of electrochemical instability and surface tension decrease at a polarized liquid/liquid interface. Polarization of the oil/liquid interface is studied in various aqueous systems including electrolytes and water-based solutions of cationic, anionic, zwitterionic, and nonionic surfactants. The physical features of the obtained emulsions, such as hydrodynamic flow patterns, droplet size distribution, and emulsion organization, are described. The efficacy of different electrode configurations is also evaluated. The theoretical model of the liquid/liquid interface polarization and experimental data obtained from various emulsification regimes are presented.
相似文献
Paul TakhistovEmail: |