Uranium oligomerization in chloride-based high temperature melts: in situ XAS studies

In situ EXAFS spectroscopic studies of uranium compounds in high temperature alkali chloride melts indicate the presence of oligomeric species. An investigation into UCl(3) and UCl(4) dissolved in LiCl reveals long range ordering of uranium atoms in the molten state which is not maintained on quenching. Studies of uranium dioxide dissolved in LiCl-KCl eutectic with HCl exhibit long range ordering in both molten and quenched states, and the EXAFS data can be modeled using multiple coordination shells.     

The decapod crustacean circulatory system: a case that is neither open nor closed.

Historically, the decapod crustacean circulatory system has been classed as open. However, recent work on the blue crab, Callinectes sapidus, suggests the circulatory system may be more complex than previously described. Corrosion casting techniques were refined and used to map the circulatory system of a variety of crab species (order: Decapoda; family: Cancridae) to determine if the complexity observed in the blue crab was present in other species. Seven arteries arose from the single chambered heart. The anterior aorta, the paired anterolateral arteries, and the paired hepatic arteries exited from the anterior aspect of the heart. The small-diameter posterior aorta exited posteriorly from the heart. Exiting from the ventral surface of the heart, the sternal artery branched to supply the legs and mouthparts of the crab. These arteries were more complex than previously described, with arterioles perfusing all areas of the body. The arterioles split into fine capillary-like vessels. Most of these capillaries were blind ending. However, in several areas (antennal gland, supraesophageal ganglion) complete capillary beds were present. After passing through the capillary-like vessels, blood drained into a series of sinuses. However, rather than being arbitrary spaces as previously described, scanning electron micrographs showed the sinuses to be distinct units. Most of the sinuses formed a series of flattened membrane-bound lacunae. This complexity may qualify the decapod crustacean circulatory system as one that is "partially closed" rather than open.     

Knowledge-based interaction fingerprint scoring: a simple method for improving the effectiveness of fast scoring functions

A new method for the postprocessing of docking outputs has been developed, based on encoding putative 3D binding modes (docking solutions) as ligand-protein interactions into simple bit strings, a method analogous to the structural interaction fingerprint. Instead of employing traditional scoring functions, the method uses a series of new, knowledge-based scores derived from the similarity of the bit strings for each docking solution to that of a known reference binding mode. A GOLD docking study was carried out using the Bissantz estrogen receptor antagonist set along with the new scoring method. Superior recovery rates, with up to 2-fold enrichments, were observed when the new knowledge-based scoring was compared to the GOLD fitness score. In addition, top ranking sets of molecules (actives and potential actives or decoys) were structurally diverse with low molecular weights and structural complexities. Principal component analysis and clustering of the fingerprints permits the easy separation of active from inactive binding modes and the visualization of diverse binding modes.     

Oxoneptunium(v) as part of the framework of a polyoxometalate

(NH4)14Na4[(Np3W4O15)(H2O)3(BiW9O33)3].62H2O (1) and (NH4)14.5Na3.5[(Np3W4O15)(H2O)3(SbW9O33)3].40.5H2O (2) each contain three neptunyl(v) moieties encapsulated within heteropolyoxotungstate frameworks in which axial {NpO2}+ oxygens form one face of a WO6 octahedron.     

Dielectric elastomer switches for smart artificial muscles

Some of the most exciting possibilities for dielectric elastomer artificial muscles consist of biologically inspired networks of smart actuators working towards common goals. However, the creation of these networks will only be realised once intelligence and feedback can be fully distributed throughout an artificial muscle device. Here we show that dielectric elastomer artificial muscles can be built with intrinsic sensor, control, and driver circuitry, bringing them closer in capability to their natural analogues. This was achieved by exploiting the piezoresistive behaviour of the actuator’s highly compliant electrodes using what we have called the dielectric elastomer switch. We developed suitable switching material using carbon loaded silicone grease and experimentally demonstrated the primitives required for self-sensing actuators and digital computation, namely compliant electromechanical NAND gates and oscillator circuits. We anticipate that dielectric elastomer switches will reduce the need for bulky and rigid external circuitry as well as provide the simple distributed intelligence required for soft, biologically inspired networks of actuators. Examples include many-degree-of-freedom robotic hearts, intestines, and manipulators; wearable assistive devices; smart sensor skins and fabrics; and ultimately new types of artificial muscle embedded, electromechanical computers.     

On the Stability of Travelling Waves Arising in Nematic Liquid Crystals

Abstract

The stability of travelling waves which occur when a nematic liquid crystal is subjected to crossed electric and magnetic fields has been studied previously where conditions on a control parameter q for stability to occur have been given. This article is concerned with the behaviour of the stable perturbations as time increases. For each of the three travelling wave solutions we can determine the long-term monotonic or oscillatory behaviour of the perturbations using knowledge of the spectrum of the operator governing the perturbation equation.     

Finding thermoacoustic limit cycles for a ducted Burke-Schumann flame

This paper examines nonlinear thermoacoustic oscillations of a ducted Burke-Schumann diffusion flame. The nonlinear dynamics of the thermoacoustic system are studied using two distinct approaches. In the first approach, a continuation analysis is performed to find limit cycle amplitudes over a range of operating conditions. The strength of this approach is that one can characterize the coupled system’s nonlinear behaviour over a large parameter space with relative ease. It is not able to give physical insight into that behaviour, however. The second approach uses a Flame Describing Function (FDF) to characterize the flame’s response to harmonic velocity fluctuations over a range of forcing frequencies and forcing amplitudes, from which limit cycle amplitudes can be found. A strength of the FDF approach is that it reveals the physical mechanisms responsible for the behaviour observed. However, the calculation of the FDF is time consuming, and it must be recalculated if the flame’s operating conditions change. With the strengths and shortcomings of the two approaches in mind, this paper advocates combining the two to provide the dynamics over a large parameter space and, furthermore, physical insight into that behaviour at judiciously-chosen points in the parameter space. Further physical insight concerning the flame’s near-linear response at all forcing amplitudes is given by studying the forced flame in the time domain. It is shown that, for this flame model, the limit cycles arise because of the flame’s nonlinear behaviour when it is close to the inlet.     

Development of high resolution resonance ionization mass spectrometry for trace analysis of 93mNb

⁹³Nb(n, n′)^93mNb reaction allows retrospective estimation of integrated fast neutron dose in nuclear reactor. We proposed isomer-selective trace analysis of ^93mNb by Resonance Ionization Mass Spectrometry (RIMS) combined with a gas-jet atomic source and an injection locked Ti:Sapphire laser system operated at several kHz. Resonant ionization spectroscopy of Nb in gas-jet using Ti:Sapphire laser was demonstrated.