New insights into the dynamics of the glutathione-ascorbate redox system of plants

The Hallilwell-Asada-Foyer redox cascade (HAF) is viewed as a H2O2 detoxifying system with a great variety of responses against environmental changes. The functional consequences of these responses are interpreted intuitively because a systemic analysis of the inherent dynamic potential of the HAF is lacking. With the help of numerical modelling we show that in wheat roots parameter patterns are established which result in homeostatic states of HAF over a vast range of environmental changes. The reduced fractions glutathione (GSH) and ascorbate (ASC) remain on high levels even during dramatic changes in the enzyme activity ratios of glutathione reductase, dehydroascorbate reductase and ascorbat peroxidase. Necessarily their oxidised counterparts dithioglutathione (GSSG) and dehydroascorbate (DHA) stay in these buffered regions on very low concentration levels. Our modelling shows that redox ratios GSH/GSSG and ASC/DHA can be modified additionally via changes in NADPH/H2O2 ratios. Thus, the redox states of GSH and ASC can not simply be regarded as indicators for oxidative stress with respect to H2O2 levels. The involvement of the redox variables in other redox processes than the HAF reaction (redox proteome) and / or their utilisation in metabolism (protein modification, detoxification of xenobiotics) are viewed to cause system relaxations of the redox variables. The re-establishment of their homeostatic ratios follow time courses which are redox moiety specific and are balanced according to the existing parameter patterns. Despite of its detoxification function the HAF balances the glutathione / ascorbate redox state in cells according to the prevailing physiological conditions

A priori convergence estimates for a rough Poisson-Dirichlet problem with natural vertical boundary conditions

Stents are medical devices designed to modify blood flow in aneurysm sacs, in order to prevent their rupture. Some of them can be considered as a locally periodic rough boundary. In order to approximate blood flow in arteries and vessels of the cardio-vascular system containing stents, we use multi-scale techniques to construct boundary layers and wall laws. Simplifying the flow we turn to consider a 2-dimensional Poisson problem that conserves essential features related to the rough boundary. Then, we investigate convergence of boundary layer approximations and the corresponding wall laws in the case of Neumann type boundary conditions at the inlet and outlet parts of the domain. The difficulty comes from the fact that correctors, for the boundary layers near the rough surface, may introduce error terms on the other portions of the boundary. In order to correct these spurious oscillations, we introduce a vertical boundary layer. Trough a careful study of its behavior, we prove rigorously decay estimates. We then construct complete boundary layers that respect the macroscopic boundary conditions. We also derive error estimates in terms of the roughness size epsilon either for the full boundary layer approximation and for the corresponding averaged wall law.Comment: Dedicated to Professor Giovanni Paolo Galdi 60' Birthda

Improving Monolithic Perovskite Silicon Tandem Solar Cells From an Optical Viewpoint

Perovskite silicon tandem solar cells are the most promising concept for a future photovoltaic technology. We report on recent progress from an optical viewpoint and disucss how we achieved more than 25 device efficienc

A branch-point approximant for the equation of state of hard spheres

Using the first seven known virial coefficients and forcing it to possess two branch-point singularities, a new equation of state for the hard-sphere fluid is proposed. This equation of state predicts accurate values of the higher virial coefficients, a radius of convergence smaller than the close-packing value, and it is as accurate as the rescaled virial expansion and better than the Pad\'e [3/3] equations of state. Consequences regarding the convergence properties of the virial series and the use of similar equations of state for hard-core fluids in $d$ dimensions are also pointed out.Comment: 6 pages, 4 tables, 3 figures; v2: enlarged version, extension to other dimensionalities; v3: typos in references correcte

Challenges to the development of antigen-specific breast cancer vaccines

Continued progress in the development of antigen-specific breast cancer vaccines depends on the identification of appropriate target antigens, the establishment of effective immunization strategies, and the ability to circumvent immune escape mechanisms. Methods such as T cell epitope cloning and serological expression cloning (SEREX) have led to the identification of a number target antigens expressed in breast cancer. Improved immunization strategies, such as using dendritic cells to present tumor-associated antigens to T lymphocytes, have been shown to induce antigen-specific T cell responses in vivo and, in some cases, objective clinical responses. An outcome of successful tumor immunity is the evolution of antigen-loss tumor variants. The development of a polyvalent breast cancer vaccine, directed against a panel of tumor-associated antigens, may counteract this form of immune escape

Effect of polarized gluon distribution on spin asymmetries for neutral and charged pion production

A longitudinal double spin asymmetry for \pi^0 production has been measured by the PHENIX collaboration. The asymmetry is sensitive to the polarized gluon distribution and is indicated to be positive by theoretical predictions. We study a correlation between behavior of the asymmetry and polarized gluon distribution in neutral and charged pion production at RHIC.Comment: 7 pages, 5 eps figures, section added, typos corrected. to be published in PR

Determination of the charge carrier compensation mechanism in Te-doped GaAs by scanning tunneling microscopy.

We identified the charge carrier compensation mechanism in Te-doped GaAs with atomically resolved scanning tunneling microscopy. Three types of defects were found: tellurium donors (Te-As), Ga vacancies (V-Ga), and Ga vacancy-donor complexes (V-Ga-Te-As). We show quantitatively that the compensation in Te-doped bulk GaAs is exclusively caused by vacancy-donor complexes in contrast to Si-doped GaAs. This is explained with the Fermi-level effect as the universal mechanism leading to Ga vacancy formation in n-doped GaAs, and a Coulomb interaction leading to the formation of the complexes. The quantification of the carrier compensation yields a -3e charge state of V-Ga in bulk GaAs. (C) 2003 American Institute of Physics

Institute of Ion Beam Physics and Materials Research: Annual Report 2001

Summary of the scientific activities of the institute in 2001 including selected highlight reports, short research contributions and an extended statistics overview

All-optical delay line using semiconductor cavity solitons

An all-optical delay line based on the lateral drift of cavity solitons in semiconductor microresonators is proposed and experimentally demonstrated. The functionalities of the device proposed as well as its performance is analyzed and compared with recent alternative methods based on the decrease of group velocity in the vicinity of resonances. We show that the current limitations can be overcome using broader devices with tailored material responses