Non-linear optical deformation potentials in uniaxially strained ZnO microwires

The emission properties of bent ZnO microwires with diameters ranging from 1.5  μm to 7.3  μm are systematically investigated by cathodoluminescence spectroscopy at T ≈ 10 K. We induced uniaxial strains along the c-axis of up to ±2.9 %. At these high strain values, we observe a nonlinear shift of the emission energy with respect to the induced strain, and the magnitude of the energy shift depends on the sign of the strain. The linear and non-linear deformation potentials were determined to be D1=−2.50±0.05 eV and D2=−15.0±0.5 eV, respectively. The nonlinearity of the energy shift is also reflected in the observed spectral broadening of the emission peak as a function of the locally induced strain, which decreases with increasing strain on the compressive side and increases on the tensile side

Tracking Down Duodenopancreatic Malignancy

Background Malignant tumours of the duodenum are rare and often difficult to diagnose. Due to the small clinical experience with duodenal malignancies their prognosis is unknown and resection is the treatment of choice

A general approach applicable to other radiation sources and biological targets

The determination of the microscopic dose-damage relationship for DNA in an aqueous environment is of a fundamental interest for dosimetry and applications in radiation therapy and protection. We combine geant4 particle- scattering simulations in water with calculations concerning the movement of biomolecules to obtain the energy deposit in the biologically relevant nanoscopic volume. We juxtaposition these results to the experimentally determined damage to obtain the dose-damage relationship at a molecular level. This approach is tested for an experimentally challenging system concerning the direct irradiation of plasmid DNA (pUC19) in water with electrons as primary particles. Here a microscopic target model for the plasmid DNA based on the relation of lineal energy and radiation quality is used to calculate the effective target volume. It was found that on average fewer than two ionizations within a 7.5-nm radius around the sugar-phosphate backbone are sufficient to cause a single strand break, with a corresponding median lethal energy deposit being E1/2=6±4 eV. The presented method is applicable for ionizing radiation (e.g., γ rays, x rays, and electrons) and a variety of targets, such as DNA, proteins, or cells

Molecular Mechanisms

Ectoine, a compatible solute and osmolyte, is known to be an effective protectant of biomolecules and whole cells against heating, freezing and extreme salinity. Protection of cells (human keratinocytes) by ectoine against ultraviolet radiation has also been reported by various authors, although the underlying mechanism is not yet understood. We present the first electron irradiation of DNA in a fully aqueous environment in the presence of ectoine and at high salt concentrations. The results demonstrate effective protection of DNA by ectoine against the induction of single-strand breaks by ionizing radiation. The effect is explained by an increase in low-energy electron scattering at the enhanced free- vibrational density of states of water due to ectoine, as well as the use of ectoine as an hydroxyl-radical scavenger. This was demonstrated by Raman spectroscopy and electron paramagnetic resonance (EPR)

Corticothalamic projections control synchronization in locally coupled bistable thalamic oscillators

Thalamic circuits are able to generate state-dependent oscillations of different frequencies and degrees of synchronization. However, only little is known how synchronous oscillations, like spindle oscillations in the thalamus, are organized in the intact brain. Experimental findings suggest that the simultaneous occurrence of spindle oscillations over widespread territories of the thalamus is due to the corticothalamic projections, as the synchrony is lost in the decorticated thalamus. Here we study the influence of corticothalamic projections on the synchrony in a thalamic network, and uncover the underlying control mechanism, leading to a control method which is applicable in wide range of stochastic driven excitable units.Comment: 4 pages with 4 figures (Color online on p.3-4) include

Direct electron irradiation of DNA in a fully aqueous environment. Damage determination in combination with Monte Carlo simulations

We report on a study in which plasmid DNA in water was irradiated with 30 keV electrons generated by a scanning electron microscope and passed through a 100 nm thick Si3N4 membrane. The corresponding Monte Carlo simulations suggest that the kinetic energy spectrum of the electrons throughout the water is dominated by low energy electrons (<100 eV). The DNA radiation damage, single-strand breaks (SSBs) and double-strand breaks (DSBs), was determined by gel electrophoresis. The median lethal dose of D1/2 = 1.7 ± 0.3 Gy was found to be much smaller as compared to partially or fully hydrated DNA irradiated under vacuum conditions. The ratio of the DSBs to SSBs was found to be 1 : 12 as compared to 1 : 88 found for hydrated DNA. Our method enables quantitative measurements of radiation damage to biomolecules (DNA, proteins) in solutions under varying conditions (pH, salinity, co-solutes) for an electron energy range which is difficult to probe by standard methods

Measurements and simulations of microscopic damage to DNA in water by 30 keV electrons: A general approach applicable to other radiation sources and biological targets

The determination of the microscopic dose-damage relationship for DNA in an aqueous environment is of a fundamental interest for dosimetry and applications in radiation therapy and protection. We combine geant4 particle-scattering simulations in water with calculations concerning the movement of biomolecules to obtain the energy deposit in the biologically relevant nanoscopic volume. We juxtaposition these results to the experimentally determined damage to obtain the dose-damage relationship at a molecular level. This approach is tested for an experimentally challenging system concerning the direct irradiation of plasmid DNA (pUC19) in water with electrons as primary particles. Here a microscopic target model for the plasmid DNA based on the relation of lineal energy and radiation quality is used to calculate the effective target volume. It was found that on average fewer than two ionizations within a 7.5-nm radius around the sugar-phosphate backbone are sufficient to cause a single strand break, with a corresponding median lethal energy deposit being E1/2=6±4 eV. The presented method is applicable for ionizing radiation (e.g., γ rays, x rays, and electrons) and a variety of targets, such as DNA, proteins, or cells

Implications for the Binding of the Protein G5P to DNA

Microorganisms accumulate molar concentrations of compatible solutes like ectoine to prevent proteins from denaturation. Direct structural or spectroscopic information on the mechanism and about the hydration shell around ectoine are scarce. We combined surface plasmon resonance (SPR), confocal Raman spectroscopy, molecular dynamics simulations, and density functional theory (DFT) calculations to study the local hydration shell around ectoine and its influence on the binding of a gene-S-protein (G5P) to a single-stranded DNA (dT(25)). Due to the very high hygroscopicity of ectoine, it was possible to analyze the highly stable hydration shell by confocal Raman spectroscopy. Corresponding molecular dynamics simulation results revealed a significant change of the water dielectric constant in the presence of a high molar ectoine concentration as compared to pure water. The SPR data showed that the amount of protein bound to DNA decreases in the presence of ectoine, and hence, the protein-DNA dissociation constant increases in a concentration- dependent manner. Concomitantly, the Raman spectra in terms of the amide I region revealed large changes in the protein secondary structure. Our results indicate that ectoine strongly affects the molecular recognition between the protein and the oligonudeotide, which has important consequences for osmotic regulation mechanisms

Successful long-term monotherapy with rituximab in a patient with chronic lymphocytic leukemia of the B-cell-lineage: a case report

<p>Abstract</p> <p>Introduction</p> <p>Treatment of chronic lymphocytic leukemia of the B-cell-lineage is strongly based upon clinical staging because of the heterogeneous clinical course of this disease.</p> <p>Case presentation</p> <p>We describe a 62-year-old patient with newly diagnosed chronic lymphocytic leukemia of the B-cell-lineage who did not respond to several chemotherapy regimens including chlorambucil, fludarabine and cyclophosphamide, developing a marked neutropenia and thrombocytopenia with life-threatening infections. Further chemotherapy appeared not feasible because of bone marrow toxicity. The patient was treated with 600 mg/m²rituximab weekly followed by eight courses of biweekly therapy and then by long-term maintenance therapy, achieving almost complete remission of the symptoms and disease control.</p> <p>Conclusion</p> <p>After resistance to standard chemotherapy with chlorambucil and fludarabine, a patient with chronic lymphocytic leukemia of the B-cell-lineage was successfully treated with rituximab.</p

Strangeness Production close to Threshold in Proton-Nucleus and Heavy-Ion Collisions

We discuss strangeness production close to threshold in p+A and A+A collision. Comparing the body of available K+, K0, K-, and Lambda data with the IQMD transport code and for some key observables as well with the HSD transport code, we find good agreement for the large majority of the observables. The investigation of the reaction with help of these codes reveals the complicated interaction of the strange particles with hadronic matter which makes strangeness production in heavy-ion collisions very different from that in elementary interactions. We show how different strange particle observables can be used to study the different facets of this interaction (production, rescattering and potential interaction) which finally merge into a comprehensive understanding of these interactions. We identify those observables which allow for studying (almost) exclusively one of these processes to show how future high precision experiments can improve our quantitative understanding. Finally, we discuss how the K+ multiplicity can be used to study the hadronic equation of state.Comment: 134 pages, pdf 3.3MB, version to be published in Physics Report