Dynamics of polymer bridge formation and disruption

In this Letter we show, with colloidal probe AFM measurements, that the formation and subsequent disruption of polymer bridges between two solid surfaces is characterized by slow relaxation times. This is due to the retardation of polymer dynamics near a surface. For colloidal particles, that are in constant (Brownian) motion, kinetic aspects are key. To understand these effects, we develop a model of polymer bridging and bridge disruption that agrees quantitatively with our experiment

Natuurherstelplan Zeeschelde: drie mogelijke inrichtingsvarianten

The Schelde estuary, with its tidal flats and marshes along an uninterrupted salinity gradient from a marine to a fresh water system, is almost unique in Europe. On top of its important contributions towards national and international biodiversity it performs multiple socio-economic functions of vital importance. To combine all these functions in a sustainable way an integrated management is needed, based on the comprehension of its functioning and aimed at an optimal tuning of all processes and functions involved. With this report we hope to initiate a productive dialogue, one step ahead towards the integrated management of the Schelde estuary. It forms part of an agreement between the Administration of Waterways and Water infrastructure and some Flemish environmental organisations. The agreement was concluded as a result of protest actions against the deepening of the Westerschelde and it should result in a fruitful cooperation towards a more integrated management for the Flemish waterways. This pilot study explores possibilities to couple ecological rehabilitation and the creation of sustainable river related nature with the security measures of the SIGMA plan (a protection plan against floods) and the navigation requisites for the Zeeschelde. It also integrates the proposals from MEIRE et al. (1992), HOFFMANN (1993) and the AMIS study (general environmental impact assessment of the Sigmaplan). The decreased self-cleaning capacity of the river, the highly fragmented ecologica1 infrastructure, the accelerated sedimentation and increased tidal amplitude inhibit a proper functioning of the estuarine ecosystem. They are combined consequences of land reclamation, channelisation, land use and water management in the catchment area, discharge manipulations and the general sea level rise. They bring about the ecosystems limited carrying capacity and resilience, its increased contribution to the eutrofication of the North Sea, impoverished biotic communities, flood hazzard and reduced navigability. Possible restoration measures can be defined at three different levels: expansion of the intertidal area through dike removal and levelling of raised grounds outside the dikes, enhancement of contacts between the river and its catchment through ecological adjustments of dike structures and restoration of the contact between waters on both sides of the dike, structural and functional restoration of inland territories. Application of these measures can yield a more complete ecological infrastructure, improved migration possibilities for biota, more diverse biotic communities, limited input of energy and matter towards the river, enhanced self-cleaning capacity and retention, reduced contribution towards the eutrofication of the North Sea, increased volume and a slow down of the sedimentation rate. According to the adhered vision for the development of the estuary, the proposed restoration measures can be applied in different combinations to enhance its ecological rehabilitation/restoration. In this report three different scenario's are traced out, each of which set a different direction for the area' s development. The first two scenario's aim at a coherent development direction for the estuary, each from a different viewpoint with respect to hydrodynamics, one of the most important guiding determinants for the estuarine gradiënts along which different biotic communities follow upon each other in space and time. The scenario 'Space for the Estuary' leaves as much space as possible for the estuary to allow the tidal wave to die out laterally and longitudinally. Processes, which are steered by tidal dynamics gradually, merge into processes, which are directed by hydrodynamics of precipitation, ground and surface water. In those areas where estuarine expansion is not possible or advisable the attention is rather focused on inland nature development. The full realisation of this scenario would result in a total of 3.544 ha tidal wetland, 846 ha controlled inundation area with a reduced tidal regime and 3.472 ha of inland wetlands. The surface of functional inundation areas would vary between minimum 1.207 and maximum 3.907 ha. The scenario' Attention for the Alluvium' judges that the greater part of this alluvium in the Schelde River Basin did not come into existence under tidal influence but through seasonal floods from upstream areas. It rather aims at the restoration of the alluvial plains as nutrient-rich wetlands in a continuous transition towards higher and more dry, nutrient -poor soils. Still, in this scenario attention is also paid to estuarine rehabilitation outside the dikes. The full realisation of this scenario would result in a total of 1.663 ha tidal wetland, 774 ha controlled inundation area with a reduced tidal regime and 5.324 ha of inland wetlands. The surface of functional inundation areas would vary between minimum 1.787 and maximum 5.687 ha.The scenario ‘Funtional and Structural Basic Quality' does not really adhere to a preconceived vision for the development of the estuary. The proposed measures mainly contain the ecological adaptations to the Sigmaprojects as they were suggested in the environmental impact assessment (AMIS-45) and the ecological restoration of all raised fields and dumping grounds outside the dikes. Implementation of this scenario would suffice for the ecological rehabilitation of the estuary, it would at the very most maintain a structural and functional basic quality with the completion of all sigmaprojects, the deepening of the Westerschelde and the structural adaptations of the Zeeschelde to contemporary navigation demands. The full realisation would result in a total of 1.878 ha tidal wetland, 496 ha controlled inundation area with a reduced tidal regime and 1.075 ha of inland wetlands. The surface of functional inundation areas would vary between minimum 1.508 and maximum 1.694 ha. Not any of these scenario's constitutes a ready-made blueprint for a ‘restored’ Zeeschelde. They picture a few possible designs for the estuary which, by means of models, can be tested for their probable impacts on the ecosystem, its functioning and potential opportunities for ecotopes, species and biotic communities. As such they should be considered as a contribution towards the social discussion that, hopefully, will yield an integrated ecosystem vision in the end

Resolved Mid-Infrared Emission Around AB Aur and V892 Tau with Adaptive Optics Nulling Interferometric Observations

We present the results of adaptive optics nulling interferometric observations of two Herbig Ae stars, AB Aur and V892 Tau. Our observations at 10.3 microns show resolved circumstellar emission from both sources. Further analysis of the AB Aur emission suggests that there is an inclined disk surrounding the star. The diameter of the disk is derived to be 24 to 30 AU with an inclination of 45 to 65 degrees from face-on, and a major-axis PA of 30 +/- 15 degrees (E of N). Differences in the physical characteristics between the mid-IR emission and emission at other wavelengths (near-IR and millimeter), found in previous studies, suggest a complex structure for AB Aur's circumstellar environment, which may not be explained by a disk alone. The similarity in the observed size of AB Aur's resolved emission and that of another Herbig Ae star, HD 100546, is likely coincidental, as their respective evolutionary states and spectral energy distributions suggest significantly different circumstellar environments.Comment: 11 pages, 1 figure, Accepted for publication in ApJ Letter

Biodiversiteit op de Scheldeschorren

The tidal marshes along the Scheldt estuary are rather unique in Europe, because they still exist along the complete salinity gradient. Key ecological factors for the vegetation are salinity, tidal regime and current and historical management. A general portrait with the most characterising plant species as well as a succession scheme are presented for salt, brackish and fresh tidal marshes separately, because they have few plant species and vegetation types in common. Tidal regime changes as a combined effect of sea level rise and the channel deepening in the Westerscheldt. This affects the marsh vegetation. Biodiversity patterns and factors affecting the distribution of species on the tidal marshes are discussed for plants, gastropodes, arthropodes and birds. In general the number of species on the tidal marshes increases from salt to fresh water and from higher to lower inundation frequencies. However salt and brackish marshes accommodate relatively more specific, rare and vulnerable species. Faunal communities are much less known and understood as compared to vegetation and need more integrated monitoring

Tuberculosis and Hepatic Steatosis Are Prevalent Liver Pathology Findings among HIV-Infected Patients in South Africa

Liver disease epidemiology in sub-Saharan Africa has shifted as a result of HIV and the increased use of antiretroviral therapy leading to a need for updated data on common causes of liver disease. We retrospectively reviewed records from all hospitalized patients who had liver biopsy at a single hospital in South Africa from 2001 to 2009 and compared diagnosis by HIV status. During the period of study 262 patients had liver biopsy, 108 (41%) were HIV-infected, 25 (10%) were HIV-sero-negative, and 129 (49%) had unknown or unrecorded HIV status. Overall 81% of biopsies provided additional diagnostic data. Malignancy was the most common finding reported on 56 (21%) biopsies followed by granuloma or TB, hepatic steatosis, and fibrosis or cirrhosis. HIV-infected patients were more likely to have granulomas and steatosis. Half of patients with granulomas were already on TB treatment, suggesting paradoxical reactions or drug induced liver injury may have been important causes of liver inflammation among these patients. We note that TB, paradoxical reactions during TB treatment, possible drug induced liver injury, and hepatic steatosis are important causes of liver pathology among HIV-infected hospitalized patients with unclear etiology of liver disease after initial assessment. Among HIV sero-negative patients, malignancy was the major cause of liver disease. Our findings re-enforce the importance of TB as a diagnosis among HIV-infected individuals.\ud \u

Variability in disease phenotypes within a single PRNP genotype suggests the existence of multiple natural sheep scarpie strains within Europe

Variability of pathological phenotypes within classical sheep scrapie cases has been reported for some time, but in many instances it has been attributed to differences in the PRNP genotype of the host. To address this issue we have examined by immunohistochemistry (IHC) and Western blotting (WB) for the disease-associated form of the prion protein (PrPd), the brains of 23 sheep from five European countries, all of which were of the same ARQ/ARQ genotype. As a result of IHC examinations, sheep were distributed into five groups with different phenotypes and the groups were the same regardless of the scoring method used, ‘long’ or ‘short’ PrPd profiling. The groups made did not respond to the geographical origin of the cases and did not correlate with the vacuolar lesion profiles, which showed a high individual variability. Discriminatory IHC and WB methods coincided to detect a ‘CH1641-like’ case but otherwise correlated poorly in the classification of disease phenotypes. No other polymorphisms of the PRNP gene were found that could account for the pathological differences, except perhaps for a sheep from Spain with a mutation at codon 103 and a unique pathological phenotype. Preliminary evidence indicates that those different IHC phenotypes correlate with distinct biological properties on bioassay, suggesting that they are indicative of strain diversity. We therefore conclude that natural scrapie strains exist and that they can be revealed by detailed pathological examinations, which can be harmonized between laboratories to produce comparable results

Relativistic electronic dressing in laser-assisted ionization of atomic hydrogen by electron impact

Within the framework of the coplanar binary geometry where it is justified to use plane wave solutions for the study of the $(e,2e)$ reaction and in the presence of a circularly polarized laser field, we introduce as a first step the DVRPWBA1 (Dirac-Volkov Plane Wave Born Approximation1) where we take into account only the relativistic dressing of the incident and scattered electrons. Then, we introduce the DVRPWBA2 (Dirac-Volkov Plane Wave Born Approximation2) where we take totally into account the relativistic dressing of the incident, scattered and ejected electrons. We then compare the corresponding triple differential cross sections for laser-assisted ionization of atomic hydrogen by electron impact both for the non relativistic and the relativistic regime.Comment: 18 pages, Latex, 7 figure

A stitch in time: Efficient computation of genomic DNA melting bubbles

Background: It is of biological interest to make genome-wide predictions of the locations of DNA melting bubbles using statistical mechanics models. Computationally, this poses the challenge that a generic search through all combinations of bubble starts and ends is quadratic. Results: An efficient algorithm is described, which shows that the time complexity of the task is O(NlogN) rather than quadratic. The algorithm exploits that bubble lengths may be limited, but without a prior assumption of a maximal bubble length. No approximations, such as windowing, have been introduced to reduce the time complexity. More than just finding the bubbles, the algorithm produces a stitch profile, which is a probabilistic graphical model of bubbles and helical regions. The algorithm applies a probability peak finding method based on a hierarchical analysis of the energy barriers in the Poland-Scheraga model. Conclusions: Exact and fast computation of genomic stitch profiles is thus feasible. Sequences of several megabases have been computed, only limited by computer memory. Possible applications are the genome-wide comparisons of bubbles with promotors, TSS, viral integration sites, and other melting-related regions.Comment: 16 pages, 10 figure

A Telephone- and Text Message-Based Telemedicine Concept for Patients with Mental Health Disorders: Results of a Randomized Controlled Trial

Background: A telemedicine care concept based on telephone contacts and individualized text messages was developed for patients with mental disorders to continue treatment after therapy in a psychiatric day hospital. The primary objective of this study was to evaluate the effectiveness of the telemedicine interventions. Methods: The study had a 3-armed, randomized design with 2 intervention arms (intervention 1: telephone contacts; intervention 2: telephone contacts and short text messages; both took place over a period of 6 months and in addition to usual care), and a control group with usual care. Primary outcomes were 18-item Brief Symptom Inventory (BSI-18) scores for anxiety, depression and somatization. All participants were recruited from psychiatric day hospitals. The study was registered in the German Clinical Trials Register (DRKS00000662). Results: 113 participants were analyzed 6 months after starting the intervention. The average BSI-18 anxiety score after 6 months was -2.04 points lower in intervention group 2 than in the control group (p value: 0.042). The difference in BSI depression score between these two groups was marginally significant (p value: 0.1), with an average treatment effect of -1.73. In an exploratory sensitivity analysis restricted to the 75% of patients with the highest symptom scores at baseline, intervention group 1 yielded a significant effect for anxiety and depression compared to the control group (p = 0.036 and 0.046, respectively). Conclusions: Telemedicine provides a novel option in psychiatric ambulatory care with statistically significant effects on anxiety. A positive tendency was observed for depression, especially in cases with higher symptom load at baseline