bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of Ochratoxin A Production in Grapes
Authors: Ponsone María Lorena , Chiotta María Laura , Palazzini Juan Manuel , Combina Mariana , Chulze Sofía
Published: May 2012

Ochratoxin A (OTA) is a mycotoxin commonly present in cereals, grapes, coffee, spices, and cocoa. Even though the main objective of the food and feed chain processors and distributors is to avoid the extended contamination of plant-derived foods and animal feeds with mycotoxins, until now, complete OTA removal from foods and feedstuffs is not feasible. Prevention through pre-harvest management is the best method for controlling mycotoxin contamination. However, in the case that the contamination occurs after this stage, the hazards associated with OTA must be managed through post-harvest strategies. Due to the increasing number of fungal strains resistant to chemical fungicides and the impact of these pesticides on the environment and human health, maximum levels of chemical residues have been regulated in many products. Alternative methods are necessary to substitute or complement treatments with fungicides to control fungi under field or storage conditions. Yeasts are considered one of the most potent biocontrol agents due to their biology and non-toxic properties. Epiphytic yeasts are the major component of the microbial community on the surface of grape berries and they are evolutionarily adapted to this ecological niche. Nowadays, several yeast species included in different genera are considered as potential biocontrol agents to control both, growth of ochratoxigenic Aspergillus species and OTA accumulation.
Islet Engraftment and Revascularization in Clinical and Experimental Transplantation
Authors: Molnár Christian , Essand Magnus , Wennberg Lars , Berne Christian , Larsson Erik , Tufveson Gunnar , Korsgren Olle
Published: May 2012

Proper revascularization after transplantation is assumed to be crucial for appropriate islet graft function. We developed a novel noninvasive imaging method, based on adenoviral transduction of islets with a hypoxia responsive reporter gene, for continuous in vivo monitoring of hypoxia in islet grafts in a mouse model. In addition, morphological data were obtained from a deceased patient previously subject to intraportal transplantation. We detected only transient hypoxia in a minority of the animals transplanted. Importantly, a clear response to hypoxia was observed in vitro after removal of the islet grafts on day 28 after transplantation. Also, the morphological data from the deceased patient demonstrated an extensive revascularization of the transplanted islets. In fact, no differences could be seen between native islets, in pancreas biopsies taken prior to islet isolation, and transplanted islets regarding the number, distribution, and shape of the blood vessels. However, fewer small islets (diameter <39 μm) were found in the liver compared to those found in native pancreases. Notably, an absolute majority of the transplanted islets were found remaining within the venous lumen, in direct contact with the vessel wall. In conclusion, the results presented show less pronounced islet graft hypoxia after subcapsular transplantation than previously reported using more invasive methods. Also, formation of an extensive intraislet capillary network, similar to that seen in native islets in the pancreas, was seen after clinical islet transplantation.
Epiphyseal Chondroprogenitors Provide a Stable Cell Source for Cartilage Cell Therapy
Authors: Darwiche Salim , Scaletta Corinne , Raffoul Wassim , Pioletti Dominique P. , Applegate Lee Ann
Published: May 2012

Articular cartilage regeneration poses particularly tough challenges for implementing cell-based therapies. Many cell types have been investigated looking for a balanced combination of responsiveness and stability, yet techniques are still far from defining a gold standard. The work presented focuses on the reliable expansion and characterization of a clinical grade human epiphyseal chondroprogenitor (ECP) cell bank from a single tissue donation. A parental human ECP cell bank was established, which provides the seed material for master and working cell banks. ECPs were investigated at both low and high cumulative population doublings looking at morphology, monolayer expansion kinetics, resistance to cryogenic shock, colony-forming efficiency, and cell surface markers. Three-dimensional micropellet assays were used to determine spontaneous extracellular matrix deposition at varying population doublings and monolayer 2D differentiation studies were undertaken to assess the propensity for commitment into other lineages and their stability. ECPs exhibited remarkable homogeneity in expansion with a steady proliferative potential averaging three population doublings over 8 days. Surface marker analysis revealed no detectable contaminating subpopulations or population enrichment during prolonged culture periods. Despite a slight reduction in Sox9 expression levels at higher population doublings in monolayer, nuclear localization was equivalent both in monolayer and in micropellet format. Equally, ECPs were capable of depositing glycosaminoglycans and producing aggrecan, collagen I, and collagen II in 3D pellets both at low and high population doublings indicating a stable spontaneous chondrogenic potential. Osteogenic induction was differentially restricted in low and high population doublings as observed by Von Kossa staining of calcified matrix, with a notable collagen X, MMP13, and ADAMTS5 downregulation. Rare adipogenic induction was seen as evidenced by cytoplasmic lipid accumulation detectable by Oil Red O staining. These findings highlight the reliability, stability, and responsiveness of ECPs over prolonged culture, making them ideal candidates in defining novel strategies for cartilage regeneration.
Development of modified diagnostic criteria for bacterial vaginosis at peripheral health centres in developing countries
Authors: Mittal Vineeta , Jain Amita , Pradeep Yashodhara
Published: May 2012

Introduction:  Bacterial vaginosis (BV) is the commonest cause of abnormal vaginal discharge in women of child-bearing age and is associated with increased susceptibility to HIV-AIDS and sexually transmitted diseases. In obstetrics, BV has been implicated in causing various complications. In clinical practice, BV is diagnosed using Amsel criteria and Nugent scoring. Using modified Amsel criteria, we determined that the fulfilling of any two instead of three criteria can be diagnostic of BV. Methodology:  This prospective cross-sectional study involved pregnant females complaining of excessive vaginal discharge admitted in a tertiary health centre in central India. Four vaginal swabs were collected for the diagnosis of BV by Amsel criteria, modified Amsel criteria, and Nugent scoring on Gram stain. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of each individual criterion and combinations of criteria were calculated by using Nugent scoring as the gold standard and by chi square test. Results: In the present study overall prevalence of BV was 12%. The sensitivity of individual or a combination of two criteria was almost same or higher than that of Amsel criteria. Specificity of each combination of criteria was comparable to that of Amsel criteria. However, a combination of high pH and amine odor test had the highest sensitivity (88%) and highest PPV (62%). Diagnostic accuracy of all combinations in our study was equal to or slightly higher than that of Amsel criteria. Conclusion: Diagnostic accuracy of new modified Amsel criteria is as reliable as that of Amsel criteria.
Study on biofilm-forming properties of clinical isolates of Staphylococcus aureus
Authors: Taj Yasmeen , Essa Farhan , Aziz Faisal , Kazmi Shahana Urooj
Published: May 2012

Introduction: The purpose of this study was to observe the formation of biofilm, an important virulence factor, by isolates of Staphylococcus aureus (S. aureus) in Pakistan by different conventional methods and through electron microscopy. Methodology: We screened 115 strains of S. aureus isolated from different clinical specimens by tube method (TM), air-liquid interface coverslip assay method, Congo red agar (CRA) method, and scanning electron microscopy (SEM). Results: Out of 115 S. aureus isolates, 63 (54.78%) showed biofilm formation by tube method. Biofilm forming bacteria were further categorized as high producers (n = 23, 20%) and moderate producers (n = 40, 34.78%). TM coordinated well with the coverslip assay for strong biofilm-producing strains in 19 (16.5%) isolates. By coverslip method, weak producers were difficult to differentiate from biofilm negative isolates. Screening on CRA showed biofilm formation only in four (3.47%) strains. Scanning electron micrographs showed the biofilm-forming strains of S. aureus arranged in a matrix on the propylene surface and correlated well with the TM. Conclusion: Biofilm production is a marker of virulence for clinically relevant staphylococcal infections. It can be studied by various methods but screening on CRA is not recommended for investigation of biofilm formation in Staphylococcus aureus. Electron micrograph images correlate well with the biofilm production as observed by TM.
Risk factors for Shiga toxin-producing Escherichia coli infections in preadolescent schoolchildren in Buenos Aires, Argentina
Authors: Bentancor Adriana Beatriz , Ameal Luis A , Calviño María F , Martinez María C , Miccio Luciano , Degregorio Osvaldo J
Published: May 2012

Introduction: Shiga toxin-producing Escherichia coli (STEC) infections are the leading cause of hemolytic uremic syndrome (HUS). STEC is the most common cause of acute kidney disease, responsible for 20% of renal transplants in Argentina. Methodology: In 2007, an epidemiological survey was conducted among 883 students from the fifth and sixth years of elementary education in the public schools of San Martin City, Buenos Aires, Argentina. Degree of exposure to the known risk factors previously detected in the region as primary causes of STEC infections was evaluated. Risk factors assessed included consumption of hamburgers, poor personal hygiene, and exposure to various types of drinking and recreational water. The study was designed to evaluate exposure to risk factors for STEC infections among different socioeconomic groups. Results: Ninety-five percent of children surveyed reported consumption of hamburgers. Most of these hamburgers were precooked. Children of high and medium strata attended private swimming-pools, while children from the low stratum attended public pools. Only 30.2% of students washed their hands after going to the toilet and only 43.5% reported hand-washing before eating. Conclusions: Students demonstrated high levels of exposure to identified risk factors for STEC infections. Reduction of these risks will require cultural changes aimed at decreasing morbidity caused by food-borne infections. Institutional framework must provide the necessary resources to implement these changes and emphasize the importance of good personal hygiene. Health education must be implemented to increase food safety awareness of the consumers.
Knowledge, attitudes, perceptions, and practices regarding cutaneous larva migrans in deprived communities in Manaus, Brazil
Authors: Lesshafft Hannah , Schuster Angela , Reichert Felix , Talhari Sinesio , Ignatius Ralf , Feldmeier Hermann
Published: May 2012

Introduction: Hookworm-related cutaneous larva migrans (HrCLM) is a neglected parasitic skin disease commonly found in resource-poor communities in tropical countries. It is acquired via skin contact with faeces of cats and dogs, and causes intense pruritus and significant morbidity. Methodology: We investigated knowledge, attitudes and practices in caregivers of patients with HrCLM by performing focus group discussions (FGDs) with 20 mothers of children with HrCLM in two endemic urban communities in Manaus, Brazil. Additionally, socio-demographic data of 70 actively detected HrCLM patients in both areas were obtained by using questionnaires. Results: We found that mainly children who lived in large households and habitually walked barefoot were affected. Family income was low, housing was poor, and food shortage common. In the FGDs, mothers described HrCLM as a severely distressing condition with considerable impact on individual and family life. Conclusion: Inadequate treatment practices and the identification of poverty-related obstacles for practical prevention of HrCLM by the mothers of affected children indicate that both health education and improvement of living conditions are required jointly.
Detection of carbapenem-resistant Escherichia coli and Klebsiella pneumoniae producing NDM-1 in Lebanon
Authors: El-Herte Rima I , Araj George F , Matar Ghassan M , Baroud Maysa , Kanafani Zeina A , Kanj Souha S
Published: May 2012

Carbapenem resistance has been encountered globally with poor outcome of infected patients. NDM-1 (New Delhi metallo-beta-lactamase) gene containing organisms have emerged and are now spreading in all continents. This is the first report of Iraqi patients referred to Lebanon from whom carbapenem resistant Enterobacteriaceae were recovered. The genes involved in carbapenem resistance were bla-OXA-48   and the novel NDM-1. This report highlights the alarming introduction of such resistance among Enterobacteriaecae to this country.
Plasmid-mediated quinolone resistance determinant qnrB19 in non-typhoidal Salmonella enterica strains isolated in Venezuela
Authors: González Fanny , Pallecchi Lucia , Rossolini Gian María , Araque María
Published: May 2012

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Logiques pastorales et de conservation de la nature : les transhumances et le Parc du W (Niger, Burkina Faso, Bénin)
Authors: Amadou Boureima , Boutrais Jean
Published: May 2012

Résumé Comment les pasteurs, souvent considérés comme proches et même respectueux de la nature, sont-ils devenus les principaux responsables des atteintes à l’intégrité des aires protégées en Afrique soudano-sahélienne ? Les entrées illégales de transhumants dans le Parc du W ont commencé de façon exceptionnelle lors des grandes sécheresses, puis elles sont devenues habituelles. Elles renvoient à un basculement zonal des mobilités pastorales. Les modalités des transhumances sont complexes et flexibles. Les interprétations de la transhumance dans le Parc du W divergent : exaltation des valeurs pastorales versus période mal vécue. En face, la logique de conservation est affirmée au Niger par une politique nationale adossée à des conventions internationales et confortée par des accords entre États africains. De nouvelles associations d’éleveurs et des projets de développement tentent de concilier les deux logiques, mais leur influence reste faible sur les pasteurs.
Un cinéma palestinien « en mal d’archive »
Authors: Fourest Laure
Published: May 2012

À partir de l’analyse de trois films palestiniens réalisés dans les années 2000, cet article propose d’interroger l’insertion d’images d’archives par les cinéastes dans leur montage : quelles stratégies mettent-ils en œuvre et à quelles fins ? Qu’apportent des images d’archives en plus des témoignages filmés ? Comment le recours à ces images permet-il de participer au débat historiographique qui sous-tend et détermine en partie le conflit israélo-palestinien ? Dans le contexte palestinien où il n’existe pas d’institution archivistique officielle, les archives sont porteuses d’enjeux particulièrement saillants, donnant lieu à un véritable « mal d’archive ». Celui-ci fait naître une multiplicité de stratégies cinématographiques visant à questionner cette zone d’inconfort, où le maniement des qualités émotionnelles et sensorielles de l’archive peut être un moyen de faire preuve.
The Beauty of the Different Views on Diffusion
Authors: Kärger Jörg
Published: May 2012

Guest diffusion in nanoporous materials reveals a wide spectrum of phenomena associated with random mass transfer in condensed matter quite in general. Taking advantage of their potentials for monitoring mass transfer over microscopic dimensions, micro-imaging (by interference microscopy and IR spectroscopy) and pulsed field gradient (PFG) NMR are exploited for providing typical examples highlighting these options. Starting with the surprise provided by the application of these microscopic measuring techniques to nanoporous materials, namely discrepancies of up to five orders of magnitude in comparison with the so far well-established data, the review covers some of the most impressive further results, including the determination of sticking coefficients on the surfaces of these materials and the specification and detection of conditions where molecular mass transfer is accelerated rather than hampered by counter fluxes.
Comparison of Elastic Constant for Borassus flabellifier in the Longitudinal and Perpendicular Direction of Fibres with Frequency
Authors: Phadke Sushil , Shrivastava Bhaktdarshan , Mishra Ashutosh , Dagaonkar Nagesh
Published: May 2012

ndia is veritable emporium of medicinal and aromatic trees. It has been estimated those trees occurring in India are commonly useful. Neera natural liquid is useful for different purpose like in bio-medical, chemical industries etc. The study of elastic behaviour of a solid is very important in fundamental and technical research. Solid bodies are not absolutely rigid by the application of suitable forces. We used the composite piezoelectric oscillator technique to calculate elastic behaviour of Borassus Flabellifier wood part from where the natural liquid NEERA collected overnight. Non-destructive testing (NDT) is a wide group of analysis techniques used in science and industry to evaluate the properties of a material, component or system without causing damage. Ultrasonic Inspection is a very useful and versatile NDT method to calculate the ultrasonic longitudinal velocity and elastic constant of male and female tree (Borassus Flabellifier) wood part in the longitudinal and perpendicular direction of fibres with frequency at room temperature of 311 K. We have measured the resonant frequencies of the specimens fs. The specimens were collected from Dhar Dist. (M.P.) India. Characterization of the samples was made by scanning electron microscope (SEM) Model JEOL JSM5400. The resonant frequencies of the specimens were measured by Ultrasonic Interferometer (for solids) dual frequency Mittal Enterprises, New Delhi.
Closed Form Solutions to Nonlinear Heat Conduction Problems
Authors: Zabadal J. , Garcia R. , Ribeiro V. , Van Der Laan F.
Published: May 2012

This work presents a new analytical method for solving nonlinear heat conduction problems in arbitrary domains. The method is based on approximate mappings which transforms nonlinear partial differential equations into linear models which can be solved using standard techniques. In order to verify whether the proposed formulation can be employed to conceive new online control systems, numerical results are reported.
Three-Dimensional Diffusion in Arbitrary Domain Using Generalized Coordinates for the Boundary Condition of the First Kind: Application in Drying
Authors: Farias V.S.O. , Pereira Silva Wilton , Silva e Silva C.M.D.P. , de Lima Antônio Gilson Barbosa
Published: May 2012

This work presents a three-dimensional numerical solution for the diffusion equation in transient state, in an arbitrary domain. For this end, the diffusion equation was discretized using the finite volume method with a fully implicit formulation and generalized coordinates, for the equilibrium boundary condition. For each time step, the system of equations obtained for a given structured mesh was solved by the Gauss-Seidel method. The computational code was developed in FORTRAN, using the CFV 6.6.0 Studio, in a Windows platform. The proposed solution was validated using analytical and numerical solutions of the diffusion equation for different geometries (orthogonal and non-orthogonal meshes). The analysis and comparison of the results showed that the proposed solution provides correct results for the cases investigated. The developed computational code was applied in the simulation of the drying of ceramic roof tiles for the following temperature: 55.6 °C. The analysis of the results makes it possible to affirm that the developed numerical solution satisfactorily describes the drying processes in this temperature.
Thermodynamics of Defect Formation and Hydration of Y2O3
Authors: Putilov L.P. , Tsidilkovski V.I. , Varaksin A.N. , Fishman Anatoly Yakovlevich
Published: May 2012

Defect formation in yttria with a small content of acceptor impurities in equilibrium with a hydrogen-containing gas phase is studied theoretically. A statistical-thermodynamic description of the yttriagas equilibrium is based on the approach developed for compounds with a complex electronic structure [Phys. Stat. Sol. B (1991) Vol. 168, p. 233]. The considered model of electronic structure for Y2O3 includes, besides valence and conduction bands, acceptor and F-center states. The energy of F-centers was calculated in the framework of the variational quantum-mechanical approach combined with the molecular statics method. It is shown that acceptor states appreciably affect the thermodynamics of defect formation, while the F-centers contribution in a wide range of external parameters is small. The concentrations of defects (protons, oxygen vacancies, electronic defects) and the Fermi level position are determined as functions of temperature and gas phase parameters.
Phase Transformation and Thermoelectric Properties of In0.25Co4-xNixSb12 Skutterudites
Authors: Kim Il Ho
Published: May 2012

In0.25Co4-xNixSb12 skutterudites were synthesized by encapsulated induction melting and consolidated by hot pressing, and their thermoelectric properties were examined at temperatures from 323 to 823 K. A single δ-phase was obtained successfully by subsequent heat treatment at 823 K for 24 h. In0.25Co4-xNixSb12 was an n-type semiconductor at all temperatures examined, indicating that Ni atoms acted as electron donors by substituting for Co atoms. The thermal conductivity was reduced considerably by In filling and Ni doping due to an increase in phonon scattering and impurity scattering. The thermoelectric properties were improved due to the low thermal conductivity as a result of In filling and the optimum carrier concentration caused by Ni doping.
Improvement of Surface Quality and Parts Functional Ability by Vibro-Mechanical Consolidation Treatment and Finishing
Authors: Djema Mohamed Amine , Hamouda Khaled , Babichev Anatoly P. , Saidi Djamel , Sayah Tahar , Benallal Mohamed Nadjib
Published: May 2012

The area of actual contact of surfaces is essential for longevity and successful operation of mobile and immobile interfaces of machine parts. Wear resistance of friction surfaces, reliability adjustments, heat conduction, conductivity and several other functional characteristics of parts are closely related to actual contact area, and thus they influence the working ability of part surfaces. In this regards, the area of actual contact can be considered as one of the parameters of surface quality. This contact area presents a formed surface of plastic deformation, after the contact of the vibro-percussion treated environment or device, and is the essential process of consolidation of vibratory treatment and finishing. The formed plastic deformation surface is also a kind of micro relief surface, characterized by multitude closed and superimposed on each other traces of contact with the particles working environment cultivated surface.
This paper presents the results of vibro-mechanical treatment research, its influence on treated surface quality and working ability of the samples contact surface made by hardened steel ShKh-15, the nickel steel 40HNS2MA and bronze alloy BROF7-0,2.
Applying Computational Analysis in Studies of Resin Transfer Moulding
Authors: Ferreira Luz F. , Amico Sandro Campos , de Lima Cunha A. , Barbosa E.Santos , de Lima Antônio Gilson Barbosa
Published: May 2012

Resin Transfer Moulding (RTM) as it is most known process in the Resin Injections family, is an extensively studied and used processing method. This process is used to manufacture advanced composite materials made of fibres embedded in a thermoset polymer matrix. Fibre reinforcement in RTM processing of polymer composites is considered as a fibrous porous medium regarding its infiltration by the polymer resin. In this sense, the present work aims the computational analysis of a fluid in a porous media for a RTM composite moulding by using the ANSYS CFX® commercial software. In order to validate the numerical study of the fluid flow in a known RTM system, experiments was carried out in laboratory to characterize the fluid (vegetal oil) flowing into the porous media (0/90 glass fibre woven), were pressure and fibre volume fraction have been fixed. The numerical simulation provides information about volume fraction, pressure and velocity distribution of the phases (resin and air) inside the porous media. The predicted results were compared with the experimental data and its has shown a solid relationship between them.
Mass Transfer of God Particle or Higgs Boson
Authors: Corral Bustamante R. Leticia , Rodríguez-Corral Aarón Raúl , Irigoyen-Chávez G. , Heiras-Torres A.
Published: May 2012

This paper presents a mathematical model to predict the behaviour of the God particle, the Higgs boson, which adds mass to elementary particles appearing and disappearing in the time of Planck. The phenomenon of turbulence in the Planck scale in the modelling of space-time is the base on which is sustained this work. We measured the flow of fluid through the boundary that contains the studied mass (composed of virtual particles with characteristics similar to the Higgs boson) in full bubbling in a gravitational field with enormous surface gravity by calculating the divergence, the rotational and circulation of the fluid. The results show evidence of mass transfer of the particles consistent with the Theory of Special Relativity. The gravitational field (with mass like field source) acts as a conservative field, since its circulation along any closed curve is zero. By Stokes theorem, the flow is irrotational and therefore without vortices. In two arbitrary points of the gravitational field is found that the mechanical energy (sum of kinetic and potential energy) of the particles is constant, satisfying the theorem of conservation of energy in this inertial system isolated from conservative forces. Green's theorem defines sources and sinks of particles around a singularity in the mass center. For heat flow, the sources represent the heat production and the sinks represent its consumption. The irrotational gravitational field where is hosted the God particle has electrostatic and gravitational potential energy.
Study of Diffusion and Water Vapor Permeability in Chitosan Films and Chitosan Emulsified Films
Authors: dos Reis Arlete Barbosa , Pedroso Yoshida Cristiana Maria , de Oliveira Farias Vera Solange , Pereira Silva Wilton
Published: May 2012

Chitosan is an abundant, natural polysaccaride obtained from fishing industry waste and films of chitosan also provide an efficient oxygen barrier. However, they are a poor water vapor barrier, which can be improved by incorporation of a hydrophobic compound, forming a emulsified film. Chitosan films were produced with the addition of palmitic acid lipid analysis and then the process in parallel with the diffusive permeability to water vapor. The objective of this work was to characterize the diffusion and water vapor permeability behavior of chitosan films and chitosan emulsified films.
Mass Transport Mechanism in the Retina of the Human Eye
Authors: Dória Silva Humberto , Pereira Dória Luiz Cláudio , Pereira Dória Cristiana , Pereira Dória Cristiane , Dória Silva Maria do Carmo Tatiana , Dória Silva Júnior Humberto , Dória Silva M.T.
Published: May 2012

The metabolic secretions produced by the cells inside the human eye are accumulated simultaneously in all of its parts; subject only to their origin. However, the symptomatology is well characterized by the location of accumulation. Genetic factors are directly related to how the clumps of metabolic secretions occur and the form of accumulation is very specific to the movement of the eyes based on the activities performed by the patient, so any outcome is unpredictable. The outer retinal layers are avascular and are supplied by diffusion from the choriocapillatis. Abnormalities of retinal blood circulation and drainage of metabolic secretions are key indicators to retinal dysfunction and may point to perturbations of systemic circulation. The weakening of the cornea bending mechanism results in the loss of variation of intraocular pressure. Consequently, due to the increase of its work activities, the weakening of the forced convection mechanism of the metabolic secretions produced in the retina initiates the accumulation of these secretions without uniformity in the retina, causing gradual obstruction of its system of mass transport, nutrients and metabolic secretions. This accumulation is readily observed by pressing ones hands for several minutes on closed eyes, subsequently, there is the perception of light in one without a region of uniformity.
This work analyzes the anatomic structure and biophysics, depicted in the scientific literature, along with the symptoms of the presbyopia treatment of the first author of this paper, to understand that the accumulation of metabolic secretions causes an agglutination and dehydration process by decanting that triggers the loss of flexibility of the fibrous coat, vascular coat (uveal tissue) and nervous coat (retina) and consequently the gradual obstruction of the system of mass transport in the retina, compromising its nutrition and obstructing the drainage of its metabolic secretion.
Failure Analysis of an Automotive Component (Cardan Yoke) by Scanning Electron Microscopy
Authors: Couto Antônio Augusto , Andrade A.H.P. , Reis Danieli A.P. , Vatavuk Jan
Published: May 2012

Two SAE 1541 (0.39%C; 1.44%Mn; 0.23%Si; 0.16%Ni; 0.16%Cr) carbon steel cardan yokes that were forged, machined, quenched and tempered, as part of the manufacturing process to ensure long term operation under specific loading conditions, failed during its manufacture. The cardan yokes ruptured in the bearing seat region while these were being straightened by bending. This study deals with fracture analysis that was carried out by visual inspection and scanning electron microscopic examination. The focus of this study was to investigate the fracture mechanism associated with the failures. Fractographs of the broken components indicated that the rupture initiated at the edges of the component, from preexisting cracks, due to the bending stresses during the straightening process. The initial stage of rupture was predominantly intergranular in the tempered martensite surface layer, revealing the brittle nature of the component. Cracks were observed at regions prone to stress concentration. Eventual rupture of the component probably initiated at these cracks. This behavior is probably related to metallurgical processing steps like quenching, that causes the formation of a banded structure and promotes circumferential and radial cracking before the tempering. The fracture surface revealed regions with micro dimples and a large smooth area with some elongated inclusions. The morphology of these inclusions was cellular and originated at the grain boundaries of the primary austenite. These inclusions are probably MnS with a dendrite structure, capable of causing brittle intergranular rupture.
Effect of Artificial Aging on the Mechanical Properties of an Aerospace Aluminum Alloy 2024
Authors: Reis Danieli A.P. , Couto Antônio Augusto , Domingues Jr. N.I. , Hirschmann Ana Cláudia , Zepka S. , de Moura Neto Carlos
Published: May 2012

Aluminum alloys have low specific weight, relatively high strength and high corrosion resistance and are used in many applications. Aluminum Alloy 2024 is widely used for aircraft fuselage structures, owing to its mechanical properties. In this investigation, Aluminum Alloy 2024 was given solid solution treatments at 495, 505, and 515°C followed by quenching in water. It was then artificially aged at 190 and 208°C. Subsequently, hardness measurements, tensile tests as well as impact and fatigue tests were carried out on the heat treated alloys to determine the mechanical properties. The tensile and hardness tests revealed similar mechanical properties for specimens of this alloy that were given the three solid solution treatments. Aluminum Alloy 2024 specimens that were solid solution treated at 515°C and artificially aged at 208°C for 2h exhibited the highest yield and tensile strength. In general, the increase in strength was accompanied by a decrease in ductility. Cyclic fatigue studies were conducted with symmetric tension-compression stresses at room temperature, using a bending-rotation test machine. The alloy solution heat treated at 515°C and aged at 208°C/2h was fatigue tested at constant frequency. The relation between stress amplitude and cycles to failure was established, enabling the fatigue strength to be predicted at more than 7.8x106 cycles, with maximum stress of 110.23 MPa. The fracture surfaces of specimens that failed after fewer cycles showed mainly precipitates and micro voids, whereas specimens that fractured after a higher number of cycles indicated that cracks initiated at the surface. The high cycle fatigue fracture surfaces revealed pores that could be due to precipitates from the matrix.
Mass Transfer in Irregularly-Shaped Solid: An Exact Solution Using the Galerkin-Based Integral Method
Authors: dos Santos I. Batista , de Lucena Silva L.P. , de Lima Antônio Gilson Barbosa
Published: May 2012

This paper presents a theoretical investigation of the mass transfer during the drying of solids of revolution with arbitrary shape. A two-dimensional mathematical model by assuming the liquid diffusion to be the sole mechanism of moisture transport, constant thermophysical properties and convective boundary condition at the surface of the solid is presented. The resulting equation is solved analytically by using the Galerkin-based integral method. Results of the mean moisture content and moisture content distribution within the porous solid are present and analyzed during the process, for different Biot number and aspect ratio. We conclude that solid drying rate is affected by Biot number and area/volume relationships, and which drying process is faster in sharp areas and closed to surface of the solid.
Study and Interpretation of the Mass Transfer Phenomena through Textile Structures in the Wet State
Authors: Geraldes Maria José , Monteiro C. , Hes Lubos
Published: May 2012

In last decades, increased attention is paid to comfort properties of textiles and garments. The most important parameters characterizing the called physiological comfort of textile structures are the evaporative resistance and water vapour permeability. Contrary to common textiles, protective and functional garments and, also some technical textiles, are also used in wet state, which affect their comfort properties. In this paper, PERMETEST commercial instrument is described, which provide reliable non-destructive measurement of evaporative resistance and water vapour permeability of fabrics in dry and wet state. By means of this instrument, evaporative resistance and water vapour permeability of cotton, polyester and cotton/polyester knitting fabrics, in the wet state, were experimentally determined and results were discussed. The effect of count yarn and composition of the above mentioned properties of these fabrics has been investigated as well. Some surprising results were achieved: with increasing fabrics moisture, the water vapour permeability also increases, especially with the presence of hydrophilic textile material.
Relations between Diffusion Paths and Interdiffusion Coefficients in the Ternary System Fe-Co-Ni
Authors: Priimets J. , Ugaste Ü.
Published: May 2012

Possible interrelations between diffusion paths and interdiffusion coefficients in the system Fe-Co-Ni are analyzed. It is found that the apparition of a straight line shape of diffusion paths imposes strong demands on the values of the conventional interdiffusion coefficients calculated from the experimental data. The possible consequences of this finding are discussed.
Phases in Austenitic Cast Steel
Authors: Garbiak Małgorzata , Piekarski Bogdan
Published: May 2012

The paper presents the characteristics of intermetallic phases occurring in heat-resistant cast austenitic 0.3% C-30% Ni-18% Cr steel with additions of niobium and titanium. Five alloys were examined, in which the content of the examined elements was (wt.%) Nb 0.03, 0.55, 1.57 and 1.92, and Ti 0.03, 0.05, 0.30, 0.83 and 1.00. The phase composition of alloys in as-cast state and after annealing (temperature of 800°C and 900°C, time of up to 300 hrs) was examined by X-ray diffraction technique. Depending on the chemical composition of cast steel, carbides of MC type (NbC, TiC, (Nb,Ti)C), M23C6, titanium carbonitrides TiCN and G phase were identified in its microstructure. The phase morphology was examined on the polished sections and surfaces of metallographic specimens after deep etching by electrolytic extraction method. It was found that M23C6 carbides assume the shape of rods, NbC carbides crystallise in the form of lamellae, and titanium carbonitrides TiCN in the form of cubes. An addition of both the stabilising elements favours the formation of double carbides (Nb,Ti)C of octahedral habit.
Thermal Properties of CuGa2 Phase in Inert Atmosphere
Authors: Kulikova T.V. , Bykov V.A. , Shunyaev K. Y. , Shubin A.B.
Published: May 2012

Thermal decomposition of copper digallide was studied using experimental (thermal analysis) and theoretical (thermodynamic modeling) methods. The temperatures of CuGa2 incongruent melting are in satisfactory agreement between experimental and calculated values. Small differences with the phase diagram can be explained by minor non-stoichiometry of the alloy samples. The experimental studies of thermal diffusivity and thermal expansion of CuGa2 were performed in the temperature range 298-500 K. The heat conductivity coefficient was further calculated using literary data concerning the density and heat capacity of the copper digallide.
Synthesis of ZnS/SiO2 Core-Shell by Sol-Gel Process and Covering then with Gold Nanoparticle and Study of its Photoluminescence Properties
Authors: Seyed Sadjadi Mirabdullah , Farhadyar Nazanin , Zare K.
Published: May 2012

Semiconductors have been suggested as ideal candidates for many electrical and optical applications and several groups have reported their successful synthesis in recent years. In particular, ZnS that is a direct wide band gap (3.91 eV) semiconductor and an important phosphor host lattice material, can be used in electroluminescent devices (ELD), due to its large band gap, which enables emission of visible light without absorption and efficient electron transport. In this work, we report synthesis and structural characteristics of gold covered core-shell nanometer size of ZnS/SiO2 thin films as a patterning materials for use as a protective layer in optical phase change discs prepared through a simple sol-gel process. The results obtained by transmission electron microscopy (TEM) images showed that, as prepared core-shell materials were well-aligned nanoprticles grew in the same direction and through X-ray diffraction (XRD) analysis, we found that ZnS/SiO2 core shell material was composed of crystalline ZnS core covered by an amorphous SiO2 shell. Photoluminescence (PL) measurements performed on core-shell samples before and after gold coverig samples have provided information regarding stoichiometric vacancies or interstitial impurities and enhenced intensity of the green emission of ZnS nanowires at room temperature due to sheelding with SiO2.
Silicon Carbide Solid-Phase Epitaxy on a Microporous Substratum
Authors: Zmievskaya Galina I. , Bondareva Anna L. , Savchenko V.V. , Levchenko Tatiana V.
Published: May 2012

The action flux of ions of inert gas on the substratum Si (100) leads to porosity into the crystal lattice and self-organization of these defects. The kinetic stochastic model of the phase transition at the initial stage is applied to find distributions of defects in sizes and on their coordinates in the layers. The accumulation of stress is determined by computer simulation. Layers of pores and cracks precede to solid state epitaxy of silicon carbide.
Determination of Pressure-Saturation-Permeability Relations by Centrifugation
Authors: Kačur Jozef , Budáčová Hana
Published: May 2012

In this work we discuss the problem of coupled saturated and unsaturated flow in porous media under centrifugation. Our mathematical model is described by Darcy's equation in saturated region and Richard's nonlinear and degenerate equation in unsaturated region. We use Van Genuchten model with soil parameters and express the Richard's equation in both head and saturation. Our numerical method is based on space discretization. We reduce the problem to an ODE system with an algebraic condition to keep the water mass balance (DAE system). In our mathematical model we consider two interfaces separating fully saturated, partially saturated and dry subregions. Our goal is the determination of soil parameters. We control the input/output of infiltrated water in the sample. The only measurements concerning the sample require the measuring of the time moments in which the moving water achieves prescribed values of momentum. These data are sufficient to determine the soil parameters.
Heat and Mass Transfer and Volume Variations during Drying of Industrial Ceramic Bricks: An Experimental Investigation
Authors: Barbosa da Silva J. , Almeida G. Silva , Neves Gelmires Araújo , Barbosa de Lima W.C.P. , de Farias Neto Severino Rodrigues , de Lima Antônio Gilson Barbosa
Published: May 2012

The purpose of this paper is to present an experimental study of brick drying. For the drying experiments, industrial brick (clay) was dried in an oven under controlled conditions of air velocity, air temperature and air relative humidity. The continuous drying experiments ended when the mass reached constant weight. In order, to obtain the balanced moisture content, each sample was kept under the same drying air temperature for 48 hours inside the oven. The tests were performed under atmospheric pressure. Results of the drying and heating kinetics and volume variations during the process are shown and analyzed. It was verified that air temperature has big influence in the drying rate during process. It was verified that the largest temperature, moisture content and stress gradients are located in the vertexes of the brick. The drying process happens in the falling drying rate period.
Hot Corrosion Resistance Properties of Al-Si Coatings Obtained by Slurry Method
Authors: Kochmańska Agnieszka
Published: May 2012

This paper presents the results of research on aluminide protective coatings manufactured on hightemperature creep resistant cast steel. The main purpose of these coatings is protection against the high temperature corrosion, at carburizing and oxidizing potential atmosphere. Coatings were obtained on cast steel type GXNiCrSi 3018 by slurry cementation in air atmosphere. The tests of carburizing and oxidizing were carried out. The structure of the coatings before and after carburizing and oxidizing is described in the present paper. The chemical composition, thickness and microstructure of coatings were determined. These coatings could protect equipment against hot corrosion at carburizing and oxidizing atmosphere and have thermal shocks resistance.
Characterisation of C-B-N Diffusion Layers Developed on High-Speed Steel Substrate
Authors: Chaus Alexander S. , Čaplovič Lubomír , Chaus Y. A. , Sojka J.
Published: May 2012

C-B-N diffusion layers on the samples of wrought and as-cast high-speed steels of AISI M2 grade have been developed thermo-chemically. Thermo-chemical treatment was carried out after full heat treatment and included holding for 1 and 3 h at 550°C in order to produce different C-B-N diffusion layers. The microstructure and component depth profiles in the C-B-N diffusion layers were studied by scanning electron microscopy and energy dispersive X-ray spectrometry. It was shown that well adhered (diffusion controlled) carbon-boron-nitrogen layers with nanosized microstructure can be thermo-chemically developed at 550°C for 1 h on the wrought and as-cast M2 high-speed steel substrates. In the samples made of the wrought M2 high-speed steel and held at 550°C for 3 h the C-B-N diffusion layer develops in the fiber-like morphology.
The Influence of Chemical Composition of Stainless Steel on the Formation of Low Temperature Nitrided Layer
Authors: Baranowska Jolanta , Kochmański Paweł , Bielawski Jarosław
Published: May 2012

This paper presents results of investigations on gas nitride layers of stainless steel. Steel with ferritic structure, containing different chromium and nickel content was used in the experiments in order to compare the influence of these two main alloying elements on layer growth kinetics and layer structure. Particular attention was paid to formation of Sphase and expanded martensite which usually are formed during lowtemperature nitriding of stainless steel. It was observed, that chromium and nickel content does not have a significant influence on layer growth kinetics but the treatment temperature does. It was also stated that Sphase formation is possible both in nickel alloyed and nickelfree steel depending on treatment parameters.
A Comparison of Thermal Dispersion Behaviour in High-Conductivity Porous Media of Various Pore Geometries
Authors: DeGroot Christopher T. , Straatman Anthony G.
Published: May 2012

The effect of pore geometry on the axial thermal dispersion conductivity for high-conductivity porous media under general thermal non-equilibrium conditions is studied numerically. Pore geometries including arrays of inline square and circular cylinders, staggered circular cylinders, and a three-dimensional idealization of a graphite foam pore geometry are used to study the effects of the solid constituent shape and arrangement, as well as the effect of a relatively complex three-dimensional pore structure. Results indicate that in general, the dispersion conductivity cannot be considered a simple function of the Péclet number due to the effects of inertia, which cause the dispersion behaviour to depend on both the Reynolds and Prandtl numbers. On the basis of the current results, it is recommended that the influences of the Reynolds and Prandtl numbers be considered separately when generating models for the dispersion conductivity.
Contaminant Transport in Partially Saturated Porous Media
Authors: Trojáková E. , Babušíková J.
Published: May 2012

We discuss the numerical modelling of unsaturated flow in porous media with contaminant transport, dispersion and adsorption. The mathematical model for unsaturated flow is based on Richard's nonlinear and degenerate equation. The model of contaminant transport is based on Darcy's law and mass balance equation. We present the operator splitting method for this problem.
In nature all of the physical processes are realized simultaneously and the time scale for adsorption differs from diffusion and convection significantly. In our numerical approximation we consider three sub-problems - first one is the problem of unsaturated flow, second one the problem of transport and dispersion and third one the adsorption problem.
Our numerical solution is based on implicit time discretization and space discretization. To achieve more correct numerical approximation we treat each of the sub-problems with another time scale and the data computed from one sub-problem, is the input data for the next sub-problem in each time interval. The convergence to the weak solution of the original problem is also discussed. Finally we show a couple of practical applications of the method and numerical experiments for direct problems.