Half Metallicity in Hybrid BCN Nanoribbons

We report a first-principles electronic-structure calculation on C and BN hybrid zigzag nanoribbons. We find that half-metallicity can arise in the hybrid nanoribbons even though stand-alone C or BN nanoribbon possesses a finite band gap. This unexpected half-metallicity in the hybrid nanos-tructures stems from a competition between the charge and spin polarizations, as well as from the pi orbital hybridization between C and BN. Our results point out a possibility of making spintronic devices solely based on nanoribbons and a new way of designing metal-free half metals

INVESTIGATION OF SELF-HEALING BY USING ETHYL CELLULOSE ENCAPSULATED BACTERIUM IN CEMENTITIOUS MATERIALS

Abstract: A new approach to microcapsule based microbial self-healing system is presented that aims to heal the crack in cementitious materials. In this work, ethyl cellulose (EC) was designed to fabricate microcapsule as a protection strategy to encapsulate an alkaliphilic spore-forming bacterium. The technical feasibility of encapsulated spores and the influence factors were studied by calcium precipitation activity (CPA) of the bacterium. The CPA of broken/unbroken microcapsules was evaluated. The micro-morphology of the precipitation produced by the bacterium was investigated through Environmental Scanning Electron Microscopy (ESEM), X-ray Diffraction (XRD) and X-ray energy dispersive spectroscopy (EDS). X-ray Computed Tomography (XCT) was applied to trace the crack development and self-healing behavior of encapsulated mineralization bacterium in cement paste specimens in three dimensions. The experimental results showed that compared with unbroken microcapsules, higher CPA was achieved by breaking the microcapsule to release the bacterium, suggesting good protection for the encapsulated spores. Subsequent production of calcium carbonate confirmed by ESEM and EDS indicated activation of encapsulated mineralization bacterium. The XCT results showed that formation of crack successfully triggered the breakage of embedded microcapsules. Compared with the specimens without embedded bacterium, the healed crack area of specimens embedded with bacterial microcapsules was monitored, suggesting effective self healing of concrete crack can be achieved by introducing encapsulated mineralization microorganisms into concrete structures

Electron transport through dipyrimidinyl-diphenyl diblock molecular wire: protonation effect

Recently, rectifying direction inversion has been observed in dipyrimidinyl-diphenyl (PMPH) diblock molecular wire [J. Am. Chem. Soc. (2005) 127, 10456], and a protonation mechanism was suggested to explain this interesting phenomena. In this paper, we study the protonation effect on transport properties of PMPH molecule by first principles calculations. No significant rectification is found for the pristine diblock molecular wire. Protonation leads to conductance enhancement and rectification. However, for all considered junctions with rectifying effect, the preferential current directions are samely from dipyrimidinyl side to diphenyl side. Effect of molecule-electrode anchoring geometry is studied, and it is not responsible for the discrepancy between experiment and theory.Comment: 17 pages, 8 figure

An Intronic Variant in the GRP78, a Stress-Associated Gene, Improves Prediction for Liver Cirrhosis in Persistent HBV Carriers

Background: Our previous study indicated that a common variant (rs430397 G>A) in the intron 5 of glucose-regulated protein 78 (GRP78) gene was associated with risk and prognosis of primary hepatocellular carcinoma (HCC), including HBV- and cirrhosis-related HCC. rs430397 polymorphism may be a contributing factor or biomarker of HBV infection or HBV-related cirrhosis. Methodology/Principal Findings: 539 non-HBV-infected individuals, 205 self-limited infection and 496 persistent HBV infection were recruited between January 2001 and April 2005 from the hospitals in Southern China. Genomic DNA was genotyped for rs430397. The associations between the variation and susceptibility to liver cirrhosis (LC) in persistent HBV infection were examined. We observed that individuals carrying allele rs430397A were more likely to become HBV-related LC. When persistently infected patients were divided into four subgroups, patients with phase IV had an increased allele A and genotype AG compared with phase I and/or phase III. Decreased serum albumin and prolonged plasma prothrombin time (PT) were showed in LC patients carrying genotype AA. Furthermore, rs430397 genotype had an increased susceptibility to LC with dose-dependent manners (P-trend = 0.005), and the genotype did constitute a risk factor for the development of advanced LC (Child-Pugh classification C and B, P-trend = 0.021). Conclusions/Significance: rs430397 polymorphism may be a contributing factor to LC in persistent HBV carriers. © 2011 Zhu et al.published_or_final_versio

Darboux integrability and Algebraic limit cycles for a class of polynomial differential Systems

Agraïments: The first and third authors are partially supported by NNSF of China grant No. 10671123 and by a CICYT grant No. 2005SGR 00550. The third author is also partially supported by NCET of China grant No. 050391.This paper deals with the existence of Darboux first integrals for the planar polynomial differential systems ˙x = λx − y + Pn+1(x, y) + xF2n(x, y), ˙y = x + λy + Qn+1(x, y)+yF2n(x, y), where Pi(x, y), Qi(x, y) and Fi(x, y) are homogeneous polynomials of degree i. Inside this class we identify some new Darboux integrable systems having either a focus or a center at the origin. For such Darboux integrable systems having degrees 5 and 9 we give the explicit expressions of their algebraic limit cycles. For the systems having degrees 3, 5, 7 and 9 we present necessary and sufficient conditions for being Darboux integrable

Influence of a dielectric layer on photon emission induced by a scanning tunneling microscope

We investigate theoretically the influence of a dielectric layer on light emission induced by a scanning tunneling microscope through a combined approach of classical electrodynamics and first-principles calculations. The modification of the junction geometry upon the insertion of a dielectric layer is treated first by using the density functional theory to calculate the effective potential along the surface normal and then by solving a one-dimensional Schrödinger equation to obtain the exact distance between the tip and the substrate for a given current and bias voltage. The modified external field with the inclusion of a dielectric layer is evaluated by using the Fresnel formula. The local-field enhancement factor and radiated power are calculated by the boundary element method for two typical systems, W-tip/C60/Au(111) and W-tip/Al2O3/NiAl(110). The calculated results indicate that the insertion of a dielectric layer tends to reduce the light emission intensity considerably but hardly changes the spectral profile with no substantial peak shifts with respect to the layer-free situation, in agreement with experimental observations. The suppression of the radiated power is mainly due to the increase in the tip-metal separation and the resultant reduction in the electromagnetic coupling between the tip and metal substrate.This work was partly supported by the National Basic Research Program of China (Grant No. 2006CB922003), CAS (Grant No. KJCX2.YW.H06), and NSFC (Grant No. 10574117).Peer reviewe