Dihydroxynaphthalene-based mimicry of fungal melanogenesis for multifunctional coatings

Material-independent adhesive action derived from polycatechol structures has been intensively studied due to its high applicability in surface engineering. Here, we for the first time demonstrate that a dihydroxynaphthalene-based fungal melanin mimetic, which exhibit a catechol-free structure, can act as a coating agent for material-independent surface modifications on the nanoscale. This mimetic was made by using laccase to catalyse the oxidative polymerization of specifically 2,7-dihydroxynaphthalene. Analyses of the product of this reaction, using Fourier transform infrared-attenuated total reflectance and X-ray photoelectron spectroscopy, bactericidal action, charge-dependent sorption behaviour, phenol content, Zeta potential measurements and free radical scavenging activity, yielded results consistent with it containing hydroxyphenyl groups. Moreover, nuclear magnetic resonance analyses of the product revealed that C-O coupling and C-C coupling were the main mechanisms for its synthesis, thus clearly excluding a catechol structure in the polymerization. This product, termed poly(2,7-DHN), was successfully deposited onto a wide variety of solid surfaces, including metals, polymeric materials, ceramics, biosurfaces and mineral complexes. The melanin-like polymerization could be used to co-immobilize other organic molecules, forming functional surfaces. In addition, the hydroxyphenyl group contained in the coated poly(2,7-DHN) induced secondary metal chelation/reduction and adhesion with proteins, suggesting the potential of this poly(2,7-DHN) layer to serve as a platform material for a variety of surface engineering applications. Moreover, the novel physicochemical properties of the poly(2,7-DHN) illuminate its potential applications as bactericidal, radical-scavenging and pollutant-sorbing agents.1143Ysciescopu

Determinants of International Tourism Demand for the Philippines: An Augmented Gravity Model Approach

This study was conducted to investigate the determinants of international tourism demand for the Philippines.This study employed a double-log augmented form of gravity model estimated using the robust random effects model.Results revealed that tourist arrival in the Philippines are generally increasing from 2001 to 2012. Empirical estimation was conducted to determine factors affecting Philippine tourism demand. These factors include income, market size, and distance. Relative prices was also identified which includes cost of living and price of goods and services in the Philippines and other related tourism destination like Malaysia, Indonesia and Thailand. Supporting variables like direct flights, conflict, commonality in language and common colonizer between the Philippines and source of origin of the tourist was also examined. Furthermore, it also includes impact of calamity in the tourist home country and common membership to ASEAN. Empirical results show that tourist inflow is positively and significantly affected by income of the origin country and is reduced by population and distance. Relative low prices of tourism in term of cost of living and prices of goods and services in the Philippines have no effect in attracting inbound tourist. Furthermore, international demand for Philippine tourism is not affected by relative prices of tourism in Malaysia, Indonesia and Thailand as the competing tourist destinations. Conflict and common colonizer between Philippines and country of origin are not significant determinants of international tourism demand. Among the variables, direct flights turned out to be the most significant factor that can contribute to the increase in tourism demand of the Philippines

Determinants of International Tourism Demand for the Philippines: An Augmented Gravity Model Approach

This study was conducted to investigate the determinants of international tourism demand for the Philippines.This study employed a double-log augmented form of gravity model estimated using the robust random effects model.Results revealed that tourist arrival in the Philippines are generally increasing from 2001 to 2012. Empirical estimation was conducted to determine factors affecting Philippine tourism demand. These factors include income, market size, and distance. Relative prices was also identified which includes cost of living and price of goods and services in the Philippines and other related tourism destination like Malaysia, Indonesia and Thailand. Supporting variables like direct flights, conflict, commonality in language and common colonizer between the Philippines and source of origin of the tourist was also examined. Furthermore, it also includes impact of calamity in the tourist home country and common membership to ASEAN. Empirical results show that tourist inflow is positively and significantly affected by income of the origin country and is reduced by population and distance. Relative low prices of tourism in term of cost of living and prices of goods and services in the Philippines have no effect in attracting inbound tourist. Furthermore, international demand for Philippine tourism is not affected by relative prices of tourism in Malaysia, Indonesia and Thailand as the competing tourist destinations. Conflict and common colonizer between Philippines and country of origin are not significant determinants of international tourism demand. Among the variables, direct flights turned out to be the most significant factor that can contribute to the increase in tourism demand of the Philippines

Antimony-doped graphene nanoplatelets

Heteroatom doping into the graphitic frameworks have been intensively studied for the development of metal-free electrocatalysts. However, the choice of heteroatoms is limited to non-metallic elements and heteroatom-doped graphitic materials do not satisfy commercial demands in terms of cost and stability. Here we realize doping semimetal antimony (Sb) at the edges of graphene nanoplatelets (GnPs) via a simple mechanochemical reaction between pristine graphite and solid Sb. The covalent bonding of the metalloid Sb with the graphitic carbon is visualized using atomic-resolution transmission electron microscopy. The Sb-doped GnPs display zero loss of electrocatalytic activity for oxygen reduction reaction even after 100,000 cycles. Density functional theory calculations indicate that the multiple oxidation states (Sb3+ and Sb5+) of Sb are responsible for the unusual electrochemical stability. Sb-doped GnPs may provide new insights and practical methods for designing stable carbon-based electrocatalystsclose0

On the Riemann Tensor in Double Field Theory

Double field theory provides T-duality covariant generalized tensors that are natural extensions of the scalar and Ricci curvatures of Riemannian geometry. We search for a similar extension of the Riemann curvature tensor by developing a geometry based on the generalized metric and the dilaton. We find a duality covariant Riemann tensor whose contractions give the Ricci and scalar curvatures, but that is not fully determined in terms of the physical fields. This suggests that \alpha' corrections to the effective action require \alpha' corrections to T-duality transformations and/or generalized diffeomorphisms. Further evidence to this effect is found by an additional computation that shows that there is no T-duality invariant four-derivative object built from the generalized metric and the dilaton that reduces to the square of the Riemann tensor.Comment: 36 pages, v2: minor changes, ref. added, v3: appendix on frame formalism added, version to appear in JHE

Influence of thermal hydrolysis pretreatment on physicochemical properties and anaerobic biodegradability of waste activated sludge with different solids content

© 2018 Elsevier Ltd The influence of thermal hydrolysis pretreatment (THP) on physicochemical properties (pH, total solids, volatile solids, chemical oxygen demand, total nitrogen, ammonium nitrogen, volatile fatty acids, viscosity, and cell morphology) and anaerobic biodegradability of highly concentrated waste activated sludge (WAS) with TS content ranging from 1 to 7% was evaluated at different temperatures ranging from 100 to 220 °C. The biomethane potential (BMP) of the WAS was systematically analyzed and evaluated. Images of its cellular structure were also analyzed. The results indicated that THP is a useful method for solubilizing volatile solids and enhancing CH 4 production regardless of the TS content of the WAS feed. The ultimate CH 4 production determined from the BMP analysis was 313–348 L CH 4 /kg VS (72.6–74.1% CH 4 ) at the optimum THP temperature of 180 °C. The results showed that THP could improve both the capacity and efficiency of anaerobic digestion, even at a high TS content, and could achieve the dual purpose of sludge reduction and higher energy recovery

A Double Sigma Model for Double Field Theory

We define a sigma model with doubled target space and calculate its background field equations. These coincide with generalised metric equation of motion of double field theory, thus the double field theory is the effective field theory for the sigma model.Comment: 26 pages, v1: 37 pages, v2: references added, v3: updated to match published version - background and detail of calculations substantially condensed, motivation expanded, refs added, results unchange

Koopman-von Neumann Formulation of Classical Yang-Mills Theories: I

In this paper we present the Koopman-von Neumann (KvN) formulation of classical non-Abelian gauge field theories. In particular we shall explore the functional (or classical path integral) counterpart of the KvN method. In the quantum path integral quantization of Yang-Mills theories concepts like gauge-fixing and Faddeev-Popov determinant appear in a quite natural way. We will prove that these same objects are needed also in this classical path integral formulation for Yang-Mills theories. We shall also explore the classical path integral counterpart of the BFV formalism and build all the associated universal and gauge charges. These last are quite different from the analog quantum ones and we shall show the relation between the two. This paper lays the foundation of this formalism which, due to the many auxiliary fields present, is rather heavy. Applications to specific topics outlined in the paper will appear in later publications.Comment: 46 pages, Late

Low-Temperature Spin Diffusion in a Spin-Polarized Fermi Gas

We present a finite temperature calculation of the transverse spin-diffusion coefficient, $D_\bot$, in a dilute degenerate Fermi gas in the presence of a small external magnetic field, $H$. While the longitudinal diffusion coefficient displays the conventional low-temperature Fermi-liquid behavior, $D_\parallel \propto T^{-2}$, the corresponding results for $D_\bot$ show three separate regimes: (a) $D_\bot \sim H^{-2}$ for $T \ll H$; (b) $D_\bot \sim T^{-2}$, $D_\bot /D_\parallel \neq 1$ for $T \gg H$ and large spin-rotation parameter $\xi \gg 1$, and (c) $D_\bot = D_\parallel \propto T^{-2}$ for $T \gg H$ and $\xi \ll 1$. Our results are qualitatively consistent with the available experimental data in weakly spin-polarized $^3{\rm He}$ and $^3{\rm He} - ^4{\rm He}$ mixtures.Comment: 13 pages, REVTEX, 3 figures available upon request, RU-94-4