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排序方式: 共有132条查询结果,搜索用时 156 毫秒
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22.
Domijan AM Peraica M Vrdoljak AL Radić B Zlender V Fuchs R 《Molecular nutrition & food research》2007,51(9):1147-1151
The aim of this study was to find out whether very low doses of nephrotoxic and hepatotoxic mycotoxins ochratoxin A (OTA) and fumonisin B1 (FB1) induce oxidative stress in rat kidney and liver and whether their effect is synergistic. Rats were treated orally with OTA (5 ng/kg b.w. and 50 microg/kg b.w.) and FB1 (200 ng/kg b.w. and 50 microg/kg b.w.), or their combinations. Malondialdehyde (MDA) and protein carbonyls (PCs) concentration in kidney was affected with lower dose of OTA than in liver (p<0.05). FB1 did not affect MDA and PCs concentrations in the liver, while in the kidney both FB1 doses increased MDA concentration (p<0.05). The combination of the lower doses of OTA+FB1 increased the MDA and PCs concentration both in the liver and the kidney, compared to controls and animals treated with respective doses of mycotoxins (p<0.05). The combinations of mycotoxins reduced the catalase activity only in the kidney when compared to controls (p<0.05). In contrast to the increased kidney concentrations of MDA and PCs even with very low doses of OTA and FB1, the activity of catalase and SOD does not change. Combinations of OTA+FB1 affected almost all parameters, which indicates their potential to produce oxidative damage. 相似文献
23.
Taxt T Jirík R Rygh CB Grüner R Bartos M Andersen E Curry FR Reed RK 《IEEE transactions on bio-medical engineering》2012,59(4):1012-1021
Multipass dynamic MRI and pharmacokinetic modeling are used to estimate perfusion parameters of leaky capillaries. Curve fitting and nonblind deconvolution are the established methods to derive the perfusion estimates from the observed arterial input function (AIF) and tissue tracer concentration function. These nonblind methods are sensitive to errors in the AIF, measured in some nearby artery or estimated by multichannel blind deconvolution. Here, a single-channel blind deconvolution algorithm is presented, which only uses a single tissue tracer concentration function to estimate the corresponding AIF and tissue impulse response function. That way, many errors affecting these functions are reduced. The validity of the algorithm is supported by simulations and tests on real data from mouse. The corresponding nonblind and multichannel methods are also presented. 相似文献
24.
This paper contains investigations of wear particles generated during the erosive wear of four different concrete, mixtures by high velocity water flow at velocities of about 700 m/s.i The wear particles were collected, dried and analyzed by sieve experiments. Based on the sieve analysis, specific surface and average grain diameter of the particle samples were estimated. 'Using simple, comminution relations, the specific crack length of every' sample is calculated. It is shown that all estimated parameters exhibit a strong relationship to characteristic material properties, such as compressive strength, Young's modulus, and absorbed fracture energy. It was found by regression analysis that the average debris wear size can be effectively characterized by the absorbed fracture energy of the concrete sample. It is concluded that these relations are the result of different paths of fracture propagation through the materials during the generation of a microcrack network. 相似文献
25.
Fanrong Kong S. Santhanakrishnan Radovan Kovacevic 《The International Journal of Advanced Manufacturing Technology》2013,68(9-12):2419-2430
The direct diode laser application has been found useful in the localized heat treatment of metal parts because of its wider beam and more uniform energy distribution with respect to other lasers with Gaussian-like energy distribution. In this study, an uncoupled thermomechanical finite element model is developed to study the temperature field and thermally induced stress evolution in high-strength dual phase (DP) 980 steel during its direct diode laser heat treatment. Thermal analysis results are experimentally validated through thermocouples and then input into a mechanical model as transient temperature loading in order to acquire the thermally induced stresses and strains. The effect of martensite phase transformation on residual stress distribution in heat-treated DP980 steel is considered. An X-ray diffraction technique is used to measure the residual stress distribution at the top surface of the heat-treated coupons of DP980 steel. The numerical results show that compressive stresses are located at the laser–material interaction zone. After heat treatment, tensile stresses are retained at the heat-treated DP980 steel coupons. There is qualitative agreement between the numerically predicted and experimentally measured residual stresses. The effect of the overlapping ratio on the residual stress and hardness of the heat-treated DP980 steel is also experimentally and numerically investigated. 相似文献
26.
Gilbert Chahine Mari Koike Toru Okabe Pauline Smith Radovan Kovacevic 《JOM Journal of the Minerals, Metals and Materials Society》2008,60(11):50-55
This paper addresses the production of customized Ti-6Al-4V ELI dental implants via electron beam melting (EBM). The melting
of Ti-6Al-4V ELI powder produces implants with great biocompatibility, fi ne mechanical performance, and a high bone ingrowth
potential. The EBM technology is used to produce one-component dental implants that mimic the exact shape of the patient’s
tooth, replacing the traditional, three-component, “screw-like” standardized dental implants currently used. The new generation
of implants provides the possibility of simplifying pre-insertion procedures leading to faster healing time, and the potential
of better and stronger osseointegration, specifi cally through incorporating lattice structure design. 相似文献
27.
Monitoring the depth of abrasive waterjet penetration 总被引:1,自引:0,他引:1
In order to control the uniformity of the abrasive waterjet penetration into the workpiece, it is necessary to devise a monitoring methodology that can indirectly monitor the depth of abrasive waterjet penetration. It was shown that the workpiece normal force generated by an abrasive waterjet could be used as the indicator of the depth of jet penetration, and that a force-feedback control holds promise as an effective way to regulate the depth of jet penetration. The effects of different abrasive waterjet process variables on both the depth of cut and the workpiece normal force are discussed. 相似文献
28.
Dr. Julio C. González‐Olvera Dr. Matúš Durec Dr. Radek Marek Dr. Radovan Fiala Dr. María del Rosario J. Morales‐García Dr. Eva González‐Jasso Dr. Reynaldo C. Pless 《Chembiochem : a European journal of chemical biology》2018,19(19):2088-2098
Single‐stranded model oligodeoxyribonucleotides, each containing a single protonatable base—cytosine, adenine, guanine, or 5‐methylcytosine—centrally located in a background of non‐protonatable thymine residues, were acid‐titrated in aqueous solution, with UV monitoring. The basicity of the central base was shown to depend on the type of the central base and its nearest neighbours and to rise with increasing oligonucleotide length and decreasing ionic strength of the solution. More complex model oligonucleotides, each containing a centrally located 5‐methylcytosine base, were comparatively evaluated in single‐stranded and double‐stranded form, by UV spectroscopy and high‐field NMR. The N3 protonation of the 5‐methylcytosine moiety in the double‐stranded case occurred at much lower pH, at which the duplex was already experiencing general dissociation, than in the single‐stranded case. The central guanine:5‐methylcytosine base pair remained intact up to this point, possibly due to an unusual alternative protonation on O2 of the 5‐methylcytosine moiety, already taking place at neutral or weakly basic pH, as indicated by UV spectroscopy, thus suggesting that 5‐methylcytosine sites in double‐stranded DNA might be protonated to a significant extent under physiological conditions. 相似文献
29.
Tomáš Ferdan Martin Pavlas Vlastimír Nevrlý Radovan Šomplák Petr Stehlík 《Frontiers of Chemical Science and Engineering》2018,12(4):815-831
This paper analyses factors affecting the production of greenhouse gases from the treatment of residual municipal waste. The analysis is conducted so that the environmentally-friendly decision-making criteria may be later implemented into an optimisation task, which allocates waste treatment capacities. A simplified method of life cycle assessment is applied to describe environmental impact of the allocation. Global warming potential (GWP) is employed as a unit to quantify greenhouse gases (GHG) emissions. The objective is to identify the environmental burdens and credits measured by GWP for the three fundamental methods for treatment of residual waste unsuitable for material recovery. The three methods are waste-to-energy (WTE), landfilling and mechanicalbiological treatment (MBT) with subsequent utilization of refuse-derived fuel. The composition of the waste itself and content of fossil-derived carbon and biogenic carbon are important parameters to identify amounts of GHG. In case of WTE, subsequent use of the energy, e.g., in district heating systems in case of heat, is another important parameter to be considered. GWP function dependant on WTE capacity is introduced. The conclusion of this paper provides an assessment of the potential benefits of the results in optimisation tasks for the planning of overall strategy in waste management.
相似文献
30.
Radovan Toth Alessandro Coslanich Maurizio Fermeglia Stanislav Miertus 《Polymer》2004,45(23):8075-8083
Molecular simulation techniques are used to explore and characterize the atomic scale structure, and to predict binding energies and basal spacing of polymer/clay nanocomposites based on polypropylene (PP) and maleated polypropylene (PPMA), montmorillonite (MMT), and different alkylammonium ions (quats) as surfactants. Our evidences suggest that shorter hydrocarbonic chains are more effective in producing favorable binding energies with respect to longer ones, and the substitutions of hydrogen atoms with polar groups on the quaternary ammonium salt (quat) generally results in greater interaction between quat and both polymer and clay. Under the hypothesis, that montmorillonite platelets are uniformly dispersed in a polymer matrix, the modified polypropylene yields higher interfacial strength with clay than neat polypropylene. The use of neat PP and quats with higher molecular volume offer the higher values of the basal spacing and thus, in principle, they should be more effective in the exfoliation process. 相似文献