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The electron-phonon scattering is one of the main microscopic mechanisms responsible for the spin-flip in the transient state of ultrafast demagnetization. Here, we present an experimental determination of the temperature-dependent electron-phonon scattering rate in Gd. Using a static x-ray emission spectroscopy method, where the reduction of the decay peak intensities when increasing the temperature is quantified, we measure independently the electron-phonon scattering rate for the 5d and the 4f electrons. We deduce the temperature dependence of scattering for the 5d electrons, while no effect on the phonon population is observed for the 4f electrons. Our results suggest that the ultrafast magnetization dynamics in Gd is triggered by the spin-flip in the 5d electrons. We also evidence the existence of a temperature threshold, above which spin-flip scattering of the 5d electrons takes place. We deduce that during the transient state of ultrafast demagnetization, the exchange energy between 5d electrons has to be overcome before the microscopic electron-phonon scattering process can occur.
The electronic and magnetic excitations of bulk NiO have been determined using the 3A2g to 3T2g crystal-field transition at the Ni M2,3 edges with resonant inelastic x-ray scattering at 66.3- and 67.9-eV photon energies and 33-meV spectral resolution. Unambiguous assignment of the high-energy side of this state to a spin-flip satellite is achieved. We extract an effective exchange field of 89±4 meV in the 3T2g excited final state from empirical two-peak spin-flip model. The experimental data is found consistent with crystal-field model calculations using exchange fields of 60–100 meV. Full agreement with crystal-field multiplet calculations is achieved for the incident photon energy dependence of line shapes. The lower exchange parameter in the excited state as compared to the ground-state value of 120 meV is discussed in terms of the modification of the orbital occupancy (electronic effects) and of the structural dynamics: (A) With pure electronic effects, the lower exchange energy is attributed to the reduction in effective hopping integral. (B) With no electronic effects, we use the S = 1 Heisenberg model of antiferromagnetism to derive a second-nearest-neighbor exchange constant J2 = 14.8±0.6 meV. Based on the linear correlation between J2 and the lattice parameter from pressure-dependent experiments, an upper limit of 2% local Ni-O bond elongation during the femtosecond scattering duration is derived.
How different microscopic mechanisms of ultrafast spin dynamics coexist and interplay is not only relevant for the development of spintronics but also for the thorough description of physical systems out-of-equilibrium. In pure crystalline ferromagnets, one of the main microscopic mechanism of spin relaxation is the electron-phonon (el-ph) driven spin-flip, or Elliott-Yafet, scattering. Unexpectedly, recent experiments with ferro- and ferrimagnetic alloys have shown different dynamics for the different sublattices. These distinct sublattice dynamics are contradictory to the Elliott-Yafet scenario. In order to rationalize this discrepancy, it has been proposed that the intra- and intersublattice exchange interaction energies must be considered in the microscopic demagnetization mechanism, too. Here, using a temperature-dependent x-ray emission spectroscopy (XES) method, we address experimentally the element specific el-ph angular momentum transfer rates, responsible for the spin-flips in the respective (sub)lattices of Fe20Ni80, Fe50Ni50 and pure nickel single crystals. We establish how the deduced rate evolution with the temperature is linked to the exchange coupling constants reported for different alloy stoichiometries and how sublattice exchange energies threshold the related el-ph spin-flip channels. Thus, these results evidence that the Elliott-Yafet spin-flip scattering, thresholded by sublattice exchange energies, is the relevant microscopic process to describe sublattice dynamics in alloys and elemental magnetic systems.
Fault zones are the locations where motion of tectonic plates, often associated with earthquakes, is accommodated. Despite a rapid increase in the understanding of faults in the last decades, our knowledge of their geometry, petrophysical properties, and controlling processes remains incomplete. The central questions addressed here in our study of the Dead Sea Transform (DST) in the Middle East are as follows: (1) What are the structure and kinematics of a large fault zone? (2) What controls its structure and kinematics? (3) How does the DST compare to other plate boundary fault zones? The DST has accommodated a total of 105 km of left-lateral transform motion between the African and Arabian plates since early Miocene (similar to 20 Ma). The DST segment between the Dead Sea and the Red Sea, called the Arava/Araba Fault (AF), is studied here using a multidisciplinary and multiscale approach from the mu m to the plate tectonic scale. We observe that under the DST a narrow, subvertical zone cuts through crust and lithosphere. First, from west to east the crustal thickness increases smoothly from 26 to 39 km, and a subhorizontal lower crustal reflector is detected east of the AF. Second, several faults exist in the upper crust in a 40 km wide zone centered on the AF, but none have kilometer-size zones of decreased seismic velocities or zones of high electrical conductivities in the upper crust expected for large damage zones. Third, the AF is the main branch of the DST system, even though it has accommodated only a part (up to 60 km) of the overall 105 km of sinistral plate motion. Fourth, the AF acts as a barrier to fluids to a depth of 4 km, and the lithology changes abruptly across it. Fifth, in the top few hundred meters of the AF a locally transpressional regime is observed in a 100-300 m wide zone of deformed and displaced material, bordered by subparallel faults forming a positive flower structure. Other segments of the AF have a transtensional character with small pull-aparts along them. The damage zones of the individual faults are only 5-20 m wide at this depth range. Sixth, two areas on the AF show mesoscale to microscale faulting and veining in limestone sequences with faulting depths between 2 and 5 km. Seventh, fluids in the AF are carried downward into the fault zone. Only a minor fraction of fluids is derived from ascending hydrothermal fluids. However, we found that on the kilometer scale the AF does not act as an important fluid conduit. Most of these findings are corroborated using thermomechanical modeling where shear deformation in the upper crust is localized in one or two major faults; at larger depth, shear deformation occurs in a 20-40 km wide zone with a mechanically weak decoupling zone extending subvertically through the entire lithosphere.
Hartz IV steht als Chiffre für eine Sozialrechtsreform, mit der 2005 die Grundsicherung für Arbeitsuchende auf ein neues Fundament gestellt wurde. Die Reform war von Anbeginn umstritten. Streitpunkte waren sowohl die organisationsrechtliche Zuordnung der Trägerschaft (ARGE, Optionskommunen) als auch Voraussetzungen, Art und Höhe der Leistungen nach dem damals neuen SGB II. Inzwischen hat das Bundesverfassungsgericht die in § 44b SGB II geregelten Arbeitsgemeinschaften als verfassungswidrige Mischverwaltung eingestuft. Die Karlsruher Richter setzten dem Gesetzgeber für die Herstellung grundgesetzkonformer Zustände eine Frist längstens bis Ende 2010. Mit Gesetz zur Änderung des Grundgesetzes (Art. 91e), in Kraft getreten am 27.07.2010, hat der Gesetzgeber den Auftrag des Bundesverfassungsgerichtes umgesetzt. Die Verfassung wurde um einen neuen Artikel 91e ergänzt. Er schafft eine verfassungsrechtliche Grundlage für die Fortsetzung der Aufgabenwahrnehmung der SGB II-Leistungsträger in gemeinsamen Einrichtungen. Dadurch wird eine Ausnahme vom Verbot der Mischverwaltung für das Gebiet der Grundsicherung für Arbeitsuchende eingeführt. Nach Art. 91e Abs. 2 GG kann eine begrenzte Anzahl von kommunalen Trägern als alleinige Träger der Grundsicherung für Arbeitssuchende zugelassen werden. Die Zulassung erfolgt auf Antrag des kommunalen Trägers und bedarf der Zustimmung der obersten Landesbehörde. Doch beschränken sich die Schwierigkeiten nicht allein auf die Verwaltungsorganisation und das Organisationsrecht. Vielmehr haben sich bei der praktischen Handhabung des SGB II auch im Leistungsrecht viele Schwachstellen gezeigt. Folge davon ist eine Klagenflut bei den Sozialgerichten, in deren Urteilen manche eine Fundgrube für gesetzgeberischen Nachbesserungsbedarf sehen. Hinzu kommen Reformvorschläge aus der Politik, die bis hin zu einer Arbeitspflicht reichen. Weitere Reformimpulse gehen vom Bundesverfassungsgericht aus, das unlängst in dem zentralen Bereich der Regelleistungen verfassungswidrige Vorschriften ausgemacht und damit weit über den konkreten Einzelfall hinaus zu einer Neubestimmung sozialstaatlicher Leistungen anregt. Die 16. Fachtagung des Kommunalwissenschaftlichen Institutes (KWI) der Universität Potsdam greift die ebenso aktuellen wie brisanten Entwicklungen bei der Trägerschaft und den Leistungen der Grundsicherung für Arbeitsuchende auf.
Grundlagen des Verwaltungsrechts : Bd. II Informationsordnung, Verwaltungsverfahren, Handlungsformen
(2008)
Die Schule steckt mitten in einem Umbruch: Dieser wird durch verschiedene Faktoren wie sinkende Schülerzahlen, Zu- und Abwanderungen von Familien mit ihren Kindern, wachsenden Zahlen von Schulpflichtigen mit Migrationshintergrund und anderes mehr gekennzeichnet. Damit steht die Schule vor neuen Herausforderungen. Außerdem hält der Trend zum Gymnasium an. Auch wechselvolle Dauerreformen schaffen unübersichtliche Schulstrukturen und erschweren sichere Orientierung. Und: Im zunehmend raueren Wettbewerb der Schultypen laufen den öffentlichen Schulen immer mehr Schüler davon und zu den Privatschulen über. Schon jetzt sehen sich zahlreiche Kommunen gezwungen, ihre Bildungsangebote zurückzuschrauben und ihre Schulen zu schließen.
Kann eine Kommune ihren Bürgern aber nicht mehr die schulische „Grundversorgung“ anbieten, so hat dies weitreichende Folgen. Wo Schulen schließen müssen, „stirbt auch der Ort“. Ein umfangreiches, vielfältiges und flächendeckendes Bildungsangebot dagegen ist für die Kommune tragender Pfeiler einer funktionsfähigen Infrastruktur. Hier setzt die 21. Fachtagung des Kommunalwissenschaftlichen Institutes der Universität Potsdam an. Sie behandelt zentrale Themen der nachhaltigen Gewährleistung schulischer Infrastruktur in den Kommunen einschließlich der dazugehörigen Erfahrungsberichte, die über Best-Practice-Modelle sowie über Erfolgsbedingungen und Fallstricke in der Verwaltungspraxis informieren. Damit gibt die Tagung zugleich Impulse den kommunalen Entscheidungsträgern für die Generierung von und den Umgang mit Gestaltungsoptionen zur Standortsicherung im kommunalen Bildungsmanagement.
The Ca Mau peninsula (CMP) is a key economic region in southern Vietnam. In recent decades, the high demand for water has increased the exploitation of groundwater, thus lowering the groundwater level and leading to risks of degradation, depletion, and land subsidence, as well as salinity intrusion in the groundwater of the whole Mekong Delta region. By using a finite element groundwater model with boundary expansion to the sea, we updated the latest data on hydrogeological profiles, groundwater levels, and exploitation. The basic model setup covers seven aquifers and seven aquitards. It is determined that the inflow along the coastline to the mainland is 39% of the total inflow. The exploitation of the study area in 2019 was 567,364 m(3)/day. The most exploited aquifers are the upper-middle Pleistocene (qp(2-3)) and the middle Pliocene (n(2)(2)), accounting for 63.7% and 24.6%, respectively; the least exploited aquifers are the upper Pleistocene and the upper Miocene, accounting for 0.35% and 0.02%, respectively. In the deeper aquifers, qp(2-3) and n(2)(2), the change in storage is negative due to the high exploitation rate, leading to a decline in the reserves of these aquifers. These groundwater model results are the calculations of groundwater reserves from the coast to the mainland in the entire system of aquifers in the CMP. This makes groundwater decision managers, stakeholders, and others more efficient in sustainable water resources planning in the CMP and Mekong Delta (MKD).
Macrophages have important protective functions during infection with herpes simplex virus type 1 (HSV-1). However, molecular mechanisms that restrict viral propagation and protect from severe disease are unclear. Here we show that macrophages take up HSV-1 via endocytosis and transport the virions into multivesicular bodies (MVBs). In MVBs, acid ceramidase (aCDase) converts ceramide into sphingosine and increases the formation of sphingosine-rich intraluminal vesicles (ILVs). Once HSV-1 particles reach MVBs, sphingosine-rich ILVs bind to HSV-1 particles, which restricts fusion with the limiting endosomal membrane and prevents cellular infection. Lack of aCDase in macrophage cultures or in Asah1(-/-) mice results in replication of HSV-1 and Asah1(-/-) mice die soon after systemic or intravaginal inoculation. The treatment of macrophages with sphingosine enhancing compounds blocks HSV-1 propagation, suggesting a therapeutic potential of this pathway. In conclusion, aCDase loads ILVs with sphingosine, which prevents HSV-1 capsids from penetrating into the cytosol.
Macrophages have important protective functions during infection with herpes simplex virus type 1 (HSV-1). However, molecular mechanisms that restrict viral propagation and protect from severe disease are unclear. Here we show that macrophages take up HSV-1 via endocytosis and transport the virions into multivesicular bodies (MVBs). In MVBs, acid ceramidase (aCDase) converts ceramide into sphingosine and increases the formation of sphingosine-rich intraluminal vesicles (ILVs). Once HSV-1 particles reach MVBs, sphingosine-rich ILVs bind to HSV-1 particles, which restricts fusion with the limiting endosomal membrane and prevents cellular infection. Lack of aCDase in macrophage cultures or in Asah1(-/-) mice results in replication of HSV-1 and Asah1(-/-) mice die soon after systemic or intravaginal inoculation. The treatment of macrophages with sphingosine enhancing compounds blocks HSV-1 propagation, suggesting a therapeutic potential of this pathway. In conclusion, aCDase loads ILVs with sphingosine, which prevents HSV-1 capsids from penetrating into the cytosol.