Pulsed KrF laser deposited GaN/TiN/Si(111) heterostructures by sequential TiN and liquid Ga laser ablation

GaN/TiN heterostructures were deposited on 4° miscut Si(111) substrates by pulsed KrF laser ablation of TiN through vacuum, followed by reactive pulsed KrF laser ablation of liquid Ga through 70-75 mTorr of microwave-activated NH₃. Deposition temperatures of 950 °C and 1050 °C were employed for the TiN layer while 900 °C was employed for the GaN layer. The targets were positioned 5 cm from the substrate and ablated by using a reimaging beamline at a nominal energy density of 3-4 J/cm². X-ray diffraction (XRD) revealed a highly textured heterostructure with GaN(0001)//TiN(111)//Si(111) and with a rocking curve width for both GaN(0001) and TiN(111) equal to ~1.1°. The mosaic spread through the TiN(001) reflection was ~1.3°, whereas that of the GaN(101_1) was undetectable because of low S/N. Scanning electron microscopy revealed large oriented 10 7m-sized hexagonal crystallites decorating large depressions in the TiN film with many smaller pits also present. The effect of substrate processing and TiN film processing on pit formation was explored.     

Use of dyes in solid medium for screening ligninolytic activity of selective actinomycetes

Applied Biochemistry and Biotechnology -     

Coupled simulated distillation-mass spectrometry for the evaluation of hydroconverted petroleum residues

The coupling of simulated distillation by gas chromatography with mass spectrometry has been applied to the characterization of the products obtained by hydroconversion of a deasphalted vacuum residue, performed either in thermal, non-catalytic conditions, or in the presence of various dispersed catalysts. Applying spectra deconvolution techniques, the relative contribution of four saturated and four aromatic classes of hydrocarbons to the spectra is obtained and simulated distillation-mass spectrometry coupling provides the distribution of these classes of compounds along the distillation profile of the products. The impact of catalysts upon the distribution of the considered calsses of hydrocarbons has been evidenced. It consists in a reduction of aromatics and an increase of saturates. This analytical data can be rationalized and correlated with hydrogen distribution during hydroconversion, indicating that the role of catalysts does not consist in a simple hydrogenation of aromatics but in a complete redistribution of hydrogen. Coupled simulated distillation-mass spectrometry appears to be a valuable tool for a fast analytical characterization of complex hydroconversion products, without the need for previous separation steps.     

Dielectric constants of acetonitrile, γ-butyrolactone,propylene carbonate,and 1,2-dimethoxyethane as a function of pressure and temperature

The dielectric constants of 1,2-dimethoxyethane, acetonitrile, -butyrolactone, and propylene carbonate were determined from capacitance measurements extrapolated to infinite frequency; ln are reported as a function of pressure up to 80 MPa at 15, 25, 35, 45°C and as a function of temperature in the range 10 to 50°C at 0.10133 MPa. The variation of ln with temperature or pressure can be expressed by a second order polynomial expression. The isothermal compressibilities of the solvents were determined at 25°C from sound velocities, densities, and heat capacities. A simple correlation can be established between ln /P and for most aprotic solvent.     

Vibro-acoustic study of a viscoelastic sandwich ring immersed in water

This work deals with the reduction of the system composed of a sandwich structure with a viscoelastic core coupled to fluids. Two reduction methods are proposed in this paper to solve this problem in the frequency domain. The first one consists in developing added mass operators to take into account the fluid. The second one is the use of iterative methods to calculate the coupled complex modes of the dissipative problem. This numerical strategy is applied to the response of a bidimensional sandwich ring coupled to internal and external fluids.     

The SMILETRAP (Stockholm-Mainz-Ion-LEvitation-TRAP) facility

Described in this paper is an experimental facility which measures atomic masses by using multiply charged ions from an electron beam ion source. The ions are injected into a Penning trap and the cyclotron frequencies measured. A precision of 2×10^–9 has been reached using highly charged carbon, nitrogen, oxygen and neon.