Haze in the Klang Valley of Malaysia

Continuous measurements of dry aerosol light scattering (Bsp) were made at two sites in the Klang Valley of Malaysia between December 1998 and December 2000. In addition 24-h PM2.5 samples were collected on a one-day-in-six cycle and the chemical composition of the aerosol was determined. Periods of excessive haze were defined as 24-h average Bsp values greater than 150 Mm-1 and these occurred on a number of occasions, between May and September 1999, during May 2000, and between July and September 2000. The evidence for smoke being a significant contributor to aerosol during periods of excessive haze is discussed and includes features of the aerosol chemistry, the diurnal cycle of Bsp, and the coincidence of forest fires on Sumatra during the southwest (SW) monsoon period, as well as transport modelling for one week of the southwest Monsoon of 2000. The study highlights that whilst transboundary smoke is a major contributor to poor visibility in the Klang Valley, smoke from fires on Peninsular Malaysia is also a contributor, and at all times, the domestic source of secondary particle production is present

Minimal Basis Iterative Stockholder: Atoms in Molecules for Force-Field Development

Atomic partial charges appear in the Coulomb term of many force-field models and can be derived from electronic structure calculations with a myriad of atoms-in-molecules (AIM) methods. More advanced models have also been proposed, using the distributed nature of the electron cloud and atomic multipoles. In this work, an electrostatic force field is defined through a concise approximation of the electron density, for which the Coulomb interaction is trivially evaluated. This approximate "pro-density" is expanded in a minimal basis of atom-centered s-type Slater density functions, whose parameters are optimized by minimizing the Kullback-Leibler divergence of the pro-density from a reference electron density, e.g. obtained from an electronic structure calculation. The proposed method, Minimal Basis Iterative Stockholder (MBIS), is a variant of the Hirshfeld AIM method but it can also be used as a density-fitting technique. An iterative algorithm to refine the pro-density is easily implemented with a linear-scaling computational cost, enabling applications to supramolecular systems. The benefits of the MBIS method are demonstrated with systematic applications to molecular databases and extended models of condensed phases. A comparison to 14 other AIM methods shows its effectiveness when modeling electrostatic interactions. MBIS is also suitable for rescaling atomic polarizabilities in the Tkatchenko-Sheffler scheme for dispersion interactions.Comment: 61 pages, 12 figures, 2 table

Randomized trial of polychromatic blue-enriched light for circadian phase shifting, melatonin suppression, and alerting responses.

Wavelength comparisons have indicated that circadian phase-shifting and enhancement of subjective and EEG-correlates of alertness have a higher sensitivity to short wavelength visible light. The aim of the current study was to test whether polychromatic light enriched in the blue portion of the spectrum (17,000 K) has increased efficacy for melatonin suppression, circadian phase-shifting, and alertness as compared to an equal photon density exposure to a standard white polychromatic light (4000 K). Twenty healthy participants were studied in a time-free environment for 7 days. The protocol included two baseline days followed by a 26-h constant routine (CR1) to assess initial circadian phase. Following CR1, participants were exposed to a full-field fluorescent light (1 × 10 14 photons/cm 2 /s, 4000 K or 17,000 K, n = 10/condition) for 6.5 h during the biological night. Following an 8 h recovery sleep, a second 30-h CR was performed. Melatonin suppression was assessed from the difference during the light exposure and the corresponding clock time 24 h earlier during CR1. Phase-shifts were calculated from the clock time difference in dim light melatonin onset time (DLMO) between CR1 and CR2. Blue-enriched light caused significantly greater suppression of melatonin than standard light ((mean ± SD) 70.9 ± 19.6% and 42.8 ± 29.1%, respectively, p \u3c 0.05). There was no significant difference in the magnitude of phase delay shifts. Blue-enriched light significantly improved subjective alertness (p \u3c 0.05) but no differences were found for objective alertness. These data contribute to the optimization of the short wavelength-enriched spectra and intensities needed for circadian, neuroendocrine and neurobehavioral regulation

Post-traumatic stress disorder following childbirth: an update of current issues and recommendations for future research

Objective: This paper aimed to report the current status of research in the field of post-traumatic stress disorder following childbirth (PTSD FC), and to update the findings of an earlier 2008 paper. Background: A group of international researchers, clinicians and service users met in 2006 to establish the state of clinical and academic knowledge relating to PTSD FC. A paper identified four key areas of research knowledge at that time. Methods: Fourteen clinicians and researchers met in Oxford, UK to update the previously published paper relating to PTSD FC. The first part of the meeting focused on updating the four key areas identified previously, and the second part on discussing new and emerging areas of research within the field. Results: A number of advances have been made in research within the area of PTSD FC. Prevalence is well established within mothers, several intervention studies have been published, and there is growing interest in new areas: staff and pathways; prevention and early intervention; impact on families and children; special populations; and post-traumatic growth. Conclusion: Despite progress, significant gaps remain within the PTSD FC knowledge base. Further research continues to be needed across all areas identified in 2006, and five areas were identified which can be seen as ‘new and emerging’. All of these new areas require further extensive research. Relatively little is still known about PTSD FC

Preface-JES Focus Issue on Electrolysis for Increased Renewable Energy Penetration

(First paragraph) Today represents a particularly exciting time, as our planet’s energy system is undergoing major changes due to dramatically decreasing renewable energy prices and increasing societal concerns over greenhouse gas emissions, criteria pollutants (arsenic, mercury, NOx, particulate matter), and climate change. These factors are pushing society toward deep decarbonization of our energy system, perhaps the most challenging issue facing the planet today. Unfortunately, wind and solar energy, while both promising generation sources, come with intermittency challenges and have limitations in their abilities to impact industrial and transportation sector demands where fossil fuel energy carriers based on chemical bonds have provided the basis for historic energy demands. Electrolysis (Hydrogen Generation) offers the potential to meet the multi-GW demand for both grid-balancing and input into the industrial and transportation sectors, as shown schematically below. In such an energy system, hydrogen acts as an energy carrying intermediate that parallels electons (electricity) within the energy system. Therefore interest in this area has increased significantly with focus on several different technological approaches, each with their own unique challenges

Charge Transfer in Partition Theory

The recently proposed Partition Theory (PT) [J.Phys.Chem.A 111, 2229 (2007)] is illustrated on a simple one-dimensional model of a heteronuclear diatomic molecule. It is shown that a sharp definition for the charge of molecular fragments emerges from PT, and that the ensuing population analysis can be used to study how charge redistributes during dissociation and the implications of that redistribution for the dipole moment. Interpreting small differences between the isolated parts' ionization potentials as due to environmental inhomogeneities, we gain insight into how electron localization takes place in H2+ as the molecule dissociates. Furthermore, by studying the preservation of the shapes of the parts as different parameters of the model are varied, we address the issue of transferability of the parts. We find good transferability within the chemically meaningful parameter regime, raising hopes that PT will prove useful in chemical applications.Comment: 12 pages, 16 figure

Projected seniority-two orbital optimization of the Antisymmetric Product of one-reference orbital Geminal

We present a new, non-variational orbital-optimization scheme for the Antisymmetric Product of one-reference orbital Geminal wave function. Our approach is motivated by the observation that an orbital-optimized seniority-zero configuration interaction (CI) expansion yields similar results to an orbital-optimized seniority-zero-plus-two CI expansion [J. Chem. Phys., 135, 044119 (2011)]. A numerical analysis is performed for the C$_2$, LiF and CH$_2$ molecules as well as for the symmetric stretching of hypothetical (linear) hydrogen chains. For these test cases, the proposed orbital-optimization protocol yields similar results to its variational orbital optimization counterpart, but prevents symmetry-breaking of molecular orbitals in most cases.Comment: 7 pages, 2 figure

Effects of Microgravity on the Formation of Aerogels

This paper describes research to investigate fundamental aspects of the effects of microgravity on the formation of the microstructure of metal oxide alcogels and aerogels. We are studying the role of gravity on pore structure and gel uniformity in collaboration with Marshall Space Flight Center (MSFC) on gelling systems under microgravity conditions. While this project was just initiated in May 1998, related research performed earlier is described along with the plans and rationale for the current microgravity investigation to provide background and describe newly developing techniques that should be useful for the current gellation studies. The role of gravity in materials processing must be investigated through the study of well-mastered systems. Sol-gel processed materials are near-perfect candidates to determine the effect of gravity on the formation and growth of random clusters from hierarchies of aggregated units. The processes of hydrolysis, condensation, aggregation and gellation in the formation of alcogels are affected by gravity and therefore provide a rich system to study under microgravity conditions. Supercritical drying of the otherwise unstable wet alcogel preserves the alcogel structure produced during sol-gel processing as aerogel. Supercritically dried aerogel provides for the study of material microstructures without interference from the effects of surface tension, evaporation, and solvent flow. Aerogels are microstructured, low density open-pore solids. They have many unusual properties including: transparency, excellent thermal resistance, high surface area, very low refractive index, a dielectric constant approaching that of air, and extremely low sound velocity. Aerogels are synthesized using sol-gel processing followed by supercritical solvent extraction that leaves the original gel structure virtually intact. These studies will elucidate the effects of microgravity on the homogeneity of the microstructure and porosity of aerogel. The presence of poorly controlled microporosity in aerogel leads to material non-uniformity that gives rise to increased light scattering. Investigation of the effect of gravity driven solute flows within microclusters and their effect on condensation and agglomeration reactions will enable us to improve the preparation and properties of aerogel. Increased clarity of images viewed through aerogel and decreased scattering from the pores of aerogel will significantly improve the prospects for large-scale adoption of aerogel in such applications as transparent insulating windows, high performance thermal insulation, and Cherenkov detectors

The influence of postpartum PTSD on breastfeeding: A longitudinal population-based study.

BACKGROUND: In most Western countries, breastfeeding rates are lower than what is recommended by the World Health Organization. Depression has been shown to influence breastfeeding outcomes; however, there is very little research on the role of postpartum posttraumatic stress disorder (PTSD). This study examined to what extent maternal postpartum PTSD predicted breastfeeding initiation, exclusive breastfeeding during the first 6 months, and continuation up to 1 and 2 years. METHODS: The study is part of the large, population-based Akershus Birth Cohort. Data from the hospital's birth record and questionnaire data from 8 weeks and 2 years postpartum were used (n = 1480). All breastfeeding variables significantly correlated with postpartum PTSD were entered into stepwise logistic regression analyses. RESULTS: Although most mothers (97.1%) initiated breastfeeding, considerably fewer adhered to the World Health Organization's breastfeeding guidelines about exclusive breastfeeding during the first 6 months (13.4%) or continued breastfeeding for 12 or 24 months postpartum (37.7% and 4.2%, respectively). Even after adjustment for important confounding variables, maternal postpartum PTSD was significantly associated with not initiating breastfeeding (aOR 5.98 [95% CI 1.79-19.97]). Postpartum PTSD was also significantly related to not continuing breastfeeding up to 12 months, although this association did not hold after adjusting for confounding variables. CONCLUSION: Identifying women at risk of not initiating breastfeeding is crucial to prevent a negative influence on infant development and the development of the mother-infant bond. Early screening and treatment of women at risk of developing postpartum PTSD might be a way forward

Postnatal mental health and mothers' processing of infant emotion: an eye-tracking study

BACKGROUND: Postnatal mental illnesses are associated with less maternal sensitivity. Differences in how mothers with and without mental illness process infant emotions could explain this. People with mental illness in non-perinatal populations show certain processing patterns when viewing emotional faces, but it is not clear whether these patterns are present in mothers. OBJECTIVE: Compared to mothers without affective symptoms (anxiety, depression and post-traumatic stress). Task 1 aimed to identify whether mothers with affective symptoms show an attentional bias towards negative infant faces; and Task 2 aimed to identify whether mothers with affective symptoms look less at infants' eyes compared to eyes and mouth. DESIGN: An experimental design was used in two tasks to answer the research objective. METHODS: Mothers with affective symptoms (n = 23) and without affective symptoms (n = 47) had their eye movements tracked whilst: Task 1, viewing pairs of infant faces; and Task 2, viewing morphed infant faces. RESULTS: In Task 1 mothers with affective symptoms were more likely to fixate first on neutral faces when the choice was between negative and neutral. In Task 2, no differences were found between groups. CONCLUSIONS: The findings from Task 1 are unexpected given previous research. More research is needed to identify potential explanations for this