Support during birth interacts with prior trauma and birth intervention to predict postnatal post-traumatic stress symptoms

Background: Many women experience childbirth as traumatic and 2% develop post-traumatic stress disorder (PTSD). This study examined the role of health practitioner support and personal control during birth as predictors of PTS symptoms, adjusting for vulnerability factors of prior trauma, depression, control beliefs and birth intervention. It also investigated interactions between support, prior trauma and birth intervention and their association with PTS symptoms. Methods: A prospective longitudinal survey of 138 women recruited from UK NHS maternity clinics. Measures were taken in pregnancy, three-weeks and three-months after the birth. Results: Support and control during birth were not predictive of postnatal PTS symptoms. However, support was predictive of PTS symptoms in a subset of women with prior trauma (beta = -.41, R2 = 16%) at both three-weeks and three-months postpartum. The interaction of birth intervention and support was associated with PTS symptoms three-months after birth, the relationship between support and PTS symptoms was stronger in women experiencing more intervention. Conclusions: Low support from health practitioners is predictive of postnatal PTS symptoms in women who have a history of trauma. Longer-term effects of low support on postnatal PTS symptoms are also found in women who had more intervention during birth

The effect of reciprocal-space sampling and basis set quality on the calculated conductance of a molecular junction

We perform density functional theory and non-equilibrium Green's function calculations of the conductance of a gold wire and a 1,4-phenylenedimethanethiol (XYL) molecule adsorbed between Au(111) electrodes using the TranSIESTA software package. The effect of varying different computational parameters is investigated. We find that the conductance is more sensitive to the reciprocal-space sampling grid than the quality of the basis set employed. The conductance can vary up to a factor of five as a result of the choice of computational parameters. We report a set of computational parameters that yields a well-converged conductance value

Problems, successes and challenges for the application of dispersion-corrected density-functional theory combined with dispersion-based implicit solvent models to large-scale hydrophobic self-assembly and polymorphism

© 2015 Taylor & Francis. The recent advent of dispersion-corrected density-functional theory (DFT) methods allows for quantitative modelling of molecular self-assembly processes, and we consider what is required to develop applications to the formation of large self-assembled monolayers (SAMs) on hydrophobic surfaces from organic solution. Focus is on application of the D3 dispersion correction of Grimme combined with the solvent dispersion model of Floris, Tomasi and Pascual-Ahuir to simulate observed scanning-tunnelling microscopy (STM) images of various polymorphs of tetraalkylporphyrin SAMs on highly oriented pyrolytic graphite surfaces. The most significant problem is identified as the need to treat SAM structures that are incommensurate with those of the substrate, providing a challenge to the use of traditional periodic-imaging boundary techniques. Using nearby commensurate lattices introduces non-systematic errors into calculated lattice constants and free energies of SAM formation that are larger than experimental uncertainties and polymorph differences. Developing non-periodic methods for polymorph interface simulation also remains a challenge. Despite these problems, existing methods can be used to interpret STM images and SAM atomic structures, distinguishing between multiple feasible polymorph types. They also provide critical insight into the factors controlling polymorphism. All this stems from a delicate balance that the intermolecular D3 and solvent Floris, Tomasi and Pascual-Ahuir corrections provide. Combined optimised treatments should yield fully quantitative approaches in the future

Optical properties of intermetallic compounds from first principles calculations: A search for the ideal plasmonic material

First principles calculations have been used to predict the optical properties for a range of intermetallic compounds for which little or no experimental optical data are currently available. Density functional theory combined with the random phase approximation is used to calculate the dielectric functions for these compounds. The aim of this work is to investigate how the band edge and plasma frequency vary with composition in order to identify materials with promising plasmonic properties. Towards this end the intermetallic compounds chosen are composed of elements which on their own have reasonable optical properties for plasmonic applications. The position of the band edge relative to the plasma frequency is most favourable in the simple binary compounds formed from the alkali plus noble metals NaAu, KAu and KAg. In particular, for KAu the band edge and plasma frequency occur at almost the same frequency, and hence the imaginary part of the dielectric function is practically zero for frequencies below the plasma frequency. In addition, the plasma frequency in this compound is at relatively low frequency, promising a material with strong plasmon response in the infrared. © 2009 IOP Publishing Ltd

Search for the ideal lasmonic nanoshell: the effects of surface scattering and alternatives to gold and silver

The optical absorption efficiency of nanospheres and nanoshells of the elements Na, K, Al, Ag, and Au are compared, and the effects of surface scattering, as introduced by the billiard model [Moroz, A. J. Phys. Chem. C 2008, 112 (29), 10641-10652] are discussed. We find that the introduction of surface scattering has comparatively little effect on the optimized absorption efficiency of nanospheres, with the maximum absorption efficiency of K nanospheres falling from 14.7 to 13.3. Conversely, the reduction in absorption efficiency in nanoshells is substantial. This effect is compounded in metals with higher plasma frequency. We show that the high comparative plasma frequencies in silver and gold result in a greatly reduced optimized absorption efficiency when compared to nanoshells in the absence of surface scattering. Whereas sodium and potassium, with low plasma frequencies, are not affected as much. © 2009 American Chemical Society

Local electromagnetic fields surrounding gold nano-cap particles

Using the discrete dipole approximation (DDA) the local electromagnetic fields surrounding gold nano-cap particles are investigated. Suitable k-vectors and polarization vectors of the incident light are used to determine the largest local electric field enhancement. The largest enhancement can be found for the 864 nm dipole resonance; where the field enhancement is approximately 30 000 times the applied field. The electric field contours surrounding the particle are used to assign the order of the surface plasmon resonances. © 2006 IEEE

Effect of dipole moment on current-voltage characteristics of single molecules

We perform empirical calculations of the tunneling current through various small organic molecules sandwiched between gold electrodes by using the Wenzel-Kramers-Brillouin (WKB) approximation. The barrier to tunneling is taken to be the work function of gold and calculated from a first principles electronic structure code. The current-voltage characteristics of these molecules are compared in the context of existing first principles and experimental results. In this model the surface dipole moment, induced by the adsorbed molecule, can have a significant effect on the current and hence dipole moments may be an important property for prediction of the conductance characteristics of a molecule. © 2006 IEEE

Superconductivity in intercalated buckled two-dimensional materials: KGe<inf>2</inf>

© the Owner Societies. Germanene has emerged as a novel two-dimensional material with various interesting properties and applications. Here we report the possibility of superconductivity in a stable potassium intercalated germanene compound, KGe2, with a transition temperature Tc ∼ 11 K, and an electron-phonon coupling of 1.9. Applying a 5% tensile strain, which reduces the buckling height by 4.5%, leads to the reduction of the electron-phonon coupling by 11% and a slight increase in Tc ∼ 12 K. That is, strong electron-phonon coupling results from the buckled structure of the germanene layers. Despite being an intercalated van der Waals material similar to intercalated graphite superconductors, it does not possess an occupied interlayer state

Single-photon emitters in hexagonal boron nitride: a review of progress.

This report summarizes progress made in understanding properties such as zero-phonon-line energies, emission and absorption polarizations, electron-phonon couplings, strain tuning and hyperfine coupling of single photon emitters in hexagonal boron nitride. The primary aims of this research are to discover the chemical nature of the emitting centres and to facilitate deployment in device applications. Critical analyses of the experimental literature and data interpretation, as well as theoretical approaches used to predict properties, are made. In particular, computational and theoretical limitations and challenges are discussed, with a range of suggestions made to overcome these limitations, striving to achieve realistic predictions concerning the nature of emitting centers. A symbiotic relationship is required in which calculations focus on properties that can easily be measured, whilst experiments deliver results in a form facilitating mass-produced calculations

Analysis of gas chromatography/mass spectrometry data for catalytic lignin depolymerization using positive matrix factorization

Various catalytic technologies are being developed to efficiently convert lignin into renewable chemicals. However, due to its complexity, catalytic lignin depolymerization often generates a wide and complex distribution of product compounds. Gas chromatography/mass spectrometry (GC-MS) is a common analytical technique to profile the compounds that comprise lignin depolymerization products. GC-MS is applied not only to determine the product composition, but also to develop an understanding of the catalytic reaction pathways and of the relationships among catalyst structure, reaction conditions, and the resulting compounds generated. Although a very useful tool, the analysis of lignin depolymerization products with GC-MS is limited by the quality and scope of the available mass spectral libraries and the ability to correlate changes in GC-MS chromatograms to changes in lignin structure, catalyst structure, and other reaction conditions. In this study, the GC-MS data of the depolymerization products generated from organosolv hybrid poplar lignin using a copper-doped porous metal oxide catalyst and a methanol/dimethyl carbonate co-solvent was analyzed by applying a factor analysis technique, positive matrix factorization (PMF). Several different solutions for the PMF model were explored. A 13-factor solution sufficiently explains the chemical changes occurring to lignin depolymerization products as a function of lignin, reaction time, catalyst, and solvent. Overall, seven factors were found to represent aromatic compounds, while one factor was defined by aliphatic compounds