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High Cr white irons (HCWIs) are often used as high-temperature components exposed to the temperatures exceeding 500 °C. Improving oxidation resistance of HCWI components is necessary for engineering applications. In the present study, oxidation behaviors of high Cr white iron (HCWI) and its composites reinforced with 1–2 μm nonstoichiometric TiCxresulting from the decomposition of Ti3AlC2(in situ TiCx/HCWI), and 2–4 μm irregular-shape of TiC (TiC/HCWI) at 600 °C for 96 h in air were investigated. Results showed that the two composites exhibited better oxidation resistance than the pure HCWI material. The oxidation test revealed a weight loss for the unreinforced HCWI but a weight gain for the composites. Among these materials, the in situ TiCx/HCWI composite has the best oxidation resistance due to its dense and fine microstructure. Oxidative thermodynamics and oxidation mechanism were discussed. This work suggests that in situ formed TiCxis an effective reinforcement to improve the oxidation resistance of HCWIs.

Background: Lectin-like oxidized LDL receptor-1 (LOX-1), a novel receptor for oxidized low-density lipoprotein, mediates oxidized low-density lipoprotein--induced apoptosis of endothelial cells, monocyte adhesion to endothelium, and phagocytosis of aged cells. [...]

The competition mechanism of ferritic recrystallization and austenitic transformation, nucleation and growth kinetics of different crystallographic orientation components during intercritical annealing of a cold-rolling Fe–Al–Mn–Mo–C deep drawing dual-phase steel were investigated by a series of continuous annealing simulation experiments. The experiments provided an insight into the microstructural characteristics and mechanical behaviors that were caused from the interaction of primary recrystallization and phase transformation. The results show that the promoting effect of austenite transformation is greater than that of ferrite recrystallization with the increase of temperature in the two-phase region, and an appropriate soaking time is contributed to the formation and development of {111} oriented grains. Austenite formation affects morphology and size of the microstructure owing to inhibiting ferrite recrystallization and growth. From these that experimental data of the observed temperature or time-dependent mechanical properties can be interpreted. An excellent comprehensive properties with tensile strength of 480 MPa and plastic strain ratio (r value) of 1.15 can be obtained at annealing temperature of 880 °C for 300 s.

Oxidation behaviors of in situ formed TiCx/high chromium white iron (TiCx/HCWI) composite containing trace alloying elements with super hardness were investigated in air at 650 °C and 700 °C for 96 h, respectively. Rich types of oxides appeared on the oxidized surfaces of the TiCx/HCWI composite both at 650 °C and 700 °C. While, MoO3appeared on the surface only at 650 °C, FeV2O4turned up only at 700 °C. The various oxides were enriched in diverse regions inside and outside the oxide layer at 700 °C due to the discrepancy of oxidation thermodynamics and oxidation partial pressure. Oxidation thermodynamics, kinetics, and oxidation mechanisms of the TiCx/HCWI composite were discussed. The present work provides enlightenment for the application of the super hard TiCx/HCWI.

•Sub-and super-critical CO2flow behaviours under three confinements.•Coal permeability recovery was examined after up to 144 h N2saturation.•Greater permeability recovery for higher N2saturation pressure and longer N2saturation duration.•Poro-elastic effect controls coal permeability in high confinement.

This study was aimed at identifying underlying strengthening mechanisms and predicting the yield strength of as-extruded Mg-Zn-Y alloys with varying amounts of yttrium (Y) element. The addition of Y resulted in the formation of ternary I (Mg 3 YZn 6 ), W (Mg 3 Y 2 Zn 3 ) and LPSO (Mg 12 YZn) phases which subsequently reinforced alloys ZM31 + 0.3Y, ZM31 + 3.2Y and ZM31 + 6Y, where the value denoted the amount of Y element (in wt%). Yield strength of the alloys was determined via uniaxial compression testing, and grain size and second-phase particles were characterized using OM and SEM. In-situ high-temperature XRD was performed to determine the coefficient of thermal expansion (CTE), which was derived to be 1.38 × 10 −5 K −1 and 2.35 × 10 −5 K −1 for W and LPSO phases, respectively. The individual strengthening effects in each material were quantified for the first time, including grain refinement, Orowan looping, thermal mismatch, dislocation density, load-bearing, and particle shearing contributions. Grain refinement was one of the major strengthening mechanisms and it was present in all the alloys studied, irrespective of the second-phase particles. Orowan looping and CTE mismatch were the predominant strengthening mechanisms in the ZM31 + 0.3Y and ZM31 + 3.2Y alloys containing I and W phases, respectively, while load-bearing and second-phase shearing were the salient mechanisms contributing largely to the superior yield strength of the LPSO-reinforced ZM31 + 6Y alloy. [ABSTRACT FROM AUTHOR]

Fracture toughness determines materials’ resistance to fracture, which is measured often using impact or bending tests. However, it is difficult to evaluate fracture toughness of coatings and small samples. In this article, using white irons as sample materials, we explore a possible approach of using electron work function (EWF) as an indicator in evaluating fracture toughness of hard metallic materials. This parameter is promising for being utilized to analyze toughness of protective coatings and small objects as well as bulk materials. Through comparison with results obtained from impact tests and elastic modulus measurement, effectiveness of this EWF approach is demonstrated. [ABSTRACT FROM AUTHOR]

Roll forming has been widely used to manufacture constant cross-section products because of high quality, efficiency and low cost. It is quite epidemic in producing automobile parts made of advanced high strength steels (AHSS) nowadays. However, with the development of the vehicle industry and diversity of the products, variable cross-section profiles have attracted more and more attention. The traditional roll forming technique is difficult to meet the requirements. Chain-die forming which was introduced in recent years makes it possible. Chain-die forming is an extension of roll forming and its key characteristic is enlarging the rotation radii of the moulds, by which the deformation zone is extended. The study focused on the finite element simulations of Chain-die forming U profiles with variable cross-section, including variable width and height. The feasibility of Chain-die forming producing variable cross-section products was verified by the perfect simulation results. The advantage of Chain-die forming was that there was no need to design the intermediate moulds except the finished-profile ones, which reduced the mould quantity immensely. Then the cost was lower.

Multiple simultaneous or sequential deformation mechanisms exist at the heart of extraordinary mechanical behavior of high-entropy alloys. As additive manufacturing (or 3D printing) is changing the landscape of materials engineering, the 3D-printed high-entropy alloys evoke unmatched potential of pragmatic structure-property relationships. Uncovering such relationships demands meticulous analysis of plastic deformation pathways and the corresponding stress responses. Here we present an electron backscatter diffraction (EBSD)-based study pertaining to the tensile deformation mechanisms of a CrMnFeCoNi high-entropy alloy fabricated via laser-beam powder bed fusion (PBF-LB). The tensile deformation of the 3D-printed high-entropy alloy exhibits distinctive recurring stress drops of ∼90 MPa (∼11% of its ultimate tensile strength), spanning ∼10% of the total strain prior to failure due to the occurrence of deformation twinning. The EBSD results reveal how the onset of deformation twinning is essentially guided by crystal orientation and exhaustion of gliding dislocations. A new twinning propensity factor, defined as a ratio of the twinning Schmid factor to the slip Schmid factor of the parent grains, is proposed to reflect the tendency of deformation twinning. The twin size increases linearly with increasing twinning propensity factor. These findings shed light on the underlying deformation mechanisms and provide a theoretical guidance for developing advanced high-entropy alloys via additive manufacturing.

In animals, core clock genes are expressed in many peripheral tissues throughout the body that contribute to tissue specific temporal regulation including those that comprise the reproductive system. The chicken ovulatory cycle seems to provide an example of a system in which circadian and interval timing mechanisms operate during ovulation-oviposition. However, little is known about the possible role of circadian regulation during egg formation and laying. To this end, we determined the rhythmic expression of several known canonical clock genes and clock controlled genes in the 4 segments of the chicken oviduct (infundibulum, magnum, isthmus, and uterus) taken from the same biological state (laying sequence and oviposition time) using real time RT-PCR. Except for Cry1, the other genes we analyzed were expressed in all 4 segments of the oviduct. Intriguingly, in a daily light-dark cycle, Bmal1, Clock, Per2, Per3, Cry2, and Rev-erbβhave highly significant rhythmic expression in the infundibulum and uterus but not in the magnum and isthmus. These results show that there is spatial specificity in the localization of clock cells in the hen reproductive tract and that peripheral clocks might have a direct role in the infundibulum and uterus where yolk is captured and the eggshell is formed, respectively.

The purpose of the present study was to identify microstructural changes at both Mg/Zn and Al/Zn interfaces of ultrasonic spot welded joints between a rare-earth containing ZEK100 magnesium alloy and an AA6022 aluminum alloy with a zinc interlayer, focusing on their effect on the tensile lap shear strength. During ultrasonic spot welding (USW), the diffusion or reaction was observed to occur at both interfaces, with the reaction being much faster at the Mg/Zn interface than at the Al/Zn interface. This was attributed to the higher diffusion rate of Zn in Mg and lower eutectic temperature in the Mg-Zn system along with the higher specific heat capacity and lower thermal conductivity of magnesium. With increasing welding energy, the diffusion layer at both interfaces increased. However, the diffusion layer at the Al/Zn interface was appreciably thinner than that at the Mg/Zn interface. While the eutectic (or eutectoid) structure containing Mg7Zn3, MgZn2and MgZn intermetallic phases appeared at the Mg/Zn interface, the diffusion layer at the Al/Zn interface consisted of only Al and Zn based solid solution. The joining mechanisms were mainly mechanical interlocking and metallurgical bonding which were enhanced by grain refinement at both interfaces stemming from dynamic crystallization during USW. The peak tensile lap shear strength of the present Mg-Al dissimilar joints was attained at a welding energy of 1000 J, and the failure occurred in the diffusion layer at the Mg/Zn interface.

The aim of this study was to evaluate the strain hardening and hot deformation behavior of as-extruded Mg–Zn–Mn (ZM31) magnesium alloy with varying Y contents (0.3, 3.2, and 6 wt%) via compression testing along the extrusion direction at room temperature, 200 °C and 300 °C. Texture and phases were identified by X-ray diffraction. Alloy ZM31 + 0.3Y consisted of a mixture of fine equiaxed grains and elongated grains with I-phase (Mg 3 YZn 6 ); alloy ZM31 + 3.2Y contained I-phase and W-phase (Mg 3 Y 2 Zn 3 ); alloy ZM31 + 6Y had long-period stacking-ordered (LPSO) X-phase (Mg 12 YZn) and Mg 24 Y 5 particles. With increasing Y content the basal texture became weakened significantly. While alloys ZM31 + 0.3Y and ZM31 + 3.2Y exhibited a skewed true stress–true stain curve with a three-stage strain hardening feature caused by the occurrence of { 10 1 ¯ 2 } extension twinning, the true stress–true stain curve of alloy ZM31 + 6Y was normal due to the dislocation slip during compression. With increasing temperature the extent of skewness decreased. While the compressive yield stress, ultimate compressive stress, strain hardening exponent, and hardening capacity all decreased as the temperature increased, the retention of the high-temperature deformation resistance increased with increasing Y content mainly due to the presence of thermally-stable LPSO X-phase. [ABSTRACT FROM AUTHOR]

Neural guidance cues are essential for a growing axon to correctly course through the body and innervate target tissues. Interestingly, the vascular network follows a parallel trajectory along nerves, suggesting that guidance cues important for neural patterning may also be required for proper vascular patterning. However, while an axon arises from one cell, a blood vessel is composed of many endothelial cells. Recent evidence suggests that neural repulsive cues are usurped by multi-cellular blood vessels to ensure vascular stabilization cues. Additional clues into the signaling mechanisms that promote vascular stabilization are emerging from cerebral cavernous malformations, a disease characterized by headache, epilepsy, and stroke. Thus, neurobiology and neurology are providing insights into the concepts of vascular stability.

It has long been recognized that the yield point of a solid material differs under different loading conditions. However, it is difficult to directly determine the yield strain or stress of the solid under complex loading conditions. As a result, the yield strain or stress measured by tensile testing is usually used for analyzing, predicting and modeling mechanical behavior of solid materials under different loading conditions. This article proposes a promising method, Kelvin probing technique, to determine the yield strain of solid materials and thin films under tensile and compressive stresses, respectively. This method could also be extended to the determination of the yield points of thin films and components in micro-devices under different types of stress.

The dry sand/rubber-wheel abrasion tester is widely used to evaluate the low-stress abrasion resistance of materials for the mining/mineral processing industry particularly for the oil sand mining industry. Since wear loss is usually proportional to the applied load, this test is often performed under a fixed load at a fixed sliding speed to rank materials. However, inaccurate or misleading information might be generated under an inadequate load. It has been observed that D2 tool steel exhibits very different responses to variations in the applied load. Above a certain load level, further increase in the applied load may lead to a decrease in wear loss of D2 steel. In order to understand this phenomenon, computer simulation was performed to investigate wear responses of several engineering materials, including D2 tool steel, stainless steel, Al 6061 and Cu 110, to variations in applied load under the dry sand/rubber-wheel abrasion condition. It was demonstrated that the decrease in wear loss of D2 tool steel with an increase in the applied load was attributed to failure of the abrasive sand. Wear losses of the materials with respect to the sliding speed were also investigated. The prediction from the simulation was compared to experimental observations.

Corrosive wear of materials is a complicated surface failure process. The synergism of wear and corrosion involves both the wear-accelerated corrosion and the corrosion-accelerated mechanical failure. In this work, attempts were made to determine mass losses from these two processes using an electrochemical scratch technique. 340 stainless steel and a cast iron were studied as sample materials. For both the materials, the wear-accelerated corrosion was significantly higher than the static corrosion, due to the failure of passive film or adsorption layer. Regarding the corrosion-accelerated wear, 304 steel showed higher resistance, attributed to its passivation capability and associated protective passive film.

Recent studies demonstrate that near equiatomic Ti–Ni alloys possess high resistance to surface damage by wear. It is suggested that the high wear resistance of Ti–Ni alloys is closely correlated to their pseudoelasticity, which is usually evaluated by tensile testing. However, when a Ti–Ni alloy is under wear, its surface is in a complex stress state. Since the thermoelastic martensitic transformation of Ti–Ni alloys responds differently to different stresses, it may not be appropriate to evaluate the pseudoelasticity by tensile testing. The present paper reports recent work on pseudoelastic behaviour of a Ti–51 at.-%Ni alloy employing a microindentation technique as well as tensile testing methods. In the present work, the wear performances of Ti–51 at.-%Ni alloy specimens with different degrees of pseudoelasticity were also investigated, and efforts were made to explain the beneficial effect of pseudoelasticity on the wear resistance of Ti–Ni alloys.

A dynamic computer model was developed to simulate wear behavior of materials on micro-scales. In this model, a material system is discretized and mapped onto a lattice or grid. Each lattice site represents a small volume of the material. During a wear process, a lattice site may move under the influence of external force and the interaction between the site and its adjacent sites. The site–site interaction is a function of mechanical properties of the material such as the elastic modulus, yield strength, work hardening and the fracture strain. Newton's law of motion is used to determine the movement of lattice sites during a wear process. The strain between a pair of sites is recoverable if it is within the elastic deformation range; otherwise plastic deformation takes place. A bond between two adjacent sites is broken when its strain exceeds a critical value. A site or a cluster of sites is worn away if all bonds connecting the site or the cluster to its nearest neighbors are broken. The model well describes the strain distribution in a contact region, in consistence with a finite element analysis. This model was applied to several metallic materials abraded under the ASTM G65 abrasion condition, and the results were compared to experimental observations. Good agreement between the modeling and the experiment was found.

Effects of an oxygen active element, yttrium, on the resistance of 304 stainless steel to corrosive siding wear in 0·1M H2SO4solution and to dry sliding wear in air, respectively, were investigated using a pin-on-disc wear tester. The worn surfaces and debris were examined by scanning electron microscopy. The results demonstrated that alloying with yttrium greatly improved the wear resistance of 304 stainless steel in both the corrosive and air environments.

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The density of PGF"2"@a (FP) and PGE"2 (EP) receptors on the cerebral microvasculature of the newborn is less than on that of the adult animal. High levels of prostaglandins in the newborn brain could be responsible for down-regulation of FP and EP receptors and their functions in the cerebral microvasculature. Cerebrovascular FP and EP receptor density, receptor-coupled second messenger production and cerebral vasoconstrictor responses to PGF"2"@a and PGE"2 were studies in newborn pigs (1 to 2 days old) treated intravenously with ibuprofen (40 mg/kg every 6 hours for 48 hours) or saline, and compared with adults. Ibuprofen treatment in the newborn increased brain microvascular FP and EP receptor densities to levels found in that of adult pigs. Likewise brain microvessel inositol 1,4,5-triphosphate production in response to PGF"2"@a, fenprostalene (PGF"2"@a analog), PGE"2, 17-phenyl trinor PGE"2 (EP"1 receptor subtype agonist) and M&B 28,767 (EP"3 agonist) was greater in ibuprofentreated newborn pigs; the latter was associated with increased vasoconstriction to these agents to levels comparable with those of adults. Steady-state levels of FP receptor mRNA in cerebral microvasculature did not differ between saline-treated newborn, and ibuprofen-treated newborn and adult pigs. It is concluded that the low FP and EP receptor densities and receptor-coupled functions on newborn brain microvessels seem to be secondary to high levels of brain prostaglandins; the changes in receptor levels do not seem to be related to steady-state levels of receptor mRNA in brain microvessels.

A coherent precipitate phase usually has a number of variants that are oriented in different but equivalent crystallographic directions. The distribution of the variants can be changed by applying stress during ageing. Under the stress constraint, the growth of differently oriented variants becomes selective, and this, in turn, varies the material's microstructure. The number of precipitate variants may be determined by decomposing the space group of the parent phase into the coset of the space group of the coherent precipitate phase; and which variants grow selectively is, however, dependent upon the coupling between the applied stress and the local strain of the variants. Selective variant growth of Ti11Ni14precipitates in Ti-51.5 at% Ni alloy was investigated. A pole projection method was proposed and used to predict the selective variant growth of Ti11Ni14precipitates under the stress constraint. TEM observation was conducted to corroborate the prediction. A positive correlation between the theoretical analysis and the experiment was established.

There exists abundant evidence that prostanoids are important messengers involved in a vast array of biological processes. Recent data suggest those prostanoids exert different roles in the regulation of cerebral and ocular circulation of the newborn compared to the adult. Not only are there ontogenic differences in the cerebral and ocular concentrations of prostanoids, which are higher in the newborn than in the adult, but also their receptor-mediated actions differ with age. Understanding of developmental changes in the characterization and regulation of prostanoid receptors on the cerebral and ocular vasculature sheds significant light on mechanisms that control brain and retinal circulation. In this paper, the results of investigation on ontogeny and developmental regulation of prostanoid receptors and their impact on nitric oxide synthase activity on cerebral and ocular vasculature are reviewed.

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Although macrophages scavenge oxidatively modified low density lipoprotein (ox-LDL) via specific receptors, the uptake of ox-LDL by endothelial cells is thought to be mediated by a different receptor (LOX-1). We examined the presence of LOX-1 on cultured human coronary artery endothelial cells (HCAECs) by RT-PCR, radioligand blot, and binding assays. LOX-1 mRNA and protein were consistently identified in HCAECs. [125I]-ox-LDL binding assay also identified high affinity binding sites for LOX-1 on HCAECs (KD:1.71 × 10−8M: Bmax:29.7 ng/mg protein). There was no change in LOX-1 expression in HCAECs treated with native-LDL. In contrast, incubation of HCAECs with ox-LDL (10–40 μg/ml) increased LOX-1 expression (mRNA and protein). The upregulation of LOX-1 expression appeared to be dependent on ox-LDL concentration. Higher concentration (100 μg/ml) however, decreased LOX-1 expression, perhaps related to its cytotoxic effect. These observations indicate that ox-LDL upregulates its own receptor on HCAECs. This phenomenon may explain enhanced uptake of ox-LDL by HCAECs in hyperlipidemia resulting in cellular dysfunction.

•A 3D FEM of track-subgrade-foundation interaction system with bidirectional seismic and moving loads is performed.•Coupled vibration characteristics in two loads are analyzed.•Influence of the coupling effect on the critical speed of the model is discussed.•Derailment coefficient and lateral deformation of the rail are introduced to predict.

Objectives: LOX-1, a lectin-like receptor on endothelial cells, facilitates the uptake of oxidized-LDL. Expression of LOX-1 is involved in the pathobiological effects of oxidized-LDL in endothelial cells, including apoptosis, suppression of cNOS activity and cell adhesion. Recent studies show that intracellular signal protein kinase B (PKB) is involved in the regulation of cNOS. Further, HMG CoA reductase inhibitors (statins) may affect LOX-1 expression. In this study, we examined the modulation of LOX-1 expression and PKB activity in response to oxidized-LDL by two different statins (simvastatin and atorvastatin). Methods and results: Cultured human coronary artery endothelial cells (HCAECs) were used in this study. Oxidized-LDL (40 µg/ml) was found to upregulate the expression of LOX-1 (mRNA and protein), enhance [125I]-ox-LDL uptake and to reduce the phosphorylation of PKB (p-PKB). Two different statins, simvastatin and atorvastatin (each 1 and 10 µM), upregulated the activity of PKB and decreased LOX-1 expression and [125I]-ox-LDL uptake. A high concentration of statins (10 µM) gave a more potent effect than the low concentration (1 µM). The effects of the two different statins were similar. Conclusions: These observations show that statins decrease LOX-1 expression, a novel oxidized-LDL endothelial receptor, and uptake of oxidized-LDL in HCAECs. The effect of statins on LOX-1 expression is associated with an increase in PKB activity in HCAECs.