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The absorption, pre-resonance, and resonance Raman spectra of 1,4,5,8-naphthalenetetracarboxy dianhydride (NTCDA) molecule are examined in terms of time-dependent density functional theory at TD-B3LYP/aug-cc-pVDZ and TD-SVWN/aug-cc-pVDZ levels. The Franck-Condon analysis performed for two 11Ag → 11B2u and 11Ag → 11B3u overlapping transitions leads to an excellent agreement between the theoretical predictions and experimental data providing that the calculated absorption is confronted with that measured in chloroform or acetonitrile but not in the ethanol (methanol) solution. We argue that absorption spectra measured in ethanol solution already known in literature do not characterize NTCDA molecule. On the basis of the absorption and resonance scattering spectra, we may deliberate that the dimerization of NTCDA is responsible for utterly different absorption observed in ethanol (methanol) comparing with less active solvents (chloroform and acetonitrile). That conclusion is supported by the dimer vibronic theory and by the TD-B97d computations at the aug-cc-pVDZ basis set level. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Results and interpretation of recent experiments on DIII-D designed to evaluate divertor geometries favourable for radiative heat dispersal are presented. Two approaches examined here involved lengthening the parallel connection in the scrape-off layer, L‖, and increasing the radius of the outer divertor separatrix strike point, ROSP, with the goal of reducing target temperature, TTAR, and increasing target density, nTAR. From one-dimensional (1D) two-point modelling based on conducted parallel heat flux, it is expected that: and , where nSEP is the midplane separatrix density. These scalings suggest that conditions conducive to a radiative divertor solution can be achieved at low nSEP by increasing either ROSP or L‖. Our data are consistent with the above L‖ scalings. On the other hand, the observed dependence of nTAR and TTAR on ROSP displayed a more complex behaviour, under certain conditions deviating from the above scalings. Our analysis indicates that deviations from the ROSP scaling were due to the presence of convected heat flux, driven by escaping neutrals, in the more open configurations of the larger ROSP cases. A comparison of ‘open’ versus ‘closed’ divertor configurations for the H-mode plasmas in this study show that the ‘closed’ case provides at least 30% reduction in the peaked heat flux at common density with the ‘open’ case and partial divertor detachment at lower plasma density. [ABSTRACT FROM AUTHOR]

Results from simulations of electromagnetic drift-resistive ballooning turbulence for tokamak edge turbulence in realistic single-null geometry are reported. The calculations are undertaken with the BOUT three-dimensional fluid code that solves Braginskii-based fluid equations [X. Q. Xu and R. H. Cohen, Contrib. Plasma Phys. 36, 158 (1998)]. The simulation setup models L-mode edge plasma parameters in the actual magnetic geometry of the DIII-D tokamak [J. L. Luxon et al., Fusion Sci. Technol. 48, 807 (2002)]. The computations track the development of drift-resistive ballooning turbulence in the edge region to saturation. Fluctuation amplitudes, fluctuation spectra, and particle and thermal fluxes are compared to experimental data near the outer midplane from Langmuir probe and beam-emission-spectroscopy for a few well-characterized L-mode discharges in DIII-D. The simulations are comprised of a suite of runs in which the physics model is varied to include more fluid fields and physics terms. The simulations yield results for fluctuation amplitudes, correlation lengths, particle and energy fluxes, and diffusivities that agree with measurements within an order of magnitude and within factors of 2 or better for some of the data. The agreement of the simulations with the experimental measurements varies with respect to including more physics in the model equations within the suite of models investigated. The simulations show stabilizing effects of sheared E × B poloidal rotation (imposed zonal flow) and of lower edge electron temperature and density. [ABSTRACT FROM AUTHOR]

A coordinated effort to measure divertor heat flux characteristics in fully attached, similarly shaped H-mode plasmas on C-Mod, DIII-D, and NSTX was carried out in 2010 in order to construct a predictive scaling relation applicable to next step devices including ITER, FNSF, and DEMO. Few published scaling laws are available and those that have been published were obtained under widely varying conditions and divertor geometries, leading to conflicting predictions for this critically important quantity. This study was designed to overcome these deficiencies. Analysis of the combined data set reveals that the primary dependence of the parallel heat flux width is robustly inverse with Ip, which all three tokamaks independently demonstrate. An improved Thomson scattering system on DIII-D has yielded very accurate scrape off layer (SOL) profile measurements from which tests of parallel transport models have been made. It is found that a flux-limited model agrees best with the data at all collisionalities, while a Spitzer resistivity model agrees at higher collisionality where it is more valid. The SOL profile measurements and divertor heat flux scaling are consistent with a heuristic drift based model as well as a critical gradient model. [ABSTRACT FROM AUTHOR]

Edge localized mode (ELM) pacing using modulated n = 3 non-axisymmetric fields has been demonstrated on DIII-D over a wide range of conditions, including significant variations in temperature, βN, density and shape. At low collisionality, the pacing results in a clear reduction in the ELM size and peak heat flux to the divertor, up to a factor of 5-6 for short time windows, although only a factor of two for sustained periods with the present hardware capability. At higher collisionality, although similar increases in the ELM frequency have been demonstrated, no meaningful reduction in the heat flux is typically observed as a direct result of the pacing. However, it appears that the ELM size may be reduced indirectly via changes in the L-H power threshold as a result of density pumpout associated with the application of non-axisymmetric fields. At this stage, it remains unclear whether the failure to reduce the ELM size with modulated fields is a limitation associated with high collisionality, high density, or relative proximity to the L-H power threshold. [ABSTRACT FROM AUTHOR]

Direct analysis of internal magnetic field pitch angles measured using the motional Stark effect diagnostic shows m/n=2/1 neoclassical tearing modes exhibit stronger poloidal magnetic flux-pumping than typical hybrids containing m/n=3/2 modes. This flux-pumping causes the avoidance of sawteeth, and is present during partial electron cyclotron current drive suppression of the tearing mode. This finding could lead to hybrid discharges with higher normalized fusion performance at lower q95. The degree of edge localized mode-neoclassical tearing mode (ELM-NTM) coupling and the strength of flux-pumping increase with beta and the proximity of the modes to the ELMing pedestal. Flux-pumping appears independent of magnetic island width. Individual ELM-NTM coupling events show a rapid timescale drop in the island width followed by a resistive recovery that is successfully modeled using the modified Rutherford equation. The fast transient drop in island width increases with ELM size. [ABSTRACT FROM AUTHOR]

This article presents a new optical set-up for illumination of a common area with a few independent light sources. The main aim is to create a uniform light distribution of a constant shape even if one of the light sources will stop working. In such a case, the shape of the light distribution should remain unchanged, however, the total light intensity will be lower. The novelty of the proposed solution is based on the usage of a small number of the independent light sources in opposite to a well known LED arrays approach. The beam shaping is made using Dammann gratings and specially designed blazed phase diffractive gratings. The article contains the theoretical analysis and the computer simulation verified by the experiment. [ABSTRACT FROM AUTHOR]

Thermal decomposition of citric acid, trans- and cis-aconitic acid has been studied using the TG-MS, TG-FTIR and DSC techniques. The measurements were carried out in an argon atmosphere over a temperature range of 293-673 K. The influence of the acid structures and configurational geometry on stability of the transition products and pathways of thermal transformations of the studied compounds studied is discussed. [ABSTRACT FROM AUTHOR]

Accurate measurement of internal magnetic field direction using motional Stark effect (MSE) polarimetry in the edge pedestal is desired for nearly all tokamak scenario work. A newly installed 500 kHz 32-channel digitizer on the MSE diagnostic of DIII-D allows full spectral information of the polarimeter signal to be recovered for the first time. Fourier analysis of this data has revealed magnetohydrodynamic (MHD) fluctuations in the plasma edge pedestal at ρ >= 0.92. By correlating edge localized mode fluctuations seen on lock-in amplifier outputs with MSE spectrograms, it has been shown that edge pedestal tearing mode fluctuations cause interference with MSE second harmonic instrument frequencies. This interference results in unrecoverable errors in the real-time polarization angle measurement that are more than an order of magnitude larger than typical polarimeter uncertainties. These errors can cause as much as a 38% difference in local q. By using a redundant measure of the linear polarization found at the fourth harmonic photo-elastic modulator (PEM) frequency, MHD interference can be avoided. However, because of poorer signal-to-noise the fourth harmonic signal computed polarization angle shows no improvement over the MHD polluted second harmonics. MHD interference could be avoided in future edge pedestal tokamak polarimeters by utilizing PEMs with higher fundamental frequencies and a greater separation between their frequencies. [ABSTRACT FROM AUTHOR]

The use of lock-in amplifiers for phase sensitive detection of motional Stark effect (MSE) diagnostic signals is of critical importance to real-time internal current profile measurements in tokamak plasmas. A digital lock-in (DLI) upgrade utilizing field programable gate array firmware has been installed on the MSE system of the DIII-D tokamak for the eventual replacement of largely obsolete analog units. While the new digital system has shown a small reduction in electronic noise over the analog, the main advantages are reduced cost, hardware simplicity, compact size, and phase tracking during plasma operations. DLI recovery of MSE polarization angles was accomplished through use of reference processing to produce only photoelastic modulator (PEM) second harmonic frequencies and electronic signal processing to maximize the fidelity of the recovered signal. A simplified discrete analytical solution was found that accurately describes the new DLI hardware. The DLI algorithm was found to cause a prohibitively large oscillating artifact atop the demodulated signal. The artifact was caused by the accumulator interval not containing an exact integer number of PEM multiplier periods. Successful MSE measurements require the minimization of this oscillating artifact amplitude. The analytical solution was used to select an appropriate accumulator interval that both reduces the artifact and maintains the greatest temporal resolution possible. Sample EFIT equilibria reconstructions and corresponding safety factor profiles showed very close agreement between the analog and digital lock-ins. [ABSTRACT FROM AUTHOR]

Abstract: To understand the formation and degradation processes of uric acid (UA) in living organisms we considered all possible tautomers–rotamers of UA by semiempirical (AM1) method, and next we used the ab initio (HF, MP2, and G2) and DFT methods to the most stable five isomers of UA selected at the AM1 level. Our calculations show evidently that at least two CH–NH forms should be considered in the tautomeric mixture of UA to understand the formation of the intermediate 5-hydroxyisourate (HIU) upon the UA oxidation by uricase. Intramolecular interactions and π-electron delocalization for UA are very similar to those occurring for its building blocks {purine (P), uracil (U), and 2-imidazolone (I)}. Tautomeric equilibrium constants for NH→OH, NH→CH, and OH→CH conversions in UA are close to those for U and I. Tautomeric equilibrium constants for NH→NH conversions in UA are close to those for P. Favored tautomers for UA, U and I are strongly stabilized by intramolecular interactions between the amide groups, whereas that for P is stabilized by π-electron delocalization and N9H⋯N3 intramolecular interaction. Aromaticity seems to be very important factor that influences the tautomeric preference for the systems which do not possess the exo functional groups. [Copyright &y& Elsevier]

Abstract: Using a modified atomic force microscope, the nanoadhesion between a silicon tip and a monolayer of 1H, 1H, 2H, 2H-perfluorodecyl trichlorosilane was measured at different loading rates. The adhesion force versus loading rate curve could be fitted with two logarithmic terms. The application of a model of thermally activated escape from a bound state to the analysis of the curves made it possible to extract quantitative information about the effective adhesion potential. Although only van der Waals interactions appear to make a major contribution to the nanoadhesion, the interaction potential characterizing the nanoadhesion still has a complex, two-transition state character. [Copyright &y& Elsevier]

Spectrometer measurements and filter upgrades to a motional Stark effect polarimeter measuring the outer half-radius of the DIII-D tokamak helped to identify asymmetries in the polarization angle of Stark-split emission. The measured polarization angle of the π components differs and is not orthogonal to the σ component. These differences persist over a range of densities and with low levels of background light. It is suggested that the difference in the polarization angle between components is from a change in the ellipticity of the emitted light across the Stark components coupled with imperfect polarization preservation from an in-vessel mirror. [ABSTRACT FROM AUTHOR]

• Overlapping effect toggling the magnetic domain states is observed in all-optical point-by-point writing of patterns. • The influence of the overlapping amount on the quality of holographic reconstructions is examined. • The optimal amount of overlapping is derived providing the globally best holographic projections, in high agreement with the numerical model. Ferrimagnetic alloys are promising media for the ultrafast, non-volatile recording of diffractive patterns for further development of computer-generated holography toward practical display applications. In this work we measure and analyze the influence of the overlapping effect during dense point-by-point recording of holographic patterns on the quality of their far field reconstructions. In particular, we numerically and experimentally derive the optimal degree of overlapping of the holographic points being written in GdFeCo alloys for the optimal fidelity of reconstructed 2-D images, which features unitary fill factor of the writing process. [ABSTRACT FROM AUTHOR]

Synthesis, structural and biological studies of pentapeptides containing two ΔPhe residues ( Z and E isomers) in position 2 and 4 in peptide chain were performed. All the investigated peptides adopted bent conformation and majority of them could exist as two different conformers in solution. Only pentapeptides, containing free N-termini appeared to act as weak inhibitors of cathepsin C with the slow-binding, competitive mechanism of inhibition, free acids being bound slightly better than their methyl esters. Results of molecular modeling suggested significant difference between peptides, depending of the type of amino acid residue in position 5 in peptide chain. Dehydropeptides containing Gly residue in this position may act as competitive slow-reacting substrates and therefore exhibit inhibitory-like properties. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Core localized Alfvén eigenmodes in DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] and Joint European Torus (JET) [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)] plasmas are driven by deuterium neutral beam ions traveling well below the Alfvén speed. Modes are observed in reverse magnetic shear discharges with deuterium ion velocities as low as 0.23 and 0.16 of the Alfvén speed parallel to the magnetic field in DIII-D and JET plasmas, respectively. Ellipticity-induced Alfvén eigenmodes in DIII-D and toroidicity-induced Alfvén eigenmodes in JET are excited by deuterium ions traveling well below the fundamental passing ion resonance condition, indicating the role of high-order resonances in driving these modes. NOVA-K analysis reveals many high-order resonances as contributing to the mode drive at high central safety factor due to the correspondingly large poloidal orbit width and the decrease in the perpendicular scale length of the modes. [ABSTRACT FROM AUTHOR]

Abstract: Franck–Condon (FC) and vibronic coupling effects in the excited 11B2 and 21A1 states of the 1,3-dicyanomethylene croconate (LD) dianion are studied using CASSCF and B3LYP methods on the aug-cc-pVDZ basis set level. The study concerns with the resonance Raman spectra measured for the laser excitation energies corresponding to the low-energy 11A1 →11B2 and 11A1 →21A1 transitions in the LD dianion absorption. It is shown that the main features of the empirical Raman spectra are clearly due to FC effect in the 11B2 and 21A1 states. We argue that certain features, like these observed at 495cm−1 and 760cm−1 may represent fundamentals of b2-symmetry modes enhanced because of vibronic coupling between 11B2 and 21A1. [Copyright &y& Elsevier]

The DIII-D Advanced Tokamak (AT) program in the DIII-D tokamak [J. L. Luxon, Plasma Physics and Controlled Fusion Research, 1986, Vol. I (International Atomic Energy Agency, Vienna, 1987), p. 159] is aimed at developing a scientific basis for steady-state, high-performance operation in future devices. This requires simultaneously achieving 100% noninductive operation with high self-driven bootstrap current fraction and toroidal beta. Recent progress in this area includes demonstration of 100% noninductive conditions with toroidal beta, βT=3.6%, normalized beta, βN=3.5, and confinement factor, H89=2.4 with the plasma current driven completely by bootstrap, neutral beam current drive, and electron cyclotron current drive (ECCD). The equilibrium reconstructions indicate that the noninductive current profile is well aligned, with little inductively driven current remaining anywhere in the plasma. The current balance calculation improved with beam ion redistribution that was supported by recent fast ion diagnostic measurements. The duration of this state is limited by pressure profile evolution, leading to magnetohydrodynamic (MHD) instabilities after about 1 s or half of a current relaxation time (τCR). Stationary conditions are maintained in similar discharges (∼90% noninductive), limited only by the 2 s duration (1τCR) of the present ECCD systems. By discussing parametric scans in a global parameter and profile databases, the need for low density and high beta are identified to achieve full noninductive operation and good current drive alignment. These experiments achieve the necessary fusion performance and bootstrap fraction to extrapolate to the fusion gain, Q=5 steady-state scenario in the International Thermonuclear Experimental Reactor (ITER) [R. Aymar et al., Fusion Energy Conference on Controlled Fusion and Plasma Physics, Sorrento, Italy (International Atomic Energy Agency, Vienna, 1987), paper IAEA-CN-77/OV-1]. The modeling tools that have been successfully employed to both plan and interpret the experiment are used to plan future DIII-D experiments with higher power and longer pulse ECCD and fast wave and co- and counterneutral beam injection in a pumped double-null configuration. The models predict our ability to control the current and pressure profiles to reach full noninductivity with increased beta, bootstrap fraction, and duration. The same modeling tools are applied to ITER, predicting favorable prospects for the success of the ITER steady-state scenario. [ABSTRACT FROM AUTHOR]

Recent improvements in the protein-structure prediction method developed in our laboratory, based on the thermodynamic hypothesis, are described. The confrontational space is searched extensively at the united-residue level by using our physics-based UNRES energy function and the confrontational space annealing method of global optimization. The lowest-energy coarse-grained structures are then converted to an all-atom representation and energy- minimized with the ECEPP/3 force field. The procedure was as- sensed in two recent blind tests of protein-structure prediction. During the first blind test we predicted large fragments of a and a+fl proteins 160-70 residues with Crams deviation (rmsd) <6 Al. However, for a-f-fl proteins, significant topological errors occurred despite low rmsd values. In the second exercise, we predicted whole structures of five proteins (two a and three a+fl, with sizes of 53-235 residues) with remarkably good accuracy. In particular, for the genomic target TM0487 (a 102-residue a+fl protein from Therrnotoga maritima), we predicted the complete, topologically correct structure with 7.3-A Ca rmsd. So far this protein is the largest a+fl protein predicted based solely on the amino acid sequence and a physics-based potential-energy function and search procedure. For target T0198, a phosphate transport system regulator PhoU from 11 maritima (a 235-residue mainly a-helical protein), we predicted the topology of the whole six-helix bundle correctly within 8 A rmsd, except the 32 C-terminal residues, most of which form a p-hairpin. These and other examples described in this work demonstrate significant progress in physics-based protein-structure prediction. [ABSTRACT FROM AUTHOR]

A local analysis technique is presented for the analysis of MSE data to deduce the safety factor q in tokamak discharges. The technique preserves as much as possible the individuality of every single measure by a simple rule of translation of magnetic field pitch angle measurements into q-values. Based on a geometric approach, and the observation that the flux surfaces shapes are strongly constrained by that of the last closed flux surface (LCFS), by the position of the magnetic axis and by a few more global parameters, it provides a robust, nonsubjective, accurate technique that is useful for the experimental study of q-profiles and for the evaluation of its uncertainties. It also provides a useful tool for plasma control experiments as it does not submit data to a preliminary search of minima in a multi-parametric domain, a procedure that may lead to jumps in the time behavior of the produced results. [ABSTRACT FROM AUTHOR]

A proof of principle magnetic feedback stabilization experiment has been carried out to suppress the resistive wall mode (RWM), a branch of the ideal magnetohydrodynamic (MHD) kink mode under the influence of a stabilizing resistive wall, on the DIII-D tokamak device [Plasma Phys. Controlled Fusion Research (Intemational Atomic Energy Agency, Vienna, 1986), p. 159; Phys. Plasmas 1, 1415 (1994)]. The RWM was successfully suppressed and the high beta duration above the no-wall limit was extended to more than 50 times the resistive wall flux diffusion time. It was observed that the mode structure was well preserved during the time of the feedback application. Several lumped parameter formulations were used to study the feedback process. The observed feedback characteristics are in good qualitative agreement with the analysis. These results provide encouragement to future efforts towards optimizing the RWM feedback methodology in parallel to what has been successfully developed for the n = 0 vertical positional control. Newly developed MHD codes have been extremely useful in guiding the experiments and in providing possible paths for the next step. [ABSTRACT FROM AUTHOR]

Transport phenomena are studied in Advanced Tokamak (AT) regimes in the DIII-D tokamak [Plasma Physics and Controlled Nuclear Fusion Research, 1986 (International Atomics Energy Agency, Vienna, 1987), Vol. I, p. 159], with the goal of developing understanding and control during each of three phases: Formation of the internal transport barrier (ITB) with counter neutral beam injection taking place when the heating power exceeds a threshold value of about 9 MW, contrasting to co-NBI injection, where P[sub threshold]<2.5 MW. Expansion of the ITB is enhanced compared to similar co-injected discharges. Both differences are believed to arise from modification of the ExB shear dynamics when the sign of the rotation contribution is reversed. Sustainment of an AT regime with β[sub N]H[sub 89]=9 for 16 confinement times has been accomplished in a discharge combining an ELMing H-mode (edge localized, high confinement mode) edge and an ITB, and exhibiting ion thermal transport down to 2-3 times neoclassical. The microinstabilities usually associated with ion thermal transport are predicted stable, implying that another mechanism limits performance. High frequency magnetohydrodynamic (MHD) activity is identified as the probable cause. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A drift-cyclotron instability is observed at low magnetic field strengths in a linear multiple mirror. It is characterized by a frequency which decreases with increasing magnetic field strength, propagation in the direction of the electron diamagnetic current, and an azimuthal mode number of 2. The mode is observed when the ion-cyclotron frequency is less than the ion diamagnetic frequency. The frequency is Doppler-shifted by an E×B drift. Effects of particles trapped in the mirror cells alter the characteristics of the instability. The frequency decreases slightly and the fluctuation level increases with increasing mirror ratio for mirror ratios less than 1.1, but then levels off at higher mirror ratios. The drift wave is analyzed by a linear theory which treats finite ion gyroradius, an electron temperature gradient, and trapped electrons. The theory predicts three unstable modes, only one of which is consistent with all of the above measurements. This instability is a Doppler-shifted drift-cyclotron instability modified by trapped particle effects. [ABSTRACT FROM AUTHOR]

Reports on experiments that explore the long-time evolution of noninductive, high beta plasmas in the DIII-D tokamak and identify a quiescent, high performance regime. Disappearance of magnetohydrodynamic activity with an increase in stored energy; Experimental conditions.