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Search Results: 1 - 10 of 692926 matches for " J.W.; Negrette-Mejía "
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Virus de transmisión sexual: relación semen y virus
Zea-Mazo,J.W.; Negrette-Mejía,Y.A.; Cardona-Maya,W.;
Actas Urológicas Espa?olas , 2010, DOI: 10.4321/S0210-48062010001000006
Abstract: introduction: the possible "infection"/interaction processes between sperm and different microorganisms are being under discussion nowadays. this process might include some viruses and even recent investigations are aiming to elucidate the mechanisms and the receptors that may be involved in this interaction. furthermore, it has been reported the presence of some viral genomes within the sperm dna, raising the possibility of transmitting the infection to the partner and offspring. objective: the aim of this review is to describe the mechanisms by how viruses could possibly infect some seminal fractions. this is pursued by performing a literature review for answering the question: how the sexually transmitted virus could be infecting sperm? materials and methods: we carried out a bibliographic review about sperm and virus interaction. results: some viruses interact with sperm cells; and sperm cells could transfer the viruses to offspring, however, in most cases, the receptors that allow this interaction are not clearly described. conclusions: based on the current information, new in vitro studies are needed to determine the role of sperm in spreading viruses of sexually transmitted infections.
The effect of α-alumina particles on the properties of EN AC-44200 Al alloy based composite materials
J.W. Kaczmar,A. Kurzawa
Journal of Achievements in Materials and Manufacturing Engineering , 2012,
Abstract: Purpose: The unreinforced EN AC-44200 aluminium alloy is characterized by the medium mechanical properties and the purpose of performed investigations was improvement of mechanical properties of this alloy by introducing stable ceramic α-alumina particles.Design/methodology/approach: The composite materials were manufactured by squeeze casting of porous ceramic preforms characterized by the open porosities of 90%, 80%, 70% and 60% with the liquid EN AC- 44200 aluminum alloy. The composite materials containing 10 vol. %, 20 vol. %, 30 vol. % and 40 vol. % were manufactured and characterized by the homogeneous distribution of alumina particles in the matrix. On the base of microscopic investigations there was ascertained good bonding at the interface matrix/strengthening particles.Findings: Manufacturing of porous ceramic preforms from alumina powders characterized by the desired open porosity was elaborated. After squeeze casting with liquid EN AC-44200 alloy there was noticed considerable increase of physical and mechanical properties: hardness HB increased from 82 HB for unreinforced alloy to 150 HB for material containing 40 vol. % of particles. There was noticed increase of tensile strength, bending strength and compression strength, although what is typical for composite materials, decrease of impact strength.Research limitations/implications: There was noticed small rest porosity with decreasing porosity of the ceramic preforms. Further investigations on porosity removal basing on modification of production parameters are forseen.Practical implications: Reinforcing of EN AC-44200 aluminum alloy with ceramic particles is effective taking into account increase of hardness and strength (tensile, bending, compression), although the relatively low impact strength can be restriction for the applications of these materials as the elements subjected to dynamic loads.Originality/value: Manufactured materials can be applied as elements subjected to static loads and the relatively large specific strength allow to diminish the weight of elements applied in the construction of means of transportation.
Predictive value of testing for multiple genetic variants in multifactorial diseases: implications for the discourse on ethical, legal and social issues
A. Cecile J.W. Janssens,Muin J. Khoury
Italian Journal of Public Health , 2006, DOI: 10.2427/5915
Abstract: Multifactorial diseases such as type 2 diabetes, osteoporosis, and cardiovascular disease are caused by a complex interplay of many genetic and nongenetic factors, each of which conveys a minor increase in the risk of disease. Unraveling the genetic origins of these diseases is expected to lead to individualized medicine, in which the prevention and treatment strategies are personalized on the basis of the results of predictive genetic tests. This great optimism is counterbalanced by concerns about the ethical, legal, and social implications of genomic medicine, such as the protection of privacy and autonomy, stigmatization, discrimination, and the psychological burden of genetic testing. These concerns are translated from genetic testing in monogenic disorders, but this translation may not be appropriate. Multiple genetic testing (genomic profiling) has essential differences from genetic testing in monogenic disorders. The differences lie in the lower predictive value of the test results, the pleiotropic effects of susceptibility genes, and the low inheritance of genomic profiles. For these reasons, genomic profiling may be more similar to nongenetic tests than to predictive tests for monogenic diseases. Therefore, ethical, legal, and social issues that apply to predictive genetic testing for monogenic diseases may not be relevant for the prediction of multifactorial disorders in genomic medicine.
Response to a major disease of poverty: the Global Partnership to Stop TB
Lee J.W.,Loevinsohn E.,Kumaresan J.A.
Bulletin of the World Health Organization , 2002,
Abstract:
Tribological properties of AC44200 based composites strenghead with AlB2BOB3 Bparticles
A. Kurzawa,E. Grodzka,A. Janus,J.W. Kaczmar
Archives of Foundry Engineering , 2011,
Abstract: The paper presents a research on abrasion resistance of aluminium-based composites consisting of EN AC-44200 matrix reinforcedwith AlB2BOB3B particles. The examinations revealed that wear intensity of the composites decreased with increasing volume fraction of the particles. Much more intensive abrasive wear was observed on the first kilometre in comparison to the wear on the subsequent distances, i.e. from 1 to 3.5 km and from 3.5 to 8.5 km of the wear distance. Microscopic examinations permitted determining the way and type of wear occurring in the examined materials. In the case of the AC-44200 matrix, typical adhesive wear is observed. In composite materials however, abrasive wear prevails over adhesive wear. Increased volume fraction of AlB2BOB3B particles in composite materials results in increasing friction factor in average by 0.250 per each 10 vol.%. Wear of the cast-iron counterspecimen is also strongly dependent on volume fraction of the reinforcing particles. The counterspecimen demonstrates the largest wear when working in contact with a composite material containing 40 vol.% of AlB2BOB3B particles.
Selected mechanical properties of aluminum composite materials reinforced with SiC particles
A. Kurzawa,J.W. Kaczmar,A. Janus
Archives of Foundry Engineering , 2008,
Abstract: This work presents the results of research concerning influence of ceramic particles’ content of silicon carbide on selected mechanical properties of type AW-AlCu4Mg2Mn - SiC composite materials. Composites produced of SiC particles with pressure infiltration method of porous preform and subject to hot plastic forming in the form of open die forging were investigated. The experimental samples contained from 5% up to 45% of reinforcing SiC particles of 8÷10μm diameter. Studies of strength properties demonstrated that the best results, in case of tensile strength as well as offset yield strength, might be obtained while applying reinforcement in the amount of 20-25% vol. of SiC. Application of higher than 25% vol. contents of reinforcing particles leads to gradual strength loss. The investigated composites were characterized by very high functional properties, such as hardness and abrasive wear resistance, whose values increase strongly with the increase of reinforcement amount. The presented results of the experiments shall allow for a more precise component selection of composite materials at the stage of planning and design of their properties.
Inhibition of the sarcoplasmic reticulum Ca2+ pump with thapsigargin to estimate the contribution of Na+-Ca2+ exchange to ventricular myocyte relaxation
Bassani, R.A.;Bassani, J.W.M.;
Brazilian Journal of Medical and Biological Research , 2003, DOI: 10.1590/S0100-879X2003001200014
Abstract: relaxation in the mammalian ventricle is initiated by ca2+ removal from the cytosol, which is performed by three main transport systems: sarcoplasmic reticulum ca2+-atpase (sr-a), na+-ca2+ exchanger (ncx) and the so-called slow mechanisms (sarcolemmal ca2+-atpase and mitochondrial ca2+ uptake). to estimate the relative contribution of each system to twitch relaxation, sr ca2+ accumulation must be selectively inhibited, usually by the application of high caffeine concentrations. however, caffeine has been reported to often cause changes in membrane potential due to ncx-generated inward current, which compromises the reliability of its use. in the present study, we estimated integrated ca2+ fluxes carried by sr-a, ncx and slow mechanisms during twitch relaxation, and compared the results when using caffeine application (cf-nt) and an electrically evoked twitch after inhibition of sr-a with thapsigargin (tg-tw). ca2+ transients were measured in 20 isolated adult rat ventricular myocytes with indo-1. for transients in which one or more transporters were inhibited, ca2+ fluxes were estimated from the measured free ca2+ concentration and myocardial ca2+ buffering characteristics. ncx-mediated integrated ca2+ flux was significantly higher with tg-tw than with cf-nt (12 vs 7 μm), whereas sr-dependent flux was lower with tg-tw (77 vs 81 μm). the relative participations of ncx (12.5 vs 8% with tg-tw and cf-nt, respectively) and sr-a (85 vs 89.5% with tg-tw and cf-nt, respectively) in total relaxation-associated ca2+ flux were also significantly different. we thus propose tg-tw as a reliable alternative to estimate ncx contribution to twitch relaxation in this kind of analysis.
Changing Rural Households` Expenditures and Coping Strategies under Deregulated Fuel Price Regime in Nigeria: A Micro-Evidence from Ikene Local Government
A.S. Oyekale,J.W. Udia
Pakistan Journal of Social Sciences , 2012,
Abstract: Deregulation of the Nigeria`s oil sector has resulted into increase in pump prices of petroleum products. Consequently, purchasing power of income has reduced as prices of goods and commodities increased. This study analyzed the changes in expenses incurred by households on energy products, food and transportation and coping strategies used. Data were collected with simple random sampling and analyzed using descriptive statistics and z-test for statistical significance. Results showed that while expenses on kerosene significantly increased (p<0.01) the number of liters of kerosene significantly decreased (p<0.01). Expenses on most carbohydrate foods significantly increased in absolute term (p<0.05) while there were significant reductions in consumption of some protein and vitamin rich foods (p<0.05). Coping strategy of fetching fuel wood was used by 29.63% while 21.30% buy food on credit. It was recommended that to minimize adverse nutritional and environmental effects of fuel price hike, government should assist in boosting economic activities of rural people and ensuring that research into safe utilization of solar energy for cooking is encouraged.
Generalized Minimum Variance Controller as a Velocity Loop Controller of a Casting Drum Drive in a Polyester Manufacturing Line
S Donoghue,J.W. Finch,D. Giaouris,A. Jones
Lecture Notes in Engineering and Computer Science , 2008,
Abstract:
An approach to assessing the financial viability of bush clearing on game ranches in savanna regions
A.G. Schmidt,J.W. Jordaan
Koedoe : African Protected Area Conservation and Science , 1999, DOI: 10.4102/koedoe.v42i2.233
Abstract: An approach to assessing the financial viability of bush clearing on game ranches in savanna regions is presented, using data on the rates of change of herbaceous phytomass and tree density following bush clearing. Financial gain is calculated from an increase in grazing capacity with an increase in herbaceous phytomass. The financial gain is offset against the financial loss due to a decrease in browsing capacity with a decrease in bush density. Profitability is calculated by calculating the net present value of the net financial gain over the effective duration of the bush clearing exercise. Shortcomings in the approach are identified and a need for more appropriate long-term data is indi-cated.
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