The Quantum Hall Effect of Interacting Electrons in a Periodic Potential

We consider the influence of an external periodic potential on the fractional quantum Hall effect of two-dimensional interacting electron systems. For many electrons on a torus, we find that the splitting of incompressible ground state degeneracies by a weak external potential diminishes as $\exp ( - L/ \xi)$ at large system size $L$. We present numerical results consistent with a scenario in which $\xi$ diverges at continuous phase transitions from fractional to integer quantum Hall states which occur with increasing external potential strength.Comment: 4 pages, REVTeX, 3 epsf-embedded color postscript figures, submitted to PRB (Rapid Comm.), added reference in revised versio

Chemical vapour deposition of chalcogenide phase change materials using digermane

The use of digermane (Ge2H6) as a Ge-source was investigated for the low temperature metal organic chemical vapour deposition (MOCVD) of GexSbyTez (GST) films. Strong influence of the reactor pressure and growth temperature on the film morphology was observed by SEM and AFM imaging. The incorporation of Ge into the GST crystalline structure was proven using Raman scattering and XPS measurements

Metal organic chemical vapor deposition of GexSbyTez layers grown by using digermane

GexSbyTez (GST) films grown on Si(111) substrates by epitaxy tend to be polycrystalline and therefore rough. Especially the incorporation of Germanium in the films is problematic. Thin and smooth film surfaces are however a prerequisite for memory applications. In the past we demonstrated that the metal organic chemical vapor deposition (MOCVD) growth of highly mismatched III/V materials such as InAs/GaAs can be accomplished conformally, if a low temperature growth process is used. This knowledge is transferred to MOCVD growth of GST. To this end as a Ge precursor digermane was employed which is expected to decompose at low temperatures. Commercial sources for Sb (triethylanthimony) and Te (diethyltellur) were chosen, which are suitable for low temperature deposition. At first the growth of Sb2Te3 layers was optimized. Than digermane was added to the growth process. Growth was evaluated by SEM, XRD and Raman measurements. It was found that GST can be deposited at the same conditions as Sb2Te3. SEM pictures show well coalesced, trigonal crystalline structures and XRD measurements verify the integration of Ge. The influence of growth parameters on layer growth will be presented

TNF\u3b1-induced endothelial activation is counteracted by polyphenol extract from UV-stressed cyanobacterium Arthrospira platensis

The cyanobacterium Arthrospira platensis (A. platensis) has been considered as a potential source of several therapeutic compounds including antioxidant molecules such as phenolics. Several studies have demonstrated that the exposure to a particular stress factor, such as UV-light, is able to modify the quality and the quantity of polyphenols produced by A. platensis. In this study we compare the effect of polyphenol extracts from A. platensis (PEAP) and from UV-stressed A. platensis (PEAPUV) on endothelial cells exposed to TNF\uf061 by evaluating the expression of endothelial Nitric Oxide Synthase (eNOS), of inducible Nitric Oxide Synthase (iNOS), of Vascular Cell Adhesion Molecule 1 (VCAM-1) and of Matrix Metalloproteinase-9 (MMP-9), key markers of endothelial dysfunction. MMP-9 activity was measured by gel zymography. Western Blot analysis was performed to analyze eNOS, iNOS and VCAM-1 expression and signal transduction. The major evidence of this study is that PEAPUV is more efficient than PEAP in counteracting the TNF\u3b1-induced endothelial activation. Treatment with PEAPUV (0.10 mg GAE/ml) restored to basal levels the TNF\u3b1-induced expression of eNOS, iNOS, VCAM-1 and MMP-9 and the TNF\u3b1- triggered activation of Akt. The use of an Akt inhibitor mimicked the inhibitory effects of PEAPUV on eNOS and MMP-9 expression, suggesting that eNOS and MMP-9 induction by TNF\u3b1 depends on Akt activation and that PEAPUV exerts its vaso-protective effect through Akt signalling inhibition. HPLC analysis confirmed a different composition both in polyphenols quality and in quantity of the two extracts. In conclusion, this study shows that a stress factor such as UV light exposure leads to the production by A. platensis of molecules to potentially be used against the onset and progression of vascular diseases associated with endothelial dysfunction

ILC Reference Design Report Volume 1 - Executive Summary

The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities. The ILC has a total footprint of about 31 km and is designed for a peak luminosity of 2x10^34 cm^-2s^-1. This report is the Executive Summary (Volume I) of the four volume Reference Design Report. It gives an overview of the physics at the ILC, the accelerator design and value estimate, the detector concepts, and the next steps towards project realization.The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities. The ILC has a total footprint of about 31 km and is designed for a peak luminosity of 2x10^34 cm^-2s^-1. This report is the Executive Summary (Volume I) of the four volume Reference Design Report. It gives an overview of the physics at the ILC, the accelerator design and value estimate, the detector concepts, and the next steps towards project realization

ILC Reference Design Report Volume 4 - Detectors

This report, Volume IV of the International Linear Collider Reference Design Report, describes the detectors which will record and measure the charged and neutral particles produced in the ILC's high energy e+e- collisions. The physics of the ILC, and the environment of the machine-detector interface, pose new challenges for detector design. Several conceptual designs for the detector promise the needed performance, and ongoing detector R&D is addressing the outstanding technological issues. Two such detectors, operating in push-pull mode, perfectly instrument the ILC interaction region, and access the full potential of ILC physics.This report, Volume IV of the International Linear Collider Reference Design Report, describes the detectors which will record and measure the charged and neutral particles produced in the ILC's high energy e+e- collisions. The physics of the ILC, and the environment of the machine-detector interface, pose new challenges for detector design. Several conceptual designs for the detector promise the needed performance, and ongoing detector R&D is addressing the outstanding technological issues. Two such detectors, operating in push-pull mode, perfectly instrument the ILC interaction region, and access the full potential of ILC physics

ILC Reference Design Report Volume 3 - Accelerator

The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities. The ILC has a total footprint of about 31 km and is designed for a peak luminosity of 2x10^34 cm^-2 s^-1. The complex includes a polarized electron source, an undulator-based positron source, two 6.7 km circumference damping rings, two-stage bunch compressors, two 11 km long main linacs and a 4.5 km long beam delivery system. This report is Volume III (Accelerator) of the four volume Reference Design Report, which describes the design and cost of the ILC.The International Linear Collider (ILC) is a 200-500 GeV center-of-mass high-luminosity linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency (SCRF) accelerating cavities. The ILC has a total footprint of about 31 km and is designed for a peak luminosity of 2x10^34 cm^-2 s^-1. The complex includes a polarized electron source, an undulator-based positron source, two 6.7 km circumference damping rings, two-stage bunch compressors, two 11 km long main linacs and a 4.5 km long beam delivery system. This report is Volume III (Accelerator) of the four volume Reference Design Report, which describes the design and cost of the ILC

International Linear Collider Reference Design Report Volume 2: PHYSICS AT THE ILC

This article reviews the physics case for the ILC. Baseline running at 500 GeV as well as possible upgrades and options are discussed. The opportunities on Standard Model physics, Higgs physics, Supersymmetry and alternative theories beyond the Standard Model are described.This article reviews the physics case for the ILC. Baseline running at 500 GeV as well as possible upgrades and options are discussed. The opportunities on Standard Model physics, Higgs physics, Supersymmetry and alternative theories beyond the Standard Model are described