Structural Phase Transitions in Niobium Hydrogen Thin Films: Mechanical Stress,Phase Equilibria and Critical Temperatures

Metal−hydrogen (M−H) systems offer grand opportunities for studies on fundamental aspects of thermodynamics and kinetics. When the system size is reduced to the nanoscale, microstructural defects as well as mechanical stress affect the systems’ properties. This is contemplated for the model system of epitaxial niobium−hydrogen (Nb−H) thin films. Hydrogen absorption in metals commonly leads to lattice expansion which is hindered when the metal adheres to a flat rigid substrate. Consequently, high mechanical stress of about −10 GPa for 1 H/Nb are predicted, in theory. However, metals cannot yield such high stresses and respond with plastic deformation, commonly limiting measured stresses to −2 to −3 GPa for 100 nm Nb−H films. It will be shown that the coherency state changes with film thickness reduction, shifting the onset of plastic deformation to larger hydrogen concentrations. Below critical film thicknesses, plastic deformation is fully absent. The system then behaves purely elastic and ultra-high stress of about −10 (±2) GPa can be obtained. Arising stress controls the phase stability of M−H systems, and the coherency state strongly affects the nucleation and growth dynamics of the phase transition. In case of Nb−H thin films of less than 8 nm thickness the common phase transformation from the α-phase solid solution to the hydride phase is completely suppressed at 300 K. Related effects can be utilised to optimise metal−hydrides used in applications.     

Diagnostics of properties of capacitor foil with extended nanostructured surface

The results of the study of nanostructured titanium coating used for producing cathode foils of electrolytic capacitors with the best operating characteristics in the world are described. The coating is produced by titanium deposition on an aluminum substrate by electron-beam evaporation in a nitrogen atmosphere. The study was performed using scanning electron microscopy, atomic-force microscopy, X-ray photoelectron spectroscopy, and thermodesorption spectroscopy.     

Data Interpretation in Mass Spectrometry

An algorithm was proposed for interpreting mass spectra. It allows sufficiently reliable determination of some individual components and improves the resolution of the procedure. The algorithm can be recommended for use with commercial instruments based on time-of-flight mass analyzers and mirror electro energy analyzers and is characterized by low resolution (today no more than 500, e.g. LAMMA-500 and LAMMA-1000).__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 8, 2005, pp. 790–793.Original Russian Text Copyright © 2005 by Burlaka, Maiboroda, Startseva.     

Superoxide- and NO-Dependent Mechanisms of the Reprogramming of Bone Marrow Cells by Tumor Cells

Electron paramagnetic resonance (EPR) experiments in vitro; spin trapping of the reactive oxygen/nitrogen species (superoxide radicals and nitric oxide, NO); gel zymography measurements in the tumor tissues, in the healthy and tumor-affected bone marrow (BM) samples of rats are carried out. The superoxide and NO generation rates are derived; matrix metalloproteinases (MMP-2 and MMP-9) concentrations are measured. Their changes after the incubation of BM samples with Guérin carcinoma cells at 37 °C are defined. It is shown that the impact of tumor cells on BM manifests in the metabolic disorder, increased concentrations of active forms of MMP-2 and MMP-9, increased production of superoxide and NO radicals. Correlation between the appearance and intensity of the broad EPR signal at g = 2.2–2.4 with the concentrations of active forms of MMP-2 and MMP-9, NO and superoxide radicals’ rates is observed. The obtained spatial and temporal changes of the measured parameters demonstrate the usefulness of the potential application of EPR imaging to study the mechanisms of tumor invasion. The EPR signal may indicate the presence of distant metastases, may become a part of diagnostics and used for the estimation of the therapeutic treatments in the pre-clinical studies. It is proposed that labile iron pool is responsible for the appearance of the EPR signal in tumor and BM samples.     

Deuterium release from lithium irradiated by deuterium plasma

Lithium targets are exposed to deuterium plasma with a fluence of 10²²–10²³ D/m² and then heated at a rate of about 5°C/s up to 600°C. Intense deuterium release starts at 400°C. Based on the TDS measurements, it is assumed that deuterium in Li exists in two equilibrium phases: a solid solution and LiD precipitates that start to actively decompose above 400°C.