Target Structure Induced Suppression of the Ionization Cross Section for Very Low Energy Antiproton-Hydrogen Collisions

Low energy antiprotons have been used previously to give benchmark data for theories of atomic collisions. Here we present measurements of the cross section for single, nondissociative ionization of molecular hydrogen for impact of antiprotons with kinetic energies in the range 2-11 keV, i.e., in the velocity interval of 0.3-0.65 a.u. We find a cross section which is proportional to the projectile velocity, which is quite unlike the behavior of corresponding atomic cross sections, and which has never previously been observed experimentally.

Structural and kinetic studies of spin crossover in an Iron(II) complex with a novel tripodal ligand

Configurational and ligand conformational influences on the kinetics of (1)A(1) reversible arrow T-5(2) spin crossover in the Fe(II) complex with the novel tripodal ligand, 1,1,1-tris((N-(2-pyridylmethyl)-N-methylamino)methyl)ethane (tptMetame), have been explored. Despite having six chelate rings and three chiral nitrogen atoms, only one enantiomeric pair of isomers, Delta, SSS, and Lambda, RRR, of the complex ion is observed. The conformation of the three rings forming the upper ''cap'' of the complex structure can be assigned delta or lambda with respect to the 3-fold molecular axis. X-ray data at 300 and 153 K, above and below the critical temperature for the spin transition, show that the conformation of the ligand ''cap'' is the same as the absolute configuration of the complex, with the same Lambda lambda(CAP)(or Delta delta(CAP)) combination prevailing for both the LS ((1)A(1)) and HS (T-5(2)) isomers. Molecular mechanics calculations further show that the ligand energy remains lowest for this Lambda lambda(CAP) (or Delta delta(CAP)) combination at all Fe-N distances over the range spanning the LS and HS isomers. Measurements of the spin crossover relaxation time have been carried out in solution over the temperature range 293-170 K. The observed monophasic relaxation traces are also consistent with the absolute configuration of the complex remaining unaltered during the spin crossover.

PHOTOMINERALIZATION OF SALICYLIC-ACID - A KINETIC-STUDY

The kinetics of the photomineralization of salicylic acid (SA) sensitized by Degussa P25 titanium dioxide (TiO2) dispersions in oxygenated aqueous solution are reported as a function of the following experimental parameters: [TiO2], percentage of O-2, [SA], temperature (T) and light intensity (I). The kinetics of SA photomineralization conform to a Langmuir-Hinshelwood kinetic scheme with SA and O-2 adsorbed at different sites with apparent Langmuir adsorption coefficients of (6.1 +/- 1.2) x 10(4) mol(-1) dm(3) and 0.061 +/- 0.007 kPa(-1) respectively. The overall activation energy for the system was determined as 4.6 +/- 0.2 kJ mol(-1). Two major stable reaction intermediates are identified (dihydroxybenzoic acids (DHBA) and catechol (C)) and the existence of a further pathway involving one or more very unstable and, as yet, unidentified reaction intermediates is proposed. A kinetic model is presented which describes the temporal behaviour of the concentrations of SA, CO2 and the major photogenerated intermediates (DHBA and C). This model is used to predict successfully the temporal behaviour of the major intermediates in the photomineralization of SA under non-standard conditions.

A KINETIC-STUDY OF THE BLEACHING OF RHODAMINE-6G PHOTOSENSITIZED BY TITANIUM-DIOXIDE

The results of a kinetic study of the bleaching of the photostable dye rhodamine 6G by dissolved oxygen, photosensitized by TiO2, are reported. The observed variations in the initial rate of dye photobleaching as a function of the O2 percentage, temperature, incident light intensity and concentrations of rhodamine 6G and sacrificial electron donor are described and the results are rationalized using a proposed photochemical reaction scheme. The photosensitized bleaching of rhodamine 6G dye by TiO2 has a formal quantum yield of 2.65 X 10(-3), but the rate of complete photomineralization is about twofold slower. The overall activation energy for the semiconductor-sensitized dye photobleaching process is 15.0 +/- 1.5 kJ mol-1.

Comparison of Dynamics of Extracellular Accesses to the β(1) and β(2) Adrenoceptors Binding Sites Uncovers the Potential of Kinetic Basis of Antagonist Selectivity.

From the molecular mechanism of antagonist unbinding in the ß(1) and ß(2) adrenoceptors investigated by steered molecular dynamics, we attempt to provide further possibilities of ligand subtype and subspecies selectivity. We have simulated unbinding of ß(1) -selective Esmolol and ß(2) -selective ICI-118551 from both receptors to the extracellular environment and found distinct molecular features of unbinding. By calculating work profiles, we show different preference in antagonist unbinding pathways between the receptors, in particular, perpendicular to the membrane pathway is favourable in the ß(1) adrenoceptor, whereas the lateral pathway involving helices 5, 6 and 7 is preferable in the ß(2) adrenoceptor. The estimated free energy change of unbinding based on the preferable pathway correlates with the experimental ligand selectivity. We then show that the non-conserved K347 (6.58) appears to facilitate in guiding Esmolol to the extracellular surface via hydrogen bonds in the ß(1) adrenoceptor. In contrast, hydrophobic and aromatic interactions dominate in driving ICI-118551 through the easiest pathway in the ß(2) adrenoceptor. We show how our study can stimulate design of selective antagonists and discuss other possible molecular reasons of ligand selectivity, involving sequential binding of agonists and glycosylation of the receptor extracellular surface. © 2012 John Wiley & Sons A/S.

Fully kinetic simulation of ion acoustic and dust-ion acoustic waves

A series of numerical simulations is presented, based on a recurrence-free Vlasov kinetic model using kinetic phase point trajectories. All plasma components are modeled kinetically via a Vlasov evolution equation, then coupled through Poisson’s equation. The dynamics of ion acoustic waves in an electron-ion and in a dusty (electron-ion-dust) plasma configuration are investigated, focusing on wave decay due to Landau damping and, in particular, on the parametric dependence of the damping rate on the dust concentration and on the electron-to-ion temperature ratio. In the absence of dust, the occurrence of damping was observed, as expected, and its dependence to the relative magnitude of the electron vs ion temperature(s) was investigated. When present, the dust component influences the charge balance, enabling dust-ion acoustic waves to survive Landau damping even in the extreme regime where Te???Ti. The Landau damping rate is shown to be minimized for a strong dust concentration or/and for a high value of the electron-to-ion temperature ratio. Our results confirm earlier theoretical considerations and contribute to the interpretation of experimental observations of dust-ion acoustic wave characteristics.

High-Order Harmonics from Bow Wave Caustics Driven by a High-Intensity Laser

We propose a new mechanism of high-order harmonic generation during an interaction of a high-intensity laser pulse with underdense plasma. A tightly focused laser pulse creates a cavity in plasma pushing electrons aside and exciting the wake wave and the bow wave. At the joint of the cavity wall and the bow wave boundary, an annular spike of electron density is formed. This spike surrounds the cavity and moves together with the laser pulse. Collective motion of electrons in the spike driven by the laser field generates high-order harmonics. A strong localization of the electron spike, its robustness to oscillations imposed by the laser field and, consequently, its ability to produce high-order harmonics is explained by catastrophe theory. The proposed mechanism explains the experimental observations of high-order harmonics with the 9 TW J-KAREN laser (JAEA, Japan) and the 120 TW Astra Gemini laser (CLF RAL, UK) [A. S. Pirozhkov, et al., arXiv:1004.4514 (2010); A. S. Pirozhkov et al, AIP Proceedings, this volume]. The theory is corroborated by high-resolution two- and three-dimensional particle-in-cell simulations.

Research activities in the MaRINET project: keeping the European marine energy development facilities at world class level

The MaRINET project aims to build a synergy in the European marine renewable energy development infrastructure network, involving a total of 28 partners across the union. Its scope extends from small to large scale testing, in both tank and field. The main activities of the project are to standardize test procedures, to provide centralized free access for European technology developers, and to innovate for improving test infrastructures and techniques.
This paper presents the work carried in this last part, which focuses on research objectives identified to be current challenges for industrial development. They are distributed in 6 topics. On the one hand are issues that concern directly one of the 3 types of energy scoped in the project: wave, tidal, and offshore wind energy. Two examples are the real time estimation of incident waves, and the measurement of turbulence in tidal flows. On the other hand, collaborative effort is drawn on aspects that are common to those technologies: electrical components, environmental monitoring, and dedicated moorings.

Hydrolysis characteristics and kinetics of waste hay biomass as a potential energy crop for fermentable sugars production using autoclave parr reactor system

The use of the organic fraction of municipal solid waste crops has received considerable attention as a sustainable feedstock that can replace fossil fuels for the production of renewable energy. Therefore, municipal bin-waste in the form of hay was investigated as a potential energy crop for fermentable sugars production. Hydrolysis of hay by dilute phosphoric acid was carried out in autoclave parr reactor, where reactor temperature (135-200 degrees c) and acid concentration (2.5-10% (w/w)) were examined. Analysis of the decomposition rate of hemicellulosic biomass was undertaken using HPLC of the reaction products. Xylose production reached a maximum value of 13.5 g/100 g dry mass corresponding to a yield of 67% at the best identified conditions of 2.5 wt% H3PO4, 175 degrees C, 10 min reaction time, and at 5 wt% H3PO4, 150 degrees C, and 5 min reaction time. For glucose, an average yield of 25% was obtained at 5 wt% H3PO4, 175 degrees C and 30 min. Glucose degradation to HMF was achieved at 10 wt% H3PO4 and 200 degrees C. The maximum yield for produced arabinose was an average of 3 g/100 g dry. mass corresponding to 100% of the total possible arabinose. The kinetic study of the acid hydrolysis was also carried out using the Saeman and the Two-fraction models. It was found for both models that the kinetic constants (k) depend on the acid concentration and temperature. For xylose and arabinose it was found that the rate of formation was more favoured than the rate of degradation. By contrast, for glucose it was found that glucose degradation was occurring faster than glucose formation. It can be concluded that dilute phosphoric acid hydrolysis of hay crop is feasible for the production of fermentable sugars which are essential for bioethanol synthesis. 

A current-driven instability in parallel, relativistic shocks

Recently, Bell ( 2004 Mon. Not. R. Astron. Soc. 353 550) has reanalysed the problem of wave excitation by cosmic rays propagating in the pre-cursor region of a supernova remnant shock front. He pointed out a strong, non-resonant, current-driven instability that had been overlooked in the kinetic treatments by Achterberg ( 1983 Astron. Astrophys. 119 274) and McKenzie and Volk ( 1982 Astron. Astrophys. 116 191), and suggested that it is responsible for substantial amplification of the ambient magnetic field. Magnetic field amplification is also an important issue in the problem of the formation and structure of relativistic shock fronts, particularly in relation to models of gamma-ray bursts. We have therefore generalized the linear analysis to apply to this case, assuming a relativistic background plasma and a monoenergetic, unidirectional incoming proton beam. We find essentially the same non-resonant instability observed by Bell and show that also, under GRB conditions, it grows much faster than the resonant waves. We quantify the extent to which thermal effects in the background plasma limit the maximum growth rate.

Energy: lessons from devolution

Geraint Ellis and Richard Cowell explain the findings of the ‘Delivering renewable energy under devolution’ project, including some reasons for Scotland’s lead.

The UK has seen massive increases in renewable energy since 1998, with installed capacity growing from 2,600 MW to 12,300 MW in 2011. This has coincided with devolution and it is within Northern Ireland, Scotland and Wales that the greatest increases have been seen.

As devolved administrations now host half of the UK’s renewable energy capacity, their policies are critical to achieving the broader UK targets. This also provides a fascinating insight into what sort of approach works best, and why. This has been the focus of a two-year study, funded by the Economic and Social Research Council, involving universities from across the UK, which indicates that Scotland is leading the way on renewable energy.

All devolved governments have offered significant support to renewable energy but have different degrees of powers in relation to energy. Scotland’s success seems to be based on the centrality of energy issues to current political aspirations, particularly the SNP, but also has cross-party support. The research suggests that the consensus on the importance of renewable energy amongst élite interests in Scotland helps to explain why Scottish governments have been empowered and enabled to make robust use of the powers available.

As it has achieved successful growth in the sector, this too helps cultivate credibility among key business interests and gives increased leverage to its position in policy discussions with the UK Government. Scotland has been more consistent over time in presenting the expansion of renewable energy as a national economic agenda, rather than just an environmental or rural development agenda. The availability of larger, windy, but relatively less contested sites for onshore wind in Scotland has meant that more projects went through central consenting procedures rather than local planning authorities. Its enhanced support for wave and tidal power technologies is also notable. These political conditions have been harder to find in the rest of the UK, making progress a little more uncertain.

Northern Ireland has used its powers (which are more extensive than Scotland’s) to facilitate small-scale renewables and bio-fuel processes, with its liberalised planning regime offering an initial boost to expanding capacity.

This has contrasted with the position in Wales, which has least control over energy but the Welsh Government has adopted a more innovative approach to strategic spatial zoning; this appears to have pulled in a larger volume of onshore wind development interest than could be expected in a comparable region of England. A downside of the Welsh approach appears to be the fact that the concentration of these wind projects in these zones has triggered public opposition and political conflict.

It therefore appears that the powers available to the devolved governments do not seem to determine which country has been able to make greatest headway, with broader political commitments being more significant. Despite this, the research does not conclude that the actions and activities undertaken by the devolved governments are necessarily the most important factors in shaping the development of renewable energy in the UK. This is because devolution is still a relatively new dimension of energy governance in the UK and decisions affecting key drivers for renewable energy investment are still made mainly in Westminster, with the Treasury exercising close budgetary control. In all areas of the UK, grid capacity expansion remains slow to achieve. The major growth in offshore wind to date has been driven mainly by Westminster and cross-UK bodies with the most significant capacity growth being in English territorial waters.

Derivation of Wave Loads for the Design of Oscillating Wave Surge Converters

This paper deals with the problem of estimating wave pressure loads acting on Oscillating Wave Surge Converters (OWSC) for assessment of fatigue on their components. Recent wave loading data issued from experimental testing of a 25th scale model of a box-shaped OWSC are here used to review the accuracy of the predictions made by an engineering method previously developed to derive wave pressure loads on OWSCs from experimental data. Predictions are shown underestimate wave pressure loads, and other methods subsequently developed are presented. A simplistic experimental method taking in consideration variations of the wetted surface area of the flap is shown to lead to relatively good estimates of wave pressure loads that could be used for fatigue calculations.

An application of bi-directional evolutionary structural optimisation for optimising energy absorbing structures using a material damage model

The Bi-directional Evolutionary Structural Optimisation (BESO) method is a numerical topology optimisation method developed for use in finite element analysis. This paper presents a particular application of the BESO method to optimise the energy absorbing capability of metallic structures. The optimisation objective is to evolve a structural geometry of minimum mass while ensuring that the kinetic energy of an impacting projectile is reduced to a level which prevents perforation. Individual elements in a finite element mesh are deleted when a prescribed damage criterion is exceeded. An energy absorbing structure subjected to projectile impact will fail once the level of damage results in a critical perforation size. It is therefore necessary to constrain an optimisation algorithm from producing such candidate solutions. An algorithm to detect perforation was implemented within a BESO framework which incorporated a ductile material damage model.

Impacts of compressed air energy storage plant on an electricity market with a large renewable energy portfolio

Renewable energy generation is expected to continue to increase globally due to renewable energy targets and obligations to reduce greenhouse gas emissions. Some renewable energy sources are variable power sources, for example wind, wave and solar. Energy storage technologies can manage the issues associated with variable renewable generation and align non-dispatchable renewable energy generation with load demands. Energy storage technologies can play different roles in each of the step of the electric power supply chain. Moreover, large scale energy storage systems can act as renewable energy integrators by smoothing the variability. Compressed air energy storage is one such technology. This paper examines the impacts of a compressed air energy storage facility in a pool based wholesale electricity market in a power system with a large renewable energy portfolio.