Dark Matter in the Dwarf Galaxy NGC 247

Dwarf galaxies are dominated by dark matter even in the innermost regions and, therefore, provide excellent probes for the investigation of dark halos. To that purpose, we analyse ROSAT PSPC-data of the dwarf galaxy NGC 247. We focus in particular on the diffuse X-ray emission in the $1/4$keV band. Assuming an isothermal density profile, we find that the mass of the hot emitting gas is about $10^8 {\rm M_{\odot}}$, corresponding to $\lesssim 0.5$ of the total dynamical mass of the galaxy. The total mass of NGC 247, as derived from the X-ray data agrees quite well with the value obtained from the measured rotation curve (Burlak). The X-ray profile in the $3/4$keV and $1.5$keV band shows an excess at a radial distance of about $15$ arcmin from the center. Such a ``hump'' in the radial X-ray profile can be explained by the presence of a cluster of young low mass stars or brown dwarfs. Therefore, NGC 247 offers the possibility to observe the formation of a halo of MACHOs.Comment: 6 pages, accepted for publication in A &

Anomalous pressure dependence of the atomic displacements in the relaxor ferroelectric PbMg1/3_{1/3}Ta2/3_{2/3}O3_3

The crystal structure of the PbMg$_{1/3}$Ta$_{2/3}$O$_3$ (PMT) relaxor ferroelectric was studied under hydrostatic pressure up to $\sim 7$ GPa by means of powder neutron diffraction. We find a drastic pressure-induced decrease of the lead displacement from the inversion centre which correlates with an increase by $\sim$ 50 % of the anisotropy of the oxygen temperature factor. The vibrations of the Mg/Ta are, in contrast, rather pressure insensitive. We attribute these changes being responsible for the previously reported pressure-induced suppression of the anomalous dielectric permittivity and diffuse scattering in relaxor ferroelectrics

Performance analysis and enhancements for the music sub-space direction-finding algorithm in the presence of wideband signals

Includes supplementary materialThe collection of signals intelligence via passive direction finding and geolocation of radio frequency signals is of great concern to the military for its contribution to the development of battlespace awareness. Basic subspace direction finding techniques provide a method of determining the direction-of-arrival (DOA) of multiple signals on an array of receivers, but they have an inherent limitation in that they are narrowband by design. The impact of various signal frequencies, bandwidths, and signal to noise ratios present in the source signals received by a sparse array using the multiple signals classification (MUSIC) subspace direction-finding algorithm are evaluated in this thesis. Additionally, two performance enhancements are presented: one that reduces the MUSIC computational load and one that provides a method of utilizing collector motion to resolve DOA ambiguities.http://archive.org/details/performancenalys1094544676Lieutenant Commander, United States NavyApproved for public release; distribution is unlimited

Propagation of defects in doped magnetic materials of different dimensionality

Defects intentionally introduced into magnetic materials often have a profound effect on the physical properties. Specifically tailored neutron spectroscopic experiments can provide detailed information on both the local exchange interactions and the local distances between the magnetic atoms around the defects. This is demonstrated for manganese dimer excitations observed for the magnetically diluted three- and two-dimensional compounds KMn(x)Zn(1-x)F(3) and K(2)Mn(x)Zn(1-x)F(4), respectively. The resulting local exchange interactions deviate up to 10% from the average, and the local Mn-Mn distances are found to vary stepwise with increasing internal pressure due to the Mn/Zn substitution. Our analysis qualitatively supports the theoretically predicted decay of atomic displacements according to 1/r**2, 1/r, and constant (for three-, two-, and one-dimensional compounds, respectively) where r denotes the distance of the displaced atoms from the defect.Comment: 21 pages, 4 figures, 3 table

Fermi surface and order parameter driven vortex lattice structure transitions in twin-free YBa2Cu3O7

We report on small-angle neutron scattering studies of the intrinsic vortex lattice (VL) structure in detwinned YBa2Cu3O7 at 2 K, and in fields up to 10.8 T. Because of the suppressed pinning to twin-domain boundaries, a new distorted hexagonal VL structure phase is stabilized at intermediate fields. It is separated from a low-field hexagonal phase of different orientation and distortion by a first-order transition at 2.0(2) T that is probably driven by Fermi surface effects. We argue that another first-order transition at 6.7(2) T, into a rhombic structure with a distortion of opposite sign, marks a crossover from a regime where Fermi surface anisotropy is dominant, to one where the VL structure and distortion is controlled by the order-parameter anisotropy.Comment: 4 pages, 3 figures (2 color), minor change

Einfluss von Phosphodiesterase 5-Inhibitoren auf die Escherichia coli Hämolysin und Lipopolysaccharid vermittelte Kardiodepression am isolierten Rattenherzen

Durch Mikroorganismen, wie Bakterien, Viren oder Pilze kommt es zu Primärinfektionen, in deren Folge sich eine Sepsis entwickeln kann. Die häufigsten Sepsisverursacher sind Bakterien, wobei der Tatsache, dass das Krankheitsbild der Sepsis nicht an die Anwesenheit intakter Bakterien in der Zirkulation gebunden ist sondern die hämatogene Streuung sezernierter Exotoxine und endotoxinhaltiger Zellfragmente zur Induktion einer Sepsis ausreichen, besondere Bedeutung beigemessen werden muss. Die während einer Sepsis auftretenden kardiovaskulären Veränderungen tragen entscheidend zur Induktion des septischen Multiorganversagens sowie des septischen Schocks bei. Es ist dem Herzen im Zuge einer akuten septischen Kardiomyopathie häufig nicht möglich, seine Pumpleistung so zu erhöhen, wie es zur Aufrechterhaltung eines adäquaten Blutdrucks bei stark erniedrigtem systemischem Widerstand nötig wäre. Die septische Kardiomyopathie kann durch die Wirkung kardiodepressiver Zytokine wie TNF-alpha und Il-1beta hervorgerufen werden; daneben sind Mikrozirkula-tionsstörungen innerhalb des Myokards, welche auch ohne globale Minderperfusion zu einer hypoxisch bedingten Pumpinsuffizienz führen können, als mögliche Ursache anzusehen. Zyklische Nukleotide stellen dabei einen wichtigen Bestandteil in der Regulation von koronarer Vasomotorik und kardialer Kontraktilität dar, überdies spielen sie auch eine Rolle in der Pathophysiologie der Sepsis. Die vorliegende Arbeit behandelt die Frage, ob Phosphodiesterase (PDE5) -Inhibitoren den kardiodepressiven Effekt gram-negativer Bakterien respektive deren Endo- und Exotoxinen zumindest teilweise aufheben und so zu einem günstigeren Verlauf der Sepsis beitragen können. Dazu wurden isolierte Rattenherzen mit Escherichia coli Hämolysin (ECH) und Lipopolysaccharid (LPS) perfundiert. Die dadurch generierte Kardiodepression sowie Vasokonstriktion im Koronargefäßsystem sollten mit Hilfe von Sildenafil und Zaprinast inhibiert werden, was partiell gelang. Desweiteren wurde durch die Aufarbeitung von Ventrikelpräparaten eine verminderte Freisetzung kardio-depressiver Mediatoren, insbesondere von TNF-alpha und Cysteinyl-Leukotrienen (Cys-LT), nachgewiesen. Eine Beeinflussung der Genexpression hingegen konnte nicht gezeigt werden. Für die LPS-Versuche stellt sich der protektive Effekt folgendermaßen dar: Der durch die PDE5-Inhibitoren erhöhte cGMP-Spiegel führt zu einer koronaren Vasodilatation, welche Mikrozirkulationsstörungen vorbeugt, was zur Verbesserung der Myokardversorgung und einer verminderten Freisetzung von TNF-alpha führt. Durch diese zeitige Intervention in die teilweise selbstunterhaltenden Mechanismen können der TNF-alpha abhängige kardiodepressive Effekt, aber auch die Aktivierung der cNOS/iNOS, des Sphingomyelinasesignalwegs, der freien Radikalliberation und der Apoptose antagonisiert werden. Im Falle der ECH-Versuche steht ebenfalls die vasodilatative Wirkung der PDE5-Inhibitoren im Koronargefäßsystem im Vordergrund. Diese beruht sowohl auf einer prolongierten cGMP Wirkung als auch auf einer herabgesetzten Cys-LT Liberation. Die verbesserte Perfusion verhindert die sich selbstunterhaltende, ischämisch bedingte Cys-LT Freisetzung und verringert so eine weitere Erhöhung des koronaren Gefäßwiderstandes. Infolge der Senkung des koronaren Gefäßwiderstandes wird die Kardiodepression nahezu vollständig aufgehoben. Die gewonnenen Ergebnisse deuten auf ein protektives Potential der PDE5-Inhibitoren bezüglich der septischen Kardiomyopathie hin.Microorganisms like bacteria, viruses and fungi cause primary infections, which can lead to sepsis. In fact, sepsis is primarily caused by bacteria. Induction of septicemia is not dependent on the presence of intact bacterial organisms in the blood circulation. Hematogenic spreading of secreted bacterial exotoxins as well as cellular fragments containing endotoxins can also lead to sepsis. Cardiovascular alterations due to sepsis crucially contribute to multiple organ dysfunction syndrome and to septic shock. The heart of septic patients is frequently unable to increase cardiac output adequately to compensate the systemic fall in blood pressure. On the one hand septic cardiomyopathy can be induced by cardiodepressive cytokines like TNF-alpha or Il-1beta and on the other hand by microcirculatory dysfunctions within the myocardium, which even without global ischemia may lead to a decreased cardiac output due to hypoxia. Cyclic nucleotides play an important role in coronary vasoconstriction and cardial depression and also in pathophysiology of sepsis. The present study investigates in how far the phosphodiesterase (PDE5) inhibitors Sildenafil and Zaprinast could be able to inhibit the cardiodepressive effect of gram–negative bacteria and their endo- and exotoxins respectively, which then could lead to an improvement of the prognosis. Isolated rat hearts were perfused with Escherichia coli hemolysin (ECH) and lipopolysaccharides (LPS) respectively which lead to cardiodepression and coronary vasoconstriction. After treatment with Sildenafil and Zaprinast respectively this effect could be partially decreased. Analysis of samples gained from ventricular tissue revealed a decreased liberation of cardiodepressive mediators, such as TNF-alpha and cysteinyl-leukotrienes (Cys-LT). Alterations in gene expression could not be shown. The protective effect of the PDE5-inhibitors in the LPS perfused rat hearts can be explained in the following way: PDE5-inhibitor elevate the cGMP levels which lead to coronary vasodilatation inhibiting microcirculatory dysfunction. This improves myocardial supply and decreases TNF-alpha liberation. The early intervention in the partially self engaging mechanisms inhibit the TNF-alpha dependent cardiodepressive effect, activation of the cNOS/iNOS in the sphingomyelinase signaling pathway, free radical liberation and apoptosis. The main effect of PDE5-inhibotor treatment on ECH perfused hearts is a coronary vasodilatation due to a prolonged cGMP impact and a decreased Cys-LT liberation. PDE5-inhibitors decrease self engaging, ischemic induced Cys-LT liberation, which in the end leads to a minimized increase in coronary vascular resistance. Due to the decrease of the coronary resistance cardiodepression can be abolished nearly completely. All results gained in this study recommend a beneficial potential of PDE5-inhibitors in septic cardiomyopathy