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ABSTRACTSolidification velocities as a function of initial bulk undercoolings were systematically investigated using high speed thermal imaging of highly undercooled pure Ni and Ni-Cu alloy samples. For pure Ni, the dendrite growth velocity increased continuously to a maximum value of about 52 m s−1at a maximum undercooling of 320 K. For Ni-Cu alloy, the dendrite growth velocity first increased continuously and then discontinuously to a maximum value of about 55 m s−1at 300 K. A clear discontinuity appeared in the growth velocity-undercooling curve is considered to be caused by the finite speed of solute diffusion in the bulk liquid ahead of the migrating solid–liquid interface.

The objective of this study was to determine the effects of different transport times on broilers during summer on stress, meat quality, and early postmortem muscle metabolites. Arbor Acres broiler chickens (n= 105) were randomly categorized into 5 treatments: unstressed control, 0.5 h, 1 h, 2 h, and 4 h transport. Each treatment consisted of 3 replicates with 7 birds each. All birds (except the control group) were transported according to a designed protocol. With the extension of transport time, the activities of plasma creatine kinase (CK) and lactate dehydrogenase (LDH) gradually increased. The content of heat shock protein 70 (Hsp70) did not change significantly during 0.5 h transport compared to the control group, but was significantly higher (P< 0.05) at 1 h or more of transport time. Also, transport times of 2 h or more resulted in a death rate of 20%–33% of broilers. We found that the breast meat in the 0.5 h transport group had significantly (P< 0.05) higher L* values, drip loss, cooking loss, AMP/ATP ratio, and phosphorylation of AMP-activated protein kinase (p-AMPK). In addition, pH24hwas lower compared to the control group, increasing the likelihood of pale, soft, and exudative (PSE)-like meat. However, no significant variations were found in meat color, drip loss, or cooking loss in other transport groups compared to the control group under the condition of this study. Muscle glycogen content decreased with time of transportation. There were significant correlations among p-AMPK and meat quality (P< 0.05). These results indicate that preslaughter transport during summer may cause severe physiological and biochemical changes of broilers. Further investigations studying the deeper relationship between biological indicators and meat quality according to the similar transport conditions would provide a better understanding of the effect of transport duration on meat quality.

The objective of this study was to determine the effects of physical restraint and electrical stunning on plasma corticosterone, postmortem metabolism, and quality of broiler breast muscle. Before slaughter, a total of 160 Arbor Acres broilers were randomly categorized into 2 replicate pens (80 broilers per pen) and every pen was randomly divided into 4 groups (free struggle, physical restraint, free struggle and electrical stunning, and physical restraint and electrical stunning; n= 20 per group). Glucose, lactate, and corticosterone were determined on blood plasma samples. Pectoralis major were removed after evisceration and used for determination of meat quality, energy metabolism, and calpain activity. In this study, reducing free struggle by physical restraint combined with electrical stunning improved (P< 0.05) meat water holding capacity. Free struggle preslaughter and during bleeding increased (P< 0.05) breast muscle redness, energy metabolism, and autolysis of μ/m-calpain and decreased (P< 0.05) meat shear values. Physical restraint and electrical stunning decreased (P< 0.05) plasma corticosterone level.

In order to improve the mechanical properties and reduce fabrication cost of large sheet metal parts, creep age forming (CAF) technology was developed, which is a process combined creep forming and heat treatment together. Springback of the workpiece in CAF is directly related to process parameters, such as, aging time, experimental stress and temperature. The aim of this paper is to establish a set of creep constitutive model, which can accurately predict the springback of 2124 aluminium alloy in CAF. A series of creep tests were carried out under different stress levels as 200, 225 and 250 MPa, and different temperatures as 185, 190 and 195°C for the solid solution treated and quenched 2124 aluminium alloy. Based on creep test data, a set of classic creep constitutive equations were established. Some important conclusions were drawn: the fitting curves of the constitutive equations could describe the test data in a good way; the creep strain increases with the increasing aging time, temperature and experimental stress. Then the springback of 2124 aluminium alloy during CAF process were analyzed by the finite element software MSC.Marc. Comparisons between the experiment analyses and finite element models show good correlation, and approve the forecast capability of FEM simulation for springback after CAF. At the end, the influence of process parameters on springback is studied, which provides essential foundation for designer to evaluate scheme and to optimise tool system design.

Undercooled solidification of hypoeutectic Ni–3·3 wt-%B alloy has been studied. The microstructure evolution of Ni–3·3 wt-%B alloy indicates that a transition from regular lamellar eutectic to anomalous eutectic exists with increasing undercooling for eutectic transformation. Here, a new model was proposed to describe the cooling curves of undercooled solidification with two-step transformation. Fits of the present model to the cooling curves after different undercoolings show that the predictions of transformed fractions are compatible with the microstructure observation. Furthermore, for hypoeutectic alloy, the size of the primary phase mainly depends on the undercooling for primary solidification, while the fraction of the primary phase mainly depends on the undercooling for eutectic solidification.

Applying fluxing method, hypercooling was achieved in Co80Pd20alloys. The rapidly solidified microstructures and substructures of hypercooled Co80Pd20alloys, subjected to rapid quenching and natural cooling after recalescence, have been studied. Transmission electron microscopy was used to investigate the substructures such as dislocations in the as solidified microstructures. X-ray diffraction line profile analysis was used for illuminating and determining the microstrain due to rapid solidification in the as solidified microstructures. In the undercooling range studied, the microstrain in the rapidly solidified structures increases with increasing undercooling. Quenching immediately after rapid solidification is helpful to preserving the microstrain in the microstructures.

Applying fluxing method, Co80Pd20alloy melts were undercooled up to 340 K. Evolution of the solidification microstructure of the undercooled alloys was investigated. Within the range of the achieved undercooling (?T), two grain refinement events were observed. The first event happens in the range of 50 K280 K. Based on experimental investigations and theoretical calculations, the mechanisms of grain refinements were illuminated. The first grain refinement event is induced by the remelting effects involved in the post-recalescence period, resulting in the formation of a spherical grained microstructure. In the narrow transition range of 265 K

Applying the fluxing method, hypercooling was achieved in Co80Pd20alloys. After recalescence, the rapidly solidified microstructures of hypercooled Co80Pd20alloys were subjected to rapid quenching. Applying transmission electron microscopy, high densities of substructures, e.g. dislocations and subgrains, and migration of high angle grain boundaries suggest the occurrence of partial recrystallisation in the hypercooled Co80Pd20alloys.

We present exciton-related optical studies of cadmium sulfide (CdS) nanobelts. Photoluminescence (PL) properties of CdS nanobelts are analyzed by using high spectral resolution spectroscopy from 10 to 300 K. The PL spectrum at 10 K shows rich spectral features which are identified, by means of temperature-dependent spectral evolution, to be the recombinations of free excitons, excitons bound to neutral impurities, and donor–acceptor pairs. The strong excitonic emission in our samples enables the observation of random lasing action at room temperature with a lasing threshold pump density of ∼0.1402 ± 0.0060 MWcm–2. Notably, temperature-dependent pump thresholds exhibit a characteristic temperature as high as 195.3 ± 12.7 K, implying a good thermal stability of the lasing behavior and potential high temperature operation. Our studies not only elucidate the intrinsic physical properties of our high quality nanomaterial but also reveal the promising applications in photonics.

In two winter wheat (Triticum aestivumL.) cultivars differing in their response to high temperature, JD8 (tolerant) and J411 (sensitive) we studied the effect of heat stress on the activities of phosphoenolpyruvate carboxylase (PEPC) and ribulose-1,5-bisphosphate carboxylase (RuBPC) in green organs during grain-filling. There were significantly higher PEPC activities and lower RuBPC activities in each of the non-leaf organs (awn, glume, lemma, peduncle, and sheath) than in the flag leaf blade. Under heat stress for 12 d, the activity of RuBPC quickly declined and the activity of PEPC first increased and later declined in all organs, resulting in a great increase of the PEPC/RuBPC ratios in the organs, particularly in non-leaf organs which had a higher PEPC/RuBPC than the flag leaf blade in all times. The PEPC activity and PEPC/RuBPC ratio in every organ of JD8 were higher than those in the same organ of J411. Thus the differences in PEPC activities and PEPC/RuBPC may be associated with the differences in photosynthetic heat tolerance among the organs of the same plant or between the two cultivars.

The martensite transformation and work hardening of metastable austenite induced by abrasive wear in an austenitic Fe-C-Cr-Mn-B alloy were studied by TEM. The results show that an a‘ martensitic transformation occurred to form an elongated and equiaxial cellular dislocation substructure and the untransformed austenite matrix produced an equiaxial cellular dislocation substructure on the abraded surface. Electron diffraction patterns of the abraded material are composed of diffraction rings with series of broken arcs resulting from a fine grain structure and the deformation texture. The work hardening zone of austenite at the subsurface reveals heavy slip bands and deformation faults, at which the dislocations pile up. Examples of ? martensite induced by abrasive wear can be detected. The a‘ martensite transformation and metastable austenite work hardening should bring about an increase in surface hardness and wear resistance. Additionally, the cellular dislocation substructure of a‘ and ?have a significant effect on increasing the hardness of the wear surface. Observation by TEM indicates that the a‘ martensite transformation happens more easily in the austenite matrix near the carbide (Fe, Cr)7C3as a result of the depletion of carbon and chromium.

D-3-Phosphoglycerate dehydrogenase (PGDH) from Escherichia coli is allosterically inhibited by L-serine, the end product of its metabolic pathway. Previous results have shown that inhibition by serine has a large effect on Vmax and only a small or negligible effect on Km. PGDH is thus classified as a V-type allosteric enzyme. In this study, the active site of PGDH has been studied by site-directed mutagenesis to assess the role of certain residues in substrate binding and catalysis. These consist of a group of cationic residues (Arg-240, Arg-60, Arg-62, Lys-39, and Lys-141') that potentially form an electrostatic environment for the binding of the negatively charged substrate, as well as the only tryptophan residue found in PGDH and which fits into a hydrophobic pocket immediately adjacent to the active site histidine residue. Interestingly, Trp-139' and Lys-141' are part of the polypeptide chain of the subunit that is adjacent to the active site. The results of mutating these residues show that Arg-240, Arg-60, Arg-62, and Lys-141' play distinct roles in the binding of the substrate to the active site. Mutants of Trp-139' show that this residue may play a role in stabilizing the catalytic center of the enzyme. Furthermore, these mutants appear to have a significant effect on the cooperativity of serine inhibition and suggest a possible role for Trp-139' in the cooperative interactions between subunits.

Abstract:  By introducing an hydroxyl group and a lipophilic branch into the middle of lipophilic head of emulsifier 12-oxy-9-octadecenoic acid, a new emulsifier was synthesized and applied in microemulsion polymerization. When the emulsifier content in the microemulsion was kept to about 12%, the highest monomer content in microemulsion could achieve 35% for BA, 20% for St and MMA. The microemulsion with high monomer content remained clear after polymerization, and the average diameters of polymer particles were 38.9 nm for St microemulsion, 47.4 nm for BA, and 50.7 nm for MMA.

The Drosophila tinman homeobox gene has a major role in early mesoderm patterning and determines the formation of visceral mesoderm, heart progenitors, specific somatic muscle precursors and glia-like mesodermal cells. These functions of tinman are reflected in its dynamic pattern of expression, which is characterized by initial widespread expression in the trunk mesoderm, then refinement to a broad dorsal mesodermal domain, and finally restricted expression in heart progenitors. Here we show that each of these phases of expression is driven by a discrete enhancer element, the first being active in the early mesoderm, the second in the dorsal mesoderm and the third in cardioblasts. We provide evidence that the early-active enhancer element is a direct target of twist, a gene encoding a basic helix-loop-helix (bHLH) protein, which is necessary for tinman activation. This 180 bp enhancer includes three E-box sequences which bind Twist protein in vitro and are essential for enhancer activity in vivo. Ectodermal misexpression of twist causes ectopic activation of this enhancer in ectodermal cells, indicating that twist is the only mesoderm-specific activator of early tinman expression. We further show that the 180 bp enhancer also includes negatively acting sequences. Binding of Even-skipped to these sequences appears to reduce twist-dependent activation in a periodic fashion, thus producing a striped tinman pattern in the early mesoderm. In addition, these sequences prevent activation of tinman by twist in a defined portion of the head mesoderm that gives rise to hemocytes. We find that this repression requires the function of buttonhead, a head-patterning gene, and that buttonhead is necessary for normal activation of the hematopoietic differentiation gene serpent in the same area. Together, our results show that tinman is controlled by an array of discrete enhancer elements that are activated successively by differential genetic inputs, as well as by closely linked activator and repressor binding sites within an early-acting enhancer, which restrict twist activity to specific areas within the twist expression domain.

Abstract: A first Born approach to intense laser modified proton-helium electron capture collision is given. Theoretical results show that the angular distribution peaks forward sharply. For a geometry of laser polarization vector parallel to the incident direction, the dressing effect on the differential cross section covers a relatively wide angular range; while for a perpendicular geometry, the result is modified only in a very small angular region. The integral cross sections get highly promoted by laser with the impact energy increasing. The modified cross sections are increasing functions of field strength, but decreasing functions of field frequency. Comparisons with the laser assisted electron capture from atomic hydrogen are made.

6FDA-pMDA polyimide membranes were implanted with 140 keV N⁺ ions to fluences between 2 × 10¹⁴ and 5 × 10¹⁵ cm⁻². Variable energy positron annihilation spectra were taken and spectral features compared to previously reported changes in gas permeability and permselectivity of these membranes as a function of ion fluence. Positron data corroborate the explanation of these changes in terms of molecular damage caused by the implant: for fluences up to about 1 × 10¹⁵ cm⁻², the concentration of irradiation-induced defects merely increases with implant fluence; while fluences exceeding this threshold value create a second type of positron annihilation site, thereby marking a distinct change in the structure of the polymer, which is responsible for the vast improvement of gas permselectivity data found at the same threshold fluence. PACS codes: 78.70.Bj—positron annihilation; 61.82.Pv—polymers, organic compounds; 61.72.Ww—doping and impurity implantation. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2413–2421, 1998

D-3-Phosphoglycerate dehydrogenase from Escherichia coli is a homotetrameric enzyme which is allosterically regulated by the end product of its pathway, L-serine. The enzyme binds 4 L-serine molecules at two interfaces formed by the noncovalent association of the regulatory domains. The two domains that comprise each interface are related by an approximately 180 degrees axis of symmetry, and two serine molecules bind at each interface by forming a hydrogen bond network between the domains. A model has been proposed that suggests that serine functions by drawing adjacent domains together and that this in turn translates a conformational change to the active site. A tryptophan residue has been engineered into the helices flanking the regulatory interfaces that displays significant quenching in response to serine binding. Residues on the adjacent subunit appear to be primarily responsible for the tryptophan quenching and thus support the hypothesis that serine binding leads to an increase in the proximity between residues on neighboring subunits. Serine binding studies show that this quenching, as well as inhibition of enzymatic activity, are essentially complete when only two of the four serine binding sites are occupied. The requirement for only one serine per interface is consistent with the notion that the interface is formed by relatively rigid domains and that hydrogen bonding at only a single site is all that is required to substantially close the interface. The fluorescence quenching in response to L-serine binding generally correlates with enzymatic inhibition, but there appears to be a slight lag in inhibition relative to quenching at low serine concentrations. The observed fluorescence quenching of residues in the regulatory domains of D-3-phosphoglycerate dehydrogenase provide the first direct evidence for a conformational change in response to effector binding and provide a means to monitor the first step in the allosteric mechanism.

A relationship between bonding strength and bonding area has been found which suggests that the increase in bonding strength is caused by the bonding area increase in the oxidised silicon wafer direct bonding (SDB) process. The bonding area shows a saturation property with bonding time. Diffusion of various species existing in bonding interface region plays a key role in SDB process over different temperature. Viscous flow of the oxides completes bonding at T > 1050°C. A rapid thermal bonding (RTB) at 1200°C for 2min following 800°C for 2hr annealing realises complete bonding with little doping profile change in the system.

A power grid reactive power optimization algorithm was proposed in this paper to ensure that distribution network systems run efficiently, which is called the opposition-based chaos shuffled frog leaping algorithm (OCSFLA). A mathematical model of reactive power optimization was established based on the consideration of the constraint conditions. The initial swarm of the model was optimized based on the opposition strategy. The leading role changed gradually from the shuffled frog leaping algorithm to chaotic search in the iterative process by setting the appropriate chaotic variables. Thus, the global optimal solution was searched more quickly. In the simulation tests of the IEEE30 system, the results show that a better compensation effect was obtained when the reactive power compensation was performed in nodes 12 and 24. After completing the reactive power optimization based on the improved leapfrog algorithm, the active network loss value of the system was reduced by 13.85%. The algorithm was more efficient compared with other traditional optimization algorithms because OCSFLA can avoid falling into local optimization.

Effects of vermiculite as a friction modifier on brake friction performance of PI-matrix materials have been tested. PI-matrix friction materials with different vermiculite content (0%, 5%, 10%, 15%, 20% in wt) were prepared by the heat-press molding method. The friction tests were carried out on a pin-on-disk tester in the speed range of 20[?]120 km/h. The experimental results indicate that the effects of vermiculite on the friction and wear performance of the materials are closely related to the friction speed. At low friction speeds (between 20[?]40 km/h), the friction coefficient increases with the increasing of vermiculite content. At high friction speeds (between 60[?]120 km/h), the friction coefficient increases at first when vermiculite content below 10 wt% and then decreases with vermiculite content increasing. The wear rate decreases by adding 5 wt% vermiculite, and then increases. As the friction speeds above 100 km/h, the wear rate changes dramatically.

Silicon wafer and quartz have been successfully bonded together by a two-step thermal treatment process. SIMS measurements shows that after molecular surface activated solvent treatment, the amount of OH on the silicon or quartz surface, which is essential to the first step (low-temperature) bonding strength, is one order of magnitude higher than that on the original silicon or quartz surface. After a high-temperature (850–1250°C) solid-state diffusion process, the bonding strength between silicon and quartz is greatly increased to 150–185 kg/cm2. The material and electrical properties of the silicon on quartz substrate compares favourably with those of the bulk silicon wafer.