Self-Assembly of Patchy Particles into Polymer Chains: A Parameter-Free Comparison between Wertheim Theory and Monte Carlo Simulation

We numerically study a simple fluid composed of particles having a hard-core repulsion, complemented by two short-ranged attractive (sticky) spots at the particle poles, which provides a simple model for equilibrium polymerization of linear chains. The simplicity of the model allows for a close comparison, with no fitting parameters, between simulations and theoretical predictions based on the Wertheim perturbation theory, a unique framework for the analytic prediction of the properties of self-assembling particle systems in terms of molecular parameter and liquid state correlation functions. This theory has not been subjected to stringent tests against simulation data for ordering across the polymerization transition. We numerically determine many of the thermodynamic properties governing this basic form of self-assembly (energy per particle, order parameter or average fraction of particles in the associated state, average chain length, chain length distribution, average end-to-end distance of the chains, and the static structure factor) and find that predictions of the Wertheim theory accord remarkably well with the simulation results

The Composition of the Interstellar Medium towards the Lockman Hole. HI, UV and X-ray observations

The Lockman Hole is well known as the region with the lowest neutral atomic hydrogen colum density on the entire sky. We present an analysis of the soft X-ray background radiation towards the Lockman Hole using ROSAT all-sky survey data. This data is correlated with the Leiden/Dwingeloo survey (Galactic HI 21cm-line emission) in order to model the soft X-ray background by using radiative transfer calculations for four ROSAT energy bands simultaneously. It turns out, that an important gas fraction, ranging between 20-50%,of the X-ray absorbing material is not entirely traced by the HI but is in the form of ionized hydrogen. Far-ultraviolet absorption line measurements by FUSE are consistent with this finding and support an ionized hydrogen component towards the Lockman Hole.Comment: 11 pages, 11 figures, Accepted for Publication in Astronomy & Astrophysics, For full resolution images, see http://www.astro.uni-bonn.de/~mkappes/pub/ms3506.pd

Localized direction selective responses in the dendrites of visual interneurons of the fly

<p>Abstract</p> <p>Background</p> <p>The various tasks of visual systems, including course control, collision avoidance and the detection of small objects, require at the neuronal level the dendritic integration and subsequent processing of many spatially distributed visual motion inputs. While much is known about the pooled output in these systems, as in the medial superior temporal cortex of monkeys or in the lobula plate of the insect visual system, the motion tuning of the elements that provide the input has yet received little attention. In order to visualize the motion tuning of these inputs we examined the dendritic activation patterns of neurons that are selective for the characteristic patterns of wide-field motion, the lobula-plate tangential cells (LPTCs) of the blowfly. These neurons are known to sample direction-selective motion information from large parts of the visual field and combine these signals into axonal and dendro-dendritic outputs.</p> <p>Results</p> <p>Fluorescence imaging of intracellular calcium concentration allowed us to take a direct look at the local dendritic activity and the resulting local preferred directions in LPTC dendrites during activation by wide-field motion in different directions. These 'calcium response fields' resembled a retinotopic dendritic map of local preferred directions in the receptive field, the layout of which is a distinguishing feature of different LPTCs.</p> <p>Conclusions</p> <p>Our study reveals how neurons acquire selectivity for distinct visual motion patterns by dendritic integration of the local inputs with different preferred directions. With their spatial layout of directional responses, the dendrites of the LPTCs we investigated thus served as matched filters for wide-field motion patterns.</p

Ensaio regional de linhagens de arroz irrigado do Programa de Melhoramento Genético da Embrapa no RS - safra 2008/09.

O Ensaio Regional de linhagens de arroz irrigado visa selecionar genótipos que apresentem alta adaptabilidade e estabilidade aos diversos ambientes em que são cultivadas e que expressem elevado rendimento de grãos, associado à características agronômicas, industriais e culinárias adequadas. Este experimento teve como objetivo avaliar linhagens do programa da Embrapa no Ensaio Regional de Rendimento

Desempenho de linhagens elites de arroz irrigado de ciclo precoce do Programa de Melhoramento Genético da Embrapa em ensaios VCU no RS - safra 2008/09.

O objetivo deste trabalho foi avaliar o desempenho em rendimento de grãos e características agronômicas de interesse das linhagens de ciclo precoce geradas pelo programa de melhoramento genético da Embrapa, em diferentes regiões orizícolas do Rio Grande do Sul, para verificar a possibilidade de indicação de novas cultivares

Risk-based early prevention in comparison with routine prevention of dental caries: a 7-year follow-up of a controlled clinical trial; clinical and economic aspects

BACKGROUND: The results in an earlier study with 2–5-year-old children indicated that, in comparison with conventional prevention, a risk-based prevention programme was effective in reducing dental caries in a low-caries community. The aim of the present study was to examine the clinical and economic findings seven years after the cessation of the targeted programme, from the perspective of public health care. METHODS: The present material was collected from the dental records of the public health care centres, and included all dental visits after the 5-year examination until the 12-year examination. The groups were compared in relation to clinically detected caries at the age of 12 years, the number of dental visits needed from 5 to 12 years of age, and the estimation of running costs during these years. Statistical analyses included univariate analysis of variance, and calculation of absolute risk reduction and number needed to treat (NNT) values. RESULTS: At the age of 12 years, DMF was significantly related to the risk category determined ten years earlier, in both study groups. In the risk-based group, the absolute risk reduction for caries in permanent dentition was 0.13 (95% confidence interval 0.06 – 0.21), and the associated NNT value was 8 (95% confidence interval 5 – 17). The total number of preventive, as well as restorative visits was lower in the risk-based than in the routine prevention group. The findings indicate that early risk-based prevention can be correctly targeted, clinically effective, and economically profitable also from the long-term point of view. CONCLUSION: Early prevention of dental caries also has long-term benefits in a 7-year follow-up perspective. This seems to hold true as regards targeting, as well as clinical and economic effectiveness. Success in risk-based prevention enables successful work division, and consequently, economic effectiveness

Contact dermatitis and other skin conditions in instrumental musicians

BACKGROUND: The skin is important in the positioning and playing of a musical instrument. During practicing and performing there is a permanent more or less intense contact between the instrument and the musician's skin. Apart from aggravation of predisposed skin diseases (e.g., atopic eczema or psoriasis) due to music-making, specific dermatologic conditions may develop that are directly caused by playing a musical instrument. METHODS: To perform a systematic review on instrument-related skin diseases in musicians we searched the PubMed database without time limits. Furthermore we studied the online bibliography "Occupational diseases of performing artist. A performing arts medicine bibliography. October, 2003" and checked references of all selected articles for relevant papers. RESULTS: The most prevalent skin disorders of instrumental musicians, in particular string instrumentalists (e.g., violinists, cellists, guitarists), woodwind players (e.g., flautists, clarinetists), and brass instrumentalists (e.g., trumpeters), include a variety of allergic contact sensitizations (e.g., colophony, nickel, and exotic woods) and irritant (physical-chemical noxae) skin conditions whose clinical presentation and localization are usually specific for the instrument used (e.g., "fiddler's neck", "cellist's chest", "guitar nipple", "flautist's chin"). Apart from common callosities and "occupational marks" (e.g., "Garrod's pads") more or less severe skin injuries may occur in musical instrumentalists, in particular acute and chronic wounds including their complications. Skin infections such as herpes labialis seem to be a more common skin problem in woodwind and brass instrumentalists. CONCLUSIONS: Skin conditions may be a significant problem not only in professional instrumentalists, but also in musicians of all ages and ability. Although not life threatening they may lead to impaired performance and occupational hazard. Unfortunately, epidemiological investigations have exclusively been performed on orchestra musicians, though the prevalence of instrument-related skin conditions in other musician groups (e.g., jazz and rock musicians) is also of interest. The practicing clinician should be aware of the special dermatologic problems unique to the musical instrumentalist. Moreover awareness among musicians needs to be raised, as proper technique and conditioning may help to prevent affection of performance and occupational impairment

Desempenho de linhagens elite de arroz irrigado de ciclo médio do Programa de Melhoramento Genético da Embrapa em ensaios VCU no RS - safra 2008/09.

O objetivo deste trabalho foi avaliar o desempenho das linhagens geradas pelo Programa de Melhoramento Genético da Embrapa, em diferente regiões orizícolas do Rio Grande do Sul, visando possível lançamento de novas cultivares