255 research outputs found
Doniach diagram for ordered, disordered and underscreened Kondo lattices
The Doniach's diagram has been originally proposed to describe the
competition between the local Kondo effect and the intersite RKKY interactions
in cerium compounds. Here we discuss the extension of this diagram to different
variations of Kondo lattice model. We consider a) ordered cerium compounds
where the competition between magnetic order and Kondo effect plays an
important role, as , b) disordered cerium systems with competing
spin glass phase, magnetic ordered phases and a Kondo phase, as the heavy
fermion cerium alloy and, c) uranium compounds where a
coexistence between Kondo effect and ferromagnetic order has been observed, as
UTe. We show that all these cases can be described by a generalized Doniach
phase diagram.Comment: Presented in the Latin American Workshop on Magnetism and Magnetic
Materials (LAW3M) Rio de Janeiro, Brazil, August 12-16, 2007. Proceedings to
be published in JMM
Rezension: Beate Binder, Katrin Ebel, Sabine Hess, Anika Keinz, Friedrich von Bose (Hg.): Eingreifen, Kritisieren, VerÀndern!? Interventionen ethnographisch und gendertheoretisch
Wirkung von Iloprost-Aerosol auf Oxygenierung, Rechtsherzfunktion, pulmonale HĂ€modynamik und inflammatorische Mediatoren nach herzchirurgischen Operationen mit extrakorporaler Zirkulation
Bei der vorliegenden prospektiven und verblindeten klinischen Vergleichsstudie wurde die Wirkung prophylaktisch inhalierten Iloprosts bei 40 Patienten ohne bekannte pulmonale Hypertonie untersucht, die sich einer elektiven chirurgischen Revaskularisierung der KoronargefĂ€Ăe unter Verwendung einer extrakorporalen Zirkulation (EKZ) unterzogen. Bei derartigen Operationen kommt es regelhaft zu einer generalisierten EntzĂŒndungsreaktion gefolgt von einer Rechtsherzbelastung unterschiedlichen AusmaĂes, was den postoperativen Verlauf teilweise erheblich kompliziert. Zur Therapie einer in diesem Rahmen aufgetretenen Rechtsherzbelastung hat sich inhaliertes Iloprost bereits vielfach als sehr wirksam erwiesen. ZusĂ€tzlich ist seit einiger Zeit auch eine antiinflammatorische Wirkung von Iloprost bekannt. Zielsetzung dieser Studie war es daher herauszufinden, ob auch die prophylaktische Applikation eine vorteilhafte Wirkung auf perioperative HĂ€modynamik und Oxygenierung sowie auf perioperative Inflammationsreaktion zeigen kann. Dazu wurde vor EKZ 20 Patienten 10”g aerosolisiertes Iloprost per inhalationem appliziert, 20 Patienten der Kontrollgruppe inhalierten 0,9%ige NaClâLösung. Nach Ende der EKZ wurden hĂ€modynamische Parameter mittels Pulskonturanalyse (PiCCOÂź) und dessen RechtsherzâErweiterungsmonitors (VoLEFÂź) protokolliert sowie arterielle und gemischtvenöse Blutgasanalysen durchgefĂŒhrt. Weiterhin wurden proâ und antiinflammatorische Zytokine (Interleukinâ1beta, 6, 8 und 10 sowie TumorâNekroseâFaktor alpha) in Blutplasma und bronchoalveolĂ€rer LavageflĂŒssigkeit bestimmt Die Ergebnisse bei den meisten beobachteten Parametern in Studienâ und Kontrollguppe unterschieden sich nicht signifikant voneinander. Jedoch zeigte sich in der Studiengruppe ein erhöhtes HZV sowie ein höherer kardialer Funktionsindex als Marker der Inotropie bei gleichzeitig niedrigerem systemischem GefĂ€Ăwiderstand. Da diese Wirkung nach Ende der ĂŒblichen Wirkdauer von Iloprost auftrat, interpretieren wir dies als einen Hinweis auf eine verbesserte hĂ€modynamische StabilitĂ€t durch die prophylaktische Inhalation von Iloprost. Ein weiteres Ergebnis war ein etwas besseres Sauerstoffangebot in der Studiengruppe gegen Ende der Untersuchung. Die Analyse der Zytokinbestimmungen aus Blutplasma und Bronchialsekret konnte keine signifikanten Unterschiede zwischen den beiden Gruppen zeigen, eine antiinflammatorische Wirkung inhalierten Iloprosts konnte hier nicht dargestellt werden. Auch eine relevante Rechtsherzbelastung wurde nicht beobachtet. Da inhaliertes Iloprost seine vorteilhafte Wirkung auf postoperative HĂ€modynamik und kardiale Pumpleistung vor allem durch Senkung pathologisch erhöhter intrapulmonaler WiderstĂ€nde entfaltet und eine antiinflammatorische Wirkung erst bei einer Inflammation zum Tragen kommen kann, ist zu erwĂ€gen ob nicht der inflammatorische Reiz bei dem untersuchten verhĂ€ltnismĂ€Ăig gesunden Patientenkollektiv zu gering war, um die vermuteten Effekte zu zeigen. Im Verlauf der Studie ist kein schwerer Zwischenfall aufgetreten, auch konnte kein nachteiliger Effekt prophylaktisch inhalierten Iloprosts bei dem vorliegenden Patientenkollektiv nachgewiesen werden. Eine Studie, die die Auswirkung von inhaliertem Iloprost auf HĂ€modynamik, Oxygenierung und Inflammation an kardial vorbelasteten Patienten mit langer Operationsâ und EKZâDauer untersucht, erscheint daher sinnvoll.In this prospective clinical trial we studied the effect of prophylactically inhaled iloprost in 40 patiens not suffering from pulmonal hypertension. Patients underwent elective surgical revascularization of their coronary arteries using extracorporeal circulation (ECC). These operations usually are associated with a generalized inflammatory reaction followed by strain of the right heart of different extent, potentially complicating the postoperative course. Inhaled iloprost has manyfoldly before proven its effectiveness in the therapy of right heart strain. Additionally, its antiinflammatory capability is already known. Aim of this study was to clarify whether prophylactically inhaled iloprost has a positive effect on perioperative hemodynamic and oxygenation als well as on perioperative inflammation. Therefore, 20 patients received 10”g of aerosolized iloprost before ECC, 20 patients in the controlgroup received an inhalation of 0,9% saline. After ECC, hemodynamic parameters were obtained using a PulseâContourâAnalysis Monitor (PiCCOÂź) and its rightâheart supplemental monitor device (VoLEFÂź). Arterial and mixed venous blood gas samples were taken at given times. Also, proâand antiinflammatory cytokines (Interleukine 1β, 6, 8 and 10 and tumorânekrosisâfactor α) were sampled from bloodâplasma and bronchioalveolar fluid. Results of most of the observed parameters were not significantly different between studyâ and control group. Hemodynamic values are within range of those measured in other studies investigating similar parameters in comparable settings. As compared to the control group, elevated cardiac output and cardiac funktion index as a marker of inotropy concurrently with lowered systemic vascular resistance at the same time were found in the study group. Since this effect was recorded after the end of the usual activity of iloprost, this could point to an improved hemodynamic stability following the prophylactic inhalation of iloprost. Another finding was a slightly better delivery of oxygen in the study group at the end of the study. Analysis of cytokines from plasma and bronchioalveolar fluid found no significant differences between the groups, an antiinflammatory effect of inhaled iloprost could not been shown in this survey. However, cytokine levels were not elevated in the control group at any measurement time. Relevant right heart strain caused by inflammation was not observed. Since the positive effect of inhaled iloprost on postoperative hemodynamics and cardiac output is mainly based on lowering pathologically raised intrapulmonary resistance, and since an antiinflammatory effect can only be seen when there is an inflammation, it has to be considered that the inflammatory stimulus in this studied group of relatively healthy patients possibly was too small to show the suspected effect. No serious adverse event occured during the study, also no negative effect of prophylactically inhaled iloprost could be detected in the studied group of patients. A survey investigating effects of inhaled iloprost on hemodynamic, oxygenation and inflammation on a group of patients with reduced cardiac function requiring operations of longer duration and longer ECC could possibly give more detailed information on this issue
Rezension: Block, Laura: Policy Frames on Spousal Migration in Germany: Regulating Membership, Regulating the Family
Rezension: Irene Messinger: Schein oder Nicht Schein. Konstruktion und Kriminalisierung von "Scheinehen" in Geschichte und Gegenwart
Transport properties of moderately disordered UCuPd
We present a detailed study on the (magneto)transport properties of as-cast
and heat treated material UCuPd. We find a pronounced sample dependence of
the resistivity of as-cast samples, and reproduce the annealing
dependence of . In our study of the Hall effect we determine a metallic
carrier density for all samples, and a temperature dependence of the Hall
constant which is inconsistent with the Skew scattering prediction. The
magnetoresistive response is very small and characteristic for spin disorder
scattering, suggesting that overall the resistivity is controlled mostly by
nonmagnetic scattering processes. We discuss possible sources for the
temperature and field dependence of the transport properties, in particular
with respect to quantum criticality and electronic localization effects.Comment: 11 pages, 9 figures, submitted PR
Effect of the strong metal-support interaction on hydrogen sorption kinetics of Pd-capped switchable mirrors
The morphology and electronic structure of Pd clusters grown on oxidized yttrium surfaces are investigated by scanning tunneling microscopy and ultraviolet photoelectron spectroscopy. The hydrogen sorption mediated by the Pd clusters is determined from the optically monitored switching kinetics of the underlying yttrium film. A strong thickness dependence of the hydrogen uptake is found. The electronic structure of the as-grown Pd clusters depends only weakly on their size. Strong changes of the photoemission spectra are found after hydrogenation, in particular the oxide peak shifts and the Pd peaks vanish. Both phenomena are due to a strong metal-support interaction (SMSI) state, characterized by a complete encapsulation of the clusters by a reduced yttrium oxide layer. Scanning tunneling spectroscopy confirms the SMSI state of small Pd clusters after hydrogen exposure. The SMSI effect is less important with increasing Pd thickness. This explains the critical thickness for the catalyzed hydrogen uptake by the Pd/Y
Zwei ZahnbĂŒrsten, ein Reiskocher und romantische Liebe: Konstruktion und Verfolgung aufenthaltsrechtlicher Scheinehen in der Bundesrepublik
Taking the example of marriages of convenience, the article argues that immigration law reproduces conservative marriage norms. We show that the administrative practices evolving around the assessment of binational marriages that are suspected of aiming at obtaining a residence permit for one of the spouses in fact establish a purpose of marriage which is not covered by legislation. These practices not only are a significant invasion of privacy for the suspected couples, but furthermore are informed by gendered and racialized conceptions of âproperâ marriages which are incorporated in influential discourses of migration, family and the nation
Sharp lines in the absorption edge of EuTe and PbEuTe in high magnetic fields
The optical absorption spectra in the region of the \fd transition energies
of epitaxial layers of of EuTe and \PbEuTe, grown by molecular beam epitaxy,
were studied using circularly polarized light, in the Faraday configuration.
Under \sigmam polarization a sharp symmetric absorption line (full width at
half-maximum 0.041 eV) emerges at the low energy side of the band-edge
absorption, for magnetic fields intensities greater than 6 T. The absorption
line shows a huge red shift (35 meV/T) with increasing magnetic fields. The
peak position of the absorption line as a function of magnetic field is
dominated by the {\em d-f} exchange interaction of the excited electron and the
\Euion spins in the lattice. The {\em d-f} exchange interaction energy was
estimated to be eV. In \PbEuTe the same absorption line
is detected, but it is broader, due to alloy disorder, indicating that the
excitation is localized within a finite radius. From a comparison of the
absorption spectra in EuTe and \PbEuTe the characteristic radius of the
excitation is estimated to be \AA.Comment: Journal of Physics: Condensed Matter (2004, at press
PET attenuation coefficients from CT images: experimental evaluation of the transformation of CT into PET 511-keV attenuation coefficients
The CT data acquired in combined PET/CT studies provide a fast and essentially noiseless source for the correction of photon attenuation in PET emission data. To this end, the CT values relating to attenuation of photons in the range of 40-140keV must be transformed into linear attenuation coefficients at the PET energy of 511keV. As attenuation depends on photon energy and the absorbing material, an accurate theoretical relation cannot be devised. The transformation implemented in the Discovery LS PET/CT scanner (GE Medical Systems, Milwaukee, Wis.) uses a bilinear function based on the attenuation of water and cortical bone at the CT and PET energies. The purpose of this study was to compare this transformation with experimental CT values and corresponding PET attenuation coefficients. In 14 patients, quantitative PET attenuation maps were calculated from germanium-68 transmission scans, and resolution-matched CT images were generated. A total of 114 volumes of interest were defined and the average PET attenuation coefficients and CT values measured. From the CT values the predicted PET attenuation coefficients were calculated using the bilinear transformation. When the transformation was based on the narrow-beam attenuation coefficient of water at 511keV (0.096cm-1), the predicted attenuation coefficients were higher in soft tissue than the measured values. This bias was reduced by replacing 0.096cm-1 in the transformation by the linear attenuation coefficient of 0.093cm-1 obtained from germanium-68 transmission scans. An analysis of the corrected emission activities shows that the resulting transformation is essentially equivalent to the transmission-based attenuation correction for human tissue. For non-human material, however, it may assign inaccurate attenuation coefficients which will also affect the correction in neighbouring tissu
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