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排序方式: 共有833条查询结果,搜索用时 31 毫秒
21.
Making Workflow Change Acceptable 总被引:1,自引:0,他引:1
Virtual professional communities are supported by network information systems composed from standard Internet tools. To satisfy
the interests of all community members, a user-driven approach to requirements engineering is proposed that produces not only
meaningful but also acceptable specifications. This approach is especially suited for workflow systems that support partially structured, evolving work
processes. To ensure the acceptability, social norms must guide the specification process. The RENISYS specification method
is introduced, which facilitates this process using composition norms as formal representations of social norms. Conceptual
graph theory is used to represent four categories of knowledge definitions: type definitions, state definitions, action norms
and composition norms. It is shown how the composition norms guide the legitimate user-driven specification process by analysing
a case on the development of an electronic law journal. 相似文献
22.
The different steps of the dehalogenation reaction carried out by LinB on three different substrates have been characterized using a combination of quantum mechanical calculations and molecular dynamics simulations. This has allowed us to obtain information in atomic detail about each step of the reaction mechanism, that is, substrate entrance and achievement of the near-attack conformation, transition state stabilization within the active site, halide stabilization, water molecule activation and subsequent hydrolytic attack on the ester intermediate with formation of alcohol, and finally product release. Importantly, no bias or external forces were applied during the whole procedure so that both intermediates and products were completely free to sample configuration space in order to adapt to the plasticity of the active site and/or search for an exit. Differences in substrate reactivity were found to be correlated with the ease of adopting the near-attack conformation and two different exit pathways were found for product release that do not interfere with substrate entrance. Additional support for the different entry and exit pathways was independently obtained from an examination of the enzyme's normal modes. 相似文献
23.
Aldo Dall''Osso 《Annals of Nuclear Energy》2003,30(18):1829-1845
The most usual method to take into account energy dependence in whole core spatial neutronics calculation is the multigroup method. In thermal spectrum reactors as PWR, two-group theory is sufficient to describe accurately the neutron spectrum variation among spatial regions. When the spectrum hardens the precision of two-group theory decreases and more groups are necessary to keep a good accuracy. The aim of the computation method presented here is to represent with a good accuracy the spectral transitions which appear in these situations, without increasing the number of unknowns (i.e. the number of energy groups). The neutron spectrum is considered as a combination of base shapes corresponding to the different modes of migration of the neutrons in the energy dimension. The resulting energy flux distribution is a continuous function that fits the real one. The spatial discretization leads to matrices having the same structure of the ones obtained with multi-group theory. Then the method can be easily applied to existing codes solving the diffusion equation on the whole core in 3D. A methodological comparison between the migration mode method and the multigroup (few-group) method as well as a numerical comparison is presented. 相似文献
24.
Proteins as biomarkers of oxidative/nitrosative stress in diseases: the contribution of redox proteomics 总被引:8,自引:0,他引:8
Dalle-Donne I Scaloni A Giustarini D Cavarra E Tell G Lungarella G Colombo R Rossi R Milzani A 《Mass spectrometry reviews》2005,24(1):55-99
Reactive oxygen species (ROS) and reactive nitrogen species (RNS) contribute to the pathogenesis and/or progression of several human diseases. Proteins are important molecular signposts of oxidative/nitrosative damage. However, it is generally unresolved whether the presence of oxidatively/nitrosatively modified proteins has a causal role or simply reflects secondary epiphenomena. Only direct identification and characterization of the modified protein(s) in a given pathophysiological condition can decipher the potential roles played by ROS/RNS-induced protein modifications. During the last few years, mass spectrometry (MS)-based technologies have contributed in a significant way to foster a better understanding of disease processes. The study of oxidative/nitrosative modifications, investigated by redox proteomics, is contributing to establish a relationship between pathological hallmarks of disease and protein structural and functional abnormalities. MS-based technologies promise a contribution in a new era of molecular medicine, especially in the discovery of diagnostic biomarkers of oxidative/nitrosative stress, enabling early detection of diseases. Indeed, identification and characterization of oxidatively/nitrosatively modified proteins in human diseases has just begun. 相似文献
25.
P. Balasubramanian L. Hupa B. Jokic R. Detsch A. Grünewald Aldo R. Boccaccini 《Journal of Materials Science》2017,52(15):8785-8792
Boron-containing bioactive glasses (BGs) are being extensively researched for the treatment and regeneration of bone defects because of their osteostimulatory and neovascularization potential. In this study, we report the effects of the ionic dissolution products (IDPs) of different boron-doped, borosilicate, and borate BG scaffolds on mouse bone marrow stromal cells in vitro, using an angiogenesis assay. Five different BG scaffolds of the system SiO2–Na2O–K2O–MgO–CaO–P2O5–B2O3 (with varying amounts of SiO2 and B2O3) were fabricated by the foam replication technique. Bone marrow stromal cells were cultivated in contact with the IDPs of the boron-containing BG scaffolds at different concentrations for 48 h. The expression and secretion of vascular endothelial growth factor (VEGF) from the cultured cells was measured quantitatively using the VEGF ELISA Kit. Cell viability and cell morphology were determined using WST-8 assay and H&E staining, respectively. The cellular response was found to be dependent on boron content and the B release profile from the glasses corresponded to the positive or negative biological activity of the BGs. 相似文献
26.
Filippo Rossi Xanthippi Chatzistavrou Giuseppe Perale Aldo R. Boccaccini 《应用聚合物科学杂志》2012,123(1):398-408
Hydrogels studied in this investigation, synthesized starting from agarose and Carbomer 974P, were chosen for their potential use in tissue engineering. The strong ability of hydrogels to mimic living tissues should be complemented with optimized degradation time profiles: a critical property for biomaterials but essential for the integration with target tissue. In this study, chosen hydrogels were characterized both from a rheological and a structural point of view before studying the chemistry of their degradation, which was performed by several analysis: infrared bond response [Fourier transform infrared (FT‐IR)], calorimetry [differential scanning Calorimetry (DSC)], and % mass loss. Degradation behaviors of Agar‐Carbomer hydrogels with different degrees of crosslinkers were evaluated monitoring peak shifts and thermal property changes. It was found that the amount of crosslinks heavily affect the time and the magnitude related to the process. The results indicate that the degradation rates of Agar‐Carbomer hydrogels can be controlled and tuned to adapt the hydrogel degradation kinetics for different cell housing and drug delivery applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
27.
Edible coatings enriched with essential oils for extending the shelf‐life of ‘Bravo de Esmolfe’ fresh‐cut apples
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Adriana C. Guerreiro Custódia M. L. Gago Maria L. Faleiro Maria G. C. Miguel Maria D. C. Antunes 《International Journal of Food Science & Technology》2016,51(1):87-95
Edible coatings based on sodium alginate (AL) and pectin (PE) at 1% and 2%(w/v) enriched with eugenol (Eug) and citral (Cit) at minimum inhibitory concentrations (MIC) (0.10% and 0.15%) and double MIC were used to preserve the quality of fresh‐cut apples ‘Bravo de Esmolfe’. Samples were taken, through 14 day at 4 °C, for analysis of colour CIE(L*h°C*), firmness, °Brix, weight loss, antioxidant activity (TEAC), microbial growth and taste panels. With those quality characteristics, three groups were formed by the principal component and hierarchical cluster analysis, for each coating base (AL or PE). Based on, for each quality parameter measured, the mean closest value to the one at harvest for colour, higher value for firmness, °Brix and TEAC, and lower value for weight loss and microbial spoilage, the best group was selected for AL and PE. From each group, two edible coatings with the highest scores in overall acceptability were selected for fresh‐cut apples: AL2% + Eug 0.1%, AL2% + Cit 0.15% + Eug 0.1%, PE 2% + Cit 0.15% and PE 2% + Eug 0.2%. 相似文献
28.
29.
Aldo Attanasio Elisabetta Ceretti Irene Fassi Claudia Pagano 《The International Journal of Advanced Manufacturing Technology》2017,92(5-8):1721-1729
In recent years, innovative materials such as carbon nanotube composites are finding growing interest in several industrial sectors, from sports and leisure to electronics, automotive, aircraft, and defence. The reinforcing influence of the carbon nanotube is of prime interest. However, technological issues concerning the production methods and the manufacturing processes of carbon nanotube components limit the industrial application of this innovative and interesting material, especially whether small features are required. For this reason, manufacturing strategy involving new production technologies must be designed and developed. This paper studies the challenges of a manufacturing chain based on two manufacturing processes: injection moulding and micro milling. A case study based on these innovative processes is reported and discussed. The propagation chain effect and the influence of each considered process parameter on cutting force and geometrical accuracy of the features (the key characteristics of the process chain) were assessed by means of statistical analysis of variance (ANOVA). The ANOVA analysis demonstrated that cutting forces in micro milling are mainly influenced by the material and percentage of carbon nanotubes, while the main parameter influencing the geometrical accuracy of micro features is the matrix material. 相似文献
30.
Irene Appolloni Sebastiano Curreli Sara Caviglia Manuela Barilari Eleonora Gambini Aldo Pagano Paolo Malatesta 《International journal of molecular sciences》2012,13(11):14667-14678
Tumor progression is a key aspect in oncology. Not even the overexpression of a powerful oncogenic stimulus such as platelet derived growth factor-B (PDGF-B) is sufficient per se to confer full malignancy to cells. In previous studies we showed that neural progenitors overexpressing PDGF-B need to undergo progression to acquire the capability to give rise to secondary tumor following transplant. By comparing the expression profile of PDGF-expressing cells before and after progression, we found that progressed tumors consistently downregulate the expression of the antiproliferative gene Btg2. We therefore tested whether the downregulation of Btg2 is sufficient and necessary for glioma progression with loss and gain of function experiments. Our results show that downregulation of Btg2 is not sufficient but is necessary for tumor progression since the re-introduction of Btg2 in fully progressed tumors dramatically impairs their gliomagenic potential. These results suggest an important role of Btg2 in glioma progression. Accordingly with this view, the analysis of public datasets of human gliomas showed that reduced level of Btg2 expression correlates with a significantly worse prognosis. 相似文献