Wetting of a Stepped Platinum (211) Surface.

Steps stabilize water adsorption on metal surfaces, providing favorable binding sites for water during wetting or ice nucleation, but there is limited understanding of the local water arrangements formed on such surfaces. Here we describe the structural evolution of water on the stepped Pt(211) surface using thermal desorption, low-energy electron diffraction, and scanning tunneling microscopy to probe the water structure. At low coverage water forms linear structures comprising zigzag chains along the steps that are decorated by H-bonded rings every one or two units along the terrace. Simple 2-coordinate H-bonded chains are not observed, indicating the Pt step binds too weakly to compensate entirely for a low water H-bond coordination number. As the coverage increases, water chains assemble into a disordered (2 × 1) structure, likely made up of the same narrow water chains along the steps with little or no H-bonding between adjacent structures. The chain structure disappears as water adsorption saturates the surface to form an incommensurate, disordered network of water rings of different size. Although the steps on Pt(211) clearly stabilize water adsorption and direct growth, the surface does not support the simple 1D chains previously proposed or an ordered 2D network such as seen on other surfaces. We discuss reasons for this and the factors that determine the behavior of the first water layer on stepped metal surfaces.

The reactivity of water and OH on Pt-Ni(111) films.

Bimetallic Pt catalysts are of interest as water redox catalysts in low temperature fuel cells. Here we compare water and hydroxyl adsorption on Pt-Ni(111) films and a PtNi(111) alloy surface with the behaviour on the pure metals. Whereas water adsorbs and desorbs intact from close packed Pt and Ni, it dissociates on PtNi surfaces to form adsorbed hydroxyl and hydrogen. Reactivity to water increases in the order Pt(111) < monolayer Pt-Ni(111) < multilayer (2-6 ML) Pt-Ni(111) ∼ PtNi(111) surface alloy and does not scale directly with the Pt strain. Hydroxyl can also be formed by reaction with pre-adsorbed O and is less stable than on pure Pt, decomposing to water and O in a broad peak near 180 K, 20 K lower than on Pt(111). The reduced stability of OH on Pt-Ni(111) films is common to all the PtNi surfaces and consistent with bimetallic PtNi surfaces showing less blocking by OH during the oxygen reduction reaction.

Monthly population density and structure patterns of an endangered seahorse Hippocampus capensis: a comparison between natural and artificial habitats.

This study investigated aspects of the population ecology of the endangered Knysna seahorse Hippocampus capensis within different habitat types. High densities of H. capensis were found within artificial Reno mattress habitat, within the Knysna Estuary, South Africa. Monthly surveys at three sites were conducted from October 2015 to August 2016 to compare population densities of H. capensis in this artificial habitat with natural eel grass Zostera capensis habitat. Hippocampus capensis densities varied significantly across all sites and highest population densities were consistently observed within the Reno mattress habitat. Hippocampus capensis were also found to be significantly larger within the Reno mattress habitat and pooled data showed that males were significantly larger than females. The overall sex ratio for all three sites was female biased, although this varied across seasons at two sites. The findings suggest that artificial Reno mattresses provide novel habitat for this endangered species and consideration should be given to the usefulness of these structures in future conservation actions.

Two-Dimensional Wetting of a Stepped Copper Surface.

Highly corrugated, stepped surfaces present regular 1D arrays of binding sites, creating a complex, heterogeneous environment to water. Rather than decorating the hydrophilic step sites to form 1D chains, water on stepped Cu(511) forms an extended 2D network that binds strongly to the steps but bridges across the intervening hydrophobic Cu(100) terraces. The hydrogen-bonded network contains pentamer, hexamer, and octomer water rings that leave a third of the stable Cu step sites unoccupied in order to bind water H down close to the step dipole and complete three hydrogen bonds per molecule.

Classifying hard and soft bone tissues using drilling sounds.

The purpose of this study was to investigate if the sounds generated during bone drilling could be used to classify between hard (cortical) and soft (cancellous) tissues. Bone drilling is performed in many surgical procedures throughout the world. Inadvertent deviation from the correct drill direction may result in injuries to sensitive anatomical structures such as nerve and vessels. Therefore, to increase the safety of such procedures, it is necessary to identify different bone tissues. The cortical and cancellous tissues of six bovine tibia pieces were drilled and the generated sounds were recorded. Each record was analyzed in different frequency regions based on the spectrograms. From each region, short-time Fourier transform (STFT) coefficients were computed and averaged accordingly to obtain n bins. The total bins of all frequency regions were chosen as the features. A support vector machine (SVM) algorithm was selected for classification and the performance was evaluated in two training/testing scenarios: leave one bone out (LOBO) and bone specific (BSP). The average total accuracy on the testing data was 70.9% and 83% for LOBO and BSP respectively. The results indicated that the drilling sounds obtained from various bone pieces could be used to develop a classification model that had promising performance on identifying hard and soft components of a new bone piece.

Chiral segregation driven by a dynamical response of the adsorption footprint to the local adsorption environment: bitartrate on Cu(110).

Local or global ordering of chiral molecules at a surface is a key step in both chiral separation and heterogeneous enantioselective catalysis. Using density functional theory and scanning probe microscopy results, we find that the accepted structural model for the well known bitartrate on Cu(110) chiral system cannot account for the chiral segregation observed. Instead, we show that this strongly bound, chiral adsorbate changes its adsorption footprint in response to the local environment. The flexible adsorption geometry allows bitartrate to form stable homochiral trimer chains in which the central molecule restructures from a rectangular to an oblique footprint, breaking its internal hydrogen bonds in order to form strong intermolecular hydrogen bonds to neighbouring adsorbates. Racemic structures containing mixed enantiomers do not form strong hydrogen bonds, providing the thermodynamic driving force for the chiral separation that is observed experimentally. This result shows the importance of considering the dynamical response of molecular adsorption footprints at the surface in directing chiral assembly and segregation. The ability of strongly-chemisorbed enantiomers to change footprint depending on the local adsorption environment indicates that supramolecular assemblies at surfaces may exhibit more complex dynamical behaviour than hitherto suspected, which, ultimately, could be tailored to lead to environment and stimuli-responsive chiral surfaces.

Advances in the development of a dissolution method for the attribution of iridium source materials.

To assist in nuclear forensic investigations, new techniques are required to evaluate radioactive materials that may be discovered outside of regulatory control. Using a recently developed pressure digestion method for iridium powder, assessments have been made of this techniques suitability for undertaking iridium target material evaluations. In addition to determining the reaction conditions necessary for total dissolution, these investigations have provided an insight into the elemental impurities that are present within unirradiated iridium targets that are used in QSA Global radiography sources, and established the speciation of the iridium solutions that are formed during this process.

The Mayak Worker Dosimetry System (MWDS-2013): A Bayesian Analysis to Quantify Pulmonary Binding of Plutonium in Lungs Using Historic Beagle Dog Data.

The revised human respiratory tract model, published in Part 1 of the International Commission on Radiological Protection's (ICRP) report on Occupational Intakes of Radionuclides (OIR), includes a bound fraction, fb, to represent radionuclides that have become chemically bound in the lungs following dissolution of particulates in lung fluid. Bound radionuclides are not subject to particle transport clearance but can be absorbed to blood at a rate, sb. The occurrence of long-term binding of plutonium can greatly increase lung doses, particularly if it occurs in the bronchial and bronchiolar regions. However, there has been little evidence that currently supports the existence of a long-term bound state for plutonium. The present work describes the analysis of measurements of lung data obtained from a life span study of Beagle dogs that were exposed by inhalation to different concentrations of plutonium-239 (239Pu) nitrate aerosol at Pacific Northwest Laboratories, USA. The data have been analysed to assess whether a bound state was required to explain the data. A Bayesian approach was adopted for the analysis that accounts for uncertainties in model parameter values, including uncertainties in the rates of particle transport clearance. Furthermore, it performs the analysis using two different modelling hypotheses: a model based on the current ICRP human respiratory tract model and its treatment of alveolar particle transport clearance; and a model of particle transport clearance that is based on the updated model developed by ICRP to calculate dose coefficients for the OIR. The current model better represents clearance in dogs at early times (up to 1 year following intake) and the latter better represents retention at greater times (>5 years following intake). The results indicate that a long-term bound fraction of between 0.16 and 1.1%, with a mean value of between 0.24 and 0.8% (depending on the model) is required to explain the data.

Pregnant Women's perceptions of exposure to brominated flame retardants.

BACKGROUND: Recent media reports on human studies associating brominated flame retardants (BFRs) in household products in pregnancy with urogenital anomalies in boys and endocrine disruption in both sexes. We sought to explore the perceptions of pregnant women of brominated flame retardant (BFR) exposure, in light of recent media reports on the adverse health effects of BFR exposure prenatally. METHODS: Pregnant women were recruited for interviews through posters and pamphlets in prenatal clinics, prenatal fairs and community centres. Interviews were audiotaped and transcribed verbatim for Charmaz-based qualitative analysis supported by NVIVO 10™. RESULTS: Theoretical sufficiency was reached after analyzing the interviews of 23 pregnant women. Themes co-constructed were: I-Lack of Awareness of BFRs; II-Factors Influencing BFR Exposure; III-Responsibility; IV-Informed Choice. Almost all participants felt it was difficult to make informed choices to avoid BFRs, and wanted communication from clinicians and regulation from governments regarding decreasing BFR exposure. CONCLUSION: Pregnant women in Canada may be unaware of the potential risks of exposure to BFRs. Professional organizations and governments should further study risk associated with BFR exposure in pregnancy and provide educational materials for pregnant women and clinicians regarding BFR exposure.

The role of lattice parameter in water adsorption and wetting of a solid surface.

Ice formation is a complex cooperative process that is almost invariably catalysed by the presence of an interface on which ice crystals nucleate. As yet there is no clear picture of what factors make a surface particularly good at nucleating ice, but the importance of having a template with a suitable lattice parameter has often been proposed. Here we report the contrasting wetting behaviour of a series of pseudomorphic surfaces, designed to form an ordered template that matches the arrangement of water in a bulk ice Ih(0001) bilayer. The close-packed M(111) surfaces (M = Pt, Pd, Rh, Cu and Ni) form a (√3 × âˆš3) R30° Sn substitutional alloy surface, with Sn atoms occupying sites that match the symmetry of an ice bilayer. The lattice constant of the alloy changes from 4% smaller to 7% greater than the lateral spacing of ice across the series. We show that only the PtSn surface, with a lattice parameter some 7% greater than that of a bulk ice layer, forms a stable water layer, all the other surfaces being non-wetting and instead forming multilayer ice clusters. This observation is consistent with the idea that the repeat spacing of the surface should ideally match the O-O spacing in ice, rather than the bulk ice lattice parameter, in order to form a continuous commensurate water monolayer. We discuss the role of the lattice parameter in stabilising the first layer of water and the factors that lead to formation of a simple commensurate structure rather than an incommensurate or large unit cell water network. We argue that lattice match is not a good criteria for a material to give low energy nucleation sites for bulk ice, and that considerations such as binding energy and mobility of the surface layer are more relevant.

Shifting from presumptive to test-based management of malaria - technical basis and implications for malaria control in Ghana.

The presumptive approach was the World Health Organisation (WHO) recommended to the management of malaria for many years and this was incorporated into syndromic guidelines such as the Integrated Management of Childhood Illnesses (IMCI). In early 2010 however, WHO issued revised treatment guidelines that call for a shift from the presumptive to the test-based approach. Practically, this implies that in all suspected cases, the diagnosis of uncomplicated malaria should be confirmed using rapid test before treatment is initiated. This revision effectively brings to an end an era of clinical practice that span several years. Its implementation has important implications for the health systems in malaria-endemic countries. On the basis of research in Ghana and other countries, and evidence from program work, the Ghana National Malaria Control Program has issued revised national treatment guidelines that call for implementation of test-based management of malaria in all cases, and across all age groups. This article reviews the evidence and the technical basis for the shift to test-based management and examines the implications for malaria control in Ghana.

Infant illness spanning the antenatal to early neonatal continuum in rural northern Ghana: local perceptions, beliefs and practices.

OBJECTIVE: To explore community understanding of perinatal illness in northern Ghana. STUDY DESIGN: A cross-sectional descriptive study design. RESULT: 253 community members participated in in-depth interviews and focus group discussions, including women with newborn infants, grandmothers and health care providers. Four overarching themes emerged: (1) Local understanding of illness affects treatment practices. Respondents recognized danger signs of illness spanning antenatal to early neonatal periods. Understanding of causation often had a distinctly local flavor, and thus treatment sometimes differed from mainstream recommendations; (2) Mothers are frequently blamed for their infant's illness; (3) Healthcare decisions regarding infant care are often influenced by community members aside from the infant's mother and (4) Confidence in healthcare providers is issue-specific, and many households use a blended approach to meet their health needs. CONCLUSION: Despite widespread recognition of danger signs and reported intentions to treat ill infants through the formal health care system, traditional approaches to perinatal illness remain common. Interventions need to be aligned with community perceptions if they are to succeed.

Urban-rural differences in the nature and prevalence of mental ill-health in adults with intellectual disabilities.

BACKGROUND: In the general population there are statistically significant urban-rural differences in the rate of common mental disorders. In people with intellectual disability (ID) no study has attempted to address this issue. AIMS: To compare the prevalence of mental illness, autism spectrum disorder (ASD) and behaviour disorder in people with ID living in urban areas with those living in rural areas. METHODS: Cross-sectional study of 2713 individuals registered with an ID service. Participants were assigned to urban or rural groups using the Department for Environment Food and Rural Affairs rural/urban local authority classification for their district. The main outcome variable was a clinical diagnosis of mental illness, ASD and behaviour disorder. Differences between diagnoses of mental illness in urban and rural areas were evaluated using the chi-squared test for the difference in two independent proportions. RESULTS: No differences were observed between gender, age and level of ID of service users based on their place of residence. But more people from an ethnic minority background were living in urban areas than rural areas. No differences were observed in the overall prevalence of mental illness by place of residence. However, the results showed that ASD was more common in people living in rural areas. CONCLUSIONS: We found these results surprising and at odds with the majority of studies carried out in the general population and propose several reasons for the differences found. We believe that the results and further studies in this area will help inform health service provision for those with ID who live in different geographical areas.

Strain relief and disorder in commensurate water layers formed on Pd(111).

Water adsorbs and desorbs intact on Pd(111), forming a hydrogen-bonded wetting layer whose structure we examine by low energy electron diffraction (LEED) and He atom scattering (HAS). LEED shows that water forms commensurate (√3 × âˆš3)R30° clusters that aggregate into a partially ordered, approximately (7 × 7) superstructure as the layer completes. HAS indicates that the water layer remains disordered on a local (approximately 10 Å) scale. Based on workfunction measurements and density functional theory simulations we propose that water forms small, flat domains of a commensurate (√3 × âˆš3)R30° water network, separated by disordered domain boundaries containing largely H-down water. This arrangement allows the water layer to adapt its density and relieve the lateral strain associated with adsorbing water in the optimum flat atop adsorption site. We discuss different possibilities for the structure of these domain walls and compare this strain relief mechanism to the highly ordered, large unit cell structures formed on surfaces such as Pt(111).

Spherical momentum distribution of the protons in hexagonal ice from modeling of inelastic neutron scattering data.

The spherical momentum distribution of the protons in ice is extracted from a high resolution deep inelastic neutron scattering experiment. Following a recent path integral Car-Parrinello molecular dynamics study, data were successfully interpreted in terms of an anisotropic Gaussian model, with a statistical accuracy comparable to that of the model independent scheme used previously, but providing more detailed information on the three dimensional potential energy surface experienced by the proton. A recently proposed theoretical concept is also employed to directly calculate the mean force from the experimental neutron Compton profile, and to evaluate the accuracy required to unambiguously resolve and extract the effective proton potential from the experimental data.

Dynamic Physical Constraints: Emulating Hard Surfaces with High Realism.

In this paper, we present a novel haptic technique for emulating hard surfaces with high realism; such a technique has significant potential utility in certain orthopedic surgery applications such as joint replacement surgery where the goal is to prevent incursions beyond a virtual surface during bone cutting operations. The Dynamic Physical Constraint (DPC) concept uses a unidirectional physical constraint that is actively positioned to limit movement between two manipulator links; the concept is applicable to providing virtual constraints in both 2D and 3D workspaces. Simulation results demonstrate the potential feasibility of the concept, and a prototype device was built for testing. The DPC device provides a convincing sensation of a real, hard virtual surface which can be smoothly tracked when the end effector is in contact with the surface. Incursion across the surface with the prototype was well submillimetric and within the accuracy constraints required for joint replacement applications.

The ultrastructure and histology of the perinotal epidermis and defensive glands of two species of Onchidella (Gastropoda: Pulmonata).

Histology and electron microscopy were used to describe and compare the structure of the perinotal epidermis and defensive glands of two species of shell-less marine Systellommatophora, Onchidella capensis and Onchidella hildae (Onchidiidae). The notum of both species is composed of a layer of epithelial and goblet cells covered by a multi-layered cuticle. Large perinotal multi-cellular glands, that produce thick white sticky mucus when irritated, are located within the sub-epidermal tissue. The glands are composed of several types of large secretory cell filled with products that stain for acidic, sulphated and neutral mucins, and some irregularly shaped support cells that surround a central lumen. The products of the secretory cells are produced by organelles that are basal in position. The entire gland is surrounded by a well-developed capsule of smooth muscle and collagen, and in addition smooth muscle surrounds the cells within the glands. Based on the size of the gland cells, their staining properties, and the appearance of their stored secretions at the transmission electron microscope level, five different types of secretory cells were identified in O. capensis and four in O. hildae. The products of these cells, which are released by holocrine secretion, presumably mix in the lumen of the duct as they are forced out by contraction of the smooth muscle. The structural similarity of these glands to those of siphonariids, suggest that they have a common ancestry.

Finding and defining the ideal patellar resection plane in total knee arthroplasty.

Asymmetric resection of the patella during total knee arthroplasty (TKA) correlates with anterior knee pain, bony impingement and patellar maltracking. Despite this, there is no consensus regarding the desired landmarks; the cut is often done freehand; and there has been no quantitative comparison of proposed resection planes. The objectives of this study were to: determine the intra- and inter-surgeon repeatability of two radiographic resection definitions (medial-divot, MD, and medial-lateral extents, MLE); calculate two additional definitions from the radiographic patellar circumferences (parallel to the anterior surface, ANT, and perpendicular to the anteroposterior tangent points, PERP); compare the clinical resection line to the previous four definitions before and after introducing the MD method clinically; and identify distinguishing features of patellae with better vs. worse resection angles. We hypothesized that the MD method would improve repeatability both radiographically and clinically, that the different radiographic definitions would produce comparable angles, and that we could identify distinguishing features. For the radiographic study, three surgeons drew lines on 40 preoperative X-rays plus 9 interspersed repetitions of 3 of these X-rays. For the clinical study, we compared the patellar resection angle for 20 patients immediately before and after implementing the new method. Given that the clinical goal is to have equal distances from the resection surface to the anterior surface, we compared all results to the ANT definition as the theoretically ideal definition. Confirming the first hypothesis, intra-surgeon repeatability (10 repetitions of 3 X-rays) and inter-surgeon repeatability (3 surgeons x 40 X-rays) were both significantly better using the new MD method compared to the MLE method (p<0.001). Contrary to the second hypothesis, clinical use of the MD method did not improve resection symmetry. Contrary to the third hypothesis, the PERP definition was significantly different from the other three definitions. In agreement with the fourth hypothesis, female patellae and more deformed patella had significantly greater asymmetry (p<0.001). Given the inherent variability shown in drawing the 'patellar horizon', we encourage researchers to draw the line several times and average the results when comparing tilt or the resection angle to this horizon. Based on the distinguishing characteristics of asymmetrically resurfaced patellae in our series, we recommend that clinicians be particularly careful when resecting laterally deformed patellae and the patellae of female patients.

Internal dosimetry: towards harmonisation and coordination of research.

The CONRAD Project is a Coordinated Network for Radiation Dosimetry funded by the European Commission 6th Framework Programme. The activities developed within CONRAD Work Package 5 ('Coordination of Research on Internal Dosimetry') have contributed to improve the harmonisation and reliability in the assessment of internal doses. The tasks carried out included a study of uncertainties and the refinement of the IDEAS Guidelines associated with the evaluation of doses after intakes of radionuclides. The implementation and quality assurance of new biokinetic models for dose assessment and the first attempt to develop a generic dosimetric model for DTPA therapy are important WP5 achievements. Applications of voxel phantoms and Monte Carlo simulations for the assessment of intakes from in vivo measurements were also considered. A Nuclear Emergency Monitoring Network (EUREMON) has been established for the interpretation of monitoring data after accidental or deliberate releases of radionuclides. Finally, WP5 group has worked on the update of the existing IDEAS bibliographic, internal contamination and case evaluation databases. A summary of CONRAD WP5 objectives and results is presented here.

A randomized, comparative study of supervised and unsupervised artesunate-amodiaquine, for the treatment of uncomplicated malaria in Ghana.

Although the use of artesunate-amodiaquine treatment is growing in Africa, data on its effectiveness are limited. In only the second published comparison of supervised and unsupervised treatments with this combination, Ghanaian children with uncomplicated malaria have recently been investigated in an open-label, randomized, comparative study. Children aged 6-120 months attending the Navrongo War Memorial hospital between November 2005 and December 2006 were enrolled if they had uncomplicated Plasmodium falciparum malaria and at least one of their parents/guardians gave their informed consent. Overall, 638 patients were screened, 357 were found to have P. falciparum infection, and 308 of these satisfied the other selection criteria and were enrolled. The subjects were divided randomly into two treatment arms. All the children were scheduled to receive 10 mg amodiaquine/kg and 4 mg artesunate/kg daily for 3 days but only 154 (the 'supervised') were given all their treatments in hospital, with each dose directly observed. Although the other 154 children (the 'unsupervised') were given their first dose in hospital, under supervision, they were then sent home with the tablets they required to complete treatment. Study participation lasted for 28 days, with follow-up on days 3, 7, 14, 21 and 28. During follow-up, axillary temperatures, any emergent signs and symptoms, and concomitant drug consumption were recorded and haemoglobin concentrations and malarial parasitaemias and gametocytaemias were measured. All but seven of the 308 subjects completed the study. At enrolment the subjects had a mean age of 45.0 months, a mean weight of 14.8 kg, a mean axillary temperature of 37.9 degrees C and a geometric mean parasitaemia of 11,367 asexual stages/microl. About 55% of the children investigated were girls. There were no significant baseline difference between the two treatment arms. Although there was also no difference in the clearance of fever and parasitaemia between the two arms by day 14, a supervised child was significantly more likely to show an adequate clinical and parasitological response, by day 21 (91.3% v. 84.1%; P= 0.05) or day 28 (80.0% v. 64.9%; P<0.01), than an unsupervised child. The reported adverse effects following treatment and the trend in haemoglobin recovery were, however, similar in the two arms. Although artesunate-amodiaquine appeared very effective in the treatment of uncomplicated P. falciparum malaria in children, whether supervised or not, it appears that supervised treatment provided stronger prevention against re-infection and recrudescence. At least in the present study, treatment at home, without medical supervision, probably led to relatively poor compliance.