3,162 research outputs found
The Supernova Remnant G296.7-0.9 in X-rays
Aims: We present a detailed study of the supernova remnant (SNR) G296.7-0.9
in the 0.2-12 keV X-ray band.
Methods: Using data from XMM-Newton we performed a spectro-imaging analysis
of G296.7-0.9 in order to deduce the basic parameters of the remnant and to
search for evidence of a young neutron star associated with it.
Results: In X-rays the remnant is characterized by a bright arc located in
the south-west direction. Its X-ray spectrum can best be described by an
absorbed non-equilibrium collisional plasma model with a hydrogen density of
N_H=1.24_{-0.05}^{+0.07} x 10^{22} cm^{-2} and a plasma temperature of
6.2^{+0.9}_{-0.8} million Kelvin. The analysis revealed a remnant age of 5800
to 7600 years and a distance of 9.8_{-0.7}^{+1.1} kpc. The latter suggests a
spatial connection with a close-by HII region. We did not find evidence for a
young neutron star associated with the remnant.Comment: accepted by A&A, 5 pages, 2 figure
The Maricunga Belt (chilean Precordillera) and its hydrothermal alteration zones as revealed by multispectral remote sensing and field studies
Remote sensing techniques offer a unique chance to analyse and map wide or nearly inaccessable areas under certain geoscientific aspects in relatively short time and at low cost. Therefore geological field campaigns together with multispectral image analysis were carried out for the Maricunga Belt in the chilenean Precordillera, south of the regional mining settlements San Salvador and Potrerillos (Atacama). On the basis of Landsat-TM 5, ASTER, radar-based DGM-data and field mapping/sampling the lithological/structural characteristics of several OH-bearing hydrothermal alteration zones of mostly Neogene age have been investigated because of their high value for future exploration. The often unknown regional tectonic framework which seems to have controlled the alteration dimensions are also discussed. In order to obtain reasonable lithological classification criteria for the remote sensing data fundamental statistical selection rules like the optimum index factor (OIF) were applied to the combination of single TM bands. Furthermore specific band ratios (5/7; 5/4, 5/1) and principal components were utilized to enhance the spectral properties of the argillized, bleached clay- and/or silica-rich alteration surfaces. Additional spectral measurements were carried out for each representative lithological unit of the alteration zones to estimate the quality of the calculated classifications/ratios for geological mapping. In some cases complementary geochemical data has been studied in order to obtain direct clues for understanding the type of some detected hydrothermal alterations. Finally the achieved data was compiled in a geological map which shows more than 20 hydrothermally altered surfaces in relation to the regional geology and the specific tectonic framework. The influence of three major fault systems (the N-S orientated West Fissure System, the NE-SW orientated Inca De Oro System and a poorly described NW-SE System) for the setting of the alterations seems to be obvious
Structural analysis of the Arunta Block and Amadeus Basin (Central Australia) by means of digital remote sensing techniques and field data
Der proterozoische Arunta Block und das altpalĂ€ozoische Amadeus Basin zeichnen sich durch jeweils eigenstĂ€ndige lithologische Abfolgen und tektonische Deformationstypen aus. Der Kontaktbereich dieser intrakratonen Blöcke wirft seit Jahren Diskussionen hinsichtlich des tektonischen Baus auf: von hypothetischen weitreichenden Ăberschiebungsdecken (nappes) bis hin zu einfachen kleindimensionierten Störungen oder Verschleppungen (thrusts). Im Rahmen dieser Arbeit wird versucht, diese Elemente anhand von multispektralen Landsat-TM-Daten und Analysen von Luftbildern und ERS-1-Daten makroskopisch zu erfassen und zu deuten. Es ist möglich, Gesteinseinheiten und die unterschiedlichen Deformationsstile reprĂ€sentativer Untersuchungsgebiete zu differenzieren, sowie auf der Basis der topographischenKarten ein digitales Höhenmodell der Region zu erstellen, das die ZusammenhĂ€nge zwischen morphologischen Gegebenheiten vor Ort und imSatellitenbild in Bezug auf die Verbreitung von Lithologien und Störungszonen verdeutlicht. Auf diese Weise entsteht das Bild eines komplexen tektonischen Spannungsfeldes, das fĂŒr jeden intrakratonen Block individuelle, zeitlich voneinander getrennt wirkende Ereignisse als Auslöser fĂŒr die anzutreffenden Strukturen vorsieht.The Proterozoic Arunta Block and the younger late Palaeozoic Amadeus Basin each show significant lithological sequences and tectonic deformation styles. Since years the contact zone of these intracratonic blocks raises controversial discussions concerning its tectonic origin: from hypothetic widespread nappes to simple faults and thrusts of smaller dimension everything is taken into consideration. Within the scope of this paper it is attempted to detect their macroscopic pattern by applying multispectral and further remote sensing data analysis of aerial photographs, Landsat-TM and ERS-1data. It is possible to distinguish rock units and different deformation styles of representative areas as well as to create a digital elevation model of the region on the basis of topographic maps that elucidates the coherence of morphological features in place and in the satellite image as far as the propagation of lithologies and fault zones is concerned. It arises the picture of a complex tectonictension field, that contains individual tectonic events separated by time for each structure within the intracratonic blocks
Die Shoemaker und Strangways-Krater: Zwei Impaktstrukturen in Australien in der GIS-gestĂŒtzten Analyse von Fernerkundungs- und GelĂ€ndedaten
Die BerĂŒcksichtigung von Fernerkundungsdaten in geologischen
Informationssystemen (GIS) bietet fĂŒr die Erkundung von terrestrischen Impaktstrukturen neuartige
Möglichkeiten. Am Beispiel der komplexen proterozoischen Impaktkrater Shoemaker und Strangways
wird gezeigt, dass die Einbindung multispektraler Landsat TM-Daten, Radardaten (ERS-2),
geophysikalischer Daten (Aeromagnetik, Aeroradiometrie), GelÀndebefunden und bereits
vorhandener geologischer Karteninformation in ein GIS raumbezogene Abfragen gestattet und z.T.
WissenslĂŒcken schlieĂen kann. So lassen sich ursprĂŒngliche Kraterdurchmesser und Erosionsniveaus
fĂŒr beide Strukturen besser abschĂ€tzen
Endogenous, or therapeutically induced, type I interferon responses differentially modulate Th1/Th17-mediated autoimmunity in the CNS
Different viruses trigger pattern recognition receptor systems, such as Toll-like receptors or cytosolic RIG-I like helicases (RLH), and thus induce early type I interferon (IFN-I) responses. Such responses may confer protection until adaptive immunity is activated to an extent that the pathogen can be eradicated. Interestingly, the same innate immune mechanisms that are relevant for early pathogen defense have a role in ameliorating experimental autoimmune encephalomyelitis (EAE), a rodent model of human multiple sclerosis. We and others found that mice devoid of a component of the IFN-I receptor (Ifnar1â/â) showed significantly enhanced autoimmune disease of the central nervous system (CNS). A detailed analysis revealed that in wild-type mice IFN-I triggering of myeloid cells was instrumental in reducing brain damage. A more recent study indicated that similar to Ifnar1â/â mice, RLH-signaling-deficient mice showed enhanced autoimmune disease of the CNS as well. Moreover, when peripherally treated with synthetic RLH ligands wild-type animals with EAE disease showed reduced clinical scores. Under such conditions, IFN-I receptor triggering of dendritic cells had a crucial role. The therapeutic effect of treatment with RLH ligands was associated with negative regulation of Th1 and Th17 T-cell responses within the CNS. These experiments are consistent with the hypothesis that spatiotemporal conditions of, and cell types involved in, disease-ameliorating IFN-I responses differ significantly, depending on whether they were endogenously induced in the context of EAE pathogenesis within the CNS or upon therapeutic RLH triggering in the periphery. It is attractive to speculate that RLH triggering represents a new strategy to treat multiple sclerosis by stimulating endogenous immunoregulatory IFN-I responses
Tuning of the Gap in a Laughlin-Bychkov-Rashba Incompressible Liquid
We report on our investigation of the influence of Bychkov-Rashba spin-orbit
interaction (SOI) on the incompressible Laughlin state. We find that
experimentally obtainable values of the spin-orbit coupling strength can induce
as much as a 25% increase in the quasiparticle-quasihole gap Eg at low magnetic
fields in InAs, thereby increasing the stability of the liquid state. The
SOI-modulated enhancement of Eg is also significant for filling factors 1/5 and
1/7, where the FQH state is usually weak. This raises the intriguing
possibility of tuning, via the SO coupling strength, the liquid to solid
transition to much lower densities.Comment: 4 pages, 3 figure
Field work in the Outback:Planning and processing a geological diploma mapping in Central Australia
Der Finke Gorge National Park liegt im Zentrum des Australischen Kontinents. Aufgrund der groĂen Dimensionen des Landes sind weite Teile nur unzureichend und kleinmaĂstĂ€blich geologisch kartiert. Im Rahmen dieser Arbeit sollte der Versuch unternommen werden, den National Park unter Zuhilfenahme von Fernerkundungsdaten, wie Landsat TM-, ASTER-Daten, hochauflösenden stereographischen Luftbildern, digitalen GelĂ€ndemodellen (DGM) und Vegetationskarten groĂmaĂstĂ€blich zu kartieren (1:10000). Die vorliegende Arbeit knĂŒpft an die Untersuchungen von BUDE & PRINZ (2003) an und soll diese durch GelĂ€ndebefunde ergĂ€nzen. DarĂŒber hinaus soll der Bericht Erfahrungen hinsichtlich der Planung und DurchfĂŒhrung einer derartigen geologischen GelĂ€ndearbeit vermitteln.The Finke Gorge National Park is situated in the centre of the Australian continent. Due to the great dimension of the outback, most of its parts are mapped geologically at a small scale. In this work we try to produce a detailed 1:10000 geological map of the National Park by applying field methods supported by remote sensing data like Landsat TM-, ASTER-Data, high resolution stereographic aerial views, digital terrain modells (DTM) and detailed geobotanic vegetation maps. This study continues the efforts of BUDE & PRINZ (2003), as it includes ground proof for representative areas. Furthermore this report gives an idea of the essential preparations in the forefield of such a geological field campaign
Optical Signatures of Spin-Orbit Interaction Effects in a Parabolic Quantum Dot
We demonstrate here that the dipole-allowed optical absorption spectrum of a
parabolic quantum dot subjected to an external magnetic field reflects the
inter-electron interaction effects when the spin-orbit interaction is also
taken into account. We have investigated the energy spectra and the
dipole-allowed transition energies for up to four interacting electrons
parabolically confined, and have uncovered several novel features in those
spectra that are solely due to the SO interaction.Comment: 4 pages, 3 figure
Three-Dimensionally Confined Optical Modes in Quantum Well Microtube Ring Resonators
We report on microtube ring resonators with quantum wells embedded as an
optically active material. Optical modes are observed over a broad energy
range. Their properties strongly depend on the exact geometry of the microtube
along its axis. In particular we observe (i) preferential emission of light on
the inside edge of the microtube and (ii) confinement of light also in
direction of the tube axis by an axially varying geometry which is explained in
an expanded waveguide model.Comment: 5 pages, 4 figure
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