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排序方式: 共有400条查询结果,搜索用时 46 毫秒
71.
72.
Upon occurrence of an internal fault on the PMSM (permanent magnet synchronous machine), the topology of the stator is amended causing structural imbalances due to the change of the connection within the windings. In this work, a state model of internal faults of the PMSM is developed. This model is in the (abc) reference frame. The modeling approach is based on the assumption that each stator phase is replaced by two major and minor sub-windings. This model is used subsequently in the residual generation for diagnosis. The fault indicators are obtained by the projection in parity space and estimated using the Luenberger observer. A scenario of fault inter-turn by the short-circuit occurring between phase (a and b) is validated by simulation. 相似文献
73.
Uciechowska U Schemies J Neugebauer RC Huda EM Schmitt ML Meier R Verdin E Jung M Sippl W 《ChemMedChem》2008,3(12):1965-1976
NAD+-dependent histone deacetylases (sirtuins) are enzymes that cleave acetyl groups from lysine residues in histones and other proteins. Potent selective sirtuin inhibitors are interesting tools for the investigation of the biological functions of these enzymes and may be future drugs for the treatment of cancer or neurodegenerative diseases. Herein we present the results from a protein-based virtual screen of a commercial database with subsequent biological testing of the most promising compounds. The combination of docking and in vitro experimental testing resulted in the identification of novel sirtuin inhibitors with thiobarbiturate structure. To rationalize the experimental results, free-energy calculations were carried out by molecular mechanics Poisson-Boltzmann/surface area (MM-PBSA) calculations. A significant correlation between calculated binding free energies and measured Sirt2 inhibitory activities was observed. The analyses suggested a molecular basis for the interaction of the identified thiobarbiturate derivatives with human Sirt2. Based on the docking and MM-PBSA calculations we synthesized and tested five further thiobarbiturates. The MM-PBSA method correctly predicted the activity of the novel thiobarbiturates. The identified compounds will be used to further explore the therapeutic potential of sirtuin inhibitors. 相似文献
74.
Mary N Mugambi Alfred Musekiwa Martani Lombard Taryn Young Reneé Blaauw 《Nutrition journal》2012,11(1):1-18
Malnutrition is a significant factor in predicting cancer patients?? quality of life (QoL). We systematically reviewed the literature on the role of nutritional status in predicting QoL in cancer. We searched MEDLINE database using the terms ??nutritional status?? in combination with ??quality of life?? together with ??cancer??. Human studies published in English, having nutritional status as one of the predictor variables, and QoL as one of the outcome measures were included. Of the 26 included studies, 6 investigated head and neck cancer, 8 gastrointestinal, 1 lung, 1 gynecologic and 10 heterogeneous cancers. 24 studies concluded that better nutritional status was associated with better QoL, 1 study showed that better nutritional status was associated with better QoL only in high-risk patients, while 1 study concluded that there was no association between nutritional status and QoL. Nutritional status is a strong predictor of QoL in cancer patients. We recommend that more providers implement the American Society of Parenteral and Enteral Nutrition (ASPEN) guidelines for oncology patients, which includes nutritional screening, nutritional assessment and intervention as appropriate. Correcting malnutrition may improve QoL in cancer patients, an important outcome of interest to cancer patients, their caregivers, and families. 相似文献
75.
Ungureanu C Kroes R Petersen W Groothuis TA Ungureanu F Janssen H van Leeuwen FW Kooyman RP Manohar S van Leeuwen TG 《Nano letters》2011,11(5):1887-1894
Gold nanorods (AuNR) can be tailored to possess an intense and narrow longitudinal plasmon (LP) absorption peak in the far-red to near-infrared wavelength region, where tissue is relatively transparent to light. This makes AuNRs excellent candidates as contrast agents for photoacoustic imaging, and as photothermal therapeutic agents. The favorable optical properties of AuNR which depend on the physical parameters of shape, size and plasmonic coupling effects, are required to be stable during use. We investigate the changes that are likely to occur in these physical parameters in the setting of photothermal therapeutics, and the influence that these changes have on the optical properties and the capacity to achieve target cell death. To this end we study 3 sets of interactions: pulsed light with AuNR, AuNR with cells, and pulsed light with cells incubated with AuNR. In the first situation we ascertain the threshold value of fluence required for photothermal melting or reshaping of AuNR to shorter AuNR or nanospheres, which results in drastic changes in optical properties. In the second situation when cells are exposed to antibody-conjugated AuNR, we observe using transmission electron microscopy (TEM) that the particles are closely packed and clustered inside vesicles in the cells. Using dark-field microscopy we show that plasmonic interactions between AuNRs in this situation causes blue-shifting of the LP absorption peak. As a consequence, no direct lethal damage to cells can be inflicted by laser irradiation at the LP peak. On the other hand, using irradiation at the transverse peak (TP) wavelength in the green, at comparative fluences, extensive cell death can be achieved. We attribute this behavior on the one hand to the photoreshaping of AuNR into spheres and on the other hand to clustering of AuNR inside cells. Both effects create sufficiently high optical absorption at 532 nm, which otherwise would have been present at the LP peak. We discuss implications of these finding on the application of these particles in biomedicine. 相似文献
76.
Direct nitrous oxide (N2O) emissions from agricultural soils contribute considerably to anthropogenic GHG emissions. Albeit a key source of emissions
in many countries, direct N2O emissions are still calculated and reported to the United Nations Convention on Climate Change using default emission factors
defined in the IPCC guidelines (IPCC 1996, 2006). It is known that processes controlling production and transport of N2O are highly sensitive to environmental conditions defined by weather, soil and management. The accuracy of N2O emission budgets and the efficiency of mitigation can be improved if those dependencies are considered with regionalized
emission factors. In this study an empirical method originating from soft computing techniques based on measured data is developed
and applied to quantify direct N2O emissions from agricultural soils at field and national level in Germany between 1990 and 2005. The method is used to derive
maps of emission factor distribution of direct N2O emissions of agricultural land in Germany. Model results are compared with alternative empirical approaches from literature.
Results from developing empirical models show that grassland and cropland have to be differentiated according to the key controls
driving N2O emissions. N2O emissions of German croplands are highly influenced by climatic conditions and soil properties. The variability of N2O fluxes on grasslands is mainly driven by the fertilizer N applied. The model comparison using measured European N2O emissions exhibits profound discrepancies between the models used on a regional scale. The nationwide budgets derived span
a narrow range of −8 to 28% relative to direct N2O emissions quantified by the German national inventory report. The emission factor of German agriculture estimated by the
developed model is 0.91% of fertilizer N applied. 相似文献
77.
Dagmar Chudobova Lukas Nejdl Jaromir Gumulec Olga Krystofova Miguel Angel Merlos Rodrigo Jindrich Kynicky Branislav Ruttkay-Nedecky Pavel Kopel Petr Babula Vojtech Adam Rene Kizek 《International journal of molecular sciences》2013,14(7):13592-13614
Polymers are currently widely used to replace a variety of natural materials with respect to their favourable physical and chemical properties, and due to their economic advantage. One of the most important branches of application of polymers is the production of different products for medical use. In this case, it is necessary to face a significant disadvantage of polymer products due to possible and very common colonization of the surface by various microorganisms that can pose a potential danger to the patient. One of the possible solutions is to prepare polymer with antibacterial/antimicrobial properties that is resistant to bacterial colonization. The aim of this study was to contribute to the development of antimicrobial polymeric material ideal for covering vascular implants with subsequent use in transplant surgery. Therefore, the complexes of polymeric substances (hyaluronic acid and chitosan) with silver nitrate or silver phosphate nanoparticles were created, and their effects on gram-positive bacterial culture of Staphylococcus aureus were monitored. Stages of formation of complexes of silver nitrate and silver phosphate nanoparticles with polymeric compounds were characterized using electrochemical and spectrophotometric methods. Furthermore, the antimicrobial activity of complexes was determined using the methods of determination of growth curves and zones of inhibition. The results of this study revealed that the complex of chitosan, with silver phosphate nanoparticles, was the most suitable in order to have an antibacterial effect on bacterial culture of Staphylococcus aureus. Formation of this complex was under way at low concentrations of chitosan. The results of electrochemical determination corresponded with the results of spectrophotometric methods and verified good interaction and formation of the complex. The complex has an outstanding antibacterial effect and this effect was of several orders higher compared to other investigated complexes. 相似文献
78.
Ronald Schnitzer Rene Radis Matthias Nöhrer Michael Schober Rainer Hochfellner Silvia Zinner E. Povoden-Karadeniz Ernst Kozeschnik Harald Leitner 《Materials Chemistry and Physics》2010
The mechanical properties of maraging steels are strongly influenced by the presence of reverted austenite. In this study, the morphology and chemical composition of reverted austenite in a corrosion resistant maraging steel was characterized using transmission electron microscopy (TEM) and atom probe tomography (APT). Two types of austenite, i.e. granular and elongated, are present after aging at 575 °C, whereby the content of the latter increases during aging. The investigations revealed that the austenite phase is enriched in Ni, which prevents the transformation to martensite during cooling. Inside and next to the austenitc areas, Mo and Cr-rich carbides, which form during the aging treatment, were found. Various aging treatments were performed to obtain the activation energy for the formation of reverted austenite. Additionally, the experimental data are compared with thermodynamic and kinetic simulations. Based on these results and the chemical composition changes of the phases, a model for the formation of reverted austenite is presented. It is concluded that precipitation of B2-ordered NiAl and formation of reverted austenite take place simultaneously during aging and that dissolution of precipitates is not essential for the initial formation of reverted austenite. 相似文献
79.
80.
Gerald A. Zickler Ronald Schnitzer Rene Radis Rainer Hochfellner Ralf Schweins Martin Stockinger Harald Leitner 《Materials Science and Engineering: A》2009,523(1-2):295-303
ATI Allvac® 718Plus™ is a novel nickel-based superalloy, which was designed for heavy-duty applications in aerospace turbines. In the present study the high-resolution investigation techniques, atom probe tomography, electron microscopy and in situ high-temperature small-angle neutron scattering were used for a comprehensive microstructural characterization. The alloy contains nanometer-sized spherical γ′ phase precipitates (Ni3(Al,Ti)) and plate-shaped δ phase precipitates (Ni3Nb) of micrometer size. The precipitation kinetics of the γ′ phase can be described by a classical model for coarsening. The precipitation strongly influences the mechanical properties and is of high scientific and technological interest. 相似文献