An Ab Initio Approach to the Solar Coronal Heating Problem

We present an ab initio approach to the solar coronal heating problem by modelling a small part of the solar corona in a computational box using a 3D MHD code including realistic physics. The observed solar granular velocity pattern and its amplitude and vorticity power spectra, as reproduced by a weighted Voronoi tessellation method, are used as a boundary condition that generates a Poynting flux in the presence of a magnetic field. The initial magnetic field is a potential extrapolation of a SOHO/MDI high resolution magnetogram, and a standard stratified atmosphere is used as a thermal initial condition. Except for the chromospheric temperature structure, which is kept fixed, the initial conditions are quickly forgotten because the included Spitzer conductivity and radiative cooling function have typical timescales much shorter than the time span of the simulation. After a short initial start up period, the magnetic field is able to dissipate 3-4 10^6 ergs cm^{-2} s^{-1} in a highly intermittent corona, maintaining an average temperature of $\sim 10^6$ K, at coronal density values for which emulated images of the Transition Region And Coronal Explorer(TRACE) 171 and 195 pass bands reproduce observed photon count rates.Comment: 12 pages, 14 figures. Submitted to Ap

Radial and latitudinal dependencies of discontinuities in the solar wind between 0.3 and 19 AU and ?80° and +10°

International audienceDirectional discontinuities (DD) from 5 missions at 7 different locations between 0.3 and 19 AU and ?80° and +10° in the 3D heliosphere are investigated during minimum solar activity. The data are surveyed using the identification criteria of Burlaga (1969) (B) and Tsurutani and Smith (1979) (TS). The rate of occurrence depends linearly on the solar wind velocity caused by the geometric effect of investigating a larger plasma volume if the solar wind velocity ?sw increases. The radial dependence is proportional to r?0.78 (TS criterion) and r?1.28 (B criterion), respectively. This dependence is not only due to an increasing miss rate with increasing distance. The DDs must be unstable or some other physical effect must exist. After normalization of the daily rates to 400 km/s and 1 AU, no dependence on heliographic latitude or on solar wind structures is observable. This means that the DDs are uniformly distributed on a spherical shell. Normalized 64 DD per day are identified with both criteria. But large variations of the daily rate still occur, indicating that other influences must exist. The ratio of the rates of rotational (RDs) and tangential discontinuities (TDs) depends on the solar wind structures. In high speed streams, relatively more RDs exist than in low speed streams. In the inner heliosphere (r r ? over the transition evolves to an increase of smaller ? with increasing distance from the sun. The evolution is yielded by the anisotropic RDs with small ?. The spatial thickness dkm in kilometers increases with distance. The thickness drg normalized to the proton gyro radius decreases by a factor of 50 between 0.3 and 19 AU, from 201.3 rg down to 4.3 rg. In the middle heliosphere, the orientation of the normals relative to the local magnetic field is essentially uniform except for the parallel direction where no DDs occur. This indicates that RDs propagating parallel to B play a special role. In addition, in only a few cases is [?] parallel to [B / ?], which is required by the MHD theory for RDs. The DDs have strongly enhanced values of proton gyro radius rg for ? ~ 90°. In contrast, in the inner heliosphere, only a small increase in rg with ? is observed

Tracking construction material over space and time: Prospective and geo-referenced modeling of building stocks and construction material flows

Construction material plays an increasingly important role in the environmental impacts of buildings. In order to investigate impacts of materials on a building level, we present a bottom-up building stock model that uses three dimensional and geo-referenced building data to determine volumetric information of material stocks in Swiss residential buildings. We used a probabilistic modeling approach to calculate future material flows for the individual buildings. We investigated six scenarios with different assumptions concerning per capita floor area, building stock turnover, and construction material. The Swiss building stock will undergo important structural changes by 2035. While this will lead to a reduced number in new constructions, material flows will increase. Total material inflow decreases by almost half while outflows double. In 2055 the total amount of material in- and outflows are almost equal, which represents an important opportunity to close construction material cycles. Total environmental impacts due to production and disposal of construction material remain relatively stable over time. The cumulated impact is slightly reduced for the wood-based scenario. The scenario with more insulation material leads to slightly higher material-related emissions. An increase per capita floor area or material turnover will lead to a considerable increase in impacts. The new modeling approach overcomes the limitations of previous bottom-up building models and allows for investigating building material flows and stocks in space and time. This supports the development of tailored strategies to reduce the material footprint and environmental impacts of buildings and settlements.ISSN:1088-1980ISSN:1530-929

Skyrmion Lattice in a Chiral Magnet

Skyrmions represent topologically stable field configurations with particle-like properties. We used neutron scattering to observe the spontaneous formation of a two-dimensional lattice of skyrmion lines, a type of magnetic vortices, in the chiral itinerant-electron magnet MnSi. The skyrmion lattice stabilizes at the border between paramagnetism and long-range helimagnetic order perpendicular to a small applied magnetic field regardless of the direction of the magnetic field relative to the atomic lattice. Our study experimentally establishes magnetic materials lacking inversion symmetry as an arena for new forms of crystalline order composed of topologically stable spin states

Automated claustrum segmentation in human brain MRI using deep learning

In the last two decades, neuroscience has produced intriguing evidence for a central role of the claustrum in mammalian forebrain structure and function. However, relatively few in vivo studies of the claustrum exist in humans. A reason for this may be the delicate and sheet-like structure of the claustrum lying between the insular cortex and the putamen, which makes it not amenable to conventional segmentation methods. Recently, Deep Learning (DL) based approaches have been successfully introduced for automated segmentation of complex, subcortical brain structures. In the following, we present a multi-view DL-based approach to segment the claustrum in T1-weighted MRI scans. We trained and evaluated the proposed method in 181 individuals, using bilateral manual claustrum annotations by an expert neuroradiologist as reference standard. Cross-validation experiments yielded median volumetric similarity, robust Hausdorff distance, and Dice score of 93.3%, 1.41 mm, and 71.8%, respectively, representing equal or superior segmentation performance compared to human intra-rater reliability. The leave-one-scanner-out evaluation showed good transferability of the algorithm to images from unseen scanners at slightly inferior performance. Furthermore, we found that DL-based claustrum segmentation benefits from multi-view information and requires a sample size of around 75 MRI scans in the training set. We conclude that the developed algorithm allows for robust automated claustrum segmentation and thus yields considerable potential for facilitating MRI-based research of the human claustrum. The software and models of our method are made publicly available

Production and Operating Strategies with Focus on the Efficiency of the Public Service

This study focuses on the strategy for efficiency in production and operation in the services of a people management sector in a public judicial organization. Identified the need to innovate practices to achieve excellence, the U and Contingency Theories were used to reach proposed objectives. The general objective was to study the strategy for efficiency in production and operation in the Department of Personnel Management, and as specific objectives characterize the strategy of efficiency in production and operation, perform the SWOT analysis on the practices of the process operation and suggest innovation for efficiency of the productive process. The question asked was: What is the strategy for efficiency in the results of the production and operation of the services provided? To achieve the objectives and answer the question asked was qualitative research. Data collection was obtained through exploratory research in loco, followed by a descriptive phase through field research, using open interviews and application of query forms. Consequently, SWOT analysis and the DMAIC model were applied to finally suggest innovation. The proposed objectives were reached, where the contingency approach with a behavioral focus and guided leadership was envisaged. The question was answered and the motivation for suggestion of innovations was firmly established in the process of presencing and knowledge management of Theory U. It was concluded that the strategy for efficiency in results should focus on the dynamic organizational complexity, acting in an integrated way, developing abilities of employees until then unincorporated, allowing the evolution of the flow of knowledge management, empowering skills

Laser treatment in diabetic retinopathy

Diabetic retinopathy is a leading cause of visual impairment and blindness in developed countries due to macular edema and proliferative diabetic retinopathy (PDR). For both complications laser treatment may offer proven therapy: the Diabetic Retinopathy Study demonstrated that panretinal scatter photocoagulation reduces the risk of severe visual loss by >= 50% in eyes with high-risk characteristics. Pan-retinal scatter coagulation may also be beneficial in other PDR and severe nonproliferative diabetic retinopathy (NPDR) under certain conditions. For clinically significant macular edema the Early Treatment of Diabetic Retinopathy Study could show that immediate focal laser photocoagulation reduces the risk of moderate visual loss by at least 50%. When and how to perform laser treatment is described in detail, offering a proven treatment for many problems associated with diabetic retinopathy based on a high evidence level. Copyright (c) 2007 S. Karger AG, Basel

Cityscapes without figures: geophysics, computing and the future of urban studies

Ye

Standardised cement augmentation of the PFNA using a perforated blade: A new technique and preliminary clinical results. A prospective multicentre trial

Producción CientíficaPertrochanteric fractures are a rising major health-care problem in the elderly and their operative stabilisation techniques are still under discussion. Furthermore, complications like cut-out are reported to be high and implant failure often is associated with poor bone quality. The PFNA1 with perforated blade offers a possibility for standardised cement augmentation using a polymethylmethacrylate (PMMA) cement which is injected through the perforated blade to enlarge the load-bearing surface and to diminish the stresses on the trabecular bone. The current prospective multicentre study was undertaken to evaluate the technical performance and the early clinical results of this new device. In nine European clinics, 59 patients (45 female, mean age 84.5 years) suffering from an osteoporotic pertrochanteric fracture (Arbeitsgemeinschaft fu¨ r Osteosynthesefragen, AO-31) were treated with the augmented PFNA1. Primary objectives were assessment of operative and postoperative complications, whereas activities of daily living, pain, mobility and radiologic parameters, such as cement distribution around the blade and the cortical thickness index, were secondary objectives. The mean follow-up time was 4 months where we observed callus healing in all cases. The surgical complication rate was 3.4% with no complication related to the cement augmentation. More than onehalf of the patients reached their prefracture mobility level within the study period. A mean volume of 4.2 ml of cement was injected. We did not find any cut-out, cut through, unexpected blade migration, implant loosening or implant breakage within the study period. Our findings lead us to conclude that the standardised cement augmentation using the perforated blade for pertrochanteric fracture fixation enhances the implant anchorage within the head–neck fragment and leads to good functional results