The persistence of phase-separation in LiFePO4 with two-dimensional Li+ transport : the Cahn-Hilliard-reaction equation and the role of defects

We examine the solution of the two-dimensional Cahn-Hilliard-reaction (CHR) equation in the xy plane as a model of Li+ intercalation into LiFePO4 material. We validate our numerical solution against the solution of the depth-averaged equation, which has been used to model intercalation in the limit of highly orthotropic diffusivity and gradient penalty tensors. We then examine the phase-change behaviour in the full CHR system as these parameters become more isotropic, and find that as the Li+ diffusivity is increased in the x direction, phase separation persists at high currents, even in small crystals with averaged coherency strain included. The resulting voltage curves decrease monotonically, which has previously been considered a hallmark of crystals that fill homogeneously.

Urban, suburban, and rural variations in separation/divorce rape/sexual assault : results from the National Crime Victimization Survey

To date, no large study has looked at whether separation/divorce sexual assault varies across urban, suburban, and rural areas. The authors use 1992-2009 NCVS (National Crime Victimization Survey) data to estimate the percentage of separation/divorce sexual assault against women in urban, suburban, and rural communities. In addition, the authors identify and compare the relative risk of sexual assault victimization for women across areas. Findings indicate that a higher percentage of rural divorced/separated women were victims of rape/sexual assault than were urban divorced/separated women. In addition, rural separated women are victims of intimate rape/sexual assault at significantly higher rates than their suburban and urban counterparts.

Peer-led diabetes self-management programme for community-dwelling older people in China : study protocol for a quasi-experimental design

Aim. A protocol for a new peer-led self-management programme for communitydwelling older people with diabetes in Shanghai, China. Background. The increasing prevalence of type 2 diabetes poses major public health challenges. Appropriate education programmes could help people with diabetes to achieve self-management and better health outcomes. Providing education programmes to the fast growing number of people with diabetes present a real challenge to Chinese healthcare system, which is strained for personnel and funding shortages. Empirical literature and expert opinions suggest that peer education programmes are promising. Design. Quasi-experimental. Methods. This study is a non-equivalent control group design (protocol approved in January, 2008). A total of 190 people, with 95 participants in each group, will be recruited from two different, but similar, communities. The programme, based on Social Cognitive Theory, will consist of basic diabetes instruction and social support and self-efficacy enhancing group activities. Basic diabetes instruction sessions will be delivered by health professionals, whereas social support and self-efficacy enhancing group activities will be led by peer leaders. Outcome variables include: self-efficacy, social support, self-management behaviours, depressive status, quality of life and healthcare utilization, which will be measured at baseline, 4 and 12 weeks. Discussion. This theory-based programme tailored to Chinese patients has potential for improving diabetes self-management and subsequent health outcomes. In addition, the delivery mode, through involvement of peer leaders and existing community networks,is especially promising considering healthcare resource shortage in China.

To separate or not to separate? Parental decision-making regarding the separation of twins in the early years of schooling

In recent times concerns about possible adverse effects of early separation and advocacy for individual rights have resulted in a movement away from organizational level policies about the separation of twin children as they enter school. Instead, individualized approaches that focus on the twin children’s characteristics and family perspectives have been proposed. This study, conducted in Australia where all but a few families had choice about the class placement of their twin children, questioned parents (N = 156) about their placement decisions. Results indicated that most parents opted for placement together in the early years of schooling. The choice to separate twins at school entry was associated with parent identification of risk in the twin relationship, while being kept together was associated with parent identification of absence of such risk. The findings are discussed in light of the current evidence against separation, and suggest that parent choices regarding the separation of twin children in the early years are informative to educational policy and practice.

Influence of electrolyte cations on electron transport and electron transfer in dye-sensitized solar cells

The influence of different electrolyte cations ((Li+, Na+, Mg2+, tetrabutyl ammonium (TBA+)) on the TiO2 conduction band energy (Ec) the effective electron lifetime (τn), and the effective electron diffusion coefficient (Dn) in dye-sensitized solar cells (DSCs) was studied quantitatively. The separation between Ec and the redox Fermi level, EF,redox, was found to decrease as the charge/radius ratio of the cations increased. Ec in the Mg2+ electrolyte was found to be 170 meV lower than that in the Na+ electrolyte and 400 meV lower than that in the TBA+ electrolyte. Comparison of Dn and τn in the different electrolytes was carried out by using the trapped electron concentration as a measure of the energy difference between Ec and the quasi-Fermi level, nEF, under different illumination levels. Plots of Dn as a function of the trapped electron density, nt, were found to be relatively insensitive to the electrolyte cation, indicating that the density and energetic distribution of electron traps in TiO2 are similar in all of the electrolytes studied. By contrast, plots of τn versus nt for the different cations showed that the rate of electron back reaction is more than an order of magnitude faster in the TBA+ electrolyte compared with the Na+ and Li+ electrolytes. The electron diffusion lengths in the different electrolytes followed the sequence of Na+ > Li+ > Mg2+ > TBA+. The trends observed in the AM 1.5 current–voltage characteristics of the DSCs are rationalized on the basis of the conduction band shifts and changes in electron lifetime.

Child mental health after parental separation: The impact of resident/non-resident parenting, parent mental health, conflict and socioeconomics

Children of separated parents tend to have poorer mental health than children of intact families. Explanations to date have tended to focus on resident mothers, neglecting the potential importance of non-resident fathers. Using recent data from the Longitudinal Study of Australian Children, and independent teacher-reports of child mental health, this study 1) compares the mental health of children with resident and non-resident fathers and 2) explores predictors of poor mental health among children with a non-resident father. Children with a non-resident father had poorer mental health than those with a resident father, but this difference was explained fully by exposure to parental conflict, and to a lesser extent by socioeconomic status, parenting, and parent mental health. For children with a non-resident father, the strongest predictors of child mental health were mothers' employment and maternal parenting consistency. Policy implications are discussed.

Enhanced hydrogen separation by vertically-aligned carbon nanotube membranes with zeolite imidazolate frameworks as a selective layer

Vertically-aligned carbon nanotube (VACNT) membranes show very high permeation fluxes due to the inherent smooth and frictionless nature of the interior of the nanotubes. However, the hydrogen selectivities are all in the Knudsen range and are quite low. In this study we grew molecular sieve zeolite imidazolate frameworks (ZIFs) via secondary seeded growth on the VACNT membranes as a gas selective layer. The ZIF layer has a thickness of 5–6 μm and shows good contact with the VACNT membrane surface. The VACNT supported ZIF membrane shows much higher H2 selectivity than Ar (7.0); O2 (13.6); N2 (15.1) and CH4 (9.8). We conclude that tailoring metal–organic frameworks on the membrane surface can be an effective route to improve the gas separation performance of the VACNT membrane.

Porous polyethersulfone-supported zeolitic imidazolate framework membranes for hydrogen separation

ZIF-8 thin layer has been synthesized on the asymmetric porous polyethersulfone (PES) substrate via secondary seeded growth. Continuous and dense ZIF-8 layer, containing microcavities, has good affinity with the PES support. Single gas permeance was measured for H2, N2, CH4, O2, and Ar at different pressure gradients and temperatures. Molecular sieving separation has been achieved for selectively separating hydrogen from larger gases. At 333 K, the H2 permeance can reach ∼4 × 10−7 mol m−2 s−1 Pa−1, and the ideal separation factors of H2 from Ar, O2, N2, and CH4 are 9.7, 10.8, 9.9, and 10.7, respectively. Long-term hydrogen permeance and H2/N2 separation performance show the stable permeability of the derived membranes.

Vertically-aligned carbon nanotube membranes for hydrogen separation

Vertically-aligned carbon nanotube membranes have been fabricated and characterized and the corresponding gas permeability and hydrogen separation were measured. The carbon nanotube diameter and areal density were adjusted by varying the catalyst vapour concentration (Fe/C ratio) in the mixed precursor. The permeances are one to two magnitudes higher than the Knudsen prediction, while the gas selectivities are still in the Knudsen range. The diameter and areal density effects were studied and compared, the temperature dependence of permeation is also discussed. The results confirm the existence of non-Knudsen transport and that surface adsorption diffusion may affect the total permeance at relative low temperature. The permeance of aligned carbon nanotube membranes can be improved by increasing areal density and operating at an optimum temperature.

Asymmetrically decorated, doped porous graphene as an effective membrane for hydrogen isotope separation

We propose a new route to hydrogen isotope separation which exploits the quantum sieving effect in the context of transmission through asymmetrically decorated, doped porous graphenes. Selectivities of D2 over H2 as well as rate constants are calculated based on ab initio interaction potentials for passage through pure and nitrogen functionalized porous graphene. One-sided dressing of the membrane with metal provides the critical asymmetry needed for an energetically favorable pathway.

A quasi-maximum likelihood method for estimating the parameters of multivariate diffusions

A quasi-maximum likelihood procedure for estimating the parameters of multi-dimensional diffusions is developed in which the transitional density is a multivariate Gaussian density with first and second moments approximating the true moments of the unknown density. For affine drift and diffusion functions, the moments are exactly those of the true transitional density and for nonlinear drift and diffusion functions the approximation is extremely good and is as effective as alternative methods based on likelihood approximations. The estimation procedure generalises to models with latent factors. A conditioning procedure is developed that allows parameter estimation in the absence of proxies.

CO2 capture and gas separation on boron carbon nanotubes

Concern about the increasing atmospheric CO2 concentration and its impact on the environment has led to increasing attention directed toward finding advanced materials and technologies suited for efficient CO2 capture, storage and purification of clean-burning natural gas. In this letter, we have performed comprehensive theoretical investigation of CO2, N2, CH4 and H2 adsorption on B2CNTs. Our study shows that CO2 molecules can form strong interactions with B2CNTs with different charge states. However, N2, CH4 and H2 can only form very weak interactions with B2CNTs. Therefore, the study demonstrates B2CNTs could sever as promising materials for CO2 capture and gas separation.