Molecular Dynamics Study of the Hydrophilic-to-Hydrophobic Switching in the Wettability of a Gold Surface Corrugated with Spherical Cavities.

This paper reports a large scale molecular dynamics (MD) simulation study of the wettability of a gold surface engraved with (hemi)spherical cavities. By increasing the depth of cavities, the contact angle (CA) of a water droplet on the surface was varied from a hydrophilic (69°) to a hydrophobic value (>109°). The nonmonotonic behavior of the CA vs the depth of the cavities was consistent with the Cassie-Baxter theory, as found in the experiment by Abdelsalam et al. (Abdelsalam, M. E.; Bartlett, P. N.; Kelf, T.; Baumberg, J. Wetting of Regularly Structured Gold Surfaces. Langmuir 2005, 21, 1753-1757). Depending on the depth of cavities, however, the droplet existed not only in the Cassie-Baxter state, but also in the Wenzel or an intermediate state, where the cavities were penetrated partially by the droplet.

Monte Carlo study on the self-assembly of nanoparticles into a nanorod structure.

It is well known that semiconductor nanoparticles (NPs) can assemble into a range of low dimensional structures, such as nanowires, nanorods and nanosheets. In this study, we investigate the self-assembly of CdTe NPs by using Monte Carlo simulation. Using a simple model for the anisotropic interaction of NPs, the present Monte Carlo simulation demonstrated that NPs with large dipole moments assemble spontaneously into a nanorod even if the short range interactions among NPs is isotropic. Interestingly, we found that the present nanorod grew by forming a transient structure which looks similar to a double ring. For NPs similar to CdTe, the dipole-dipole interaction had a dominant effect over van der Waals attractions and steric repulsion on the final structure of the NP aggregates. The simulated rods are similar to those observed in the experimental self-assembly of CdTe NPs. The NPs with relatively small electric dipole moments aggregated into more or less isotropic structures.

Association between intimate partner violence and child morbidity in South Asia.

BACKGROUND: This study investigates the association between intimate partner violence (IPV) against women and its impact on child morbidity in the south Asian region. METHODS: The analysis uses logistic regression models with cross sectional nationally representative data from three countries - Bangladesh, India and Nepal. The data have been pooled from 'Demographic and Health Surveys' (DHS) of Bangladesh, Nepal and 'National Family and Health Survey' (NFHS) of India. RESULTS: The study revealed that after controlling for potential confounders, children of mothers experiencing physical violence, sexual violence or both were more likely to have Acute Respiratory Infection (ARI) (OR(adj) 1.57; 95% CI 1.48-1.67), fever (OR(adj) 1.44; 95% CI 1.35-1.54) and diarrhea (OR(adj )1.56; 95% CI 1.44-1.69). CONCLUSIONS: The results highlight that IPV can influence childhood morbidity and support the need to address IPV with a greater focus within current child nutrition and health programs and policies.

Density functional theory study on the cross-linking of mussel adhesive proteins.

The water-resistant adhesion of mussel adhesive proteins (MAPs) to a wet surface requires a cross-linking step, where the catecholic ligands of MAPs coordinate to various transition-metal ions. Fe(III), among the range of metal ions, induces particularly strong cross-linking. The molecular details underlying this cross-linking mediated by transition-metal ions are largely unknown. Of particular interest is the metal-ligand binding energy, which is the molecular origin of the mechanical properties of cross-linked MAPs. Using density functional theory, this study examined the structures and binding energies of various trivalent metal ions (Ti-Ga) forming coordination complexes with a polymeric ligand similar to a MAP. These binding energies were 1 order of magnitude larger than the physisorption energy of a catechol molecule on a metallic surface. On the other hand, the coordination strength of Fe(III) with the ligand was not particularly strong compared to the other metal ions studied. Therefore, the strong cross-linking in the presence of Fe(III) is ascribed to its additional ability as an oxidant to induce covalent cross-linking of the catecholic groups of MAPs.