Low-temperature oxidation reactions of ethane over a Pt/Al2O3 catalyst

Oxidative dehydrogenation of ethane was performed under conventional microreactor and TAP reactor conditions over a Pt/Al2O3 catalyst between 100 and 600 degreesC. During TAP studies, no ethene was produced whereas under flow conditions small but significant ethene formation was observed. This is consistent with a mechanism involving the gas-phase production of ethene rather than via a surface reaction. In comparison, both hydrogen and methane formation were found under TAP conditions and the trends with temperature and surface oxide composition are interpreted in terms of successive dehydrogenation steps on the catalyst surface. It is further observed that periodic introduction of the reactants can minimize deactivation processes. (C) 2003 Elsevier Inc. All rights reserved.

Dye adsorption onto mesoporous materials: PH influence, kinetics and equilibrium in buffered and saline media

Mesoporous materials were used as adsorbents for dye removal in different media: non-ionic, buffered and saline. The mesoporous materials used were commercial (silica gel) as well as as-synthesised materials (SBA-15 and a novel mesoporous carbon). Dye adsorption onto all the materials was very fast and the equilibrium was reached before 1h. The pH has a significant influence on the adsorption capacity for the siliceous materials since the electrostatic interactions are the driving forces. However, the influence of the pH on the adsorption capacity of the carbonaceous material was lower, since the van der Waals interactions are the driving forces. The ionic strength has a great impact on the siliceous materials adsorption capacity, being their adsorption capacity in a buffered medium six times higher than the corresponding to a non-ionic medium. Nevertheless, ionic strength does not influence on the dye adsorption on the mesoporous carbon. Overall, the as-synthesised carbon material presents a clear potential to treat dye effluents, showing high adsorption capacity (q_e≈200mg/g) in all the pH range studied (from 3 to 11); even at low concentrations (C_e≈10mg/L) and at short contact times (t_e<30min).

Comparison of a centralised and distributed approach for a generic scheduling system

PEGS (Production and Environmental Generic Scheduler) is a generic production scheduler that produces good schedules over a wide range of problems. It is centralised, using search strategies with the Shifting Bottleneck algorithm. We have also developed an alternative distributed approach using software agents. In some cases this reduces run times by a factor of 10 or more. In most cases, the agent-based program also produces good solutions for published benchmark data, and the short run times make our program useful for a large range of problems. Test results show that the agents can produce schedules comparable to the best found so far for some benchmark datasets and actually better schedules than PEGS on our own random datasets. The flexibility that agents can provide for today's dynamic scheduling is also appealing. We suggest that in this sort of generic or commercial system, the agent-based approach is a good alternative.

Dilute acid hydrolysis of cellulose and cellulosic bio-waste using a microwave reactor system

The dilute acid hydrolysis of grass and cellulose with phosphoric acid was undertaken in a microwave reactor system. The experimental data and reaction kinetic analysis indicate that this is a potential process for cellulose and hemi-cellulose hydrolysis, due to a rapid hydrolysis reaction at moderate temperatures. The optimum conditions for grass hydrolysis were found to be 2.5% phosphoric acid at a temperature of 175 degrees C. It was found that sugar degradation occurred at acid concentrations greater than 2.5% (v/v) and temperatures greater than 175 degrees C. In a further series of experiments, the kinetics of dilute acid hydrolysis of cellulose was investigated varying phosphoric acid concentration and reaction temperatures. The experimental data indicate that the use of microwave technology can successfully facilitate dilute acid hydrolysis of cellulose allowing high yields of glucose in short reaction times. The optimum conditions gave a yield of 90% glucose. A pseudo-homogeneous consecutive first order reaction was assumed and the reaction rate constants were calculated as: k(1) = 0.0813 s(-1); k(2) = 0.0075 s(-1), which compare favourably with reaction rate constants found in conventional non-microwave reaction systems. The kinetic analysis would indicate that the primary advantages of employing microwave heating were to: achieve a high rate constant at moderate temperatures: and to prevent 'hot spot' formation within the reactor, which would have cause localised degradation of glucose.

RNA interference in a cestode reveals specific silencing of selected highly expressed gene transcripts

Evolving RNA interference (RNAi) platforms are providing opportunities to probe gene function in parasitic helminths using reverse genetics. Although relatively robust methods for the application of RNAi in parasitic flatworms have been established, reports of successful RNAi are confined to three genera and there are no known reports of the application of RNAi to the class Cestoda. Here we report the successful application of RNAi to a cestode. Our target species was the common ruminant tapeworm, Moniezia expansa which can significantly impact the health/productivity of cattle, sheep and goats. Initial efforts aimed to silence the neuronally expressed neuropeptide F gene (Me-npf-1), which encodes one of the most abundant neuropeptides in flatworms and a homologue of vertebrate neuropeptide Y (NPY). Double stranded (ds)RNAs, delivered by electroporation and soaking (4-8 h), failed to trigger consistent Me-npf-1 transcript knock-down in adult worms; small interfering RNAs (siRNAs) were also ineffective. Identical approaches resulted in significant and consistent transcript knock-down of actin transcript (71 +/- 4%) following soaking in Me-act-1 dsRNA. Similar successes were seen with hydrophobic lipid-binding protein (Me-lbp-1), with a dsRNA inducing significant target transcript reduction (72 +/- 5%). To confirm the validity of the observed transcript knock-downs we further investigated Me-act-1 RNAi worms for associated changes in protein levels, morphology and phenotype. Me-act-1 RNAi worms displayed significant reductions in both filamentous actin immunostaining (62 +/- 3%) and the amount of actin detected in Western blots (54 +/- 13%). Morphologically, Me-act-1 RNAi worms displayed profound tegumental disruption/blebbing. Further, muscle tension recordings from Me-act-1 RNAi worms revealed a significant reduction in both the number of worms contracting in response to praziquantel (20 +/- 12%) and in their contractile ability. These data demonstrate, to our knowledge for the first time, a functional RNAi pathway in a cestode and show that the robust knock-down of abundant gene transcripts is achievable using long dsRNAs following short exposure times. (C) 2009 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

Rheological Evaluation of the Isothermal Cure Characteristics of Medical Grade Silicone Elastomers

Silicone elastomer systems have been shown to offer potential for the fabrication of medical devices and sustained release drug delivery devices comprising low molecular weight drugs and protein therapeutics. For drug delivery systems in particular, there is often no clear rationale for selection of the silicone elastomer grade, particularly in respect of optimizing the manufacturing conditions to ensure thermal stability of the active agent and short cycle times. In this study, the cure characteristics of a range of addition-cure and condensation-cure, low-consistency, implant-grade silicone elastomers, either as supplied or loaded with the model protein bovine serum albumin (BSA) and the model hydrophilic excipient glycine, were investigated using oscillatory rheology with a view to better understanding the isothermal cure characteristics. The results demonstrate the influence of elastomer type, cure temperature, protein loading, and glycine loading on isothermal cure properties. By measuring the cure time required to achieve tan delta values representative of early and late-stage cure conditions, a ratio t(1)/t(2) was defined that allowed the cure characteristics of the various systems to be compared. Sustained in vitro release of BSA from glycine-loaded silicone elastomer covered rod devices was also demonstrated over 14 days. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 2320-2327, 2010

Acid-catalyzed hydrolysis of cellulose and cellulosic waste using a microwave reactor system

A microwave reactor system was investigated as a potential technique to maximize sugar yield for the hydrolysis of municipal solid waste for ethanol production. Specifically, dilute acid hydrolysis of a-cellulose and waste cellulosic biomass (grass clippings) with phosphoric acid was undertaken within the microwave reactor system. The experimental data and reaction kinetic analysis indicate that the use of a microwave reactor system can successfully facilitate dilute acid hydrolysis of cellulose and waste cellulosic biomass, producing high yields of total sugars in short reaction times. The maximum yield of reducing sugars was obtained at 7.5% (w/v) phosphoric acid and 160 degrees C, corresponding to 60% of the theoretical total sugars, with a reaction time of 5 min. When using a very low acid concentration (0.4% w/v) for the hydrolysis in the microwave reactor, it was found that 10 g of total sugars/100 g dry mass was produced, which is significant considering the low acid concentration. When hydrolyzing grass clippings using the microwave reactor, the optimum conditions were an acid concentration of 2.5% (w/v), 175 degrees C with a 15 min reaction time, giving 18 g/100 g dry mass of total sugars, with xylose being the sugar with the highest yield. It was observed that pentose sugars were more easily formed but also more easily degraded, these being significantly affected by increases in acid concentration and temperature. Kinetic modeling of the data indicated that the use of microwave heating may account for an increase in reaction rate constant, k(1), found in this study in comparison with conventional systems described in the literature.

Factors influencing the activity of taurolidine against spores of Bacillus subtilis (NCTC 10073)

The cidal activities of aqueous taurolidine (2.0% w/v containing 5.0% wlv polyvinylpyrrolidone as a solubilising agent) and alcoholic taurolidine (2.0% w/v dissolved in Isopropyl alcohol 50% v/v) against spores of Bacillus subtilis NCTC 10073 were evaluated at 20 degrees C, 37 degrees C, 45 degrees C and 55 degrees C. Increased temperature increased both the rate and extent of sporicidal activity of both solutions. Total spore kill was not observed in either solution type over the range of temperatures and contact times examined. There were no observed differences between the sporicidal activities of aqueous and alcoholic taurolidine solutions at all temperatures examined. Ultrasonic energy (50 Hz operating frequency in a 150 W ultrasonic bath in conjunction with increasing temperature allowed to rise naturally from ambient temperature to 41 degrees C over 4 h) enhanced the sporicidal activities of both solution types. However, the difference in activity between the two solution types was not significant. Compared to normal spores, alteration of spore coat layers (hydrogen-form spores) did not alter spore susceptibility to aqueous taurolidine at elevated temperatures of 37 degrees C and 55 degrees C.

Investigating the efficiency of fitting Coxian phase-type distributions to health care data

Coxian phase-type distributions are becoming a popular means of representing survival times within a health care environment. They are favoured as they show a distribution as a system of phases and can allow for an easy visual representation of the rate of flow of patients through a system. Difficulties arise, however, in determining the parameter estimates of the Coxian phase-type distribution. This paper examines ways of making the fitting of the Coxian phase-type distribution less cumbersome by outlining different software packages and algorithms available to perform the fit and assessing their capabilities through a number of performance measures. The performance measures rate each of the methods and help in identifying the more efficient. Conclusions drawn from these performance measures suggest SAS to be the most robust package. It has a high rate of convergence in each of the four example model fits considered, short computational times, detailed output, convergence criteria options, along with a succinct ability to switch between different algorithms.

Methylation using dimethylcarbonate catalysed by ionic liquids under continuous flow conditions

The ionic liquid, tributylmethylammonium methylcarbonate, has been employed as a catalytic base for clean N-methylation of indole with dimethylcarbonate. The reaction conditions were optimised under microwave heating to give 100% conversion and 100% selectivity to N-methylindole, and subsequently transferred to a high temperature/high pressure (285 degrees C/150 bar) continuous flow process using a short (3 min) residence time and 2 mol% of the catalyst to efficiently methylate a variety of different amines, phenols, thiophenols and carboxylic acid substrates. The extremely short residence times, versatility, and high selectivity have significant implications for the synthesis of a wide range of pharmaceutical intermediates, as high product throughputs can be obtained via this scalable continuous flow protocol. It has also been shown that the ionic liquid can be generated in situ from tributylamine, which has the net effect of transforming an ineffective stoichiometric base into a highly efficient catalyst for this broad class of reactions.

Super-luminous Type Ic Supernovae: Catching a Magnetar by the Tail

We report extensive observational data for five of the lowest redshift Super-Luminous Type Ic Supernovae (SL-SNe Ic) discovered to date, namely, PTF10hgi, SN2011ke, PTF11rks, SN2011kf, and SN2012il. Photometric imaging of the transients at +50 to +230 days after peak combined with host galaxy subtraction reveals a luminous tail phase for four of these SL-SNe. A high-resolution, optical, and near-infrared spectrum from xshooter provides detection of a broad He I ?10830 emission line in the spectrum (+50 days) of SN2012il, revealing that at least some SL-SNe Ic are not completely helium-free. At first sight, the tail luminosity decline rates that we measure are consistent with the radioactive decay of 56Co, and would require 1-4 M ? of 56Ni to produce the luminosity. These 56Ni masses cannot be made consistent with the short diffusion times at peak, and indeed are insufficient to power the peak luminosity. We instead favor energy deposition by newborn magnetars as the power source for these objects. A semi-analytical diffusion model with energy input from the spin-down of a magnetar reproduces the extensive light curve data well. The model predictions of ejecta velocities and temperatures which are required are in reasonable agreement with those determined from our observations. We derive magnetar energies of 0.4 <~ E(1051 erg) lsim 6.9 and ejecta masses of 2.3 <~ M ej(M ?) lsim 8.6. The sample of five SL-SNe Ic presented here, combined with SN 2010gx—the best sampled SL-SNe Ic so far—points toward an explosion driven by a magnetar as a viable explanation for all SL-SNe Ic.

Geophysical and hydrogeological characterisation of the impacts of on-site wastewater treatment discharge to groundwater in a poorly productive bedrock acquifer

Contaminants discharging from on-site wastewater treatment systems (OSWTSs) can impact groundwater quality, threatening human health and surface water ecosystems. Risk of negative impacts becomes elevated in areas of extreme vulnerability with high water tables, where thin unsaturated intervals limit vadose zone attenuation. A combined geophysical/hydrogeological investigation into the effects of an OSWTS, located over a poorly productive aquifer (PPA) with thin subsoil cover, aimed to characterise effluent impacts on groundwater. Groundwater, sampled from piezometers down-gradient of the OSWTS percolation area displayed spatially erratic, yet temporally consistent, contaminant distributions. Electrical resistivity tomography identified an area of gross groundwater contamination close to the percolation area and, when combined with seismic refraction and water quality data, indicated that infiltrating effluent reaching the water table discharged to a deeper more permeable zone of weathered shale resting on more competent bedrock. Subsurface structure, defined by geophysics, indicated that elevated chemical and microbiological contaminant levels encountered in groundwater samples collected from piezometers, down-gradient of sampling points with lower contaminant levels, corresponded to those locations where piezometers were screened close to the weathered shale/competent rock interface; those immediately up-gradient were too shallow to intercept this interval, and thus the more impacted zone of the contaminant plume. Intermittent occurrence of faecal indicator bacteria more than 100 m down gradient of the percolation area suggested relatively short travel times. Study findings highlight the utility of geophysics as part of multidisciplinary investigations for OSWTS contaminant plume characterisation, while also demonstrating the capacity of effluent discharging to PPAs to impact groundwater quality at distance. Comparable geophysical responses observed in similar settings across Ireland suggest the phenomena observed in this study are more widespread than previously suspected.

Sequential measurement-based quantum computing with memories

We introduce a general scheme for sequential one-way quantum computation where static systems with long-living quantum coherence (memories) interact with moving systems that may possess very short coherence times. Both the generation of the cluster state needed for the computation and its consumption by measurements are carried out simultaneously. As a consequence, effective clusters of one spatial dimension fewer than in the standard approach are sufficient for computation. In particular, universal computation requires only a one-dimensional array of memories. The scheme applies to discrete-variable systems of any dimension as well as to continuous-variable ones, and both are treated equivalently under the light of local complementation of graphs. In this way our formalism introduces a general framework that encompasses and generalizes in a unified manner some previous system-dependent proposals. The procedure is intrinsically well suited for implementations with atom-photon interfaces.

More bang for your buck: Super-adiabatic quantum engines

The practical untenability of the quasi-static assumption makes any realistic engine intrinsically irreversible and its operating time finite, thus implying friction effects at short cycle times. An important technological goal is thus the design of maximally efficient engines working at the maximum possible power. We show that, by utilising shortcuts to adiabaticity in a quantum engine cycle, one can engineer a thermodynamic cycle working at finite power and zero friction. Our findings are illustrated using a harmonic oscillator undergoing a quantum Otto cycle.

Bioavailability of 2,4-dichlorophenol associated with soil water-soluble humic material

Interaction of organic xenobiotics with soil water-soluble humic material (WSHM) may influence their environmental fate and bioavailability. We utilized bacterial assays (lux-based toxicity and mineralization by Burkholderia sp. RASC) to assess temporal changes in the bioavailability of [¹⁴C]-2,4-dichlorophenol (2,4-DCP) in soil water extracts (29.5 μg mL^-1 2,4-DCP; 840.2 μg mL^-1 organic carbon). HPLC determined and bioavailable concentrations were compared. Gel permeation chromatography (GPC) was used to confirm the association of a fraction (>50%) of [¹⁴C]-2,4-DCP with WSHM. Subtle differences in parameters describing 2,4-DCP mineralization curves were recorded for different soil-2,4-DCP contact times. Problems regarding the interpretation of mineralization data when assessing the bioavailability of toxic compounds are discussed. The lux-bioassay revealed a time-dependent reduction in 2,4-DCP bioavailability: after 7 d, less than 20% was bioavailable. However, GPC showed no quantitative difference in the amount of WSHM-associated 2,4-DCP over this time. These data suggest qualitative changes in the nature of the 2,4-DCP-WSHM association and that associated 2,4-DCP may exert a toxic effect. Although GPC distinguished between free- and WSHM-associated 2,4-DCP, it did not resolve the temporal shift in bioavailability revealed by the lux biosensor. These results stress that assessment of risk posed by chemicals must be considered using appropriate biological assays.