bluuebunny/crossref_metadata_2025 huggingface dataset:
Roof Coatings for Reducing Warehouse Condensation Potential1
Authors: Smith John S.
Published: April 2010

White ceramic roof coatings were found to be significantly better than galvanized sheet metal in reducing the solar heat gain on roof panels like those used for the roof of a farmers stock peanut warehouse. However, the ceramic coatings were not better than a white acrylic latex paint in reducing solar heat gain. After four years of testing, there was no apparent difference in the durability of the ceramic coatings or paint. The ceramic coatings were reputed to have good thermal insulating properties, but these were not apparent in the study. The maximum mean two-hour temperature during the study occurred on September 14, 1991 with the galvanized control panel reaching a high of 69.3 C. The ceramic coated and painted panels due to their solar radiation reflective properties were approximately 19 C cooler than the galvanized control and approximately 14 C warmer than ambient temperature.
Development of a Large-Scale Field System for Screening Peanut for Resistance to Preharvest Aflatoxin Contamination1
Authors: Holbrook C. Corley , Matheron Michael E. , Wilson David M. , Anderson William F. , Will M. Elizabeth , Norden Alan J.
Published: April 2010

Preharvest aflatoxin contamination (PAC) of peanut occurs under prolonged periods of drought and heat stress. Evaluation of peanut germplasm may identify valuable sources of resistance to PAC, but will require a large scale screening system. The objective of this research was to develop a large-scale field system for screening peanut germplasm for resistance to PAC at Yuma, Arizona. Yuma is located in a desert and has great potential as a site for evaluating germplasm for resistance to PAC. Field studies were conducted in 1990 to determine if aflatoxin contamination would occur in drought stressed peanuts grown at Yuma. Aflatoxin levels up to 2,260 ppb were observed, however, 52% of the plots escaped contamination and the coefficient of variation (C.V.) were unacceptably large. During testing at Yuma in 1990 it was noted that drought stressed plants died quickly due to the rapid exhaustion of soil moisture. A subsurface irrigation system was installed in 1991 to alleviate this problem and allow for an extended period of drought stress in the pod zone. Results for 1991 showed a greatly increased mean aflatoxin contamination, a 50% reduction in the C.V., and a virtual elimination in the occurrence of escapes. A study was conducted in 1992 to compare plots with and without subsurface irrigation to determine if the differences observed between 1990 and 1991 were due to the use of subsurface irrigation. The use of subsurface irrigation in 1992 increased the mean contamination by over 100%, reduced the C.V. by over 50%, and reduced the percentage of escapes by over 90%.
Estimated Impact of Various Consumer and Policy Factors on Peanut Product Consumption1
Authors: Carley D. H. , Fletcher S. M. , Zhang P.
Published: April 2010

After reaching 585,000 mt of shelled peanuts (Arachis hypogaea L.) used in peanut butter and snack peanuts in 1989, use has decreased. In a national survey consumers agreed strongly that peanuts were good tasting, a good source of protein, and could be part of a balanced diet. Less than one-half agreed that peanuts are a healthy snack and are low in saturated fat. When thinking of snack foods, peanuts were placed low on the list of preferences.

In policy discussions, price is mentioned as the factor that may inhibit consumption growth. Retail price data on peanut butter and peanut snacks indicated a wide range in prices among cities, among stores within cities, and among brands.

The farmer's share of the retail price of a jar of peanut butter averages 26%. Retail prices increased 39 cents per 510 g jar from 1984 to 1992, while the farm value of the peanuts increased seven cents. Decreasing the support price for peanuts by $250 per 907 kg, decreases the farm value of peanuts in a jar of peanut butter from 56 cents to 35 cents. The decrease would result in an increase in peanut butter use of about five percent or about 35,000 mt. Price may be only one of several factors impacting consumption trends.
Possible DNA Viral Factors of Human Breast Cancer
Authors: Hsu Chun-Ru , Lu Tsong-Ming , Chin Lengsu William , Yang Chi-Chiang
Published: April 2010

Viruses are considered to be one of the high-risk factors closely related to human breast cancer. However, different studies of viruses in breast cancer present conflicting results and some of these works remain in dispute. DNA viruses, such as specific types of human papillomaviruses (HPV), Epstein–Barr virus (EBV), human cytomegalovirus (HCMV), herpes simplex virus (HSV), and human herpes virus type 8 (HHV-8), have emerged as causal factors of some human cancers. These respective exogenous viruses and the possibility of multiple viral factors are discussed in this review.
Imperatoxin A, a Cell-Penetrating Peptide from Scorpion Venom, as a Probe of Ca2+-Release Channels/Ryanodine Receptors
Authors: Gurrola Georgina B. , Capes E. Michelle , Zamudio Fernando Z. , Possani Lourival D. , Valdivia Héctor H.
Published: April 2010

Scorpion venoms are rich in ion channel-modifying peptides, which have proven to be invaluable probes of ion channel structure-function relationship. We previously isolated imperatoxin A (IpTxa), a 3.7 kDa peptide activator of Ca2+-release channels/ryanodine receptors (RyRs) [1,2,3] and founding member of the calcin family of scorpion peptides. IpTxa folds into a compact, mostly hydrophobic molecule with a cluster of positively-charged, basic residues polarized on one side of the molecule that possibly interacts with the phospholipids of cell membranes. To investigate whether IpTxa permeates external cellular membranes and targets RyRs in vivo, we perfused IpTxa on intact cardiomyocytes while recording field-stimulated intracellular Ca2+ transients. To further investigate the cell-penetrating capabilities of the toxin, we prepared thiolated, fluorescent derivatives of IpTxa. Biological activity and spectroscopic properties indicate that these derivatives retain high affinity for RyRs and are only 5- to 10-fold less active than native IpTxa. Our results demonstrate that IpTxa is capable of crossing cell membranes to alter the release of Ca2+ in vivo, and has the capacity to carry a large, membrane-impermeable cargo across the plasma membrane, a finding with exciting implications for novel drug delivery.
Clostridial Neurotoxins: Mechanism of SNARE Cleavage and Outlook on Potential Substrate Specificity Reengineering
Authors: Binz Thomas , Sikorra Stefan , Mahrhold Stefan
Published: April 2010

The clostridial neurotoxin family consists of tetanus neurotoxin and seven distinct botulinum neurotoxins which cause the diseases tetanus and botulism. The extreme potency of these toxins primarily relies not only on their ability to specifically enter motoneurons but also on the activity their catalytic domains display inside presynaptic motoneuronal terminals. Subsequent to neurotoxin binding and endocytosis the catalytic domains become translocated across endosomal membranes and proteolyze unique peptide bonds of one of three soluble N-ethylmaleimide-sensitive fusion protein attachment receptors (SNAREs), vesicle associated membrane protein/synaptobrevin, synaptosome associated protein of 25 kDa, or syntaxin. As these substrate proteins are core components of the vesicular membrane fusion apparatus, cleavage of any of the substrate molecules results in the blockade of neurotransmitter release. This review summarizes the present knowledge about the molecular basis of the specific substrate recognition and cleavage mechanism and assesses the feasibility of reengineering catalytic domains to hydrolyze non-substrate members of the three SNARE families in order to expand the therapeutic application of botulinum neurotoxins.
Understanding spikelet orientation in Paniceae (Poaceae)
Authors: Zanotti Christian A. , Pozner Raúl , Morrone Osvaldo
Published: April 2010

Spikelet structure and grouping are key characters to identify grasses. Here we tested the possibility that spikelet pairs, a distinctive morphological structure of many Andropogoneae and Paniceae, are the starting point for a secondary single spikelet condition that can also explain the change of spikelet orientation among Paniceae genera. As a first approach, we studied the inflorescence development of Paspalum simplex, P. stellatum, and Axonopus sufultus to clarify the origin of the spikelet orientation and other basic homologies. The results support that solitary spikelets of A. suffultus are homologous to the subsessile spikelets of P. simplex and that solitary spikelets of P. stellatum are homologous to the pedicellate spikelet of P. simplex. This last homology supports that spikelet orientation results from a differential reduction/abortion of either the pedicellate or the subsessile spikelet primordia. We also discuss the possibility that the RAMOSA and polar auxin pathways could play a role in the abortion of the lateral subsessile spikelets in P. stellatum. However, the apical meristem inhibition observed in A. suffultus and P. stellatum seems to depend on a very different genetic control, suggesting that the single spikelet condition is homoplasic within Paniceae and derived from at least two different genetic mechanisms.
Population genetic analysis of safflower (Carthamus tinctorius; Asteraceae) reveals a Near Eastern origin and five centers of diversity
Authors: Chapman Mark A. , Hvala John , Strever Jason , Burke John M.
Published: April 2010

Analyses of genetic variation in crop gene pools are a powerful tool for investigating the origin and early evolution of crop lineages. Such analyses also have the potential to identify unique genetic resources for continued crop improvement. The oilseed crop safflower (Carthamus tinctorius) is believed to have been domesticated in the Fertile Crescent region, but up to 10 geographic centers of similarity throughout the world have been proposed based on morphology. Nuclear microsatellite analysis of accessions from each of the 10 proposed centers of similarity, as well as individuals of the progenitor species, suggested the presence of five genetic clusters (1, Europe; 2, Turkey–Iran–Iraq–Afghanistan; 3, Israel–Jordan–Syria; 4, Egypt–Ethiopia; and 5, the Far East–India–Pakistan). North American accessions, products of a secondary introduction from the native range, suggest that a subset of the native accessions harbor unique genetic diversity that could be useful in future breeding efforts. Overall, a Near Eastern origin of safflower was confirmed based on the genetic similarity between the progenitor and the Near Eastern safflower accessions, as well as previous archaeological finds. Genetic differentiation between geographical clusters of accessions is evident, although not to the degree proposed based on morphology.
Cycad mutualist offers more than pollen transport
Authors: Marler Thomas E.
Published: April 2010

Specialist insects share obligate mutualisms with some contemporary cycad species whereby the insect's pollination services are rewarded with a nursery in which the insect's larvae consume the postdispersal male cone. I prevented visits of the pollinator moth Anatrachyntis sp. to male Cycas micronesica (Cycadaceae) cones to show that consumption of the cone tissue by the mutualist hastened initiation of the plant's subsequent reproductive event. This is the first documented case where removal of a postdispersal cycad pollination organ speeds up subsequent reproductive events, and the current paradigm that the offering of cone tissue as a nursery is a sacrifice by the plant in return for the pollination services is therefore inaccurate. In C. micronesica, the herbivory stage of pollination mutualism confers a cryptic benefit of cone tissue disposal, which translates into an increase in ultimate lifetime reproductive effort. The plant population relies on the pollinator for moving gametes, as well as for increasing the number of male coning events. The dual benefits afforded to the plant by associating with this pollinator shows that mutualism can operate simultaneously on very different traits.
Caricaturing 'The Colonial Good Life' in French Indochina
Authors: Vann Michael G.
Published: April 2010

André Joyeux's La Vie large des colonies ['The Colonial Good Life'] is an insider's portrait of the French colonial encounter in Southeast Asia. Published in Paris in 1912 but most likely penned in Saigon, the collection of cartoons explores the racial order of the colony. Although the artist critiques many aspects of the colony and highlights certain gross injustices, such as the coloniser's sexual predation and physical violence, he also articulates many of the bluntly racist French stereotypes of the Vietnamese, Chinese and other Asians in the colony. Joyeux, as an artist and as an art teacher, contributed to the development of cartoon and caricature as a medium in Vietnam, which would eventually be used in the anti-colonial, nationalist and communist movements. La Vie large des colonies is of importance as a primary source in the study of empire.
The Spanish Tebeo
Authors: Alary Viviane
Published: April 2010

It seems difficult to speak about comic art in Spain without considering what tebeos mean to Spaniards. This term is not simply a Spanish translation of bande dessinée. It refers to a special kind of comic strip aimed at children, which appeared in the late 1920s. Tebeos were the only available mass medium in Spain after the Civil War (1936-1939). In this contribution we want to analyse tebeos as an editorial, social and cultural phenomenon, with the aim of demonstrating that 'tebeo-culture' survived even after the collapse of the 'tebeo-industry' in the 1970s and 1980s. In addition, we will examine the question of the cultural legitimacy of comic art in Spanish society.
Naître femme en Chine : une perspective démographique
Authors: Attané Isabelle
Published: April 2010

Résumé Un traitement différencié des hommes et des femmes a des répercussions dans de multiples domaines de la société. En Chine, des inégalités entre les sexes demeurent en particulier dans l’accès à l’instruction, à l’emploi et à la santé, mais aussi en matière d’héritage, de salaire, de représentation politique ou de prise de décision au sein de la famille. La démographie, parce qu’elle est étroitement liée aux caractéristiques comportementales et sociétales prévalant au sein de la population, n’échappe pas à ce contexte d’inégalités. La Chine présente diverses caractéristiques démographiques atypiques qui traduisent des traitements inégalitaires des hommes et des femmes. Compte tenu de la préférence traditionnelle pour les fils, ces dernières connaissent en effet, eu égard à la situation généralement observée, une moindre probabilité de naître et, dans l’ensemble, elles ne survivent pas aussi longtemps qu’elles le pourraient compte tenu du contexte sanitaire et socioéconomique global. Par conséquent, la population de la Chine devient de plus en plus masculine. Il apparaît en outre que, à chaque étape de leur existence, les femmes peinent à accéder à une véritable autonomie. Elles subissent encore de fortes contraintes concernant leur vie reproductive et, plus nombreuses que les hommes lorsqu’elles vieillissent, elles sont bien souvent exposées à plus de précarité sociale et économique que ces derniers.
Ultrasound Effects on the Mass Transfer Processes during Drying Kinetic of Olive Leaves (Olea Europea, var. Serrana)
Authors: Cárcel J.A. , Nogueira Regina Isabel , García-Pérez J.V. , Sanjuán N. , Riera E.
Published: April 2010

The large amount of materials derived from olive trees pruning may constitute a source of compounds with antioxidant activity. The air drying of raw matter is a previous stage before extraction preserving the raw matter and avoiding the interference of water on the process but it constitutes a slow and high energy demanding process. In this sense, the application of high intensity ultrasound could affect the mass transfer rate. In order to address the influence of ultrasound on the drying process of olive leaves, air drying experiments were carried out (40°C and1 m/s) without (0 W) and with ultrasound application (8, 16, 25 and 33 kW/m3). The different drying conditions were tested by triplicate. To model the experimental data, diffusional models considering or not the external resistance to mass transfer were used. The model without considering external resistance did not fit well to the experimental data. However, the model including external resistance achieved percentages of explained variance above 99.7%. The influence of ultrasound on diffusivity was not significant but a significant dependence was found for the mass transfer coefficient, proportional to the power density applied.
A Kinetic Model for Dissolution of Second Phases in Die-Cast Mg Alloy AM50
Authors: Han Li Hong , Hu Henry , Northwood Derek O. , Nie Xueyuan
Published: April 2010

Dissolution of secondary phases during thermal treatment in cast magnesium alloys influences their engineering properties. In this study, a kinetic model based on a Kissinger-type method has been developed for describing dissolution of secondary phases in the high pressure die cast magnesium alloy AM50 during a thermally activated heating process. Also, differential scanning calorimetry (DSC) was effectively used for investigating the dissolution kinetics of secondary phases in the AM50 alloy. By fitting a kinetic model to the DSC results, the activation energy of the dissolution of the secondary phases can be determined. In parallel, the microstructure of the alloy was analyzed by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS). It was found that the distribution of secondary phases and the concentration of alloying elements both at the grain boundaries and in the grains play an important role in the solid-state transformation kinetics of die cast magnesium alloy AM50.
Ultra Fine Grain via Friction Stir Processing of 7075-T6 Grade Aluminum Alloy
Authors: Esmaily M. , Shokuhfar Ali
Published: April 2010

In this research work, characterization of a broad area zone with ultra fine grain size of 7075-T6 grade aluminum sheets with the thickness of 8 mm was carried out using friction stir processing (FSP) and quenching by liquid nitrogen on both, i.e. upper and lower, surfaces. In the first step, ability and competence of two tools with different designs in creating a stir zone without any defects were examined; selected samples were exposed to FSP by efficient tools and in a highly extensive quenching media. Friction stir processing was carried out on the samples in three different rates (fast, medium and slow), the mechanism of ultra fine grain size as well as the creation of dislocation in thermo-mechanical affected zone was evaluated. Micro structural evaluation using transmission electron microscopy showed that the samples exposed to FSP in slow manner, had the finest grain size (20 nm) in the stir zone, and the lowest amount of dislocation in the thermo-mechanical affected zone. More details are discussed in the presented results.
Synthesis and Characterization of Gd2O3 Doped CeO2 Nanopowders by a Glycothermal Process
Authors: Kim Hyun Ju , Park Hoy Yul , Chu Min Cheol , Bae Dong Sik
Published: April 2010

Gd2O3 doped CeO2 nanopowders were prepared under high temperature and pressure conditions by precipitation from metal nitrates with aqueous ammonium hydroxide. Spherical shape Gd2O3 doped CeO2 nanopowders were obtained By a reaction at the temperature range of 200°C – 230°C for 6 h. The average size and size distribution of the synthesized particles were below 10 nm and narrow, respectively. The XRD diffraction pattern shows that the synthesized powders were crystalline. This study has shown that the synthesis of Gd2O3 doped CeO2 nanopowders is possible under glycothermal conditions in ethylene glycol solution. The effects of synthesis parameters, such as the solvent ratio of starting solution, pH of starting solution, reaction temperature and time, are discussed.
Analysis of Cryogenic Refrigeration Cycle Using Two Stage Intercooler
Authors: Lee Ho Saeng , Oh S.T. , Yoon Jung In , Lee S.G. , Choi K.H.
Published: April 2010

This paper presents the comparison of performance characteristics for the several natural gas liquefaction cycles. The liquefaction cycle with the staged compression was designed and simulated for improving the cycle efficiency using HYSYS software. This includes a cascade cycle with a two-stage intercooler which is consisted of a Propane, Ethylene and Methane cycle. In addition, these cycles are compared with a modified staged compression process. The key parameters of the above cascade cycles were compared and analyzed. The COP (Coefficient of Performance) of the cascade cycle with a two-stage intercooler and a modified staged compression process is 13.7% and 29.7% higher than that of basic cycle. Also, the yield efficiency of LNG (Liquefied Natural Gas) improved compared with the basic cycle by 28.5%.
Comparative Tribological Behavior of V(N,C) and VC Diffusion Coatings
Authors: Fazlalipour F. , Niki Nushari M. , Shakib N. , Shokuhfar Ali
Published: April 2010

Hard coatings show various tribological behaviors against different contact materials (counter-faces) during dry sliding depended on their microstructure, surface morphology and encountered tribological systems and condition. In this work, the tribological and wear mechanisms of vanadium carbide (VC) and vanadium nitrocarbide (V(N,C)) layers were examined against WC/Co cemented tungsten carbide pin during pin-on-disk sliding wear testing. The V(N,C) layer was produced by a duplex surface treatment involving the gas pre-nitrocarburising followed by thermo-reactive diffusion (TRD) vanadizing technique. The coating layers were characterized by a cross sectional and morphological examination methods and X-ray diffraction analysis to identify damages of the coating’s surface. Wear mechanisms were determined by SEM microscope in BSI and SE mode accompanied by EDS analysis. Results revealed that the surface morphology of the V(N,C) coating consist of dense and smooth layer in comparison with the VC coating surface which reveals a non-uniform structure with chasms. It was determined that the activation of tribo-chemical system and oxidizing of the coating layer together with minor plastic deformation are the dominant wear mechanism in the V(N,C) coated steel. In the case of the VC coating, combination of abrasive wear and adhesion of pin material to coating and vice versa are the major impairing mechanisms.
Experimental and Analytical Study of Contaminant Transport Resulting from Dissolution of a Flat Surface Buried in a Packed Bed
Authors: Delgado João M.P.Q. , Vázquez da Silva M.
Published: April 2010

The present work describes the mass transfer process between a moving fluid and a slightly soluble flat surface buried in a packed bed of small inert particles with uniform voidage, by both advection and diffusion/dispersion. Numerical solutions of the differential equations describing solute mass conservation were undertaken to obtain the concentration profiles, for each concentration level. A simple mathematical expression that relates the dependence between concentration and axial distance is proposed to describe the approximate size of the diffusion wake downstream of the reactive solid mass.
Mathematical Model of Forecasting the Coke Quality Indicators
Authors: Dmitriev Andrey N. , Chesnokov Yu.A. , Arzhadeeva G.Yu.
Published: April 2010

A mathematical model for the forecasting of the basic metallurgical properties of coke depending on the quality indicators of coals and carbonization parameters is developed. The base of the model are the theoretical and statistical dependences of the physico-chemical and petrographic properties of initial coals on the reactivity and mechanical strength of the coke. These indicators depend on diffusion processes during carbonization. On the basis of initial data, the material and heat balance of the coking process are made and the product price is calculated. The full-function program includes: the initial database interactively formed on the basis of the coals quality certificates and concentrates; the calculating unit of forecasting of the coke properties, allowing to fulfil the mathematical model adapting for the concrete industrial conditions of carbonization process; the unit to calculate results. The calculated values, i.e. the Coke Reactivity Index (CRI) and the Coke Strength after Reaction (CSR) can be used further for technical and economical calculations in the balance logic-statistic model of the blast furnace smelting operation. Or using the feedback, it is possible to calculate necessary relations of the burden components for the carbonization.
Influence of Elements Oxides Microadditives with Major Cationic Radius on Properties of Silicate Bundle
Authors: Dmitriev Andrey N. , Perepechaev V.P. , Chesnokov Yu.A.
Published: April 2010

For the agglomerates of the Kachkanar deposit iron ore the role of elements with ionic radius larger than for magnesium and calcium in the formation of the strength characteristics and parameters of the viscous-plastic state of iron-ore materials is shown. The strength characteristics of high-quality sinters are largely defined by the low stressed state of a silicate bundle which is formed in the cake cooling-down period. The diffusion processes at the glasses recrystallization at the cakes refrigeration can be reduced by injection of the elements impeding these processes and having low -strength cation-oxygen connections, that, apparently, should ¬ hinder in formation of the crystals with their participation. From these positions the stabilizing additions are the cations of heavy elements having major radius and remote from the valence electrons¬. It according to the theory of the stressed state of the oxide ¬ systems is accompanied by the grain refinement, decrease of the microstresses ¬ and fissurings of the glass matrix and therefore the defectiveness of cake structure. On the basis of the mathematical model leaning on the results of the dilatometric explorations the positive influence of the microadditives of the barium oxide on increase of temperature of beginning and narrowing of the softening range of sinters is revealed.
Diffusion in SC Ni-Base Superalloy under Viscoplastic Deformation
Authors: Kommel Lembit A. , Straumal Boris B.
Published: April 2010

Deformation-enhanced diffusion in single-crystalline Ni-based superalloy specimens have been investigated under the conditions of hard cyclic viscoplastic tension-compression deformation. The chemical composition of phases before and after cyclic deformation was investigated by filed-emission scanning electron microscopy. At low strain amplitude values (0-0.05%; 0-0.2%; 0-0.5%) the material shows upscaled viscoelastic behavior and microstructural stability. At the increase of strain amplitude in the γ+γ’-phase (0-1%), the Ni, Re and Co content decreases, whereas Al and Mo content increases significantly. On the contrary, in the single γ’-phase area, the Ni and Co content was increased, which was accompanied by a decrease of Nb, Cr, Ta and Al content. The length of dendrite arms was significantly decreased as compared to primary dendrite arms and γ+γ’-rafts were formed parallel to the stress axis direction. As a result of the deformation-enhanced, diffusion the necking of dendrites accompanied with longitudinal cracking by the dendrite axis and cross-sectional radial cracking by interdendritic region of single crystalline specimen occurs.
Effect of Reactive Elements and Microstructure of Steel on High Temperature Oxidation Behaviour of Ferritic Stainless Steels
Authors: Fujikawa Hisao
Published: April 2010

The effect of different carbonitride forming elements on the oxidation performance of a 17Cr steel has been investigated. Whilst C and N are shown to have deleterious effects on the formation of protective oxides on unstabilised steel, a relationship has been found between the strength of the carbonitride former and the relative improvement in the oxidation performance. Furthermore, the appearance of the austenite phase has harmful influence on the oxidation resistance of the ferritic steel because the diffusion rate of Cr, Fe and so on is much slower in the austenitic structure than in the ferritic structure. The improvement is the most pronounced when the stabilizing element is Zr. The formation of the scale observed using transmission electron microscopy has been shown to be strongly controlled by the inward diffusion of the oxidant.
On the Grain-Boundary Diffusion in Polycrystalline Materials and Thin Films
Authors: Beke Dezső L. , Bernardini Jean
Published: April 2010

In this paper, examples of some of the most challenging features of GB diffusion are considered covering selected problems, strongly related to the research activity at our Laboratories and to the scientific interest of Boris Bokstein too. The following problems (and still open questions related to them) are addressed: i) Diffusion in a random network of grain boundaries with different structures and diffusion coefficients in polycrystalline materials; ii) Segregation effects; iii) Stress effects and iv) Effect of the presence of moving and/or non-equilibrium grain boundaries.
Air Oxidation Behaviour of a Ti-6Al-7Nb Alloy
Authors: Unlu Mehtap Deniz , Meydanoglu Onur , Çimenoğlu H.
Published: April 2010

Air oxidation behavior of a Ti6Al7Nb alloy was examined over the temperature range of 873 –1173 K for different time intervals ranging in between 12 and 72 h. The rate of oxidation evaluated according to the weight gain measurements, fitted parabolic kinetics by yielding oxidation activation energy of 226 kJ/mol. Rutile and anatase modifications of TiO2 formed on the surface as the result of air oxidation. Oxidation temperatures higher than 923 K encouraged rutile formation rather than anatase. As temperature of oxidation was increased, the thickness of the oxide layer increased. Thicker oxide layer provided higher surface hardness and better protection against a corrosive media (5 M HCl solution) was provided.
The Effect of Oxidation on The Structure and Hardness of (Zr, Hf)N Coatings
Authors: Atar Erdem , Kayali E.S. , Çimenoğlu H.
Published: April 2010

In the present study, the effect of oxidation on the structure and the hardness of ternary (Zr, Hf)N coatings, whose Hf content was varied between 0 and 21 wt.%, has been systematically examined. Coatings were applied on AISI D2 tool steel plates by arc physical vapor deposition (PVD). Oxidation was conducted at 400oC for times up to 12 h in air. Ternary (Zr, Hf)N coatings are found to be more susceptible towards oxidation compared to binary ZrN coating. Oxidation caused the formation of a mixed oxide layer composed of ZrO2 and HfO2. Formation of oxide layer was accompanied by a reduction in hardness. Hardness values of Hf free and Hf alloyed (Zr, Hf)N coatings were very close to each other both in as-deposited and oxidized states.
The Influence of Stress on Interstitial Diffusion - Carbon Diffusion Data in Austenite Revisited
Authors: Christiansen Thomas L. , Somers Marcel A.J.
Published: April 2010

The present paper addresses the influence of chemical induced stresses on diffusion in interstitial systems. This is exemplified by simulations of carbon diffusion in austenite at high temperatures and it is shown that old well established literature data is flawed by the occurrence of composition induced stress. For the technological relevant system of expanded austenite the diffusion can be dramatically affected by composition induced stress.
A Limited Condition for Bifurcate or Trifurcate Kirkendall Planes in Multiple Phase Diffusion Couples
Authors: Shimozaki Toshitada , Okino Takahisa , Lee C.G. , Taguchi O.
Published: April 2010

In general, only one Kirkendall plane can be seen in a diffusion couple. However, bifurcate or trifurcate Kirkendall planes have been reported in Ti/TiAl3 or Co/CoSi2 multi-phase diffusion couples (M-couple) [1,2].
The authors [3] have previously shown a numerical technique to analyze the movement of multiple markers (M-M) embedded in a M-couple taking the molar volume change effect to the diffusion direction into account. Using this technique, one can visualize the places where vacancies (lattice planes) are annihilated or generated in the couple. Here, we try to demonstrate the bifurcate or trifurcate Kirkendall planes in the M-couple and clarify the limited conditions of bifurcate or trifurcate Kirkendall planes by using this numerical technique.
Empirical Expression for Estimation of Thermal Characteristics of Materials Used for Thermal Protection
Authors: Essiptchouk Alexei M. , Charakhovski L.I. , Silva W. , Filho G.P. , Maciel Homero S.
Published: April 2010

A formula for quick calculation of thermal characteristics of materials used for thermal protection is proposed. The mode of heating of the sample external surface (subjected to thermal exposure) is approximated by two regions, which differ by corresponding boundary conditions on the heating surface: T_f=cτ (linear growing with time) and T_f=const (with permanent temperature of destruction). That approximation permits to obtain an analytical solution in integral form. In order to simplify and accelerate data treatment, a simple empirical formula is proposed. A contribution of each thermal region is proportional to the regime duration. A good agreement with an analytical solution is shown.
Ultra Rapid Sintering of Ceramics
Authors: Hing Peter
Published: April 2010

The paper presents some preliminary investigations on the sintering of alumina ceramics to translucency in a low thermal mass furnace. It is found that extremely fast sintering occurs in a forming gas atmosphere. Rapid densification occurs in minutes rather than hours normally encountered in conventional sintering of ceramics.
Molecular Dynamics Calculation of Hydrogen and Iron Diffusion in Molten Tantalum under an Electric Field
Authors: Pastukhov E.A. , Vostrjakov A.A. , Sidorov N.I. , Chentsov V.P.
Published: April 2010

The molecular dynamics (MD) method for analysis of the electric field intensity affecting iron impurities removal from tantalum in the presence of hydrogen is used. The radial distribution functions and diffusivities of hydrogen and iron atoms in a tantalum melt at 3400K under an electric field and without are obtained. An electric field imposed on liquid tantalum with an iron impurity increases the tantalum diffusivity more considerably than for iron atoms. Hydrogen introduction into the MD - cell without an electric field gives a much lower increase of the tantalum diffusivity, but a more considerable increase for iron. Simultaneous imposing an electric field and hydrogen introduction into the MD – cell keeps the tantalum and iron diffusivities at the level of the effect of an electric field. Thus the imposition of an electric field is a main parameter of the increase of the iron diffusivity.
Synthesis and Characterization of Ag Doped Hydroxylapatite via the Decomposition of EDTA Chelate
Authors: Cayir Dilara , Ergun Celaletdin , Guvendik Sabahattin
Published: April 2010

It has been proven that HA coatings on implant materials treated with silver exhibited excellent antibacterial effects. Silver (Ag) ions were successfully incorporated into HA structure with the precipitation method. Although this method was pretty much suitable for the synthesis in powder form, it is not applicable to in-situ coating processes. The aim of the current study is to synthesize Ag ion incorporating HA via the decomposition of EDTA Chelate. For this reason, Ag doped crystalline-sodium and carbonate-containing HA solutions will be prepared using calcium-EDTA in a sodium phosphate solution, hydrogen peroxide and silver nitrate. As the source of Ag ions, silver nitrate was added into the solution in the desired proportions. Then, the samples were sintered at temperatures from 800oC to 1100oC and characterized with XRD and SEM.
Thermo-Mechanical Materials Analysis
Authors: Koštial Pavel , Ružiak Ivan , Jonšta Zdenĕk , Tvrdý Miroslav
Published: April 2010

In this paper, we present the results of complex thermo-mechanical analysis (CTMA). In the technical point of view CTMA contains both thermovision camera and tensile machine which are in a perpendicular position. We have measured the cooling curve of the sample after its tensile deformation. On the basis of an exponential model of cooling body with respect to Biot number Bi value it is possible to calculate the specific heat capacity , thermal diffusivity and thermal conductivity . The method has been tested on a variety of materials and the results have been compared to those in charts or obtained by reference independent experiments. We obtained a very good agreement of all gathered experimental results with those of comparative ones. We also measured mechanical properties of materials such as yield stress, tensile strength, Young´s modulus of elasticity and ductility.
Effect of Homogenization Time and Cooling Rate on Martensitic Transformations in Ti-57.5%wtNi Alloy
Authors: Movahed P. , Shokuhfar Ali , Kaffash H. , Etaati A. , Bolvardi H. , Tavakoli H.
Published: April 2010

NiTi alloys containing more than 55%wt nickel undergo precipitation of Ni4Ti3, Ni3Ti2, and Ni3Ti phases during various heat treatments which could have a great effect on the chemical composition of the matrix and behavior of alloy. In this investigation, a NiTi alloy with Ti-57.5%wt nickel content, produced by vacuum induction melting in a graphite crucible, were subjected to the homogenization heat treatments in 1100oC and for various time periods (0.5, 1, 2, and 4 hours). The subsequent cooling was conducted in different cooling media (furnace and air) in order to examine the effect of cooling rate. Microstructural investigations show Ni4Ti3 particles with bimodal size distribution in furnace cooling. Differential scanning calorimetry demonstrates the correlation between homogenization time and transformation temperatures of the alloy.
Desorption of Hydrogen from CeNi3 Intermetallic Hydrides
Authors: Lushnikov Stepan Alexandrovich
Published: April 2010

After hydrogen desorption from hydrides based on crystal and partly amorphous CeNi3 compounds samples were obtained with a composition CeNi3Нx (x = 0.5, 0.9). All samples were investigated by X-ray diffraction under the usual conditions. It was revealed that samples after hydrogen desorption have hexagonal and orthorhombic structure of the metallic matrix with cell parameters close to the initial alloy CeNi3. Such structural behavior under hydrogen desorption is determined by the desorption conditions and depends on different hydrogen diffusion in the lattice.
Unifying Theory for Natural and Man-Made Flow Systems: an Application to Design of Porous Material for Particulate Control
Authors: Miguel Antonio Ferreira
Published: April 2010

According to constructal theory, the flow architecture emerges in time such that it provides progressively greater access to its currents. The emergence of flow architecture in nature is analogous to emergence of configuration in man-made (engineered) flow systems, and that features of materialization of design can be predicted based on the constructal theory. To support this view, we show that the emergence of configuration in natural flow systems can be approached based on the constructal law. Man-made flow systems achieve high performance by acquiring the suitable architecture (configuration). In this study, we also rely on the constuctal law to design a device for particulate matter control with an optimized function. Therefore, the emergence of optimal flow architecture is analogous to both natural and man-made systems. The features of materialization of design do not occur by chance, and can be explained or predicted based on this physical law.
Heat Transfer Enhancement of Jet Impingement on a Flat Plate Attached by a Porous Medium with a Center Cavity
Authors: Wu Pey Shey , Hsieh Chia Yu , Tsai Shen Ta
Published: April 2010

Jet impingement heat transfer on a target plate covered with a thick porous layer with or without a cylindrical center cavity is experimentally investigated using the transient liquid crystal technique. Based on the results of jet impingement on a bare flat plate, heat transfer enhancement due to the attachment of porous medium is assessed. The varying parameters in the experiments include the nozzle-to-plate distance, jet Reynolds number, jet-to-cavity diameter ratio, and the cavity depth. Results of Nusselt number distribution, stagnation-zone Nusselt number, and averaged Nusselt number over a region of 3 times the hole diameter are documented. Experimental results show that the attachment of the porous layer with a center cavity can either hamper, or effectively enhance the jet impingement heat transfer over a flat plate. The maximum enhancement occurs at jet Reynolds number of 12400 when the cavity is a through hole and the cavity has the same diameter as the jet. The stagnation-zone Nusselt number increases 58.3% and the averaged Nusselt number increases 77.5% at the maximum enhancement condition. On the other hand, the addition of the thick porous layer without a center cavity gave rise to severe adverse effect on jet impingement heat transfer.
Numerical Simulation of Natural Convection in a Mold
Authors: Pirmohammadi Mohsen , Sheikhzadeh Ghanbar Ali , Ghassemi Majid , Hamedi Mohsen
Published: April 2010

Numerical study of natural convection heat transfer inside a differentially heated square enclosure with adiabatic horizontal walls and vertical isothermal walls is investigated.
Two insulated ribs are symmetrically located on horizontal walls. The governing non-linear equations are solved in a two-dimensional domain using a control volume method and the SIMPLER algorithm for the velocity–pressure coupling is employed. The results will be presented in forms of streamlines, isotherms and Nusselt number for Rayleigh number 106. It is shown that for small rib height the isotherms indicate the laminar boundary regime with high temperature gradient near the bottom of the hot surface and the top of cold one. However, as rib height increases this boundary layer is vanished. Also it is found that as the length and height of the ribs increase the mean Nusselt number decreases.
Study on Homogenization Time and Cooling Rate on Microstructure and Hardness of Ni-42.5wt%Ti-3wt%Cu Alloy
Authors: Etaati A. , Shokuhfar Ali , Omrani E. , Movahed P. , Bolvardi H. , Tavakoli H.
Published: April 2010

Over the last decades, numerous investigations have been conducted on Nitinol properties. However, the effects of alloying elements on Ni-rich NiTi alloys have been considered less. In this research, different effects of homogenization time and cooling rate on the behaviors of Ni-42.5wt%Ti-3wt%Cu alloy were evaluated. The mentioned alloy was fabricated by vacuum arc melting method. Three different homogenization times (half, one and two hours) and three cooling media (water, air and furnace) were selected. The microstructure and hardness were examined by means of optical and scanning electron microscope (SEM) equipped with an energy dispersive X-ray (EDX) analysis and hardness test, respectively. According to the microscopic investigations, no significant changes were observed after half an hour. However, results indicate that increasing time of homogenization leads to finer precipitations and a uniform distribution of them. The various cooling environments result in the formation of two types of precipitation phases. It was seen that in the high cooling rate, the majority of precipitations consisted of Ti2(Ni,Cu) while by decreasing cooling rate NiTiCu precipitates appeared too, which affect the hardness.
Numerical Studies of the Diffusion Processes and First Step Oxidation in Nickel-Oxygen Systems by Variable Charge Molecular Dynamics
Authors: Garruchet Sébastien , Politano Olivier , Arnoux Patrick , Vignal Vincent
Published: April 2010

Variable charge molecular dynamic simulations have been performed to study the diffusion mechanisms of oxygen atoms (O) in nickel (Ni) in the temperature range 950-1600 K and the very first steps of oxidation of monocrystalline nickel surfaces at 300 K and 950 K. The oxygen diffusivity can be well described by an Arrhenius law over the temperature range considered. The oxygen diffusion coefficient has been analysed and values of Ea = 1.99 eV for the activation energy and D0 = 39 cm2.s-1 for the pre-exponential factor were obtained. The first steps growth of the oxide layer show that after the dissociative chemisorption of the oxygen molecules on nickel surface, the oxidation leads to an island growth mode as observed experimentally.
Intermetallic Growth: Structure-Sensitive Effects
Authors: Paritskaya Lyudmila N. , Kaganovsky Yuri S. , Bogdanov V.V.
Published: April 2010

The kinetics of intermetallic growth in the bulk, along the surface and grain boundaries (GBs) was studied in the Cd-Ni, Cd-Cu and Cu-Sn systems. Bulk dynamic diffusion coefficients exceed by a few orders of magnitudes the tracer self-diffusion coefficients in homogeneous phases. The reasons for this difference are discussed in terms of departure of growing intermetallics from stoichiometry due to the simultaneous existence of two processes: interdiffusion through the growing phase layer and chemical reactions at interfaces. Accelerating contribution of GBs and free surfaces, as fast diffusion paths, into diffusion penetrability of growing intermetallics has been investigated. It was found that the rates of lateral phase spreading along free surfaces and GBs exceed several times the rate of phase growth in the bulk. Accelerating GB contribution depends on the grain size. Nano-dispersed thin films demonstrate maximal phase propagation rates, which several times exceed even the rates of lateral phase spreading along free surfaces in coarse-grained polycrystals.
Investigation of Dynamic Recrystallization in an Al-Li-Cu-Zr(-Mg) Alloy
Authors: Rezaei Arash , Ahmadi Shahram , Shokuhfar Ali
Published: April 2010

In this investigation, the dynamic recrystallization phenomenon (DRP) of an Al-Li-Cu-Mg-Zr alloy was studied at two temperatures, 350°C and 400°C. Wedge samples were subjected to hot rolling deformation in both temperature and one passes. For wedge specimens, reduction up to 70% was considered. Results showed that the grain size of the specimens after hot rolling decreases from 100 μm to 30 μm because of DRP. Furthermore, it is observed that critical reduction for starting DR at 400°C is 40% and at 350°C reduction must increase to 50%.
Effect of a Shield on Mixed Convection in a Rectangular Enclosure with Moving Cold Sidewalls and a Heat Source on the Bottom Wall
Authors: Sheikhzadeh Ghanbar Ali , Musavi S.H. , Sadoughi N.
Published: April 2010

In this work, the mixed convention of air inside a rectangular cavity with moving cold sidewalls is studied numerically. A constant flux heat source is attached to the bottom wall of the cavity. A thin thermal shield is located at a specific distance above the heat source. The governing equations are solved using appropriate numerical methods. A parametric study has been conducted and the effects of heat source length, its location and the shield distance from the source on the heat transfer have been investigated. The results show that the heat dissipation increases as the heat source and the shield are moved up to a certain distance towards either sidewall. However, moving them beyond this limiting distance results in the reduction of heat dissipation. It is shown that the presence of shield results in the reduction of the heat transfer coefficient. However, for the normalized distance of the shield from the heat source greater than , the shield’s effect on the reduction of the heat transfer coefficient is less than.