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71.
Beata Butruk Maciej Trzaskowski Tomasz Ciach 《Materials science & engineering. C, Materials for biological applications》2012,32(6):1601-1609
In this paper the authors present a simple method of coating polyurethane (PU) surface with poly(vinyl pirrolidone) (PVP) hydrogel. The hydrogel-coated materials were designed for use in biomedical applications, especially in blood-contacting devices. The coating is formed due to free radical macromolecular grafting–crosslinking. Polymer surface was first immersed in an organic solution containing radical source: cumene hydroperoxide (CHP) with an addition of a branching and anchoring agent: ethylene glycol dimethylacrylate (EGDMA). In the second step, the substrate was immersed in a water solution containing given concentration of PVP and Fe2+. The novelty of the process consists in the fact that free radicals are formed mostly at the polymer/solution interface, what assures high grafting efficiency together with the formation of covalent bonds between polymer substrate and modifying layer.The process was optimized for reagents concentrations. The coating properties: thickness and the swelling ratio were strongly influenced by CHP, Fe2+, PVP and EGMDA concentrations. The chemical composition of the surface analyzed with FTIR-ATR spectroscopy confirmed the presence of PVP coating. In vitro biocompatibility tests with L929 fibroblasts confirmed non-cytotoxicity of the coatings. Hydrogel coating significantly improved polyurethane hemocompatibility. Studies with human whole blood revealed that both, the platelet consumption and the level of platelet activation were as low as for negative control. 相似文献
72.
Tomasz WilkAuthor VitaeMichal WozniakAuthor Vitae 《Neurocomputing》2012,75(1):185-193
The paper shows the possibilities of generalizing the two-class classification into multi-class classification by means of a fuzzy inference system. Fuzzy combiner harnesses the support values from classifiers to provide final response having no other restrictions on their structure. We compare proposed combination methods with ECOC and two variations of decision templates, based on Euclidean and symmetric distance. The effectiveness of the proposed combination method based on the fuzzy logic theory is also evaluated via computer experiments carried out on benchmark datasets. 相似文献
73.
This paper presents the design of an open photoacoustic Helmholtz cell in which high acoustic volumes with quarter-wave ducts act as high-impedance separators between the main Helmholtz cell structure and the exterior. As a result, penetration of the external acoustic noise into the cell was substantially reduced in comparison to earlier open Helmholtz cell designs. Although the presented cell is not windowless, the photoacoustic background signal resulting from the absorption of the light by the windows is significantly lower in comparison to standard Helmholtz cells. Such an effect was obtained by locating the windows not at the relatively small sample cavity, but at the acoustic buffers, for which the volumes are two orders of magnitude higher. The proposed cell is dedicated for gas or liquid measurements, and its design allows for constant flow of the fluid. Hence, it can be used in continuous, real-time photoacoustic measurements. 相似文献
74.
Ewa Watorek Tomasz Golebiowski Mariusz Kusztal Krzysztof Letachowicz Waldemar Letachowicz Hanna Augustyniak Bartosik Jerzy Garcarek Katarzyna Madziarska Wacław Weyde Marian Klinger 《Hemodialysis international. International Symposium on Home Hemodialysis》2014,18(1):113-117
Elderly patients, defined as octogenarians and nonagenarians, are an increasing population entering renal replacement therapy. Advanced age appears as an exclusive factor negatively influencing dialysis practice. Elderly patients are referred late for the initiation of hemodialysis and more likely are offered catheters rather than arteriovenous fistulae (AVF), which increase mortality and negatively affect quality of life. We present our approach to the creation of vascular access for hemodialysis in this demanding population. In 2006–2012, 39 patients aged 85.9 ± 2.05 with end‐stage renal disease, mainly resulting from ischemic nephropathy, were admitted to the Department of Nephrology to establish permanent vascular access for hemodialysis: preferably AVF. Temporary dialysis catheters were implanted in uremic emergency to bridge the time to fistula creation/maturation. AVF was attempted in 87.2% of the patients. Primary AVF function was achieved in 54% of the patients. Cumulative proportional survival of AVF at months 12 and 24 was 81.5%. Ninety‐four percent of AVF were localized on the forearm: 74% in the distal and 20% in the proximal part. Mean duration of hemodialysis therapy was 20.80 ± 19.45 months. The mean time of AVF use was 15.9 ± 20.2 months. Until present, 38% have been dialyzed using AVF for 31.0 ± 18.8 months. Five patients died with functioning fistula. Eight patients initiated hemodialysis therapy with fistula. During further observation, the use of AVF increased to 62%. Elderly patients should not be denied creation of AVF as a rule. The outcome of AVF benefits more from acknowledging individual vascular conditions rather than age of the patient. 相似文献
75.
Cecilia Poletti Tomasz Wójcik Christof Sommitsch 《Metallurgical and Materials Transactions A》2013,44(3):1577-1586
Hot deformation of AA6082 aluminum alloy was studied by compression tests carried out between 573 K and 823 K (300 °C and 550 °C) under a wide range of strain rates. Light optical and scanning electron microscopy were used to study the as-received microstructure, which consisted of elongated, partially recrystallized grains containing fine Mg2Si and AlFeMnSi particles. The hot-deformed material showed the effects of dynamic recovery, i.e., small low angle grain boundary formation and dislocation pinning by fine particles. The flow data were used to calculate the constitutive equations, obtaining high values of n exponent. This behavior was attributed to the interaction of particles with dislocations during hot deformation. Threshold stresses were introduced to adjust the constitutive equation to a n exponent value of 5 at high stresses and a value of 3 in the low stresses range, which was related to dislocations’ climbing and sliding and thus to dynamic recovery. The threshold values were related to the detachment stresses in close connection with the precipitation state which was a function of the deformation temperature. 相似文献
76.
Tomasz A. Prokop Katarzyna Berent Hiroshi Iwai Janusz S. Szmyd Grzegorz Brus 《International Journal of Hydrogen Energy》2018,43(21):10016-10030
In this paper a fully three dimensional, multiphase, micro-scale solid oxide fuel cell anode transport phenomena numerical model is proposed and verified. The Butler-Volmer model was combined with empirical relations for conductivity and diffusivity - notably the Fuller-Shetler-Giddings equation, and the Fickian model for transport of gas reagents. FIB-SEM tomography of a commercial SOFC stack anode was performed and the resulting images were processed to acquire input data. A novel method for estimating local values of Triple Phase Boundary length density for use in a three-phase, three-dimensional numerical mesh was proposed. The model equations are solved using an in-house code and the results were verified by comparison to an analytical solution within the range of its applicability. A limited parametric study was performed to qualitatively assess simulation performance and impact of heterogeneity. Despite the high dependence of the SOFC anode performance on the geometry of its anisotropic, three-phase microstructure there are very few micro-scale numerical models simulating transport phenomena within these electrodes. 相似文献
77.
Tomasz Piechowiak Piotr Antos Radosław Józefczyk Patryk Kosowski Karol Skrobacz 《臭氧:科学与工程》2019,41(4):376-385
In the studies conducted, the impact of the innovative ozonation procedure on the microbial state and antioxidant potential of highbush blueberry (Vaccinum corymbosum L.) stored under cold storage conditions was assessed. Microbiological analysis was carried out to determine the total number of mesophilic aerobic bacteria and the total number of fungi during the storage experiment. In addition, changes in the flavonoid, anthocyanins, and vitamin C content and the total antioxidant capacity were monitored during the storage. The degree of fruit infection with gray mold and anthracnose was determined. It was found that daily ozonation of fruits with a dose of 15 ppm for 30 min, every 12 h, for 28 days effectively reduced the development of aerobic mesophilic bacteria and fungi. On the last day of storage, symptoms of the infection by gray mold were observed in 27.5% of the control fruit, while the absence of symptoms was observed in case of the ozonated fruit. On the other hand, ozone was ineffective in case of inhibiting the infection by anthracnose. Nevertheless, the ozonation process allowed maintaining a high antioxidant potential of the fruit and substantially reduced losses of flavonoids, anthocyanins, and vitamin C. The utilized procedure has proved to be effective, providing the possibility of extensive use of ozone as a factor allowing sustaining a high commercial and consumption value of the fruit over extended time. 相似文献
78.
79.
Tomasz Gancarz Katarzyna Berent Wojciech Skuza Katarzyna Janik 《Metallurgical and Materials Transactions A》2018,49(7):2684-2691
Magnesium has applications in the automotive and aerospace industries that can significantly contribute to greater fuel economy and environmental conservation. The Mg alloys used in the automotive industry could reduce mass by up to 70 pct, providing energy savings. However, alongside the advantages there are limitations and technological barriers to use Mg alloys. One of the advantages concerns phenomena occurring at the interface when joining materials investigated in this study, in regard to the effect of temperature and soldering time for pure Mg joints. Eutectic Zn-Al and Zn-Al alloys with 0.05 (wt pct) Li and 0.2 (wt pct) Na were used in the soldering process. The process was performed for 3, 5, and 8 minutes of contact, at temperatures of 425 °C, 450 °C, 475 °C, and 500 °C. Selected, solidified solder-substrate couples were cross-sectioned, and their interfacial microstructures were investigated by scanning electron microscopy. The experiment was designed to demonstrate the effect of time, temperature, and the addition of Li and Na on the kinetics of the dissolving Mg substrate. The addition of Li and Na to eutectic Zn-Al caused to improve mechanical properties. Higher temperatures led to reduced joint strength, which is caused by increased interfacial reaction. 相似文献
80.
The studies of soldered joints were carried out in systems: Al/solder/Al, Al/solder/Cu, Cu/solder/Cu, where the solder was (Al-Zn)EUT, (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Ag and (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Cu addition. Brazing was performed at 500 °C for 3 min. The EDS analysis indicated that the composition of the layers starting from the Cu pad was CuZn, Cu5Zn8, and CuZn4, respectively. Wetting tests were performed at 500 °C for 3, 8, 15, and 30 min, respectively. Thickness of the layers and their kinetics of growth were measured based on the SEM micrographs. The formation of interlayers was not observed from the side of Al pads. On the contrary, dissolution of the Al substrate and migration of Al-rich particles into the bulk of the solder were observed. 相似文献