The amino acids of Escherichia coli enterotoxin B subunit involved in binding to Bio-Gel A-5m or to the glycoprotein from mouse intestinal epithelial cells

We determined whether Arg13, Met31, and Ser95 of the heat-labile enterotoxin B subunit (LT-B) might be involved in Lt-B binding to oligosaccharides, which did not bind to the B subunit of the cholera toxin (CT-B). Three LT-B mutants, R13H, M31L, and S95A were prepared by substituting three amino acid residues that differ in CT-B. These mutants formed a pentamer and exhibited the same binding ability to the GM1 ganglioside as native LT-B. Although these mutants did not bind to Bio-Gel A-5m, they did bind to the glycoprotein from mouse intestinal cells in the order R13H > M31L > S95A. These data suggest that Ser95, Met31, and Arg13 are important for LT-B binding to Bio-Gel A-5m, and that although Ser95 is also partially responsible for LT-B binding to the glycoprotein, Arg13 has no significant involvement in it.     

Spin Gap and Hole Pairing of Sr14−x A x Cu24O41(A = Ca and La) Single Crystals Studied by the Electrical Resistivity and Thermal Conductivity

We have measured the electrical resistivity and the thermal conductivity of Sr _14–x A _x Cu ₂₄ O ₄₁(A = Ca and La) single crystals. The Arrhenius plot of ln vs T ^–1 gives two kinds of activation energy with a boundary temperature T . The activation energy at T < T is in approximate agreement with the spin gap in the ladder estimated from the NMR measurements, suggesting that holes in the ladder are paired and localized at T < T. The observed has been analyzed to be composed of _ph , _spin and _hole due to phonons, spins and holes, respectively. The _ph exhibits a small peak at 30 K in every direction of every single-crystal. The contribution of _spin is observed along the c-axis except for x(Ca) 6, and the spin gap, which corresponds to the spin excitation from spin-singlet to spin-triplet, has been estimated to be 420 K. For x(Ca) 6, the spin gap, which corresponds to the destruction of spin-singlet pairs i. e. the dissociation of hole pairs, has been estimated from along the c-axis at T > T to decrease with increasing x(Ca).     

Deformation mechanism of bimodal microstructure in Ti-6Al-4V alloy: The effects of intercritical annealing temperature and constituent hardness

The so-called bimodal microstructure of Ti-6Al-4V alloy,composed of primary α grains (αp) and transformed β areas (βtrans),can be regarded as a "dual-phase" structure to some extent,the mechanical properties of which are closely related to the sizes,volume fractions,distributions as well as nano-hardness of the two constituents.In this study,the volume fractions of primary α grains (vol.％(αp)) were systematically modified in three series of bimodal microstructures with fixed primary α grain sizes (0.8 μm,2.4 μm and 5.0μm),by changing the intercritical annealing temperature (Tint).By evaluating the tensile properties at room temperature,it was found that with increasing Tint (decreasing vol.％(αp)),the yield strength of bimodal microstructures monotonically increased,while the uniform elongation firstly increased with Tint until 910 ℃ and then drastically decreased afterwards,thereby dividing the Tint into two regions,namely region Ⅰ (830-910 ℃) and region Ⅱ (910-970 ℃).The detailed deformation behaviors within the two regions were studied and compared,from the perspectives of strain distribution analysis,slip system analysis as well as dislocation analysis.For bimodal microstructures in region Ⅰ,due to the much lower nano-hardness of βtrans than αp,there was a clear strain partitioning between the two constituents as well as a strain gradient from the αp/βtrans interface to the grain interior of αp.This activated a large number of geometrically necessary dislocations (GNDs) near the interface,mostly with components,which contributed greatly to the extraordinary work-hardening abilities of bimodal microstructures in region Ⅰ.With increasing Tint,the αp/βtrans interface length density gradually increased and so was the density of GNDs with components,which explained the continuous increase of uniform elongation with Tint in this region.For bimodal microstructures in region Ⅱ,where the nano-hardness ofβtrans and αp were comparable,neither a clear strain-partitioning tendency nor a strain gradient across the αp/βtrans interface was observed.Consequently,only statistically stored dislocations (SSDs) with component were activated inside αp.The absence of dislocations together with a decreased volume fraction of αp resulted into a dramatic loss of uniform elongation for bimodal microstructures in region Ⅱ.     

Grain size altering yielding mechanisms in ultrafine grained high-Mn austenitic steel:Advanced TEM investigations

The underlying mechanism of discontinuous yielding behavior in an ultrafine-grained(UFG)Fe-31Mn-3Al-3Si(wt.％)austenitic TWIP steel was investigated by the use of advanced TEM technique with taking the plastic deformation mechanisms and their correlation with grains size near the macroscopic yield point into account.Typical yield drop mechanisms such as the dislocation locking by the Cottrell atmo-sphere due to the presence of interstitial impurities cannot explain the origin of this phenomenon in the UFG high-Mn austenitic TWIP steel.Here,we experimentally revealed that the plastic deformation mechanisms in the early stage of deformation,around the macroscopic yield point,show an obvious association with grain size.More specifically,the main mechanism shifts from the conventional slip in grain interior to twinning nucleated from grain boundaries with decreasing the grain size down to less than 1 μm.Our observation indicates that the grain size dependent deformation mechanisms transition is also deeply associated with the discontinuous yielding behavior as it could govern the changes in the grain interior dislocation density of mobile dislocations around the macroscopic yield point.     

Resolved CFD–DEM coupling simulation using Volume Penalisation method

A resolved CFD–DEM coupling model for the simulation of particulate flows is proposed in this work. The Volume Penalisation (VP) method, which is a family of the continuous forcing Immersed Boundary (IB) method, is employed to express the particle–fluid interaction. A smooth mask function is used to avoid sharp transition between the solid (particle) and fluid domains that may cause numerical oscillation with moving particles. Optimal permeability is employed to reduce the model error associated with the VP method. It is determined as a function of only the interface thickness and fluid kinematic viscosity. The proposed model is accurate, easy to implement with any discretisation scheme, and only requires small computational overhead for particle–fluid interaction. Several simulations are performed to test the validity of the proposed model in various systems, i.e. from dilute to relatively dense flows, and the results show good agreement with the exact solution or empirical correlation. It is found that the error can be scaled with the ratio between the gap and interface thickness. The proposed model is also applied to predict the relative viscosity of suspensions and the density segregation in fluidised beds.     

On the performance of Krylov smoothing for fully coupled AMG preconditioners for VMS resistive MHD

This study explores the performance and scaling of a GMRES Krylov method employed as a smoother for an algebraic multigrid preconditioned Newton-Krylov solution approach applied to a fully implicit variational multiscale finite element resistive magnetohydrodynamics formulation. In this context, a Newton iteration is used for the nonlinear system and a parallel MPI-based Krylov method is employed for the linear subsystems. The efficiency of this approach is critically dependent on the scalability and performance of the parallel algebraic multigrid preconditioner for the linear solutions and the performance of the multigrid smoothers play a critical role. Krylov multigrid smoothers are considered in an attempt to reduce the time and memory requirements of existing robust smoothers based on additive Schwarz domain decomposition with incomplete LU factorization solves on each subdomain. Three time-dependent resistive magnetohydrodynamics test cases are considered to evaluate the method. Compared with a domain decomposition incomplete LU smoother, the GMRES smoother can reduce the solve time due to a significant decrease in the preconditioner setup time and often a reduction in outer Krylov solver iterations, and requires less memory, typically 35% less memory.     

EMG-Based Motion Discrimination Using a Novel Recurrent Neural Network

This paper presents a pattern discrimination method for electromyogram (EMG) signals for application in the field of prosthetic control. The method uses a novel recurrent neural network based on the hidden Markov model. This network includes recurrent connections, which enable modeling time series, such as EMG signals. Weight coefficients in the network can be learned using a well-known back-propagation through time algorithm. Pattern discrimination experiments were conducted to demonstrate the feasibility and performance of the proposed method. We were able to successfully discriminate forearm motions using the EMG signals, and achieved considerably high discrimination performance compared with other discrimination methods.     

Reactivity of oxygen-deficient Mn(II)-bearing ferrites (Mn x Fe3-x O4-δ, O⩽x⩽1, δ>0) toward CO2 decomposition to carbon

The reduction of CO₂ to carbon was studied in oxygen-deficient Mn(II)-bearing ferrites (Mn _x Fe_3-x O_4-, Ox1, >0) at 300 °C. They were prepared by reducing Mn(II)-bearing ferrites with H₂ gas at 300°C. The oxygen-deficient Mn(II)-bearing ferrites showed a single phase with a spinel structure having an oxygen deficiency. The decomposition reaction of CO₂ to carbon was accompanied by oxidation of the oxygen-deficient Mn(II)-bearing ferrites. The decomposition rate slowed when the Mn(II) content in the Mn(II)-bearing ferrites increased. A Mössbauer study of the phase changes of the solid samples during the H₂ reduction and CO₂ decomposition indicated the following. Increases in the Mn(II) content lowered the electron conductivity of the Mn(II)-bearing ferrites. Increases in the oxygen deficiency, , contributed to an increase in electron conductivity and suggested that electron conduction due to the electron hopping determines the reductivity of CO₂ to carbon by the donation of an electron at adsorption sites.     

Effects of Ni-Ti-Cu alloy composition and heat treatment temperature after cold working on phase transformation characteristics

With regard to Ni-50Ti-Cu (at%) shape memory alloys, phase transformation characteristics under no stress were studied at the copper content of 6–9 at% using differential scanning calorimetry and X-ray diffraction analysis. In solution-treated materials, B2-orthorhombic transformation occurs at the copper content of 7.6 at% or more. With the increase in copper content, the temperature for B2-orthorhombic transformation gradually increases, whereas the temperature for the orthorhombic-monoclinic phase transformation resulting from decreasing temperature rapidly falls. The phase transformation temperature in 27% cold-worked materials remains virtually constant, despite the copper content, and increases with increasing heat-treatment temperature. The hysteresis in the B2-orthorhombic transformation stabilized via cold working is as low as 18 K.