Numerical analysis on various models of pressure snubbers in the hydrogen gas compressing system

This paper explains about numerical modeling of gas flow passing through a snubber, pulsation damper, in a hydrogen gas compressor system. The verification of the preliminary model was done successfully by comparing it with experimental results. Numerical analysis for various snubber dimensions is the focus of this present study. Thirty models of snubber were created by varying snubber height and buffer angle, and then simulated with the real working condition of a hydrogen gas compressing system. The CFD code package used was a Star CD with transient analysis and k-ε / high Reynolds number as the turbulence model. The study was done by comparing pressure loss and pressure pulsation, since these two parameters are the objective functions in snubber optimization. The best snubber is the one that has the minimum pressure loss and pressure pulsation. Numerical result shows that the pressure loss grows with the increment of snubber volume. To the contrary, however, the pressure pulsation is decreased. Determining the buffer angle as the adjusted variable, the minimum pressure loss occurred at 30°. But pressure pulsation trend was escalating.     

Field stimulation of cardiac fibers with random spatial structure

Polarization of individual cells ("sawtooth") has been proposed as a mechanism for field stimulation and defibrillation. To date, the modeling work has concentrated on the myocardium with periodic spatial structure; this paper investigates potentials arising in cardiac fibers with random spatial structure. Ten different random fibers consisting of cells with varying length (l(c) = 100 +/- 50 microm), diameter (d(c) = 20 +/- 10 microm), thickness of extracellular space (t(e) = 1.18 +/- 0.59 microm), and junctional resistance (R(j) = 2 +/- 1 M(omega)) are studied. Simulations demonstrate that randomizing spatial structure introduces to the field-induced potential (V(m)) a randomly varying baseline, which arises due to polarization of groups of cells. This polarization appears primarily in response to randomizing t(e); R(j), l(c), and d(c) have less influence. The maximum V(m) increases from 3.5 mV in a periodic fiber to 20.5+/-4.7 mV in random fibers (1 V/cm field applied for 5 ms). Field stimulation threshold E(th) decreases from 6.9 to 1.59 +/- 0.43 V/cm, which is within the range of experimental measurements. Thresholds for normal and reversed field polarities are statistically equivalent: 1.59 +/- 0.43 versus 1.44 +/- 0.41 V/cm (p value = 0.453). Thus, V(m) arising due to random structure of the myocardium may play an important role in field stimulation and defibrillation.     

The effect of acid treatment on dilatometric properties of coal

The demineralization of orthocoking coals by treatment with hydrochloric and hydrofluoric acids causes significant changes in their dilatometric properties. The changes are attributed to chemisorption of HCI and/or HF on basic nitrogen atoms present in pyridine-like structures as well as to physical adsorption of the acids. The orthcoking coals were also treated with naphthalene anion in tetrahydrofuran. It was found that the treatment leads to a decrease in melting point and to a considerable increase in dilatation.     

A study on Saccharomyces cerevisiae and Candida utilis cell wall capacity for binding magnesium

The capacity for binding magnesium by bakery's yeast strain Saccharomyces cerevisiae No. 102 (Pure Culture Collection, Faculty Food Technology, Warsaw) and fodder yeast strain Candida utilis (ATCC 9950) was investigated in media supplemented with that element. The capacities of C. utilis (ATCC 9950) and S. cerevisiae (No. 102) biomass for binding magnesium were not statistically different in the first 24 h. In the next 24 h of cultivation the cells of C. utilis (ATCC 9950) were still able to bind magnesium ions, whereas those of S. cerevisiae (No. 102) released a part of previously bound magnesium to the medium. The major part of magnesium bound by the cells of C. utilis (ATCC 9950) was accumulated in cytosole. It was opposite to the cells of bakery yeast S. cerevisiae (No. 102) that accumulated magnesium mainly in the cell wall. The cells of C. utilis (ATCC 9950) yeast were smaller and their cell walls were thinner as compared to those of S. cerevisiae (No. 102) yeast. The thickness of the external mannoprotein layers was similar in both strains analyzed.     

强制干燥条件对木家具水性封闭底漆水分挥发的影响

在温、湿度变化的强制干燥条件下,探讨在重涂间隔时间内干燥空气的温湿度对水分挥发量的影响以枫木薄木贴面家具板件为基材,以单组分水性封闭底漆为涂料,以空气温度、湿度为变量进行正交实验强制干燥涂层,研究涂层的水分挥发规律。结果表明,水性封闭底漆的干燥受临界温度和临界湿度的影响,温度、湿度以及两者的交互作用对水分挥发率均有显著影响,其中湿度的影响较大,温度其次,第三是两者的交互作用。较优的温湿度干燥条件为温度15℃、湿度30%     

A deeper understanding of the spontaneous derepression of the URA3 gene in MaV203 Saccharomyces cerevisiae and its implications for protein engineering and the reverse two-hybrid system

Within the field of protein-based biomaterials, the need exists for both covalent and oriented bioconjugation strategies for improved performance. Such bioconjugation reactions can be facilitated by engineering proteins with chemically activated amino acids at strategically chosen sites. The incorporation of these unnatural amino acids (uAAs) can be achieved by using the nonsense suppression technique. This requires an aminoacyl-tRNA-synthetase (aaRS) that exclusively recognizes the uAA and loads it to the corresponding tRNA. Appropriate (aaRS) mutants can be found through reverse engineering using the Saccharomyces cerevisiae strain MaV203. This strain contains a counterselectable, Gal4p-inducible SPAL10::URA3 fusion and deletions in the endogenous GAL80 and GAL4 genes. Therefore, it has been used extensively for the screening of aaRS mutant libraries. It is generally assumed that the SPAL10 promoter actively represses the URA3 gene in the absence of Gal4p, resulting in MaV203 cells with a Ura ⁻ phenotype. The current contribution reveals that in a small fraction of MaV203 cells, a basal expression of the URA3 gene occurs. The unexpected URA3 expression is reported for the first time, and the nature of the mutation causing this expression was identified as a spontaneous recessive mutation in a single gene of a protein involved in the repression of the SPAL10 promoter. The basal URA3 expression causes aaRS mutants to be missed, which affects the outcome of the library screening. It is demonstrated that the use of diploid cells can circumvent the MaV203 Ura⁺ phenotype, allowing for an optimization of S. cerevisiae library screening.     

Wayfinding by children and adults: Response to instructions to use look-back and retrace strategies.

The wayfinding abilities of 6- and 12-yr-old children were compared with those of 22-yr-old adults. After their 1st walk across a university campus, participants were asked to lead the way back along the same route. Participants in 2 conditions (look back and retrace) were given instructions intended to prevent wandering, whereas those in a 3rd (uninstructed) condition were only told that they were going on a tour. A series of instructions to look back at the return path increased subsequent travel on route by the 2 older age groups. Instructions to monitor the familiarity of landmarks and to stop and retrace to a known portion of the path when feeling unsure did not effectively reduce travel off route. In general, wayfinding performance by 12-yr-old children did not reliably differ from that of 22-yr-old adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trustworthiness in electronic commerce: the role of privacy, security, and site attributes

While the growth of business-to-consumer electronic commerce seems phenomenal in recent years, several studies suggest that a large number of individuals using the Internet have serious privacy concerns, and that winning public trust is the primary hurdle to continued growth in e-commerce. This research investigated the relative importance, when purchasing goods and services over the Web, of four common trust indices (i.e. (1) third party privacy seals, (2) privacy statements, (3) third party security seals, and (4) security features). The results indicate consumers valued security features significantly more than the three other trust indices. We also investigated the relationship between these trust indices and the consumer's perceptions of a marketer's trustworthiness. The findings indicate that consumers' ratings of trustworthiness of Web merchants did not parallel experts' evaluation of sites' use of the trust indices. This study also examined the extent to which consumers are willing to provide private information to electronic and land merchants. The results revealed that when making the decision to provide private information, consumers rely on their perceptions of trustworthiness irrespective of whether the merchant is electronic only or land and electronic. Finally, we investigated the relative importance of three types of Web attributes: security, privacy and pleasure features (convenience, ease of use, cosmetics). Privacy and security features were of lesser importance than pleasure features when considering consumers' intention to purchase. A discussion of the implications of these results and an agenda for future research are provided.