12 research outputs found
Branching of negative streamers in free flight
We recently have shown that a negative streamer in a sufficiently high
homogeneous field can branch spontaneously due to a Laplacian instability,
rather than approach a stationary mode of propagation with fixed radius. In our
previous simulations, the streamer started from a wide initial ionization seed
on the cathode. We here demonstrate in improved simulations that a streamer
emerging from a single electron branches in the same way. In fact, though the
evolving streamer is much more narrow, it branches after an even shorter
propagation distance.Comment: 4 pages, 3 figure
Review of recent results on streamer discharges and discussion of their relevance for sprites and lightning
It is by now well understood that large sprite discharges at the low air
densities of the mesosphere are physically similar to small streamer discharges
in air at standard temperature and pressure. This similarity is based on
Townsend scaling with air density. First the theoretical basis of Townsend
scaling and a list of six possible corrections to scaling are discussed; then
the experimental evidence for the similarity between streamers and sprites is
reviewed. We then discuss how far present sprite and streamer theory has been
developed, and we show how streamer experiments can be interpreted as sprite
simulations. We review those results of recent streamer research that are
relevant for sprites and other forms of atmospheric electricity and discuss
their implications for sprite understanding. These include the large range of
streamer diameters and velocities and the overall 3D morphology with branching,
interaction and reconnection, the dependence on voltage and polarity, the
electron energies in the streamer head and the consecutive chemical efficiency
and hard radiation. New theoretical and experimental results concern
measurements of streamer spectra in air, the density dependence of streamer
heating (hot leaders are unlikely at 80 km altitude and cold streamers are
unlikely in liquids), and a discussion of the influence of magnetic fields on
thermal electrons or on energetic electrons in streamers or sprites.Comment: 38 pages, 4 figures, article accepted for publication in J. Geophys.
Res. - Space Physic
A study of the possibility of sprites in the atmospheres of other planets
Sprites are a spectacular type of transient luminous events (TLE) which occur
above thunderstorms immediately after lightning. They have shapes of giant
jellyfish, carrots or columns and last tens of milliseconds. In Earth's
atmosphere, sprites mostly emit in red and blue wavelengths from excited N2 and
N2+ and span a vertical range between 50 and 90 km above the surface. The
emission spectra, morphology and occurrence heights of sprites reflect the
properties of the planetary atmosphere they inhabit and are related to the
intensity of the initiating parent lightning.. This paper presents results of
theoretical calculations of the expected occurrence heights of sprites above
lightning discharges in the CO2 atmosphere of Venus, the N2 atmosphere of Titan
and the H2-He atmosphere of Jupiter. The expected emission features are
presented and the potential of detecting sprites in planetary atmospheres by
orbiting spacecraft is discussed.Comment: 26 pages, 4 figures, to appear in J. Geophys. Res. - Planet
Integration und Willkommenskultur im ländlichen Raum
INTEGRATION UND WILLKOMMENSKULTUR IM LÄNDLICHEN RAUM
Integration und Willkommenskultur im ländlichen Raum / Klimach, Cornelia (Rights reserved) ( -
Gesundheit fördern in vernetzten Strukturen
Kolip P, Gerken U, Schaefer I, Mühlbach A, Gebhardt B. Gesundheit fördern in vernetzten Strukturen. Weinheim: Beltz Juventa; 2013
Evaluation der Förderinitiative "Aktionsbündnisse Gesunde Lebensstile und Lebenswelten" - Instrumentarium und erste Ergebnisse zur Planungsqualität
Gerken U, Schaefer I, Mühlbach A, Morin Elias G, Gebhardt B, Kolip P. Evaluation der Förderinitiative "Aktionsbündnisse Gesunde Lebensstile und Lebenswelten" - Instrumentarium und erste Ergebnisse zur Planungsqualität. Das Gesundheitswesen. 2012;74(2):112-116
Treatment With Grazoprevir/Elbasvir for Renal Transplant Recipients With Chronic Hepatitis C Virus Infection and Impaired Allograft Function
Background. Direct-acing antiviral agents are highly efficient treatment options for chronic hepatitis C virus (HCV) infection after renal allograft transplantation. Treatment options for patients with impaired graft function remain limited. Therefore, we assessed the effectiveness and safety of grazoprevir/elbasvir therapy for patients with chronic HCV infection and impaired renal allograft function.
Methods. Eleven renal allograft recipients with therapy-naïve HCV genotype (GT) 1a, 1b, or 4 were treated with the fixed-dose combination of elbasvir/grazoprevir without ribavirin for 12 weeks. All recipients exhibited impaired graft function with an average glomerular filtration rate lower than 30 mL/min per 1.73 m2. Clinical data were retrospectively reviewed for renal and liver function parameters. Patients were closely monitored for trough levels of immunosuppressive agents, viral load, laboratory values, and potential adverse effects.
Results. Seven (64%) patients exhibited a rapid virologic response within 4 weeks (HCV GT1a, n = 2; HCV GT1b, n = 5). The other 4 patients exhibited a virologic response within 8 weeks (HCV GT1b, n = 3; HCV GT 4, n = 1). All patients exhibited a sustained virologic response at week 12 after the end of treatment. Clinical measures of liver function improved substantially for all patients. Few adverse effects were reported. Impaired renal allograft function and proteinuria remained stable. For most patients, only moderate adjustments to the tacrolimus dosage were necessary for maintaining sufficient trough levels.
Conclusions. This treatment appears to be safe and effective for renal transplant recipients with impaired allograft function and is a promising treatment option for eradicating HCV infection in this patient population
Tumour stage distribution and survival of malignant melanoma in Germany 2002-2011
Background
Over the past two decades, there has been a rising trend in malignant melanoma incidence worldwide. In 2008, Germany introduced a nationwide skin cancer screening program starting at age 35. The aims of this study were to analyse the distribution of malignant melanoma tumour stages over time, as well as demographic and regional differences in stage distribution and survival of melanoma patients.
Methods
Pooled data from 61 895 malignant melanoma patients diagnosed between 2002 and 2011 and documented in 28 German population-based and hospital-based clinical cancer registries were analysed using descriptive methods, joinpoint regression, logistic regression and relative survival.
Results
The number of annually documented cases increased by 53.2% between 2002 (N = 4 779) and 2011 (N = 7 320). There was a statistically significant continuous positive trend in the proportion of stage UICC I cases diagnosed between 2002 and 2011, compared to a negative trend for stage UICC II. No trends were found for stages UICC III and IV respectively. Age (OR 0.97, 95% CI 0.97–0.97), sex (OR 1.18, 95% CI 1.11–1.25), date of diagnosis (OR 1.05, 95% CI 1.04–1.06), ‘diagnosis during screening’ (OR 3.24, 95% CI 2.50–4.19) and place of residence (OR 1.23, 95% CI 1.16–1.30) had a statistically significant influence on the tumour stage at diagnosis. The overall 5-year relative survival for invasive cases was 83.4% (95% CI 82.8–83.9%).
Conclusions
No distinct changes in the distribution of malignant melanoma tumour stages among those aged 35 and older were seen that could be directly attributed to the introduction of skin cancer screening in 2008.
Emergence of sprite streamers from screening-ionization waves in the lower ionosphere
Sprite discharges above thunderclouds at altitudes of 40-90 km (refs1-5) are usually created by a strong positive cloud-to-ground lightning flash6. Sometimes these sprite discharges emerge from a visible halo 5,7-9, and during the first stage they always propagate downwards and branch on their way 5,7,9-11. Modelling efforts have been restricted to conditions of non-ionized air of constant density and show double-headed sprites12 or sprites starting from metal electrodes, but they do not explain why observations exclusively record sprites that propagate downwards. Here we present simulations with a numerical discharge model on a non-uniform, dynamically adapted computational grid13 to capture the wide range of emerging spatial scales, and we use realistic air and electron densities that vary with altitude. Our model shows a downward-propagating screening-ionization wave in the lower ionosphere that sharpens and collapses into a sprite streamer as it propagates farther down. Streamer velocity, diameter and length until branching agree with observations9 within measuring accuracy. We speculate that sprites generically emerge through the collapse of a wide screening-ionization wave into a sprite streamer, although this wave is only sometimes visible as a luminous halo. © 2009 Macmillan Publishers Limited. All rights reserved