Uranium removal from contaminated groundwater by synthetic resins

Synthetic resins are shown to be effective in removing uranium from contaminated groundwater. Batch and field column tests showed that strong-base anion-exchange resins were more effective in removing uranium from both near-neutral-pH (6.5)- and high-pH (8)-low-nitrate-containing groundwaters, than metal-chelating resins, which removed more uranium from acidic-pH (5)-high-nitrate-containing groundwater from the Oak Ridge Reservation (ORR) Y-12 S-3 Ponds area in Tennessee, USA. Dowex 1-X8 and Purolite A-520E anion-exchange resins removed more uranium from high-pH (8)-low-nitrate-containing synthetic groundwater in batch tests than metal-chelating resins. The Dowex™ 21K anion-exchange resin achieved a cumulative loading capacity of 49.8 mg g^-1 before breakthrough in a field column test using near-neutral-pH (6.5)-low-nitrate-containing groundwater. However, in an acidic-pH (5)-high-nitrate-containing groundwater, metal-chelating resins Diphonix and Chelex-100 removed more uranium than anion-exchange resins. In 15 mL of acidic-pH (5)-high-nitrate-containing groundwater spiked with 20 mg L^-1 uranium, the uranium concentrations ranged from 0.95 mg L^-1 at 1-h equilibrium to 0.08 mg L^-1 at 24-h equilibrium for Diphonix and 0.17 mg L^-1 at 1-h equilibrium to 0.03 mg L^-1 at 24-h equilibrium for Chelex-100. Chelex-100 removed more uranium in the first 10 min in the 100 mL of acidic-(pH 5)-high-nitrate-containing groundwater (~5 mg L^-1 uranium); however, after 10 min, Diphonix equaled or out-performed Chelex-100. This study presents an improved understanding of the selectivity and sorption kenetics of a range of ion-exchange resins that remove uranium from both low- and high-nitrate-containing groundwaters with varying pHs..

Electrode field penetration: A new interpretation of tunneling currents in barium strontium titanate (BST) thin films

This paper shows that penetration of the applied electric field into the electrodes of a ferroelectric thin film capacitor produces both an interfacial capacitance and an effective mechanism for electron tunneling. The model predictions are compared with experimental results on Au-BST-SrRuO3 capacitors of varying thicknesses, and the agreement is excellent.

Serendipitous Asteroid Lightcurve Survey Using SuperWASP

The SuperWASP project is an ultra-wide angle search for extra solar planetary transits. However, it can also serendipitously detect solar system objects, such as asteroids and comets. Each SuperWASP instrument consists of up to eight cameras, combined with high-quality peltier-cooled CCDs, which photometrically survey large numbers of stars in the magnitude range 7 15. Each camera covers a 7.8 × 7.8 degree field of view. Located on La Palma, the SuperWASP-I instrument has been observing the Northern Hemisphere with five cameras since its inauguration in April 2004. The ultra-wide angle field of view gives SuperWASP the possibility of discovering new fast moving (near to Earth) asteroids that could have been missed by other instruments. However, it provides an excellent opportunity to produce a magnitude-limited lightcurve survey of known main belt asteroids. As slow moving asteroids stay within a single SuperWASP field for several weeks, and may be seen in many fields, a survey of all objects brighter than magnitude 15 is possible. This will provide a significant increase in the total number of lightcurves available for statistical studies without the inherent bias against longer periods present in the current data sets. We present the methodology used in the automated collection of asteroid data from SuperWASP and some of the first examples of lightcurves from numbered asteroids.

Decision rules, energy metabolism and vigour of hermit-crab fights

Aggressive interactions between animals are often settled by the use of repeated signals that reduce the risk of injury from combat but are expected to be costly. The accumulation of lactic acid and the depletion of energy stores may constrain activity rates during and after fights and thus represent significant costs of signalling. We tested this by analysing the concentrations of lactate and glucose in the haemolymph of hermit crabs following agonistic interactions over the ownership of the gastropod shells that they inhabit. Attackers and defenders play distinct roles of sender and receiver that are fixed for the course of the encounter. Attackers perform bouts of 'shell rapping', which vary in vigour between attackers and during the course of the encounter, and are a key predictor of victory. In contrast to the agonistic behaviour of other species, we can quantify the vigour of fighting. We demonstrate, to our knowledge for the first time, an association between the vigour of aggressive activity and a proximate cost of signalling. We show that the lactate concentration in attackers increases with the amount of shell rapping, and that this appears to constrain the vigour of subsequent rapping. Furthermore, attackers, but not defenders, give up when the concentration of lactate is high. Glucose levels in attackers also increase with the amount of rapping they perform, but do not appear to influence their decision to give up. Defenders are more likely to lose when they have particularly low levels of glucose. We conclude that the two roles use different decision rules during these encounters.

Steric effects in the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol using an Ir/C catalyst

The liquid phase selective hydrogenation of cinnamaldehyde to cinnamyl alcohol has been carried out over a graphite-supported iridium catalyst. The effect of reaction parameters such as temperature, pressure, concentration of reactant, the effect of addition of product to the feed and pre-reduction of the catalyst were studied. In situ pre-reduction of the catalyst with hydrogen had a very significant enhancing effect on the conversion of cinnamaldehyde and selectivity of the catalyst to cinnamyl alcohol. Kinetic analysis of the pre-reduced catalyst showed that the reaction is zero order with respect to cinnamaldehyde and first order with respect to hydrogen. The reaction follows an Arrhenius behaviour with an activation energy of 37 kJ mol(-1). Detailed analysis of the reaction showed that hydrogenation of the C=C double bond to give hydrocinnamaldehyde predominantly occurred at low conversions of cinnamaldehyde (

Haptic information stabilizes and destabilizes coordination dynamics

Goal-directed, coordinated movements in humans emerge from a variety of constraints that range from 'high-level' cognitive strategies based oil perception of the task to 'low-level' neuromuscular-skeletal factors such as differential contributions to coordination from flexor and extensor muscles. There has been a tendency in the literature to dichotomize these sources of constraint, favouring one or the other rather than recognizing and understanding their mutual interplay. In this experiment, subjects were required to coordinate rhythmic flexion and extension movements with an auditory metronome, the rate of which was systematically increased. When subjects started in extension on the beat of the metronome, there was a small tendency to switch to flexion at higher rates, but not vice versa. When subjects: were asked to contact a physical stop, the location of which was either coincident with or counterphase to the auditor) stimulus, two effects occurred. When haptic contact was coincident with sound, coordination was stabilized for both flexion and extension. When haptic contact was counterphase to the metronome, coordination was actually destabilized, with transitions occurring from both extension to flexion on the beat and from flexion to extension on the beat. These results reveal the complementary nature of strategic and neuromuscular factors in sensorimotor coordination. They also suggest the presence of a multimodal neural integration process-which is parametrizable by rate and context - in which intentional movement, touch and sound are bound into a single, coherent unit.

Resistance training enhances the stability of sensorimotor coordination

Strategics for the control of human movement are constrained by the neuroanatomical characteristics of the motor system. In particular, there is evidence that the capacity of muscles for producing force has a strong influence on the stability of coordination in certain movement tasks. In the present experiment, our aim was to determine whether physiological adaptations that cause relatively long-lasting changes in the ability of muscles to produce force can influence the stability of coordination in a systematic manner. We assessed the effects of resistance training on the performance of a difficult coordination task that required participants to synchronize or syncopate movements of their index finger with an auditory metronome. Our results revealed that training that increased isometric finger strength also enhanced the stability of movement coordination. These changes were accompanied by alterations in muscle recruitment patterns. In Particular, the trained muscles were recruited in a more consistent fashion following the programme of resistance training. These results indicate that resistance training produces functional adaptations of the neuroanatomical constraints that underlie the control of voluntary movement.