Quantum Phase Transitions for Bosons in One Dimension

We study the ground state phase diagram and the critical properties of interacting Bosons in one dimension by means of a quantum Monte Carlo technique. The direct experimental realization is a chain of Josephson junctions. For finite-range interactions we find a novel intermediate phase which shows neither solid order nor superfluidity. We determine the location of this phase and study the critical behaviour of the various transitions. For on-site interaction only, we map out the phase diagram as a function of the hopping strength and the chemical potential.Comment: 11 pages, revtex, 2 eps-figure

Flux Noise near the Berezinskii-Kosterlitz-Thouless Transition

We study the flux noise in Josephson junction arrays in the critical regime above the Berezinskii-Kosterlitz-Thouless transition. In proximity coupled arrays a local ohmic damping for the phases is relevant, giving rise to anomalous vortex diffusion and a dynamic scaling of the flux noise in the critical region. It shows a crossover from white to $1/f$-noise at a frequency $\omega_\xi\propto\xi^{-z}$ with a dynamic exponent $z=2$.Comment: Revised version to be published in JETP Letter

The role of recombinant epidermal growth factor and serotonin in the stimulation of tumor growth in a SCCHN xenograft model

One challenge of squamous cell carcinoma of the head and neck (SCCHN) chemotherapy is a small percentage of tumor cells that arrest in the G0 phase of the cell cycle and are thus not affected by chemotherapy. This could be one reason for tumor recurrence at a later date. The recruitment of these G0-arresting cells into the active cell cycle and thus, proliferation, may increase the efficacy of chemotherapeutic agents. The aim of this study was to investigate whether stimulation with recombinant epidermal growth factor (EGF) or serotonin leads to an increased tumor cell proliferation in xenografts. Detroit 562 cells were injected into NMRI-Foxn1nu mice. Treatment was performed with 15 µg murine or human EGF, or 200 µg serotonin. The control mice were treated with Lactated Ringer's solution (5 mice/group). Tumor size was measured on days 4, 8 and 12 after tumor cell injection. The EGF stimulated mice showed a significantly higher tumor growth compared to the serotonin-stimulated mice and the untreated controls. In the present study, we show that it is possible to stimulate tumor cells in xenografts by EGF and thus, enhance cell proliferation, resulting in a higher tumor growth compared to the untreated control group. In our future investigations, we plan to include a higher number of mice, an adjustment of the EGF dosage and cell subanalysis, considering the heterogeneity of SCCHN tumors

Molar mass distribution of accumulated hydroxyethyl starch (HES) in spleen and liver after intravenous application : polymer analytic studies using size exclusion chromatography coupled with multi angle laser light scattering

Hydroxyethylstärke (HES) ist ein kolloidales Volumenersatzmittel, das zur Volumenbehandlung bei Trauma und bei Schock und zur Verbesserung der Rheologie bei Durchblutungsstörungen angewendet wird. Amylopektin, die Grundlage von HES, wird zur Veränderung der physikalischen Eigenschaften substituiert, um eine für die Infusion geeignete Lösung herstellen zu können. Ein wichtiger Begleiteffekt dieser Substitution ist, dass durch die dadurch erzeugten Störstellen der enzymatische Abbau der Volumenersatzmittel durch Serumglykosidasen minimiert wird. Die molekularen Eigenschaften der HES können anhand der Molekulargewichtsverteilung, beschrieben durch den Gewichtsmittelwert der Molmassen Mw, den Zahlenmittelwert der Molmassen Mn und die Molmasse im Peakmaximum Mp, sowie nach dem Ausmaß der Substitution beschrieben werden. Im Handel befindliche HES-Lösungen werden anhand des Gewichtsmittelwertes der Molmassen (Mw) und der molaren Substitution (MS) gekennzeichnet. Nach bisherigen Erkenntnissen zur Speicherung der HES in Organen stellten sich die Fragen, ob die Hypothese, dass HES durch lysosomale Enzyme abgebaut wird untermauert werden kann und ob es möglich ist, die Sicherheit der HES für die Anwendung am Patienten durch gezielte Verwendung bestimmter HES-Fraktionen zu verbessern. Ziel dieser Arbeit war daher, erstmals die Molekulargewichtsverteilung der nach Infusion von HES in Milz und Leber gespeicherten HES mittels Ausschluss-Chromatographie gekoppelt mit Mehrwinkel-Laser-Streulicht-Detektion zu bestimmen. Untersucht wurden drei handelsübliche HES-Präparate mit unterschiedlichem Mw und unterschiedlicher Substitution (die Bezeichnung schließt Mw (kDa) und MS ein): HES 130/0,4 und HES 200/0,5 sowie HES 450/0,7. Je acht Wistar-Ratten pro Versuchsgruppe erhielten 18 ml HES infundiert. Die Organe wurden für die Molmassenbestimmung bis zu fünfzig Tagen nach Infusion entnommen. Die Hämoglobinkonzentrationen und Hämatokritwerte bei den Blutabnahmen in den ersten 48 Stunden wurden ermittelt und gaben Aufschluss über die Hämodilution. Als wichtigstes Ergebnis wurde eine unterschiedliche Molmassenverteilung der HES aus Milz und Leber festgestellt. In der Leber werden vorwiegend niedermolekulare Anteile gespeichert. Das Mw der HES in der Leber lag direkt nach Infusion bei 89.606±8.570 (HES 450/0,7), 20.038±1.600 (HES 200/0,5) und 23.769±2.489 (HES 130/0,4). Im Verlauf der Untersuchungen stieg das Mw in der Leber bis maximal Tag 5 (HES 450/0,7) nach Infusion zwar an, fiel dann aber bei den weiteren Bestimmungen nach mehr als 5 Tagen wieder ab. Das Peakmaximum der Molmassenverteilung der HES in der Leber blieb dabei größtenteils konstant (HES 450/0,7: ~60 kDa; HES 200/0,5: ~30 kDa; HES 130/0,4: ~30 kDa). Die Molmassenverteilung der Milz wies hingegen hochmolekulare HES auf, wobei die Molmassen im Verlauf der Zeit noch zunahmen. Das Mw nach Infusion von HES 450/0,7 stieg dabei von 148.220 Da auf 229.617 Da im Mittel an. Möglicherweise erfolgt in der Milz vor allem eine Speicherung schwer zu spaltender HES. In der Leber konnte nach Infusion aller HES-Präparate und bereits unmittelbar nach Infusion HES gefunden werden. In der Milz war nur nach Infusion der hochmolekularen, hochsubstituierten HES 450/0,7 und der mittelmolekularen, mittelsubstituierten HES 200/0,5 gespeicherte HES nachzuweisen. Nach Infusion der HES 200/0,5 war dabei nur vereinzelt und erst ab einem Tag HES in der Milz auszumachen. In der Leber war die Speicherung der HES 450/0,7 ebenfalls am längsten festzustellen, während bei HES 130/0,4 die Speicherung in der Leber nur bis 3 Tage nach Infusion bestand. Der Verlauf der Molmassenverteilung in der Leber deutet auf einen intrazellulären Abbau der HES durch lysosomale Enzyme hin, während in der Milz über einen langen Zeitraum nicht gespaltene hochmolekulare HES angereichert wird. Die niedermolekulare, niedrigsubstituierte HES ist hinsichtlich der vorhersehbaren Dauer der Speicherung als besonders günstig anzusehen. In der Leber werden jedoch bei allen HES-Präparaten niedermolekulare Anteile in Konkurrenz zur renalen Elimination aufgenommen. Daher ist die wiederholte, hochdosierte Anwendung von HES bei dekompensierter Niereninsuffizienz aufgrund der Gefahr einer mechanischen Beeinträchtigung der Leber durch dort kumulierte HES stets kritisch zu betrachten.Hydroxyethyl starch (HES) is a colloidal volume substitute, which is used for fluid replacement in trauma and shock and for improvement of rheology after disturbance in microcirculation. HES is based on amylopectin. Amylopectin is substituted in order to modify its physical properties rendering it suitable for infusion. An important side effect of this substitution is the fact, that enzymatic degradation of volume substitutes via serum-glycosidases is minimized by so produced disruptive sites. Molecular characteristics of HES can be specified by molecular weight distribution, described as weight-average molecular weight Mw, number-average molecular weight Mn and peak maximum molecular weight Mp, and by extent of substitution. Commonly used HES-solutions are labeled by weight-average molecular weight (Mw) and by molar substitution (MS). According to present knowledge about accumulation of HES in the organs, the questions whether the hypothesis, that HES is broken down by lysosomal enzymes and if it is possible to improve the safety of HES given to patients by using specific HES fractions can be supported. Aim of the study was to determine the molecular weight distribution of HES accumulation in spleen and liver after infusion using Size Exclusion Chromatography coupled with Multi Angle Laser Light Scattering for the first time. Three customary HES-preparations with different molecular weights and different substituents, HES 130/0,4, HES 200/0,5 and HES 450/0,7 (declaration includes Mw (kDa) and MS), were investigated. Each experimental group of eight Wistar-rats, were given an infusion of 18 ml HES. The organs were extracted for molar mass detection up to fifty days after infusion. Hemoglobin concentration and hematocrit values were determined from blood samples taken in the first 48 h which gave a break down of the hemodilution. The most important result is that a different molar mass distribution of HES in spleen and liver was detected. In the liver fractions with low molecular weight accumulated predominantly. In the liver the Mw of HES were at 89.606±8.570 (HES 450/0,7), 20.038±1.600 (HES 200/0,5) and 23.769±2.489 (HES 130/0,4) directly after infusion. In course of the experiments the Mw increased in the liver to a maximum up to day 5 (HES 450/0,7) after infusion, but it decreased again after more than 5 days in further determinations. At the same time peak molecular mass of molar mass distribution of HES in liver remained mostly constant (HES 450/0,7: ~60 kDa; HES 200/0,5: ~ 30 kDa; HES 130/0,4: ~30 kDa). In contrast molecular weight distribution in the spleen showed high molecular HES. Thereby the molecular mass increases steadily. Mean Mw increased after infusion of HES 450/0,7 from 148.220 Da to 229.617 Da in so doing. It is possible that accumulation of particularly persistent HES occurs in the spleen. In each group HES could be detected in the liver immediately after infusion. In the spleen stored HES was found only after infusion of high-molecular weight, highly substituted HES 450/0,7 and medium-molecular weight, medium substituted HES 200/0,5. Using HES 200/0,5 HES was found in spleen only sporadically and not until one day post infusion. In the liver accumulation of HES 450/0,7 also was found longest, whereas HES 130/0,4 was detected only until 3 days after infusion. The course of molar mass distribution in the liver indicates a continuous intracellular degradation of HES-molecules by lysosomal enzymes. In contrast, non-degraded high-molecular weight HES exists over a long period in the spleen. Low-molecular weight, low substituted HES in particular is favored with regard to the foreseen accumulation. However, low-molecular weight fractions of all HES-preparations are taken up in the liver in competition to renal elimination. That is why repeated, high-dosed usage of HES in spite of decompensated renal insufficiency should be regarded critically because of the risk of mechanical impairment due to accumulated HES

Competition between local and nonlocal dissipation effects in two-dimensional quantum Josephson junction arrays

We discuss the local and nonlocal dissipation effects on the existence of the global phase coherence transitions in two dimensional Josephson-coupled junctions. The quantum phase transitions are also examined for various lattice geometries: square, triangular and honeycomb. The T=0 superconductor-insulator phase transition is analyzed as a function of several control parameters which include self-capacitance and junction capacitance and both local and nonlocal dissipation effects. We found the critical value of the nonlocal dissipation parameter \alpha_{1} depends on a geometry of the lattice. The critical value of the normal state conductance seems to be difficult to obtain experimentally if we take into consideration different damping mechanisms which are presented in real physical systems.Comment: accepted to Physica C Ref. No.: PHYSC-D-06-00244R

Blue phosphorescent nitrile containing C^C* cyclometalated NHC platinum(II) complexes

Since C^C* cyclometalated Pt(II) complexes with N-heterocyclic carbene (NHC) ligands have been identified as potential emitter materials in organic light-emitting devices (OLEDs), very promising results regarding quantum yields, colour and stability have been presented. Herein, we report on four nitrile substituted complexes with a chelating NHC ligand (1-(4-cyanophenyl)-3-isopropyl-1H-benzo[d]imidazole or 4-(tert-butyl)-1-(4-cyanophenyl)-3-methyl-1H-imidazole) and a bidentate monoanionic auxiliary ligand (acetylacetone or dimesitoylmethane). The complexes have been fully characterized including extensive 2D NMR studies (COSY, HSQC, HMBC, NOESY, 195Pt NMR), three of them also by solid-state structures. Photophysical measurements in amorphous PMMA films and pure emitter films at room temperature reveal the impact of the mesityl groups in the auxiliary ligand, which led to a significant increase of the quantum yield, while the decay lifetimes decreased. The electron withdrawing nitrile groups shift the emission towards blue colour coordinates