Dissipation function of the first-order phase transformation in solids via internal-friction measurements

Reconstruction and displacement of crystal structure and motion of the phase interface induces dissipation of energy, and latent heat appears during a first-order phase transition (FOPT) in solids. In this series of investigations, we first express the energy dissipation as a function of four physical parameters. Since there are more unknowns than the number of equations, we introduce four more equations describing the dynamics of the system on which internal friction (IF, the dissipation of vibration energy) measurements are conducted. Via IF measurements during FOPT, we can then calculate the relevant four parameters and hence the dissipation function. We have completed the first step in establishing a phenomenological theory to describe FOPT in solids.published_or_final_versio

Influence of mixed culture system on the growth performance of Aspergillus oryzae and Saccharomyces cerevisiae

This study describes a novel strategy to improve the α-galactosidase and invertase production of Saccharomyces cerevisiae by co-cultivating it with Aspergillus oryzae. In the mixed culture, the growth of the both strains was repressed, and the protein synthesis for the yeast cell wall was promoted significantly. As a result, α-galactosidase and invertase activities of the mixed culture reached 85.16 and 561.60 Uml-1, over 9 and 15 fold greater than the values obtained in the cultures of single strain, respectively. During the simultaneous saccharification and fermentation procedure, ethanol with the concentration of 15.2% (v/v) was obtained from soybean sirup in 60 h at 30°C, and the conversion efficiency of total sugar to ethanol was 96.3% of the theoretical ethanol yield.Keywords: Co-cultivation, Aspergillus oryzae, Saccharomyces cerevisiae, α-galactosidase, invertaseAfrican Journal of Biotechnology Vol. 12(21), pp. 3272-327

An Experimental Study on Kinetics-Controlled Ca-Carbonate Aqueous Reduction into CH4 (1 and 2 GPa, 550 degrees C): Implications for C Mobility in Subduction Zones

Abiotic methane (CH4) generation under subduction zone conditions has been experimentally investigated through aqueous reduction of pure C-bearing materials (e.g. carbonate minerals and organic matter). However, quantitative assessments of CH(4 )production in these experiments, as well as the potential effects of other components such as SiO2 on the reduction processes, have not yet been well established. Here, we performed experiments to quantitatively evaluate the time-resolved Ca-carbonate aqueous reduction into CH4 at P = 1 and 2 GPa and T = 550 degrees C in the CaO + COH, CaO + SiO2 COH, and CaO + SiO2 + MgO + COH systems, employing calcite + water +/- quartz +/- serpentine (synthetic chlorine (Cl)-bearing chrysotile and natural Fe-Al-bearing antigorite) as starting materials. Redox conditions of the experiments were buffered by iron-wilstite (IW) using a double capsule setting, corresponding to oxygen fugacity (fO(2)) values (expressed as log units relative to the fayalite-magnetite-quartz buffer, Delta FMQ) in the inner capsule of Delta FMQ approximate to -5.5 at 1 GPa and Delta FMQ approximate to -6.0 at 2 GPa. The solid products are mainly composed of portlandite +/- larnite +/- wollastonite +/- brucite, while Ca-carbonate and/or silicate reactants commonly occur as relicts. Quadrupole mass spectrometric analysis shows that CH4 and H2O are the major COH molecular species in the fluid products, with molar ratios between CH4 and starting calcite representing the reaction progress ranging from similar to 0.13 to similar to 1.00. Comparisons of experimental run products with thermodynamically predicted phase assemblages, together with time-series experiments, indicate that the reduction processes are primarily controlled by reaction kinetics. At 1 GPa and 550 degrees C, rate constants of 4.0 x 10(-6) s(-1), 7.4 x 10(-6) s(-1) , and 2.6 x 10(-6 )s(-1) were retrieved for reactions starting with calcite + quartz + water, calcite + synthetic Cl-bearing chrysotile + water, and calcite + natural Fe-Al-bearing antigorite + water, respectively, significantly higher than the constant of 0.8 x 10(-6) s(-1 )for the silicate-absent reaction. Besides, an increase in pressures can also enhance the reduction efficiency of Ca-carbonates until reaching equilibrium with the fluids. Our data provide experimental evidence for kinetics-controlled Ca-carbonate aqueous reduction into CH4 in subduction zones, indicating that silicate involvement and/or pressure increase can accelerate the reaction rates through short-lived fluid-rock interactions, which may have important implications for deep C mobility

Entanglement generation outside a Schwarzschild black hole and the Hawking effect

We examine the Hawking effect by studying the asymptotic entanglement of two mutually independent two-level atoms placed at a fixed radial distance outside a Schwarzschild black hole in the framework of open quantum systems. We treat the two-atom system as an open quantum system in a bath of fluctuating quantized massless scalar fields in vacuum and calculate the concurrence, a measurement of entanglement, of the equilibrium state of the system at large times, for the Unruh, Hartle-Hawking and Boulware vacua respectively. We find, for all three vacuum cases, that the atoms turn out to be entangled even if they are initially in a separable state as long as the system is not placed right at the even horizon. Remarkably, only in the Unruh vacuum, will the asymptotic entanglement be affected by the backscattering of the thermal radiation off the space-time curvature. The effect of the back scatterings on the asymptotic entanglement cancels in the Hartle-Hawking vacuum case.Comment: 15 pages, no figures, Revte

STM Spectroscopy of ultra-flat graphene on hexagonal boron nitride

Graphene has demonstrated great promise for future electronics technology as well as fundamental physics applications because of its linear energy-momentum dispersion relations which cross at the Dirac point. However, accessing the physics of the low density region at the Dirac point has been difficult because of the presence of disorder which leaves the graphene with local microscopic electron and hole puddles, resulting in a finite density of carriers even at the charge neutrality point. Efforts have been made to reduce the disorder by suspending graphene, leading to fabrication challenges and delicate devices which make local spectroscopic measurements difficult. Recently, it has been shown that placing graphene on hexagonal boron nitride (hBN) yields improved device performance. In this letter, we use scanning tunneling microscopy to show that graphene conforms to hBN, as evidenced by the presence of Moire patterns in the topographic images. However, contrary to recent predictions, this conformation does not lead to a sizable band gap due to the misalignment of the lattices. Moreover, local spectroscopy measurements demonstrate that the electron-hole charge fluctuations are reduced by two orders of magnitude as compared to those on silicon oxide. This leads to charge fluctuations which are as small as in suspended graphene, opening up Dirac point physics to more diverse experiments than are possible on freestanding devices.Comment: Nature Materials advance online publication 13/02/201

Improving corporate governance in state-owned corporations in China: which way forward?

This article discusses corporate governance in China. It outlines the basic agency problem in Chinese listed companies and questions the effectiveness of the current mechanisms employed to improve their standards of governance. Importantly, it considers alternative means through which corporate practice in China can be brought into line with international expectations and stresses the urgency with which this task must be tackled. It concludes that regulators in China must construct a corporate governance model which is compatible with its domestic setting and not rush to adopt governance initiatives modelled on those in cultures which are fundamentally different in the hope of also reproducing their success

Electronic Structure Calculations with LDA+DMFT

The LDA+DMFT method is a very powerful tool for gaining insight into the physics of strongly correlated materials. It combines traditional ab-initio density-functional techniques with the dynamical mean-field theory. The core aspects of the method are (i) building material-specific Hubbard-like many-body models and (ii) solving them in the dynamical mean-field approximation. Step (i) requires the construction of a localized one-electron basis, typically a set of Wannier functions. It also involves a number of approximations, such as the choice of the degrees of freedom for which many-body effects are explicitly taken into account, the scheme to account for screening effects, or the form of the double-counting correction. Step (ii) requires the dynamical mean-field solution of multi-orbital generalized Hubbard models. Here central is the quantum-impurity solver, which is also the computationally most demanding part of the full LDA+DMFT approach. In this chapter I will introduce the core aspects of the LDA+DMFT method and present a prototypical application.Comment: 21 pages, 7 figures. Chapter of "Many-Electron Approaches in Physics, Chemistry and Mathematics: A Multidisciplinary View", eds. V. Bach and L. Delle Site, Springer 201

Thermo – mechanical properties of SPS produced self-healing thermal barrier coatings containing pure and alloyed MoSi2 particles

Yttria – partially stabilised zirconia (YPSZ) MoSi2 composites have been designed to prolong the lifetime of the matrix by self – healing cracks during thermal cycling. The healing reaction at high temperatures is based on the decomposition of MoSi2, leading to a volumetrically expanding reaction product, which seals the crack. In this work, coefficient of thermal expansion (CTE) and the fracture toughness of composites containing MoSi2 particles, produced by spark plasma sintering (SPS) have been compared to conventional YPSZ. The CTE mismatch between YPSZ and MoSi2 was found to be small, implying that thermally induced mismatch stresses will be small and the composites have a similar CTE to conventional YPSZ. Fracture toughness was found not to be affected by the particles and showed similar values to unreinforced YPSZ. Cracks introduced by indentation have been shown neither to prefer, or avoid, the particles suggesting that such a composite system is capable of autonomously activating the self – healing reaction