Cosmological HII Bubble Growth During Reionization

We present general properties of ionized hydrogen (HII) bubbles and their growth based on a state-of-the-art large-scale (100 Mpc/h) cosmological radiative transfer simulation. The simulation resolves all halos with atomic cooling at the relevant redshifts and simultaneously performs radiative transfer and dynamical evolution of structure formation. Our major conclusions include: (1) for significant HII bubbles, the number distribution is peaked at a volume of $\sim 0.6 {\rm Mpc^{3}/h^{3}}$ at all redshifts. But, at $z\le 10$, one large, connected network of bubbles dominates the entire HII volume. (2) HII bubbles are highly non-spherical. (3) The HII regions are highly biased with respect to the underlying matter distribution with the bias decreasing with time. (4) The non-gaussianity of the HII region is small when the universe becomes 50% ionized. The non-gaussianity reaches its maximal near the end of the reionization epoch $z\sim 6$. But at all redshifts of interest there is a significant non-gaussianity in the HII field. (5) Population III galaxies may play a significant role in the reionization process. Small bubbles are initially largely produced by Pop III stars. At $z\ge 10$ even the largest HII bubbles have a balanced ionizing photon contribution from Pop II and Pop III stars, while at $z\le 8$ Pop II stars start to dominate the overall ionizing photon production for large bubbles, although Pop III stars continue to make a non-negligible contribution. (6) The relationship between halo number density and bubble size is complicated but a strong correlation is found between halo number density and bubble size for large bubbles.Comment: 10 pages, 14 figures; accepted version; higher resolution figures and supplementary material can be found at http://www.astro.princeton.edu/~msshin/reionization/web.ht

Numerical solution of cracked thin plates subjected to bending, twisting and shear loads

A semi-analytical method namely fractal finite element method is presented for the determination of mode I and mode II moment intensity factors for thin plate with crack using Kirchhoff's theory. Using the concept of fractal geometry, infinite many of finite elements is generated virtually around the crack border. Based on the analytical global displacement function, numerous degrees of freedom (DOF) are transformed to a small set of generalised coordinates in an expeditious way. The stress intensity factors can be obtained directly from the generalized coordinates. No post-processing and special finite elements are required to develop for extracting the stress intensity factors. Examples of cracked plate subjected to bending, twisting and shear loads are given to illustrate the accuracy and efficiency of the present method. The influence of finite boundaries on the calculation of the moment intensity factors is studied in details. Very accuracy results when compare with the theoretical and numerical counterparts are found.postprin

A brief note on elastic T-stress for centred crack in anisotropic plate

The stress intensity factors (SIFs) and the T-stress for a planar crack with anisotropic materials are evaluated by the fractal finite element method (FFEM). The FFEM combines an exterior finite element model and a localized inner model near the crack tip. The mesh geometry of the latter is self-similar in radial layers around the tip. A higher order displacement series derived from Laurent series and Goursat functions is used to condense the large numbers of nodal displacements at the inner model near the crack tip into a small set of unknown coefficients. In this study, the variations of the SIFs and the T-stress with material properties and orientations of a crack are presented. The separation of the analytical displacement series into four fundamental cases has shown to be necessary in order to cover all the material variations and the orientations of a crack in the plate with general rectilinear anisotropic materials. © Springer 2005.postprin

Numerical solutions of two-dimensional anisotropic crack problems

A complete set of series form solutions of stress and displacement functions, including all higher order terms, around the crack tip for anisotropic crack problems have been newly derived by eigenfunction expansion approach. The analytical solutions of displacement functions were classified into four cases with respect to different types of complex parameters and different corresponding physical meanings. By employing these displacement functions as global interpolation functions, fractal two-level finite element method (F2LFEM) was applied to evaluate the stress intensity factors (SIFs) for various kinds of anisotropic crack problems. In the method of F2LFEM, the infinite number of nodal displacements was transformed to a small set of generalized coordinates by fractal transformation technique. New element matrices need not be generated and the singular numerical integration was avoided completely. Numerical examples of the four cases were studied and high accurate results of SIFs were obtained. © 2003 Elsevier Ltd. All rights reserved.postprin

Numerical solution of cracked thin plates subjected to bending, twisting and shear loads

A semi-analytical method namely fractal finite element method is presented for the determination of mode I and mode II moment intensity factors for thin plate with crack using Kirchhoff's theory. Using the concept of fractal geometry, infinite many of finite elements is generated virtually around the crack border. Based on the analytical global displacement function, numerous degrees of freedom (DOF) are transformed to a small set of generalised coordinates in an expeditious way. The stress intensity factors can be obtained directly from the generalized coordinates. No post-processing and special finite elements are required to develop for extracting the stress intensity factors. Examples of cracked plate subjected to bending, twisting and shear loads are given to illustrate the accuracy and efficiency of the present method. The influence of finite boundaries on the calculation of the moment intensity factors is studied in details. Very accuracy results when compare with the theoretical and numerical counterparts are found.postprin

An Efficient Novel Acetate Anion Receptor based on Isatin

An anion recognition receptor, a kind of thiourea derivative, was designed and synthesized by combining indoline-2,3-dione and 1,3-diaminothiourea. The anion recognition can be easily monitored by anion complexation induced changes in UV-vis absorption spectra. In particular, the binding ratio between the receptor and fluoride is 1:2 but in the case of dihydrogenphosphate and acetate are 1:1. Moreover, the affinity constants revealed that the receptor can recognize acetate well. Finally, H-1 NMR experiments were carried out to explore the nature of interaction between this new receptor and acetate

An acetate sensor based on azo in aqueous media

A colorimetric sensor 1,N,N'-di-(2-hydroxy-5-(phenldiazenyl)benzaldehyde)-1,3-diiminothiourea for acetate in DMSO and 9/1 DMSO/H(2)O (v/v) mixtures was designed and synthesized. The binding ability evaluated by UV-vis experiment reveals that sensor 1 can selectively recognize acetate. In addition, the color changes induced by anions can provide a way of detection by 'naked-eye'. The further insights to the nature of interactions between the sensor 1 and AcO(-) were investigated by (1)H NMR titration experiments in 9/1 DMSO-d(6)/H(2)O (v/v). (c) 2010 Elsevier B.V. All rights reserved

Ultraviolet Lasing Characteristics of ZnS Microbelt Lasers

published_or_final_versio

Can vouchers make a difference to the use of private primary care services by older people? Experience from the healthcare reform programme in Hong Kong

<p>Abstract</p> <p>Background</p> <p>As part of its ongoing healthcare reform, the Hong Kong Government introduced a voucher scheme, intended for encouraging older patients to use primary healthcare services in the private sector, thereby, reducing burden on the overwhelmed public sector. The voucher program is also considered one of the strategies to further develop the public private partnership in healthcare, a policy direction of high political priority as indicated in the Chief Executive Policy Address in 2008-09. This study assessed whether the voucher scheme, as implemented so far, has reached its intended goals, and how it might be further improved in the context of public-private partnership.</p> <p>Methods</p> <p>This was a cross-sectional study using structured questionnaires by face-to-face interviews with older people aged 70 or above in Hong Kong, the target group of the demand-side voucher program.</p> <p>Results</p> <p>71.2% of 1,026 older people were aware of the new voucher scheme but only 35.0% had ever used it. The majority of the older people used the vouchers for acute curative services in the private sector (82.4%) and spent less on preventive services. Despite the provision of vouchers valued US$30 per year as an incentive to encourage the use of private primary care services, after 12-months of implementation, 66.2% of all respondents agreed with the statement that "the voucher scheme does not change their health seeking behaviours on seeing public or private healthcare professionals". The most common reasons for no change in their behaviours included "I am used to seeing doctors in the public system" and "The amount of the subsidy is too low". Those who usually used a mix of public and private doctors and those with better self-reported health condition compared to last year were more likely to perceive a change in their own health seeking behaviours.</p> <p>Conclusions</p> <p>Our study showed that despite a reasonably high awareness of the voucher scheme, its usage was low. The voucher alone was not enough to realize the government's policy of greater use of the private primary care services. Greater publicity and more variety of media promotion would increase awareness but the effectiveness of vouchers in changing older people's behaviour needs to be revisited. Designating vouchers for use of preventive services with evidence-based practice could be considered. In addition to the demand-side subsidies, improving transparency and comparability of private services against the public sector might be necessary.</p

Angle-Resolved Photoemission Spectroscopy of Tetragonal CuO: Evidence for Intralayer Coupling Between Cupratelike Sublattices

We investigate by angle-resolved photoemission the electronic structure of in situ grown tetragonal CuO, a synthetic quasi-two-dimensional edge-sharing cuprate. We show that, in spite of the very different nature of the copper oxide layers, with twice as many Cu in the CuO layers of tetragonal CuO as compared to the CuO2 layers of the high-T-c cuprates, the low-energy electronic excitations are surprisingly similar, with a Zhang-Rice singlet dispersing on weakly coupled cupratelike sublattices. This system should thus be considered as a member of the high-T-c cuprate family, with, however, interesting differences due to the intralayer coupling between the cupratelike sublattices.open1199sciescopu