bluuebunny/crossref_metadata_2025_split huggingface dataset:
Virulence Mechanisms of Coccidioides
Authors: HUNG CHIUNG‐YU , XUE JIANMIN , COLE GARRY T. 
Published: October 2007

Abstract:
Coccidioides is a fungal respiratory pathogen of humans that can cause disease in both immunosuppressed and immunocompetent individuals. We describe here three mechanisms by which the pathogen survives in the hostile host environment: production of a dominant spherule outer wall glycoprotein (SOWgp) that modulates host immune response and results in compromised cell‐mediated immunity to coccidioidal infection, depletion of SOWgp presentation on the surface of endospores, which prevents host recognition of the pathogen when the fungal cells are most vulnerable to phagocytic defenses, and induction of elevated production of host arginase I and coccidioidal urease, which contribute to tissue damage at sites of infection. Arginase I competes with inducible nitric oxide synthase (iNOS) in macrophages for the common substrate, L‐arginine, and thereby reduces nitric oxide (NO) production and increases the synthesis of host orinithine and urea. Host‐derived L‐ornithine may promote pathogen growth and proliferation by providing a pool of the monoamine, which could be taken up and used for synthesis of polyamines via metabolic pathways of the parasitic cells. We have shown that high concentrations of Coccidioides‐ and host‐derived urea at infection sites in the presence of urease produced and released by the pathogen, results in secretion of ammonia and contributes to alkalinization of the microenvironment. We propose that ammonia and enzymatically active urease released from spherules during the parasitic cycle of Coccidioides exacerbate the severity of coccidioidal infection by contributing to a compromised immune response to infection and damage of host tissue at foci of infection.
Multidisciplinary optimization of an automotive door with a tailored blank
Authors: Song S-I , Park G-J 
Published: October 2007

The automotive door has many design requirements such as stiffness, natural frequency, side impact, etc. Thus, various related governing equations should be solved for systematic analysis and design. It is almost impossible to solve them simultaneously. Instead, they are separately handled and the analysis results are incorporated into the design separately. Multi-disciplinary optimization (MDO) can be exploited well to include various analysis disciplines. Firstly, single optimization methods are carried out by considering one discipline for the automobile door design. Various optimization formulations are defined and the formulated problems are solved to determine the topology, shape, and size of the door with a tailored blank. The design is expanded to MDO to consider multiple disciplines. Although existing MDO methods are mathematically excellent, they are only adequate for the design of airplane wings. In this research, a few MDO methods are proposed to solve problems that share design variables among disciplines. This idea is from the fixed-point root finding method for multidiscipline analysis. Firstly, optimization of the entire system is divided into multiple domains according to the required analysis methods. Secondly, design variables are assigned to one domain according to the contribution or sensitivity. An optimization formulation is defined for each domain. Thirdly, optimization is performed at each domain where only the assigned variables are regarded as design variables and others are constant. If all the design variables are updated, then the single optimizations are iteratively conducted until the design is not changed. The developed method is verified by a standard mathematical problem. Then the developed methods are applied to the design of an automobile door. The design considers the stiffness, the natural frequency, and the side impact of the door. Most of the optimization processes use mathematical optimization. When mathematical optimization is too complicated, an approximation method such as the response surface method (RSM) is utilized. The developed methods show stable convergence and the weight of the door is reduced by 15 per cent. Since commercial systems are employed for analysis and design by coding the interfacing parts, the developed methods can be easily utilized in design practice.
Wear at the wheel/rail interface when sanding is used to increase adhesion
Authors: Lewis R , Dwyer-Joyce R S 
Published: October 2007

Sanding is used in train operation to improve adhesion at the wheel/rail interface during both braking and traction. An experimental study has been carried out to determine the effect of sanding on the wear of wheel and rail materials. Static tests were performed using actual wheel and rail sections. Dynamic tests were carried out with and without sand on a twin disc machine, where wheel and rail steel discs are loaded together and driven under controlled conditions of rolling and sliding. Sand was fed into the disc contact through a standard compressed air sanding valve. In both static and dynamic tests, sand caused severe surface damage. During the dynamic tests, because of the application of sand, wear increased by factors between 2 and 10. The wheel steel wear rates showed the largest increases. Wear in wet conditions was higher than that in dry conditions because the wet discs entrained a larger amount of sand through the contact that otherwise was ejected when the discs were run dry. The mechanisms of sanding wear have been investigated. Severe plastic flow as well as a high material removal rate and surface corrugation takes place. The rail discs are scored by sand particles that embed and stick in the softer wheel disc. As well as wear by abrasion, the discs were subject to a rapid fatigue process and large chunks of material fractured from the surface. A simple abrasive wear model has been developed to predict wear of rail material caused by sand in the wheel/rail contact, which shows good correlation with test results. There are a number of idealizations inherent in the test simulations that lead to increased severity over the actual wheel/rail contact. These include the amount of sand entering the contacts in both types of test and the disc geometry and motion in the dynamic tests. While the twin disc specimens have been scaled down, the sand is as used on the railway network, which may lead to surface damage appearing more severe than it would be in an actual wheel/rail contact. Results are therefore only to be taken as a guide to what happens in the full size wheel/rail interface.
Static wheel/rail contact isolation due to track contamination
Authors: Lewis R , Masing J 
Published: October 2007

An experimental study has been carried out to investigate the effect of contaminants such as sand and leaves on the electrical isolation of a wheel/rail contact. Train detection, for signalling purposes, can be by means of track circuits. Signalling block occupancy is triggered by the wheelset of the train ‘shorting out’ the track circuit. Contaminants in the wheel/rail interface mean that contact between the wheelsets and the track may be compromised, inhibiting train identification. Tests were performed using sections cut from wheels and rail sections loaded together hydraulically with different combinations of contaminants in wet and dry conditions. The electrical circuit used was a simplified simulation of the TI21 track circuit. The sand results indicated that a transition exists in the amount of sand in the contact above which isolation occurred. This amount is higher than the specified sand application rate for train operation at 4.5 m/s (10 mile/h), much of which will not actually make it into the contact. At lower speeds, down to zero, however, if the applied sand rate is not reduced, there is a possibility that this amount could enter the contact leading to isolation. Dead leaves were found to present the greatest problem in terms of isolation. The addition of sand used to mitigate the problem of adhesion loss caused by leaf fall made the likelihood of isolation greater. With water, breakdown loads were lower and partial conductance was seen to occur, although it is not clear whether these levels of conductance could be detected by a track circuit. This needs further investigation. Leaves with a higher level of sclerophylly (leatheriness) were found to be harder to break down. Loads used represented an average value for the tread contact. It was clear that for tests with dead leaves, particularly, the breakdown loads were around this level. With train masses gradually reducing leading to lower wheel/rail contact forces, the problem could get worse. At the present stage of development, the test method is best used as a means to qualitatively assess relative effects on electrical isolation of different contaminants, but can provide information that may be able to help in assessing where greater attention to leaf clearance may be necessary.
Tribological principles in metal-on-metal hip joint design
Authors: Dowson D 
Published: October 2007

An analysis of some 100 published and communicated findings on running-in volumetric wear and steady state wear rates from simulator tests carried out in eight laboratories in three countries has been undertaken. Powerful indications have emerged of the dominant role of mixed lubrication in current metal-on-metal hip replacements, with elastohydrodynamic film thickness controlling wear. The background to the calculation of film thickness in the elastic-isoviscous mode of lubrication has been outlined and graphs of representative film thickness and lambda ratio have been presented. For minimum wear and wear rate the diameter of the femoral component should be as large as possible, while the clearance should be as small as is practicable. The findings are valid for both monolithic and surface replacement implants. A tentative proposal is made for the prediction of lifetime wear in metal-on-metal total hip replacements.
Metal-on-metal bearings surfaces: Materials, manufacture, design, optimization, and alternatives
Authors: Isaac G H , Thompson J , Williams S , Fisher J 
Published: October 2007

When first introduced, total hip replacements offered pain relief and improved mobility in elderly patients. The success of this procedure in terms of long-term durability and restoration of function has led to its use in younger, more active patients. This has resulted in a commensurate increase in patient expectation regarding longevity and the degree to which function and lifestyle is restored. The bearing surface is a key feature of the performance of replacement joints. It is generally accepted that excessive amounts of wear debris preclude their long-term survivorship and hence there is an ongoing requirement for bearing surfaces which minimize debris generation. The purpose of this paper is to review the factors which affect the performance of so-called metal-on-metal bearings, to compare their performance with that of the other commonly used contemporary alternatives, metal and ceramic articulating against highly cross-linked polyethylene, and ceramic-on-ceramic, and finally to consider the potential solutions offered by new developments such as ceramic-on-metal and coatings applied to metal-on-metal bearings.
Head replacement, head rotation, and surface damage effects on metal-on-metal total hip replacements: A hip simulator study
Authors: Hardaker C , Dowson D , Isaac G H 
Published: October 2007

The possibility of replacing the femoral head alone, in either solid or articular surface replacement form, during revision operations on metal-on-metal total hip replacements remains an attractive feature of such implants. In the present investigation, laboratory simulator studies of the influence upon volumetric wear of inserting a new femoral head, of introducing some head rotation, and of damaging the femoral head by scratches have all been explored. New and rotated heads both involve an additional running-in period, but the experimental studies show that the volumetric wear associated with this process is less than the initial running-in wear. The beneficial effects upon volumetric wear of small clearances have been confirmed, while the processing of high-carbon Co-Cr-Mo materials appears to be much less influential. Scratches did not affect wear as much as head replacement or head rotation, but the ongoing wear rates were somewhat higher.
Real-time efficiency index of a steam power plant: A systems approach
Authors: Mohan M , Gandhi O. P. , Agrawal V. P. 
Published: October 2007

The present system of recording efficiency parameters under process performance of a steam power plant (SPP) includes specific fuel consumption, auxiliary power consumption, and demineralized water for make-up used during past-specific period, without their integration into a single process performance or efficiency index. For developing integrated efficiency index in real time frame, the use of a process performance digraph (PPD) comprising of P i's as nodes and p ij's as interconnection among the nodes as obtained from the system structure graph (SSG) of SPP has been demonstrated. Each c ij of SSG corresponds to a process, such as air fuel mixing, combustion of mixtuer, generation and expansion of steam and its condensation back into water for recirculation in boiler, etc., taking place in the SPP and corresponds to a P i of PPD. The PPD is then analysed for determining the efficiency of the SPP using matrix method following systems approach. Variable permanent process performance matrix and its variable permanent function (VPF-p) have been derived from the PPD for the analysis. The real-time efficiency index (RTEI) has been introduced which is the ratio of the values of (VPF-p) in realtime (RT) situation (VPF-p)RT to its achievable design value (VPF-p). It reflects the RT rate of consumption of various inputs like demineralized water make-up, auxiliary power and fuel consumption, etc. It provides a more scientific method for ranking the performance of an SPP. The proposed model is capable of analysing in RT the performance of various systems of the SPP, taking into account simultaneously the failure of various equipments in these systems. A step-by-step procedure for calculation of RTEI has also been suggested and illustrated by giving an example.
Energy and economic assessment of IGCC power plants integrated with DME synthesis processes
Authors: Cocco D , Pettinau A , Cau G 
Published: October 2007

The combined production of dimethylether (DME) and electrical energy in Integrated Gasification Combined Cycle (IGCC) power plants is a very attractive option for exploiting the world's huge coal reserves achieving high efficiency and low pollutant emissions, as well as for enhancing the flexibility and economic performance of coal gasification plants. Besides being used for power generation in combined cycle plants, the clean synthesis gas produced by coal gasification processes can also be used as raw material for producing hydrogen, methanol, DME, and other chemicals. In particular, recent studies show the growing interest of DME as a new clean fuel for diesel engines, gas turbines, fuel cells, and household uses. This article concerns an energy and economic assessment of two different IGCC power plants integrated with a once-through DME synthesis process. In particular, the study has been carried out by examining two different solutions for the gasification process: one based on a dry-fed and the other on a slurry-fed entrained-flow gasifier. The energy assessment has shown that the DME production in IGCC power plants leads to a DME/coal energy conversion of ∼31—32 per cent and an electrical/coal energy conversion of ∼22—25 per cent. Overall, the solution based on the dry-fed gasifier exhibits the best exergy performance (50.8 versus 52.7 per cent). Finally, the economic analysis reveals DME production costs (6—6.5$/GJ) comparable with other premium fuels such as natural gas, liquefied petroleum gases, and so on.
A comparison of conjugate heat transfer methods applied to an axial helium turbine
Authors: Verstraete T , Alsalihi Z , Van den Braembussche R. A. 
Published: October 2007

The current paper presents a numerical investigation of the conjugate heat transfer (CHT) in an axial helium turbine. The objective is the prediction of the cooling needed to keep the blade temperature below the allowable material limits. The cooling is applied at the hub by means of internal cooling channels. A CHT solver has been developed for this purpose. It combines a three-dimensional heat conduction calculation inside the blade with a three-dimensional Navier-Stokes flow calculation around the turbine blade. The required cooling at the blade root is calculated by imposing the temperature limit as boundary conditions at the bottom plane. Various alternative methods to implement the CHT are tested and compared. The results indicate that the so-called h-method is superior both in terms of accuracy and convergence speed.
Analysis of the dynamics of a defective V-belt and diagnostic possibilities
Authors: Mikalauskas R , Volkovas V 
Published: October 2007

To investigate parametrically forced excitation and transverse oscillations of the belt with local heterogeneity, a new dynamic model of a V-belt drive with longitudinal motion has been developed. The model shows that when an appropriate quantitative and qualitative level of local heterogeneity is achieved, the oscillation mode of the belt starts to change, and the belt tensile force developing due to deformation of the belt significantly increases. Another V-belt drive dynamic model was developed based on the finite element model (FEM) analysis. This was used to examine the interaction of the belt, containing local heterogeneity, with the pulley in the area of contact angle. The natural frequencies of the system were calculated and the system's response to harmonic excitation was established. The correlation between the presence of defects in the belt and vibration activity of the driving pulley bearing housing was established. Using the developed model, the relationship between the defective belt and the dynamic component of the vibration reaction force of the driven pulley was studied. Spectrum components are identified and are used in the belt drive's practical diagnostics. The method developed based on these models enables non-destructive assessment of the failure state of the mounted belt to be performed in order to assess the failure state of different belt drive types.
Towards understanding selenocysteine incorporation into bacterial proteins
Authors: Fischer Niels , Paleskava Alena , Gromadski Kirill B. , Konevega Andrey L. , Wahl Markus C. , Stark Holger , Rodnina Marina V. 
Published: October 2007

Abstract
In bacteria, UGA stop codons can be recoded to direct the incorporation of selenocysteine into proteins on the ribosome. Recoding requires a selenocysteine incorporation sequence (SECIS) downstream of the UGA codon, a specialized translation factor SelB, and the non-canonical Sec-tRNASec, which is formed from Ser-tRNASec by selenocysteine synthase, SelA, using selenophosphate as selenium donor. Here we describe a rapid-kinetics approach to study the mechanism of selenocysteine insertion into proteins on the ribosome. Labeling of SelB, Sec-tRNASec and other components of the translational machinery allows direct observation of the formation or dissociation of complexes by monitoring changes in the fluorescence of single dyes or fluorescence resonance energy transfer between two fluorophores. Furthermore, the structure of SelA was studied by electron cryomicroscopy (cryo-EM). We report that intact SelA from the thermophilic bacterium Moorella thermoacetica (mthSelA) can be vitrified for cryo-EM using a controlled-environment vitrification system. Two-dimensional image analysis of vitrified mthSelA images shows that SelA can adopt the wide range of orientations required for high-resolution structure determination by cryo-EM. The results indicate that mthSelA forms a homodecamer that has a ring-like structure with five bilobed wings, similar to the structure of the E. coli complex determined previously.
Selenium in mammalian spermiogenesis
Authors: Flohé Leopold 
Published: October 2007

Abstract
The role of selenium in male fertility is reviewed with special emphasis on selenoprotein P and phospholipid hydroperoxide glutathione peroxidase (GPx4) in spermiogenesis. Inverse genetics reveal that selenoprotein P is required for selenium supply to the testis. GPx4 is abundantly synthesized in spermatids. As a moonlighting protein it is transformed in the later stages of spermiogenesis from an active selenoperoxidase into a structural protein that becomes a constituent of the mitochondrial sheath of spermatozoa. The transformation is paralleled by loss of glutathione. Mechanistically, the process is an alternate substrate inactivation of GPx4 resulting from reactions of its selenenic form with thiols of GPx4 itself and other proteins. Circumstantial evidence and ongoing experimental genetics indicate that the mitochondrially expressed form of the GPx4 gene is the most relevant one in spermiogenesis, with the nuclear form being dispensable for fertility and the role of cytosolic GPx4 remaining unclear. Clinical data reveal a strong association of low sperm GPx4 with infertility. Thus, impaired GPx4 biosynthesis, due to selenium deficiency or to genetic defects in gpx4 itself or in proteins involved in Se distribution and selenoprotein biosynthesis, causes male infertility, but can also be an epiphenomenon due to any perturbation of testicular function.
Influence of pH and flanking serine on the redox potential of S-S and S-Se bridges of Cys-Cys and Cys-Sec peptides
Authors: Schneider Alex , Brandt Wolfgang , Wessjohann Ludger A. 
Published: October 2007

Abstract
In selenocysteine (Sec, U)-containing proteins the selenenylsulfide bridge and its reduced thiol-selenol counterpart are usually the significant species. An important role for serine as flanking amino acid in the redox potential of S-S and S-Se bridges was proposed for some thioredoxin reductases. To check the generality of this proposal, model tetrapeptides (GCCG, SCCG, GCCS, SCCS, GCUG, SCUG, GCUS, SCUS) were synthesized, including the GCUG sequence of human thioredoxin reductase. The influence on the redox potential of S-Se and S-S bridges as a function of pH and of serine at different positions reveals (i) a strong general pH dependence, and (ii) a significant influence of flanking serine on disulfide only at basic pH.
Effect of age on sexually dimorphic selenoprotein expression in mice
Authors: Schomburg Lutz , Riese Cornelia , Renko Kostja , Schweizer Ulrich 
Published: October 2007

Abstract
Clinical data suggest that selenium (Se) supplementation decreases disease predisposition and severity and accelerates recovery in a variety of pathologies. Pre-supplementation Se levels and sex represent important determinants of these Se-dependent health effects. Accordingly, we previously reported on sexually dimorphic expression patterns of Se-dependent glutathione peroxidase 1, type I deiodinase, and selenoprotein P in young mice. In the present study we investigated whether these differences vary with age. The strong sexual dimorphic expression of hepatic type I deiodinase that was observed in young mice vanished both at the mRNA and enzyme activity level by 1 year of age. In contrast, the strong sex-specific differences in renal type I deiodinase mRNA expression were sustained with age. Accordingly, deiodinase enzymatic activities differed in male and female kidneys, largely independent of age [average of 6.8 vs. 15.7 pmol/(min mg) in males vs. females]. In parallel, hepatic Se concentrations and glutathione peroxidase activities increased in female mice compared to male littermates, establishing a new sexual dimorphism in liver. Thus, age represents another important modifier of the dynamic sex- and tissue-specific selenoprotein expression patterns. These data highlight again the unique physiological regulatory mechanisms that have evolved to control Se metabolism according to the actual needs of the organism.