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排序方式: 共有198条查询结果,搜索用时 281 毫秒
61.
The adhesive properties of wear-resistant poly(m-, p-phenylene isophtalamide) coatings to substrates of ferrous and non-ferrous metal materials which are the most common in mechanical engineering were investigated experimentally. The results of measurements of adhesive characteristics taken with the help of such methods as a cross cutting test, a quantitative peel test, a lap shear strength test, a contact angle test and a spreading radius test are discussed in terms of the three most common mechanisms of adhesion: mechanical coupling, molecular bonding, and thermodynamic adhesion. It was established that the adhesive properties of poly(m-, p-phenylene isophtalamide) coatings depend on the content of a ferrite component in the structure of carbon steel substrates. 相似文献
62.
Gulsum Melike Urper Reyhan Sengur-Tasdemir Turker Turken Volodymyr V. Tarabara Ismail Koyuncu 《分离科学与技术》2017,52(13):2120-2136
Membrane-based separation is now established as one of staple technologies used in water treatment and reuse applications. Nanofiltration, in particular, can be a cost-effective solution for removing large ions and low-molecular-weight compounds from water. Nanofiltration membranes have been manufactured mostly as flat sheets and used in spiral wound modules. Hollow fiber geometry, however, offers several advantages over flat sheet and other configurations. This paper overviews recent developments in the design of hollow fiber nanofiltration membranes and provides a comparative analysis of two main methods of their fabrication: interfacial polymerization and phase inversion. 相似文献
63.
Adam Olichwier Volodymyr V. Balatskyi Marcin Wolosiewicz James M. Ntambi Pawel Dobrzyn 《International journal of molecular sciences》2021,22(1)
Stearoyl-CoA desaturase 1 (SCD1), an enzyme that is involved in the biosynthesis of monounsaturated fatty acids, induces the reprogramming of cardiomyocyte metabolism. Thyroid hormones (THs) activate both lipolysis and lipogenesis. Many genes that are involved in lipid metabolism, including Scd1, are regulated by THs. The present study used SCD1 knockout (SCD1−/−) mice to test the hypothesis that THs are important factors that mediate the anti-steatotic effect of SCD1 downregulation in the heart. SCD1 deficiency decreased plasma levels of thyroid-stimulating hormone and thyroxine and the expression of genes that regulate intracellular TH levels (i.e., Slc16a2 and Dio1-3) in cardiomyocytes. Both hypothyroidism and SCD1 deficiency affected genomic and non-genomic TH pathways in the heart. SCD1 deficiency is known to protect mice from genetic- or diet-induced obesity and decrease lipid content in the heart. Interestingly, hypothyroidism increased body adiposity and triglyceride and diacylglycerol levels in the heart in SCD1−/− mice. The accumulation of triglycerides in cardiomyocytes in SCD1−/− hypothyroid mice was caused by the activation of lipogenesis, which likely exceeded the upregulation of lipolysis and fatty acid oxidation. Lipid accumulation was also observed in the heart in wildtype hypothyroid mice compared with wildtype control mice, but this process was related to a reduction of triglyceride lipolysis and fatty acid oxidation. We also found that simultaneous SCD1 and deiodinase inhibition increased triglyceride content in HL-1 cardiomyocytes, and this process was related to the downregulation of lipolysis. Altogether, the present results suggest that THs are an important part of the mechanism of SCD1 in cardiac lipid utilization and may be involved in the upregulation of energetic metabolism that is associated with SCD1 deficiency. 相似文献
64.
65.
This paper presents a poly(dimethyl siloxane) (PDMS) polymer microfluidic device using alternating current (ac) dielectrophoresis (DEP) for separating live cells from interfering particles of similar sizes by their polarizabilities under continuous flow and for characterizing DEP behaviors of cells in stagnant flow. The ac-DEP force is generated by three-dimensional (3D) conducting PDMS composite electrodes fabricated on a sidewall of the device main channel. Such 3D PDMS composite electrodes are made by dispersing microsized silver (Ag) fillers into PDMS gel. The sidewall AgPDMS electrodes can generate a 3D electric field that uniformly distributes throughout the channel height and varies along the channel lateral direction, thereby producing stronger lateral DEP effects over the entire channel. This allows not only easy observation of cell/particle lateral motion but also using the lateral DEP force for manipulation of cells/particles. The former feature is used to characterize the frequency-dependent DEP behaviors of Saccharomyces cerevisiae (yeast) and Escherichia coli (bacteria). The latter is utilized for continuous separation of live yeast and bacterial cells from similar-size latex particles as well as live yeast cells from dead yeast cells. The separation efficiency of 97% is achieved in all cases. The demonstration of these functions shows promising applications of the microfluidic device. 相似文献
66.
Pervak V 《Applied optics》2011,50(9):C55-C61
A dispersive-mirror-based laser permits a dramatic simplification of high-power femtosecond and attosecond systems and affords promise for their further development toward shorter pulse durations, higher peak powers, and higher average powers with user-friendly systems. The result of the continuous development of dispersive mirrors permits pulse compression down to almost single cycle pulses of 3?fs duration. These design approaches together with the existing modern deposition technology pave the way for the manufacture of dielectric multilayer coatings able to compress pulses of tens of picoseconds duration down to a few femtoseconds. 相似文献
67.
Daniela-Monica Hangan Volodymyr Bobkov Franz Braun Rodolphe D’Inca Helmut Faugel Jean-Marie Noterdaeme 《Fusion Engineering and Design》2011,86(6-8):736-741
The ICRF (Ion Cyclotron Range of Frequencies) system, used to heat the plasma of ASDEX Upgrade, consists of RF generators, 3 dB hybrids, coaxial transmission lines, matching networks and inductive loop antennas. The maximum power achievable by the generator strongly depends on the amplitude and phase of the reflection coefficient. Hence, matching of the antenna input impedance to the generator output impedance is essential for the ICRF heating system. The coupling between the ICRF antennas and the plasma is subject to relatively fast variations (few ms). The changes are caused by the modification of plasma edge conditions, such as L–H mode transitions, gas puffing or ELMs (Edge Localized Modes). These variations change the impedance of the ICRF antennas. For optimal operation of the ICRF system, a continuous, and fast matching is therefore preferable. A MATLAB® based simulation tool has been developed to analyse matching networks for the ICRF system at ASDEX Upgrade. The program is highly flexible, and can solve the matching calculations for different conditions and configurations of the system. The results are presented in a Smith chart. 相似文献
68.
Tryndyak VP Han T Muskhelishvili L Fuscoe JC Ross SA Beland FA Pogribny IP 《Molecular nutrition & food research》2011,55(3):411-418
Scope : A methyl‐deficient diet induces liver injury similar to human nonalcoholic steatohepatitis, one of the main risk factors for the development of hepatocellular carcinoma. Previous studies have demonstrated that this diet perturbs DNA methylation by causing a profound loss of global cytosine methylation, predominantly at heavily methylated repetitive sequences. However, whether methyl deficiency affects the methylation status of gene promoters has not been explored. Methods and results : Mouse gene expression and CpG island microarrays were used to characterize the gene expression and CpG island methylation profiles in the livers of C57BL/6J mice fed a methyl‐deficient diet. We detected 164 genes that were differentially expressed and exhibited an inverse relationship between the gene expression and the extent of CpG island methylation. Furthermore, these genes were associated with altered lipid and glucose metabolism, DNA damage and repair, apoptosis, the development of fibrosis, and liver tissue remodeling. Although there were both increased and decreased levels of CpG island methylation, the number of hypomethylated genes was substantially greater than the number of hypermethylated genes. Conclusion : The results this study demonstrate that pairing methylation profiles with gene expression profiles is a powerful approach to identify dysregulated high‐priority fundamental pathophysiological pathways associated with disease development. 相似文献
69.
Volodymyr Serhiyenko John N. Ivan Nalini Ravishanker Md Saidul Islam 《Accident; analysis and prevention》2014
Uncovering the temporal trend in crash counts provides a good understanding of the context for pedestrian safety. With a rareness of pedestrian crashes it is impossible to investigate monthly temporal effects with an individual segment/intersection level data, thus the time dependence should be derived from the aggregated level data. Most previous studies have used annual data to investigate the differences in pedestrian crashes between different regions or countries in a given year, and/or to look at time trends of fatal pedestrian injuries annually. Use of annual data unfortunately does not provide sufficient information on patterns in time trends or seasonal effects. This paper describes statistical methods uncovering patterns in monthly pedestrian crashes aggregated on urban roads in Connecticut from January 1995 to December 2009. We investigate the temporal behavior of injury severity levels, including fatal (K), severe injury (A), evident minor injury (B), and non-evident possible injury and property damage only (C and O), as proportions of all pedestrian crashes in each month, taking into consideration effects of time trend, seasonal variations and VMT (vehicle miles traveled). This type of dependent multivariate data is characterized by positive components which sum to one, and occurs in several applications in science and engineering. We describe a dynamic framework with vector autoregressions (VAR) for modeling and predicting compositional time series. Combining these predictions with predictions from a univariate statistical model for total crash counts will then enable us to predict pedestrian crash counts with the different injury severity levels. We compare these predictions with those obtained from fitting separate univariate models to time series of crash counts at each injury severity level. We also show that the dynamic models perform better than the corresponding static models. We implement the Integrated Nested Laplace Approximation (INLA) approach to enable fast Bayesian posterior computation. 相似文献
70.
Michael Bratychak Witold Brostow Volodymyr Donchak 《Materials Research Innovations》2002,5(6):250-256
A series of peroxy oligomers has been synthesized on the basis of pyromellitic dianhydride and tetrachloroanhydride of pyromellitic
acid by condensation with polyethylene glycols and tert-butylhydroperoxide. The resulting oligoesters contain two types of functional groups: carboxylic – which can participate
in ionic reactions and peroxide – able to initiate certain radical processes. Concentrations of these groups depend on the
method of synthesis, the nature of starting monomers, and the molecular mass of polyethylene glycol. Structures of oligoesters
have been determined by IR and 1H-NMR spectroscopy. The oligoesters are able to form three-dimensional networks when heated to 400 K. A mechanism of the network
formation is proposed. These materials can be used as curing agents for unsaturated polyesters and also for epoxy + unsaturated
polyester resin compositions.
Electronic Publication 相似文献