bluuebunny/crossref_metadata_2025 huggingface dataset:
Stem Cell Marker Nestin Is Critical for TGF-β1-Mediated Tumor Progression in Pancreatic Cancer
Authors: Su Huei-Ting , Weng Ching-Chieh , Hsiao Pi-Jung , Chen Li-Hua , Kuo Tzu-Lei , Chen Yu-Wen , Kuo Kung-Kai , Cheng Kuang-Hung
Published: April 2013

The stem cell marker nestin is an intermediate filament protein that plays an important role in cell integrity, migration, and differentiation. Nestin expression occurs in approximately one third of pancreatic ductal adenocarcinoma (PDAC), and its expression strongly correlates with tumor staging and metastasis. Little is known about the mechanisms by which nestin influences PDAC progression. Here, nestin overexpression in PDAC cells increased cell motility and drove phenotypic changes associated with the epithelial-mesenchymal transition (EMT) in vitro; conversely, knockdown of endogenous nestin expression reduced the migration rate and reverted cells to a more epithelial phenotype. Mouse xenograft studies showed that knockdown of nestin significantly reduced tumor incidence and volume. Nestin protein expression was associated with Smad4 status in PDAC cells; hence, nestin expression might be regulated by the TGF-β1/Smad4 pathway in PDAC. We examined nestin expression after TGF-β1 treatment in human pancreatic cancer PANC-1 and PANC-1 shSmad4 cells. The TGF-β1/Smad4 pathway induced nestin protein expression in PDAC cells in a Smad4-dependent manner. Moreover, increased nestin expression caused a positive feedback regulator of the TGF-β1 signaling system. In addition, hypoxia was shown to induce nestin expression in PDAC cells, and the hypoxia-induced expression of nestin is mediated by the TGF-β1/Smad4 pathway. Finally, the antimicrotubule inhibitors, cytochalasin D and withaferin A, exhibited anti-nestin activity; these inhibitors might be potential antimetastatic drugs. Our findings uncovered a novel role of nestin in regulating TGF-β1-induced EMT. Anti-nestin therapeutics may serve as a potential treatment for PDAC metastasis. Mol Cancer Res; 11(7); 768–79. ©2013 AACR.
Prevention of Helicobacter pylori–Induced Gastric Cancers in Gerbils by a DNA Demethylating Agent
Authors: Niwa Tohru , Toyoda Takeshi , Tsukamoto Tetsuya , Mori Akiko , Tatematsu Masae , Ushijima Toshikazu
Published: April 2013

Suppression of aberrant DNA methylation is a novel approach to cancer prevention, but, so far, the efficacy of the strategy has not been evaluated in cancers associated with chronic inflammation. Gastric cancers induced by Helicobacter pylori infection are known to involve aberrant DNA methylation and associated with severe chronic inflammation in their early stages. Here, we aimed to clarify whether suppression of aberrant DNA methylation can prevent H. pylori–induced gastric cancers using a Mongolian gerbil model. Administration of a DNA demethylating agent, 5-aza-2′-deoxycytidine (5-aza-dC), to gerbils (0.125 mg/kg for 50–55 weeks) decreased the incidence of gastric cancers induced by H. pylori infection and N-methyl-N-nitrosourea (MNU) treatment from 55.2% to 23.3% (P < 0.05). In gastric epithelial cells, DNA methylation levels of six CpG islands (HE6, HG2, SB1, SB5, SF12, and SH6) decreased to 46% to 68% (P < 0.05) of gerbils without 5-aza-dC treatment. Also, the global DNA methylation level decreased from 83.0% ± 4.5% to 80.3% ± 4.4% (mean ± SD) by 5-aza-dC treatment (P < 0.05). By 5-aza-dC treatment, Il1b and Nos2 were downregulated (42% and 58% of gerbils without, respectively) but Tnf was upregulated (187%), suggesting that 5-aza-dC treatment induced dysregulation of inflammatory responses. No obvious adverse effect of 5-aza-dC treatment was observed, besides testicular atrophy. These results showed that 5-aza-dC treatment can prevent H. pylori–induced gastric cancers and suggested that removal of induced DNA methylation and/or suppression of DNA methylation induction can become a target for prevention of chronic inflammation–associated cancers. Cancer Prev Res; 6(4); 263–70. ©2013 AACR.
Angiotensinogen Polymorphisms and Post-Transplantation Diabetes Mellitus in Korean Renal Transplant Subjects
Authors: Lee Sul ra , Moon Joo Young , Lee Sang Ho , Ihm Chun Gyoo , Lee Tae Won , Kim Su Kang , Chung Joo-Ho , Kang Sun Woo , Kim Tae Hee , Park Seok Ju , Kim Yeong Hoon , Jeong Kyung Hwan
Published: April 2013

Background: Post-transplant diabetes mellitus (PTDM) is a common and serious metabolic complication. Genetic polymorphisms of angiotensin-converting enzyme (ACE) and angiotensinogen (AGT) genes have been reported to be related to diabetes mellitus and insulin sensitivity; however, the role of these genes in the development of PTDM is not known. For this purpose, we investigated the association of ACE and AGT genetic polymorphisms with PTDM. Methods: A total of 302 subjects without previously diagnosed diabetes who had received kidney transplants were included. One ACE single nucleotide polymorphism (SNP) (rs4291) and two AGT SNPs (rs 699 and rs 4762) were genotyped from genomic DNA with direct sequencing. Results: PTDM developed in 49 (16.2%) of 302 subjects. Subjects in the PTDM were older than those in the non-PTDM. There was a significant difference between the two groups in tacrolimus use (p=0.03). Of the three SNPs, the rs4762 of the AGT gene was significantly associated with the development of PTDM in the dominant models (p = 0.03) after adjusting for age and tacrolimus usage. Conclusions: AGT gene rs4762 polymorphisms may serve as genetic markers for the development of PTDM. The exact molecular mechanisms still need to be clarified.
What Do Male Medical Students Know about the Pill? Study of Knowledge and Attitudes at the University of Belgrade
Authors: Gazibara Tatjana , Trajkovic Goran , Kurtagic Ilma , Kovacevic Nikolina , Nurkovic Selmina , Kisic-Tepavcevic Darija , Pekmezovic Tatjana
Published: April 2013

Background: Women have been traditionally more involved in birth control than men. The purpose of this survey is to analyze knowledge of and attitudes towards oral contraceptives (OC) use in a population of male medical students of the Faculty of Medicine, Belgrade, Serbia. Methods: In November/December 2011, a total of 237 male medical students were recruited at the Faculty of Medicine before the start of compulsory practical sessions in their classrooms. Data were obtained through a 26-item questionnaire regarding knowledge of and attitude towards OC use. Results: Less than a half (40.4%) had a partner and 3.2% did not know whether their partner used the pill. Approximately one fifth of the students (28.5%) did not inform themselves about the pill at all. The average knowledge score differed according to the relationship status (Z = -3.414, p = 0.001). The average attitude score did not statistically differ according to the relationship status (Z = -1.384, p = 0.166). An advanced study year was statistically associated with higher knowledge and attitude scores (ρ = 0.575, p < 0.001; ρ = 0.206, p = 0.002, respectively). Conclusion: Our students demonstrated a moderate level of comprehension. The results of our study indicate that the use of the OC pill needs further promotion to raise awareness of male involvement in health-related decisions of their partners.
Pathophysiology of genetic deficiency in tissue kallikrein activity in mouse and man
Authors: Waecke Ludovic , Potier Louis , Richer Christine , Roussel Ronan , Bouby Nadine , Alhenc-Gelas Francois
Published: April 2013

Study of mice rendered deficient in tissue kallikrein (TK) by gene inactivation and human subjects partially deficient in TK activity as consequence of an active site mutation has allowed recognising the physiological role of TK and its peptide products kinins in arterial function and in vasodilatation, in both species. TK appears as the major kinin forming enzyme in arteries, heart and kidney. Non-kinin mediated actions of TK may occur in epithelial cells in the renal tubule. In basal condition, TK deficiency induces mild defective phenotypes in the cardiovascular system and the kidney. However, in pathological situations where TK synthesis is typically increased and kinins are produced, TK deficiency has major, deleterious consequences. This has been well documented experimentally for cardiac ischaemia, diabetes renal disease, peripheral ischaemia and aldosterone-salt induced hypertension. These conditions are all aggravated by TK deficiency. The beneficial effect of ACE/kininase II inhibitors or angiotensin II AT1 receptor antagonists in cardiac ischaemia is abolished in TK-deficient mice, suggesting a prominent role for TK and kinins in the cardioprotective action of these drugs. Based on findings made in TK-deficient mice and additional evidence obtained by pharmacological or genetic inactivation of kinin receptors, development of novel therapeutic approaches relying on kinin receptor agonism may be warranted.
United Nations Treaty Body Monitoring of Migrant Workers in the Middle East
Authors: Weissbrodt David , Rhodes Justin
Published: April 2013

This article provides an overview of international instruments and institutions that monitor the status and treatment of migrant workers. Special focus is given to the Middle East and the dynamics of labor migration in that region.
The Decapoda described by Henri Filhol: checklist and dates of publication (Crustacea: Anomura, Brachyura, Caridea)
Authors: LOW MARTYN E. Y.
Published: April 2013

Henri Filhol authored thirteen publications that established new names for decapod crustaceans in 1884 and 1885. The accurate dates of these publications are determined utilising notices of Filhol’s publications in contemporary journals and library date-stamps. A checklist of the names for the Decapoda established by Filhol and their current identities is present-ed. Labophrys Filhol, 1885, and not Lobophrys, is shown to be the correct spelling for the junior objective synonym of Paramithrax H. Milne Edwards, 1834 (type species Pisa barbicornis Latreille, in Latreille, Le Peletier, Serville & Guérin, 1825) (Brachyura: Majidae Samouelle, 1819).
A new species of porcupine, genus Coendou (Rodentia: Erethizontidae) from the Atlantic forest of northeastern Brazil
Authors: PONTES ANTONIO ROSSANO MENDES , GADELHA JOSÉ RAMON , MELO ÉVERTON R. A. , DE SÁ FABRÍCIO BEZERRA , LOSS ANA CAROLINA , JUNIOR VILACIO CALDARA , COSTA LEONORA PIRES , LEITE YURI L. R.
Published: April 2013

We report the discovery of a new species of Coendou (Rodentia, Erethizontidae), here designated Coendou speratus sp. nov. This small porcupine, locally known as coandu-mirim, is found in the Pernambuco Endemism Centre in the Atlantic coast of northeastern Brazil north of the São Francisco river, one of the most important known biodiversity hotspots. The geographic range of C. speratus overlaps with that of the larger, widespread C. prehensilis, but not with that of C. insidio-sus from the southeastern Atlantic forest, nor with that of C. nycthemera, an eastern Amazonian species. Coendou speratus is a small-bodied, long-tailed species that appears to be completely spiny because it lacks long dorsal fur. The dorsal quills have conspicuously brownish red tips that contrast with the blackish dorsal background color. The new species is overall similar to C. nycthemera, but the dorsal body quills are typically tricolored in the former and bicolored in the latter. The new species is externally very distinct from C. insidiosus, especially because the latter has bicolored dorsal quills that are almost completely hidden beneath longer and homogeneous pale or dark hairs.
Description of immatures and natural history of the weevil Loncophorus pustulatus (Champion, 1903) (Coleoptera: Curculionidae: Curculioninae) associated with flowers of Ceiba speciosa (A. St.-Hil.) Ravenna (Bombacoidea: Malvaceae) in southeast Brazil
Authors: VANIN SERGIO ANTONIO , BENÁ DANIELA DE CASSIA , ALBERTONI FABIANO FABIAN
Published: April 2013

Larva and pupa of Loncophorus pustulatus (Champion, 1903) (Curculionidae: Curculioninae: Anthonomini) are de-scribed, illustrated and compared with descriptions of immatures of two other species of Loncophorus. Weevil larvae were found inside aborted flowers on the ground under Ceiba speciosa (A. St.-Hil.) Ravenna (Malvaceae), in the city of São Paulo, State of São Paulo, and reared to adults in laboratory. Data obtained in the field and under laboratory conditions are presented. Parasitoidism of weevil larvae by wasps of the genus Catolaccus (Hymenoptera: Pteromalidae) is reported.
A new species of Bolitoglossa (Caudata, Plethodontidae) from the continental divide of western Panama
Authors: HERTZ ANDREAS , LOTZKAT SEBASTIAN , KÖHLER GUNTHER
Published: April 2013

We describe the new salamander species Bolitoglossa jugivagans from the Atlantic slopes of the Fortuna depression in western Panama on the basis of morphological and molecular data. Based on mtDNA data, the new species seems to be closely related to B. aureogularis and B. robinsoni, with which it forms a subclade within the subgenus Eladinea.
Review of the genus Camptochaeta Hippa & Vilkamaa (Diptera, Sciaridae), with the description of nine new species
Authors: VILKAMAA PEKKA , HIPPA HEIKKI , HELLER KAI
Published: April 2013

The following new species of the genus Camptochaeta Hippa & Vilkamaa, 1994 are described and illustrated: Camp-tochaeta anceps, C. filifera, C. formosa, C. kajsae, C. mixta, C. orthochaeta, C. spatula, C. truncata, and C. winchesteri. For some previously described species, morphological characters are redefined. Camptochaeta pentacantha Komarova, Hippa & Vilkamaa, 2007 is regarded as a junior synonym of C. subcamptochaeta (Mohrig, 1992).
Family Panorpodidae (Insecta, Mecoptera) from Baltic amber (upper Eocene): new species, redescription and palaeogeographic remarks of relict scorpionflies
Authors: SOSZYŃSKA-MAJ AGNIESZKA , KRZEMIŃSKI WIESŁAW
Published: April 2013

The history of the species-poor family Panorpodidae is very interesting due to its uneven present distribution. The only fossils of the genus Panorpodes are two species known from Baltic amber, described in 1856 and 1954. A third species, Panorpodes weitschati sp. nov., is herein described. New diagnoses and descriptions as well as new drawings of all fossil species of Panorpodes are provided, including the first illustration of the wing of P. hageni. Fossil Panorpodes display three diametrically opposed patterns of wings markings, from the highly transparent wings of P. brevicauda, through transparent wings with dark bands and spots of P. weitschati sp. nov., to the dark wings with only narrow transparent bands of P. hageni. The fossil specimens are characterized by a great variability in wing venation, even in a single specimen, similar to that of living species.
Yousefi, S., Rahimian, H., Nabavi, S.M.B. & Glasby, C.J. (2011) Nereididae (Annelida: Polychaeta) from intertidal habitats in the Gulf of Oman, Iran. Zootaxa, 3013, 48–64.
Authors: Yousefi S , Rahimian H. , Nabavi S. M.B. , Glasby C. J.
Published: April 2013

It has come to our attention that in the work referenced above we unintentionally referred to the body of water sep­arating the Iranian Plateau from the Arabian Peninsula as the ‘Arabian Gulf ‘(Abstract, line 9). The words ‘Arabian Gulf’ should be replaced with the words ‘Persian Gulf’, which is the name for this water mass recognised by the International Hydrographic Organization (1953) and endorsed by the UN Group of Experts on Geographical Names (2006).International Hydrographic Organization (1953). Limits of Oceans and Seas (special publication No 23). 3rd edi­tion. [pdf accessed at http://www.iho.int/iho_pubs/IHO_Download.htm 22 Jan 2013]Report of the United Nations Group of Experts on Geographical Names on the work of its twenty-third session. Document E/2006/57, Economic and Social Council, United Nations. New York, 2006 [pdf accessed at http://unstats.un.org/unsd/geoinfo/UNGEGN/docs/23-gegn/wp/gegn23wp61.pdf 22 Jan 2013]
Under-representation of males in the early years
Authors: Mistry Malini , Sood Krishan
Published: April 2013

This article investigates why there appears to be an under-representation of males in comparison to their female colleagues in the Early Years (EY) sector, and the perception of male teachers progressing more quickly to leadership positions when they do enter this context. Using case studies of final year male students on an Initial Teacher Training (ITT) undergraduate degree course at one university, we attempt to analyse data on male under-representation in Early Years against contemporary theories of identity, power and leadership. Questionnaires and interviews were conducted with the male sample group and male senior leaders in primary schools to gain an overview as to the leadership support they needed and provided. Our tentative findings suggested that male trainees are happy to work in an Early Years context and take leadership positions, but the challenge for leaders is that male trainees require strong leadership mentoring processes to help overcome perceived contextual barriers.
Nugget quality prediction of resistance spot welding on aluminium alloy based on structureborne acoustic emission signals
Authors: Luo Y , Li J L , Wu W
Published: April 2013

The structureborne acoustic emission signals during resistance spot welding on 2024 aluminium alloy were detected in real time and analysed to find the characteristics of signals corresponding to the physical phase of welding process. The curve fitting models were developed based on the acoustic emission count and positive peak of nugget nucleation event. These mathematical models were used to predict the tensile–shear strength of spot weld. The results showed that the physical phases of welding process can be characterised by the acoustic emission signals detected during the resistance spot welding process. The acoustic emission count and the positive peak of nugget nucleation event of resistance spot welding on 2024 aluminium alloy have good relevance to the tensile–shear strength of spot weld, and these correlations were fitted to comply with some functional relationships, which can be used to realise the prediction of the strength of spot weld. It can be concluded that the prediction of weld strength based on the acoustic emission count of nugget nucleation event has good performance, but the prediction of weld strength based on the positive peak of nugget nucleation event is more susceptible to the expulsions and has poor performance when there are expulsions.
Interface shape and microstructure controlled dissimilar friction stir lap welded steels
Authors: Fujii H , Chung Y D , Sun Y F , Tanigawa H
Published: April 2013

When fusion welding is conducted on the dissimilar materials between a reduced activation ferritic/martensitic steel F82H steel and an austenite stainless steel SUS 316 steel, δ ferrite is generally formed and inevitably deteriorates the weld properties. In this study, dissimilar welding of F82H to SUS 316 steel was successfully achieved by friction stir lap welding technique. It revealed that the shape and microstructure of the joint interface can be controlled by controlling the welding temperature, in another word, by changing the applied load. By controlling the welding temperature at ∼710°C, a sound dissimilar joint can be obtained with a smooth joint interface and no mixed microstructure, despite the relative overlapping position of the steel plates. All the dissimilar joints showed high shear tensile strength and fracture in the base metal of F82H steel plate, which has lower strength than the SUS 316 steel plate at room temperature.
Interface properties and thermodynamic analysis of laser–arc hybrid welded Al/steel joint
Authors: Mei S W , Gao M , Yan J , Zhang C , Li G , Zeng X Y
Published: April 2013

Fibre laser–cold metal transfer hybrid welding was introduced to join AA 6061 aluminium alloy with AISI 304 stainless steel using Al–12Si filler wire. Interface properties and microstructure of welded joints were observed by optical microscope, scanning electron microscope, energy dispersive spectrometry and X-ray diffraction techniques. A serrated intermetallic compound (IMC) layer was found at the interface between fusion zone and stainless steel. The morphology of IMC layer was uniform from the top to the bottom, and its average thickness was 3 μm. The IMC layer consisted of two layers: Al8(Fe,Cr)2Si layer close to fusion zone and (Al,Si)13Fe4 layer close to stainless steel. The joint fractured at the IMC layer and presented a tensile strength of 165 MPa. The formation of the IMC layer was closely related with the thermodynamic and kinetic behaviours of the interface and fast cooling rate of hybrid welding.
Investigation of induced magnetic force on liquid nugget during resistance spot welding
Authors: Li Y , Luo Z , Bai Y , Ao S S
Published: April 2013

This paper investigates the source, magnitude and direction of magnetic force on the liquid nugget during resistance spot welding (RSW). High speed photography was used to observe the nugget formation process during half-sectioned RSW of steel (ferromagnetic substance) and aluminium alloy (paramagnetic substance). The induced magnetic force acting on half-sectioned and regular nugget was afterwards analysed and calculated. The results show that in the case of steel RSW, the magnetised workpieces generated a very strong magnetic field around the spot welding zone, while weak magnetic field appeared in the case of aluminium alloy RSW. This strong magnetic field causes a strong convection in the liquid nugget of steel even when the welding current is low. This strong convection will promote that the dimensions of nugget in the steel RSW become larger and closer to rectangle (observed on the cross-section) than in the aluminium alloy RSW.
Effect of welding parameters on lap shear tensile properties of dissimilar friction stir spot welded AA 5754-H22/2024-T3 joints
Authors: Bozkurt Y , Salman S , Çam G
Published: April 2013

In this study, the effect of weld parameters on mechanical properties, such as lap shear fracture load, of friction stir spot welded dissimilar lap joints was studied. The effects of the plate positioning, the plunge depth and the dwell time as well as the tool tilt angle on the joint strength were investigated. The experimental results showed that the positioning of the sheets played an important role on the strength of the joints. The joint strength was higher when AA 5754 sheet is placed on the top, whereas lower strength values were displayed by dissimilar joints produced by placing AA 2024 as the upper sheet. It was also observed that the plunge depth, dwell time and tool tilt angle had a strong effect on the failure mode of the friction stir spot welded lap joints produced. The joints exhibited two different fracture modes, namely cross and pullout nugget under lap shear tensile testing conditions.
Effects of Zn content on microstructures and mechanical properties of as cast Mg–Zn–Y–Zr alloys
Authors: Ji D W , Liu C M , Chen Z Y , Wang H H , Wang B
Published: April 2013

In the present work, the effects of Zn content on the microstructures and mechanical properties of as cast Mg– xZn–5Y–0·6Zr alloys ( x = 2, 5, 8 and 13 wt-) have been investigated. The results show that the ternary Mg–Zn–Y phase compositions change with Zn/Y ratios induced by the change in Zn content. It is found that the fracture is mainly decided by the characteristics and distribution of second phase rather than the grain size. The influences of these phases, especially the W phase, on the mechanical properties of the alloys have been discussed. Both ultimate tensile strength (UTS) and elongation decrease with the increase in Zn content, while the instance of yield strength (YS) is just the reverse. The W phase is easily cracked because of its brittleness and easy to result in decohesion from the matrix because of the weak atomic bonding, which greatly degrade the UTS and elongation. It can be concluded that the YS closely depends on the grain size, while UTS and elongation closely depend on the volume fraction of eutectic compound ( α-Mg+W phase).
Influence of strain rate on hot ductility of austenitic stainless steel slab
Authors: Hou G Q , Zhu L
Published: April 2013

The effect of strain rate on the deformation behaviour of Cr15Mn9Cu2NiN slab has been studied through hot tensile tests on Thermorestor-W. Results showed that, as the strain rate increases from 0·1 to 10 s−1 at a given test temperature, the reduction in area (RA) in slab shell decreases by 20, and the positions of crack nucleus were changed from δ ferrite dendrites to austenite grain boundary, while in slab core, RA only decreased by 5 and the crack nucleus was on austenite grain boundary all the time. There are many ferrite/austenite interfaces in the microstructure of shell. As the materials deform at higher strain rate, dislocations will be generated and piled up at the interface quickly, and improve the strength in both austenite and ferrite, which will result in the stress concentration at austenite grain boundary and lead to crack nucleation.
Study of matrix microstructure of SiCf/Ti–43Al–9V composites
Authors: Wei W , Yang Y Q , Zhang W , Luo X , Zhao G M , Huang B
Published: April 2013

Four different microstructures of the Ti–43Al–9V alloy were obtained through heat treatment or thermal deformation process. Alloys with different microstructures were cut and ground into thin foils. The foils would be used to fabricate the SiC fibre reinforced composites via foil–fibre–foil method. Then, the matrix microstructures of composites were investigated by means of optical microscopy, scanning electron microscopy and microarea X-ray diffraction. The results show that near lamellae and massive gamma microstructure transform into duplex during the consolidation process, but the transformation mechanism of the two microstructure is different. Fully lamellae microstructure remains in the matrix, while B2 phase precipitates in the matrix. Duplex microstructure does not change during the consolidation process. No matter what kind of microstructure the foils have, there is only gamma phase formed close to the fibres in the matrix of composites.
Study of grain refinement and eutectic transformation of undercooled IN718 superalloy
Authors: Peng Z C , Xie F Q , Wu X Q , Zhang J
Published: April 2013

A substantial undercooling up to 250 K was produced in the IN718 superalloy melt by employing the method of molten salt denucleating, and the microstructure evolution with undercooling was investigated. Within the achieved undercooling, 0–250 K, the solidification microstructure of IN718 undergoes two grain refinements: the first grain refinement occurs in a lower range of undercooling, which results from the ripening and remelting of the primary dendrite, and at a larger range of undercooling, grain refinement attributes to solidification shrinkage stress and lattice distortion energy originating from the rapid solidification process. A ‘lamellar eutectic anomalous eutectic’ transition was observed when undercooling exceeds a critical value of ∼250 K. When undercooling is small, owing to niobium enrichment in interdendrite, the remaining liquid solidifies as eutectic ( γ+Laves phase); whereas, if the undercooling achieves 250 K, the interdendrite transforms from eutectic ( γ+Laves phase) to Laves phase, which results from the formation of divorced eutectic arising from the huge variance of the growth velocities of γ and Laves phases.
Determination of Ms temperature: methods, meaning and influence of ‘slow start’ phenomenon
Authors: Sourmail T , Smanio V
Published: April 2013

Knowledge of the martensite start temperature in low and medium alloy steels is of critical importance for steel makers, or any industry involved in the transformation of hardenable steels. Its determination is often carried out by length change measurements in quenching dilatometers. The present paper focuses on the meaning of the information obtained in these experiments and discusses two alternative methods and their respective benefits, particularly with respect to the phenomenon sometimes referred to as ‘slow start’ for the martensite transformation.
Effect of solidification rate on representative impurities distribution in Si–Cu alloy
Authors: Fang M , Lu C H , Lai H X , Huang L Q , Chen J , Ma W H , Sheng Z L , Shen J N , Li J T , Luo X T
Published: April 2013

The main purpose of this article is to demonstrate that solvent refining in combination with directional solidification can be used for preparation of high purity metallurgical grade silicon for solar cells. Silicon was alloyed with copper and grew under different solidification rates from Si–Cu alloy melt. A detailed analysis of the microstructures and morphologies of Si–Cu alloy has been carried out, focusing on the distribution characteristic of representative impurities affected by solidification rate. The experimental results indicated that copper addition promotes segregation of metal impurities Fe, Al and Ca from metallurgical grade silicon, and the purification effect is more pronounced with the solidification rate decreases. It was also determined that the representative non-metallic impurity phosphorus has a remarkable separation performance after alloying with copper, which can be helpful for the phosphorus removal.
Analysis of indentation size effect in copper and its alloys
Authors: Chicot D , Puchi-Cabrera E S , Iost A , Staia M H , Decoopman X , Roudet F , Louis G
Published: April 2013

For describing the indentation size effect (ISE), numerous models, which relate the load or hardness to the indent dimensions, have been proposed. Unfortunately, it is still difficult to associate the different parameters involved in such relationships with physical or mechanical properties of the material. This is an unsolved problem since the ISE can be associated with various causes such as workhardening, roughness, piling-up, sinking-in, indenter tip geometry, surface energy, varying composition and crystal anisotropy. For interpreting the change in hardness with indent size, an original approach is proposed on the basis of composite hardness modelling together with the use of a simple model, which allows the determination of the hardness–depth profile. Applied to copper and copper alloys, it is shown that it is possible to determine the maximum hardness value reached at the outer surface of the material and the distance over which both the ISE and the workhardening take place.
Five parameter distribution of planes in AA 5182 aluminium alloys with relevance to intergranular corrosion resistance
Authors: Hill L R , Randle V , Engler O
Published: April 2013

Alloys of AA 5182 are commonly used in the automotive industry to provide weight reductions in vehicle chassis. The strength of such alloys is based on the Mg content, with Mg causing the precipitation of a β-Al8Mg5 phase along the length of the grain boundaries in the microstructure. These precipitates are vulnerable to intergranular corrosion (IGC) in acidic environments. For this reason, the proportions of Mg in the microstructure must be limited, with >3 wt-Mg causing intergranular attack. The alloys used in this study had an Mg content of 4·43, so were vulnerable to IGC. Standard nitric acid mass loss tests were applied to determine the level of corrosion resistance in two samples subjected to various treatments. Using ‘five parameter’ analysis, the importance of the grain boundary plane and thermomechanical history to IGC resistance was determined. ‘Special’ planes were identified in the microstructure and their impact on IGC resistance was assessed. From such analysis, it was found that a high deformation level of 50 together with a simulated batch annealing heat treatment yielded the highest proportions of ‘special’ boundaries within the microstructure. ‘Special’ boundaries in this study were identified to be low angle boundaries, <111> twist boundaries and <110> tilt boundaries, which are associated with a reduced energy compared to random high angle boundaries. As precipitation generally occurs along high energy boundaries, ‘special’ boundaries reduce precipitate formation, thus reducing IGC intensity. Future implications include the introduction of a higher proportion of ‘special’ boundaries into the microstructure, allowing for an increase in Mg content in these alloys.
Effective mechanical properties of nanocomposites reinforced with wavy carbon nanotubes
Authors: Golestanian H , Gahruei M H
Published: April 2013

Carbon nanotubes (CNTs) possess exceptional mechanical properties and are therefore suitable reinforcements for composite materials. Nanotube efficiency in reinforcing the matrix depends on the CNT alignment, volume fraction and configuration, as well as matrix properties. In this investigation, finite element method (FEM) is used to investigate the effects of nanotube waviness ratio, volume fraction, and matrix modulus on properties of CNT based polymer nanocomposites. Nanocomposite mechanical properties are evaluated using a 3D nanoscale representative volume element. Models consisting of CNTs with different waviness ratios are created to investigate the effects of nanotube configuration on nanocomposite mechanical properties. Next, the effect of nanotube volume fraction on nanocomposite moduli of elasticity is investigated. Finally, the effects of matrix modulus are investigated by analysing models consisting of matrices with different moduli. The results of this investigation are compared with those found in the literature and good agreement is observed.
Role of Al additions in wear control of nanocrystalline Mo(Si1−xAlx)2 coatings prepared by double cathode glow discharge technique
Authors: Xu J , Fan H S , Li Z Y
Published: April 2013

Four kinds of nanocrystalline Mo(Si1−xAlx)2 coatings with differing Al contents are prepared onto a Ti–6Al–4V substrates by a double cathode glow discharge apparatus. The microstructural features of the deposited coatings were characterised by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. These coatings are composed of the equiaxed C40–MoSi2 grains with the average grain size of ∼5 nm. Nano-indentation measurements indicated that the hardness H, elastic modulus E and the H/ E or H3/ E2 ratio of the nanocrystalline Mo(Si1−xAlx)2 coatings slightly increase with the increase in Al content. The tribological behaviour of the nanocrystalline Mo(Si1−xAlx)2 coating sliding against a ZrO2 ceramic ball at room temperature has been compared using a ball-on-disc type tribometer under unlubricated conditions. Experimental results showed that the specific wear rates of the nanocrystalline Mo(Si1−xAlx)2 coatings decrease with increasing Al content and are dramatically reduced by more than 1–2 orders of magnitude over the uncoated Ti–6A1–4V. The enhancement of wear resistance of the nanocrystalline Mo(Si1−xAlx)2 coatings by Al additions is correlated with the increased mechanical properties and the forming oxide layer by tribochemical reactions.
Microstructural evolution of cast TiAlNb intermetallics for third generation gas turbine components
Authors: Chen Z Y , Gong Z Q , Chai L H , Xiang Z L , Nie Z R
Published: April 2013

The microstructural evolution of Ti–45·9Al–8Nb and Ti–45·9Al–8Nb–0·2C (at-) alloys fabricated by centrifugal investment casting is studied. It is found that both Ti–45·9Al–8Nb and Ti–45·9Al–8Nb–0·2C are mainly composed of γ phase and a small amount of α2 phase, and the microstructure is mainly fully lamellar in C containing alloy but again the C free alloy is mainly nearly fully lamellar. Nb distributes homogeneously in the γ and α2 phases but is depleted in the interdendritic regions. The addition of C reduces the lamellar spacing of Ti–45·9Al–8Nb alloy. The mean interlamellar spacings between α2 and α2 of Ti–45·9Al–8Nb and Ti–45·9Al–8Nb–0·2C alloys are about 950 and 700 nm, and those between γ and α2 lamellae are about 320 and 220 nm respectively. Oil cooling from the α phase field after 1h treatment at 1360°C leads to massive transformation to γm for both Ti–45·9Al–8Nb and Ti–45·9Al–8Nb–0·2C alloys. Subsequent aging in the α+ γ phase field results in α phase precipitates within the γm phase, which leads to convoluted microstructures. However, the C addition retards the precipitation of α2 phase.
Tempering stability of retained austenite in nanostructured dual phase steels
Authors: Hu F , Wu K M , Hou T P , Shirzadi A A
Published: April 2013

The tempering resistance and stability of retained austenite in superbainitic and quenching–partitioning martensitic steels were investigated over the temperature range of 400 to 700°C. The X-ray diffraction analysis and hardness tests showed that the quenching–partitioning martensitic steel contained a considerable amount of retained austenite (26·6 vol.-) and had a relatively high hardness up to 556 HV1 after tempering at ∼600°C. In contrast, the fraction of retained austenite and hardness of superbainitic steel were considerably lower (24·5 vol.- and 385 HV1) after the same tempering cycle. The present work also showed that the quenching–partitioning steel had a higher tempering stability, probably due to the higher fraction of carbon rich retained austenite.
Analysis on embrittlement phenomenon of flux cored Zn–Al wire
Authors: Chen Y , Sun Z P , Yan X Q , Huang J L , Long W M , Liu S X
Published: April 2013

The microstructures and properties of fresh, artificial aged and natural aged flux cored ZnAl15 wires were investigated by scanning electron microscope (SEM) and energy dispersive X-ray (EDX) spectrometer techniques. The results of SEM showed that continuous precipitation of ηs phase occurred and the dissolved contents of both αs phase and ηs phase reduced during the aging process of ZnAl15 wire, which led to the increase in Vickers microhardness. The results of the EDX presented that the oxygen absorption corrosion led to the embrittlement of ZnAl15 wire, which decreased the number of reverse bends. In addition, the phase transformation stress accelerated the corrosion, and finally, the natural aged ZnAl15 wire resulted in stress corrosion crack under the comprehensive effects of corrosion and phase transformation stress.
Influence of γ/γ′ lattice misfit on creep behaviours of FGH95 Ni based superalloy
Authors: Xie J , Tian S-G , Li J-J , Zhou X-M , Su Y
Published: April 2013

By means of microstructure observation and X-ray diffraction (XRD) analysis and creep properties measurement, an investigation has been made into the effects of γ/ γ′ lattice misfit on creep behaviours of FGH95 Ni based superalloy. The results showed that, compared with the ‘oil cooling’ alloy, the fine γ′ particles with larger size and better cube degree distribute in the alloy quenched in molten salt bath. By XRD analysis, it indicates that the γ/ γ′ interface of the ‘molten salt cooling’ alloy possesses bigger lattice misfit, which may hinder the dislocation movement to enhance the creep resistance of the alloy. During creep, the deformation mechanism of the oil cooling alloy is that the dislocations with different orientations slip in the matrix and form dislocation tangles. Moreover, the configuration of the partial dislocations plus stacking fault may be activated in the molten salt cooling alloy, and the deformed dislocations may bypass γ′ phase by Orowan mechanism, shear or climb over γ′ phase.
Effect of volume fraction and size of B4C particles on production and microstructure properties of B4C reinforced aluminium alloy composites
Authors: Canakci A , Arslan F , Varol T
Published: April 2013

A stir casting process was developed to produce aluminium alloy composites containing two different sizes and volume fractions of B4C particles up to 10 vol.-. Manufacturing of B4C particle reinforced 2024 aluminium alloy composites was modified so as to reduce the processing temperature. In the present study, in order to improve incorporation of the B4C particles by 2024 aluminium alloy melt, a novel pretreatment process before stir casting was attempted, and a significant improvement was gained. This finding showed that the treatment modified the surface condition of boron carbide powders via the removal of oxides. The comparison of added and incorporated particle ratios (the yield rate) indicated that the amount of incorporated particles decreased with increasing volume fraction and decreasing size of particles. Scanning electron microscopic observations of the microstructures revealed that the dispersion of the coarser sizes of particles was more uniform, while finer particles led to agglomeration of the particles and porosity. The results showed that the density of the composites decreased with increasing particle volume fraction and decreasing particle size, whereas the porosity and hardness values increased with increasing particle volume fraction and decreasing particle size.
Microstructure based modelling of flow behaviour of Al–Mg–Si alloy at different temper conditions
Authors: Anjabin N , Karimi Taheri A
Published: April 2013

A new integrated physically based constitutive model was developed for an age hardenable Al–Mg–Si alloy. The kinetics of precipitation during various stages of aging was modelled. The precipitate features consisted of particle radius and volume fraction obtained from the kinetics model, which was used to compute the alloy yield strength/hardness. A published multiinternal variable workhardening model was improved to take into account the effects of solute solution and precipitates on the alloy hardening capacity after performing different cycles of aging treatment. The flow curves and hardness predicted by the model were in good agreement with the experimental results. The model is able to predict the microstructure evolution such as cell/subgrain size and dislocation density in the cell interior during the plastic straining of material at different temper conditions.
Grain size effect on deformation twinning in Mg–Al–Zn alloy
Authors: Tsai M S , Chang C P
Published: April 2013

Specimens of Mg–3Al–1Zn alloy with a wide range of grain size distribution were compressed along different directions. The compressed microstructure was examined to clarify the grain size effect on deformation twinning in magnesium alloys. Small strains were used to reveal the twinning behaviour. The results show that the grain size affects the formation of deformation twins in an Mg–Al–Zn alloy. The reason for a different result being previously reported is given. This study also reports the different deformation microstructures in specimens compressed along different directions.
Phase transformations during diffusion brazing of IN718/Ni–Cr–B/IN718
Authors: Pouranvari M , Ekrami A , Kokabi A H
Published: April 2013

The production of robust joints after diffusion brazing necessitates the advanced understanding of phase transformations during the bonding process. This paper aims to investigate the solidification and the solid state precipitation during diffusion brazing of wrought IN718 nickel base superalloy using Ni–15Cr–4B (wt-) filler alloy. It was found that intermetallics containing eutectic type microconstituents were formed in the joint centreline by solidification which is controlled by segregation behaviour of B and its low solubility in Ni rich solid solution. In addition, extensive Cr–Mo–Nb rich precipitates were formed in the substrate region by solid state precipitation induced by B diffusion into base metal. The implications of the phase transformations on the joint properties are discussed.
Mechanical property evaluation of corrosion protection sol–gel nanocomposite coatings
Authors: Hojjati Najafabadi A , Mozaffarinia R , Rahimi H , Shoja Razavi R , Paimozd E
Published: April 2013

Organic–inorganic nanocomposite coatings were prepared from tetraethylorthosilicate and 3-glycidoxypropyltrimethoxysilane (GPTMS) by sol–gel method. These ormosil films were deposited by dip coating on aluminium alloy 5083. The effect of the concentration of GPTMS on the adhesion, mechanical and corrosion performance of coated samples was investigated. Adhesive strength of sol–gel coatings to the substrate was evaluated using pull-off and tape tests. Bending, impact resistance, pencil scratch and potentiodynamic polarisation tests were employed to characterise mechanical and corrosion performance of coated substrates with different GPTMS content. The chemical composition and the microstructure of the hybrid films were studied by attenuated total reflectance–Fourier transform infrared spectroscopy and field emission scanning electron microscopy respectively. The results indicate that the hybrid films had good mechanical properties, and the coating with minimum organic content had minimum corrosion current density, but the corrosion current density did not have any specific trend with an increased organic content.
Effect of tungsten content on properties of PVD sputtered Al–WX alloys
Authors: Kek Merl D , Panjan P , Milošev I
Published: April 2013

Al–Wx alloys with the W content ranging from 0·6 to 11 at-% were sputter deposited at a low temperature on AA7075 alloy substrates. The sputtered Al–W alloys exhibit a remarkably broad range of microstructures and were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). For the alloys with a W content from 0·6 to 3·5 at-%, increasing tungsten additions lead to a decrease in the grain size from a few hundred nm to 10 nm. At 11 at-%W, a lamella-like microstructure forms, accompanied by an amorphous phase. Nanoindentation tests revealed that the increasing tungsten additions lead to an increase in the hardness. A polarisation corrosion test in a near neutral 0·1M NaCl solution revealed that increasing the tungsten additions leads to an increasing passive range and, therefore, the pitting potential.
Effects of carbon nanotubes on crystallisation in amorphous Ni–P electroplating coating
Authors: Liu B , Liu L R , Liu X J
Published: April 2013

The amorphous nickel–phosphorus coating and its carbon nanotube (CNT) composite coating were prepared by brush electroplating technology. After 1 h heat treatment at 400°C, the coatings translated into the crystalline state, which consists of α-Ni matrix and Ni3P precipitated phase. The results of energy dispersive X-ray, X-ray diffraction analysis and differential thermal analysis showed that, due to CNTs, the phosphorus content in the coating decreased from 8·42 to 7·34 wt-%. Carbon nanotubes also had an effect on crystallisation kinetics of the amorphous coating. The crystallisation activation energy in Ni–P/2 g CNT composite coating was 25 kJ mol−1 higher than that in Ni–P coating. The time and temperature of the 50% crystallised were 5 min longer and 29°C higher respectively than that in Ni–P coating. Further study showed that CNTs played a role in obstruction in the crystallisation because CNTs block nucleation and growth of crystallisation for Ni3P phase.
Colorando Auro: third century colouring surface treatment of fire gildings
Authors: Crabbé A , Vandendael I , Dewanckel G , Terryn H , Wouters H J M
Published: April 2013

A few decades ago, heritage scientists and art historians started to study the ancient surface colouring techniques of metal art pieces. Colouring of copper and silver has already been broadly studied but no works on gold have been reported yet. This knowledge can be very important for art and technology history, conservation–restoration and surface sciences. This paper contributes to the investigation of the oldest recipe known so far to colour fire gildings. The chosen model samples, the mixture and the application of the recipe have been summarised by referring to the ancient writings known as the Arab and Syrian Alchemist Collection of M. Berthelot. The main aim of this research is to study the colour change obtained by applying the above mentioned recipe, and to identify the processes involved during this colour change. Digital imaging and scanning electron microscopy in combination with colorimetric measurements and elemental analysis have been performed to characterise the colour change and to identify its origins.