bluuebunny/crossref_metadata_2025 huggingface dataset:
Human Bone Marrow Mesenchymal Stem Cell-Derived Hepatocytes Improve the Mouse Liver after Acute Acetaminophen Intoxication by Preventing Progress of Injury
Authors: Stock Peggy , Brückner Sandra , Winkler Sandra , Dollinger Matthias , Christ Bruno
Published: April 2014

Mesenchymal stem cells from human bone marrow (hMSC) have the potential to differentiate into hepatocyte-like cells in vitro and continue to maintain important hepatocyte functions in vivo after transplantation into host mouse livers. Here, hMSC were differentiated into hepatocyte-like cells in vitro (hMSC-HC) and transplanted into livers of immunodeficient Pfp/Rag2−/− mice treated with a sublethal dose of acetaminophen (APAP) to induce acute liver injury. APAP induced a time- and dose-dependent damage of perivenous areas of the liver lobule. Serum levels of aspartate aminotransferase (AST) increased to similar levels irrespective of hMSC-HC transplantation. Yet, hMSC-HC resided in the damaged perivenous areas of the liver lobules short-term preventing apoptosis and thus progress of organ destruction. Disturbance of metabolic protein expression was lower in the livers receiving hMSC-HC. Seven weeks after APAP treatment, hepatic injury had completely recovered in groups both with and without hMSC-HC. Clusters of transplanted cells appeared predominantly in the periportal portion of the liver lobule and secreted human albumin featuring a prominent quality of differentiated hepatocytes. Thus, hMSC-HC attenuated the inflammatory response and supported liver regeneration after acute injury induced by acetaminophen. They hence may serve as a novel source of hepatocyte-like cells suitable for cell therapy of acute liver diseases.
Surface-Functionalized Hyperbranched Poly(Amido Acid) Magnetic Nanocarriers for Covalent Immobilization of a Bacterial γ-Glutamyltranspeptidase
Authors: Juang Tzong-Yuan , Kan Shao-Ju , Chen Yi-Yu , Tsai Yi-Lin , Lin Min-Guan , Lin Long-Liu
Published: April 2014

In this study, we synthesized water-soluble hyperbranched poly(amido acid)s (HBPAAs) featuring multiple terminal CO2H units and internal tertiary amino and amido moieties and then used them in conjunction with an in situ Fe2+/Fe3+ co-precipitation process to prepare organic/magnetic nanocarriers comprising uniformly small magnetic iron oxide nanoparticles (NP) incorporated within the globular HBPAAs. Transmission electron microscopy revealed that the HBPAA-γ-Fe2O3 NPs had dimensions of 6–11 nm, significantly smaller than those of the pristine γ-Fe2O3 (20–30 nm). Subsequently, we covalently immobilized a bacterial γ-glutamyltranspeptidase (BlGGT) upon the HBPAA-γ-Fe2O3 nanocarriers through the formation of amide linkages in the presence of a coupling agent. Magnetization curves of the HBPAA-γ-Fe2O3/BlGGT composites measured at 300 K suggested superparamagnetic characteristics, with a saturation magnetization of 52 emu g−1. The loading capacity of BlGGT on the HBPAA-γ-Fe2O3 nanocarriers was 16 mg g−1 support; this sample provided a 48% recovery of the initial activity. The immobilized enzyme could be recycled 10 times with 32% retention of the initial activity; it had stability comparable with that of the free enzyme during a storage period of 63 days. The covalent immobilization and stability of the enzyme and the magnetization provided by the HBPAA-γ-Fe2O3 NPs suggests that this approach could be an economical means of depositing bioactive enzymes upon nanocarriers for BlGGT-mediated bio-catalysis.
Natural Dibenzo-α-Pyrones and Their Bioactivities
Authors: Mao Ziling , Sun Weibo , Fu Linyun , Luo Haiyu , Lai Daowan , Zhou Ligang
Published: April 2014

Natural dibenzo-α-pyrones are an important group of metabolites derived from fungi, mycobionts, plants and animal feces. They exhibit a variety of biological activities such as toxicity on human and animals, phytotoxicity as well as cytotoxic, antioxidant, antiallergic, antimicrobial, antinematodal, and acetylcholinesterase inhibitory properties. Dibenzo-α-pyrones are biosynthesized via the polyketide pathway in microorganisms or metabolized from plant-derived ellagitannins and ellagic acid by intestinal bacteria. At least 53 dibenzo-α-pyrones have been reported in the past few decades. This mini-review aims to briefly summarize the occurrence, biosynthesis, biotransformation, as well as their biological activities and functions. Some considerations related to synthesis, production and applications of dibenzo-α-pyrones are also discussed.
Rain-Use-Efficiency: What it Tells us about the Conflicting Sahel Greening and Sahelian Paradox
Authors: Dardel Cécile , Kergoat Laurent , Hiernaux Pierre , Grippa Manuela , Mougin Eric , Ciais Philippe , Nguyen Cam-Chi
Published: April 2014

Rain Use Efficiency (RUE), defined as Aboveground Net Primary Production (ANPP) divided by rainfall, is increasingly used to diagnose land degradation. Yet, the outcome of RUE monitoring has been much debated since opposite results were found about land degradation in the Sahel region. The debate is fueled by methodological issues, especially when using satellite remote sensing data to estimate ANPP, and by differences in the ecological interpretation. An alternative method which solves part of these issues relies on the residuals of ANPP regressed against rainfall (“ANPP residuals”). In this paper, we use long-term field observations of herbaceous vegetation mass collected in the Gourma region in Mali together with remote sensing data (GIMMS-3g Normalized Difference Vegetation Index) to estimate ANPP, RUE, and the ANPP residuals, over the period 1984–2010. The residuals as well as RUE do not reveal any trend over time over the Gourma region, implying that vegetation is resilient over that period, when data are aggregated at the Gourma scale. We find no conflict between field-derived and satellite-derived results in terms of trends. The nature (linearity) of the ANPP/rainfall relationship is investigated and is found to have no impact on the RUE and residuals interpretation. However, at odds with a stable RUE, an increased run-off coefficient has been observed in the area over the same period, pointing towards land degradation. The divergence of these two indicators of ecosystem resilience (stable RUE) and land degradation (increasing run-off coefficient) is referred to as the “second Sahelian paradox”. When shallow soils and deep soils are examined separately, high resilience is diagnosed on the deep soil sites. However, some of the shallow soils show signs of degradation, being characterized by decreasing vegetation cover and increasing run-off coefficient. Such results show that contrasted changes may co-exist within a region where a strong overall re-greening pattern is observed, highlighting that both the scale of observations and the scale of the processes have to be considered when performing assessments of vegetation changes and land degradation.
Novel Paradigm for Constructing Masses in Dempster-Shafer Evidence Theory for Wireless Sensor Network’s Multisource Data Fusion
Authors: Zhang Zhenjiang , Liu Tonghuan , Zhang Wenyu
Published: April 2014

Dempster-Shafer evidence theory (DSET) is a flexible and popular paradigm for multisource data fusion in wireless sensor networks (WSNs). This paper presents a novel and easy implementing method computing masses from the hundreds of pieces of data collected by a WSN. The transfer model is based on the Mahalanobis distance (MD), which is an effective method to measure the similarity between an object and a sample. Compared to the existing methods, the proposed method concerns the statistical features of the observed data and it is good at transferring multi-dimensional data to belief assignment correctly and effectively. The main processes of the proposed method, which include the calculation of the intersection classes of the power set and the algorithm mapping MDs to masses, are described in detail. Experimental results in transformer fault diagnosis show that the proposed method has a high accuracy in constructing masses from multidimensional data for DSET. Additionally, the results also prove that higher dimensional data brings higher accuracy in transferring data to mass.
Angular Rate Optimal Design for the Rotary Strapdown Inertial Navigation System
Authors: Yu Fei , Sun Qian
Published: April 2014

Due to the characteristics of high precision for a long duration, the rotary strapdown inertial navigation system (RSINS) has been widely used in submarines and surface ships. Nowadays, the core technology, the rotating scheme, has been studied by numerous researchers. It is well known that as one of the key technologies, the rotating angular rate seriously influences the effectiveness of the error modulating. In order to design the optimal rotating angular rate of the RSINS, the relationship between the rotating angular rate and the velocity error of the RSINS was analyzed in detail based on the Laplace transform and the inverse Laplace transform in this paper. The analysis results showed that the velocity error of the RSINS depends on not only the sensor error, but also the rotating angular rate. In order to minimize the velocity error, the rotating angular rate of the RSINS should match the sensor error. One optimal design method for the rotating rate of the RSINS was also proposed in this paper. Simulation and experimental results verified the validity and superiority of this optimal design method for the rotating rate of the RSINS.
Tracking and Recognition of Multiple Human Targets Moving in a Wireless Pyroelectric Infrared Sensor Network
Authors: Xiong Ji , Li Fangmin , Zhao Ning , Jiang Na
Published: April 2014

With characteristics of low-cost and easy deployment, the distributed wireless pyroelectric infrared sensor network has attracted extensive interest, which aims to make it an alternate infrared video sensor in thermal biometric applications for tracking and identifying human targets. In these applications, effectively processing signals collected from sensors and extracting the features of different human targets has become crucial. This paper proposes the application of empirical mode decomposition and the Hilbert-Huang transform to extract features of moving human targets both in the time domain and the frequency domain. Moreover, the support vector machine is selected as the classifier. The experimental results demonstrate that by using this method the identification rates of multiple moving human targets are around 90%.
A Review of Sustainable Urban Drainage Systems Considering the Climate Change and Urbanization Impacts
Authors: Zhou Qianqian
Published: April 2014

Climate change and urbanization are converging to challenge city drainage infrastructure due to their adverse impacts on precipitation extremes and the environment of urban areas. Sustainable drainage systems have gained growing public interest in recent years, as a result of its positive effects on water quality and quantity issues and additional recreational amenities perceived in the urban landscape. This paper reviews recent progress in sustainable drainage development based on literature across different disciplinary fields. After presenting the key elements and criteria of sustainable drainage design, various devices and examples of sustainable drainage systems are introduced. The state-of-the-art model approaches and decision-aid tools for assessing the sustainable alternatives are discussed and compared. The paper further explores some limitations and difficulties in the application of the innovative solutions and suggests an integrated and trans-disciplinary approach for sustainable drainage design.
De la démocratie sociale à la démocratie sanitaire : une évolution paradigmatique ?
Authors: Domin Jean-Paul
Published: April 2014

Ce travail envisage l’émergence de la démocratie sanitaire en contrepoint de la démocratie sociale. Si celle-ci a garanti pendant longtemps un égal accès de tous les citoyens au système de santé, la première prend appui sur le malade-acteur, intervenant dans le colloque singulier sur un pied d’égalité avec le médecin et qui est désormais capable de choix en univers risqué. C’est en cela qu’il faut y voir un nouveau paradigme où l’universalité s’efface devant les individualités.
Québec : le rendez-vous manqué de la participation citoyenne
Authors: Malone Antoine
Published: April 2014

La santé constitue un enjeu politique majeur pour les Québécois. Pourtant, si les lois qui encadrent le système de santé prévoient une place pour les citoyens dans sa gouvernance, la participation citoyenne a souvent été qualifiée de rendez-vous manqué. Cet échec trouve ses causes dans les choix qui ont présidé à la création du système de santé moderne, il y a cinquante ans. Ces choix ont conduit à concentrer la totalité des questions réellement politiques au sein et autour de l’hôpital et des médecins. En retour, cette situation a conduit à l’émergence de groupes puissants qui évincent le citoyen de la gouvernance du système. Ce constat n’est pas nouveau, mais l’étude de ce phénomène et des luttes pour la légitimité au sein du système a été quelque peu abandonnée ces quinze dernières années. Cet article vise donc à encourager le débat sur la question.
Le calcul économique en santé : leurre ou boîte à outils à l'intention du décideur ?
Authors: Abecassis Philippe
Published: April 2014

Le calcul économique public a, dans le domaine de la santé, pris un poids prépondérant en imposant le critère économique comme principal critère de décision, en quelques années et deux étapes de rationalisation des politiques de santé. Ce faisant, le calcul économique s’est focalisé sur une approche utilitariste de haute technicité, imposant une forme d’éthique et une justice sociale largement remises en cause sur les plans méthodologique, théorique, pratique et opérationnel.
Concilier priorité de santé et liberté réelle : l'action du “care” capacitant
Authors: Léonard Christian
Published: April 2014

Les critiques formulées à l’égard de l’État-providence prennent la forme de privatisations, essentiellement implicites, notamment dans le domaine des soins de santé. Les priorités qui sont alors fixées, tout aussi implicitement, imposent une charge croissante à un patient « financièrement responsabilisé ». Nous montrons que le “care” est de nature à libérer l’individu, à le responsabiliser réellement afin qu’il devienne acteur de sa santé. Une responsabilité individuelle qui se déploie vers une responsabilité collective nécessaire à la refondation de la solidarité.
L'avis du bien-portant doit-il plus compter que celui du malade pour décider de la distribution des soins de santé ? Un examen par les théories de la justice sociale
Authors: Tovar Élisabeth
Published: April 2014

La dimension sanitaire de la vie en société pose d’épineuses difficultés aux théories de la justice sociale. A-sanitaires par nature, ces théories proposent des critères d’équité décrivant la juste répartition des ressources de la société entre des personnes égales en dignité mais inégales en dotations naturelles et en positions sociales. Dans cet article, deux questions sont discutées, à la lumière, notamment, des travaux menés en éthique empirique : l’incorporation de la santé dans l’étalon de mesure de la justice dans la société et la légitimité des malades à énoncer les critères d’équité.
À la recherche de la justification perdue des ordres de priorités en santé
Authors: Batifoulier Philippe , Braddock Louise , Latsis John
Published: April 2014

Le développement de la privatisation du financement du soin a conduit à activer des processus de ciblage qui visent à réserver une couverture complète à certains patients ou pour certains soins et à faire payer davantage les autres. Ces priorités sont réduites à des moyens nécessaires à la poursuite de la stratégie de privatisation. Elles sont définies par défaut et se révèlent insuffisantes. Nous développons au contraire une approche positive des priorités qui en fait des objectifs à part entière. Les ordres de priorités ont un caractère normatif en faisant appel à des justifications éthiques qui sont converties en dispositifs spécifiques à l’issue d’un arbitrage politique. On repère un tel processus à l’issue d’une analyse des dispositifs européens et on propose de s’appuyer sur le concept de besoin vital, forgé par la philosophie morale, pour identifier la notion de besoin de soin acceptable qui doit déclencher un financement public.
La “méthode de l'Arucah” pour élaborer des priorités de santé : un exemple de démocratie de terrain
Authors: Bréchat Pierre-Henri , Batifoulier Philippe , Jeunet Odile , Magnin-Feysot Christian
Published: April 2014

La “méthode de l’Arucah” permet à la société civile de s’approprier la question des priorités de santé, de leur identification à leur hiérarchisation. C’est une méthode de sondage des priorités par les citoyens eux-mêmes et donc un exemple de démocratie de terrain qui, de plus, permet de faire des priorités de santé basées sur des valeurs sociétales partagées et des préférences morales. Cette méthode comporte cinq étapes successives et complémentaires : 1) une méthode d’enquête statistique, complétée par 2) une méthode délibérative ou argumentative, 3) une étape de compréhension des paradoxes que les résultats peuvent soulever, suivie par 4) un débat public qui permet à la société civile de trouver des compromis avec les représentants de l’État et de l’assurance maladie, ainsi 5) qu’une évaluation. Ces travaux peuvent être utiles au ministère en charge de la santé et à l’agence régionale de santé pour identifier ou valider des priorités et définir des actions. Ils peuvent également être utilisés dans le cadre de l’expérimentation d’une allocation de financements issue d’une enveloppe régionale contrainte.
Removal of Terephthalic Acid from Waste Water Using Diatomite Adsorbent
Authors: Linghu Wen Sheng , Shen Run Pu
Published: April 2014

Adsorption-catalytic oxidation of terephthalic acid (TA) from waster water using modified diatomite adsorbent was studied in this paper. Two diatomites were chosen for adsorbents and TA was used as a model compound. The process consists of physic adsorption of TA and catalytic oxidation of TA. The concentration of TA was determined by UV spectrometry. The results indicate that adsorption capacity of diatomite increased with the decrease of pH value of waster water. The equilibrium adsorbed amount of modified diatomite increased with the increase of metal content in the initial metal content range from 0 to 5% for both of Ni, Fe and Cu modified diatomite, and then the equilibrium adsorbed amount decreased after 5% metal content for Ni modified diatomite and in general kept constant for Fe and Cu modified diatomite. The maximum amount of TA adsorbed at the equilibrium stage was 4.40mg/g for Ni-5/RD. The adsorption capacity of raw and modified diatomite decreased obviously with the increase of cycle number in the initial first-fourth of cycle and then decreased very slowly in the 5th-10th of cycle. The Qe of Ni-5/RD, Fe-5/RD, Cu-5/RD and RD in the 10th cycle were 3.12, 2.44, 1.87 and 0.12mg/g, respectively. The result indicated that the modified could be repeatedly used and maintained the adsorption/regeneration performance stably through many batches of operation.
Erosion Behavior of Al-12Si-2Mg-15Cu Alloy against 304 Stainless Steel Surface
Authors: Zhang Xiao Hua , Yu Si Rong , Xu Jun
Published: April 2014

The compatibility between phase change alloys and container steels at the high temperature is limiting their potential applications in energy storage systems. In this paper, we investigated the erosion behavior of Al-12Si-2Mg-15Cu alloy against 304 stainless steel surface. The effect of temperature and immersion time on the erosion behavior was studied. The erosion rate and erosion thickness increased with the temperature increasing. With the increase of time, the erosion layer thickness increased, but the erosion rate decreased. The mechanisms which accounted for the formation and growth of diffusion layer were studied. The results show that the corrosion is mainly due to the diffusion of Al. The presence of Si element resists the growth of Fe-Al compounds and make erosion layer brittle. Ni-compounds can decrease the diffusion rate of Al atoms. Furthermore, the erosion layer adjacent to the steel substrate is brittle and its micro-hardness is higher.
Preparation and Evaluation of a Novel Al-5.4Si-0.5Mg Welding Wire
Authors: Wang Hao , He Chang Shu , Wang Dong , Zhao Xiang , Zuo Liang
Published: April 2014

An Al-5.4Si-0.5Mg filler wire was developed and produced by direct chill (DC) casting, extrusion, and roll-die and hole-die drawing for the welding of newly developed Mg-containing high-Si aluminum alloys. The Al-12.7Si-0.7Mg alloy plates were butt-welded by tungsten inert gas arc welding (TIG) method using the as-produced welding wire. The microstructures and mechanical properties of these welded joints in different solid solution and artificial aging treatment conditions were studied to evaluate the weld qualities of the novel welding wire. The results showed that the Al-5.4Si-0.5Mg welding wire was an ideal special welding wire of the Al-12.7Si-0.7Mg alloy and the filler metal proved to be heat-treatable. The welded joints exhibited much higher mechanical properties after the post-weld heat treatment (PWHT). All of this provides the possibility of wide application of the novel Al-5.4Si-0.5Mg welding wire and the Al-12.7Si-0.7Mg alloy weldments.
Microstructures and Mechanical Properties of a Squeeze-Casted Al-Zn-Mg-Cu Alloy after Heat Treatment
Authors: Lu Lei , Zhang Da Tong , Li Yuan Yuan
Published: April 2014

The effects of heat treatment on the microstructures and mechanical properties of a squeeze-casted Al-6.8%Zn-2.7%Mg-2.0%Cu alloy were studied by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). It is found that squeeze casting can refine the microstructure of the alloy markedly accelerates the diffusion process of solute atoms during solution heat treatment. After solution heat treatment at 470°C for 10h and artificial aging at 130°C for 24h, the tensile strength and the elongation of the squeeze-casted alloy reach 590MPa and 5.0%, respectively, which are almost equal to those of the wrought alloy, and are significantly higher than those of the gravity-casted alloy (435MPa and 1.3%). Based on the experimental results, the mechanism of microstructural evolution and the effect of squeeze casting on the kinetics of solute diffusion and aging precipitation of the squeeze-casted Al-Zn-Mg-Cu alloy were discussed.
Morphologies and Formation Mechanism of Interconnected Pores in a Spray Formed 7XXX Aluminum Alloy
Authors: Yin Yi Bin , Zhang Yong An , Xiong Bai Qing , Wang Feng , Liu Hong Wei , Li Zhi Hui , Li Xi Wu
Published: April 2014

In this paper, Al-Zn-Mg-Cu alloys were produced through spray forming technique. Microstructures of interconnected porosity defects in spray-deposited preforms were characterized by means of field emission scanning electron microscopy (FESEM). The formation mechanisms of different types of interconnected pores were investigated. The densification of deposited alloy preforms with interconnected pores was also analyzed. Interconnected pores in deposited alloys may be classified into four types, interconnected pores between interstices, between gas pores, between interstices and gas pores, and interconnected pores associated with solidification shrinkage, according to morphology and formation mechanism.
Microstructures of Infiltrated Layer and Friction Properties of Low-Carbon Cr-Ni-Mo Bearing Steel during Duplex Surface Finishing Process
Authors: Xu Chuan , Yang Mao Sheng , Ma Ai Qiong , Zheng Shan Ju
Published: April 2014

The carburizing behavior of low-carbon Cr-Ni-Mo, the nitriding behavior of C-Cr-W bearing steel and the carburizing process prior to nitriding of low-carbon Cr-Ni-Mo bearing steel were mainly investigated in this paper through the contrastive analysis of microstructures and properties by employing scanning electron microscope (SEM), transmission electron microscope (TEM) and X-Ray Diffraction XRD, etc. The result indicated that compared to the simple carburizing and nitriding process, the material that experienced the duplex surface finishing process could obtain a good infiltrated layer’s microstructure and excellent mechanical properties. The thickness of infiltrated layer was 1.8mm. The hardness of surface could reach 1100HV, and the infiltrated layer had a reasonable hardness gradient distribution. Meanwhile the test materials through duplex surface finishing process exhibited good friction properties in the aspect of point contact in dry friction.
Effects of Quenching and Partitioning Process on Mechanical Properties of a Hot-Stamping Steel
Authors: Cheng Ming , Song Hong Wu , Li Xin , Zhang Shi Hong , Cheng Ming , Lin Tao
Published: April 2014

As a novel heat treatment process, Q&P (quenching and partitioning) process can be applied to enhance the ductility of steels. In this paper, the effects of different parameters of Q&P process (such as quenching temperature, partitioning temperature and partitioning time) on mechanical properties and microstructure of 22MnB5 steel was investigated. Analysis demonstrated that austenite can be stabilized via Q&P process and the volume fraction of retained austenite increases with the partitioning temperature and the partitioning time. The mechanical properties of the steel can be controlled to acquire the steel with excellent strength-ductility balance by Q&P process.
Research on Deformation Permeability Changing Law during Snake Rolling Process
Authors: Liu Xiao Jin , Jiang Lian Yun , Yuan Guo , Wang Guo Dong
Published: April 2014

In order to refine the microstructure and improve the mechanical properties of the thicker steel plate, the large rolling reduction should be conducted. Confined to the biting angle of rolling mill, the maximum press quantity is constant. The research indicates that shear stress produced in the deformation region during snake rolling process is helpful and the snake rolling method can be used in the thick steel plate production. The effective strain of steel plate with various roller speed ratio, plate thickness, fraction and roller speed was determined by numerical calculation method. By comparison, the effective strain changing law was obtained. The calculation results indicate that compared to traditional rolling process, the effective strain produced in the plate can be improved with the increase of roller speed ratio, and the deformation permeability can also be improved.
Dynamic Recrystallization Behavior of N08028 Corrosion Resistant Alloy
Authors: Wang Lei , Liu Feng
Published: April 2014

The dynamic recrystallization (DRX) of N08028 corrosion resistant alloy was investigated by hot compression tests which were performed at the deformation temperatures from 1000°C to 1200°C and strain rate from 0.01s-1 to 1s-1 on a Gleeble-1500 thermo-mechanical simulator. The stress-strain curves at all strain rates showed the characteristics of DRX and exhibited a peak in the flow stress before reaching steady state. The microstructures after deformation demonstrated that DRX took place in all specimens. The results show that DRX occurs more easily with the decrease of strain rate and the increase of deformation temperature. By regression analysis, the activation energy in the entire range of deformation conditions, and the relationship of critical strain as well as strain for 50% DRX with deformation conditions were determined. A good agreement between the experimental and predicted results shows that the proposed DRX kinetic equations can give an accurate estimate of the DRX behavior in hot deformed N08028 corrosion resistant alloy.
Influence of Master Alloy on the Cleanliness of Spray Formed Superalloy
Authors: Xu Wen Yong , Li Zhou , Yuan Hua , Wang Yue , Liu Na , Zhang Guo Qing
Published: April 2014

Three kinds of master alloys, including scrap material, vacuum induction melting (VIM) ingot and electro slag remelting (ESR) ingot, were spray formed into different billets. The influence of master alloy on the cleanliness of spray formed superalloy was investigated by means of electron beam (EB) button melting and Scanning Electron Microscopy (SEM), on the basis of optimized process of spray forming and EB button melting. The results show that the inclusions in spray formed preform are mainly composed of alumina and magnesia, stem from master alloy and some refractory materials in the process of remelting. The cleaner the master alloy, the lower level of inclusion contents of the billet. Among three kinds of master alloys, the ESR ingot exhibit the cleanest melt surface in the process of re-melting and contains much smaller inclusions in EB button. The cleanliness of spray formed billet is better than ingot stack for deposition. Superclean sprayforming billet with smaller size inclusions (<100μm) can be attained by the ESR ingots.
Effect of Ta on the Solidification Behavior of Ni3Al-Base Single-Crystal Superalloys
Authors: Zheng Tian Tian , Li Shu Suo , Pei Yan Ling , Ai Cheng , Gong Sheng Kai
Published: April 2014

Two kinds of Ni3Al-base SC superalloys, including IC31A (3wt.%Ta) and IC31B (6wt.%Ta) were investigated in the present study by using the differential scanning calorimetry (DSC) and isothermal quenching technology. The results showed that the larger amount of blocky γ′ phases existed in IC31B than that in IC31A. In the solidification process, the primary phase in IC31B was γ′ phases while in alloy IC31A the primary phase was γ phases. Besides, the solidification rate of IC31B in the early stage was lower than that in IC31A.
Uniaxial Compression Test and FEM Simulation for GH4145 Superalloy at Room Temperature
Authors: Hua Pei Tao , Zhang Wei Hong , Sun Wen Ru , Huang Lin Jie , Li Sheng Chao
Published: April 2014

In this paper, uniaxial compression testsfor GH4145 superalloywere conducted on Gleeble-3800 at room temperature and 60°C with strain rates ranging from 0.5s-1 to 10s-1. No cracks were observed in all the specimens deformed from 10% to 70%, indicating that the GH4145 superalloy possesses great ductility under room temperature. The flow stress of GH4145 superalloywas not sensitive to strain rate deformed around room temperature and it decreased slightly with the temperature increasing. Dynamic recovery during deformation will start to balance the effect of work hardening when the true strain was arisen up to 0.4. Good agreement between the calculated and simulated temperature and strain shows that calculation method is accurate enough for the prediction.
Coarsening Behavior of Precipitates in a Conventional Cast Nickel Base Superalloy during Long Term Thermal Exposure
Authors: Zeng Qiang , Yan Ping , Zhao Jing Chen , Zhang Long Fei , Li Lian
Published: April 2014

A long term aging treatment at 900oC for 3000h was carried out on a conventional cast nickel base superalloy with standard solution and aging treatment. The microstructural evolution including the phases within grains and at grain boundaries (GBs) during thermal exposure in the alloy was observed using OM and SEM. It was shown that the major phases in the alloy after standard heat treatment were γ' precipitates and coarse blocky MC carbides, both of which were distributed not only within grains but also at GBs. During aging, the size of MC carbides and γ' precipitates both within grains and at GBs increased with increasing aging time. It was found that two characteristics of MC carbide and γ' precipitates evolved with aging time: the one is that the coarsening ratio of carbides and γ' precipitates at GBs were significantly higher than that of carbide and γ' precipitates inside the grains; the other is that the coarsening ratio of carbides was markedly higher than that of γ' precipitates. M6C carbide and η phase initially formed in the edge of MC carbide at the expense of MC carbides and γ' precipitates in the vicinity of MC during the early stage of aging. After 3000h, MC carbides inside the grains were covered by η phase films, while those distributed at GBs were completely decomposed into η phase and M6C particles.
Improvement of Tensile Property of Ni-Based a Single Crystal Superalloy by Ru Addition
Authors: Shi Zhen Xue , Li Jia Rong , Liu Shi Zhong , Han Mei
Published: April 2014

Two experimental single crystal superalloys, the Ru-free alloy and the Ru-containing alloy with [001] orientation, were prepared in a directionally solidified furnace, while other alloying element contents were kept unchanged. The effects of Ru on the microstructure and tensile property at 25°C, 760°C, 980°C and 1100°C of the single crystal superalloy were investigated. The results show that the size of γ′ particles became uniform, and the cubic shape of the particles turned a little regular after Ru addition. The yield and ultimate tensile strengths of the single crystal superalloy increased with variant degree at different temperatures. The fracture elongation and area deduction decreased at the testing temperatures of 25°C and 760°C, but those increased at 980°C and 1100°C. The tensile fracture mechanism of the single crystal superalloy at different temperature did not change. Finally the relationship between the improvement of tensile strength and Ru addition was discussed.
Heat Treatment Microstructures of a Directionally Solidified Nickel Base Superalloy under High Temperature Gradient
Authors: Zhang Wei Guo , Yi Xue Mei , Feng Chu Ang
Published: April 2014

The heat treatment of a directionally solidified superalloy under high temperature gradient with different dendritic size was studied. The evolution rules of each phase in DZ125 alloy after heat treatment were analyzed. The results show that γ' phase presents cube and uniform distribution after heat treatment. Its size is about 0.4μm and its area ratio is about 65%. MC carbide transforms into MC(2) carbide with high concentration of Hf. The morphology of MC carbide changes from Chinese-script to block and its size reduces gradually with increasing solidification rate under directional solidification. There is bulk γ' phase around carbide. MC(2) carbide and γ' phase in the grain boundary form chain along grain boundary, and effectively retard grain boundary sliding. γ+γ' eutectic is basically eliminated by solution treatment and only a little γ+γ' eutectic exists around carbide.
Interaction between Polyacrylonitrile (PAN) and Plasticizer at Different Temperature: Infrared Analysis
Authors: Li Xiang , Liu Chun Yi , Qin Ai Wen , Zhao Xin Zhen , Ma Bo Mou , He Chun Ju
Published: April 2014

The interaction between polyacrylonitrile (PAN) and various plasticizer at different temperature was discussed by infrared analysis. At the room temperature, the interaction between nitrile groups of polymer is so strong that the conventional plasticizer propylene carbonate (PC) or new-type plasticizer ionic liquid can’t have interaction with nitrile groups. However, the interaction between nitrile groups weakens at higher temperature, i.e. 160°C, and the interaction between the nitrile groups and IL is formed, which is maintained when natural cooling to 90°C. The interaction between the nitrile groups and IL weakens again when natural cooling to room temperature, it may be attributed to the interaction between IL and water is stronger than that of IL and PAN.
Research Progress of Interface on Diamond/Copper Composites for Thermal Management
Authors: Wang Peng Peng , Guo Hong , Zhang Xi Min , Yin Fa Zhang , Fan Ye Ming , Han Yuan Yuan
Published: April 2014

Diamond/Copper composite (Diamond/Cu) is a kind of ideal thermal management material, with high thermal conductivity and low thermal expansion. While the interface control is the center of the Diamond/Cu composites design. This paper summarizes the relevant studies on Diamond/Cu composite interface, including the researches of author’s group and other researchers. In addition, the prospect of research is mainly elaborated from following three parts: using carbide elements to control and improve the diamond/Cu composite interface bonding; the introduction of the research on Diamond/Cu composite interface with technologies of powder metallurgy, high temperature and high pressure process, spark plasma sintering and pressure infiltration; studying the thermal conductivity of Diamond/Cu composite by SThM analysis and testing technology and the Hasselman-Johnson model. The results show that controlling and improving the quality of Diamond/Cu composite interface bonding can improve the performance and stability of the composite.
Grain Refinement and Mechanism of Carbon Inoculation in Mg-Al Magnesium Alloys
Authors: Wang Zhao Hui , Zhang Xiao Long , Li Shu Bo , Liu Ke , Du Wen Bo
Published: April 2014

Grain refinement is important for improving the microstructure and mechanical properties of magnesium alloys. Carbon inoculation is an effective method of grain refinement process for magnesium alloys containing aluminum. In this paper, the C2Cl6 and graphite powder were used as the potential grain refiners for AM60 and AZ91 alloys, respectively. The results show that the microstructure and mechanical properties of these Mg-Al magnesium alloys have been improved with these grain refiners. The mechanism and thermodynamics analyses of grain refinement with carbon inoculation in Mg-Al magnesium alloy have been discussed.
The Number of Responding CD4 T Cells and the Dose of Antigen Conjointly Determine the Th1/Th2 Phenotype by Modulating B7/CD28 Interactions
Authors: Rudulier Christopher D. , McKinstry K. Kai , Al-Yassin Ghassan A. , Kroeger David R. , Bretscher Peter A.
Published: April 2014

Our previous in vivo studies show that both the amount of Ag and the number of available naive CD4 T cells affect the Th1/Th2 phenotype of the effector CD4 T cells generated. We examined how the number of OVA-specific CD4 TCR transgenic T cells affects the Th1/Th2 phenotype of anti-SRBC CD4 T cells generated in vivo upon immunization with different amounts of OVA-SRBC. Our observations show that a greater number of Ag-dependent CD4 T cell interactions are required to generate Th2 than Th1 cells. We established an in vitro system that recapitulates our main in vivo findings to more readily analyze the underlying mechanism. The in vitro generation of Th2 cells depends, as in vivo, upon both the number of responding CD4 T cells and the amount of Ag. We demonstrate, using agonostic/antagonistic Abs to various costimulatory molecules or their receptors, that the greater number of CD4 T cell interactions, required to generate Th2 over Th1 cells, does not involve CD40, OX40, or ICOS costimulation, but does involve B7/CD28 interactions. A comparison of the level of expression of B7 molecules by APC and CD4 T cells, under different conditions resulting in the substantial generation of Th1 and Th2 cells, leads us to propose that the critical CD28/B7 interactions, required to generate Th2 cells, may directly occur between CD4 T cells engaged with the same B cell acting as an APC.
Soluble HLA-I/Peptide Monomers Mediate Antigen-Specific CD8 T Cell Activation through Passive Peptide Exchange with Cell-Bound HLA-I Molecules
Authors: Allard Mathilde , Oger Romain , Benlalam Houssem , Florenceau Laetitia , Echasserieau Klara , Bernardeau Karine , Labarrière Nathalie , Lang François , Gervois Nadine
Published: April 2014

Accumulating evidence that serum levels of soluble class I HLA molecules (sHLA-I) can, under various pathological conditions, correlate with disease stage and/or patient survival, has stimulated interest in defining whether sHLA-I can exert immunological functions. However, despite a mounting number of publications suggesting the ability of sHLA-I to affect immune effectors in vitro, the precise underlying mechanism still remains controversial. In this article, we address potential functions of both classical and nonclassical sHLA-I, using soluble recombinant HLA-I/peptide monomers, and clearly demonstrate their ability to trigger Ag-specific activation of CD8 T cells in vitro. Furthermore, we provide strong evidence that this behavior results from the passive transfer of peptides from monomers to T cell–bound HLA-I molecules, allowing for fratricide representation and activation. Hence, we proposed a unifying model of T cell activation by HLA-I/peptide monomers, reappraising the potential involvement of sHLA-I molecules in the immune response.
Cutting Edge: A Soluble Form of CTLA-4 in Patients with Autoimmune Thyroid Disease
Authors: Oaks Martin K. , Hallett Karen M.
Published: April 2014

We have recently identified a novel transcript of the CTLA-4 gene that may represent a native soluble form of CTLA-4 (sCTLA-4). To determine whether sCTLA-4 was expressed in humans, we applied a sensitive enzyme immunoassay on serum from patients with autoimmune thyroid disease (ATD). Eleven of 20 patients with ATD had circulating levels of sCTLA-4 ranging from 28 to 78 ng/ml, whereas only 1 of 30 apparently healthy volunteers had a level greater than 4 ng/ml. sCTLA-4 immunoreactivity was inhibited by its binding to B7.1, suggesting that sCTLA-4 is a functional receptor. Immunoprecipitation analysis of serum from patients with ATD revealed a polypeptide consistent with the predicted size of sCTLA-4. We conclude that a native soluble form of CTLA-4 is derived from an alternate transcript of the CTLA-4 gene, and its level in plasma is elevated among a population of patients with ATD.
Perinatal Deletion of B Cells Expressing Surface Ig Molecules That Lack V(D)J-Encoded Determinants in the Bursa of Fabricius Is Not Due to Intrafollicular Competition
Authors: Sayegh Camil E. , Ratcliffe Michael J. H.
Published: April 2014

During embryonic development, the avian bursa of Fabricius selects B cell precursors that have undergone productive V(D)J recombination for expansion in oligoclonal follicles. During this expansion, Ig diversity is generated by gene conversion. We have used retroviral gene transfer in vivo to introduce surface Ig molecules that lack V(D)J-encoded determinants into B cell precursors. This truncated μ heavy chain supports both B cell expansion within embryo bursal lymphoid follicles and gene conversion. We show that individual follicles can be colonized exclusively by cells expressing the truncated μ chain and lacking endogenous surface IgM, ruling out a requirement for V(D)J-encoded determinants in the establishment of bursal lymphoid follicles. In striking contrast to their normal development in the embryo, bursal cells expressing the truncated μ-chain exhibit reduced rates of cell division and increased levels of apoptosis after hatching. The level of apoptosis in individual follicles reflects the proportion of cells within the follicle that express the truncated μ-chain. In particular, high levels of apoptosis are associated with follicles containing exclusively cells expressing the truncated μ receptor. Thus, apoptotic elimination of such cells is not due to competition within the follicle by cells expressing endogenous surface IgM receptors. This provides the first direct demonstration that the regulation of B cell development in the avian bursa after hatching differs fundamentally from that seen in the embryo. The requirement for intact IgM expression when the bursa is exposed to exogenous Ag implicates a role for Ag in avian B cell development after hatching.
Sequential Cleavage by Metallopeptidases and Proteasomes Is Involved in Processing HIV-1 ENV Epitope for Endogenous MHC Class I Antigen Presentation
Authors: López Daniel , Gil-Torregrosa Beatriz C. , Bergmann Cornelia , Del Val Margarita
Published: April 2014

Antigenic peptides derived from viral proteins by multiple proteolytic cleavages are bound by MHC class I molecules and recognized by CTL. Processing predominantly takes place in the cytosol of infected cells by the action of proteasomes. To identify other proteases involved in the endogenous generation of viral epitopes, specifically those derived from proteins routed to the secretory pathway, we investigated presentation of the HIV-1 ENV 10-mer epitope 318RGPGRAFVTI327 (p18) to specific CTL in the presence of diverse protease inhibitors. Both metalloproteinase and proteasome inhibitors decreased CTL recognition of the p18 epitope expressed from either native gp160 or from a chimera based on the hepatitis B virus secretory core protein as carrier protein. Processing of this epitope from both native ENV and the hepatitis B virus secretory core chimeric protein appeared to proceed by a TAP-dependent pathway that involved sequential cleavage by proteasomes and metallo-endopeptidases; however, other protease activities could replace the function of the lactacystin-sensitive proteasomes. By contrast, in a second TAP-independent pathway we detected no contribution of metallopeptidases for processing the ENV epitope from the chimeric protein. These results show that, in the classical TAP-dependent MHC class I pathway, endogenous Ag processing of viral proteins to yield the p18 10-mer epitope requires metallo-endopeptidases in addition to proteasomes.
Systemic Immune Deviation in the Brain That Does Not Depend on the Integrity of the Blood-Brain Barrier
Authors: Wenkel Hartmut , Streilein J. Wayne , Young Michael J.
Published: April 2014

OVA injected into the brain of normal mice evoked a deviant immune response (brain-associated immune deviation (BRAID)) that was deficient in OVA-specific delayed-type hypersensitivity. This response was not dependent on an intact blood-brain barrier since BRAID was induced even when OVA was injected into a newly created lesion site with extensive BBB leakage. However, newly activated microglia at the injection site 2 days after ablation of the striatum correlated with the loss of BRAID. At day 4 after trauma, when activated microglia were only visible further away from the injection site, BRAID was again able to be induced. In contrast to immune deviation elicited via the eye, an intact spleen was not required for BRAID, nor was BRAID adoptively transferable with spleen cells. In contrast i.v. injection of cervical lymph node cells harvested 8 days after OVA injection into the striatum was able to transfer BRAID into naive animals. Together, these data indicate that immune privilege in the brain is actively maintained and is mediated by an immune deviation mechanism that differs from eye-derived immune deviation and arises even when the BBB is compromised.
Human Vascular Endothelial Cells Stimulate Memory But Not Naive CD8+ T Cells to Differentiate into CTL Retaining an Early Activation Phenotype
Authors: Dengler Thomas J. , Pober Jordan S.
Published: April 2014

Endothelial cell (EC)-selective alloreactive CTL may mediate alloimmune vascular injury. In the present study, EC-selective CTL were generated in cocultures of purified human CD8+ T cells with allogeneic EC and were compared with conventional CTL against corresponding B lymphoblastoid cells (BLC). EC caused activation and expansion of memory but not naive CD8+ T cells, which differentiated into EC-selective CTL that retained high surface expression of CD69, CD25, and CD62L and displayed low intracellular perforin content. In contrast, BLC-stimulated CTL could be generated from naive or memory CD8+ T cells and showed a more mature phenotype (low CD69, CD25, and CD62L with higher levels of perforin). The expansion of alloreactive T cells by EC stimulation was 5- to 20-fold less effective than in corresponding BLC-stimulated cultures, accounting for a reduction in the assayable cytotoxicity of individual microcultures. In these IL-2-supplemented cocultures, no effect on CTL generation or phenotype was observed by mAb blocking of costimulation provided by LFA-3, ICAM-1, or CD40, by addition of comitogenic anti-CD28 mAb, or by preactivation of EC with CD40 ligand. Cyclosporine inhibited CTL expansion and cytotoxicity similarly in both EC- and BLC-stimulated cultures but did not affect the phenotype of those CTL that did emerge. This study extends the characterization of endothelium as an immunoregulatory cell type distinct from conventional APC and may explain why graft rejection within the arterial intima, an anatomic compartment in which EC may be the primary type of APC, is separable from rejection in the graft parenchyma.