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1.
Document caching and connection caching are extensively studied problems. In document caching, one has to maintain caches
containing documents accessible in a network. In connection caching, one has to maintain a set of open network connections
that handle data transfer. Previous work investigated these two problems separately while in practice the problems occur together:
In order to load a document, one has to establish a connection between network nodes if the required connection is not already
open. In this paper we present the first study that integrates document and connection caching. We first consider a very basic
model in which all documents have the same size and the cost of loading a document or establishing a connection is equal to
1. We present deterministic and randomized online algorithms that achieve nearly optimal competitive ratios unless the size
of the connection cache is extremely small. We then consider general settings where documents have varying sizes. We investigate
a FAULT model in which the loading cost of a document is 1 as well as a BIT model in which the loading cost is equal to the
size of the document. 相似文献
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Funke SA Otte N Eggert T Bocola M Jaeger KE Thiel W 《Protein engineering, design & selection : PEDS》2005,18(11):509-514
Chiral compounds can be produced efficiently by using biocatalysts. However, wild-type enzymes often do not meet the requirements of a production process, making optimization by rational design or directed evolution necessary. Here, we studied the lipase-catalyzed hydrolysis of the model substrate 1-(2-naphthyl)ethyl acetate both theoretically and experimentally. We found that a computational equivalent of alanine scanning mutagenesis based on QM/MM methodology can be applied to identify amino acid positions important for the activity of the enzyme. The theoretical results are consistent with concomitant experimental work using complete saturation mutagenesis and high-throughput screening of the target biocatalyst, a lipase from Bacillus subtilis. Both QM/MM-based calculations and molecular biology experiments identify histidine 76 as a residue that strongly affects the catalytic activity. The experiments demonstrate its important influence on enantioselectivity. 相似文献
7.
Köhler K Lellouch AC Vollmer S Stoevesandt O Hoff A Peters L Rogl H Malissen B Brock R 《Chembiochem : a European journal of chemical biology》2005,6(1):152-161
Cellular signal transduction proceeds through a complex network of molecular interactions and enzymatic activities. The timing of these molecular events is critical for the propagation of a signal and the generation of a specific cellular response. To define the timing of signalling events, we introduce the combination of high-resolution confocal microscopy with the application of small-molecule inhibitors at various stages of signal transduction in T cells. Inhibitors of Src-family tyrosine kinases and actin dynamics were employed to dissect the role of the lymphocyte-specific tyrosine kinase Lck in the formation and maintenance of T cell receptor/CD3-dependent contacts. Anti-CD3epsilon-coated coverslips served as a highly defined stimulus. The kinetics of the recruitment of the yellow fluorescent protein-tagged signalling protein ZAP-70 were detected by high-resolution confocal microscopy. The analysis revealed that at 5 min after receptor engagement, Lck activity was required for maintenance of contacts. In contrast, after 20 min of receptor engagement, the contacts were Lck-independent. The relevance of the timing of inhibitor application provides a pharmacological concept for the maturation of T cell-substrate contacts. 相似文献
8.
Weizeng Shao Susanne Lehner Changlong Guan 《International journal of remote sensing》2014,35(11-12):4046-4063
In this article, the polarization ratio (PR) of TerraSAR-X (TS-X) vertical–vertical (VV) and horizontal–horizontal (HH) polarization data acquired over the ocean is investigated. Similar to the PR of C-band synthetic aperture radar (SAR), the PR of X-band SAR data also shows significant dependence on incidence angle. The normalized radar cross-section (NRCS) in VV polarization data is generally larger than that in HH polarization for incidence angles above 23°. Based on the analysis, two PR models proposed for C-band SAR were retuned using TS-X dual-polarization data. A new PR model, called X-PR hereafter, is proposed as well to convert the NRCS of TS-X in HH polarization to that in VV polarization. By using the developed geophysical model functions of XMOD1 and XMOD2 and the tuned PR models, the sea surface field is retrieved from the TS-X data in HH polarization. The comparisons with in situ buoy measurements show that the combination of XMOD2 and X-PR models yields a good retrieval with a root mean square error (RMSE) of 2.03 m s–1 and scatter index (SI) of 22.4%. A further comparison with a high-resolution analysis wind model in the North Sea is also presented, which shows better agreement with RMSE of 1.76 m s–1 and SI of 20.3%. We also find that the difference between the fitting of the X-PR model and the PR derived from TS-X dual-polarization data is close to a constant. By adding the constant to the X-PR model, the accuracy of HH polarization sea surface wind speed is further improved with the bias reduced by 0.3 m s–1. A case acquired at the offshore wind farm in the East China Sea further demonstrates that the improvement tends to be more effective for incidence angles above 40°. 相似文献
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Schwaiger Josef Hammerl Timo Florian Johannsen Leist Susanne 《Information Systems and E-Business Management》2021,19(4):1275-1320
Information Systems and e-Business Management - The digital transformation, with its ongoing trend towards electronic business, confronts companies with increasingly growing amounts of data which... 相似文献
10.
Susanne Bødker 《Personal and Ubiquitous Computing》2016,20(4):533-544
Technology is often seen as seamless, or making (life/work) boundaries go away. Ubicomp designs for that and for seamlessness in general. However, there may be better ways of understanding boundaries, as to design technologies in the space of changing work/life boundaries, which is the topic of this special issue. This paper makes a theoretical argument to insist that boundaries are not fixed, neither can or should they be made away with technologically, through seamless technologies. Based on this argument, it discusses various presumed technology-mediated boundaries of work and home, life, etc., as they can be found in the Ubicomp, CSCW and HCI literature: The ways in which work and work technologies are stereotypically connected to effectiveness and hard labor, and non-work technologies to fun and enjoyment; the ways in which technologies move back and forth between mediating work activity and non-work; the role of place and time boundaries in relation to the ability to work any time, anywhere and the metaphors used to address these boundaries; and the perceived boundaries of private versus public, and the new boundaries created by technologies in and across our lives and work. Using an empirical case, the paper offers an alternative use of boundaries as resources to be activated and used in design. It suggests that we need to more carefully design technologies that provide seamfulness on these specific and dynamic boundaries. 相似文献