Typicality approach to the optical conductivity in thermal and many-body localized phases

We study the frequency dependence of the optical conductivity $\text{Re} \, \sigma(\omega)$ of the Heisenberg spin-$1/2$ chain in the thermal and near the transition to the many-body localized phase induced by the strength of a random $z$-directed magnetic field. Using the method of dynamical quantum typicality, we calculate the real-time dynamics of the spin-current autocorrelation function and obtain the Fourier transform $\text{Re} \, \sigma(\omega)$ for system sizes much larger than accessible to standard exact-diagonalization approaches. We find that the low-frequency behavior of $\text{Re} \, \sigma(\omega)$ is well described by $\text{Re} \, \sigma(\omega) \approx \sigma_\text{dc} + a \, |\omega|^\alpha$, with $\alpha \approx 1$ in a wide range within the thermal phase and close to the transition. We particularly detail the decrease of $\sigma_\text{dc}$ in the thermal phase as a function of increasing disorder for strong exchange anisotropies. We further find that the temperature dependence of $\sigma_\text{dc}$ is consistent with the existence of a mobility edge.Comment: 5 pages, 5 figures (+ 3 pages, 5 figures

Non-palindromic (C^C^D) gold(III) pincer complexes are not accessible by intramolecular oxidative addition of biphenylenes – an experimental and quantum chemical study

We herein report on the synthesis of biphenylenes substituted with a pyridine (N), a phosphine (P) and a carbene (C′) donor as well as a carbene donor with additional pyridine in the lateral position. We describe the synthesis and structures of derived gold(I) complexes, which we tried to use for the synthesis of non-palindromic [(C^C^D)AuIII] pincer complexes by means of an intramolecular oxidative addition of the strained biphenylene ring. However, the anticipated formation of gold(III) complexes failed due to kinetic and thermodynamic reasons, which we extensively investigated by quantum chemical calculations. Furthermore, we shed light on the oxidative addition of biphenylene to two different gold(I) systems reported in the literature. Our comprehensive quantum-chemical analysis is complemented by NMR experiments

Synthetic access to a phosphorescent non-palindromic pincer complex of palladium by a double oxidative addition-comproportionation sequence

A highly luminescent non-palindromic [(C^C^N)Pd] pincer complex forms upon reacting pyridine-substituted 2,2′-diiodo-biphenyl with [Pd(PPh$_{3}$)$_{4}$]. This case study establishes for the first time that the title compound is formed via a double oxidative addition – comproportionation sequence. DFT and TDDFT calculations complement mechanistic and photophysical characterizations

Complete lung ultrasound using liquid filling: a review of methods regarding sonographic findings and clinical relevance

(200w) Lung ultrasound (LUS) is widely used for the diagnosis of pulmonary diseases such as solid nodules and consolidations in contact with the pleural cavity. However, sonography for processes of central disease remains impaired due to total sound reflection at the air tissue interfaces in the ventilated lung. These acoustic barriers can be overcome by replacing intra-alveolar air with liquid. Such filling has been reported using perfluorocarbon, saline or emulsions out of those. In order to achieve acoustic access enabling the use of LUS, complete gas free content is required. Such lung tissue - liquid compound will have untypical physical properties that might impact upon the sonographic visualization of central structures. Up to now, the filling of the lung has been reported for very specific applications and not classified regarding their sonographic findings. This work was therefore motivated to review the literature for methods of lung liquid instillation, classifying their methodological strength and limitations for achieving acoustic access and sonographic findings. Finally, their use for ultrasound based clinical applications will be discussed and the need for research will be outlined

On the degenerated soft-mode instability

We consider instabilities of a single mode with finite wavenumber in inversion symmetric spatially one dimensional systems, where the character of the bifurcation changes from sub- to supercritical behaviour. Starting from a general equation of motion the full amplitude equation is derived systematically and formulas for the dependence of the coefficients on the system parameters are obtained. We emphasise the importance of nonlinear derivative terms in the amplitude equation for the behaviour in the vicinity of the bifurcation point. Especially the numerical values of the corresponding coefficients determine the region of coexistence between the stable trivial solution and stable spatially periodic patterns. Our approach clearly shows that similar considerations fail for the case of oscillatory instabilities.Comment: 16 pages, uses iop style files, manuscript also available at ftp://athene.fkp.physik.th-darmstadt.de/pub/publications/wolfram/jpa_97/ or at http://athene.fkp.physik.th-darmstadt.de/public/wolfram_publ.html. J. Phys. A in pres

Economic and legal aspects of international environmental agreements: The case of enforcing and stabilising an international CO 2 agreement

The protection of the global environment is impeded by multilateral externalities which the international community attempts to bring under control by entering into international agreements. International agreements, however, can suffer from non-compliance and free-riding behaviour by sovereign states and must therefore be enforced and stabilised internationally. This paper describes instruments for the enforcement and stabilisation of an international CO2 agreement and evaluates them in the light of economic and legal theory. Economic instruments build on repetition and use utility transfers, economic sanctions and flexible treaty adjustments. Important legal instruments are reciprocal obligations and cooperation duties, international funding and transfer rules, treaty suspension, retorsions and reprisals, treaty revision, and monitoring. The paper shows that economic and legal instruments are compatible to a considerable extent. It develops proposals for the enforcement and stabilisation of a global CO2 agreement and other multilateral treaties.International environmental agreements,international cooperation,non-compliance,enforcement,global warming,international law

Untersuchungen zur Ablation des Bronchialkarzinoms am Modell der flüssigkeitsgefüllten Lunge mit Hilfe therapeutischer Schallfelder

Die vorliegende Arbeit befasst sich mit der Wirkung therapeutischer Schallfelder (HIFU) auf das Bronchialkarzinom. Zur Erzeugung eines akustischen Zuganges wird mit Hilfe der unilateralen Lungenflutung (OLF) die pulmonale Gasfraktion durch Lösung ersetzt. Durch Kombination beider Verfahren (HIFU, OLF) ergibt sich ein neuartiger Verfahrensansatz zur lokal-thermischen Ablation des Bronchialkarzinoms. Im Rahmen der Dissertation wurden diesbezüglich die ersten theoretischen Grundlagen erarbeitet und die Machbarkeit einer Ablation des Bronchialkarzinoms durch HIFU unter Lungenflutung experimentell durchgeführt. Zur Modellierung wurden akustische Gewebeeigenschaften bestimmt. Die Absorption im Lungentumor ist hoch und entspricht Werten bekannter maligner Gewebe. Geflutete Lunge ist ein guter Schallleiter mit sehr geringer Absorption. Die Simulation zeigt, dass mit einer ausgeprägten Läsionsbildung durch HIFU im Lungentumor zu rechnen ist, wobei das Lungengewebe keine thermische Schädigung erfährt. Volumetrische Ablationsschemata sind dem Rasterscan Verfahren zu bevorzugen. Experimentell wurde durch sonographisch gestützte HIFU Applikation Temperaturen über 60°C im zentral-pulmonalen Bronchialkarzinom induziert. Lungengewebe wechselwirkt aufgrund des Lösungsgehaltes thermisch nicht mit HIFU, jedoch kann es bei sehr hohen Schallintensitäten zu kavitationsinduzierter Gewebeerosion kommen. Die experimentellen und theoretischen Untersuchungen zeigen eine gute Übereinstimmung. Die sonographisch gestützte HIFU-Ablation am Bronchialkarzinom ist machbar und führt zu dessen Nekrotisierung. Durch Kombination von HIFU unter OLF entsteht ein neuartiges minimal-invasives Verfahren zur Therapie des Bronchialkarzinoms. Dieses ist in-vivo einsetzbar und in dem zur Verfügung stehenden Therapiezeitraum können T1 Tumore unter kurativer Zielstellung abladiert werden

Initial interaction of citrate-coated iron oxide nanoparticles with the glycocalyx of THP-1 monocytes assessed by real-time magnetic particle spectroscopy and electron microscopy

Interaction with biological material can alter physicochemical parameters of magnetic nanoparticles and might thereby change their magnetic behavior with potentially important implications for various nanoparticle applications. Little is known about changes of the magnetic behavior that occur during the initial phase of cell binding and uptake. We investigate the magnetic behavior of very small superparamagnetic iron-oxide nanoparticles (VSOP) during initial contact with THP-1 monocytes. We combine real-time magnetic particle spectroscopy (MPS), a fast and sensitive method for specific detection of magnetic nanoparticles in biological specimen with high-pressure-freezing/freeze-substitution transmission electron microscopy (HPF/FS-TEM), enabling us to generate snapshots of the interaction of VSOP with the cellular glycocalyx. MPS reveals significant changes of the dynamic magnetic behavior within seconds after VSOP injection into monocyte suspensions that correlate with the formation of nanoparticle clusters in the glycocalyx. The combination of real-time MPS and HPF/FS-TEM provides an ideal platform to analyze magnetic behaviors of nanoparticles upon interaction with cells and tissues