Psychosocial impact of visual impairment in working age adults

This is an open access article - Copyright @ 2010 BMJ Publishing GroupAim: To review the evidence for the presence of lower levels of psychosocial well-being in working-age adults with visual impairment and for interventions to improve such levels of psychosocial well-being. Methods: Systematic review of quantitative studies published in English from 2001 to July 2008 that measured depression/mental health, anxiety, quality of life, social functioning or social support. Results: Included were 29 studies that measured one or more outcomes (N=52). Working-age adults with visual impairment were significantly more likely to report lower levels of mental health (mean difference=14.51/100), social functioning (MD=11.55/100) and quality of life. Studies regarding the prevalence of depressive symptoms produced inconsistent results but had methodological limitations. Conclusions: Future research is required into the prevalence of loneliness, anxiety and depression in adults with visual impairment, and to evaluate the effectiveness of interventions for improving psychosocial well-being such as counselling, peer support and employment programmes.Funding was obtained from the Thomas Pocklington Trust, 5 Castle Row, Horticultural Place, Chiswick, London W4 4JQ

Counselling for people with sight loss in the UK: The need for provision and the need for evidence

This is an open access article - Copyright @ 2010 BMJ Publishing Group.The Department of Ophthalmology at UCSF is supported by a core grant from the National Eye Institute, EY02162, That Man May See and the South Asia Research Fund. In addition, this work was supported in part by a grant from the Doris Duke Charitable Foundation to UCSF to fund Clinical Research Fellow Allison Loh

Export Prices of U.S. Firms

Using confidential firm-level data from the United States in 2002, we show that exporting firms charge prices for narrowly defined goods that differ substantially with the characteristics of firms and export markets. We control for selection into export markets using a three-stage estimator. We have three main results. First, we find that highly productive and skill-intensive firms charge higher prices, while capital-intensive firms charge lower prices. Second, U.S. firms charge slightly higher prices to larger and richer markets, and substantially higher prices to markets other than Canada and Mexico. Third, the correlation between distance and product-level export prices is largely due to a composition effect.

Charging of Aggregate Grains in Astrophysical Environments

The charging of dust grains in astrophysical environments has been investigated with the assumption these grains are homogeneous spheres. However, there is evidence which suggests many grains in astrophysical environments are irregularly-shaped aggregates. Recent studies have shown that aggregates acquire higher charge-to-mass ratios due to their complex structures, which in turn may alter their subsequent dynamics and evolution. In this paper, the charging of aggregates is examined including secondary electron emission and photoemission in addition to primary plasma currents. The results show that the equilibrium charge on aggregates can differ markedly from spherical grains with the same mass, but that the charge can be estimated for a given environment based on structural characteristics of the grain. The "small particle effect" due to secondary electron emission is also important for determining the charge of micron-sized aggregates consisting of nano-sized particles.Comment: 9 figures. arXiv admin note: substantial text overlap with arXiv:1107.028

Success factors for new business start-up in Hong Kong: a study of the external networks of small business start-up

Most small new firms face problems in surviving the gestation process and achieving a viable performance thereafter because of the very fact of their smallness and newness. Due to a lack of internal resources, entrepreneurs of small new firms find it necessary to seek resources from outside the firm through their external social network. The theory of social capital that prescribes valuable resources are embedded in social relations is, thus, particularly relevant to the small business start-up situation. The embedded resources within an external network are hypothesized to have a positive impact on the business performance of these new firms. The main objective of the present study is to empirically investigate the impact of external networks, and in particular the initial social network of entrepreneurs, to the success of small firm start-up in Hong Kong. The second objective is to determine whether there is any interaction effect of the entrepreneur’s networking capability with the external network structure on the start-up success of small Hong Kong firms.To carry out the research, this study offers a conceptual model linking initial network start-up success to initial network structure of start-up, and including an interaction effect from the entrepreneur’s networking capability. The study operationalizes social capital in four types of network constructs: network size, trustworthiness, network support and network diversity. A series of hypotheses relating to these four dimensions asserting external network determinants of the start-up success of small firms is posited. Other hypotheses which assert the interaction effect between an entrepreneur’s networking capability and the initial network structure on the success of small firm start-up, are also posited. A field survey, administered to 1,000 small Hong Kong firms of various industries, is used to gather the data. The questionnaire survey was developed in two languages – Chinese and English – to ensure a good level of understanding in the bilingual business environment of Hong Kong. Of the 1,000 questionnaires dispatched, a final sample of 89 small firms was used to empirically test the hypotheses using multiple regression analysis and multiple hierarchical regression analysis. Control variables such as entrepreneurs’ experiences and education prior to the firm start-up are included.Empirical results indicate that the verification of social capital theory’s prescription for start-up success cannot be supported unequivocally. The results suggest that some initial network conditions such as initial size of strong tie network, network support and network diversity are positively associated with some measures of start-up success, but trustworthiness of network ties and the size of weak tie network do not figure among them. No evidence is found to support that entrepreneurs’ networking capability can positively enhance the effect of the initial network structure on start-up success. Overall, the study raises some questions on the positive linear relationship of certain operationalized constructs such as network size and trustworthiness of social capital with start-up success. Following the findings of this research, future studies may choose to further investigate social capital theory on small start-up success by refining the operationalization of social capital, and verify other interaction effects of entrepreneurs’ networking capabilities

Modeling Agglomeration of Dust Particles in Plasma

The charge on an aggregate immersed in a plasma environment distributes itself over the aggregate's surface; this can be approximated theoretically by assuming a multipole distribution. The dipole-dipole (or higher order) charge interactions between fractal aggregates lead to rotations of the grains as they interact. Other properties of the dust grains also influence the agglomeration process, such as the monomer shape (spherical or ellipsoidal) or the presence of magnetic material. Finally, the plasma and grain properties also determine the morphology of the resultant aggregates. Porous and fluffy aggregates are more strongly coupled to the gas, leading to reduced collisional velocities, and greater collisional cross sections. These factors in turn can determine the growth rate of the aggregates and evolution of the dust cloud. This paper gives an overview of the numerical and experimental methods used to study dust agglomeration at CASPER and highlights some recent results

Feedback first: the surprisingly weak effects of magnetic fields, viscosity, conduction, and metal diffusion on galaxy formation

Using high-resolution simulations with explicit treatment of stellar feedback physics based on the FIRE (Feedback in Realistic Environments) project, we study how galaxy formation and the interstellar medium (ISM) are affected by magnetic fields, anisotropic Spitzer-Braginskii conduction and viscosity, and sub-grid metal diffusion from unresolved turbulence. We consider controlled simulations of isolated (non-cosmological) galaxies but also a limited set of cosmological "zoom-in" simulations. Although simulations have shown significant effects from these physics with weak or absent stellar feedback, the effects are much weaker than those of stellar feedback when the latter is modeled explicitly. The additional physics have no systematic effect on galactic star formation rates (SFRs) . In contrast, removing stellar feedback leads to SFRs being over-predicted by factors of $\sim 10 -100$. Without feedback, neither galactic winds nor volume filling hot-phase gas exist, and discs tend to runaway collapse to ultra-thin scale-heights with unphysically dense clumps congregating at the galactic center. With stellar feedback, a multi-phase, turbulent medium with galactic fountains and winds is established. At currently achievable resolutions and for the investigated halo mass range $10^{10}-10^{13} M_{\odot}$, the additional physics investigated here (MHD, conduction, viscosity, metal diffusion) have only weak ($\sim10\%$-level) effects on regulating SFR and altering the balance of phases, outflows, or the energy in ISM turbulence, consistent with simple equipartition arguments. We conclude that galactic star formation and the ISM are primarily governed by a combination of turbulence, gravitational instabilities, and feedback. We add the caveat that AGN feedback is not included in the present work