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排序方式: 共有185条查询结果,搜索用时 15 毫秒
1.
To provide insight into the stream of Medicare payments over time, a sixteen-year longitudinal study examines three age cohorts of beneficiaries, looking separately at beneficiaries who died during the study period and those who survived. The common wisdom that a small minority of the population accounts for a large majority of health care expenditures is tempered when health care use is examined over an extended period of time. By putting high average costs in the final years of life in the context of a cohort's total lifetime experience, the study shows a leveling of spending over time, resulting in a lower concentration of health care resources on a small fraction of the population. 相似文献
2.
Kocur C.M. Rogers S.K. Myers L.R. Burns T. Kabrisky M. Hoffmeister J.W. Bauer K.W. Steppe J.M. 《IEEE engineering in medicine and biology magazine》1996,15(3)
This study focuses on improving microcalcification classification by establishing an efficient computer-aided diagnosis system that extracts Daubechies-4 and biorthogonal wavelet features. These wavelets were chosen because they have been used in military target recognition and fingerprint recognition research with images characterized by low contrast, similar to mammography. Feature selection techniques are employed to further increase classification performance. The artificial neural network feature selection techniques are complemented by a conventional decision boundary-based feature selection method. The results using the wavelet features are compared to more conventional measures of image texture, angular second moment, and Karhunen Loeve coefficients. The use of alternative signal processing to compare wavelet and neural techniques allows for a measure of the problem difficulty. It is concluded that advances and contributions have been made with the introduction of two novel feature extraction methods for breast cancer diagnosis, wavelets and eigenmasses. Additionally, feature selection techniques are demonstrated, compared, and validated, transforming adequate discrimination power into promising classification results 相似文献
3.
Advances in Modeling and Simulation of Grinding Processes 总被引:6,自引:1,他引:6
E. Brinksmeier E. Govekar H.-W. Hoffmeister J. Peters D.J. Stephenson K. Weinert 《CIRP Annals》2006,55(2):667-696
In the last decade the relevance of modeling and simulation of grinding processes has significantly risen which is caused by industrial needs and is indicated by the number of publications and research activities in this area. This keynote paper results from a collaborative work within the STC G and gives an overview of the current state of the art in modeling and simulation of grinding processes: Physical process models (analytical and numerical models) and empirical process models (regression analysis, artificial neural net models) as well as heuristic process models (rule based models) are taken into account, and outlined with respect to their achievements in this paper. The models are characterized by the process parameters such as grinding force, grinding temperature, etc. as well as work results including surface topography and surface integrity. Furthermore, the capabilities and the limitations of the presented model types and simulation approaches will be exemplified. 相似文献
4.
Liquid-crystalline thermosets (LCT) are a new class of materials which combine typical properties of LC polymers with those of conventional thermosets. This article reports on the development of a lyotropic LC thermoset (LLCT) in which the solvent is a vinyl monomer. Such an LLCT is expected to have several advantages compared to conventional unsaturated polyester resins. The synthesis and characterization of a variety of novel substituted para-linked aromatic polyesters and copolyesters containing unsaturated fumaroyl units is presented. The thermal and liquid crystal properties were investigated. It is demonstrated that it is possible to prepare a lyotropic LC solution in styrene. These lyotropic solutions are capable of thermal crosslinking by the addition of a free-radical initiator. © 1995 John Wiley & Sons, Inc. 相似文献
5.
An Iterative O‐Methyltransferase Catalyzes 1,11‐Dimethylation of Aspergillus fumigatus Fumaric Acid Amides 下载免费PDF全文
Dr. Daniel Kalb Dr. Thorsten Heinekamp Dr. Sebastian Schieferdecker Prof. Dr. Markus Nett Prof. Dr. Axel A. Brakhage Prof. Dr. Dirk Hoffmeister 《Chembiochem : a European journal of chemical biology》2016,17(19):1813-1817
S‐adenosyl‐l ‐methionine (SAM)‐dependent methyltransfer is a common biosynthetic strategy to modify natural products. We investigated the previously uncharacterized Aspergillus fumigatus methyltransferase FtpM, which is encoded next to the bimodular fumaric acid amide synthetase FtpA. Structure elucidation of two new A. fumigatus natural products, the 1,11‐dimethyl esters of fumaryl‐l ‐tyrosine and fumaryl‐l ‐phenylalanine, together with ftpM gene disruption suggested that FtpM catalyzes iterative methylation. Final evidence that a single enzyme repeatedly acts on fumaric acid amides came from an in vitro biochemical investigation with recombinantly produced FtpM. Size‐exclusion chromatography indicated that this methyltransferase is active as a dimer. As ftpA and ftpM homologues are found clustered in other fungi, we expect our work will help to identify and annotate natural product biosynthesis genes in various species. 相似文献
6.
The real toughness response of RPV material can only be determined after the final shut down of the NPP. Such a chance is given now by investigating material from the former Greifswald NPP (VVER-440/230).In the first part the paper deals with fast neutron fluence calculations and retrospective dosimetry based on Niobium. Unfortunately, a second neutron reaction besides 93Nb(n,n’) leading to 93mNb-activity is the reaction 92Mo(n,γ)93Mo. Based on the found Nb and Mo contents in the RPV material, it turned out that the 93mNb generation on the Mo path mostly dominates over the fast neutron induced generation from Nb.The comparison between the calculated and the measured 93mNb activities typically resulted in deviations of 50%. Possible reasons for the observed differences are discussed.In the second part first results of fracture mechanic investigations are reported. SE(B) specimens from three thickness positions were tested and evaluated according to the test standard ASTM E1921-05. Cleavage fracture toughness values, KJc, were determined and Master Curve based reference temperatures (T0) were evaluated. The T0 measured at the inner surface of the RPV did not represent the conservative condition. The T0 of disc 1-1.3 located between the surface and 1/4 thickness is about 40K higher compared with those of the surface.The measured KJc values are not enveloped by the 5% fractile indexed with T0 according to the Master Curve concept. However, the 5% fractile indexed with the VERLIFE reference temperature RTTo that includes an additional margin envelops the measured KJc values. Therefore the VERLIFE lower bound curve conservatively describes the fracture toughness of the investigated weld metal. 相似文献
7.
8.
Quenching from ferritizing temperatures of 1350 and 1250 °C the isothermal δ-γ transformation of two iron-chromium-nickel alloys with 26.0% Cr, 6.9% Ni resp. 30.0% Cr, 7.05% Ni at temperatures between 700 and 1200 °C is studied. Three different transformation stages are revealed indicating grain boundary diffusion controlled growth in the first and last stage while volume diffusion seems to act at least partially in the second stage. Isothermal TTT diagrams are established and activation energies calculated. 相似文献
9.
10.
Daniel Kalb Dr. Gerald Lackner Marcus Rappe Prof. Dr. Dirk Hoffmeister 《Chembiochem : a European journal of chemical biology》2015,16(10):1426-1430
L ‐α‐Aminoadipic acid reductases catalyze the ATP‐ and NADPH‐dependent reduction of L ‐α‐aminoadipic acid to the corresponding 6‐semialdehyde during fungal L ‐lysine biosynthesis. These reductases resemble peptide synthetases with regard to their multidomain composition but feature a unique domain of elusive function—now referred to as an adenylation activating (ADA) domain—that extends the reductase N‐terminally. Truncated enzymes based on NPS3, the L ‐α‐aminoadipic acid reductase of the basidiomycete Ceriporiopsis subvermispora, lacking the ADA domain either partially or entirely were tested for activity in vitro, together with an ADA‐adenylation didomain and the ADA domainless adenylation domain. We provide evidence that the ADA domain is required for substrate adenylation: that is, the initial step of the catalytic turnover. Our biochemical data are supported by in silico modeling that identified the ADA domain as a partial peptide synthetase condensation domain. 相似文献