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51.
52.
Ivan Jirka Marta Vandrovcová Otakar Frank Zdeněk Tolde Jan Plšek Thomas Luxbacher Lucie Bačáková Vladimír Starý 《Materials science & engineering. C, Materials for biological applications》2013,33(3):1636-1645
β-Stabilized titanium (Ti) alloys containing non-toxic elements, particularly niobium (Nb), are promising materials for the construction of bone implants. Their biocompatibility can be further increased by oxidation of their surface. Therefore, in this study, the adhesion, growth and viability of human osteoblast-like MG 63 cells in cultures on oxidized surfaces of a β-TiNb alloy were investigated and compared with the cell behavior on thermally oxidized Ti, i.e. a metal commonly used for constructing bone implants. Four experimental groups of samples were prepared: Ti or TiNb samples annealed to 600 °C for 60 min in a stream of dry air, and Ti and TiNb samples treated in Piranha solution prior to annealing. We found that on all TiNb-based samples, the cell population densities on days 1, 3 and 7 after seeding were higher than on the corresponding Ti-based samples. As revealed by XPS and Raman spectroscopy, and also by isoelectric point measurements, these results can be attributed to the presence of T-Nb2O5 oxide phase in the surface of the alloy sample, which decreased its negative zeta (ζ)-potential in comparison with zeta (ζ)-potential of the Ti sample at physiological pH. This effect was tentatively explained by the presence of positively charged defects acting as Lewis sites of the surface Nb2O5 phase. Piranha treatment slightly decreases the biocompatibility of the samples, which for the alloy samples may be explained by a decrease in the number of defective sites with this treatment. Thus, the presence of Nb and thermal oxidation of β-stabilized Ti alloys play a significant role in the increased biocompatibility of TiNb alloys. 相似文献
53.
Zdeňka Kolská Alena ?ezní?ková Vladimír Hnatowicz Václav ?vor?ík 《Journal of Materials Science》2012,47(17):6429-6435
Surface properties of commercially available poly(ethylene terephthalate) (PET) foils of different thicknesses (3, 13, 23, 50, and 100 μm) were characterized using different analytical methods. Surface roughness and morphology were determined by atomic force microscopy, goniometry was used for determination of contact angle (wettability of surface) and electrokinetical analysis (zeta potential) for characterization of surface polarity and conductivity. X-ray photoelectron spectroscopy was used for characterization of PET surface chemistry. Infrared spectroscopy and differential scanning calorimetry (DSC) were used for determination of crystallinity portion. By DSC analysis, it was confirmed that the crystallinity portion depends on the foil thickness. Most important result of this study is that the surface properties of PET foils depend not only on the foil thickness but also on the foil side under study. This finding may be of importance for future experiments performed on PET foils and for their application in tissue engineering or microelectronics. 相似文献
54.
Amplified oligonucleotide sensing in microliter volumes containing copper ions by solution streaming
We present a simple, cost-effective design for amplifying oligodeoxynucleotide (ODN) sensing, in microliter ODN volumes containing copper ions, by solution streaming (bubbling). The inert gas streaming (bubbling) at a constant pressure of 0.04 bar drives the motion of a 30-microL ODN droplet containing a three-electrode circuit (inverted drop microcell), and in the presence of copper ions offers an approximately 50-times improvement in the detection of ODN samples. The detection of ODNs at the carbon paste electrode is based on the enhancement of the oxidation peaks of purine bases (adenine and guanine) by the anodic stripping of the electrochemically accumulated complex of Cu(I) with purine base residues of acid hydrolyzed ODN samples (Cu(I)-ahODN complex). We used the proposed method for (i) the determination of the percentage content of adenine and guanine units within analyzed ODN samples at subnanomolar concentrations (related to monomer content) and (ii) the detection of the (TTC)n triplet expansion using magnetic DNA hybridization with reporter probes containing guanine units (the TTC trinucleotide repeat expansion is associated with serious hereditary diseases, including Friedreich ataxia). 相似文献
55.
Jean Titze Manuel Christian Fritz Jacob Harun Parlar Vladimír Ilberg 《Journal of the Institute of Brewing》2010,116(4):405-412
Long‐term stability is one of the most important quality criteria of beer. Three groups of measuring methods are available for its determination: real time tests, predictive tests and indicative tests. One of the most common methods is the predictive forcing test, which is a time‐consuming method for accelerating beer ageing, e.g., at 0°C and 60°C. Two ways exist to perform this test: (1) follow‐up of haze development and determination of the lag phase or (2) the measurement of haze values after several days. The first option was evaluated by performing a long‐term Forcing test over a period of 4 months by analyzing a bottom‐fermented beer. It was shown that the haze curve followed a typical course with a lag phase, an increase phase and a stationary phase. Significant differences between the measurement after the cooling and the warm period were shown. In search of quicker methods and more accurate predictive indicators, the charge titration method was developed as an alternative to determine the particle charge of filtered beers, whereupon the relationship was elucidated between the increase in hazing and decrease of potential along with the advanced aging of beer. The results showed that with increased particle size due to agglomeration, the total charge decreased. In this array of trials, two differently stabilized beers were examined. Although both beers showed different haze values in the beginning (0.32 EBC and 1.30 EBC), the less stabilized beer had only 10 warm days and in contrast the beer with the good stabilization had over 20 warm days. With the help of the total charge, predictions were possible regarding the long‐term stability of the beer. 相似文献
56.
Dr. Maroš Bella Dr. Monika Poláková Dr. Vladimír Puchart 《Chembiochem : a European journal of chemical biology》2023,24(9):e202200743
A chemical synthesis of two novel phenyl glycosides of trisaccharides related to acetylarabinoxylan is described. The trisaccharides bear acetyl and arabinofuranosyl moieties at the non-reducing-end xylopyranosyl residue, which is substituted at positions 2 and 3. Both compounds were treated with various xylan deacetylases classified in different carbohydrate esterase (CE) families and significant differences between the families were found. While the arabinosylation hampers deacetylation by CE2-CE5 and CE12 family members, both epitopes are deesterified by CE1 and in particular CE6 enzymes. The 3-O-acetylated 2-O-arabinosylated compound is also processed by CE7 and majority of CE16 esterases, but not by a hitherto non-classified Flavobacterium johnsoniae acetylxylan esterase. The data suggests that a slow deesterification of the 2-O-acetylated 3-O-arabinosylated compound may be due to the acetyl group migration followed by deacetylation of this migration product. 相似文献
57.
Koľveková Gabriela Raisová Manuela Zoričak Martin Gazda Vladimír 《Computational Economics》2021,58(1):57-81
Computational Economics - Population growth and greater human well-being imply increased use of scarce resources, which makes innovative proposals for fair redistribution policies necessary. The... 相似文献
58.
59.
Vladimír Bužek 《Journal of Modern Optics》2013,60(4):801-812
Abstract We analyse the dynamics of the q-deformed quantum harmonic oscillator initially prepared in the q-analogue of the coherent state. Non-trivial behaviour of the mean values of the q-position operator is observed. The squeezing of the second-order moments of this operator is studied. 相似文献
60.
Jan Rathouský Vladimír Havlena 《International Journal of Adaptive Control and Signal Processing》2013,27(11):974-999
This paper proposes a method to approximate a dual controller by a computationally feasible algorithm. Dual control that optimally solves the problem of simultaneous control and identification of a system with uncertain parameters is known to be both analytically and computationally unsolvable. This paper proposes a multiple‐step active control algorithm that gives a suboptimal but tractable solution to the original dual control problem. The algorithm is based on model predictive control (MPC) and approximates persistent system excitation in terms of the increase of the lowest eigenvalue of the parameter estimate information matrix. The problem is formulated as a two‐phase optimization problem, where first an MPC solution is found and then the lowest eigenvalue of the information matrix is maximized in the next step within a given permitted input perturbation. Unlike similar methods, the proposed algorithm predicts the information matrix for more than one step of control, which makes it possible to uniformly excite the parameter space. The use of MPC in the first design phase instead of a cautious controller is justified by showing unfavorable properties of cautious control. The advantage of the multiple‐step prediction over single‐step prediction is shown by examples and simulations. The proposed algorithm is analyzed in terms of convergence and complexity, and stability issues are addressed. The formal proofs are included in the Appendix. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献