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The National Spherical Torus Experiment (NSTX) at Princeton University, Princeton, NJ, is designed to assess the potential of the low-aspect-ratio spherical torus concept for magnetic plasma confinement. The plasma has been heated by up to 7 MW of neutral beam injection (NBI) at an injection energy of 100 keV and up to 6 MW of high harmonic fast wave (HHFW) at 30 MHz. NSTX has achieved /spl beta//sub T/ of 32%. A variety of MHD phenomena have been observed to limit /spl beta/. NSTX has now begun addressing /spl tau//sub E/ scaling, /spl beta/ limits, and current drive issues. During the NBI heating experiments, a broad T/sub i/ profile with T/sub i/ up to 2 keV, T/sub i/>T/sub e/ and a large toroidal rotation were observed. Transport analysis suggests that the impurity ions have diffusivities approaching neoclassical. For L-Mode plasmas, /spl tau//sub E/ is up to two times the ITER97L L-Mode scaling and exceeds the ITER98pby2 H-Mode scaling in some cases. Transitions to H-Mode have been observed which result in an approximate doubling of /spl tau//sub E/ after the transition in some conditions. During HHFW heating, T/sub e/>T/sub i/ and T/sub e/ up to 3.5 keV were observed. Current drive has been studied using both coaxial helicity injection with up to 390 kA of toroidal current and HHFW. HHFW has produced H-modes with significant bootstrap current fraction at low I/sub p/, high q, and high /spl beta//sub p/.

This paper describes a first-order model of a Reciprocating Joule Cycle (RJC) engine, which is then used to investigate its thermodynamic design with a view to establishing its optimum performance for a given set of operating conditions. The RJC engine is essentially the reciprocating counterpart of the gas turbine. Its performance is determined by the characteristics of a reciprocating, as opposed to a rotodynamic, compressor and expander. The thermodynamic cycle investigated incorporates regenerative heat exchange. An air standard model modified to include the effects of friction, combustion, clearance volumes, leakage and pressure drops, shows that the performance of the RJC engine is strongly dependent on its operating pressure ratio and dependent to a much lesser extent on its expander to compressor swept volume ratio. It is shown that a thermal efficiency approaching 50 per cent might be achievable under realistic conditions. Using a maximum operating temperature of 1300 K, optimum thermal efficiency with a high specific work output occurs when its nominal operating pressure ratio is in the range 6 to 8, and its expander to compressor swept volume ratio is in the range 2 to 3. The RJC engine is proposed as a suitable prime mover for micro-CHP systems, small stand-alone power units, or hybrid vehicles.

Two experiments were conducted during autumn 1997 and 1998 in west-central Florida to evaluate the effectiveness of soil solarization alone and in combination with the biological control agents Streptomyces lydicus (Actinovate) and Pseudomonas chlororaphis (syn. P. aureofasciens, AtEze) and the reduced-risk fungicide fludioxonil (Medallion) in managing soilborne pathogens of impatiens (Impatiens × wallerana, ‘Accent Burgundy’). Naturally infested soil was solarized for 47 or 48 days during September and October using two layers of 25-μm clear, low-density polyethylene mulch, separated by an air space of up to 7.5 cm. Solarization decreased the final incidence and progress of Rhizoctonia crown rot and blight, incidence of Pythium spp. in roots, and root discoloration, and increased shoot biomass in both experiments. The technique also consistently reduced root-knot severity and population densities of Meloidogyne incognita, Dolichodorus heterocephalus, Paratrichodorus minor, and Criconemella spp. The incidence of Rhizoctonia crown rot and blight was reduced by fludioxonil, but not by the biological control agents.

The excess chemical potentials of a series of molecules dissolved in the ionic liquid dimethyl imidazolium chloride have been determined by a series of transformations. The molecules are water, methanol, dimethyl ether, acetone and propane. Water and methanol have large negative values of the excess chemical potential (-29kJmol−1 and — 14kJ mol−1 respectively); the polar molecules dimethyl ether and acetone have positive values of about 7kJmol−1 while the value for propane is +26 kJ mol−1. Hydrogen bonding to the anion plays an important part in the stabilization of water and methanol.

We have performed calculations of the solvation effects on a number of equilibrium constants in water using a recently proposed hybrid quantum–classical scheme in which the liquid environment is modelled using classical solvent molecules and the solute electronic structure is computed using modern quantum chemical methods. The liquid phase space is sampled from a fully classical simulation. We find that solvation effects on both triazole tautomeric equilibrium constants and piperidinol conformational equilibrium constants can be interpreted in terms of subtle differences in the local environment which can be seen in probability densities and radial distribution functions. Lower level calculations were performed for comparison and we conclude that the solvation thermodynamics can be predicted from a good classical model of solvent and solute molecules, but the implicit models that we tried are less successful.

A simulation scheme is proposed for determining the excess chemical potential of a substance in solution. First, a Monte Carlo simulation is performed with classical models for solute and solvent molecules. A representative sample of these configurations is then used in a hybrid quantum/classical (QM/MM) calculation, where the solute is treated quantum-mechanically, and the average electronic structure is used to construct an improved classical model. This procedure is iterated to self-consistency in the classical model, which in practice is attained in one or two steps, depending on the quality of the initial guess. The excess free energy of the molecule within the QM/MM approach is determined relative to the classical model using thermodynamic perturbation theory with a cumulant expansion. The procedure provides a method of constructing classical point charge models appropriate for the solution and gives a measure of the importance of solvent fluctuations.

Research on the stability of spherical torus plasmas at and above the no-wall beta limit is being addressed on the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 40, 557 (2000)], that has produced low aspect ratio plasmas, R/a∼1.27 at plasma current exceeding 1.4 MA with high energy confinement (TauE/TauE_ITER89P>2). Toroidal and normalized beta have exceeded 25% and 4.3, respectively, in q∼7 plasmas. The beta limit is observed to increase and then saturate with increasing li. The stability factor βN/li has reached 6, limited by sudden beta collapses. Increased pressure peaking leads to a decrease in βN. Ideal stability analysis of equilibria reconstructed with EFIT [L. L. Lao et al., Nucl. Fusion 25, 1611 (1985)] shows that the plasmas are at the no-wall beta limit for the n=1 kink/ballooning mode. Low aspect ratio and high edge q theoretically alter the plasma stability and mode structure compared to standard tokamak configurations. Below the no-wall limit, stability calculations show the perturbed radial field is maximized near the center column and mode stability is not highly effected by a nearby conducting wall due to the short poloidal wavelength in this region. In contrast, as beta reaches and exceeds the no-wall limit, the mode becomes strongly ballooning with long poloidal wavelength at large major radius and is highly wall stabilized. In this way, wall stabilization is more effective at higher beta in low aspect ratio geometry. The resistive wall mode has been observed in plasmas exceeding the ideal no-wall beta limit and leads to rapid toroidal rotation damping across the plasma core.

We compare the electrostatic properties of individual water molecules in ab initio simulations and in some potential models used in classical simulations. We find that the standard rigid water models at room temperature and ambient pressure describe the average electrostatic properties of molecules quite well, although there are considerable fluctuations. Preliminary results show that the dipole moment of water molecules near either a sodium ion or a methane molecule are not significantly different from its average value in bulk water, which may justify the use of non-polarisable water models in simulations of biological molecules. In ice, however, the dipole induced by the surroundings is appreciably higher. Incorrect freezing points can be attributed to a bad description of the solid phase rather than to a bad description of the liquid phase.

Rapidly developing diagnostic, operational, and analysis capability is enabling the first detailed local physics studies to begin in high β plasmas of the National Spherical Torus Experiment (NSTX). These studies are motivated in part by the observation of energy confinement times in neutral-beam-heated discharges that are favourable with respect to predictions from the ITER-89P scaling expression. For plasmas heated with neutral beam injection (NBI), analysis based on profile measurements suggests that electron heat conduction is the dominant thermal loss channel. Cases where early analysis indicates that ion thermal conduction may be exceptionally low is motivating studies of possible sources of ion heating not presently accounted for by classical collisional processes. Gyrokinetic microstability studies indicate that long wavelength turbulence with kθρi~0.1-1 may be stable or suppressed by E×B shear in these plasmas, while modes with kθρi~50 may be robust. High harmonic fast wave (HHFW) heating efficiently heats electrons on NSTX, and studies have begun using it to assess transport in the electron channel. Regarding edge transport, H-mode transitions occur with either NBI or HHFW heating. The power required for L- to H-mode transitions far exceeds that expected from empirical ELM-free H-mode scaling laws derived from moderate aspect ratio devices. Finally, initial fluctuation measurements made with two techniques are permitting the first characterizations of edge turbulence.

Often the rate of passage of gaseous molecules through model zeolites is too small to be computed directly. An estimate for the rate of passage of $CCl_4$ through the 8-ring window in a model of zeolite A has been obtained by combining a direct evaluation of the free energy pro®le and an adaptation of the rare events method. First the free energy pro®le is found from a direct evaluation of the canonical partition function at high dilution and the transition state theory rate constant obtained. The dynamic correction factor is then estimated from molecular dynamics runs and used to compute the actual rate $k_e_f_f$ . The method is used to estimate the rate of passage through the 8-ring window in a rigid model of zeolite A, and the results are compared with those obtained from rigid models with expanded windows and from the flexible model. Even a small expansion in the 8-ring window diameter increases the rate signi®cantly, but the changes associated with a flexible cage are small.

Boronization of NSTX has allowed access to higher density higher confinement plasmas. A glow discharge with 4 mtorr helium and 10% deuterated trimethyl boron deposited 1.7 g of boron on the plasma facing surfaces. Ion beam analysis of witness coupons showed a B + C areal density of 1018 cm-2 corresponding to a film thickness of 100 nm. Subsequent ohmic discharges showed oxygen emission lines reduced by a factor of 15, carbon emission reduced by a factor of two and copper reduced to undetectable levels. After boronization, the plasma current flat-top time increased by 70% enabling access to higher density higher confinement plasmas.

Ab initio calculations of the density of states for adsorbed monolayers of water on a MgO(1 0 0) surface are compared with metastable impact electron spectra (MIES) and ultraviolet photoelectron spectra (UPS). The calculations confirm the suggested assignments and in particular show that there is good evidence that some, but not all, molecules have dissociated to hydroxide ions. Density of state calculations are shown for configurations with no dissociated molecules, one third of the molecules dissociated and half the molecules dissociated; the agreement with experiment is best for the configuration with one third of the molecules dissociated.

Molecular dynamics simulations of a number of small molecules dissolved in dimethylimidazolium chloride at 400 K have been performed. The molecules chosen were water, methanol, dimethyl ether and propane, which have a range of properties from polar and hydrogen-bonding to non-polar. The local structure was analysed through ranked radial distribution functions and three dimensional probability functions, and the interaction energy with the anions and cations determined. The energetics and local structure show that the strongest interactions are hydrogen bonding to the chloride ion for water and methanol, while dimethyl ether and propane interact more strongly with the cation.

A systematic search using an ab initio density-functional method has been carried out for energy minima for a monolayer of water on MgO. Minima were sought in which one third of the water molecules were dissociated, and the observed p(3×2) symmetry satisfied. Six such minima were found, three of which are within 300 k B per water molecule of the lowest energy structure. We also found a structure with a similar energy with (2×2) symmetry and half the water molecules dissociated. The structures are stabilised by the donation of three hydrogen bonds to each hydroxide ion.

In the November 2016 President's Page, Past President John Bradford highlighted the challenges SEG needs to address: we need to broaden our base, we need to do a better job of retaining members as they make the transition from student to professional, and we need to demonstrate our value and relevance if we are to grow our membership. Bradford went on to highlight the strategy adopted last year, which would address these issues and, in particular, broaden both the base of knowledge and career opportunities for our membership.

David Dutton's many friends have long known that his pursuit of historical understanding and his keen enthusiasm for archival research have led him to become an immensely productive writer. His boo...

${\mathrm{SmFeO}}_{3}$ has attracted considerable attention very recently due to its reported multiferroic properties above room temperature. We have performed powder and single crystal neutron diffraction as well as complementary polarization dependent soft X-ray absorption spectroscopy measurements on floating-zone grown ${\mathrm{SmFeO}}_{3}$ single crystals in order to determine its magnetic structure. We found a $k=0$ $G$-type collinear antiferromagnetic structure that is not compatible with inverse Dzyaloshinskii-Moriya interaction driven ferroelectricity. While the structural data reveal a clear sign for magneto-elastic coupling at the N\'eel-temperature of $\ensuremath{\sim}675\text{ }\text{ }\mathrm{K}$, the dielectric measurements remain silent as far as ferroelectricity is concerned.

The parting of the ways, 1940 a complicated war - Britain, Vichy and de Gaulle, 1940-1942 a complicated war - Britain and de Gaulle, 1943-1944 the aftermath of war and the Treaty of Dunkirk, 1945-1947 Cold War and the emergence of "Europe", 1947-1949 separation - Schuman Plan and after, 1950-1955 the Suez Crisis, 1956 and a strange offer of union a new France confronts an uncertain Britain, 1957-1960 the general says no, 1961-1963 to join or not to join? - Britain, France and the EEC, 1963-1969 Britain joins the club - with second thoughts, 1969-1975 unhappy partners, 1975-1990 views across the Channel, c.1970-1990 a new Europe and some old memories, 1989-1994. Some snapshots by way of a conclusion.

Background Pediatric discoid lupus erythematosus (DLE) is rare. The risk of progression to systemic lupus erythematosus (SLE) is uncertain. Objective We sought to determine the risk of progression of pediatric DLE to SLE and to characterize its phenotype. Methods This was a retrospective review of 40 patients with DLE. Results Six (15%) of 40 patients presented with DLE as a manifestation of concurrent SLE. Of the remaining 34, 9 (26%) eventually met SLE criteria and 15 (44%) developed laboratory abnormalities without meeting SLE criteria. Only 10 (29%) maintained skin-limited disease. The average age at progression to SLE was 11 years, with greatest risk in the first year after DLE diagnosis. Most (89%) patients with SLE met diagnostic criteria with mucocutaneous disease (discoid lesions, malar rash, oral and nasal ulcers, photosensitivity), positive antibodies, and/or cytopenia without developing end-organ damage over 5 years of median follow-up. Limitations The study was retrospective. Conclusions In pediatric patients, DLE carries a significant risk of progression to SLE but may predict a milder phenotype of systemic disease. All patients require careful monitoring for SLE, particularly within the first year of diagnosis.

BackgroundThe US Army suicide rate has increased sharply in recent years. Identifying significant predictors of Army suicides in Army and Department of Defense (DoD) administrative records might help focus prevention efforts and guide intervention content. Previous studies of administrative data, although documenting significant predictors, were based on limited samples and models. A career history perspective is used here to develop more textured models.MethodThe analysis was carried out as part of the Historical Administrative Data Study (HADS) of the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS). De-identified data were combined across numerous Army and DoD administrative data systems for all Regular Army soldiers on active duty in 2004–2009. Multivariate associations of sociodemographics and Army career variables with suicide were examined in subgroups defined by time in service, rank and deployment history.ResultsSeveral novel results were found that could have intervention implications. The most notable of these were significantly elevated suicide rates (69.6–80.0 suicides per 100 000 person-years compared with 18.5 suicides per 100 000 person-years in the total Army) among enlisted soldiers deployed either during their first year of service or with less than expected (based on time in service) junior enlisted rank; a substantially greater rise in suicide among women than men during deployment; and a protective effect of marriage against suicide only during deployment.ConclusionsA career history approach produces several actionable insights missed in less textured analyses of administrative data predictors. Expansion of analyses to a richer set of predictors might help refine understanding of intervention implications.

Many disruptions in the Tokamak Fusion Test Reactor (TFTR) [D. Meade and the TFTR Group, in Proceedings of the International Conference on Plasma Physics and Controlled Nuclear Fusion, Washington, DC, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 1, pp. 9-24] produced populations of runaway electrons which carried a significant fraction of the original plasma current. In this paper, we describe experiments where, following a disruption of a low-beta, reversed shear plasma, currents of up to 1 MA carried mainly by runaway electrons were controlled and then ramped down to near zero using the ohmic transformer. In the longer lasting runaway plasmas, Parail-Pogutse instabilities were observed.

The decay of highly excited states of xenon after absorption of extreme ultraviolet light is directly tracked via attosecond transient absorption spectroscopy using a time-delayed near-infrared perturbing pulse. The lifetimes of the autoionizing 5$s$5${p}^{6}$6$p$ and 5$s$5${p}^{6}$7$p$ channels are determined to be (21.9 \ifmmode\pm\else\textpm\fi{} 1.3) fs and (48.4 \ifmmode\pm\else\textpm\fi{} 5.0) fs, respectively. The observed values support lifetime estimates obtained by traditional linewidth measurements. The experiment additionally obtains the temporal evolution of the decay as a function of energy detuning from the resonance center, and a quantum mechanical formalism is introduced that correctly accounts for the observed energy dependence.

This study examines the mortality rates of men and women from coronary heart disease (CHD) in a number of Asia-Pacific countries with very different incidences of this disorder. In all countries, mortality rates from CHD were higher in men. In women, no unequivocal change in mortality rate from CHD attributable to the menopause could be detected.

In this study, we simulated heterotrophic CO2 (Rh) fluxes at six European peatland sites using the ECOSSE model and compared them to estimates of Rh made from eddy covariance (EC) measurements. The sites are spread over four countries with different climates, vegetation and management. Annual Rh from the different sites ranged from 110 to 540 g C m−2. The maximum annual Rh occurred when the water table (WT) level was between −10 and −25 cm and the air temperature was above 6.2 °C. The model successfully simulated seasonal trends for the majority of the sites. Regression relationships (r 2) between the EC-derived and simulated Rh ranged from 0.28 to 0.76, and the root mean square error and relative error were small, revealing an acceptable fit. The overall relative deviation value between annual EC-derived and simulated Rh was small (−1 %) and model efficiency ranges across sites from −0.25 to +0.41. Sensitivity analysis highlighted that increasing temperature, decreasing precipitation and lowering WT depth could significantly increase Rh from soils. Thus, management which lowers the WT could significantly increase anthropogenic CO2, so from a carbon emissions perspective, it should be avoided. The results presented here demonstrate a robust basis for further application of the ECOSSE model to assess the impacts of future land management interventions on peatland carbon emissions and to help guide best practice land management decisions.

The development of attosecond technology is one of the most significant recent achievements in the field of ultrafast optics; it opens up new frontiers in atomic and molecular spectroscopy and dynamics. A unique attosecond pump-probe apparatus using a compact Mach-Zehnder interferometer is developed. The interferometer system is compact (∼290 cm2) and completely located outside of the vacuum chamber. The location reduces the mechanical vibration from vacuum components such as turbopumps and roughing pumps. The stability of the interferometer is ∼50 as RMS over 24 hours, stabilized with an active feedback loop. The pump and probe fields can be easily altered to incorporate multiple colors. In the interferometer, double optical gating optics are arranged to generate isolated attosecond pulses with a supercontinuum spectrum. The frequencies of the attosecond pulses can be selected to be in the extreme ultraviolet (XUV) region (25–55 eV, 140 as) or the vacuum ultraviolet (VUV) region (15–24 eV, ∼400 as) by metal filters. Furthermore, the near infrared probe field (1.65 eV) can be upconverted to the ultraviolet (3.1 eV). The frequency tunability in the XUV and VUV is critical for selecting excited states of target atoms and molecules.

Unlike normal rats, adrenalectomized rats do not voluntarily drink sweet saccharin solutions. To test whether this is a function of corticosterone in the circulation, and if corticosterone also increases the impetus for drinking saccharin after a period of withdrawal, we performed the following experiments. Young male rats were sham adrenalectomized (sham) or adrenalectomized (ADX); the ADX rats were provided with subcutaneous pellets containing (percent replacement of corticosterone, %B) 0%B, 15%B, 30%B or 100%B. Sham and ADX rats were immediately provided with saline (0.5%) and saccharin (2 mM) bottles in their home cages. Saccharin was allowed for 4 days on, 3 days off, 4 days on, 3 days off and a final day on, over the 15 days experiment. The dose of corticosterone determined both how much saccharin was voluntarily drunk by the ADX rats and the degree of overshoot after days off. Corticosterone also determined energy balance of the groups of ADX rats. The 30%B pellets restored food intake, body weight gain, insulin and caloric efficiency to the normal levels observed in sham rats. White fat depot weights and uncoupling protein concentration in brown adipose tissue were restored to sham levels by 100%B, suggesting that these variables which depend on activity in the sympathetic nervous system require considerable glucocorticoid receptor occupancy. We conclude that corticosterone increases the willingness to ingest sweetened water in a unimodal, dose-related manner, while moderate doses of corticosterone restore energy balance.

A new method of actively modifying the plasma-wall interaction was tested on the Tokamak Fusion Test Reactor. A laser was used to introduce a directed lithium aerosol into the discharge scrape-off layer. The lithium introduced in this fashion ablated and migrated preferentially to the limiter contact points. This allowed the plasma-wall interaction to be influenced in situ and in real time by external means. Significant improvement in energy confinement and fusion neutron production rate as well as a reduction in the plasma Zeff have been documented in a neutral beam heated plasma. The introduction of a metallic aerosol into the plasma edge increased the internal inductance of the plasma column and also resulted in prompt heating of core electrons in ohmic plasmas. Preliminary evidence also suggests that the introduction of an aerosol leads to both edge poloidal velocity shear and edge electric field shear.

The behaviour of silica-supported films of liquid n-hexane and n-perfluorohexane has been investigated by means of molecular dynamics simulations of model compounds. Thin films of both neat liquids and equimolar mixtures were studied with different surface interaction strengths at room temperature (300 K). The molecules tend to form layers parallel to the surface of the substrate. In agreement with recent experimental results for hexane, a low density region was found near the surface, provided that the interaction strength was low. There is no corresponding low density region for perfluorohexane. The study of the mixture indicates that perfluorohexane is preferentially adsorbed at both solid-liquid and liquid-vapour interfaces while the molecules of hexane are concentrated inside the film.

The mobility of simple ions such as alkali–metal and halide ions at room temperature shows two anomalies. Firstly, there are maxima in mobilities as a function of ion size for both positive and negative ions and, secondly, the maximum for negative ions occurs at a larger ionic radius than the maximum for positive ions. Theoretical treatments of this problem are reviewed and it is concluded that a molecular treatment of the system is needed to understand the results. Computer simulation using the simple point charge model (SPC/E) for water reproduced the observations and is used to discuss the application of theories. In particular, the nature of the first solvation shell is correlated with ion mobility. Simulation reveals a further anomaly, namely that if the charge is removed from a large ion, then it moves more slowly. This is interpreted as the result of formation of a solvent cage around the hydrophobic solute. The changes in local structure resulting from changes in charge and size also affect the solvation thermodynamics. Simulations show that the solvation entropy has a double maximum when viewed as a function of charge. The local minimum near zero charge is interpreted as being due to hydrophobic order, and the maxima as the result of structure breaking. This double maximum in the entropy of solvation is a signature of the hydrophobic cage effect. Comparisons are made between ion mobilities in liquid water at ambient and supercritical conditions.

We present a practical scheme for performing ab initio supercell calculations of charged slabs at constant electron chemical potential μ, rather than at constant number of electrons Ne. To this end, we define the chemical potential relative to a plane (or “reference electrode”) at a finite distance from the slab (the distance should reflect the particular geometry of the situation being modeled). To avoid a net charge in the supercell, and thus make possible a standard supercell calculation, we restore the electroneutrality of the periodically repeated unit by means of a compensating charge, whose contribution to the total energy and potential is subtracted afterwards. The “constant μ” mode enables one to perform supercell calculation on slabs, where the slab is kept at a fixed potential relative to the reference electrode. We expect this to be useful in modeling many experimental situations, especially in electro-chemistry.

The properties of water as a solvent are related to the structure of its liquid phase which in turn depends on the intermolecular potential. In order to explore this relationship we investigate the properties of liquids formed by a number of modified water models. Changing the molecular geometry changes short-range molecular correlations and the network of hydrogen bonds. The solubility and anomalously low entropy of non-polar solutes is only slightly reduced. Reducing the hydrogen-bond strength increases the solubility and removes the low entropy of solution of uncharged spheres. We conclude that the hydrophobic effect depends on the existence of hydrogen bonds and other strong intermolecular interactions but not on the presence of a three-dimensional network.

The triiodide ion shows evidence of symmetry breaking due to spontaneous polarisation and distortion when dissolved in hydrogen-bonding solvents, but in polar solvents such as acetonitrile with no hydrogen bonds the symmetry appears to be D ∞h . In this Letter we use Monte Carlo simulations to show that there is a symmetry breaking in model triiodide ion in acetonitrile solution but the barrier between the two equivalent forms is less than kT . This result is contrasted with our previous work on aqueous solutions. The instantaneous vibrational frequencies of the triiodide ion in acetonitrile solution were determined. In agreement with experiment we find that the mean value of the antisymmetric mode is less shifted to the blue and the spread of frequencies is less than in aqueous solution.

Intermolecular potentials suitable for molecular dynamics or Monte Carlo simulations have been developed for dimethyl imidazolium and methyl ethyl imidazolium ions. The predicted crystal structures were compared with experimental crystal structures for chloride and PF− 6 salts and found to be satisfactory when the dominant electrostatic interactions were modelled by either an accurate distributed multipole description or a simplified atomic point charge model. A further simplification of using united atoms in place of methyl or methylene groups on the side chains gave a much less satisfactory reproduction of the crystal structures. Liquid dimethyl imidazolium chloride and dimethyl imidazolium PF− 6 were simulated using the explicit atom and united atom potentials. The local structure showed a strong preference for the chloride ions to be located in certain regions around the cation, and a similar, but less strong localization of the larger PF− 6. Significant differences in density and diffusion rates were...

The mission of the National Spherical Torus Experiment (NSTX) is to extend the understanding of toroidal physics to low aspect ratio (R/a approximately equal to 1.25) in low collisionality regimes. NSTX is designed to operate with up to 6 MW of High Harmonic Fast Wave (HHFW) heating and current drive, 5 MW of Neutral Beam Injection (NBI) and Co-Axial Helicity Injection (CHI) for non-inductive startup. Initial experiments focused on establishing conditions that will allow NSTX to achieve its aims of simultaneous high-bt and high-bootstrap current fraction, and to develop methods for non-inductive operation, which will be necessary for Spherical Torus power plants. Ohmic discharges with plasma currents up to 1 MA and with a range of shapes and configurations were produced. Density limits in deuterium and helium reached 80% and 120% of the Greenwald limit respectively. Significant electron heating was observed with up to 2.3 MW of HHFW. Up to 270 kA of toroidal current for up to 200 msec was produced noninductively using CHI. Initial NBI experiments were carried out with up to two beam sources (3.2 MW). Plasmas with stored energies of up to 140 kJ and bt =21% were produced.

Analyses both support and are in opposition to the hypothesis that the Martian meteorite ALH84001 contains evidence for possible biogenic activity on Mars. New observations in two additional Martian meteorites, Nakhla (1.3 Ga old) and Shergotty (300–165 Ma old) indicate possible biogenic features. Features in the three Martian meteorites compare favorably with the accepted criteria for terrestrial microfossils and evidence for early life on the Earth. There is strong evidence for the presence of indigenous reduced carbon, biogenic magnetite, and the low-temperature formation of carbonate globules. The morphological similarities between terrestrial microfossils, biofilms, and the features found in the three Martian meteorites are intriguing but have not been conclusively proven. Every investigation must recognize the possibility of terrestrial contamination of the meteorites, whether or not the meteorites are Martian. The search for evidence of ancient life in Martian meteorites has emphasized the difficulties confronting the scientific community with the respect to the positive identification of evidence of past biogenic activity.

Simulations of simple solutes (charged and uncharged spheres) in model water have been performed in order to elucidate aspects of solvation in water at ambient and supercritical states. The variation of solvation entropy as a function of solute charge has been used to investigate hydrophobic and hydrophilic ordering and the structure-making and structure-breaking effects of ions. Simulations with model solvents, which differ from water in certain features, have been used to try to identify the particular properties of water that are associated with these phenomena.

The vibrational wavenumbers of crystalline ammonium fluoride were calculated using the density functional method. The results support the experimental conclusions that the symmetric stretching mode in NH4F lies at a higher wavenumber than the asymmetric stretch, that these wavenumbers are reversed in ND4F and that the librational wavenumbers lie at ∼560 cm–1. Copyright © 2001 John Wiley & Sons, Ltd.