Growth, structure and electrical conduction of WO3 nanorods

We present a very simple method to obtain tungsten trioxide nanorods. The nanorods are epitaxially grown on a mica substrate in low supersaturation conditions. Investigations of morphology, crystallographic structure and chemical composition of the nanorods allow us to propose a growth model in which the potassium ions of the substrate play a major role inducing the one-dimensional structure. The nanorod growth is initiated by the formation of a hexagonal tungsten bronze (HTB) epitaxially oriented on the mica. By using a conductive atomic force microscopy technique, we characterise the electrical conduction of WO₃ networks.     

Incorporating partial matches within multiobjective pharmacophore identification

This paper describes the extension of our earlier multiobjective method for generating plausible pharmacophore hypotheses to incorporate partial matches. Diverse sets of molecules rarely adopt exactly the same binding mode, and so allowing the identification of partial matches allows our program to be applied to larger and more diverse datasets. The method explores the conformational space of a series of ligands simultaneously with their alignment using a multiobjective genetic algorithm (MOGA). The principles of Pareto ranking are used to evolve a diverse set of pharmacophore hypotheses that are optimised on conformational energy of the ligands, the goodness of the overlay and the volume of the overlay. A partial match is defined as a pharmacophoric feature that is present in at least two, but not all, of the ligands in the set. The number of ligands that map to a given pharmacophore point is taken into account when evaluating an overlay. The method is applied to a number of test cases extracted from the Protein Data Bank (PDB) where the true overlay is known.     

Integrated receiver architectures for board-to-board free-space optical interconnects

In many computer and server communications copper cables and wires are currently being used for data transmission and interconnects. However, due to significant shortcomings, such as long transmission time, high noise level, unstable electrical properties, and high power consumption for cooling, researchers are increasingly turning their research interests toward alternatives, such as fiber optic interconnects and free-space optical communication technologies. In this paper, we present design considerations for an integrated receiver for high-speed free-space line-of-sight optical interconnects for distortion-free data transmission in an environment with mechanical vibrations and air turbulences. The receiver consists of an array of high-speed photodiodes for data communication and an array of quadrant photodiodes for real-time beam tracking in order to compensate for the beam misalignment caused by vibrations in servers. Different configurations for spatially positioning the quadrant and data photodiodes are discussed for 4×4 and 9×9 multielement optical detector arrays. We also introduce a new beam tracking device, termed the strip quadrant photodiodes, in order to accurately track highly focused optical beams with very small beam diameter.     

Hydrostatic pressure effect on commensurate—incommensurate transition in K2SeO4-Elastic anomalies studied by Brillouin scattering

A Brillouin scattering study of the commensurate—incommensurate transition in K₂SeO₄ submitted to a hydrostatic pressure was performed. It was found that an increasing pressure lowers the transition temperature (dT_i/dP_i = ?59 K/GPa). The strong anomalies of velocity and damping of the longitudinal acoustic wave propagating along [0 0 1] are weakly affected when pressure acts. The effect of pressure on these anomalies has been calculated on the basis of the lowest order couplings eQ² and e²Q² between strain e and order parameter Q.     

Structure and electrical conduction of WO3 nanorods epitaxially grown on mica

Tunsten oxide nanorods are grown on mica substrate in air from WO₃ vapor at 590 °C. They are epitaxially oriented on the substrate in three directions according to the hexagonal symmetry of the mica. Their morphology was investigated by Atomic Force Microscopy (AFM), their structure by Electron Diffraction (ED) and High Resolution Electron Microscopy (HRTEM). The energy dispersive X-ray analysis (EDX) associated with the TEM revealed the presence of potassium in the first step of the nanostructures growth suggesting the formation of a tungsten bronze. According to their thickness the nanorods have a structure either hexagonal or monoclinic. The structural investigations showed that numerous kinds of planar defects parallel to the growth direction are formed. The electrical conduction was analyzed with a Conductive Atomic Force Microscopy (CAFM) method which allows to obtain either an image of the resistance variations along the nanorods or a current-voltage response. The result demonstrates that the WO₃ nanorods form electrically networks suitable for gas sensing experiments.