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Sample records for 2h nqr parameters

  1. A systematic investigation of hydrogen-bonding effects on the 17O, 14N, and 2H nuclear quadrupole resonance parameters of anhydrous and monohydrated cytosine crystalline structures: a density functional theory study.

    PubMed

    Mirzaei, Mahmoud; Elmi, Fatemeh; Hadipour, Nasser L

    2006-06-08

    A systematic computational study was carried out to characterize the 17O, 14N, and 2H nuclear quadrupole resonance (NQR) parameters in the anhydrous and monohydrated cytosine crystalline structures. To include the hydrogen-bonding effects in the calculations, the most probable interacting molecules with the central molecule in the crystalline phase were considered in the pentameric clusters of both structures. To calculate the parameters, couples of the methods B3LYP and B3PW91 and the basis sets 6-311++G** and CC-pVTZ were employed. The mentioned methods calculated reliable values of 17O, 14N, and 2H NQR tensors in the pentameric clusters, which are in good agreements with the experiment. The different influences of various hydrogen-bonding interactions types, N-H...N, N-H...O, and O-H...O, were observed on the 17O, 14N, and 2H NQR tensors. Lower values of quadrupole coupling constants and higher values of asymmetry parameters in the crystalline monohydrated cytosine indicate the presence of stronger hydrogen-bonding interactions in the monohydrated form rather than that of crystalline anhydrous cytosine.

  2. Spectroscopic Line Parameters in the Infrared Bands of CH3CN and C2H6

    NASA Astrophysics Data System (ADS)

    Devi, V. Malathy

    2010-10-01

    In this paper, measurements of critical spectroscopic line parameters such as positions, absolute intensities and pressure broadened (self- and N2) half-width coefficients for transitions in the ν4 band of CH3CN (acetonitile, ethanenitrile, methyl cyanide) and the ν9 band of C2H6 (ethane) are presented. CH3CN has been measured by remote sensing in the earth's atmosphere, in comets and in interstellar molecular clouds. It is also a constituent in the atmospheres of Titan, Saturn's largest moon. Likewise, C2H6 is also an important constituent in the atmosphere of earth, the giant planets and comets. The 12- μm(˜720-850 cm-1) emission features of this molecule have been observed in spectra from outer solar system bodies of Jupiter, Saturn, Neptune and Titan. Because of their importance in remote sensing measurements, we recently recorded and analyzed a large number of laboratory infrared absorption spectra of pure and N2-broadened spectra of both these molecular bands. Spectra used in these analyses were recorded using either the Bruker IFS 125HR or the Bruker IFS 120HR FTS located at the Pacific Northwest National Laboratory (PNNL), in Richland Washington. To retrieve the various spectral line parameters, a multispectrum nonlinear least squares fitting algorithm was employed and all spectra belonging to each band were fitted simultaneously. Using this fitting technique, the same spectral regions from multiple spectra were fit all at once to maximize the accuracy of the retrieved parameters. The results obtained from present analyses are briefly discussed. In the case of C2H6 both room- and low temperature (˜210-296 K) spectra were recorded, but results from analyzing only room-temperature spectra will be discussed in this work.

  3. 14 N NQR spectrum of sildenafil citrate

    NASA Astrophysics Data System (ADS)

    Stephenson, David; Singh, Nadia

    2015-04-01

    The 14N nuclear quadrupole resonance (NQR) spectrum of sildenafil citrate tablets has been recorded allowing the quadrupole coupling constants and asymmetry parameters of all six unique nitrogen atoms in its structure to be determined. A density function calculation gives results that are largely in agreement with the experimental values.

  4. On the Nature of the "Bleaching out" Process of the 35Cl NQR Signals in 1,2,3-Trichlorobenzene

    NASA Astrophysics Data System (ADS)

    Wigand, Silvia; Weiden, Norbert; Weiss, Alarich

    1990-04-01

    The 35Cl NQR frequencies, linewidths, and spin-lattice relaxation times T1(35Cl) of 1,2,3-trichlorotrideuterobenzene were measured at various temperatures. The deuterated compound shows the same bleaching out phenomenon as 1,2,3-trichlorobenzene. Single crystal 2H NMR measurements were carried out at 295 and 193 K. The nuclear quadrupole coupling constants at room temperature are in the range of 175.8 ≦ e2qQh-1 (2H)/kHz ≦ 179.5, and the asymmetry parameters η in the range of 0.060 ≦ η (2H) ≦ 0.073. As for the principal axes of the electric field gradient tensor, it was found that Φzz(2H) is parallel to the C - D bond, Φyy (2H) is perpendicular to the benzene ring plane and Φxx(2H) lies in the ring plane. The linewidths of the 2H NMR satellites are idependent of temperature. For the undeuterated compound, the temperature dependence of T1(1H) was also measured. The mechanism leading to the bleaching out of the 35Cl NQR signals is discussed.

  5. Mixed H(2)/H(sub infinity): Control with output feedback compensators using parameter optimization

    NASA Technical Reports Server (NTRS)

    Schoemig, Ewald; Ly, Uy-Loi

    1992-01-01

    Among the many possible norm-based optimization methods, the concept of H-infinity optimal control has gained enormous attention in the past few years. Here the H-infinity framework, based on the Small Gain Theorem and the Youla Parameterization, effectively treats system uncertainties in the control law synthesis. A design approach involving a mixed H(sub 2)/H-infinity norm strives to combine the advantages of both methods. This advantage motivates researchers toward finding solutions to the mixed H(sub 2)/H-infinity control problem. The approach developed in this research is based on a finite time cost functional that depicts an H-infinity bound control problem in a H(sub 2)-optimization setting. The goal is to define a time-domain cost function that optimizes the H(sub 2)-norm of a system with an H-infinity-constraint function.

  6. NQR in Alanine and Lysine Iodates

    NASA Astrophysics Data System (ADS)

    Petrosyan, A. M.; Burbelo, V. M.; Tamazyan, R. A.; Karapetyan, H. A.; Sukiasyan, R. P.

    2000-02-01

    The structure o f iodates of α- and β-alanine ( Ala) (2(β-Ala • HIO3) • H2O , β-Ala-2HIO3 , D L-Ala• HIO3 • 2H2O, L-Ala • HIO3) and L-lysine (L-Lys) (L-Lys • HIO3, L-Lys • 2HIO3,L-Lys • 3HIO3, L-Lys • 6HIO3) have been investigated by means of iodine-127 NQR, IR spectroscopy and X-ray diffraction

  7. Scientific Support for NQR Explosive Detection Development

    DTIC Science & Technology

    2006-07-01

    Final 3. DATES COVERED (From - To) 8 March 2004 - 7 March 2006 4. TITLE AND SUBTITLE Scientific Support for NQR Explosive Detection Development...Laboratory (NRL) to improve explosive detection using nuclear quadrupole resonance ( NQR ) is summarized. The work includes studies of the effects...superconducting coils for explosive detection. Additional studies involving slowly rotating NQR measurements were also pursued. 15. SUBJECT TERMS Nuclear

  8. Line Parameters of Ethane (12C_2H_6) at 12 μm with Constrained Multispectrum Fitting

    NASA Astrophysics Data System (ADS)

    Devi, V. Malathy; Benner, D. Chris; Rinsland, C. P.; Smith, M. A. H.; Sams, R. L.; Blake, T. A.; Flaud, J.-M.; Sung, K.; Brown, L. R.; Mantz, A. W.

    2010-06-01

    A multispectrum nonlinear least squares technique was applied to simultaneously fit 43 infrared absorption spectra of C_2H_6 between 795 and 850 cm-1. The high resolution (0.0016-0.005 cm-1) spectra were recorded with two different Bruker Fourier transform spectrometers at PNNL and JPL to support Earth and planetary atmosphere studies, e.g. Titan's cold stratosphere. Accurate line positions and absolute intensities at room temperature were retrieved for over 1750 transitions of ν_9. N_2- and self-broadened halfwidth coefficients with their temperature dependences were obtained for over 1330 lines using sample temperatures between ˜150 and 298 K. Constraints to intensity ratios, torsional splittings, halfwidth coefficients and their temperature dependence exponents were incorporated in the analysis to determine these parameters for both torsional split components. The variations of the observed halfwidth coefficients and their temperature dependences with respect to J, K quanta are discussed. No pressure-induced shifts were measured or even required to fit the spectra to their noise levels. Present results are compared with previously reported measurements and predictions. D. Chris Benner, C. P. Rinsland, V. M. Devi, M. A. H. Smith, and D. A. Atkins, JQSRT 1995;53:705-21. Part of the research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, the College of William and Mary, Connecticut College, and NASA Langley Research Center under contracts and cooperative agreements with the National Aeronautics and Space Administration.

  9. Explosives detection by nuclear quadrupole resonance (NQR)

    NASA Astrophysics Data System (ADS)

    Garroway, Allen N.; Buess, Michael L.; Yesinowski, James P.; Miller, Joel B.; Krauss, Ronald A.

    1994-10-01

    Pure nuclear quadrupole resonance (NQR) of 14N nuclei is quite promising as a method for detecting explosives such as RDX and contraband narcotics such as cocaine and heroin in quantities of interest. Pure NQR is conducted without an external applied magnetic field, so potential concerns about damage to magnetically encoded data or exposure of personnel to large magnetic fields are not relevant. Because NQR frequencies of different compounds are quite distinct, we do not encounter false alarms from the NQR signals of other benign materials. We have constructed a laboratory prototype NQR explosives detector which interrogates a volume of 300 liters (10 ft3). This paper presents abbreviated results from a demonstration of the laboratory prototype NQR explosives detector conducted at the Federal Aviation Administration Technical Center in May 1994 on RDX-based explosives.

  10. Reinvestigation of the elementary chemical kinetics of the reaction C2H5(•) + HBr (HI) → C2H6 + Br(•) (I(•)) in the range 293-623 K and its implication on the thermochemical parameters of C2H5(•) free radical.

    PubMed

    Leplat, N; Wokaun, A; Rossi, M J

    2013-11-14

    A reinvestigation of the absolute rate constants of the metathesis reactions C2H5• + HBr → C2H6 + Br• (R1) and C2H5• + HI → C2H6 + I• (R2) has been performed and led to the following Arrhenius expressions: k1 = 3.69(±0.95) × 10–11 exp(−10.62(±0.66)/RT), k2 = 1.20(±0.38) × 10–11 exp(−7.12(±1.059)/RT) in the temperature range 293–623 K (A/cm3 molecule–1 s–1, Ea/kJ mol–1). The study has been performed using a Knudsen reactor coupled to single-photon (VUV) photoionization mass spectrometer (SPIMS). Hydrocarbon free radicals have been generated externally before admission into the Knudsen reactor according to two different chemical schemes, enabling the generation of thermalized C2H5• free radicals. A minor correction to k1 and k2 for the wall loss of C2H5• (kw) has been applied throughout the temperature range. The obtained results are consistent regarding both the disappearance of C2H5• and the formation of closed shell products (n-C4H10, C2H4, C2H6), indicating that the chemical mechanism is largely understood and complete. Thermochemical parameters for C2H5• free radical resulting from the present kinetic measurements are discussed and point toward a slightly lower value for the standard heat of formation ΔfH298°(C2H5•) compared to some presently recommended values. On the basis of the present results and suitable data on the reverse reaction taken from the literature, we recommend ΔfH298°(C2H5•) = 117.3 ± 3.1 kJ/mol resulting from an average of “third law” evaluations using S298°(C2H5•) = 242.9 ± 4.6 J/K mol. The present work yields a standard heat of formation in satisfactory agreement with the results obtained by W. Tsang (ΔfH298°(C2H5•) = 119 ± 2 kJ/mol) despite using two very different experimental techniques.

  11. Calculations of multipulse sequence in NQR of spins 32.

    PubMed

    Odin, C

    1999-12-01

    The general formalism of the interaction representation with respect to an operator which is its own inverse is developed and applied to pure NQR of spins I = 32. Under the assumption of no relaxation and no dipolar coupling, it is shown that the calculation of the response to pure NQR multipulse sequences can be performed with the same concepts used in high field NMR, such as coherence pathways. All the tools and mathematical expressions to predict the time evolution of the signal created by a pure NQR multipulse sequence are presented explicitly. It takes into account the off-resonance irradiation as well as the angular dependence of the excitation and detection for every value of the electric field gradient asymmetry parameter. Particular attention is devoted to the powder average, which is performed via a probability function derived analytically for the first time, leading to a drastic reduction of simulation times. The theory is illustrated by the study of the optimization and excitation bandwidths of one- to three-pulse sequences and compared to experimental results on Chloranil. We show that the three-pulse "stimulated echo" sequence gives a more uniform excitation profile than the traditional two-pulse echo sequence for powder samples. Thus, the "stimulated echo" sequence could be useful to cover a large spectrum when the experiment duration, or the signal to noise ratio, are not critical parameters. Analytical expressions for the nutation spectra obtained by one or two-pulse sequences are also derived for the first time.

  12. A new approach to mixed H2/H infinity controller synthesis using gradient-based parameter optimization methods

    NASA Technical Reports Server (NTRS)

    Ly, Uy-Loi; Schoemig, Ewald

    1993-01-01

    In the past few years, the mixed H(sub 2)/H-infinity control problem has been the object of much research interest since it allows the incorporation of robust stability into the LQG framework. The general mixed H(sub 2)/H-infinity design problem has yet to be solved analytically. Numerous schemes have considered upper bounds for the H(sub 2)-performance criterion and/or imposed restrictive constraints on the class of systems under investigation. Furthermore, many modern control applications rely on dynamic models obtained from finite-element analysis and thus involve high-order plant models. Hence the capability to design low-order (fixed-order) controllers is of great importance. In this research a new design method was developed that optimizes the exact H(sub 2)-norm of a certain subsystem subject to robust stability in terms of H-infinity constraints and a minimal number of system assumptions. The derived algorithm is based on a differentiable scalar time-domain penalty function to represent the H-infinity constraints in the overall optimization. The scheme is capable of handling multiple plant conditions and hence multiple performance criteria and H-infinity constraints and incorporates additional constraints such as fixed-order and/or fixed structure controllers. The defined penalty function is applicable to any constraint that is expressible in form of a real symmetric matrix-inequity.

  13. Effect of hydrogen ratio on plasma parameters of N{sub 2}-H{sub 2} gas mixture glow discharge

    SciTech Connect

    El-Brulsy, R. A.; Abd Al-Halim, M. A.; Abu-Hashem, A.; Rashed, U. M.; Hassouba, M. A.

    2012-05-15

    A dc plane glow discharge in a nitrogen-hydrogen (N{sub 2}-H{sub 2}) gas mixture has been operated at discharge currents of 10 and 20 mA. The electron energy distribution function (EEDF) at different hydrogen concentrations is measured. A Maxwellian EEDF is found in the positive column region, while in both cathode fall and negative glow regions, a non-Maxwellian one is observed. Langmuir electric probes are used at different axial positions, gas pressures, and hydrogen concentrations to measure the electron temperature and plasma density. The electron temperature is found to increase with increasing H{sub 2} concentration and decrease with increasing both the axial distance from the cathode and the mixture pressure. At first, with increasing distance from the cathode, the ion density decreases, while the electron density increases; then, as the anode is further approached, they remain nearly constant. At different H{sub 2} concentrations, the electron and ion densities decrease with increasing the mixture pressure. Both the electron and ion densities slightly decrease with increasing H{sub 2} concentration.

  14. Determination of the band parameters of bulk 2H-MX2 (M = Mo, W; X = S, Se) by angle-resolved photoemission spectroscopy

    PubMed Central

    Kim, Beom Seo; Rhim, Jun-Won; Kim, Beomyoung; Kim, Changyoung; Park, Seung Ryong

    2016-01-01

    Monolayer MX2 (M = Mo, W; X = S, Se) has recently been drawn much attention due to their application possibility as well as the novel valley physics. On the other hand, it is also important to understand the electronic structures of bulk MX2 for material applications since it is very challenging to grow large size uniform and sustainable monolayer MX2. We performed angle-resolved photoemission spectroscopy and tight binding calculations to investigate the electronic structures of bulk 2H-MX2. We could extract all the important electronic band parameters for bulk 2H-MX2, including the band gap, direct band gap size at K (-K) point and spin splitting size. Upon comparing the parameters for bulk 2H-MX2 (our work) with mono- and multi-layer MX2 (published), we found that stacked layers, substrates for thin films, and carrier concentration significantly affect the parameters, especially the band gap size. The origin of such effect is discussed in terms of the screening effect. PMID:27805019

  15. The Photon Polarization Parameter of 2H(n, γ)3H reaction with Inclusion of the Electric Quadrupole Contribution

    NASA Astrophysics Data System (ADS)

    Sadeghi, H.; Mosavi-Khansari, M.

    2014-09-01

    We use effective field theory (EFT) for the calculation of neutron—deuteron radiative capture at very low energies. We present here the use of EFT to calculate a low-energy photo-nuclear observable in three-body systems, the photon polarization parameter and fore—aft asymmetry at thermal neutron energies up to next-to-next to leading order (N2LO), with inclusion of the electric quadrupole contribution. The photon polarization parameter in total is found to be Rc = -0.421 ± 0.003 and is in good agreement with the other modern theoretical calculations based on modern nucleon—nucleon potentials. In comparison with our previous work, a satisfactory agreement with the available experimental data is found by inclusion of the electric quadrupole contribution.

  16. Optical detection of low frequency NQR signals: a step forward from conventional NQR

    NASA Astrophysics Data System (ADS)

    Begus, S.; Pirnat, J.; Jazbinsek, V.; Trontelj, Z.

    2017-03-01

    In searching for the more sensitive 14N nuclear quadrupole resonance (NQR) detecting system for illicit substances, a promising combination of a classic RF pulse NQR spectrometer and a K optically pumped magnetometer was tested. The initial results are encouraging. The principles of such a combination are described, and the detection limits in the low frequency RF region, where the 14N pulse NQR frequencies are usually positioned, are presented. Several illicit substances which are difficult to detect with a classic pulse NQR spectrometer were detected with both types of spectrometers. We noticed that with the proposed combination of classic RF excitation of 14N nuclei, using a pulse NQR spectrometer and subsequent optical detection of the sample’s response, a gain in S/N of up to a factor of 10 was possible.

  17. Line Positions, Intensities, - and N_2-BROADENING Parameters in the ν_9 Band of Ethane (C_2H_6)

    NASA Astrophysics Data System (ADS)

    Rinsland, Curtis P.; Devi, V. Malathy; Benner, D. Chris; Sams, Robert L.; Blake, Thomas A.

    2009-06-01

    High-resolution infrared spectra of ethane have been recorded using the Bruker IFS 120 HR Fourier transform spectrometer (FTS) at the Pacific Northwest National Laboratory (PNNL), in Richland, Washington. Several spectra of pure ethane and ethane in N_2 mixtures were obtained with absorption paths of 20 cm and 3.2 m. Room temperature spectra were obtained in both 20 cm and 3.2 m paths while cold spectra were obtained using only the 20 cm path cell. The spectra were obtained at ˜0.0028 cm^{-1} resolution with sample pressures ranging from 0.3 to ˜36 torr for pure ethane and 11 to 180 torr in ethane-N_2 mixtures. The volume mixing ratios of ethane in the ethane-N_2 mixtures varied between 0.01 and 0.2. The gas temperatures varied from -66^°C to 24^°C. Positions, intensities, self- and N_2-broadening parameters were determined by processing 16 or 17 room temperature spectra using the multispectrum nonlinear least squares spectrum fitting technique. The results obtained for transitions in a few select ^PQ and ^RQ sub-bands will be reported at this time. D. Chris Benner, C.P. Rinsland, V. Malathy Devi, M.A.H. Smith, and D. Atkins, J. Quant. Spectrosc. Radiat. Transfer 53, 705-721 (1995)

  18. A miniaturized NQR spectrometer for a multi-channel NQR-based detection device.

    PubMed

    Beguš, Samo; Jazbinšek, Vojko; Pirnat, Janez; Trontelj, Zvonko

    2014-10-01

    A low frequency (0.5-5 MHz) battery operated sensitive pulsed NQR spectrometer with a transmitter power up to 5 W and a total mass of about 3 kg aimed at detecting (14)N NQR signals, predominantly of illicit materials, was designed and assembled. This spectrometer uses a standard software defined radio (SDR) platform for the data acquisition unit. Signal processing is done with the LabView Virtual instrument on a personal computer. We successfully tested the spectrometer by measuring (14)N NQR signals from aminotetrazole monohydrate (ATMH), potassium nitrate (PN), paracetamol (PCM) and trinitrotoluene (TNT). Such a spectrometer is a feasible component of a portable single or multichannel (14)N NQR based detection device.

  19. A miniaturized NQR spectrometer for a multi-channel NQR-based detection device

    NASA Astrophysics Data System (ADS)

    Beguš, Samo; Jazbinšek, Vojko; Pirnat, Janez; Trontelj, Zvonko

    2014-10-01

    A low frequency (0.5-5 MHz) battery operated sensitive pulsed NQR spectrometer with a transmitter power up to 5 W and a total mass of about 3 kg aimed at detecting 14N NQR signals, predominantly of illicit materials, was designed and assembled. This spectrometer uses a standard software defined radio (SDR) platform for the data acquisition unit. Signal processing is done with the LabView Virtual instrument on a personal computer. We successfully tested the spectrometer by measuring 14N NQR signals from aminotetrazole monohydrate (ATMH), potassium nitrate (PN), paracetamol (PCM) and trinitrotoluene (TNT). Such a spectrometer is a feasible component of a portable single or multichannel 14N NQR based detection device.

  20. Spin 3/2 Zeeman perturbed NQR in the presence of slow sample rotation.

    PubMed

    Panguluri, R P; Suits, B H

    2006-09-01

    Theoretical and experimental results are presented for the case of Zeeman perturbed nuclear quadrupole resonance (NQR) using spin-3/2 nuclei with a small Zeeman interaction, gammaB0, while the sample is very slowly rotated. It is found that the decay envelope for a simple two-pulse echo measurement can be strongly affected even though the sample may rotate only a few degrees or less during the course of the measurement. To lowest order the decay envelope can be described using a one dimensional function of the product of gammaB0, the rotation rate, and the square of the pulse spacing. Aside from an indirect and weak dependence on the quadrupole asymmetry parameter, eta, the result is independent of the NQR frequency. Identical results are expected for a stationary sample in a small rotating magnetic field. The effect seen here may be used to advantage to measure rotational motion, for example of particles in fluids, or may be an additional complication for some Zeeman perturbed NQR measurements, including some NQR detection and imaging methods.

  1. Influence of operational key parameters on the photocatalytic decolorization of Rhodamine B dye using Fe2+/H2O2/Nb2O5/UV system.

    PubMed

    Hashemzadeh, Fatemeh; Rahimi, Rahmatollah; Gaffarinejad, Ali

    2014-04-01

    The present research deals with the development of a new heterogeneous photocatalysis and Fenton hybrid system for the removal of color from textile dyeing wastewater as Rhodamine B (RhB) solutions by using Fe(2+)/H2O2/Nb2O5 as a photocatalytic system. The application of this photocatalytic system for the decolorization of dye contaminants is not reported in the literature yet. Different parameters like dye concentration, Nb2O5/Fe(2+) catalyst amount, pH, and H2O2 concentration have been studied. The optimum conditions for the decolorization of the dye were initial concentration of 10 mg L(-1) of dye, pH 4, and Nb2O5/Fe(2+) catalyst concentration of 0.5 g L(-1)/50 mg L(-1). The optimum value of H2O2 concentration for the conditions used in this study was 700 mg L(-1). Moreover, the efficiency of the Nb2O5/photo-Fenton hybrid process in comparison to photo-Fenton alone and a dark Fenton process as a control experiment to decolorize the RhB solution has been investigated. The combination of photo-Fenton and Nb2O5 catalysts has been proved to be the most effective for the treatment of such type of wastewaters. The results revealed that the RhB dye was decolorized in a higher percent (78 %) by the Nb2O5/photo-Fenton hybrid process (Fe(2+)/H2O2/Nb2O5/UV) than by the photo-Fenton process alone (37 %) and dark Fenton process (14 %) after 120 min of treatment. Moreover, the Nb2O5 catalyst as a heterogeneous part of the photocatalytic system was demonstrated to have good stability and reusability.

  2. Investigating a Quadrant Surface Coil Array for NQR Remote Sensing

    DTIC Science & Technology

    2014-10-23

    UNCLASSIFIED 1  Abstract—this paper is on the design and fabrication of a surface coil array in a quadrant layout for NQR (Nuclear Quadrupole...coupling and SNR (Signal-to-Noise Ratio) at standoff distances perpendicular from each coil. Index Terms— Nuclear Quadrupole Resonance, NQR ...Coil Array, probe, Nuclear Magnetic Resonance, tuning, decoupling, RLC, mutual coupling, RLC I. INTRODUCTION N Nuclear quadrupole resonance ( NQR

  3. Derivation of force field parameters for SnO2-H2O surface systems from plane-wave density functional theory calculations.

    PubMed

    Bandura, A V; Sofo, J O; Kubicki, J D

    2006-04-27

    Plane-wave density functional theory (DFT-PW) calculations were performed on bulk SnO2 (cassiterite) and the (100), (110), (001), and (101) surfaces with and without H2O present. A classical interatomic force field has been developed to describe bulk SnO2 and SnO2-H2O surface interactions. Periodic density functional theory calculations using the program VASP (Kresse et al., 1996) and molecular cluster calculations using Gaussian 03 (Frisch et al., 2003) were used to derive the parametrization of the force field. The program GULP (Gale, 1997) was used to optimize parameters to reproduce experimental and ab initio results. The experimental crystal structure and elastic constants of SnO2 are reproduced reasonably well with the force field. Furthermore, surface atom relaxations and structures of adsorbed H2O molecules agree well between the ab initio and force field predictions. H2O addition above that required to form a monolayer results in consistent structures between the DFT-PW and classical force field results as well.

  4. Broadband quantitative NQR for authentication of vitamins and dietary supplements.

    PubMed

    Chen, Cheng; Zhang, Fengchao; Bhunia, Swarup; Mandal, Soumyajit

    2017-03-24

    We describe hardware, pulse sequences, and algorithms for nuclear quadrupole resonance (NQR) spectroscopy of medicines and dietary supplements. Medicine and food safety is a pressing problem that has drawn more and more attention. NQR is an ideal technique for authenticating these substances because it is a non-invasive method for chemical identification. We have recently developed a broadband NQR front-end that can excite and detect (14)N NQR signals over a wide frequency range; its operating frequency can be rapidly set by software, while sensitivity is comparable to conventional narrowband front-ends over the entire range. This front-end improves the accuracy of authentication by enabling multiple-frequency experiments. We have also developed calibration and signal processing techniques to convert measured NQR signal amplitudes into nuclear spin densities, thus enabling its use as a quantitative technique. Experimental results from several samples are used to illustrate the proposed methods.

  5. NQR detection of explosive simulants using RF atomic magnetometers

    NASA Astrophysics Data System (ADS)

    Monti, Mark C.; Alexson, Dimitri A.; Okamitsu, Jeffrey K.

    2016-05-01

    Nuclear Quadrupole Resonance (NQR) is a highly selective spectroscopic method that can be used to detect and identify a number of chemicals of interest to the defense, national security, and law enforcement community. In the past, there have been several documented attempts to utilize NQR to detect nitrogen bearing explosives using induction sensors to detect the NQR RF signatures. We present here our work on the NQR detection of explosive simulants using optically pumped RF atomic magnetometers. RF atomic magnetometers can provide an order of magnitude (or more) improvement in sensitivity versus induction sensors and can enable mitigation of RF interference, which has classically has been a problem for conventional NQR using induction sensors. We present the theory of operation of optically pumped RF atomic magnetometers along with the result of laboratory work on the detection of explosive simulant material. An outline of ongoing work will also be presented along with a path for a fieldable detection system.

  6. Crystallization and preliminary analysis of the NqrA and NqrC subunits of the Na+-translocating NADH:ubiquinone oxidoreductase from Vibrio cholerae

    PubMed Central

    Vohl, Georg; Nedielkov, Ruslan; Claussen, Björn; Casutt, Marco S.; Vorburger, Thomas; Diederichs, Kay; Möller, Heiko M.; Steuber, Julia; Fritz, Günter

    2014-01-01

    The Na+-translocating NADH:ubiquinone oxidoreductase (Na+-NQR) from Vibrio cholerae is a membrane protein complex consisting of six different subunits NqrA–NqrF. The major domains of the NqrA and NqrC subunits were heterologously expressed in Escherichia coli and crystallized. The structure of NqrA1–377 was solved in space groups C2221 and P21 by SAD phasing and molecular replacement at 1.9 and 2.1 Å resolution, respectively. NqrC devoid of the transmembrane helix was co-expressed with ApbE to insert the flavin mononucleotide group covalently attached to Thr225. The structure was determined by molecular replacement using apo-NqrC of Parabacteroides distasonis as search model at 1.8 Å resolution. PMID:25005105

  7. Nitrogen-14 NQR Study of Energetic Materials

    DTIC Science & Technology

    1982-09-01

    Army Research Office Research Triangle Park North Carolina 27709 Contract No. DAAG-29-79-0025 I Submitted by: BLOCK ENGINEERING Division of Bio-Rad...NQR Lines C-i F APPENDIX D Princeton Applied Research Interface D-1 References R-1 BLOCK 󈨑 7T - %. LIST OF TABLES Tables Page 2.2-I Lorentzian FID and...as can be seen by the seemingly incongruous pairing of v and v + lines in Figure 3.1-1. In fact, it will be shown that the chemical inequivalence of "o

  8. Frequency selective detection of nuclear quadrupole resonance (NQR) spin echoes

    NASA Astrophysics Data System (ADS)

    Somasundaram, Samuel D.; Jakobsson, Andreas; Smith, John A. S.; Althoefer, Kaspar A.

    2006-05-01

    Nuclear Quadrupole Resonance (NQR) is a radio frequency (RF) technique that can be used to detect the presence of quadrupolar nuclei, such as the 14N nucleus prevalent in many explosives and narcotics. The technique has been hampered by low signal-to-noise ratios and is further aggravated by the presence of RF interference (RFI). To ensure accurate detection, proposed detectors should exploit the rich form of the NQR signal. Furthermore, the detectors should also be robust to any remaining residual interference, left after suitable RFI mitigation has been employed. In this paper, we propose a new NQR data model, particularly for the realistic case where multiple pulse sequences are used to generate trains of spin echoes. Furthermore, we refine two recently proposed approximative maximum likelihood (AML) detectors, enabling the algorithm to optimally exploit the data model of the entire echo train and also incorporate knowledge of the temperature dependent spin-echo decay time. The AML-based detectors ensure accurate detection and robustness against residual RFI, even when the temperature of the sample is not precisely known, by exploiting the dependencies of the NQR resonant lines on temperature. Further robustness against residual interference is gained as the proposed detector is frequency selective; exploiting only those regions of the spectrum where the NQR signal is expected. Extensive numerical evaluations based on both simulated and measured NQR data indicate that the proposed Frequency selective Echo Train AML (FETAML) detector offers a significant improvement as compared to other existing detectors.

  9. Detection of {sup 14}N and {sup 35}Cl in cocaine base and hydrochloride using NQR, NMR, and SQUID techniques

    SciTech Connect

    Yesinowski, J.P.; Buess, M.L.; Garroway, A.N.; Ziegeweid, M.; Pines, A. |

    1995-07-01

    Results from {sup 14}N pure NQR of cocaine in the free base form (cocaine base) yield a nuclear quadrupole coupling constant (NQCC) e{sup 2}Qq/h of 5.0229 ({+-}0.0001) MHz and an asymmetry parameter {eta} of 0.0395 ({+-}0.0001) at 295 K, with corresponding values of 5.0460 ({+-}0.0013) MHz and 0.0353 ({+-}0.0008) at 77 K. Both pure NQR (at 295-77 K) and a superconducting quantum interference device (SQUID) detector (at 4.2 K) were used to measure the very low (<1 MHz) {sup 14}N transition frequencies in cocaine hydrochloride; at 295 K the NQCC is 1.1780 ({+-}0.0014) MHz and the asymmetry parameter is 0.2632 ({+-}0.0034). Stepping the carrier frequency enables one to obtain a powder pattern without the severe intensity distortions that otherwise arise from finite pulse power. A powder pattern simulation using an NQCC value of 5.027 MHz and an asymmetry parameter {eta} of 0.2 agrees reasonably well with the experimental stepped-frequency spectrum. The use of pure NQR for providing nondestructive, quantitative, and highly specific detection of crystalline compounds is discussed, as are experimental strategies. 31 refs., 8 figs., 1 tab.

  10. Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds.

    PubMed

    Perić, Berislav; Gautier, Régis; Pickard, Chris J; Bosiočić, Marko; Grbić, Mihael S; Požek, Miroslav

    2014-01-01

    Two hexanuclear niobium halide cluster compounds with a [Nb6X12](2+) (X=Cl, Br) diamagnetic cluster core, have been studied by a combination of experimental solid-state NMR/NQR techniques and PAW/GIPAW calculations. For niobium sites the NMR parameters were determined by using variable Bo field static broadband NMR measurements and additional NQR measurements. It was found that they possess large positive chemical shifts, contrary to majority of niobium compounds studied so far by solid-state NMR, but in accordance with chemical shifts of (95)Mo nuclei in structurally related compounds containing [Mo6Br8](4+) cluster cores. Experimentally determined δiso((93)Nb) values are in the range from 2,400 to 3,000 ppm. A detailed analysis of geometrical relations between computed electric field gradient (EFG) and chemical shift (CS) tensors with respect to structural features of cluster units was carried out. These tensors on niobium sites are almost axially symmetric with parallel orientation of the largest EFG and the smallest CS principal axes (Vzz and δ33) coinciding with the molecular four-fold axis of the [Nb6X12](2+) unit. Bridging halogen sites are characterized by large asymmetry of EFG and CS tensors, the largest EFG principal axis (Vzz) is perpendicular to the X-Nb bonds, while intermediate EFG principal axis (Vyy) and the largest CS principal axis (δ11) are oriented in the radial direction with respect to the center of the cluster unit. For more symmetrical bromide compound the PAW predictions for EFG parameters are in better correspondence with the NMR/NQR measurements than in the less symmetrical chlorine compound. Theoretically predicted NMR parameters of bridging halogen sites were checked by (79/81)Br NQR and (35)Cl solid-state NMR measurements.

  11. Numerical simulation of NQR/NMR: Applications in quantum computing.

    PubMed

    Possa, Denimar; Gaudio, Anderson C; Freitas, Jair C C

    2011-04-01

    A numerical simulation program able to simulate nuclear quadrupole resonance (NQR) as well as nuclear magnetic resonance (NMR) experiments is presented, written using the Mathematica package, aiming especially applications in quantum computing. The program makes use of the interaction picture to compute the effect of the relevant nuclear spin interactions, without any assumption about the relative size of each interaction. This makes the program flexible and versatile, being useful in a wide range of experimental situations, going from NQR (at zero or under small applied magnetic field) to high-field NMR experiments. Some conditions specifically required for quantum computing applications are implemented in the program, such as the possibility of use of elliptically polarized radiofrequency and the inclusion of first- and second-order terms in the average Hamiltonian expansion. A number of examples dealing with simple NQR and quadrupole-perturbed NMR experiments are presented, along with the proposal of experiments to create quantum pseudopure states and logic gates using NQR. The program and the various application examples are freely available through the link http://www.profanderson.net/files/nmr_nqr.php.

  12. 35Cl NQR and 1H NMR Studies of Molecular Motions in Guanidinium Salt of Chloroacetic Acid

    NASA Astrophysics Data System (ADS)

    Zdanowska-Fnjczek, Maria; Grottel, Małgorzata; Jakubas, Ryszard

    1998-07-01

    Multinuclear NQR and NMR techniques have been applied in order to study the molecular dynamics in [C(NH2)3](ClH2CCOO). The 35Cl NQR frequency was measured over a wide range of temperature. The experimental results were described by using the theories of Bayer and Brown which take into account the torsional oscillations of the CClH2 -group of the anion. A study of the proton NMR second moment as well as relaxation times T1, and T1p performed in a wide temperature range revealed an onset of the guanidinium cation reorientation around its two-fold symmetry axis. Activation parameters for this motion were determined.

  13. Nuclear Quadrupole Resonance (NQR) Method and Probe for Generating RF Magnetic Fields in Different Directions to Distinguish NQR from Acoustic Ringing Induced in a Sample

    DTIC Science & Technology

    1997-08-01

    77,719 TITLE OF THE INVENTION NUCLEAR QUADRUPOLE RESONANCE ( NQR ) METHOD AND PROBE FOR GENERATING RF MAGNETIC FIELDS IN DIFFERENT DIRECTIONS TO...DISTINGUISH NQR FROM ACOUSTIC RINGING INDUCED IN A SAMPLE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a...nuclear quadrupole 15 resonance ( NQR ) method and probe for generating RF magnetic fields in different directions towards a sample. More specifically

  14. Relaxation of Lattice Inperfections as Studied by Chlorine NQR

    NASA Astrophysics Data System (ADS)

    Hashimoto, Masao; Adachi, Masahiro; Mano, Koichi

    1986-02-01

    The intensities, linewidths, and frequencies of 35Cl NQR signals in 6-nitro-2,4-bis(trichlorom ethyl)-benzo[1,3]dioxine were found to vary remarkably depending on the crystallization methods and annealing. This finding was correlated to the degree of crystal disorder. For a sample obtained by slow crystallization from an ethanolic solution of the compound, the growth of the height of the NQR absorption signal due to annealing was measured as a function of the isothermal annealing time. A kinetic analysis of the growth process gave an activation energy of approx. 110 kJ/mole for the relaxation process of the imperfection dominating the NQR signals. The dimorphism of the compound and the magnitude of the activation energy suggest the presence of misoriented molecules accompanied by vacancies in the crystal lattice of the stable phase.

  15. Rapid detection of arsenic minerals using portable broadband NQR

    NASA Astrophysics Data System (ADS)

    Lehmann-Horn, J. A.; Miljak, D. G.; O'Dell, L. A.; Yong, R.; Bastow, T. J.

    2014-10-01

    The remote real-time detection of specific arsenic species would significantly benefit in minerals processing to mitigate the release of arsenic into aquatic environments and aid in selective mining. At present, there are no technologies available to detect arsenic minerals in bulk volumes outside of laboratories. Here we report on the first room-temperature broadband 75As nuclear quadrupole resonance (NQR) detection of common and abundant arsenic ores in the Earth crust using a large sample (0.78 L) volume prototype sensor. Broadband excitation aids in detection of natural minerals with low crystallinity. We briefly discuss how the proposed NQR detector could be employed in mining operations.

  16. NqrM (DUF539) Protein Is Required for Maturation of Bacterial Na+-Translocating NADH:Quinone Oxidoreductase

    PubMed Central

    Kostyrko, Vitaly A.; Bertsova, Yulia V.; Serebryakova, Marina V.; Baykov, Alexander A.

    2015-01-01

    ABSTRACT Na+-translocating NADH:quinone oxidoreductase (Na+-NQR) catalyzes electron transfer from NADH to ubiquinone in the bacterial respiratory chain, coupled with Na+ translocation across the membrane. Na+-NQR maturation involves covalent attachment of flavin mononucleotide (FMN) residues, catalyzed by flavin transferase encoded by the nqr-associated apbE gene. Analysis of complete bacterial genomes has revealed another putative gene (duf539, here renamed nqrM) that usually follows the apbE gene and is present only in Na+-NQR-containing bacteria. Expression of the Vibrio harveyi nqr operon alone or with the associated apbE gene in Escherichia coli, which lacks its own Na+-NQR, resulted in an enzyme incapable of Na+-dependent NADH or reduced nicotinamide hypoxanthine dinucleotide (dNADH) oxidation. However, fully functional Na+-NQR was restored when these genes were coexpressed with the V. harveyi nqrM gene. Furthermore, nqrM lesions in Klebsiella pneumoniae and V. harveyi prevented production of functional Na+-NQR, which could be recovered by an nqrM-containing plasmid. The Na+-NQR complex isolated from the nqrM-deficient strain of V. harveyi lacks several subunits, indicating that nqrM is necessary for Na+-NQR assembly. The protein product of the nqrM gene, NqrM, contains a single putative transmembrane α-helix and four conserved Cys residues. Mutating one of these residues (Cys33 in V. harveyi NqrM) to Ser completely prevented Na+-NQR maturation, whereas mutating any other Cys residue only decreased the yield of the mature protein. These findings identify NqrM as the second specific maturation factor of Na+-NQR in proteobacteria, which is presumably involved in the delivery of Fe to form the (Cys)4[Fe] center between subunits NqrD and NqrE. IMPORTANCE Na+-translocating NADH:quinone oxidoreductase complex (Na+-NQR) is a unique primary Na+ pump believed to enhance the vitality of many bacteria, including important pathogens such as Vibrio cholerae, Vibrio

  17. Influence of different organic fertilizers on quality parameters and the delta(15)N, delta(13)C, delta(2)H, delta(34)S, and delta(18)O values of orange fruit (Citrus sinensis L. Osbeck).

    PubMed

    Rapisarda, Paolo; Camin, Federica; Fabroni, Simona; Perini, Matteo; Torrisi, Biagio; Intrigliolo, Francesco

    2010-03-24

    To investigate the influence of different types of fertilizers on quality parameters, N-containing compounds, and the delta(15)N, delta(13)C, delta(2)H, delta (34)S, and delta(18)O values of citrus fruit, a study was performed on the orange fruit cv. 'Valencia late' (Citrus sinensis L. Osbeck), which was harvested in four plots (three organic and one conventional) located on the same farm. The results demonstrated that different types of organic fertilizers containing the same amount of nitrogen did not effect important changes in orange fruit quality parameters. The levels of total N and N-containing compounds such as synephrine in fruit juice were not statistically different among the different treatments. The delta(15)N values of orange fruit grown under fertilizer derived from animal origin as well as from vegetable compost were statistically higher than those grown with mineral fertilizer. Therefore, delta(15)N values can be used as an indicator of citrus fertilization management (organic or conventional), because even when applied organic fertilizers are of different origins, the natural abundance of (15)N in organic citrus fruit remains higher than in conventional ones. These treatments also did not effect differences in the delta(13)C, delta(2)H, delta(34)S, and delta(18)O values of fruit.

  18. 35Cl NQR study of geometric isotope effect in hydrogen bonded chlorooctanes

    NASA Astrophysics Data System (ADS)

    Zdanowska-Fraçzek, M.

    1994-05-01

    35Cl NQR spectroscopy was applied to study the geometric isotope effect in a wide range of 2 : 1 salts of chloroacetic, trichloroacetic and difluorochloroacetic acids. The NQR results were correlated with IR spectroscopic studies, which provided information on the potential shape for proton motion. The NQR results were discussed on the basis of a variational correlated ground state wave function theory of a single hydrogen bond.

  19. The single NqrB and NqrC subunits in the Na(+)-translocating NADH: quinone oxidoreductase (Na(+)-NQR) from Vibrio cholerae each carry one covalently attached FMN.

    PubMed

    Casutt, Marco S; Schlosser, Andreas; Buckel, Wolfgang; Steuber, Julia

    2012-10-01

    The Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) is the prototype of a novel class of flavoproteins carrying a riboflavin phosphate bound to serine or threonine by a phosphodiester bond to the ribityl side chain. This membrane-bound, respiratory complex also contains one non-covalently bound FAD, one non-covalently bound riboflavin, ubiquinone-8 and a [2Fe-2S] cluster. Here, we report the quantitative analysis of the full set of flavin cofactors in the Na(+)-NQR and characterize the mode of linkage of the riboflavin phosphate to the membrane-bound NqrB and NqrC subunits. Release of the flavin by β-elimination and analysis of the cofactor demonstrates that the phosphate group is attached at the 5'-position of the ribityl as in authentic FMN and that the Na(+)-NQR contains approximately 1.7mol covalently bound FMN per mol non-covalently bound FAD. Therefore, each of the single NqrB and NqrC subunits in the Na(+)-NQR carries a single FMN. Elimination of the phosphodiester bond yields a dehydro-2-aminobutyrate residue, which is modified with β-mercaptoethanol by Michael addition. Proteolytic digestion followed by mass determination of peptide fragments reveals exclusive modification of threonine residues, which carry FMN in the native enzyme. The described reactions allow quantification and localization of the covalently attached FMNs in the Na(+)-NQR and in related proteins belonging to the Rhodobacter nitrogen fixation (RNF) family of enzymes. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).

  20. NMR and NQR study of the thermodynamically stable quasicrystals

    SciTech Connect

    Shastri, A.

    1995-02-10

    {sup 27}Al and {sup 61,65}Cu NMR measurements are reported for powder samples of stable AlCuFe and AlCuRu icosahedral quasicrystals and their crystalline approximants, and for a AlPdMn single grain quasicrystal. Furthermore, {sup 27}Al NQR spectra at 4.2 K have been observed in the AlCuFe and AlCuRu samples. From the quadrupole perturbed NMR spectra at different magnetic fields, and from the zero field NQR spectra, a wide distribution of local electric field gradient (EFG) tensor components and principal axis system orientations was found at the Al site. A model EFG calculation based on a 1/1 AlCuFe approximant was successful in explaining the observed NQR spectra. It is concluded that the average local gradient is largely determined by the p-electron wave function at the Al site, while the width of the distribution is due to the lattice contribution to the EFG. Comparison of {sup 63}Cu NMR with {sup 27}Al NMR shows that the EFG distribution at the two sites is similar, but that the electronic contribution to the EFG is considerably smaller at the Cu site, in agreement with a more s-type wave function of the conduction electrons.

  1. SQUID detected NMR and NQR. Superconducting Quantum Interference Device.

    PubMed

    Augustine, M P; TonThat, D M; Clarke, J

    1998-03-01

    The dc Superconducting QUantum Interference Device (SQUID) is a sensitive detector of magnetic flux, with a typical flux noise of the order 1 muphi0 Hz(-1/2) at liquid helium temperatures. Here phi0 = h/2e is the flux quantum. In our NMR or NQR spectrometer, a niobium wire coil wrapped around the sample is coupled to a thin film superconducting coil deposited on the SQUID to form a flux transformer. With this untuned input circuit the SQUID measures the flux, rather than the rate of change of flux, and thus retains its high sensitivity down to arbitrarily low frequencies. This feature is exploited in a cw spectrometer that monitors the change in the static magnetization of a sample induced by radio frequency irradiation. Examples of this technique are the detection of NQR in 27Al in sapphire and 11B in boron nitride, and a level crossing technique to enhance the signal of 14N in peptides. Research is now focused on a SQUID-based spectrometer for pulsed NQR and NMR, which has a bandwidth of 0-5 MHz. This spectrometer is used with spin-echo techniques to measure the NQR longitudinal and transverse relaxation times of 14N in NH4ClO4, 63+/-6 ms and 22+/-2 ms, respectively. With the aid of two-frequency pulses to excite the 359 kHz and 714 kHz resonances in ruby simultaneously, it is possible to obtain a two-dimensional NQR spectrum. As a third example, the pulsed spectrometer is used to study NMR spectrum of 129Xe after polariza-tion with optically pumped Rb. The NMR line can be detected at frequencies as low as 200 Hz. At fields below about 2 mT the longitudinal relaxation time saturates at about 2000 s. Two recent experiments in other laboratories have extended these pulsed NMR techniques to higher temperatures and smaller samples. In the first, images were obtained of mineral oil floating on water at room temperature. In the second, a SQUID configured as a thin film gradiometer was used to detect NMR in a 50 microm particle of 195Pt at 6 mT and 4.2 K.

  2. Polymorphism and disorder in natural active ingredients. Low and high-temperature phases of anhydrous caffeine: Spectroscopic ((1)H-(14)N NMR-NQR/(14)N NQR) and solid-state computational modelling (DFT/QTAIM/RDS) study.

    PubMed

    Seliger, Janez; Žagar, Veselko; Apih, Tomaž; Gregorovič, Alan; Latosińska, Magdalena; Olejniczak, Grzegorz Andrzej; Latosińska, Jolanta Natalia

    2016-03-31

    The polymorphism of anhydrous caffeine (1,3,7-trimethylxanthine; 1,3,7-trimethyl-1H-purine-2,6-(3H,7H)-dione) has been studied by (1)H-(14)N NMR-NQR (Nuclear Magnetic Resonance-Nuclear Quadrupole Resonance) double resonance and pure (14)N NQR (Nuclear Quadrupole Resonance) followed by computational modelling (Density Functional Theory, supplemented Quantum Theory of Atoms in Molecules with Reduced Density Gradient) in solid state. For two stable (phase II, form β) and metastable (phase I, form α) polymorphs the complete NQR spectra consisting of 12 lines were recorded. The assignment of signals detected in experiment to particular nitrogen sites was verified with the help of DFT. The shifts of the NQR frequencies, quadrupole coupling constants and asymmetry parameters at each nitrogen site due to polymorphic transition were evaluated. The strongest shifts were observed at N(3) site, while the smallest at N(9) site. The commercial pharmaceutical sample was found to contain approximately 20-25% of phase I and 75-80% of phase II. The orientational disorder in phase II with a local molecular arrangement mimics that in phase I. Substantial differences in the intermolecular interaction phases I and II of caffeine were analysed using computational (DFT/QTAIM/RDS) approach. The analysis of local environment of each nitrogen nucleus permitted drawing some conclusions on the topology of interactions in both polymorphs. For the most stable orientations in phase I and phase II the maps of the principal component qz of EFG tensor and its asymmetry parameter at each point of the molecular system were calculated and visualized. The relevant maps calculated for both phases I and II indicates small variation in electrostatic potential upon phase change. Small differences between packings in phases slightly disturb the neighbourhood of the N(1) and N(7) nitrogens, thus are meaningless from the biological point of view. The composition of two phases in pharmaceutical material

  3. Studies of the electronic structure and biological activity of chosen 1,4-benzodiazepines by 35Cl NQR spectroscopy and DFT calculations

    NASA Astrophysics Data System (ADS)

    Bronisz, K.; Ostafin, M.; Poleshchuk, O. Kh.; Mielcarek, J.; Nogaj, B.

    2006-11-01

    Selected derivatives of 1,4-benzodiazepine: lorazepam, lormetazepam, oxazepam and temazepam, used as active substances in anxiolytic drugs, have been studied by 35Cl NQR method in order to find the correlation between electronic structure and biological activity. The 35Cl NQR resonance frequencies ( νQ) measured at 77 K have been correlated with the following parameters characterising their biological activity: biological half-life period ( t0.5), affinity to benzodiazepine receptor (IC 50) and mean dose equivalent. The results of experimental study of some benzodiazepine derivatives by nuclear quadrupole resonance of 35Cl nuclei are compared with theoretical results based on DFT calculations which were carried out by means of Gaussian'98 W software.

  4. Multispectrum measurements of spectral line parameters including temperature dependences of N2- and self-broadened half-width coefficients in the region of the v9 band of 12C2H6

    SciTech Connect

    Malathy Devi, V.; Benner, D. C.; Rinsland, C.P.; Smith, M.A.H.; Sams, Robert L.; Blake, Thomas A.; Flaud, Jean Marie; Sung, Keeyoon; Brown, L.R.; Mantz, A. W.

    2010-11-01

    Ethane is a prominent contributor to the spectrum of Titan, particularly in the region of the v9 band at 12μm. A multispectrum nonlinear least squares fitting program was applied to laboratory spectra of ethane to measure accurate positions, absolute intensities, N2- and selfbroadened half- width coefficients and their temperature dependences for a large number transitions. These measurements include several pQ and rQ sub-bands (and other sub-bands such as pP, rR) in the v9 fundamental band of 12C2H6 centered near 822 cm-1. Positions were measured for 2958 transitions and intensities for 3771 transitions. N2- and self-broadened half-width coefficients were determined for over 1700 transitions while temperature dependence exponents were retrieved for over 1350 of those transitions. Of these, many measurements (mostly line positions and intensities) belong to the v9+v4-v4 hot band, v9+2v4-2v4 hot band, 13C12CH6 v9 band and unidentified transitions. Forty-three high resolution (0.0016-0.005 cm-1) infrared laboratory absorption spectra recorded at temperatures between 148 and 298 K were fitted simultaneously to retrieve these parameters. Forty-one of these spectra were obtained in the temperature range of 211-298 K using the Bruker IFS 120HR interferometer located at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington. Two additional spectra at 148 K were recorded using a new temperature stabilized cryogenic cell designed to work inside the sample compartment of the high resolution Bruker IFS 125HR interferometer of the Jet Propulsion Laboratory (JPL) in Pasadena California. The specialized cooling cell developed at Connecticut College and capable of achieving gas sample temperatures down to 70 K with a temperature stability and uniformity of better than ±0.05 K was employed to record the 148 K spectra. Constraints to intensity ratios, doublet separations, half-width coefficients and their temperature dependence exponents were required to

  5. 35Cl NQR study of lattice dynamic and magnetic property of a crystalline coordination polymer {CuCA(phz)(H 2O) 2} n

    NASA Astrophysics Data System (ADS)

    Gotoh, Kazuma; Terao, Takeshi; Asaji, Tetsuo

    2007-01-01

    Copper(II) compounds {CuCA(phz)(H 2O) 2} n (H 2CA = chloranilic acid, phz = phenazine) having a layer structure of -CuCA(H 2O) 2- polymer chains and phenazine were studied by 35Cl nuclear quadrupole resonance (NQR). The single NQR line observed at 35.635 MHz at 261.5 K increased to 35.918 MHz at 4.2 K. The degree of reduction of electric field gradient due to lattice vibrations was similar to that of chloranilic acid crystal. Temperature dependence of spin-lattice relaxation time, T1, of the 35Cl NQR signal below 20 K, between 20 and 210 K, and above 210 K, was explained by (1) a decrease of effective electron-spin density caused by antiferromagnetic interaction, (2) a magnetic interaction between Cl nuclear-spin and electron-spins on paramagnetic Cu(II) ions, and (3) an increasing contribution from reorientation of ligand molecules, respectively. The electron spin-exchange parameter ∣ J∣ between the neighboring Cu(II) electrons was estimated to be 0.33 cm -1 from the T1 value of the range 20-210 K. Comparing this value with that of J = -1.84 cm -1 estimated from the magnetic susceptibility, it is suggested that the magnetic dipolar coupling with the electron spins on Cu(II) ions must be the principal mechanism for the 35Cl NQR spin-lattice relaxation of {CuCA(phz)(H 2O) 2} n but a delocalization of electron spin over the chloranilate ligand has to be taken into account.

  6. Increasing 14N NQR signal by 1H-14N level crossing with small magnetic fields.

    PubMed

    Thurber, Kent R; Sauer, Karen L; Buess, Michael L; Klug, Christopher A; Miller, Joel B

    2005-11-01

    NQR detection of materials, such as TNT, is hindered by the low signal-to-noise ratio at low NQR frequencies. Sweeping small (0-26 mT) magnetic fields to shift the (1)H NMR frequency relative to the (14)N NQR frequencies can provide a significant increase of the (14)N NQR signal-to-noise ratio. Three effects of (1)H-(14)N level crossing are demonstrated in diglycine hydrochloride and TNT. These effects are (1) transferring (1)H polarization to one or more of the (14)N transitions, including the use of an adiabatic flip of the (1)H polarization during the field sweep, (2) shortening the effective (14)N T(1) by the interaction of (1)H with the (14)N transitions, (3) "level transfer" effect where the third (14)N (spin 1) energy level or other (14)N sites with different NQR frequency are used as a reservoir of polarization which is transferred to the measured (14)N transition by the (1)H. The (14)N NQR signal-to-noise ratio can be increased by a factor of 2.5 for one (14)N site in diglycine hydrochloride (and 2.2 in TNT), even though the maximum (1)H frequency used in this work, 111 6 kHz, is only 30% larger than the measured (14)N frequencies (834 kHz for diglycine hydrochloride and 843 kHz for TNT).

  7. An analytical method for estimating the {sup 14}N nuclear quadrupole resonance parameters of organic compounds with complex free induction decays for radiation effects studies

    SciTech Connect

    Iselin, L.H.

    1992-12-31

    The use of {sup 14}N nuclear quadrupole resonance (NQR) as a radiation dosimetry tool has only recently been explored. An analytical method for analyzing {sup 14}N NQR complex free induction decays is presented with the background necessary to conduct pulsed NQR experiments. The {sup 14}N NQR energy levels and possible transitions are derived in step-by-step detail. The components of a pulsed NQR spectrometer are discussed along with the experimental techniques for conducting radiation effects experiments using the spectrometer. Three data analysis techniques -- the power spectral density Fourier transform, state space singular value decomposition (HSVD), and nonlinear curve fitting (using the downhill simplex method of global optimization and the Levenberg-Marquart method) -- are explained. These three techniques are integrated into an analytical method which uses these numerical techniques in this order to determine the physical NQR parameters. Sample data sets of urea and guanidine sulfate data are used to demonstrate how these methods can be employed to analyze both simple and complex free induction decays. By determining baseline values for biologically significant organics, radiation effects on the NQR parameters can be studied to provide a link between current radiation dosimetry techniques and the biological effects of radiation.

  8. Dependence of nuclear quadrupole resonance transitions on the electric field gradient asymmetry parameter for nuclides with half-integer spins

    SciTech Connect

    Cho, Herman

    2016-02-28

    Allowed transition energies and eigenstate expansions have been calculated and tabulated in numerical form as functions of the electric field gradient asymmetry parameter for the zero field Hamiltonian of quadrupolar nuclides with I = 3/2,5/2,7/2, and 9/2. These results are essential to interpret nuclear quadrupole resonance (NQR) spectra and extract accurate values of the electric field gradient tensors. Furthermore, applications of NQR methods to studies of electronic structure in heavy element systems are proposed.

  9. Dependence of nuclear quadrupole resonance transitions on the electric field gradient asymmetry parameter for nuclides with half-integer spins

    NASA Astrophysics Data System (ADS)

    Cho, Herman

    2016-09-01

    Allowed transition energies and eigenstate expansions have been calculated and tabulated in numerical form as functions of the electric field gradient asymmetry parameter for the zero field Hamiltonian of quadrupolar nuclides with I = 3 / 2 , 5 / 2 , 7 / 2, and 9 / 2. These results are essential to interpret nuclear quadrupole resonance (NQR) spectra and extract accurate values of the electric field gradient tensors. Applications of NQR methods to studies of electronic structure in heavy element systems are proposed.

  10. NMR and NQR study of Si-doped (6,0) zigzag single-walled aluminum nitride nanotube as n or P-semiconductors.

    PubMed

    Baei, Mohammad T; Peyghan, Ali Ahmadi; Tavakoli, Khadijeh; Babaheydari, Ali Kazemi; Moghimi, Masoumeh

    2012-09-01

    Density functional theory (DFT) calculations were performed to investigate the electronic structure properties of pristine and Si-doped aluminum nitride nanotubes as n or P-semiconductors at the B3LYP/6-31G* level of theory in order to evaluate the influence of Si-doped in the (6,0) zigzag AlNNTs. We extended the DFT calculation to predict the electronic structure properties of Si-doped aluminum nitride nanotubes, which are very important for production of solid-state devices and other applications. To this aim, pristine and Si-doped AlNNT structures in two models (Si(N) and Si(Al)) were optimized, and then the electronic properties, the isotropic (CS(I)) and anisotropic (CS(A)) chemical shielding parameters for the sites of various (27)Al and (14)N atoms, NQR parameters for the sites of various of (27)Al and (14)N atoms, and quantum molecular descriptors were calculated in the optimized structures. The optimized structures, the electronic properties, NMR and NQR parameters, and quantum molecular descriptors for the Si(N) and Si(Al) models show that the Si(N) model is a more reactive material than the pristine or Si(Al) model.

  11. Electronic effects in alkyl 4-chlorophenyl sulfone and sulfoxide molecules according to Cl 35 NQR data

    SciTech Connect

    Feshin, V.P.; Voronkov, M.G.; Dolgushin, G.V.; Romanenko, L.S.; Aliev, I.A.; Mirzoeva, M.A.

    1986-11-20

    Compounds of the 4-ClC/sub 6/H/sub 4/S(O)CH/sub n/ x (CH/sub 3/)/sub 3-n/ and 4-ClC/sub 6/H/sub 4/SO/sub 2/R series (R = (CH/sub 2/)/sub n/H and CH/sub n/(CH/sub 3/)/sub 3-n/) were synthesized and studied by the /sup 35/Cl NQR method. It was found that their NQR frequencies change regularly with increase in the number n.

  12. Local angular momentum-local impact parameter analysis: derivation and properties of the fundamental identity, with applications to the F+H2, H+D2, and Cl+HCl chemical reactions.

    PubMed

    Monks, P D D; Xiahou, Chengkui; Connor, J N L

    2006-10-07

    The technique of local angular momentum-local impact parameter (LAM-LIP) analysis has recently been shown to provide valuable dynamical information on the angular scattering of chemical reactions under semiclassical conditions. The LAM-LIP technique exploits a nearside-farside (NF) decomposition of the scattering amplitude, which is assumed to be a Legendre partial wave series. In this paper, we derive the "fundamental NF LAM identity," which relates the full LAM to the NF LAMs (there is a similar identity for the LIP case). Two derivations are presented. The first uses complex variable techniques, while the second exploits an analogy between the motion of the scattering amplitude in the Argand plane with changing angle and the classical mechanical motion of a particle in a plane with changing time. Alternative forms of the fundamental LAM-LIP identity are described, one of which gives rise to a CLAM-CLIP plot, where CLAM denotes (Cross section) x LAM and CLIP denotes (Cross section) x LIP. Applications of the NF LAM theory, together with CLAM plots, are reported for state-to-state transitions of the benchmark reactions F+H2-->FH+H, H+D2-->HD+D, and Cl+HCl-->ClH+Cl, using as input both numerical and parametrized scattering matrix elements. We use the fundamental LAM identity to explain the important empirical observation that a NF cross section analysis and a NF LAM analysis provide consistent (and complementary) information on the dynamics of chemical reactions.

  13. Cu-NQR study for stripe ordering in La-based cuprate

    NASA Astrophysics Data System (ADS)

    Matsumura, M.; Sawa, T.; Tamura, T.; Yamamoto, N.; Sera, M.; Yamagata, H.

    2003-05-01

    Cu-NQR spectra were measured in La 2- x- yM ySr xCuO 4, (M=Nd, Gd, Eu, Pr and Y), and La 2- xBa xCuO 4 with x= {1}/{8}. The low temperature tetragonal (LTT) structure is stabilized below Td2 in all the samples other than M=Pr. The usual NQR spectra observed in T> Td2 in all the samples change to abnormally broad ones after a complete wipeout of NQR signal below Td2 except for the cases of M=Nd, Gd and Pr. In the cases of M=Nd and Gd, the complete wipeout continues to 1.5 K probably due to the extrinsic nuclear relaxation path through the paramagnetic fluctuation of Nd and Gd moment. In the case of M=Pr with no LTT phase, usual NQR spectrum continues to 1.5 K. These results support a pinning model for the static stripe ordering in the LTT phase.

  14. Chlorine Substituted Acetic Acids and Salts. Effect of Salification on Chlorine-35 NQR

    NASA Astrophysics Data System (ADS)

    David, Serge; Gourdji, Michel; Guibé, Lucien; Péneau, Alain

    1996-06-01

    The NQR of a quadrupolar probe nucleus is often used to investigate the effect of substituent in molecules. The inductive effect, based on a partial charge migration along the molecular skeleton is the only one present in saturated aliphatics, the conjugative effect appearing in conjugated molecules, especially aromatics. As the stepwise charge migration mechanism, formerly used to explain the inductive effect, is now believed obsolete, we have wanted to reexamined the case of chlorine substituted acetic acids and salts. The data in literature was extended by observing reso-nances and determining NQR frequencies in several acids and salts. The present analysis of the salification of mono-, di-and tri-chloroacetic acids, which is equivalent to a deprotonation or the substitution of the acid hydrogen by a negative unit charge, shows that a model based on the polarization of the chlorine atom(s) by the carboxyle group is consistent with experimental results: the polarization energy appears to be proportional to the NQR frequency shifts; experimental data show a correlation between the NQR frequency shifts accompanying salification and the variations of the intrinsic acidity measured in the gas phase; this, in turn shows that there is a proportionality between the polarization energy and the variations in the acid free enthalpy of dissociation. From the comparison between fluorine, chlorine, bromine and iodine, it also appears that an alternative mechanism, the polarization of the carboxyl group by the halogen, would be important only in the case of the fluoroacetic acid.

  15. 35Cl NQR and Crystal Structure Studies of Salts of Chlorodifluoro- and Dichloroacetic Acid

    NASA Astrophysics Data System (ADS)

    Basaran, Reha; Dou, Shi-qi; Weiss, Alarich

    1992-02-01

    The 35Cl NQR spectra of several chlorodifluoroacetates were studied as a function of temperature, including the acid ClF2CCOOH. The cations were: Ammonium, guanidinium, paramethylanilinium. Also some acid salts M⊕ClF2CCOO⊖ • n - ClF2CCOOH ( n > l ) were studied by 35Cl NQR. The bleaching temperatures of the NQR signals were determined. In the para-methylanilinium salt and in the guanidinium salt a phase transition has been observed. The crystal structure of guanidinium chlorodifluoroacetate has been determined at room temperature (a = 1089 pm, 6 = 845 pm, c = 832 pm, space group Pnma, Z = 4). For comparison, guanidinium dichloroacetate was studied by 35Cl NQR and by X-ray diffraction, too: P21/c, Z = 4 , a = 804pm, b = 1202 pm, c = 1080 pm, ß = 131.58°. For guanidinium chlorodifluoroacetate and chlorodifluoroacetic acid, the 35Cl spin lattice relaxation time T1 and the line width have been followed up as a function of temperature. Therefrom, the activation energies of the reorientation motion of the group -CF2C1 have been determined to be 14 kJ • mol-1 (from T1) and 12.5 kJ • mol- 1 (from Δv) for the pure acid and 9.2 kJ • mol-1 and 8.8 kJ • mol-1 , respectively, for the guanidinium salt.

  16. Unconventional superconductivity near quantum critical point revealed by Co-NQR measurements on Nax(H3O)CoO2·yH2O

    NASA Astrophysics Data System (ADS)

    Ihara, Y.; Takeya, H.; Ishida, K.; Michioka, C.; Yoshimura, K.; Takada, K.; Sasaki, T.; Sakurai, H.; Takayama-Muromachi, E.

    2007-11-01

    The nuclear quadrupole resonance (NQR) frequency of Co nuclei and the nuclear spin lattice relaxation rate 1/T1 were measured on several bilayered hydrate (BLH) Nax(H3O)CoO2·yH2O (y˜1.3) with variety of superconducting (SC) and magnetic transition temperatures, Tc and TM, together with non-SC mono-layered hydrate (MLH) Nax(H3O)CoO2·yH2O (y˜0.7). In the high temperature region above 70 K, 1/T1T in all the samples follows the same temperature dependence which is interpreted as the pseudogap behavior. In the BLH compounds, 1/T1T increases with decreasing temperature below 70 K, and the values of 1/T1T at Tc are large in high-Tc samples. The magnetic ordering is ascertained from the observation of the prominent divergence of 1/T1T at TM in the samples whose NQR frequency is higher than 12.5 MHz. The temperature dependence of 1/T1T is found to be consistently expressed by a unique function with two fitting parameters. We analyze the temperature dependence of 1/T1T on the basis of this function, and investigate the relationship between the magnetic fluctuations and superconductivity in the BLH compounds.

  17. Methyl quantum tunneling and nitrogen-14 NQR NMR studies using a SQUID magnetic resonance spectrometer

    SciTech Connect

    Black, B.E. |

    1993-07-01

    Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) techniques have been very successful in obtaining molecular conformation and dynamics information. Unfortunately, standard NMR and NQR spectrometers are unable to adequately detect resonances below a few megahertz due to the frequency dependent sensitivity of their Faraday coil detectors. For this reason a new spectrometer with a dc SQUID (Superconducting Quantum Interference Device) detector, which has no such frequency dependence, has been developed. Previously, this spectrometer was used to observe {sup 11}B and {sup 27}Al NQR resonances. The scope of this study was increased to include {sup 23}Na, {sup 51}V, and {sup 55}Mn NQR transitions. Also, a technique was presented to observe {sup 14}N NQR resonances through cross relaxation of the nitrogen polarization to adjacent proton spins. When the proton Zeeman splitting matches one nitrogen quadrupoler transition the remaining two {sup 14}N transitions can be detected by sweeping a saturating rf field through resonance. Additionally, simultaneous excitation of two nitrogen resonances provides signal enhancement which helps to connect transitions from the same site. In this way, nitrogen-14 resonances were observed in several amino acids and polypeptides. This spectrometer has also been useful in the direct detection of methyl quantum tunneling splittings at 4.2 K. Tunneling, frequencies of a homologous series of carboxylic acids were measured and for solids with equivalent crystal structures, an exponential correlation between the tunneling frequency and the enthalpy of fusion is observed. This correlation provides information about the contribution of intermolecular interactions to the energy barrier for methyl rotation.

  18. The Conformational Changes Induced by Ubiquinone Binding in the Na+-pumping NADH:Ubiquinone Oxidoreductase (Na+-NQR) Are Kinetically Controlled by Conserved Glycines 140 and 141 of the NqrB Subunit*

    PubMed Central

    Strickland, Madeleine; Juárez, Oscar; Neehaul, Yashvin; Cook, Darcie A.; Barquera, Blanca; Hellwig, Petra

    2014-01-01

    Na+-pumping NADH:ubiquinone oxidoreductase (Na+-NQR) is responsible for maintaining a sodium gradient across the inner bacterial membrane. This respiratory enzyme, which couples sodium pumping to the electron transfer between NADH and ubiquinone, is not present in eukaryotes and as such could be a target for antibiotics. In this paper it is shown that the site of ubiquinone reduction is conformationally coupled to the NqrB subunit, which also hosts the final cofactor in the electron transport chain, riboflavin. Previous work showed that mutations in conserved NqrB glycine residues 140 and 141 affect ubiquinone reduction and the proper functioning of the sodium pump. Surprisingly, these mutants did not affect the dissociation constant of ubiquinone or its analog HQNO (2-n-heptyl-4-hydroxyquinoline N-oxide) from Na+-NQR, which indicates that these residues do not participate directly in the ubiquinone binding site but probably control its accessibility. Indeed, redox-induced difference spectroscopy showed that these mutations prevented the conformational change involved in ubiquinone binding but did not modify the signals corresponding to bound ubiquinone. Moreover, data are presented that demonstrate the NqrA subunit is able to bind ubiquinone but with a low non-catalytically relevant affinity. It is also suggested that Na+-NQR contains a single catalytic ubiquinone binding site and a second site that can bind ubiquinone but is not active. PMID:25006248

  19. Temperature variation of ultralow frequency modes and mean square displacements in solid lasamide (diuretic drug) studied by 35Cl-NQR, X-ray and DFT/QTAIM.

    PubMed

    Latosińska, Jolanta Natalia; Latosińska, Magdalena; Kasprzak, Jerzy; Tomczak, Magdalena; Maurin, Jan Krzysztof

    2012-10-25

    The application of combined (35)Cl-NQR/X-ray/DFT/QTAIM methods to study the temperature variation of anisotropic displacement parameters and ultralow frequency modes of anharmonic torsional vibrations in the solid state is illustrated on the example of 2,4-dichloro-5-sulfamolybenzoic acid (lasamide, DSBA) which is a diuretic and an intermediate in the synthesis of furosemide and thus its common impurity. The crystallographic structure of lasamide is solved by X-ray diffraction and refined to a final R-factor of 3.06% at room temperature. Lasamide is found to crystallize in the triclinic space group P-1, with two equivalent molecules in the unit cell a = 7.5984(3) Å, b = 8.3158(3) Å, c = 8.6892(3) Å; α = 81.212(3)°, β = 73.799(3)°, γ = 67.599(3)°. Its molecules form symmetric dimers linked by two short and linear intermolecular hydrogen bonds O-H···O (O-H···O = 2.648 Å and ∠OHO = 171.5°), which are further linked by weaker and longer intermolecular hydrogen bonds N-H···O (N-H···O = 2.965 Å and ∠NHO = 166.4°). Two (35)Cl-NQR resonance frequencies, 36.899 and 37.129 MHz, revealed at room temperature are assigned to chlorine sites at the ortho and para positions, relative to the carboxyl functional group, respectively. The difference in C-Cl(1) and C-Cl(2) bond lengths only slightly affects the value of (35)Cl-NQR frequencies, which results mainly from chemical inequivalence of chlorine atoms but also involvement in different intermolecular interactions pattern. The smooth decrease in both (35)Cl-NQR frequencies with increasing temperature in the range of 77-300 K testifies to the averaging of EFG tensor at each chlorine site due to anharmonic torsional vibrations. Lasamide is thermally stable; no temperature-induced release of chlorine or decomposition of this compound is detected. The temperature dependence of ultralow frequency modes of anharmonic small-angle internal torsional vibrations averaging EFG tensor and mean square angle

  20. The interaction strengths and spectroscopy parameters of the C2H2∙∙∙HX and HCN∙∙∙HX complexes (X = F, Cl, CN, and CCH) and related ternary systems valued by fluxes of charge densities: QTAIM, CCFO, and NBO calculations.

    PubMed

    Viana, Marco A A; Araújo, Regiane C M U; Neto, José A Maia; Chame, Henrique C; Pereira, Arquimedes M; Oliveira, Boaz G

    2017-04-01

    This theoretical work exhibits a new systematic study of structural parameters, electronic properties, infrared vibration modes, and molecular topography of hydrogen complexes, namely linear-type HCN⋯HX and T-type C2H2⋯HX (X = F, Cl, CN, and CCH). Ideally, the knowledge of the ternary systems of C2H2⋯HCN⋯HF and HCN⋯HCN⋯HF whose subparts integrate the linear and T-shaped complexes were used to give support in this current research. By means of computational calculations carried out in both levels B3LYP and MP2, the variations of the HX bond lengths are clearly overestimated in the HCN⋯HX linear complexes. In agreement with the analyses of the electrostatic potentials, the higher intermolecular energies of these complexes agree with the larger red-shifts in the stretch frequencies in HX. Also, the QTAIM descriptors and NBO calculations were used to inspect the interaction strength as well as to confirm the π cloud as a proton accepting center. By taking into account the absorption intensity ratio as a standard parameter to predict the interaction strength and intermolecular characterization, the formalism of the charge-charge flux-overlap modified (CCFO) was applied.

  1. C2H observations toward the Orion Bar

    NASA Astrophysics Data System (ADS)

    Nagy, Z.; Ossenkopf, V.; Van der Tak, F. F. S.; Faure, A.; Makai, Z.; Bergin, E. A.

    2015-06-01

    Context. The ethynyl radical (C2H) is one of the first radicals to be detected in the interstellar medium. Its higher rotational transitions have recently become available with the Herschel Space Observatory. Aims: We aim to constrain the physical parameters of the C2H emitting gas toward the Orion Bar. Methods: We analyze the C2H line intensities measured toward the Orion Bar CO+ Peak and Herschel/HIFI maps of C2H, CH, and HCO+ and a NANTEN map of [Ci]. We interpret the observed C2H emission using the combination of Herschel/HIFI and NANTEN data with radiative transfer and PDR models. Results: Five rotational transitions of C2H (from N = 6-5 up to N = 10-9) have been detected in the HIFI frequency range toward the CO+ peak of the Orion Bar. Based on the five detected C2H transitions, a single component rotational diagram analysis gives a rotation temperature of ~64 K and a beam-averaged C2H column density of 4 × 1013 cm-2. The rotational diagram is also consistent with a two-component fit, resulting in rotation temperatures of 43 ± 0.2 K and 123 ± 21 K and in beam-averaged column densities of ~8.3 × 1013 cm-2 and ~2.3 × 1013 cm-2 for the three lower-N and for the three higher-N transitions, respectively. The measured five rotational transitions cannot be explained by any single parameter model. According to a non-LTE model, most of the C2H column density produces the lower-N C2H transitions and traces a warm (Tkin ~ 100-150 K) and dense (n(H2) ~ 105-106 cm-3) gas. A small fraction of the C2H column density is required to reproduce the intensity of the highest-N transitions (N = 9-8 and N = 10-9) originating in a high-density (n(H2) ~5 × 106 cm-3) hot (Tkin ~ 400 K) gas. The total beam-averaged C2H column density in the model is 1014 cm-2. A comparison of the spatial distribution of C2H to those of CH, HCO+, and [Ci] shows the best correlation with CH. Conclusions: Both the non-LTE radiative transfer model and a simple PDR model representing the Orion Bar

  2. NQR application to the study of hydrogen dynamics in hydrogen-bonded molecular dimers

    NASA Astrophysics Data System (ADS)

    Asaji, Tetsuo

    2016-12-01

    The temperature dependences of 1H NMR as well as 35Cl NQR spin-lattice relaxation times T 1 were investigated in order to study the hydrogen transfer dynamics in carboxylic acid dimers in 3,5-dichloro- and 2,6-dichlorobenzoic acids. The asymmetry energy A/ k B and the activation energy V/ k B for the hydrogen transfer were estimated to be 240 K and 900 K, and 840 K and 2500 K, respectively, for these compounds. In spite of a large asymmetric potential the quantum nature of hydrogen transfer is recognized in the slope of the temperature dependence of T 1 on the low-temperature side of the T 1 minimum. The NQR T 1 measurements was revealed to be a good probe for the hydrogen transfer dynamics.

  3. N-14 NQR using a high-Tc rf SQUID with a normal metal transformer

    NASA Astrophysics Data System (ADS)

    He, D. F.; Tachiki, M.; Itozaki, H.

    2008-01-01

    We have improved our high-Tc SQUID-based N-14 nuclear quadrupole resonance (NQR) detection system. By using a reed relay SIL5-1A72-71L (MEDER electronic) in the normal metal transformer, the isolation to the excitation field was much improved. The high-Tc rf SQUID could operate stably when the rf excitation field was over 20 mT. By optimizing the input coil of the transformer, better sensitivity of 0.5 fT Hz-1/2 was obtained at the resonant frequency of the tuned normal metal transformer. A spin-locking spin-echo (SLSE) multi-pulse sequence was also used in the system to detect the weak NQR signals produced by samples with longer spin-spin relaxation time T2, such as trinitrotoluene (TNT).

  4. Measurement of temperature and temperature gradient in millimeter samples by chlorine NQR

    NASA Astrophysics Data System (ADS)

    Lužnik, Janko; Pirnat, Janez; Trontelj, Zvonko

    2009-09-01

    A mini-thermometer based on the 35Cl nuclear quadrupole resonance (NQR) frequency temperature dependence in the chlorates KClO3 and NaClO3 was built and successfully tested by measuring temperature and temperature gradient at 77 K and higher in about 100 mm3 active volume of a mini Joule-Thomson refrigerator. In the design of the tank-circuit coil, an array of small coils connected in series enabled us (a) to achieve a suitable ratio of inductance to capacity in the NQR spectrometer input tank circuit, (b) to use a single crystal of KClO3 or NaClO3 (of 1-2 mm3 size) in one coil as a mini-thermometer with a resolution of 0.03 K and (c) to construct a system for measuring temperature gradients when the spatial coordinates of each chlorate single crystal within an individual coil are known.

  5. Pressure and temperature dependence of the chlorine NQR in caesium and sodium chlorates.

    PubMed

    Ramesh, K P; Suresh, K S; Raghavendra Rao, C; Ramakrishna, J

    2008-06-01

    The (35)Cl nuclear quadrupole resonance (NQR) frequencies (nu(Q)) in caesium and sodium chlorates were measured as a function of temperature, from 77 to 300 K at different pressures up to 5.1 kbar, and the data were analysed to estimate the volume dependence of the electric field gradient (EFG), torsional frequency and also the contributions to the NQR frequency from static and dynamic effects. The variation of spin-lattice relaxation time with pressure at different temperatures was studied in the case of sodium chlorate and at room temperature in case of caesium chlorate. The pressure dependence of the spin-lattice relaxation time (T(1)) suggests that the relaxation is mainly due to the torsional motions.

  6. Quadrupole interactions: NMR, NQR, and in between from a single viewpoint.

    PubMed

    Bain, Alex D

    2017-03-01

    Nuclear spins with quantum numbers >1/2 can interact with a static magnetic field, or a local electric field gradient, to produce quantized energy levels. If the magnetic field interaction dominates, we are doing nuclear magnetic resonance (NMR). If the interaction of the nuclear electric quadrupole with electric field gradients is much stronger, this is nuclear quadrupole resonance (NQR). The two are extremes of a continuum, as the ratio of one interaction to the other changes. In this work, we look at this continuum from a single, unified viewpoint based on a Liouville-space approach: the direct method. This method does not require explicit operators and their commutators, unlike Hamiltonian methods. We derive both the quadrupole-perturbed NMR solution and also the Zeeman-perturbed NQR results. Furthermore, we examine the polarization of these signals, because this is different between pure NMR and pure NQR spectroscopy. Spin 3/2 is the focus here, but the approach is perfectly general and can be applied to any spin. Copyright © 2016 John Wiley & Sons, Ltd.

  7. Strong pH dependence of coupling efficiency of the Na+ - translocating NADH:quinone oxidoreductase (Na+-NQR) of Vibrio cholerae.

    PubMed

    Toulouse, Charlotte; Claussen, Björn; Muras, Valentin; Fritz, Günter; Steuber, Julia

    2017-02-01

    The Na+-translocating NADH:quinone oxidoreductase (NQR) is the entry site for electrons into the respiratory chain of Vibrio cholerae, the causative agent of cholera disease. NQR couples the electron transfer from NADH to ubiquinone to the translocation of sodium ions across the membrane. We investigated the pH dependence of electron transfer and generation of a transmembrane voltage (ΔΨ) by NQR reconstituted in liposomes with Na+ or Li+ as coupling cation. ΔΨ formation was followed with the voltage-sensitive dye oxonol. With Na+, ΔΨ was barely influenced by pH (6.5-8.5), while Q reduction activity exhibited a maximum at pH 7.5-8.0. With Li+, ΔΨ was generally lower, and the pH profile of electron transfer activity did not reveal a pronounced maximum. We conclude that the coupling efficiency of NQR is influenced by the nature of the transported cation, and by the concentration of protons. The 3D structure of NQR reveals a transmembrane channel in subunit NqrB. It is proposed that partial uncoupling of the NQR observed with the smaller Li+, or with Na+ at pH 7.5-8.0, is caused by the backflow of the coupling cation through the channel in NqrB.

  8. Effect of the oxygen protonation on the electronic structure of urea in the solid state: A 14N NQR study

    NASA Astrophysics Data System (ADS)

    Murgich, Juan; Santana R., Magaly

    1981-04-01

    The 14N NQR frequencies of urea complexes with H2O2 (1:1), NH4Cl (1:1), oxalic (2:1), phosphoric (1:1), and nitric acid (1:1) at 77 °K are reported. The analysis of the NQR data indicates that the population of the N nonbonding orbital decreases and that the population of the s N-H and N-C bonds increases as the degree of protonation of the O atom of urea increases. These changes are consistent with a larger weight of structures like C = N+H2 as the protonation increases. The NQR results are in agreement with those obtained from a CNDO/2 calculation for the uronioum ion [Yu. A. Panteleev and A. A. Lipovskii, Zhu. Struk. Khim. 17, 2 (1976)].

  9. THz spectroscopy of D2H+

    NASA Astrophysics Data System (ADS)

    Yu, S.; Pearson, J. C.; Amano, T.; Matsushima, F.

    2017-01-01

    We extended the measurements of the rotational transitions of D2H+ up to 3 THz by using the JPL frequency multiplier chains and a TuFIR system at Toyama. D2H+ was generated in an extended negative glow discharge cell cooled to liquid nitrogen temperature. We observed five new THz lines. All the available rotational transition frequencies together with the combination differences derived from the three fundamental bands were subject to least square analysis to determine the molecular constants. New THz measurements are definitely useful for better characterization of spectroscopic properties. The improved molecular constants provide better predictions of other unobserved rotational transitions.

  10. Inhibition of the sodium-translocating NADH-ubiquinone oxidoreductase [Na+-NQR] decreases cholera toxin production in Vibrio cholerae O1 at the late exponential growth phase.

    PubMed

    Minato, Yusuke; Fassio, Sara R; Reddekopp, Rylan L; Häse, Claudia C

    2014-01-01

    Two virulence factors produced by Vibrio cholerae, cholera toxin (CT) and toxin-corregulated pilus (TCP), are indispensable for cholera infection. ToxT is the central regulatory protein involved in activation of CT and TCP expression. We previously reported that lack of a respiration-linked sodium-translocating NADH-ubiquinone oxidoreductase (Na(+)-NQR) significantly increases toxT transcription. In this study, we further characterized this link and found that Na(+)-NQR affects toxT expression only at the early-log growth phase, whereas lack of Na(+)-NQR decreases CT production after the mid-log growth phase. Such decreased CT production was independent of toxT and ctxB transcription. Supplementing a respiratory substrate, l-lactate, into the growth media restored CT production in the nqrA-F mutant, suggesting that decreased CT production in the Na(+)-NQR mutant is dependent on electron transport chain (ETC) activity. This notion was supported by the observations that two chemical inhibitors, a Na(+)-NQR specific inhibitor 2-n-Heptyl-4-hydroxyquinoline N-oxide (HQNO) and a succinate dehydrogenase (SDH) inhibitor, thenoyltrifluoroacetone (TTFA), strongly inhibited CT production in both classical and El Tor biotype strains of V. cholerae. Accordingly, we propose the main respiratory enzyme of V. cholerae, as a potential drug target to treat cholera because human mitochondria do not contain Na(+)-NQR orthologs.

  11. 35CI NQR Spectroscopy on Salts and Molecular Compounds of Trichloroacetic Acid

    NASA Astrophysics Data System (ADS)

    Fichtner, Winfried; Markworth, Axel; Weiden, Norbert; Weiss, Alarich

    1986-02-01

    The temperature dependence of salts M(1)H(Cl3CCOO)2 and molecular compounds of trichloroacetic acid with amines and benzaldehydes, TCA · X, was studied, The data fit rather well to the known dependence of the mean frequency shift Δ on the pkadifference of X with respect to TCA. A linear relation is observed between the bleaching out temperature Tb of the 35Cl NQR lines and Δ for M(1)H(Cl3CCOO)2 and for TCA · X, X = benzaldehydes.

  12. Dependence of nuclear quadrupole resonance transitions on the electric field gradient asymmetry parameter for nuclides with half-integer spins

    SciTech Connect

    Cho, Herman

    2016-09-01

    Allowed transition energies and eigenstate expansions have been calculated and tabulated in numerical form as functions of the electric field gradient asymmetry parameter for the zero field Hamiltonian of quadrupolar nuclides with I = 3/2, 5/2, 7/2, and 9/2. These results may be used to interpret nuclear quadrupole resonance (NQR) spectra and extract accurate values of the electric field gradient tensors. Applications of NQR methods to studies of electronic structure in heavy element systems are proposed. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences, Heavy Element Chemistry program.

  13. Search for the isomers of C2H3NO and C2H3NS in the Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Etim, Emmanuel; Chakrabarti, Sandip Kumar; Das, Ankan; Gorai, Prasanta; Arunan, Elangannan

    2016-07-01

    With about 40% of all the known interstellar and circumstellar molecules having their isomeric analogues as known astromolecules, isomerism remains one of the leading themes in interstellar chemistry. In this regard, the recent detection of methyl isocyanate (with a number of isomeric analogues) in the Sgr B2(N) giant molecular cloud opens a new window for the possible astronomical detection of other C_2H_3NO isomers. The present work looks at the possibility of detecting other isomers of methyl isocyanate by considering different factors such as thermodynamic stability of the different isomers with respect to the Energy, Stability and Abundance (ESA) relationship, effect of interstellar hydrogen bonding with respect to the formation these isomers on the surface of the interstellar dust grains, possible formation routes for these isomers, spectroscopic parameters for potential astromolecules among these isomers, chemical modeling among other studies. The same studies are repeated for the C_2H_3NS isomers which are the isoelectroninc analogues of the C_2H_3NO isomers taking into account the unique chemistry of S and O-containing interstellar molecular species. Among the C_2H_3NS isomers, methyl isothiocyanate remains the most potential candidate for astronomical observation.

  14. Measurement of in-situ stress in salt and rock using NQR techniques

    SciTech Connect

    Schempp, E.; Hirschfeld, T.; Klainer, S.

    1980-12-01

    A discussion of how stress and strain affect the quantities which can be measured in an NQR experiment shows that, for stresses of the magnitude to be expected at depths up to about 10,000 feet, quadrupole coupling constants will fall in the range of 1 to 10 kHz for both the sodium and chloride ions in NaCl. The most promising system involves pulsed nuclear double resonance detection; and alterative is to observe the quadrupolar splitting of the NMR signal. Choices to be made in the measurement and mapping techniques are discussed. The well-known perturbation of the homogenous stress field in the neighborhood of a borehole is shown to be advantageous from the point of view of obtaining directional information on the stress. Construction and operation of a borehole stress sensor are considered. The NQR technique seems feasible for measuring the magnitude and direction of underground stress with a resolution of about 25 psi, or 2.5% at 1000 psi. Downhole instrumentation suitable for in-situ determinations of stress appears within the state of the art. Additional tasks required on the project are identified.

  15. Synthesis Of [2h, 13c] And [2h3, 13c]Methyl Aryl Sulfides

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.

    2004-03-30

    The present invention is directed to labeled compounds, [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfides wherein the .sup.13 C methyl group attached to the sulfur of the sulfide includes exactly one, two or three deuterium atoms and the aryl group is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, and R.sub.5 are each independently, hydrogen, a C.sub.1 -C.sub.4 lower alkyl, a halogen, an amino group from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each a C.sub.1 -C.sub.4 lower alkyl, a phenyl, or an alkoxy group. The present invention is also directed to processes of preparing [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2,.sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfides wherein the .sup.13 C methyl group attached to the sulfur of the sulfide includes exactly one, two or three deuterium atoms. The present invention is also directed to the labeled compounds of [.sup.2 H.sub.1, .sup.13 C]methyl iodide and [.sup.2 H.sub.2, .sup.13 C]methyl iodide.

  16. An electronically tuned wideband probehead for NQR spectroscopy in the VHF range

    NASA Astrophysics Data System (ADS)

    Scharfetter, Hermann

    2016-10-01

    Nuclear quadrupole resonance spectroscopy is an analytical method which allows to characterize materials which contain quadrupolar nuclei, i.e. nuclei with spin ⩾1. The measurement technology is similar to that of NMR except that no static magnetic field is necessary. In contrast to NMR, however, it is frequently necessary to scan spectra with a very large bandwidth with a span of several tens of % of the central frequency so as to localize unknown peaks. Standard NMR probeheads which are typically constructed as resonators must be tuned and matched to comparatively narrow bands and must thus be re-tuned and re-matched very frequently when scanning over a whole NQR spectrum. At low frequencies up to few MHz dedicated circuits without the need for tuning and matching have been developed, but many quadrupole nuclei have transitions in the VHF range between several tens of MHz up to several hundreds of MHz. Currently available commercial NQR probeheads employ stepper motors for setting mechanically tuneable capacitors in standard NMR resonators. These yield high quality factors (Q) and thus high SNR but are relatively large and clumsy and do not allow for fast frequency sweeps. This article presents a new concept for a NQR probehead which combines a previously published no-tune no-match wideband concept for the transmit (TX) pulse with an electronically tuneable receive (RX) part employing varactor diodes. The prototype coil provides a TX frequency range of 57 MHz with a center frequency of 97.5 MHz with a return loss of ⩽-15 dB. During RX the resonator is tuned and matched automatically to the right frequency via control voltages which are read out from a previously generated lookup table, thus providing high SNR. The control voltages which bias the varactors settle very fast and allow for hopping to the next frequency point in the spectrum within less than 100 μs. Experiments with a test sample of ZnBr2 proved the feasibility of the method.

  17. Zero-field NMR and NQR studies of magnetically ordered state in charge-ordered EuPtP

    NASA Astrophysics Data System (ADS)

    Koyama, T.; Maruyama, T.; Ueda, K.; Mito, T.; Mitsuda, A.; Umeda, M.; Sugishima, M.; Wada, H.

    2015-03-01

    EuPtP undergoes two valence transitions and has two kinds of valence states of Eu ions at low temperatures. In the charge-ordered state, this compound shows an antiferromagnetic order ascribed to magnetic divalent Eu ions. We investigated the antiferromagnetically ordered state of EuPtP by nuclear magnetic resonance (NMR) measurement and nuclear quadrupole resonance (NQR) measurement in a zero external magnetic field. The observed 153Eu NMR signals of a magnetic divalent state and Eu,153151 NQR signals of a nonmagnetic trivalent state clearly demonstrate that the spins order in the hexagonal basal plane and the internal magnetic field is not canceled out, even at the Eu3 + layers which are in the middle of magnetic Eu2 + layers. In addition, the observation of 31P and 195Pt NMR spectra allowed us to discuss a possible magnetic structure. We also evaluated the nuclear quadrupole frequencies for both Eu2 + and Eu3 + ion states.

  18. Structural and Functional Investigation of Flavin Binding Center of the NqrC Subunit of Sodium-Translocating NADH:Quinone Oxidoreductase from Vibrio harveyi

    PubMed Central

    Bertsova, Yulia; Polovinkin, Vitaly; Gushchin, Ivan; Ishchenko, Andrii; Kovalev, Kirill; Mishin, Alexey; Kachalova, Galina; Popov, Alexander; Bogachev, Alexander; Gordeliy, Valentin

    2015-01-01

    Na+-translocating NADH:quinone oxidoreductase (NQR) is a redox-driven sodium pump operating in the respiratory chain of various bacteria, including pathogenic species. The enzyme has a unique set of redox active prosthetic groups, which includes two covalently bound flavin mononucleotide (FMN) residues attached to threonine residues in subunits NqrB and NqrC. The reason of FMN covalent bonding in the subunits has not been established yet. In the current work, binding of free FMN to the apo-form of NqrC from Vibrio harveyi was studied showing very low affinity of NqrC to FMN in the absence of its covalent bonding. To study structural aspects of flavin binding in NqrC, its holo-form was crystallized and its 3D structure was solved at 1.56 Å resolution. It was found that the isoalloxazine moiety of the FMN residue is buried in a hydrophobic cavity and that its pyrimidine ring is squeezed between hydrophobic amino acid residues while its benzene ring is extended from the protein surroundings. This structure of the flavin-binding pocket appears to provide flexibility of the benzene ring, which can help the FMN residue to take the bended conformation and thus to stabilize the one-electron reduced form of the prosthetic group. These properties may also lead to relatively weak noncovalent binding of the flavin. This fact along with periplasmic location of the FMN-binding domains in the vast majority of NqrC-like proteins may explain the necessity of the covalent bonding of this prosthetic group to prevent its loss to the external medium. PMID:25734798

  19. Investigation of Some New Nonlinear Optical Crystals by Means of NQR, IR and X-Ray Diffraction Methods

    NASA Astrophysics Data System (ADS)

    Petrosyan, A. M.; Terzyan, S. S.; Burbelo, V. M.; Sukiasyan, R. P.

    1998-07-01

    Some new analogues of the nonlinear optical crystal L-arginine phosphate monohydrate (LAP) (Arg • HIO3 , Arg • 2HIO3 , Lys • HIO3 , Lys • 2HIO3 , Lys • 3HIO3 , Bet • 3HIO3) were obtained and investigated by means of IR, NQR, X-ray diffraction and SHG methods. The importance of this class of crystals for revealing new nonlinear optical crystals is pointed out.

  20. Determination of Transformation Coefficients of the C2H4 Molecule

    NASA Astrophysics Data System (ADS)

    Fomchenko, A. L.; Belova, A. S.; Berezkin, K. B.; Ziatkova, A. G.

    2016-11-01

    The object of theoretical research is the C 2 H 4 molecule, as it is important to know its properties to address numerous problems of molecular physics. The "expanded" local mode approach developed earlier was used for a X2Y4 molecule. This approach makes it possible to obtain simple expressions for the transformation coefficients of the investigated molecule, which subsequently allows one to determine various spectroscopic parameters of the C 2 H 4 molecule in a simple form.

  1. One dimensional 1H, 2H and 3H

    NASA Astrophysics Data System (ADS)

    Vidal, A. J.; Astrakharchik, G. E.; Vranješ Markić, L.; Boronat, J.

    2016-05-01

    The ground-state properties of one-dimensional electron-spin-polarized hydrogen 1H, deuterium 2H, and tritium 3H are obtained by means of quantum Monte Carlo methods. The equations of state of the three isotopes are calculated for a wide range of linear densities. The pair correlation function and the static structure factor are obtained and interpreted within the framework of the Luttinger liquid theory. We report the density dependence of the Luttinger parameter and use it to identify different physical regimes: Bogoliubov Bose gas, super-Tonks-Girardeau gas, and quasi-crystal regimes for bosons; repulsive, attractive Fermi gas, and quasi-crystal regimes for fermions. We find that the tritium isotope is the one with the richest behavior. Our results show unambiguously the relevant role of the isotope mass in the properties of this quantum system.

  2. Kinetics of the hydrogen abstraction C2H3* + alkane --> C2H4 + alkyl radical reaction class.

    PubMed

    Muszyńska, Marta; Ratkiewicz, Artur; Huynh, Lam K; Truong, Thanh N

    2009-07-23

    This paper presents an application of the reaction class transition state theory (RC-TST) to predict thermal rate constants for hydrogen abstraction reactions of the type C(2)H(3) + alkane --> C(2)H(4) + alkyl radical. The linear energy relationship (LER) was proven to hold for both noncyclic and cyclic hydrocarbons. We have derived all parameters for the RC-TST method from rate constants of 19 representative reactions, coupling with LER and the barrier height grouping (BHG) approach. Both the RC-TST/LER, where only reaction energy is needed, and the RC-TST/BHG, where no other information is needed, can predict rate constants for any reaction in this reaction class with satisfactory accuracy for combustion modeling. Our analysis indicates that less than 90% systematic errors on the average exist in the predicted rate constants using the RC-TST/LER or RC-TST/BHG method, while in comparison to explicit rate calculations, the differences are within a factor of 2 on the average.

  3. Association reactions at low pressure. III. The C2H2+/C2H2 system.

    PubMed

    Anicich, V G; Sen, A D; Huntress, W T; McEwan, M J

    1990-11-15

    The association reactions, C4H2(+) + C2H2 and C4H3(+) + C2H2 have been examined at pressures between 8 x 10(-8) and 1 x 10(-4) Torr at 298 K in an ion cyclotron resonance mass spectrometer. Association occurred via two different mechanisms. At pressures below approximately 2 x 10(-6) Torr, the association was bimolecular having rate coefficients k2 = 2.7 x 10(-10) cm3 s-1 and 2.0 x 10(-10) cm3 s-1 for C4H2+ and C4H3+, respectively. At pressures above approximately 2 x 10(-6) Torr, termolecular association was observed with rate coefficients, k3 = 5.7 x 10(-23) cm6 s-1 and 1.3 x 10(-23) cm6 s-1 for C4H2+ and C4H3+, respectively, when M = C2H2. The termolecular rate constants with N2, Ar, Ne, and He as the third body, M, are also reported. We propose that the low pressure bimolecular association process was the result of radiative stabilization of the complex and the termolecular association process was the result of collisional stabilization. Elementary rate coefficients were obtained and the lifetime of the collision complex was > or = 57 microseconds for (C6H4+)* and > or = 18 microseconds for (C6H5+)*. At pressures below 1 x 10(-6) Torr, approximately 11% of the (C6H4+)* were stabilized by photon emission and the remaining approximately 89% reverted back to reactants, while approximately 24% of the (C6H5+)* were stabilized by photon emission and the remaining approximately 76% reverted back to reactants. The ionic products of the C2H2(+) + C2H2 reaction, C4H2+ and C4H3+, were found to be formed with enough internal energy that they did not react by the radiative association channel until relaxed by several nonreactive collisions with the bath gas.

  4. Robustness of N2H+ as tracer of the CO snowline

    NASA Astrophysics Data System (ADS)

    van't Hoff, M. L. R.; Walsh, C.; Kama, M.; Facchini, S.; van Dishoeck, E. F.

    2017-03-01

    assumed: for the investigated parameters, the N2H+ column density peaks at least 5 AU outside the CO snowline. Moreover, the N2H+ emission can peak much further out, as far as 50 AU beyond the snowline. Hence, chemical modeling, as performed here, is necessary to derive a CO snowline location from N2H+ observations.

  5. Reactions of Fe+ and FeO+ with C2H2, C2H4, and C2H6: temperature-dependent kinetics.

    PubMed

    Ard, Shaun G; Melko, Joshua J; Fournier, Joseph A; Shuman, Nicholas S; Viggiano, Albert A

    2013-10-10

    We present the first temperature-dependent rate constants and branching ratios for the reactions of Fe(+) and FeO(+) with C2H2, C2H4, and C2H6 from 170 to 700 K. Fe(+) is observed to react only by association with the three hydrocarbons, with temperature dependencies of T(-2) to T(-3). FeO(+) reacts with C2H2 and C2H4 at the collision rate over the temperature range, and their respective product branchings show similar temperature dependences. In contrast, the reaction with ethane is collisional at 170 K but varies as T(-0.5), while the product branching remains essentially flat with temperature. These variations in reactivity are discussed in terms of the published reactive potential surfaces. The effectiveness of Fe(+) as an oxygen-transfer catalyst toward the three hydrocarbons is also discussed.

  6. Rate constant for the reaction C2H5 + HBr → C2H6 + Br.

    PubMed

    Golden, David M; Peng, Jingping; Goumri, A; Yuan, J; Marshall, Paul

    2012-06-21

    RRKM theory has been employed to analyze the kinetics of the title reaction, in particular, the once-controversial negative activation energy. Stationary points along the reaction coordinate were characterized with coupled cluster theory combined with basis set extrapolation to the complete basis set limit. A shallow minimum, bound by 9.7 kJ mol(-1) relative to C(2)H(5) + HBr, was located, with a very small energy barrier to dissociation to Br + C(2)H(6). The transition state is tight compared to the adduct. The influence of vibrational anharmonicity on the kinetics and thermochemistry of the title reaction were explored quantitatively. With adjustment of the adduct binding energy by ∼4 kJ mol(-1), the computed rate constants may be brought into agreement with most experimental data in the literature, including new room-temperature results described here. There are indications that at temperatures above those studied experimentally, the activation energy may switch from negative to positive.

  7. Rate Coefficients of C2H with C2H4, C2H6, and H2 from 150 to 359 K

    NASA Technical Reports Server (NTRS)

    Opansky, Brian J.; Leone, Stephen R.

    1996-01-01

    Rate coefficients for the reactions C2H with C2H4, C2H6, and H2 are measured over the temperature range 150-359 K using transient infrared laser absorption spectroscopy. The ethynyl radical is formed by photolysis of C2H2 with a pulsed excimer laser at 193 nm, and its transient absorption is monitored with a color center laser on the Q(sub 11)(9) line of the A(sup 2) Pi-Chi(sup 2) Sigma transition at 3593.68 cm(exp -1). Over the experimental temperature range 150-359 K the rate constants of C2H with C2H4, C2H6, and H2 can be fitted to the Arrhenius expressions k(sub C2H4) = (7.8 +/- 0.6) x 10(exp -11) exp[(134 +/- 44)/T], k(sub C2H6) = (3.5 +/- 0.3) x 10(exp -11) exp[(2.9 +/- 16)/T], and k(sub H2) = (1.2 +/- 0.3) x 10(exp -11) exp[(-998 +/- 57)]/T cm(exp 3) molecule(exp -1) sec(exp -1). The data for C2H with C2H4 and C2H6 indicate a negligible activation energy to product formation shown by the mild negative temperature dependence of both reactions. When the H2 data are plotted together with the most recent high-temperature results from 295 to 854 K, a slight curvature is observed. The H2 data can be fit to the non-Arrhenius form k(sub H2) = 9.2 x 10(exp -18) T(sup 2.17 +/- 0.50) exp[(-478 +/- 165)/T] cm(exp 3) molecules(exp -1) sec(exp -1). The curvature in the Arrhenius plot is discussed in terms of both quantum mechanical tunneling of the H atom from H2 to the C2H radical and bending mode contributions to the partition function.

  8. Synthesis of 2-Alkenyl-2H-indazoles from 2-(2-Carbonylmethyl)-2H-indazoles.

    PubMed

    Lin, Mei-Huey; Liang, Kung-Yu; Tsai, Chang-Hsien; Chen, Yu-Chun; Hsiao, Hung-Chang; Li, Yi-Syuan; Chen, Chung-Hao; Wu, Hau-Chun

    2016-02-19

    A procedure has been developed for synthesis of 2-alkenyl-2H-indazoles starting from 2-(2-carbonylmethyl)-2H-indazoles, which are prepared by gallium/aluminium- and aluminium-mediated, direct, regioselective alkylation of indazoles with α-bromocarbonyl compounds. The structure of 3-(2H-indazol-2-yl)-2H-chromen-2-one was proven by X-ray crystallography. The styrene- and coumarin-2H-indazoles produced by using the new method were found to have interesting fluorescence properties.

  9. Quantitation of methadone enantiomers in humans using stable isotope-labeled (2H3)-, (2H5)-, and (2H8)Methadone

    SciTech Connect

    Nakamura, K.; Hachey, D.L.; Kreek, M.J.; Irving, C.S.; Klein, P.D.

    1982-01-01

    A new technique for simultaneous stereoselective kinetic studies of methadone enantiomers was developed using three deuterium-labeled forms of methadone and GLC-chemical-ionization mass spectrometry. A racemic mixture (1:1) of (R)-(-)-(2H5)methadone (l-form) and (S)-(R)-(2H3)methadone (d-form) was administered orally in place of a single daily dose of unlabeled (+/-)-(2H0)methadone in long-term maintenance patients. Racemic (+/-)-(2H8)methadone was used as an internal standard for the simultaneous quantitation of (2H0)-, (2H3)-, and (2H5)methadone in plasma and urine. A newly developed extraction procedure, using a short, disposable C18 reversed-phase cartridge and improved chemical-ionization procedures employing ammonia gas, resulted in significant reduction of the background impurities contributing to the ions used for isotopic abundance measurements. These improvements enabled the measurement of labeled plasma methadone levels for 120 hr following a single dose. This methodology was applied to the study of methadone kinetics in two patients; in both patients, the analgesically active l-enantiomer of the drug had a longer plasma elimination half-life and a smaller area under the plasma disappearance curve than did the inactive d-form.

  10. 35Cl-NQR and DFT study of electronic structure of amlodipine and felodipine vascular-selective drugs from the dihydropyridine Ca ++ antagonists group

    NASA Astrophysics Data System (ADS)

    Latosińska, J. N.; Latosińska, M.; Kasprzak, J.

    2008-09-01

    Amlodipine (AM) and felodipine (FL) have been studied in solid state by the nuclear quadrupole resonance (NQR) and density functional theory (DFT). The results have shown that NQR data do not permit a differentiation between R and S enantiomers, which is a consequence of the symmetry of the 4-aryl ring, whereas they permit a differentiation between free bases and salts. The HOMO-LUMO gap is smaller for AM than for FL, which suggests smaller energy of excitation for AM. The absolute hardness, chemical potential and electrophilicity of both AM enantiomers are lower than the corresponding values for FL enantiomers, suggesting that AM should be more reactive than FL in unimolecular reactions.

  11. Synthesis Of [2h, 13c]M [2h2m 13c], And [2h3,, 13c] Methyl Aryl Sulfones And Sulfoxides

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.; Schmidt, Jurgen G.

    2004-07-20

    The present invention is directed to labeled compounds, [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfones and [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfoxides, wherein the .sup.13 C methyl group attached to the sulfur of the sulfone or sulfoxide includes exactly one, two or three deuterium atoms and the aryl group is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently, hydrogen, a C.sub.1 -C.sub.4 lower alkyl, a halogen, an amino group from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each a C.sub.1 -C.sub.4 lower alkyl, a phenyl, or an alkoxy group. The present invention is also directed to processes of preparing methyl aryl sulfones and methyl aryl sulfoxides.

  12. TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OL)

    Atmospheric Science Data Center

    2016-10-25

    TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OL) News:  TES News ... Level:  L2 Platform:  TES/Aura L2 Water Vapor Spatial Coverage:  27 x 23 km Limb ... Access: OPeNDAP Parameters:  H2O Water Volume Mixing Radio Precision Vertical Resolution Order ...

  13. Synthesis and properties of 3-nitro-2H-chromenes

    NASA Astrophysics Data System (ADS)

    Korotaev, V. Yu; Sosnovskikh, V. Ya; Barkov, A. Yu

    2013-12-01

    Methods of synthesis and chemical properties of 3-nitro-2H-chromenes, including reactions with nucleophiles, cycloaddition, oxidation and reduction, have been reviewed. Enantioselective reactions involving 3-nitro-2H-chromenes, as well as the stereochemistry of the products, are discussed. The ways of practical use of these compounds are shown. The bibliography includes 115 references.

  14. Variations of δ2H in an idealised extratropical cyclone

    NASA Astrophysics Data System (ADS)

    Dütsch, Marina; Pfahl, Stephan; Wernli, Heini

    2016-04-01

    Numerical model simulations of stable water isotopes help to improve our understanding of the complex processes driving isotopic variability in atmospheric waters. We use the isotope-enabled COSMO model to study the governing mechanisms of δ2H variations in an idealised extratropical cyclone. A set of experiments with differing initial conditions of δ2H in vapour and partially deactivated isotopic fractionation allows us to quantify the relative roles of cloud fractionation and vertical and horizontal advection for the simulated δ2H signals associated with the cyclone and fronts. Horizontal transport determines the large-scale pattern of δ2H in both vapour and precipitation, while fractionation and vertical transport are more important on a smaller scale, near the fronts. During the passage of the cold front fractionation leads to a V-shaped trend of δ2H in precipitation and vapour, which is, for vapour, superimposed on a gradual decrease caused by horizontal advection.

  15. QUEST-QUadrupolar Exact SofTware: a fast graphical program for the exact simulation of NMR and NQR spectra for quadrupolar nuclei.

    PubMed

    Perras, Frédéric A; Widdifield, Cory M; Bryce, David L

    2012-01-01

    We present a new program for the exact simulation of solid-state NMR spectra of quadrupolar nuclei in stationary powdered samples which employs diagonalization of the combined Zeeman-quadrupolar Hamiltonian. The program, which we call QUEST (QUadrupolar Exact SofTware), can simulate NMR spectra over the full regime of Larmor and quadrupolar frequency ratios, which encompasses scenarios ranging from high-field NMR to nuclear quadrupole resonance (NQR, where the Larmor frequency is zero) and does not make use of approximations when treating the quadrupolar interaction. With the use of the fast powder averaging scheme of Alderman, Solum, and Grant, exact NMR spectral simulations are only marginally slower than the second-order perturbation theory counterpart. The program, which uses a graphical user interface, also incorporates chemical shift anisotropy and non-coincident chemical shift and quadrupolar tensor frames. The program is validated against newly-acquired experimental data through several examples including: the low-field (79/81)Br NMR spectra of CaBr(2), the (14)N overtone NMR spectrum of glycine, the (187)Re NQR spectra of Re(2)(CO)(10), and lastly the (127)I overtone NQR spectrum of SrI(2), which, to the best of our knowledge, represents the first direct acquisition of an overtone NQR spectrum for a powdered sample.

  16. 35Cl NQR spectra of phosphorus chlorides and their molecular conformations in crystals. Part 1. Phosphorus (III) chlorides RPCl 2

    NASA Astrophysics Data System (ADS)

    Kozlov, E. S.; Kapustin, E. G.; Soifer, G. B.

    2000-09-01

    For the phosphorus chlorides RPCl 2 (R=Cl, Me, ClCH 2, CF 3, Et, i-Pr, Me 2C=CH, PhCH=CH, Me 2N, Et 2N, Pr 2N, MeO, PhO) and R'PCl 2 (R'=Ar, 2-thienyl) two linear correlations between the 35Cl NQR frequencies and charges on the chlorine atoms of the PCl 2 groups calculated by the MNDO procedure have been found. It was shown that the 35Cl NQR spectra and the relative magnitudes of the charges on the chlorine atoms of the PCl 2 groups can be used to determine conformation of the RPCl 2 molecules in crystal. Ab initio (RHF/6-31 G ∗ and MP2/6-31 G ∗) calculations showed that the gauche conformation of Me 2NPCl 2 molecule is more stable than trans conformation. In light of ab initio calculations electron diffraction results (Vilkov L.V., Khaikin L.S., Dokl. Akad. Nauk SSSR, 168 (1966) 810) are erroneous. The NBO analysis confirmed the presence of donor-acceptor interactions between the lone pair orbital of the nitrogen atom and the antibonding orbitals of the P-Cl bonds.

  17. 14N NQR Studies of Impurity Effects on the Local Structure of NaNO2 -based Mixed Systems

    NASA Astrophysics Data System (ADS)

    Song, S. K.; Park, Y. M.; Jung, J. K.; Seo, Y. M.; Choh, S. H.

    2000-02-01

    The influence of impurities on the 14N NQR lineshape of Na1-xAgxNO2 and [NaNO2]1-x-[BNO3]x (B = Na, K) at room temperature has been investigated. Carrying out spectral analysis in conjunction with classification of the local field inhomogeneities according to the structurally isomorphic, Na1-xAgxNO2 , and anisomorphic [NaNO2]1-x[BNO3]x systems, enabled an under-standing of the microscopic nature of impurity-induced local disorder. The iso-and anisomorphic systems reveal their own unique features of the impurity induced local disorder. They are charac-terized by a static, random distribution of impurities in the isomorphic system and a fast motion of the impurity-induced mobile point defects in the anisomorphic system. However, for both systems, neither a change of the 14N NQR frequency nor a multisplitting of the lines is observed because of the relatively low symmetry.

  18. Chemical structure and intra-molecular effects on NMR-NQR tensors of harmine and harmaline alkaloids

    NASA Astrophysics Data System (ADS)

    Ahmadinejad, Neda; Tahan, Arezoo; Talebi Tari, Mostafa

    2016-02-01

    Density functional theory (DFT) methods were used to analyze the effects of molecular structure and ring currents on the NMR chemical shielding tensors and NQR frequencies of harmine and harmaline alkaloids in the gas phase. The results demonstrated that NMR tensors and NQR frequencies of 15N nuclei in these compounds depend on chemical environment and resonance interactions. Hence, their values are obviously different in the mentioned structures. The interpretation of natural bond orbital (NBO) data suggests that in harmine structure, the lone pair participation of N9 in π-system electron clouds causes to development of aromaticity nature in pyrrole ring. However, the chemical shielding around N9 atom in harmine structure is higher than in harmaline, while in harmaline structure, lone pair participation of N2 in π-system electron clouds causes to development of aromaticity nature in pyridine ring. Hence, chemical shielding around N2 atom in harmaline structure is higher than in harmine. It can be deduced that by increasing lone pair electrons contribution of nitrogen atoms in ring resonance interactions and aromaticity development, the values of NMR chemical shielding around them increase, while χ and q zz values of these nuclei decrease.

  19. 35Cl NQR and Structural Studies of Chloroacetanilides C6H3Cl2NHCOCH3-xClx, 1 ≤ x ≤ 3

    NASA Astrophysics Data System (ADS)

    Groke, Dirk; Dou, Shi-Qi; Weiss, Alarich

    1992-02-01

    The temperature dependence of 35Cl NQR frequencies and the phase transition behaviour of chloroacetanilides (N-[2,6-dichlorophenyl]-2-chloroacetamide, -2,2-dichloroacetamide, -2,2,2-trichloroacetamide) were investigated. The crystal structure determination of N-[2,6-dichlorophenyl]- 2-chloroacetamide leads to the following: a = 1893.8 pm, b = 1110.7 pm, c = 472.1 pm, space group P212121 = D24 with Z = 4 molecules per unit cell. The arrangement of the molecules and their geometry is comparable to the high temperature phase of the acetyl compound N-[2,6-dichlorophenyl]- acetamide. For N-[2,6-diclorophenyl]-2,2,2-trichloroacetamide it was found: a = 1016.6 pm, b = 1194.3 pm, c = 1006.7 pm, ß= 101.79°, space group P21/c = C52h, Z = 4. The structure is similar to the low temperature phase of N-[2,6-dichlorophenyl]-acetamide. Parallelism between the temperature dependence of the 35C1 NQR lines of the CCl3 group and the X-ray diffraction results concerning the different behaviour of the chlorine atoms was observed. The structures of the compounds show intermolecular hydrogen bonding of the N - H • • • O - C type. The phenyl group and the HNCO function are nearly planar. A bleaching out of several 35Cl NQR lines at a temperature far below the melting point of the substances was observed. The different types of chlorine atoms (aromatic, chloromethyl) can be distinguished by their temperature coefficients of the 35Cl NQR frequencies. All the resonances found show normal "Bayer" temperature behaviour. N-[2,6-dichlorophenyl]-2,2-diehloroacetamide shows several solid phases. One stable low temperature phase and an instable high temperature phase (at room temperature) were observed. The different phases were detected by means of 35Cl NQR spectroscopy and thermal analysis

  20. Temperature and pressure dependent rate coefficients for the reaction of C2H4 + HO2 on the C2H4O2H potential energy surface.

    PubMed

    Guo, JunJiang; Xu, JiaQi; Li, ZeRong; Tan, NingXin; Li, XiangYuan

    2015-04-02

    The potential energy surface (PES) for reaction C2H4 + HO2 was examined by using the quantum chemical methods. All rates were determined computationally using the CBS-QB3 composite method combined with conventional transition state theory(TST), variational transition-state theory (VTST) and Rice-Ramsberger-Kassel-Marcus/master-equation (RRKM/ME) theory. The geometries optimization and the vibrational frequency analysis of reactants, transition states, and products were performed at the B3LYP/CBSB7 level. The composite CBS-QB3 method was applied for energy calculations. The major product channel of reaction C2H4 + HO2 is the formation C2H4O2H via an OH(···)π complex with 3.7 kcal/mol binding energy which exhibits negative-temperature dependence. We further investigated the reactions related to this complex, which were ignored in previous studies. Thermochemical properties of the species involved in the reactions were determined using the CBS-QB3 method, and enthalpies of formation of species were compared with literature values. The calculated rate constants are in good agreement with those available from literature and given in modified Arrhenius equation form, which are serviceable in combustion modeling of hydrocarbons. Finally, in order to illustrate the effect for low-temperature ignition of our new rate constants, we have implemented them into the existing mechanisms, which can predict ethylene ignition in a shock tube with better performance.

  1. Theoretical study of the bonding of Nb(2+) to CH2, C2H2, and C2H4

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Partridge, Harry

    1991-01-01

    The bonding of Nb(2+) with CH2, C2H2, and C2H4 is studied by using electronic structure calculations that include high levels of electron correlation. The binding energy for NbCH2(2+) is in good agreement with the lower bound determined from the reaction with CH4 but is significantly smaller than the value determined from the binding energy and ionization potential of NbCH2(+). The calculations and a new interpretation of the experiment indicate that the larger value is in error primarily because the ionization potential of NbCH2(+) determined from bracketing charge-exchange reactions is too small. The computed binding energy of NbC2H2(2+) is in good agreement with experiment. The calculations show that the bonding is predominantly covalent in character for both NbCH2(2+) and NbC2H2(2+), whereas for NbC2H4(2+) the electronic states that are predominantly ionic and covalent are nearly degenerate. The trend in binding energies, CH2 greater than C2H2 greater than C2H4, is consistent with the energy required to prepare the ligands for bonding.

  2. Efficient C2 functionalisation of 2H-2-imidazolines.

    PubMed

    Bon, Robin S; Sprenkels, Nanda E; Koningstein, Manoe M; Schmitz, Rob F; de Kanter, Frans J J; Dömling, Alexander; Groen, Marinus B; Orru, Romano V A

    2008-01-07

    Alkylation and oxidation of 2H-2-imidazolines, followed by regioselective deprotection, thionation and microwave-assisted Liebeskind-Srogl reaction, efficiently led to 2-aryl-2-imidazolines as new analogues of p53-hdm2 interaction inhibitors (Nutlins).

  3. Crystal Structures and 35Cl NQR Spectra of the Metastable and the Stable Phase of Guanidinium bis-Monochloroacetate, [C(NH2)3 ]⊕[(ClH2C)COOH ••• OOC(CH2Cl)l⊖

    NASA Astrophysics Data System (ADS)

    Basaran, Reha; Dou, Shi-qi; Weiss, Alarich

    1993-03-01

    From acid aqueous solutions of guanidinium carbonate and monochloroacetic acid, (ClH2C)COOH :H2 NC( = NH)NH2 ≧ 2.5, the compound [C(NH2)3]⊕ [(ClH2C)COOH • • • OOC(CH2Cl)]⊖ crystallizes with the space group Ci1P1¯,Z = 4, a = 1147.4 (5) pm, b= 1113.2 (5) pm, c = 876.5 (4) pm, α = 88.66 (2)°, β = 80.31 (2)°, γ = 84.41 (2)° (metastable phase I). Cooled to 77 K once, phase I transforms at room temperature slowly into the stable phase II, orthorhombic, D2h15 - Pbca, Z = 8, a= 1299.2 (4) pm, b= 1533.7 (4) pm, c= 1073.9 (3) pm. The crystal structure determinations show for both phases an ionic lattice with guanidinium cations [C(NH2)3]⊕ and acid bis-(monochloroacetate) anions [(ClH2C)COOH • • • OOC(CH2Cl)]⊖ in which a monochloroacetic acid molecule and a monochloroacetate ion are bound to the dimer anion by an asymmetric hydrogen bond O-H • • • O. A strong crystal field effect, much dependent on temperature, is observed in the 35Cl NQR quadruplet spectrum of phase I, with a frequency spread of ≈4 MHz at 300 K, whereas in phase II the frequency splitting of the observed 35Cl NQR doublet is almost constant between 77 K and 310 K, about 700 kHz. The phase transition I → II is very sluggish and unidirectional. The transition II → I needs the recrystallization of II from water. Structure and dynamics of the two solid phases are discussed.

  4. Calculation of the solubility diagrams in the system Ca(OH) 2-H 3PO 4-KOH-HNO 3-CO 2-H 2O

    NASA Astrophysics Data System (ADS)

    Vereecke, Guy; Lemaître, Jacques

    1990-09-01

    A computer program has been developed for calculating the solubility isotherms of sparingly soluble calcium phosphates (including octacalcium phosphate and β-tricalcium phosphate) and calcite in the system Ca(OH) 2-H 3PO 4-KOH-HNO 3-CO 2-H 2O. It allows the influence of such parameters as temperature, pH, partial CO 2 pressure and ionic strength to be investigated. The calculation process takes into account the effects of ion-pair formation and ionic strength. Selected solubility isotherms are presented and compared to literature data. The influence of temperature, Ca/P ratio, ionic strength and CO 2 pressure on the stability isotherms of hydroxyapatite and dicalcium phosphate are discussed in detail.

  5. N 2- and O 2-broadening coefficients of C 2H 2 IR lines

    NASA Astrophysics Data System (ADS)

    Bouanich, J. P.; Lambot, D.; Blanquet, G.; Walrand, J.

    1990-04-01

    Pressure-broadening parameters of six lines belonging to the ν5 band of C 2H 2 in collision with N 2 have been measured with a tunable diode-laser spectrometer in order to complete up to J = 33 our earlier measurements (D. Lambot, G. Blanquet, and J. P. Bouanich, J. Mol. Spectrosc.136, 86-92 (1989)) on the broadening of C 2H 2 by N 2 and O 2 at 297 K. These N 2- and O 2-broadening coefficients have been first calculated on the basis of the Anderson-Tsao-Curnutte theory; in this approach, we show that the short-range interactions which contribute significantly to the linewidths are not correctly treated. Next, we consider the improved semiclassical model proposed by Robert and Bonamy. The intermolecular potential consists in the addition of the atom-atom interaction model to the quadrupolar interactions. The limited radial spherical harmonics expansion of the atom-atom potential, from which expressions for the differential cross section were derived, appears to be quite insufficient at short intermolecular distances. Therefore, we use a more accurate representation of this potential, avoiding an inadequate truncation and keeping the analytic expressions obtained by Bonamy and Robert. In the calculations we take into account the contributions derived from the radial functions U000( r), U200( r), and U220( r), as well as from U400( r). A theoretical expression is obtained for the U400 contribution to the differential cross section. The results of the calculations arising from the exact radial expansion of the atom-atom potential appear to be significantly larger for high J lines than those arising from the truncated expansion. The latter results, which do not include adjustable atom-atom parameters, are in good agreement with experimental broadening coefficients for C 2H 2O 2 and in reasonable agreement (except at large J values) for C 2H 2N 2. It is also shown that the contributions to the linewidths derived from U400 are rather small for C 2H 2N 2 and more

  6. Meridional Variations of C2H2 and C2H6 in Jupiter's Atmosphere from Cassini CIRS Infrared Spectra

    NASA Technical Reports Server (NTRS)

    Nixon, C. A.; Achterberg, R. K.; Conrath, B. J.; Irwin, P. G. J.; Fouchet, T.; Parrish, P. D.; Romani, P. N.; Abbas, M.; LeClair, A.; Strobel, D.

    2004-01-01

    Hydrocarbons such as acetylene (C2H2) and ethane (C2H6) are important tracers in Jupiter's atmosphere, constraining our models of the chemical and dynamical processes. However, our knowledge of the vertical and meridional variations of their abundances has remained sparse. During the flyby of the Cassini spacecraft in December 2000, the Composite Infrared Spectrometer (CIRS) instrument was used to map the spatial variation of emissions from 10-1400 cm(sup -1) (1000-7 microns). In this paper we analyze a zonally-averaged set of CIRS spectra taken at the highest (0.5 cm(sup -1)) resolution, to infer atmospheric temperatures in the stratosphere at 0.5-20 mbar via the v4 band of CH4, and in the troposphere at 150-400 mbar, via the H2 absorption at 600-800 cm(sup -1). Simultaneously, we retrieve the abundances of C2H2 and C2H6 via the v5 and vg bands respectively. Tropospheric absorption and stratospheric emission are highly anti-correlated at the CIRS resolution, introducing a non-uniqueness into the retrievals, such that vertical gradient and column abundance cannot both be found without additional constraints. Assuming profile gradients from photochemical calculations, we show that the column abundance of C2H2 decreases sharply towards the poles by a factor approximately 4, while C2H6 is unchanged in the north and increasing in the south, by a factor approximately 1.8. An explanation for the meridional trends is proposed in terms of a combination of photochemistry and dynamics. Poleward, the decreasing UV flux is predicted to decrease the abundances of C2H2 and C2H6 by factors 2.7 and 3.5 respectively at a latitude 70 deg. However, the lifetime of C2H6 in the stratosphere (5 x 10(exp 9)) is much longer than the dynamical timescale for meridional motions inferred from SL-9 debris (5 x 10(exp 8 s)), and therefore the constant or rising abundance towards high latitudes likely indicates that meridional mixing dominates over photochemical effects. For C2H2, the opposite

  7. TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OLS)

    Atmospheric Science Data Center

    2016-10-25

    TES/Aura L2 Water Vapor (H2O) Limb (TL2H2OLS) News:  TES News ... Level:  L2 Platform:  TES/Aura L2 Water Vapor Spatial Coverage:  27 x 23 km Limb ... Access:  OPeNDAP Parameters:  H2O Water Volume Mixing Radio Precision Vertical Resolution Order ...

  8. Phase Transitions in CsSnCl3 and CsPbBr3 An NMR and NQR Study

    NASA Astrophysics Data System (ADS)

    Sharma, Surendra; Weiden, Norbert; Weiss, Alarich

    1991-04-01

    The phase transitions in CsSnCl3 and CsPbBr3 have been studied by X-ray powder diffraction, by 81Br-NQR and by 'H-, 119Sn-, and 113Cs-NMR. At room temperature in air CsSnCl3 forms a hydrate which can be dehydrated to the monoclinic phase II of CsSnCl3. The high temperature phase I has the Perovskite structure, as the X-ray and NMR experiments show. The three phases of CsPbBr3, known from literature, have been corroborated. The results are discussed in the framework of the group ABX3, A = alkalimetal ion, B = IV main group ion, and X = Halogen ion

  9. Magnetic correlations in La(2-x)Sr(x)CuO4 from NQR relaxation and specific heat

    NASA Technical Reports Server (NTRS)

    Borsa, F.; Rigamonti, A.

    1991-01-01

    La-139 and Cu-63 Nuclear Quadrupole Resonance (NQR) relaxation measurements in La(2-x)Sr(x)CuO4 for x ranging from 0 up to 0.3, with particular emphasis on the effect of doping on the Cu(2+) magnetic correlations and dynamics, are reviewed. In the low doping limit, x less than or equal to 0.05, the results can be interpreted consistently in terms of a simple phenomenological 'two-fluids' model whereby the effect of thermally-activated mobile O(2p) holes is the one of disrupting locally the Cu(2+) spin correlations. For x greater than or equal to 0.1, the results indicate the onset, as T approaches T(sub c)(+), of a strong coupling between Cu(2+) spins and the Fermi liquid of O(2p) holes leading to the apparent disappearance of localized Cu(2+) moment in connection with the opening of a superconducting gap.

  10. Infrared spectroscopy of V2+(H2O) complexes

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, B.; Duncan, M. A.

    2012-03-01

    Doubly charged vanadium-water complexes are produced by laser vaporization in a pulsed supersonic expansion. Size-selected ions are studied with infrared photodissociation spectroscopy in the O-H stretch region using argon complex predissociation. Density functional theory calculations provide structures and vibrational spectra of these ions. The O-H stretches of V2+(H2O) appear at lower frequencies than those of the free water molecule or V+(H2O). The symmetric stretch is more intense than the asymmetric stretch in both V+(H2O) and V2+(H2O) complexes. Spectra of V2+(H2O)Arn (n = 2-7) show that the coordination of the V2+ is filled with six ligands, i.e. one water and five argon atoms.

  11. First-principles characterization of potassium intercalation in the hexagonal 2H-MoS2

    SciTech Connect

    Andersen, Amity; Kathmann, Shawn M.; Lilga, Michael A.; Albrecht, Karl O.; Hallen, Richard T.; Mei, Donghai

    2012-01-12

    Periodic density functional theory calculations were performed to study the structural and electronic properties of potassium intercalated into hexagonal MoS{sub 2} (2H-MoS{sub 2}). Metallic potassium (K) atoms are incrementally loaded in the hexagonal sites of the interstitial spaces between MoS2 sheets of the 2H-MoS{sub 2} bulk structure generating 2H-KxMoS2 (0.125 {<=} x {<=} 1.0) structures. To accommodate the potassium atoms, the interstitial spacing c parameter in the 2H-MoS{sub 2} bulk expands from 12.816 {angstrom} in 2H-MoS{sub 2} to 16.086 {angstrom} in 2H-K{sub 0.125}MoS{sub 2}. The second lowest potassium loading concentration (K{sub 0.25}MoS{sub 2}) results in the largest interstitial spacing expansion (to c = 16.726 {angstrom}). Our calculations show that there is a small gradual contraction of the interstitial spacing as the potassium loading increases with c = 14.839 {angstrom} for KMoS{sub 2}. This interstitial contraction is correlated with an in-plane expansion of the MoS{sub 2} sheets, which is in good agreement with experimental X-ray diffraction (XRD) measurements. The electronic analysis shows that potassium readily donates its 4s electron to the conduction band of the 2H-K{sub x}MoS{sub 2}, and is largely ionic in character. As a result of the electron donation, the 2H-K{sub x}MoS{sub 2} system changes from a semiconductor to a more metallic system with increasing potassium intercalation. For loadings 0.25 {<=} x {<=} 0.625, triangular Mo-Mo-Mo moieties are prominent and tend to form rhombitrihexagonal motifs. Intercalation of H{sub 2}O molecules that solvate the K atoms is likely to occur in catalytic conditions. The inclusion of two H{sub 2}O molecules per K atom in the K{sub 0.25}MoS{sub 2} structure shows good agreement with XRD measurements.

  12. 127I NQR and spectroscopic investigation of impurity-doped and mixed lithium iodate Li 1- xH xIO 3 crystals

    NASA Astrophysics Data System (ADS)

    Barabash, A.; Gavrilko, T.; Eshimov, K.; Baran, J.; Ratajczak, H.

    2004-12-01

    The 127I NQR, IR absorption and Raman spectra of impurity-doped and mixed lithium iodate Li 1- xH xIO 3 crystals grown from water solutions with different LiIO 3/HIO 3 ratios were investigated depending on the content of the impurity hydrogen x. The NQR results suggested that, at small concentration of doping iodic acid x<0.22, the lattice dynamics of the crystal grown from water solution changes significantly though the crystal retains hexagonal symmetry. Spectroscopic studies are compatible with average hexagonal symmetry of the grown doped crystals. From the results of Raman studies at room temperature and 100 K, the concentration range of hydrogen dopant 0.22< x<0.36 was found where disordered solid solution crystals Li 1- xH xIO 3 are formed.

  13. Volovik effect and Fermi-liquid behavior in the s -wave superconductor CaPd2As2: 75As NMR-NQR measurements

    NASA Astrophysics Data System (ADS)

    Ding, Q.-P.; Wiecki, P.; Anand, V. K.; Sangeetha, N. S.; Lee, Y.; Johnston, D. C.; Furukawa, Y.

    2016-04-01

    The electronic and magnetic properties of the collapsed-tetragonal CaPd2As2 superconductor (SC) with a transition temperature of 1.27 K have been investigated by 75As nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements. The temperature (T ) dependence of the nuclear spin lattice relaxation rates (1 /T1) and the Knight shifts indicate the absence of magnetic correlations in the normal state. In the SC state, 1 /T1 measured by 75As NQR shows a clear Hebel-Slichter (HS) peak just below Tc and decreases exponentially at lower T , confirming a conventional s -wave SC. In addition, the Volovik effect, also known as the Doppler shift effect, has been clearly evidenced by the observation of the suppression of the HS peak with applied magnetic field.

  14. Stability and molecular dynamics of chloroxylenol (API of antiseptics and drugs) in solid state studied by 35Cl-NQR spectroscopy and DFT calculations

    NASA Astrophysics Data System (ADS)

    Latosińska, J. N.; Tomczak, M. A.; Kasprzak, J.

    2009-02-01

    Thermal stability of 4-chloro-3,5-dimethyl-phenol (chloroxylenol) in solid state has been studied by 35Cl-NQR spectroscopy. Two NQR resonance lines at the frequencies 34.348 and 34.415 MHz at 77 K have been assigned to chlorine atoms from two crystallographically inequivalent molecules on the basis of the B3LYP/6-311++G∗∗ results. The temperature dependence of the resonance frequency and full width at half maximum suggest the occurrence of small-angle torsional oscillations of the mean activation energy of 3.83 kJ/mol and rotation of both methyl groups around their symmetry axis C3 with the activation energies 12.49 and 11.27 kJ/mol for CH3 in molecule A and B, respectively. B3LYP/6-311++G∗∗ method reproduced very well the activation energies of both motions.

  15. Volovik effect and Fermi-liquid behavior in the s-wave superconductor CaPd2As2: As75 NMR-NQR measurements

    DOE PAGES

    Ding, Q. -P.; Wiecki, P.; Anand, V. K.; ...

    2016-04-07

    The electronic and magnetic properties of the collapsed-tetragonal CaPd2As2 superconductor (SC) with a transition temperature of 1.27 K have been investigated by 75As nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements. The temperature (T) dependence of the nuclear spin lattice relaxation rates (1/T1) and the Knight shifts indicate the absence of magnetic correlations in the normal state. In the SC state, 1/T1 measured by 75As NQR shows a clear Hebel-Slichter (HS) peak just below Tc and decreases exponentially at lower T, confirming a conventional s-wave SC. Additionally, the Volovik effect, also known as the Doppler shift effect, hasmore » been clearly evidenced by the observation of the suppression of the HS peak with applied magnetic field.« less

  16. Hunting for hydrogen: random structure searching and prediction of NMR parameters of hydrous wadsleyite† †Electronic supplementary information (ESI) available: Further information on the structures generated by AIRSS, alternative structural models, supercell calculations, total enthalpies of all computed structures and further information on 1H/2H NMR parameters. Example input and all raw output files from AIRSS and CASTEP NMR calculations are also included. See DOI: 10.1039/c6cp01529h Click here for additional data file.

    PubMed Central

    Moran, Robert F.; McKay, David; Pickard, Chris J.; Berry, Andrew J.; Griffin, John M.

    2016-01-01

    The structural chemistry of materials containing low levels of nonstoichiometric hydrogen is difficult to determine, and producing structural models is challenging where hydrogen has no fixed crystallographic site. Here we demonstrate a computational approach employing ab initio random structure searching (AIRSS) to generate a series of candidate structures for hydrous wadsleyite (β-Mg2SiO4 with 1.6 wt% H2O), a high-pressure mineral proposed as a repository for water in the Earth's transition zone. Aligning with previous experimental work, we solely consider models with Mg3 (over Mg1, Mg2 or Si) vacancies. We adapt the AIRSS method by starting with anhydrous wadsleyite, removing a single Mg2+ and randomly placing two H+ in a unit cell model, generating 819 candidate structures. 103 geometries were then subjected to more accurate optimisation under periodic DFT. Using this approach, we find the most favourable hydration mechanism involves protonation of two O1 sites around the Mg3 vacancy. The formation of silanol groups on O3 or O4 sites (with loss of stable O1–H hydroxyls) coincides with an increase in total enthalpy. Importantly, the approach we employ allows observables such as NMR parameters to be computed for each structure. We consider hydrous wadsleyite (∼1.6 wt%) to be dominated by protonated O1 sites, with O3/O4–H silanol groups present as defects, a model that maps well onto experimental studies at higher levels of hydration (J. M. Griffin et al., Chem. Sci., 2013, 4, 1523). The AIRSS approach adopted herein provides the crucial link between atomic-scale structure and experimental studies. PMID:27020937

  17. Meridional Variations of C2H2 and C2H6 in Jupiter's Atmosphere from Cassini CIRS Infrared Spectra

    NASA Technical Reports Server (NTRS)

    Nixon, C. A.; Achterberg, R. K.; Conrath, B. J.; Irwin, P. G. J.; Fouchet, T.; Parrish, P. D.; Abbas, M.; LeClaire, A.; Romani, P. N.; Simon-Miller, A. A.

    2004-01-01

    The abundances of hydrocarbons such as acetylene (C2H2) and ethane (C2H6) in Jupiter's atmosphere are important physical quantities, constraining our models of the chemical and dynamical processes. However, our knowledge of these quantities and their vertical and latitudinal variations has remained sparse. The flyby of the Cassini spacecraft with Jupiter at the end of 2000 provided an excellent opportunity to observe the infrared spectrum with the Composite Infrared Spectrometer (CIRS) instrument, mapping the spatial variation of emissions from 10-1400 cm-1. CIRS spectra taken at the highest resolution (0.5 cm-1) in early December 2000 have been analysed to infer atmospheric temperatures in the stratosphere at 0.5-20 mbar via the v4 of CH4, and in the troposphere at 100-400 mbar, via the hydrogen collision-induced continuum absorption at 600-800 cm. Simultaneously, we have searched for meridional abundance variations in C2H2 and C2H6 via the v5 and vg bands respectively. Tropospheric absorption and stratospheric emission are highly anti-correlated at the CIM resolution, introducing a non-uniqueness into the retrievals, which means that vertical gradient and column abundance cannot be simultaneously found without additional constraints. If we assume the profile shapes from photochemical model calculations, we show that the column abundance of C2H2 must decrease sharply towards the poles, while C2H6 is constant or slightly increasing. The relevance of these results to current photochemical and dynamical knowledge of Jupiter's atmosphere is discussed.

  18. The distribution and abundance of interstellar C2H

    NASA Technical Reports Server (NTRS)

    Huggins, P. J.; Carlson, W. J.; Kinney, A. L.

    1984-01-01

    C2H(N = 1-0) emission has been extensively observed in a variety of molecular clouds, including: 12 hot, dense, cloud cores, 3 bright-rimmed clouds (in NGC 1977, IC 1396, and IC 1848), and across the extended OMC - 1 cloud. It has also been observed in the circumstellar envelopes IRC + 10216 and AFGL 2688. Abundance analyses of the molecular clouds yield C2H/(C-13)O abundance ratios of about 0.01, with little variation (less than about a factor of 4) either between clouds or across individual clouds. In the Orion plateau source, the C2H abundance is enhanced by less than a factor of 4, relative to the extended cloud. The generally high levels of C2H found in the molecular clouds are not readily accounted for by simple, steady-state chemical models, and suggest, as do earlier observations of atomic carbon, that the carbon chemistry in dense clouds is more active than is commonly assumed.

  19. Evaluation of an electrochemical N2/H2 gas separator

    NASA Technical Reports Server (NTRS)

    Marshall, R. D.; Wynveen, R. A.; Carlson, J. N.

    1973-01-01

    A program was successfully completed to evaluate an electrochemical nitrogen/hydrogen (N2/H2) separator for use in a spacecraft nitrogen (N2) generator. Based on the technical data obtained a N2/H2 separator subsystem consisting of an organic polymer gas permeator first stage and an electrochemical second and third stage was estimated to have the lowest total spared equivalent weight, 257 kg (566 lb), for a 15 lb/day N2 generation rate. A pre-design analysis of the electrochemical N2/H2 separator revealed that its use as a first stage resulted in too high a power requirement to be competitive with the organic polymer membrane and the palladium-silver membrane separation methods. As a result, program emphasis was placed on evaluating the electrochemical. A parametric test program characterized cell performance and established second- and third-stage electrochemical N2/H2 separator operating conditions. A design verification test was completed on the second and third stages. The second stage was then successfully endurance tested for 200 hours.

  20. NMR and NQR study of Ca-substituted superconducting YBa{sub 2}Cu{sub 4}O{sub 8}

    SciTech Connect

    Mali, M.; Roos, J.; Brinkmann, D.

    1996-02-01

    We report a set of nuclear quadrupole resonance (NQR) measurements including a spin-echo double-resonance (SEDOR) experiment which provides convincing evidence that the additional chain Cu NQR line in Ca-substituted YBa{sub 2}Cu{sub 4}O{sub 8} does stem from chain Cu sites disturbed by the {open_quote}{open_quote}impurity{close_quote}{close_quote} Ca ions. From an analysis of signal intensities we conclude that {open_quote}{open_quote}impurity{close_quote}{close_quote} Ca ions, responsible for the additional line, substitute Y{sup 3+}. At high Ca doping, the concentration of the substituted Y sites, {ital x}{sup {prime}}, is appreciably smaller than the nominal Ca concentration, {ital x}. Since it is {ital x}{sup {prime}} which is responsible for a direct increase of the hole charge-carrier concentration, {ital n}, effects connected with the increase of {ital n} such as the planar Cu spin-lattice relaxation rate, the NQR frequency, and the magnetic shift are only weakly dependent on {ital x}. Thus, the substantial increase of {ital T}{sub {ital c}} with {ital x} suggests that, besides the increase of {ital n}, other effects have to play a role in the {ital T}{sub {ital c}} enhancement. One such effect might be the opening of the spin pseudogap. At 150 K, both the main and additional Cu NQR lines in nominal YBa{sub 1.9}Ca{sub 0.1}Cu{sub 4}O{sub 8} show distinctly anomalies not seen in pure YBa{sub 2}Cu{sub 4}O{sub 8} that point out the Ca doping induced structural phase transition recently observed in specific-heat, elastic-neutron-scattering, and x-ray-diffraction measurements. {copyright} {ital 1996 The American Physical Society.}

  1. X-Ray and 35Cl NQR Studies on the Trichloroacetyl Group in Covalent and Ionic Compounds of L-Valine and DL-Valine

    NASA Astrophysics Data System (ADS)

    Ofial, A. R.; Dou, S.-q.; Krishnan, V. G.; Paulus, H.; Fuess, H.; Weiss, Al.

    1997-03-01

    The crystal structures and 35Cl NQR of trichloroacetyl-DL-valine (1), trichloroacetyl-L-valine (2), as well as the salts of trichloroacetic acid with DL-valine (3) and L-valine (4) have been investigated. Crystal data are for (1): Monoclinic, C2/c, a= 15.835(4) Å, b= 10.481 (3) Å, c = 14.046(4) Å, β = 103.28(1), Z = 8; (2): Orthorhombic, P212121, a = 12.117(3) Å, 6=10.896(3) Å, c= 8.718(2) Å, Z = 4; (3): Triclinic, P1¯, a= 17.269(3) Å, 6 = 8.504(3) Å, c = 10.427(4) A, a = 105.38(2), β = 96.98(2), γ = 96.24(2), Z = 2; (4): Monoclinic, P21, a = 10.378(4) Å, b = 20.349(8) Å, c= 11.890(5) Å, β = 95.28(2), Z = 8. The onset of rotational motion within the trichloroacetyl groups bleaches out 35Cl NQR lines between 115 K and 185 K for (1)-(4). While TCA-L-valine (1), TCA-DL-valine (2), and TCA(-) · DL-valine(+) (3) do not show any phase transition in the temperature range 77 K to 295 K, TCA(-) · L-valine(+) (4) shows more than one phase transition above 77 K before the three NQR signals bleach out at 164 K.

  2. New Evidences for the observation of the Higgs boson in the Superconductor 2H-NbSe2

    NASA Astrophysics Data System (ADS)

    Measson, Marie-Aude; Clair, Bertrand; Gallais, Yann; Cazayous, Maximilien; Rodière, Pierre; Cario, Laurent; Sacuto, Alain; Squap Team; Systèmes À Fortes Corrélations Électroniques Collaboration; Imn Collaboration

    2013-03-01

    We provide here new evidences for the observation of the amplitude mode of the superconducting order parameter, the so-called Higgs Boson, in 2H-NbSe2. We report quantitatively comparative electronic Raman measurements on the dichalcogenides 2H-NbSe2, whose superconductivity (SC) coexists with a charge density wave order (CDW), and 2H-NbS2, which exhibits only the SC. A SC pair breaking peak develops below Tc in 2H-NbS2 whose intensity is much smaller than the peak associated with the SC in 2H-NbSe2. Thus, the peak observed in 2H-NbSe2 below Tc certainly doesn't get its intensity only from the superconducting condensate. Moreover, we measure precisely a spectral weight transfer from the amplitude mode of the CDW to the SC peak in 2H-NbSe2, versus decreasing temperature. The total spectral weight for both peaks is constant within +/- 3 % . This result is consistent with the theory of the observation of a Higgs mode thanks to its coupling with an amplitudon developed by Littlewood and Varma. This result complements what was firstly observed by Sooryakumar et Klein under magnetic field.

  3. Observations of CH4, C2H6, and C2H2 in the stratosphere of Jupiter.

    PubMed

    Sada, P V; Bjoraker, G L; Jennings, D E; McCabe, G H; Romani, P N

    1998-12-01

    We have performed high-resolution spectral observations at mid-infrared wavelengths of CH4 (8.14 micrometers), C2H6 (12.16 micrometers), and C2H2 (13.45 micrometers) on Jupiter. These emission features probe the stratosphere of the planet and provide information on the carbon-based photochemical processes taking place in that region of the atmosphere. The observations were performed using our cryogenic echelle spectrometer CELESTE, in conjunction with the McMath-Pierce 1.5-m solar telescope between November 1994 and February 1995. We used the methane observations to derive the temperature profile of the jovian atmosphere in the 1-10 mbar region of the stratosphere. This profile was then used in conjunction with height-dependent mixing ratios of each hydrocarbon to determine global abundances for ethane and acetylene. The resulting mixing ratios are 3.9(+1.9)(-1.3) x 10(-6) for C2H6 (5 mbar pressure level), and 2.3 +/- 0.5 x 10(-8) for C2H2 (8 mbar pressure level), where the quoted uncertainties are derived from model variations in the temperature profile which match the methane observation uncertainties.

  4. CN and C2H in IRC +10216

    NASA Technical Reports Server (NTRS)

    Huggins, P. J.; Glassgold, A. E.; Morris, M.

    1984-01-01

    The effects of the production of the radicals CN and C2H from the dissociation of HCN and C2H2 by ambient UV photons in the outer envelope of IRC +10216 are investigated. The spatial distribution of the radicals and their observable millimeter emission-line characteristics are calculated from the inferred abundances of the progenitor species in the envelope of IRC +10216 using photochemical and radiative transfer models. These are compared with available observations to examine whether photoproduction is a possible explanation of the observed emission from these species. The results suggest that the variable abundances induced by photodestruction of their progenitors do affect the observed emission from the radicals.

  5. Mechanisms of CO2/H+ Sensitivity of Astrocytes

    PubMed Central

    Turovsky, Egor; Theparambil, Shefeeq M.; Kasymov, Vitaliy; Deitmer, Joachim W.; del Arroyo, Ana Gutierrez; Ackland, Gareth L.; Corneveaux, Jason J.; Allen, April N.; Huentelman, Matthew J.; Kasparov, Sergey; Marina, Nephtali

    2016-01-01

    Ventral regions of the medulla oblongata of the brainstem are populated by astrocytes sensitive to physiological changes in PCO2/[H+]. These astrocytes respond to decreases in pH with elevations in intracellular Ca2+ and facilitated exocytosis of ATP-containing vesicles. Released ATP propagates Ca2+ excitation among neighboring astrocytes and activates neurons of the brainstem respiratory network triggering adaptive increases in breathing. The mechanisms linking increases in extracellular and/or intracellular PCO2/[H+] with Ca2+ responses in chemosensitive astrocytes remain unknown. Fluorescent imaging of changes in [Na+]i and/or [Ca2+]i in individual astrocytes was performed in organotypic brainstem slice cultures and acute brainstem slices of adult rats. It was found that astroglial [Ca2+]i responses triggered by decreases in pH are preceded by Na+ entry, markedly reduced by inhibition of Na+/HCO3− cotransport (NBC) or Na+/Ca2+ exchange (NCX), and abolished in Na+-free medium or by combined NBC/NCX blockade. Acidification-induced [Ca2+]i responses were also dramatically reduced in brainstem astrocytes of mice deficient in the electrogenic Na+/HCO3− cotransporter NBCe1. Sensitivity of astrocytes to changes in pH was not affected by inhibition of Na+/H+ exchange or blockade of phospholipase C. These results suggest that in pH-sensitive astrocytes, acidification activates NBCe1, which brings Na+ inside the cell. Raising [Na+]i activates NCX to operate in a reverse mode, leading to Ca2+ entry followed by activation of downstream signaling pathways. Coupled NBC and NCX activities are, therefore, suggested to be responsible for functional CO2/H+ sensitivity of astrocytes that contribute to homeostatic regulation of brain parenchymal pH and control of breathing. SIGNIFICANCE STATEMENT Brainstem astrocytes detect physiological changes in pH, activate neurons of the neighboring respiratory network, and contribute to the development of adaptive respiratory responses to

  6. Measurement of regional cerebral blood flow in cat brain using intracarotid 2H2O and 2H NMR imaging

    SciTech Connect

    Detre, J.A.; Subramanian, V.H.; Mitchell, M.D.; Smith, D.S.; Kobayashi, A.; Zaman, A.; Leigh, J.S. Jr. )

    1990-05-01

    Cerebral blood flow (CBF) was measured in cat brain in vivo at 2.7 T using 2H NMR to monitor the washout of deuterated saline injected into both carotid arteries via the lingual arteries. In anesthetized cats, global CBF varied directly with PaCO{sub 2} over a range of 20-50 mm Hg, and the corresponding global CBF values ranged from 25 to 125 ml.100 g-1.min-1. Regional CBF was measured in a 1-cm axial section of cat brain using intracarotid deuterated saline and gradient-echo 2H NMR imaging. Blood flow images with a maximum pixel resolution of 0.3 x 0.3 x 1.0 cm were generated from the deuterium signal washout at each pixel. Image derived values for CBF agreed well with other determinations, and decreased significantly with hypocapnia.

  7. Hydrogenation and Deuteration of C2H2 and C2H4 on Cold Grains: A Clue to the Formation Mechanism of C2H6 with Astronomical Interest

    NASA Astrophysics Data System (ADS)

    Kobayashi, Hitomi; Hidaka, Hiroshi; Lamberts, Thanja; Hama, Tetsuya; Kawakita, Hideyo; Kästner, Johannes; Watanabe, Naoki

    2017-03-01

    We quantitatively investigated the hydrogen addition reactions of acetylene (C2H2) and ethylene (C2H4) on amorphous solid water (ASW) at 10 and 20 K relevant to the formation of ethane (C2H6) on interstellar icy grains. We found that the ASW surface enhances the reaction rates for C2H2 and C2H4 by approximately a factor of 2 compared to those on the pure-solid C2H2 and C2H4 at 10 K, probably due to an increase in the sticking coefficient and adsorption energy of the H atoms on ASW. In contrast to the previous proposal that the hydrogenation rate of C2H4 is orders of magnitude larger than that of C2H2, the present results show that the difference in hydrogenation rates of C2H2 and C2H4 is only within a factor of 3 on both the surfaces of pure solids and ASW. In addition, we found the small kinetic isotope effect for hydrogenation/deuteration of C2H2 and C2H4 at 10 K, despite the requirement of quantum tunneling. At 20 K, the reaction rate of deuteration becomes even larger than that of hydrogenation. These unusual isotope effects might originate from a slightly larger number density of D atoms than H atoms on ASW at 20 K. The hydrogenation of C2H2 is four times faster than CO hydrogenation and can produce C2H6 efficiently through C2H4 even in the environment of a dark molecular cloud.

  8. Theoretical study on the rate constants for the C2H5 + HBr --> C2H6 + Br reaction.

    PubMed

    Sheng, Li; Li, Ze-Sheng; Liu, Jing-Yao; Xiao, Jing-Fa; Sun, Chia-Chung

    2004-02-01

    The reaction C(2)H(5) + HBr --> C(2)H(6) + Br has been theoretically studied over the temperature range from 200 to 1400 K. The electronic structure information is calculated at the BHLYP/6-311+G(d,p) and QCISD/6-31+G(d) levels. With the aid of intrinsic reaction coordinate theory, the minimum energy paths (MEPs) are obtained at the both levels, and the energies along the MEP are further refined by performing the single-point calculations at the PMP4(SDTQ)/6-311+G(3df,2p)//BHLYP and QCISD(T)/6-311++G(2df,2pd)//QCISD levels. The calculated ICVT/SCT rate constants are in good agreement with available experimental values, and the calculate results further indicate that the C(2)H(5) + HBr reaction has negative temperature dependence at T < 850 K, but clearly shows positive temperature dependence at T > 850 K. The current work predicts that the kinetic isotope effect for the title reaction is inverse in the temperature range from 200 to 482 K, i.e., k(HBr)/k(DBr) < 1.

  9. Solubilities of salts in the ternary systems NaCl + CaCl2 + H2O and KCl + CaCl2 + H2O at 75°C

    NASA Astrophysics Data System (ADS)

    Yang, Ji-Min; Liu, Xiao-Lin; Liang, Pei-Pei

    2011-07-01

    The solubility in the NaCl-CaCl2-H2O and KCl-CaCl2-H2O systems were determined at 75°C and the phase diagrams and the diagram of physicochemical property vs composition were plotted. One invariant point, two univariant curves, and two crystallization zones, corresponding to potassium chloride, dihydrate (CaCl2 · 2H2O) showed up in the phase diagrams of the ternary systems. The mixing parameters θM, Ca and ΨM, Ca, Cl (M = Na or K) and equilibrium constant K sp were evaluated in NaCl-CaCl2-H2O and KCl-CaCl2-H2O systems by least-squares optimization procedure, in which the single-salt Pitzer parameters of NaCl, KCl, and CaCl2 β(0), β(1), β(2), and C Φ were directly calculated from the literature. The results obtained were in good agreement with the experimental data.

  10. Theoretical kinetics of O + C2H4

    DOE PAGES

    Li, Xiaohu; Jasper, Ahren W.; Zádor, Judit; ...

    2016-06-01

    The reaction of atomic oxygen with ethylene is a fundamental oxidation step in combustion and is prototypical of reactions in which oxygen adds to double bonds. For 3O+C2H4 and for this class of reactions generally, decomposition of the initial adduct via spin-allowed reaction channels on the triplet surface competes with intersystem crossing (ISC) and a set of spin-forbidden reaction channels on the ground-state singlet surface. The two surfaces share some bimolecular products but feature different intermediates, pathways, and transition states. In addition, the overall product branching is therefore a sensitive function of the ISC rate. The 3O+C2H4 reaction has beenmore » extensively studied, but previous experimental work has not provided detailed branching information at elevated temperatures, while previous theoretical studies have employed empirical treatments of ISC. Here we predict the kinetics of 3O+C2H4 using an ab initio transition state theory based master equation (AITSTME) approach that includes an a priori description of ISC. Specifically, the ISC rate is calculated using Landau–Zener statistical theory, consideration of the four lowest-energy electronic states, and a direct classical trajectory study of the product branching immediately after ISC. The present theoretical results are largely in good agreement with existing low-temperature experimental kinetics and molecular beam studies. Good agreement is also found with past theoretical work, with the notable exception of the predicted product branching at elevated temperatures. Above ~1000 K, we predict CH2CHO+H and CH2+CH2O as the major products, which differs from the room temperature preference for CH3+HCO (which is assumed to remain at higher temperatures in some models) and from the prediction of a previous detailed master equation study.« less

  11. Mechanisms of CO2/H+ Sensitivity of Astrocytes.

    PubMed

    Turovsky, Egor; Theparambil, Shefeeq M; Kasymov, Vitaliy; Deitmer, Joachim W; Del Arroyo, Ana Gutierrez; Ackland, Gareth L; Corneveaux, Jason J; Allen, April N; Huentelman, Matthew J; Kasparov, Sergey; Marina, Nephtali; Gourine, Alexander V

    2016-10-19

    Ventral regions of the medulla oblongata of the brainstem are populated by astrocytes sensitive to physiological changes in PCO2/[H(+)]. These astrocytes respond to decreases in pH with elevations in intracellular Ca(2+) and facilitated exocytosis of ATP-containing vesicles. Released ATP propagates Ca(2+) excitation among neighboring astrocytes and activates neurons of the brainstem respiratory network triggering adaptive increases in breathing. The mechanisms linking increases in extracellular and/or intracellular PCO2/[H(+)] with Ca(2+) responses in chemosensitive astrocytes remain unknown. Fluorescent imaging of changes in [Na(+)]i and/or [Ca(2+)]i in individual astrocytes was performed in organotypic brainstem slice cultures and acute brainstem slices of adult rats. It was found that astroglial [Ca(2+)]i responses triggered by decreases in pH are preceded by Na(+) entry, markedly reduced by inhibition of Na(+)/HCO3(-) cotransport (NBC) or Na(+)/Ca(2+) exchange (NCX), and abolished in Na(+)-free medium or by combined NBC/NCX blockade. Acidification-induced [Ca(2+)]i responses were also dramatically reduced in brainstem astrocytes of mice deficient in the electrogenic Na(+)/HCO3(-) cotransporter NBCe1. Sensitivity of astrocytes to changes in pH was not affected by inhibition of Na(+)/H(+) exchange or blockade of phospholipase C. These results suggest that in pH-sensitive astrocytes, acidification activates NBCe1, which brings Na(+) inside the cell. Raising [Na(+)]i activates NCX to operate in a reverse mode, leading to Ca(2+) entry followed by activation of downstream signaling pathways. Coupled NBC and NCX activities are, therefore, suggested to be responsible for functional CO2/H(+) sensitivity of astrocytes that contribute to homeostatic regulation of brain parenchymal pH and control of breathing.

  12. Direct dynamics study on the hydrogen abstraction reactions N2H4+R→N2H3+RH (R=NH2,CH3)

    NASA Astrophysics Data System (ADS)

    Li, Qian Shu; Zhang, Xin

    2006-08-01

    We present a direct ab initio dynamics study on the hydrogen abstraction reactions N2H4+R→N2H3+RH (R=NH2,CH3), which are predicted to have six possible reaction channels for NH2 abstraction and four for CH3 abstraction caused by the different N2H4 isomers and various attacking orientations of foreign radical to N2H4. The structures and frequencies at the stationary points and the points along the minimum energy paths (MEPs) of all reaction channels are obtained at the UMP2(full)/6-31+G(d,p) level of theory. Energetic information of stationary points and the points along the MEPs is further refined by means of MC-QCISD method. The rate constants of these channels are calculated using the improved canonical variational transition-state theory with the small-curvature tunneling correction (ICVT/SCT) method. The calculated results show that the favorable reaction channels are channels (n1) and (n4) as well as (c1) and (c3) (refer to Scheme 1) in the whole temperature range. The total ICVT/SCT rate constants of all channels for the two reactions at the MC-QCISD //UMP2(full)/6-31+G(d,p) level are both in good agreement with the available experimental data, and corresponding three-parameter expressions of kICVT /SCT in 220-3000K are fitted as 6.46×10-15(T/298)3.60exp(-386/T)cm3mol-1s-1 for NH2 abstraction and 1.04×10-14 (T/298)4.00exp(-2037/T)cm3mol-1s-1 for CH3 abstraction. Additionally, the long range interaction between the H atom of X -H bond in foreign radicals and the lone pair on the nonreactive N atom of the transition states is further discussed to explain the various transition-state numbers of the two similar hydrogen abstraction reactions.

  13. Synthesis of 2H- and 13C-substituted dithanes

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.

    2003-01-01

    The present invention is directed to labeled compounds, [2-.sup.13 C]dithiane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to processes of preparing [2-.sup.13 C]dithiane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to labeled compounds, e.g., [.sup.2 H.sub.1-2, .sup.13 C]methanol (arylthio)-, acetates wherein the .sup.13 C atom is directly bonded to exactly one or two deuterium atoms.

  14. Synthesis Of 2h- And 13c-Substituted Dithanes

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.

    2004-05-04

    The present invention is directed to labeled compounds, [2-.sup.13 C]dithane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to processes of preparing [2-.sup.13 C]dithane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to labeled compounds, e.g., [.sup.2 H.sub.1-2, .sup.13 C]methanol (arylthio)-, acetates wherein the .sup.13 C atom is directly bonded to exactly one or two deuterium atoms.

  15. A 2H and 14N NMR study of molecular motion in polycrystalline choline salts

    NASA Astrophysics Data System (ADS)

    Pratum, T. K.; Klein, M. P.

    2H and 14N solid-state NMR spectra of polycrystalline choline chloride, bromide, and iodide indicate that 180° cation flipping motion occurs in all three salts. From the temperature dependence of these spectra, the activation energy for this motion is determined to be 5.8 ± I kcal/mol in the iodide salt and 11 ± 1.5 kcal/mol in the chloride salt. In the bromide salt the reorientation rate is too rapid to be determined from the NMR lineshape, but the temperature dependence of the 2H quadrupole coupling parameters is indicative of a second-order phase transition at approximately 273 K. The spectral distortions in the 14N NMR spectra of the chloride and iodide salts are adequately explained using the motional model derived from the 2H NMR results, while the 14N spectra of the bromide salt show no motional effects. The axis of reorientation which is inferred from these data appears to be consistent with that indicated in a previous X-ray crystallographic study.

  16. 1H-2H cross-polarization NMR in fast spinning solids by adiabatic sweeps

    NASA Astrophysics Data System (ADS)

    Wi, Sungsool; Schurko, Robert; Frydman, Lucio

    2017-03-01

    Cross-polarization (CP) experiments employing frequency-swept radiofrequency (rf) pulses have been successfully used in static spin systems for obtaining broadband signal enhancements. These experiments have been recently extended to heteronuclear I, S = spin-1/2 nuclides under magic-angle spinning (MAS), by applying adiabatic inversion pulses along the S (low-γ) channel while simultaneously applying a conventional spin-locking pulse on the I-channel (1H). This study explores an extension of this adiabatic frequency sweep concept to quadrupolar nuclei, focusing on CP from 1H (I = 1/2) to 2H spins (S = 1) undergoing fast MAS (νr = 60 kHz). A number of new features emerge, including zero- and double-quantum polarization transfer phenomena that depend on the frequency offsets of the swept pulses, the rf pulse powers, and the MAS spinning rate. An additional mechanism found operational in the 1H-2H CP case that was absent in the spin-1/2 counterpart, concerns the onset of a pseudo-static zero-quantum CP mode, driven by a quadrupole-modulated rf/dipolar recoupling term arising under the action of MAS. The best CP conditions found at these fast spinning rates correspond to double-quantum transfers, involving weak 2H rf field strengths. At these easily attainable (ca. 10 kHz) rf field conditions, adiabatic level-crossings among the {|1 ⟩ ,|0 ⟩ ,|-1 ⟩ } mS energy levels, which are known to complicate the CP MAS of quadrupolar nuclei, are avoided. Moreover, the CP line shapes generated in this manner are very close to the ideal 2H MAS spectral line shapes, facilitating the extraction of quadrupolar coupling parameters. All these features were corroborated with experiments on model compounds and justified using numerical simulations and average Hamiltonian theory models. Potential applications of these new phenomena, as well as extensions to higher spins S, are briefly discussed.

  17. Photodissociation spectroscopy of Ca+(C2H4)

    NASA Astrophysics Data System (ADS)

    Holmes, J. H.; Kleiber, P. D.; Olsgaard, D. A.; Yang, K.-H.

    2000-04-01

    We have studied Ca+(C2H4) by photodissociation spectroscopy in a reflectron time-of-flight mass spectrometer over the spectral range 440-790 nm. Ca+ is the only photofragment observed. We find four absorption bands of the complex and assign them to metal-centered transitions correlating with excitation of Ca+(3d and 4p). Spectral assignment is supported by ab initio electronic structure calculations of the complex and isotope substitution experiments. Calculations find a weakly bound ground state equilibrium structure with C2V π-bonding geometry and a dissociation energy of De″=0.506 eV. Theoretical and experimental results show the 4pπ(2 2B2 & 2 2B1) excited states to be relatively weakly bound at long range. Spectral analysis gives vibrational constants for the Ca+--C2H4 intermolecular a1-stretch in the 1 2A1, 2 2B1, and 2 2B2 states, and for the CH2-CH2 a1-wag and the HCH a1-bend in 2 2B2. The results offer an interesting comparison with previous studies of similar weakly bound bimolecular complexes of light metal ions with alkene or alkane hydrocarbons.

  18. Electronic properties of Y-Ba-Cu-O superconductors as seen by Cu and O NMR/NQR

    NASA Technical Reports Server (NTRS)

    Brinkmann, D.

    1995-01-01

    Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) allow the investigation of electronic properties at the atomic level. We will report on such studies of typical members of the the Y-Ba-Cu-O family such as YBa2Cu30(6 + x) (1-2-3-(6 + x)), YBa2Cu4O8 (1-2-4) and Y2Ba4Cu7015 (2-4-7) with many examples of recent work performed in our laboratory. In particular, we will deal with Knight shift and relaxation studies of copper and oxygen. We will discuss important issues of current studies such as: (1) Existence of a common electronic spin-susceptibility in the planes (and perhaps in the chains) of 1-2-4; (2) Strong evidence for the existence of a pseudo spin-gap of the antiferromagnetic fluctuations in 1-2-4 and 2-4-7; (3) Evidence for d-wave pairing in 1-2-4; (4) Strong coupling of inequivalent Cu-O planes in 2-4-7 and possible origin for the high Tc value of this compound; and (5) The possibility to describe NMR data in the framework of a charge-excitation picture.

  19. Magnetic correlations in La(2-x)Sr(x)CuO4 from NQR relaxation and specific heat

    NASA Technical Reports Server (NTRS)

    Borsa, F.; Rigamonti, A.

    1990-01-01

    La-139 and Cu-63 Nuclear Quadrupole Resonance (NQR) relaxation measurements in La(2-x)Sr(x)CuO4 for O = to or less than 0.3 and in the temperature range 1.6 + 450 K are analyzed in terms of Cu(++) magnetic correlations and dynamics. It is described how the magnetic correlations that would result from Cu-Cu exchange are reduced by mobile charge defects related to x-doping. A comprehensive picture is given which explains satisfactorily the x and T dependence of the correlation time, of the correlation length and of the Neel temperature T(sub n)(x) as well as being consistent with known electrical resistivity and magnetic susceptibility measurements. It is discussed how, in the superconducting samples, the mobile defects also cause the decrease, for T yields T(sub c)(+) of the hyperfine Cu electron-nucleus effective interaction, leading to the coexistence of quasi-localized, reduced magnetic moments from 3d Cu electrons and mobile oxygen p-hole carriers. The temperature dependence of the effective hyperfine field around the superconducting transition yields an activation energy which could be related to the pairing energy. New specific heat measurements are also presented and discussed in terms of the above picture.

  20. Physical and spectroscopic properties of pure C2H4 and CH4:C2H4 ices

    NASA Astrophysics Data System (ADS)

    Molpeceres, Germán; Satorre, Miguel Angel; Ortigoso, Juan; Zanchet, Alexandre; Luna, Ramón; Millán, Carlos; Escribano, Rafael; Tanarro, Isabel; Herrero, Víctor J.; Maté, Belén

    2017-04-01

    Physical and spectroscopic properties of ices of C2H4 and CH4:C2H4 mixtures with 3:1, 1:1 and 1:3 ratios have been investigated at 30 K. Two laboratories are involved in this work. In one of them, the density and refractive index of the samples have been measured by using a cryogenic quartz microbalance and laser interferometric techniques. In the other one, IR spectra have been recorded in the near- and mid-infrared regions, and band shifts with respect to the pure species, band strengths of the main bands, and the optical constants in both regions have been determined. Previous data on ethylene and the mixtures studied here were scarce. For methane, both the wavenumbers and band strengths have been found to follow a regular pattern of decrease with increasing dilution, but no pattern has been detected for ethylene vibrations. The method employed for the preparation of the samples, by vapour deposition under vacuum, is thought to be adequate to mimic the structure of astrophysical ices. Possible astrophysical implications, especially by means of the optical constants reported here, have been discussed.

  1. 2H NMR studies of supercooled and glassy aspirin

    NASA Astrophysics Data System (ADS)

    Nath, R.; Nowaczyk, A.; Geil, B.; Bohmer, R.

    2007-11-01

    Acetyl salicylic acid, deuterated at the methyl group, was investigated using 2H-NMR in its supercooled and glassy states. Just above the glass transition temperature the molecular reorientations were studied using stimulated-echo spectroscopy and demonstrated a large degree of similarity with other glass formers. Deep in the glassy phase the NMR spectra look similar to those reported for the crystal [A. Detken, P. Focke, H. Zimmermann, U. Haeberlen, Z. Olejniczak, Z. T. Lalowicz, Z. Naturforsch. A 50 (1995) 95] and below 20 K they are indicative for rotational tunneling with a relatively large tunneling frequency. Measurements of the spin-lattice relaxation times for temperatures below 150 K reveal a broad distribution of correlation times in the glass. The dominant energy barrier characterizing the slow-down of the methyl group is significantly smaller than the well defined barrier in the crystal.

  2. Vibrational and Rotational Spectroscopy of CD_2H^+

    NASA Astrophysics Data System (ADS)

    Asvany, Oskar; Jusko, Pavol; Brünken, Sandra; Schlemmer, Stephan

    2016-06-01

    The lowest rotational levels (J=0-5) of the CD_2H^+ ground state have been probed by high-resolution rovibrational and pure rotational spectroscopy in a cryogenic 22-pole ion trap. For this, the ν_1 rovibrational band has been revisited, detecting 107 transitions, among which 35 are new. The use of a frequency comb system allowed to measure the rovibrational transitions with high precision and accuracy, typically better than 1 MHz. The high precision has been confirmed by comparing combination differences in the ground and vibrationally excited state. For the ground state, this allowed for equally precise predictions of pure rotational transitions, 24 of which have been measured directly by a novel IR - mm-wave double resonance method. M.-F. Jagod et al, J. Molec. Spectrosc. 153, 666, 1992 S. Gartner et al, J. Phys. Chem. A 117, 9975, 2013

  3. 2H and 18O Freshwater Isoscapes of Scotland

    NASA Astrophysics Data System (ADS)

    Meier-Augenstein, Wolfram; Hoogewerff, Jurian; Kemp, Helen; Frew, Danny

    2013-04-01

    Scotland's freshwater lochs and reservoirs provide a vital resource for sustaining biodiversity, agriculture, food production as well as for human consumption. Regular monitoring of freshwaters by the Scottish Environment Protection Agency (SEPA) fulfils legislative requirements with regards to water quality but new scientific methods involving stable isotope analysis present an opportunity combining these mandatory monitoring schemes with fundamental research to inform and deliver on current and nascent government policies [1] through gaining a greater understanding of Scottish waters and their importance in the context of climate change, environmental sustainability and food security. For example, 2H and 18O isoscapes of Scottish freshwater could be used to underpin research and its applications in: • Climate change - Using longitudinal changes in the characteristic isotope composition of freshwater lochs and reservoirs as proxy, isoscapes will provide a means to assess if and how changes in temperature and weather patterns might impact on precipitation patterns and amount. • Scottish branding - Location specific stable isotope signatures of Scottish freshwater have the potential to be used as a tool for provenancing and thus protecting premium Scottish produce such as Scottish beef, Scottish soft fruit and Scottish Whisky. During 2011 and 2012, with the support of SEPA more than 110 samples from freshwater lochs and reservoirs were collected from 127 different locations across Scotland including the Highlands and Islands. Here we present the results of this sampling and analysis exercise isotope analyses in form of 2H and 18O isoscapes with an unprecedented grid resolution of 26.5 × 26.5 km (or 16.4 × 16.4 miles). [1] Adaptation Framework - Adapting Our Ways: Managing Scotland's Climate Risk (2009): Scotland's Biodiversity: It's in Your Hands - A strategy for the conservation and enhancement of biodiversity in Scotland (2005); Recipe For Success - Scotland

  4. Copper Nqr and NMR Study of Metal-Substituted Yttrium BARIUM(2) COPPER(3) OXYGEN(7) and Yttrium BARIUM(2) COPPER(4) OXYGEN(8)

    NASA Astrophysics Data System (ADS)

    Cheng, Show-Jye

    Pulsed nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) have been used to investigate the effect of metal-substitution for copper in YBa_2Cu_3O_7 (YBCO123) and YBa_2Cu_4O_8 (YBCO124). Among many metal substitutions, Zn has an especially dramatic effect in suppressing the superconducting temperature T_{c}, and hence superconductivity. More interesting is that Zn and Fe have the same T_{c} suppression effect in YBCO124. This study focuses on the Zn substitutions in YBCO123 and Zn, Fe, and Co substitutions in YBCO124. In Zn doped YBCO123, Cu(2), plane site, NQR spectra and the frequency dependence of the spin-lattice relaxation rates have been measured over a temperature range from 77 K to 300 K to study the correlation of the suppression of the relaxation rate with the distance between the probe Cu nuclei and the impurity. It is found that the relaxation rate is insensitive to the variation of the NQR resonance frequency. However, by comparing the results of the Zn doped YBCO124 with those of YBCO123, it can be concluded that the suppression of the relaxation rate for both YBCO compounds in the normal state is caused by destruction of short-range antiferromagnetic correlation with substitution of nonmagnetic ion Zn on the Cu(2) sites. NQR and NMR measurements were carried out on both Cu(2), plane, and Cu(1), chain sites, for various concentrations of Zn, Fe, and Co dopants in YBCO124 over a temperature range from 77 K to 300 K. A strong correlation of the enhancement of Cu(2) spin lattice relaxation rate and suppression of superconductivity by impurities was found. The temperature dependence of the Cu(2) NMR linewidth exhibits a strong RKKY type exchange interaction below 225 K for Zn and Fe doped samples, which indicates the formation of the local magnetic moment. The enhancement of the relaxation rate is caused by the local magnetic moment Fe^ {+3} ion and the moments on Cu(2) neighbors when Zn^{+2} is substituted on Cu(2). This study gives

  5. Antiferromagnetic properties of a water-vapor-inserted YBa2 Cu3 O6.5 compound studied byNMR, NQR, and μSR

    NASA Astrophysics Data System (ADS)

    Dooglav, A. V.; Egorov, A. V.; Mukhamedshin, I. R.; Savinkov, A. V.; Alloul, H.; Bobroff, J.; Macfarlane, W. A.; Mendels, P.; Collin, G.; Blanchard, N.; Picard, P. G.; King, P. J. C.; Lord, J.

    2004-08-01

    We present a detailed NQR, nuclear magnetic resonance (NMR), and μSR study of the magnetic phase obtained during a topotactic chemical reaction of YBa2Cu3O6.5 high-temperature superconductor with low-pressure water vapor. Cu65 -enriched samples have been used for NQR/NMR studies which allows to get a good resolution in the Cu(1) NQR and Cu(2) zero field NMR (ZFNMR) spectra. It is shown that the NQR spectrum of the starting material transforms progressively under insertion of water, and almost completely disappears when about one H2O molecule is inserted per unit cell. Similarly, a Cu65 ZFNMR signal characteristic of this water inserted material appears and grows with increasing water content, which indicates that the products of the reaction are nonsuperconducting antiferromagnetic phases in which the copper electronic magnetic moments in the CuO2 bilayers are ordered. The use of Cu65 -enriched samples allowed us to reliably resolve three different copper resonances which correspond to different internal magnetic fields. The antiferromagnetic phases are also felt by proton NMR which reveals two sites with static internal fields of 150 and about 15 Gauss, respectively. μSR studies performed on a series of samples prepared in the same way as the C65u -enriched ones reveal two muon sites with the same local fields as the proton sites, which vanish at T≈400K . This indicates that muons preferentially occupy proton vacancy sites, and that the magnetic phases have similar Néel temperatures as the other bilayer undoped cuprate compounds. An analysis of the internal fields on the different spin probes suggests that they can be all assigned to a single magnetic phase at large water content in which the Cu(1) electron spins order with those of the Cu(2) . The detailed evolution of the spectra with the progressive increase of water content is shown to be compatible with a coexistence of phases during the early stages ot the reaction. It appears that even samples packed

  6. Probing Perturbation of Bovine Lung Surfactant Extracts by Albumin using DSC and 2H-NMR

    PubMed Central

    Nag, Kaushik; Keough, Kevin M. W.; Morrow, Michael R.

    2006-01-01

    Lung surfactant (LS), a lipid-protein mixture, forms films at the lung air-water interface and prevents alveolar collapse at end expiration. In lung disease and injury, the surface activity of LS is inhibited by leakage of serum proteins such as albumin into the alveolar hypophase. Multilamellar vesicular dispersions of a clinically used replacement, bovine lipid extract surfactant (BLES), to which (2% by weight) chain-perdeuterated dipalmitoylphosphatidycholine (DPPG mixtures-d62) had been added, were studied using deuterium-NMR spectroscopy (2H-NMR) and differential scanning calorimetry (DSC). DSC scans of BLES showed a broad gel to liquid-crystalline phase transition between 10–35°C, with a temperature of maximum heat flow (Tmax) around 27°C. Incorporation of the DPPC-d62 into BLES-reconstituted vesicles did not alter the Tmax or the transition range as observed by DSC or the hydrocarbon stretching modes of the lipids observed using infrared spectroscopy. Transition enthalpy change and 2H-NMR order parameter profiles were not significantly altered by addition of calcium and cholesterol to BLES. 2H-NMR spectra of the DPPC-d62 probes in these samples were characteristic of a single average lipid environment at all temperatures. This suggested either continuous ordering of the bilayer through the transition during cooling or averaging of the DPPC-d62 environment by rapid diffusion between small domains on a short timescale relative to that characteristic of the 2H-NMR experiment. Addition of 10% by weight of soluble bovine serum albumin (1:0.1, BLES/albumin, dry wt/wt) broadened the transition slightly and resulted in the superposition of 2H-NMR spectral features characteristic of coexisting fluid and ordered phases. This suggests the persistence of phase-separated domains throughout the transition regime (5–35°C) of BLES with albumin. The study suggests albumin can cause segregation of protein bound-lipid domains in surfactant at NMR timescales (10−5 s

  7. Ab initio study of {sup 2}H(d,{gamma}){sup 4}He, {sup 2}H(d,p){sup 3}H, and {sup 2}H(d,n){sup 4}He reactions and the tensor force

    SciTech Connect

    Arai, K.; Aoyama, S.; Suzuki, Y.; Descouvemont, P.; Baye, D.

    2012-11-12

    The {sup 2}H(d,p){sup 3}H, {sup 2}H(d,n){sup 3}He, and {sup 2}H(d,{gamma}){sup 4}He reactions at low energies are studied with realistic nucleon-nucleon interactions in an ab initio approach. The obtained astrophysical S-factors are all in very good agreement with experiment. The most important channels for both transfer and radiative capture are all found to dominate thanks to the tensor force.

  8. Human organic cation transporter 2 (hOCT2): Inhibitor studies using S2-hOCT2 cells.

    PubMed

    Chiba, Shoetsu; Ikawa, Toru; Takeshita, Hiroshi; Kanno, Sanae; Nagai, Tomonori; Takada, Meri; Mukai, Toshiji; Wempe, Michael F

    2013-08-09

    Highly expressed in kidney and located on the basolateral membrane, human organic cation transporter 2 (hOCT2) can transport various compounds (i.e. drugs and toxins) into the proximal tubular cell. Using cultured proximal tubule cells stably expressing hOCT2 (i.e. S2-hOCT2 cells), we sought to probe different compound classes (e.g. analgesics, anti-depressants, anti-psychotics, disinfectant, herbicides, insecticides, local anesthetic, muscarinic acetylcholine receptor antagonist, sedatives, steroid hormone, stimulants and toxins) for their ability to inhibit (14)C-TEA uptake, a prototypical OCT2 substrate. Aconitine, amitriptyline, atropine, chlorpyrifos, diazepam, fenitrothion, haloperidol, lidocaine, malathion, mianserin, nicotine and triazolam significantly inhibited (14)C-TEA uptake; IC50 values were 59.2, 2.4, 2.0, 20.7, 32.3, 13.2, 32.5, 104.6, 71.1, 17.7, 52.8 and 65.5μM, respectively. In addition, aconitine, amitriptyline, atropine, chlorpyrifos, fenitrothion, haloperidol, lidocaine, and nicotine displayed competitive inhibition with Ki values of 145.6, 2.5, 2.4, 24.8, 16.9, 51.6, 86.8 and 57.7μM, respectively. These in vitro data support the notion that compounds pertaining to a wide variety of different drug classes have the potential to decrease renal clearance of drugs transported via hOCT2. Consequently, these data warrant additional studies to probe hOCT2 and its role to influence drug pharmacokinetics.

  9. A neutron scattering study of hydrogen dynamics in coarse-grained and nanostructured ZrCr2H3

    NASA Astrophysics Data System (ADS)

    Skripov, A. V.; Udovic, T. J.; Rush, J. J.; Uimin, M. A.

    2011-02-01

    The vibrational spectra of hydrogen and parameters of H diffusion in the coarse-grained C15-type system ZrCr2H3 and in nanostructured ZrCr2H3 have been studied by means of inelastic and quasielastic neutron scattering. It is found that the diffusive motion of hydrogen in coarse-grained ZrCr2H3 can be described in terms of at least two jump processes: a fast localized H motion with the jump rate τl - 1 over the hexagons formed by interstitial Zr2Cr2 sites and a slower process with the rate τd - 1 associated with H jumps leading to long-range diffusion. While τd - 1(T) in the range 250-380 K follows the Arrhenius law with the activation energy of 142 ± 4 meV, the temperature dependence of τl - 1 deviates from Arrhenius behavior. The nanostructured ZrCr2H3 samples prepared by ball milling consist of C15-type grains and strongly distorted (amorphous-like) regions. H atoms in the strongly distorted regions are found to be immobile on the time scale of our experiments. The microscopic picture of H jump motion in the C15-type grains of the nanostructured samples is similar to that in coarse-grained ZrCr2H3; however, the ball milling leads to a considerable decrease in the jump rate τd - 1.

  10. Site-resolved 2H relaxation experiments in solid materials by global line-shape analysis of MAS NMR spectra

    NASA Astrophysics Data System (ADS)

    Lindh, E. L.; Stilbs, P.; Furó, I.

    2016-07-01

    We investigate a way one can achieve good spectral resolution in 2H MAS NMR experiments. The goal is to be able to distinguish between and study sites in various deuterated materials with small chemical shift dispersion. We show that the 2H MAS NMR spectra recorded during a spin-relaxation experiment are amenable to spectral decomposition because of the different evolution of spectral components during the relaxation delay. We verify that the results are robust by global least-square fitting of the spectral series both under the assumption of specific line shapes and without such assumptions (COmponent-REsolved spectroscopy, CORE). In addition, we investigate the reliability of the developed protocol by analyzing spectra simulated with different combinations of spectral parameters. The performance is demonstrated in a model material of deuterated poly(methacrylic acid) that contains two 2H spin populations with similar chemical shifts but different quadrupole splittings. In 2H-exchanged cellulose containing two 2H spin populations with very similar chemical shifts and quadrupole splittings, the method provides new site-selective information about the molecular dynamics.

  11. Thermal decomposition of (UO2)O2(H2O)2·2H2O: Influence on structure, microstructure and hydrofluorination

    NASA Astrophysics Data System (ADS)

    Thomas, R.; Rivenet, M.; Berrier, E.; de Waele, I.; Arab, M.; Amaraggi, D.; Morel, B.; Abraham, F.

    2017-01-01

    The thermal decomposition of uranyl peroxide tetrahydrate, (UO2)O2(H2O)2.2H2O, was studied by combining high temperature powder X-ray diffraction, scanning electron microscopy, thermal analyses and spectroscopic techniques (Raman, IR and 1H NMR). In situ analyses reveal that intermediates and final uranium oxides obtained upon heating are different from that obtained after cooling at room temperature and that the uranyl precursor used to synthesize (UO2)O2(H2O)2·2H2O, sulfate or nitrate, has a strong influence on the peroxide thermal behavior and morphology. The decomposition of (UO2)O2(H2O)2·2H2O ex sulfate is pseudomorphic and leads to needle-like shaped particles of metastudtite, (UO2)O2(H2O)2, and UO3-x(OH)2x·zH2O, an amorphous phase found in air in the following of (UO2)O2(H2O)2 dehydration. (UO2)O2(H2O)2·2H2O and the compounds resulting from its thermal decomposition are very reactive towards hydrofluorination as long as their needle-like morphology is kept.

  12. Ca2+/H+ exchange in acidic vacuoles of Trypanosoma brucei.

    PubMed Central

    Vercesi, A E; Moreno, S N; Docampo, R

    1994-01-01

    The use of digitonin to permeabilize the plasma membrane of Trypanosoma brucei procyclic and bloodstream trypomastigotes allowed the identification of a non-mitochondrial nigericin-sensitive Ca2+ compartment. The proton ionophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) was able to cause Ca2+ release from this compartment, which was also sensitive to sodium orthovanadate. Preincubation of the cells with the vacuolar H(+)-ATPase inhibitor bafilomycin A1 greatly reduced the nigericin-sensitive Ca2+ compartment. Bafilomycin A1 inhibited the initial rate of ATP-dependent non-mitochondrial Ca2+ uptake and stimulated the initial rate of nigericin-induced Ca2+ release by permeabilized procyclic trypomastigotes. ATP-dependent and bafilomycin A1- and 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl)-sensitive Acridine Orange uptake was demonstrated in permeabilized cells. Under these conditions Acridine Orange was concentrated in abundant cytoplasmic round vacuoles by a process inhibited by bafilomycin A1, NBD-Cl, nigericin, and Ca2+. Vanadate or EGTA significantly increased Acridine Orange uptake, while Ca2+ released Acridine Orange from these preparations, thus suggesting that the dye and Ca2+ were being accumulated in the same acidic vacuole. Acridine Orange uptake was reversed by nigericin, bafilomycin A1 and NH4Cl. The results are consistent with the presence of a Ca2+/H(+)-ATPase system pumping Ca2+ into an acidic vacuole, that we tentatively named the acidocalcisome. Images Figure 5 PMID:7998937

  13. High/variable mixture ratio O2/H2 engine

    NASA Technical Reports Server (NTRS)

    Adams, A.; Parsley, R. C.

    1988-01-01

    Vehicle/engine analysis studies have identified the High/Dual Mixture Ratio O2/H2 Engine cycle as a leading candidate for an advanced Single Stage to Orbit (SSTO) propulsion system. This cycle is designed to allow operation at a higher than normal O/F ratio of 12 during liftoff and then transition to a more optimum O/F ratio of 6 at altitude. While operation at high mixture ratios lowers specific impulse, the resultant high propellant bulk density and high power density combine to minimize the influence of atmospheric drag and low altitude gravitational forces. Transition to a lower mixture ratio at altitude then provides improved specific impulse relative to a single mixture ratio engine that must select a mixture ratio that is balanced for both low and high altitude operation. This combination of increased altitude specific impulse and high propellant bulk density more than offsets the compromised low altitude performance and results in an overall mission benefit. Two areas of technical concern relative to the execution of this dual mixture ratio cycle concept are addressed. First, actions required to transition from high to low mixture ratio are examined, including an assessment of the main chamber environment as the main chamber mixture ratio passes through stoichiometric. Secondly, two approaches to meet a requirement for high turbine power at high mixture ratio condition are examined. One approach uses high turbine temperature to produce the power and requires cooled turbines. The other approach incorporates an oxidizer-rich preburner to increase turbine work capability via increased turbine mass flow.

  14. 2H NMR studies of glycerol dynamics in protein matrices.

    PubMed

    Herbers, C R; Sauer, D; Vogel, M

    2012-03-28

    We use (2)H NMR spectroscopy to investigate the rotational motion of glycerol molecules in matrices provided by the connective tissue proteins elastin and collagen. Analyzing spin-lattice relaxation, line-shape properties, and stimulated-echo decays, we determine the rates and geometries of the motion as a function of temperature and composition. It is found that embedding glycerol in an elastin matrix leads to a mild slowdown of glycerol reorientation at low temperatures and glycerol concentrations, while the effect vanishes at ambient temperatures or high solvent content. Furthermore, it is observed that the nonexponential character of the rotational correlation functions is much more prominent in the elastin matrix than in the bulk liquid. Results from spin-lattice relaxation and line shape measurements indicate that, in the mixed systems, the strong nonexponentiality is in large part due to the existence of distributions of correlation times, which are broader on the long-time flank and, hence, more symmetric than in the neat system. Stimulated-echo analysis of slow glycerol dynamics reveals that, when elastin is added, the mechanism for the reorientation crosses over from small-angle jump dynamics to large-angle jump dynamics and the geometry of the motion changes from isotropic to anisotropic. The results are discussed against the background of present and previous findings for glycerol and water dynamics in various protein matrices and compared with observations for other dynamically highly asymmetric mixtures so as to ascertain in which way the viscous freezing of a fast component in the matrix of a slow component differs from the glassy slowdown in neat supercooled liquids.

  15. 2H NMR studies of glycerol dynamics in protein matrices

    NASA Astrophysics Data System (ADS)

    Herbers, C. R.; Sauer, D.; Vogel, M.

    2012-03-01

    We use 2H NMR spectroscopy to investigate the rotational motion of glycerol molecules in matrices provided by the connective tissue proteins elastin and collagen. Analyzing spin-lattice relaxation, line-shape properties, and stimulated-echo decays, we determine the rates and geometries of the motion as a function of temperature and composition. It is found that embedding glycerol in an elastin matrix leads to a mild slowdown of glycerol reorientation at low temperatures and glycerol concentrations, while the effect vanishes at ambient temperatures or high solvent content. Furthermore, it is observed that the nonexponential character of the rotational correlation functions is much more prominent in the elastin matrix than in the bulk liquid. Results from spin-lattice relaxation and line shape measurements indicate that, in the mixed systems, the strong nonexponentiality is in large part due to the existence of distributions of correlation times, which are broader on the long-time flank and, hence, more symmetric than in the neat system. Stimulated-echo analysis of slow glycerol dynamics reveals that, when elastin is added, the mechanism for the reorientation crosses over from small-angle jump dynamics to large-angle jump dynamics and the geometry of the motion changes from isotropic to anisotropic. The results are discussed against the background of present and previous findings for glycerol and water dynamics in various protein matrices and compared with observations for other dynamically highly asymmetric mixtures so as to ascertain in which way the viscous freezing of a fast component in the matrix of a slow component differs from the glassy slowdown in neat supercooled liquids.

  16. Ion-neutral reaction of the C2H2N+ cation with C2H2: An experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Fathi, P.; Geppert, W. D.; Kaiser, A.; Ascenzi, D.

    2016-03-01

    The ion-neutral reactions of the C2H2N+ cation with C2H2 have been investigated using a Guided Ion Beam Mass Spectrometer (GIB-MS). The following ionic products were observed: CH3+, C2H2+, C2H3+, HNC+ /HCN+ , HCNH+, C3H+ , C2N+ , C3H3+, HCCN+ and C4H2N+ . Theoretical calculations have been carried out to propose reaction pathways leading to the observed products. These processes are of relevance for the generation of long chain nitrogen-containing species and they may be of interest for the chemistry of Titan's ionosphere or circumstellar envelopes.

  17. Synthesis, antimicrobial activity and QSAR studies of new 2,3-disubstituted-3,3a,4,5,6,7-hexahydro-2H-indazoles.

    PubMed

    Minu, Maninder; Thangadurai, Ananda; Wakode, Sharad Ramesh; Agrawal, Shyam Sundar; Narasimhan, Balasubramanian

    2009-06-01

    Antimicrobial activity of synthesized 2,3-disubstituted-3,3a,4,5,6,7-hexahydro-2H-indazole derivatives indicated that 3-(4-chlorophenyl)-2-(4-nitrophenylsulfonyl)-3,3a,4,5,6,7-hexahydro-2H-indazole (6) and 3-(4-fluorophenyl)-2-(4-nitrophenylsulfonyl)-3,3a,4,5,6,7-hexahydro-2H-indazole (20) were the most active compounds. Further, the results of QSAR studies indicated the importance of topological parameters (2)chi and (2)chi(v) in defining the antimicrobial activity of hexahydroindazoles.

  18. Herman-Wallis factors in the C2H2nu5 infrared fundamental near 14 microns

    NASA Technical Reports Server (NTRS)

    Maguire, William C.; Hillman, John J.; Weber, Mark; Blass, William E.

    1991-01-01

    The presence of acetylene has been confirmed for some time in the atmospheres of the outer planets Jupiter, Saturn, Neptune, and Saturn's satellite Titan. For these atmospheres, the determination of C2H2 abundances using its strong nu5 fundamental requires laboratory line position and intensity measurements. The 1-m Fourier transform spectrometer at McMath solar telescope of Kitt Peak National Observatory was used to measure C2H2 at an unapodized spectral resolution of 0.0025/cm. Synthetic spectra are generated by convolving a Voigt line shape with an instrument function and varying intensity parameters by means of a nonlinear least squares technique. Intensities of 37 nu5 lines spanning P18 through R20 were measured using 0.123 torr of gas in a 1-cm cell. A Herman-Wallis intensity correction parameter of 1.3(4) x 10 to the -3rd has been derived using a least squares linear fit.

  19. The FORMAMIDE_2-H_2O Complex: Structure and Hydrogen Bond Cooperative Effects

    NASA Astrophysics Data System (ADS)

    Blanco, Susana; Pinacho, Pablo; Lopez, Juan Carlos

    2016-06-01

    The adduct formamide_2-H_20 has been detected in a supersonic expansion and its rotational spectra in the 5-13 GHz frequency region characterized by narrow-band molecular beam Fourier transform microwave spectroscopy (MB-FTMW). The spectrum shows the hyperfine structure due to the presence of two 14N-nuclei. This hyperfine structure has been analyzed and the determined quadrupole coupling constants together with the rotational constants have been a key for the identification of the adduct structure on the light of ab initio computations. The rotational parameters are consistent with the formation of a three body cycle thanks to the double proton acceptor/proton donor character of both formamide and water. The low value of the planar moment of inertia Pcc indicates that the heavy atom skeleton of the cluster is essentially planar. A detailed analysis of the results reveals the subtle effects of hydrogen bond cooperative effects in this system.

  20. High-resolution vibrational and rotational spectroscopy of CD2H+ in a cryogenic ion trap

    NASA Astrophysics Data System (ADS)

    Jusko, Pavol; Stoffels, Alexander; Thorwirth, Sven; Brünken, Sandra; Schlemmer, Stephan; Asvany, Oskar

    2017-02-01

    The low-lying rotational states (J = 0, … , 5) of CD2H+ have been probed by high-resolution ro-vibrational and pure rotational spectroscopy, applying several action spectroscopic methods in a cryogenic 22-pole ion trap. For this, the ν1 ro-vibrational band has been revisited, detecting 108 transitions, among which 36 are new. The use of a frequency comb system allowed us to measure the ro-vibrational transitions with high precision and accuracy, typically better than 1 MHz. The high precision has been confirmed by comparing equal combination differences in the ground and excited state. Moreover, precise predictions of pure rotational transitions were possible for the ground state. Twenty-five rotational transitions have been detected directly by a novel IR-mm-wave double resonance method, giving rise to highly accurate ground state spectroscopic parameters.

  1. Rotational Spectroscopy of Vibrationally Excited N_2H^+ and N_2D^+ up to 2 Thz

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Pearson, John; Drouin, Brian; Crawford, Timothy J.; Daly, Adam M.; Elliott, Ben; Amano, Takayoshi

    2015-06-01

    Terahertz absorption spectroscopy was employed to extend the measurements on the pure rotational transitions of N_2H^+, N_2D^+ and their 15N-containing isotopologues in the ground state and first excited vibrational states for the three fundamental vibrational modes. In total 88 new pure rotational transitions were observed in the range of 0.7--2.0~THz. The observed transition frequencies were fit to experimental accuracy, and the improved molecular parameters were obtained. The new measurements and predictions will support the analysis of high-resolution astronomical observations made with facilities such as SOFIA and ALMA where laboratory rest frequencies with uncertainties of 1 MHz or smaller are required for proper analysis of velocity resolved astrophysical components.

  2. An ignored but most favorable channel for NCO +C2H2 reaction

    NASA Astrophysics Data System (ADS)

    Xie, Hong-bin; Wang, Jian; Zhang, Shao-wen; Ding, Yi-hong; Sun, Chia-chung

    2006-09-01

    The NCO +C2H2 reaction has been considered as a prototype for understanding the chemical reactivity of the isocyanate radical towards unsaturated hydrocarbons in fuel-rich combustion. It has also been proposed to provide an effective route for formation of oxazole-containing compounds in organic synthesis, and might have potential applications in interstellar processes. Unfortunately, this reaction has met mechanistic controversy both between experiments and between experiments and theoretical calculations. In this paper, detailed theoretical investigations at the Becke's three parameter Lee-Yang-Parr-B3LYP /6-31G(d), B3LYP /6-311++G(d,p), quadratic configuration interaction with single and double excitations QCISD /6-31G(d), and Gaussian-3 levels are performed for the NCO +C2H2 reaction, covering various entrance, isomerization, and decomposition channels. Also, the highly cost-expensive coupled-cluster theory including single and double excitations and perturbative inclusion of triple excitations CCSD(T)/aug-cc-pVTZ single-point energy calculation is performed for the geometries obtained at the Becke's three parameter Lee-Yang-Parr-B3LYP /6-311++G(d,p) level. A previously ignored yet most favorable channel via a four-membered ring intermediate with allyl radical character is found. However, formation of P3 H +HCCNCO and the five-membered ring channel predicted by previous experimental and theoretical studies is kinetically much less competitive. With the new channel, master equation rate constant calculations over a wide range of temperatures (298-1500K) and pressures (10-560Torr) show that the predicted total rate constants exhibit a positive-temperature dependence and no distinct pressure dependence effect. This is in qualitative agreement with available experimental results. Under the experimental conditions, the predicted values are about 50% lower than the latest experimental results. Also, the branching ratio variations of the fragments P2 HCN +HCCO and P5

  3. Remarkably efficient synthesis of 2H-indazole 1-oxides and 2H-indazoles via tandem carbon-carbon followed by nitrogen-nitrogen bond formation.

    PubMed

    Bouillon, Isabelle; Zajícek, Jaroslav; Pudelová, Nadĕzda; Krchnák, Viktor

    2008-11-21

    Base-catalyzed tandem carbon-carbon followed by nitrogen-nitrogen bond formations quantitatively converted N-alkyl-2-nitro-N-(2-oxo-2-aryl-ethyl)-benzenesulfonamides to 2H-indazoles 1-oxides under mild conditions. Triphenylphosphine or mesyl chloride/triethylamine-mediated deoxygenation afforded 2H-indazoles.

  4. ANALYTICAL FORMULAE OF MOLECULAR ION ABUNDANCES AND THE N{sub 2}H{sup +} RING IN PROTOPLANETARY DISKS

    SciTech Connect

    Aikawa, Yuri; Furuya, Kenji; Nomura, Hideko; Qi, Chunhua

    2015-07-10

    We investigate the chemistry of ion molecules in protoplanetary disks, motivated by the detection of the N{sub 2}H{sup +} ring around TW Hya. While the ring inner radius coincides with the CO snow line, it is not apparent why N{sub 2}H{sup +} is abundant outside the CO snow line in spite of the similar sublimation temperatures of CO and N{sub 2}. Using the full gas-grain network model, we reproduced the N{sub 2}H{sup +} ring in a disk model with millimeter grains. The chemical conversion of CO and N{sub 2} to less volatile species (sink effect hereinafter) is found to affect the N{sub 2}H{sup +} distribution. Since the efficiency of the sink depends on various parameters such as activation barriers of grain-surface reactions, which are not well constrained, we also constructed the no-sink model; the total (gas and ice) CO and N{sub 2} abundances are set constant, and their gaseous abundances are given by the balance between adsorption and desorption. Abundances of molecular ions in the no-sink model are calculated by analytical formulae, which are derived by analyzing the full-network model. The N{sub 2}H{sup +} ring is reproduced by the no-sink model, as well. The 2D (R-Z) distribution of N{sub 2}H{sup +}, however, is different among the full-network model and no-sink model. The column density of N{sub 2}H{sup +} in the no-sink model depends sensitively on the desorption rate of CO and N{sub 2} and the cosmic-ray flux. We also found that N{sub 2}H{sup +} abundance can peak at the temperature slightly below the CO sublimation, even if the desorption energies of CO and N{sub 2} are the same.

  5. Ab initio and RRKM calculations for multichannel rate constants of the C{sub 2}H{sub 3}+O{sub 2} reaction

    SciTech Connect

    Mebel, A.M.; Diau, E.W.G.; Lin, M.C.; Morokuma, K.

    1996-10-09

    A potential energy surface for the reaction of vinyl radical with molecular oxygen has been studied using the ab initio G2M(RCC, MP2) method. The most favorable reaction pathway leading to the major CHO+CH{sub 2}O products is described. The C{sub 2}H{sub 3}O+O products can be formed by elimination of the oxygen atom from C{sub 2}H{sub 3}OO via TS 23, which is by 7.8 kcal/mol lower in energy than the reactants, but by 6.5 kcal/mol higher than TS 9`. The hydrogen migration in 1` gives rise to another significant product channel: C{sub 2}H{sub 3}+O{sub 2} {yields} 1` {yields} TS 25` {yields} C{sub 2}H{sub 2}+O{sub 2}H, with TS 25` lying below C{sub 2}H{sub 3}+O{sub 2} by 3.5 kcal/mol. Multichannel RRKM calculations have been carried out for the total and individual rate constants for various channels using the G2M(RCC, MP2) energetics and molecular parameters of the intermediates and transition states. The computed low pressure reaction rate constant is in quantitative agreement with experiment. At atmospheric pressure, the title reaction is dominated by the stabilization of vinylperoxy radical C{sub 2}H{sub 3}OO at room temperature. In the 500-900 K temperature range, the CHO+CH{sub 2}O channel has the highest rate constant, and at T >= 900 K, C{sub 2}H{sub 3}O+O are the major products. At very high temperatures, the channel producing C{sub 2}H{sub 2} + O{sub 2}H becomes competitive. 15 refs., 3 figs., 4 tabs.

  6. A theoretical study of the CH[sub 3]+C[sub 2]H[sub 2] reaction

    SciTech Connect

    Diau, E.W.; Lin, M.C. ); Melius, C.F. )

    1994-09-01

    The rate constants for the formation of various products in the CH[sub 3]+C[sub 2]H[sub 2] reaction have been computed by multichannel RRKM calculations using the molecular and transition-state parameters predicted by the BAC-MP4 method. The results of the calculations agree quantitatively with experimental data obtained under varying conditions: [ital T]=300--2200 K, [ital P]=30--2500 Torr. At low temperatures ([ital T][lt]1300 K), the CH[sub 3]+C[sub 2]H[sub 2] reaction is dominated by the addition-stabilization process producing CH[sub 3]C[sub 2]H[sub 2]. Under high-temperature ([ital T][gt]1400 K) and atmospheric-pressure conditions, the reaction occurs primarily by the CH[sub 3]-for-H displacement process producing CH[sub 3]C[sub 2]H, a likely source of the C[sub 3]H[sub 3] radical (which has recently been shown to be a key precursor of C[sub 6]H[sub 6] in hydrocarbon combustion reactions).

  7. Measurements of intracellular volumes by 59Co and 2H/1H NMR and their physiological applications.

    PubMed

    Askenasy, Nadir; Navon, Gil

    2005-04-01

    Determination of the intracellular water volumes using NMR spectroscopy was performed using the NMR-visible nuclei: 59Co and 2H or 1H. Accurate measurement of intracellular water in cell suspensions and perfused organs is an important physiological parameter in the context of electrolyte homeostasis and energy metabolism, in particular when these parameters are monitored by non-invasive NMR spectroscopy. Furthermore, repeated or continuous monitoring of intracellular water provided significant insights into the physiology of cardiac muscle and sarcolemmal membrane permeability and integrity.

  8. Part I. Analyzing the distribution of gas law questions in chemistry textbooks. Part II. Chlorine-35 NQR spectra of group 1 and silver dichloromethanesulfonates

    NASA Astrophysics Data System (ADS)

    Gillette, Gabriel

    Part I. Two studies involving the gas law questions in eight high school and Advanced Placement/college chemistry textbooks were performed using loglinear analysis to look for associations among six variables. These variables included Bloom's Taxonomy (higher-order, lower-order), Book Type (high school, college), Question Format (multiple-choice, problem, short answer), Question Placement (in-chapter, end-of-chapter, test bank), Representation (macroscopic, microscopic, symbolic), and Arkansas Science Standard (conceptual, mathematical; gas laws, pressure conversion, stoichiometry). The first study, involving the conceptual gas law questions, found the Book Type and Question Placement variables had the biggest impact, each appearing in 5 of the 11 significant associations. The second study, involving the mathematical gas law questions, found the Question Placement had the biggest impact, appearing in 7 of the 11 significant associations, followed by Book Type and the Arkansas Science Standard variables, which appeared in 5 of the 11 significant associations. These studies showed that compared to the high school books, college books have fewer multiple-choice questions (compared to short-answer and problem questions), fewer in-chapter questions (compared to end-of-chapter and test bank questions), fewer questions in the chapters and more questions at the end of the chapters and fewer multiple-choice questions in and at the end of the books and more multiple-choice questions in the test banks. Part II. The dichloromethanesulfonate salts of several +1 charged cations, M+Cl2CHSO3 - (M = Li, Na, K, Rb Ag, Cs Tl) were synthesized and studied by 35Cl nuclear quadrupole resonance (NQR). Dichloromethanesulfonic acid was prepared by the methanolysis of dichloromethanesulfonyl chloride, which was neutralized with the metal carbonates to produce the corresponding metal dichloromethanesulfonate salts. This study completed the NQR investigation of the family of chloroacetates

  9. Production of C2H4Cl+ by dissociative photoionization of weak molecular complexes in C2H4 + HCl mixtures

    NASA Astrophysics Data System (ADS)

    Walters, E. A.; Grover, J. R.; Arneberg, D. L.; Santandrea, C. J.; White, M. G.

    1990-12-01

    The photoionization efficiency (PIE) spectrum from 600 to 1200 Å for the production of the ion C2H4Cl+ by dissociative photoionization of the products of room-temperature jet expansions of a 1:4 mixture of C2H4 and HCl was measured at several nozzle pressures. The results were resolved into the PIE yield curve for the heterodimer process C2H4·HCl+ hv→C2H4Cl++H+ e. This reaction is necessarily characterized by a large change in geometry between neutral complex and ionic product. The observed spectrum exhibits an unusual and conspicuous peak at 15.2 eV that is characterized by a sharp cutoff to the high energy side. This feature points to the onset of strongly nonstatistical channels for the production of C2H4Cl+ at this energy such that product formation proceeds through very few states. The observed onset of C2H4Cl+ at 11.92±0.24 eV is 17±6 kcal mol-1 above the true threshold. An important conclusion is that at all energies above the onset the yield of dissociative ionization of the heterodimer to the cation C2H4Cl+ is determined by dynamical factors.

  10. Systematic Variations in CO2/H2O Ice Abundance Ratios in Nearby Galaxies Found with AKARI Near-infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamagishi, M.; Kaneda, H.; Ishihara, D.; Oyabu, S.; Onaka, T.; Shimonishi, T.; Suzuki, T.

    2015-07-01

    We report CO2/H2O ice abundance ratios in seven nearby star-forming galaxies based on the AKARI near-infrared (2.5-5.0 μm) spectra. The CO2/H2O ice abundance ratios show clear variations between 0.05 and 0.2 with the averaged value of 0.14 ± 0.01. The previous study on M82 revealed that the CO2/H2O ice abundance ratios strongly correlate with the intensity ratios of the hydrogen recombination Brα line to the polycyclic aromatic hydrocarbon (PAH) 3.3 μm feature. In the present study, however, we find no correlation for the seven galaxies as a whole due to systematic differences in the relation between CO2/H2O ice abundance and Brα/PAH 3.3 μm intensity ratios from galaxy to galaxy. This result suggests that there is another parameter that determines the CO2/H2O ice abundance ratios in a galaxy in addition to the Brα/PAH 3.3 μm ratios. We find that the CO2/H2O ice abundance ratios positively correlate with the specific star formation rates of the galaxies. From these results, we conclude that CO2/H2O ice abundance ratios tend to be high in young star-forming galaxies.

  11. Synthesis of (R)-[2-2H]isopentenyl diphosphate and determination of its enantiopurity by 2H NMR spectroscopy in a lyotropic medium.

    PubMed

    Leyes, A E; Poulter, C D

    1999-10-07

    [formula: see text] The synthesis of (R)-[2-2H]isopentenyl diphosphate from D-mannitol 1,2:5,6-bis-acetonide in 10 steps is reported. Stereospecific incorporation of the label is achieved by a BF3-catalyzed NaCNBD3 reduction of the enantiomerically pure (S)-isopropylidene oxirane intermediate. The enantiomeric excess of the penultimate precursor [2-2H]isopentenyl tosylate (> 95% ee) was determined by 2H NMR spectroscopy in a poly-gamma-benzyl-L-glutamate/CH2Cl2 liquid crystal at -50 degrees C.

  12. Environmental, trophic, and ecological factors influencing bone collagen δ2H

    NASA Astrophysics Data System (ADS)

    Topalov, Katarina; Schimmelmann, Arndt; David Polly, P.; Sauer, Peter E.; Lowry, Mark

    2013-06-01

    Organic deuterium/hydrogen stable isotope ratios (i.e., 2H/1H, expressed as δ2H value in ‰) in animal tissues are related to the 2H/1H in diet and ingested water. Bone collagen preserves the biochemical 2H/1H isotopic signal in the δ2H value of collagen's non-exchangeable hydrogen. Therefore, δ2H preserved in bone collagen has the potential to constrain environmental and trophic conditions, which is of interest to researchers studying of both living and fossil vertebrates. Our data examine the relationship of δ2H values of collagen with geographic variation in δ2H of meteoric waters, with local variations in the ecology and trophic level of species, and with the transition from mother's milk to adult diet. Based on 97 individuals from 22 marine and terrestrial vertebrates (predominately mammals), we found the relationships of collagen δ2H to both geographic variation in meteoric water δ2H (R2 = 0.55) and to δ15N in bone collagen (R2 = 0.17) statistically significant but weaker than previously reported. The second strongest control on collagen δ2H in our data is dietary, with nearly 50 percent of the variance in δ2H explained by trophic level (R2 = 0.47). Trophic level effects potentially confound the local meteoric signal if not held constant: herbivores tend to have the lowest δ2H values, omnivores have intermediate ones, and carnivores have the highest values. Body size (most likely related to mass-specific metabolic rates) has a strong influence on collagen δ2H (R2 = 0.30), by causing greater sensitivity in smaller animals to seasonal climate variations and/or high evapotranspiration leading to 2H-enrichment in tissues. In marine mammals weaning produces a dramatic effect on collagen δ2H with adult values being universally higher than pup values (R2 = 0.79). Interestingly, the shift in δ15N at weaning is downward, even though normally hydrogen and nitrogen isotope ratios are positively correlated with one another in respect to trophic level. Our

  13. Dehydrocoupling of dimethylamine borane catalyzed by Rh(PCy3)2H2Cl.

    PubMed

    Sewell, Laura J; Huertos, Miguel A; Dickinson, Molly E; Weller, Andrew S; Lloyd-Jones, Guy C

    2013-04-15

    The Rh(III) species Rh(PCy3)2H2Cl is an effective catalyst (2 mol %, 298 K) for the dehydrogenation of H3B·NMe2H (0.072 M in 1,2-F2C6H4 solvent) to ultimately afford the dimeric aminoborane [H2BNMe2]2. Mechanistic studies on the early stages in the consumption of H3B·NMe2H, using initial rate and H/D exchange experiments, indicate possible dehydrogenation mechanisms that invoke turnover-limiting N-H activation, which either precedes or follows B-H activation, to form H2B═NMe2, which then dimerizes to give [H2BNMe2]2. An additional detail is that the active catalyst Rh(PCy3)2H2Cl is in rapid equilibrium with an inactive dimeric species, [Rh(PCy3)H2Cl]2. The reaction of Rh(PCy3)2H2Cl with [Rh(PCy3)H2(H2)2][BAr(F)4] forms the halide-bridged adduct [Rh(PCy3)2H2(μ-Cl)H2(PCy3)2Rh][BAr(F)4] (Ar(F) = 3,5-(CF3)2C6H3), which has been crystallographically characterized. This dinuclear cation dissociates on addition of H3B·NMe2H to re-form Rh(PCy3)2H2Cl and generate [Rh(PCy3)2H2(η(2)-H3B·NMe2H)][BAr(F)4]. The fate of the catalyst at low catalyst loadings (0.5 mol %) is also addressed, with the formation of an inactive borohydride species, Rh(PCy3)2H2(η(2)-H2BH2), observed. On addition of H3B·NMe2H to Ir(PCy3)2H2Cl, the Ir congener Ir(PCy3)2H2(η(2)-H2BH2) is formed, with concomitant generation of the salt [H2B(NMe2H)2]Cl.

  14. Terahertz Spectroscopy of the Bending Vibrations of Acetylene 12C2H2 and 12C2D2

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Drouin, B.; Pearson, J.

    2009-12-01

    Several fundamental interstellar molecules, e.g., C2H2, CH4 and C3, are completely symmetric molecules and feature no permanent dipole moment and no pure rotation spectrum. As a result they have only previously been observed in the infrared. However, directly observing them with the rest of the molecular column especially when the source is spatially resolved would be very valuable in understanding chemical evolution. Vibrational difference bands provide a means to detect symmetric molecules with microwave precision using terahertz techniques. Herschel, SOFIA and ALMA have the potential to identify a number of vibrational difference bands of light symmetric species. This paper reports laboratory results on 12C2H2 and 12C2D2. Symmetric acetylene isotopologues have two bending modes, the trans bending and the cis bending. Their difference bands are allowed and occur in the microwave, terahertz, and far-infrared wavelengths, with band origins at 3500 GHz for 12C2H2 and 900 GHz for 12C2D2. Twenty 12C2H2 P branch high-J transitions and two hundred and fifty-one 12C2D2 P Q and R branch transitions have been measured in the 0.2 - 1.6 THz region with precision of 50 to 100 kHz. These lines were modeled together with prior data on the pure bending levels. Significantly improved molecular parameters were obtained for 12C2H2 and 12C2D2 with the combined data set, and new frequency and intensity predictions were made to support astrophysics applications. The research was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. S. Y. was supported by an appointment to the NASA Postdoctoral Program, administrated by Oak Ridge Associated Universities through a contract with NASA.

  15. Solubilization and Reconstitution of the Mg2+/2H+ Antiporter of the Lutoid Tonoplast from Hevea brasiliensis Latex.

    PubMed Central

    Amalou, Z.; Gibrat, R.; Trouslot, P.; D'Auzac, J.

    1994-01-01

    The Mg2+/2H+ antiporter recently described on lutoid membrane (Z. Amalou, R. Gibrat, C. Brugidou, P. Trouslot, J.d'Auzac [1992] Plant Physiol 100: 255-260) was solubilized by octylglucoside and reconstituted into soybean liposomes using the detergent dilution method. Magnesium efflux or influx experiments were used to generate a H+ influx or efflux, respectively, monitored with the fluorescent probe 9-amino-6-chloro-2-methoxyacridine. Both experiments gave saturable H+ fluxes as a function of internal or external Mg2+ concentrations with similar kinetic parameters Km and Vmax. The Km value for Mg2+ (about 2 mM) was identical to that previously found in lyophilized-resuspended lutoid (reference therein), whereas the Vmax value was 14-fold higher. Since only 10% of the initial proteins were recovered in proteoliposomes, and electrophoretic patterns of the two kinds of vesicles differed significantly, it was inferred that the increase in Vmax was due essentially to an enrichment of the protein antiporter in the reconstituted fraction, owing to a selective effect of octylglucoside at both solubilization and reconstitution steps. None of the various divalent cations used could dissipate the pH gradient of control liposomes of soybean lipids, unless the divalent/H+ exchanger A23187 was added, whereas a rapid dissipation of the pH gradient was observed with reconstituted proteoliposomes from lutoid proteins, with the cation selectivity sequence Zn2+ > Cd2+ > Mg2+ in the millimolar concentration range. The divalent ions Ca2+, Ba2+, and Mn2+ were incapable of generating a H+ efflux in reconstituted proteoliposomes, whereas both Mg2+/H+ and Ca2+/H+ exchanges were observed in lyophilized-resuspended lutoids. Therefore, the lutoid membrane seems to contain separate Mg2+/H+ and Ca2+/H transport systems, the latter being eliminated during the solubilization/reconstitution of lutoid membrane proteins. PMID:12232305

  16. Raftlike Mixtures of Sphingomyelin and Cholesterol Investigated by Solid-State 2H NMR Spectroscopy

    PubMed Central

    Bartels, Tim; Lankalapalli, Ravi S.; Bittman, Robert; Beyer, Klaus; Brown, Michael F.

    2009-01-01

    Sphingomyelin is a lipid that is abundant in the nervous systems of mammals, where it is associated with putative microdomains in cellular membranes and undergoes alterations due to aging or neurodegeneration. We investigated the effect of varying the concentration of cholesterol in binary and ternary mixtures with N-palmitoylsphingomyelin (PSM) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) using deuterium nuclear magnetic resonance (2H NMR) spectroscopy in both macroscopically aligned and unoriented multilamellar dispersions. In our experiments, we used PSM and POPC perdeuterated on the N-acyl and sn-1 acyl chains, respectively. By measuring solid-state 2H NMR spectra of the two lipids separately in mixtures with the same compositions as a function of cholesterol mole fraction and temperature, we obtained clear evidence for the coexistence of two liquid-crystalline domains in distinct regions of the phase diagram. According to our analysis of the first moments M1 and the observed 2H NMR spectra, one of the domains appears to be a liquid-ordered phase. We applied a mean-torque potential model as an additional tool to calculate the average hydrocarbon thickness, the area per lipid, and structural parameters such as chain extension and thermal expansion coefficient in order to further define the two coexisting phases. Our data imply that phase separation takes place in raftlike ternary PSM/POPC/cholesterol mixtures over a broad temperature range but vanishes at cholesterol concentrations equal to or greater than a mole fraction of 0.33. Cholesterol interacts preferentially with sphingomyelin only at smaller mole fractions, above which a homogeneous liquid-ordered phase is present. The reasons for these phase separation phenomena seem to be differences in the effects of cholesterol on the configurational order of the palmitoyl chains in PSM-d31 and POPC-d31 and a difference in the affinity of cholesterol for sphingomyelin observed at low temperatures

  17. Probing the aromaticity of the [(HtAc)3(μ2-H)6], [(HtTh)3(μ2-H)6],+, and [(HtPa)3(μ2-H)6] clusters

    NASA Astrophysics Data System (ADS)

    Ramírez-Tagle, Rodrigo; Alvarado-Soto, Leonor; Arratia-Perez, Ramiro; Bast, Radovan; Alvarez-Thon, Luis

    2011-09-01

    In this study we report about the aromaticity of the prototypical [(HtAc)3(μ2-H)6], [(HtTh)3(μ2-H)6]+, and [(HtPa)3(μ2-H)6] clusters via two magnetic criteria: nucleus-independent chemical shifts (NICS) and the magnetically induced current density. All-electron density functional theory calculations were carried out using the two-component zeroth-order regular approach and the four-component Dirac-Coulomb Hamiltonian, including scalar and spin-orbit relativistic effects. Four-component current density maps and the integration of induced ring-current susceptibilities clearly show that the clusters [(HtAc)3(μ2-H)6] and [(HtTh)3(μ2-H)6]+ are non-aromatic whereas [(HtPa)3(μ2-H)6] is anti-aromatic. However, for the thorium cluster we find a discrepancy between the current density plots and the classification through the NICS index. Our results also demonstrate the increasing influence of f orbitals, on bonding and magnetic properties, with increasing atomic number in these clusters. We think that the enhanced electron mobility in [(HtPa)3(μ2-H)6] is due the significant 5f character of its valence shell. Also the participation of f orbitals in bonding is the reason why the protactinium cluster has the shortest bond lengths of the three clusters. This study provides another example showing that the magnetically induced current density approach can give more reliable results than the NICS index.

  18. Probing the aromaticity of the [(H(t)Ac)3(μ2-H)6], [(H(t)Th)3(μ2-H)6],(+), and [(H(t)Pa)3(μ2-H)6] clusters.

    PubMed

    Ramírez-Tagle, Rodrigo; Alvarado-Soto, Leonor; Arratia-Perez, Ramiro; Bast, Radovan; Alvarez-Thon, Luis

    2011-09-14

    In this study we report about the aromaticity of the prototypical [(H(t)Ac)(3)(μ(2)-H)(6)], [(H(t)Th)(3)(μ(2)-H)(6)](+), and [(H(t)Pa)(3)(μ(2)-H)(6)] clusters via two magnetic criteria: nucleus-independent chemical shifts (NICS) and the magnetically induced current density. All-electron density functional theory calculations were carried out using the two-component zeroth-order regular approach and the four-component Dirac-Coulomb Hamiltonian, including scalar and spin-orbit relativistic effects. Four-component current density maps and the integration of induced ring-current susceptibilities clearly show that the clusters [(H(t)Ac)(3)(μ(2)-H)(6)] and [(H(t)Th)(3)(μ(2)-H)(6)](+) are non-aromatic whereas [(H(t)Pa)(3)(μ(2)-H)(6)] is anti-aromatic. However, for the thorium cluster we find a discrepancy between the current density plots and the classification through the NICS index. Our results also demonstrate the increasing influence of f orbitals, on bonding and magnetic properties, with increasing atomic number in these clusters. We think that the enhanced electron mobility in [(H(t)Pa)(3)(μ(2)-H)(6)] is due the significant 5f character of its valence shell. Also the participation of f orbitals in bonding is the reason why the protactinium cluster has the shortest bond lengths of the three clusters. This study provides another example showing that the magnetically induced current density approach can give more reliable results than the NICS index.

  19. Flexibility of Ras Lipid Modifications Studied by 2H Solid-State NMR and Molecular Dynamics Simulations

    PubMed Central

    Vogel, Alexander; Tan, Kui-Thong; Waldmann, Herbert; Feller, Scott E.; Brown, Michael F.; Huster, Daniel

    2007-01-01

    Human posttranslationally modified N-ras oncogenes are known to be implicated in numerous human cancers. Here, we applied a combination of experimental and computational techniques to determine structural and dynamical details of the lipid chain modifications of an N-ras heptapeptide in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes. Experimentally, 2H NMR spectroscopy was used to study oriented membranes that incorporated ras heptapeptides with two covalently attached perdeuterated hexadecyl chains. Atomistic molecular dynamics simulations of the same system were carried out over 100 ns including 60 DMPC and 4 ras molecules. Several structural and dynamical experimental parameters could be directly compared to the simulation. Experimental and simulated 2H NMR order parameters for the methylene groups of the ras lipid chains exhibited a systematic difference attributable to the absence of collective motions in the simulation and to geometrical effects. In contrast, experimental 2H NMR spin-lattice relaxation rates for Zeeman order were well reproduced in the simulation. The lack of slower collective motions in the simulation did not appreciably influence the relaxation rates at a Larmor frequency of 115.1 MHz. The experimental angular dependence of the 2H NMR relaxation rates with respect to the external magnetic field was also relatively well simulated. These relaxation rates showed a weak angular dependence, suggesting that the lipid modifications of ras are very flexible and highly mobile in agreement with the low order parameters. To quantify these results, the angular dependence of the 2H relaxation rates was calculated by an analytical model considering both molecular and collective motions. Peptide dynamics in the membrane could be modeled by an anisotropic diffusion tensor with principal values of D‖ = 2.1 × 109 s−1 and D⊥ = 4.5 × 105 s−1. A viscoelastic fitting parameter describing the membrane elasticity, viscosity, and temperature

  20. Suppression of electron correlations in the collapsed tetragonal phase of CaFe2As2 under ambient pressure demonstrated by As75 NMR/NQR measurements

    NASA Astrophysics Data System (ADS)

    Furukawa, Y.; Roy, B.; Ran, S.; Bud'ko, S. L.; Canfield, P. C.

    2014-03-01

    The static and the dynamic spin correlations in the low-temperature collapsed tetragonal and the high-temperature tetragonal phase in CaFe2As2 have been investigated by As75 nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements. Through the temperature (T) dependence of the nuclear spin lattice relaxation rates (1/T1) and the Knight shifts, although stripe-type antiferromagnetic (AFM) spin correlations are realized in the high-temperature tetragonal phase, no trace of the AFM spin correlations can be found in the nonsuperconducting, low-temperature, collapsed tetragonal (cT) phase. Given that there is no magnetic broadening in As75 NMR spectra, together with the T-independent behavior of magnetic susceptibility χ and the T dependence of 1/T1Tχ, we conclude that Fe spin correlations are completely quenched statically and dynamically in the nonsuperconducting cT phase in CaFe2As2.

  1. The Microwave Spectrum of the HCOOCD_2H Species of Methyl Formate

    NASA Astrophysics Data System (ADS)

    Coudert, L. H.; Huet, T. R.; Margulès, L.; Motiyenko, R.; Mollendal, H.

    2010-06-01

    Methyl formate is a non-rigid molecule displaying internal rotation of its methyl group. The microwave spectra of its normal and mono deuterated HCOOCH_2D species have already been studied and values for the tunneling splitting due to the internal rotation were determined. The normal species displays a 405 MHz A/E splitting, the mono deuterated one, a smaller 84.76 MHz A'/A'' splitting. For the bideuterated species HCOOCD_2H, the value of this splitting is not known as its microwave spectrum has not been studied yet. In this paper experimental and theoretical investigations of the microwave spectrum of HCOOCD_2H are presented. More than 9000 transitions were measured with a submillimeter wave spectrometer. About 20 lines were recorded with a molecular beam spectrometer. Like for the mono deuterated species,^c depending on the location of the only hydrogen atom of the methyl group, two configurations arise. The C_s-symmetry H-in plane configuration displays a rigid rotator spectrum and its data was analyzed using a Watson-type Hamiltonian. The C_1-symmetry H-out of plane configuration undergoes the large amplitude internal rotation. Its data was analyzed using the so called water dimer formalism which allowed us to accurately reproduce the observed frequencies and to obtain the value of the tunneling splitting as well as the parameters involved in its rotational dependence. The hyperfine structure due to quadrupole coupling at the two deuterium atoms was also analyzed. Unexpectedly, for the H-out of plane configuration, the observed hyperfine patterns are neither those expected for two equivalent deuterium atoms nor those of a rigid molecule. Ilyushin, Kryvda, and Alekseev, J. Mol. Spec. 255 (2009) 32. Margulès, Coudert, Mollendal, Guillemin, Huet, and Janeckovà, J. Mol. Spec. 254 (2009) 55. Hougen, J. Mol. Spec. 114 (1985) 395; and Coudert and Hougen, J. Mol. Spec. 130 (1988) 86.

  2. First Observation of the nu(17)-nu(4) Difference Bands of Diborane (10)B(2)H(6) and (11)B(2)H(6).

    PubMed

    Flaud; Lafferty; Bürger; Pawelke; Domenech; Bermejo

    2000-10-01

    An analysis of the nu(17)-nu(4) difference bands near 800 cm(-1) of two isotopic species, (10)B(2)H(6) and (11)B(2)H(6), of diborane has been carried out using infrared spectra recorded with a resolution of ca. 0.003 cm(-1). In addition, the nu(17) band of (10)B(2)H(6) has been recorded and assigned. Since this band in (11)B(2)H(6) had already been studied (R. L. Sams, T. A. Blake, S. W. Sharpe, J.-M. Flaud, and W. J. Lafferty, J. Mol. Spectrosc. 191, 331-342 (1998)), it was possible to derive precise energy levels and Hamiltonian constants for the 4(1) vibrational states of both isotopic species. Copyright 2000 Academic Press.

  3. First-principles studies of complex hydride YMn2H6 and its synthesis from metal hydride YMn2H4.5

    NASA Astrophysics Data System (ADS)

    Matsuo, Motoaki; Miwa, Kazutoshi; Semboshi, Satoshi; Li, Hai-Wen; Kano, Mika; Orimo, Shin-ichi

    2011-05-01

    First-principles calculations were performed for a complex hydride YMn2H6 to investigate its electronic structure and thermodynamic stability. The results indicated that an Y atom and one of two Mn atoms were ionized as Y3+ and Mn2+, respectively, and another Mn atom bound covalently to H atoms to form a [MnH6]5- complex anion. Based on the enthalpy change of -65 kJ/mol estimated from the calculation, we experimentally verified a possible low-pressure synthesis of YMn2H6 from a metal hydride YMn2H4.5. X-ray diffractometry confirmed the formation of YMn2H6 after hydrogenation below 5 MPa, much lower than the previously reported value of 170 MPa.

  4. Strong enhancement of superconductivity at high pressures within the charge-density-wave states of 2 H -TaS2 and 2 H -TaSe2

    NASA Astrophysics Data System (ADS)

    Freitas, D. C.; Rodière, P.; Osorio, M. R.; Navarro-Moratalla, E.; Nemes, N. M.; Tissen, V. G.; Cario, L.; Coronado, E.; García-Hernández, M.; Vieira, S.; Núñez-Regueiro, M.; Suderow, H.

    2016-05-01

    We present measurements of the superconducting and charge-density-wave (CDW) critical temperatures (Tc and TCDW) as a function of pressure in the transition metal dichalchogenides 2 H -TaSe2 and 2 H -TaS2 . Resistance and susceptibility measurements show that Tc increases from temperatures below 1 K up to 8.5 K at 9.5 GPa in 2 H -TaS2 and 8.2 K at 23 GPa in 2 H -TaSe2 . We observe a kink in the pressure dependence of TCDW at about 4 GPa that we attribute to the lock-in transition from incommensurate CDW to commensurate CDW. Above this pressure, the commensurate TCDW slowly decreases, coexisting with superconductivity within our full pressure range.

  5. Bis(ethylenediammonium) decaaquadisodium decavanadate, (C2H10N2)2[Na2(H2O)10][V10O28].

    PubMed

    Li, Guo Bao; Yang, Si Hai; Xiong, Ming; Lin, Jian Hua

    2004-12-01

    In the title compound, the decavanadate anion, [V(10)O(28)](6-), and the bridged [Na(2)(H(2)O)(10)](2+) dication lie across inversion centers. The charge balance is achieved by ethylenediammonium cations, H(3)NCH(2)CH(2)NH(3)(2+), which are disordered. The decavanadate anions are surrounded by the [Na(2)(H(2)O)(10)](2+) dications, thus forming layers, and the ethylenediammonium cations are located between these layers.

  6. C2H2 adsorption in three isostructural metal-organic frameworks: boosting C2H2 uptake by rational arrangement of nitrogen sites.

    PubMed

    Song, Chengling; Jiao, Jingjing; Lin, Qiyi; Liu, Huimin; He, Yabing

    2016-03-21

    Replacing the benzene spacer in the organic linker 5,5'-(benzene-1,4-diyl)diisophthalate with the nitrogen containing heterocyclic rings, namely, pyrazine, pyridazine, and pyrimidine results in three organic linkers, which were reacted with copper ions under solvothermal conditions to form three isostructural metal-organic frameworks (ZJNU-46, ZJNU-47 and ZJNU-48) exhibiting exceptionally high sorption capacities with regard to acetylene due to the simultaneous immobilization of open metal sites and Lewis basic nitrogen sites in the frameworks. At 1 atm and 295 K, the gravimetric C2H2 adsorption uptakes reach 187, 213 and 193 cm(3) (STP) g(-1) for these three compounds. The gravimetric C2H2 adsorption amount of ZJNU-47a is the second highest reported for MOF materials. Notably, despite their same porosities, and densities of open metal sites and uncoordinated nitrogen sites, distinctly different C2H2 adsorption capacities were observed for these three compounds, which we think are mainly associated with the difference in the relative position of nitrogen atoms leading to different binding affinities of the frameworks towards C2H2 guest molecules, and thus different C2H2 adsorptions. This work demonstrates that the rational arrangement of open nitrogen sites will favorably improve the C2H2 uptake and thus provides useful information for future design of porous MOFs with high acetylene storage capacities.

  7. Microwave Spectra and Geometries of C2H2\\cdots AuI and C2H4\\cdots AuI

    NASA Astrophysics Data System (ADS)

    Stephens, Susanna Louise; Mullaney, John Connor; Sprawling, Matt John; Tew, David Peter; Walker, Nick; Legon, Anthony

    2014-06-01

    A chirped-pulse Fourier transform microwave spectrometer has been used to measure the microwave spectra of both C2H2\\cdots AuI and C2H4\\cdots AuI. These complexes are generated via laser ablation at 532 nm of a gold surface in the presence of CF3I and either C2H2 or C2H4 and argon and are stabilized by a supersonic expansion. Rotational (A0, B0, C0) and centrifugal distortion constants (ΔJ, ΔJK and δJ) of each molecule have been determined as well the nuclear electric quadrupole coupling constants of gold and iodine atoms (χaa(Au}, χbb-χcc(Au), χaa(I) and χbb-χcc(I)). The spectrum of each molecule is consistent with a C2v structure in which the metal atom interacts with the π-orbital of the ethene or ethyne molecule. Isotopic substitutions of atoms within the C2H2 or C2H4 subunits are in progress and in conjunction with high level ab initio calculations will allow for accurate determination of the geometry of each molecule.

  8. Tensor Force Manifestations in Ab Initio Study of the {sup 2}H(d,{gamma}){sup 4}He, {sup 2}H(d,p){sup 3}H, and {sup 2}H(d,n){sup 3}He Reactions

    SciTech Connect

    Arai, K.; Aoyama, S.; Suzuki, Y.; Descouvemont, P.; Baye, D.

    2011-09-23

    The {sup 2}H(d,p){sup 3}H, {sup 2}H(d,n){sup 3}He, and {sup 2}H(d,{gamma}){sup 4}He reactions are studied at low energies in a multichannel ab initio model that takes into account the distortions of the nuclei. The internal wave functions of these nuclei are given by the stochastic variational method with the AV8{sup '} realistic interaction and a phenomenological three-body force included to reproduce the two-body thresholds. The obtained astrophysical S factors are all in very good agreement with the experiment. The most important channels for both transfer and radiative capture are identified by comparing to calculations with an effective central force. They are all found to dominate thanks to the tensor force.

  9. Redetermination of metarossite, CaV5+ 2O6·2H2O

    PubMed Central

    Kobsch, Anaïs; Downs, Robert T.; Domanik, Kenneth J.

    2016-01-01

    The crystal structure of metarossite, ideally CaV2O6·2H2O [chemical name: calcium divanadium(V) hexa­oxide dihydrate], was first determined using precession photographs, with fixed isotropic displacement parameters and without locating the positions of the H atoms, leading to a reliability factor R = 0.11 [Kelsey & Barnes (1960 ▸). Can. Mineral. 6, 448–466]. This communication reports a structure redetermination of this mineral on the basis of single-crystal X-ray diffraction data of a natural sample from the Blue Cap mine, San Juan County, Utah, USA (R1 = 0.036). Our study not only confirms the structural topology reported in the previous study, but also makes possible the refinement of all non-H atoms with anisotropic displacement parameters and all H atoms located. The metarossite structure is characterized by chains of edge-sharing [CaO8] polyhedra parallel to [100] that are themselves connected by chains of alternating [VO5] trigonal bipyramids parallel to [010]. The two H2O mol­ecules are bonded to Ca. Analysis of the displacement parameters show that the [VO5] chains librate around [010]. In addition, we measured the Raman spectrum of metarossite and compared it with IR and Raman data previously reported. Moreover, heating of metarossite led to a loss of water, which results in a transformation to the brannerite-type structure, CaV2O6, implying a possible dehydration pathway for the compounds M 2+V2O6·xH2O, with M = Cu, Cd, Mg or Mn, and x = 2 or 4. PMID:27920917

  10. Five years of CO, HCN, C2H6, C2H2, CH3OH, HCOOH and H2CO total columns measured in the Canadian high Arctic

    NASA Astrophysics Data System (ADS)

    Viatte, C.; Strong, K.; Walker, K. A.; Drummond, J. R.

    2014-06-01

    Northern Hemisphere, attributed to fossil fuel emission decrease. The importance of poleward transport for the atmospheric budgets of HCN and C2H2 is highlighted. Columns and variabilities of CH3OH and HCOOH at PEARL are comparable to previous measurements performed at other remote sites. However, the small columns of H2CO in early May might reflect its large atmospheric variability and/or the effect of the updated spectroscopic parameters used in our retrievals. Overall, emissions from biomass burning contribute to the day-to-day variabilities of the seven tropospheric species observed at Eureka.

  11. Five years of CO, HCN, C2H6, C2H2, CH3OH, HCOOH, and H2CO total columns measured in the Canadian High Arctic

    NASA Astrophysics Data System (ADS)

    Viatte, C.; Strong, K.; Walker, K. A.; Drummond, J. R.

    2013-12-01

    the Northern Hemisphere, attributed to fossil fuel emission decrease. The importance of poleward transport on the atmospheric budgets of HCN and C2H2 is highlighted. Columns and variabilities of CH3OH, and HCOOH at PEARL are comparable to previous measurements performed at other remote sites. However, the small columns of H2CO in early May might reflect its large atmospheric variability, and/or the effect of the updated spectroscopic parameters used in our retrievals. Overall, emissions from biomass burning contribute to the day-to-day variabilities of the seven tropospheric species observed at Eureka.

  12. Observation of the pi...H hydrogen-bonded ternary complex, (C(2)H(4))(2)H(2)O, using matrix isolation infrared spectroscopy.

    PubMed

    Thompson, Matthew G K; Lewars, Errol G; Parnis, J Mark

    2005-10-27

    FTIR absorption spectra of water-containing ethene:Ar matrices, with compositions of ethene up to 1:10 ethene:Ar, have been recorded. Systematically increasing the concentration of ethene reveals features in the spectra consistent with the known 1:1 ethene:water complex, which subsequently disappear on further increase in ethene concentration. At high concentrations of ethene, new features are observed at 3669 and 3585 cm(-1), which are red-shifted with respect to matrix-isolated nu(3) and nu(1) O-H stretching modes of water and the 1:1 ethene:water complex. These shifts are consistent with a pi...H interaction of a 2:1 ethene:water complex of the form (C(2)H(4)...H-O-H...C(2)H(4)). The analogous (C(2)D(4))(2)H(2)O complex shows little shifting from positions associated with (C(2)H(4))(2)H(2)O, while the (C(2)H(4))(2)D(2)O isotopomer shows large shifts to 2722.3 and 2617.2 cm(-1), having identical nu(3)(H(2)O)/nu(3)(D(2)O) and nu(1)(H(2)O)/nu(1)(D(2)O) values when compared with monomeric water isotopomers. Features at 3626.1 and 2666.2 cm(-1) are also observed and are attributed to (C(2)H(4))(2)HDO. DFT calculations at the B3LYP/6-311+G(d,p) level for each isotopomer are presented, and the predicted vibrational frequencies are directly compared with experimental values. The interaction energy for the formation of the 2:1 ethene:water complex from the 1:1 ethene:water complex is also presented.

  13. Magnetic Field Effects on Relaxation Parameters of The Hexamethylenetetramine (HMT)

    NASA Astrophysics Data System (ADS)

    Dogan, Nurcan

    2013-03-01

    The use of low magnetic field is one of the method for improvement of the signal to noise ratio (SNR) of detection of the chemical compounds by nuclear quadrupole resonance (NQR). We investigated the FID phenomenon of nuclear quadrupole resonance (NQR) from hexamethylenetetramine (HMT), C6H12N4, under magnetic field. The influence of the low magnetic field (up to 30 mT) was investigated for the detection of the pulse NQR signal for HMT We detected the pure NQR FID signal of HMT with a short pulse interval. The intensity of the FID signal changed with applied magnetic field. The application of the low magnetic field produces the splitting and brodening of the NQR line. We observed T1, T2 and T2*. HMT has a long T2*(near 1.5ms). This one represents the suitable sample for investigation of the influence of low magnetic field for NQR detection. The application of the low magnetic field produces the splitting and brodening of the NQR line.

  14. Measured Total Cross Sections of Slow Neutrons Scattered by Gaseous and Liquid 2H2

    NASA Astrophysics Data System (ADS)

    Atchison, F.; van den Brandt, B.; Bryś, T.; Daum, M.; Fierlinger, P.; Hautle, P.; Henneck, R.; Kirch, K.; Kohlbrecher, J.; Kühne, G.; Konter, J. A.; Pichlmaier, A.; Wokaun, A.; Bodek, K.; Kasprzak, M.; Kuźniak, M.; Geltenbort, P.; Giersch, M.; Zmeskal, J.; Hino, M.; Utsuro, M.

    2005-06-01

    The total scattering cross sections for slow neutrons with energies E in the range 300 neV to 3 meV for gaseous and liquid ortho-2H2 have been measured. The cross sections for 2H2 gas are found to be in excellent agreement with both the Hamermesh and Schwinger and the Young and Koppel models. For liquid 2H2, we confirm the existing experimental data in the cold neutron range and the discrepancy with the gas models. We find a clear 1/√(E') dependence at low energies for both states. A simple explanation for the liquid 2H2 cross section is offered.

  15. SNF2H promotes hepatocellular carcinoma proliferation by activating the Wnt/β-catenin signaling pathway

    PubMed Central

    Wang, Yanan; Qin, Juanxiu; Liu, Qian; Hong, Xufen; Li, Tianming; Zhu, Yuanjun; He, Lei; Zheng, Bing; Li, Min

    2016-01-01

    Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide and has an extremely poor prognosis. Surgical resection is always inapplicable to HCC patients diagnosed at an advanced tumor stage. The mechanisms underlying HCC cell proliferation remain obscure. In the present study, SWItch/sucrose nonfermentable catalytic subunit SNF2 (SNF2H) expression was tested in HCC tissues and Wnt/β-catenin pathway activation upon overexpression of SNF2H or knockdown of SNF2H expression was investigated in cultured HCC cells. It was demonstrated that SNF2H is a vital factor for HCC growth. The SNF2H expression level is increased in HCC tissues compared with paratumoral liver tissues. SNF2H promotes HCC cell proliferation and colony formation ability in vitro. SNF2H may increase the protein level of β-catenin and enhance its nuclear accumulation in HCC cells, thereby leading to the activation of the Wnt/β-catenin signaling pathway. In conclusion, the present results indicate that SNF2H plays a vital role in HCC cell growth, suggesting that SNF2H may be a promising therapeutic target for HCC treatment. PMID:27446433

  16. Calculational and Experimental Investigations of the Pressure Effects on Radical - Radical Cross Combinations Reactions: C2H5 + C2H3

    NASA Technical Reports Server (NTRS)

    Fahr, Askar; Halpern, Joshua B.; Tardy, Dwight C.

    2007-01-01

    Pressure-dependent product yields have been experimentally determined for the cross-radical reaction C2H5 + C2H3. These results have been extended by calculations. It is shown that the chemically activated combination adduct, 1-C4H8*, is either stabilized by bimolecular collisions or subject to a variety of unimolecular reactions including cyclizations and decompositions. Therefore the "apparent" combination/disproportionation ratio exhibits a complex pressure dependence. The experimental studies were performed at 298 K and at selected pressures between about 4 Torr (0.5 kPa) and 760 Torr (101 kPa). Ethyl and vinyl radicals were simultaneously produced by 193 nm excimer laser photolysis of C2H5COC2H3 or photolysis of C2H3Br and C2H5COC2H5. Gas chromatograph/mass spectrometry/flame ionization detection (GC/MS/FID) were used to identify and quantify the final reaction products. The major combination reactions at pressures between 500 (66.5 kPa) and 760 Torr are (1c) C2H5 + C2H3 yields 1-butene, (2c) C2H5 + C2H5 yields n-butane, and (3c) C2H3 + C2H3 yields 1,3-butadiene. The major products of the disproportionation reactions are ethane, ethylene, and acetylene. At moderate and lower pressures, secondary products, including propene, propane, isobutene, 2-butene (cis and trans), 1-pentene, 1,4-pentadiene, and 1,5-hexadiene are also observed. Two isomers of C4H6, cyclobutene and/or 1,2-butadiene, were also among the likely products. The pressure-dependent yield of the cross-combination product, 1-butene, was compared to the yield of n-butane, the combination product of reaction (2c), which was found to be independent of pressure over the range of this study. The [ 1-C4H8]/[C4H10] ratio was reduced from approx.1.2 at 760 Torr (101 kPa) to approx.0.5 at 100 Torr (13.3 kPa) and approx.0.1 at pressures lower than about 5 Torr (approx.0.7 kPa). Electronic structure and RRKM calculations were used to simulate both unimolecular and bimolecular processes. The relative importance

  17. Predicting leaf wax n-alkane 2H/1H ratios: controlled water source and humidity experiments with hydroponically grown trees confirm predictions of Craig-Gordon model.

    PubMed

    Tipple, Brett J; Berke, Melissa A; Hambach, Bastian; Roden, John S; Ehleringer, James R

    2015-06-01

    The extent to which both water source and atmospheric humidity affect δ(2)H values of terrestrial plant leaf waxes will affect the interpretations of δ(2)H variation of leaf waxes as a proxy for hydrological conditions. To elucidate the effects of these parameters, we conducted a long-term experiment in which we grew two tree species, Populus fremontii and Betula occidentalis, hydroponically under combinations of six isotopically distinct waters and two different atmospheric humidities. We observed that leaf n-alkane δ(2)H values of both species were linearly related to source water δ(2)H values, but with slope differences associated with differing humidities. When a modified version of the Craig-Gordon model incorporating plant factors was used to predict the δ(2)H values of leaf water, all modelled leaf water values fit the same linear relationship with n-alkane δ(2)H values. These observations suggested a relatively constant biosynthetic fractionation factor between leaf water and n-alkanes. However, our calculations indicated a small difference in the biosynthetic fractionation factor between the two species, consistent with small differences calculated for species in other studies. At present, it remains unclear if these apparent interspecies differences in biosynthetic fractionation reflect species-specific biochemistry or a common biosynthetic fractionation factor with insufficient model parameterization.

  18. Optimization of photocatalytic degradation of biodiesel using TiO2/H2O2 by experimental design.

    PubMed

    Ambrosio, Elizangela; Lucca, Diego L; Garcia, Maicon H B; de Souza, Maísa T F; de S Freitas, Thábata K F; de Souza, Renata P; Visentainer, Jesuí V; Garcia, Juliana C

    2017-03-01

    This study reports on the investigation of the photodegradation of biodiesel (B100) in contact with water using TiO2/H2O2. The TiO2 was characterized by X-ray diffraction analysis (XRD), pH point of zero charge (pHpzc) and textural analysis. The results of the experiments were fitted to a quadratic polynomial model developed using response surface methodology (RSM) to optimize the parameters. Using the three factors, three levels, and the Box-Behnken design of experiment technique, 15 sets of experiments were designed considering the effective ranges of the influential parameters. The responses of those parameters were optimized using computational techniques. After 24h of irradiation under an Hg vapor lamp, removal of 22.0% of the oils and greases (OG) and a 33.54% reduction in the total of fatty acid methyl ester (FAME) concentration was observed in the aqueous phase, as determined using gas chromatography coupled with flame ionization detection (GC/FID). The estimate of FAMEs undergo base-catalyzed hydrolysis is at least 3years (1095days) and after photocatalytic treatment using TiO2/H2O2, it was reduced to 33.54% of FAMEs in only 1day.

  19. Hyperfine excitation of N2H+ by H2: towards a revision of N2H+ abundance in cold molecular clouds

    NASA Astrophysics Data System (ADS)

    Lique, François; Daniel, Fabien; Pagani, Laurent; Feautrier, Nicole

    2015-01-01

    The modelling of emission spectra of molecules seen in interstellar clouds requires the knowledge of collisional rate coefficients. Among the commonly observed species, N2H+ is of particular interest since it was shown to be a good probe of the physical conditions of cold molecular clouds. Thus, we have calculated hyperfine-structure-resolved excitation rate coefficients of N2H+(X1Σ+) by H2(j = 0), the most abundant collisional partner in the cold interstellar medium. The calculations are based on a new potential energy surface, obtained from highly correlated ab initio calculations. State-to-state rate coefficients between the first hyperfine levels were calculated, for temperatures ranging from 5 to 70 K. By comparison with previously published N2H+-He rate coefficients, we found significant differences which cannot be reproduced by a simple scaling relationship. As a first application, we also performed radiative transfer calculations, for physical conditions typical of cold molecular clouds. We found that the simulated line intensities significantly increase when using the new H2 rate coefficients, by comparison with the predictions based on the He rate coefficients. In particular, we revisited the modelling of the N2H+ emission in the LDN 183 core, using the new collisional data, and found that all three of the density, gas kinetic temperature and N2H+ abundance had to be revised.

  20. Oxidative degradation of dyes in water using Co2+/H2O2 and Co2+/peroxymonosulfate.

    PubMed

    Ling, Sie King; Wang, Shaobin; Peng, Yuelian

    2010-06-15

    Dye degradation using advanced oxidation processes with Co(2+)/H(2)O(2) and Co(2+)/peroxymonosulfate (PMS) systems has been investigated. Two types of dyes, basic blue 9 and acid red 183, were employed. Several parameters affecting dye degradation such as Co(2+), PMS, H(2)O(2), and dye concentrations were investigated. The optimal ratio of oxidant (PMS, H(2)O(2))/Co(2+) for the degradation of two dyes was determined. It is found that dye decomposition is much faster in Co(2+)/PMS system than in Co(2+)/H(2)O(2). For Co(2+)/H(2)O(2), an optimal ratio of H(2)O(2) to Co(2+) at 6 is required for the maximum decomposition of the dyes. For Co(2+)/PMS, higher concentrations of Co(2+) and PMS will increase dye degradation rate with an optimal ratio of 3, achieving 95% decolourisation. For basic blue 9, a complete decolourisation can be achieved in 5 min at 0.13 mM Co(2+), 0.40 mM PMS and 7 mg/l basic blue 9 while the complete degradation of acid red 183 will be achieved at 30 min at 0.13 mM Co(2+), 0.40 mM PMS and 160 mg/l of acid red 183. The degradation of acid red 183 follows the second-order kinetics.

  1. Identification of New {CIS} Vibrational Levels in the S1 State of C2H2

    NASA Astrophysics Data System (ADS)

    Baraban, J. H.; Changala, P. B.; Shaver, R. G.; Field, R. W.; Stanton, J. F.; Merer, A. J.

    2012-06-01

    Although the S_1 (tilde{A} ^1A_u) state of the trans conformer of acetylene has been known for many years, the corresponding S_1 (tilde{A} ^1A_2) state of the cis conformer was only discovered recently. Transitions to it from the ground state are electronically forbidden, but its vibrational levels acquire intensity by tunneling through the isomerization barrier and interacting with levels of the trans conformer. We have recently identified two new vibrational levels (32 and 41 61) of the {cis} conformer of S1 C2H2, bringing the total number of levels observed to six out of an expected ten up to the energies studied in this work. The appearance of these levels in IR-UV double resonance LIF spectra will be discussed, along with their vibrational assignments. Experimentally determined vibrational parameters and {ab initio} anharmonic force fields for both the {trans} and {cis} conformers will be presented as part of the evidence supporting these assignments. These results shed new light on the vibrational level structure of both conformers in this isomerizing system. A. J. Merer, A. H. Steeves, J. H. Baraban, H. A. Bechtel, and R. W. Field. J. Chem. Phys., 134(24):244310, 2011.

  2. Syntheses, crystal structures and vibrational spectra of KLn(SO{sub 4}){sub 2}.H{sub 2}O (Ln=La, Nd, Sm, Eu, Gd, Dy)

    SciTech Connect

    Kazmierczak, Karolina; Hoeppe, Henning A.

    2010-09-15

    The potassium lanthanide double sulphates KLn(SO{sub 4}){sub 2}.H{sub 2}O (Ln=La, Nd, Sm, Eu, Gd, Dy) were obtained by evaporation of aqueous reaction mixtures of rare earth (III) sulphates and potassium thiocyanate at 298 K. X-ray single-crystal investigations show that KLn(SO{sub 4}){sub 2}.H{sub 2}O (Ln=Nd, Sm, Eu, Gd, Dy) crystallise monoclinically (Ln=Sm: P2{sub 1}/c, Z=4, a=10.047(1), b=8.4555(1), c=10.349(1) A, wR2=0.060, R1=0.024, 945 reflections, 125 parameters) while KLa(SO{sub 4}){sub 2}.H{sub 2}O adopts space group P3{sub 2}21 (Z=3, a=7.1490(5), c=13.2439(12) A, wR2=0.038, R1=0.017, 695 reflections, 65 parameters). The coordination environment of the lanthanide ions in KLn(SO{sub 4}){sub 2}.H{sub 2}O is different in the case of the Nd/Sm/Gd and the Eu/Dy compounds, respectively. In the first case the Ln atoms are nine-fold coordinated in contrast to the latter where the Ln ions are eight-fold coordinated by oxygen atoms. The vibrational spectra of KLn(SO{sub 4}){sub 2}.H{sub 2}O and the UV-vis reflection spectra of KEu(SO{sub 4}){sub 2}.H{sub 2}O and KNd(SO{sub 4}){sub 2}.H{sub 2}O are also reported. - Graphical abstract: The lanthanide potassium double sulphates exhibit an unexpected change in the coordination mode by a simple rotation of sulphate tetrahedron 2.

  3. Negative thermal expansion in 2H CuScO2 originating from the cooperation of transverse thermal vibrations of Cu and O atoms.

    PubMed

    Chang, Dahu; Yu, Weiyang; Sun, Qiang; Jia, Yu

    2017-01-18

    Negative thermal expansion (NTE) originating from the transverse thermal vibrations of metal atoms is seldom reported, which is why the transparent conducting oxide 2H CuScO2 is such a unique case. Using the density functional theory (DFT) and the quasi-harmonic approximation (QHA), the thermal properties of 2H CuScO2 were investigated. The coefficient of thermal expansion (CTE) and the Grüneisen parameters of different vibrational modes were calculated, and we found that, up to a temperature of 200 K, 2H CuScO2 displays a strong NTE behavior along the c-axis (i.e. along the O-Cu-O linkage), with an average CTE of approximately -2 × 10(-6) K(-1). Our calculations are consistent with the experimental values. Furthermore, we reveal that low energy modes (0-150 cm(-1)) originating from the cooperation of transverse vibrations of Cu and O atoms, which result in larger negative Grüneisen parameters and vibrational frequency softening phenomenon under pressure, are the main reasons for the NTE of such materials with a 2H structure. Our findings not only provide a better understanding of the NTE mechanism, but also present a report on detailed abnormal thermal properties in 2H CuScO2 that have applications in electronic, electrochemical and optoelectronic devices.

  4. Photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 in the VUV region

    NASA Technical Reports Server (NTRS)

    Xia, T. J.; Chien, T. S.; Wu, C. Y. Robert; Judge, D. L.

    1991-01-01

    Using synchrotron radiation as a continuum light source, the photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 have been measured from their respective ionization thresholds to 1060 A. The vibrational constants associated with the nu(2) totally symmetric, out-of-plane bending vibration of the ground electronic state of PH3(+) have been obtained. The cross sections and quantum yields for producing neutral products through photoexcitation of these molecules in the given spectral regions have also been determined. In the present work, autoionization processes were found to be less important than dissociation and predissociation processes in NH3, PH3, and C2H4. Several experimental techniques have been employed in order to examine the various possible systematic errors critically.

  5. A density functional theory study of phenyl formation initiated by ethynyl radical (C2H*) and ethyne (C2H2).

    PubMed

    Santiago, Romero M; Indarto, Antonius

    2008-12-01

    An ab initio computational density functional theory (DFT) was used to study the formation of the first cyclic molecule (phenyl) initiated by the ethynyl radical (C(2)H*). The study covers a competition reaction between the addition reactions of C(2)H* with ethyne (C(2)H(2)) and some molecular re-arrangement schemes. The minimum energy paths of the preferred cyclic formation route were characterized. A thorough thermochemical analysis was performed by evaluating the differences in the energy of activation (DeltaE), enthalpy (DeltaH), and Gibb's free energy (DeltaG) of the optimized stable and transition state (TS) molecules. The reaction temperatures were set to normal (T = 298 K) and combustion (T = 1,200 K) conditions.

  6. Hydricities of BzNADH, CH5Mo(PMe3)(CO)2H, and C5Me5Mo(PMe3)(CO)2H in acetonitrile.

    PubMed

    Ellis, William W; Raebiger, James W; Curtis, Calvin J; Bruno, Joseph W; DuBois, Daniel L

    2004-03-10

    The thermodynamic hydride donor abilities of 1-benzyl-1,4-dihydronicotinamide (BzNADH, 59 +/- 2 kcal/mol), C(5)H(5)Mo(PMe(3))(CO)(2)H (55 +/- 3 kcal/mol), and C(5)Me(5)Mo(PMe(3))(CO)(2)H (58 +/- 2 kcal/mol) have been measured in acetonitrile by calorimetric and/or equilibrium methods. The hydride donor abilities of BzNADH and C(5)H(5)Mo(PMe(3))(CO)(2)H differ by 13 and 24 kcal/mol, respectively, from those reported previously for these compounds in acetonitrile. These results require significant revisions of the hydricities reported for related NADH analogues and metal hydrides. These compounds are moderate hydride donors as compared to previously determined compounds.

  7. The reaction OH + C2H4: an example of rotational channel switching.

    PubMed

    Golden, David M

    2012-05-03

    The low-temperature data for the reaction between OH and C(2)H(4) is treated canonically as either a two-well or one-well problem using the "Multiwell" suite of codes, in which a "well" refers to a minimum in the potential energy surface. The former is analogous to the two transition state model of Greenwald et al. [Greenwald, E. E.; North, S. W.; Georgievskii, Y.; Klippenstein, S. J. J. Phys. Chem. A2005, 109, 6031], while the latter reflects the dominance of the so-called "inner transition state". External rotations are treated adiabatically, causing changes in the magnitude of effective barriers as a function of temperature. Extant data are well-described with either model using only the average energy transferred in a downward direction, upon collision, ΔE(d)(T), as a fitting parameter. The best value for the parameters describing the rate coefficient as a function of temperature (200 < T/K < 400) (Data at lower temperature is too sparse to yield a recommendation.) and pressure in the form used in the NASA/JPL format [Sander, S. P.; Abbatt, J.; Barker, J. R.; Burkholder, J. B.; Friedl, R. R.; Golden, D. M.; Huie, R. E.; Kolb, C. E.; Kurylo, M. J.; Moortgat, G. K et al., Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation Number 17, Jet Propulsion Laboratory, 2011] are k(0) = 1.0 × 10(-28)(T/300)(-3.5) cm(6) molecule(-2) s(-1) and k(∞) to 8.0 × 10(-12)(T/300)(-2.3) cm(3) molecule(-1) s(-1).

  8. MICROWAVE SPECTRA AND GEOMETRIES OF C2H_{2\\cdots AgI} and C2H_{4\\cdots AgI}

    NASA Astrophysics Data System (ADS)

    Stephens, Susanna L.; Tew, David Peter; Walker, Nick; Legon, Anthony

    2015-06-01

    A chirped-pulse Fourier transform microwave spectrometer has been used to measure the microwave spectra of both C2H_{2\\cdots AgI} and C2H_{4\\cdots AgI}. These complexes are generated via laser ablation at 532 nm of a silver surface in the presence of CF3I and either C2H_{2} or C2H_{4} and argon and are stabilized by a supersonic expansion. Rotational (A0, B0, C0) and centrifugal distortion constants (ΔJ and ΔJK) of each molecule have been determined as well the nuclear electric quadrupole coupling constants the iodine atom (χaa(I) and χbb-χcc(I)). The spectrum of each molecule is consistent with a C2v structure in which the metal atom interacts with the π-orbital of the ethene or ethyne molecule. Isotopic substitutions of atoms within the C2H_{2} or C2H_{4} subunits are in progress and in conjunction with high level ab initio calculations will allow for accurate determination of the geometry of each molecule. These to complexes are put in the context of the recently studied H2S\\cdots AgI, OC\\cdotsAgI, H3N\\cdots AgI and (CH3)_{3N\\cdots AgI}. S.Z. Riaz, S.L. Stephens, W. Mizukami, D.P. Tew, N.R. Walker, A.C. Legon, Chem. Phys. Let., 531, 1-12 (2012) S.L. Stephens, W. Mizukami, D.P. Tew, N.R. Walker, A.C. Legon, J. Chem. Phys., 136(6), 064306 (2012) D.M. Bittner, D.P. Zaleski, S.L. Stephens, N.R. Walker, A.C. Legon, Study in progress.

  9. Water vapor d2H dynamics over China derived from SCIAMACHY satellite measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study investigates water vapor isotopic patterns and controls over China using high-quality water vapor delta2H data retrieved from Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) observations. The results show that water vapor delta2H values on both annual and...

  10. Synthesis of 2H-indazoles by the [3 + 2] dipolar cycloaddition of sydnones with arynes.

    PubMed

    Fang, Yuesi; Wu, Chunrui; Larock, Richard C; Shi, Feng

    2011-11-04

    A rapid and efficient synthesis of 2H-indazoles has been developed using a [3 + 2] dipolar cycloaddition of sydnones and arynes. A series of 2H-indazoles have been prepared in good to excellent yields using this protocol, and subsequent Pd-catalyzed coupling reactions can be applied to the halogenated products to generate a structurally diverse library of indazoles.

  11. The transcriptional regulator c2h2 accelerates mushroom formation in Agaricus bisporus.

    PubMed

    Pelkmans, Jordi F; Vos, Aurin M; Scholtmeijer, Karin; Hendrix, Ed; Baars, Johan J P; Gehrmann, Thies; Reinders, Marcel J T; Lugones, Luis G; Wösten, Han A B

    2016-08-01

    The Cys2His2 zinc finger protein gene c2h2 of Schizophyllum commune is involved in mushroom formation. Its inactivation results in a strain that is arrested at the stage of aggregate formation. In this study, the c2h2 orthologue of Agaricus bisporus was over-expressed in this white button mushroom forming basidiomycete using Agrobacterium-mediated transformation. Morphology, cap expansion rate, and total number and biomass of mushrooms were not affected by over-expression of c2h2. However, yield per day of the c2h2 over-expression strains peaked 1 day earlier. These data and expression analysis indicate that C2H2 impacts timing of mushroom formation at an early stage of development, making its encoding gene a target for breeding of commercial mushroom strains.

  12. Modeling of collision-induced infrared absorption spectra of H2-H2 pairs in the fundamental band at temperatures from 20 to 300 K. [Planetary atmospheres

    SciTech Connect

    Borysow, A. )

    1991-08-01

    The 20-300 K free-free rotovibrational collision-induced absorption (RV CIA) spectra of H2-H2 pairs are presently obtained by a numerical method which, in addition to closely matching known CIA spectra of H2-H2, can reproduce the results of the quantum-mechanical computations to within a few percent. Since the spectral lineshape parameters are derivable by these means from the lowest three quantum-mechanical spectral moments, these outer-planet atmosphere-pertinent model spectra may be computed on even small computers. 35 refs.

  13. Structural characterization of (C2H2)1-6+ cluster ions by vibrational predissociation spectroscopy

    NASA Astrophysics Data System (ADS)

    Relph, Rachael A.; Bopp, Joseph C.; Roscioli, Joseph R.; Johnson, Mark A.

    2009-09-01

    Vibrational predissociation spectra are reported for the cationic acetylene clusters, (C2H2)n+, n =1-6, in the region of the C-H stretching fundamentals. For n =1 and 2, predissociation could only be observed for the Ar-tagged clusters. These were prepared by charge-transfer collisions of Ark+ with C2H2 to create C2H2+ṡArm clusters, which were then converted into larger members of the (C2H2)n+ṡAr series by sequential addition of acetylene molecules. The (C2H2)2+ṡAr spectrum indicates that this species is predominantly present as the cyclobutadiene cation. Although mobility measurements on the electron-impact-generated (C2H2)3+ ion indicated that it primarily occurs as the benzene cation, [P. O. Momoh, J. Am. Chem. Soc. 128, 12408 (2006)] photofragmentation of (C2H2)3+ṡAr in the C-H stretching region is dominated by the loss of C2H2 in addition to the weakly bound Ar atom. This suggests that the dominant n =3 species formed by sequential addition of C2H2 is based on a covalently bound C4H4+ core ion. Interestingly, the spectrum of this core C4H4+ species is different from that found for the cyclobutadiene cation, displaying instead a new band pattern that is retained in the higher (C2H2)3-6+ clusters. Multiple isomers are clearly involved, as yet another pattern of bands is recovered when the (C2H2)3+ṡAr action spectrum is recorded in the (minor) Ar loss fragmentation channel. One of these features does appear in the location of the single band characteristic of the Ar-tagged benzene cation reported earlier [Phys. Chem. Chem. Phys. 4, 24 (2002)], supporting a scenario where the benzene cation is one of the isomers present. We then compare the Ar predissociation results with (C2H2)n+ spectra obtained when the ions are prepared by electron impact ionization of neutral acetylene clusters. The photofragmentation behavior and vibrational spectra indicate that the dominant species formed in this way also occur with a covalently bound C4H4+ core. There are

  14. The determination of deep temperatures by means of the CO-CO2-H2-H2O geothermometer: an example using fumaroles in the Campi Flegrei, Italy

    NASA Astrophysics Data System (ADS)

    Tedesco, D.; Sabroux, J. C.

    1987-02-01

    Chromatographic analyses of fumarolic gases, collected in sampling bottles containing an alkaline solution, have been carried out using a thermal conductivity detector and a flame ionization detector, after catalytic conversion of CO and CH4. The latter method enables the concentration of carbon monoxide to be measured with sufficient accuracy for use in a CO-CO2-H2-H2O geothermometer. Application of this geothermometer to fumaroles in the crater of Solfatara in the Campi Flegrei, Italy, indicates that they are fed from a steam reservoir at 250±15 °C and at 10-36±2atm of oxygen. On the other hand, the CH4-CO2-H2-H2O geothermobarometer seems to re-equilibrate at superficial temperatures and cannot be used for infering thermodynamic conditions at depth. Regular sampling of these fumaroles together with a geothermometric interpretation of the gas analyses provides a means of monitoring, with comparative accuracy, the chemical and thermal evolution of the hydrothermal reservoir below the Solfatara crater. Such monitoring would probably detect an increase in temperature at depth and the injection of magmatic gas into the reservoir.

  15. Synthesis of [.sup.13C] and [.sup.2H] substituted methacrylic acid, [.sup.13C] and [.sup.2H] substituted methyl methacrylate and/or related compounds

    DOEpatents

    Alvarez, Marc A.; Martinez, Rodolfo A.; Unkefer, Clifford J.

    2008-01-22

    The present invention is directed to labeled compounds of the formulae ##STR00001## wherein Q is selected from the group consisting of --S--, --S(.dbd.O)--, and --S(.dbd.O).sub.2--, Z is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure ##STR00002## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently selected from the group consisting of hydrogen, a C.sub.1-C.sub.4 lower alkyl, a halogen, and an amino group selected from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each independently selected from the group consisting of a C.sub.1-C.sub.4 lower alkyl, an aryl, and an alkoxy group, and X is selected from the group consisting of hydrogen, a C.sub.1-C.sub.4 lower alkyl group, and a fully-deuterated C.sub.1-C.sub.4 lower alkyl group. The present invention is also directed to a process of preparing labeled compounds, e.g., process of preparing [.sup.13C]methacrylic acid by reacting a (CH.sub.3CH.sub.2O--.sup.13C(O)--.sup.13CH.sub.2)-- aryl sulfone precursor with .sup.13CHI to form a (CH.sub.3CH.sub.2O--.sup.13C(O)--.sup.13C(.sup.13CH.sub.3).sub.2)-- aryl sulfone intermediate, and, reacting the (CH.sub.3CH.sub.2O--.sup.13C(O)--.sup.13C(.sup.13CH.sub.3).sub.2)-- aryl sulfone intermediate with sodium hydroxide, followed by acid to form [.sup.13C]methacrylic acid. The present invention is further directed to a process of preparing [.sup.2H.sub.8]methyl methacrylate by reacting a (HOOC--C(C.sup.2H.sub.3).sub.2-- aryl sulfinyl intermediate with CD.sub.3I to form a (.sup.2H.sub.3COOC--C(C.sup.2H.sub.3).sub.2)-- aryl sulfinyl intermediate, and heating the(.sup.2H.sub.3COOC--C(C.sup.2H.sub.3).sub.2)-- aryl sulfinyl intermediate at temperatures and for time sufficient to form [.sup.2H.sub.8]methyl methacrylate.

  16. Trends and variations in CO, C2H6, and HCN in the Southern Hemisphere point to the declining anthropogenic emissions of CO and C2H6

    NASA Astrophysics Data System (ADS)

    Zeng, G.; Wood, S. W.; Morgenstern, O.; Jones, N. B.; Robinson, J.; Smale, D.

    2012-08-01

    We analyse the carbon monoxide (CO), ethane (C2H6) and hydrogen cyanide (HCN) partial columns (from the ground to 12 km) derived from measurements by ground-based solar Fourier Transform Spectroscopy at Lauder, New Zealand (45° S, 170° E), and at Arrival Heights, Antarctica (78° S, 167° E), from 1997 to 2009. Significant negative trends are calculated for all species at both locations, based on the daily-mean observed time series, namely CO (-0.94 ± 0.47% yr-1), C2H6 (-2.37 ± 1.18% yr-1) and HCN (-0.93 ± 0.47% yr-1) at Lauder and CO (-0.92 ± 0.46% yr-1), C2H6 (-2.82 ± 1.37% yr-1) and HCN (-1.41 ± 0.71% yr-1) at Arrival Heights. The uncertainties reflect the 95% confidence limits. However, the magnitudes of the trends are influenced by the anomaly associated with the 1997-1998 El Niño Southern Oscillation event at the beginning of the time series reported. We calculate trends for each month from 1997 to 2009 and find negative trends for all months. The largest monthly trends of CO and C2H6 at Lauder, and to a lesser degree at Arrival Heights, occur during austral spring during the Southern Hemisphere tropical and subtropical biomass burning period. For HCN, the largest monthly trends occur in July and August at Lauder and around November at Arrival Heights. The correlations between CO and C2H6 and between CO and HCN at Lauder in September to November, when the biomass burning maximizes, are significantly larger that those in other seasons. A tropospheric chemistry-climate model is used to simulate CO, C2H6, and HCN partial columns for the period of 1997-2009, using interannually varying biomass burning emissions from GFED3 and annually periodic but seasonally varying emissions from both biogenic and anthropogenic sources. The model-simulated partial columns of these species compare well with the measured partial columns and the model accurately reproduces seasonal cycles of all three species at both locations. However, while the model satisfactorily

  17. I: Low Frequency NMR and NQR Using a dc SQUID. II: Variable-temperature 13C CP/MAS of Organometallics

    SciTech Connect

    Ziegeweid, Marcia A.

    1995-11-01

    NMR and NQR at low frequencies are difficult prospects due to small nuclear spin polarization. Furthermore, the sensitivity of the inductive pickup circuitry of standard spectrometers is reduced as the frequency is lowered. I have used a cw-SQUID (Superconducting Quantum Interference Device) spectrometer, which has no such frequency dependence, to study the local atomic environment of 14N via the quadrupolar interaction. Because 14N has spin I = 1 and a 0-6 MHz frequency range, it is not possible to obtain well-resolved spectra in high magnetic fields. I have used a technique to observe 14N NQR resonances via their effect on neighboring protons mediated by the heteronuclear dipolar interaction to study peptides and narcotics. The sensitivity of the SQUID is not enough to measure low-frequency surface (or other low spin density) systems. The application of spin-polarized xenon has been previously used to enhance polarization in conventional NMR experiments. Because xenon only polarizes spins with which it is in contact, it is surface selective. While differences in chemical shifts between surface and bulk spins are not large, it is expected that the differences in quadrupole coupling constant should be very large due to the drastic change of the electric field gradient surrounding spins at the surface. With this in mind, I have taken preliminary steps to measure SQUID detected polarization transfer from Xe to another spin species at 4.2 K and in small magnetic fields (<50 G). In this regime, the spin-lattice relaxation of xenon is dependent on the applied magnetic field. The results of our efforts to characterize the relaxation of xenon are presented. The final section describes the solid-state variable-temperature (VT) one- and two-dimensional 13C cross polarization (CP)/magic angle spinning (MAS) NMR of Hf(η5-C5H5)21-C5H5)2, Zr

  18. Electron paramagnetic resonance spectral study of [Mn(acs)2(2-pic)2(H2O)2] single crystals

    NASA Astrophysics Data System (ADS)

    Kocakoç, Mehpeyker; Tapramaz, Recep

    2016-03-01

    Acesulfame potassium salt is a synthetic and non-caloric sweetener. It is also important chemically for its capability of being ligand in coordination compounds, because it can bind over Nitrogen and Oxygen atoms of carbonyl and sulfonyl groups and ring oxygen. Some acesulfame containing transition metal ion complexes with mixed ligands exhibit solvato and thermo chromic properties and these properties make them physically important. In this work single crystals of Mn+2 ion complex with mixed ligand, [Mn(acs)2(2-pic)2(H2O)2], was studied with electron paramagnetic resonance (EPR) spectroscopy. EPR parameters were determined. Zero field splitting parameters indicated that the complex was highly symmetric. Variable temperature studies showed no detectable chance in spectra.

  19. Homotopy Algorithm for Fixed Order Mixed H2/H(infinity) Design

    NASA Technical Reports Server (NTRS)

    Whorton, Mark; Buschek, Harald; Calise, Anthony J.

    1996-01-01

    Recent developments in the field of robust multivariable control have merged the theories of H-infinity and H-2 control. This mixed H-2/H-infinity compensator formulation allows design for nominal performance by H-2 norm minimization while guaranteeing robust stability to unstructured uncertainties by constraining the H-infinity norm. A key difficulty associated with mixed H-2/H-infinity compensation is compensator synthesis. A homotopy algorithm is presented for synthesis of fixed order mixed H-2/H-infinity compensators. Numerical results are presented for a four disk flexible structure to evaluate the efficiency of the algorithm.

  20. Identification of acetylene /C2H2/ in infrared atmospheric absorption spectra

    NASA Technical Reports Server (NTRS)

    Goldman, A.; Murcray, F. J.; Blatherwick, R. D.; Gillis, J. R.; Bonomo, F. S.; Murcray, F. H.; Murcray, D. G.; Cicerone, R. J.

    1981-01-01

    Infrared atmospheric absorption spectra at 0.02/cm resolution were obtained during a balloon flight on March 23, 1981 from the Holloman AFB, New Mexico. The absorption features, attributed to C2H2, were used to derive a preliminary mixing ratio of about 25 pptv near 9 km, accurate to + or - 40%. This mixing ratio falls into the range of values calculated for the upper troposphere C2H2 in a photochemical/transport model. However, previous measurements from aircraft grab sampling (Cronn and Robinson, 1979) show four to twelve times this C2H2 concentration 1.5 km below the tropopause.

  1. Determination of the delta(2H/1H)of Water: RSIL Lab Code 1574

    USGS Publications Warehouse

    Revesz, Kinga; Coplen, Tyler B.

    2008-01-01

    Reston Stable Isotope Laboratory (RSIL) lab code 1574 describes a method used to determine the relative hydrogen isotope-ratio delta(2H,1H), abbreviated hereafter as d2H of water. The d2H measurement of water also is a component of the National Water Quality Laboratory (NWQL) schedules 1142 and 1172. The water is collected unfiltered in a 60-mL glass bottle and capped with a Polyseal cap. In the laboratory, the water sample is equilibrated with gaseous hydrogen using a platinum catalyst (Horita, 1988; Horita and others, 1989; Coplen and others, 1991). The reaction for the exchange of one hydrogen atom is shown in equation 1.

  2. The Effect of N2 Photoabsorption Cross Section Resolution on C2H6 Production in Titan’s Ionosphere

    NASA Astrophysics Data System (ADS)

    Luspay-Kuti, Adrienn; Mandt, Kathleen E.; Plessis, Sylvain; Greathouse, Thomas K.

    2014-11-01

    Titan’s rich organic chemistry begins with the photochemistry of only two molecules: N2 and CH4. The details on how higher-order hydrocarbons and nitriles are formed from these molecules have key implications for both the structure and evolution of Titan’s atmosphere, and for its surface-atmosphere interactions. Of high importance is the production of C2H6, which is a sink for CH4, and a main component in the polar lakes. Results of photochemical models, though, may be sensitive to the choice of input parameters, such as the N2 photoabsorption cross section resolution, as previously shown for nitrogen (Liang et al. (2007) ApJL 664, 115-118), and CH4 (Lavvas et al. (2011) Icarus 213, 233-251). Here we investigate the possibility of the same effect on the production rates of C2H6. We modeled production and loss rates, as well as mixing ratio and density profiles between an altitude of 600 and 1600 km for low and high resolution N2 cross sections via a coupled ion-neutral-thermal model (De La Haye et al. (2008) Icarus 197, 110-136; Mandt et al. (2012) JGR 117, E10006). Our results show a clear impact of photoabsorption cross section resolution used on all neutral and ion species contributing to C2H6 production. The magnitude of the influence varies amongst species. Ethane production profiles exhibit a significant increase with better resolution; a factor of 1.2 between 750 and 950 km, and a factor of 1.1 in the total column-integrated production rate. These values are lower limits, as additional reactions involving C2H5 not included in the model may also contribute to the production rates. The clear effect on C2H6 (which is not a parent molecule, nor does it bear nitrogen) may have important implications for other molecules in Titan’s atmosphere as well. The possible non-negligible impact of an isotope of nitrogen may argue for the inclusion of isotopes in photochemical models. For future analysis, development of a more efficient and streamlined model called

  3. SYSTEMATIC VARIATIONS IN CO{sub 2}/H{sub 2}O ICE ABUNDANCE RATIOS IN NEARBY GALAXIES FOUND WITH AKARI NEAR-INFRARED SPECTROSCOPY

    SciTech Connect

    Yamagishi, M.; Kaneda, H.; Ishihara, D.; Oyabu, S.; Onaka, T.; Shimonishi, T.; Suzuki, T.

    2015-07-01

    We report CO{sub 2}/H{sub 2}O ice abundance ratios in seven nearby star-forming galaxies based on the AKARI near-infrared (2.5–5.0 μm) spectra. The CO{sub 2}/H{sub 2}O ice abundance ratios show clear variations between 0.05 and 0.2 with the averaged value of 0.14 ± 0.01. The previous study on M82 revealed that the CO{sub 2}/H{sub 2}O ice abundance ratios strongly correlate with the intensity ratios of the hydrogen recombination Brα line to the polycyclic aromatic hydrocarbon (PAH) 3.3 μm feature. In the present study, however, we find no correlation for the seven galaxies as a whole due to systematic differences in the relation between CO{sub 2}/H{sub 2}O ice abundance and Brα/PAH 3.3 μm intensity ratios from galaxy to galaxy. This result suggests that there is another parameter that determines the CO{sub 2}/H{sub 2}O ice abundance ratios in a galaxy in addition to the Brα/PAH 3.3 μm ratios. We find that the CO{sub 2}/H{sub 2}O ice abundance ratios positively correlate with the specific star formation rates of the galaxies. From these results, we conclude that CO{sub 2}/H{sub 2}O ice abundance ratios tend to be high in young star-forming galaxies.

  4. High-resolution spectroscopy of Saturn at 3 microns: CH 4, CH 3D, C 2H 2, C 2H 6, PH 3, clouds, and haze

    NASA Astrophysics Data System (ADS)

    Kim, Joo Hyeon; Kim, Sang J.; Geballe, Thomas R.; Kim, Sungsoo S.; Brown, Linda R.

    2006-12-01

    We report observation and analysis of a high-resolution 2.87-3.54 μm spectrum of the southern temperate region of Saturn obtained with NIRSPEC at Keck II. The spectrum reveals absorption and emission lines of five molecular species as well as spectral features of haze particles. The ν+ν band of CH 3D is detected in absorption between 2.87 and 2.92 μm; and we derived from it a mixing ratio approximately consistent with the Infrared Space Observatory result. The ν band of C 2H 2 also is detected in absorption between 2.95 and 3.05 μm; analysis indicates a sudden drop in the C 2H 2 mixing ratio at 15 mbar (130 km above the 1 bar level), probably due to condensation in the low stratosphere. The presence of the ν+ν+ν band of C 2H 6 near 3.07 μm, first reported by Bjoraker et al. [Bjoraker, G.L., Larson, H.P., Fink, U., 1981. Astrophys. J. 248, 856-862], is confirmed, and a C 2H 6 condensation altitude of 10 mbar (140 km) in the low stratosphere is determined. We assign weak emission lines within the 3.3 μm band of CH 4 to the ν band of C 2H 6, and derive a mixing ratio of 9±4×10 for this species. Most of the C 2H 6 3.3 μm line emission arises in the altitude range 460-620 km (at ˜μbar pressure levels), much higher than the 160-370 km range where the 12 μm thermal molecular line emission of this species arises. At 2.87-2.90 μm the major absorber is tropospheric PH 3. The cloud level determined here and at 3.22-3.54 is 390-460 mbar (˜30 km), somewhat higher than found by Kim and Geballe [Kim, S.J., Geballe, T.R., 2005. Icarus 179, 449-458] from analysis of a low resolution spectrum. A broad absorption feature at 2.96 μm, which might be due to NH 3 ice particles in saturnian clouds, is also present. The effect of a haze layer at about 125 km (˜12 mbar level) on the 3.20-3.54 μm spectrum, which was not apparent in the low resolution spectrum, is clearly evident in the high resolution data, and the spectral properties of the haze particles suggest that

  5. Alcohol Chemistry: Tentative Detections of Two New Interstellar Big Molecules CH_3OC_2H_5 and (C_2H_5)_2O

    NASA Astrophysics Data System (ADS)

    Kuan, Y.-J.; Charnley, S. B.; Wilson, T. L.; Ohishi, M.; Huang, H.-C.; Snyder, L. E.

    1999-05-01

    Recent modeling of gas-grain chemistry demonstrated that many of the organic species are not the products of grain-surface reactions but are in fact synthesized in the warm gas from simpler species produced on grains. To test gas-grain chemistry, in particular alcohol chemistry, we have thus searched for (C_2H_5)_2O (diethyl ether) and CH_3OC_2H_5 (methyl ethyl ether), using the NRAO 12-m, in the giant molecular cloud cores Sgr B2(N), W51 e1/e2 and Orion-KL, where alcohols have been evaporated from ice mantles. In addition, we have also used the BIMA array to observe the 3-mm transitions of the two molecules toward Sgr B2. The preliminary 12-m results indicate clean detections of various line transitions of the two molecular species in the 1-mm, 2-mm and 3-mm regimes in all 3 molecular cloud cores. Furthermore our BIMA maps show a clear concentration of CH_3OH toward Sgr B2(N), the Large Molecule Heimat; sole detections of CH_3OC_2H_5 and (C_2H_5)_2O toward Sgr B2(N), instead of the more evolved Sgr B2(M), are also observed unambiguously as predicted by alcohol chemistry. Our detections of the two complex molecules not only further confirm the gas-grain chemistry but also require specifically that methanol (CH_3OH) and ethanol (C_2H_5OH) to be formed in grain mantles. In addition, the detections of diethyl ether and methyl ethyl ether lead to the discovery of two new molecules, including the largest ever, (C_2H_5)_2O. This work was partially supported by: NSC grants 87-2112-M-003-007 and 88-2112-M-003-013 of Taiwan, National Taiwan Normal University, Academia Sinica Institute of Astronomy and Astrophysics, NSF AST 96-13999, the University of Illinois, and NASA's Exobiology Program.

  6. Hydrogen isotope systematics of H2-H2O-CH4 during hydrogenotrophic methanogenesis

    NASA Astrophysics Data System (ADS)

    Kobayashi, M.; Kawagucci, S.; Hattori, S.; Yamada, K.; Ueno, Y.; Takai, K.; Yoshida, N.

    2011-12-01

    Hydrogen and carbon isotopes of CH4 have been utilized to trace microbial processes. The isotope fractionations during hydrogenotrophic methanogenesis, one of the major processes of environmental CH4, have been studied by several laboratory incubations. For the carbon isotope, H2 concentration is thought to be the major parameter controlling the carbon isotope fractionation by hydrogenotrophic methanogenesis. For the hydrogen, on the other hand, factors controlling isotope fractionation remain poorly understood, although H2 concentration is suggested to be important. This uncertainty prevents us to utilize δD-CH4 value as the tracer. The most important and principal question is whether all hydrogen atoms in microbially-generated CH4 come from environmental H2O or not. To answer the question, we investigated the D/H systematics of H2-H2O-CH4 during hydrogenotrophic methanogenesis by pure culture incubation with softly deuterium-enriched H2 and/or H2O. Our results demonstrate that δD-CH4 value produced by hydrogenotrophic methanogens depends not only on δD-H2O value but also on δD-H2 value. We observed constant correlation between δD-H2 and δD-CH4 values as well as between δD-H2O and δD-CH4 values, which suggests that hydrogen (/deuterium) atom of substrate H2 is also transferred to the product CH4. This implies that the range of δD-CH4 value produced by hydrogenotrophic methanogenesis should be re-evaluated considering the distribution of δD-H2 and δD-H2O values in natural environments.

  7. Monte Carlo simulations of high-pressure phase equilibria of CO2-H2O mixtures.

    PubMed

    Liu, Yang; Panagiotopoulos, Athanassios Z; Debenedetti, Pablo G

    2011-05-26

    Histogram-reweighting grand canonical Monte Carlo simulations were used to obtain the phase behavior of CO(2)-H(2)O mixtures over a broad temperature and pressure range (50 °C ≤ T ≤ 350 °C, 0 ≤ P ≤ 1000 bar). We performed a comprehensive test of several existing water (SPC, TIP4P, TIP4P2005, and exponential-6) and carbon dioxide (EPM2, TraPPE, and exponential-6) models using conventional Lorentz-Berthelot combining rules for the unlike-pair parameters. None of the models we studied reproduce adequately experimental data over the entire temperature and pressure range, but critical assessments were made on the range of T and P where particular model pairs perform better. Away from the critical region (T ≤ 250 °C), the exponential-6 model combination yields the best predictions for the CO(2)-rich phase, whereas the TraPPE/TIP4P2005 model combination provides the most accurate coexistence composition and pressure for the H(2)O-rich phase. Near the critical region (250 °C < T ≤ 350 °C), the critical points are not accurately estimated by any of the models studied, but the exponential-6 models are able to qualitatively capture the critical loci and the shape of the phase envelopes. Local improvements can be achieved at specific temperatures by introducing modification factors to the Lorentz-Berthelot combining rules, but the modified combining rule is still not able to achieve global improvements over the entire temperature and pressure range. Our work points to the challenge and importance of improving current atomistic models so as to accurately predict the phase behavior of this important binary mixture.

  8. Infrared and Ultraviolet Spectra of Diborane(6): B2H6 and B2D6.

    PubMed

    Peng, Yu-Chain; Chou, Sheng-Lung; Lo, Jen-Iu; Lin, Meng-Yeh; Lu, Hsiao-Chi; Cheng, Bing-Ming; Ogilvie, J F

    2016-07-21

    We recorded absorption spectra of diborane(6), B2H6 and B2D6, dispersed in solid neon near 4 K in both mid-infrared and ultraviolet regions. For gaseous B2H6 from 105 to 300 nm, we report quantitative absolute cross sections; for solid B2H6 and for B2H6 dispersed in solid neon, we measured ultraviolet absorbance with relative intensities over a wide range. To assign the mid-infrared spectra to specific isotopic variants, we applied the abundance of (11)B and (10)B in natural proportions; we undertook quantum-chemical calculations of wavenumbers associated with anharmonic vibrational modes and the intensities of the harmonic vibrational modes. To aid an interpretation of the ultraviolet spectra, we calculated the energies of electronically excited singlet and triplet states and oscillator strengths for electronic transitions from the electronic ground state.

  9. Oxydifluoromethylation of Alkenes by Photoredox Catalysis: Simple Synthesis of CF2H-Containing Alcohols.

    PubMed

    Arai, Yusuke; Tomita, Ren; Ando, Gaku; Koike, Takashi; Akita, Munetaka

    2016-01-22

    We have developed a novel and simple protocol for the direct incorporation of a difluoromethyl (CF2 H) group into alkenes by visible-light-driven photoredox catalysis. The use of fac-[Ir(ppy)3] (ppy=2-pyridylphenyl) photocatalyst and shelf-stable Hu's reagent, N-tosyl-S-difluoromethyl-S-phenylsulfoximine, as a CF2 H source is the key to success. The well-designed photoredox system achieves synthesis of not only β-CF2 H-substituted alcohols but also ethers and an ester from alkenes through solvolytic processes. The present method allows a single-step and regioselective formation of C(sp(3))-CF2 H and C(sp(3))-O bonds from C=C moiety in alkenes, such as hydroxydifluoromethylation, regardless of terminal or internal alkenes. Moreover, this methodology tolerates a variety of functional groups.

  10. The growth of phenanthrene from naphthalene by C2H2 additions

    NASA Astrophysics Data System (ADS)

    Bauschlicher, Charles W., Jr.

    2015-07-01

    Two paths are investigated for the growth of phenanthrene from naphthalene by the addition of C2H2 groups. The first series of steps leads to acenaphthylene (ACN), which is consistent with the path found previously. The addition of C2H2 to ACN can yield a product with two adjacent five-membered rings. Opening one five-membered ring produces a five-membered ring with CH2 side group. This can be converted to a six-membered ring in a manner analogous to the hydrogen atom catalysed fulvene to benzene conversion. A second path, with a somewhat higher barrier, can also lead to the phenanthrene product. The transition state for the second path is essentially isoenergetic with the stating material of ACN + C2H2 + H.

  11. Ecocatalysis for 2H-chromenes synthesis: an integrated approach for phytomanagement of polluted ecosystems.

    PubMed

    Escande, Vincent; Velati, Alicia; Grison, Claude

    2015-04-01

    A direct, general and efficient method to synthesize 2H-chromenes (2H-benzo[b]pyrans), identified as environmentally friendly pesticides, has been developed. This approach lays on the new concept of ecocatalysis, which involves the use of biomass from phytoextraction processes, as a valuable source of metallic elements for chemical synthesis. This methodology is similar or superior to known methods, affording 2H-chromenes with good to excellent yields (60-98%), including the preparation of precocene I, a natural insect growth regulator, with 91% yield. The approach is ideal for poor reactive substrates such as phenol or naphthol, classically transformed into 2H-chromenes by methodologies associated with environmental issues. These results illustrate the interest of combining phytoextraction and green synthesis of natural insecticides.

  12. Epitaxial growth and electronic structure of oxyhydride SrVO2H thin films

    NASA Astrophysics Data System (ADS)

    Katayama, Tsukasa; Chikamatsu, Akira; Yamada, Keisuke; Shigematsu, Kei; Onozuka, Tomoya; Minohara, Makoto; Kumigashira, Hiroshi; Ikenaga, Eiji; Hasegawa, Tetsuya

    2016-08-01

    Oxyhydride SrVO2H epitaxial thin films were fabricated on SrTiO3 substrates via topotactic hydridation of oxide SrVO3 films using CaH2. Structural and composition analyses suggested that the SrVO2H film possessed one-dimensionally ordered V-H--V bonds along the out-of-plane direction. The synthesis temperature could be lowered by reducing the film thickness, and the SrVO2H film was reversible to SrVO3 by oxidation through annealing in air. Photoemission and X-ray absorption spectroscopy measurements revealed the V3+ valence state in the SrVO2H film, indicating that the hydrogen existed as hydride. Furthermore, the electronic density of states was highly suppressed at the Fermi energy, consistent with the prediction that tetragonal distortion induces metal to insulation transition.

  13. Synthesis of 2H-indazoles by the [3 + 2] cycloaddition of arynes and sydnones.

    PubMed

    Wu, Chunrui; Fang, Yuesi; Larock, Richard C; Shi, Feng

    2010-05-21

    A rapid and efficient synthesis of 2H-indazoles has been developed, which involves the [3 + 2] dipolar cycloaddition of arynes and sydnones. The process proceeds under mild reaction conditions in good to excellent yields.

  14. Large-scale Spectroscopic Mapping of the ρ Ophiuchi Molecular Cloud Complex. I. The C2H-to-N2H+ Ratio as a Signpost of Cloud Characteristics

    NASA Astrophysics Data System (ADS)

    Pan, Zhichen; Li, Di; Chang, Qiang; Qian, Lei; Bergin, Edwin A.; Wang, Junzhi

    2017-02-01

    We present 2.5-square-degree C2H N = 1–0 and N2H+ J = 1–0 maps of the ρ Ophiuchi molecular cloud complex. These are the first large-scale maps of the ρ Ophiuchi molecular cloud complex with these two tracers. The C2H emission is spatially more extended than the N2H+ emission. One faint N2H+ clump, Oph-M, and one C2H ring, Oph-RingSW, are identified for the first time. The observed C2H-to-N2H+ abundance ratio ([C2H]/[N2H+]) varies between 5 and 110. We modeled the C2H and N2H+ abundances with 1D chemical models, which show a clear decline of [C2H]/[N2H+] with chemical age. Such an evolutionary trend is little affected by temperatures when they are below 40 K. At high density (n H > 105 cm‑3), however, the time it takes for the abundance ratio to drop at least one order of magnitude becomes less than the dynamical time (e.g., turbulence crossing time of ∼105 yr). The observed [C2H]/[N2H+] difference between L1688 and L1689 can be explained by L1688 having chemically younger gas in relatively less dense regions. The observed [C2H]/[N2H+] values are the results of time evolution, accelerated at higher densities. For the relatively low density regions in L1688 where only C2H emission was detected, the gas should be chemically younger.

  15. Synthesis of 2H-Indazoles by the [3 + 2] Dipolar Cycloaddition of Sydnones with Arynes

    PubMed Central

    Fang, Yuesi; Wu, Chunrui; Larock, Richard C.; Shi, Feng

    2011-01-01

    A rapid and efficient synthesis of 2H-indazoles has been developed using a [3 + 2] dipolar cycloaddition of sydnones and arynes. A series of 2H-indazoles have been prepared in good to excellent yields using this protocol, and subsequent Pd-catalyzed coupling reactions can be applied to the halogenated products to generate a structurally diverse library of indazoles. PMID:21970468

  16. Natural-abundance solid-state 2H NMR spectroscopy at high magnetic field.

    PubMed

    Aliev, Abil E; Mann, Sam E; Iuga, Dinu; Hughes, Colan E; Harris, Kenneth D M

    2011-06-09

    High-resolution solid-state (2)H NMR spectroscopy provides a method for measuring (1)H NMR chemical shifts in solids and is advantageous over the direct measurement of high-resolution solid-state (1)H NMR spectra, as it requires only the application of routine magic angle sample spinning (MAS) and routine (1)H decoupling methods, in contrast to the requirement for complex pulse sequences for homonuclear (1)H decoupling and ultrafast MAS in the case of high-resolution solid-state (1)H NMR. However, a significant obstacle to the routine application of high-resolution solid-state (2)H NMR is the very low natural abundance of (2)H, with the consequent problem of inherently low sensitivity. Here, we explore the feasibility of measuring (2)H MAS NMR spectra of various solids with natural isotopic abundances at high magnetic field (850 MHz), focusing on samples of amino acids, peptides, collagen, and various organic solids. The results show that high-resolution solid-state (2)H NMR can be used successfully to measure isotropic (1)H chemical shifts in favorable cases, particularly for mobile functional groups, such as methyl and -N(+)H(3) groups, and in some cases phenyl groups. Furthermore, we demonstrate that routine (2)H MAS NMR measurements can be exploited for assessing the relative dynamics of different functional groups in a molecule and for assessing whole-molecule motions in the solid state. The magnitude and field-dependence of second-order shifts due to the (2)H quadrupole interaction are also investigated, on the basis of analysis of simulated and experimental (1)H and (2)H MAS NMR spectra of fully deuterated and selectively deuterated samples of the α polymorph of glycine at two different magnetic field strengths.

  17. Analysis of dissolved C2H2 in transformer oils using laser Raman spectroscopy.

    PubMed

    Somekawa, Toshihiro; Kasaoka, Makoto; Kawachi, Fumio; Nagano, Yoshitomo; Fujita, Masayuki; Izawa, Yasukazu

    2013-04-01

    We have developed a laser Raman spectroscopy technique for assessing the working conditions of transformers by measuring dissolved C2H2 gas concentrations present in transformer oils. A frequency doubled Q-switched Nd:YAG laser (532 nm) was used as a laser source, and Raman signals at ~1972 cm(-1) originating from C2H2 gas dissolved in oil were detected. The results show that laser Raman spectroscopy is a useful alternative method for detecting transformer faults.

  18. Structural aspects of nucleotide ligand binding by a bacterial 2H phosphoesterase

    PubMed Central

    Myllykoski, Matti; Kursula, Petri

    2017-01-01

    The 2H phosphoesterase family contains enzymes with two His-X-Ser/Thr motifs in the active site. 2H enzymes are found in all kingdoms of life, sharing little sequence identity despite the conserved overall fold and active site. For many 2H enzymes, the physiological function is unknown. Here, we studied the structure of the 2H family member LigT from Escherichia coli both in the apo form and complexed with different active-site ligands, including ATP, 2′-AMP, 3′-AMP, phosphate, and NADP+. Comparisons to the well-characterized vertebrate myelin enzyme 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase) highlight specific features of the catalytic cycle and substrate recognition in both enzymes. The role played by the helix α7, unique to CNPases within the 2H family, is apparently taken over by Arg130 in the bacterial enzyme. Other residues and loops lining the active site groove are likely to be important for RNA substrate binding. We visualized conformational changes related to ligand binding, as well as the position of the nucleophilic water molecule. We also present a low-resolution model of E. coli LigT bound to tRNA in solution, and provide a model for RNA binding by LigT, involving flexible loops lining the active site cavity. Taken together, our results both aid in understanding the common features of 2H family enzymes and help highlight the distinct features in the 2H family members, which must result in different reaction mechanisms. Unique aspects in different 2H family members can be observed in ligand recognition and binding, and in the coordination of the nucleophilic water molecule and the reactive phosphate moiety. PMID:28141848

  19. A Classical Trajectory Study of the Dissociation and Isomerization of C2H5

    DTIC Science & Technology

    2013-01-01

    C2H5) plays an important role in combustion chemistry. Because the reverse reactions constitute the addition of a hydrogen atom to a stable molecule...primary reaction zones of premixed flames. The hydrogen atom thus produced acts to promote chain branching through the H + O2 ⇌ OH + O reaction . Thus...calculations of reaction paths on the electronically excited-state potential energy surfaces (PESs) of C2H5 14 predict that the nonclassical bridge structure is

  20. Synthesis of a library of 2-alkyl-3-alkyloxy-2H-indazole-6-carboxamides.

    PubMed

    Mills, Aaron D; Maloney, Patrick; Hassanein, Elsayed; Haddadin, Makhluf J; Kurth, Mark J

    2007-01-01

    A library of 200 2-alkyl-3-alkyloxy-2H-indazole-6-carboxamides was synthesized using parallel solution-phase methods. The indazole cyclization reaction was optimized for library production with the best yields resulting from controlled alcohol/water solvent ratios. The key step, a heterocyclization reaction, proceeds by N,N-bond formation and delivers the 2H-indazole scaffold. Automated preparative HPLC was utilized to provide pure compounds on a 10+ mg scale.

  1. A copper–polyol complex: [Na2(C2H6O2)6][Cu(C2H4O2)2

    PubMed Central

    Rivers, Joseph H.; Carroll, Kyler J.; Jones, Richard A.; Carpenter, Everett E.

    2010-01-01

    The ionic title complex, bis(μ-ethyl­ene glycol)-κ3 O,O′:O′;κ3 O:O,O′-bis[(ethyl­ene glycol-κ2 O,O′)(ethyl­ene glycol-κO)sodium] bis(ethyl­ene glycolato-κ2 O,O′)copper(II), [Na2(C2H6O2)6][Cu(C2H4O2)2], was obtained from a basic solution of CuCl2 in ethyl­ene glycol and consists of discrete ions inter­connected by O—H⋯O hydrogen bonds. This is the first example of a disodium–ethyl­ene glycol complex cation cluster. The cation lies about an inversion center and the CuII atom of the anion lies on another independent inversion center. PMID:20203401

  2. Direct ab initio study of the C6H6 + CH3/C2H5 = C6H5 + CH4/C2H6 reactions

    NASA Astrophysics Data System (ADS)

    Mai, Tam V.-T.; Ratkiewicz, Artur; Duong, Minh v.; Huynh, Lam K.

    2016-02-01

    A kinetic study of the reactions C6H6 + CH3/C2H5 = C6H5 + CH4/C2H6 was carried out in the temperature range of 300-2500 K using high levels of electronic structure theory, namely, CCSD(T)/CBS//BH&HLYP/cc-pVDZ, and canonical variational transition state theory (CVT) with corrections for small curvature tunneling (SCT) and hindered internal rotation (HIR) treatments. It is found that variational effect is not important and both SCT and HIR corrections noticeably affect the rate constants. Being in good agreement with literature data, the calculated results provide solid basis information for the investigation of the polyaromatic hydrocarbon (PAH) + alkyl radical reaction, an important class in combustion and soot formation.

  3. Multiparameter functional diversity of human C2H2 zinc finger proteins

    PubMed Central

    Schmitges, Frank W.; Radovani, Ernest; Najafabadi, Hamed S.; Barazandeh, Marjan; Campitelli, Laura F.; Yin, Yimeng; Jolma, Arttu; Zhong, Guoqing; Guo, Hongbo; Kanagalingam, Tharsan; Dai, Wei F.; Taipale, Jussi; Emili, Andrew; Greenblatt, Jack F.; Hughes, Timothy R.

    2016-01-01

    C2H2 zinc finger proteins represent the largest and most enigmatic class of human transcription factors. Their C2H2-ZF arrays are highly variable, indicating that most will have unique DNA binding motifs. However, most of the binding motifs have not been directly determined. In addition, little is known about whether or how these proteins regulate transcription. Most of the ∼700 human C2H2-ZF proteins also contain at least one KRAB, SCAN, BTB, or SET domain, suggesting that they may have common interacting partners and/or effector functions. Here, we report a multifaceted functional analysis of 131 human C2H2-ZF proteins, encompassing DNA binding sites, interacting proteins, and transcriptional response to genetic perturbation. We confirm the expected diversity in DNA binding motifs and genomic binding sites, and provide motif models for 78 previously uncharacterized C2H2-ZF proteins, most of which are unique. Surprisingly, the diversity in protein–protein interactions is nearly as high as diversity in DNA binding motifs: Most C2H2-ZF proteins interact with a unique spectrum of co-activators and co-repressors. Thus, multiparameter diversification likely underlies the evolutionary success of this large class of human proteins. PMID:27852650

  4. C2H4 adsorption on Cu(210), revisited: bonding nature and coverage effects.

    PubMed

    Amino, Shuichi; Arguelles, Elvis; Agerico Diño, Wilson; Okada, Michio; Kasai, Hideaki

    2016-08-24

    With the aid of density functional theory (DFT)-based calculations, we investigate the adsorption of C2H4 on Cu(210). We found two C2H4 adsorption sites, viz., the top of the step-edge atom (S) and the long bridge between two step-edge atoms (SS) of Cu(210). The step-edge atoms on Cu(210) block the otherwise active terrace sites found on copper surfaces with longer step sizes. This results in the preference for π-bonded over di-σ-bonded C2H4. We also found two stable C2H4 adsorption orientations on the S- and SS-sites, viz., with the C2H4 C[double bond, length as m-dash]C bond parallel (fit) and perpendicular (cross) to [001]. Furthermore, we found that the three peaks observed in previous temperature programmed desorption (TPD) experiment [Surf. Sci., 2011, 605, 934-940] could be attributed to C2H4 in the S-fit or S-cross, S-fit and S-cross-fit (S-cross and S-fit configurations that both exist in the same unit cell) configurations on Cu(210).

  5. DISSOCIATION OF B2H6 AND ADSORPTION OF THE FRAGMENTS OF B2H6 ON THE STEPPED Ge(100) SURFACE

    NASA Astrophysics Data System (ADS)

    Türkmenoğlu, Mustafa; Katircioğlu, Şenay

    2012-06-01

    In this work, the p-type doping of the SA type stepped Ge(100) surface by a diborane (B2H6) gas flow has been simulated by the possible dissociation and adsorption models. The most probable dissociation model of B2H6 and adsorption models of the fragments of B2H6 on the stepped Ge(100) surface have been determined by the local minimum total energy and/or binding energy calculations based on the Density functional (B3LYP/6-3g) and Hartree-Fock (HF/STO-3g) theories, respectively. The present calculations have shown that, the step region (for both up and down terraces) of the stepped Ge(100) surface has the most attractive sites for BH3 molecules determined to be the first dissociation fragments of B2H6 by an external energy of 1.3 eV. It has been found that, at the first step of the adsorption, BH3 can dissociate to BH2 and BH fragments on the stepped Ge(100) surface. While BH3 and BH2 products prefer to be attached to a single surface Ge atom, BH is bridged between two adjacent surface Ge atoms. According to the present optimization calculations, the p-type doping process of the stepped Ge(100) surface has started with the adsorption of BH3 on the electron deficient site (buckled down) of the Ge dimer bond close to the step edge and ended with the substitutional occupation of the Ge site in the layers of the surface by B atom. The beginning of the p-type doping of the stepped Ge(100) surface has been illustrated by the electronic states of B appeared in the optical energy gap of Ge very close to the edge of the HOMO.

  6. Laboratory studies of 2H evaporator scale dissolution in dilute nitric acid

    SciTech Connect

    Oji, L.

    2014-09-23

    The rate of 2H evaporator scale solids dissolution in dilute nitric acid has been experimentally evaluated under laboratory conditions in the SRNL shielded cells. The 2H scale sample used for the dissolution study came from the bottom of the evaporator cone section and the wall section of the evaporator cone. The accumulation rate of aluminum and silicon, assumed to be the two principal elemental constituents of the 2H evaporator scale aluminosilicate mineral, were monitored in solution. Aluminum and silicon concentration changes, with heating time at a constant oven temperature of 90 deg C, were used to ascertain the extent of dissolution of the 2H evaporator scale mineral. The 2H evaporator scale solids, assumed to be composed of mostly aluminosilicate mineral, readily dissolves in 1.5 and 1.25 M dilute nitric acid solutions yielding principal elemental components of aluminum and silicon in solution. The 2H scale dissolution rate constant, based on aluminum accumulation in 1.5 and 1.25 M dilute nitric acid solution are, respectively, 9.21E-04 ± 6.39E-04 min{sup -1} and 1.07E-03 ± 7.51E-05 min{sup -1}. Silicon accumulation rate in solution does track the aluminum accumulation profile during the first few minutes of scale dissolution. It however diverges towards the end of the scale dissolution. This divergence therefore means the aluminum-to-silicon ratio in the first phase of the scale dissolution (non-steady state conditions) is different from the ratio towards the end of the scale dissolution. Possible causes of this change in silicon accumulation in solution as the scale dissolution progresses may include silicon precipitation from solution or the 2H evaporator scale is a heterogeneous mixture of aluminosilicate minerals with several impurities. The average half-life for the decomposition of the 2H evaporator scale mineral in 1.5 M nitric acid is 12.5 hours, while the half-life for the decomposition of the 2H evaporator scale in 1.25 M nitric acid is 10

  7. Thermal rate constants for R+N2H2 --> RH+N2H (R=H, OH, NH2) determined from multireference configuration interaction and variational transition state theory calculations

    NASA Astrophysics Data System (ADS)

    Linder, Douglas P.; Duan, Xiaofeng; Page, Michael

    1996-04-01

    Ab initio electronic structure calculations were performed to determine features of the potential energy surface for abstraction of a hydrogen atom from N2H2 by H, OH, and NH2. Based on multireference configuration interaction calculations with basis sets up to correlation consistent polarized valence triple zeta, the barrier heights determined for these reactions are 4.3, 3.0, and 4.4 kcal/mol, respectively. Using features of the potential energy surface along minimum energy paths determined at the complete active space self-consistent-field level of theory, variational transition state theory calculations were performed to determine the rate coefficients over the temperature range 300-3000 K. The temperature dependent computed rate coefficients for the three reactions are well represented by the following three-parameter expressions: kH(T) =1.41×10-19T2.63 exp(115.8/T) cm3 molec-1 s-1, kOH(T)=9.84×10-23 T3.40 exp(686.3/T) cm3 molec-1 s-1, and kNH2(T)=1.46×10-25T4.05 exp(810.5/T) cm3 molec-1 s-1. Abstraction from N2H2 is predicted to occur at a significantly slower rate than analogous abstractions from the isoelectronic HNO.

  8. Precision measurements of {sup 2}H(d,p){sup 3}H and {sup 2}H(d,n){sup 3}He total cross sections at Big Bang nucleosynthesis energies

    SciTech Connect

    Leonard, D.S.; Karwowski, H.J.; Brune, C.R.; Fisher, B.M.; Ludwig, E.J.

    2006-04-15

    Recent Wilkinson Microwave Anisotropy Probe (WMAP) measurements have determined the baryon density of the Universe {omega}{sub b} with a precision of about 4%. With {omega}{sub b} tightly constrained, comparisons of Big Bang nucleosynthesis (BBN) abundance predictions to primordial abundance observations can be made and used to test BBN models and/or to further constrain abundances of isotopes with weak observational limits. To push the limits and improve constraints on BBN models, uncertainties in key nuclear reaction rates must be minimized. To this end, we made new precise measurements of the {sup 2}H(d,p){sup 3}H and {sup 2}H(d,n){sup 3}He total cross sections at lab energies from 110 to 650 keV. A complete fit was performed in energy and angle to both angular distribution and normalization data for both reactions simultaneously. By including parameters for experimental variables in the fit, error correlations between detectors, reactions, and reaction energies were accurately tabulated by computational methods. With uncertainties around 2%{+-}1% scale error, these new measurements significantly improve on the existing data set. At relevant temperatures, by using the data of the present work, both reaction rates are found to be about 7% higher than those in the widely used NACRE (nuclear astrophysics compilation of reaction rates) database. These data will thus lead not only to reduced uncertainties, but also to modifications in the BBN abundance predictions.

  9. Poster 1: Global frequency and intensity analysis of the ν10/ν7/ν4/ν12 band system of 12C2H4 at 10 µm using the D2h Top Data System

    NASA Astrophysics Data System (ADS)

    Alkadrou, Abdulsamee; Bourgeois, Marie-Therese; Rotger, Maud; Boudon, Vincent; Vander Auwera, Jean

    2016-06-01

    A global frequency and intensity analysis of the infrared tetrad of 12C2H4 located in the 600-1500 cm-1 region was carried out using the tensorial formalism developed in Dijon for X2Y4 asymmetric-top molecules. It relies on spectroscopic information available in the literature and retrieved from high-resolution Fourier transform infrared spectra recorded in Brussels in the frame of either the present or previous work. In particular, 645 and 131 lines intensities have been respectively measured for the weak ν10 and ν4 bands. Including the Coriolis interactions affecting the upper vibrational levels 101, 71, 41 and 121 , a total of 10,737 line positions and 1,867 line intensities have been assigned and fitted with global root mean square deviations of 2.6 10-4 cm-1 and 2.4 %, respectively. Relying on the results of the present work and available in the literature, a list of parameters for 65,420 lines in the ν10, ν7, ν4 and ν12 bands of 12C2H4 was generated. To the best of our knowledge, this is the first time that a global intensity analysis is carried out in this range of the ethylene spectrum.

  10. Global frequency and intensity analysis of the ν10/ν7/ν4/ν12 band system of 12C2H4 at 10 μm using the D2h Top Data System

    NASA Astrophysics Data System (ADS)

    Alkadrou, A.; Bourgeois, M.-T.; Rotger, M.; Boudon, V.; Vander Auwera, J.

    2016-10-01

    A global frequency and intensity analysis of the infrared tetrad of 12C2H4 located in the 600 - 1500cm-1 region was carried out using the tensorial formalism developed in Dijon for X2Y4 asymmetric-top molecules. It relied on spectroscopic information available in the literature and retrieved from high-resolution Fourier transform infrared spectra recorded in Brussels in the frame of either the present or previous work. In particular, 645 and 131 line intensities have been respectively measured for the weak ν10 and ν4 bands. Including the Coriolis interactions affecting the upper vibrational levels 101, 71, 41 and 121, a total of 10 757 line positions and 1645 line intensities have been assigned and fitted with global root mean square deviations of 2.6 ×10-4cm-1 and 2.5%, respectively. Relying on the results of the present work and available in the literature, a list of parameters for 65 776 lines in the ν10, ν7, ν4 and ν12 bands of 12C2H4 was generated. To the best of our knowledge, this is the first time that a global intensity analysis is carried out in this range of the ethylene spectrum.

  11. Accumulation of 2H2O in plasma and eccrine sweat during exercise-heat stress.

    PubMed

    Armstrong, Lawrence E; Klau, Jennifer F; Ganio, Matthew S; McDermott, Brendon P; Yeargin, Susan W; Lee, Elaine C; Maresh, Carl M

    2010-02-01

    The purpose of this research was to characterize the movement of ingested water through body fluids, during exercise-heat stress. Deuterium oxide ((2)H(2)O) accumulation in plasma and eccrine sweat was measured at two sites (back and forehead). The exercise of 14 males was controlled via cycle ergometry in a warm environment (60 min; 28.7 degrees C, 51%rh). Subjects consumed (2)H(2)O (0.15 mg kg(-1), 99.9% purity) mixed in flavored, non-caloric, colored water before exercise, then consumed 3.0 ml kg(-1) containing no (2)H(2)O every 15 min during exercise. We hypothesized that water transit from mouth to skin would occur before 15 min. (2)H(2)O appeared rapidly in both plasma and sweat (P < 0.05), within 10 min of water consumption. The ratio (2)H(2)O/H(2)O (D:H) was 47.3-55.0 times greater in plasma than in back sweat at minutes 10, 20, and 30 (DeltaD:H relative to baseline). At elapsed minute 20, the mean rate of deuterium accumulation (DeltaD:H min(-1)) in plasma was 14.9 and 23.7 times greater than in forehead and back sweat samples, respectively. Mean (+/-SE) whole-body sweat rate was 1.04 +/- 0.05 L h(-1) and subjects with the greatest whole-body sweat rate exhibited the greatest peak deuterium enrichment in sweat (r(2) = 0.87, exponential function); the peak (2)H(2)O enrichment in sweat was not proportional (P > 0.05) to body mass, volume of the deuterium dose, or total volume of fluid consumed. These findings clarify the time course of fluid movement from mouth to eccrine sweat glands, and demonstrate considerable differences of (2)H(2)O enrichment in plasma versus sweat.

  12. Potential energy surface for C2H4I2+ dissociation including spin-orbit effects

    SciTech Connect

    Siebert, Matthew R.; Aquino, Adelia J.; De Jong, Wibe A.; Granucci, Giovanni; Hase, William L.

    2012-10-24

    Previous experiments [Baer, et al. J. Phys. Chem. A 116, 2833 (2012)] have studied the dissociation of 1,2-diiodoethane radical cation (C2H4I2+•) and found a one-dimensional distribution of translational energy; an odd finding considering most product relative translational energy distributions are two-dimensional. The goal of this study is to obtain an accurate understanding of the potential energy surface (PES) topology for the unimolecular decomposition reaction C2H4I2+• - C2H4I+ + I•. This is done through comparison of many single-reference electronic structure methods, coupled-cluster single point (energy) calculations, and multi-reference calculations used to quantify spin-orbit (SO) coupling effects. We find that the structure of the C2H4I2+• reactant has a substantial effect on the role of SO coupling on the reaction energy. Both the BHandH and MP2 theories with an ECP/6-31++G** basis set, and without SO coupling corrections, provide accurate models for the reaction energetics. MP2 theory gives an unsymmetric structure with different C-I bond lengths, resulting in a SO energy for C2H4I2+• similar to that for the product I-atom and a negligible SO correction to the reaction energy. In contrast, DFT gives a symmetric structure for C2H4I2+•, similar to that of the neutral C2H4I2 parent, resulting in a substantial SO correction and increasing the reaction energy by 6.0-6.5 kcal/mol. Also, we find that for this system single point energy calculations are inaccurate, since a small change in geometry can lead to a large change in energy.

  13. Hydrogen jump diffusion in C14-type ZrMn2H3 : Quasielastic neutron scattering study

    NASA Astrophysics Data System (ADS)

    Skripov, A. V.; Udovic, T. J.; Rush, J. J.

    2007-09-01

    In order to study the mechanism and parameters of hydrogen diffusion in the hexagonal (C14-type) Laves-phase ZrMn2 , we have performed quasielastic neutron scattering measurements for ZrMn2H3 over the temperature range 10-390K . It is found that the diffusive motion of hydrogen in this system can be described in terms of at least two jump processes: a fast localized H motion with the jump rate τl-1 and a slower process with the rate τd-1 associated with H jumps leading to long-range diffusion. The temperature dependence of τd-1 in the range 225-390K follows the Arrhenius law with the activation energy of 124±4meV . In the same range, the temperature dependence of τl-1 deviates from the Arrhenius behavior and is considerably weaker than that of τd-1 . The Q dependence of the elastic incoherent structure factor (studied up to Qmax≈3.8Å-1 ) suggests that the fast localized H motion in ZrMn2H3 corresponds to two-site jumps within pairs of closely spaced interstitial Zr2Mn2 sites.

  14. Rototranslational collision-induced absorption by H2-H2 pairs at temperatures from 600 to 7000 K

    NASA Technical Reports Server (NTRS)

    Zheng, Chunguang; Borysow, Aleksandra

    1995-01-01

    The computation of the far-infrared, rototranslational (RT) collision-induced absorption (CIA) spectra of H2-H2 pairs is presented at temperatures from 600 to 7000 K for the first time. Theoretical results are based on the quantum mechanical and semiclassical, three lowest translational spectral moments obtained for H2 pairs. The effective, isotropic H2-H2 interaction potential, suitable for the high-temperature computations, and the ab initio induced dipoles, have been used as input. Special effort has been made to account for the rotational and vibrational states dependence of the dipoles, since it was found to be relevant at the high temperatures employed. The computations of the entire RT band account for all populated vibrational states of hydrogen molecule and include vibrational transitions v tends towards v-prime = v, with v = 0, 1, 2 and 3. The described method makes use of the adequately selected model line shapes with the temperature-dependent parameters. The presented model is useful for the 'model atmospheres' of zero- and low-metallicity, cool and dense stellar atmospheres, where CIA is known to be imporatnt.

  15. The condensation and vaporization behavior of ices containing SO2, H2S, and CO2: Implications for Io

    NASA Technical Reports Server (NTRS)

    Sandford, Scott A.; Allamandola, Louis J.

    1993-01-01

    In an extension of previously reported work on ices containing CO, CO2, H2O, CH3OH, NH3, and H2, measurements of the physical and infrared spectral properties of ices containing molecules relevant to Jupiter's moon Io are presented. These include studies on ice systems containing SO2, H2S, and CO2. The condensation and sublimation behaviors of each ice system and surface binding energies of their components are discussed. The surface binding energies can be used to calculate the residence times of the molecules on a surface as a function of temperature and thus represent important parameters for any calculation that attempts to model the transport of these molecules on Io's surface. The derived values indicate that SO2 frosts on Io are likely to anneal rapidly, resulting in less fluffy, 'glassy' ices and that H2S can be trapped in the SO2 ices of Io during night-time hours provided that SO2 deposition rates are on the order of 5 micrometers/hr or larger.

  16. The C2H2 zinc finger genes of Strongylocentrotus purpuratus and their expression in embryonic development.

    PubMed

    Materna, Stefan C; Howard-Ashby, Meredith; Gray, Rachel F; Davidson, Eric H

    2006-12-01

    The C2H2 zinc finger is one of the most abundant protein domains and is thought to have been extensively replicated in diverse animal clades. Some well-studied proteins that contain this domain are transcriptional regulators. As part of an attempt to delineate all transcription factors encoded in the Strongylocentrotus purpuratus genome, we identified the C2H2 zinc finger genes indicated in the sequence, and examined their involvement in embryonic development. We found 377 zinc finger genes in the sea urchin genome, about half the number found in mice or humans. Their expression was measured by quantitative PCR. Up to the end of gastrulation less than a third of these genes is expressed, and about 75% of the expressed genes are maternal; both parameters distinguish these from all other classes of regulatory genes as measured in other studies. Spatial expression pattern was determined by whole mount in situ hybridization for 43 genes transcribed at a sufficient level, and localized expression was observed in diverse embryonic tissues. These genes may execute important regulatory functions in development. However, the functional meaning of the majority of this large gene family remains undefined.

  17. The condensation and vaporization behavior of ices containing SO2, H2S, and CO2: implications for Io.

    PubMed

    Sandford, S A; Allamandola, L J

    1993-12-01

    In an extension of previously reported work on ices containing CO, CO2, H2O, CH3OH, NH3, and H2, measurements of the physical and infrared spectral properties of ices containing molecules relevant to Jupiter's moon Io are presented. These include studies on ice systems containing SO2, H2S, and CO2. The condensation and sublimation behaviors of each ice system and surface binding energies of their components are discussed. The surface binding energies can be used to calculate the residence times of the molecules on a surface as a function of temperature and thus represent important parameters for any calculation that attempts to model the transport of these molecules on Io's surface. The derived values indicate that SO2 frosts on Io are likely to anneal rapidly, resulting in less fluffy, "glassy" ices and that H2S can be trapped in the SO2 ices of Io during night-time hours provided that SO2 deposition rates are on the order of 5 micrometers/hr or larger.

  18. Critical behaviour in DOPC/DPPC/cholesterol mixtures: static (2)H NMR line shapes near the critical point.

    PubMed

    Davis, James H; Schmidt, Miranda L

    2014-05-06

    Static (2)H NMR spectroscopy is used to study the critical behavior of mixtures of 1,2-dioleoyl-phosphatidylcholine/1,2-dipalmitoyl-phosphatidylcholine (DPPC)/cholesterol in molar proportion 37.5:37.5:25 using either chain perdeuterated DPPC-d62 or chain methyl deuterated DPPC-d6. The temperature dependence of the first moment of the (2)H spectrum of the sample made with DPPC-d62 and of the quadrupolar splittings of the chain-methyl-labeled DPPC-d6 sample are directly related to the temperature dependence of the critical order parameter η, which scales as [Formula: see text] near the critical temperature. Analysis of the data reveals that for the chain perdeuterated sample, the value of Tc is 301.51 ± 0.1 K, and that of the critical exponent, βc = 0.391 ± 0.02. The line shape analysis of the methyl labeled (d6) sample gives Tc = 303.74 ± 0.07 K and βc = 0.338 ± 0.009. These values obtained for βc are in good agreement with the predictions of a three-dimensional Ising model. The difference in critical temperature between the two samples having nominally the same molar composition arises because of the lowering of the phase transition temperature that occurs due to the perdeuteration of the DPPC.

  19. Conformations and intermolecular interactions pattern in solid chloroxylenol and triclosan (API of anti-infective agents and drugs). A (35)Cl NQR, (1)H-(14)N NQDR, X-ray and DFT/QTAIM study.

    PubMed

    Latosińska, J N; Latosińska, M; Tomczak, M A; Seliger, J; Zagar, V; Maurin, J K

    2012-02-01

    Two antibacterial and antifungal agents, chloroxylenol (4-chloro-3,5-dimethyl-phenol) and triclosan (5-chloro-2-(2',4'-dichlorophenoxy)-phenol), were studied experimentally in solid state with an X-ray, (35)Cl-nuclear quadrupole resonance (NQR) and (17)O-nuclear quadrupole double resonance (NQDR) spectroscopies and, theoretically, with the density functional theory/quantum theory of atoms in molecules (DFT/QTAIM). The crystallographic structure of triclosan, which crystallises in space group P31 with one molecule in the asymmetric unit [a = 12.64100(10), b = 12.64100(10), c = 6.71630(10) Å], was solved with an X-ray and refined to a final R-factor of 2.81% at room temperature. The NQR frequencies of (35)Cl and (17)O were detected with the help of the density functional theory (DFT) assigned to particular chlorine and oxygen sites in the molecules of both compounds. The NQR frequencies at (35)Cl sites in chloroxylenol and triclosan were found to be more differentiated than frequencies at the (17)O site. The former better describes the substituent withdrawing effects connected to π-electron delocalization within the benzene rings and the influence of temperature; whereas, those at the (17)O site provide more information on O-H bond and intermolecular interactions pattern. The conformation adopted by diphenyl ether of triclosan in solid state was found to be typical of diphenyl ethers, but the opposite to those adopted when it was bound to different inhibitors. According to an X-ray study, temperature had no effect on the conformation of the diphenyl ring of triclosan, which was the same at 90 K and at room temperature (RT). The scattering of NQR frequencies reproduced by the DFT under assumption of the X-ray data at 90 K and RT is found to be a good indicator of the quality of resolution of the crystallographic structure.

  20. A density functional study of (17)O, (14)N and (2)H electric field gradient tensors in the real crystalline structure of alpha-glycine.

    PubMed

    Behzadi, Hadi; Hadipour, Nasser L; Mirzaei, Mahmoud

    2007-01-01

    A density functional theory (DFT) study was carried out to calculate (17)O, (14)N and (2)H electric field gradient (EFG) tensors in accurate neutron diffraction structures of alpha-glycine at 288 and 427 K. B3LYP is the used method and 6-311+G(*) and 6-311++G(**) are the basis sets in the calculations of EFG tensors at the sites of (17)O, (14)N and (2)H nuclei in the monomer and the octameric cluster of alpha-glycine at two temperatures. Quadrupole coupling constants and asymmetry parameters are the converted parameters of calculated EFG tensors to experimentally measurable ones. The calculated results of monomer and the target molecule in octameric cluster reveal that hydrogen-bonding interactions play an important role in the crystalline structure of alpha-glycine where the results of the target molecule in octameric cluster are in good agreement with the experiments.

  1. Synthesis, spectral characterization and larvicidal activity of acridin-1(2H)-one analogues.

    PubMed

    Subashini, R; Bharathi, A; Roopan, Selvaraj Mohana; Rajakumar, G; Abdul Rahuman, A; Gullanki, Pavan Kumar

    2012-09-01

    Acridin-1(2H)-one analogue of 7-chloro-3,4-dihydro-9-phenyl-2-[(pyridine-2yl) methylene] acridin-1(2H)-one, 5 was prepared by using 7-chloro-3,4-dihydro-9-phenylacridin-1(2H)-one, 3 and picolinaldehyde, 4 in the presence of KOH at room temperature. These compounds were characterized by analytical and spectral analyses. The purpose of the present study was to assess the efficacy of larvicidal and repellent activity of synthesized 7-chloro-3,4-dihydro-9-phenyl-acridin-1(2H)-one analogues such as compounds 3 and 5 against the early fourth instar larvae of filariasis vector, Culex quinquefasciatus and Japanese encephalitis vector, Culex gelidus (Diptera: Culicidae). The compound exhibited high larvicidal effects at 50mg/L against both the mosquitoes with LC(50) values of 25.02 mg/L (r(2)=0.998) and 26.40 mg/L (r(2)=0.988) against C. quinquefasciatus and C. gelidus, respectively. The 7-chloro-3,4-dihydro-9-phenyl-acridin-1(2H)-one analogues that are reported for the first time to our best of knowledge can be better explored for the control of mosquito population. This is an ideal ecofriendly approach for the control of Japanese encephalitis vectors, C. quinquefasciatus and C. gelidus.

  2. Drivers of δ2H variations in an idealized extratropical cyclone

    NASA Astrophysics Data System (ADS)

    Dütsch, Marina; Pfahl, Stephan; Wernli, Heini

    2016-05-01

    Numerical model simulations of stable water isotopes help to improve our understanding of the complex processes driving isotopic variability in atmospheric moisture. We use the isotope-enabled Consortium for Small-Scale Modelling (COSMO) model to study the governing mechanisms of δ2H variations in an idealized extratropical cyclone. A set of experiments with differing initial conditions of δ2H in vapor and partly deactivated isotopic fractionation allows us to quantify the relative roles of cloud fractionation and vertical and horizontal advection for the simulated δ2H signals associated with the cyclone and fronts. Horizontal transport determines the large-scale pattern of δ2H in both vapor and precipitation, while fractionation and vertical transport are more important on a smaller scale, near the fronts. During the passage of the cold front fractionation leads to a V-shaped trend of δ2H in precipitation and vapor, which is, for vapor, superimposed on a gradual decrease caused by the arrival of colder air masses.

  3. Detection and quantification of 2H and 3R phases in commercial graphene-based materials

    PubMed Central

    Seehra, Mohindar S.; Geddam, Usha K.; Schwegler-Berry, Diane; Stefaniak, Aleksandr B.

    2017-01-01

    Graphene-based material (GBM) samples acquired from commercial sources are investigated using X-ray diffraction (XRD). Of the 18 GBM samples investigated here, seven samples show XRD patterns with features characteristic of the graphite structure. The XRD patterns of the seven samples are analyzed showing the presence of both the ABA (2H) structure and the ABCA (3R) structure. After de-convoluting the (101) lines of the 2H and 3R structures, the areas under the peaks are used to determine the relative concentrations of the 2H and 3R phases present, typically yielding the ratio 60/40 for 2H/3R. The presence of the 3R structure is important since the 3R structure is a semiconductor with tunable band gap and it is less stable than the 2H structure. The number of layers determined from the analysis of the XRD data varies between 65 and 109 for different samples yielding thickness of the graphite sheets varying between 22 nm and 37 nm. Scanning electron microscopy and transmission electron microscopy of three representative samples confirms the sheet-like morphology and stacking of the graphene layers in the samples. Relevance of these results in connection with their potential applications and toxicology is briefly discussed.

  4. Synthesis, spectral characterization and larvicidal activity of acridin-1(2H)-one analogues

    NASA Astrophysics Data System (ADS)

    Subashini, R.; Bharathi, A.; Roopan, Selvaraj Mohana; Rajakumar, G.; Abdul Rahuman, A.; Gullanki, Pavan Kumar

    Acridin-1(2H)-one analogue of 7-chloro-3,4-dihydro-9-phenyl-2-[(pyridine-2yl) methylene] acridin-1(2H)-one, 5 was prepared by using 7-chloro-3,4-dihydro-9-phenylacridin-1(2H)-one, 3 and picolinaldehyde, 4 in the presence of KOH at room temperature. These compounds were characterized by analytical and spectral analyses. The purpose of the present study was to assess the efficacy of larvicidal and repellent activity of synthesized 7-chloro-3,4-dihydro-9-phenyl-acridin-1(2H)-one analogues such as compounds 3 and 5 against the early fourth instar larvae of filariasis vector, Culex quinquefasciatus and Japanese encephalitis vector, Culex gelidus (Diptera: Culicidae). The compound exhibited high larvicidal effects at 50 mg/L against both the mosquitoes with LC50 values of 25.02 mg/L (r2 = 0.998) and 26.40 mg/L (r2 = 0.988) against C. quinquefasciatus and C. gelidus, respectively. The 7-chloro-3,4-dihydro-9-phenyl-acridin-1(2H)-one analogues that are reported for the first time to our best of knowledge can be better explored for the control of mosquito population. This is an ideal ecofriendly approach for the control of Japanese encephalitis vectors, C. quinquefasciatus and C. gelidus.

  5. Dissociative Recombination of N2H+: Evidence for Fracture of the NN Bond

    NASA Astrophysics Data System (ADS)

    Geppert, W. D.; Thomas, R.; Semaniak, J.; Ehlerding, A.; Millar, T. J.; Österdahl, F.; af Ugglas, M.; Djurić, N.; Paál, A.; Larsson, M.

    2004-07-01

    Branching ratios and absolute cross sections have been measured for the dissociative recombination of N2H+ using the CRYRING ion storage ring. It has been found that the channel N2H++e--->N2+H accounts for only 36% of the total reaction and that the branching into the other exoergic pathway, N2H++e--->NH+N, consequently amounts to 64%. The cross section of the reaction could be fitted by the expression σ=(2.4+/-0.4)×10-16E-1.04+/-0.02 cm2, which leads to a thermal reaction rate of k(T)=(1.0+/-0.2)×10-7(T/300)-0.51+/-0.02 cm3 s-1, in favorable agreement with previous flowing afterglow Langmuir probe measurements at room temperature, although our temperature dependence is very different. The implications of these measurements for the chemistry of interstellar clouds are discussed. A standard model calculation for a dark cloud predicts a slight increase of N2H+ in the dark clouds but a five- to sevenfold increase of the NH concentration as steady state is reached.

  6. Imidacloprid inhibits IgE-mediated RBL-2H3 cell degranulation and passive cutaneous anaphylaxis

    PubMed Central

    Shi, Linbo; Zou, Li; Gao, Jinyan; Xu, Huaing; Shi, Xiaoyun

    2016-01-01

    Background Imidacloprid has been commonly used as a pesticide for crop protection and acts as nicotinic acetylcholine receptor agonists. Little information about the relationship between imidacloprid and allergy is available. Objective This study aims to examine the effects of imidacoprid on IgE-mediated mast cell activation. Methods The rat basophilic leukemia cell line RBL-2H3 (RBL-2H3 cells) were treated with 10-3 – 10-12 mol/L imidacloprid, followed by measuring the mediator production, influx of Ca2+ in IgE-activated RBL-2H3 cells, and the possible effects of imidacoprid on anti-dinitrophenyl IgE-induced passive cutaneous anaphylaxis (PCA). Results It was shown that imidacoprid suppressed the production of histamine, β-hexosaminidase, leukotriene C4, interleukin-6, tumor necrosis factor-α, and Ca2+ mobilization in IgE-activated RBL-2H3 cells and decreased vascular extravasation in IgE-induced PCA. Conclusion It is the first time to show that imidacloprid suppressed the activation of RBL-2H3 cells. PMID:27803884

  7. Titan's ionic species: theoretical treatment of N2H+ and related ions.

    PubMed

    Brites, V; Hochlaf, M

    2009-10-22

    We use different ab initio methods to compute the three-dimensional potential energy surface (3D-PES) of the ground state of N(2)H(+). This includes the standard coupled cluster, the complete active space self-consistent field, the internally contacted multi reference configuration interaction, and the newly developed CCSD(T)-F12 methods. For the description of H and N atoms, several basis sets are tested. Then, we incorporate the 3D-PES analytical representations into variational calculations of the rovibrational spectrum of N(2)H(+)(X(1)Sigma(+)) up to 7200 cm(-1) above the zero point vibrational energy. Our data show that the CCSD(T)-F12/aug-cc-pVTZ approach represents a compromise for good description of the PES and computation cost. This technique is recommended for full dimensional PES generation of atmospheric and astrophysical relevant polyatomic systems. We applied this method to derive the rovibrational spectra of N(2)H(+)(X(1)Sigma(+)) and of N(2)H(++)(X(2)Sigma(+)). Finally, we discuss the existence of the N(2)H(++)(X(2)Sigma(+)) in Titan's atmosphere.

  8. Tunable electronic behavior in 3d transition metal doped 2H-WSe2

    NASA Astrophysics Data System (ADS)

    Liu, Shuai; Huang, Songlei; Li, Hongping; Zhang, Quan; Li, Changsheng; Liu, Xiaojuan; Meng, Jian; Tian, Yi

    2017-03-01

    Structural and electronic properties of 3d transition metal Sc, Ti, Cr and Mn incorporated 2H-WSe2 have been systematically investigated by first-principles calculations based on density functional theory. The calculated formation energies reveal that all the doped systems are thermodynamically more favorable under Se-rich condition than W-rich condition. The geometry structures almost hold that of the pristine 2H-WSe2 albeit with slight lattice distortion. More importantly, the electronic properties have been significantly tuned by the dopants, i.e., metal and semimetal behavior has been found in Sc, Ti and Mn-doped 2H-WSe2, respectively, semiconducting nature with narrowed band gap is expected in Cr-doped case, just as that of the pristine 2H-WSe2. In particular, magnetic character is realized by incorporation of Mn impurity with a total magnetic moment of 0.96 μB. Our results suggest chemical doping is an effective way to precisely tailor the electronic structure of layered transition metal dichalcogenide 2H-WSe2 for target technological applications.

  9. Vibration-rotation spectroscopic database on acetylene, X ˜ 1 Σg + (12C2H2)

    NASA Astrophysics Data System (ADS)

    Amyay, B.; Fayt, A.; Herman, M.; Vander Auwera, J.

    2016-06-01

    A complete set of calculated vibration-rotation energies of 12C2H2 ( X ˜ 1 Σg + ) is provided for all vibrational states up to 13 000 cm-1 and some at higher energies, with rotational (J) and vibrational angular momentum (l) quantum numbers such that 0 ≤ J ≤ 100 and 0 ≤ |l| ≤ 20, respectively. The calculation is performed using a global effective Hamiltonian and related spectroscopic constants from the literature [B. Amyay et al., J. Mol. Spectrosc. 267, 80 (2011)], based on the polyad model. The numerical values of all related polyad matrix elements are also provided. The model and equations for the Hamiltonian matrix elements are gathered. The experimental acetylene database used for determining the parameters is listed.

  10. Elastic positron scattering by C{sub 2}H{sub 2}: Differential cross sections and virtual state formation

    SciTech Connect

    Carvalho, Claudia R.C. de; Varella, Marcio T. do N; Lima, Marco A.P.; Silva, Euclimar P. da

    2003-12-01

    We present calculated elastic differential cross sections for positron-acetylene scattering, obtained by using the Schwinger multichannel method. Our results are in very good agreement with quasielastic experimental data of Kauppila et al. [Nucl. Instrum. Meth. Phys. Res. B 192, 162 (2002)]. We also discuss the existence of a virtual state (zero-energy resonance) in e{sup +}-C{sub 2}H{sub 2} collisions, based on the behavior of the integral cross section and of the s-wave phase shift. As expected the fixed-nuclei cross section and annihilation parameter (Z{sub eff}) present the same energy dependence at very low impact energies. As the virtual state energy approaches zero, the magnitude of both cross section and Z{sub eff} are extremely enhanced (at zero impact energy). The possibility of shifting from a low-lying virtual state to a shallow bound state is not expected to significantly affect room-temperature annihilation rates.

  11. Rotational spectroscopy of vibrationally excited N2H+ and N2D+ up to 2.7 THz

    NASA Astrophysics Data System (ADS)

    Yu, S.; Pearson, J. C.; Drouin, B. J.; Crawford, T.; Daly, A. M.; Elliott, B.; Amano, T.

    2015-08-01

    Terahertz absorption spectroscopy was employed to extend the measurements on the pure rotational transitions of N2H+, N2D+ and their 15N-containing isotopologues in the ground state and first excited vibrational states for the three fundamental vibrational modes. In total, 91 new pure rotational transitions were observed in the range of 0.7-2.7 THz. The observed transition frequencies were fit to experimental accuracy, and the improved molecular parameters were obtained. The new measurements and predictions reported here will support the analysis of high-resolution astronomical observations made with facilities such as SOFIA and ALMA where laboratory rest frequencies with uncertainties of 1 MHz or smaller are required for proper analysis of velocity resolved astrophysical components.

  12. Abstraction and addition kinetics of C2H radicals with CH4, C2H6, C3H8, C2H4, and C3H6: CVT/SCT/ISPE and hybrid meta-DFT methods.

    PubMed

    Dash, Manas Ranjan; Rajakumar, B

    2015-02-07

    Rate coefficients for the reactions of C2H radicals with methane (k1), ethane (k2), propane (k3), ethylene (k4), and propylene (k5) were computed using canonical variational transition state theory (CVT) coupled with hybrid-meta density functional theory (DFT) over a wide range of temperatures from 150 to 5000 K. The quantum chemical tunneling effect was corrected by the small curvature tunneling (SCT) method. The dynamic calculations are performed using the variational transition state theory (VTST) with the interpolated single-point energies (ISPE) method at the CCSD(T)/cc-pVTZ//M06-2X/6-31+G(d,p) level of theory. Intrinsic reaction coordinate (IRC) calculations were performed to verify that the transition states are connected to the reactants and products. The rate coefficients obtained over the studied temperature range yield the following Arrhenius expressions (cm(3) molecule(-1) s(-1)): k1 = 4.69 × 10(-19)T(2.44) exp[331/T], k2 = 4.29 × 10(-17)T(2.11) exp[432/T], k3 = 4.81 × 10(-17)T(1.98) exp[697/T], k4 = 7.54 × 10(-21)T(2.96) exp[1942/T], and k5 = 8.04 × 10(-23)T(3.44) exp[3011/T] cm(3) molecule(-1) s(-1). Branching ratio calculation for the reactions of C2H radicals with ethylene and propylene shows that the abstraction reactions are not important at lower temperatures. However, as the temperature increases, abstraction reactions become more important.

  13. A pulse sequence for singlet to heteronuclear magnetization transfer: S2hM

    NASA Astrophysics Data System (ADS)

    Stevanato, Gabriele; Eills, James; Bengs, Christian; Pileio, Giuseppe

    2017-04-01

    We have recently demonstrated, in the context of para-hydrogen induced polarization (PHIP), the conversion of hyperpolarized proton singlet order into heteronuclear magnetisation can be efficiently achieved via a new sequence named S2hM (Singlet to heteronuclear Magnetisation). In this paper we give a detailed theoretical description, supported by an experimental illustration, of S2hM. Theory and experiments on thermally polarized samples demonstrate the proposed method is robust to frequency offset mismatches and radiofrequency field inhomogeneities. The simple implementation, optimisation and the high conversion efficiency, under various regimes of magnetic equivalence, makes S2hM an excellent candidate for a widespread use, particularly within the PHIP arena.

  14. Photodetectors and birefringence in ZnP2-С2h5 crystals

    NASA Astrophysics Data System (ADS)

    Stamov, I. G.; Syrbu, N. N.; Dorogan, A. V.

    2013-03-01

    The spectral dependences of refractive indexes no(n⊥), ne(n||) and Δn=no(n⊥)-ne(n||) were studied in ZnP2-C2h5 crystals. The intersection of no(n⊥) and ne(n||) was found for λ0=0.906 μm. The crystal possesses positive dispersion Δn=no(n⊥)-ne(n||) in the region where λ>λ0, and a negative dispersion is observed in the region where λ<λ0. The electrical, spectral and azimuth characteristics of monolith n-р- and Ме-n-р-ZnP2C2h5 and discrete ZnP2-C2h5-ZnP2-D48 structures were studied, and a prognosis was made on the usage perspective of these devices.

  15. Analysis Of 2H-Evaporator Scale Pot Bottom Sample [HTF-13-11-28H

    SciTech Connect

    Oji, L. N.

    2013-07-15

    Savannah River Remediation (SRR) is planning to remove a buildup of sodium aluminosilicate scale from the 2H-evaporator pot by loading and soaking the pot with heated 1.5 M nitric acid solution. Sampling and analysis of the scale material from the 2H evaporator has been performed so that the evaporator can be chemically cleaned beginning July of 2013. Historically, since the operation of the Defense Waste Processing Facility (DWPF), silicon in the DWPF recycle stream combines with aluminum in the typical tank farm supernate to form sodium aluminosilicate scale mineral deposits in the 2H-evaporator pot and gravity drain line. The 2H-evaporator scale samples analyzed by Savannah River National Laboratory (SRNL) came from the bottom cone sections of the 2H-evaporator pot. The sample holder from the 2H-evaporator wall was virtually empty and was not included in the analysis. It is worth noting that after the delivery of these 2H-evaporator scale samples to SRNL for the analyses, the plant customer determined that the 2H evaporator could be operated for additional period prior to requiring cleaning. Therefore, there was no need for expedited sample analysis as was presented in the Technical Task Request. However, a second set of 2H evaporator scale samples were expected in May of 2013, which would need expedited sample analysis. X-ray diffraction analysis (XRD) confirmed the bottom cone section sample from the 2H-evaporator pot consisted of nitrated cancrinite, (a crystalline sodium aluminosilicate solid), clarkeite and uranium oxide. There were also mercury compound XRD peaks which could not be matched and further X-ray fluorescence (XRF) analysis of the sample confirmed the existence of elemental mercury or mercuric oxide. On ''as received'' basis, the scale contained an average of 7.09E+00 wt % total uranium (n = 3; st.dev. = 8.31E-01 wt %) with a U-235 enrichment of 5.80E-01 % (n = 3; st.dev. = 3.96E-02 %). The measured U-238 concentration was 7.05E+00 wt % (n=3, st

  16. Theoretical study of the C-H bond dissociation energy of C2H

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

    1990-01-01

    A theoretical study of the convergence of the C-H bond dissociation energy D(0) in C2H with respect to both the one- and n-particle spaces is presented. The calculated C-H bond energies of C2H2 and C2H4, which are in excellent agreement with experiment, are used for calibration. The best estimate for D(0) of 112.4 + or - 2.0 kcal/mol is slightly below the recent experimental value of 116.3 + or - 2.6 kcal/mol, but substantially above a previous theoretical estimate of 102 kcal/mol. The remaining discrepancy with experiment may reflect primarily the uncertainty in the experimental D(0) value of C2 required in the analysis.

  17. Detection of C2H4 Neptune from ISO/PHT-S Observations

    NASA Technical Reports Server (NTRS)

    Schulz, B.; Encrenaz, Th.; Bezard, B.; Romani, P. N.; Lellouch, E.; Atreya, S. K.

    1999-01-01

    The 6-12 micrometer spectrum of Neptune has been recorded with the PHT-S instrument of the Infrared Space Observatory (ISO) at a resolution of 0.095 micrometer. In addition to the emissions of CH4, CH3D and C2H6 previously identified, the spectrum shows the first firm identification of ethylene C2H4. The inferred column density above the 0.2-mbar level is in the range (1.1 - 3) x 10(exp 14) molecules/cm. To produce this low amount, previous photochemical models invoked rapid mixing between the source and sink regions of C2H4. We show that this requirement can be relaxed if recent laboratory measurements of CH4 photolysis branching ratios at Lyman alpha are used.

  18. Anharmonic suppression of charge density waves in 2H-NbS2

    NASA Astrophysics Data System (ADS)

    Leroux, M.; Le Tacon, M.; Calandra, M.; Cario, L.; Méasson, M.-A.; Diener, P.; Borrissenko, E.; Bosak, A.; Rodière, P.

    2012-10-01

    The temperature dependence of the phonon spectrum in the superconducting transition-metal dichalcogenide 2H-NbS2 is measured by diffuse and inelastic x-ray scattering. A deep, wide, and strongly temperature-dependent softening of the two lowest-energy longitudinal phonon bands appears along the ΓM symmetry line in reciprocal space. In sharp contrast to the isoelectronic compound 2H-NbSe2, the soft phonons energies are finite, even at very low temperature, and no charge density wave instability occurs, in disagreement with harmonic ab initio calculations. We show that 2H-NbS2 is at the verge of the charge density wave transition and its occurrence is only suppressed by the large anharmonic effects. Moreover, the anharmonicity and the electron phonon coupling both show a strong in-plane anisotropy.

  19. N2H(+) in the Orion ambient ridge - Cloud clumping versus rotation

    NASA Technical Reports Server (NTRS)

    Womack, Maria; Ziurys, L. M.; Sage, L. J.

    1993-01-01

    The IRAM 30-m telescope is used to obtain spectra of the J = 1 yields 0 transition of N2H(+) over a 2 x 2 arcsec area toward the Orion-KL/IRc2 star-forming region with 26-arcsec angular resolution. The N2H(+) emission, which exclusively traces the ridge gas, exhibits multiple radial velocities which appear to arise from the presence of at least four clouds of quiescent material. It is argued that the velocity structure of N2H(+) does not uniformly change across OMC-1 and, consequently, is inconsistent with the presence of large-scale differential rotation of the extended ridge along the SW-NE axis about IRc2. The coincidence of the two larger clouds with star-forming activity in Orion-KL suggests that either the quiescent gas is being pushed apart or that the star formation may have been triggered by a cloud-cloud interaction.

  20. A one-pot-three-step route to triazolotriazepinoindazolones from oxazolino-2H-indazoles.

    PubMed

    Conrad, Wayne E; Rodriguez, Kevin X; Nguyen, Huy H; Fettinger, James C; Haddadin, Makhluf J; Kurth, Mark J

    2012-08-03

    A one-pot-three-step method has been developed for the conversion of oxazolino-2H-indazoles into triazolotriazepinoindazolones with three points of diversity. Step one of this process involves a propargyl bromide-initiated ring opening of the oxazolino-2H-indazole (available by the Davis-Beirut reaction) to give an N(1)-(propargyl)-N(2)-(2-bromoethyl)-disubstituted indazolone, which then undergoes -CH(2)Br → -CH(2)N(3) displacement (step two) followed by an uncatalyzed intramolecular azide-alkyne 1,3-dipolar cycloaddition (step three) to form the target heterocycle. Employing 7-bromooxazolino-2H-indazole allows for further diversification through, for example, palladium-catalyzed coupling chemistry, as reported here.

  1. Collisions of slow polyatomic ions with surfaces: dissociation and chemical reactions of C2H2+*, C2H3+, C2H4+*, C2H5+, and their deuterated variants C2D2+* and C2D4+* on room-temperature and heated carbon surfaces.

    PubMed

    Jasík, Juraj; Zabka, Jan; Feketeova, Linda; Ipolyi, Imre; Märk, Tilmann D; Herman, Zdenek

    2005-11-17

    Interaction of C2Hn+ (n = 2-5) hydrocarbon ions and some of their isotopic variants with room-temperature and heated (600 degrees C) highly oriented pyrolytic graphite (HOPG) surfaces was investigated over the range of incident energies 11-46 eV and an incident angle of 60 degrees with respect to the surface normal. The work is an extension of our earlier research on surface interactions of CHn+ (n = 3-5) ions. Mass spectra, translational energy distributions, and angular distributions of product ions were measured. Collisions with the HOPG surface heated to 600 degrees C showed only partial or substantial dissociation of the projectile ions; translational energy distributions of the product ions peaked at about 50% of the incident energy. Interactions with the HOPG surface at room temperature showed both surface-induced dissociation of the projectiles and, in the case of radical cation projectiles C2H2+* and C2H4+*, chemical reactions with the hydrocarbons on the surface. These reactions were (i) H-atom transfer to the projectile, formation of protonated projectiles, and their subsequent fragmentation and (ii) formation of a carbon chain build-up product in reactions of the projectile ion with a terminal CH3-group of the surface hydrocarbons and subsequent fragmentation of the product ion to C3H3+. The product ions were formed in inelastic collisions in which the translational energy of the surface-excited projectile peaked at about 32% of the incident energy. Angular distributions of reaction products showed peaking at subspecular angles close to 68 degrees (heated surfaces) and 72 degrees (room-temperature surfaces). The absolute survival probability at the incident angle of 60 degrees was about 0.1% for C2H2+*, close to 1% for C2H4+* and C2H5+, and about 3-6% for C2H3+.

  2. Filamentary Structure of Serpens Main and Serpens South Seen in N2H+, HCO+, and HCN

    NASA Astrophysics Data System (ADS)

    Cox, Erin Guilfoil; Fernandez-Lopez, Manuel; Looney, Leslie; Arce, Héctor; Mundy, Lee; Storm, Shaye; Harris, Robert J.; Teuben, Peter J.

    2016-06-01

    We present the N2H+ (J = 1 → 0) map of the Serpens Main and Serpens South molecular cloud obtained as part of the CARMA Large Area Star Formation Survey (CLASSy). The observations cover 150 arcmin2 and 250 arcmin2, respectively, and fully sample structures from 3000 AU to 3 pc with a velocity resolution of 0.16 km s-1. They can be used to constrain the origin and evolution of molecular cloud filaments. The spatial distribution of the N2H+ emission is characterized by long filaments that resemble those observed in the dust continuum emission by Herschel. However, the gas filaments are typically narrower such that, in some cases, two or three quasi-parallel N2H+ filaments comprise a single observed dust continuum filament. Our results suggest that single filaments seen in Serpens South by Herschel may in fact be comprised of multiple narrower filaments. Some molecular filaments show velocity gradients along their major axis, and two are characterized by a steep velocity gradient in the direction perpendicular to the filament axis. The observed velocity gradient along one of these filaments was previously postulated as evidence for mass infall toward the central cluster, but these kind of gradients can be interpreted as projection of large-scale turbulence. Finally we compare the morphologies of these N2H+ filaments with those detected in HCO+ and HCN. In Serpens South we find that the N2H+ and dust maps are well correlated, whereas HCO+ and HCN do not have regularly have N2H+ counterparts. We postulate that this difference is due to large-scale shocks creating the HCO+ and HCN emission.

  3. Low-energy elastic electron scattering form chloroethane, C2H5Cl

    NASA Astrophysics Data System (ADS)

    Sakaamini, A.; Navarro, C.; Cross, J.; Hargreaves, L. R.; Khakoo, M. A.; Fedus, Kamil; Winstead, C.; McKoy, V.

    2015-10-01

    We report theoretical as well as (normalized) experimental differential and integral cross sections for vibrationally elastic scattering of low-energy electrons from chloroethane, C2H5Cl, also known as ethyl chloride. The theoretical cross sections were computed using the Schwinger multichannel variational method in the single-channel approximation, with polarization effects included via virtual excitations. Cross section measurements were made at incident energies ranging from 1 to 30 eV and at scattering angles from {10}\\circ to {125}\\circ . We compare our data to previous results for C2H5Cl and for the related molecule chloromethane.

  4. Calculation of the Aluminosilicate Half-Life Formation Time in the 2H Evaporator

    SciTech Connect

    Fondeur, F.F.

    2000-09-21

    The 2H Evaporator contains large quantities of aluminosilicate solids deposited on internal fixtures. The proposed cleaning operations will dissolve the solids in nitric acid. Operations will then neutralize the waste prior to transfer to a waste tank. Combining recent calculations of heat transfer for the 2H Evaporator cleaning operations and laboratory experiments for dissolution of solid samples from the pot, the authors estimated the re-formation rate for aluminosilicates during cooling. The results indicate a half-life formation of 17 hours when evaporator solution cools from 60 degrees C and 9 hours when cooled from 90 degrees C.

  5. Low-temperature solid-state phase transformations in 2H silicon carbide

    NASA Technical Reports Server (NTRS)

    Will, H. A.; Powell, J. A.

    1972-01-01

    Single crystals of 2H SiC were observed to undergo phase transformations at temperatures as low as 400 C. Some 2H crystals transformed to a structure with one-dimensional disorder along the crystal c axis. Others transformed to a faulted cubic/6H structure. The transformation is time and temperature dependent and is greatly enhanced by dislocations. Observations indicate that the transformation takes place by means of a slip process perpendicular to the c axis. Cubic SiC crystals were observed to undergo a solid state transformation above 1400 C.

  6. Identification of acetylene (C2H2) in infrared atmospheric absorption spectra

    NASA Astrophysics Data System (ADS)

    Goldman, A.; Murcray, F. J.; Blatherwick, R. D.; Gillis, J. R.; Bonomo, F. S.; Murcray, F. H.; Murcray, D. G.; Cicerone, R. J.

    1981-12-01

    Infrared atmospheric absorption spectra at ˜0.02 cm-1 resolution obtained during a balloon flight made on March 23, 1981, show absorption features attributable to C2H2. These features are used to derive a preliminary mixing ratio of ˜25 pptv near 9 km. This mixing ratio falls into the range of values we calculate for upper tropospheric C2H2 in a photochemical/transport model but well below values measured previously in samples collected by other researchers.

  7. Implications of C2H photochemistry on the modeling of C2 distributions in comets

    NASA Technical Reports Server (NTRS)

    Jackson, William M.; Bao, Yihan; Urdahl, Randall S.

    1991-01-01

    Laboratory studies of the secondary photolysis of the C2H radical are summarized and used to explain some discrepancies between models of C2 emission in comets. These studies show that several states of the C2 radicals produced in the photolysis of C2H2 at 193 nm have bimodal rotational distributions when plotted as a Boltzmann diagram. They also establish that the C2 radicals are formed with varying degrees of vibrational excitation, so that if they are formed in a similar manner in comets, the C2 radicals must start out with this initial vibrational excitation.

  8. Effects of deuterium oxide on cell growth and vesicle speed in RBL-2H3 cells

    PubMed Central

    Triplett, Ashley R.

    2014-01-01

    For the first time we show the effects of deuterium oxide on cell growth and vesicle transport in rat basophilic leukemia (RBL-2H3) cells. RBL-2H3 cells cultured with 15 moles/L deuterium showed decreased cell growth which was attributed to cells not doubling their DNA content. Experimental observations also showed an increase in vesicle speed for cells cultured in deuterium oxide. This increase in vesicle speed was not observed in deuterium oxide cultures treated with a microtubule-destabilizing drug, suggesting that deuterium oxide affects microtubule-dependent vesicle transport. PMID:25237603

  9. Multicomponent synthesis of 3,6-dihydro-2H-1,3-thiazine-2-thiones.

    PubMed

    Kruithof, Art; Ploeger, Marten L; Janssen, Elwin; Helliwell, Madeleine; de Kanter, Frans J J; Ruijter, Eelco; Orru, Romano V A

    2012-02-08

    Non-fused 3,6-dihydro-2H-1,3-thiazine-2-thiones constitute a so far rather unexplored class of compounds, with the latest report dating back more than two decades. Thiazine-2-thiones contain an endocyclic dithiocarbamate group, which is often found in pesticides, in substrates for radical chemistry and in synthetic intermediates towards thioureas and amidines. We now report the multicomponent reaction (MCR) of in situ-generated 1-azadienes with carbon disulfide. With this reaction, a one-step protocol towards the potentially interesting 3,6-dihydro-2H-1,3-thiazine-2-thiones was established and a small library was synthesized.

  10. Electron-Impact Total Ionization Cross Sections of CH and C2H2

    PubMed Central

    Kim, Yong-Ki; Ali, M. Asgar; Rudd, M. Eugene

    1997-01-01

    Electron-impact total ionization cross sections for the CH radical and C2H2 (acetylene) have been calculated using the Binary-Encounter-Bethe (BEB) model. The BEB model combines the Mott cross section and the asymptotic form of the Bethe theory, and has been shown to generate reliable ionization cross sections for a large variety of molecules. The BEB cross sections for CH and C2H2 are in good agreement with the available experimental data from ionization thresholds to hundreds of eV in incident energies. PMID:27805116

  11. Davis-Beirut reaction: route to thiazolo-, thiazino-, and thiazepino-2H-indazoles.

    PubMed

    Farber, Kelli M; Haddadin, Makhluf J; Kurth, Mark J

    2014-08-01

    Methods for the construction of thiazolo-, thiazino-, and thiazepino-2H-indazoles from o-nitrobenzaldehydes or o-nitrobenzyl bromides and S-trityl-protected 1°-aminothioalkanes are reported. The process consists of formation of the requisite N-(2-nitrobenzyl)(tritylthio)alkylamine, subsequent deprotection of the trityl moiety with TFA, and immediate treatment with aq. KOH in methanol under Davis-Beirut reaction conditions to deliver the target thiazolo-, thiazino-, or thiazepino-2H-indazole in good overall yield. Subsequent S-oxidation gives the corresponding sulfone.

  12. Effect of salinity on 2H/1H fractionation in lipids from continuous cultures of the coccolithophorid Emiliania huxleyi

    NASA Astrophysics Data System (ADS)

    Sachs, Julian P.; Maloney, Ashley E.; Gregersen, Josh; Paschall, Christopher

    2016-09-01

    Salinity and temperature dictate the buoyancy of seawater, and by extension, ocean circulation and heat transport. Yet there remain few widely applicable proxies for salinity with the precision necessary to infer all but the largest hydrographic variations in the past. In the last decade the hydrogen isotope composition (2H/1H or δ2H) of microalgal lipids has been shown to increase systematically with salinity, providing a foundation for its use as a paleosalinity proxy. Culture and field studies have indicated a wide range of sensitivities for this response, ranging from about 0.6-3.3‰ ppt-1 depending on the lipid, location and/or culturing conditions. Lacking in these studies has been the controlled conditions necessary to isolate the response to salinity while keeping all other growth parameters constant. Here we show that the hydrogen isotope composition of lipids in the marine coccolithophorid Emiliania huxleyi grown in chemostats increased by 1.6 ± 0.3‰ ppt-1 (p < 0.05) in eight individual alkenones and by 2.0 ± 0.1‰ ppt-1 (p < 0.05) in three individual fatty acids over the salinity range 20-42 ppt. Hydrogen isotope ratios of phytol and the sterol 24-methyl-cholest-5,22-dien-3β-ol (brassicasterol) also increased with salinity but correlations were weaker than for the acetogenic lipids. For eight individual alkenones, linear regression analyses of the fractionation factors on salinity yielded slopes of 1.2-2.2‰ ppt-1. This sensitivity of δ2Halkenone to salinity is 45-71% of that previously reported for E. huxleyi, which can be attributed to the fact that previous experiments were performed with batch cultures in which growth rates and other parameters differed between salinity treatments. The underlying cause of this response to salinity remains unknown, but may result from changes in (1) the proportion of lipid hydrogen derived from NADPH versus water, (2) the proportion of lipid hydrogen derived from NADPH from Photosystem I versus the oxidative

  13. Unfolding the Quantum Nature of Proton Bound Symmetric Dimers of (MeOH)2H+ and (Me2O)2H+: a Theoretical Study

    NASA Astrophysics Data System (ADS)

    Tan, Jake Acedera; Kuo, Jer-Lai

    2014-06-01

    A proton under a tug of war between two competing Lewis bases is a common motif in biological systems and proton transfer processes. Over the past decades, model compounds for such motifs can be prepared by delicate stoichiometric control of salt solutions. Unfortunately, condensed phase studies, which aims to identify the key vibrational signatures are complicated to analyze. As a result, gas-phase studies do provide promising insights on the behavior of the shared proton. This study attempts to understand the quantum nature of the shared proton under theoretical paradigms. Proton bound symmetric dimers of (MeOH)2H+ and (Me2O)2H+ are chosen as the model compounds. The simulation is performed using Density Functional Theory (DFT) at the B3LYP level with 6-311+G(d,p) as the basis set. It was found out that stretching mode of shared proton couples with several other normal modes and its corresponding oscillator strength do distribute to other normal modes. J.R. Roscioli, L.R. McCunn and M.A. Johnson. Science 2007, 316, 249 T.E. DeCoursey. Physiol. Rev., 2003, 83, 475 E.S. Stoyanov. Psys. Chem. Phys., 2000,2,1137

  14. The conformational dynamics of H2-H3n and S2-H6 in gating ligand entry into the buried binding cavity of vitamin D receptor

    PubMed Central

    Tee, Wei-Ven; Ripen, Adiratna Mat; Mohamad, Saharuddin Bin

    2016-01-01

    Crystal structures of holo vitamin D receptor (VDR) revealed a canonical conformation in which the ligand is entrapped in a hydrophobic cavity buried in the ligand-binding domain (LBD). The mousetrap model postulates that helix 12 is positioned away from the domain to expose the interior cavity. However, the extended form of helix 12 is likely due to artifacts during crystallization. In this study, we set out to investigate conformational dynamics of apo VDR using molecular dynamics simulation on microsecond timescale. Here we show the neighboring backbones of helix 2-helix 3n and beta strand 2-helix 6 of LBD, instead of the helix 12, undergo large-scale motion, possibly gating the entrance of ligand to the ligand binding domain. Docking analysis to the simulated open structure of VDR with the estimated free energy of −37.0 kJ/mol, would emphasise the role of H2-H3n and S2-H6 in facilitating the entrance of calcitriol to the LBD of VDR. PMID:27786277

  15. Laser-induced fluorescence studies of excited Sr reactions: II. Sr(3P1)+CH3F, C2H5F, C2H4F2

    NASA Astrophysics Data System (ADS)

    Teule, J. M.; Janssen, M. H. M.; Bulthuis, J.; Stolte, S.

    1999-06-01

    The vibrational and rotational energy distributions of ground state SrF(X 2Σ) formed in the reactions of electronically excited Sr(3P1) with methylfluoride, ethylfluoride, and 1,1-difluoroethane have been studied by laser-induced fluorescence. Although the reactions of ground state Sr with these reactants are exothermic, no SrF products are observed for those reactions in this study. The fraction of available energy disposed into the sum of rotational and vibrational energy of the SrF(X 2Σ) product is approximately the same for all three reactions, i.e., 40%. The reaction of Sr(3P1) with CH3F results in very low vibrational excitation in the SrF reaction product. The product vibration increases in going to C2H5F and C2H4F2. It is concluded that the alkyl group influences the energy disposal mechanism in these reactions, and some suggestions are given for a partial explanation of the observations.

  16. Chemistry of TMC-1 with multiply deuterated species and spin chemistry of H2, H2+, H3+ and their isotopologues

    NASA Astrophysics Data System (ADS)

    Majumdar, L.; Gratier, P.; Ruaud, M.; Wakelam, V.; Vastel, C.; Sipilä, O.; Hersant, F.; Dutrey, A.; Guilloteau, S.

    2016-12-01

    Deuterated species are unique and powerful tools in astronomy since they can probe the physical conditions, chemistry, and ionization level of various astrophysical media. Recent observations of several deuterated species along with some of their spin isomeric forms have rekindled the interest for more accurate studies on deuterium fractionation. This paper presents the first publicly available chemical network of multiply deuterated species along with spin chemistry implemented on the latest state-of-the-art gas-grain chemical code `NAUTILUS'. D/H ratios for all deuterated species observed at different positions of TMC-1 are compared with the results of our model, which considers multiply deuterated species along with the spin chemistry of light hydrogen bearing species H2, H2+, H3+ and their isotopologues. We also show the differences in the modeled abundances of non-deuterated species after the inclusion of deuteration and spin chemistry in the model. Finally, we present a list of potentially observable deuterated species in TMC-1 awaiting detection.

  17. Synthesis of (11,11,12,12-2H4)progesterone for mass spectral investigations of peripheral metabolism

    SciTech Connect

    Kirk, D.N.; Smith, C.Z.; Honour, J.W. )

    1990-05-01

    Hecogenin has been transformed into (11,11,12,12-2H4)progesterone via base-catalyzed isotope exchange with D2O (at C-11), carbenic decomposition of the 12-tosylhydrazone formed by the use of (N,N,N'-2H3)toluene-p-sulfonylhydrazine, and reduction with (2H2)diimide to give (11,11,12,12-2H4)tigogenin, followed by standard degradation of the spiroketal side chain and dehydrogenation in ring A.

  18. Distortion of ethyne on coordination to silver acetylide, C2H2ṡṡṡAgCCH, characterised by broadband rotational spectroscopy and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Stephens, Susanna L.; Zaleski, Daniel P.; Mizukami, Wataru; Tew, David P.; Walker, Nicholas R.; Legon, Anthony C.

    2014-03-01

    The rotational spectra of six isotopologues of a complex of ethyne and silver acetylide, C2H2ṡṡṡAgCCH, are measured by both chirped-pulse and Fabry-Perot cavity versions of Fourier-transform microwave spectroscopy. The complex is generated through laser ablation of a silver target in the presence of a gas sample containing 1% C2H2, 1% SF6, and 98% Ar undergoing supersonic expansion. Rotational, A0, B0, C0, and centrifugal distortion ΔJ and ΔJK constants are determined for all isotopologues of C2H2ṡṡṡAgCCH studied. The geometry is planar, C2v and T-shaped in which the C2H2 sub-unit comprises the bar of the "T" and binds to the metal atom through its π electrons. In the r0 geometry, the distance of the Ag atom from the centre of the triple bond in C2H2 is 2.2104(10) Å. The r(HC≡CH) parameter representing the bond distance separating the two carbon atoms and the angle, ∠(CCH), each defined within the C2H2 sub-unit, are determined to be 1.2200(24) Å and 186.0(5)°, respectively. This distortion of the linear geometry of C2H2 involves the hydrogen atoms moving away from the silver atom within the complex. The results thus reveal that the geometry of C2H2 changes measurably on coordination to AgCCH. A value of 59(4) N m-1 is determined for the intermolecular force constant, kσ, confirming that the complex is significantly more strongly bound than hydrogen and halogen-bonded analogues. Ab initio calculations of the re geometry at the CCSD(T)(F12*)/ACVTZ level of theory are consistent with the experimental results. The spectra of the 107Ag13C13CH and 109Ag13C13CH isotopologues of free silver acetylide are also measured for the first time allowing the geometry of the AgCCH monomer to be examined in greater detail than previously.

  19. 2H-CuScO2 Prepared by Low-Temperature Hydrothermal Methods and Post-Annealing Effects on Optical and Photoelectrochemical Properties.

    PubMed

    Draskovic, Thomas I; Yu, Mingzhe; Wu, Yiying

    2015-06-01

    The delafossite structured CuScO2 is a p-type, wide band gap oxide that has been shown to support significant oxygen intercalation, leading to darkened color and increased conductivity. Control of this oxidation proves difficult by the conventional high-temperature solid-state syntheses. In addition, a pure hexagonal (2H) or rhombohedral (3R) polytype of CuScO2 requires careful control of synthetic parameters or intentional doping. Lower-temperature hydrothermal syntheses have thus far led to only a mixed 2H/3R product. Herein, control of hydrothermal conditions with the consideration of copper and scandium hydrolysis led to the synthesis of light beige, hierarchically structured particles of 2H-CuScO2. Absorption of the particles in the visible range was found to increase upon annealing of the sample in air, most likely due to the Cu(II) formation from oxygen interstitials. X-ray photoelectron spectroscopy confirmed purely Cu(I) in the as-synthesized 2H-CuScO2 and increased Cu(II) amounts upon annealing. Oxidation of the samples also led to shifts of the Fermi level toward the valence band as observed by increases in the measured flat band potentials versus normal hydrogen electrode, confirming increased hole carrier densities.

  20. The C-H Dissociation Energy of C2H6

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Langhoff, Stephen R. (Technical Monitor)

    1994-01-01

    The C-H bond energy in C2H6 is computed to be 99.76 +/- 0.35 kcal/mol, which is in excellent agreement with the most recent experimental values. The calculation of the C-H bond energy by direct dissociation and by an isodesmic reaction is discussed.

  1. Photo-induced reactions in the ion-molecule complex Mg+-OCNC2H5

    NASA Astrophysics Data System (ADS)

    Sun, Ju-Long; Liu, Haichuan; Han, Ke-Li; Yang, Shihe

    2003-06-01

    Ion-molecule complexes of magnesium cation with ethyl isocyanate were produced in a laser-ablation supersonic expansion nozzle source. Photo-induced reactions in the 1:1 complexes have been studied in the spectral range of 230-410 nm. Photodissociation mass spectrometry revealed the persistent product Mg+ from nonreactive quenching throughout the entire wavelength range. As for the reactive channels, the photoproducts, Mg+OCN and C2H5+, were produced only in the blue absorption band of the complex with low yields. The action spectrum of Mg+(OCNC2H5) consists of two pronounced peaks on the red and blue sides of the Mg+ 32P←32S atomic transition. The ground state geometry of Mg+-OCNC2H5 was fully optimized at B3LYP/6-31+G** level by using GAUSSIAN 98 package. The calculated absorption spectrum of the complex using the optimized structure of its ground state agrees well with the observed action spectrum. Photofragment branching fractions of the products are almost independent of the photolysis photon energy for the 3Px,y,z excitations. The very low branching ratio of reactive products to nonreactive fragment suggests that evaporation is the main relaxation pathway in the photo-induced reactions of Mg+(OCNC2H5).

  2. An improved technique for the 2H/1H analysis of urines from diabetic volunteers

    USGS Publications Warehouse

    Coplen, T.B.; Harper, I.T.

    1994-01-01

    The H2-H2O ambient-temperature equilibration technique for the determination of 2H/1H ratios in urinary waters from diabetic subjects provides improved accuracy over the conventional Zn reduction technique. The standard deviation, ~ 1-2???, is at least a factor of three better than that of the Zn reduction technique on urinary waters from diabetic volunteers. Experiments with pure water and solutions containing glucose, urea and albumen indicate that there is no measurable bias in the hydrogen equilibration technique.The H2-H2O ambient-temperature equilibration technique for the determination of 2H/1H ratios in urinary waters from diabetic subjects provides improved accuracy over the conventional Zn reduction technique. The standard deviation, approximately 1-2%, is at least a factor of three better than that of the Zn reduction technique on urinary waters from diabetic volunteers. Experiments with pure water and solutions containing glucose, urea and albumen indicate that there is no measurable bias in the hydrogen equilibration technique.

  3. Fluorescence from photoexcitation of C2H5OH by vacuum ultraviolet radiation

    NASA Technical Reports Server (NTRS)

    Han, J. C.; Suto, Masako; Lee, L. C.

    1989-01-01

    The photoabsorption and fluorescence cross sections of C2H5OH have been measured in the 46-200 nm region. Fluorescence is dispersed to identify the emission systems, which are mainly OH(A-X), CH(A,B-X), and the H Balmer series. The photodissociation processes that produce the observed emissions are discussed.

  4. 77 FR 44441 - Swap Transaction Compliance and Implementation Schedule: Clearing Requirement Under Section 2(h...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-30

    ... From the Federal Register Online via the Government Publishing Office COMMODITY FUTURES TRADING... Requirement Under Section 2(h) of the CEA AGENCY: Commodity Futures Trading Commission. ACTION: Final rule. SUMMARY: The Commodity Futures Trading Commission (Commission or CFTC) is adopting regulations...

  5. Growth mode of carbide from C 2H 4 or CO on Ni( 1 1 1 )

    NASA Astrophysics Data System (ADS)

    Nakano, H.; Ogawa, J.; Nakamura, J.

    2002-08-01

    The growth of carbide on a Ni(1 1 1) surface by the decomposition of C 2H 4 and the Boudouard reaction (2CO g→C a+CO 2,g) was studied using scanning tunneling microscopy (STM), Auger electron spectroscopy and low energy electron diffraction. STM results showed that the carbide growth by the Boudouard reaction started at step edges on Ni(1 1 1), while for the C 2H 4 decomposition the carbide was formed preferentially at terrace sites with very low concentration of carbide at the step edge. The different behavior for the carbide growth was ascribed to the difference in the dissociation sites of CO and C 2H 4. As for the Boudouard reaction, CO was dissociated at the step edge and then carbon migrated into the bulk at a reaction temperature of 500 K. The carbon was then segregated at room temperature to the surface from the bulk to form a single domain of the ( 39× 39) R16.1° structure at the step edge. On the other hand, the C 2H 4 decomposition took place on the terrace leading to an isolated carbide unit or carbide short strings on the terrace.

  6. Improved watermelon quality using bottle gourd rootstock expressing a Ca(2+)/H(+) antiporter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bottle gourd ("Lagenaria siceraria" Standl.) has been commonly used as a source of rootstock for watermelon. To improve its performance as a rootstock without adverse effects on the scion, the bottle gourd was genetically engineered using a modified "Arabidopsis" Ca(2+)/H(+) exchanger sCAX2B. This t...

  7. Slow recrystallization of tripalmitoylglycerol from MCT oil observed by 2H NMR.

    PubMed

    Smith, Kevin W; Smith, Paul R; Furó, István; Pettersson, Erik Thyboll; Cain, Fred W; Favre, Loek; Talbot, Geoff

    2007-10-17

    The crystallization and recrystallization of fats have a significant impact on the properties and quality of many food products. While crystallization has been the subject of a number of studies using pure triacylglycerols (TAG), recrystallization in similarly pure systems is rarely studied. In this work, perdeuterated tripalmitoylglycerol ( (2)H-PPP) was dissolved in medium chain triacylglycerol oil (MCT) to yield a saturated solution. The solution was heated to cause partial melting of the solid and dissolution of the molten fraction of (2)H-PPP in MCT and was then cooled to the original temperature to induce recrystallization from the supersaturated solution. (2)H NMR was used to monitor the disappearance of (2)H-PPP from the solution and showed that recrystallization occurred in two steps. The first step was rapid, taking place over a few minutes, and accounted for more than two-thirds of the total recrystallization. The second step was much slower, taking place over a remarkably long timescale of hours to days. It is proposed that dissolution occurs from all parts of the crystals, leaving an etched and pitted surface. The first step of crystallization is the infilling of these pits, while the second step is the continued growth on the smoothed crystal faces.

  8. SO2:H2O surface complex found at the vapor/water interface.

    PubMed

    Tarbuck, Teresa L; Richmond, Geraldine L

    2005-12-07

    A weakly bonded SO2:H2O surface complex is found at the vapor/water interface prior to the reaction and dissolution of SO2 into the aqueous phase. The results have important implications for understanding the formation of atmospheric aerosols and understanding the atmospheric sulfur cycle.

  9. "In planta" regulation of the "Arabidopsis" Ca(2+)/H(+) antiporter CAX1

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vacuolar localized Ca(2+)/H(+) exchangers such as "Arabidopsis thaliana" cation exchanger 1 (CAX1) play important roles in Ca(2+) homeostasis. When expressed in yeast, CAX1 is regulated via an N-terminal autoinhibitory domain. In yeast expression assays, a 36 amino acid N-terminal truncation of CAX1...

  10. Identification of microdomains involved in association of "Arabidopsis" Ca(2+)/H(+) exchangers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In planta, high capacity tonoplast Ca2+/H+ antiport is mediated in part by a family of CAtion Exchangers (CAX). Each CAX can be divided into two weakly homologous halves (N- and C-) at the negatively charged loop between transmembrane (TM) 6 and TM7. Some CAX halves (N+C) co-expressed in yeast cells...

  11. Characterization of Radionuclides for 2H Evaporator Cleaning Transfers to Tank 42

    SciTech Connect

    O'Bryant, R.F.

    2001-06-04

    This document contains the characterization methodology for sludge-contaminated waste generated from the 2H Evaporator cleaning transfers to Tank 42, based on process knowledge and available analytical data. The scaling factors developed for Tank 42 in this document supercede those presented in Reference 6, and any other previously developed radionuclide characterizations for Tank 42 sludge-contaminated waste.

  12. Turbulence in Supercritical O2/H2 and C7H16/N2 Mixing Layers

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth; Okong'o, Nora

    2003-01-01

    This report presents a study of numerical simulations of mixing layers developing between opposing flows of paired fluids under supercritical conditions, the purpose of the study being to elucidate chemical-species-specific aspects of turbulence. The simulations were performed for two different fluid pairs O2/H2 and C7H16/N2 at similar reduced initial pressures (reduced pressure is defined as pressure divided by critical pressure). Thermodynamically, O2/H2 behaves more nearly like an ideal mixture and has greater solubility, relative to C7H16/N2, which departs strongly from ideality. Because of a specified smaller initial density stratification, the C7H16/N2 layers exhibited greater levels of growth, global molecular mixing, and turbulence. However, smaller density gradients at the transitional state for the O2/H2 system were interpreted as indicating that locally, this system exhibits enhanced mixing as a consequence of its greater solubility and closer approach to ideality. These thermodynamic features were shown to affect entropy dissipation, which was found to be larger for O2/H2 and concentrated in high-density-gradient-magnitude regions that are distortions of the initial density-stratification boundary. In C7H16/N2, the regions of largest dissipation were found to lie in high-density-gradient-magnitude regions that result from mixing of the two fluids.

  13. N,N-bond-forming heterocyclization: synthesis of 3-alkoxy-2H-indazoles.

    PubMed

    Mills, Aaron D; Nazer, Musa Z; Haddadin, Makhluf J; Kurth, Mark J

    2006-03-31

    A one-step heterocyclization of o-nitrobenzylamines to 3-alkoxy-2H-indazoles is reported. The electronic nature of the nitrophenyl group, the steric and electronic nature of the R1-functionalized benzylic amine, and the nature of the alcoholic solvent affect the efficiency of this heterocyclization reaction (approximately 40-90%).

  14. The Rate Constant for the Reaction H + C2H5 at T = 295 - 150K

    NASA Technical Reports Server (NTRS)

    Pimentel, Andre S.; Payne, Walter A.; Nesbitt, Fred L.; Cody, Regina J.; Stief, Louis J.

    2004-01-01

    The reaction between the hydrogen atom and the ethyl (C2H3) radical is predicted by photochemical modeling to be the most important loss process for C2H5 radicals in the atmospheres of Jupiter and Saturn. This reaction is also one of the major sources for the methyl radicals in these atmospheres. These two simplest hydrocarbon radicals are the initial species for the synthesis of larger hydrocarbons. Previous measurements of the rate constant for the H + C2H5 reaction varied by a factor of five at room temperature, and some studies showed a dependence upon temperature while others showed no such dependence. In addition, the previous studies were at higher temperatures and generally higher pressures than that needed for use in planetary atmospheric models. The rate constant for the reaction H + C2H5 has been measured directly at T = 150, 202 and 295 K and at P = 1.0 Torr He for all temperatures and additionally at P = 0.5 and 2.0 Torr He at T = 202 K. The measurements were performed in a discharge - fast flow system. The decay of the C2H5 radical in the presence of excess hydrogen was monitored by low-energy electron impact mass spectrometry under pseudo-first order conditions. H atoms and C2H5 radicals were generated rapidly and simultaneously by the reaction of fluorine atoms with H2 and C2H6, respectively. The total rate constant was found to be temperature and pressure independent. The measured total rate constant at each temperature are: k(sub 1)(295K) = (1.02+/-0.24)x10(exp -10), k(sub 1)(202K) = (1.02+/-0.22)x10(exp -10) and k(sub 1)(150K) = (0.93+/-0.21)x10(exp -10), all in units of cu cm/molecule/s. The total rate constant derived from all the combined measurements is k(sub 1) = (l.03+/-0.17)x10(exp -10) cu cm/molecule/s. At room temperature our results are about a factor of two higher than the recommended rate constant and a factor of three lower than the most recently published study.

  15. LITERATURE REVIEW ON IMPACT OF GLYCOLATE ON THE 2H EVAPORATOR AND THE EFFLUENT TREATMENT FACILITY

    SciTech Connect

    Adu-Wusu, K.

    2012-05-10

    Glycolic acid (GA) is being studied as an alternate reductant in the Defense Waste Processing Facility (DWPF) feed preparation process. It will either be a total or partial replacement for the formic acid that is currently used. A literature review has been conducted on the impact of glycolate on two post-DWPF downstream systems - the 2H Evaporator system and the Effluent Treatment Facility (ETF). The DWPF recycle stream serves as a portion of the feed to the 2H Evaporator. Glycolate enters the evaporator system from the glycolate in the recycle stream. The overhead (i.e., condensed phase) from the 2H Evaporator serves as a portion of the feed to the ETF. The literature search revealed that virtually no impact is anticipated for the 2H Evaporator. Glycolate may help reduce scale formation in the evaporator due to its high complexing ability. The drawback of the solubilizing ability is the potential impact on the criticality analysis of the 2H Evaporator system. It is recommended that at least a theoretical evaluation to confirm the finding that no self-propagating violent reactions with nitrate/nitrites will occur should be performed. Similarly, identification of sources of ignition relevant to glycolate and/or update of the composite flammability analysis to reflect the effects from the glycolate additions for the 2H Evaporator system are in order. An evaluation of the 2H Evaporator criticality analysis is also needed. A determination of the amount or fraction of the glycolate in the evaporator overhead is critical to more accurately assess its impact on the ETF. Hence, use of predictive models like OLI Environmental Simulation Package Software (OLI/ESP) and/or testing are recommended for the determination of the glycolate concentration in the overhead. The impact on the ETF depends on the concentration of glycolate in the ETF feed. The impact is classified as minor for feed glycolate concentrations {le} 33 mg/L or 0.44 mM. The ETF unit operations that will have

  16. Microbial H2 cycling does not affect δ2H values of ground water

    USGS Publications Warehouse

    Landmeyer, J.E.; Chapelle, F.H.; Bradley, P.M.

    2000-01-01

    Stable hydrogen-isotope values of ground water (δ2H) and dissolved hydrogen concentrations (H(2(aq)) were quantified in a petroleum-hydrocarbon contaminated aquifer to determine whether the production/consumption of H2 by subsurface microorganisms affects ground water &delta2H values. The range of &delta2H observed in monitoring wells sampled (-27.8 ‰c to -15.5 ‰c) was best explained, however, by seasonal differences in recharge temperature as indicated using ground water δ18O values, rather than isotopic exchange reactions involving the microbial cycling of H2 during anaerobic petroleum-hydrocarbon biodegradation. The absence of a measurable hydrogen-isotope exchange between microbially cycled H2 and ground water reflects the fact that the amount of H2 available from the anaerobic decomposition of petroleum hydrocarbons is small relative to the amount of hydrogen present in water, even though milligram per liter concentrations of readily biodegradable contaminants are present at the study site. Additionally, isotopic fractionation calculations indicate that in order for H2 cycling processes to affect δ2H values of ground water, relatively high concentrations of H2 (>0.080 M) would have to be maintained, considerably higher than the 0.2 to 26 nM present at this site and characteristic of anaerobic conditions in general. These observations suggest that the conventional approach of using δ2H and δ18O values to determine recharge history is appropriate even for those ground water systems characterized by anaerobic conditions and extensive microbial H2 cycling.

  17. Equations of state for H2, H2O, and H2-H2O fluid mixtures at temperatures above 0.01° C and at high pressures

    NASA Astrophysics Data System (ADS)

    Rimbach, Helmut; Chatterjee, Niranjan D.

    1987-11-01

    Modified Redlich-Kwong (MRK) equations of state have been derived for the pure fluid species H2 and H2O by expressing the parameter a as a function of T and P, and b as as a function of P only. These equations are valid above 0° and 0.01° C, respectively. For H2O, the prediction of volumes is successful not only in the supercritical, but also in the subcritical range. As a result of this, the saturation curve of H2O can be calculated with a maximum deviation of ±1.4 bar in the range 100 350° C. Between 350° C and the critical point (374.15° C), the uncertainty increases somewhat; this is due to a fundamental inadequacy of the Redlich-Kwong equation itself. These equations of state permit extrapolations to pressures of 100 kbar for H2 and at least 200 kbar for H2O and are, therefore, eminently suited for geochemical applications. Formulation of the MRK of the binary H2-H2O mixtures was achieved by assuming the quadratic mixing rule for the parameters a mix and b+mix. To derive the cross coefficients, aH2-H2Oand b H 2-H 2O, adjustable corrective factors ɛ and τ had to be introduced. The T- and P-dependences of ɛ and τ are based on P-V-T-X H 2 data (Seward and Franck 1981) to 440° C and 2500 bar. The resulting equation of state very satisfactorily reproduces the volumes observed experimentally at various sets of T, P, and X H 2. At a total pressure of 2 kbar, positive deviation from ideal mixing behaviour is still perceptible at as high a temperature as 1000° C. At some temperature around 380° C, phase separation sets in, an aqueous solution with dissolved H2 coexisting in equilibrium with an H2-rich fluid with dissolved H2O. The computed P-T-X H 2 surface of this two-phase region agrees well with that observed in Seward and Franck's (1981) experiments. An independent proof of the validity of this equation of state is the accuracy with which H {m/ex}can be predicted. Calorimetric measurements of H {m/ex}(Smith et al. 1983, Wormald and Colling 1985

  18. Effects of leaf water evaporative (2) H-enrichment and biosynthetic fractionation on leaf wax n-alkane δ(2) H values in C3 and C4 grasses.

    PubMed

    Gamarra, B; Sachse, D; Kahmen, A

    2016-11-01

    Leaf wax n-alkane δ(2) H values carry important information about environmental and ecophysiological processes in plants. However, the physiological and biochemical drivers that shape leaf wax n-alkane δ(2) H values are not completely understood. It is particularly unclear why n-alkanes in grasses are typically (2) H-depleted compared with plants from other taxonomic groups such as dicotyledonous plants and why C3 grasses are (2) H-depleted compared with C4 grasses. To resolve these uncertainties, we quantified the effects of leaf water evaporative (2) H-enrichment and biosynthetic hydrogen isotope fractionation on n-alkane δ(2) H values for a range of C3 and C4 grasses grown in climate-controlled chambers. We found that only a fraction of leaf water evaporative (2) H-enrichment is imprinted on the leaf wax n-alkane δ(2) H values in grasses. This is interesting, as previous studies have shown in dicotyledonous plants a nearly complete transfer of this (2) H-enrichment to the n-alkane δ(2) H values. We thus infer that the typically observed (2) H-depletion of n-alkanes in grasses (as opposed to dicots) is because only a fraction of the leaf water evaporative (2) H-enrichment is imprinted on the δ(2) H values. Our experiments also show that differences in n-alkane δ(2) H values between C3 and C4 grasses are largely the result of systematic differences in biosynthetic fractionation between these two plant groups, which was on average -198‰ and-159‰ for C3 and C4 grasses, respectively.

  19. Methylamphetamine synthesis: does an alteration in synthesis conditions affect the δ(13) C, δ(15) N and δ(2) H stable isotope ratio values of the product?

    PubMed

    Salouros, Helen; Collins, Michael; Cawley, Adam; Longworth, Mitchell

    2012-05-01

    Conventional chemical profiling of methylamphetamine has long been employed by national forensic laboratories to determine the synthetic route and where possible the precursor chemicals used in its manufacture. This laboratory has been studying the use of stable isotope ratio mass spectrometry (IRMS) analysis as a complementary technique to conventional chemical profiling of fully synthetic illicit drugs such as methylamphetamine. As part of these investigations the stable carbon (δ(13) C), nitrogen (δ(15) N), and hydrogen (δ(2) H) isotope values in the precursor chemicals of ephedrine and pseudoephedrine and the resulting methylamphetamine end-products have been measured to determine the synthetic origins of methylamphetamine. In this study, results are presented for δ(13) C, δ(15) N, and δ(2) H values in methylamphetamine synthesized from ephedrine and pseudoephedrine by two synthetic routes with varying experimental parameters. It was demonstrated that varying parameters, such as stoichiometry, reaction temperature, reaction time, and reaction pressure, had no effect on the δ(13) C, δ(15) N, and δ(2) H isotope values of the final methylamphetamine product, within measurement uncertainty. Therefore the value of the IRMS technique in identifying the synthetic origin of precursors, such as ephedrine and pseudoephedrine, is not compromised by the potential variation in synthetic method that is expected from one batch to the next, especially in clandestine laboratories where manufacture can occur without stringent quality control of reactions.

  20. Helix-Capping Histidines: Diversity of N–H···N Hydrogen Bond Strength Revealed by 2hJNN Scalar Couplings

    PubMed Central

    2016-01-01

    In addition to its well-known roles as an electrophile and general acid, the side chain of histidine often serves as a hydrogen bond (H-bond) acceptor. These H-bonds provide a convenient pH-dependent switch for local structure and functional motifs. In hundreds of instances, a histidine caps the N-terminus of α- and 310-helices by forming a backbone NH···Nδ1 H-bond. To characterize the resilience and dynamics of the histidine cap, we measured the trans H-bond scalar coupling constant, 2hJNN, in several forms of Group 1 truncated hemoglobins and cytochrome b5. The set of 19 measured 2hJNN values were between 4.0 and 5.4 Hz, generally smaller than in nucleic acids (∼6–10 Hz) and indicative of longer, weaker bonds in the studied proteins. A positive linear correlation between 2hJNN and the difference in imidazole ring 15N chemical shift (Δ15N = |δ15Nδ1 – δ15Nε2|) was found to be consistent with variable H-bond length and variable cap population related to the ionization of histidine in the capping and noncapping states. The relative ease of 2hJNN detection suggests that this parameter can become part of the standard arsenal for describing histidines in helix caps and other key structural and catalytic elements involving NH···N H-bonds. The combined nucleic acid and protein data extend the utility of 2hJNN as a sensitive marker of local structural, dynamic, and thermodynamic properties in biomolecules. PMID:26523621

  1. A Newly Developed Model for Fluorescence of C2H6 ν5 in Comets and Application to Infrared Spectra Acquired with NIRSPEC at Keck II

    NASA Astrophysics Data System (ADS)

    Radeva, Yana L.; Mumma, M. J.; Villanueva, G. L.; A'Hearn, M. F.

    2010-01-01

    Exploring the compositional diversity of cometary nuclei is key to understanding the formation and evolution of the Solar System, and the origin of water and prebiotic organics on the Earth. For most polyatomic gases, a production rate can be obtained from measured ro-vibrational intensities if an accurate rotational temperature is available, and the comparison of temperatures displayed by individual molecular species can reveal additional insights into physics in the cometary inner coma. Until now, accurate temperatures could be derived for HCN, CO, and H2O, but not for ethane (C2H6). As a symmetric hydrocarbon, C2H6 is uniquely sampled in the infrared, but the fine rotational structure of the ν7 Q-branches at 3.3 μm cannot be resolved by current infrared spectrometers, ultimately limiting the retrievals of rotational temperatures from these lines. However, the complex ro-vibrational structure (P- and R-branches) of the ν5 band at 3.5 μm is resolved by the Near Infrared Echelle Spectrograph on the Keck II telescope (NIRSPEC). We developed a fluorescence model for the infrared ν5 band of C2H6, and applied it to interpret high-resolution infrared spectra acquired with NIRSPEC. We present rotational temperatures and production rates for C2H6 in multiple comets. We compare the extracted rotational temperatures for ethane with those obtained from simultaneous measurements of other species (H2O and HCN). We also compare mixing ratios derived from the C2H6 ν5 band with those derived from the previously analyzed (by NASA GSFC team members) ν7 band. This work now establishes a robust method for quantifying additional physical parameters for ethane in comets.

  2. Evaluation of branched GDGTs and leaf wax n-alkane δ2H as (paleo) environmental proxies in East Africa

    NASA Astrophysics Data System (ADS)

    Coffinet, Sarah; Huguet, Arnaud; Pedentchouk, Nikolai; Bergonzini, Laurent; Omuombo, Christine; Williamson, David; Anquetil, Christelle; Jones, Martin; Majule, Amos; Wagner, Thomas; Derenne, Sylvie

    2017-02-01

    The role of mountain evolution on local climate is poorly understood and potentially underestimated in climate models. One prominent example is East Africa, which underwent major geodynamic changes with the onset of the East African Rift System (EARS) more than 250 Myr ago. This study explores, at the regional East African scale, a molecular approach for terrestrially-based paleo-climatic reconstructions that takes into account both changes in temperature and in altitude, potentially leading to an improved concept in paleo-climatic reconstructions. Using surface soils collected along pronounced altitudinal gradients in Mt. Rungwe (n = 40; Southwest Tanzania) and Mt. Kenya (n = 20; Central Kenya), we investigate the combination of 2 terrestrial proxies, leaf wax n-alkane δ2H (δ2Hwax) and branched glycerol dialkyl glycerol tetraether (br GDGT) membrane lipids, as (paleo) elevation and (paleo) temperature proxies, respectively. At the mountain scale, a weak link between δ2Hwax and altitude (R2 = 0.33) is observed at Mt. Kenya, but no relationship is observed at Mt. Rungwe. It is likely that additional parameters, such as decreasing relative humidity (RH) or vegetation changes with altitude, are outcompeting the expected 2H-depletion trend along Mt. Rungwe. In contrast, br GDGT-derived absolute mean annual air temperature (MAAT) and temperature lapse rate (0.65 °C/100 m) for both mountains are in good agreement with direct field measurements, further supporting the robustness of this molecular proxy for (paleo) temperature reconstructions. At the regional scale, estimated and observed δ2H data in precipitation along 3 mountains in East Africa (Mts. Rungwe, Kenya and Kilimanjaro) highlight a strong spatial heterogeneity, preventing the establishment of a regional based calibration of δ2Hwax for paeloaltitudinal reconstructions. Different from that, an improved regional soil calibration is developed between br GDGT distribution and MAAT by combining the data from

  3. Articulatory Parameters.

    ERIC Educational Resources Information Center

    Ladefoged, Peter

    1980-01-01

    Summarizes the 16 parameters hypothesized to be necessary and sufficient for linguistic phonetic specifications. Suggests seven parameters affecting tongue shapes, three determining the positions of the lips, one controlling the position of the velum, four varying laryngeal actions, and one controlling respiratory activity. (RL)

  4. Characterization of the myristoyl lipid modification of membrane-bound GCAP-2 by 2H solid-state NMR spectroscopy.

    PubMed

    Vogel, Alexander; Schröder, Thomas; Lange, Christian; Huster, Daniel

    2007-12-01

    Guanylate cyclase-activating protein-2 (GCAP-2) is a retinal Ca2+ sensor protein. It is responsible for the regulation of both isoforms of the transmembrane photoreceptor guanylate cyclase, a key enzyme of vertebrate phototransduction. GCAP-2 is N-terminally myristoylated and full activation of its target proteins requires the presence of this lipid modification. The structural role of the myristoyl moiety in the interaction of GCAP-2 with the guanylate cyclases and the lipid membrane is currently not well understood. In the present work, we studied the binding of Ca2+-free myristoylated and non-myristoylated GCAP-2 to phospholipid vesicles consisting of dimyristoylphosphatidylcholine or of a lipid mixture resembling the physiological membrane composition by a biochemical binding assay and 2H solid-state NMR. The NMR results clearly demonstrate the full-length insertion of the aliphatic chain of the myristoyl group into the membrane. Very similar geometrical parameters were determined from the 2H NMR spectra of the myristoyl group of GCAP-2 and the acyl chains of the host membranes, respectively. The myristoyl chain shows a moderate mobility within the lipid environment, comparable to the acyl chains of the host membrane lipids. This is in marked contrast to the behavior of other lipid-modified model proteins. Strikingly, the contribution of the myristoyl group to the free energy of membrane binding of GCAP-2 is only on the order of -0.5 kJ/mol, and the electrostatic contribution is slightly unfavorable, which implies that the main driving forces for membrane localization arises through other, mainly hydrophobic, protein side chain-lipid interactions. These results suggest a role of the myristoyl group in the direct interaction of GCAP-2 with its target proteins, the retinal guanylate cyclases.

  5. The Dissociation Energies of CH4 and C2H2 Revisited

    NASA Technical Reports Server (NTRS)

    Partridge, Harry; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    The bond dissociation energies of CH4 and C2H2 and their fragments are investigated using basis set extrapolations and high levels of correlation. The computed bond dissociation energies (D(sub e)) are accurate to within 0.2 kcal/mol. The agreement with the experimental (D(sub 0)) values is excellent if we assume that the zero-point energy of C2H is 9.18 kcal/mol. The effect of core (1s) correlation on the bond dissociation energies of C-H bonds is shown to vary from 0.2 to 0.7 kcal/mol and that for C-C bonds varies from 0.4 to 2.2 kcal/mol.

  6. 2H-DNP-enhanced 2H–13C solid-state NMR correlation spectroscopy

    PubMed Central

    Maly, Thorsten; Andreas, Loren B.; Smith, Albert A.

    2015-01-01

    Perdeuteration of biological macromolecules for magic angle spinning solid-state NMR spectroscopy can yield high-resolution 2H–13C correlation spectra and the method is therefore of great interest for the structural biology community. Here we demonstrate that the combination of sample deuteration and dynamic nuclear polarization yields resolved 2H–13C correlation spectra with a signal enhancement of ε ≥ 700 compared to a spectrum recorded with microwaves off and otherwise identical conditions. To our knowledge, this is the first time that 2H-DNP has been employed to enhance MAS-NMR spectra of a biologically relevant system. The DNP process is studied using several polarizing agents and the technique is applied to obtain 2H–13C correlation spectra of U-[2H, 13C] proline. PMID:20458422

  7. Near infrared second overtone cw-cavity ringdown spectroscopy of D2H+ ions

    NASA Astrophysics Data System (ADS)

    Hlavenka, P.; Plasil, R.; Bano, G.; Korolov, I.; Gerlich, D.; Ramanlal, J.; Tennyson, J.; Glosik, J.

    2006-09-01

    A study of D2H+ ions in their lowest rotational states is presented. The ions are generated in pulsed discharge in liquid N2 cooled He/Ar/H2/D2 gas mixture. Near infrared (NIR) second overtone transitions in the 6534-6536 cm-1 (1.529-1.530 [mu]m) region are used to identify the ions and determine their degree of rotational excitation. The data were obtained using NIR cavity ringdown absorption spectroscopy (NIR-CRDS). The sensitivity obtained was typically 5 x 10-9 cm-1. The measured second overtone transition frequencies are in very good agreement (better than 0.02 cm-1) with ab initio predictions. From the Doppler broadening the kinetic temperature of ions is estimated to be (220 +/- 50) K. The absolute number density of D2H+ as a function of H2/D2 mixing ratio and time is measured.

  8. VUV photoionization cross sections of HO2, H2O2, and H2CO.

    PubMed

    Dodson, Leah G; Shen, Linhan; Savee, John D; Eddingsaas, Nathan C; Welz, Oliver; Taatjes, Craig A; Osborn, David L; Sander, Stanley P; Okumura, Mitchio

    2015-02-26

    The absolute vacuum ultraviolet (VUV) photoionization spectra of the hydroperoxyl radical (HO2), hydrogen peroxide (H2O2), and formaldehyde (H2CO) have been measured from their first ionization thresholds to 12.008 eV. HO2, H2O2, and H2CO were generated from the oxidation of methanol initiated by pulsed-laser-photolysis of Cl2 in a low-pressure slow flow reactor. Reactants, intermediates, and products were detected by time-resolved multiplexed synchrotron photoionization mass spectrometry. Absolute concentrations were obtained from the time-dependent photoion signals by modeling the kinetics of the methanol oxidation chemistry. Photoionization cross sections were determined at several photon energies relative to the cross section of methanol, which was in turn determined relative to that of propene. These measurements were used to place relative photoionization spectra of HO2, H2O2, and H2CO on an absolute scale, resulting in absolute photoionization spectra.

  9. Optically pumped CHClF2 and C2H5I submillimeter wave lasers

    NASA Astrophysics Data System (ADS)

    Tobin, M. S.; Daley, T. W.

    1980-06-01

    Submillimeter wave laser action is reported for optically pumped chlorodifluoromethane gas and ethyl iodide vapor. The compounds were pumped by an electrically chopped CO2 laser at 10 Hz coupled to a metallic waveguide unoptimized 3.5 mm output-hole-coupled resonator with plunger mirrors. Coincidences between CO2 pump lines and molecular absorption lines were detected at three lines in the 9-micron R region in CHClF2 and two lines in the 10-micron R and P regions in C2H5I for chopped and not CW laser regimes. Comparison of the molecular structures of the two species with the CW FIR laser material selection criteria of Danielewicz and Weiss (1978) reveals that CHClF2 satisfies these criteria (although CHClF2 absorption does not overlap with many CO2 pump lines), while C2H5I does not, in agreement with experimental results.

  10. Electron Impact Ionization and Dissociative Ionization of C2H2

    NASA Technical Reports Server (NTRS)

    Srivastava, S. K.

    1995-01-01

    By utilizing a crossed electron beam collision geometry, a combination of time-of-flight (TOF) and quadrupole mass spectrometers, and the relative flow technique1 normalized values of cross sections and appearance energies (AP) were obtained for the formation of singly and multiply ionized species resulting from the ionization and dissociation of C2H2. Details ont he apparatus and technique have been published previously.2,3.

  11. DYNC2H1 mutation causes Jeune syndrome and recurrent lung infections associated with ciliopathy.

    PubMed

    Emiralioglu, Nagehan; Wallmeier, Julia; Olbrich, Heike; Omran, Heymut; Ozcelik, Ugur

    2017-03-03

    Asphyxiating thoracic dystrophy, also known as Jeune syndrome, is included in a group of syndromic skeletal ciliopathies associated with mutations in genes encoding proteins involved in the formation or function of motile cilia. Herein, we report a 6-mo-old male admitted to hospital with recurrent lung infections, thoracic dystrophy, and respiratory distress that was diagnosed as Jeune syndrome; DYNC2H1 mutation was detected via genetic analysis and ciliary dysfunction was noted via high-speed video microscopy.

  12. The Abundance of C2H4 in the Circumstellar Envelope of IRC+10216

    PubMed Central

    Fonfría, J. P.; Hinkle, K. H.; Cernicharo, J.; Richter, M. J.; Agúndez, M.

    2017-01-01

    High spectral resolution mid-IR observations of ethylene (C2H4) towards the AGB star IRC+10216 were obtained using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF). Eighty ro-vibrational lines from the 10.5 µm vibrational mode ν7 with J ≲ 30 were detected in absorption. The observed lines are divided into two groups with rotational temperatures of 105 and 400 K (warm and hot lines). The warm lines peak at ≃ −14 km s−1 with respect to the systemic velocity, suggesting that they are mostly formed outwards from ≃ 20R⋆. The hot lines are centered at −10 km s−1 indicating that they come from a shell between 10 and 20R⋆. 35% of the observed lines are unblended and can be fitted with a code developed to model the emission of a spherically symmetric circumstellar envelope. The analysis of several scenarios reveal that the C2H4 abundance relative to H2 in the range 5 − 20R⋆ is 6.9 × 10−8 in average and it could be as high as 1.1 × 10−7. Beyond 20R⋆, it is 8.2 × 10−8. The total column density is (6.5 ± 3.0) × 1015 cm−2. C2H4 is found to be rotationally under local thermodynamical equilibrium (LTE) and vibrationally out of LTE. One of the scenarios that best reproduce the observations suggests that up to 25% of the C2H4 molecules at 20R⋆ could condense onto dust grains. This possible depletion would not influence significantly the gas acceleration although it could play a role in the surface chemistry on the dust grains. PMID:28184097

  13. Characterization Results for the March 2016 H-Tank Farm 2H Evaporator Overhead Samples

    SciTech Connect

    Nicholson, J. C.

    2016-05-09

    This report contains the radioanalytical results of the 2H evaporator overhead sample received at SRNL on March 16, 2016. Specifically, concentrations of 137Cs, 90Sr, and 129I are reported and compared to the corresponding Waste Acceptance Criteria (WAC) limits of the Effluent Treatment Project (ETP) Waste Water Collection Tank (WWCT) (rev. 6). All of the radionuclide concentrations in the sample were found to be in compliance with the ETP WAC limits.

  14. Establishment of the C(2)H(5)+O(2) reaction mechanism: a combustion archetype.

    PubMed

    Wilke, Jeremiah J; Allen, Wesley D; Schaefer, Henry F

    2008-02-21

    The celebrated C(2)H(5)+O(2) reaction is an archetype for hydrocarbon combustion, and the critical step in the process is the concerted elimination of HO(2) from the ethylperoxy intermediate (C(2)H(5)O(2)). Master equation kinetic models fitted to measured reaction rates place the concerted elimination barrier 3.0 kcal mol(-1) below the C(2)H(5)+O(2) reactants, whereas the best previous electronic structure computations yield a barrier more than 2.0 kcal mol(-1) higher. We resolve this discrepancy here by means of the most rigorous computations to date, using focal point methods to converge on the ab initio limit. Explicit computations were executed with basis sets as large as cc-pV5Z and correlation treatments as extensive as coupled cluster through full triples with a perturbative inclusion of quadruple excitations [CCSDT(Q)]. The final predicted barrier is -3.0 kcal mol(-1), bringing the concerted elimination mechanism into precise agreement with experiment. This work demonstrates that higher correlation treatments such as CCSDT(Q) are not only feasible on systems of chemical interest but are necessary to supply accuracy beyond 0.5 kcal mol(-1), which is not obtained with the "gold standard" CCSD(T) method. Finally, we compute the enthalpy of formation of C(2)H(5)O(2) to be Delta(f)H degrees (298 K)=-5.3+/-0.5 kcal mol(-1) and Delta(f)H degrees (0 K)=-1.5+/-0.5 kcal mol(-1).

  15. OVRO N2H+ Observations of Class 0 Protostars: Constraints on the Formation of Binary Stars

    NASA Astrophysics Data System (ADS)

    Chen, Xuepeng; Launhardt, Ralf; Henning, Thomas

    2007-11-01

    We present the results of an interferometric study of the N2H+ (1-0) emission from nine nearby, isolated, low-mass protostellar cores, using the Owens Valley Radio Observatory (OVRO) millimeter array. The main goal of this study is the kinematic characterization of the cores in terms of rotation, turbulence, and fragmentation. Eight of the nine objects have compact N2H+ cores with FWHM radii of 1200-3500 AU, spatially coinciding with the thermal dust continuum emission. The one more evolved (Class I) object in the sample (CB 188) shows only faint and extended N2H+ emission. The mean N2H+ line width was found to be 0.37 km s-1. Estimated virial masses range from 0.3 to 1.2 Msolar. We find that thermal and turbulent energy support are about equally important in these cores, while rotational support is negligible. The measured velocity gradients across the cores range from 6 to 24 km s-1 pc-1. Assuming these gradients are produced by bulk rotation, we find that the specific angular momenta of the observed Class 0 protostellar cores are intermediate between those of dense (prestellar) molecular cloud cores and the orbital angular momenta of wide pre-main-sequence (PMS) binary systems. There appears to be no evolution (decrease) of angular momentum from the smallest prestellar cores via protostellar cores to wide PMS binary systems. In the context that most protostellar cores are assumed to fragment and form binary stars, this means that most of the angular momentum contained in the collapse region is transformed into orbital angular momentum of the resulting stellar binary systems.

  16. Temporal and spatial distributions of δ18O and δ2H in precipitation in Romania

    NASA Astrophysics Data System (ADS)

    Nagavciuc, Viorica; Bădăluță, Carmen-Andreea; Perșoiu, Aurel

    2015-04-01

    Stable isotope ratios of meteoric water have an important role in climatic, paleoclimatic, hydrological and meteorological studies. While such data are available from most of Europe, so far, in Romania (East Central Europe), no systematic study of the stable isotopic composition of precipitation exists. In this context, the aim of this study is to analyze the isotopic composition of rainwater, its temporal and spatial distribution, the identification of the main factors influencing these variations and the creation of the first map of spatial distribution of stable isotopes in precipitation in Romania. Between March 2012 and March 2014 we have collected monthly samples from 22 stations in Romania, which were subsequently analyzed for their δ18O and δ2H at the Stable Isotopes Laboratory, Stefan cel Mare University, Suceava, Romania. Precipitation in W and NW Romania plot along the GMWL, while those in the East are slightly below it, on an evaporative trend. The LMWL for Romania is defined as δ2H=7,27*δ18O + 6,92. The W-E gradient in the distribution of δ18O and δ2H are less marked than the N-S ones, with local influences dominating in areas of strong evaporation (intramountain basins, rain-shadow areas etc). In SW, and especially in autumn and winter, Meditteranean cyclones carry moisture from the Eastern Mediterranean, the δ18O and δ2H values in precipitation in the area plotting between the GMWL and the Eastern Mediterranean Meteoric Water Line. The isotopic composition of rainwater in Romania correlates well with air temperature, and is influenced to a lesser extent by other factors such as the amount of precipitation, topography configuration, the effect of continentalism and season of the year.

  17. The Abundance of C2H4 in the Circumstellar Envelope of IRC+10216.

    PubMed

    Fonfría, J P; Hinkle, K H; Cernicharo, J; Richter, M J; Agúndez, M; Wallace, L

    2017-02-01

    High spectral resolution mid-IR observations of ethylene (C2H4) towards the AGB star IRC+10216 were obtained using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF). Eighty ro-vibrational lines from the 10.5 µm vibrational mode ν7 with J ≲ 30 were detected in absorption. The observed lines are divided into two groups with rotational temperatures of 105 and 400 K (warm and hot lines). The warm lines peak at ≃ -14 km s(-1) with respect to the systemic velocity, suggesting that they are mostly formed outwards from ≃ 20R⋆. The hot lines are centered at -10 km s(-1) indicating that they come from a shell between 10 and 20R⋆. 35% of the observed lines are unblended and can be fitted with a code developed to model the emission of a spherically symmetric circumstellar envelope. The analysis of several scenarios reveal that the C2H4 abundance relative to H2 in the range 5 - 20R⋆ is 6.9 × 10(-8) in average and it could be as high as 1.1 × 10(-7). Beyond 20R⋆, it is 8.2 × 10(-8). The total column density is (6.5 ± 3.0) × 10(15) cm(-2). C2H4 is found to be rotationally under local thermodynamical equilibrium (LTE) and vibrationally out of LTE. One of the scenarios that best reproduce the observations suggests that up to 25% of the C2H4 molecules at 20R⋆ could condense onto dust grains. This possible depletion would not influence significantly the gas acceleration although it could play a role in the surface chemistry on the dust grains.

  18. Ionized state of hydroperoxy radical-water hydrogen-bonded complex: (HO2-H2O)+.

    PubMed

    Joshi, Ravi; Ghanty, Tapan K; Naumov, Sergej; Mukherjee, Tulsi

    2007-12-27

    Ab initio molecular orbital calculations have been employed to characterize the structure and bonding of the (HO2-H2O)+ radical cation system. Geometry optimization of this system was carried out using unrestricted density functional theory in conjunction with the BHHLYP functional and 6-311++G(2df,2p) as well as 6-311++G(3df,3p) basis sets, the second-order Møller-Plesset perturbation (MP2) method with the 6-311++G(3df,3p) basis set, and the couple cluster (CCSD) method with the aug-cc-pVTZ basis set. The effect of spin multiplicity on the stability of the (HO2-H2O)+ system has been studied and also compared with that of oxygen. The calculated results suggest a proton-transferred hydrogen bond between HO2 and H2O in H3O3+ wherein a proton is partially transferred to H2O producing the O2...H3O+ structure. The basis set superposition error and zero-point energy corrected results indicate that the H3O3+ system is energetically more stable in the triplet state; however, the singlet state of H3O3+ is more stable with respect to its dissociation into H3O+ and singlet O2. Since the resulting proton-transferred hydrogen-bonded complex (O2...H3O+) consists of weakly bound molecular oxygen, it might have important implications in various chemical processes and aquatic life systems.

  19. The Abundance of C2H4 in the Circumstellar Envelope of IRC+10216

    NASA Astrophysics Data System (ADS)

    Fonfría, J. P.; Hinkle, K. H.; Cernicharo, J.; Richter, M. J.; Agúndez, M.; Wallace, L.

    2017-02-01

    High spectral resolution mid-IR observations of ethylene ({{{C}}}2{{{H}}}4) toward the AGB star IRC+10216 were obtained using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF). 80 ro-vibrational lines from the 10.5 μm vibrational mode {ν }7 with J ≲ 30 were detected in absorption. The observed lines are divided into two groups with rotational temperatures of 105 and 400 K (warm and hot lines). The warm lines peak at ≃ ‑14 km s‑1 with respect to the systemic velocity, suggesting that they are mostly formed outwards from ≃ 20{R}\\star . The hot lines are centered at ‑10 km s‑1 indicating that they come from a shell between 10 and 20{\\text{}}{R}\\star . 35% of the observed lines are unblended and can be fitted with a code developed to model the emission of a spherically symmetric circumstellar envelope. The analysis of several scenarios reveals that the {{{C}}}2{{{H}}}4 abundance relative to H2 in the range 5‑20R⋆ is 6.9× {10}-8 on average and it could be as high as 1.1 × 10‑7. Beyond 20{\\text{}}{R}\\star , it is 8.2 × 10‑8. The total column density is (6.5 ± 3.0) × 1015 cm‑2. {{{C}}}2{{{H}}}4 is found to be rotationally under local thermodynamical equilibrium (LTE) and vibrationally out of LTE. One of the scenarios that best reproduce the observations suggests that up to 25% of the {{{C}}}2{{{H}}}4 molecules at 20{\\text{}}{R}\\star could condense onto dust grains. This possible depletion would not significantly influence the gas acceleration although it could play a role in the surface chemistry on the dust grains.

  20. Establishment of the C2H5+O2 reaction mechanism: A combustion archetype

    NASA Astrophysics Data System (ADS)

    Wilke, Jeremiah J.; Allen, Wesley D.; Schaefer, Henry F.

    2008-02-01

    The celebrated C2H5+O2 reaction is an archetype for hydrocarbon combustion, and the critical step in the process is the concerted elimination of HO2 from the ethylperoxy intermediate (C2H5O2). Master equation kinetic models fitted to measured reaction rates place the concerted elimination barrier 3.0kcalmol-1 below the C2H5+O2 reactants, whereas the best previous electronic structure computations yield a barrier more than 2.0kcalmol-1 higher. We resolve this discrepancy here by means of the most rigorous computations to date, using focal point methods to converge on the ab initio limit. Explicit computations were executed with basis sets as large as cc-pV5Z and correlation treatments as extensive as coupled cluster through full triples with a perturbative inclusion of quadruple excitations [CCSDT(Q)]. The final predicted barrier is -3.0kcalmol-1, bringing the concerted elimination mechanism into precise agreement with experiment. This work demonstrates that higher correlation treatments such as CCSDT(Q) are not only feasible on systems of chemical interest but are necessary to supply accuracy beyond 0.5kcalmol-1, which is not obtained with the "gold standard" CCSD(T) method. Finally, we compute the enthalpy of formation of C2H5O2 to be ΔfH °(298K)=-5.3±0.5kcalmol-1 and ΔfH°(0K)=-1.5±0.5kcalmol-1.

  1. Kinetics Studies of Radical-Radical Reactions: The NO2 + N2H3 System

    DTIC Science & Technology

    2013-10-01

    investigating the kinetics of this elementary reaction . 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES...Viewgraph 3. DATES COVERED (From - To) September 2013- October 2013 4. TITLE AND SUBTITLE Kinetics Studies of Radical-Radical Reactions (I): The NO2...characteristics in relevant operating environments. Here we report theoretical results obtained on the prototypical radical- radical reaction : NO2 + N2H3

  2. Kinetics Studies of Radical-Radical Reactions (I): The NO2 + N2H3 System

    DTIC Science & Technology

    2013-08-01

    the potential energy surface for the NO2 + N2H3 system and have established the most likely reaction mechanism. The technique of laser photolysis...configuration interactions and coupled-cluster theories with single and double excitations, and correction for triple excitations. Specifically, the...differentially pumped chamber containing an electron impact ionization quadrupole mass spectrometer. 4. Results and Discussion To our knowledge

  3. Sensitivity of 2H NMR spectroscopy to motional models: Proteins and highly viscous liquids as examples

    NASA Astrophysics Data System (ADS)

    Kruk, D.; Mielczarek, A.; Korpala, A.; Kozlowski, A.; Earle, K. A.; Moscicki, J.

    2012-06-01

    In order to study to what extent mechanisms of molecular motion can be unambiguously revealed by 2H NMR spectroscopy, 2H spectra for proteins (chicken villin protein headpiece HP36, selectively methyl-deuterated at leucine-69, Cδ D3) and binary systems of high viscosity (benzene-d6 in tricresyl phosphate) have been carefully analyzed as illustrative examples (the spectra are taken from the literature). In the first case, a model of restricted diffusion mediated by jumps between rotameric orientations has been tested against jump- and free diffusion models which describe rotational motion combined with jump dynamics. It has been found that the set of 2H spectra of methyl-deuterated at leucine-69 chicken villin protein headpiece HP36 can be consistently explained by different motional models as well as by a Gaussian distribution of correlation times assuming isotropic rotation (simple Brownian diffusion model). The last finding shows that when the possible distribution of correlation times is not very broad one might not be able to distinguish between heterogeneous and homogenous (but more complex) dynamics by analyzing 2H lineshapes. For benzene-d6 in tricresyl phosphate, the dynamics is heterogeneous and it has been demonstrated that a Gaussian distribution of correlation times reproduces well the experimental lineshapes, while for a Cole-Davidson distribution the agreement is somewhat worse. For inquires into the sensitivity of quadrupolar NMR spectral analysis (by "quadrupolar NMR spectroscopy we understand NMR spectroscopy of nuclei possessing quadrupole moment), the recently presented theoretical approach [Kruk et al., J. Chem. Phys. 135, 224511 (2011)], 10.1063/1.3664783 has been used as it allows simulating quadrupolar spectra for arbitrary motional conditions by employing the stochastic Liouville equation.

  4. Helicity in Supercritical O2/H2 and C7H16/N2 Mixing Layers

    NASA Technical Reports Server (NTRS)

    Okongo, Nora; Bellan, Josette

    2004-01-01

    This report describes a study of databases produced by direct numerical simulation of mixing layers developing between opposing flows of two fluids under supercritical conditions, the purpose of the study being to elucidate chemical-species-specific aspects of turbulence, with emphasis on helicity. The simulations were performed for two different fluid pairs -- O2/H2 and C7H16/N2 -- at similar values of reduced pressure.

  5. Efficient and convenient synthesis of indazol-3(2H)-ones and 2-aminobenzonitriles.

    PubMed

    Dou, Guolan; Shi, Daqing

    2009-01-01

    A mild, efficient, one-pot protocol for the synthesis of indazole-3(2H)-ones via cyclization of nitro-aryl substrates through low-valent titanium reagent has been described. The method used Triethylamine (TEA) to control pH. Particularly, 2-aminobenzonitriles were synthesized by one step easily. The mechanistic course of the reaction suggests the involvement of an anion leading to an intramolecular cyclization via N-N bond formation.

  6. Regulated release of Ca2+ from respiring mitochondria by Ca2+/2H+ antiport.

    PubMed

    Fiskum, G; Lehninger, A L

    1979-07-25

    Simultaneous measurements of oxygen consumption and transmembrane transport of Ca2+, H+, and phosphate show that the efflux of Ca2+ from respiring tightly coupled rat liver mitochondria takes place by an electroneutral Ca2+/2H+ antiport process that is ruthenium red-insensitive and that is regulated by the oxidation-reduction state of the mitochondrial pyridine nucleotides. When mitochondrial pyridine nucleotides are kept in a reduced steady state, the efflux of Ca2+ is inhibited; when they are in an oxidized state, Ca2+ efflux is activated. These processes were demonstrated by allowing phosphate-depleted mitochondria respiring on succinate in the presence of rotenone to take up Ca2+ from the medium. Upon subsequent addition of ruthenium red to block Ca2+ transport via the electrophoretic influx pathway, and acetoacetate, to bring mitochondrial pyridine nucleotides into the oxidized state, Ca2+ efflux and H+ influx ensued. The observed H+ influx/Ca2+ efflux ratio was close to the value 2.0 predicted for the operation of an electrically neutral Ca2+/2H+ antiport process.

  7. Electronic structure and charge-density-wave mechanism in 2H-TaSe_2

    NASA Astrophysics Data System (ADS)

    Rossnagel, Kai; Rotenberg, Eli; Smith, Neville V.; Seifarth, Olaf; Kipp, Lutz

    2004-03-01

    The simple layered charge-density-wave system 2H-TaSe2 has received renewed interest recently because it may share important physical properties with the high-temperature superconducting cuprates, such as quasi-two-dimensionality, qualitatively similar resisitivity curves and optical responses, saddle bands close to the chemical potential, and a possible correlation between the opening of a gap on parts of the Fermi surface and the occurence of a strong energy renormalization on ungapped parts. We present here a detailed angle-resolved photoelectron spectroscopy study of the near-EF electronic structure of 2H-TaSe_2, focusing on Fermi surface topology, energy gaps, and band renormalization effects. Our results provide important clues as to the origin of the still-debated charge-density-wave mechanism in 2H-TaSe2 and possible similarities to the electronic structure of cuprates. The experiments were carried out at the Electronic Structure Factory at beamline 7 of the Advanced Light Source in Berkeley. K.R. gratefully acknowledges support by the Alexander von Humboldt Foundation. Work at the University of Kiel is supported by DFG Forschergruppe FOR 353.

  8. Liquid water on Mars - An energy balance climate model for CO2/H2O atmospheres

    NASA Technical Reports Server (NTRS)

    Hoffert, M. I.; Callegari, A. J.; Hsieh, C. T.; Ziegler, W.

    1981-01-01

    A simple climatic model is developed for a Mars atmosphere containing CO2 and sufficient liquid water to account for the observed hydrologic surface features by the existence of a CO2/H2O greenhouse effect. A latitude-resolved climate model originally devised for terrestrial climate studies is applied to Martian conditions, with the difference between absorbed solar flux and emitted long-wave flux to space per unit area attributed to the divergence of the meridional heat flux and the poleward heat flux assumed to equal the atmospheric eddy heat flux. The global mean energy balance is calculated as a function of atmospheric pressure to assess the CO2/H2O greenhouse liquid water hypothesis, and some latitude-resolved cases are examined in detail in order to clarify the role of atmospheric transport and temperature-albedo feedback. It is shown that the combined CO2/H2O greenhouse at plausible early surface pressures may account for climates hot enough to support a hydrological cycle and running water at present-day insolation and visible albedo levels.

  9. Exotic SiO2H2 Isomers: Theory and Experiment Working in Harmony.

    PubMed

    McCarthy, Michael C; Gauss, Jürgen

    2016-05-19

    Replacing carbon with silicon can result in dramatic and unanticipated changes in isomeric stability, as the well-studied CO2H2 and the essentially unknown SiO2H2 systems illustrate. Guided by coupled-cluster calculations, three SiO2H2 isomers have been detected and spectroscopically characterized in a molecular beam discharge source using rotational spectroscopy. The cis,trans conformer of dihydroxysilylene HOSiOH, the ground-state isomer, and the high-energy, metastable dioxasilirane c-H2SiO2 are abundantly produced in a dilute SiH4/O2 electrical discharge, enabling precise structural determinations of both by a combination of isotopic measurements and calculated vibrational corrections. The isotopic studies also provide insight into their formation route, suggesting that c-H2SiO2 is formed promptly in the expansion but that cis,trans-HOSiOH is likely formed by secondary reactions following formation of the most stable dissociation pair, SiO + H2O. Although less abundant, the rotational spectrum of trans-silanoic acid, the silicon analogue of formic acid, HSi(O)OH, has also been observed.

  10. 2Q NMR of 2H2O ordering at solid interfaces

    NASA Astrophysics Data System (ADS)

    Krivokhizhina, Tatiana V.; Wittebort, R. J.

    2014-06-01

    Solvent ordering at an interface can be studied by multiple-quantum NMR. Quantitative studies of 2H2O ordering require clean double-quantum (2Q) filtration and an analysis of 2Q buildup curves that accounts for relaxation and, if randomly oriented samples are used, the distribution of residual couplings. A pulse sequence with absorption mode detection is extended for separating coherences by order and measuring relaxation times such as the 2Q filtered T2. Coherence separation is used to verify 2Q filtration and the 2Q filtered T2 is required to extract the coupling from the 2Q buildup curve when it is unresolved. With our analysis, the coupling extracted from the buildup curve in 2H2O hydrated collagen was equivalent to the resolved coupling measured in the usual 1D experiment and the 2Q to 1Q signal ratio was in accord with theory. Application to buildup curves from 2H2O hydrated elastin, which has an unresolved coupling, revealed a large increase in the 2Q signal upon mechanical stretch that is due to an increase in the ordered water fraction while changes in the residual coupling and T2 are small.

  11. Angular momentum of the N2H+ cores in the Orion A cloud

    NASA Astrophysics Data System (ADS)

    Tatematsu, Ken'ichi; Ohashi, Satoshi; Sanhueza, Patricio; Nguyen Luong, Quang; Umemoto, Tomofumi; Mizuno, Norikazu

    2016-04-01

    We have analyzed the angular momentum of the molecular cloud cores in the Orion A giant molecular cloud observed in the N2H+ J = 1-0 line with the Nobeyama 45 m radio telescope. We have measured the velocity gradient using position-velocity diagrams passing through core centers, and made sinusoidal fits against the position angle. Twenty-seven out of 34 N2H+ cores allowed us to measure the velocity gradient without serious confusion. The derived velocity gradient ranges from 0.5 to 7.8 km s-1 pc-1. We marginally found that the specific angular momentum J/M (against the core radius R) of the Orion N2H+ cores tends to be systematically larger than that of molecular cloud cores in cold dark clouds obtained by Goodman et al., in the J/M-R relation. The ratio β of rotational to gravitational energy is derived to be β = 10-2.3±0.7, and is similar to that obtained for cold dark cloud cores in a consistent definition. The large-scale rotation of the ∫-shaped filament of the Orion A giant molecular cloud does not likely govern the core rotation at smaller scales.

  12. Laboratory IR Studies and Astrophysical Implications of C2H2-Containing Binary Ices

    NASA Technical Reports Server (NTRS)

    Knez, C.; Moore, M.; Ferrante, R.; Hudson, R.

    2012-01-01

    Studies of molecular hot cores and protostellar environments have shown that the observed abundance of gas-phase acetylene (C2H2) cannot be matched by chemical models without the inclusion of C2H2 molecules subliming from icy grain mantles. Searches for infrared (IR) spectral features of solid-phase acetylene are under way, but few laboratory reference spectra of C2H2 in icy mixtures, which are needed for spectral fits to observational data, have been published. Here, we report a systematic study of the IR spectra of condensed-phase pure acetylene and acetylene in ices dominated by carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and water (H2O). We present new spectral data for these ices, including band positions and intrinsic band strengths. For each ice mixture and concentration, we also explore the dependence of acetylene's nu5-band position (743 cm-1, 13.46 micrometers) and FWHM on temperature. Our results show that the nu5 feature is much more cleanly resolved in ices dominated by non-polar and low-polarity molecules, specifically CO, CO2, and CH4, than in mixtures dominated by H2O-ice. We compare our laboratory ice spectra with observations of a quiescent region in Serpens.

  13. Preparation of bis-(1(2)H-tetrazol-5-yl)-amine monohydrate

    DOEpatents

    Naud, Darren L.; Hiskey, Michael A.

    2003-05-27

    A process of preparing bis-(1(2)H-tetrazol-5-yl)-amine monohydrate is provided including combining a dicyanamide salt, an azide salt and water to form a first reaction mixture, adding a solution of a first strong acid characterized as having a pKa of less than about 1 to said first reaction mixture over a period of time characterized as providing a controlled reaction rate so as to gradually form hydrazoic acid without loss of significant quantities of hydrazoic acid from the solution while heating the first reaction mixture at temperatures greater than about 65.degree. C., heating the resultant reaction mixture at temperatures greater than about 65.degree. C. for a period of time sufficient to substantially completely form a reaction product, treating the reaction product with a solution of a second strong acid to form a product of bis-(1(2)H-tetrazol-5-yl)-amine monohydrate, and, recovering the bis-(1(2)H-tetrazol-5-yl)-amine monohydrate product.

  14. Mechanism and kinetics of the reaction NO3 + C2H4.

    PubMed

    Nguyen, Thanh Lam; Park, Jaehee; Lee, Kyungjun; Song, Kihyung; Barker, John R

    2011-05-19

    The reaction of NO(3) radical with C(2)H(4) was characterized using the B3LYP, MP2, B97-1, CCSD(T), and CBS-QB3 methods in combination with various basis sets, followed by statistical kinetic analyses and direct dynamics trajectory calculations to predict product distributions and thermal rate constants. The results show that the first step of the reaction is electrophilic addition of an O atom from NO(3) to an olefinic C atom from C(2)H(4) to form an open-chain adduct. A concerted addition reaction mechanism forming a five-membered ring intermediate was investigated, but is not supported by the highly accurate CCSD(T) level of theory. Master-equation calculations for tropospheric conditions predict that the collisionally stabilized NO(3)-C(2)H(4) free-radical adduct constitutes 80-90% of the reaction yield and the remaining products consist mostly of NO(2) and oxirane; the other products are produced in very minor yields. By empirically reducing the barrier height for the initial addition step by 1 kcal mol(-1) from that predicted at the CBS-QB3 level of theory and treating the torsional modes explicitly as one-dimensional hindered internal rotations (instead of harmonic oscillators), the computed thermal rate constants (including quantum tunneling) can be brought into very good agreement with the experimental data for the overall reaction rate constant.

  15. NMR resonance splitting of urea in stretched hydrogels: proton exchange and (1)H/(2)H isotopologues.

    PubMed

    Kuchel, Philip W; Naumann, Christoph; Chapman, Bogdan E; Shishmarev, Dmitry; Håkansson, Pär; Bacskay, George; Hush, Noel S

    2014-10-01

    Urea at ∼12 M in concentrated gelatin gel, that was stretched, gave (1)H and (2)H NMR spectral splitting patterns that varied in a predictable way with changes in the relative proportions of (1)H2O and (2)H2O in the medium. This required consideration of the combinatorics of the two amide groups in urea that have a total of four protonation/deuteration sites giving rise to 16 different isotopologues, if all the atoms were separately identifiable. The rate constant that characterized the exchange of the protons with water was estimated by back-transformation analysis of 2D-EXSY spectra. There was no (1)H NMR spectral evidence that the chiral gelatin medium had caused in-equivalence in the protons bonded to each amide nitrogen atom. The spectral splitting patterns in (1)H and (2)H NMR spectra were accounted for by intra-molecular scalar and dipolar interactions, and quadrupolar interactions with the electric field gradients of the gelatin matrix, respectively.

  16. Frequency Comb Assisted IR Measurements of H_3^+, H_2D^+ and D_2H^+ Transitions

    NASA Astrophysics Data System (ADS)

    Jusko, Pavol; Asvany, Oskar; Schlemmer, Stephan

    2016-06-01

    We present recent measurements of the fundamental transitions of H_3^+, H_2D^+ and D_2H^+ in a 4 K 22-pole trap by action spectroscopic techniques. Either Laser Induced Inhibition of Cluster Growth (He attachment at T≈4 K), endothermic reaction of H_3^+ with O_2, or deuterium exchange has been used as measurement scheme. We used a 3 μm optical parametric oscillator coupled to a frequency comb in order to achieve accuracy generally below 1 MHz. Five transitions of H_3^+, eleven of H_2D^+ and ten of D_2H^+ were recorder in our spectral range. We compare our H_3^+ results with two previous frequency comb assisted works. Moreover, accurate determination of the frequency allows us to predict pure rotational transitions for H_2D^+ and D_2H^+ in the THz range. P. Jusko, C. Konietzko, S. Schlemmer, O. Asvany, J. Mol. Spec. 319 (2016) 55 O. Asvany, S. Brünken, L. Kluge, S. Schlemmer, Appl. Phys. B 114 (2014) 203 O. Asvany, J. Krieg, S. Schlemmer, Rev. Sci. Instr. 83 (2012) 093110 J.N. Hodges, A.J. Perry, P.A. Jenkins, B.M. Siller, B.J. McCall, J. Chem. Phys. 139 (2013) 164201 H.-C. Chen, C.-Y. Hsiao, J.-L. Peng, T. Amano, J.-T. Shy, Phys. Rev. Lett. 109 (2012) 263002

  17. 2H Stable Isotope Analysis of Tooth Enamel: A Pilot Study

    NASA Astrophysics Data System (ADS)

    Holobinko, Anastasia; Kemp, Helen; Meier-Augenstein, Wolfram; Prowse, Tracy; Ford, Susan

    2010-05-01

    Stable isotope analysis of biogenic tissues such as tooth enamel and bone mineral has become a well recognized and increasingly important method for determining provenance of human remains, and has been used successfully in bioarchaeological studies as well as forensic investigations (Lee-Thorp, 2008; Meier-Augenstein and Fraser, 2008). Particularly, 18O and 2H stable isotopes are well established proxies as environmental indicators of climate (temperature) and source water and are therefore considered as indicators of geographic life trajectories of animals and humans (Hobson et al., 2004; Schwarcz and Walker, 2006). While methodology for 2H analysis of human hair, fingernails, and bone collagen is currently used to determine geographic origin and identify possible migration patterns, studies involving the analysis of 2H in tooth enamel appear to be nonexistent in the scientific literature. The apparent lack of research in this area is believed to have two main reasons. (1) Compared to the mineral calcium hydroxylapatite Ca10(PO4)6(OH)2, in tooth enamel forming bio-apatite carbonate ions replace some of the hydroxyl ions at a rate of one CO32 replacing two OH, yet published figures for the degree of substitution vary (Wopenka and Pasteris, 2005). (2) Most probably due to the aforementioned no published protocols exist for sample preparation and analytical method to obtain δ2H-values from the hydroxyl fraction of tooth enamel. This dilemma has been addressed through a pilot study to establish feasibility of 2H stable isotope analysis of ground tooth enamel by continuous-flow isotope ratio mass spectrometry (IRMS) coupled on-line to a high-temperature conversion elemental analyzer (TC/EA). An array of archaeological and modern teeth has been analyzed under different experimental conditions, and results from this pilot study are being presented. References: Lee-Thorp, J.A. (2008) Archaeometry, 50, 925-950 Meier-Augenstein, W. and Fraser, I. (2008) Science & Justice

  18. High-frequency observations of δ2H and δ18O in storm rainfall

    NASA Astrophysics Data System (ADS)

    Stoecker, F.; Klaus, J.; Pangle, L. A.; Garland, C.; McDonnell, J. J.

    2012-12-01

    Stable isotopes ratios of hydrogen (2H/1H) and oxygen (18O/16O) are indispensable tools for investigation of the hydrologic cycle. Recent technological advances with laser spectroscopy now enable high-frequency measurement of key water cycle components. While the controls on rainfall isotope composition have been known generally for some time, our understanding of the effect of inter- and intra-storm processes on fine scale rainfall isotope composition is poorly understood. Here we present a new approach to observe inter- and intra-storm isotope variability in precipitation in high-frequency. We investigate the temporal development of δ2H and δ18O within and between discrete rainstorm. δ2H and δ18O in precipitation was measured from November 2011 to February 2012 in Corvallis, OR using a flow-cell combined with a Liquid Water Isotope Analyzer (LWIA-24d, Los Gatos Research, Inc.). The average sample frequency was 15 samples per hour, resulting in more than 3100 samples during the observation period. 27 separate rainstorms were identified in the dataset based on minimum inter-event time, minimum precipitation depth, and minimum number of isotope measurements. Event meteoric water lines were developed for each event. We observed short-term isotopic patterns (e.g., V-shaped trends), high-rate changes (5.3‰/h) and large absolute changes in isotopic composition (20‰) on intra-event scale. V-shaped trends appeared to be related to individual storm fronts detected by air temperature, cloud heights (NEXRAD radar echo tops) and cloud trajectories (Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT)). Despite this, we could detect no linear correlation between event-based isotopic variables (slope, δ2H-intercept, δ2H, δ18O) and the event meteoric water line. Furthermore, the composite event meteoric water line (i.e. the local meteoric water line) showed a wider spread for heavy isotopes than for light isotopes, caused presumably by different

  19. A highly selective fluorescent probe based on coumarin for the imaging of N2H4 in living cells

    NASA Astrophysics Data System (ADS)

    Chen, Song; Hou, Peng; Wang, Jing; Liu, Lei; Zhang, Qi

    2017-02-01

    A turn-on fluorescence probe for highly sensitive and selective detection of N2H4 was developed based on hydrazine-triggered a substitution- cyclization-elimination cascade. Upon the treatment with N2H4, probe 1, 4-methyl-coumarin-7-yl bromobutanoate, displayed a remarkable fluorescence enhancement (25-fold) with a maximum at 450 nm. This probe can quantitatively detect N2H4 with a extremely low detection limit as 7 × 10- 8 M. Moreover, cell imaging experiments have indicated that probe 1 has potential ability to detect and image N2H4 in biological systems.

  20. Cometary implications of recent laboratory experiments on the photochemistry of the C2H and C3H2 radicals

    NASA Technical Reports Server (NTRS)

    Jackson, William M.; Bao, Yihan; Urdahl, Randall S.; Song, Xueyu; Gosine, Jai; Lu, Chi

    1992-01-01

    Recent laboratory results on the photodissociation of the C2H and C3H2 radicals are described. These studies show that the C2 and C3 radicals are produced by the 193 nm photolysis of the C2H and C3H2 radicals, respectively. The quantum state distributions that were determined for the C2 radicals put certain constraints on the initial conditions for any models of the observed C2 cometary spectra. Experimental observations of C2 formed by the 212.8 nm photolysis of C2H are used to calculate a range of photochemical lifetimes for the C2H radical.

  1. Hydrogen dynamics in soil organic matter as determined by 13C and 2H labeling experiments

    NASA Astrophysics Data System (ADS)

    Paul, Alexia; Hatté, Christine; Pastor, Lucie; Thiry, Yves; Siclet, Françoise; Balesdent, Jérôme

    2016-12-01

    Understanding hydrogen dynamics in soil organic matter is important to predict the fate of 3H in terrestrial environments. One way to determine hydrogen fate and to point out processes is to examine the isotopic signature of the element in soil. However, the non-exchangeable hydrogen isotopic signal in soil is complex and depends on the fate of organic compounds and microbial biosyntheses that incorporate water-derived hydrogen. To decipher this complex system and to understand the close link between hydrogen and carbon cycles, we followed labeled hydrogen and labeled carbon throughout near-natural soil incubations. We performed incubation experiments with three labeling conditions: 1 - 13C2H double-labeled molecules in the presence of 1H2O; 2 - 13C-labeled molecules in the presence of 2H2O; 3 - no molecule addition in the presence of 2H2O. The preservation of substrate-derived hydrogen after 1 year of incubation (ca. 5 % in most cases) was lower than the preservation of substrate-derived carbon (30 % in average). We highlighted that 70 % of the C-H bonds are broken during the degradation of the molecule, which permits the exchange with water hydrogen. Added molecules are used more for trophic resources. The isotopic composition of the non-exchangeable hydrogen was mainly driven by the incorporation of water hydrogen during microbial biosynthesis. It is linearly correlated with the amount of carbon that is degraded in the soil. The quantitative incorporation of water hydrogen in bulk material and lipids demonstrates that non-exchangeable hydrogen exists in both organic and mineral-bound forms. The proportion of the latter depends on soil type and minerals. This experiment quantified the processes affecting the isotopic composition of non-exchangeable hydrogen, and the results can be used to predict the fate of tritium in the ecosystem or the water deuterium signature in organic matter.

  2. Volume-discharge formed in SF6 and C2H6 mixtures without preionization

    NASA Astrophysics Data System (ADS)

    Zhang, Ge; Ke, Changjun; Zhang, Shujuan

    2014-11-01

    A new approach to obtain glow discharge in working mixtures of non-chain HF laser has been brought forward. The most advantage of the approach is without pre-ionization, so the contamination of pre-ionization will not happen and the laser equipment is compact and simple. It is found, if the cathode surface is equally rough, we can obtain uniform volume-discharge in SF6 mixtures without any pre-ionization, and dispense with uniform electric field electrode profile. The form of Self-Sustained Volume Discharge (SSVD) is a Self-Initiated Volume Discharge (SIVD). We show here the possibility of obtaining SIVD with a uniform energy deposition in a system of electrodes with non-uniform electric field. Experiments show that, with rough cathode and even anode, a volume discharge is forming in non-uniform electric-field without pre-ionization in SF6 and C2H6 mixtures. At the beginning of the discharge, many diffuse channels attached to bright circular cathode spots, then, diverge towards the anode, with the channels overlapping, form a spatially uniform glow discharge. SIVD has been performed at a total mixture pressure up to 8kPa and energy deposition up to 200J/l. We also report measurements of the V-I characteristics of SIVD with SF6 and C2H6 mixtures at pressure up to about 8kPa. The experimental results indicate that SSVD in SF6 and C2H6 mixtures develops in the form of SIVD is promising for creation of high energy and pulse-periodic HF laser.

  3. Obstruction of dengue virus maturation by Fab fragments of the 2H2 antibody.

    PubMed

    Wang, Zhiqing; Li, Long; Pennington, Janice G; Sheng, Ju; Yap, Moh Lan; Plevka, Pavel; Meng, Geng; Sun, Lei; Jiang, Wen; Rossmann, Michael G

    2013-08-01

    The 2H2 monoclonal antibody recognizes the precursor peptide on immature dengue virus and might therefore be a useful tool for investigating the conformational change that occurs when the immature virus enters an acidic environment. During dengue virus maturation, spiky, immature, noninfectious virions change their structure to form smooth-surfaced particles in the slightly acidic environment of the trans-Golgi network, thereby allowing cellular furin to cleave the precursor-membrane proteins. The dengue virions become fully infectious when they release the cleaved precursor peptide upon reaching the neutral-pH environment of the extracellular space. Here we report on the cryo-electron microscopy structures of the immature virus complexed with the 2H2 antigen binding fragments (Fab) at different concentrations and under various pH conditions. At neutral pH and a high concentration of Fab molecules, three Fab molecules bind to three precursor-membrane proteins on each spike of the immature virus. However, at a low concentration of Fab molecules and pH 7.0, only two Fab molecules bind to each spike. Changing to a slightly acidic pH caused no detectable change of structure for the sample with a high Fab concentration but caused severe structural damage to the low-concentration sample. Therefore, the 2H2 Fab inhibits the maturation process of immature dengue virus when Fab molecules are present at a high concentration, because the three Fab molecules on each spike hold the precursor-membrane molecules together, thereby inhibiting the normal conformational change that occurs during maturation.

  4. Validation of SCALE (SAS2H) isotopic predictions for BWR spent fuel

    SciTech Connect

    Hermann, O.W.; DeHart, M.D.

    1998-09-01

    Thirty spent fuel samples obtained from boiling-water-reactor (BWR) fuel pins have been modeled at Oak Ridge National Laboratory using the SAS2H sequence of the SCALE code system. The SAS2H sequence uses transport methods combined with the depletion and decay capabilities of the ORIGEN-S code to estimate the isotopic composition of fuel as a function of its burnup history. Results of these calculations are compared with chemical assay measurements of spent fuel inventories for each sample. Results show reasonable agreement between measured and predicted isotopic concentrations for important actinides; however, little data are available for most fission products considered to be important for spent fuel concerns (e.g., burnup credit, shielding, source-term calculations, etc.). This work is a follow-up to earlier works that studied the ability to predict spent fuel compositions in pressurized-water-reactor (PWR) fuel pins. Biases and uncertainties associated with BWR isotopic predictions are found to be larger than those of PWR calculations. Such behavior is expected, as the operation of a BWR is significantly more complex than that of a PWR plant, and in general the design of a BWR has a more heterogeneous configuration than that of a PWR. Nevertheless, this work shows that the simple models employed using SAS2H to represent such complexities result in agreement to within 5% (and often less than 1%) or less for most nuclides important for spent fuel applications. On the other hand, however, the set of fuel samples analyzed represent a small subset of the BWR fuel population, and results reported herein may not be representative of the full population of BWR spent fuel.

  5. Validation of SCALE (SAS2H) Isotopic Predictions for BWR Spent Fuel

    SciTech Connect

    Hermann, O.W.

    1998-01-01

    Thirty spent fuel samples obtained from boiling-water-reactor (BWR) fuel pins have been modeled at Oak Ridge National Laboratory using the SAS2H sequence of the SCALE code system. The SAS2H sequence uses transport methods combined with the depletion and decay capabilities of the ORIGEN-S code to estimate the isotopic composition of fuel as a function of its burnup history. Results of these calculations are compared with chemical assay measurements of spent fuel inventories for each sample. Results show reasonable agreement between measured and predicted isotopic concentrations for important actinides; however, little data are available for most fission products considered to be important for spent fuel concerns (e.g., burnup credit, shielding, source-term calculations, etc.). This work is a follow-up to earlier works that studied the ability to predict spent fuel compositions in pressurized-water-reactor (PWR) fuel pins. Biases and uncertainties associated with BWR isotopic predictions are found to be larger than those of PWR calculations. Such behavior is expected, as the operation of a BWR is significantly more complex than that of a PWR plant, and in general the design of a BWR has a more heterogeneous configuration than that of a PWR. Nevertheless, this work shows that the simple models employed using SAS2H to represent such complexities result in agreement to within 5% (and often less than 1%) or less for most nuclides important for spent fuel applications. On the other hand, however, the set of fuel samples analyzed represent a small subset of the BWR fuel population, and results reported herein may not be representative of the full population of BWR spent fuel.

  6. The leptonic CP phase from T2(H)K and μ+ decay at rest

    DOE PAGES

    Evslin, Jarah; Ge, Shao-Feng; Hagiwara, Kaoru

    2016-02-22

    Combining v oscillations at T2K or T2HK withmore » $$\\bar{v}$$ oscillations from μ+ decay at rest (DAR) allows a determination of the leptonic CP-violating phase . The degeneracies of this phase with θ13 and θ23 are broken and δ can be reliably distinguished from 180° - δ. In this study, we present the sensitivity to δ of T2(H)K together with a μ+ DAR experiment using Super-K as a near detector and Hyper-K at the Tochibora site as a far detector.« less

  7. Smoothed orientational order profile of lipid bilayers by 2H-nuclear magnetic resonance.

    PubMed Central

    Lafleur, M; Fine, B; Sternin, E; Cullis, P R; Bloom, M

    1989-01-01

    A new method has been developed to determine the complete orientational order profile of lipid bilayers using 2H-NMR. The profile is obtained from a single powder spectrum of a lipid which has a saturated chain fully deuteriated. The smoothed order profile is determined directly from the normalized dePaked spectrum assuming a monotonic decrease of the order along the acyl chain. The oscillatory variations of the order at the beginning of the chain are not described by this method. However the smoothed order profile reveals in a straightforward way the crucial features of the anisotropic order of the bilayer. PMID:2605294

  8. Characterization of Post-Cleaning Solids Samples from the 2H Evaporator Pot

    SciTech Connect

    WILMARTH, WILLIAM

    2004-03-15

    Samples retrieved from the 2H Evaporator Pot in October of 2003 were of a similar nature as previous materials. The bulk of the sample was comprised of a sodium aluminosilicate phase, cancrinite. The concentration of uranium in the evaporator solids,however, was very low:less than 0.1 percentage weight. The uranium enrichment was depleted as expected and measured 0.6 percent. These data agree with uranium contents generated during experimental testing. Additionally, the overall specific radionuclide content is lower for this sample than previous measured on samples from the Gravity Drain Line in 1997 and the cone and wall in 2000.

  9. Fermi surface, charge-density-wave gap, and kinks in 2H- TaSe2

    NASA Astrophysics Data System (ADS)

    Rossnagel, K.; Rotenberg, Eli; Koh, H.; Smith, N. V.; Kipp, L.

    2005-09-01

    The Fermi surface of the layered charge-density-wave compound 2H-TaSe2 is measured by angle-resolved photoemission as a function of temperature. A surprising Fermi-surface topology and a Fermi-surface branch-dependent charge-density-wave gap are found. In the charge-density-wave state band hybridization effects are strong and responsible for kinks in the band dispersions at relatively high binding energy. The implications of the results on the charge-density-wave mechanism are discussed.

  10. Characterization Results for the 2014 HTF 3H & 2H Evaporator Overhead Samples

    SciTech Connect

    Washington, A.

    2015-05-11

    This report tabulates the radiochemical analysis of the 3H and 2H evaporator overhead samples for 137Cs, 90Sr, and 129I to meet the requirements in the Effluent Treatment Project (ETP) Waste Acceptance Criteria (WAC) (rev. 6). This report identifies the sample receipt date, preparation method, and analysis performed in the accumulation of the listed values. All data was found to be within the ETP WAC (rev. 6) specification for the Waste Water Collection Tanks (WWCT).

  11. 5-[(tert-Butyl-diphenyl-sil-yloxy)meth-yl]pyridazin-3(2H)-one.

    PubMed

    Costas-Lago, María Carmen; Costas, Tamara; Vila, Noemí; Terán, Carmen

    2013-11-27

    In the title compound, C21H24N2O2Si, a new pyridazin-3(2H)-one derivative, the carbonyl group of the heterocyclic ring and the O atom of the silyl ether are located on the same side of the pyridazinone ring and the C-C-O-Si torsion angle is -140.69 (17)°. In the crystal, mol-ecules are linked by pairs of strong N-H⋯O hydrogen bonds into centrosymmetric dimers with graph-set notation R 2 (2)(8). Weak C-H⋯π inter-actions are also observed.

  12. Early Gravitropic Events in Roots of Arabidopsis: Ca(2+)H(+) Fluxes in the Columella Cells

    NASA Technical Reports Server (NTRS)

    Feldman, Lewis

    2003-01-01

    Despite the wealth of information derived from physiological approaches, molecular mechanisms for sensing and responding to gravity in plants remain largely uncharacterized. Roots of higher plants offer many advantages for studying the sensing and responding phases. In roots, gravisensing occurs in specialized cells, the columella cells in which earlier studies have indicated an involvement of the cytoskeleton, Ca(2+), H(+) and auxin in processing the gravity signal. The overall goal of this project was to characterize gravity-stimulated Ca(2+) and H(+) fluxes in the columella cells of a model plant Arabidopsis thaliana and to define their regulation. For this work we used intact Arabidopsis roots.

  13. Development of homotopy algorithms for fixed-order mixed H2/H(infinity) controller synthesis

    NASA Technical Reports Server (NTRS)

    Whorton, M.; Buschek, H.; Calise, A. J.

    1994-01-01

    A major difficulty associated with H-infinity and mu-synthesis methods is the order of the resulting compensator. Whereas model and/or controller reduction techniques are sometimes applied, performance and robustness properties are not preserved. By directly constraining compensator order during the optimization process, these properties are better preserved, albeit at the expense of computational complexity. This paper presents a novel homotopy algorithm to synthesize fixed-order mixed H2/H-infinity compensators. Numerical results are presented for a four-disk flexible structure to evaluate the efficiency of the algorithm.

  14. Laboratory Spectra of Mixtures of CH4, C2H6, and CH3OH

    NASA Technical Reports Server (NTRS)

    Mastrapa, Rachel; Berry, Matthew T.; Sandford, Scott

    2011-01-01

    Infrared spectroscopy is commonly used as a tool for identifying the composition of objects in the Solar System and beyond. Using laboratory spectra, optical constants can be calculated and used to create model spectra for comparison to spectra obtained from infrared telescopes. In this study, the optical constants of mixtures of simple organics, including CH4, C2H6, and CH3OH were calculated from 15 to 70 K, in the frequency range of 9000-500 cm(sup -1) (1.1-20 micrometers), at a spectral resolution of 1 cm(sup -1).

  15. Mixed H2/H Infinity Optimization with Multiple H Infinity Constraints

    DTIC Science & Technology

    1994-06-01

    DMD -),X p(QM): 2-7 2.3.1 Structured Singular Value in Control Systems The structured singular value is a framework based on the small gain theorem, in...sensitivity problem, and the mixed H2/H. controller. In this section, the value of the upper bound on t(a( DMD -’)) will simply be called IL for convenience. A...Casa 283 Ciudadela Kennedy Quito-Ecuador r1 I’ Form Approved REPORT DOCUMENTATION PAGE OM No. 0704-0188 putb4C reporting tburdtn for this collectiont

  16. Total lattice potential energy of sodium bromide dihydrate NaBr · 2H 2O

    NASA Astrophysics Data System (ADS)

    Herzig, P.; Jenkins, H. D. B.; Pritchett, M. S. F.

    1984-08-01

    In addition to presenting comparative calculations by two approaches for the total lattice potential energy of sodium bromide dihydrate, NaBr · 2H 2O, found to take the value 803.9 kJ mol -1, we investigate the influence of the size and nature of the basis set used to generate multipole moments in a Hartee-Fock calculation which are in turn used to calculate the Madelung constant. The requirement is one of critical size of the basis set and once this is reached the electrostatic energy will be reliable.

  17. Nanocrystallite Mg ferrite LPG, Cl2 and C2H5OH sensor

    NASA Astrophysics Data System (ADS)

    Gadkari, Ashok B.; Shinde, Tukaram J.; Vasambekar, Pramod N.

    2012-06-01

    The magnesium ferrite was synthesized by oxalate co-precipitation method. The crystal structure and surface morphology were examined by X-ray diffraction and SEM respectively. The nanocrystallite MgFe2O4 sensor was tested for gases like LPG, Cl2 and C2H5OH. Sensitivity was measured at various operating temperatures between 100-400°C. The sensor shows highest sensitivity to LPG at 225°C. The response and recovery time was measured at operating temperature of 225°C. The sensor exhibits a good response and recovery for LPG at operating temperature.

  18. Theoretical study of the dynamics of AR collisions with C2H6 and C2F6 at hyperthermal energy.

    PubMed

    Tasić, Uros; Hein, Pyae; Troya, Diego

    2007-05-10

    We present a classical-trajectory study of the dynamics of high-energy (5-12 eV) collisions between Ar atoms and the C2H6 and C2F6 molecules. We have constructed the potential-energy surfaces for these systems considering separately the Ar-molecule interactions (intermolecular potential) and the interactions within the molecule (intramolecular potential). The intermolecular surfaces consist of pairwise empirical potentials derived from high-accuracy ab initio calculations. The intramolecular potentials for C2H6 and C2F6 are described using specific-reaction-parameters semiempirical Hamiltonians and are calculated "on the fly", i.e., while the trajectories are evolving. Trajectory analysis shows that C2F6 absorbs more energy than C2H6 and is more susceptible to collision-induced dissociation (CID). C-C bond-breakage processes are more important than C-H or C-F bond breakage at the energies explored in this work. Analysis of the reaction mechanism for CID processes indicates that, although C-C breakage is mostly produced by side-on collisions, head-on collisions are more efficient in producing C-F or C-H dissociation. Our results suggest that high-energy collisions between closed-shell species of the natural low-Earth-orbit environment and spacecraft can contribute to the observed degradation of polymers that coat spacecraft surfaces.

  19. Mean annual temperatures of mid-latitude regions derived from δ(2)H values of wood lignin methoxyl groups and its implications for paleoclimate studies.

    PubMed

    Anhäuser, Tobias; Greule, Markus; Polag, Daniela; Bowen, Gabriel J; Keppler, Frank

    2017-01-01

    Tree-rings are widely used climate archives providing annual resolutions on centennial to millennial timescales. Stable isotope ratios of tree-rings have been applied to assist with the delineation of climate parameters such as temperature and precipitation. Here, we investigated stable hydrogen isotope ratios (expressed as δ(2)H values) of lignin methoxyl groups of wood from various tree species collected along a ~3500km north-south transect across Europe with mean annual temperatures (MAT) ranging from -4 to +17°C. We found a strong linear relationship between MATs and δ(2)H values of wood lignin methoxyl groups. We used this relationship to predict MATs from randomly collected wood samples and found general agreement between predicted and observed MATs for the mid-latitudes on a global scale. Our results are discussed in context of their paleoclimate relevance and suggest that δ(2)H values of lignin methoxyl groups might have the potential to reconstruct MATs when applied on mid-latitudinal tree-ring chronologies of the Late Holocene.

  20. Stable (2)H isotope analysis of modern-day human hair and nails can aid forensic human identification.

    PubMed

    Fraser, Isla; Meier-Augenstein, Wolfram

    2007-01-01

    Continuous-flow isotope ratio mass spectrometry (CF-IRMS) was used to compare (2)H isotopic composition at natural abundance level of human scalp hair and fingernail samples collected from subjects worldwide with interpolated delta(2)H precipitation values at corresponding locations. The results showed a strong correlation between delta(2)H values of meteoric water and hair (r(2) = 0.86), while the corresponding correlation for nails was not as strong (r(2) = 0.6). Offsets of -180 per thousand and -127 per thousand were observed when calculating solutions of the linear regression analyses for delta(2)H vs. delta(18)O correlation plots of hair and nail samples, respectively. Compared with the +10 per thousand offset of the global meteoric water line equation these findings suggested that delta(18)O data from hair and nail would be of limited diagnostic value. The results of this pilot study provide for the first time tentative correlations of (2)H isotopic composition of human hair and nails with local water. Linear regression analyses for measured delta(2)H values of human hair and nails vs. water yielded delta(2)H(hair) = 0.49 x delta(2)H(water) - 35 and delta(2)H(nails) = 0.38 x delta(2)H(water) - 49, respectively. The results suggest that (2)H isotopic analysis of hair and nail samples can be used to provide information regarding an individual's recent geographical life history and, hence, location. The benefit of this technique is to aid identification of victims of violent crime and mass disasters in circumstances where traditional methods such as DNA and fingerprinting cannot be brought to bear (or at least not immediately).

  1. Specific heat anomaly in ferroelectric: Bis(imidazolium) pentachloroantimonate(III) (C3 N2 H5)2[SbCl5

    NASA Astrophysics Data System (ADS)

    Przesławski, J.; Piecha-Bisiorek, A.; Jakubas, R.

    2016-04-01

    Single crystals of ferroelectric bis(imidazolium) pentachloroantimonate(III) (C3N2H5)2 [SbCl5 ] have been grown and the heat capacity was measured by the use of AC calorimetric method. The temperature dependence of excess heat capacity and excess entropy in the ferroelectric phase can be described in the frame of the classical Landau-Devonshire theory of phase transitions. The results of experimental studies were analyzed and the α, γ and δ values of the Landau potential coefficients were calculated. The temperature dependence of the order parameter was also evaluated from the heat capacity data.

  2. Genes and environment as predisposing factors in autoimmunity: acceleration of spontaneous thyroiditis by dietary iodide in NOD.H2(h4) mice.

    PubMed

    Kolypetri, Panayota; King, Justin; Larijani, Mani; Carayanniotis, George

    2015-01-01

    In the field of autoimmune thyroiditis, NOD.H2(h4) mice have attracted significant and increasing attention since they not only develop spontaneous disease but they present thyroiditis with accelerated incidence and severity if they ingest iodide through their drinking water. This animal model highlights the interplay between genetic and dietary factors in the triggering of autoimmune disease and offers new opportunities to study immunoregulatory parameters influenced by both genes and environment. Here, we review experimental findings with this mouse model of thyroiditis.

  3. Persistence of singlet fluctuations in the coupled spin tetrahedra system Cu2Te2O5Br2 revealed by high-field magnetization, 79Br NQR, and 125Te NMR

    NASA Astrophysics Data System (ADS)

    Baek, S.-H.; Choi, K.-Y.; Berger, H.; Büchner, B.; Grafe, H.-J.

    2012-11-01

    We present high-field magnetization and 79Br nuclear quadrupole resonance (NQR) and 125Te nuclear magnetic resonance (NMR) studies in the weakly coupled Cu2+ (S=1/2) tetrahedral system Cu2Te2O5Br2. The field-induced level crossing effects were observed by the magnetization measurements in a long-ranged magnetically ordered state which was confirmed by a strong divergence of the spin-lattice relaxation rate T1-1 at T0=13.5 K. In the paramagnetic state, T1-1 reveals an effective singlet-triplet spin gap much larger than that observed by static bulk measurements. Our results imply that the inter- and the intratetrahedral interactions compete, but at the same time they cooperate strengthening effectively the local intratetrahedral exchange couplings. We discuss that the unusual feature originates from the frustrated intertetrahedral interactions.

  4. Order and dynamics in mixtures of membrane glucolipids from Acholeplasma laidlawii studied by sup 2 H NMR

    SciTech Connect

    Eriksson, P.O.; Rilfors, L.; Lundberg, A.; Lindblom, G.; Wieslander, A. )

    1991-05-21

    The two dominant glucolipids in Acholeplasma laidlawii, viz., 1,2-diacyl-3-O-({alpha}-D-glucopyranosyl)-sn-glycerol (MGlcDG) and 1,2-diacyl-3-O-({alpha}-D-glucopyranosyl-(1{yields}2)-O-{alpha}-D-glucopyranosyl)-sn-glycerol (DGlcDG), have markedly different phase behavior. MGlcDG has an ability to form nonlamellar phases, whereas DGlcDG only forms lamellar phases. For maintenance of a stable lipid bilayer, the polar headgroup composition in A. laidlawii is metabolically regulated in vivo, in response to changes in the growth conditions. To investigate the mechanism behind the lipid regulation the authors have here studied bilayers of mixtures of unsaturated MGlcDG and DGlcDG, containing a small fraction of biosynthetically incorporated per-deuterated palmitic acid, with {sup 2}H NMR. The order-parameter profile of the acyl chains and an apparent transverse spin relaxation rate (R{sub 2}) were determined from dePaked quadrupole-echo spectra. The variation of order with lipid composition is rationalized from simple packing constraints. The relaxation data indicate the presence of slow reorientational motions, such as collective bilayer fluctuations and/or lipid lateral diffusion over a curved bilayer surface. The variation of acyl-chain order and bilayer curvature and/or fluctuations with sample composition are discussed in relation to the tendency of MGlcDG to form nonlamellar phases in vitro and in relation to the lipid regulation in vivo.

  5. Emergence of coherence in the charge-density wave state of 2H-NbSe2

    PubMed Central

    Chatterjee, U.; Zhao, J.; Iavarone, M.; Di Capua, R.; Castellan, J. P.; Karapetrov, G.; Malliakas, C. D.; Kanatzidis, M. G.; Claus, H.; Ruff, J. P. C.; Weber, F.; van Wezel, J.; Campuzano, J. C.; Osborn, R.; Randeria, M.; Trivedi, N.; Norman, M. R.; Rosenkranz, S.

    2015-01-01

    A charge-density wave (CDW) state has a broken symmetry described by a complex order parameter with an amplitude and a phase. The conventional view, based on clean, weak-coupling systems, is that a finite amplitude and long-range phase coherence set in simultaneously at the CDW transition temperature Tcdw. Here we investigate, using photoemission, X-ray scattering and scanning tunnelling microscopy, the canonical CDW compound 2H-NbSe2 intercalated with Mn and Co, and show that the conventional view is untenable. We find that, either at high temperature or at large intercalation, CDW order becomes short-ranged with a well-defined amplitude, which has impacts on the electronic dispersion, giving rise to an energy gap. The phase transition at Tcdw marks the onset of long-range order with global phase coherence, leading to sharp electronic excitations. Our observations emphasize the importance of phase fluctuations in strongly coupled CDW systems and provide insights into the significance of phase incoherence in ‘pseudogap’ states. PMID:25687135

  6. The chemistry of 5-(tetrazol-1-yl)-2H-tetrazole: an extensive study of structural and energetic properties.

    PubMed

    Fischer, Niko; Izsák, Dániel; Klapötke, Thomas M; Stierstorfer, Jörg

    2013-07-01

    5-(Tetrazol-1-yl)-2H-tetrazole (1), or 1,5'-bistetrazole, was synthesized by the cyclization of 5-amino-1H-tetrazole, sodium azide and triethyl orthoformate in glacial acetic acid. A derivative of 1, 2-methyl-5-(tetrazol-1-yl)tetrazole (2) can be obtained by this method starting from 5-amino-2-methyl-tetrazole. Furthermore, selected salts of 1 with nitrogen-rich and metal (alkali and transition metal) cations, including hydroxylammonium (4), triaminoguanidinium (5), copper(I) (8) and silver (9), as well as copper(II) complexes of both 1 and 2 were prepared. An intensive characterization of the compounds is given, including vibrational (IR, Raman) and multinuclear NMR spectroscopy, mass spectrometry, DSC and single-crystal X-ray diffraction. Their sensitivities towards physical stimuli (impact, friction, electrostatic) were determined according to Bundesamt für Materialforschung (BAM) standard methods. Energetic performance (detonation velocity, pressure, etc.) parameters were calculated with the EXPLO5 program, based on predicted heats of formation derived from enthalpies computed at the CBS-4M level of theory and utilizing the atomization energy method. From the analytical and calculated data, their potential as energetic materials in different applications was evaluated and discussed.

  7. Magnesium cinnamate complex, [Mg(cinn)2(H2O)2]n; structural, spectroscopic, thermal, biological and pharmacokinetical characteristics

    NASA Astrophysics Data System (ADS)

    Puszyńska-Tuszkanow, Mariola; Zierkiewicz, Wiktor; Grabowski, Tomasz; Daszkiewicz, Marek; Maciejewska, Gabriela; Adach, Anna; Kucharska-Ziembicka, Katarzyna; Wietrzyk, Joanna; Filip-Psurska, Beata; Cieślak-Golonka, Maria

    2017-04-01

    The composition and structure of the magnesium complex with cinnamic acid, [Mg(cinn)2(H2O)2]n(1), were determined using single crystal X-ray diffraction data, IR, NMR spectroscopies, thermal and mass spectrometry analysis. Magnesium cinnamate complex, like the isostructural cobalt(II) species reported in the literature, appears to belong to the group of coordination polymers forming layered solids with pseudooctahedral coordination around the metal centre and Osbnd Csbnd O bridging units. The vibrational assignments of the experimental spectra of the complex (1) were performed on the basis of the DFT results obtained for the [Mg(cinn)4(H2O)2]2- ion, serving as a model. The complex was found to exhibit a very low cytotoxicity against neoplastic: A549 (lung), MCF-7 (breast), P388 (murine leukemia) and normal BALB3T3 (mouse fibroblasts) cell lines. In silico pharmacokinetical parameter calculations for (1) and seven known magnesium complexes with carboxylic acids: lactic, malic, glutamic, hydroaspartic and aspartic allowed for comparison of their potential bioavailability. Magnesium cinnamate complex appeared to exhibit a superior lipophilic property that suggests an optimal pharmacokinetics profile.

  8. Computational and spectral studies of 6-phenylazo-3-(p-tolyl)-2H-chromen-2-one

    NASA Astrophysics Data System (ADS)

    Manimekalai, A.; Vijayalakshmi, N.

    2015-02-01

    6-Phenylazo-3-(p-tolyl)-2H-chromen-2-one 4 was prepared and characterized by IR, 1H, and 13C NMR spectral studies. The optimized structure of the chromen-2-one 4 was investigated by the Gaussian 03 B3LYP density functional method calculations at 6-31G(d,p) basis set. The gauge-independent atomic orbital (GIAO) 13C and 1H chemical shift calculations for the synthesized chromen-2-one in CDCl3 were also made by the same method. The computed IR frequencies of the chromen-2-one and the corresponding vibrational assignments were analyzed by means of potential energy distribution (PED%) calculation using vibrational energy distribution analysis (VEDA) program. The first order hyperpolarizability (βtot), polarizability (α) and dipole moment (μ) were calculated using 6-311G(d,p) basis set and the nonlinear optical (NLO) properties are also addressed theoretically. Stability of the chromen-2-one 4 molecule has been analyzed by calculating the intramolecular charge transfer using natural bond order (NBO) analysis. The molecular electrostatic potentials, HOMO-LUMO energy gap and geometrical parameters were also computed. Topological properties of the electronic charge density in chromen-2-one 4 were analyzed employing the Bader's Atoms in Molecule (AIM) theory which indicated the presence of intramolecular hydrogen bond in the molecule.

  9. Computational and spectral studies of 6-phenylazo-3-(p-tolyl)-2H-chromen-2-one.

    PubMed

    Manimekalai, A; Vijayalakshmi, N

    2015-02-05

    6-Phenylazo-3-(p-tolyl)-2H-chromen-2-one 4 was prepared and characterized by IR, (1)H, and (13)C NMR spectral studies. The optimized structure of the chromen-2-one 4 was investigated by the Gaussian 03 B3LYP density functional method calculations at 6-31G(d,p) basis set. The gauge-independent atomic orbital (GIAO) (13)C and (1)H chemical shift calculations for the synthesized chromen-2-one in CDCl3 were also made by the same method. The computed IR frequencies of the chromen-2-one and the corresponding vibrational assignments were analyzed by means of potential energy distribution (PED%) calculation using vibrational energy distribution analysis (VEDA) program. The first order hyperpolarizability (βtot), polarizability (α) and dipole moment (μ) were calculated using 6-311G(d,p) basis set and the nonlinear optical (NLO) properties are also addressed theoretically. Stability of the chromen-2-one 4 molecule has been analyzed by calculating the intramolecular charge transfer using natural bond order (NBO) analysis. The molecular electrostatic potentials, HOMO-LUMO energy gap and geometrical parameters were also computed. Topological properties of the electronic charge density in chromen-2-one 4 were analyzed employing the Bader's Atoms in Molecule (AIM) theory which indicated the presence of intramolecular hydrogen bond in the molecule.

  10. Isoscapes of δ18O and δ2H reveal climatic forcings on Alaska and Yukon precipitation

    NASA Astrophysics Data System (ADS)

    Lachniet, Matthew S.; Lawson, Daniel E.; Stephen, Haroon; Sloat, Alison R.; Patterson, William P.

    2016-08-01

    Spatially extensive Arctic stable isotope data are sparse, inhibiting the climatic understanding required to interpret paleoclimate proxy records. To fill this need, we constrained the climatic and physiographic controls on δ18O and δD values of stream waters across Alaska and the Yukon to derive interpolated isoscape maps. δ18O is strongly correlated to winter temperature parameters and similarity of the surface water line (δ2H = 8.0 × δ18O + 6.4) to the Global Meteoric Water Line suggests stream waters are a proxy for meteoric precipitation. We observe extreme orographic δ18O decreases and a trans-Alaskan continental gradient of -8.3‰ 1000 km-1. Continental gradients are high in coastal zones and low in the interior. Localized δ18O increases indicate inland air mass penetration via topographic lows. Using observed δ18O/temperature gradients, we show that δ18O decreases in a ˜24 ka permafrost ice wedge relative to the late Holocene indicate mean annual and coldest quarter temperature reductions of 8.9 ± 1.7°C and 17.2 ± 3.2°C, respectively.

  11. Primary and secondary relaxation process in plastically crystalline cyanocyclohexane studied by 2H nuclear magnetic resonance. II. Quantitative analysis

    NASA Astrophysics Data System (ADS)

    Micko, B.; Kruk, D.; Rössler, E. A.

    2013-02-01

    We analyze the results of our previously reported 2H nuclear magnetic resonance (NMR) experiments in the plastically crystalline (PC) phase of cyanocyclohexane (Part I of this work) to study the fast secondary relaxation (or β-process) in detail. Both, the occurrence of an additional minimum in the spin-lattice relaxation T1 and the pronounced effects arising in the solid-echo spectrum above the glass transition temperature Tg = 134 K, allow for a direct determination of the restricting geometry of the β-process in terms of the "wobbling-in-a-cone" model. Whereas at temperatures below Tg the reorientation is confined to rather small solid angles (below 10°), the spatial restriction decreases strongly with temperature above Tg, i.e., the distribution of cone angles shifts continuously towards higher values. The β-process in the PC phase of cyanocyclohexane proceeds via the same mechanism as found in structural glass formers. This is substantiated by demonstrating the very similar behavior (for T < Tg) of spin-lattice relaxation, stimulated echo decays, and spectral parameters when plotted as a function of ⟨log τβ⟩ (taken from dielectric spectroscopy). We do, however, not observe a clear-cut relation between the relaxation strength of the β-process observed by NMR (calculated within the wobbling-in-a-cone model) and dielectric spectroscopy.

  12. Emergence of coherence in the charge-density wave state of 2H-NbSe2

    DOE PAGES

    Chatterjee, U.; Zhao, J.; Iavarone, M.; ...

    2015-02-17

    A charge-density wave (CDW) state has a broken symmetry described by a complex order parameter with an amplitude and a phase. The conventional view, based on clean, weak-coupling systems, is that a finite amplitude and long-range phase coherence set in simultaneously at the CDW transition temperature Tcdw. Here we investigate, using photoemission, X-ray scattering and scanning tunnelling microscopy, the canonical CDW compound 2H-NbSe2 intercalated with Mn and Co, and show that the conventional view is untenable. We find that, either at high temperature or at large intercalation, CDW order becomes short-ranged with a well-defined amplitude, which has impacts on themore » electronic dispersion, giving rise to an energy gap. The phase transition at Tcdw marks the onset of long-range order with global phase coherence, leading to sharp electronic excitations. As a result, our observations emphasize the importance of phase fluctuations in strongly coupled CDW systems and provide insights into the significance of phase incoherence in ‘pseudogap’ states.« less

  13. Probing anisotropic interaction potentials of unsaturated hydrocarbons with He*(2 3S) metastable atom: Attractive-site preference of σ-direction in C2H2 and π-direction in C2H4

    NASA Astrophysics Data System (ADS)

    Horio, Takuya; Hatamoto, Takuro; Maeda, Satoshi; Kishimoto, Naoki; Ohno, Koichi

    2006-03-01

    State-resolved collision energy dependence of Penning ionization cross sections of acetylene (C2H2) and ethylene (C2H4) with He*(2S3) metastable atoms was observed in a wide collision energy range from 20to350meV. A recently developed discharge nozzle source with a liquid N2 circulator was employed for the measurements in the low-energy range from 20to80meV. Based on classical trajectory calculations for the energy dependence of the partial ionization cross sections, anisotropic potential energy surfaces for the present systems were obtained by optimizing ab initio model potentials for the chemically related systems Li +C2H2 and C2H4. In the case of C2H2, the global minimum was found to be located around the H atom along the molecular axis with a well depth of 48meV (ca. 1.1kcal/mol). On the other hand, a dominant attractive well with a depth of 62meV (ca. 1.4kcal/mol) was found in the πCC electron region of C2H4. These findings were discussed in connection with orbital interactions between molecular orbitals of the target molecules and atomic orbitals of the metastable atom. It is concluded that σ-type unoccupied molecular orbitals of C2H2 and a πCC-type highest occupied molecular orbital of C2H4 play a significant role for the attractive-site preference of σ direction in C2H2 and π direction in C2H4, respectively.

  14. Towards the study of 2H(p, γ)3He reaction in the Big Bang Nucleosynthesis energy range in LUNA

    NASA Astrophysics Data System (ADS)

    Kochanek, Izabela

    2016-04-01

    The Big Bang Nucleosynthesis began a few minutes after the Big Bang, when the Universe was sufficiently cold to allow deuterium nuclei to survive photo-disintegration. The total amount of deuterium produced in the Universe during the first minutes depends on the cosmological parameters (like the energy density in baryons, Ω bh 2, and the effective neutrino number, Neff ) and on the nuclear cross sections of the relevant reactions. The main source of uncertainty in the deuterium estimation comes from the 2H(p, γ)3He cross section. Measurements of Cosmic Microwave Background (CMB) anisotropies obtained by the Planck satellite are in very good agreement with the theoretical predictions of the minimal ΛCDM cosmological model, significantly reducing the uncertainty on its parameters. The Planck data allows to indirectly deduce with very high precision the abundances of primodial nuclides, such as the primodial deuterium fraction 2H/H = (2.65 ± 0.07) .10-5 (68% C.L.). The astrophysical observations in damped Lyman-a systems at high redshifts provide a second high accuracy measurement of the primodial abundance of deuterium 2H/H = (2.53 ± 0.04) · 10-5 (68% C.L.). The present experimental status on the astrophysical S-factor of the 2H(p, γ)3He reaction in the BBN energy range, gives a systematic uncertainties of 9%. Also the difference between ab-initio calculations and experimental values of S12 is at the level of 10%. In order to clarify the actual scenario, a measurement of 2H(p, γ)3He cross section with a precision of a few percent in the 70-400 keV energy range is planned at LUNA in 2016. A feasibility test of the measurement has been performed in October 2014, giving the preliminary results on the cross section. The experimental setup for the test and final measurement campaign will be presented.

  15. FIRST MEASUREMENTS OF {sup 15}N FRACTIONATION IN N{sub 2}H{sup +} TOWARD HIGH-MASS STAR-FORMING CORES

    SciTech Connect

    Fontani, F.; Caselli, P.; Bizzocchi, L.; Palau, A.; Ceccarelli, C.

    2015-08-01

    We report on the first measurements of the isotopic ratio {sup 14}N/{sup 15}N in N{sub 2}H{sup +} toward a statistically significant sample of high-mass star-forming cores. The sources belong to the three main evolutionary categories of the high-mass star formation process: high-mass starless cores, high-mass protostellar objects, and ultracompact H ii regions. Simultaneous measurements of the {sup 14}N/{sup 15}N ratio in CN have been made. The {sup 14}N/{sup 15}N ratios derived from N{sub 2}H{sup +} show a large spread (from ∼180 up to ∼1300), while those derived from CN are in between the value measured in the terrestrial atmosphere (∼270) and that of the proto-solar nebula (∼440) for the large majority of the sources within the errors. However, this different spread might be due to the fact that the sources detected in the N{sub 2}H{sup +} isotopologues are more than those detected in the CN ones. The {sup 14}N/{sup 15}N ratio does not change significantly with the source evolutionary stage, which indicates that time seems to be irrelevant for the fractionation of nitrogen. We also find a possible anticorrelation between the {sup 14}N/{sup 15}N (as derived from N{sub 2}H{sup +}) and the H/D isotopic ratios. This suggests that {sup 15}N enrichment could not be linked to the parameters that cause D enrichment, in agreement with the prediction by recent chemical models. These models, however, are not able to reproduce the observed large spread in {sup 14}N/{sup 15}N, pointing out that some important routes of nitrogen fractionation could be still missing in the models.

  16. Charge-transfer processes in F{sup 2+}+H{yields}F{sup +}+H{sup +} collisions and the reverse process at low-keV energies

    SciTech Connect

    Dutta, C. M.; Nordlander, P.; Gu, J. P.; Hirsch, G.; Buenker, R. J.; Kimura, M.

    2005-11-15

    Theoretical investigations on single charge-transfer processes in collisions of F{sup 2+}+H{yields}F{sup +}+H{sup +} and its reverse process have been carried out at collision energies from 20 eV/u to 10 keV/u. The molecular orbital expansion method within the semiclassical impact parameter formalism has been employed for the scattering dynamics, while the ab initio multireference single- and double-excitation configuration interaction (MRD-CI) method was adopted for determination of molecular electronic states. The initial channels correspond to the quintet and triplet states for the corresponding collision processes, respectively. Four molecular states in the quintet manifold and eight molecular states in the triplet manifold were coupled. In the quintet manifold, the charge-transfer cross sections for F{sup 2+}+H{yields}F{sup +}+H{sup +} range from 1.3x10{sup -22} cm{sup 2} at 20 eV/u to 2.5x10{sup -15}cm{sup 2} at 10 keV/u. The cross sections of the reverse process, F{sup +}+H{sup +}{yields}F{sup 2+}+H, range from 3.0x10{sup -22} cm{sup 2}to 2.3x10{sup -15} cm{sup 2} in the same energy range. In the triplet states, the charge-transfer cross sections for F{sup 2+}+H{yields}F{sup +}+H{sup +} range from 1.1x10{sup -18} cm{sup 2} to 2.5x10{sup -16} cm{sup 2}, and its reverse process gives charge-transfer cross sections ranging from 1.7x10{sup -24} cm{sup 2} to 1.5x10{sup -17} cm{sup 2}.

  17. Advanced Low-Cost O2/H2 Engines for the SSTO Application

    NASA Technical Reports Server (NTRS)

    Goracke, B. David; Levack, Daniel J. H.; Nixon, Robert F.

    1994-01-01

    The recent NASA Access to Space study examined future Earth to orbit (ETO) transportation needs and fleets out to 2030. The baseline in the option 3 assessment was a single stage to orbit (SSTO) vehicle. A study was conducted to assess the use of new advanced low cost O2/H2 engines for this SSTO application. The study defined baseline configurations and ground rules and defined six engine cycles to explore engine performance. The cycles included an open cycle, and a series of closed cycles with varying abilities to extract energy from the propellants to power he turbomachinery. The cycles thus varied in the maximum chamber pressure they could reach and in their weights at any given chamber pressure. The weight of each cycle was calculated for two technology levels versus chamber pressure up to the power limit of the cycle. The performance in the SSTO mission was then modeled using the resulting engine weights and specific impulse performance using the Access to Space option 3 vehicle. The results showed that new O2/H2 engines are viable and competitive candidates for the SSTO application using chamber pressures of 4,000 psi.

  18. Interlayer electron-phonon coupling in WSe2/hBN heterostructures

    NASA Astrophysics Data System (ADS)

    Jin, Chenhao; Kim, Jonghwan; Suh, Joonki; Shi, Zhiwen; Chen, Bin; Fan, Xi; Kam, Matthew; Watanabe, Kenji; Taniguchi, Takashi; Tongay, Sefaattin; Zettl, Alex; Wu, Junqiao; Wang, Feng

    2016-10-01

    Engineering layer-layer interactions provides a powerful way to realize novel and designable quantum phenomena in van der Waals heterostructures. Interlayer electron-electron interactions, for example, have enabled fascinating physics that is difficult to achieve in a single material, such as the Hofstadter's butterfly in graphene/boron nitride (hBN) heterostructures. In addition to electron-electron interactions, interlayer electron-phonon interactions allow for further control of the physical properties of van der Waals heterostructures. Here we report an interlayer electron-phonon interaction in WSe2/hBN heterostructures, where optically silent hBN phonons emerge in Raman spectra with strong intensities through resonant coupling to WSe2 electronic transitions. Excitation spectroscopy reveals the double-resonance nature of such enhancement, and identifies the two resonant states to be the A exciton transition of monolayer WSe2 and a new hybrid state present only in WSe2/hBN heterostructures. The observation of an interlayer electron-phonon interaction could open up new ways to engineer electrons and phonons for device applications.

  19. P-selectin targeting to secretory lysosomes of Rbl-2H3 cells.

    PubMed

    Kaur, Jasber; Cutler, Daniel F

    2002-03-22

    The biogenesis of secretory lysosomes, which combine characteristics of both lysosomes and secretory granules, is currently of high interest. In particular, it is not clear whether delivery of membrane proteins to the secretory lysosome requires lysosomal, secretory granule, or some novel targeting determinants. Heterologous expression of P-selectin has established that this membrane protein contains targeting signals for both secretory granules and lysosomes. P-selectin is therefore an ideal probe with which to determine the signals required for targeting to secretory lysosomes. We have exploited subcellular fractionation and immunofluorescence microscopy to monitor targeting of transiently expressed wild-type and mutant horseradish peroxidase (HRP)-P-selectin chimeras to secretory lysosomes of Rbl-2H3 cells. The exposure of the HRP chimeras to intracellular proteolysis was also determined as a third monitor of secretory lysosome targeting. Our data show that HRP-P-selectin accumulates in secretory lysosomes of Rbl-2H3 cells using those cytoplasmic sequences previously found to be sufficient for targeting to conventional lysosomes. This work highlights the similar sorting signals used for targeting of membrane proteins to conventional lysosomes and secretory lysosomes.

  20. CCQE, 2p2h excitations and ν—energy reconstruction

    SciTech Connect

    Nieves, J.; Simo, I. Ruiz; Sánchez, F.; Vacas, M. J. Vicente

    2015-05-15

    We analyze the MiniBooNE muon neutrino CCQE-like dσ/dT{sub μ} d cos θ{sub μ} data using a theoretical model that, among other nuclear effects, includes RPA correlations and 2p2h (multinucleon) mechanisms. These corrections turn out to be essential for the description of the data. We find that MiniBooNE CCQE-like data are fully compatible with former determinations of the nucleon axial mass M{sub A} ∼ 1.05 GeV. This is in sharp contrast with several previous analysis where anomalously large values of M{sub A} ∼ 1.4 GeV have been suggested. We also show that because of the the multinucleon mechanism effects, the algorithm used to reconstruct the neutrino energy is not adequate when dealing with quasielastic-like events. Finally, we analyze the MiniBooNE unfolded cross section, and show that it exhibits an excess (deficit) of low (high) energy neutrinos, which is an artifact of the unfolding process that ignores 2p2h mechanisms.

  1. Low Temperature Flux Growth of 2H-SiC and Beta-Gallium Oxide

    NASA Technical Reports Server (NTRS)

    Singh, N. B.; Choa, Fow-Sen; Su, Ching-Hua; Arnold, Bradley; Kelly, Lisa

    2016-01-01

    We present brief overview of our study on the low temperature flux growth of two very important novel wide bandgap materials 2H-SiC and Beta-gallium oxide (Beta-Ga2O3). We have synthesized and grown 5 millimeter to 1 centimeter size single crystals of Beta-gallium oxide (Beta-Ga2O3). We used a flux and semi wet method to grow transparent good quality crystals. In the semi-wet method Ga2O3 was synthesized with starting gallium nitrate solution and urea as a nucleation agent. In the flux method we used tin and other metallic flux. This crystal was placed in an alumina crucible and temperature was raised above 1050 degrees Centigrade. After a time period of thirty hours, we observed prismatic and needle shaped crystals of gallium oxide. Scanning electron microscopic studies showed step growth morphology. Crystal was polished to measure the properties. Bandgap was measured 4.7electronvolts using the optical absorption curve. Another wide bandgap hexagonal 2H-SiC was grown by using Si-Al eutectic flux in the graphite crucible. We used slight AlN also as the impurity in the flux. The temperature was raised up to 1050 degrees Centigrade and slowly cooled to 850 degrees Centigrade. Preliminary characterization results of this material are also reported.

  2. NO Removal in High Pressure Plasmas of N_2/H_2O/NO Mixtures

    NASA Astrophysics Data System (ADS)

    Fresnet, F.; Baravian, G.; Magne, L.; Pasquiers, S.; Postel, C.; Puech, V.; Rousseau, A.

    2001-10-01

    Influence of H_2O on NO removal has been studied using a homogeneous photo-triggered discharge with a time resolved LIF measurement of the NO density, in N_2/H_2O/NO mixtures at 460 mbar. The H_2O maximum concentration was 2.5 was between 70 and 160 J/l. Measurement of NO density has been performed up to 180 µs after the current pulse excitation of short duration, 50 ns. Kinetic analysis has been made using a self-consistent 0D-discharge model. NO is in great part dissociated, in N_2/NO, through collisions with the excited singlet states of N_2. We have previously shown that addition of ethene induces de-excitation of these states, leading to a decrease of the NO removal ( F. Fresnet, G. Baravian, L. Magne, S. Pasquiers, C. Postel, V. Puech, A. Rousseau, Appl. Phys. Lett., 77 (2000) 4118.). Similar processes take place when C_2H4 is replaced by H_2O. The value of the rate constant for collision of singlet states with water, 3.10-10 cm^3 s-1, is obtained from our study.

  3. Volumetric Properties and Fluid Phase Equilibria of CO2 + H2O

    SciTech Connect

    Capobianco, Ryan; Gruszkiewicz, Miroslaw {Mirek} S; Wesolowski, David J; Cole, David R; Bodnar, Robert

    2013-01-01

    The need for accurate modeling of fluid-mineral processes over wide ranges of temperature, pressure and composition highlighted considerable uncertainties of available property data and equations of state, even for the CO2 + H2O binary system. In particular, the solubility, activity, and ionic dissociation equilibrium data for the CO2-rich phase, which are essential for understanding dissolution/precipitation, fluid-matrix reactions, and solute transport, are uncertain or missing. In this paper we report the results of a new experimental study of volumetric and phase equilibrium properties of CO2 + H2O, to be followed by measurements for bulk and confined multicomponent fluid mixtures. Mixture densities were measured by vibrating tube densimetry (VTD) over the entire composition range at T = 200 and 250 C and P = 20, 40, 60, and 80 MPa. Initial analysis of the mutual solubilities, determined from volumetric data, shows good agreement with earlier results for the aqueous phase, but finds that the data of Takenouchi and Kennedy (1964) significantly overestimated the solubility of water in supercritical CO2 (by a factor of more than two at 200 C). Resolving this well-known discrepancy will have a direct impact on the accuracy of predictive modeling of CO2 injection in geothermal reservoirs and geological carbon sequestration through improved equations of state, needed for calibration of predictive molecular-scale models and large-scale reactive transport simulations.

  4. Quantifying unfrozen water in frozen soil by high-field 2H NMR.

    PubMed

    Sparrman, Tobias; Oquist, Mats; Klemedtsson, Leif; Schleucher, Jürgen; Nilsson, Mats

    2004-10-15

    To understand wintertime controls of biogeochemical processes in high latitude soils it is essential to distinguish between direct temperature effects and the effects of changes in water availability mediated by freezing. Efforts to separate these controls are hampered by a lack of adequate methods to determine the proportion of unfrozen water. In this study we present a high-field 2H2O NMR method for quantifying unfrozen water content in frozen soil. The experimental material consisted of the humic layer of a boreal spruce forest soil mixed with varying proportions of quartz sand and humidified with deuterium-enriched water. The relative standard deviation of unfrozen water content (measured as NMR signal integral) was less than 2% for repeated measurements on a given sample and 3.5% among all samples, based on a total of 16 measurements. As compared to 1H NMR, this 2H NMR method was found to be superior for several reasons: it is less sensitive to field inhomogeneity and paramagnetic impurities, it gives a bigger line shape difference between the ice and liquid signal, it shows a sharper response to water fusion, and it excludes the possibility of hydrogen in the organic material interfering with the measurement.

  5. Induced DNA demethylation can reshape chromatin topology at the IGF2-H19 locus

    PubMed Central

    Ito, Yoko; Nativio, Raffaella; Murrell, Adele

    2013-01-01

    Choriocarcinomas are embryonal tumours with loss of imprinting and hypermethylation at the insulin-like growth factor 2 (IGF2)-H19 locus. The DNA methyltransferase inhibitor, 5-Aza-2′deoxycytidine (5-AzaCdR) is an approved epigenetic cancer therapy. However, it is not known to what extent 5-AzaCdR influences other epigenetic marks. In this study, we set out to determine whether 5-AzaCdR treatment can reprogram the epigenomic organization of the IGF2-H19 locus in a choriocarcinoma cancer cell line (JEG3). We found that localized DNA demethylation at the H19 imprinting control region (ICR) induced by 5-AzaCdR, reduced IGF2, increased H19 expression, increased CTCF and cohesin recruitment and changed histone modifications. Furthermore chromatin accessibility was increased locus-wide and chromatin looping topography was altered such that a CTCF site downstream of the H19 enhancers switched its association with the CTCF site upstream of the IGF2 promoters to associate with the ICR. We identified a stable chromatin looping domain, which forms independently of DNA methylation. This domain contains the IGF2 gene and is marked by a histone H3 lysine 27 trimethylation block between CTCF site upstream of the IGF2 promoters and the Centrally Conserved Domain upstream of the ICR. Together, these data provide new insights into the responsiveness of chromatin topography to DNA methylation changes. PMID:23585276

  6. Study of C2H2 optic-fiber monitoring system on spectrum absorption

    NASA Astrophysics Data System (ADS)

    Wang, Yutian; Li, Xiao-Xin; Wang, Zhong-Dong

    2005-02-01

    We report our research on the development of optical fiber trace gas sensors for environmental applications. A novel optical fiber sensor for monitoring acetylene (C2H2) gases is described. Through studying the measure theory, we use the Beer-Lambert law to monitor the gas. And after analyzing the C2H2 spectrum, we select Distributed Feedback Laser Diode (DFB LD) as light source. Comparing many kinds" sensor detection head, the gas absorbing cell with tail fiber can have good coupling with optical fiber and improve the coupling stability. In the data processing system, signals are distilled by lock-in amplifiers and then harmonic measure technology processes that distilled faint signals. After the all, the electronic signals are transmitted into computer to process, alarm and display. We design the instrument who can remote and on-line measuring acetylene. Through theory analysis and system experiment, the design of the system is practicable, and has a better precision and some apply foreground.

  7. Free radical scavenging potency of quercetin catecholic colonic metabolites: Thermodynamics of 2H(+)/2e(-) processes.

    PubMed

    Amić, Ana; Lučić, Bono; Stepanić, Višnja; Marković, Zoran; Marković, Svetlana; Dimitrić Marković, Jasmina M; Amić, Dragan

    2017-03-01

    Reaction energetics of the double (2H(+)/2e(-)), i.e., the first 1H(+)/1e(-) (catechol→ phenoxyl radical) and the second 1H(+)/1e(-) (phenoxyl radical→ quinone) free radical scavenging mechanisms of quercetin and its six colonic catecholic metabolites (caffeic acid, hydrocaffeic acid, homoprotocatechuic acid, protocatechuic acid, 4-methylcatechol, and catechol) were computationally studied using density functional theory, with the aim to estimate the antiradical potency of these molecules. We found that second hydrogen atom transfer (HAT) and second sequential proton loss electron transfer (SPLET) mechanisms are less energy demanding than the first ones indicating 2H(+)/2e(-) processes as inherent to catechol moiety. The Gibbs free energy change for reactions of inactivation of selected free radicals indicate that catecholic colonic metabolites constitute an efficient group of more potent scavengers than quercetin itself, able to deactivate various free radicals, under different biological conditions. They could be responsible for the health benefits associated with regular intake of flavonoid-rich diet.

  8. Affordable uniform isotope labeling with (2)H, (13)C and (15)N in insect cells.

    PubMed

    Sitarska, Agnieszka; Skora, Lukasz; Klopp, Julia; Roest, Susan; Fernández, César; Shrestha, Binesh; Gossert, Alvar D

    2015-06-01

    For a wide range of proteins of high interest, the major obstacle for NMR studies is the lack of an affordable eukaryotic expression system for isotope labeling. Here, a simple and affordable protocol is presented to produce uniform labeled proteins in the most prevalent eukaryotic expression system for structural biology, namely Spodoptera frugiperda insect cells. Incorporation levels of 80% can be achieved for (15)N and (13)C with yields comparable to expression in full media. For (2)H,(15)N and (2)H,(13)C,(15)N labeling, incorporation is only slightly lower with 75 and 73%, respectively, and yields are typically twofold reduced. The media were optimized for isotope incorporation, reproducibility, simplicity and cost. High isotope incorporation levels for all labeling patterns are achieved by using labeled algal amino acid extracts and exploiting well-known biochemical pathways. The final formulation consists of just five commercially available components, at costs 12-fold lower than labeling media from vendors. The approach was applied to several cytosolic and secreted target proteins.

  9. Mobility of Core Water in Bacillus subtilis Spores by 2H NMR

    PubMed Central

    Kaieda, Shuji; Setlow, Barbara; Setlow, Peter; Halle, Bertil

    2013-01-01

    Bacterial spores in a metabolically dormant state can survive long periods without nutrients under extreme environmental conditions. The molecular basis of spore dormancy is not well understood, but the distribution and physical state of water within the spore is thought to play an important role. Two scenarios have been proposed for the spore’s core region, containing the DNA and most enzymes. In the gel scenario, the core is a structured macromolecular framework permeated by mobile water. In the glass scenario, the entire core, including the water, is an amorphous solid and the quenched molecular diffusion accounts for the spore’s dormancy and thermal stability. Here, we use 2H magnetic relaxation dispersion to selectively monitor water mobility in the core of Bacillus subtilis spores in the presence and absence of core Mn2+ ions. We also report and analyze the solid-state 2H NMR spectrum from these spores. Our NMR data clearly support the gel scenario with highly mobile core water (∼25 ps average rotational correlation time). Furthermore, we find that the large depot of manganese in the core is nearly anhydrous, with merely 1.7% on average of the maximum sixfold water coordination. PMID:24209846

  10. Refinements in an Mg/MgH2/H2O-Based Hydrogen Generator

    NASA Technical Reports Server (NTRS)

    Kindler, Andrew; Huang, Yuhong

    2010-01-01

    Some refinements have been conceived for a proposed apparatus that would generate hydrogen (for use in a fuel cell) by means of chemical reactions among magnesium, magnesium hydride, and steam. The refinements lie in tailoring spatial and temporal distributions of steam and liquid water so as to obtain greater overall energy-storage or energy-generation efficiency than would otherwise be possible. A description of the prior art is prerequisite to a meaningful description of the present refinements. The hydrogen-generating apparatus in question is one of two versions of what was called the "advanced hydrogen generator" in "Fuel-Cell Power Systems Incorporating Mg-Based H2 Generators" (NPO-43554), NASA Tech Briefs, Vol. 33, No. 1 (January 2009), page 52. To recapitulate: The apparatus would include a reactor vessel that would be initially charged with magnesium hydride. The apparatus would exploit two reactions: The endothermic decomposition reaction MgH2-->Mg + H2, which occurs at a temperature greater than or equal to 300 C, and The exothermic oxidation reaction MgH2 + H2O MgO + 2H2, which occurs at a temperature greater than or equal to 330 C.

  11. A method for direct in vivo measurement of drug concentrations from a single 2H NMR spectrum.

    PubMed

    Evelhoch, J L; McCoy, C L; Giri, B P

    1989-03-01

    The use of 2H-labeled drugs provides a measure of drug concentration in situ directly from a single 2H NMR spectrum obtained with any antenna by correcting only for differential saturation effects. The limit of detection for a drug labeled with three equivalent deuterons is roughly 0.5 mM.

  12. Mining the Brassica oleracea genome for Q-type C2H2 zinc finger transcription factor proteins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Q-type zinc finger proteins have been studied in several plant species and have been associated with response to stress. A whole genome analysis of Arabidopsis identified 176 putative C2H2 transcription factors (TF). Q-type C2H2 TFs containing the QALGGH motif and are a subset of these. In Arabidops...

  13. 3R phase of MoS2 and WS2 outperforms the corresponding 2H phase for hydrogen evolution.

    PubMed

    Toh, Rou Jun; Sofer, Zdeněk; Luxa, Jan; Sedmidubský, David; Pumera, Martin

    2017-03-09

    Herein, we compare the bulk, 2H and 3R phases of two most prevalent TMD materials: MoS2 and WS2. The 3R phase outperforms its 2H phase counterpart in hydrogen evolution reaction catalysis and is even comparable with the exfoliated, 1T phase in the case of MoS2.

  14. The Davis-Beirut Reaction: a novel entry into 2H-indazoles and indazolones. Recent biological activity of indazoles.

    PubMed

    Haddadin, Makhluf J; Conrad, Wayne E; Kurth, Mark J

    2012-10-01

    A novel, easy method for the syntheses of richly diversified 2H-indazoles and indazolones, called the Davis-Beirut reaction, and other recent 2H-indazole synthetic routes are briefly reviewed. An update on the biological activity of indazoles is also surveyed.

  15. Low-Temperature Rate Coefficients of C2H with CH4 and CD4 from 154 to 359 K

    NASA Technical Reports Server (NTRS)

    Opansky, Brian J.; Leone, Stephen R.

    1996-01-01

    Rate coefficients for the reaction C2H + CH4 yields C2H2 + CH3 and C2H + CD4 yields C2HD + CD3 are measured over the temperature range 154-359 K using transient infrared laser absorption spectroscopy. Ethynyl radicals are produced by pulsed laser photolysis of C2H2 in a variable temperature flow cell, and a tunable color center laser probes the transient removal of C2H (Chi(exp 2) Sigma(+) (0,0,0)) in absorption. The rate coefficients for the reactions of C2H with CH4 and CD4 both show a positive temperature dependence over the range 154-359 K, which can be expressed as k(sub CH4) = (1.2 +/- 0.1) x 10(exp -11) exp((-491 +/- 12)/T) and k(sub CD4) = (8.7 +/- 1.8) x 10(exp -12) exp((-650 +/- 61)/T) cm(exp 3) molecule(exp -1) s(exp -1), respectively. The reaction of C2H + CH4 exhibits a significant kinetic isotope effect at 300 K of k(sub CH4)/k(sub CD4) = 2.5 +/- 0.2. Temperature dependent rate constants for C2H + C2H2 were also remeasured over an increased temperature range from 143 to 359 K and found to show a slight negative temperature dependence, which can be expressed as k(sub C2H2) = 8.6 x 10(exp -16) T(exp 1.8) exp((474 +/- 90)/T) cm(exp 3) molecule(exp -1) s(exp -1).

  16. Volovik effect and Fermi-liquid behavior in the s-wave superconductor CaPd2As2: As75 NMR-NQR measurements

    SciTech Connect

    Ding, Q. -P.; Wiecki, P.; Anand, V. K.; Sangeetha, N. S.; Lee, Y.; Johnston, D. C.; Furukawa, Y.

    2016-04-07

    The electronic and magnetic properties of the collapsed-tetragonal CaPd2As2 superconductor (SC) with a transition temperature of 1.27 K have been investigated by 75As nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements. The temperature (T) dependence of the nuclear spin lattice relaxation rates (1/T1) and the Knight shifts indicate the absence of magnetic correlations in the normal state. In the SC state, 1/T1 measured by 75As NQR shows a clear Hebel-Slichter (HS) peak just below Tc and decreases exponentially at lower T, confirming a conventional s-wave SC. Additionally, the Volovik effect, also known as the Doppler shift effect, has been clearly evidenced by the observation of the suppression of the HS peak with applied magnetic field.

  17. Modeling Ice Giant Interiors Using Constraints on the H2-H2O Critical Curve

    NASA Astrophysics Data System (ADS)

    Bailey, E.; Stevenson, D. J.

    2015-12-01

    We present a range of models of Uranus and Neptune, taking into account recent experimental data (Bali, 2013) implying the location of the critical curve of the H2-H2O system at pressures up to 2.6 GPa. The models presented satisfy the observed total mass of each planet and the radius at the observed 1-bar pressure level. We assume the existence of three regions at different depths: an outer adiabatic envelope composed predominately of H2 and He, with a helium mass fraction 0.26, a water-rich layer including varied amounts of rock and hydrogen, and a chemically homogeneous rock core. Using measured rotation rates of Uranus and Neptune, and a density profile obtained for each model using constituent equations of state and the assumption of hydrostatic equilibrium, we calculate the gravitational harmonics J2 and J4 for comparison with observed values as an additional constraint. The H2-H2O critical curve provides information about the nature of the boundary between the outer, hydrogen-rich envelope and underlying water-rich layer. The extrapolated critical curve for hydrogen-water mixtures crosses the adiabat of the outer atmospheric shell in these models at two depths, implying a shallow outer region of limited miscibility, an intermediate region between ~90 and 98 percent of the total planet radius within which hydrogen and water can mix in all proportions, and another, deeper region of limited miscibility at less than ~90 percent of the total planet radius. The pressure and temperature of the gaseous adiabatic shell at the depth of the shallowest extent of the water-rich layer determines whether a gradual compositional transition or an ocean surface boundary may exist at depth in these planets. To satisfy the observed J2, the outer extent of the water-rich layer in these models must be located between approximately 80 and 85 percent of the total planet radius, within the deep region of limited H2-H2O miscibility, implying an ocean surface is possible within the

  18. Pseudomorphic 2A--> 2M--> 2H phase transitions in lanthanum strontium germanate electrolyte apatites.

    PubMed

    Pramana, Stevin S; White, T J; Schreyer, Martin K; Ferraris, Cristiano; Slater, Peter R; Orera, Alodia; Bastow, T J; Mangold, Stefan; Doyle, Stephen; Liu, Tao; Fajar, Andika; Srinivasan, Madhavi; Baikie, Tom

    2009-10-21

    Apatite-like materials are of considerable interest as potential solid oxide fuel cell electrolytes, although their structural vagaries continue to attract significant discussion. Understanding these features is crucial both to explain the oxide ion conduction process and to optimise it. As the composition of putative P6(3)/m apatites with ideal formula [A(I)(4)][A(II)(6)][(BO(4))(6)][X](2) is varied the [A(I)(4)(BO(4))(6)] framework will flex to better accommodate the [A(II)(6)X(2)] tunnel component through adjustment of the A(I)O(6) metaprism twist angle (varphi). The space group theory prescribes that framework adaptation during phase changes must lead to one of the maximal non-isomorphic subgroups of P6(3)/m (P2(1), P2(1)/m, P1[combining macron]). These adaptations correlate with oxygen ion conduction, and become crucial especially when the tunnels are filled by relatively small ions and/or partially occupied, and if interstitial oxygens are located in the framework. Detecting and completely describing these lower symmetry structures can be challenging, as it is difficult to precisely control apatite stoichiometry and small departures from the hexagonal metric may be near the limits of detection. Using a combination of diffraction and spectroscopic techniques it is shown that lanthanum strontium germanate oxide electrolytes crystallise as triclinic (A), monoclinic (M) and hexagonal (H) bi-layer pseudomorphs with the composition ranges: [La(10-x)Sr(x)][(GeO(4))(5+x/2)(GeO(5))(1-x/2)][O(2)] (0 2)][H(delta)] (2 2)][H(delta)] (2.96 2H, with the latter showing the highest conduction. The results show that small twist angles and high symmetry

  19. 242-16H 2H EVAPORATOR POT SAMPLING FINAL REPORT

    SciTech Connect

    Krementz, D; William Cheng, W

    2008-06-11

    Due to the materials that are processed through 2H Evaporator, scale is constantly being deposited on the surfaces of the evaporator pot. In order to meet the requirements of the Nuclear Criticality Safety Analysis/Evaluation (NCSA/NCSE) for 2H Evaporator, inspections of the pot are performed to determine the extent of scaling. Once the volume of scale reaches a certain threshold, the pot must be chemically cleaned to remove the scale. Prior to cleaning the pot, samples of the scale are obtained to determine the concentration of uranium and plutonium and also to provide information to assist with pot cleaning. Savannah River National Laboratory (SRNL) was requested by Liquid Waste Organization (LWO) Engineering to obtain these samples from two locations within the evaporator. Past experience has proven the difficulty of successfully obtaining solids samples from the 2H Evaporator pot. To mitigate this risk, a total of four samplers were designed and fabricated to ensure that two samples could be obtained. Samples had previously been obtained from the cone surface directly below the vertical access riser using a custom scraping tool. This tool was fabricated and deployed successfully. A second scraper was designed to obtain sample from the nearby vertical thermowell and a third scraper was designed to obtain sample from the vertical pot wall. The newly developed scrapers both employed a pneumatically actuated elbow. The scrapers were designed to be easily attached/removed from the elbow assembly. These tools were fabricated and deployed successfully. A fourth tool was designed to obtain sample from the opposite side of the pot under the tube bundle. This tool was fabricated and tested, but the additional modifications required to make the tool field-ready could not be complete in time to meet the aggressive deployment schedule. Two samples were obtained near the pot entry location, one from the pot wall and the other from the evaporator feed pipe. Since a third

  20. 2H 2O quadrupolar splitting used to measure water exchange in erythrocytes

    NASA Astrophysics Data System (ADS)

    Kuchel, Philip W.; Naumann, Christoph

    2008-05-01

    The 2H NMR resonance from HDO (D = 2H) in human red blood cells (RBCs) suspended in gelatin that was held stretched in a special apparatus was distinct from the two signals that were symmetrically arranged on either side of it, which were assigned to extracellular HDO. The large extracellular splitting is due to the interaction of the electric quadrupole moment of the 2H nuclei with the electric field gradient tensor of the stretched, partially aligned gelatin. Lack of resolved splitting of the intracellular resonance indicated greatly diminished or absent ordering of the HDO inside RBCs. The separate resonances enabled the application of a saturation transfer method to estimate the rate constants of transmembrane exchange of water in RBCs. However both the theory and the practical applications needed modifications because even in the absence of RBCs the HDO resonances were maximally suppressed when the saturating radio-frequency radiation was applied exactly at the central frequency between the two resonances of the quadrupolar HDO doublet. More statistically robust estimates of the exchange rate constants were obtained by applying two-dimensional exchange spectroscopy (2D EXSY), with back-transformation analysis. A monotonic dependence of the estimates of the efflux rate constants on the mixing time, tmix, used in the 2D EXSY experiment were seen. Extrapolation to tmix = 0, gave an estimate of the efflux rate constant at 15 °C of 31.5 ± 2.2 s -1 while at 25 °C it was ˜50 s -1. These values are close to, but less than, those estimated by an NMR relaxation-enhancement method that uses Mn 2+ doping of the extracellular medium. The basis for this difference is thought to include the high viscosity of the extracellular gel. At the abstract level of quantum mechanics we have used the quadrupolar Hamiltonian to provide chemical shift separation between signals from spin populations across cell membranes; this is the first time, to our knowledge, that this has been

  1. Kinetics of the WF 6 and Si 2H 6 surface reactions during tungsten atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Elam, J. W.; Nelson, C. E.; Grubbs, R. K.; George, S. M.

    2001-05-01

    The atomic layer deposition (ALD) of tungsten (W) films has been demonstrated using alternating exposures to tungsten hexafluoride (WF 6) and disilane (Si 2H 6). The present investigation explored the kinetics of the WF 6 and Si 2H 6 surface reactions during W ALD at 303-623 K using Auger electron spectroscopy techniques. The reaction of WF 6 with the Si 2H 6-saturated W surface proceeded to completion at 373-573 K. The WF 6 reaction displayed a reactive sticking coefficient of S=0.4 and required an exposure of 30 L (1 L=1×10 -6 Torr s) to achieve saturation at 573 K. The WF 6 exposures necessary to reach saturation increased with decreasing temperature. At surface temperatures <373 K, the WF 6 reaction did not consume all the silicon (Si) surface species remaining from the previous Si 2H 6 exposure. The reaction of Si 2H 6 with the WF 6-saturated W surface displayed three kinetic regimes. In the first region at low Si 2H 6 exposures⩽50 L, the Si 2H 6 reaction was independent of temperature and had a reactive sticking coefficient of S˜5×10 -2. In the second kinetic region at intermediate Si 2H 6 exposures of 50-300 L, the Si 2H 6 reaction showed an apparent saturation behavior with a Si thickness at saturation that increased with substrate temperature. At high Si 2H 6 exposures of 300-1×10 5 L, additional Si was deposited with an approximately logarithmic dependence on Si 2H 6 exposure. The Si 2H 6 reaction in this third kinetic region had an activation energy E=2.6 kcal/mol and the Si thickness deposited by a 1.6×10 5 L Si 2H 6 exposure increased with temperature from 3.0 Å at 303 K to 6.6 Å at 623 K. These kinetic results should help to explain W ALD growth rates observed at different reactant exposures and substrate temperatures.

  2. Understanding 2H/1H systematics of leaf wax n-alkanes in coastal plants at Stiffkey saltmarsh, Norfolk, UK

    NASA Astrophysics Data System (ADS)

    Eley, Yvette; Dawson, Lorna; Black, Stuart; Andrews, Julian; Pedentchouk, Nikolai

    2014-03-01

    Interpretation of sedimentary n-alkyl lipid δ2H data is complicated by a limited understanding of factors controlling interspecies variation in biomarker 2H/1H composition. To distinguish between the effects of interrelated environmental, physical and biochemical controls on the hydrogen isotope composition of n-alkyl lipids, we conducted linked δ2H analyses of soil water, xylem water, leaf water and n-alkanes from a range of C3 and C4 plants growing at a UK saltmarsh (i) across multiple sampling sites, (ii) throughout the 2012 growing season, and (iii) at different times of the day. Soil waters varied isotopically by up to 35‰ depending on marsh sub-environment, and exhibited site-specific seasonal shifts in δ2H up to a maximum of 31‰. Maximum interspecies variation in xylem water was 38‰, while leaf waters differed seasonally by a maximum of 29‰. Leaf wax n-alkane 2H/1H, however, consistently varied by over 100‰ throughout the 2012 growing season, resulting in an interspecies range in the ɛwax/leaf water values of -79‰ to -227‰. From the discrepancy in the magnitude of these isotopic differences, we conclude that mechanisms driving variation in the 2H/1H composition of leaf water, including (i) spatial changes in soil water 2H/1H, (ii) temporal changes in soil water 2H/1H, (iii) differences in xylem water 2H/1H, and (iv) differences in leaf water evaporative 2H-enrichment due to varied plant life forms, cannot explain the range of n-alkane δ2H values we observed. Results from this study suggests that accurate reconstructions of palaeoclimate regimes from sedimentary n-alkane δ2H require further research to constrain those biological mechanisms influencing species-specific differences in 2H/1H fractionation during lipid biosynthesis, in particular where plants have developed biochemical adaptations to water-stressed conditions. Understanding how these mechanisms interact with environmental conditions will be crucial to ensure accurate

  3. Crystal structure of NH4[La(SO4)2(H2O)

    PubMed Central

    Benslimane, Meriem; Redjel, Yasmine Kheira; Merazig, Hocine; Daran, Jean-Claude

    2015-01-01

    The principal building units in the crystal structure of ammonium aqua­bis(sulfato)­lanthanate(III) are slightly distorted SO4 tetra­hedra, LaO9 polyhedra in the form of distorted tricapped trigonal prisms, and NH4 + ions. The La3+ cation is coordinated by eight O atoms from six different sulfate tetra­hedra, two of which are bidentate coordinating and four monodentate, as well as one O atom from a water mol­ecule; each sulfate anion bridges three La3+ cations. These bridging modes result in the formation of a three-dimensional anionic [La(SO4)2(H2O)]− framework that is stabilized by O—H⋯O hydrogen-bonding inter­actions. The disordered ammonium cations are situated in the cavities of this framework and are hydrogen-bonded to six surrounding O atoms. PMID:26090145

  4. Effect of 2H and 18O water isotopes in kinesin-1 gliding assay

    PubMed Central

    Herskowitz, Lawrence J.; Koch, Steven J.

    2014-01-01

    We show for the first time the effects of heavy-hydrogen water (2H2O) and heavy-oxygen water (H218O) on the gliding speed of microtubules on kinesin-1 coated surfaces. Increased fractions of isotopic waters used in the motility solution decreased the gliding speed of microtubules by a maximum of 21% for heavy-hydrogen and 5% for heavy-oxygen water. We also show that gliding microtubule speed returns to its original speed after being treated with heavy-hydrogen water. We discuss possible interpretations of these results and the importance for future studies of water effects on kinesin and microtubules. We also discuss the implication for using heavy waters in biomolecular devices incorporating molecular motors. PMID:24711961

  5. Synthesis of (3) H, (2) H4 and (14) C-SCH 417690 (Vicriviroc).

    PubMed

    Hesk, D; Borges, S; Hendershot, S; Koharski, D; McNamara, P; Ren, S; Saluja, S; Truong, V; Voronin, K

    2016-05-15

    Vicriviroc or SCH 417690 is a potent and selective antagonist of the CCR5 receptor. CCR5 receptor antagonists have the potential for the treatment of HIV infections. Four distinct isotopically labelled forms of SCH 417690 were synthesized. Low specific activity [(3) H]SCH 417690 was prepared for a preliminary absorption, distribution, metabolism and excretion evaluation of the compound and [(14) C]SCH 417690 for more definitive absorption, distribution, metabolism and excretion work, including an absorption, metabolism and excretion study in man. In addition, high specific activity [(3) H]SCH 417690 was prepared for CCR5 receptor binding work and [(2) H4 ]SCH 417690 was prepared as an internal standard for a liquid chromatography-mass spectrometry bioanalytical method. The paper discusses the synthesis of four isotopically labelled forms of SCH 417690.

  6. Understanding H2- H2 interactions in Metal Organic Frameworks (MOFs) with unsaturated metal centers

    NASA Astrophysics Data System (ADS)

    Nijem, Nour; Veyan, Jean F.; Kong, Lingzhu; Zhao, Yonggang; Li, Jing; Langreth, David; Chabal, Yves J.

    2011-03-01

    Unsaturated Metal Organic Frameworks (MOFs) are particularly interesting due to their high H2 uptakes with relatively large isosteric heats of adsorption (Qst > 8 kJ / mol) . ThisworkexploresH 2 - H 2 interactionsbetweenadsorbedH 2 atthedifferentsitesinMOF - 74 (M 2 (dhtp) , dhtp = 2 , 5 - dihydroxyterephthalate) andcombinesIRspectroscopywithvdW - DFTcalculations . TheadsorptionsitesinMOF - 74 arefromhighesttolowestbindingenergiesthemetal , oxygen , benzeneandpore - centersites . ThefrequencyofadsorbedH 2 atthemetalsitesuffersanadditional ~ - 30 cm -1 redshift (forMgandZn) and ~ - 84 cm -1 (forCo) whentheneighboringoxygensiteisoccupied . ThedipolemomentofadsorbedH 2 isalsoaffected . TheseinteractionsextendtothebenzenesitesforMOF - 74 - Co . AdecreaseindipolemomentofH 2 adsorbedatthemetalsiteisobservedwiththepartialoccupationofthebenzenesites . However , thecompleteoccupationofthebenzenesitesinducesanadditional ~ - 10 cm -1 red shift. DOE Grant No. DE-FG02-08ER46491.

  7. RNF20-SNF2H Pathway of Chromatin Relaxation in DNA Double-Strand Break Repair.

    PubMed

    Kato, Akihiro; Komatsu, Kenshi

    2015-07-14

    Rapid progress in the study on the association of histone modifications with chromatin remodeling factors has broadened our understanding of chromatin dynamics in DNA transactions. In DNA double-strand break (DSB) repair, the well-known mark of histones is the phosphorylation of the H2A variant, H2AX, which has been used as a surrogate marker of DSBs. The ubiquitylation of histone H2B by RNF20 E3 ligase was recently found to be a DNA damage-induced histone modification. This modification is required for DSB repair and regulated by a distinctive pathway from that of histone H2AX phosphorylation. Moreover, the connection between H2B ubiquitylation and the chromatin remodeling activity of SNF2H has been elucidated. In this review, we summarize the current knowledge of RNF20-mediated processes and the molecular link to H2AX-mediated processes during DSB repair.

  8. Ca2+/H+ exchange by acidic organelles regulates cell migration in vivo

    PubMed Central

    Melchionda, Manuela; Pittman, Jon K.

    2016-01-01

    Increasing evidence implicates Ca2+ in the control of cell migration. However, the underlying mechanisms are incompletely understood. Acidic Ca2+ stores are fast emerging as signaling centers. But how Ca2+ is taken up by these organelles in metazoans and the physiological relevance for migration is unclear. Here, we identify a vertebrate Ca2+/H+ exchanger (CAX) as part of a widespread family of homologues in animals. CAX is expressed in neural crest cells and required for their migration in vivo. It localizes to acidic organelles, tempers evoked Ca2+ signals, and regulates cell-matrix adhesion during migration. Our data provide new molecular insight into how Ca2+ is handled by acidic organelles and link this to migration, thereby underscoring the role of noncanonical Ca2+ stores in the control of Ca2+-dependent function. PMID:27002171

  9. Spectrum sensing of trace C(2)H(2) detection in differential optical absorption spectroscopy technique.

    PubMed

    Chen, Xi; Dong, Xiaopeng

    2014-09-10

    An improved algorithm for trace C(2)H(2) detection is presented in this paper. The trace concentration is accurately calculated by focusing on the absorption spectrum from the frequency domain perspective. The advantage of the absorption spectroscopy frequency domain algorithm is its anti-interference capability. First, the influence of the background noise on the minimum detectable concentration is greatly reduced. Second, the time-consuming preprocess of spectra calibration in the differential optical absorption spectroscopy technique is skipped. Experimental results showed the detection limit of 50 ppm is achieved at a lightpath length of 0.2 m. This algorithm can be used in real-time spectrum analysis with high accuracy.

  10. Competition between charge exchange and chemical reaction - The D2/+/ + H system

    NASA Technical Reports Server (NTRS)

    Preston, R. K.; Cross, R. J., Jr.

    1973-01-01

    Study of the special features of molecular charge exchange and its competition with chemical reaction in the case of the D2(+) + H system. The trajectory surface hopping (TSH) model proposed by Tully and Preston (1971) is used to study this competition for a number of reactions involving the above system. The diatomics-in-molecules zero-overlap approximation is used to calculate the three adiabatic surfaces - one triplet and two singlet - which are needed to describe this system. One of the significant results of this study is that the chemical reaction and charge exchange are strongly coupled. It is also found that the number of trajectories passing into the chemical regions of the three surfaces depends very strongly on the surface crossings.-

  11. Characterization Results for the March 2016 H-Tank Farm 2H Evaporator Overhead Samples

    SciTech Connect

    Nicholson, J. C.

    2016-09-28

    This report contains the radioanalytical results of the 2H evaporator overhead sample received at SRNL on March 16, 2016. Specifically, concentrations of 137Cs, 90Sr, and 129I are reported and compared to the corresponding Waste Acceptance Criteria (WAC) limits of the Effluent Treatment Project (ETP) Waste Water Collection Tank (WWCT) (rev. 6). All of the radionuclide concentrations in the sample were found to be in compliance with the ETP WAC limits. Revision 1 of this document corrects the cumulative beta count initially reported for 90Sr content with the sole 90Sr count obtained after recharacterization of the sample. The initial data was found to be a cumulative beta count rather than the 90Sr count requested.

  12. Equilibrium concentrations of N2H4 and its decomposition products at elevated temperatures and pressures

    NASA Technical Reports Server (NTRS)

    Smetana, F. O.; Fairchild, H. N., III; Martin, G. L.

    1973-01-01

    Liquid hydrazine is considered as a convenient source of hydrogen rather than just as a rocket fuel. For such purposes, the hydrogen is usually obtained by passing the hydrazine through a heated catalytic bed. One convenient measure of the effectiveness of a catalytic decomposition device as a whole is to compare the quantity of hydrogen produced with the equilibrium concentration of the gaseous species N2H4, NH3, N3, and H2 which would exist at the temperature and pressure found in various parts of the device. Calculations of the concentrations were carried out and are reported here. Following presentation of the results in both tabular and graphical forms is a comparison between the computed equilibrium concentrations and available experimental data.

  13. Inhibition of myeloperoxidase: evaluation of 2H-indazoles and 1H-indazolones.

    PubMed

    Roth, Aaron; Ott, Sean; Farber, Kelli M; Palazzo, Teresa A; Conrad, Wayne E; Haddadin, Makhluf J; Tantillo, Dean J; Cross, Carroll E; Eiserich, Jason P; Kurth, Mark J

    2014-11-15

    Myeloperoxidase (MPO) produces hypohalous acids as a key component of the innate immune response; however, release of these acids extracellularly results in inflammatory cell and tissue damage. The two-step, one-pot Davis-Beirut reaction was used to synthesize a library of 2H-indazoles and 1H-indazolones as putative inhibitors of MPO. A structure-activity relationship study was undertaken wherein compounds were evaluated utilizing taurine-chloramine and MPO-mediated H2O2 consumption assays. Docking studies as well as toxicophore and Lipinski analyses were performed. Fourteen compounds were found to be potent inhibitors with IC50 values <1μM, suggesting these compounds could be considered as potential modulators of pro-oxidative tissue injury pertubated by the inflammatory MPO/H2O2/HOCl/HOBr system.

  14. a Rotational Study of 2H-3H-PERFLUOROPENTANE and its Isotopologues

    NASA Astrophysics Data System (ADS)

    Duong, Chinh H.; Obenchain, Daniel A.; Novick, Stewart E.; Cooke, S. A.

    2012-06-01

    The chirped pulse Fourier transform microwave spectrum of 2H-3H-perfluoropentane has been observed and assigned. Given a racemic mixture sample of the four available structural isomers, only the (S,S) structure was observed in the broadband spectrum. Attempts at observing the 13C isotopologues on a Balle-Flygare cavity type spectrometer and their assignments will be discussed, along with an examination of the theoretical predictions for the structure and rotational constants of the molecule against their experimental values. Structural results of the monomer will also be compared with those of the helical structure of C2 perfluoropentane. Joseph A. Fournier, Robert K. Bohn, John A. Montgomery Jr., Masao Onda. J. Phys. Chem. 114 (1118), 2010.

  15. Interplay of charge density wave and multiband superconductivity in 2H-PdxTaSe2

    NASA Astrophysics Data System (ADS)

    Bhoi, D.; Khim, S.; Nam, W.; Lee, B. S.; Kim, Chanhee; Jeon, B.-G.; Min, B. H.; Park, S.; Kim, Kee Hoon

    2016-04-01

    2H-TaSe2 has been one of unique transition metal dichalcogenides exhibiting several phase transitions due to a delicate balance among competing electronic ground states. An unusual metallic state at high-T is sequentially followed by an incommensurate charge density wave (ICDW) state at ≈122 K and a commensurate charge density wave (CCDW) state at ≈90 K, and superconductivity at TC ~ 0.14 K. Upon systematic intercalation of Pd ions into TaSe2, we find that CCDW order is destabilized more rapidly than ICDW to indicate a hidden quantum phase transition point at x ~ 0.09–0.10. Moreover, TC shows a dramatic enhancement up to 3.3 K at x = 0.08, ~24 times of TC in 2H-TaSe2, in proportional to the density of states N(EF). Investigations of upper critical fields Hc2 in single crystals reveal evidences of multiband superconductivity as temperature-dependent anisotropy factor γH = , quasi-linear increase of , and an upward, positive-curvature in near TC. Furthermore, analysis of temperature-dependent electronic specific heat corroborates the presence of multiple superconducting gaps. Based on above findings and electronic phase diagram vs x, we propose that the increase of N(EF) and effective electron-phonon coupling in the vicinity of CDW quantum phase transition should be a key to the large enhancement of TC in PdxTaSe2.

  16. Morphology-defined interaction of copper phthalocyanine with O2/H2O

    DOE PAGES

    Muckley, Eric S.; Miller, Nicholas; Jacobs, Christopher B.; ...

    2016-11-01

    Copper phthalocyanine (CuPc) is an important hole transport layer for organic photovoltaics (OPVs), but its interaction with ambient gas/vapor may lead to changes in electronic properties of the material which subsequently limits the lifetime of OPV devices. CuPc films of thickness 25 nm and 100 nm were grown by thermal sublimation at 25°C, 150°C, and 250°C in order to vary morphology. Using a source-measure unit and a quartz crystal microbalance (QCM), we measured changes in electrical resistance and film mass in situ during exposure to controlled pulses of O2 and H2O vapor. Mass loading by O2 was enhanced by amore » factor of 5 in films deposited at 250 C, possibly due to the ~200° C CuPc -> transition which allows higher O2 mobility between stacked molecules. While gas/vapor sorption occurred over timescales of < 10 minutes, resistance change occurred over timescales > 1 hour, suggesting that mass change occurs by rapid adsorption at active surface sites, whereas resistive response is dominated by slow diffusion of adsorbates into the film bulk. Resistive response generally increases with film deposition temperature due to increased porosity associated with larger crystalline domains. The 25 nm thick films exhibit higher resistive response than 100 nm thick films after an hour of O2/H2O exposure due to the smaller analyte diffusion length required for reaching the film/electrode interface. We found evidence of decoupling of CuPc from the gold-coated QCM crystal due to preferential adsorption of O2/H2O molecules on gold, which is consistent with findings of other studies.« less

  17. Aryl Hydrocarbon Receptor Ligand Effects in RBL2H3 Cells

    PubMed Central

    Maaetoft-Udsen, Kristina; Shimoda, Lori M.N.; Frøkiær, Hanne; Turner, Helen

    2012-01-01

    The aryl hydrocarbon receptor (AHR) mediates toxic effects of dioxin and xenobiotic metabolism. AHR has an emerging role in the immune system but its physiological ligands and functional role in immunocytes remain poorly understood. Mast cells are immunocytes that are central to inflammatory responses and release a spectrum of pro-inflammatory mediators including histamine, mast cell proteases, and pro-inflammatory cytokines such as IL-6 upon stimulation. Our aim was to investigate the AHR in model mast cells and examine how both putative and known AHR ligands, e.g., kynurenine, kynurenic acid (KA), Resveratrol, indolmycin, and violacein, affect mast cell activation and signaling. We tested these ligands on calcium signaling, degranulation, and gene expression. Our data show that AHR is present in three model mast cell lines, and that various known and putative AHR ligands regulate gene expression of Cyp1a1, a gene down-stream of AHR. Furthermore, we found that calcium influxes and mast cell secretory responses were enhanced or suppressed after chronic treatment with AHR agonists or antagonists, and that AHR ligands modified RBL2H3 cell degranulation. AHR ligands can chronically change cytokine gene expression in activated mast cells, as exemplified by IL-6. The antagonist Resveratrol repressed expression of induced IL-6 gene expression. Though KA and kynurenine are both AHR agonists, these ligands behaved differently in regards to degranulation and IL-6 expression, indicating that they may function outside of AHR pathways. These data suggest considerable complexity in RBL2H3 responses to AHR ligands, with implications for our understanding of both dioxin pathology and the immunological effects of endogenous AHR ligands. PMID:22471748

  18. Interplay of charge density wave and multiband superconductivity in 2H-PdxTaSe2

    PubMed Central

    Bhoi, D.; Khim, S.; Nam, W.; Lee, B. S.; Kim, Chanhee; Jeon, B.-G.; Min, B. H.; Park, S.; Kim, Kee Hoon

    2016-01-01

    2H-TaSe2 has been one of unique transition metal dichalcogenides exhibiting several phase transitions due to a delicate balance among competing electronic ground states. An unusual metallic state at high-T is sequentially followed by an incommensurate charge density wave (ICDW) state at ≈122 K and a commensurate charge density wave (CCDW) state at ≈90 K, and superconductivity at TC ~ 0.14 K. Upon systematic intercalation of Pd ions into TaSe2, we find that CCDW order is destabilized more rapidly than ICDW to indicate a hidden quantum phase transition point at x ~ 0.09–0.10. Moreover, TC shows a dramatic enhancement up to 3.3 K at x = 0.08, ~24 times of TC in 2H-TaSe2, in proportional to the density of states N(EF). Investigations of upper critical fields Hc2 in single crystals reveal evidences of multiband superconductivity as temperature-dependent anisotropy factor γH = , quasi-linear increase of , and an upward, positive-curvature in near TC. Furthermore, analysis of temperature-dependent electronic specific heat corroborates the presence of multiple superconducting gaps. Based on above findings and electronic phase diagram vs x, we propose that the increase of N(EF) and effective electron-phonon coupling in the vicinity of CDW quantum phase transition should be a key to the large enhancement of TC in PdxTaSe2. PMID:27045426

  19. The thermal decomposition of C{sub 2}H{sub 5}I

    SciTech Connect

    Kumaran, S.S.; Su, M.C.; Lim, K.P.; Michael, J.V.

    1996-06-01

    The high temperature thermal dissociation of C{sub 2}H{sub 5}I has been characterized in this study. Kinetics and overall yield experiments were performed over the temperature range, 946--2,046 K, using the atomic resonance absorption spectrometric technique (ARAS) for the temporal detection of both product H- and I-atoms behind reflected shock waves. The C{sub 2}H{sub 5}I decomposition proceeds by both C-I fission and HI elimination. Rate constants for the C-I fission process, measured over the temperature and density ranges, 946--1,303 K and 0.82--4.4 {times} 10{sup 18} cm{sup {minus}3}, respectively, can be well represented to within {+-}37% by the first-order expression: k = 6.34 {times} 10{sup 9} exp({minus}15,894 K/T) s{sup {minus}1}. Overall yield data for atomic product gave a branching ratio for C-I fission of (0.87 {+-} 0.11) suggesting that 13% of the reaction proceeds through molecular HI elimination. This conclusion is consistent with earlier studies that showed C-I fission to be the dominant dissociation channel. The temperature and pressure dependences of the dissociation rate constants and the yield data have been theoretically described using three formulations of unimolecular rate theory. The best description was obtained with a full Master`s equation analysis. However, all three calculations confirm that the HI elimination pathway is lower lying than the C-I fission process by {approximately} 3 kcal/mole.

  20. CO(2)/H(+) chemoreception in the cat pre-Bötzinger complex in vivo.

    PubMed

    Solomon, I C; Edelman, N H; O'Neal, M H

    2000-06-01

    We examined the effects of focal tissue acidosis in the pre-Bötzinger complex (pre-BötC; the proposed locus of respiratory rhythm generation) on phrenic nerve discharge in chloralose-anesthetized, vagotomized, paralyzed, mechanically ventilated cats. Focal tissue acidosis was produced by unilateral microinjection of 10-20 nl of the carbonic anhydrase inhibitors acetazolamide (AZ; 50 microM) or methazolamide (MZ; 50 microM). Microinjection of AZ and MZ into 14 sites in the pre-BötC reversibly increased the peak amplitude of integrated phrenic nerve discharge and, in some sites, produced augmented bursts (i.e., eupneic breath ending with a high-amplitude, short-duration burst). Microinjection of AZ and MZ into this region also reversibly increased the frequency of eupneic phrenic bursts in seven sites and produced premature bursts (i.e., doublets) in five sites. Phrenic nerve discharge increased within 5-15 min of microinjection of either agent; however, the time to the peak increase and the time to recovery were less with AZ than with MZ, consistent with the different pharmacological properties of AZ and MZ. In contrast to other CO(2)/H(+) brain stem respiratory chemosensitive sites demonstrated in vivo, which have only shown increases in amplitude of integrated phrenic nerve activity, focal tissue acidosis in the pre-BötC increases frequency of phrenic bursts and produces premature (i.e., doublet) bursts. These data indicate that the pre-BötC has the potential to play a role in the modulation of respiratory rhythm and pattern elicited by increased CO(2)/H(+) and lend additional support to the concept that the proposed locus for respiratory rhythm generation has intrinsic chemosensitivity.

  1. The photodissociation dynamics of the ethyl radical, C2H5, investigated by velocity map imaging

    NASA Astrophysics Data System (ADS)

    Steinbauer, Michael; Giegerich, Jens; Fischer, Kathrin H.; Fischer, Ingo

    2012-07-01

    The photodissociation dynamics of the ethyl radical C2H5 has been investigated by velocity map imaging. Ethyl was produced by flash pyrolysis from n-propyl nitrite and excited to the à 2A' (3s) Rydberg state around 250 nm. The energetically most favorable reaction channel in this wavelength region is dissociation to C2H4 (ethene) + H. The H-atom dissociation products were ionized in a [1+1'] process via the 1s-2p transition. The observed translational energy distribution is bimodal: A contribution of slow H-atoms with an isotropic angular distribution peaks at low translational energies. An expectation value for the fraction of excess energy released into translation of ⟨fT⟩ = 0.19 is derived from the data, typical for statistical dissociation reactions. In addition, a fast H-atom channel is observed, peaking around 1.8 eV. The latter shows an anisotropic distribution with β = 0.45. It originates from a direct dissociation process within less than a rotational period. Time-delay scans with varying extraction voltages indicate the presence of two rates for the formation of H-atoms. One rate with a sub-nanosecond time constant is associated with H-atoms with large translational energy; a second one with a time constant on the order of 100 ns is associated with H-atoms formed with low translational energy. The data confirm and extend those from previous experiments and remove some inconsistencies. Possible mechanisms for the dissociation are discussed in light of the new results as well as previous ones.

  2. A classical trajectory study of the dissociation and isomerization of C2H5.

    PubMed

    Wagner, Albert F; Rivera-Rivera, Luis A; Bachellerie, Damien; Perry, Jamin W; Thompson, Donald L

    2013-11-21

    Motivated by photodissociation experiments in which non-RRKM nanosecond lifetimes of the ethyl radical were reported, we have performed a classical trajectory study of the dissociation and isomerization of C2H5 over the energy range 100-150 kcal/mol. We used a customized version of the AIREBO semiempirical potential (Stuart, S. J.; et al. J. Chem. Phys. 2000, 112, 6472-6486) to more accurately describe the gas-phase decomposition of C2H5. This study constitutes one of the first gas-phase applications of this potential form. At each energy, 10,000 trajectories were run and all underwent dissociation in less than 100 ps. The calculated dissociation rate constants are consistent with RRKM models; no evidence was found for nanosecond lifetimes. An analytic kinetics model of isomerization/dissociation competition was developed that incorporated incomplete mode mixing through a postulated divided phase space. The fits of the model to the trajectory data are good and represent the trajectory results in detail through repeated isomerizations at all energies. The model correctly displays single exponential decay at lower energies, but at higher energies, multiexponential decay due to incomplete mode mixing becomes more apparent. At both ends of the energy range, we carried out similar trajectory studies on CD2CH3 to examine isotopic scrambling. The results largely support the assumption that a H or a D atom is equally likely to dissociate from the mixed-isotope methyl end of the molecule. The calculated fraction of products that have the D atom dissociation is ∼20%, twice the experimental value available at one energy within our range. The calculated degree of isotopic scrambling is non-monotonic with respect to energy due to a non-monotonic ratio of the isomerization to dissociation rate constants.

  3. The First Detailed 2H and 18O Isoscapes of Freshwater in Scotland

    NASA Astrophysics Data System (ADS)

    Meier-Augenstein, W.; Hoogewerff, J.; Kemp, H. F.; Frew, D.

    2012-04-01

    Scotland's freshwater lochs and reservoirs provide a vital resource for sustaining biodiversity, agriculture, food production as well as for human consumption. Regular monitoring of freshwater quality by the Scottish Environmental Protection Agency (SEPA) fulfils the legislative requirements but new scientific methods involving stable isotope analysis present an opportunity for delivering on current and nascent government policies [1] and gaining a greater understanding of Scottish waters and their importance in the context of climate change, environmental sustainability and the aforementioned functions. In brief, 2H and 18O isoscapes of Scottish freshwater could be used to support fundamental and applied research in: • Climate change - These first ever isoscapes will provide a baseline against which future environmental impact can be assessed due to changes in the characteristic isotope composition of freshwater lochs and reservoirs. • Scottish branding - Location specific stable isotope signatures of Scottish freshwater have the potential to be used as a tool for provenancing and thus protecting premium Scottish produce such as Scottish beef, Scottish berries and Scottish Whisky. During 2011, freshwater samples were collected with the support of SEPA from more than 80 freshwater lochs and reservoirs across Scotland. Here we present the result of the 2H and 18O stable isotope analyses of these water samples together with the first isoscapes generated based on these data. [1] Adaptation Framework - Adapting Our Ways: Managing Scotland's Climate Risk (2009): Scotland's Biodiversity: It's in Your Hands - A strategy for the conservation and enhancement of biodiversity in Scotland (2005); Recipe For Success - Scotland's National Food and Drink Policy (2009); Scottish Planning Policy Environmental Report (2009); Scottish Planning Policy (SPP) 15 Planning for Rural Development (2005); National Planning Policy Guideline (NPPG) 14: Natural Heritage (1999).

  4. Context-dependent DNA recognition code for C2H2 zinc-finger transcription factors

    PubMed Central

    Liu, Jiajian; Stormo, Gary D.

    2008-01-01

    Motivation: Modeling and identifying the DNA-protein recognition code is one of the most challenging problems in computational biology. Several quantitative methods have been developed to model DNA-protein interactions with specific focus on the C2H2 zinc-finger proteins, the largest transcription factor family in eukaryotic genomes. In many cases, they performed well. But the overall the predictive accuracy of these methods is still limited. One of the major reasons is all these methods used weight matrix models to represent DNA-protein interactions, assuming all base-amino acid contacts contribute independently to the total free energy of binding. Results: We present a context-dependent model for DNA–zinc-finger protein interactions that allows us to identify inter-positional dependencies in the DNA recognition code for C2H2 zinc-finger proteins. The degree of non-independence was detected by comparing the linear perceptron model with the non-linear neural net (NN) model for their predictions of DNA–zinc-finger protein interactions. This dependency is supported by the complex base-amino acid contacts observed in DNA–zinc-finger interactions from structural analyses. Using extensive published qualitative and quantitative experimental data, we demonstrated that the context-dependent model developed in this study can significantly improves predictions of DNA binding profiles and free energies of binding for both individual zinc fingers and proteins with multiple zinc fingers when comparing to previous positional-independent models. This approach can be extended to other protein families with complex base-amino acid residue interactions that would help to further understand the transcriptional regulation in eukaryotic genomes. Availability:The software implemented as c programs and are available by request. http://ural.wustl.edu/softwares.html Contact: stormo@ural.wustl.edu PMID:18586699

  5. Adaptor protein-3: A key player in RBL-2H3 mast cell mediator release

    PubMed Central

    da Silva, Elaine Zayas Marcelino; Freitas-Filho, Edismauro Garcia; de Souza-Júnior, Devandir Antonio; daSilva, Luis Lamberti Pinto; Jamur, Maria Celia

    2017-01-01

    Mast cell (MC) secretory granules are Lysosome-Related Organelles (LROs) whose biogenesis is associated with the post-Golgi secretory and endocytic pathways in which the sorting of proteins destined for a specific organelle relies on the recognition of sorting signals by adaptor proteins that direct their incorporation into transport vesicles. The adaptor protein 3 (AP-3) complex mediates protein trafficking between the trans-Golgi network (TGN) and late endosomes, lysosomes, and LROs. AP-3 has a recognized role in LROs biogenesis and regulated secretion in several cell types, including many immune cells such as neutrophils, natural killer cells, and cytotoxic T lymphocytes. However, the relevance of AP-3 for these processes in MCs has not been previously investigated. AP-3 was found to be expressed and distributed in a punctate fashion in rat peritoneal mast cells ex vivo. The rat MC line RBL-2H3 was used as a model system to investigate the role of AP-3 in mast cell secretory granule biogenesis and mediator release. By immunofluorescence and immunoelectron microscopy, AP-3 was localized both to the TGN and early endosomes indicating that AP-3 dependent sorting of proteins to MC secretory granules originates in these organelles. ShRNA mediated depletion of the AP-3 δ subunit was shown to destabilize the AP-3 complex in RBL-2H3 MCs. AP-3 knockdown significantly affected MC regulated secretion of β-hexosaminidase without affecting total cellular enzyme levels. Morphometric evaluation of MC secretory granules by electron microscopy revealed that the area of MC secretory granules in AP-3 knockdown MCs was significantly increased, indicating that AP-3 is involved in MC secretory granule biogenesis. Furthermore, AP-3 knockdown had a selective impact on the secretion of newly formed and newly synthesized mediators. These results show for the first time that AP-3 plays a critical role in secretory granule biogenesis and mediator release in MCs. PMID:28273137

  6. Seasonal patterns in δ(2) H values of multiple tissues from Andean birds provide insights into elevational migration.

    PubMed

    Villegas, Mariana; Newsome, Seth D; Blake, John G

    2016-12-01

    Elevational migration is a widespread phenomenon in tropical avifauna but it is difficult to identify using traditional approaches. Hydrogen isotope (δ(2) H) values of precipitation decrease with elevation so δ(2) H analysis of multiple bird tissues with different isotopic incorporation rates may be a reliable method for characterizing seasonal elevational migration. Here we compare δ(2) H values in metabolically inert (feathers and claws) and metabolically active (whole blood) tissues to examine whether an upslope migration occurs prior to the breeding season in the Yungas Manakin (Chiroxiphia boliviana). We compare results from C. boliviana with data from a known elevational migrant, the Streak-necked Flycatcher (Mionectes striaticollis). Opposite to our expectations, tissue δ(2) H values increased over time, largely reflecting seasonal patterns in precipitation δ(2) H rather than elevational effects; linear mixed-effects models with strongest support included ordinal date, tissue type, and elevation. This seasonal increase in precipitation δ(2) H is a general phenomenon in both tropical and temperate mountain ranges. We use these data to propose a hypothetical framework that predicts different patterns in tissue δ(2) H values collected in different seasons from residents and elevational migrants. This framework can serve as a reference for future studies that assess elevational migration in birds and other animals.

  7. Satellite observations of ethylene (C2H4) from the Aura Tropospheric Emission Spectrometer: A scoping study

    NASA Astrophysics Data System (ADS)

    Dolan, Wayana; Payne, Vivienne H.; Kualwik, Susan S.; Bowman, Kevin W.

    2016-09-01

    We present a study focusing on detection and initial quantitative estimates of ethylene (C2H4) in observations from the Tropospheric Emission Spectrometer (TES), a Fourier transform spectrometer aboard the Aura satellite that measures thermal infrared radiances with high spectral resolution (0.1 cm-1). We analyze observations taken in support of the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission and demonstrate the feasibility of future development of C2H4 into a TES standard product. In the Northern Hemisphere, C2H4 is commonly associated with boreal fire plumes, motor vehicle exhaust and petrochemical emissions. It has a short lifetime (∼14-32 h) in the troposphere due to its reaction with OH and O3. Chemical destruction of C2H4 in the atmosphere leads to the production of ozone and other species such as carbon monoxide (CO) and formaldehyde. Results indicate a correlation between C2H4 and CO in boreal fire plumes. Quantitative C2H4 estimates are sensitive to assumptions about the plume height and width. We find that C2H4 greater than 2-3 ppbv can be detected in a single TES observation (for a fire plume at 3 km altitude and 1.5 km width). Spatial averaging will be needed for surface-peaking profiles where TES sensitivity is lower.

  8. Stability evaluation of a rocket engine for gaseous oxygen difluoride (OF2) and gaseous diborane (B2H6) propellants

    NASA Technical Reports Server (NTRS)

    Clayton, R. M.

    1972-01-01

    Results of an experimental evaluation of the dynamic stability of a candidate combustor for the space storable propellants gaseous OF2/B2H6 show that the combustor is unstable without supplementary damping. A computer analysis indicated that the uninhibited engine could be unstable. The experiments, conducted with O2/C2H4 substitute propellants and with 70-30 FLOX/B2H6 (OF2 simulated with FLOX), show that the uninhibited combustor has a low stability margin to starting transient perturbations, but that is relatively insensitive to bomb disturbances. Damping cavities are shown to provide stability.

  9. A study of dipolar interactions and dynamic processes of water molecules in tendon by 1H and 2H homonuclear and heteronuclear multiple-quantum-filtered NMR spectroscopy.

    PubMed

    Eliav, U; Navon, G

    1999-04-01

    The effect of proton exchange on the measurement of 1H-1H, 1H-2H, and 2H-2H residual dipolar interactions in water molecules in bovine Achilles tendons was investigated using double-quantum-filtered (DQF) NMR and new pulse sequences based on heteronuclear and homonuclear multiple-quantum filtering (MQF). Derivation of theoretical expressions for these techniques allowed evaluation of the 1H-1H and 1H-2H residual dipolar interactions and the proton exchange rate at a temperature of 24 degrees C and above, where no dipolar splitting is evident. The values obtained for these parameters at 24 degrees C were 300 and 50 Hz and 3000 s-1, respectively. The results for the residual dipolar interactions were verified by repeating the above measurements at a temperature of 1.5 degrees C, where the spectra of the H2O molecules were well resolved, so that the 1H-1H dipolar interaction could be determined directly from the observed splitting. Analysis of the MQF experiments at 1.5 degrees C, where the proton exchange was in the intermediate regime for the 1H-2H dipolar interaction, confirmed the result obtained at 24 degrees C for this interaction. A strong dependence of the intensities of the MQF signals on the proton exchange rate, in the intermediate and the fast exchange regimes, was observed and theoretically interpreted. This leads to the conclusion that the MQF techniques are mostly useful for tissues where the residual dipolar interaction is not significantly smaller than the proton exchange rate. Dependence of the relaxation times and signal intensities of the MQF experiments on the orientation of the tendon with respect to the magnetic field was observed and analyzed. One of the results of the theoretical analysis is that, in the fast exchange regime, the signal decay rates in the MQF experiments as well as in the spin echo or CPMG pulse sequences (T2) depend on the orientation as the square of the second-rank Legendre polynomial.

  10. Theoretical and Laboratory Studies on the Interaction of Cosmic-Ray Particles with Interstellar Ices. III. Suprathermal Chemistry-Induced Formation of Hydrocarbon Molecules in Solid Methane (CH4), Ethylene (C2H4), and Acetylene (C2H2)

    NASA Astrophysics Data System (ADS)

    Kaiser, R. I.; Roessler, K.

    1998-08-01

    Methane, ethylene, and acetylene ices are irradiated in a ultra high vacuum vessel at 10 K with 9.0 MeV α-particles and 7.3 MeV protons to elucidate mechanisms to form hydrocarbon molecules upon interaction of Galactic cosmic-ray particles with extraterrestrial, organic ices. Theoretical calculations focus on computer simulations of ion-induced collision cascades in irradiated targets. Our experimental and computational investigations reveal that each MeV particle transfers its kinetic energy predominantly through inelastic encounters to the target leading to electronic excitation and ionization of the target molecules. Here electronically excited CH4 species can fragment to mobile H atoms and nonmobile CH3 radicals. The potential energy stored in Coulomb interaction of the CH+4 ions release energetic H and C atoms not in thermal equilibrium with the 10 K target (suprathermal species). Moderated to 1-10 eV kinetic energy, these carbon atoms and those triggered by the elastic energy transfer of the MeV projectile to the target are found to abstract up to two H atoms to yield suprathermal CH and CH2 species. C and CH, as well as CH2, can insert into a CH bond of a CH4 molecule to form methylcarbene (HCCH3), the ethyl radical (C2H5), and ethane (C2H6). HCCH3 either loses H2/2H to form acetylene, C2H2, rearranges to ethylene, C2H4, or adds two H atoms to form ethane, C2H6. C2H5 can abstract or lose an H atom, giving ethane and ethylene, respectively. C2H2 and C2H4 are found to react with suprathermal H atoms to form C2H3 and C2H5, respectively. Overlapping cascades and an increasing MeV ion exposure transforms C2Hx (x = 2, ..., 6) to even more complex alkanes up to C14H30. These elementary reactions of suprathermal species to insert, abstract, and add in/to bonds supply a powerful pathway to form new molecules in icy grain mantles condensed on interstellar grains or in hydrocarbon rich bodies in our solar system even at temperatures as low as 10 K.

  11. A novel dilithiation approach to 3,4-dihydro-2H-1,3-benzothiazines, 3,4-Dihydro-2H-1,3-benzoxazines, and 2,3,4,5-tetrahydro-1,3-benzothiazepines.

    PubMed

    Katritzky, Alan R; Xu, Yong-Jiang; Jain, Ritu

    2002-11-15

    3,4-Dihydro-2H-1,3-benzothiazines 4, 3,4-dihydro-2H-1,3-benzoxazines 9, and 2,3,4,5-tetrahydro-1,3-benzothiazepines 6 were synthesized by directed ortho-lithiation of thiophenols and phenols and by side-chain lithiation of substituted thiophenols, respectively, in one-pot by reacting with N,N-bis[(benzotriazol-1-yl)methyl]amines 3 as 1,3-biselectrophile synthons.

  12. Full-dimensional, high-level ab initio potential energy surfaces for H2(H2O) and H2(H2O)2 with application to hydrogen clathrate hydrates.

    PubMed

    Homayoon, Zahra; Conte, Riccardo; Qu, Chen; Bowman, Joel M

    2015-08-28

    New, full-dimensional potential energy surfaces (PESs), obtained using precise least-squares fitting of high-level electronic energy databases, are reported for intrinsic H2(H2O) two-body and H2(H2O)2 three-body potentials. The database for H2(H2O) consists of approximately 44 000 energies at the coupled cluster singles and doubles plus perturbative triples (CCSD(T))-F12a/haQZ (aug-cc-pVQZ for O and cc-pVQZ for H) level of theory, while the database for the three-body interaction consists of more than 36 000 energies at the CCSD(T)-F12a/haTZ (aug-cc-pVTZ for O, cc-pVTZ for H) level of theory. Two precise potentials are based on the invariant-polynomial technique and are compared to computationally faster ones obtained via "purified" symmetrization. All fits use reduced permutational symmetry appropriate for these non-covalent interactions. These intrinsic potentials are employed together with existing ones for H2, H2O, and (H2O)2, to obtain full PESs for H2(H2O) and H2(H2O)2. Properties of these full PESs are presented, including a diffusion Monte Carlo calculation of the zero-point energy and wavefunction, and dissociation energy of the H2(H2O) dimer. These PESs together with an existing one for water clusters are used in a many-body representation of the PES of hydrogen clathrate hydrates, illustrated for H2@(H2O)20. An analysis of this hydrate is presented, including the electronic dissociation energy to remove H2 from the calculated equilibrium structure.

  13. Supergranular Parameters

    NASA Astrophysics Data System (ADS)

    Udayashankar, Paniveni

    2016-07-01

    I study the complexity of supergranular cells using intensity patterns from Kodaikanal solar observatory. The chaotic and turbulent aspect of the solar supergranulation can be studied by examining the interrelationships amongst the parameters characterizing supergranular cells namely size, horizontal flow field, lifetime and physical dimensions of the cells and the fractal dimension deduced from the size data. The findings are supportive of Kolmogorov's theory of turbulence. The Data consists of visually identified supergranular cells, from which a fractal dimension 'D' for supergranulation is obtained according to the relation P α AD/2 where 'A' is the area and 'P' is the perimeter of the supergranular cells. I find a fractal dimension close to about 1.3 which is consistent with that for isobars and suggests a possible turbulent origin. The cell circularity shows a dependence on the perimeter with a peak around (1.1-1.2) x 105 m. The findings are supportive of Kolmogorov's theory of turbulence.

  14. New Ni(II)-sulfonamide complexes: synthesis, structural characterization and antibacterial properties. X-ray diffraction of [Ni(sulfisoxazole)2(H2O)4].2H2O and [Ni(sulfapyridine)2].

    PubMed

    Mondelli, Melina; Bruné, Verónica; Borthagaray, Graciela; Ellena, Javier; Nascimento, Otaciro R; Leite, Clarice Q; Batista, Alzir A; Torre, María H

    2008-02-01

    The synthesis, structural characterization, voltammetric experiments and antibacterial activity of [Ni(sulfisoxazole)(2)(H(2)O)(4)].2H(2)O and [Ni(sulfapyridine)(2)] were studied and compared with similar previously reported copper complexes. [Ni(sulfisoxazole)(2)(H(2)O)(4)].2H(2)O crystallized in a monoclinic system, space group C2/c where the nickel ion was in a slightly distorted octahedral environment, coordinated with two sulfisoxazole molecules through the heterocyclic nitrogen and four water molecules. [Ni(sulfapyridine)(2)] crystallized in a orthorhombic crystal system, space group Pnab. The nickel ion was in a distorted octahedral environment, coordinated by two aryl amine N from two sulfonamides acting as monodentate ligands and four N atoms (two sulfonamidic N and two heterocyclic N) from two different sulfonamide molecules acting as bidentate ligands. Differential pulse voltammograms were recorded showing irreversible peaks at 1040 and 1070 mV, respectively, attributed to Ni(II)/Ni(III) process. [Ni(sulfisoxazole)(2)(H(2)O)(4)].2H(2)O and [Ni(sulfapyridine)(2)] presented different antibacterial behavior against Staphylococcus aureus and Escherichia coli from the similar copper complexes and they were inactive against Mycobacterium tuberculosis.

  15. Structure and Dynamics of the Myristoyl Lipid Modification of Src Peptides Determined by 2H Solid-State NMR Spectroscopy

    PubMed Central

    Scheidt, Holger A.; Huster, Daniel

    2009-01-01

    Lipid modifications of proteins are widespread in nature and play an important role in numerous biological processes. The nonreceptor tyrosine kinase Src is equipped with an N-terminal myristoyl chain and a cluster of basic amino acids for the stable membrane association of the protein. We used 2H NMR spectroscopy to investigate the structure and dynamics of the myristoyl chain of myr-Src(2–19), and compare them with the hydrocarbon chains of the surrounding phospholipids in bilayers of varying surface potentials and chain lengths. The myristoyl chain of Src was well inserted in all bilayers investigated. In zwitterionic 1,2-dimyristoyl-sn-glycero-3-phosphocholine membranes, the myristoyl chain of Src was significantly longer and appears “stiffer” than the phospholipid chains. This can be explained by an equilibrium between the attraction attributable to the insertion of the myristoyl chain and the Born repulsion. In a 1,2-dimyristoyl-sn-glycero-3-phosphocholine/1,2-dimyristoyl-sn-glycero-3-[phospho-L-serine] membrane, where attractive electrostatic interactions come into play, the differences between the peptide and the phospholipid chain lengths were attenuated, and the molecular dynamics of all lipid chains were similar. In a much thicker 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1,2-dipalmitoyl-sn-glycero-3-[phospho-L-serine]/cholesterol membrane, the length of the myristoyl chain of Src was elongated nearly to its maximum, and the order parameters of the Src chain were comparable to those of the surrounding membrane. PMID:19413971

  16. Structure and dynamics of the myristoyl lipid modification of SRC peptides determined by 2H solid-state NMR spectroscopy.

    PubMed

    Scheidt, Holger A; Huster, Daniel

    2009-05-06

    Lipid modifications of proteins are widespread in nature and play an important role in numerous biological processes. The nonreceptor tyrosine kinase Src is equipped with an N-terminal myristoyl chain and a cluster of basic amino acids for the stable membrane association of the protein. We used (2)H NMR spectroscopy to investigate the structure and dynamics of the myristoyl chain of myr-Src(2-19), and compare them with the hydrocarbon chains of the surrounding phospholipids in bilayers of varying surface potentials and chain lengths. The myristoyl chain of Src was well inserted in all bilayers investigated. In zwitterionic 1,2-dimyristoyl-sn-glycero-3-phosphocholine membranes, the myristoyl chain of Src was significantly longer and appears "stiffer" than the phospholipid chains. This can be explained by an equilibrium between the attraction attributable to the insertion of the myristoyl chain and the Born repulsion. In a 1,2-dimyristoyl-sn-glycero-3-phosphocholine/1,2-dimyristoyl-sn-glycero-3-[phospho-L-serine] membrane, where attractive electrostatic interactions come into play, the differences between the peptide and the phospholipid chain lengths were attenuated, and the molecular dynamics of all lipid chains were similar. In a much thicker 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1,2-dipalmitoyl-sn-glycero-3-[phospho-L-serine]/cholesterol membrane, the length of the myristoyl chain of Src was elongated nearly to its maximum, and the order parameters of the Src chain were comparable to those of the surrounding membrane.

  17. Measured Total Cross Sections of Slow Neutrons Scattered by Gaseous and Liquid {sup 2}H{sub 2}

    SciTech Connect

    Atchison, F.; Brandt, B. van den; Brys, T.; Daum, M.; Fierlinger, P.; Hautle, P.; Henneck, R.; Kirch, K.; Kohlbrecher, J.; Kuehne, G.; Konter, J.A.; Pichlmaier, A.; Wokaun, A.; Bodek, K.; Kasprzak, M.; Kuzniak, M.; Geltenbort, P.; Giersch, M.; Zmeskal, J.; Hino, M.

    2005-06-03

    The total scattering cross sections for slow neutrons with energies E in the range 300 neV to 3 meV for gaseous and liquid ortho-{sup 2}H{sub 2} have been measured. The cross sections for {sup 2}H{sub 2} gas are found to be in excellent agreement with both the Hamermesh and Schwinger and the Young and Koppel models. For liquid {sup 2}H{sub 2}, we confirm the existing experimental data in the cold neutron range and the discrepancy with the gas models. We find a clear 1/{radical}(E{sup '}) dependence at low energies for both states. A simple explanation for the liquid {sup 2}H{sub 2} cross section is offered.

  18. New Mo6 Te6 Sub-Nanometer-Diameter Nanowire Phase from 2H-MoTe2.

    PubMed

    Zhu, Hui; Wang, Qingxiao; Zhang, Chenxi; Addou, Rafik; Cho, Kyeongjae; Wallace, Robert M; Kim, Moon J

    2017-03-10

    A novel phase transition, from multilayered 2H-MoTe2 to a parallel bundle of sub-nanometer-diameter metallic Mo6 Te6 nanowires (NWs) driven by catalyzer-free thermal-activation (400-500 °C) under vacuum, is demonstrated. The NWs form along the 〈11-20〉 2H-MoTe2 crystallographic directions with lengths in the micrometer range. The metallic NWs can act as an efficient hole injection layer on top of 2H-MoTe2 due to favorable band-alignment. In particular, an atomically sharp MoTe2 /Mo6 Te6 interface and van der Waals gap with the 2H layers are preserved. The work highlights an alternative pathway for forming a new transition metal dichalcogenide phase and will enable future exploration of its intrinsic transportation properties.

  19. The Chromatin Remodelling Enzymes SNF2H and SNF2L Position Nucleosomes adjacent to CTCF and Other Transcription Factors

    PubMed Central

    Wiechens, Nicola; Gkikopoulos, Triantaffyllos; Schofield, Pieta; Rocha, Sonia; Owen-Hughes, Tom

    2016-01-01

    Within the genomes of metazoans, nucleosomes are highly organised adjacent to the binding sites for a subset of transcription factors. Here we have sought to investigate which chromatin remodelling enzymes are responsible for this. We find that the ATP-dependent chromatin remodelling enzyme SNF2H plays a major role organising arrays of nucleosomes adjacent to the binding sites for the architectural transcription factor CTCF sites and acts to promote CTCF binding. At many other factor binding sites SNF2H and the related enzyme SNF2L contribute to nucleosome organisation. The action of SNF2H at CTCF sites is functionally important as depletion of CTCF or SNF2H affects transcription of a common group of genes. This suggests that chromatin remodelling ATPase’s most closely related to the Drosophila ISWI protein contribute to the function of many human gene regulatory elements. PMID:27019336

  20. Hydrochemistry and 18O/16O and 2H/1H Ratios of Ugandan Waters

    NASA Astrophysics Data System (ADS)

    Gebremichael, M. G.; Jasechko, S.

    2013-12-01

    Today, 70% of the 35 million people living in Uganda have access to an improved water source, ranking Uganda 148 out of 179 nations reporting in 2010 (Millennium Development Goals Indicators). 80% of Ugandans rely on groundwater as their primary drinking water source, collecting at springs or from shallow wells. Similarly, 80% of Ugandans rely upon agriculture - usually rain fed - as their primary income source. Despite lack of access to protected water sources faced by 10 million Ugandans, and the importance of the blue economy to Uganda's continued development, a country-wide investigation of the chemistry and the stable oxygen and hydrogen isotope compositions of waters has yet to be completed. Here we present 250 analyses of 18O/16O, 2H/1H and dissolved ion concentrations of Ugandan lakes, rivers, groundwaters and springs collected during July, 2013. We use the new data to characterize regional scale groundwater recharge sources, advection pathways and interactions with surface waters. Large lakes - Albert, Edward and Victoria - show increases in 18O/16O and 2H/1H ratios consistent with open water evaporation, and are shown to be distinct from nearby groundwaters, suggesting minimal recharge from large lakes to the subsurface. Salinities of eastern Ugandan groundwaters are elevated relative to samples collected from the central and western regions, suggesting that longer groundwater residence times and enhanced water-rock interactions characterize these waters. Springs from western Uganda show a shift in 18O/16O to higher values as a result of hydrothermal water-rock exchanges. Dissolved ion and noble gas concentrations show potential for use in assessing geothermal energy resources, perhaps aiding the Ugandan Ministry for Energy, Minerals and Development to meet their goal of increasing renewable energy from 4% (current) to 61% of total use by 2017 (Nyakabwa-Atwoki, 2013). Millennium Development Goals Indicators. mdgs.un.org/unsd/mdg/data.aspx Nyakabwa

  1. The effects of maternal anxiety during pregnancy on IGF2/H19 methylation in cord blood

    PubMed Central

    Mansell, T; Novakovic, B; Meyer, B; Rzehak, P; Vuillermin, P; Ponsonby, A-L; Collier, F; Burgner, D; Saffery, R; Ryan, J; Vuillermin, Peter; Ponsonby, Anne-Louise; Carlin, John B; Allen, Katie J; Tang, Mimi L; Saffery, Richard; Ranganathan, Sarath; Burgner, David; Dwyer, Terry; Jachno, Kim; Sly, Peter

    2016-01-01

    Compelling evidence suggests that maternal mental health in pregnancy can influence fetal development. The imprinted genes, insulin-like growth factor 2 (IGF2) and H19, are involved in fetal growth and each is regulated by DNA methylation. This study aimed to determine the association between maternal mental well-being during pregnancy and differentially methylated regions (DMRs) of IGF2 (DMR0) and the IGF2/H19 imprinting control region (ICR) in newborn offspring. Maternal depression, anxiety and perceived stress were assessed at 28 weeks of pregnancy in the Barwon Infant Study (n=576). DNA methylation was measured in purified cord blood mononuclear cells using the Sequenom MassArray Platform. Maternal anxiety was associated with a decrease in average ICR methylation (Δ=−2.23% 95% CI=−3.68 to −0.77%), and across all six of the individual CpG units in anxious compared with non-anxious groups. Birth weight and sex modified the association between prenatal anxiety and infant methylation. When stratified into lower (⩽3530 g) and higher (>3530 g) birth weight groups using the median birth weight, there was a stronger association between anxiety and ICR methylation in the lower birth weight group (Δ=−3.89% 95% CI=−6.06 to −1.72%), with no association in the higher birth weight group. When stratified by infant sex, there was a stronger association in female infants (Δ=−3.70% 95% CI=−5.90 to −1.51%) and no association in males. All the linear regression models were adjusted for maternal age, smoking and folate intake. These findings show that maternal anxiety in pregnancy is associated with decreased IGF2/H19 ICR DNA methylation in progeny at birth, particularly in female, low birth weight neonates. ICR methylation may help link poor maternal mental health and adverse birth outcomes, but further investigation is needed. PMID:27023171

  2. Effect of endocannabinoids on IgE-mediated allergic response in RBL-2H3 cells.

    PubMed

    Yoo, Jae-Myung; Sok, Dai-Eun; Kim, Mee Ree

    2013-09-01

    Recently, some endocannabinoids were reported to show anti-inflammatory and anti-allergic activities. In this respect, various arachidonoyl endocannabinoids were screened for the inhibition of allergic response in IgE-activated RBL-2H3 cells. Among arachidonoyl endocannabinoids with a low cytotoxicity, only NA-5HT remarkably inhibited the release of β-hexosaminidase (IC(50), 13.58 μM), a marker of degranulation, and tumor necrosis factor-α (IC(50), 12.52 μM), a pro-inflammatory cytokine, in IgE-activated RBL-2H3 cells. Additionally, NA-5HT markedly suppressed the formation of prostaglandin D(2) (PGD(2)) with IC(50) value of 1.27 μM and leukotriene B(4) (LTB(4)) with IC(50) value of 1.20 μM, and slightly LTC4. When effect of NA-5HT on early stage of FcεRI cascade was investigated, it significantly inhibited phosphorylation of Syk, but not Lyn. Furthermore, NA-5HT suppressed phosphorylation of PLCγ1/2 and PKCδ, related to degranulation process, as well as phosphorylation of LAT, ERK1/2, p38, JNK, Gab2, PI3K and Akt, implicated in the expression of pro-inflammatory cytokines. Relative to its effect on the late stage, NA-5HT slightly reduced phosphorylation of 5-lipoxygenase (5-LO) and cyclooxygenase-2 (COX-2). Additionally, NA-5HT significantly reduced the level of p40(phox), and partially inhibited the expression of p47(phox) and p67(phox). From these results, it is suggested that NA-5HT expresses anti-allergic action by suppressing the activation of Syk, LAT, p38, JNK, PI3K and Akt, as well as the expression of ERK1/2 and NADPH oxidase subunits. Further, a strong inhibition of PGD(2) or LTB(4) biosynthesis by NA-5HT may be an additional mechanism for its anti-allergic action. Such anti-allergic actions of NA-5HT may contribute to further information about its biological functions.

  3. Equilibrium 2H/1H fractionation in organic molecules: III. Cyclic ketones and hydrocarbons

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Sessions, Alex L.; Nielsen, Robert J.; Goddard, William A.

    2013-04-01

    Quantitative interpretation of stable hydrogen isotope ratios (2H/1H) in organic compounds is greatly aided by knowledge of the relevant equilibrium fractionation factors (ɛeq). Previous efforts have combined experimental measurements and hybrid Density Functional Theory (DFT) calculations to accurately predict equilibrium fractionations in linear (acyclic) organic molecules (Wang et al., 2009a,b), but the calibration produced by that study is not applicable to cyclic compounds. Here we report experimental measurements of equilibrium 2H/1H fractionation in six cyclic ketones, and use those data to evaluate DFT calculations of fractionation in diverse monocyclic and polycyclic compounds commonly found in sedimentary organic matter and petroleum. At 25, 50, and 75 °C, the experimentally measured ɛeq values for secondary and tertiary Hα in isotopic equilibrium with water are in the ranges of -130‰ to -150‰ and +10‰ to -40‰ respectively. Measured data are similar to DFT calculations of ɛeq for axial Hα but not equatorial Hα. In tertiary Cα positions with methyl substituents, this can be understood as a result of the methyl group forcing Hα atoms into a dominantly axial position. For secondary Cα positions containing both axial and equatorial Hα atoms, we propose that axial Hα exchanges with water significantly faster than the equatorial Hα does, due to the hyperconjugation-stabilized transition state. Interconversion of axial and equatorial positions via ring flipping is much faster than isotopic exchange at either position, and as a result the steady-state isotopic composition of both H's is strongly weighted toward that of axial Hα. Based on comparison with measured ɛeq values, a total uncertainty of 10-30‰ remains for theoretical ɛeq values. Using DFT, we systematically estimated the ɛeq values for individual H positions in various cyclic structures. By summing over all individual H positions, the molecular equilibrium fractionation was

  4. Pseudo-Jahn-Teller origin of the low barrier hydrogen bond in N2H7+

    NASA Astrophysics Data System (ADS)

    García-Fernández, P.; García-Canales, L.; García-Lastra, J. M.; Junquera, J.; Moreno, M.; Aramburu, J. A.

    2008-09-01

    The microscopic origin and quantum effects of the low barrier hydrogen bond (LBHB) in the proton-bound ammonia dimer cation N2H7+ were studied by means of ab initio and density-functional theory (DFT) methods. These results were analyzed in the framework of vibronic theory and compared to those obtained for the Zundel cation H5O2+. All geometry optimizations carried out using wavefunction-based methods [Hartree-Fock, second and fourth order Möller-Plesset theory (MP2 and MP4), and quadratic configuration interaction with singles and doubles excitations (QCISD)] lead to an asymmetrical H3N-H+⋯NH3 conformation (C3v symmetry) with a small energy barrier (1.26kcal/mol in MP4 and QCISD calculations) between both equivalent minima. The value of this barrier is underestimated in DFT calculations particularly at the local density approximation level where geometry optimization leads to a symmetric H3N⋯H+⋯NH3 structure (D3d point group). The instability of the symmetric D3d structure is shown to originate from the pseudo-Jahn-Teller mixing of the electronic A1g1 ground state with five low lying excited states of A2u symmetry through the asymmetric α2u vibrational mode. A molecular orbital study of the pseudo-Jahn-Teller coupling has allowed us to discuss the origin of the proton displacement and the LBHB formation in terms of the polarization of the NH3 molecules and the transfer of electronic charge between the proton and the NH3 units (rebonding). The parallel study of the H5O2+ cation, which presents a symmetric single-well structure, allows us to analyze why these similar molecules behave differently with respect to proton transfer. From the vibronic analysis, a unified view of the Rudle-Pimentel three-center four-electron and charge transfer models of LBHBs is given. Finally, the large difference in the N-N distance in the D3d and C3v configurations of N2H7+ indicates a large anharmonic coupling between α2u-α1g modes along the proton

  5. Reactivity of organic complexes at mineral-CO2-H2O interfaces

    NASA Astrophysics Data System (ADS)

    Miller, Q. R.; Schaef, T.; Kaszuba, J. P.; Qiu, L.; Bowden, M. E.; McGrail, B. P.

    2015-12-01

    Understanding the interactions between minerals and organics in H2O-CO2 fluids is important, as they are the two most abundant volatiles in the crust. CO2-rich fluids in natural and anthropogenic environments, such as metamorphic aureoles and carbon storage reservoirs, respectively, produce a complex geochemical setting in which CO2-rich fluids containing dissolved water and organic compounds interact with rocks and minerals. We have undertaken experimental and theoretical studies to evaluate how organics impact carbonate mineralization and to determine the partitioning behavior of organic complexes between CO2, H2O, and mineral interfaces. The first groups of experiments have clarified how the type and concentration of simple organic ligands impact the degree and type of carbonation in interfacial water films. In these experiments, salts of simple organic ligands were equilibrated with wet supercritical CO2, which was reacted with the model mineral forsterite (Mg2SiO4). The forsterite dissolution and coupled carbonate precipitation reactions were followed with time-resolved pressurized X-ray diffraction (XRD) at 50 °C and 90 bar. The extent of carbonation and the relative abundance of anhydrous magnesite (MgCO3) precipitated relative to hydrated nesquehonite (MgCO3·3H2O) was impacted by the type of organic ligand. Magnesite enhancement was observed with the trend of citrate>oxalate≈malonate>acetate>organic-free control. This indicates that the organic ligands complexed Mg2+ in the interfacial water film environment and helped alleviate kinetic barriers to magnesite formation. Additional XRD experiments with varying concentrations of citrate verified the dependence of magnesite enhancement and the degree of overall carbonation on the amount of organic present in the water film. Lastly, our ongoing work concerning the partitioning of organic and metal-organic complexes between CO2, H2O, and interfacial water films will be presented. This experimental work, which

  6. Full CI calibration of model hamiltonian, large basis set studies of the H 2-H 2 van der Waals interaction.

    NASA Astrophysics Data System (ADS)

    Burton, P. G.

    1983-08-01

    The non-variational CEPA2 PNO ansatz, recently employed in detailed studies of the H 2-H 2 van der Waals interaction by Burton and Senff and the full CI extrapolation studies on the same system by Burton are discussed in relation to the explicit full CI study of Harrison and Handy for the planar T configuration of H 2-H 2 ( R = 6.5 ao) in a basis of 80 functions.

  7. Pressure dependence of the absolute rate constant for the reaction Cl + C2H2 from 210-361 K

    NASA Technical Reports Server (NTRS)

    Brunning, J.; Stief, L. J.

    1985-01-01

    In recent years, considerable attention has been given to the role of chlorine compounds in the catalytic destruction of stratospheric ozone. However, while some reactions have been studied extensively, the kinetic data for the reaction of Cl with C2H2 is sparse with only three known determinations of the rate constant k3. The reactions involved are Cl + C2H2 yields reversibly ClC2H2(asterisk) (3a) and ClC2H2(asterisk) + M yields ClC2H2 + M (3b). In the present study, flash photolysis coupled with chlorine atomic resonance fluorescence have been employed to determine the pressure and temperature dependence of k3 with the third body M = Ar. Room temperature values are also reported for M = N2. The pressure dependence observed in the experiments confirms the expectation that the reaction involves addition of Cl to the unsaturated C2H2 molecule followed by collisional stabilization of the resulting adduct radical.

  8. Linking Hydrogen (δ2H) Isotopes in Feathers and Precipitation: Sources of Variance and Consequences for Assignment to Isoscapes

    PubMed Central

    Hobson, Keith A.; Van Wilgenburg, Steven L.; Wassenaar, Leonard I.; Larson, Keith

    2012-01-01

    Background Tracking small migrant organisms worldwide has been hampered by technological and recovery limitations and sampling bias inherent in exogenous markers. Naturally occurring stable isotopes of H (δ2H) in feathers provide an alternative intrinsic marker of animal origin due to the predictable spatial linkage to underlying hydrologically driven flow of H isotopes into foodwebs. This approach can assess the likelihood that a migrant animal originated from a given location(s) within a continent but requires a robust algorithm linking H isotopes in tissues of interest to an appropriate hydrological isotopic spatio-temporal pattern, such as weighted-annual rainfall. However, a number of factors contribute to or alter expected isotopic patterns in animals. We present results of an extensive investigation into taxonomic and environmental factors influencing feather δ2H patterns across North America. Principal Findings Stable isotope data were measured from 544 feathers from 40 species and 140 known locations. For δ2H, the most parsimonious model explaining 83% of the isotopic variance was found with amount-weighted growing-season precipitation δ2H, foraging substrate and migratory strategy. Conclusions/Significance This extensive H isotopic analysis of known-origin feathers of songbirds in North America and elsewhere reconfirmed the strong coupling between tissue δ2H and global hydrologic δ2H patterns, and accounting for variance associated with foraging substrate and migratory strategy, can be used in conservation and research for the purpose of assigning birds and other species to their approximate origin. PMID:22509393

  9. Ligand-induced substrate steering and reshaping of [Ag2(H)](+) scaffold for selective CO2 extrusion from formic acid.

    PubMed

    Zavras, Athanasios; Khairallah, George N; Krstić, Marjan; Girod, Marion; Daly, Steven; Antoine, Rodolphe; Maitre, Philippe; Mulder, Roger J; Alexander, Stefanie-Ann; Bonačić-Koutecký, Vlasta; Dugourd, Philippe; O'Hair, Richard A J

    2016-06-06

    Metalloenzymes preorganize the reaction environment to steer substrate(s) along the required reaction coordinate. Here, we show that phosphine ligands selectively facilitate protonation of binuclear silver hydride cations, [LAg2(H)](+) by optimizing the geometry of the active site. This is a key step in the selective, catalysed extrusion of carbon dioxide from formic acid, HO2CH, with important applications (for example, hydrogen storage). Gas-phase ion-molecule reactions, collision-induced dissociation (CID), infrared and ultraviolet action spectroscopy and computational chemistry link structure to reactivity and mechanism. [Ag2(H)](+) and [Ph3PAg2(H)](+) react with formic acid yielding Lewis adducts, while [(Ph3P)2Ag2(H)](+) is unreactive. Using bis(diphenylphosphino)methane (dppm) reshapes the geometry of the binuclear Ag2(H)(+) scaffold, triggering reactivity towards formic acid, to produce [dppmAg2(O2CH)](+) and H2. Decarboxylation of [dppmAg2(O2CH)](+) via CID regenerates [dppmAg2(H)](+). These gas-phase insights inspired variable temperature NMR studies that show CO2 and H2 production at 70 °C from solutions containing dppm, AgBF4, NaO2CH and HO2CH.

  10. Ligand-induced substrate steering and reshaping of [Ag2(H)]+ scaffold for selective CO2 extrusion from formic acid

    PubMed Central

    Zavras, Athanasios; Khairallah, George N.; Krstić, Marjan; Girod, Marion; Daly, Steven; Antoine, Rodolphe; Maitre, Philippe; Mulder, Roger J.; Alexander, Stefanie-Ann; Bonačić-Koutecký, Vlasta; Dugourd, Philippe; O'Hair, Richard A. J.

    2016-01-01

    Metalloenzymes preorganize the reaction environment to steer substrate(s) along the required reaction coordinate. Here, we show that phosphine ligands selectively facilitate protonation of binuclear silver hydride cations, [LAg2(H)]+ by optimizing the geometry of the active site. This is a key step in the selective, catalysed extrusion of carbon dioxide from formic acid, HO2CH, with important applications (for example, hydrogen storage). Gas-phase ion-molecule reactions, collision-induced dissociation (CID), infrared and ultraviolet action spectroscopy and computational chemistry link structure to reactivity and mechanism. [Ag2(H)]+ and [Ph3PAg2(H)]+ react with formic acid yielding Lewis adducts, while [(Ph3P)2Ag2(H)]+ is unreactive. Using bis(diphenylphosphino)methane (dppm) reshapes the geometry of the binuclear Ag2(H)+ scaffold, triggering reactivity towards formic acid, to produce [dppmAg2(O2CH)]+ and H2. Decarboxylation of [dppmAg2(O2CH)]+ via CID regenerates [dppmAg2(H)]+. These gas-phase insights inspired variable temperature NMR studies that show CO2 and H2 production at 70 °C from solutions containing dppm, AgBF4, NaO2CH and HO2CH. PMID:27265868

  11. High-solids biphasic CO2-H2O pretreatment of lignocellulosic biomass.

    PubMed

    Luterbacher, Jeremy S; Tester, Jefferson W; Walker, Larry P

    2010-10-15

    A high pressure (200 bar) CO(2)-H(2)O process was developed for pretreating lignocellulosic biomass at high-solid contents, while minimizing chemical inputs. Hardwood was pretreated at 20 and 40 (wt.%) solids. Switchgrass, corn stover, big bluestem, and mixed perennial grasses (a co-culture of big bluestem and switchgrass) were pretreated at 40 (wt.%) solids. Operating temperatures ranged from 150 to 250 degrees C, and residence times from 20 s to 60 min. At these conditions a biphasic mixture of an H(2)O-rich liquid (hydrothermal) phase and a CO(2)-rich supercritical phase coexist. Following pretreatment, samples were then enzymatically hydrolyzed. Total yields, defined as the fraction of the theoretical maximum, were determined for glucose, hemicellulose sugars, and two degradation products: furfural and 5-hydroxymethylfurfural. Response surfaces of yield as a function of temperature and residence time were compared for different moisture contents and biomass species. Pretreatment at 170 degrees C for 60 min gave glucose yields of 77%, 73%, and 68% for 20 and 40 (wt.%) solids mixed hardwood and mixed perennial grasses, respectively. Pretreatment at 160 degrees C for 60 min gave glucan to glucose yields of 81% for switchgrass and 85% for corn stover.

  12. Synthesis, structural and spectroscopic studies of 2-oxoacenaphthylen-1(2H)-ylidene nicotinohydrazide

    NASA Astrophysics Data System (ADS)

    Henriques, M. S. C.; Del Amparo, R.; Pérez-Álvarez, D.; Nogueira, B. A.; Rodríguez-Argüelles, M. C.; Paixão, J. A.

    2017-02-01

    The synthesis of a new hydrazone, 2-oxoacenaphthylen-1(2H)-ylidene nicotinohydrazide, and its structural and spectroscopic characterization is reported. The obtained powder was recrystallized from DMSO and ethanol that afforded small crystals used for single-crystal X-ray diffraction studies. The compound was found to crystallize in two polymorphs, depending on the crystallization conditions. One of the polymorphs (form I) crystallizes in the centrosymmetric P21/c monoclinic space group, the other (form II) crystallizes in the non-centrosymmetric, but achiral, orthorhombic space group P212121. Conformation of the molecules is similar in both polymorphs, but the network of weak intermolecular interactions determining the crystal packing is different. In form II an additional C-H⋯O bond connects molecules related by the screw-axis running parallel to the a-axis. Crystals of both polymorphs were also screened by FT-IR and Raman microscopy; a detailed analysis of the spectra and comparison with those of the isolated molecule calculated by ab-initio HF/MP2 and DFT/B3LYP methods using a correlation consistent cc-pVDZ basis set is presented. In addition, UV-vis and NMR studies were performed in solution.

  13. Spatial structures of CO2, H2O, temperature and vertical wind velocity observed by aircraft

    NASA Astrophysics Data System (ADS)

    Selbach, Christoph; Schween, Jan; Crewell, Susanne; Geiss, Heiner; Neininger, Bruno

    2010-05-01

    During the FLUXPAT campaigns in 2008 and 2009 the MetAir Dimona research aricraft performed several fligths above a patchy, agricultural dominated landscape near Juelich/Germany. The measurements are aimed to capture the variability of water vapor and CO2 and derive turbulent fluxes in the atmospheric boundary layer close to the ground. Flights took place at two main levels around 150 m and 250 m above ground. Agriculture in this region is dominated by two different crops: sugar beet and wheat. Flights were scheduled in April and August as at these times of the year strong contrasts can be found between different fields. In April sugar beet is usually just seeded whereas wheat already forms a closed canopy. In August wheat unlike sugar beat is already harvested. We analyse the correlation lengths (L*) of CO2, H2O, temperature and vertical wind velocity on flight legs. L* is the median of the power spectrum i.e. 50 percent of the variance is in structures larger than L*. For the different quantities L* shows different behaviours during the day and between different flight levels. The structure lengthscales of CO2 have a large dependency on daytime and strongly decrease during noon and afternoon. We will present some approaches to explain this behaviour.

  14. Hexagonal 2H-MoSe2 broad spectrum active photocatalyst for Cr(VI) reduction

    PubMed Central

    Chu, Haipeng; Liu, Xinjuan; Liu, Baibai; Zhu, Guang; Lei, Wenyan; Du, Huigang; Liu, Junying; Li, Jianwei; Li, Can; Sun, Changqing

    2016-01-01

    To make full use of the solar energy, exploring broad spectrum active photocatalysts has become one of the core issues for photocatalysis. Here we report a novel hexagonal 2H-MoSe2 photocatalyst with ultraviolet (UV)-visible-near infrared (NIR) light response for the first time. The results indicate that the MoSe2 displays excellent photo-absorption and photocatalytic activity in the reduction of Cr(VI) under UV and visible even NIR light irradiation. MoSe2 synthesized at pH value of 2 achieves the highest Cr(VI) reduction rates of 99%, 91% and 100% under UV, visible and NIR light irradiation, respectively, which should be attributed to its comparatively higher light absorption, efficient charge separation and transfer as well as relatively large number of surface active sites. The excellent broad spectrum active photocatalytic activity makes the MoSe2 to be a promising photocatalyst for the effective utilization of solar energy. PMID:27734974

  15. Removal of Boron in Silicon by H2-H2O Gas Mixtures

    NASA Astrophysics Data System (ADS)

    Tang, Kai; Andersson, Stefan; Nordstrand, Erlend; Tangstad, Merete

    2012-08-01

    The removal of boron in pure silicon by gas mixtures has been examined in the laboratory. Water-vapor-saturated hydrogen was used to remove boron doped in electronic-grade silicon in a vacuum frequency furnace. Boron concentrations in silicon were reduced from 52 ppm initially to 0.7 ppm and 3.4 ppm at 1450°C and 1500°C, respectively, after blowing a H2-3.2%H2O gas mixture for 180 min. The experimental results indicate that the boron removal as a function of gas-blowing time follows the law of exponential decay. After 99% of the boron is removed, approximately 90% of the silicon can be recovered. In order to better understand the gaseous refining mechanism, the quantum chemical coupled cluster with single and double excitations and a perturbative treatment of triple excitations method was used to accurately predict the enthalpy and entropy of formation of the HBO molecule. A simple refining model was then used to describe the boron refining process. This model can be used to optimize the refining efficiency.

  16. Supramolecular order and structural dynamics: A STM study of 2H-tetraphenylporphycene on Cu(111)

    SciTech Connect

    Stark, Michael; Träg, Johannes; Ditze, Stefanie; Steinrück, Hans-Peter; Marbach, Hubertus; Brenner, Wolfgang; Jux, Norbert

    2015-03-14

    The adsorption of 2H-tetraphenylporphycene (2HTPPc) on Cu(111) was investigated by scanning tunneling microscopy (STM). At medium coverages, supramolecular ordered islands are observed. The individual 2HTPPc molecules appear as two pairs of intense protrusions which are separated by an elongated depression. In the islands, the molecules are organized in rows oriented along one of the close packed Cu(111) substrate rows; the structure is stabilized by T-type interactions of the phenyl substituents of neighboring molecules. Two types of rows are observed, namely, highly ordered rows in which all molecules exhibit the same orientation, and less ordered rows in which the molecules exhibit two perpendicular orientations. Altogether, three different azimuthal orientations of 2HTPPc are observed within one domain, all of them rotated by 15° ± 1° relative to one closed packed Cu direction. The highly ordered rows are always separated by either one or two less ordered rows, with the latter structure being the thermodynamically more stable one. The situation in the islands is highly dynamic, such that molecules in the less ordered rows occasionally change orientation, also complete highly ordered rows can move. The supramolecular order and structural dynamics are discussed on the basis of the specific molecule-substrate and molecule-molecule interactions.

  17. Isomerization, Perturbations, Calculations and the S_{1} State of C_{2}H_{2}

    NASA Astrophysics Data System (ADS)

    Baraban, J. H.; Changala, P. B.; Berk, J. R. P.; Field, R. W.; Stanton, J. F.; Merer, A. J.

    2013-06-01

    Preliminary analysis of the energy region of the cis-trans isomerization transition state on the S_{1} surface of C_{2}H_{2} has revealed novel patterns and surprising perturbations, including unusually large (and high-order) anharmonicities, as well as K-staggerings of several vibrational levels. These effects complicate the analysis considerably, and require new models and calculations to account for and predict features of the observed spectra. The ˜{A}-˜{X} spectrum of acetylene has been studied both experimentally and theoretically for almost a century, and this cycle of unexpected phenomena eliciting innovative responses is found throughout its history. Especially in the last ten years, progress in understanding the S_{1} state rovibrational level structure and cis-trans isomerization has been accelerated by combining the information available from both ab initio computation and spectroscopic observations. The resulting dialogue has then frequently suggested fruitful avenues for further experiments and calculations. Current challenges and recent results in understanding the cis-trans isomerization transition state region will be discussed in this context.

  18. The safety of histamine 2 (H2) blockers in pregnancy: a meta-analysis.

    PubMed

    Gill, Simerpal Kaur; O'Brien, Lisa; Koren, Gideon

    2009-09-01

    Heartburn and acid reflux increase the severity of nausea and vomiting of pregnancy, and may lead to more serious medical conditions. The fetal safety of histamine 2 (H2) blockers, the most common antireflux medication, during pregnancy needs to be determined. The aim herein is to determine the fetal safety of H2 blockers during pregnancy through systematic review. All original research assessing the safety of H2 blockers in pregnancy was sought. Data included congenital malformations, spontaneous abortions, preterm delivery, and small for gestational age. A random-effects model combined results. With data from 2,398 exposed and 119,892 nonexposed to H2 blockers, overall odds ratio was 1.14 [0.89, 1.45]. Further analysis revealed no increased risks for spontaneous abortions, preterm delivery, and small for gestational age with odds ratios and 95% confidence intervals (CIs) of 0.62 [0.36-1.05], 1.17 [0.94, 1.147], and 0.28 [0.06, 1.22], respectively. H2 blockers can be used safely in pregnancy.

  19. ZAS: C2H2 zinc finger proteins involved in growth and development.

    PubMed

    Wu, Lai-Chu

    2002-01-01

    A ZAS gene encodes a large protein with two separate C2H2 zinc finger pairs that independently bind to specific DNA sequences, including the kappaB motif. Three paralogous mammalian genes, ZAS1, ZAS2, and ZAS3, and a related Drosophila gene, Schnurri, have been cloned and characterized. The ZAS genes encode transcriptional proteins that activate or repress the transcription of a variety of genes involved in growth, development, and metastasis. In addition, ZAS3 associates with a TNF receptor-associated factor to inhibit NF-kappaB- and JNK/ SAPK-mediated signaling of TNF-alpha. Genetic experiments show that ZAS3 deficiency leads to proliferation of cells and tumor formation in mice. The data suggest that ZAS3 is important in controlling cell growth, apoptosis, and inflammation. The potent vasoactive hormone endothelin and transcription factor AP2 gene families also each consist of three members. The ZAS, endothelin, and transcription factor AP2 genes form several linkage groups. Knowledge of the chromosomal locations of these genes provides valuable clues to the evolution of the vertebrate genome.

  20. Monascus secondary metabolites monascin and ankaflavin inhibit activation of RBL-2H3 cells.

    PubMed

    Chang, Yu-Ying; Hsu, Wei-Hsuan; Pan, Tzu-Ming

    2015-01-14

    Monascus-fermented products have been used as dietary food and traditional medicine due to their beneficial effects on circulation and digestive systems in Asia for thousands of years. Besides, monascin and ankaflavin, secondary metabolites from Monascus-fermented products, have proven anti-inflammatory and immunomodulatory effects. In previous research, monascin and ankaflavin ameliorated ovalbumin-induced airway allergic reaction often used as a type I allergy asthma model. Additionally, mast cells play critical roles in type I allergy. Therefore, RBL-2H3 cells were used as the mast cell model to determine whether the improving effects on asthma of monascin and ankaflavin came from influencing mast cells. PMA and ionomycin are common activators of mast cells because they stimulate the main signaling molecules during mast cell activation. Forty micromolar monascin and ankaflavin inhibited PMA/ionomycin-induced mast cell degranulation and TNF-α secretion through suppressing the phosphorylation of PKC and MAPK family ERK, JNK, and p38. Consequently, monascin and ankaflavin affected the activation of mast cells and may have the potential to improve type I allergy.

  1. The H2O2-H2O Hypothesis: Extremophiles Adapted to Conditions on Mars?

    NASA Astrophysics Data System (ADS)

    Houtkooper, Joop M.; Schulze-Makuch, Dirk

    2007-08-01

    The discovery of extremophiles on Earth is a sequence of discoveries of life in environments where it had been deemed impossible a few decades ago. The next frontier may be the Martian surface environment: could life have adapted to this harsh environment? What we learned from terrestrial extremophiles is that life adapts to every available niche where energy, liquid water and organic materials are available so that in principle metabolism and propagation are possible. A feasible adaptation mechanism to the Martian surface environment would be the incorporation of a high concentration of hydrogen peroxide in the intracellular fluid of organisms. The H2O2-H2O hypothesis suggests the existence of Martian organisms that have a mixture of H2O2 and H2O instead of salty water as their intracellular liquid (Houtkooper and Schulze-Makuch, 2007). The advantages are that the freezing point is low (the eutectic freezes at 56.5°C) and that the mixture is hygroscopic. This would enable the organisms to scavenge water from the atmosphere or from the adsorbed layers of water molecules on mineral grains, with H2O2 being also a source of oxygen. Moreover, below its freezing point the H2O2-H2O mixture has the tendency to supercool. Hydrogen peroxide is not unknown to biochemistry on Earth. There are organisms for which H2O2 plays a significant role: the bombardier beetle, Brachinus crepitans, produces a 25% H2O2 solution and, when attacked by a predator, mixes it with a fluid containing hydroquinone and a catalyst, which produces an audible steam explosion and noxious fumes. Another example is Acetobacter peroxidans, which uses H2O2 in its metabolism. H2O2 plays various other roles, such as the mediation of physiological responses such as cell proliferation, differentiation, and migration. Moreover, most eukaryotic cells contain an organelle, the peroxisome, which mediates the reactions involving H2O2. Therefore it is feasible that in the course of evolution, water-based organisms

  2. 4-Benzyl-6-p-tolyl­pyridazin-3(2H)-one

    PubMed Central

    Oubair, Ahmad; Daran, Jean-Claude; Fihi, Rachid; Majidi, Lhou; Azrour, Mohamed

    2009-01-01

    The title compound, C18H16N2O, is a new dihydro­pyridazin-3(2H)-one derivative synthesized in one step by condensation of α-benzyl­idene-γ-tolyl­butenolide with hydrazine. The mol­ecule is not planar; the tolyl and pyridazine rings are twisted with respect to each other making a dihedral angle of 27.35 (9)° and the benzyl ring is nearly perpendicular to the pyridazine ring with a dihedral angle of 85.24 (5)°. In the crystal structure, inversion dimers arise, being linked by pairs of N—H⋯O hydrogen bonds. Weak C—H⋯O hydrogen bonds and weak offset π–π stacking stabilize the packing. The π–π stacking occurs between the pyridazine rings of symmetry-related mol­ecules, with a centroid–centroid distance of 3.748 Å, an inter­planar distance of 3.605 Å and a slippage of 1.024 Å. PMID:21583202

  3. High pressure-temperature Raman spectroscopy of H2-H2O clathrate.

    NASA Astrophysics Data System (ADS)

    Somayazulu, Maddury; Levedahl, Alexander; Goncharov, Alexander; Mao, Ho-Kwang; Hemley, Russell

    2007-03-01

    The melting curve of the C2 clathrate H2-H2O has been determined by in-situ Raman spectroscopy measurements in an externally heated diamond anvil cell. We have determined the melting curve to a maximum pressure of 27 GPa. These are the first measurements on the melting line in this clathrate. Depending on the stoichiometry of the starting mixture of H2 and H2O, we are able to study either a mixture of C2 and H2O or C2 and H2. In either case, we were able to pinpoint the melting of the clathrate from the measurements of the molecular stretching mode (vibron) in the clathrate. In the case of C2 + Ice VII, we observe the vibron in the clathrate at a frequency higher than in pure H2 at the same pressure. We have cross-calibrated the melting temperatures using the Stokes-anti Stokes ratio of the diamond first order and Raman active TO phonon of cubic Boron Nitride. We find that the clathrate melts well above the H2 melting at all pressures studied indicating that the stabilization of this clathrate at high pressures is indeed due to interactions between the host and guest molecules.

  4. Synthesis, structural and spectroscopic studies of 2-oxoacenaphthylen-1(2H)-ylidene nicotinohydrazide.

    PubMed

    Henriques, M S C; Del Amparo, R; Pérez-Álvarez, D; Nogueira, B A; Rodríguez-Argüelles, M C; Paixão, J A

    2017-02-05

    The synthesis of a new hydrazone, 2-oxoacenaphthylen-1(2H)-ylidene nicotinohydrazide, and its structural and spectroscopic characterization is reported. The obtained powder was recrystallized from DMSO and ethanol that afforded small crystals used for single-crystal X-ray diffraction studies. The compound was found to crystallize in two polymorphs, depending on the crystallization conditions. One of the polymorphs (form I) crystallizes in the centrosymmetric P21/c monoclinic space group, the other (form II) crystallizes in the non-centrosymmetric, but achiral, orthorhombic space group P212121. Conformation of the molecules is similar in both polymorphs, but the network of weak intermolecular interactions determining the crystal packing is different. In form II an additional C-H⋯O bond connects molecules related by the screw-axis running parallel to the a-axis. Crystals of both polymorphs were also screened by FT-IR and Raman microscopy; a detailed analysis of the spectra and comparison with those of the isolated molecule calculated by ab-initio HF/MP2 and DFT/B3LYP methods using a correlation consistent cc-pVDZ basis set is presented. In addition, UV-vis and NMR studies were performed in solution.

  5. Investigating Enhanced Multiple Ionization Near Conical Intersections in C2H 2 +

    NASA Astrophysics Data System (ADS)

    McCracken, Greg; Liekhus-Schmaltz, Chelsea; Kaldun, Andreas; Bucksbaum, Phil

    2016-05-01

    Nonadiabatic behavior near conical intersections (CIs) leads to strong nonradiative mixing between different electronic states in polyatomic molecules. Recently, evidence was shown that strong field multiple ionization was significantly enhanced near the CI driving the isomerization of CHD. An interesting question is if it is a general feature that conical intersections enhance ionization rates. In this talk, we investigate the possibility of enhanced multiple ionization near the CI between the A and X states of the C2H2 cation, which is involved in the isomerization pathway to vinylidene. The cation is prepared in the A state nonlinearly using 50 fs pulses at 266 nm. The evolution of the nuclear wavepacket through the CI is then probed by a strong ultrafast pulse at 800 nm. Using a newly designed system to reconstruct the momenta of all ion fragments from a single Coulomb explosion event, we are able to see any enhancement of highly charged channels over doubly charged ones from events that are probed near the CI. This work was supported by NSF Grant PHY-0649578.

  6. Scattering matrix approach to the dissociative recombination of HCO+ and N2H+.

    PubMed

    Fonseca dos Santos, S; Douguet, N; Kokoouline, V; Orel, A E

    2014-04-28

    We present a theoretical study of the indirect dissociative recombination of linear polyatomic ions at low collisional energies. The approach is based on the computation of the scattering matrix just above the ionization threshold and enables the explicit determination of all diabatic electronic couplings responsible for dissociative recombination. In addition, we use the multi-channel quantum-defect theory to demonstrate the precision of the scattering matrix by reproducing accurately ab initio Rydberg state energies of the neutral molecule. We consider the molecular ions N2H(+) and HCO(+) as benchmark systems of astrophysical interest and improve former theoretical studies, which had repeatedly produced smaller cross sections than experimentally measured. Specifically, we demonstrate the crucial role of the previously overlooked stretching modes for linear polyatomic ions with large permanent dipole moment. The theoretical cross sections for both ions agree well with experimental data over a wide energy range. Finally, we consider the potential role of the HOC(+) isomer in the experimental cross sections of HCO(+) at energies below 10 meV.

  7. Optimization of electrode characteristics for the Br-2/H-2 redox flow cell

    SciTech Connect

    Tucker, MC; Cho, KT; Weber, AZ; Lin, GY; Nguyen, TV

    2014-10-17

    The Br-2/H-2 redox flow cell shows promise as a high-power, low-cost energy storage device. The effect of various aspects of material selection, processing, and assembly of electrodes on the operation, performance, and efficiency of the system is determined. In particular, (+) electrode thickness, cell compression, hydrogen pressure, and (-) electrode architecture are investigated. Increasing hydrogen pressure and depositing the (-) catalyst layer on the membrane instead of on the carbon paper backing layers have a large positive impact on performance, enabling a limiting current density above 2 A cm(-2) and a peak power density of 1.4 W cm(-2). Maximum energy efficiency of 79 % is achieved. In addition, the root cause of limiting-current behavior in this system is elucidated, where it is found that Br- reversibly adsorbs at the Pt (-) electrode for potentials exceeding a critical value, and the extent of Br- coverage is potential-dependent. This phenomenon limits maximum cell current density and must be addressed in system modeling and design. These findings are expected to lower system cost and enable higher efficiency.

  8. Automated extraction of backbone deuteration levels from amide H/2H mass spectrometry experiments

    PubMed Central

    Hotchko, Matthew; Anand, Ganesh S.; Komives, Elizabeth A.; Ten Eyck, Lynn F.

    2006-01-01

    A Fourier deconvolution method has been developed to explicitly determine the amount of backbone amide deuterium incorporated into protein regions or segments by hydrogen/deuterium (H/D) exchange with high-resolution mass spectrometry. Determination and analysis of the level and number of backbone amide exchanging in solution provide more information about the solvent accessibility of the protein than do previous centroid methods, which only calculate the average deuterons exchanged. After exchange, a protein is digested into peptides as a way of determining the exchange within a local area of the protein. The mass of a peptide upon deuteration is a sum of the natural isotope abundance, fast exchanging side-chain hydrogens (present in MALDI-TOF H/2H data) and backbone amide exchange. Removal of the components of the isotopic distribution due to the natural isotope abundances and the fast exchanging side-chains allows for a precise quantification of the levels of backbone amide exchange, as is shown by an example from protein kinase A. The deconvoluted results are affected by overlapping peptides or inconsistent mass envelopes, and evaluation procedures for these cases are discussed. Finally, a method for determining the back exchange corrected populations is presented, and its effect on the data is discussed under various circumstances. PMID:16501228

  9. Particle-in-Cell Simulations of Atmospheric Pressure He/2%H2O Discharges

    NASA Astrophysics Data System (ADS)

    Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.; Graves, D. B.; Gopalakrishnan, R.

    2015-09-01

    Atmospheric pressure micro-discharges in contact with liquid surfaces are of increasing interest, especially in the bio-medical field. We conduct 1D3v particle-in-cell (PIC) simulations of a voltage-driven 1 mm width atmospheric pressure He/2% H2O plasma discharge in series with an 0.5 mm width liquid H2O layer and a 1mm width quartz dielectric layer. A previously developed two-temperature hybrid global model of atmospheric pressure He/H2O discharges was used to determine the most important species and collisional reactions to use in the PIC simulations. We found that H13O6+, H5O3-, and electrons were the most prominent charged species, while most of the metastable helium He* was quenched via Penning ionization. The ion-induced secondary emission coefficient γi was assumed to be 0.15 at all surfaces. A series of simulations were conducted at 27.12 MHz with Jrf ~ 800-2200 A/m2. The H2O rotational and vibrational excitation losses were so high that electrons reached the walls at thermal temperatures. We also simulated a much lower frequency case of 50 kHz with Vrf = 10 kV. In this case, the discharge ran in a pure time-varying γ-mode. This work was supported by the Department of Energy Office of Fusion Energy Science Contract DE-SC0001939.

  10. Inclusive electron scattering from 2H,3He, and 4He

    NASA Astrophysics Data System (ADS)

    Dytman, S. A.; Bernstein, A. M.; Blomqvist, K. I.; Pavel, T. J.; Quinn, B. P.; Altemus, R.; McCarthy, J. S.; Mechtel, G. H.; Ueng, T. S.; Whitney, R. R.

    1988-08-01

    We present new results for inclusive electron scattering in 2H, 3He, and 4He in order to test the reaction mechanism for quasielastic scattering as a function of nuclear density. Radiative corrections are applied to the cross section data and Rosenbluth separations are made for three-momentum transfer (q) between 300 and 600 MeV/c. The A and q dependencies of the data are discussed for the quasielastic peak and the region between the quasielastic peak and the Δ resonance peak (dip region). Comparisons are shown between the data and models based on a quasielastic reaction mechanism. The models give a reasonable representation of the peak at q~500 MeV/c, but the longitudinal data for the helium isotopes are significantly suppressed with respect to the quasielastic predictions at q<400 MeV/c. None of the calculations predict the rapid rise with q and A in the transverse strength in the dip region seen in the data. A significant breakdown of the quasielastic picture is seen in the data as A increases from 2 to 4.

  11. 3-Phenylalkyl-2H-chromenes and -chromans as novel rhinovirus infection inhibitors.

    PubMed

    Conti, Cinzia; Proietti Monaco, Luca; Desideri, Nicoletta

    2017-02-10

    Following our studies on structure-activity relationships of anti-rhinovirus chromene and chroman derivatives, we designed and synthesized new series of 3-phenylalkyl-2H-chromenes and -chromans bearing differently sized, aliphatic linker chains between the two cycles. The cytotoxicity and the antiviral activity of the new compounds on human rhinovirus (HRV) serotype 1B and 14 infection were evaluated in HeLa cell cultures. Most of the tested compounds interfered with HRV1B multiplication in the micromolar or submicromolar concentrations while HRV14 was less susceptible. 3-[3-(4-Chlorophenyl)propyl]chroman (9c) was selected for preliminary mechanism of action studies due to its potent activity against both serotypes (IC50 of 0.48μM and 1.36μM towards HRV1B and 14, respectively) coupled with high selectivity (SI=206.18 and 73.26, respectively). Results of time of addition/removal studies suggest that 9c, similarly to related derivatives, behaves as a capsid binder interfering with some early events of the HRV1B infectious cycle.

  12. Hexagonal 2H-MoSe2 broad spectrum active photocatalyst for Cr(VI) reduction.

    PubMed

    Chu, Haipeng; Liu, Xinjuan; Liu, Baibai; Zhu, Guang; Lei, Wenyan; Du, Huigang; Liu, Junying; Li, Jianwei; Li, Can; Sun, Changqing

    2016-10-13

    To make full use of the solar energy, exploring broad spectrum active photocatalysts has become one of the core issues for photocatalysis. Here we report a novel hexagonal 2H-MoSe2 photocatalyst with ultraviolet (UV)-visible-near infrared (NIR) light response for the first time. The results indicate that the MoSe2 displays excellent photo-absorption and photocatalytic activity in the reduction of Cr(VI) under UV and visible even NIR light irradiation. MoSe2 synthesized at pH value of 2 achieves the highest Cr(VI) reduction rates of 99%, 91% and 100% under UV, visible and NIR light irradiation, respectively, which should be attributed to its comparatively higher light absorption, efficient charge separation and transfer as well as relatively large number of surface active sites. The excellent broad spectrum active photocatalytic activity makes the MoSe2 to be a promising photocatalyst for the effective utilization of solar energy.

  13. Momentum-resolved hot electron dynamics at the 2 H -MoS2 surface

    NASA Astrophysics Data System (ADS)

    Hein, P.; Stange, A.; Hanff, K.; Yang, L. X.; Rohde, G.; Rossnagel, K.; Bauer, M.

    2016-11-01

    Time- and angle-resolved photoelectron spectroscopy (trARPES) is employed to study hot electron dynamics in the conduction band of photoexcited 2 H -MoS2. Momentum-dependent rise times of up to 150 fs after near-ultraviolet photoexcitation and decay times of the order of several-hundred fs allow us to locate areas of light absorption in the conduction-band energy landscape as well as to track the relaxation of hot electrons into the lowest-energy states. The conduction-band minima are finally depopulated within ≈1 ps, although a residual population remains up to the maximum investigated pump-probe delay of 15 ps. The presence of the fast depopulation channel differs from the results of experiments of bulk MoS2 performed with all-optical methods. It conforms, however, with recent findings for monolayer MoS2. We attribute this similarity to defect and surface states being of considerable relevance for the near-surface electron dynamics of bulk MoS2, as probed in a trARPES experiment.

  14. Comparative analysis of the orientation of transmembrane peptides using solid-state (2)H- and (15)N-NMR: mobility matters.

    PubMed

    Grage, Stephan L; Strandberg, Erik; Wadhwani, Parvesh; Esteban-Martín, Santiago; Salgado, Jesús; Ulrich, Anne S

    2012-05-01

    Many solid-state nuclear magnetic resonance (NMR) approaches for membrane proteins rely on orientation-dependent parameters, from which the alignment of peptide segments in the lipid bilayer can be calculated. Molecules embedded in liquid-crystalline membranes, such as monomeric helices, are highly mobile, leading to partial averaging of the measured NMR parameters. These dynamic effects need to be taken into account to avoid misinterpretation of NMR data. Here, we compare two common NMR approaches: (2)H-NMR quadrupolar waves, and separated local field (15)N-(1)H polarization inversion spin exchange at magic angle (PISEMA) spectra, in order to identify their strengths and drawbacks for correctly determining the orientation and mobility of α-helical transmembrane peptides. We first analyzed the model peptide WLP23 in oriented dimyristoylphosphatidylcholine (DMPC) membranes and then contrasted it with published data on GWALP23 in dilauroylphosphatidylcholine (DLPC). We only obtained consistent tilt angles from the two methods when taking dynamics into account. Interestingly, the two related peptides differ fundamentally in their mobility. Although both helices adopt the same tilt in their respective bilayers (~20°), WLP23 undergoes extensive fluctuations in its azimuthal rotation angle, whereas GWALP23 is much less dynamic. Both alternative NMR methods are suitable for characterizing orientation and dynamics, yet they can be optimally used to address different aspects. PISEMA spectra immediately reveal the presence of large-amplitude rotational fluctuations, which are not directly seen by (2)H-NMR. On the other hand, PISEMA was unable to define the azimuthal rotation angle in the case of the highly dynamic WLP23, though the helix tilt could still be determined, irrespective of any dynamics parameters.

  15. The NER-related gene GTF2H5 predicts survival in high-grade serous ovarian cancer patients

    PubMed Central

    Kamieniak, Marta M.; Muñoz-Repeto, Ivan; Borrego, Salud; Hernando, Susana; Hernández-Agudo, Elena; Heredia Soto, Victoria; Márquez-Rodas, Ivan; Echarri, María José; Lacambra-Calvet, Carmen; Sáez, Raquel; Redondo, Andrés; Benítez, Javier

    2016-01-01

    Objective We aimed to evaluate the prognostic and predictive value of the nucleotide excision repair-related gene GTF2H5, which is localized at the 6q24.2-26 deletion previously reported by our group to predict longer survival of high-grade serous ovarian cancer patients. Methods In order to test if protein levels of GTF2H5 are associated with patients' outcome, we performed GTF2H5 immunohistochemical staining in 139 high-grade serous ovarian carcinomas included in tissue microarrays. Upon stratification of cases into high- and low-GTF2H5 staining categories (> and ≤ median staining, respectively) Kaplan-Meier and log-rank test were used to estimate patients’ survival and assess statistical differences. We also evaluated the association of GTF2H5 with survival at the transcriptional level by using the on-line Kaplan-Meier plotter tool, which includes gene expression and survival data of 855 high-grade serous ovarian cancer patients from 13 different datasets. Finally, we determined whether stable short hairpin RNA-mediated GTF2H5 downregulation modulates cisplatin sensitivity in the SKOV3 and COV504 cell lines by using cytotoxicity assays. Results Low expression of GTF2H5 was associated with longer 5-year survival of patients at the protein (hazard ratio [HR], 0.52; 95% CI, 0.29 to 0.93; p=0.024) and transcriptional level (HR, 0.80; 95% CI, 0.65 to 0.97; p=0.023) in high-grade serous ovarian cancer patients. We confirmed the association with 5-year overall survival (HR, 0.55; 95% CI, 0.38 to 0.78; p=0.0007) and also found an association with progression-free survival (HR, 0.72; 95% CI, 0.54 to 0.96; p=0.026) in a homogenous group of 388 high-stage (stages III-IV using the International Federation of Gynecology and Obstetrics staging system), optimally debulked high-grade serous ovarian cancer patients. GTF2H5-silencing induced a decrease of the half maximal inhibitory concentration upon cisplatin treatment in GTF2H5-silenced ovarian cancer cells. Conclusion Low

  16. 2H2O incorporation into hepatic acetyl-CoA and de novo lipogenesis as measured by Krebs cycle-mediated 2H-enrichment of glutamate and glutamine.

    PubMed

    Silva, Ana Maria; Martins, Fatima; Jones, John G; Carvalho, Rui

    2011-12-01

    Deuterated water is widely used for measuring de novo lipogenesis on the basis of quantifying lipid (2)H-enric