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Sample records for 13co c18o hcn

  1. 13CO/C18O Gradients across the Disks of Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Jiménez-Donaire, María J.; Cormier, Diane; Bigiel, Frank; Leroy, Adam K.; Gallagher, Molly; Krumholz, Mark R.; Usero, Antonio; Hughes, Annie; Kramer, Carsten; Meier, David; Murphy, Eric; Pety, Jérôme; Schinnerer, Eva; Schruba, Andreas; Schuster, Karl; Sliwa, Kazimierz; Tomicic, Neven

    2017-02-01

    We use the IRAM Large Program EMPIRE and new high-resolution ALMA data to measure 13CO(1-0)/C18O(1-0) intensity ratios across nine nearby spiral galaxies. These isotopologues of 12CO are typically optically thin across most of the area in galaxy disks, and this ratio allows us to gauge their relative abundance due to chemistry or stellar nucleosynthesis effects. Resolved 13CO/C18O gradients across normal galaxies have been rare due to the faintness of these lines. We find a mean 13CO/C18O ratio of 6.0 ± 0.9 for the central regions of our galaxies. This agrees well with results in the Milky Way, but differs from results for starburst galaxies (3.4 ± 0.9) and ultraluminous infrared galaxies (1.1 ± 0.4). In our sample, the 13CO/C18O ratio consistently increases with increasing galactocentric radius and decreases with increasing star formation rate surface density. These trends could be explained if the isotopic abundances are altered by fractionation; the sense of the trends also agrees with those expected for carbon and oxygen isotopic abundance variations due to selective enrichment by massive stars.

  2. CHIMPS: the 13CO/C18O (J = 3 → 2) Heterodyne Inner Milky Way Plane Survey

    NASA Astrophysics Data System (ADS)

    Rigby, A. J.; Moore, T. J. T.; Plume, R.; Eden, D. J.; Urquhart, J. S.; Thompson, M. A.; Mottram, J. C.; Brunt, C. M.; Butner, H. M.; Dempsey, J. T.; Gibson, S. J.; Hatchell, J.; Jenness, T.; Kuno, N.; Longmore, S. N.; Morgan, L. K.; Polychroni, D.; Thomas, H.; White, G. J.; Zhu, M.

    2016-03-01

    We present the 13CO/C18O (J = 3 → 2) Heterodyne Inner Milky Way Plane Survey (CHIMPS) which has been carried out using the Heterodyne Array Receiver Program on the 15 m James Clerk Maxwell Telescope (JCMT) in Hawaii. The high-resolution spectral survey currently covers |b| ≤ 0.5° and 28° ≲ l ≲ 46°, with an angular resolution of 15 arcsec in 0.5 km s-1 velocity channels. The spectra have a median rms of ˜0.6 K at this resolution, and for optically thin gas at an excitation temperature of 10 K, this sensitivity corresponds to column densities of NH2 ˜ 3 × 1020 cm-2 and NH2 ˜ 4 × 1021 cm-2 for 13CO and C18O, respectively. The molecular gas that CHIMPS traces is at higher column densities and is also more optically thin than in other publicly available CO surveys due to its rarer isotopologues, and thus more representative of the three-dimensional structure of the clouds. The critical density of the J = 3 → 2 transition of CO is ≳104 cm-3 at temperatures of ≤20 K, and so the higher density gas associated with star formation is well traced. These data complement other existing Galactic plane surveys, especially the JCMT Galactic Plane Survey which has similar spatial resolution and column density sensitivity, and the Herschel infrared Galactic Plane Survey. In this paper, we discuss the observations, data reduction and characteristics of the survey, presenting integrated-emission maps for the region covered. Position-velocity diagrams allow comparison with Galactic structure models of the Milky Way, and while we find good agreement with a particular four-arm model, there are some significant deviations.

  3. The JCMT Legacy Survey of the Gould Belt: mapping 13CO and C18O in Orion A

    NASA Astrophysics Data System (ADS)

    Buckle, J. V.; Davis, C. J.; Francesco, J. Di; Graves, S. F.; Nutter, D.; Richer, J. S.; Roberts, J. F.; Ward-Thompson, D.; White, G. J.; Brunt, C.; Butner, H. M.; Cavanagh, B.; Chrysostomou, A.; Curtis, E. I.; Duarte-Cabral, A.; Etxaluze, M.; Fich, M.; Friberg, P.; Friesen, R.; Fuller, G. A.; Greaves, J. S.; Hatchell, J.; Hogerheijde, M. R.; Johnstone, D.; Matthews, B.; Matthews, H.; Rawlings, J. M. C.; Sadavoy, S.; Simpson, R. J.; Tothill, N. F. H.; Tsamis, Y. G.; Viti, S.; Wouterloot, J. G. A.; Yates, J.

    2012-05-01

    The Gould Belt Legacy Survey will map star-forming regions within 500 pc, using Heterodyne Array Receiver Programme (HARP), Submillimetre Common-User Bolometer Array 2 (SCUBA-2) and Polarimeter 2 (POL-2) on the James Clerk Maxwell Telescope (JCMT). This paper describes HARP observations of the J= 3 → 2 transitions of 13CO and C18O towards Orion A. The 15 arcsec resolution observations cover 5 pc of the Orion filament, including OMC 1 (including BN-KL and Orion bar), OMC 2/3 and OMC 4, and allow a comparative study of the molecular gas properties throughout the star-forming cloud. The filament shows a velocity gradient of ˜1 km s-1 pc-1 between OMC 1, 2 and 3, and high-velocity emission is detected in both isotopologues. The Orion Nebula and Bar have the largest masses and linewidths, and dominate the mass and energetics of the high-velocity material. Compact, spatially resolved emission from CH3CN, 13CH3OH, SO, HCOOCH3, CH3CHO and CH3OCHO is detected towards the Orion Hot Core. The cloud is warm, with a median excitation temperature of ˜24 K; the Orion Bar has the highest excitation temperature gas, at >80 K. The C18O excitation temperature correlates well with the dust temperature (to within 40 per cent). The C18O emission is optically thin, and the 13CO emission is marginally optically thick; despite its high mass, OMC 1 shows the lowest opacities. A virial analysis indicates that Orion A is too massive for thermal or turbulent support, but is consistent with a model of a filamentary cloud that is threaded by helical magnetic fields. The variation of physical conditions across the cloud is reflected in the physical characteristics of the dust cores. We find similar core properties between starless and protostellar cores, but variations in core properties with position in the filament. The OMC 1 cores have the highest velocity dispersions and masses, followed by OMC 2/3 and OMC 4. The differing fragmentation of these cores may explain why OMC 1 has formed

  4. Gas Emissions in Planck Cold Dust Clumps—A Survey of the J = 1-0 Transitions of 12CO, 13CO, and C18O

    NASA Astrophysics Data System (ADS)

    Wu, Yuefang; Liu, Tie; Meng, Fanyi; Li, Di; Qin, Sheng-Li; Ju, Bing-Gang

    2012-09-01

    A survey toward 674 Planck cold clumps of the Early Cold Core Catalogue (ECC) in the J = 1-0 transitions of 12CO, 13CO, and C18O has been carried out using the Purple Mountain Observatory 13.7 m telescope. Six hundred seventy-three clumps were detected with 12CO and 13CO emission, and 68% of the sample has C18O emission. Additional velocity components were also identified. A close consistency of the three line peak velocities was revealed for the first time. Kinematic distances are given for all the velocity components, and half of the clumps are located within 0.5 and 1.5 kpc. Excitation temperatures range from 4 to 27 K, slightly larger than those of Td . Line width analysis shows that the majority of ECC clumps are low-mass clumps. Column densities N_{H_{2}} span from 1020 to 4.5 × 1022 cm-2 with an average value of (4.4 ± 3.6) × 1021 cm-2. N_{H_{2}} cumulative fraction distribution deviates from the lognormal distribution, which is attributed to optical depth. The average abundance ratio of the 13CO to C18O in these clumps is 7.0 ± 3.8, higher than the terrestrial value. Dust and gas are well coupled in 95% of the clumps. Blue profile asymmetry, red profile asymmetry, and total line asymmetry were found in less than 10% of the clumps, generally indicating that star formation is not yet developed. Ten clumps were mapped. Twelve velocity components and 22 cores were obtained. Their morphologies include extended diffuse, dense, isolated, cometary, and filament, of which the last is the majority. Twenty cores are starless, and only seven cores seem to be in a gravitationally bound state. Planck cold clumps are the most quiescent among the samples of weak red IRAS, infrared dark clouds, UC H II candidates, extended green objects, and methanol maser sources, suggesting that Planck cold clumps have expanded the horizon of cold astronomy.

  5. Properties of Dense Cores Embedded in Musca Derived from Extinction Maps and 13CO, C18O, and NH3 Emission Lines

    NASA Astrophysics Data System (ADS)

    Machaieie, Dinelsa A.; Vilas-Boas, José W.; Wuensche, Carlos A.; Racca, Germán A.; Myers, Philip C.; Hickel, Gabriel R.

    2017-02-01

    Using near-infrared data from the Two Micron All Sky Survey catalog and the Near Infrared Color Excess method, we studied the extinction distribution in five dense cores of Musca, which show visual extinction greater than 10 mag and are potential sites of star formation. We analyzed the stability in four of them, fitting their radial extinction profiles with Bonnor–Ebert isothermal spheres, and explored their properties using the J = 1–0 transition of 13CO and C18O and the J = K = 1 transition of NH3. One core is not well described by the model. The stability parameter of the fitted cores ranges from 4.5 to 5.7 and suggests that all cores are stable, including Mu13, which harbors one young stellar object (YSO), the IRAS 12322-7023 source. However, the analysis of the physical parameters shows that Mu13 tends to have larger A V, n c, and P ext than the remaining starless cores. The other physical parameters do not show any trend. It is possible that those are the main parameters to explore in active star-forming cores. Mu13 also shows the most intense emission of NH3. Its 13CO and C18O lines have double peaks, whose integrated intensity maps suggest that they are due to the superposition of clouds with different radial velocities seen in the line of sight. It is not possible to state whether these clouds are colliding and inducing star formation or are related to a physical process associated with the formation of the YSO.

  6. Photosynthetic Gas Exchange and Discrimination against 13CO2 and C18O16O in Tobacco Plants Modified by an Antisense Construct to Have Low Chloroplastic Carbonic Anhydrase.

    PubMed Central

    Williams, T. G.; Flanagan, L. B.; Coleman, J. R.

    1996-01-01

    The physiological role of chloroplastic carbonic anhydrase (CA) was examined by antisense suppression of chloroplastic CA (on average 8% of wild type) in Nicotiana tabacum. Photosynthetic gas-exchange characteristics of low-CA and wild-type plants were measured concurrently with short-term, on-line stable isotope discrimination at varying vapor pressure deficit (VPD) and light intensity. Low-CA and wild-type plants were indistinguishable in the responses of assimilation, transpiration, stomatal conductance, and intercellular CO2 concentration to changing VPD or light intensity. At saturating light intensity, low-CA plants had lower discrimination against 13CO2 than wild-type plants by 1.2 to 1.8[per mille (thousand) sign]. Consequently, tissue of the low-CA plants was higher in 13C than the control plants. It was calculated that low-CA plants had chloroplast CO2 concentrations 13 to 22 [mu]mol mol-1 lower than wild-type plants. Discrimination against C18O16O in low-CA plants was 20% of that of the wild type, confirming a role of chloroplastic CA in the mechanism of discrimination against C18O16O ([delta]C18O16O). As VPD increased, stomatal closure caused a reduction in chloroplastic C02 concentration, and since VPD and chloroplastic CO2 concentration act in opposing directions on [delta]C18O16O, no effect of VPD was seen on [delta]C18O16O. PMID:12226395

  7. A statistical study of giant molecular clouds traced by 13CO, C18O, CS, and CH3OH in the disk of NGC 1068 based on ALMA observations

    NASA Astrophysics Data System (ADS)

    Tosaki, Tomoka; Kohno, Kotaro; Harada, Nanase; Tanaka, Kunihiko; Egusa, Fumi; Izumi, Takuma; Takano, Shuro; Nakajima, Taku; Taniguchi, Akio; Tamura, Yoichi

    2017-01-01

    We present 1{^''.}4 (98 pc) resolution ALMA observations of 13CO(J = 1-0), C18O(J = 1-0), CS(J = 2-1), and CH3OH(JK = 2K-1K) molecular rotational lines in the central 1' (4.2 kpc) diameter region of NGC 1068 to study the physical and chemical properties of giant molecular clouds (GMCs) and to test whether these GMC-scale properties are linked to the larger-scale galactic environment. Using the derived 13CO cube, we have identified 187 high-significance (>8 σ) GMCs by employing the CLUMPFIND algorithm. The molecular gas masses of GMCs (M_^{13CO}), derived from the 13CO data, range from 1.8 × 104 M⊙ to 4.2 × 107 M⊙. A mass function of GMCs in NGC 1068 has been obtained for the first time at ˜100 pc resolution. We find the slope of the mass function γ = -1.25 ± 0.07 for a mass range of M_^{13CO} ≥ 105 M⊙. This is shallower than the GMCs in the disk regions of the Milky Way, M 51, and NGC 300. Further, we find that the high mass cut-off of the GMC mass function occurs at M_^{13CO} ˜ 6 × 107 M⊙, which is an order of magnitude larger than that in the nuclear bar region of M 51, indicating that the more massive clouds dominate the mass budget in NGC 1068. The observed C18O(J = 1-0)/13CO(J = 1-0) intensity ratios are found to be fairly uniform (0.27 ± 0.05) among the identified GMCs. In contrast, the CH3OH(JK = 2K-1K)/13CO(J = 1-0) ratios exhibit striking spatial variation across the disk, with the smallest values around the bar-end (<0.03), and larger ratios along the spiral arms (˜0.1-0.2). We find that GMCs with detectable methanol emission tend to have systematically larger velocity widths than those without methanol emission, suggesting that (relatively weak) shocks are responsible for the enhancement of the CH3OH/13CO ratios of GMCs in the disk of NGC 1068.

  8. Revealing the Physical Properties of Molecular Gas in Orion with a Large-scale Survey in J = 2-1 Lines of 12CO, 13CO, and C18O

    NASA Astrophysics Data System (ADS)

    Nishimura, Atsushi; Tokuda, Kazuki; Kimura, Kimihiro; Muraoka, Kazuyuki; Maezawa, Hiroyuki; Ogawa, Hideo; Dobashi, Kazuhito; Shimoikura, Tomomi; Mizuno, Akira; Fukui, Yasuo; Onishi, Toshikazu

    2015-01-01

    We present fully sampled ~3' resolution images of 12CO(J = 2-1), 13CO(J = 2-1), and C18O(J = 2-1) emission taken with the newly developed 1.85 m millimeter-submillimeter telescope over the entire area of the Orion A and B giant molecular clouds. The data were compared with J = 1-0 of the 12CO, 13CO, and C18O data taken with the Nagoya 4 m telescope and the NANTEN telescope at the same angular resolution to derive the spatial distributions of the physical properties of the molecular gas. We explore the large velocity gradient formalism to determine the gas density and temperature using line combinations of 12CO(J = 2-1), 13CO(J = 2-1), and 13CO(J = 1-0) assuming a uniform velocity gradient and abundance ratio of CO. The derived gas density is in the range of 500 to 5000 cm-3, and the derived gas temperature is mostly in the range of 20 to 50 K along the cloud ridge with a temperature gradient depending on the distance from the star forming region. We found that the high-temperature region at the cloud edge faces the H II region, indicating that the molecular gas is interacting with the stellar wind and radiation from the massive stars. In addition, we compared the derived gas properties with the young stellar objects distribution obtained with the Spitzer telescope to investigate the relationship between the gas properties and the star formation activity therein. We found that the gas density and star formation efficiency are positively well correlated, indicating that stars form effectively in the dense gas region.

  9. Large-Scale Molecular Gas Survey in 12CO, 13CO and C18O (J=2-1) with the Osaka 1.85m mm-submm Telescope

    NASA Astrophysics Data System (ADS)

    Onishi, Toshikazu; Nishimura, Atsushi; Tokuda, Kazuki; Harada, Ryohei; Dobashi, Kazuhito; Shimoikura, Tomomi; Kimura, Kimihiro; Ogawa, Hideo

    2015-08-01

    Molecular clouds are sites of star formation, and rotational transition lines of carbon monoxide (CO) have been widely used to investigate the distribution, physical properties, and kinematics to understand the star formation process in the Galaxy and external galaxies. Although J=1-0 lines of CO are powerful tools to investigate the mass of molecular content of the interstellar medium, the other transitions with different critical densities for the excitation are needed to investigate the local density and temperature, which are important to know the evolutionary status of molecular clouds. We have thus developed a new mm-submm telescope with a diameter of 1.85m installed at the Nobeyama Radio Observatory (Onishi et al. 2013). The scientific goal is to precisely reveal physical properties of molecular clouds in the Galaxy by obtaining a large-scale distribution of molecular gas, which also can be compared with large-scale observations in various wavelengths. The target frequency is ~230 GHz; simultaneous observations in J=2-1 lines of 12CO, 13CO, C18O are achieved with a beam size (HPBW) of 2.7 arcmin. Currently, about 1500 square degrees are covered including the galactic plane (L = 5° ~ 220° with |B| ≤ 1° and star forming regions (Orion, Taurus, Cygnus OB7/X, Opuichus, Aquila and so on). The observations of Orion A and B were compared with J=1-0 of the 12CO, 13CO, and C18O data at the same angular resolution to derive the spatial distributions of the physical properties of the molecular gas (Nishimura et al. 2015). We then explored the large velocity gradient formalism to determine the gas density and temperature using line combinations of 12CO(2-1), 13CO(2-1), and 13CO(1-0). We found that this line combination effectively can solve the density and temperature of the molecular cloud in this size scale, which can be compared with the star formation activity there. These J=2-1 data of the Galactic molecular clouds will be precious for the comparison with

  10. A 1.85-m mm-submm Telescope for Large-Scale Molecular Gas Surveys in 12CO, 13CO, and C18O (J = 2-1)

    NASA Astrophysics Data System (ADS)

    Onishi, Toshikazu; Nishimura, Atsushi; Ota, Yuya; Hashizume, Akio; Kojima, Yoshiharu; Minami, Akihito; Tokuda, Kazuki; Touga, Shiori; Abe, Yasuhiro; Kaiden, Masahiro; Kimura, Kimihiro; Muraoka, Kazuyuki; Maezawa, Hiroyuki; Ogawa, Hideo; Dobashi, Kazuhito; Shimoikura, Tomomi; Yonekura, Yoshinori; Asayama, Shin'ichiro; Handa, Toshihiro; Nakajima, Taku; Noguchi, Takashi; Kuno, Nario

    2013-08-01

    We have developed a new mm-submm telescope with a diameter of 1.85-m installed at the Nobeyama Radio Observatory. The scientific goal is to precisely reveal the physical properties of molecular clouds in the Milky Way Galaxy by obtaining a large-scale distribution of molecular gas, which can also be compared with large-scale observations at various wavelengths. The target frequency is ˜ 230 GHz; simultaneous observations at the molecular rotational lines of J = 2-1 of three carbon monoxide isotopes (12CO, 13CO, C18 O) are achieved with a beam size (HPBW) of 2.7'. In order to accomplish the simultaneous observations, we have developed waveguide-type sideband-separating SIS mixers to obtain spectra separately in the upper and lower side bands. A Fourier digital spectrometer with a 1 GHz bandwidth having 16384 channels is installed, and the bandwidth of the spectrometer is divided into three parts, corresponding to each of the three spectra; the IF system has been designed so as to inject these three lines into the spectrometer. A flexible observation system was created mainly in Python on Linux PCs, enabling effective OTF (On-The-Fly) scans for large-area mapping. The telescope is enclosed in a radome with a membrane covered to prevent any harmful effects of sunlight, strong wind, and precipitation in order to minimize errors in the telescope pointing, and to stabilize the receiver and the IF devices. From 2011 November, we started science operation, resulting in a large-scale survey of the Orion A/B clouds, Cygnus OB7, Galactic Plane, Taurus, and so on. We also updated the receiver system for dual-polarization observations.

  11. Analysis and theoretical modeling of 18O enriched carbon dioxide spectrum by CRDS near 1.35 μm: (II) 16O13C18O, 16O13C17O, 12C18O2, 17O12C18O, 12C17O2, 13C18O2 and 17O13C18O

    NASA Astrophysics Data System (ADS)

    Karlovets, E. V.; Campargue, A.; Kassi, S.; Tashkun, S. A.; Perevalov, V. I.

    2017-04-01

    This contribution is the second part of the analysis of the room temperature absorption spectrum of 18O enriched carbon dioxide by very high sensitivity Cavity Ring Down spectroscopy between 6977 and 7918 cm-1 (1.43-1.26 μm). Overall, more than 8600 lines belonging to 166 bands of eleven carbon dioxide isotopologues were rovibrationnally assigned. In a first part (Kassi et al. J Quant Spectrosc Radiat Transfer 187 (2017) 414-425, http://dx.doi.org/10.1016/j.jqsrt.2016.09.002), the results relative to mono-substituted isotopologues, 16O12C18O, 16O12C17O, 12C16O2 and 13C16O2, were presented. This second contribution is devoted to the multiply-substituted isotopologues or clumped isotopologues of particular importance in geochemistry: 16O13C18O, 16O13C17O, 12C18O2, 17O12C18O, 12C17O2, 13C18O2 and 17O13C18O. On the basis of the predictions of effective Hamiltonian models, a total of 3195 transitions belonging to 73 bands were rovibrationnally assigned for these seven species. Among the 73 observed bands, 55 are newly reported. All the identified bands correspond to ΔP=10 and 11 series of transitions, where P= 2V1+V2+3V3 is the polyad number (Vi are vibrational quantum numbers). The accurate spectroscopic parameters of 70 bands have been determined from the standard band-by-band analysis. Global fits of the measured line intensities of the ΔP=10 series of transitions of 17O12C18O and 16O13C18O and of the ΔP=11 series of transitions of 12C18O2, 17O12C18O, 16O13C18O and 13C18O2 were performed to determine the corresponding sets of the effective dipole moment parameters.

  12. Large and unexpected enrichment in stratospheric 16O13C18O and its meridional variation

    PubMed Central

    Yeung, Laurence Y.; Affek, Hagit P.; Hoag, Katherine J.; Guo, Weifu; Wiegel, Aaron A.; Atlas, Elliot L.; Schauffler, Sue M.; Okumura, Mitchio; Boering, Kristie A.; Eiler, John M.

    2009-01-01

    The stratospheric CO2 oxygen isotope budget is thought to be governed primarily by the O(1D)+CO2 isotope exchange reaction. However, there is increasing evidence that other important physical processes may be occurring that standard isotopic tools have been unable to identify. Measuring the distribution of the exceedingly rare CO2 isotopologue 16O13C18O, in concert with 18O and 17O abundances, provides sensitivities to these additional processes and, thus, is a valuable test of current models. We identify a large and unexpected meridional variation in stratospheric 16O13C18O, observed as proportions in the polar vortex that are higher than in any naturally derived CO2 sample to date. We show, through photochemical experiments, that lower 16O13C18O proportions observed in the midlatitudes are determined primarily by the O(1D)+CO2 isotope exchange reaction, which promotes a stochastic isotopologue distribution. In contrast, higher 16O13C18O proportions in the polar vortex show correlations with long-lived stratospheric tracer and bulk isotope abundances opposite to those observed at midlatitudes and, thus, opposite to those easily explained by O(1D)+CO2. We believe the most plausible explanation for this meridional variation is either an unrecognized isotopic fractionation associated with the mesospheric photochemistry of CO2 or temperature-dependent isotopic exchange on polar stratospheric clouds. Unraveling the ultimate source of stratospheric 16O13C18O enrichments may impose additional isotopic constraints on biosphere–atmosphere carbon exchange, biosphere productivity, and their respective responses to climate change. PMID:19564595

  13. VizieR Online Data Catalog: NGC 1333-IRAS 4A C18O, NO and O2 spectra (

    NASA Astrophysics Data System (ADS)

    Yildiz, U. A.; Acharyya, K.; Goldsmith, P. F.; van Dishoeck, E. F.; Melnick, G.; Snell, R.; Liseau, R.; Chen, J.-H.; Pagani, L.; Bergin, E.; Caselli, P.; Herbst, E.; Kristensen, L. E.; Visser, R.; Lis, D. C.; Gerin, M.

    2013-10-01

    Files contain the observations of O2, C18O 1- C18O 5-4, and NO toward NGC 1333 IRAS 4A low mass protostar. C18O 1-0 and 3-2 observations conducted in mapping mode, therefore they were convolved to 44-arcsec beam in order to compare with the Herschel-HIFI observations of molecular oxygen. (2 data files).

  14. - and Air-Broadening of 12C16O, 13C16O and 12C18O at 2.3 μm

    NASA Astrophysics Data System (ADS)

    Devi, V. Malathy; Benner, D. Chris; Smith, Mary Ann H.; Mantz, Arlan W.; Sung, Keeyoon; Brown, Linda R.

    2011-06-01

    High resolution (0.005 Cm-1) absorption spectra of CO and two of its isotopologues (13CO and C18O) were recorded between 3550 and 5250 Cm-1 using the Bruker IFS-125HR Fourier transform spectrometer (FTS) located at the Jet Propulsion Laboratory (JPL) and a specially designed and built coolable 20.38 cm long absorption cell placed within the sample compartment of the FTS. More than 50 spectra of both pure and air-broadened samples of CO, 13CO and C18O were recorded at various temperatures from 150 K to 298 K, with maximum total pressures up to ˜700 Torr. A multispectrum nonlinear least squares spectrum fitting technique was used to determine the spectral line shape parameters including speed dependence, Lorentz halfwidth coefficients, pressure-induced shift coefficients, and off-diagonal relaxation matrix element coefficients for line mixing. These line shape parameters were obtained for both self- and air-broadening, and temperature dependences of these parameters were determined where possible. As previously done in studies of CO_2, rather than retrieving individual line positions and intensities, we constrained them to their theoretical relationships, including Herman-Wallis terms, determining only the band intensities and rovibrational constants. The results are discussed and compared with values reported in the literature. K. Sung, A. W. Mantz, M. A. H. Smith, L. R. Brown, T. J. Crawford, V. Malathy Devi and D. C. Benner, JMS 262 (2010) 122-134. D. C. Benner, C. P. Rinsland, V. Malathy Devi, M. A. H. Smith and D. A. Atkins, JQSRT 53 (1995) 705-721. V. Malathy Devi, D. C. Benner, L. R. Brown, C. E. Miller and R. A. Toth, JMS 242 (2007) 90-117. Research described in this paper was performed at Connecticut College, the College of William and Mary, NASA Langley Research Center and the Jet Propulsion Laboratory, California Institute of Technology, under contracts and cooperative agreements with the National Aeronautics and Space Administration.

  15. O18O and C18O observations of ρ Ophiuchi A

    NASA Astrophysics Data System (ADS)

    Liseau, R.; Larsson, B.; Bergman, P.; Pagani, L.; Black, J. H.; Hjalmarson, Å.; Justtanont, K.

    2010-02-01

    Context. Contrary to theoretical expectation, surprisingly low concentrations of molecular oxygen, O2, have been found in the interstellar medium. Telluric absorption makes ground based O2 observations essentially impossible and observations had to be done from space. Millimetre-wave telescopes on space platforms were necessarily small, which resulted in large, several arcminutes wide, beam patterns. Observations of the (NJ = 11-10) ground state transition of O2 with the Odin satellite resulted in a ≳ 5σ detection toward the dense core ρ {Oph A}. At the frequency of the line, 119 GHz, the Odin telescope has a beam width of 10', larger than the size of the dense core. Aims: The precise nature of the emitting source and its exact location and extent are therefore unknown. The current investigation is intended to remedy this. Methods: Although the Earth's atmosphere is entirely opaque to low-lying O2 transitions, it allows ground based observations of the much rarer 16O18O in favourable conditions and at much higher angular resolution with larger telescopes. In addition, ρ {Oph A} exhibits both multiple radial velocity systems and considerable velocity gradients. Extensive mapping of the region in the proxy C18O (J = 3-2) line can be expected to help identify the O2 source on the basis of its line shape and Doppler velocity. Line opacities were determined from observations of optically thin 13C18O (J = 3-2). During several observing periods, two C18O intensity maxima in ρ {Oph A} were searched for O18O in the (21-01) line at 234 GHz with the 12 m APEX telescope. These positions are associated also with peaks in the mm-continuum emission from dust. Results: Our observations resulted in an upper limit on the integrated O18O intensity of int T*A d\\upsilon < 0.01 K km s-1 (3 σ) into the 26.6 arcsec beam. Together with the C18O data, this leads to a ratio of N(C18O)/N(O18O) > 16. Combining Odin's O2 with the present O18O observations we infer an O2 abundance 5

  16. 13C-18O isotope signatures and ‘clumped isotope’ thermometry in foraminifera and coccoliths

    NASA Astrophysics Data System (ADS)

    Tripati, Aradhna K.; Eagle, Robert A.; Thiagarajan, Nivedita; Gagnon, Alexander C.; Bauch, Henning; Halloran, Paul R.; Eiler, John M.

    2010-10-01

    Accurate constraints on past ocean temperatures and compositions are critical for documenting climate change and resolving its causes. Most proxies for temperature are not thermodynamically based, appear to be subject to biological processes, require regional calibrations, and/or are influenced by fluid composition. As a result, their interpretation becomes uncertain when they are applied in settings not necessarily resembling those in which they were empirically calibrated. Independent proxies for past temperature could provide an important means of testing and/or expanding on existing reconstructions. Here we report measurements of abundances of stable isotopologues of calcitic and aragonitic benthic and planktic foraminifera and coccoliths, relate those abundances to independently estimated growth temperatures, and discuss the possible scope of equilibrium and kinetic isotope effects. The proportions of 13C- 18O bonds in these samples exhibits a temperature dependence that is generally similar to that previously been reported for inorganic calcite and other biologically precipitated carbonate-containing minerals (apatite from fish, reptile, and mammal teeth; calcitic brachiopods and molluscs; aragonitic coral and mollusks). Most species that exhibit non-equilibrium 18O/ 16O (δ 18O) and 13C/ 12C (δ 13C) ratios are characterized by 13C- 18O bond abundances that are similar to inorganic calcite and are generally indistinguishable from apparent equilibrium, with possible exceptions among benthic foraminiferal samples from the Arctic Ocean where temperatures are near-freezing. Observed isotope ratios in biogenic carbonates can be explained if carbonate minerals generally preserve a state of ordering that reflects the extent of isotopic equilibration of the dissolved inorganic carbon species.

  17. Air-Broadened Line Parameters for the 2←0 Bands of 13C16O and 12C18O at 2.3 μm

    NASA Astrophysics Data System (ADS)

    Devi, V. Malathy; Benner, D. Chris; Smith, M. A. H.; Mantz, A. W.; Sung, K.; Brown, L. R.

    2012-06-01

    Air-broadened line shape parameters were determined for the first time in the 2←0 bands of 13C16O near 4166.8 cm-1 and 12C18O near 4159.0 cm-1. Spectra were recorded at 0.005 cm-1 resolution using a coolable absorption cell in the sample compartment of the Bruker IFS 125HR Fourier transform spectrometer at Jet Propulsion Laboratory. Gas temperatures and pressures ranged from 150 to 298 K and 20 to 700 Torr, respectively. Line parameters were determined by broad-band multispectrum least-squares fitting of the 4000-4360 cm-1 region in 16 spectra simultaneously; each set included 4 isotope-enriched pure sample scans and 12 air+CO samples (13CO or C18O, as appropriate). The air-broadened parameters measured were Lorentz half-width coefficients, their temperature dependence exponents; pressure-induced shift coefficients, their temperature dependences; and off-diagonal relaxation matrix elements. Speed dependence parameters were included to minimize the fit residuals. For both isotopologues the individual line positions and intensities were constrained to their theoretical relationships in order to obtain the rovibrational (G, B, D, and H) and band intensity parameters, including Herman-Wallis coefficients. The results for 13C16O and 12C18O are compared with those for the 12C16O 2←0 band and discussed. K. Sung, A. W. Mantz, M. A. H. Smith, et al., JMS 262 (2010) 122-134. D. C. Benner, C. P. Rinsland, V. Malathy Devi, M. A. H. Smith and D. A. Atkins, JQSRT 53 (1995) 705-721. V. Malathy Devi, D. C. Benner, L. R. Brown, C. E. Miller and R. A. Toth, JMS 242 (2007) 90-117. V. Malathy Devi, D. C. Benner, M. A. H. Smith, et al., JQSRT (2012) in press. Research described in this paper was performed at Connecticut College, the College of William and Mary, NASA Langley Research Center and the Jet Propulsion Laboratory, California Institute of Technology, under contracts and cooperative agreements with the National Aeronautics and Space Administration.

  18. LED-based Fourier transform spectroscopy of 16O12C18O and 12C18O2 in the 11,260-11,430 cm-1 range

    NASA Astrophysics Data System (ADS)

    Serdyukov, V. I.; Sinitsa, L. N.; Lugovskoi, A. A.; Borkov, Yu. G.; Tashkun, S. A.; Perevalov, V. I.

    2016-07-01

    The absorption spectrum of the 16O12C18O and 12C18O2 carbon dioxide isotopologues has been recorded in the 11,260- 11,430 cm-1 spectral range using Bruker IFS 125 HR Fourier transform spectrometer with resolution 0.05 cm-1 at temperature 297 K and path length 24 m. The 18O enriched sample of carbon dioxide at total pressure 96.5 mbar was used for these purposes. The spectrometer used LED emitter as a light source. This gave possibility to reach the minimal detectable absorption coefficient αmin~1.4×10-7 cm-1 using 23,328 scans. In the recorded spectrum we have assigned the 00051-00001 band for both 16O12C18O and 12C18O2 isotopologues using the predictions performed within the framework of the method of effective operators. The line positions and intensities of the observed bands are found. The comparison of the observed and predicted line positions and intensities is performed confirming good accuracy of the predictions. The spectroscopic parameters for the observed bands are determined.

  19. Body temperatures of modern and extinct vertebrates from 13C-18O bond abundances in bioapatite

    PubMed Central

    Eagle, Robert A.; Schauble, Edwin A.; Tripati, Aradhna K.; Tütken, Thomas; Hulbert, Richard C.; Eiler, John M.

    2010-01-01

    The stable isotope compositions of biologically precipitated apatite in bone, teeth, and scales are widely used to obtain information on the diet, behavior, and physiology of extinct organisms and to reconstruct past climate. Here we report the application of a new type of geochemical measurement to bioapatite, a “clumped-isotope” paleothermometer, based on the thermodynamically driven preference for 13C and 18O to bond with each other within carbonate ions in the bioapatite crystal lattice. This effect is dependent on temperature but, unlike conventional stable isotope paleothermometers, is independent from the isotopic composition of water from which the mineral formed. We show that the abundance of 13C-18O bonds in the carbonate component of tooth bioapatite from modern specimens decreases with increasing body temperature of the animal, following a relationship between isotope “clumping” and temperature that is statistically indistinguishable from inorganic calcite. This result is in agreement with a theoretical model of isotopic ordering in carbonate ion groups in apatite and calcite. This thermometer constrains body temperatures of bioapatite-producing organisms with an accuracy of 1–2 °C. Analyses of fossilized tooth enamel of both Pleistocene and Miocene age yielded temperatures within error of those derived from similar modern taxa. Clumped-isotope analysis of bioapatite represents a new approach in the study of the thermophysiology of extinct species, allowing the first direct measurement of their body temperatures. It will also open new avenues in the study of paleoclimate, as the measurement of clumped isotopes in phosphorites and fossils has the potential to reconstruct environmental temperatures. PMID:20498092

  20. 13C 18O clumping in speleothems: Observations from natural caves and precipitation experiments

    NASA Astrophysics Data System (ADS)

    Daëron, M.; Guo, W.; Eiler, J.; Genty, D.; Blamart, D.; Boch, R.; Drysdale, R.; Maire, R.; Wainer, K.; Zanchetta, G.

    2011-06-01

    The oxygen isotope composition of speleothems is an important proxy of continental paleoenvironments, because of its sensitivity to variations in cave temperature and drip water δ 18O. Interpreting speleothem δ 18O records in terms of absolute paleotemperatures and δ 18O values of paleo-precipitation requires quantitative separation of the effects of these two parameters, and correcting for possible kinetic isotope fractionation associated with precipitation of calcite out of thermodynamic equilibrium. Carbonate clumped-isotope thermometry, based on measurements of Δ47 (a geochemical variable reflecting the statistical overabundance of 13C 18O bonds in CO 2 evolved from phosphoric acid digestion of carbonate minerals), potentially provides a method for absolute speleothem paleotemperature reconstructions independent of drip water composition. Application of this new technique to karst records is currently limited by the scarcity of published clumped-isotope studies of modern speleothems. The only modern stalagmite reported so far in the literature yielded a lower Δ47 value than expected for equilibrium precipitation, possibly due to kinetic isotope fractionation. Here we report Δ47 values measured in natural speleothems from various cave settings, in carbonate produced by cave precipitation experiments, and in synthetic stalagmite analogs precipitated in controlled laboratory conditions designed to mimic natural cave processes. All samples yield lower Δ47 and heavier δ 18O values than predicted by experimental calibrations of thermodynamic equilibrium in inorganic calcite. The amplitudes of these isotopic disequilibria vary between samples, but there is clear correlation between the amount of Δ47 disequilibrium and that of δ 18O. Even pool carbonates believed to offer excellent conditions for equilibrium precipitation of calcite display out-of-equilibrium δ 18O and Δ47 values, probably inherited from prior degassing within the cave system. In addition

  1. A C(18)O survey of dense cores in the Taurus molecular cloud: Signatures of evolution and protostellar collapse

    NASA Technical Reports Server (NTRS)

    Zhou, Shudong; Evans, Neal J., II; Wang, Yangsheng; Peng, Ruisheng; Lo, K. Y.

    1994-01-01

    We have mapped 11 dense cores in the Taurus molecular cloud in the C(18)O J = 2 goes to 1 line at a linear resolution of 0.02 pc. The core masses derived from C(18)O range from 0.06 to 5 solar mass. Five of them have embedded infrared sources, and six do not. Dense cores without infrared sources show multiple emission peaks. In contrast, dense cores with infrared sources have a single peak and smaller sizes. The cores with infrared sources have line widths that are 2-3 times the value expected from correlations found in previous surveys. This enhancement may be accounted for by models of gravitational collapse. The data are consistent with the idea that dense cores evolve first toward smaller sizes and smaller line width along the line width-size relation, and then toward larger line width and constant or smaller sizes as an infrared source becomes observable. A good collapse candidate, L1527, is identified based on the shapes of C(18)O and H2CO lines.

  2. Quantitative analysis of two-neutron correlations in the 12C(18O,16O)14C reaction

    NASA Astrophysics Data System (ADS)

    Cavallaro, M.; Cappuzzello, F.; Bondì, M.; Carbone, D.; Garcia, V. N.; Gargano, A.; Lenzi, S. M.; Lubian, J.; Agodi, C.; Azaiez, F.; De Napoli, M.; Foti, A.; Franchoo, S.; Linares, R.; Nicolosi, D.; Niikura, M.; Scarpaci, J. A.; Tropea, S.

    2013-11-01

    The 12C(18O,16O)14C and 12,13C(18O,17O)13,14C reactions are studied at 84 MeV. Mass distributions and energy spectra of the ejectiles are measured, indicating the selectivity of these reactions to populate two- and one-neutron configurations in the states of the residual nucleus, respectively. The measured absolute cross-section angular distributions are analyzed by exact finite range coupled reaction channel calculations based on a parameter free double-folding optical potential. The form factors for the (18O,16O) reaction are extracted within an extreme cluster and independent particles scheme with shell-model-derived coupling strengths. The results show that the measured cross sections are accurately described for the first time without the need for any arbitrary scaling factor. The (18O,16O) reaction is thus found to be a powerful tool for quantitative spectroscopic studies of pair configurations in nuclear states.

  3. Biomolecules from HCN

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Wos, J. D.; Ryan, T. J.; Lobo, A. P.; Donner, D. B.

    1974-01-01

    It has been suggested by Sanchez et al. (1967) that HCN might have been one of the more important precursors of biological molecules on the primitive earth. Studies were conducted to determine the mechanisms involved in HCN oligomerizations in dilute aqueous solutions and to identify the compounds which are produced in these oligomerization mixtures. Indirect evidence for the formation of cyanate was obtained along with direct evidence for the formation of citrulline, aspartic acid, and orotic acid.

  4. Adenine formation without HCN.

    PubMed

    Merz, Kenneth M; Aguiar, Eduardo C; da Silva, Joao Bosco P

    2014-05-22

    From a historic point of view adenine was always presumed to be the product of HCN pentamerization. In this work a new mechanism for adenine synthesis in the gas phase without HCN is proposed. The concept of retrosynthetic analysis was employed to create a tautomer of adenine, which can be reached from previously observed interstellar molecules C3NH and HNCNH and its isomer H2NCN. MP2/6-311++G(2d,2p) calculations were performed to calculate the Gibbs free energy of the minimum and the transition state (TS) structures involved in the six step mechanism. This new mechanism requires a smaller number of steps, the reaction energy is twice as exergonic, and the rate determining TS is lower in energy than the corresponding ones proposed elsewhere in the literature.

  5. Intensity calculations of HCN molecules

    NASA Astrophysics Data System (ADS)

    Yasmin, Kausar

    2006-10-01

    Accurate spectroscopic data of HCN are required for many astronomical calculations and modeling. HCN molecules are present in the atmosphere of carbon stars and in galactic centers. Ro-vibrational energy levels and intensity calculations were carried out using the full coupled cluster model and radau coordinates. Accurate ab initio calculated potential energy surface^1 and dipole moment surface^2 were used for computation. The computed values were compared with Hitran^99.^

  6. An ALMA Survey of DCN/H13CN and DCO+/H13CO+ in Protoplanetary Disks

    NASA Astrophysics Data System (ADS)

    Huang, Jane; Öberg, Karin I.; Qi, Chunhua; Aikawa, Yuri; Andrews, Sean M.; Furuya, Kenji; Guzmán, Viviana V.; Loomis, Ryan A.; van Dishoeck, Ewine F.; Wilner, David J.

    2017-02-01

    The deuterium enrichment of molecules is sensitive to their formation environment. Constraining patterns of deuterium chemistry in protoplanetary disks is therefore useful for probing how material is inherited or reprocessed throughout the stages of star and planet formation. We present ALMA observations at ∼0.″6 resolution of DCO+, H13CO+, DCN, and H13CN in the full disks around T Tauri stars AS 209 and IM Lup, in the transition disks around T Tauri stars V4046 Sgr and LkCa 15, and in the full disks around Herbig Ae stars MWC 480 and HD 163296. We also present ALMA observations of HCN in the IM Lup disk. DCN, DCO+, and H13CO+ are detected in all disks, and H13CN in all but the IM Lup disk. We find efficient deuterium fractionation for the sample, with estimates of disk-averaged DCO+/HCO+ and DCN/HCN abundance ratios ranging from ∼0.02–0.06 and ∼0.005–0.08, respectively, which is comparable to values reported for other interstellar environments. The relative distributions of DCN and DCO+ vary between disks, suggesting that multiple formation pathways may be needed to explain the diverse emission morphologies. In addition, gaps and rings observed in both H13CO+ and DCO+ emission provide new evidence that DCO+ bears a complex relationship with the location of the midplane CO snowline.

  7. A paleothermometer based on abundances of 13C-18O bonds in bioapatite: Calibration and reconstruction of the body temperatures of extinct Cenozoic mammals and Mesozoic dinosaurs

    NASA Astrophysics Data System (ADS)

    Eagle, R.; Schauble, E. A.; Tripati, A. K.; Fricke, H. C.; Tuetken, T.; Eiler, J. M.

    2009-12-01

    The stable isotope compositions of biologically precipitated apatite in bone, teeth, and scales are widely used to obtain information on the diet, behavior, and physiology of extinct organisms, and to reconstruct past climate in terrestrial and marine settings. Here we report the application of a new type of geochemical measurement to bioapatite, a ‘clumped isotope’ thermometer based on the thermodynamically driven preference for 13C and 18O to bond with each other within carbonate ions in the crystal lattice of apatite. This effect is dependent on temperature but unlike conventional stable isotope paleotemperature proxies, is independent from the isotopic composition of water from which the mineral formed. We show that the abundance of 13C-18O bonds in the carbonate component of apatite from modern teeth is proportional to the body temperature of the organism, with an accuracy of 1-2oC, and that the empirical calibration is supported by a theoretical model of isotopic ordering. We also report initial paleothermometry results from analyses of Cenozoic fossil mammal teeth and Mesozoic dinosaur teeth. Therefore, clumped isotope analysis of bioapatite represents a new approach in the study of the physiology of extinct species by allowing the first relatively assumption-free measurement of their body temperatures. It will also open new avenues in the study of paleoclimate, as the measurements of clumped isotopes in apatite from fossils, such as conodonts and brachiopods, as well as phosphorites, have the potential to record environmental temperatures.

  8. The 12CO/13CO ratio in turbulent molecular clouds

    NASA Astrophysics Data System (ADS)

    Szűcs, László; Glover, Simon C. O.; Klessen, Ralf S.

    2014-12-01

    The 13CO molecule is often used as a column density tracer in regions where the 12CO emission saturates. The 13CO column density is then related to that of 12CO by a uniform isotopic ratio. A similar approximation is frequently used when deriving 13CO emission maps from numerical simulations of molecular clouds. To test this assumption, we calculate the 12CO/13CO ratio self-consistently, taking the isotope-selective photodissociation and the chemical fractionation of CO into account. We model the coupled chemical, thermal and dynamical evolution and the emergent 13CO emission of isolated, starless molecular clouds in various environments. Selective photodissociation has a minimal effect on the ratio, while the chemical fractionation causes a factor of 2-3 decrease at intermediate cloud depths. The variation correlates with both the 12CO and the 13CO column densities. Neglecting the depth dependence results in ≤60 per cent error in 12CO column densities derived from 13CO. The same assumption causes ≤50 per cent disparity in the 13CO emission derived from simulated clouds. We show that the discrepancies can be corrected by a fitting formula. The formula is consistent with millimetre-wavelength isotopic ratio measurements of dense molecular clouds, but underestimates the ratios from the ultraviolet absorption of diffuse regions.

  9. Morphology and kinematics of the gas envelope of protostar L1527 as obtained from ALMA observations of the C18O(2-1) line emission

    NASA Astrophysics Data System (ADS)

    Tuan-Anh, P.; Nhung, P. T.; Hoai, D. T.; Diep, P. N.; Phuong, N. T.; Thao, N. T.; Darriulat, P.

    2016-12-01

    Using Atacama Large Millimeter/submillimeter Array observations of the C18O(2-1) line emission of the gas envelope of protostar L1527, we have reconstructed its morphology and kinematics under the assumption of axisymmetry about the west-east axis. The main original contribution to our understanding of the formation process of L1527 is the presentation of a simple 3D parametrization based solely on regions that are not dominated by absorption. In the explored range (˜0.7 to 5 arcsec from the star), the model reproduces observations better than earlier attempts. The main results include: a measurement of the rotation velocity that confirms its evolution to Keplerian towards short distances; a measurement of the mean in-fall velocity, 0.43 ± 0.10 km s-1, lower than free-fall velocity, with no evidence for the significant r-dependence suggested by an earlier analysis; a measurement of the central mass, 0.23 ± 0.06 M⊙ within a distance of 1.5 arcsec from the star, in agreement with earlier estimates obtained from a different range of distances; evidence for a strong disc plane depression of the in-falling flux resulting in an X-shaped flow possibly caused by the freeze-out of CO molecules on dust grains; a measurement of the accretion rate, 3.5 ± 1.0 10-7 M⊙ yr-1at a distance of 1 arcsec (140 au) from the star; evidence for a 10° tilt of the symmetry plane of the envelope about the line of sight, cancelling below ˜3 arcsec from the star, but matching infrared observations and being also apparent on the sky map of the mean Doppler velocity.

  10. FT-IR spectra of 18O-, and 13C-enriched CO2 in the ν3 region: High accuracy frequency calibration and spectroscopic constants for 16O12C18O, 18O12C18O, and 16O13C16O

    NASA Astrophysics Data System (ADS)

    Elliott, Ben M.; Sung, Keeyoon; Miller, Charles E.

    2015-06-01

    In this report, we extend our Fourier transform infrared (FT-IR) spectroscopy measurements of CO2 in the ν3 region (2200-2450 cm-1, 65-75 THz) to the 18O-, and 13C-substituted isotopologues, using the JPL Bruker IFS-125HR Fourier Transform Spectrometer (JPL-FTS). High quality (S/N ∼ 2000) spectra were obtained separately for each of the 18O-, and 13C-isotopically enriched samples. The absolute wavenumber accuracies were better than 3 × 10-6 cm-1 (∼100 kHz) for strong, isolated transitions, calibrated against the highest accuracy reported CO and 16O12C16O (626) frequency measurements. The JPL-FTS performance and calibration procedure is shown to be reliable and consistent, achievable through vigorous maintenance of the optical alignment and regular monitoring of its instrumental line shape function. Effective spectroscopic constant fits of the 00011 ← 00001 fundamental bands for 16O12C18O (628), 18O12C18O (828), and 16O13C16O (636) were obtained with RMS residuals of 2.9 × 10-6 cm-1, 2.8 × 10-6 cm-1, and 2.9 × 10-6 cm-1, respectively. The observed bands encompassed 79 lines over the Jmax range of P67/R67, 47 lines over P70/R62, and 60 lines over P70/R70 for 628, 828, and 636, respectively. These results complement our recent work on the 17O-enriched isotopologues (Elliott et al., 2014), providing additional high-quality frequency measurements for atmospheric remote sensing applications.

  11. Glacial- interglacial temperature change based on 13C18O carbonate bond with in fish bone otoliths from Red Sea sediments

    NASA Astrophysics Data System (ADS)

    Ghosh, P.; Eiler, J.; Feeney, R.

    2006-12-01

    Determining the past record of temperature and salinity of ocean surface waters is essential for understanding past changes in climate, such as those which occur across glacial-interglacial transitions. As a useful proxy, the clumped isotope of CO2 in carbonate (13C18O16O or ?47) from inorganic precipitation experiment has been shown to reflect surface temperature with high degree of confidence (Ghosh et al., 2006). The last glacial cycle was characterized by climate fluctuations, but the extent of any associated changes in global sea level (or, equivalently, ice volume) remains elusive. High stands of sea level can be reconstructed from dated fossil and isotopic analyses of foraminifera and terapods, and these data are complemented by a compilation of global sea-level estimates based on deep-sea oxygen isotope ratios. Salinity derived from the records of oxygen isotopes ratios, however, contains uncertainties due to lack of information about the sea surface temperature change. Here we used combination of clumped isotopes technique and oxygen isotope measurement from fish otoliths (Myctophiformes; lanternfishes) extracted from two piston cores (Ku et al., 1969) (CH-154 and CH-153) to understand the temperature evolution and salinity variation of Red Sea water (300-800m) during the last 70 k.y. We analyzed well preserved unaltered otoliths from 7 different stratigraphic horizons from sediment core CH-154. Our preliminary observation suggests ~20 degree Celsius differences in sea water temperatures between glacial and interglacial time. We showed that the region has experienced fluctuation in climatic and tectonic processes during glacial interglacial time and the otoliths developed within the fishes captured the information about temperature change and salinity variation. Our results indicate a drop in temperature and restricted exchange of water with the open ocean during glaciations. The Red Sea environment was also highly saline even during the interglacial event

  12. 13. CO'S STATEROOM (CABIN'S QUARTERS), PORT EXTERIOR. NOTE PORTHOLE AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. CO'S STATEROOM (CABIN'S QUARTERS), PORT EXTERIOR. NOTE PORTHOLE AND WOODEN FRAME WINDOWS. - U.S. Coast Guard Cutter WHITE LUPINE, U.S. Coast Guard Station Rockland, east end of Tillson Avenue, Rockland, Knox County, ME

  13. Dysfunctional HCN ion channels in neurological diseases.

    PubMed

    DiFrancesco, Jacopo C; DiFrancesco, Dario

    2015-01-01

    Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed as four different isoforms (HCN1-4) in the heart and in the central and peripheral nervous systems. HCN channels are activated by membrane hyperpolarization at voltages close to resting membrane potentials and carry the hyperpolarization-activated current, dubbed If (funny current) in heart and Ih in neurons. HCN channels contribute in several ways to neuronal activity and are responsible for many important cellular functions, including cellular excitability, generation, and modulation of rhythmic activity, dendritic integration, transmission of synaptic potentials, and plasticity phenomena. Because of their role, defective HCN channels are natural candidates in the search for potential causes of neurological disorders in humans. Several data, including growing evidence that some forms of epilepsy are associated with HCN mutations, support the notion of an involvement of dysfunctional HCN channels in different experimental models of the disease. Additionally, some anti-epileptic drugs are known to modify the activity of the Ih current. HCN channels are widely expressed in the peripheral nervous system and recent evidence has highlighted the importance of the HCN2 isoform in the transmission of pain. HCN channels are also present in the midbrain system, where they finely regulate the activity of dopaminergic neurons, and a potential role of these channels in the pathogenesis of Parkinson's disease has recently emerged. The function of HCN channels is regulated by specific accessory proteins, which control the correct expression and modulation of the neuronal Ih current. Alteration of these proteins can severely interfere with the physiological channel function, potentially predisposing to pathological conditions. In this review we address the present knowledge of the association between HCN dysfunctions and neurological diseases, including clinical, genetic, and physiopathological

  14. HCN channels: function and clinical implications.

    PubMed

    Benarroch, Eduardo E

    2013-01-15

    The hyperpolarization-activated cyclic nucleotide-gated (HCN) channels belong to the superfamily of pore-loop cation channels. In mammals, the HCN channel family comprises 4 members (HCN1-4) that are expressed in heart and nervous system. HCN channels are activated by membrane hyperpolarization, are permeable to Na+ and K+, and are constitutively open at voltages near the resting membrane potential. In many cases, activation is facilitated by direct interaction with cyclic nucleotides, particularly cyclic adenosine monophosphate (cAMP). The cation current through HCN channels is known as I(h); opening of HCN channels elicits membrane depolarization toward threshold for action potential generation, and reduces membrane resistance and thus the magnitude of excitatory and inhibitory postsynaptic potentials. HCN channels have a major role in controlling neuronal excitability, dendritic integration of synaptic potentials, synaptic transmission, and rhythmic oscillatory activity in individual neurons and neuronal networks. These channels participate in mechanisms of synaptic plasticity and memory, thalamocortical rhythms, and somatic sensation. Experimental evidence indicates that HCN channels may also contribute to mechanisms of epilepsy and pain. The physiologic functions of HCN channels and their implications for neurologic disorders have been recently reviewed.(1-10).

  15. Cortical HCN channels: function, trafficking and plasticity

    PubMed Central

    Shah, Mala M

    2014-01-01

    The hyperpolarization-activated cyclic nucleotide-gated (HCN) channels belong to the superfamily of voltage-gated potassium ion channels. They are, however, activated by hyperpolarizing potentials and are permeable to cations. Four HCN subunits have been cloned, of which HCN1 and HCN2 subunits are predominantly expressed in the cortex. These subunits are principally located in pyramidal cell dendrites, although they are also found at lower concentrations in the somata of pyramidal neurons as well as other neuron subtypes. HCN channels are actively trafficked to dendrites by binding to the chaperone protein TRIP8b. Somato-dendritic HCN channels in pyramidal neurons modulate spike firing and synaptic potential integration by influencing the membrane resistance and resting membrane potential. Intriguingly, HCN channels are present in certain cortical axons and synaptic terminals too. Here, they regulate synaptic transmission but the underlying mechanisms appear to vary considerably amongst different synaptic terminals. In conclusion, HCN channels are expressed in multiple neuronal subcellular compartments in the cortex, where they have a diverse and complex effect on neuronal excitability. PMID:24756635

  16. HCN1 channels significantly shape retinal photoresponses.

    PubMed

    Tanimoto, Naoyuki; Brombas, Arne; Müller, Frank; Seeliger, Mathias W

    2012-01-01

    In this chapter, the impact of HCN1 channels on the retinal functional properties was presented. HCN1 channel loss led to an intensity-dependent prolongation of the rod system response, in agreement with the threshold mechanism of activation of the channel. Rod outer segment functionality was not altered, supporting the main site of action in the inner segment. Fixed-intensity variable frequency flicker series showed a regular amplitude decline near threshold and a reduced flicker fusion frequency above threshold due to increased waveform width. It was suggested that shortening and shaping of light responses by activation of HCN1 is an important step at least in the scotopic pathways. The retina of HCN1 knockout animals provides a valuable system with which to study the role of HCN1 in the shaping and processing of retinal light responses especially to repetitive stimulation.

  17. Immunolocalization of hyperpolarization-activated cationic HCN1 and HCN3 channels in the rat nephron: regulation of HCN3 by potassium diets.

    PubMed

    López-González, Zinaeli; Ayala-Aguilera, Cosete; Martinez-Morales, Flavio; Galicia-Cruz, Othir; Salvador-Hernández, Carolina; Pedraza-Chaverri, José; Medeiros, Mara; Hernández, Ana Maria; Escobar, Laura I

    2016-01-01

    Hyperpolarization-activated cationic and cyclic nucleotide-gated channels (HCN) comprise four homologous subunits (HCN1-HCN4). HCN channels are found in excitable and non-excitable tissues in mammals. We have previously shown that HCN2 may transport ammonium (NH4 (+)), besides sodium (Na(+)), in the rat distal nephron. In the present work, we identified HCN1 and HCN3 in the proximal tubule (PT) and HCN3 in the thick ascending limb of Henle (TALH) of the rat kidney. Immunoblot assays detected HCN1 (130 kDa) and HCN3 (90 KDa) and their truncated proteins C-terminal HCN1 (93 KDa) and N-terminal HCN3 (65 KDa) in enriched plasma membranes from cortex (CX) and outer medulla (OM), as well as in brush-border membrane vesicles. Immunofluorescence assays confirmed apical localization of HCN1 and HCN3 in the PT. HCN3 was also found at the basolateral membrane of TALH. We evaluated chronic changes in mineral dietary on HCN3 protein abundance. Animals were fed with three different diets: sodium-deficient (SD) diet, potassium-deficient (KD) diet, and high-potassium (HK) diet. Up-regulation of HCN3 was observed in OM by KD and in CX and OM by HK; the opposite effect occurred with the N-terminal truncated HCN3 in CX (KD) and OM (HK). SD diet did not produce any change. Since HCN channels activate with membrane hyperpolarization, our results suggest that HCN channels may play a role in the Na(+)-K(+)-ATPase activity, contributing to Na(+), K(+), and acid-base homeostasis in the rat kidney.

  18. The excitation of HCN and HCO{sup +} in the galactic center circumnuclear disk

    SciTech Connect

    Mills, E. A. C.; Güsten, R.; Requena-Torres, M. A.; Morris, M. R.

    2013-12-10

    We present new observations of HCN and HCO{sup +} in the circumnuclear disk (CND) of the Galaxy, which we obtained with the Atacama Pathfinder Experiment telescope. We mapped emission in rotational lines of HCN J = 3-2, 4-3, and 8-7, as well as of HCO{sup +} J = 3-2, 4-3, and 9-8. We also present spectra of H{sup 13}CN J = 3-2 and 4-3 as well as H{sup 13}CO{sup +} J = 3-2 and 4-3 toward four positions in the CND. Using the intensities of all of these lines, we present an excitation analysis for each molecule using the non-LTE radiative transfer code RADEX. The HCN line intensities toward the northern emission peak of the CND yield log densities (cm{sup –3}) of 5.6{sub −0.6}{sup +0.6}, consistent with those measured with HCO{sup +} as well as with densities recently reported for this region from an excitation analysis of highly excited lines of CO. These densities are too low for the gas to be tidally stable. The HCN line intensities toward the CND's southern emission peak yield log densities of 6.5{sub −0.7}{sup +0.5}, higher than densities determined for this part of the CND with CO (although the densities measured with HCO{sup +}, log [n] = 5.6{sub −0.2}{sup +0.2}, are more consistent with the CO-derived densities). We investigate whether the higher densities we infer from HCN are affected by midinfrared radiative excitation of this molecule through its 14 μm rovibrational transitions. We find that radiative excitation is important for at least one clump in the CND, where we additionally detect the J = 4-3, v {sub 2} = 1 vibrationally excited transition of HCN, which is excited by dust temperatures of ≳125-150 K. If this hot dust is present elsewhere in the CND, it could lower our inferred densities, potentially bringing the HCN-derived densities for the southern part of the CND into agreement with those measured using HCO{sup +} and CO. Additional sensitive, high-resolution submillimeter observations, as well as midinfrared observations, would be

  19. The Excitation of HCN and HCO+ in the Galactic Center Circumnuclear Disk

    NASA Astrophysics Data System (ADS)

    Mills, E. A. C.; Güsten, R.; Requena-Torres, M. A.; Morris, M. R.

    2013-12-01

    We present new observations of HCN and HCO+ in the circumnuclear disk (CND) of the Galaxy, which we obtained with the Atacama Pathfinder Experiment telescope. We mapped emission in rotational lines of HCN J = 3-2, 4-3, and 8-7, as well as of HCO+ J = 3-2, 4-3, and 9-8. We also present spectra of H13CN J = 3-2 and 4-3 as well as H13CO+ J = 3-2 and 4-3 toward four positions in the CND. Using the intensities of all of these lines, we present an excitation analysis for each molecule using the non-LTE radiative transfer code RADEX. The HCN line intensities toward the northern emission peak of the CND yield log densities (cm-3) of 5.6^{+0.6}_{-0.6}, consistent with those measured with HCO+ as well as with densities recently reported for this region from an excitation analysis of highly excited lines of CO. These densities are too low for the gas to be tidally stable. The HCN line intensities toward the CND's southern emission peak yield log densities of 6.5^{+0.5}_{-0.7}, higher than densities determined for this part of the CND with CO (although the densities measured with HCO+, log [n] = 5.6^{+0.2}_{-0.2}, are more consistent with the CO-derived densities). We investigate whether the higher densities we infer from HCN are affected by midinfrared radiative excitation of this molecule through its 14 μm rovibrational transitions. We find that radiative excitation is important for at least one clump in the CND, where we additionally detect the J = 4-3, v 2 = 1 vibrationally excited transition of HCN, which is excited by dust temperatures of gsim125-150 K. If this hot dust is present elsewhere in the CND, it could lower our inferred densities, potentially bringing the HCN-derived densities for the southern part of the CND into agreement with those measured using HCO+ and CO. Additional sensitive, high-resolution submillimeter observations, as well as midinfrared observations, would be useful to assess the importance of the radiative excitation of HCN in this environment.

  20. Health Code Number (HCN) Development Procedure

    SciTech Connect

    Petrocchi, Rocky; Craig, Douglas K.; Bond, Jayne-Anne; Trott, Donna M.; Yu, Xiao-Ying

    2013-09-01

    This report provides the detailed description of health code numbers (HCNs) and the procedure of how each HCN is assigned. It contains many guidelines and rationales of HCNs. HCNs are used in the chemical mixture methodology (CMM), a method recommended by the department of energy (DOE) for assessing health effects as a result of exposures to airborne aerosols in an emergency. The procedure is a useful tool for proficient HCN code developers. Intense training and quality assurance with qualified HCN developers are required before an individual comprehends the procedure to develop HCNs for DOE.

  1. HCN and chromophore formation on Jupiter

    NASA Technical Reports Server (NTRS)

    Ferris, James P.; Ishikawa, Yoji

    1987-01-01

    Reaction paths for the formation of HCN and chromophores on Jupiter are suggested. The reactions involve photolysis of ammonia/acetylene mixtures. Experimental data supporting these pathways are reported.

  2. HNC, HCN and CN in Seyfert galaxies

    NASA Astrophysics Data System (ADS)

    Pérez-Beaupuits, J. P.; Aalto, S.; Gerebro, H.

    2007-12-01

    Aims:Bright HNC 1-0 emission, rivalling that of HCN 1-0, has been found towards several Seyfert galaxies. This is unexpected since traditionally HNC is a tracer of cold (10 K) gas, and the molecular gas of luminous galaxies like Seyferts is thought to have bulk kinetic temperatures surpassing 50 K. There are four possible explanations for the bright HNC: (a) large masses of hidden cold gas; (b) chemistry dominated by ion-neutral reactions; (c) chemistry dominated by X-ray radiation; and (d) HNC enhanced through mid-IR pumping. In this work, we distinguish the cause of the bright HNC and to model the physical conditions of the HNC and HCN emitting gas. Methods: We have used SEST, JCMT and IRAM 30 m telescopes to observe HNC 3-2 and HCN 3-2 line emission in a selection of 5 HNC-luminous Seyfert galaxies. We estimate and discuss the excitation conditions of HCN and HNC in NGC 1068, NGC 3079, NGC 2623 and NGC 7469, based on the observed 3-2/1-0 line intensity ratios. We also observed CN 1-0 and 2-1 emission and discuss its role in photon and X-ray dominated regions. Results: HNC 3-2 was detected in 3 galaxies (NGC 3079, NGC 1068 and NGC 2623). Not detected in NGC 7469. HCN 3-2 was detected in NGC 3079, NGC 1068 and NGC 1365, it was not detected in NGC 2623. The HCN 3-2/1-0 ratio is lower than 0.3 only in NGC 3079, whereas the HNC 3-2/1-0 ratio is larger than 0.3 only in NGC 2623. The HCN/HNC 1-0 and 3-2 line ratios are larger than unity in all the galaxies. The HCN/HNC 3-2 line ratio is lower than unity only in NGC 2623, which makes it comparable to galaxies like Arp 220, Mrk 231 and NGC 4418. Conclusions: We conclude that in three of the galaxies the HNC emissions emerge from gas of densities n ⪉ 105 cm-3, where the chemistry is dominated by ion-neutral reactions. The line shapes observed in NGC 1365 and NGC 3079 show that these galaxies have no circumnuclear disk. In NGC 1068 the emission of HNC emerges from lower (<105 cm-3) density gas than HCN (>105 cm-3

  3. HCN Channels Modulators: The Need for Selectivity

    PubMed Central

    Romanelli, Maria Novella; Sartiani, Laura; Masi, Alessio; Mannaioni, Guido; Manetti, Dina; Mugelli, Alessandro; Cerbai, Elisabetta

    2016-01-01

    Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels, the molecular correlate of the hyperpolarization-activated current (If/Ih), are membrane proteins which play an important role in several physiological processes and various pathological conditions. In the Sino Atrial Node (SAN) HCN4 is the target of ivabradine, a bradycardic agent that is, at the moment, the only drug which specifically blocks If. Nevertheless, several other pharmacological agents have been shown to modulate HCN channels, a property that may contribute to their therapeutic activity and/or to their side effects. HCN channels are considered potential targets for developing drugs to treat several important pathologies, but a major issue in this field is the discovery of isoform-selective compounds, owing to the wide distribution of these proteins into the central and peripheral nervous systems, heart and other peripheral tissues. This survey is focused on the compounds that have been shown, or have been designed, to interact with HCN channels and on their binding sites, with the aim to summarize current knowledge and possibly to unveil useful information to design new potent and selective modulators. PMID:26975509

  4. The HNC/HCN ratio in comets

    NASA Technical Reports Server (NTRS)

    Irvine, W. M.; Dickens, J. E.; Lovell, A. J.; Schloerb, F. P.; Senay, M.; Bergin, E. A.; Jewitt, D.; Matthews, H. E.; Ferris, J. P. (Principal Investigator)

    1997-01-01

    The abundance ratio of the isomers HCN and HNC has been investigated in comet Hale-Bopp (C/1995 O1) through observations of the J = 4-3 rotational transitions of both species for heliocentric distances 0.93 < r < 3 AU, both pre- and post-perihelion. After correcting for the optical depth of the stronger HCN line, we find that the column density ratio of HNC/HCN in our telescope beam increases significantly as the comet approaches the Sun. We compare this behavior to that predicted from an ion-molecule chemical model and conclude that the HNC is produced in significant measure by chemical processes in the coma; i.e., for comet Hale-Bopp, HNC is not a parent molecule sublimating from the nucleus.

  5. Microscopic cluster model for the description of new experimental results on the 13C(18O,16O) 15C two-neutron transfer at 84 MeV incident energy

    NASA Astrophysics Data System (ADS)

    Carbone, D.; Ferreira, J. L.; Cappuzzello, F.; Lubian, J.; Agodi, C.; Cavallaro, M.; Foti, A.; Gargano, A.; Lenzi, S. M.; Linares, R.; Santagati, G.

    2017-03-01

    The 13C(18O,16O) 15C reaction is studied at 84 MeV incident energy. Excitation energy spectra and absolute cross-section angular distributions for the strongest transitions are measured with good energy and angular resolutions. Strong selectivity for two-neutron configurations in the states of the residual nucleus is found. The measured cross-section angular distributions are analyzed by exact finite-range coupled reaction channel calculations. The two-particle wave functions are extracted using the extreme cluster and the independent coordinate scheme with shell-model derived coupling strengths. A new approach also is introduced, the microscopic cluster, in which the spectroscopic amplitudes in the center-of-mass reference frame are derived from shell-model calculations using the Moshinsky transformation brackets. This new model is able to describe well the experimental cross section and to highlight cluster configurations in the involved wave functions.

  6. An N-terminal deletion variant of HCN1 in the epileptic WAG/Rij strain modulates HCN current densities.

    PubMed

    Wemhöner, Konstantin; Kanyshkova, Tatyana; Silbernagel, Nicole; Fernandez-Orth, Juncal; Bittner, Stefan; Kiper, Aytug K; Rinné, Susanne; Netter, Michael F; Meuth, Sven G; Budde, Thomas; Decher, Niels

    2015-01-01

    Rats of the Wistar Albino Glaxo/Rij (WAG/Rij) strain show symptoms resembling human absence epilepsy. Thalamocortical neurons of WAG/Rij rats are characterized by an increased HCN1 expression, a negative shift in I h activation curve, and an altered responsiveness of I h to cAMP. We cloned HCN1 channels from rat thalamic cDNA libraries of the WAG/Rij strain and found an N-terminal deletion of 37 amino acids. In addition, WAG-HCN1 has a stretch of six amino acids, directly following the deletion, where the wild-type sequence (GNSVCF) is changed to a polyserine motif. These alterations were found solely in thalamus mRNA but not in genomic DNA. The truncated WAG-HCN1 was detected late postnatal in WAG/Rij rats and was not passed on to rats obtained from pairing WAG/Rij and non-epileptic August Copenhagen Irish rats. Heterologous expression in Xenopus oocytes revealed 2.2-fold increased current amplitude of WAG-HCN1 compared to rat HCN1. While WAG-HCN1 channels did not have altered current kinetics or changed regulation by protein kinases, fluorescence imaging revealed a faster and more pronounced surface expression of WAG-HCN1. Using co-expression experiments, we found that WAG-HCN1 channels suppress heteromeric HCN2 and HCN4 currents. Moreover, heteromeric channels of WAG-HCN1 with HCN2 have a reduced cAMP sensitivity. Functional studies revealed that the gain-of-function of WAG-HCN1 is not caused by the N-terminal deletion alone, thus requiring a change of the N-terminal GNSVCF motif. Our findings may help to explain previous observations in neurons of the WAG/Rij strain and indicate that WAG-HCN1 may contribute to the genesis of absence seizures in WAG/Rij rats.

  7. An N-terminal deletion variant of HCN1 in the epileptic WAG/Rij strain modulates HCN current densities

    PubMed Central

    Wemhöner, Konstantin; Kanyshkova, Tatyana; Silbernagel, Nicole; Fernandez-Orth, Juncal; Bittner, Stefan; Kiper, Aytug K.; Rinné, Susanne; Netter, Michael F.; Meuth, Sven G.; Budde, Thomas; Decher, Niels

    2015-01-01

    Rats of the Wistar Albino Glaxo/Rij (WAG/Rij) strain show symptoms resembling human absence epilepsy. Thalamocortical neurons of WAG/Rij rats are characterized by an increased HCN1 expression, a negative shift in Ih activation curve, and an altered responsiveness of Ih to cAMP. We cloned HCN1 channels from rat thalamic cDNA libraries of the WAG/Rij strain and found an N-terminal deletion of 37 amino acids. In addition, WAG-HCN1 has a stretch of six amino acids, directly following the deletion, where the wild-type sequence (GNSVCF) is changed to a polyserine motif. These alterations were found solely in thalamus mRNA but not in genomic DNA. The truncated WAG-HCN1 was detected late postnatal in WAG/Rij rats and was not passed on to rats obtained from pairing WAG/Rij and non-epileptic August Copenhagen Irish rats. Heterologous expression in Xenopus oocytes revealed 2.2-fold increased current amplitude of WAG-HCN1 compared to rat HCN1. While WAG-HCN1 channels did not have altered current kinetics or changed regulation by protein kinases, fluorescence imaging revealed a faster and more pronounced surface expression of WAG-HCN1. Using co-expression experiments, we found that WAG-HCN1 channels suppress heteromeric HCN2 and HCN4 currents. Moreover, heteromeric channels of WAG-HCN1 with HCN2 have a reduced cAMP sensitivity. Functional studies revealed that the gain-of-function of WAG-HCN1 is not caused by the N-terminal deletion alone, thus requiring a change of the N-terminal GNSVCF motif. Our findings may help to explain previous observations in neurons of the WAG/Rij strain and indicate that WAG-HCN1 may contribute to the genesis of absence seizures in WAG/Rij rats. PMID:26578877

  8. Isotopic effects in the collision of HCN with He: substitution of HCN by DCN

    NASA Astrophysics Data System (ADS)

    Denis-Alpizar, Otoniel; Stoecklin, Thierry; Halvick, Philippe

    2015-10-01

    The HCN molecule is among the main tracers of the interstellar medium (ISM) and the observation of its isotopologue DCN should help to understand the physical properties and chemical history of the molecular clouds. We analyse the effects of the substitution of H by D in the collision of HCN with He. The bound levels of the DCN-He complex are reported and compared with the HCN-He levels. The close-coupling equations were solved in the space-fixed frame using the potential energy surface recently published for the HCN-He system. These calculations were performed with two different approaches in which the triatomic molecule was modelized as a rigid rotor or as a rigid bender, the latter approach allowing us to investigate rovibrational transitions. Rovibrational rate coefficients of DCN in collision with He were computed and compared with those for HCN-He. The ratio of the rate coefficients between both isotopologues varies from 0.4 to 3.9 for rotational transitions in the ground vibrational level. In the case of the first l-type doubling transition, we found that the rate coefficients have the same order of magnitude than those for pure rotational transitions. Therefore, in regions of ISM where the first vibrationally excited level of DCN can be populated, l-type doubling transitions are expected to be as important as pure rotational transitions.

  9. THE NITROGEN ISOTOPIC COMPOSITION OF METEORITIC HCN

    SciTech Connect

    Pizzarello, Sandra

    2014-12-01

    HCN is ubiquitous in extraterrestrial environments and is central to current theories on the origin of early solar system organic compounds such as amino acids. These compounds, observed in carbonaceous meteorites, were likely important in the origin and/or evolution of early life. As part of our attempts to understand the origin(s) of meteoritic CN{sup –}, we have analyzed the {sup 15}N/{sup 14}N isotopic composition of HCN gas released from water extracts of the Murchison meteorite and found its value to be near those of the terrestrial atmosphere. The findings, when evaluated viz-a-viz molecular abundances and isotopic data of meteoritic organic compounds, suggest that HCN formation could have occurred during the protracted water alteration processes known to have affected the mineralogy of many asteroidal bodies during their solar residence. This was an active synthetic stage, which likely involved simple gasses, organic molecules, their presolar precursors, as well as mineral catalysts and would have lead to the formation of molecules of differing isotopic composition, including some with solar values.

  10. Functional presynaptic HCN channels in the rat globus pallidus.

    PubMed

    Boyes, Justin; Bolam, J Paul; Shigemoto, Ryuichi; Stanford, Ian M

    2007-04-01

    Hyperpolarization-activated, cyclic nucleotide-gated cation (HCN) channels are expressed postsynaptically in the rodent globus pallidus (GP), where they play several important roles in controlling GP neuronal activity. To further elucidate the role of HCN channels in the GP, immunocytochemical and electrophysiological approaches were used to test the hypothesis that HCN channels are also expressed presynaptically on the local axon collaterals of GP neurons. At the electron microscopic level, immunoperoxidase labelling for HCN1 and HCN2 was localized in GP somata and dendritic processes, myelinated and unmyelinated axons, and axon terminals. One population of labelled terminals formed symmetric synapses with somata and proximal dendrites and were immunoreactive for parvalbumin, consistent with the axon collaterals of GABAergic GP projection neurons. In addition, labelling for HCN2 and, to a lesser degree, HCN1 was observed in axon terminals that formed asymmetric synapses and were immunoreactive for the vesicular glutamate transporter 2. Immunogold labelling demonstrated that HCN1 and HCN2 were located predominantly at extrasynaptic sites along the plasma membrane of both types of terminal. To determine the function of presynaptic HCN channels in the GP, we performed whole-cell recordings from GP neurons in vitro. Bath application of the HCN channel blocker ZD7288 resulted in an increase in the frequency of mIPSCs but had no effect on their amplitude, implying that HCN channels tonically regulate the release of GABA. Their presence, and predicted role in modulating transmitter release, represents a hitherto unidentified mechanism whereby HCN channels influence the activity of GP neurons.

  11. Structural studies on HCN oligomers. [catalysts for prebiotic processes

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Edelson, E. H.; Auyeung, J. M.; Joshi, P. C.

    1981-01-01

    NMR spectral studies on the HCN oligomers suggest the presence of carboxamide and urea groupings. The release of CO2, H2O, HCN, CH3CN, HCONH2 and pyridine on pyrolysis is consistent with the presence of these groupings as well as carboxylic acid groups. No basic primary amine groupings could be detected with fluorescamine. Hydrazinolysis of the HCN oligomers releases 10% of the amino acids normally released by acid hydrolysis. The oligomers give a positive biuret test but this is not due to the presence of peptide bonds. There is no conclusive evidence for the presence of peptide bonds in the HCN oligomers. No diglycine was detected on partial hydrolysis of the HCN oligomers at pH 8.5 suggesting that HCN oligomers were not a source of prebiotic peptides.

  12. Impact of oceanic circulation changes on atmospheric δ13CO2

    NASA Astrophysics Data System (ADS)

    Menviel, L.; Mouchet, A.; Meissner, K. J.; Joos, F.; England, M. H.

    2015-12-01

    δ13CO2 measured in Antarctic ice cores provides constraints on oceanic and terrestrial carbon cycle processes linked with millennial-scale and glacial/interglacial changes in atmospheric CO2. However, the interpretation of δ13CO2 is not straightforward. Using two Earth system models of intermediate complexity we perform a set of sensitivity experiments in which the formation rates of North Atlantic Deep Water (NADW), North Pacific Deep Water (NPDW), Antarctic Bottom Water (AABW) and Antarctic Intermediate Water (AAIW) are varied. We study the impact of these circulation changes on atmospheric δ13CO2 as well as on the oceanic δ13C distribution. In general, we find that the formation rates of AABW, NADW, NPDW and AAIW are negatively correlated with changes in δ13CO2: namely strong oceanic ventilation decreases atmospheric δ13CO2. However, since large scale ocean circulation reorganizations also impact nutrient utilization and the Earth's climate the relationship between atmospheric δ13CO2 levels and ocean ventilation rate is not unequivocal. In both models atmospheric δ13CO2 is very sensitive to changes in AABW formation rates: increased AABW formation enhances the upwelling of low δ13C waters to the surface and decreases atmospheric δ13CO2. By contrast, the impact of NADW changes on atmospheric δ13CO2 is less robust and might be model dependent.

  13. Theoretical study on the excited states of HCN

    NASA Astrophysics Data System (ADS)

    Nayak, Malaya K.; Chaudhuri, Rajat K.; Krishnamachari, S. N. L. G.

    2005-05-01

    In the flash-photolysis of oxazole, iso-oxazole, and thiozole a transient band system was observed in the region 2500-3050 Å. This band system was attributed to a meta-stable form of HCN, i.e., either HNC or triplet HCN. Theoretical investigations have been carried out on the ground and excited states of HCN to characterize this and other experimentally observed transitions. The predicted geometries are compared with the experiment and earlier theoretical calculations. The present calculations show that the band system in the region 2500-3050 Å corresponds to the transition 43-A'←13-A' of HCN.

  14. Functional Characterization of HCN Channels in Rat Pancreatic β Cells

    PubMed Central

    Zhang, Yi; Liu, Yunfeng; Qu, Jihong; Hardy, Alexandre; Zhang, Nina; Diao, Jingyu; Strijbos, Paul J.; Tsushima, Robert; Robinson, Richard B.; Gaisano, Herbert Y.; Wang, Qinghua; Wheeler, Michael B.

    2010-01-01

    Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels regulate pacemaker activity in some cardiac cells and neurons. In the present study, we have identified the presence of HCN channels in pancreatic β-cells. We then examined the functional characterization of these channels in β-cells via modulating HCN channel activity genetically and pharmacologically. Voltage-clamp experiments showed that over-expression of HCN2 in rat β-cells significantly increased HCN current (Ih), whereas expression of dominant-negative HCN2 (HCN2-AYA) completely suppressed endogenous Ih. Compared to control β-cells, over-expression of Ih increased insulin secretion at 2.8 mmol/l glucose. However, suppression of Ih did not affect insulin secretion at both 2.8 mmol/l and 11.1 mmol/l glucose. Current-clamp measurements revealed that HCN2 over-expression significantly reduced β-cell membrane input resistance (Rin), and resulted in a less hyperpolarizing membrane response to the currents injected into the cell. Conversely, dominant negative HCN2-AYA expression led to a substantial increase of Rin, which was associated with a more hyperpolarizing membrane response to the currents injected. Remarkably, under low extracellular potassium conditions (2.5mmol/l K+), suppression of Ih resulted in increased membrane hyperpolarization and decreased insulin secretion. We conclude that Ih in β-cells possess the potential to modulate β-cell membrane potential and insulin secretion under hypokalemic conditions. PMID:19654142

  15. A {sup 13}CO SURVEY OF INTERMEDIATE-MASS STAR-FORMING REGIONS

    SciTech Connect

    Lundquist, Michael J.; Kobulnicky, Henry A.; Kerton, Charles R.; Arvidsson, Kim

    2015-06-10

    We have conducted a {sup 13}CO survey of a sample of 128 infrared color-selected intermediate-mass star-forming region (IM SFR) candidates. We utilized the Onsala 20 m telescope to observe {sup 13}CO (1–0) toward 67 northern IM SFRs, used the 12 m Atacama Pathfinder Experiment telescope to observe {sup 13}CO (2–1) toward 22 southern IM SFRs, and incorporated an additional 39 sources from the Boston University Five College Radio Astronomy Observatory Galactic Ring Survey which observed {sup 13}CO (1–0). We detect {sup 13}CO (1–0) in 58 of the 67 northern sources and {sup 13}CO (2–1) in 20 of the 22 southern sources. The mean molecular column densities and {sup 13}CO linewidths in the inner Galaxy are higher by factors of 3.4 and 1.5, respectively, than the outer Galaxy. We attribute this difference to molecular clouds in the inner Galaxy being more massive and hosting star forming regions with higher luminosities on average than the outer Galaxy. IM SFRs have mean a molecular column density of 7.89 × 10{sup 21} cm{sup −2}, a factor of 3.1 lower than that for a sample of high-mass regions, and have a mean {sup 13}CO linewidth of 1.84 km s{sup −1}, a factor of 1.5 lower than that for high-mass regions. We demonstrate a correlation between {sup 13}CO linewidth and infrared luminosity as well as between molecular column density and infrared luminosity for the entire sample of intermediate-mass and high-mass regions. IM SFRs appear to form in distinctly lower-density environments with mean linewidths and beam-averaged column densities a factor of several lower than high-mass star-forming regions.

  16. Analysis and theoretical modeling of the 18O enriched carbon dioxide spectrum by CRDS near 1.35 μm: (I) 16O12C18O, 16O12C17O, 12C16O2 and 13C16O2

    NASA Astrophysics Data System (ADS)

    Kassi, S.; Karlovets, E. V.; Tashkun, S. A.; Perevalov, V. I.; Campargue, A.

    2017-01-01

    The room temperature absorption spectrum of 18O enriched carbon dioxide has been recorded by very high-sensitivity Cavity Ring Down spectroscopy between 6977 and 7918 cm-1 (1.43-1.26 μm). The achieved sensitivity (noise equivalent absorption αmin 8×10-11 cm-1) has allowed for the detection of more than 8600 lines belonging to 166 bands of eleven carbon dioxide isotopologues. Line intensities of the weakest observed transitions are on the order of 2×10-30 cm/molecule. In this first part, we present the results relative to the 16O12C18O, 16O12C17O, 12C16O2 and 13C16O2 isotopologues. Their absorption lines were rovibrationally assigned on the basis of the predictions of their respective effective Hamiltonian model. Overall 5476 lines were measured and assigned to 93 bands. Forty nine of them, all belonging to 16O12C18O and 16O12C17O, are reported for the first time. The studied spectral region is formed by ΔP=10-12 series of transitions, where P=2V1+V2+3V3 is the polyad number (Vi are vibrational quantum numbers). The spectroscopic parameters of 58 bands of 16O12C18O and 16O12C17O were determined from a fit of the measured line positions. An inter- and an intrapolyad resonance perturbation were identified and analyzed in the 16O12C18O spectrum. The comparison with the line positions and line intensities included in the AMES line list is discussed. Global fits of the line intensities were performed in order to (i) improve the ΔP=10 and 11 sets of the effective dipole moment parameters of 16O12C18O and the ΔP=11 set of parameters of 16O12C17O and (ii) derive for the first time the ΔP=10 and 12 parameters of 16O12C17O and 16O12C18O, respectively.

  17. In vitro characterization of HCN channel kinetics and frequency dependence in myocytes predicts biological pacemaker functionality

    PubMed Central

    Zhao, Xin; Bucchi, Annalisa; Oren, Ronit V; Kryukova, Yelena; Dun, Wen; Clancy, Colleen E; Robinson, Richard B

    2009-01-01

    The pacemaker current, mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, contributes to the initiation and regulation of cardiac rhythm. Previous experiments creating HCN-based biological pacemakers in vivo found that an engineered HCN2/HCN1 chimeric channel (HCN212) resulted in significantly faster rates than HCN2, interrupted by 1–5 s pauses. To elucidate the mechanisms underlying the differences in HCN212 and HCN2 in vivo functionality as biological pacemakers, we studied newborn rat ventricular myocytes over-expressing either HCN2 or HCN212 channels. The HCN2- and HCN212-over-expressing myocytes manifest similar voltage dependence, current density and sensitivity to saturating cAMP concentrations, but HCN212 has faster activation/deactivation kinetics. Compared with HCN2, myocytes expressing HCN212 exhibit a faster spontaneous rate and greater incidence of irregular rhythms (i.e. periods of rapid spontaneous rate followed by pauses). To explore these rhythm differences further, we imposed consecutive pacing and found that activation kinetics of the two channels are slower at faster pacing frequencies. As a result, time-dependent HCN current flowing during diastole decreases for both constructs during a train of stimuli at a rapid frequency, with the effect more pronounced for HCN2. In addition, the slower deactivation kinetics of HCN2 contributes to more pronounced instantaneous current at a slower frequency. As a result of the frequency dependence of both instantaneous and time-dependent current, HCN2 exhibits more robust negative feedback than HCN212, contributing to the maintenance of a stable pacing rhythm. These results illustrate the benefit of screening HCN constructs in spontaneously active myocyte cultures and may provide the basis for future optimization of HCN-based biological pacemakers. PMID:19171659

  18. Neurophysiology of HCN channels: from cellular functions to multiple regulations.

    PubMed

    He, Chao; Chen, Fang; Li, Bo; Hu, Zhian

    2014-01-01

    Hyperpolarization-activated cyclic nucleotide-gated (HCN) cation channels are encoded by HCN1-4 gene family and have four subtypes. These channels are activated upon hyperpolarization of membrane potential and conduct an inward, excitatory current Ih in the nervous system. Ih acts as pacemaker current to initiate rhythmic firing, dampen dendritic excitability and regulate presynaptic neurotransmitter release. This review summarizes recent insights into the cellular functions of Ih and associated behavior such as learning and memory, sleep and arousal. HCN channels are excellent targets of various cellular signals to finely regulate neuronal responses to external stimuli. Numerous mechanisms, including transcriptional control, trafficking, as well as channel assembly and modification, underlie HCN channel regulation. In the next section, we discuss how the intracellular signals, especially recent findings concerning protein kinases and interacting proteins such as cGKII, Ca(2+)/CaMKII and TRIP8b, regulate function and expression of HCN channels, and subsequently provide an overview of the effects of neurotransmitters on HCN channels and their corresponding intracellular mechanisms. We also discuss the dysregulation of HCN channels in pathological conditions. Finally, insight into future directions in this exciting area of ion channel research is provided.

  19. Simple Organics and Biomonomers Identified in HCN Polymers: An Overview

    PubMed Central

    Ruiz-Bermejo, Marta; Zorzano, María-Paz; Osuna-Esteban, Susana

    2013-01-01

    Hydrogen cyanide (HCN) is a ubiquitous molecule in the Universe. It is a compound that is easily produced in significant yields in prebiotic simulation experiments using a reducing atmosphere. HCN can spontaneously polymerise under a wide set of experimental conditions. It has even been proposed that HCN polymers could be present in objects such as asteroids, moons, planets and, in particular, comets. Moreover, it has been suggested that these polymers could play an important role in the origin of life. In this review, the simple organics and biomonomers that have been detected in HCN polymers, the analytical techniques and procedures that have been used to detect and characterise these molecules and an exhaustive classification of the experimental/environmental conditions that favour the formation of HCN polymers are summarised. Nucleobases, amino acids, carboxylic acids, cofactor derivatives and other compounds have been identified in HCN polymers. The great molecular diversity found in HCN polymers encourages their placement at the central core of a plausible protobiological system. PMID:25369814

  20. The HNC/HCN ratio in star-forming regions

    SciTech Connect

    Graninger, Dawn M.; Öberg, Karin I.; Herbst, Eric; Vasyunin, Anton I.

    2014-05-20

    HNC and HCN, typically used as dense gas tracers in molecular clouds, are a pair of isomers that have great potential as a temperature probe because of temperature dependent, isomer-specific formation and destruction pathways. Previous observations of the HNC/HCN abundance ratio show that the ratio decreases with increasing temperature, something that standard astrochemical models cannot reproduce. We have undertaken a detailed parameter study on which environmental characteristics and chemical reactions affect the HNC/HCN ratio and can thus contribute to the observed dependence. Using existing gas and gas-grain models updated with new reactions and reaction barriers, we find that in static models the H + HNC gas-phase reaction regulates the HNC/HCN ratio under all conditions, except for very early times. We quantitatively constrain the combinations of H abundance and H + HNC reaction barrier that can explain the observed HNC/HCN temperature dependence and discuss the implications in light of new quantum chemical calculations. In warm-up models, gas-grain chemistry contributes significantly to the predicted HNC/HCN ratio and understanding the dynamics of star formation is therefore key to model the HNC/HCN system.

  1. Ab initio rotation-vibration spectra of HCN and HNC

    NASA Astrophysics Data System (ADS)

    Harris, Gregory J.; Polyansky, Oleg L.; Tennyson, Jonathan

    2002-03-01

    We have calculated an ab initio HCN/HNC linelist for all transitions up to J=25 and 18 000 cm -1 above the zero point energy. This linelist contains more than 200 million lines each with frequencies and transition dipoles. The linelist has been calculated using our semi-global HCN/HNC VQZANO+PES and dipole moment surface, which were reported in van Mourik et al. (J. Chem. Phys. 115 (2001) 3706). With this linelist we synthesise absorption spectra of HCN and HNC at 298 K and we present the band centre and band transition dipoles for the bands which are major features in these spectra. Several of the HCN bands and many of the HNC bands have not been previously studied. Our line intensities reproduce via fully ab initio methods the unusual intensity structure of the HCN CN stretch fundamental (00 01) for the first time and also the forbidden (02 20) HCN bending overtone. We also compare the J=1→0 pure rotational transition dipole in the HCN/HNC ground and vibrationally excited states with experimental and existing ab initio results.

  2. Vibrationally Excited HCN in the Galactic Center Circumnuclear Disk

    NASA Astrophysics Data System (ADS)

    Mills, Elisabeth A.; Morris, M. R.; Güsten, R.

    2012-05-01

    Recent GREAT observations of CO in the Galactic center Circumnuclear Disk (CND) indicate that this structure is transitory, having gas densities on the order of 10^4 to 10^5 cm^-3, much less than those previously determined using high-density tracers such as HCN. We investigate this discrepancy with new HCN data from the APEX telescope in which we detect for the first time vibrationally-excited transitions of HCN in the CND. This suggests that the source of the disagreement in densities inferred from CO and HCN is the assumption that collisional excitation dominates the excitation of both molecules. We find that radiative excitation of HCN is an important contributor in the environment of the CND. We model the radiative excitation using observed rotational lines of HCN and H13CN from J=3-2 to J=8-7 in both the vibrational ground state and the v2=1 excited state. Our results suggest that ignoring radiative pumping from a strong infrared radiation field, such as in the Galactic center or actively star forming galaxies, can lead to overestimates of the density when using HCN and similar molecules.

  3. Processing of Retinal Signals in Normal and HCN Deficient Mice

    PubMed Central

    Caputo, Antonella; Ludwig, Andreas; Cervetto, Luigi; Gargini, Claudia

    2012-01-01

    This study investigates the role of two different HCN channel isoforms in the light response of the outer retina. Taking advantage of HCN-deficient mice models and of in vitro (patch-clamp) and in vivo (ERG) recordings of retinal activity we show that HCN1 and HCN2 channels are expressed at distinct retinal sites and serve different functions. Specifically, HCN1 operate mainly at the level of the photoreceptor inner segment from where, together with other voltage sensitive channels, they control the time course of the response to bright light. Conversely, HCN2 channels are mainly expressed on the dendrites of bipolar cells and affect the response to dim lights. Single cell recordings in HCN1−/− mice or during a pharmacological blockade of Ih show that, contrary to previous reports, Ikx alone is able to generate the fast initial transient in the rod bright flash response. Here we demonstrate that the relative contribution of Ih and Ikx to the rods' temporal tuning depends on the membrane potential. This is the first instance in which the light response of normal and HCN1- or HCN2-deficient mice is analyzed in single cells in retinal slice preparations and in integrated full field ERG responses from intact animals. This comparison reveals a high degree of correlation between single cell current clamp data and ERG measurements. A novel picture emerges showing that the temporal profile of the visual response to dim and bright luminance changes is separately determined by the coordinated gating of distinct voltage dependent conductances in photoreceptors and bipolar cells. PMID:22279546

  4. Spectroscopic measurements of atmospheric HCN at northern and southern latitudes

    NASA Technical Reports Server (NTRS)

    Smith, M. A. H.; Rinsland, C. P.

    1985-01-01

    A number of lines belonging to the nu(3) fundamental vibration-rotation band of hydrogen cyanide (HCN) have been identified in atmospheric infrared absorption spectra obtained on high-altitude balloon flights at 32 deg N in 1976 and at 30 deg S in 1977. Quantitative analysis of these spectral features has resulted in the first determination of atmospheric HCN concentrations in the Southern Hemisphere, as well as an independent estimate of stratospheric HCN abundance in the Northern Hemisphere. Within the uncertainties of the present and previous measurements, the Northern Hemisphere result is consistent with those of other investigators, and Southern Hemisphere HCN concentrations appear to be similar to those in the Northern Hemisphere.

  5. Theoretical study on the excited states of HCN

    SciTech Connect

    Nayak, Malaya K.; Chaudhuri, Rajat K.; Krishnamachari, S.N.L.G.

    2005-05-08

    In the flash-photolysis of oxazole, iso-oxazole, and thiozole a transient band system was observed in the region 2500-3050 A. This band system was attributed to a meta-stable form of HCN, i.e., either HNC or triplet HCN. Theoretical investigations have been carried out on the ground and excited states of HCN to characterize this and other experimentally observed transitions. The predicted geometries are compared with the experiment and earlier theoretical calculations. The present calculations show that the band system in the region 2500-3050 A corresponds to the transition 4 {sup 3}-A{sup '}<{sup -}1 {sup 3}-A{sup '} of HCN.

  6. Near Infrared Spectra of H2O/HCN Mixtures

    NASA Technical Reports Server (NTRS)

    Mastrapa, R. M.; Bernstein, M. P.; Sanford, S. A.

    2006-01-01

    Cassini's VIMS has already returned exciting results interpreting spectra of Saturn's icy satellites. The discovery of unidentified features possibly due to CN compounds inspired the work reported here. We wanted to test HCN as a possibility for explaining these features, and also explore how the features of HCN change when mixed with H2O. We have previously noted that mixing H20 and CO2 produces new spectral features and that those features change with temperature and mixing ratio.

  7. mm-wave observations of stratospheric HCN at tropical latitudes

    NASA Technical Reports Server (NTRS)

    Jaramillo, M.; De Zafra, R. L.; Barrett, J. W.; Parrish, A.; Solomon, P. M.

    1988-01-01

    Middle and upper stratospheric HCN has been measured using ground-based mm-wave emission spectroscopy during a series of observations made in Mauna Kea, HI, in June 1986. A volume mixing ratio of 190 + or - 40 pptv at about 40 km, and a decrease of concentration with altitude that is considerably slower than that predicted by current models are found. This could be an indication of an atmospheric source of HCN as yet unidentified.

  8. Regulation of epileptiform discharges in rat neocortex by HCN channels.

    PubMed

    Albertson, Asher J; Williams, Sidney B; Hablitz, John J

    2013-10-01

    Hyperpolarization-activated, cyclic nucleotide-gated, nonspecific cation (HCN) channels have a well-characterized role in regulation of cellular excitability and network activity. The role of these channels in control of epileptiform discharges is less thoroughly understood. This is especially pertinent given the altered HCN channel expression in epilepsy. We hypothesized that inhibition of HCN channels would enhance bicuculline-induced epileptiform discharges. Whole cell recordings were obtained from layer (L)2/3 and L5 pyramidal neurons and L1 and L5 GABAergic interneurons. In the presence of bicuculline (10 μM), HCN channel inhibition with ZD 7288 (20 μM) significantly increased the magnitude (defined as area) of evoked epileptiform events in both L2/3 and L5 neurons. We recorded activity associated with epileptiform discharges in L1 and L5 interneurons to test the hypothesis that HCN channels regulate excitatory synaptic inputs differently in interneurons versus pyramidal neurons. HCN channel inhibition increased the magnitude of epileptiform events in both L1 and L5 interneurons. The increased magnitude of epileptiform events in both pyramidal cells and interneurons was due to an increase in network activity, since holding cells at depolarized potentials under voltage-clamp conditions to minimize HCN channel opening did not prevent enhancement in the presence of ZD 7288. In neurons recorded with ZD 7288-containing pipettes, bath application of the noninactivating inward cationic current (Ih) antagonist still produced increases in epileptiform responses. These results show that epileptiform discharges in disinhibited rat neocortex are modulated by HCN channels.

  9. CN and HCN in the infrared spectrum of IRC + 10216

    NASA Technical Reports Server (NTRS)

    Wiedemann, G. R.; Deming, D.; Jennings, D. E.; Hinkle, Kenneth H.; Keady, John J.

    1991-01-01

    The abundance of HCN in the inner circumstellar shell of IRC + 10216 has been remeasured using the 12-micron nu2 band. The 12-micron lines are less saturated than HCN 3-micron lines previously detected in the spectrum of IRC + 10216. The observed 12-micron HCN line is formed in the circumstellar shell from about 4 to 12 R sub * in accord with a photospheric origin for HCN. The derived HCN abundance in the 4 to 12 R sub* region is 4 x 10 exp-5 and the column density is 7 x 10 exp 18/sq cm. The 5-micron CN vibration-rotation fundamental band was detected for the first time in an astronomical source. Using four CN lines, the CN column density was determined to be 2.6 x 10 exp 15/sq cm and the rotational temperature to be 8 +/-2 K. The peal radial abundance is 1 x 10 exp -5. The values for the temperature and abundance are in good agreement with microwave results and with the formation of CN from the photolysis of HCN.

  10. CN and HCN in the infrared spectrum of IRC + 10216

    NASA Astrophysics Data System (ADS)

    Wiedemann, G. R.; Deming, D.; Jennings, D. E.; Hinkle, Kenneth H.; Keady, John J.

    1991-11-01

    The abundance of HCN in the inner circumstellar shell of IRC + 10216 has been remeasured using the 12-micron nu2 band. The 12-micron lines are less saturated than HCN 3-micron lines previously detected in the spectrum of IRC + 10216. The observed 12-micron HCN line is formed in the circumstellar shell from about 4 to 12 R* in accord with a photospheric origin for HCN. The derived HCN abundance in the 4 to 12 R sub* region is 4 x 10 exp-5 and the column density is 7 x 10 exp 18/sq cm. The 5-micron CN vibration-rotation fundamental band was detected for the first time in an astronomical source. Using four CN lines, the CN column density was determined to be 2.6 x 10 exp 15/sq cm and the rotational temperature to be 8 +/-2 K. The peal radial abundance is 1 x 10 exp -5. The values for the temperature and abundance are in good agreement with microwave results and with the formation of CN from the photolysis of HCN.

  11. Does the differential photodissociation and chemical fractionation reaction of 13CO affect the column density estimates?

    NASA Astrophysics Data System (ADS)

    Szücs, László; Glover, Simon

    2013-07-01

    Carbon monoxide (CO) and its isotopes are frequently used as a tracer of column density in studies of the dense interstellar medium. The most abundant CO isotope, 12CO, is usually optically thick in intermediate and high density regions and so provides only a lower limit for the column density. In these regions, less abundant isotopes are used, such as 13CO. To relate observations of 13CO to the 12CO column density, a constant 12CO/13CO isotopic ratio is often adopted. In this work, we examine the impact of two effects -- selective photodissociation of 13CO and chemical fractionation -- on the 12CO/13CO isotopic ratio, with the aid of numerical simulations. Our simulations follow the coupled chemical, thermal and dynamical evolution of isolated molecular clouds in several different environments. We post-process our simulation results with line radiative transfer and produce maps of the emergent 13CO emission. We compare emission maps produced assuming a constant isotopic ratio with ones produced using the results from a more self-consistent calculation, and also compare the column density maps derived from the emission maps. We find that at low and high column densities, the column density estimates that we obtain with the approximation of constant isotopic ratio agree well with those derived from the self-consistent model. At intermediate column densities, 10^12 cm^-2 < N(13CO)< 10^15 cm^-2, the approximate model under-predicts the column density by a factor of a few, but we show that we can correct for this, and hence obtain accurate column density estimates, via application of a simple correction factor.

  12. Structural Basis for the cAMP-dependent Gating in the Human HCN4 Channel

    SciTech Connect

    X Xu; Z Vysotskaya; Q Liu; L Zhou

    2011-12-31

    Hyperpolarization-activated cAMP-regulated (HCN) channels play important physiological roles in both cardiovascular and central nervous systems. Among the four HCN isoforms, HCN2 and HCN4 show high expression levels in the human heart, with HCN4 being the major cardiac isoform. The previously published crystal structure of the mouse HCN2 (mHCN2) C-terminal fragment, including the C-linker and the cyclic-nucleotide binding domain (CNBD), has provided many insights into cAMP-dependent gating in HCN channels. However, structures of other mammalian HCN channel isoforms have been lacking. Here we used a combination of approaches including structural biology, biochemistry, and electrophysiology to study cAMP-dependent gating in HCN4 channel. First we solved the crystal structure of the C-terminal fragment of human HCN4 (hHCN4) channel at 2.4 {angstrom}. Overall we observed a high similarity between mHCN2 and hHCN4 crystal structures. Functional comparison between two isoforms revealed that compared with mHCN2, the hHCN4 protein exhibited marked different contributions to channel function, such as a {approx}3-fold reduction in the response to cAMP. Guided by structural differences in the loop region between {beta}4 and {beta}5 strands, we identified residues that could partially account for the differences in response to cAMP between mHCN2 and hHCN4 proteins. Moreover, upon cAMP binding, the hHCN4 C-terminal protein exerts a much prolonged effect in channel deactivation that could have significant physiological contributions.

  13. The Photodissociation of HCN and HNC: Effects on the HNC/HCN Abundance Ratio in the Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Aguado, Alfredo; Roncero, Octavio; Zanchet, Alexandre; Agúndez, Marcelino; Cernicharo, José

    2017-03-01

    The impact of the photodissociation of HCN and HNC isomers is analyzed in different astrophysical environments. For this purpose, the individual photodissociation cross sections of HCN and HNC isomers have been calculated in the 7–13.6 eV photon energy range for a temperature of 10 K. These calculations are based on the ab initio calculation of three-dimensional adiabatic potential energy surfaces of the 21 lower electronic states. The cross sections are then obtained using a quantum wave packet calculation of the rotational transitions needed to simulate a rotational temperature of 10 K. The cross section calculated for HCN shows significant differences with respect to the experimental one, and this is attributed to the need to consider non-adiabatic transitions. Ratios between the photodissociation rates of HCN and HNC under different ultraviolet radiation fields have been computed by renormalizing the rates to the experimental value. It is found that HNC is photodissociated faster than HCN by a factor of 2.2 for the local interstellar radiation field and 9.2 for the solar radiation field, at 1 au. We conclude that to properly describe the HNC/HCN abundance ratio in astronomical environments illuminated by an intense ultraviolet radiation field, it is necessary to use different photodissociation rates for each of the two isomers, which are obtained by integrating the product of the photodissociation cross sections and ultraviolet radiation field over the relevant wavelength range.

  14. Detection of CO and HCN in Pluto's atmosphere with ALMA

    NASA Astrophysics Data System (ADS)

    Lellouch, E.; Gurwell, M.; Butler, B.; Fouchet, T.; Lavvas, P.; Strobel, D. F.; Sicardy, B.; Moullet, A.; Moreno, R.; Bockelée-Morvan, D.; Biver, N.; Young, L.; Lis, D.; Stansberry, J.; Stern, A.; Weaver, H.; Young, E.; Zhu, X.; Boissier, J.

    2017-04-01

    Observations of the Pluto-Charon system, acquired with the ALMA interferometer on June 12-13, 2015, have led to the detection of the CO(3-2) and HCN(4-3) rotational transitions from Pluto (including the hyperfine structure of HCN), providing a strong confirmation of the presence of CO, and the first observation of HCN in Pluto's atmosphere. The CO and HCN lines probe Pluto's atmosphere up to ∼450 km and ∼900 km altitude, respectively, with a large contribution due to limb emission. The CO detection yields (i) a much improved determination of the CO mole fraction, as 515 ± 40 ppm for a 12 μbar surface pressure (ii) strong constraints on Pluto's mean atmospheric dayside temperature profile over ∼50-400 km, with clear evidence for a well-marked temperature decrease (i.e., mesosphere) above the 30-50 km stratopause and a best-determined temperature of 70 ± 2 K at 300 km, somewhat lower than previously estimated from stellar occultations (81 ± 6 K), and in agreement with recent inferences from New Horizons / Alice solar occultation data. The HCN line shape implies a high abundance of this species in the upper atmosphere, with a mole fraction >1.5 × 10-5 above 450 km and a value of 4 × 10-5 near 800 km. Assuming HCN at saturation, this would require a warm (>92 K) upper atmosphere layer; while this is not ruled out by the CO emission, it is inconsistent with the Alice-measured CH4 and N2 line-of-sight column densities. Taken together, the large HCN abundance and the cold upper atmosphere imply supersaturation of HCN to a degree (7-8 orders of magnitude) hitherto unseen in planetary atmospheres, probably due to a lack of condensation nuclei above the haze region and the slow kinetics of condensation at the low pressure and temperature conditions of Pluto's upper atmosphere. HCN is also present in the bottom ∼100 km of the atmosphere, with a 10-8-10-7 mole fraction; this implies either HCN saturation or undersaturation there, depending on the precise

  15. Biosynthesis of Nudicaulins: A (13) CO2 -pulse/chase labeling study with Papaver nudicaule.

    PubMed

    Tatsis, Evangelos C; Eylert, Eva; Maddula, Ravi Kumar; Ostrozhenkova, Elena; Svatoš, Aleš; Eisenreich, Wolfgang; Schneider, Bernd

    2014-07-21

    Nudicaulins are unique alkaloids responsible for the yellow color of the petals of some papaveraceaous plants. To elucidate the unknown biosynthetic origin of the skeleton, a (13) CO2 -pulse/chase experiment was performed with growing Papaver nudicaule plants. (13) C NMR analysis revealed more than 20 multiple (13) C-enriched isotopologues in nudicaulins from the petals of (13) CO2 -labeled plants. The complex labeling pattern was compared with the isotopologue composition of a kaempferol derivative that was isolated from petals of the same (13) CO2 -labeled plants. The deconvolution of the labeling profiles indicated that the nudicaulin scaffold is assembled from products or intermediates of indole metabolism, the phenylpropanoid pathway, and the polyketide biosynthesis. Naringenin-type compounds and tryptophan/tryptamine are potential substrates for the condensation reaction finally generating the aglycone skeleton of nudicaulins.

  16. HCN2 channels: a permanent open state and conductance changes.

    PubMed

    Pittoors, François; Van Bogaert, Pierre Paul

    2015-02-01

    Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in the membranes of heart and brain cells can conduct Na(+) and K(+) ions and activate between -30 and -120 mV. We express the α subunit of HCN2 channels in Xenopus laevis oocytes and are confronted with two unexpected problems. First, we observe a rise in membrane conductance at resting potential proportional to the amount of expression. On activation to hyperpolarizing potentials, the instantaneous conductance rises in proportion to the amount of activated current. CsCl reduces the observed effects. This can be explained by the expression in oocytes membranes of a fraction of permanently open HCN2 channels. Second, using TEVC technique, our data show a completely different behaviour in physiological solutions of heterogeneously expressed HCN2 currents from what is observed in wild-type currents in the absence of drugs. During pulse trains, we frequently observe (1) a fast and significant decline of the amplitude of HCN2 current during hyperpolarizing steps, (2) no recovery of this decline after a long period at resting membrane potential, (3) a different behaviour of the tail currents at depolarization with other and slower changes than during activation, (4) recovery of this decline in high K(+)/low Na(+) bath solution. The decline of the HCN2 current in physiological conditions is caused by a reduction of the conductance of the HCN2 channel presumably caused by the mere presence of sodium in the channel, in competition with potassium ions and with a limitative effect on the channel conductance.

  17. HCN production from impact ejecta on the early Earth

    NASA Astrophysics Data System (ADS)

    Parkos, Devon; Pikus, Aaron; Alexeenko, Alina; Melosh, H. J.

    2016-11-01

    Major impact events have drastically altered the evolution of life on Earth. The reentry of ejecta formed from these events can trigger widespread chemical changes to the atmosphere on a global scale. This mechanism was proposed as a source of HCN during the Late Heavy Bombardment (LHB), 4.1 to 3.8 billion years ago. Significant concentrations of HCN in surface water could directly lead to adenine formation, a precursor for RNA. This work uses the Direct Simulation Monte Carlo (DSMC) method to examine the production of CN and HCN due to the reentry of impact ejecta. We use the Statistical Modeling in Low-Density Environment (SMILE) code, which utilizes the Total Collisional Energy (TCE) model for reactions. The collisions are described by the Variable Soft Sphere (VSS) and Larsen-Borgnakke (LB) models. We compare this nonequilibrium production to equilibrium concentrations from bulk atmospheric heating. The equilibrium HCN yield for a 1023 J impact is 7.0×104 moles, corresponding to a 2.5×1014 molecules per m2 surface deposition. We find that additional CN and HCN is produced under thermochemical nonequilibrium, particularly at higher altitudes. The total nonequilibrium yield for a 1023 J impact is 1.2×106 moles of HCN, a value 17 times the equilibrium result. This corresponds to a surface deposition of 1.4×1015 molecules per m2. This increase in production indicates that thermochemical nonequilibrium effects play a strong role in HCN from impact ejecta, and must be considered when investigating impacts as a plausible mechanism for significant adenine production during the LHB.

  18. HCN1 and HCN2 in Rat DRG Neurons: Levels in Nociceptors and Non-Nociceptors, NT3-Dependence and Influence of CFA-Induced Skin Inflammation on HCN2 and NT3 Expression

    PubMed Central

    Acosta, Cristian; McMullan, Simon; Djouhri, Laiche; Gao, Linlin; Watkins, Roger; Berry, Carol; Dempsey, Katherine; Lawson, Sally N.

    2012-01-01

    Ih, which influences neuronal excitability, has recently been measured in vivo in sensory neuron subtypes in dorsal root ganglia (DRGs). However, expression levels of HCN (hyperpolarization-activated cyclic nucleotide-gated) channel proteins that underlie Ih were unknown. We therefore examined immunostaining of the most abundant isoforms in DRGs, HCN1 and HCN2 in these neuron subtypes. This immunostaining was cytoplasmic and membrane-associated (ring). Ring-staining for both isoforms was in neurofilament-rich A-fiber neurons, but not in small neurofilament-poor C-fiber neurons, although some C-neurons showed cytoplasmic HCN2 staining. We recorded intracellularly from DRG neurons in vivo, determined their sensory properties (nociceptive or low-threshold-mechanoreceptive, LTM) and conduction velocities (CVs). We then injected fluorescent dye enabling subsequent immunostaining. For each dye-injected neuron, ring- and cytoplasmic-immunointensities were determined relative to maximum ring-immunointensity. Both HCN1- and HCN2-ring-immunointensities were positively correlated with CV in both nociceptors and LTMs; they were high in Aβ-nociceptors and Aα/β-LTMs. High HCN1 and HCN2 levels in Aα/β-neurons may, via Ih, influence normal non-painful (e.g. touch and proprioceptive) sensations as well as nociception and pain. HCN2-, not HCN1-, ring-intensities were higher in muscle spindle afferents (MSAs) than in all other neurons. The previously reported very high Ih in MSAs may relate to their very high HCN2. In normal C-nociceptors, low HCN1 and HCN2 were consistent with their low/undetectable Ih. In some C-LTMs HCN2-intensities were higher than in C-nociceptors. Together, HCN1 and HCN2 expressions reflect previously reported Ih magnitudes and properties in neuronal subgroups, suggesting these isoforms underlie Ih in DRG neurons. Expression of both isoforms was NT3-dependent in cultured DRG neurons. HCN2-immunostaining in small neurons increased 1 day after cutaneous

  19. Search for H2COH+ and H2(13)CO in dense interstellar molecular clouds

    NASA Technical Reports Server (NTRS)

    Minh, Y. C.; Irvine, W. M.; McGonagle, D.

    1993-01-01

    We have searched for the 2 mm transitions of H2COH+ (2(02) - 1(01)) and H2(13)CO (2(02) - 1(01), 2(12) - 1(11), and 2(11) - 1(10)) toward the dense interstellar molecular clouds Orion A, TMC-1 and L134N using the FCRAO 14m telescope. None of the transitions have been detected except the H2(13)CO transitions toward Orion-KL. We set upper limits for the abundances of the protonated formaldehyde ion (H2COH+), which are close to the abundances expected from ion-molecule chemistry.

  20. Alma Observations of HCN and its Isotopologues on Titan

    NASA Technical Reports Server (NTRS)

    Molter, Edward M.; Nixon, C. A.; Cordiner, M. A.; Serigano, J.; Irwin, P. G. J.; Teanby, N. A.; Charnley, S. B.; Lindberg, J. E.

    2016-01-01

    We present sub-millimeter spectra of HCN isotopologues on Titan, derived from publicly available ALMA flux calibration observations of Titan taken in early 2014. We report the detection of a new HCN isotopologue on Titan, H13C15N, and confirm an earlier report of detection of DCN. We model high signal-to-noise observations of HCN, H13CN, HC15N, DCN, and H13C15N to derive abundances and infer the following isotopic ratios: 12C/13C = 89.8 +/- 2.8, 14N/15N = 72.3 +/- 2.2, D/H = (2.5 +/- 0.2) × 10-4, and HCN/H13C15N = 5800 +/- 270 (1sigma errors). The carbon and nitrogen ratios are consistent with and improve on the precision of previous results, confirming a factor of approximately 2.3 elevation in 14N/15N in HCN compared to N2 and a lack of fractionation in 12C/13C from the protosolar value. This is the first published measurement of D/H in a nitrile species on Titan, and we find evidence for a factor of approximately 2 deuterium enrichment in hydrogen cyanide compared to methane. The isotopic ratios we derive may be used as constraints for future models to better understand the fractionation processes occurring in Titan's atmosphere.

  1. ALMA Observations of HCN and Its Isotopologues on Titan

    NASA Astrophysics Data System (ADS)

    Molter, Edward M.; Nixon, C. A.; Cordiner, M. A.; Serigano, J.; Irwin, P. G. J.; Teanby, N. A.; Charnley, S. B.; Lindberg, J. E.

    2016-08-01

    We present sub-millimeter spectra of HCN isotopologues on Titan, derived from publicly available ALMA flux calibration observations of Titan taken in early 2014. We report the detection of a new HCN isotopologue on Titan, H13C15N, and confirm an earlier report of detection of DCN. We model high signal-to-noise observations of HCN, H13CN, HC15N, DCN, and H13C15N to derive abundances and infer the following isotopic ratios: 12C/13C = 89.8 ± 2.8, 14N/15N = 72.3 ± 2.2, D/H = (2.5 ± 0.2) × 10-4, and HCN/H13C15N = 5800 ± 270 (1σ errors). The carbon and nitrogen ratios are consistent with and improve on the precision of previous results, confirming a factor of ˜2.3 elevation in 14N/15N in HCN compared to N2 and a lack of fractionation in 12C/13C from the protosolar value. This is the first published measurement of D/H in a nitrile species on Titan, and we find evidence for a factor of ˜2 deuterium enrichment in hydrogen cyanide compared to methane. The isotopic ratios we derive may be used as constraints for future models to better understand the fractionation processes occurring in Titan’s atmosphere.

  2. Optimization of the HCN interferometer on J-TEXT tokamak

    NASA Astrophysics Data System (ADS)

    Shi, P.; Gao, L.; Xiong, C. Y.; Liu, Y.; Chen, J.; Zhuang, G.

    2015-12-01

    Recently, the HCN interferometer on J-TEXT has been optimized in many aspects. Firstly, the output power of laser source is more stable after using a new designed movable mirror frame and upgrading the oil thermostatic system. Secondly, the electromagnetic interferences have been eliminated by designing a shielding system. Additionally, the signal-to-noise ratio of intermediate frequency (IF) signal has been increased more than five times by improving the detector circuit. The density resolution has been increased from 1×1018 m-3 to 2×1017 m-3 and the sawtooth oscillation has also been measured by the HCN interferometer on J- TEXT after optimizations.

  3. Nitric oxide selectively suppresses IH currents mediated by HCN1-containing channels

    PubMed Central

    Kopp-Scheinpflug, Cornelia; Pigott, Beatrice M; Forsythe, Ian D

    2015-01-01

    Key points The superior olivary complex (SOC) exhibits a spectrum of HCN1 and HCN2 subunit expression, which generate IH currents with fast and slow kinetics, respectively. Neuronal nitric oxide synthase (nNOS) was broadly distributed across the SOC. NO hyperpolarizes the half-activation voltage of HCN1-mediated currents and caused a slowing of the IH current kinetics in the respective nuclei (medial and lateral superior olives and superior paraolivary nucleus). This signalling was independent of cGMP. NO also caused a depolarizing shift in the half-activation voltage of HCN2-mediated IH currents, increasing activation at resting potentials; this was cGMP-dependent. Thus, NO signalling suppressed fast HCN1-mediated currents and potentiated slow HCN2-mediated currents, modulating the overall kinetics and magnitude of the endogenous IH. Abstract Hyperpolarization-activated non-specific cation-permeable channels (HCN) mediate IH currents, which are modulated by cGMP and cAMP and by nitric oxide (NO) signalling. Channel properties depend upon subunit composition (HCN1–4 and accessory subunits) as demonstrated in expression systems, but physiological relevance requires investigation in native neurons with intact intracellular signalling. Here we use the superior olivary complex (SOC), which exhibits a distinctive pattern of HCN1 and HCN2 expression, to investigate NO modulation of the respective IH currents, and compare properties in wild-type and HCN1 knockout mice. The medial nucleus of the trapezoid body (MNTB) expresses HCN2 subunits exclusively, and sends inhibitory projections to the medial and lateral superior olives (MSO, LSO) and the superior paraolivary nucleus (SPN). In contrast to the MNTB, these target nuclei possess an IH with fast kinetics, and they express HCN1 subunits. NO is generated in the SOC following synaptic activity and here we show that NO selectively suppresses HCN1, while enhancing IH mediated by HCN2 subunits. NO hyperpolarizes the half

  4. Effects of N-glycosylation on hyperpolarization-activated cyclic nucleotide-gated (HCN) channels.

    PubMed

    Li, Mo; Tonggu, Lige; Tang, Lan; Wang, Liguo

    2015-02-15

    Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are activated by membrane hyperpolarization and conduct an inward cation current, which contributes to rhythmic electrical activity of neural and cardiac pacemaker cells. HCN channels have been shown to undergo N-linked glycosylation, and the N-glycosylation has been shown to be required for membrane trafficking and possibly function. In this study, recombinant wild-type (WT) and glycosylation-defective N380Q HCN2 channels were individually or co-expressed in HEK-293 cells. We demonstrate that glycosylation is required for trafficking to the plasma membrane and for the stability of HCN channels in the cell. Interestingly, the heteromeric HCN2 channels of WT and glycosylation-defective N380Q have been observed on cell membranes, indicating that not all four subunits of a tetrameric HCN2 channel need to be glycosylated for HCN2 channels to traffic to plasma membranes. Subsequently, we investigate the effect of N-glycosylation on the function of HCN2 channels. We developed a fluorescence-based flux assay, which makes it possible to establish a negative potential inside liposomes to open HCN2 channels. Using this flux assay, we demonstrate that glycosylation-defective N380Q HCN2 channels reconstituted into liposomes function similarly to WT HCN2 channels. This suggests that N-glycosylation is not required for HCN2 channels to function.

  5. Cannabinoid control of learning and memory through HCN channels

    PubMed Central

    Maroso, Mattia; Szabo, Gergely G.; Kim, Hannah K.; Alexander, Allyson; Bui, Anh D.; Lee, Sang-Hun; Lutz, Beat; Soltesz, Ivan

    2016-01-01

    Summary The mechanisms underlying the effects of cannabinoids on cognitive processes are not understood. Here we show that cannabinoid type-1 receptors (CB1Rs) control hippocampal synaptic plasticity and spatial memory through the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels that underlie the h-current (Ih), a key regulator of dendritic excitability. The CB1R-HCN pathway, involving c-Jun-N-terminal kinases (JNKs), nitric oxide synthase and intracellular cGMP, exerts a tonic enhancement of Ih selectively in pyramidal cells located in the superficial portion of the CA1 pyramidal cell layer, whereas it is absent from deep-layer cells. Activation of CB1R-HCN pathway impairs dendritic integration of excitatory inputs, long-term potentiation (LTP) and spatial memory formation. Strikingly, pharmacological inhibition of Ih or genetic deletion of HCN1 abolishes CB1R-induced deficits in LTP and memory. These results demonstrate that the CB1R-Ih pathway in the hippocampus is obligatory for the action of cannabinoids on LTP and spatial memory formation. PMID:26898775

  6. VIBRATIONALLY EXCITED HCN IN THE LUMINOUS INFRARED GALAXY NGC 4418

    SciTech Connect

    Sakamoto, Kazushi; Aalto, Susanne; Evans, Aaron S.; Wiedner, Martina C.; Wilner, David J.

    2010-12-20

    Infrared pumping and its effect on the excitation of HCN molecules can be important when using rotational lines of HCN to probe dense molecular gas in galaxy nuclei. We report the first extragalactic detection of (sub)millimeter rotational lines of vibrationally excited HCN, in the dust-enshrouded nucleus of the luminous infrared galaxy NGC 4418. We estimate the excitation temperature of T{sub vib} {approx} 230 K between the vibrational ground and excited (v{sub 2} = 1) states. This excitation is most likely due to infrared radiation. At this high vibrational temperature the path through the v{sub 2} = 1 state must have a strong impact on the rotational excitation in the vibrational ground level, although it may not be dominant for all rotational levels. Our observations also revealed nearly confusion-limited lines of CO, HCN, HCO{sup +}, H{sup 13}CN, HC{sup 15}N, CS, N{sub 2}H{sup +}, and HC{sub 3}N at {lambda} {approx} 1 mm. Their relative intensities may also be affected by the infrared pumping.

  7. HCN Polymers: Toward Structure Comprehension Using High Resolution Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Bonnet, Jean-Yves; Thissen, Roland; Frisari, Ma; Vuitton, Veronique; Quirico, Eric; Le Roy, Léna; Fray, Nicolas; Cottin, Hervé; Horst, Sarah; Yelle, Roger

    A lot of solar system materials, including cometary ices and Titan aerosols, contain dark matter that can be interpreted as complex nitrogen bearing organic matter [1]. In laboratory experi-ments, HCN polymers are thus analogs of great interest. In fact they may be present in Titan atmosphere and in comet nuclei and then reprocessed as a CN distributed source [2], when ices began to sublimate and ejects from the nucleus organic matter grains [3]. The presence of HCN polymers is suggested because HCN molecule has been directly observed in 1P/Halley comet [4] and others. HCN polymers are also of prebiotic interest [5] as it can form amino acid under hydrolysis conditions. Even if they have been studied during the last decades, their chemical composition and structure are still poorly understood, and a great analytical effort has to be continued. In this way we present a high resolution mass spectrometry (HRMS) and a high resolution tandem mass spectrometry (MS/HRMS) analysis of HCN polymers. It was shown [6] that this is a suitable technique to elucidate composition and structure of the soluble part of tholins analogs of Titan's atmosphere aerosols. HCN polymers have never been studied by HRMS, thus we used a LTQ-Orbitrap XL high resolution mass spectrometer to analyse the HCN polymers. These are produced at LISA by direct polymerisation of pure liquid HCN, catalyzed by ammonia. HCN polymers have been completely dissolved in methanol and then injected in the mass spectrometer by ElectroSpray Ionization (ESI). This atmospheric pressure ionization process produces protonated or deprotonated ions, but it does not fragment molecules. Thus HRMS, allows a direct access to the stoechiometry of all the ionizable molecules present in the samples. Fragmentation analyses (MS/MS) of selected ions have also been performed. Thess analysis provide information about the different chemical fonctionnalities present in HCN poly-mers and also about their structure. Thus we are able to

  8. 13CO2 as a universal metabolic tracer in isotopologue perturbation experiments.

    PubMed

    Römisch-Margl, Werner; Schramek, Nicholas; Radykewicz, Tanja; Ettenhuber, Christian; Eylert, Eva; Huber, Claudia; Römisch-Margl, Lilla; Schwarz, Christine; Dobner, Maria; Demmel, Norbert; Winzenhörlein, Bernhard; Bacher, Adelbert; Eisenreich, Wolfgang

    2007-01-01

    A tobacco plant was illuminated for 5h in an atmosphere containing (13)CO(2) and then maintained for 10 days under standard greenhouse conditions. Nicotine, glucose, and amino acids from proteins were isolated chromatographically. Isotopologue abundances of isolated metabolites were determined quantitatively by NMR spectroscopy and mass spectrometry. The observed non-stochastic isotopologue patterns indicate (i) formation of multiply labeled photosynthetic carbohydrates during the (13)CO(2) pulse phase followed by (ii) partial catabolism of the primary photosynthetic products, and (iii) recombination of the (13)C-labeled fragments with unlabeled intermediary metabolites during the chase period. The detected and simulated isotopologue profiles of glucose and amino acids reflect carbon partitioning that is dominated by the Calvin cycle and glycolysis/glucogenesis. Retrobiosynthetic analysis of the nicotine pattern is in line with its known formation from nicotinic acid and putrescine via aspartate, glyceraldehyde phosphate and alpha-ketoglutarate as basic building blocks. The study demonstrates that pulse/chase labeling with (13)CO(2) as precursor is a powerful tool for the analysis of quantitative aspects of plant metabolism in completely unperturbed whole plants.

  9. Functional Characterization of Cnidarian HCN Channels Points to an Early Evolution of Ih

    PubMed Central

    Baker, Emma C.; Layden, Michael J.; van Rossum, Damian B.; Kamel, Bishoy; Medina, Monica; Simpson, Eboni; Jegla, Timothy

    2015-01-01

    HCN channels play a unique role in bilaterian physiology as the only hyperpolarization-gated cation channels. Their voltage-gating is regulated by cyclic nucleotides and phosphatidylinositol 4,5-bisphosphate (PIP2). Activation of HCN channels provides the depolarizing current in response to hyperpolarization that is critical for intrinsic rhythmicity in neurons and the sinoatrial node. Additionally, HCN channels regulate dendritic excitability in a wide variety of neurons. Little is known about the early functional evolution of HCN channels, but the presence of HCN sequences in basal metazoan phyla and choanoflagellates, a protozoan sister group to the metazoans, indicate that the gene family predates metazoan emergence. We functionally characterized two HCN channel orthologs from Nematostella vectensis (Cnidaria, Anthozoa) to determine which properties of HCN channels were established prior to the emergence of bilaterians. We find Nematostella HCN channels share all the major functional features of bilaterian HCNs, including reversed voltage-dependence, activation by cAMP and PIP2, and block by extracellular Cs+. Thus bilaterian-like HCN channels were already present in the common parahoxozoan ancestor of bilaterians and cnidarians, at a time when the functional diversity of voltage-gated K+ channels was rapidly expanding. NvHCN1 and NvHCN2 are expressed broadly in planulae and in both the endoderm and ectoderm of juvenile polyps. PMID:26555239

  10. TRIP8b Is Required for Maximal Expression of HCN1 in the Mouse Retina

    PubMed Central

    Pan, Yuan; Bhattarai, Sajag; Modestou, Modestos; Drack, Arlene V.; Chetkovich, Dane M.; Baker, Sheila A.

    2014-01-01

    Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are cation-selective channels present in retina, brain and heart. The activity of HCN channels contributes to signal integration, cell excitability and pacemaker activity. HCN1 channels expressed in photoreceptors participate in keeping light responses transient and are required for normal mesopic vision. The subcellular localization of HCN1 varies among cell types. In photoreceptors HCN1 is concentrated in the inner segments while in other retinal neurons, HCN1 is evenly distributed though the cell. This is in contrast to hippocampal neurons where HCN1 is concentrated in a subset of dendrites. A key regulator of HCN1 trafficking and activity is tetratricopeptide repeat-containing Rab8b interacting protein (TRIP8b). Multiple splice isoforms of TRIP8b are expressed throughout the brain and can differentially regulate the surface expression and activity of HCN1. The purpose of the present study was to determine which isoforms of TRIP8b are expressed in the retina and to test if loss of TRIP8b alters HCN1 expression or trafficking. We found that TRIP8b colocalizes with HCN1 in multiple retina neurons and all major splice isoforms of TRIP8b are expressed in the retina. Photoreceptors express three different isoforms. In TRIP8b knockout mice, the ability of HCN1 to traffic to the surface of retinal neurons is unaffected. However, there is a large decrease in the total amount of HCN1. We conclude that TRIP8b in the retina is needed to achieve maximal expression of HCN1. PMID:24409334

  11. Characteristics of HCN removal using CaO at high temperatures

    SciTech Connect

    Houzhang Tan; Xuebin Wang; Congling Wang; Tongmo Xu

    2009-03-15

    Experimental investigation on the removal of hydrogen cyanide (HCN) using calcium oxide (CaO) was carried out in a fixed bed reactor at temperature ranging from 300 to 1173 K, and the original HCN was produced during the pyrolysis of pyridine. Effects of temperature, volume space velocity, and initial HCN concentration on HCN removal were discussed. The results of temperature-programmed experiments show that temperature is the main factor affecting HCN removal. With the formation of CO, HCN starts to decrease from 473 K, and remains unchanged from 673 to 873 K. At 873 K, there is a further decrease in HCN without CO formation, and when temperature is higher than 1023 K, HCN is removed completely. In the isothermal experiments, CaCN{sub 2} was detected at 723 K, but at higher temperatures of 923 and 1123 K, there was no CaCN{sub 2} in the solid residues, and the nitrogen in the removed HCN was equal to that in the formed N{sub 2}. This indicates that at a lower temperature CaO is consumed to remove HCN, CaO + 2HCN {yields} CaCN{sub 2} + CO + H{sub 2}; but at a higher temperature, CaO acts as a catalyst for HCN removal, 2C{sub i}H{sub j} + 2HCN {yields} N{sub 2} + (j + 1 - k)H{sub 2} + 2C{sub I} + 1H{sub k}. The investigation on the removal efficiency shows that there is a critical temperature and a critical volume space velocity at which the HCN removal efficiency is able to reach up to 100%. 41 refs., 9 figs., 2 tabs.

  12. HCN2 channels account for mechanical (but not heat) hyperalgesia during long-standing inflammation.

    PubMed

    Schnorr, Sabine; Eberhardt, Mirjam; Kistner, Katrin; Rajab, Hamsa; Käßer, Johannes; Hess, Andreas; Reeh, Peter; Ludwig, Andreas; Herrmann, Stefan

    2014-06-01

    There is emerging evidence that hyperpolarization-activated cation (HCN) channels are involved in the development of pathological pain, including allodynia and hyperalgesia. Mice lacking the HCN isoform 2 display reduced heat but unchanged mechanical pain behavior, as recently shown in preclinical models of acute inflammatory pain. However, the impact of HCN2 to chronic pain conditions is less clear and has not been examined so far. In this report, we study the role of HCN2 in the complete Freund's adjuvant inflammation model reflecting chronic pain conditions. We used sensory neuron-specific as well as inducible global HCN2 mutants analyzing pain behavior in persistent inflammation and complemented this by region-specific administration of an HCN channel blocker. Our results demonstrate that the absence of HCN2 in primary sensory neurons reduces tactile hypersensitivity in chronic inflammatory conditions but leaves heat hypersensitivity unaffected. This result is in remarkable contrast to the recently described role of HCN2 in acute inflammatory conditions. We show that chronic inflammation results in an increased expression of HCN2 and causes sensitization in peripheral and spinal terminals of the pain transduction pathway. The contribution of HCN2 to peripheral sensitization mechanisms was further supported by single-fiber recordings from isolated skin-nerve preparations and by conduction velocity measurements of saphenous nerve preparations. Global HCN2 mutants revealed that heat hypersensitivity-unaffected in peripheral HCN2 mutants-was diminished by the additional disruption of central HCN2 channels, suggesting that thermal hyperalgesia under chronic inflammatory conditions is mediated by HCN2 channels beyond primary sensory afferents.

  13. HCN Hyperfine Ratio Analysis of Massive Molecular Clumps

    NASA Astrophysics Data System (ADS)

    Schap, William; Barnes, Peter; Ginsburg, Adam; Ordonez, Antonio

    2017-03-01

    The CHaMP project has identified a uniform sample of 303 massive (20-8000 M⊙), dense (200-30,000 cm-3) molecular clumps in a large sector of the southern Milky Way that includes much of the Carina Arm. These are the kinds of clumps that are likely to be the precursors to IRDCs, large stellar clusters, and massive stars. We report new results of the physical conditions in these clouds based on the J=1 -> 0 emission at 3mm from the HCN molecule. Analysis of the HCN emission from these clumps reveals that the physical conditions in the gas (i.e., the excitation temperature, optical depth, and column density) do not follow the molecular line emissivity in a straightforward way. This means that large fractions of the molecular material involved in massive cluster formation, while not completely``dark'', are under-luminous and easily missed in certain studies.

  14. Isotope effect in dissociative electron attachment to HCN

    SciTech Connect

    Chourou, S. T.; Orel, A. E.

    2011-03-15

    We performed nuclear dynamics calculations on HCN and DCN to study the isotope effect in dissociative electron attachment. Our previous calculations at 333 K led to a ratio {sigma}{sup (CN-/HCN)}/{sigma}{sup (CN-/DCN)} of about 13, which is significantly higher than recent experimental findings. This discrepancy is attributed to the neglect of correlation and polarization effects in the scattering calculation performed. We carried out a relaxed-self-consistent field calculation to determine the variation of the resonance parameters under these effects. We observe a shift in the positions of the shape resonance as well as a narrowing of the autoionization widths resulting in an isotope ratio of 3.2 at T=333 K; in closer agreement with the measured value.

  15. Dynamics of radiation induced isomerization for HCN-CNH

    SciTech Connect

    Na, Kyungsun; Jung, Christof; Reichl, L. E.

    2006-07-21

    We have analyzed the dynamics underlying the use of sequential radiation pulses to control the isomerization between the HCN and the CNH molecules. The appearance of avoided crossings among Floquet eigenphases as the molecule interacts with the radiation pulses is the key to understanding the isomerization dynamics, both in the adiabatic and nonadiabatic regimes. We find that small detunings of the incident pulses can have a significant effect on the outcome of the isomerization process for the model we consider.

  16. NMR determination of photorespiration in intact leaves using in vivo 13CO 2 labeling

    NASA Astrophysics Data System (ADS)

    Cegelski, Lynette; Schaefer, Jacob

    2006-01-01

    Solid-state 13C NMR measurements of intact soybean leaves labeled by 13CO 2 lead to the conclusion that photorespiration is 17% of photosynthesis for a well-watered and fertilized plant. This is the first direct assessment of the level of photorespiration in a functioning plant. A 13C{ 31P} rotational-echo double-resonance (REDOR) measurement tracked the incorporation of 13C label into intermediates in the Calvin cycle as a function of time. For labeling times of 5 min or less, the isotopic enrichment of the Calvin cycle depends on the flux of labeled carbon from 13CO 2, relative to the flux of unlabeled carbon from glycerate returned from the photorespiratory cycle. Comparisons of these two rates for a fixed value of the 13CO 2 concentration indicate that the ratio of the rate of photosynthesis to the rate of photorespiration of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in soybean leaves is 5.7. This translates into a photorespiratory CO 2 loss that is 21% of net CO 2 assimilation, about 80% of the value estimated from Rubisco kinetics parameters. The ratio of rates is reduced at low external CO 2 concentrations, as measured by net carbon assimilation rates. The carbon assimilation was determined from 13C-label spin counts converted into total carbon by the REDOR-determined isotopic enrichments of the Calvin cycle. The net carbon assimilation rates indicate that the rate of decarboxylation of glycine is not directly proportional to the oxygenase activity of Rubisco as is commonly assumed.

  17. NMR determination of photorespiration in intact leaves using in vivo 13CO2 labeling.

    PubMed

    Cegelski, Lynette; Schaefer, Jacob

    2006-01-01

    Solid-state 13C NMR measurements of intact soybean leaves labeled by 13CO2 lead to the conclusion that photorespiration is 17% of photosynthesis for a well-watered and fertilized plant. This is the first direct assessment of the level of photorespiration in a functioning plant. A 13C{31P} rotational-echo double-resonance (REDOR) measurement tracked the incorporation of 13C label into intermediates in the Calvin cycle as a function of time. For labeling times of 5 min or less, the isotopic enrichment of the Calvin cycle depends on the flux of labeled carbon from 13CO2, relative to the flux of unlabeled carbon from glycerate returned from the photorespiratory cycle. Comparisons of these two rates for a fixed value of the 13CO2 concentration indicate that the ratio of the rate of photosynthesis to the rate of photorespiration of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in soybean leaves is 5.7. This translates into a photorespiratory CO2 loss that is 21% of net CO2 assimilation, about 80% of the value estimated from Rubisco kinetics parameters. The ratio of rates is reduced at low external CO2 concentrations, as measured by net carbon assimilation rates. The carbon assimilation was determined from 13C-label spin counts converted into total carbon by the REDOR-determined isotopic enrichments of the Calvin cycle. The net carbon assimilation rates indicate that the rate of decarboxylation of glycine is not directly proportional to the oxygenase activity of Rubisco as is commonly assumed.

  18. Src Tyrosine Kinase Alters Gating of Hyperpolarization-Activated HCN4 Pacemaker Channel through Tyr531

    PubMed Central

    Li, Chen-Hong; Zhang, Qi; Teng, Bunyen; Mustafa, S. Jamal; Huang, Jian-Ying; Yu, Han-Gang

    2009-01-01

    We recently discovered that the constitutively active Src tyrosine kinase can enhance the HCN4 channel activity by binding to the channel protein. To investigate the mechanism of modulation by Src of HCN channels, we studied the effects of a selective inhibitor of Src tyrosine kinase, PP2, on HCN4 and its mutant channels ex pressed in HEK293 cells using whole-cell patch clamp technique. We found that PP2 can inhibit HCN4 currents by negatively shifting the voltage dependence of channel activation, decreasing the whole-cell channel conductance, and slowing activation and deactivation kinetics. Screening putative tyrosine residues subject to phosphorylation yielded two candidates: Tyr531 and Tyr554. Substituting HCN4-Tyr531 with phenylalanine largely abolished the effects of PP2 on HCN4 channels. Replacing HCN4-Tyr554 by phenylalanine did not abolish the effects of PP2 on voltage-dependent activation, but did eliminate PP2-induced slowing of channel kinetics. The inhibitory effects of HCN channels associated with reduced Src tyrosine activity is confirmed in HL-1 cardiomyocytes. Finally, we found that PP2 can decrease the heart rate in a mouse model. These results demonstrate that Src tyrosine kinase enhances HCN4 currents by shifting their activation to more positive potentials and increasing the whole-cell channel conductance as well as speeding the channel kinetics. The tyrosine residue that mediates most of Src actions on HCN4 channels is Tyr531. PMID:17977941

  19. Spironolactone Regulates HCN Protein Expression Through Micro-RNA-1 in Rats With Myocardial Infarction.

    PubMed

    Yu, Hua-Dong; Xia, Shuang; Zha, Cheng-Qin; Deng, Song-Bai; Du, Jian-Lin; She, Qiang

    2015-06-01

    Emerging evidence has shown that aldosterone blockers reduced the incidence of ventricular arrhythmias in patients with myocardial infarction (MI). However, the mechanism remains unknown. In this study, we investigated the mechanism by which spironolactone, a classic aldosterone blocker, regulates hyperpolarization-activated cyclic nucleotide-gated channel (HCN) protein expression in ischemic rat myocardium after MI. Eighteen rats surviving 24 hours after MI were randomly assigned into 3 groups: MI, spironolactone, and spironolactone + antagomir-1. Six sham-operated rats had a suture loosely tied around the left coronary artery, without ligation. The border zone of the myocardial infarct was collected from each rat at 1 week after MI. HCN2 and HCN4 protein and messenger RNA (mRNA) level were measured in addition to miRNA-1 levels. Spironolactone significantly increased miRNA-1 levels and downregulated HCN2 and HCN4 protein and mRNA levels. miRNA-1 suppression with antagomir-1 increased HCN2 and HCN4 protein levels; however, HCN2 and HCN4 mRNA levels were not affected. These results suggested that spironolactone could increase miRNA-1 expression in ischemic rat myocardium after MI and that the upregulation of miRNA-1 expression partially contributed to the posttranscriptional repression of HCN protein expression, which may contribute to the effect of spironolactone to reduce the incidence of MI-associated ventricular arrhythmias.

  20. An ab initio HCN/HNC rotational-vibrational line list and opacity function for astronomy

    NASA Astrophysics Data System (ADS)

    Harris, Gregory John

    HCN/HNC is an important molecule which is found throughout the universe. For example HCN/HNC is known to exist in comets, planetary atmospheres and the interstellar medium. HCN is also an important opacity source in carbon rich stars (C-stars). HCN masers have been observed in the circumstellar material around these C-stars and also in galaxies. Jorgensen and co-workers investigated model carbon star atmospheres in which they included HCN as an opacity source. They found that including a HCN opacity function had a remarkable effect: the atmosphere expanded by five times and the pressure of the atmosphere in the surface layers dropped by one or two orders of magnitude. This suggests that a full and detailed treatment of the rotational-vibrational spectrum of HCN/HNC could have a profound effect on the models of carbon stars, this provides the main motivation in this work. The temperatures of the stars in which HCN is an important opacity source Teff = 2000 - 3000 K. If HCN and HNC are in thermodynamic equilibrium it would be expected that HNC as well as HCN are found in significant populations. The transition dipoles of the fundamental bands of HNC are more than twice as strong as their HCN counter parts. These factors mean that both HCN and HNC will be considered, which makes a semiglobal treatment of the [H,C,N] system necessary. In this thesis an ab initio HCN/HNC linelist, from which accurate spectra and opacity functions can be calculated, is computed. Within this thesis I present least squares fits for ab initio semiglobal potential energy, dipole moment, relativistic correction and adiabatic correction surfaces. The potential energy surface (PES) is morphed for HNC geometries of the potential to improve the HNC representation of the surface. The PES and dipole moment surface (DMS) are used to perform quantum mechanical nuclear motion (rotational-vibrational) calculations with the DVR3D suite of codes. Preliminary calculations are made to optimise a ro

  1. Interaction of 13 CO 2 and bicarbonate with human hemoglobin preparations.

    PubMed

    Morrow, J S; Keim, P; Visscher, R B; Marshall, R C; Gurd, F R

    1973-05-01

    Formation of (13)C-resonances attributable to carbamino derivatives has been observed in human erythrocyte hemolysate preparations equilibrated with (13)CO(2) at 33 degrees . Carbamino formation is most marked in deoxyhemoglobin and at alkaline pH, and is very largely inhibited by the addition of 2,3-diphosphoglycerate or conversion to oxyhemoglobin. The prominent carbamino resonance at 30.0 ppm upfield of CS(2) is visible in the spectrum of packed, deoxygenated erythrocytes equilibrated in (13)CO(2). This chemical shift falls close to that observed with sperm-whale myoglobin and within 2 ppm upfield of that seen with simple amino acids and peptides. The bicarbonate-carbonate resonance near 33 ppm is broad in the hemoglobin preparations, which always contain some carbonic anhydrase, but becomes narrow in the presence of the carbonic anhydrase inhibitor, acetazolamide. The nuclear magnetic resonance condition of intermediate exchange rate with dissolved CO(2) (68.4 ppm) obtains in the absence of inhibitor. The process has marked consequences in reducing the spin-lattice relaxation time, T(1), of the bicarbonate resonance by more than 10 times. The deoxyhemoglobin carbamino resonance has a T(1) value of 700 msec, indistinguishable from that of the protein carbonyl resonance envelope.

  2. The RMS survey. 13CO observations of candidate massive YSOs in the northern Galactic plane

    NASA Astrophysics Data System (ADS)

    Urquhart, J. S.; Busfield, A. L.; Hoare, M. G.; Lumsden, S. L.; Oudmaijer, R. D.; Moore, T. J. T.; Gibb, A. G.; Purcell, C. R.; Burton, M. G.; Maréchal, L. J. L.; Jiang, Z.; Wang, M.

    2008-08-01

    Context: The Red MSX Source (RMS) survey is an ongoing multi-wavelength observational programme designed to return a large, high-resolution mid-infrared colour-selected sample of massive young stellar objects (MYSOs). We have identified 2000 MYSO candidates located within our Galaxy by comparing the colours of MSX and 2MASS point sources to those of known MYSOs. The aim of our follow-up observations is to identify other objects with similar colours such as ultra compact (UC) HII regions, evolved stars and planetary nebulae (PNe) and distinguish between genuine MYSOs and nearby low-mass YSOs. Aims: A critical part of our follow-up programme is to conduct 13CO molecular line observations in order to determine kinematic distances to all of our MYSO candidates. These distances will be used in combination with far-IR and (sub)millimetre fluxes to determine bolometric luminosities which will allow us to identify and remove nearby low-mass YSOs. In addition these molecular line observations will help in identifying evolved stars which are weak CO emitters. Methods: We have used the 15 m James Clerk Maxwell Telescope (JCMT), the 13.7 m telescope of the Purple Mountain Observatory (PMO), the 20 m Onsala telescope and the 22 m Mopra telescope to conduct molecular line observations towards 508 MYSOs candidates located in the 1st and 2nd Quadrants. These observations have been made at the J=1-0 (Mopra, Onsala and PMO) and J=2-1 (JCMT) rotational transition frequency of 13CO molecules and have a spatial resolution of 20´´-55´´, a sensitivity of T{A}* ≃ 0.1 K and a velocity resolution of 0.2 km s-1. We complement these targeted observations with 13CO spectra extracted from the Galactic Ring Survey (GRS), which have a velocity resolution of 0.21 km s-1 and sensitivity T{A}* ≃ 0.13-0.2 K, towards a further 403 RMS sources. Results: In this paper we present the results and analysis of the 13CO spectra obtained towards 911 MYSO candidates. We detect 13CO emission towards 780

  3. Structural mechanism for the regulation of HCN ion channels by the accessory protein TRIP8b

    PubMed Central

    DeBerg, Hannah A.; Bankston, John R.; Rosenbaum, Joel C.; Brzovic, Peter S.; Zagotta, William N.; Stoll, Stefan

    2015-01-01

    Summary Hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels underlie the cationic Ih current present in many neurons. The direct binding of cAMP to HCN channels increases the rate and extent of channel opening and results in a depolarizing shift in the voltage dependence of activation. TRIP8b is an accessory protein that regulates the cell surface expression and dendritic localization of HCN channels and reduces the cyclic nucleotide dependence of these channels. Here we use electron paramagnetic resonance (EPR) to show that TRIP8b binds to the apo state of the cyclic nucleotide-binding domain (CNBD) of HCN2 channels without changing the overall domain structure. With EPR and nuclear magnetic resonance (NMR), we locate TRIP8b relative to the HCN channel and identify the binding interface on the CNBD. These data provide a structural framework for understanding how TRIP8b regulates the cyclic nucleotide dependence of HCN channels. PMID:25800552

  4. HCN Producing Bacteria Enable Sensing Of Non-Bioavailable Hg Species by the Whole Cell Biosensor

    NASA Astrophysics Data System (ADS)

    Horvat, M.; Rijavec, T.; Koron, N.; Lapanje, A.

    2015-12-01

    Bacteria play an important role in Hg transformation reactions. The production of cyanide (HCN) and other secondary metabolites seems to be key elements involved in these transformations. Current hypotheses link the role of HCN production to growth inhibition of nonHCN producing competitor organisms (role of an antimicrobial agent). Our past investigations showed that HCN production did not correlate with antimicrobial activity and since pK value of HCN is very high (pK = 9,21), it can be expected that most of the produced HCN is removed from the microenvironment. This way, the expected inhibitory concentrations can hardly be reached. Accordingly, we proposed a new concept, where the ability of complexation of transient metals by HCN served as a regulation process for the accessibility of micro-elements. In our study, we focused on the presence of HCN producing bacteria and carried it out in the Hg contaminated environment connected to the Idrija Mercury Mine, Slovenia. We characterised the isolates according to the presence of Hg resistance (HgR), level of HCN production and genetic similarities. In laboratory setups, using our merR whole cell based biosensor, we determined the transformation of low bioavailable Hg0 and HgS forms into bioavailable Hg by these HCN producing bacteria. We observed that HgR strains producing HCN had the highest impact on increased Hg bioavailability. In the proposed ecological strategy HgR HCN producing bacteria increase their competitive edge over non-HgR competitors through the increase of Hg toxicity. Due to their activity, Hg is made available to other organisms as well and thus enters into the ecosystem. Finally, using some of the characteristics of bacteria (e.g. Hg resistance genetic elements), we developed a fully automated sensing approach, combining biosensorics and mechatronics, to measure the bioavailability of Hg in situ.

  5. On The Effect of Electron Collisions in the Excitation of Cometary HCN

    NASA Technical Reports Server (NTRS)

    Lovell, Amy J.; Kallivayalil, Nitya; Schloerb, F. Peter; Combi, Michael R.; Hansen, Kenneth C.; Gombosi, T. I.

    2004-01-01

    The electron-HCN collision rate for the excitation of rotational transitions of the HCN molecule is evaluated in comets C/1995 01 (Hale-Bopp) and C/1996 B2 (Hyakutake). Based on theoretical models of the cometary atmosphere, we show that collisions with electrons can provide a significant excitation mechanism for rotational transitions in the HCN molecule. Computed values of the cross section sigma(sub e-HCN) can be as high as 1.3 x cm2, more than 2 orders of magnitude greater than the commonly assumed HCN-H2O cross section. For the ground rotational transitions of HCN, the electron-HCN collision rate is found to exceed the HCN-H2O collision rate at distances greater than 3000 km from the cometary nucleus of Hale-Bopp and 1000 km from that of Hyakutake. Collisional excitation processes dominate over radiative excitation processes up to a distance of 160,000 km from the cometary nucleus of Hale-Bopp and 50,000 km from that of Hyakutake. Excitation models that neglect electron collisions can underestimate the HCN gas production rates by as much as a factor of 2.

  6. Photochemistry of methane and the formation of hydrocyanic acid (HCN) in the earth's early atmosphere

    NASA Technical Reports Server (NTRS)

    Zahnle, K. J.

    1986-01-01

    A one-dimensional photochemical model is used to analyze the photochemistries of CH4 and HCN in the primitive terrestrial atmosphere. CH4, N2, and HCN photolysis are examined. The background atmosphere and boundary conditions applied in the analysis are described. The formation of HCN as a by-product of N2 and CH4 photolysis is investigated; the effects of photodissociation and rainfall on HCN is discussed. The low and high CH4 mixing ratios and radical densities are studied.

  7. The change of HCN1/HCN2 mRNA expression in peripheral nerve after chronic constriction injury induced neuropathy followed by pulsed electromagnetic field therapy

    PubMed Central

    Liu, Hui; Zhou, Jun; Gu, Lianbing; Zuo, Yunxia

    2017-01-01

    Neuropathic pain is usually defined as a chronic pain state caused by peripheral or central nerve injury as a result of acute damage or systemic diseases. It remains a difficult disease to treat. Recent studies showed that the frequency of action potentials in nociceptive afferents is affected by the activity of hyperpolarization-activated cyclic nucleotide-gated cation channels (HCN) family. In the current study, we used a neuropathy rat model induced by chronic constriction injury (CCI) of sciatic nerve to evaluate the change of expression of HCN1/HCN2 mRNA in peripheral nerve and spinal cord. Rats were subjected to CCI with or without pulsed electromagnetic field (PEMF) therapy. It was found that CCI induced neural cell degeneration while PEMF promoted nerve regeneration as documented by Nissl staining. CCI shortened the hind paw withdrawal latency (PWL) and hind paw withdrawal threshold (PWT) and PEMF prolonged the PWL and PWT. In addition, CCI lowers the expression of HCN1 and HCN2 mRNA and PEMF cannot restore the expression of HCN1 and HCN2 mRNA. Our results indicated that PEMF can promote nerve regeneration and could be used for the treatment of neuropathic pain. PMID:27901476

  8. Lidocaine Inhibits HCN Currents in Rat Spinal Substantia Gelatinosa Neurons

    PubMed Central

    Hu, Tao; Liu, Nana; Lv, Minhua; Ma, Longxian; Peng, Huizhen; Peng, Sicong

    2016-01-01

    BACKGROUND: Lidocaine, which blocks voltage-gated sodium channels, is widely used in surgical anesthesia and pain management. Recently, it has been proposed that the hyperpolarization-activated cyclic nucleotide (HCN) channel is one of the other novel targets of lidocaine. Substantia gelatinosa in the spinal dorsal horn, which plays key roles in modulating nociceptive information from primary afferents, comprises heterogeneous interneurons that can be electrophysiologically categorized by firing pattern. Our previous study demonstrated that a substantial proportion of substantia gelatinosa neurons reveal the presence of HCN current (Ih); however, the roles of lidocaine and HCN channel expression in different types of substantia gelatinosa neurons remain unclear. METHODS: By using the whole-cell patch-clamp technique, we investigated the effect of lidocaine on Ih in rat substantia gelatinosa neurons of acute dissociated spinal cord slices. RESULTS: We found that lidocaine rapidly decreased the peak Ih amplitude with an IC50 of 80 μM. The inhibition rate on Ih was not significantly different with a second application of lidocaine in the same neuron. Tetrodotoxin, a sodium channel blocker, did not affect lidocaine’s effect on Ih. In addition, lidocaine shifted the half-activation potential of Ih from −109.7 to −114.9 mV and slowed activation. Moreover, the reversal potential of Ih was shifted by −7.5 mV by lidocaine. In the current clamp, lidocaine decreased the resting membrane potential, increased membrane resistance, delayed rebound depolarization latency, and reduced the rebound spike frequency. We further found that approximately 58% of substantia gelatinosa neurons examined expressed Ih, in which most of them were tonically firing. CONCLUSIONS: Our studies demonstrate that lidocaine strongly inhibits Ih in a reversible and concentration-dependent manner in substantia gelatinosa neurons, independent of tetrodotoxin-sensitive sodium channels. Thus, our

  9. Ecological and Molecular Study of Soil Chemoautotrophic Microorganisms via the Sequestration of Atmospheric 13CO2

    NASA Astrophysics Data System (ADS)

    Hart, K. M.; Kelleher, B.; Allen, C.; Simpson, A.

    2009-05-01

    Soil Organic Matter (SOM) is the most complicated biomaterial on Earth and stores significantly more carbon than is currently present in the atmosphere [1]. It has been recently reported that humic material in SOM is a highly complex mixture of microbial and plant biopolymers and not a distinct chemical fraction as previously thought [2]. Furthermore, it has been reported that the microbial biomass contribution to SOM is not comprised of mainly humic materials and that in fact the contribution to SOM by soil microorganisms has been seriously underestimated [3]. Therefore, the question arises if we underestimate microbial biomass in soil do we also underestimate carbon sequestration by soil microbes? Soil microorganisms consist of a large range of diverse species with soil bacteria contributing a large proportion of the biomass content. Autotrophs are organisms that can produce organic compounds from CO2 as the sole carbon source, using either light (photoautotroph) or inorganic reactions (chemoautotroph) as the energy source. The aim of this project is to enrich chemoautotrophic soil microbes with carbon-13 (13C) sequestered as 13CO2. Once labeled, these target microbes can be differentiated from other microbes using techniques such as Stable Isotope Probing (SIP) and carbon NMR. This enrichment is facilitated via incubation in a custom built environmental chamber and the controlled introduction of 13CO2. Before introduction of 13CO2 the chambers capabilities had to be fully characterized to ensure that it was fit for purpose. Mixed cultures of soil chemoautotrophic microorganisms were propagated from different soils and data collected using the environmental chamber demonstrated that CO2 fluctuations mimicked the natural activity of actively growing chemoautotrophic cultures. Therefore using this soil slurry approach, a mixed culture of soil autotrophs will be exposed to 13CO2 prior to the harvesting of the microbial biomass. Ion chromatographic analysis of the

  10. Molecular dynamics simulations of laser induced surface melting in orthorhombic Al13Co4

    NASA Astrophysics Data System (ADS)

    Sonntag, S.; Roth, J.; Trebin, H.-R.

    2010-10-01

    Laser induced surface melting of the aluminum-cobalt alloy Al13Co4 is investigated. For the simulations of the lattice ions we use molecular dynamics, while for the time evolution of the electron temperature a generalized heat-conduction equation is solved. Energy transfer between the sub-systems is allowed by an electron-phonon coupling term. This combined treatment of the electronic and atomic systems is an extension of the well-known two-temperature model [Anisimov et al. in JETP Lett. 39(2), 1974]. The alloy shows large structural affinity to decagonal quasicrystals, which have an in-plane five-fold symmetry,while in perpendicular direction the planes are stacked periodically. As a consequence we observe slight anisotropic melting behavior.

  11. Cotton-Mouton polarimeter with HCN laser on CHS

    SciTech Connect

    Akiyama, T.; Kawahata, K.; Ito, Y.; Okajima, S.; Nakayama, K.; Okamura, S.; Matsuoka, K.; Isobe, M.; Nishimura, S.; Suzuki, C.; Yoshimura, Y.; Nagaoka, K.; Takahashi, C.

    2006-10-15

    Polarimeters based on the Cotton-Mouton effect hold promise for electron density measurements. We have designed and installed a Cotton-Mouton polarimeter on the Compact Helical System. The Cotton-Mouton effect is measured as the phase difference between probe and reference beams. In this system, an interferometric measurement can be performed simultaneously with the same probe chord. The light source is a HCN laser (wavelength of 337 {mu}m). Digital complex demodulation is adopted for small phase analysis. The line averaged density evaluated from the polarimeter along a plasma center chord is almost consistent with that from the interferometer.

  12. Frequency analysis of the laser driven nonlinear dynamics of HCN.

    PubMed

    Lopez-Pina, A; Losada, J C; Benito, R M; Borondo, F

    2016-12-28

    We study the vibrational dynamics of a model for the HCN molecule in the presence of a monochromatic laser field. The variation of the structural behavior of the system as a function of the laser frequency is analyzed in detail using the smaller alignment index, frequency maps, and diffusion coefficients. It is observed that the ergodicity of the system depends on the frequency of the excitation field, especially in its transitions from and into chaos. This provides a roadmap for the possibility of bond excitation and dissociation in this molecule.

  13. The presence of pacemaker HCN channels identifies theta rhythmic GABAergic neurons in the medial septum.

    PubMed

    Varga, Viktor; Hangya, Balázs; Kránitz, Kinga; Ludányi, Anikó; Zemankovics, Rita; Katona, István; Shigemoto, Ryuichi; Freund, Tamás F; Borhegyi, Zsolt

    2008-08-15

    The medial septum (MS) is an indispensable component of the subcortical network which synchronizes the hippocampus at theta frequency during specific stages of information processing. GABAergic neurons exhibiting highly regular firing coupled to the hippocampal theta rhythm are thought to form the core of the MS rhythm-generating network. In recent studies the hyperpolarization-activated, cyclic nucleotide-gated non-selective cation (HCN) channel was shown to participate in theta synchronization of the medial septum. Here, we tested the hypothesis that HCN channel expression correlates with theta modulated firing behaviour of MS neurons by a combined anatomical and electrophysiological approach. HCN-expressing neurons represented a subpopulation of GABAergic cells in the MS partly overlapping with parvalbumin (PV)-containing neurons. Rhythmic firing in the theta frequency range was characteristic of all HCN-expressing neurons. In contrast, only a minority of HCN-negative cells displayed theta related activity. All HCN cells had tight phase coupling to hippocampal theta waves. As a group, PV-expressing HCN neurons had a marked bimodal phase distribution, whereas PV-immunonegative HCN neurons did not show group-level phase preference despite significant individual phase coupling. Microiontophoretic blockade of HCN channels resulted in the reduction of discharge frequency, but theta rhythmic firing was perturbed only in a few cases. Our data imply that HCN-expressing GABAergic neurons provide rhythmic drive in all phases of the hippocampal theta activity. In most MS theta cells rhythm genesis is apparently determined by interactions at the level of the network rather than by the pacemaking property of HCN channels alone.

  14. Quantifying the emissions of HCN from on-road vehicles in urban areas

    NASA Astrophysics Data System (ADS)

    Moussa, S. G.; Leithead, A.; Wentzell, J. J.; Lu, G.; Li, S.; Brook, J.; Liggio, J.

    2013-12-01

    Hydrogen Cyanide (HCN), has been considered a marker for biomass burning emissions. Despite its adverse health impacts, estimate of its global sources and sinks are highly uncertain due to a limited number of field and laboratory studies. In particular, HCN emissions from automobile exhaust are not well constrained for modern vehicles, and thought to be relatively small compared to emissions from biomass burning. In the current study, HCN emissions from individual diesel and gasoline vehicles were quantified as a function of engine driving mode, and fuel type. Proton transfer Reaction-Time of Flight-Mass spectrometry (PTR-ToF-MS) was used to measure HCN emissions from diesel engines operating on ultra-low sulfur diesel (ULSD) and various bio-diesel blends including Soy, Tallow, and Canola. Significant emissions of HCN were observed from all vehicles, and enhanced with the use of biodiesel. In addition, ambient measurements of HCN in a traffic dominated urban area in Toronto, Canada demonstrated that a correlation between HCN, and traditional vehicle emissions markers such as benzene and xylenes exists and indicating that HCN has the potential to be a marker of fuel combustion. The ambient data and the calculated emission factors further suggest that vehicular emissions are a major source of HCN even in the presence of biomass burning, and that near roadway conditions may represent the dominant exposure pathway to HCN in urban areas. Results of this study have important implications on HCN global budget, health impacts in urban areas and the effect of alternate fuels on the emissions of this toxic species.

  15. Unraveling Subunit Cooperativity in Homotetrameric HCN2 Channels

    PubMed Central

    Benndorf, Klaus; Thon, Susanne; Schulz, Eckhard

    2012-01-01

    In a multimeric receptor protein, the binding of a ligand can modulate the binding of a succeeding ligand. This phenomenon, called cooperativity, is caused by the interaction of the receptor subunits. By using a complex Markovian model and a set of parameters determined previously, we analyzed how the successive binding of four ligands leads to a complex cooperative interaction of the subunits in homotetrameric HCN2 pacemaker channels. The individual steps in the model were characterized by Gibbs free energies for the equilibria and activation energies, specifying the affinity of the binding sites and the transition rates, respectively. Moreover, cooperative free energies were calculated for each binding step in both the closed and the open channel. We show that the cooperativity sequence positive-negative-positive determined for the binding affinity is generated by the combined effect of very different cooperativity sequences determined for the binding and unbinding rates, which are negative-negative-positive and no-negative-no, respectively. It is concluded that in the ligand-induced activation of HCN2 channels, the sequence of cooperativity based on the binding affinity is caused by two even qualitatively different sequences of cooperativity that are based on the rates of ligand binding and unbinding. PMID:23199914

  16. HCN1 channels reduce the rate of exocytosis from a subset of cortical synaptic terminals

    PubMed Central

    Huang, Zhuo; Li, Gengyu; Aguado, Carolina; Lujan, Rafael; Shah, Mala M.

    2017-01-01

    The hyperpolarization-activated cyclic nucleotide-gated (HCN1) channels are predominantly located in pyramidal cell dendrites within the cortex. Recent evidence suggests these channels also exist pre-synaptically in a subset of synaptic terminals within the mature entorhinal cortex (EC). Inhibition of pre-synaptic HCN channels enhances miniature excitatory post-synaptic currents (mEPSCs) onto EC layer III pyramidal neurons, suggesting that these channels decrease the release of the neurotransmitter, glutamate. Thus, do pre-synaptic HCN channels alter the rate of synaptic vesicle exocytosis and thereby enhance neurotransmitter release? To address this, we imaged the release of FM1-43, a dye that is incorporated into synaptic vesicles, from EC synaptic terminals using two photon microscopy in slices obtained from forebrain specific HCN1 deficient mice, global HCN1 knockouts and their wildtype littermates. This coupled with electrophysiology and pharmacology showed that HCN1 channels restrict the rate of exocytosis from a subset of cortical synaptic terminals within the EC and in this way, constrain non-action potential-dependent and action potential-dependent spontaneous release as well as synchronous, evoked release. Since HCN1 channels also affect post-synaptic potential kinetics and integration, our results indicate that there are diverse ways by which HCN1 channels influence synaptic strength and plasticity. PMID:28071723

  17. Chemical evolution. XXII - The hydantoins released on hydrolysis of HCN oligomers

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Wos, J. D.; Lobo, A. P.

    1974-01-01

    The isolation of three hydantoins from HCN oligomers is described. One of these hydantoins, 5-carboxymethylidine hydantoin (5-CMH), rearranges to pyrimidine orotic acid in basic solution. The isolation of 5-CMH suggests the possibility that pyrimidines were formed directly from HCN on the primitive earth.

  18. First Principles Study of HCN Adsorption on Graphene Doped with 5d Transition Metal

    NASA Astrophysics Data System (ADS)

    Dong, Hai-Kuan; Wang, Yong-Ping; Shi, Li Bin

    2016-11-01

    Hydrogen cyanide (HCN) adsorption on graphene doped with 5d transition metal (TM) is investigated by the first principles based on density functional theory. It is observed that Hg atom cannot be doped into graphene due to saturated valence electron configurations of 5d106s2. Three kinds of HCN adsorption configurations are investigated, in which H, C and N in HCN are close to the adsorption site, respectively. The most stable adsorption configuration is obtained by total energy optimization. HCN adsorption can be studied by adsorption energy and electron density difference. HCN can only be physisorbed on Ir, Pt and Au-doped graphenes, while chemisorption is observed for Lu, Hf, Ta, W, Re and Os-doped graphenes. The band structure is calculated by B3LYP and Generalized gradient approximation (GGA) functionals. It is observed from B3LYP method that the conductivity of Lu, Hf, Re and Os-doped graphenes does not obviously change before and after HCN adsorption. Ta and W-doped graphenes change from semiconductor to metal after adsorption of HCN molecule. The results indicate that Ta and W-doped graphenes may be a promising sensor for detecting HCN. This study provides a useful basis for understanding of a wide variety of physical properties on graphene.

  19. Improvement of the positive bias stability of a-IGZO TFTs by the HCN treatment

    NASA Astrophysics Data System (ADS)

    Kim, Myeong-Ho; Choi, Myung-Jea; Kimura, Katsuya; Kobayashi, Hikaru; Choi, Duck-Kyun

    2016-12-01

    In recent years, many researchers have attempted to improve the bias stability of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). In this study, the hydrogen cyanide (HCN) treatment was carried out to improve the positive bias stability of bottom-gate a-IGZO TFTs. The HCN treatment was performed using a 0.1 M HCN solution with a pH of 10 at room temperature. Before applying the positive bias stress, there were no differences in the major electrical properties, including the saturation mobility (μsat), threshold voltage (Vth), and subthreshold swing (S/S), between HCN-treated and non-HCN-treated devices. However, after applying the positive bias stress, the HCN-treated device showed superior bias stability compared to the non-HCN-treated device. This difference is associated with the passivation of the defect states and the surface of the back-channel layer of the HCN-treated device by cyanide ions.

  20. The RMS survey. 13CO observations of candidate massive YSOs in the southern Galactic plane

    NASA Astrophysics Data System (ADS)

    Urquhart, J. S.; Busfield, A. L.; Hoare, M. G.; Lumsden, S. L.; Oudmaijer, R. D.; Moore, T. J. T.; Gibb, A. G.; Purcell, C. R.; Burton, M. G.; Marechal, L. J. L.

    2007-11-01

    Context: The Red MSX Source (RMS) survey is an ongoing multi-wavelength observational programme designed to return a large, well-selected sample of massive young stellar objects (MYSOs). We have identified 2000 MYSOs candidates located within our Galaxy by comparing the colours of MSX and 2MASS point sources to those of known MYSOs. The aim of our follow-up observations is to identify other contaminating objects such as ultra compact (UC) HII regions, evolved stars and planetary nebulae (PNe) and distinguish between genuine MYSOs and nearby low-mass YSOs. Aims: A critical part of our follow-up programme is to conduct 13CO molecular line observations in order to determine kinematic distances to all of our MYSO candidates. These distances will be used in combination with far-IR and (sub)millimetre fluxes to determine bolometric luminosities which will allow us to identify and remove nearby low-mass YSOs. In addition these molecular line observations will help in identifying evolved stars which are weak CO emitters. Methods: We have used the 22 m Mopra telescope, the 15 m JCMT and the 20 m Onsala telescope to conduct molecular line observations towards 854 MYSOs candidates located in the 3rd and 4th quadrants. These observations have been made at the J = 1-0 (Mopra and Onsala) and J = 2-1 (JCMT) rotational transition frequency of 13CO molecules and have a spatial resolution of 20´´-40´´, a sensitivity of T{A}* ≃ 0.1 K and a velocity resolution of 0.2 km s-1. Results: We detect 13CO emission towards a total of 752 of the 854 RMS sources observed ( 88%). In total 2132 emission components are detected above 3σ level (typically T^*{A} ≥ 0.3 K). Multiple emission profiles are observed towards the majority of these sources - 461 sources ( 60%) - with an average of 4 molecular clouds detected along the line of sight. These multiple emission features make it difficult to assign a kinematic velocity to many of our sample. We have used archival CS (J = 2-1) and maser

  1. Determination of the HNC to HCN abundance ratio in giant molecular clouds

    NASA Astrophysics Data System (ADS)

    Goldsmith, P. F.; Langer, W. D.; Ellder, J.; Kollberg, E.; Irvine, W.

    1981-10-01

    The lines of the rare isotopes (H-13)CN, H(C-15)N, H(N-13)C, and (H-15)NC, which are sufficiently weak to be little affected by saturation, are used to measure the relative abundance of the isomers HCN and HNC in four giant molecular clouds. The low values of the HNC/HCN abundance ratio, which range from 0.015 to 0.40, are (1) similar to those found in warm sources from the common isotopes by Wootten et al. (1978), (2) not consistent with HNC and HCN production solely from various sources of the precursor ion H2CN(+), and (3) indicate that another source of HCN is required in warm, giant molecular clouds. It is suggested that neutral atom-molecule reactions may be an important contribution to the HCN production rate in such regions.

  2. Tracing photosynthetic carbon in leaves with nanoSIMS after 13CO2 labelling

    NASA Astrophysics Data System (ADS)

    Dannoura, Masako; Takeuchi, Miyuki; Kominami, Yuji; Takanashi, Satoru; Kenichi, Yoshimura; Ataka, Mioko

    2015-04-01

    To understand the carbon allocation of the tree and forest ecosystem, it is important to consider the residence time of carbon in different pools at suitable time scales. For example the carbon used for respiration will stay a few minutes to a few days in the tree, the carbon used for storage or structure of leaves will stay months to years, and the carbon used for wood structure, it will stay over the whole lifespan of the tree. The leaves are the entrance of carbon in trees where it can be used for foliage growth and maintenance or exported to the other organs or the other forest ecosystem compartments. Tracing carbon isotope using NanoSIMS technique is one of useful methods to estimate where and how long the carbon stay in the tree organs. In this study, 13CO2 pulse labelling were conducted and 13C was measured by IRMS to see the amount of C remaining in the leaves with time.NanoSIMS was used to localize where the labelled C remained within the leaf tissue. Twice labelling were done on branches of Quercus serrata at FFPRI(Forest and Forest Products research Institute) in Kyoto, Japan. The first labelling was in 30 April 2012 when the leaves start flushing and the second one was in 29 May 2012 when the leaves were completely deployed. For both labelling experiment, one branch was selected and covered with transparent plastic bag. CO2 concentration was recorded with IRGA and air temperature inside the chamber was monitored. Then 13CO2 was injected into the bag, and after 1 hour, the bag was removed and the branch was again exposed to ambient air. Leaves were collected before and 10-12 times after labelling and their isotope compositions were measured by IRMS. The leaf collected just after labelling and 6 days after labelling were used for NanoSIMS observation. Samples for nanoSIMS were preserved in glutaraldehyde and then embed in epoxy resin. The sliced sample were placed on the silicon wafer and observed by NanoSIMS 50L(Cameca, France). The 13C was highest just

  3. Src tyrosine kinase alters gating of hyperpolarization-activated HCN4 pacemaker channel through Tyr531.

    PubMed

    Li, Chen-Hong; Zhang, Qi; Teng, Bunyen; Mustafa, S Jamal; Huang, Jian-Ying; Yu, Han-Gang

    2008-01-01

    We recently discovered that the constitutively active Src tyrosine kinase can enhance hyperpolarization-activated, cyclic nucleotide-gated (HCN) 4 channel activity by binding to the channel protein. To investigate the mechanism of modulation by Src of HCN channels, we studied the effects of a selective inhibitor of Src tyrosine kinase, 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2), on HCN4 and its mutant channels expressed in HEK 293 cells by using a whole cell patch-clamp technique. We found that PP2 can inhibit HCN4 currents by negatively shifting the voltage dependence of channel activation, decreasing the whole cell channel conductance, and slowing activation and deactivation kinetics. Screening putative tyrosine residues subject to phosphorylation yielded two candidates: Tyr(531) and Tyr(554). Substituting HCN4-Tyr(531) with phenylalanine largely abolished the effects of PP2 on HCN4 channels. Replacing HCN4-Tyr(554) with phenylalanine did not abolish the effects of PP2 on voltage-dependent activation but did eliminate PP2-induced slowing of channel kinetics. The inhibitory effects of HCN channels associated with reduced Src tyrosine activity is confirmed in HL-1 cardiomyocytes. Finally, we found that PP2 can decrease the heart rate in a mouse model. These results demonstrate that Src tyrosine kinase enhances HCN4 currents by shifting their activation to more positive potentials and increasing the whole cell channel conductance as well as speeding the channel kinetics. The tyrosine residue that mediates most of Src's actions on HCN4 channels is Tyr(531).

  4. HCN4 Dynamically Marks the First Heart Field and Conduction System Precursors

    PubMed Central

    Lin, Lizhu; Lowe, Jennifer; Zhang, Qingquang; Bu, Lei; Chen, Yihan; Chen, Ju; Sun, Yunfu; Evans, Sylvia M.

    2013-01-01

    Rationale To date, there has been no specific marker of the first heart field to facilitate understandings of contributions of the first heart field to cardiac lineages. Cardiac arrhythmia is a leading cause of death, often resulting from abnormalities in the cardiac conduction system (CCS). Understanding origins and identifying markers of CCS lineages is an essential step toward modeling diseases of the CCS and for development of biological pacemakers. Objective To investigate HCN4 as a marker for the first heart field and for precursors of distinct components of the CCS, and gain insight into contributions of first and second heart lineages to the CCS. Methods and Results HCN4-CreERT2, -nuclear LacZ and -H2BGFP mouse lines were generated. HCN4 expression was examined by means of immunostaining with HCN4 antibody and reporter gene expression. Lineage studies were performed using HCN4CreERT2, Isl1Cre, Nkx2.5Cre, and Tbx18Cre, coupled to co-immunostaining with CCS markers. Results demonstrated that, at cardiac crescent stages, HCN4 marks the first heart field, with HCN4CreERT2 allowing assessment of cell fates adopted by first heart field myocytes. Throughout embryonic development, HCN4 expression marked distinct CCS precursors at distinct stages, marking the entire CCS by late fetal stages. We also noted expression of HCN4 in distinct subsets of endothelium at specific developmental stages. Conclusions This study provides insight into contributions of first and second heart lineages to the CCS and highlights the potential utility of HCN4 in conjunction with other markers for optimization of protocols for generation and isolation of specific conduction system precursors. PMID:23743334

  5. A joint global carbon inversion system using both CO2 and 13CO2 atmospheric concentration data

    NASA Astrophysics Data System (ADS)

    Chen, Jing M.; Mo, Gang; Deng, Feng

    2017-03-01

    Observations of 13CO2 at 73 sites compiled in the GLOBALVIEW database are used for an additional constraint in a global atmospheric inversion of the surface CO2 flux using CO2 observations at 210 sites (62 collocated with 13CO2 sites) for the 2002-2004 period for 39 land regions and 11 ocean regions. This constraint is implemented using prior CO2 fluxes estimated with a terrestrial ecosystem model and an ocean model. These models simulate 13CO2 discrimination rates of terrestrial photosynthesis and ocean-atmosphere diffusion processes. In both models, the 13CO2 disequilibrium between fluxes to and from the atmosphere is considered due to the historical change in atmospheric 13CO2 concentration. This joint inversion system using both13CO2 and CO2 observations is effectively a double deconvolution system with consideration of the spatial variations of isotopic discrimination and disequilibrium. Compared to the CO2-only inversion, this 13CO2 constraint on the inversion considerably reduces the total land carbon sink from 3.40 ± 0.84 to 2.53 ± 0.93 Pg C year-1 but increases the total oceanic carbon sink from 1.48 ± 0.40 to 2.36 ± 0.49 Pg C year-1. This constraint also changes the spatial distribution of the carbon sink. The largest sink increase occurs in the Amazon, while the largest source increases are in southern Africa, and Asia, where CO2 data are sparse. Through a case study, in which the spatial distribution of the annual 13CO2 discrimination rate over land is ignored by treating it as a constant at the global average of -14. 1 ‰, the spatial distribution of the inverted CO2 flux over land was found to be significantly modified (up to 15 % for some regions). The uncertainties in our disequilibrium flux estimation are 8.0 and 12.7 Pg C year-1 ‰ for land and ocean, respectively. These uncertainties induced the unpredictability of 0.47 and 0.54 Pg C year-1 in the inverted CO2 fluxes for land and ocean, respectively. Our joint inversion system is therefore

  6. ALMA observations of the variable 12CO/13CO ratio around the asymptotic giant branch star R Sculptoris

    NASA Astrophysics Data System (ADS)

    Vlemmings, W. H. T.; Maercker, M.; Lindqvist, M.; Mohamed, S.; Olofsson, H.; Ramstedt, S.; Brunner, M.; Groenewegen, M. A. T.; Kerschbaum, F.; Wittkowski, M.

    2013-08-01

    The 12CO/13CO ratio is often used as a measure of the 12C/13C ratio in the circumstellar environment, carrying important information about the stellar nucleosynthesis. External processes can change the 12CO and 13CO abundances, and spatially resolved studies of the 12CO/13CO ratio are needed to quantify the effect of these processes on the globally determined values. Additionally, such studies provide important information on the conditions in the circumstellar environment. The detached-shell source R Scl, displaying CO emission from recent mass loss, in a binary-induced spiral structure as well as in a clumpy shell produced during a thermal pulse, provides a unique laboratory for studying the differences in CO isotope abundances throughout its recent evolution. We observed both the 12CO(J = 3 → 2) and the 13CO(J = 3 → 2) line using ALMA. We find significant variations in the 12CO/13CO intensity ratios and consequently in the abundance ratios. The average CO isotope abundance ratio is at least a factor three lower in the shell (~19) than that in the present-day (≲300 years) mass loss (>60). Additionally, variations in the ratio of more than an order of magnitude are found in the shell itself. We attribute these variations to the competition between selective dissociation and isotope fractionation in the shell, of which large parts cannot be warmer than ~35 K. However, we also find that the 12CO/13CO ratio in the present-day mass loss is significantly higher than the 12C/13C ratio determined in the stellar photosphere from molecular tracers (~19). The origin of this discrepancy is still unclear, but we speculate that it is due to an embedded source of UV-radiation that is primarily photo-dissociating 13CO. This radiation source could be the hitherto hidden companion. Alternatively, the UV-radiation could originate from an active chromosphere of R Scl itself. Our results indicate that caution should be taken when directly relating the 12CO/13CO intensity and 12

  7. 13C Tracking after 13CO2 Supply Revealed Diurnal Patterns of Wood Formation in Aspen.

    PubMed

    Mahboubi, Amir; Linden, Pernilla; Hedenström, Mattias; Moritz, Thomas; Niittylä, Totte

    2015-06-01

    Wood of trees is formed from carbon assimilated in the photosynthetic tissues. Determining the temporal dynamics of carbon assimilation, subsequent transport into developing wood, and incorporation to cell walls would further our understanding of wood formation in particular and tree growth in general. To investigate these questions, we designed a (13)CO2 labeling system to study carbon transport and incorporation to developing wood of hybrid aspen (Populus tremula × tremuloides). Tracking of (13)C incorporation to wood over a time course using nuclear magnetic resonance spectroscopy revealed diurnal patterns in wood cell wall biosynthesis. The dark period had a differential effect on (13)C incorporation to lignin and cell wall carbohydrates. No (13)C was incorporated into aromatic amino acids of cell wall proteins in the dark, suggesting that cell wall protein biosynthesis ceased during the night. The results show previously unrecognized temporal patterns in wood cell wall biosynthesis, suggest diurnal cycle as a possible cue in the regulation of carbon incorporation to wood, and establish a unique (13)C labeling method for the analysis of wood formation and secondary growth in trees.

  8. A Tentative Identification of HCN Ice on Triton

    NASA Astrophysics Data System (ADS)

    Burgdorf, M.; Cruikshank, D. P.; Dalle Ore, C. M.; Sekiguchi, T.; Nakamura, R.; Orton, G.; Quirico, E.; Schmitt, B.

    2010-08-01

    Spectra of Triton between 1.8 and 5.5 μm, obtained in 2007 May and 2009 November, have been analyzed to determine the global surface composition. The spectra were acquired with the grism and the prism of the Infrared Camera on board AKARI with spectral resolutions of 135 and 22, respectively. The data from 4 to 5 μm are shown in this Letter and compared to the spectra of N2, CO, and CO2, i.e., all the known ices on this moon that have distinct bands in this previously unexplored wavelength range. We report the detection of a 4σ absorption band at 4.76 μm (2101 cm-1), which we attribute tentatively to the presence of solid HCN. This is the sixth ice to be identified on Triton and an expected component of its surface because it is a precipitating photochemical product of Triton's thin N2 and CH4 atmosphere. It is also formed directly by irradiation of mixtures of N2 and CH4 ices. Here we consider only pure HCN, although it might be dissolved in N2 on the surface of Triton because of the evaporation and recondensation of N2 over its seasonal cycle. The AKARI spectrum of Triton also covers the wavelengths of the fundamental (1-0) band of β-phase N2 ice (4.296 μm, 2328 cm-1), which has never been detected in an astronomical body before, and whose presence is consistent with the overtone (2-0) band previously reported. Fundamental bands of CO and CO2 ices are also present. This work is based on observations with AKARI, a JAXA project with the participation of ESA.

  9. A TENTATIVE IDENTIFICATION OF HCN ICE ON TRITON

    SciTech Connect

    Burgdorf, M.; Cruikshank, D. P.; Dalle Ore, C. M.; Sekiguchi, T.; Nakamura, R.; Orton, G.; Quirico, E.; Schmitt, B.

    2010-08-01

    Spectra of Triton between 1.8 and 5.5 {mu}m, obtained in 2007 May and 2009 November, have been analyzed to determine the global surface composition. The spectra were acquired with the grism and the prism of the Infrared Camera on board AKARI with spectral resolutions of 135 and 22, respectively. The data from 4 to 5 {mu}m are shown in this Letter and compared to the spectra of N{sub 2}, CO, and CO{sub 2}, i.e., all the known ices on this moon that have distinct bands in this previously unexplored wavelength range. We report the detection of a 4{sigma} absorption band at 4.76 {mu}m (2101 cm{sup -1}), which we attribute tentatively to the presence of solid HCN. This is the sixth ice to be identified on Triton and an expected component of its surface because it is a precipitating photochemical product of Triton's thin N{sub 2} and CH{sub 4} atmosphere. It is also formed directly by irradiation of mixtures of N{sub 2} and CH{sub 4} ices. Here we consider only pure HCN, although it might be dissolved in N{sub 2} on the surface of Triton because of the evaporation and recondensation of N{sub 2} over its seasonal cycle. The AKARI spectrum of Triton also covers the wavelengths of the fundamental (1-0) band of {beta}-phase N{sub 2} ice (4.296 {mu}m, 2328 cm{sup -1}), which has never been detected in an astronomical body before, and whose presence is consistent with the overtone (2-0) band previously reported. Fundamental bands of CO and CO{sub 2} ices are also present.

  10. HCN hyperfine ratio analysis of massive molecular clumps

    NASA Astrophysics Data System (ADS)

    Schap, W. J.; Barnes, P. J.; Ordoñez, A.; Ginsburg, A.; Yonekura, Y.; Fukui, Y.

    2017-03-01

    We report a new analysis protocol for HCN hyperfine data, based on the PYSPECKIT package, and results of using this new protocol to analyse a sample area of seven massive molecular clumps from the Census of High- and Medium-mass Protostars (CHaMP) survey, in order to derive maps of column density for this species. There is a strong correlation between the HCN integrated intensity, IHCN, and previously reported I_HCO+ in the clumps, but I_N_{2H+} is not well correlated with either of these other two 'dense gas tracers'. The four fitted parameters from PYSPECKIT in this region fall in the range of VLSR = 8-10 km s-1, σV = 1.2-2.2 km s-1, Tex = 4-15 K, and τ = 0.2-2.5. These parameters allow us to derive a column density map of these clouds, without limiting assumptions about the excitation or opacity. A more traditional (linear) method of converting IHCN to total mass column gives much lower clump masses than our results based on the hyperfine analysis. This is primarily due to areas in the sample region of low I, low Tex, and high τ. We conclude that there may be more dense gas in these massive clumps not engaged in massive star formation than previously recognized. If this result holds for other clouds in the CHaMP sample, it would have dramatic consequences for the calibration of the Kennicutt-Schmidt star formation laws, including a large increase in the gas depletion time-scale in such regions.

  11. ALMA HCN and HCO+ J =3-2 Observations of Optical Seyfert and Luminous Infrared Galaxies: Confirmation of Elevated HCN-to-HCO+ Flux Ratios in AGNs

    NASA Astrophysics Data System (ADS)

    Imanishi, Masatoshi; Nakanishi, Kouichiro; Izumi, Takuma

    2016-12-01

    We present the results of our ALMA observations of three active galactic nucleus (AGN)-dominated nuclei in optical Seyfert 1 galaxies (NGC 7469, I Zw 1, and IC 4329 A) and eleven luminous infrared galaxies (LIRGs) with various levels of infrared estimated energetic contributions by AGNs at the HCN and HCO+ J = 3 - 2 emission lines. The HCN and HCO+ J = 3 - 2 emission lines are clearly detected at the main nuclei of all sources, except for IC 4329 A. The vibrationally excited (v 2 = 1f) HCN J = 3 - 2 and HCO+ J = 3 - 2 emission lines are simultaneously covered, and HCN v 2 = 1f J = 3 - 2 emission line signatures are seen in the main nuclei of two LIRGs, IRAS 12112+0305 and IRAS 22491-1808, neither of which shows clear buried AGN signatures in the infrared. If the vibrational excitation is dominated by infrared radiative pumping, through the absorption of infrared 14 μm photons, primarily originating from AGN-heated hot dust emission, then these two LIRGs may contain infrared-elusive, but (sub)millimeter-detectable, extremely deeply buried AGNs. These vibrationally excited emission lines are not detected in the three AGN-dominated optical Seyfert 1 nuclei. However, the observed HCN v 2 = 1f to v = 0 flux ratios in these optical Seyferts are still consistent with the intrinsic flux ratios in LIRGs with detectable HCN v 2 = 1f emission lines. The observed HCN-to-HCO+ J = 3 - 2 flux ratios tend to be higher in galactic nuclei with luminous AGN signatures compared with starburst-dominated regions, as previously seen at J = 1 - 0 and J = 4 - 3.

  12. Decoding Biosynthetic Pathways in Plants by Pulse-Chase Strategies Using 13CO2 as a Universal Tracer †

    PubMed Central

    Bacher, Adelbert; Chen, Fan; Eisenreich, Wolfgang

    2016-01-01

    13CO2 pulse-chase experiments monitored by high-resolution NMR spectroscopy and mass spectrometry can provide 13C-isotopologue compositions in biosynthetic products. Experiments with a variety of plant species have documented that the isotopologue profiles generated with 13CO2 pulse-chase labeling are directly comparable to those that can be generated by the application of [U-13C6]glucose to aseptically growing plants. However, the application of the 13CO2 labeling technology is not subject to the experimental limitations that one has to take into account for experiments with [U-13C6]glucose and can be applied to plants growing under physiological conditions, even in the field. In practical terms, the results of biosynthetic studies with 13CO2 consist of the detection of pairs, triples and occasionally quadruples of 13C atoms that have been jointly contributed to the target metabolite, at an abundance that is well above the stochastic occurrence of such multiples. Notably, the connectivities of jointly transferred 13C multiples can have undergone modification by skeletal rearrangements that can be diagnosed from the isotopologue data. As shown by the examples presented in this review article, the approach turns out to be powerful in decoding the carbon topology of even complex biosynthetic pathways. PMID:27429012

  13. Spatially Resolved HCN Absorption Features in the Circumnuclear Region of NGC 1052

    NASA Astrophysics Data System (ADS)

    Sawada-Satoh, Satoko; Roh, Duk-Gyoo; Oh, Se-Jin; Lee, Sang-Sung; Byun, Do-Young; Kameno, Seiji; Yeom, Jae-Hwan; Jung, Dong-Kyu; Kim, Hyo-Ryoung; Hwang, Ju-Yeon

    2016-10-01

    We present the first VLBI detection of HCN molecular absorption in the nearby active galactic nucleus NGC 1052. Utilizing the 1 mas resolution achieved by the Korean VLBI Network, we have spatially resolved the HCN absorption against a double-sided nuclear jet structure. Two velocity features of HCN absorption are detected significantly at the radial velocity of 1656 and 1719 km s-1, redshifted by 149 and 212 km s-1 with respect to the systemic velocity of the galaxy. The column density of the HCN molecule is estimated to be 1015-1016 cm-2, assuming an excitation temperature of 100-230 K. The absorption features show high optical depth localized on the receding jet side, where the free-free absorption occurred due to the circumnuclear torus. The size of the foreground absorbing molecular gas is estimated to be on approximately one-parsec scales, which agrees well with the approximate size of the circumnuclear torus. HCN absorbing gas is likely to be several clumps smaller than 0.1 pc inside the circumnuclear torus. The redshifted velocities of the HCN absorption features imply that HCN absorbing gas traces ongoing infall motion inside the circumnuclear torus onto the central engine.

  14. Prefrontal Cortex HCN1 Channels Enable Intrinsic Persistent Neural Firing and Executive Memory Function

    PubMed Central

    Thuault, Sébastien J.; Malleret, Gaël; Constantinople, Christine M.; Nicholls, Russell; Chen, Irene; Zhu, Judy; Panteleyev, Andrey; Vronskaya, Svetlana; Nolan, Matthew F.; Bruno, Randy

    2013-01-01

    In many cortical neurons, HCN1 channels are the major contributors to Ih, the hyperpolarization-activated current, which regulates the intrinsic properties of neurons and shapes their integration of synaptic inputs, paces rhythmic activity, and regulates synaptic plasticity. Here, we examine the physiological role of Ih in deep layer pyramidal neurons in mouse prefrontal cortex (PFC), focusing on persistent activity, a form of sustained firing thought to be important for the behavioral function of the PFC during working memory tasks. We find that HCN1 contributes to the intrinsic persistent firing that is induced by a brief depolarizing current stimulus in the presence of muscarinic agonists. Deletion of HCN1 or acute pharmacological blockade of Ih decreases the fraction of neurons capable of generating persistent firing. The reduction in persistent firing is caused by the membrane hyperpolarization that results from the deletion of HCN1 or Ih blockade, rather than a specific role of the hyperpolarization-activated current in generating persistent activity. In vivo recordings show that deletion of HCN1 has no effect on up states, periods of enhanced synaptic network activity. Parallel behavioral studies demonstrate that HCN1 contributes to the PFC-dependent resolution of proactive interference during working memory. These results thus provide genetic evidence demonstrating the importance of HCN1 to intrinsic persistent firing and the behavioral output of the PFC. The causal role of intrinsic persistent firing in PFC-mediated behavior remains an open question. PMID:23966682

  15. High-resolution spectroscopy of the {A}^{1}{\\rm{\\Pi }}(v^{\\prime} =0{--}10){--}{X}^{1}{{\\rm{\\Sigma }}}^{+}(v^{\\prime\\prime} =0) bands in 13C18O: term values, ro-vibrational oscillator strengths and Hönl-London corrections

    NASA Astrophysics Data System (ADS)

    Lemaire, J. L.; Eidelsberg, M.; Heays, A. N.; Gavilan, L.; Federman, S. R.; Stark, G.; Lyons, J. R.; de Oliveira, N.; Joyeux, D.

    2016-08-01

    Our knowledge of astronomical environments containing CO depends on accurate molecular data to reproduce and interpret observations. The constant improvement in UV space instrumentation, both in sensitivity and resolution, requires increasingly detailed laboratory data. Following a long-term experimental campaign at the SOLEIL Synchrotron facility, we have acquired complete datasets on the CO isotopologues in the vacuum ultraviolet. Absorption spectra were recorded using the Fourier-transform spectrometer installed on the DESIRS beamline, providing a resolving power R > 106 in the 8-12 eV range. Such resolution allows the analysis of individual line positions and strengths in electronic transitions and the location of perturbations. We continue our previous work on A-X bands of 12C16O and 13C16O, reporting here measurements for the 13C18O isotopologue. Gas column densities in the differentially-pumped system were calibrated using the B {}1{{{Σ }}}+-X {}1{{{Σ }}}+({v}\\prime =0,v\\prime\\prime =0) band. Absorption bands are analyzed by synthesizing line and band profiles and fitting them to measured spectra. New results for A {}1{{\\Pi }}({v}\\prime =0{--}10)-X {}1{{{Σ }}}+(v\\prime\\prime =0) bands include precise line assignments, term values, band-integrated oscillator strengths as well as individual ro-vibrational oscillator strengths and Hönl-London corrections. For ({v}\\prime =1) our results are compared with earlier studies. The interpretation of mixed perturbing bands, complementing an earlier study, is also presented as well as precise line assignments and term values for the B {}1{{{Σ }}}+-X {}1{{{Σ }}}+(0-0) band calibrator, and the nearby B-X (1-0) and C {}1{{{Σ }}}+-X {}1{{{Σ }}}+(0-0) bands.

  16. A Novel Trafficking-defective HCN4 Mutation is Associated with Early-Onset Atrial Fibrillation

    PubMed Central

    Zhang, Michael L.; Sinner, Moritz F.; Dolmatova, Elena V.; Tucker, Nathan R.; McLellan, Micheal; Shea, Marisa A.; Milan, David J.; Lunetta, Kathryn L.; Benjamin, Emelia J.; Ellinor, Patrick T.

    2014-01-01

    Background Atrial fibrillation (AF) is the most common arrhythmia, and a recent genome-wide association study identified HCN4 as a novel AF susceptibility locus. HCN4 encodes for the cardiac pacemaker channel and HCN4 mutations are associated with familial sinus bradycardia and AF. Objective To determine whether novel variants in the coding region of HCN4 contribute to the susceptibility for AF. Methods We sequenced the coding region of HCN4 for novel variants from 527 cases with early-onset AF from the Massachusetts General Hospital AF Study and 443 referents from the Framingham Heart Study. We used site-directed mutagenesis, cellular electrophysiology, immunocytochemistry and confocal microscopy to functionally characterize novel variants. Results We found the frequency of novel coding HCN4 variants was 2-fold greater for individuals with AF (seven variants) compared to the referents (three variants). We determined that one, (p.Pro257Ser, located in the amino-terminus adjacent to the first transmembrane spanning domain) of the seven novel HCN4 variants in our AF cases did not traffick to cell membrane while the remaining six were not functionally different from wild type. Also, the three novel variants in our referents did not alter function compared to wild type. Co-expression studies showed that the p.Pro257Ser mutant channel failed to co-localize with the wild type HCN4 channel on the cell membrane. Conclusion Our findings are consistent with HCN4 haploinsufficiency as the likely mechanism for early-onset AF in the p.Pro257Ser carrier. PMID:24607718

  17. Adaptation of the NDIR technology to 13CO2 breath tests under increased inspiratory O2 concentrations.

    PubMed

    Vogt, Josef A; Wachter, Ulrich; Mehring, Jürgen; Radermacher, Peter; Georgieff, Michael; Fischer, Heinz; Hölscher, Uvo; Moede, Michael; Fabinski, Walter

    2009-07-01

    Nondispersive infrared spectroscopy (NDIR) allows the continuous analysis of respiratory gases. Due to its high selectivity, simple and robust setup, and small footprint, it is also used to support (13)CO(2) breath tests to assess bacterial growth in the stomach, gut, or liver function. CO(2) NDIR signals, however, are biased by oxygen in the gas matrix. This complicates NDIR-based breath tests, if the inspired oxygen concentration has to be adjusted to the subject's requirements, or hyperoxia-induced effects were studied. To avoid the oxygen-induced bias, a "dilution" approach was developed: expired gas is mixed with N(2) to lower the oxygen content down to the usual range of 15-20%. Accuracy and precision were tested using synthetic gas mixtures with increasing (13)CO(2)-to-(12)CO(2) ratios ((13)CO(2)/(12)CO(2)), either based on synthetic air with approximately 20% volume O(2) or on pure O(2). For samples with delta(13)C values smaller than 300 (or (13)CO(2)/(12)CO(2) smaller than 0.003), the dilution does not significantly increase the bias in the (13)CO(2)/(12)CO(2) determination, and the within-run imprecision is smaller than 1 delta(13)C. The practical use of this approach was validated in a pig study using a sepsis model reflecting a clinical situation that requires an increased oxygen concentration for respiration. The N(2) dilution eliminated the high bias in NDIR measurement, thus allowing the determination of the impact of oxygenation on glucose oxidation in patients ventilated with increased oxygen.

  18. Dimerization of HCN in the gas phase: A theoretical mechanistic study

    NASA Astrophysics Data System (ADS)

    Yim, Min Kyoung; Choe, Joong Chul

    2012-06-01

    Potential energy surfaces for the formation of covalently bound HCN dimers from two molecules of HCN or HNC were determined from CBS-QB3/APNO calculations. Several novel pathways, with and without the aid of protons, were found for the formation of iminoacetonitrile (HNdbnd CHCN), an intermediate in adenine synthesis from HCN by oligomerization. Covalent C-C or C-N bonds between the two monomers were formed after rearrangement of bimolecular complex intermediates. Energetic and kinetic analyses suggest that the proton-catalyzed dimerizations substantially lower reaction barriers but cannot occur efficiently under interstellar conditions.

  19. Clay-mediated reactions of HCN oligomers - The effect of the oxidation state of the clay

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Alwis, K. W.; Edelson, E. H.; Mount, N.; Hagan, W. J., Jr.

    1981-01-01

    Montmorillonite clays which contain Fe(III) inhibit the oligomerization of aqueous solutions of HCN. The inhibitory effect is due to the rapid oxidation of diaminomaleonitrile, a key intermediate in HCN oligomerization, by the Fe(III) incorporated into the aluminosilicate lattice of the clay. The Fe(III) oxidizes diaminomaleonitrile to diiminosuccinonitrile, a compound which is rapidly hydrolyzed to HCN and oxalic acid derivatives. Diaminomaleonitrile is not oxidized when Fe(III) in the montmorillonite is reduced with hydrazine. The oxidation state of the clay is an important variable in experiments designed to simulate clay catalysis on the primitive earth.

  20. HCN - A plausible source of purines, pyrimidines and amino acids on the primitive earth

    NASA Technical Reports Server (NTRS)

    Ferris, J.-P.; Joshi, P. C.; Edelson, E. H.; Lawless, J. G.

    1978-01-01

    Dilute (0.1 M) solutions of HCN condense to oligomers at pH 9.2, and hydrolysis of these oligomers yields 4,5-dihydroxypyrimidine, orotic acid, 5-hydroxyuracil, adenine, 4-aminoimidazole-5-carboxamide, and amino acids. It is suggested that the three main classes of nitrogen-containing biomolecules - purines, pyrimidines, and amino acids may have originated from HCN on the primitive earth. It is also suggested that the presence of orotic acid and 4-aminoimidazole-5-carboxamide might indicate that contemporary biosynthetic pathways for nucleotides evolved from the compounds released on hydrolysis of HCN oligomers.

  1. The Puzzle of HCN in Comets: Is it both a Product and a Primary Species?

    NASA Astrophysics Data System (ADS)

    Mumma, Michael J.; Bonev, Boncho P.; Charnley, Steven B.; Cordiner, Martin A.; DiSanti, Michael A.; Gibb, Erika L.; Magee-Sauer, Karen; Paganini, Lucas; Villanueva, Geronimo L.

    2014-11-01

    Hydrogen cyanide has long been regarded as a primary volatile in comets, stemming from its presence in dense molecular cloud cores and its supposed storage in the cometary nucleus. Here, we examine the observational evidence for and against that hypothesis, and argue that HCN may also result from near-nucleus chemical reactions in the coma. The distinction (product vs. primary species) is important for multiple reasons: 1. HCN is often used as a proxy for water when the dominant species (H2O) is not available for simultaneous measurement, as at radio wavelengths. 2. HCN is one of the few volatile carriers of nitrogen accessible to remote sensing. If HCN is mainly a product species, its precursor becomes the more important metric for compiling a taxonomic classification based on nitrogen chemistry. 3. The stereoisomer HNC is now confirmed as a product species. Could reaction of a primary precursor (X-CN) with a hydrocarbon co-produce both HNC and HCN? 4. The production rate for CN greatly exceeds that of HCN in some comets, demonstrating the presence of another (more important) precursor of CN. Several puzzling lines of evidence raise issues about the origin of HCN: a. The production rates of HCN measured through rotational (radio) and vibrational (infrared) spectroscopy agree in some comets - in others the infrared rate exceeds the radio rate substantially. b. With its strong dipole moment and H-bonding character, HCN should be linked more strongly in the nuclear ice to other molecules with similar properties (H2O, CH3OH), but instead its spatial release in some comets seems strongly coupled to volatiles that lack a dipole moment and thus do not form H-bonds (methane, ethane). c. The nucleus-centered rotational temperatures measured for H2O and other species (C2H6, CH3OH) usually agree within error, but those for HCN are often slightly smaller. d. In comet ISON, ALMA maps of HCN and the dust continuum show a slight displacement 80 km) in the centroids. We will

  2. The puzzle of HCN in comets: Is it both a product and a primary species?

    NASA Astrophysics Data System (ADS)

    Mumma, M.; Bonev, B.; Charnley, S.; Cordiner, M.; DiSanti, M.; Gibb, E.; Magee-Sauer, K.; Paganini, L.; Villanueva, G.

    2014-07-01

    Hydrogen cyanide has long been regarded as a primary volatile in comets, stemming from its presence in dense molecular-cloud cores and its supposed storage in the cometary nucleus. Here, we examine the observational evidence for and against that hypothesis, and argue that HCN may also result from near-nucleus chemical reactions in the coma. The distinction (product vs. primary species) is important for multiple reasons: - HCN is often used as a proxy for water when the dominant species (H_2O) is not available for simultaneous measurement, as at radio wavelengths. If much HCN is sometimes produced in the coma, its adoption as a water proxy could introduce unwanted bias to taxonomies based on composition. - HCN is one of the few volatile carriers of nitrogen accessible to remote sensing, with NH_3 being the dominant nitrile. If HCN is mainly a product species, its precursor becomes the more important metric for compiling a taxonomic classification based on nitrogen chemistry. - The stereoisomer HNC is regarded as a product species, thought to result from coma chemistry involving HCN. But, could another reaction of a primary precursor (X-CN) with a hydrocarbon co-produce both HNC and HCN? - The production rate for CN greatly exceeds the possible production from HCN in some comets, demonstrating the presence of another (more important) precursor of CN radicals in them. - The production rates of HCN measured through rotational (radio) and vibrational (infrared) spectroscopy agree in some comets, but in others the infrared rate exceeds the radio rate substantially. Is prompt emission from vibrationally excited HCN responsible? - With its strong dipole moment and H-bonding character, HCN should be linked more strongly in the nuclear ice to other molecules with similar properties (H_2O, CH_3OH), but instead its spatial release in some comets seems strongly coupled to volatiles that lack a dipole moment and thus do not form H-bonds (methane, ethane). We will present the

  3. Effect of dronedarone on Na+, Ca2+ and HCN channels.

    PubMed

    Bogdan, Roman; Goegelein, Heinz; Ruetten, Hartmut

    2011-04-01

    Previous studies showed that amiodarone causes state-dependent inhibition of Na(+) channels thereby mediating an atrial-selective drug effect. The aim of the present study was to investigate the impact of the new antiarrhythmic compound dronedarone on Na(+), Ca(2+) and hyperpolarization-activated cyclic nucleotide-gated ion channels. Monophasic action potentials (MAP) and effective refractory period (ERP) were studied in arterially perfused left atria and ventricular wedge preparations of the pig. Fast Na(+) and Ca(2+) currents in isolated guinea pig ventricular myocytes as well as human HCN4 channels expressed in Chinese hamster ovary (CHO) cells were investigated with the patch-clamp technique. In left atrial epicardial tissue, dronedarone (3 μM) had no effect on the MAP duration, but the drug caused a significant prolongation of the ERP from 145 ± 9 to 184 ± 17 ms (n = 6; p < 0.05). In guinea pig ventricular myocytes, dronedarone exhibited a state-dependent inhibition of the fast Na(+) channel current with an IC(50) of 0.7 ± 0.1 μM, when the holding potential (V (hold)) was -80 mV. The maximal block at the highest concentration used was 77 ± 8%. In contrast, when V (hold) was -100 mV, inhibition with 10 μM dronedarone was only 9 ± 3% (n = 7). Dronedarone blocked Ca(2+) currents elicited by rectangular pulses at V (hold) = -40 mV with an IC(50) value of 0.4 ± 0.1 μM (maximal block by 10 μM dronedarone, 80 ± 6%), whereas at V (hold) = -80 mV, 10 μM dronedarone blocked only 20 ± 6% (n = 4) of the current. Applying an action potential clamp (V (hold) = -80 mV) yielded an IC(50) of 0.4 ± 0.3 μM. Human HCN4 channels expressed in CHO cells were blocked by dronedarone with an IC(50) of 1.0 ± 0.1 μM. Inhibition of fast Na(+) and Ca(2+) channels by dronedarone depends on the cell's resting membrane potential (state-dependent block) favouring an atrial-selective mode of

  4. Constraining Ecosystem Gross Primary Production and Transpiration with Measurements of Photosynthetic 13CO2 Discrimination

    NASA Astrophysics Data System (ADS)

    Blonquist, J. M.; Wingate, L.; Ogeé, J.; Bowling, D. R.

    2011-12-01

    The stable carbon isotope composition of atmospheric CO2 (δ13Ca) can provide useful information on water use efficiency (WUE) dynamics of terrestrial ecosystems and potentially constrain models of CO2 and water fluxes at the land surface. This is due to the leaf-level relationship between photosynthetic 13CO2 discrimination (Δ), which influences δ13Ca, and the ratio of leaf intercellular to atmospheric CO2 mole fractions (Ci / Ca), which is related to WUE and is determined by the balance between C assimilation (CO2 demand) and stomatal conductance (CO2 supply). We used branch-scale Δ derived from tunable diode laser absorption spectroscopy measurements collected in a Maritime pine forest to estimate Ci / Ca variations over an entire growing season. We combined Ci / Ca estimates with rates of gross primary production (GPP) derived from eddy covariance (EC) to estimate canopy-scale stomatal conductance (Gs) and transpiration (T). Estimates of T were highly correlated to T estimates derived from sapflow data (y = 1.22x + 0.08; r2 = 0.61; slope P < 0.001) and T predictions from an ecosystem model (MuSICA) (y = 0.88x - 0.05; r2 = 0.64; slope P < 0.001). As an alternative to estimating T, Δ measurements can be used to estimate GPP by combining Ci / Ca estimates with Gs estimates from sapflow data. Estimates of GPP were determined in this fashion and were highly correlated to GPP values derived from EC (y = 0.82 + 0.07; r2 = 0.61; slope P < 0.001) and GPP predictions from MuSICA (y = 1.10 + 0.42; r2 = 0.50; slope P < 0.001). Results demonstrate that the leaf-level relationship between Δ and Ci / Ca can be extended to the canopy-scale and that Δ measurements have utility for partitioning ecosystem-scale CO2 and water fluxes.

  5. On a hypothetical generational relationship between HCN and constituents of the reductive citric acid cycle.

    PubMed

    Eschenmoser, Albert

    2007-04-01

    Encouraged by observations made on the course of reactions the HCN-tetramer can undergo with acetaldehyde, I delineate a constitutional and potentially generational relationship between HCN and those constituents of the reductive citric acid cycle that are direct precursors of amino acids in contemporary metabolism. In this context, the robustness postulate of classical prebiotic chemistry is questioned, and, by an analysis of the (hypothetical) reaction-tree of a stepwise hydrolysis of the HCN-tetramer, it is shown how such a non-robust chemical reaction platform could harbor the potential for the emergence of autocatalytic cycles. It is concluded that the chemistry of HCN should be revisited by focussing on its non-robust parts in order to demonstrate its full potential as one of the possible roots of prebiotic self-organizing chemical processes.

  6. HCN4 subunit expression in fast-spiking interneurons of the rat spinal cord and hippocampus.

    PubMed

    Hughes, D I; Boyle, K A; Kinnon, C M; Bilsland, C; Quayle, J A; Callister, R J; Graham, B A

    2013-05-01

    Hyperpolarisation-activated (Ih) currents are considered important for dendritic integration, synaptic transmission, setting membrane potential and rhythmic action potential (AP) discharge in neurons of the central nervous system. Hyperpolarisation-activated cyclic nucleotide-gated (HCN) channels underlie these currents and are composed of homo- and hetero-tetramers of HCN channel subunits (HCN1-4), which confer distinct biophysical properties on the channel. Despite understanding the structure-function relationships of HCN channels with different subunit stoichiometry, our knowledge of their expression in defined neuronal populations remains limited. Recently, we have shown that HCN subunit expression is a feature of a specific population of dorsal horn interneurons that exhibit high-frequency AP discharge. Here we expand on this observation and use neuroanatomical markers to first identify well-characterised neuronal populations in the lumbar spinal cord and hippocampus and subsequently determine whether HCN4 expression correlates with high-frequency AP discharge in these populations. In the spinal cord, HCN4 is expressed in several putative inhibitory interneuron populations including parvalbumin (PV)-expressing islet cells (84.1%; SD: ±2.87), in addition to all putative Renshaw cells and Ia inhibitory interneurons. Similarly, virtually all PV-expressing cells in the hippocampal CA1 subfield (93.5%; ±3.40) and the dentate gyrus (90.9%; ±6.38) also express HCN4. This HCN4 expression profile in inhibitory interneurons mirrors both the prevalence of Ih sub-threshold currents and high-frequency AP discharge. Our findings indicate that HCN4 subunits are expressed in several populations of spinal and hippocampal interneurons, which are known to express both Ih sub-threshold currents and exhibit high-frequency AP discharge. As HCN channel function plays a critical role in pain perception, learning and memory, and sleep as well as the pathogenesis of several

  7. HCN4 subunit expression in fast-spiking interneurons of the rat spinal cord and hippocampus

    PubMed Central

    Hughes, D.I.; Boyle, K.A.; Kinnon, C.M.; Bilsland, C.; Quayle, J.A.; Callister, R.J.; Graham, B.A.

    2013-01-01

    Hyperpolarisation-activated (Ih) currents are considered important for dendritic integration, synaptic transmission, setting membrane potential and rhythmic action potential (AP) discharge in neurons of the central nervous system. Hyperpolarisation-activated cyclic nucleotide-gated (HCN) channels underlie these currents and are composed of homo- and hetero-tetramers of HCN channel subunits (HCN1–4), which confer distinct biophysical properties on the channel. Despite understanding the structure–function relationships of HCN channels with different subunit stoichiometry, our knowledge of their expression in defined neuronal populations remains limited. Recently, we have shown that HCN subunit expression is a feature of a specific population of dorsal horn interneurons that exhibit high-frequency AP discharge. Here we expand on this observation and use neuroanatomical markers to first identify well-characterised neuronal populations in the lumbar spinal cord and hippocampus and subsequently determine whether HCN4 expression correlates with high-frequency AP discharge in these populations. In the spinal cord, HCN4 is expressed in several putative inhibitory interneuron populations including parvalbumin (PV)-expressing islet cells (84.1%; SD: ±2.87), in addition to all putative Renshaw cells and Ia inhibitory interneurons. Similarly, virtually all PV-expressing cells in the hippocampal CA1 subfield (93.5%; ±3.40) and the dentate gyrus (90.9%; ±6.38) also express HCN4. This HCN4 expression profile in inhibitory interneurons mirrors both the prevalence of Ih sub-threshold currents and high-frequency AP discharge. Our findings indicate that HCN4 subunits are expressed in several populations of spinal and hippocampal interneurons, which are known to express both Ih sub-threshold currents and exhibit high-frequency AP discharge. As HCN channel function plays a critical role in pain perception, learning and memory, and sleep as well as the pathogenesis of several

  8. Measurements of the H2(13)CO ortho/para ratio in cold dark molecular clouds

    NASA Technical Reports Server (NTRS)

    Minh, Y. C.; Dickens, J. E.; Irvine, W. M.; McGonagle, D.

    1995-01-01

    H2(13)CO has been detected for the first time toward cold dark molecular clouds using the NRAO 12 m telescope. The H2(13)CO ortho/para abundance ratio R for B335, which we report as R approximately 1.7, suggests equilibrium at the local kinetic temperature and appears to be distinctly different from that for both TMC-1 and L134N, where R is close to or higher than the statistical value 3. Since only B335 among the observed positions includes an imbedded IR source, this difference may result from heating of the grain surfaces, providing the energy necessary for desorption of formaldehyde formed on the grains.

  9. Effects of Yiqi Tongyang on HCN4 Protein Phosphorylation in Damaged Rabbit Sinoatrial Node Cells

    PubMed Central

    Liu, Jinfeng; Liu, Ruxiu; Peng, Jie; Wang, Yanli

    2016-01-01

    The hyperpolarization-activated cyclic nucleotide-gated cation channel (If) is closely associated with sinoatrial node pacing function. The present study aimed to investigate the molecular mechanisms involved in pacing function improvements of damaged sinoatrial node cells and the consequent treatment effects on sick sinus syndrome (SSS) after the use of Yiqi Tongyang. HCN4 channel protein expression and phosphorylation were measured by immunoblotting and fluorescent quantitation. After ischemia-reperfusion injury (model group), the HCN4 protein and the optical density (OD) of the phosphorylated HCN4 protein as well as intracellular PKA activity in the sinoatrial node cells decreased significantly. However, the OD values and PKA activity increased to different degrees after treatment with serum containing different doses of Yiqi Tongyang; in contrast, no significant improvement was seen in the control group compared to the model group. These findings demonstrated that the use of the traditional Chinese medicine Yiqi Tongyang could increase HCN4 protein expression and phosphorylation as well as PKA activity within sinoatrial node cells damaged by ischemia-reperfusion. The HCN4 protein is involved in the If-related ion channel. Here, we speculated that these effects could be associated with upregulation of HCN4 protein phosphorylation, which consequently improved cell automaticity, increased heart rate, and had treatment effects on SSS. PMID:27069490

  10. WARM HCN IN THE PLANET FORMATION ZONE OF GV TAU N

    SciTech Connect

    Fuente, Asuncion; Cernicharo, Jose; Agundez, Marcelino

    2012-07-20

    The Plateau de Bure Interferometer has been used to map the continuum emission at 3.4 mm and 1.1 mm together with the J = 1{yields}0 and J = 3{yields}2 lines of HCN and HCO{sup +} toward the binary star GV Tau. The 3.4 mm observations did not resolve the binary components, and the HCN J = 1{yields}0 and HCO{sup +} J 1{yields}0 line emissions trace the circumbinary disk and the flattened envelope. However, the 1.1 mm observations resolved the individual disks of GV Tau N and GV Tau S and allowed us to study their chemistry. We detected the HCN 3{yields}2 line only toward the individual disk of GV Tau N, and the emission of the HCO{sup +} 3{yields}2 line toward GV Tau S. Simple calculations indicate that the 3{yields}2 line of HCN is formed in the inner R < 12 AU of the disk around GV Tau N where the HCN/HCO{sup +} abundance ratio is >300. On the contrary, this ratio is <1.6 in the disk around GV Tau S. The high HCN abundance measured in GV Tau N is well explained by photochemical processes in the warm (>400 K) and dense (n > 10{sup 7} cm{sup -3}) disk surface.

  11. Detection of Macromolecular Fractions in HCN Polymers Using Electrophoretic and Ultrafiltration Techniques.

    PubMed

    Marín-Yaseli, Margarita R; Cid, Cristina; Yagüe, Ana I; Ruiz-Bermejo, Marta

    2017-02-01

    Elucidating the origin of life involves synthetic as well as analytical challenges. Herein, for the first time, we describe the use of gel electrophoresis and ultrafiltration to fractionate HCN polymers. Since the first prebiotic synthesis of adenine by Oró, HCN polymers have gained much interest in studies on the origins of life due to the identification of biomonomers and related compounds within them. Here, we demonstrate that macromolecular fractions with electrophoretic mobility can also be detected within HCN polymers. The migration of polymers under the influence of an electric field depends not only on their sizes (one-dimensional electrophoresis) but also their different isoelectric points (two-dimensional electrophoresis, 2-DE). The same behaviour was observed for several macromolecular fractions detected in HCN polymers. Macromolecular fractions with apparent molecular weights as high as 250 kDa were detected by tricine-SDS gel electrophoresis. Cationic macromolecular fractions with apparent molecular weights as high as 140 kDa were also detected by 2-DE. The HCN polymers synthesized were fractionated by ultrafiltration. As a result, the molecular weight distributions of the macromolecular fractions detected in the HCN polymers directly depended on the synthetic conditions used to produce these polymers. The implications of these results for prebiotic chemistry will be discussed.

  12. Bima Array Detections of HCN in Comets Linear (C/2002 T7) and Neat (C/2001 Q4)

    NASA Technical Reports Server (NTRS)

    Friedel, D. N.; Remijan, A.; Snyder, L. E.; AHearn, M. F.; Blake, Geoffrey A.; dePater, Imke; Dickel, H. R.; Forster, J. R.; Hogerheijde, M. R.

    2004-01-01

    We present interferometric detections of HCN in comets LINEAR (C/2002 T7) and NEAT (C/2001 Q4) with the Berkeley-Illinois-Maryland Association (BIMA) Array in its D-configuration cross-correlation mode. We detected the HCN J = 1 - 0 emission line in both comets. With a 25".4 x 20".3 synthesized beam around Comet LINEAR, we found a total beam averaged HCN column density (assuming a rotation temperature of 146 K) of < N(sub T) > = 2.1(11)x 10(sup 13) cm(exp -2), and a HCN production rate of Q(HCN)=2.8(15)x 10(sup 27) s(exp -1). With a 21".3 x 17".5 synthesized beam around Comet NEAT, we found a total beam averaged HCN column density (assuming a rotation temperature of 107 K) of < N(sub T) > = 5.7(30) x 10(sup l2) cm(exp -2), and a HCN production rate of Q(HCN)=8.3(44) x 10(sup 26) s(exp -l) giving a production rate of HCN relative to H2O of approximately 0.09(5)%. The production rates relative to H2O and spatial extent of HCN are similar to previous comet observations.

  13. Hyperfine anomalies of HCN in cold dark clouds

    SciTech Connect

    Walmsley, C.M.; Churchwell, E.; Nash, A.; Fitzpatrick, E.

    1982-07-15

    We report observations of the J = 1..-->..0 line of HCN measured toward six positions in nearby low-temperature dark clouds. The measured relative intensities of the hyperfine components of the J = 1..-->..0 line are anomalous in that the F = 0..-->..1 transition is stronger than would be expected if all three components (F = 2..-->..1, F = 1..-->..1, F = 0..-->..1) had equal excitation temperatures. Differences of approximately 20% in the populations per sublevel of J = 1 could account for the observations. The results are in contrast to the situation observed in warmer molecular clouds associated with H II regions where the F = 1..-->..1 line is anomalously weak. The apparent overpopulation of J = 1, F = 0 in dark clouds may be related to the phenomenon observed in the J = 1..-->..0 transitions of HCO/sup +/ and HNC in the same objects where /sup 13/C substituted version of these species is found to be stronger than the /sup 12/C species.

  14. Method for tracing simulated CO2 leak in terrestrial environment with a 13CO2 tracer

    NASA Astrophysics Data System (ADS)

    Moni, Christophe; Rasse, Daniel

    2013-04-01

    Facilities for the geological storage of carbon dioxide (CO2) as part of carbon capture and storage (CCS) schemes will be designed to prevent any leakage from the defined 'storage complex'. However, developing regulations and guidance throughout the world (e.g. the EC Directive and the USEPA Vulnerability Evaluation Framework) recognize the importance of assessing the potential for environmental impacts from CO2 storage. RISCS, a European (FP7) project, aims to improve understanding of those impacts that could plausibly occur in the hypothetical case that unexpected leakage occurs. As part of the RISCS project the potential impacts that an unexpected CO2 leaks might have on a cropland ecosystems was investigated. A CO2 exposure field experiment based on CO2 injection at 85 cm depth under an oats culture was designed. To facilitate the characterization of the simulated leaking zone the gas used for injection was produced from natural gas and had a δ13C of -46‰. The aim of the present communication is to depict how the injected gas was traced within the soil-vegetation-atmosphere continuum using 13CO2 continuous cavity ring-down spectrometry (CRDS). Four subsurface experimental injection plots (6m x 3m) were set up. In order to test the effects of different intensity of leakage, the field experiment was designed as to create a longitudinal CO2 gradient for each plot. For this purpose gas supply pipes were inserted at one extremity of each plot at the base of a 45 cm thick layer of sand buried 40 cm below the surface under the clayey plough layer of Norwegian moraine soils. Soil CO2 concentration and isotopic signature were punctually recorded: 1) in the soil at 20 cm depth at 6 positions distributed on the central transect, 2) at the surface following a (50x50 cm) grid sampling pattern, and 3) in the canopy atmosphere at 10, 20, 30 cm along three longitudinal transects (seven sampling point per transect). Soil CO2 fluxes and isotopic signature were finally

  15. Rotational excitation of HCN by para- and ortho-H{sub 2}

    SciTech Connect

    Vera, Mario Hernández; Kalugina, Yulia; Denis-Alpizar, Otoniel; Stoecklin, Thierry; Lique, François

    2014-06-14

    Rotational excitation of the hydrogen cyanide (HCN) molecule by collisions with para-H{sub 2}( j = 0, 2) and ortho-H{sub 2}( j = 1) is investigated at low temperatures using a quantum time independent approach. Both molecules are treated as rigid rotors. The scattering calculations are based on a highly correlated ab initio 4-dimensional (4D) potential energy surface recently published. Rotationally inelastic cross sections among the 13 first rotational levels of HCN were obtained using a pure quantum close coupling approach for total energies up to 1200 cm{sup −1}. The corresponding thermal rate coefficients were computed for temperatures ranging from 5 to 100 K. The HCN rate coefficients are strongly dependent on the rotational level of the H{sub 2} molecule. In particular, the rate coefficients for collisions with para-H{sub 2}( j = 0) are significantly lower than those for collisions with ortho-H{sub 2}( j = 1) and para-H{sub 2}( j = 2). Propensity rules in favor of even Δj transitions were found for HCN in collisions with para-H{sub 2}( j = 0) whereas propensity rules in favor of odd Δj transitions were found for HCN in collisions with H{sub 2}( j ⩾ 1). The new rate coefficients were compared with previously published HCN-para-H{sub 2}( j = 0) rate coefficients. Significant differences were found due the inclusion of the H{sub 2} rotational structure in the scattering calculations. These new rate coefficients will be crucial to improve the estimation of the HCN abundance in the interstellar medium.

  16. Synthesis of HCN and HNC in Ion-Irradiated N2-Rich Ices

    NASA Technical Reports Server (NTRS)

    Moore, M. H.; Hudson, R. L.; Ferrante, R. F.

    2002-01-01

    Near-IR observations reveal that N2-rich ice containing small amounts of CH4, and CO, is abundant on the surfaces of Triton, a moon of Neptune, and Pluto. N2-rich ices may also exist, in interstellar environments. To investigate the radiation chemistry of such ices we performed a systematic IR study of ion-irradiated Nz-rich mixtures containing CH4 and CO. Irradiation of N2 + CH4 mixtures at 12 K, showed that HCN, HNC, diazomethane, and NH3 were produced. We also found that UV photolysis of these ices produced detectable HCN and HNC. Intrinsic band strengths, A(HCN) and A(HNC), were measured and used to calculate yields of HCN and HNC. Similar results were obtained on irradiation of N2 + CH4 + CO ices at 12 K, with the main difference being the formation of HNCO. In all cases we observed changes on warming. For example, when the temperature of irradiated Nz + CH4 + CO was raised from 12 to 30 K, HCN, HNC, and HNCO reacted with NH3, and OCN-, CN-, N3-, and NH4+ were produced. These ions, appearing at 30 K, are expected to form and survive on the surfaces of Triton, Pluto, and interstellar grains. Our results have astrobiological implications since some of these radiation products are involved in the syntheses of biomolecules such as amino acids and peptides.

  17. Organics Produced by Irradiation of Frozen and Liquid HCN Solutions: Implications for Chemical Evolution Studies

    NASA Astrophysics Data System (ADS)

    Colín-García, M.; Negrón-Mendoza, A.; Ramos-Bernal, S.

    2009-04-01

    Hydrogen cyanide (HCN), an important precursor of organic compounds, is widely present in extraterrestrial environments. HCN is also readily synthesized in prebiotic simulation experiments. To gain insight into the radiation chemistry of one of the most important and highly versatile constituents of cometary ices, we examined the behavior of over-irradiated frozen and liquid HCN solutions under ionizing radiation. The samples were exposed to gamma radiation at a dose range from 0 up to 419 kGy. Ultraviolet spectroscopy and gas chromatography were used to follow the process. The analyses confirmed that gamma-ray irradiation of liquid HCN solutions generates several organic products. Many of them are essential to life; we verified the presence of carboxylic acids (some of them members of the Krebs cycle) as well as free amino acids and urea. These are the first studies to reveal the presence of these compounds in experiments performed at low temperatures and bulk irradiation. Organic material was produced even at low temperatures and low radiation doses. This work strongly supports the presumption that, as a parent molecule, HCN played a central essential role in the process of chemical evolution on early Earth, comets, and other extraterrestrial environments.

  18. HCN polymers characterized by SSNMR: Solid state reaction of crystalline tetramer (diaminomaleonitrile)

    NASA Astrophysics Data System (ADS)

    Mamajanov, Irena; Herzfeld, Judith

    2009-04-01

    The HCN tetramer, diaminomaleonitrile, crystallizes in sheets with amine and nitrile groups of neighboring molecules in close proximity. This suggests the possibility of relatively facile acid-base addition to form a protopeptide polymer. We find that moderate heating under argon indeed results in an unmistakable reaction, with the abrupt transformation of pale crystallites to shrunken dark particles that become electrically conductive upon doping with iodine. Since nearly a quarter of the mass is lost in the process and the released gas condenses, polymerizes, and reacts with aqueous AgNO3 like HCN, it seems likely that the dark solid is a polymer of HCN trimer. C13 and N15 solid state NMR spectra show the formation of new N-C bonds, and entirely different functional groups from those observed in polymers formed by liquid HCN. These include three different types of nitrogen functionalities and an absence of saturated carbon or nitrile. The observed chemical shifts, optical properties, and electrical conductivity are consistent with polymers of HCN trimer that have undergone cyclization to form poly-[aminoimidazole].

  19. (abstract) Neptune: CO and HCN Distributions from Observations at the CSO

    NASA Technical Reports Server (NTRS)

    Spilker, T. R.; Gulkis, S.; Salez, M.; Encrenaz, T.

    1994-01-01

    We used the Caltech Submillimeter Observatory (CSO ) to make spatially unresolved observations of the 230.538 GHz 2-1 transition of CO and the 265.886 GHz 3-2 transition of HCN at Neptune. All observations used the 10.4 meter antenna with a double sideband SIS junction heterodyne receiver. Spectra were observed with parallel acousto-optic spectrometers simultaneously providing 580 MHz bandwidth at 0.57 MHz resolution and 50 MHz bandwidth at 0.049 MHz resolution. Observed line shapes agree with prior observations by Rosenqvist et al and Marten et al. Analysis of the line shapes and intensities will yield information about the distributions of CO and HCN in the stratosphere of Neptune, and these results will be compared with previous results. The data imply that the mixing ratios of CO and HCN must decrease with altitude somewhere within the pressure range from 1 to 0.001 mbar. HCN data will also address the sharp saturation-induced decrease in the HCN mixing ratio at the lower levels in the stratosphere.

  20. Novel HCN sorbents based on layered double hydroxides: sorption mechanism and performance.

    PubMed

    Zhao, Qian; Tian, Senlin; Yan, Linxia; Zhang, Qiulin; Ning, Ping

    2015-03-21

    Layered double hydroxides (LDHs) and layered double oxides (LDOs) have been prepared and used as sorbents for hydrogen cyanide (HCN). Based on results from sorbent optimization experiments, the optimal performance for HCN removal was found in Ni-Al LDH. As evidenced by fixed-bed sorption studies, the Ni-Al LDO with the greatest surface area showed better performance and outperformed products calcined at 200, 400, or 500 °C, whereas, the Ni-Al LDH showed a more twofold higher sorption capacity than the Ni-Al LDO. Investigation of the mechanisms between HCN and sorbents reveals that the HCN removal by the Ni-Al LDH and Ni-Al LDO leads to the formation of the complex anion, [Ni(CN)4](2-). Nevertheless, the [Ni(CN)4](2-) can enter interlayer region of the Ni-Al LDH due to its anion exchangeability, which endows this LDH with more binding sites, not only on its external surfaces, but also on its internal surfaces located in the interlayer region. In contrast, [Ni(CN)4](2-) were only adsorbed on the external surface of the Ni-Al LDO. As a result, the sorption capacity of the Ni-Al LDH for HCN is twice as high as that of the Ni-Al LDO, which is at 21.55 mg/g.

  1. Serotonin modulates spike probability in the axon initial segment through HCN channels

    PubMed Central

    Ko, Kwang Woo; Rasband, Matthew N.; Meseguer, Victor; Kramer, Richard H.; Golding, Nace L.

    2016-01-01

    The axon initial segment (AIS) serves as the site of action potential initiation in most neurons, but difficulties in isolating the effects of voltage-gated ion channels in the AIS from those of the soma and dendrites have hampered understanding how AIS properties influence neural coding. Here we have combined confocal microscopy, patch-clamp recordings and light-sensitive channel blockers (“photoswitches”) in binaural auditory neurons to show that hyperpolarization and cyclic nucleotide-gated (HCN) channels are expressed in the AIS and decrease spike probability, distinct from the role of HCN channels in the soma and dendrites. Furthermore, the control of spike threshold by HCN channels in the AIS can be altered through serotonin modulation of 5-HT1A receptors, which hyperpolarizes the activation range of HCN channels. As release of serotonin signals changes in motivation and attention states, axonal HCN channels provide a mechanism to translate these signals into changes in the threshold for sensory stimuli. PMID:27110919

  2. Opacity Broadening of 13CO Linewidths and its Effect on the Variance-Sonic Mach Number Relation

    NASA Astrophysics Data System (ADS)

    Correia, C.; Burkhart, B.; Lazarian, A.; Ossenkopf, V.; Stutzki, J.; Kainulainen, J.; Kowal, G.; de Medeiros, J. R.

    2014-04-01

    We study how the estimation of the sonic Mach number (Ms ) from 13CO linewidths relates to the actual three-dimensional sonic Mach number. For this purpose we analyze MHD simulations that include post-processing to take radiative transfer effects into account. As expected, we find very good agreement between the linewidth estimated sonic Mach number and the actual sonic Mach number of the simulations for optically thin tracers. However, we find that opacity broadening causes Ms to be overestimated by a factor of ≈1.16-1.3 when calculated from optically thick 13CO lines. We also find that there is a dependence on the magnetic field: super-Alfvénic turbulence shows increased line broadening compared with sub-Alfvénic turbulence for all values of optical depth for supersonic turbulence. Our results have implications for the observationally derived sonic Mach number-density standard deviation (σρ/langρrang) relationship, \\sigma ^2_{\\rho /\\langle \\rho \\rangle }=b^2M_s^2, and the related column density standard deviation (σ N/langNrang) sonic Mach number relationship. In particular, we find that the parameter b, as an indicator of solenoidal versus compressive driving, will be underestimated as a result of opacity broadening. We compare the σ N/langNrang-Ms relation derived from synthetic dust extinction maps and 13CO linewidths with recent observational studies and find that solenoidally driven MHD turbulence simulations have values of σ N/langNrangwhich are lower than real molecular clouds. This may be due to the influence of self-gravity which should be included in simulations of molecular cloud dynamics.

  3. Loss of HCN1 enhances disease progression in mouse models of CNG channel-linked retinitis pigmentosa and achromatopsia.

    PubMed

    Schön, Christian; Asteriti, Sabrina; Koch, Susanne; Sothilingam, Vithiyanjali; Garcia Garrido, Marina; Tanimoto, Naoyuki; Herms, Jochen; Seeliger, Mathias W; Cangiano, Lorenzo; Biel, Martin; Michalakis, Stylianos

    2016-03-15

    Most inherited blinding diseases are characterized by compromised retinal function and progressive degeneration of photoreceptors. However, the factors that affect the life span of photoreceptors in such degenerative retinal diseases are rather poorly understood. Here, we explore the role of hyperpolarization-activated cyclic nucleotide-gated channel 1 (HCN1) in this context. HCN1 is known to adjust retinal function under mesopic conditions, and although it is expressed at high levels in rod and cone photoreceptor inner segments, no association with any retinal disorder has yet been found. We investigated the effects of an additional genetic deletion of HCN1 on the function and survival of photoreceptors in a mouse model of CNGB1-linked retinitis pigmentosa (RP). We found that the absence of HCN1 in Cngb1 knockout (KO) mice exacerbated photoreceptor degeneration. The deleterious effect was reduced by expression of HCN1 using a viral vector. Moreover, pharmacological inhibition of HCN1 also enhanced rod degeneration in Cngb1 KO mice. Patch-clamp recordings revealed that the membrane potentials of Cngb1 KO and Cngb1/Hcn1 double-KO rods were both significantly depolarized. We also found evidence for altered calcium homeostasis and increased activation of the protease calpain in Cngb1/Hcn1 double-KO mice. Finally, the deletion of HCN1 also exacerbated degeneration of cone photoreceptors in a mouse model of CNGA3-linked achromatopsia. Our results identify HCN1 as a major modifier of photoreceptor degeneration and suggest that pharmacological inhibition of HCN channels may enhance disease progression in RP and achromatopsia patients.

  4. Origins of Scatter in the Relationship between HCN 1-0 and Dense Gas Mass in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Mills, Elisabeth A. C.; Battersby, Cara

    2017-01-01

    We investigate the correlation of HCN 1-0 with gas mass in the central 300 pc of the Galaxy. We find that on the ∼10 pc size scale of individual cloud cores, HCN 1-0 is well correlated with dense gas mass when plotted as a log–log relationship. There is ∼0.75 dex of scatter in this relationship from clouds like Sgr B2, which has an integrated HCN 1-0 intensity of a cloud less than half its mass, and others that have HCN 1-0 enhanced by a factor of 2–3 relative to clouds of comparable mass. We identify the two primary sources of scatter to be self-absorption and variations in HCN abundance. We also find that the extended HCN 1-0 emission is more intense per unit mass than in individual cloud cores. In fact the majority (80%) of HCN 1-0 emission comes from extended gas with column densities below 7 × 1022 cm‑2, accounting for 68% of the total mass. We find variations in the brightness of HCN 1-0 would only yield a ∼10% error in the dense gas mass inferred from this line in the Galactic center. However, the observed order of magnitude HCN abundance variations, and the systematic nature of these variations, warn of potential biases in the use of HCN as dense gas mass tracer in more extreme environments such as an active galactic nucleus and shock-dominated regions. We also investigate other 3 mm tracers, finding that HNCO is better correlated with mass than HCN, and might be a better tracer of cloud mass in this environment.

  5. Output power stability of a HCN laser using a stepping motor for the EAST interferometer system

    NASA Astrophysics Data System (ADS)

    Zhang, J. B.; Wei, X. C.; Liu, H. Q.; Shen, J. J.; Zeng, L.; Jie, Y. X.

    2015-11-01

    The HCN laser on EAST is a continuous wave glow discharge laser with 3.4 m cavity length and 120 mW power output at 337 μ m wavelength. Without a temperature-controlled system, the cavity length of the laser is very sensitive to the environmental temperature. An external power feedback control system is applied on the HCN laser to stabilize the laser output power. The feedback system is composed of a stepping motor, a PLC, a supervisory computer, and the corresponding control program. One step distance of the stepping motor is 1 μ m and the time response is 0.5 s. Based on the power feedback control system, a stable discharge for the HCN laser is obtained more than eight hours, which satisfies the EAST experiment.

  6. Raman spectroscopic investigation of 13CO 2 labeling and leaf dark respiration of Fagus sylvatica L. (European beech).

    PubMed

    Keiner, Robert; Gruselle, Marie-Cécile; Michalzik, Beate; Popp, Jürgen; Frosch, Torsten

    2015-03-01

    An important issue, in times of climate change and more extreme weather events, is the investigation of forest ecosystem reactions to these events. Longer drought periods stress the vitality of trees and promote mass insect outbreaks, which strongly affect ecosystem processes and services. Cavity-enhanced Raman gas spectrometry was applied for online multi-gas analysis of the gas exchange rates of O2 and CO2 and the labeling of Fagus sylvatica L. (European beech) seedlings with (13)CO2. The rapid monitoring of all these gases simultaneously allowed for the separation of photosynthetic uptake of CO2 by the beech seedlings and a constant (12)CO2 efflux via respiration and thus for a correction of the measured (12)CO2 concentrations in course of the labeling experiment. The effects of aphid infestation with the woolly beech aphid (Phyllaphis fagi L.) as well as the effect of a drought period on the respirational gas exchange were investigated. A slightly decreased respirational activity of drought-stressed seedlings in comparison to normally watered seedlings was found already for a low drought intensity. Cavity-enhanced Raman gas monitoring of O2, (12)CO2, and (13)CO2 was proven to be a powerful new tool for studying the effect of drought stress and aphid infestation on the respirational activity of European beech seedlings as an example of important forest species in Central Europe.

  7. Negative ion mass spectrometry and the detection of carbonyls and HCN from clover

    NASA Astrophysics Data System (ADS)

    Custer, Thomas G.; Kato, Shuji; Fall, Ray; Bierbaum, Veronica M.

    2000-12-01

    We have demonstrated that negative ion-chemical ionization mass spectrometry (NI-CIMS) can be used to distinguish several isomeric volatile organic compounds (VOCs) that are emitted from wounded plants. Reaction chemistry with HO-, hydrogen/deuterium exchange patterns, and collision-induced dissociation spectra allow identification of the isomers. Laboratory studies of emissions from wounded clover using NI-CIMS show several previously detected VOCs, but also clearly demonstrate the emission of HCN. This compound is presumably formed by the decomposition of cyanogenic glycosides which also form aldehyde and ketone byproducts. These results suggest that NI-CIMS may be a valuable tool for investigating VOCs and HCN release from vegetation.

  8. Long-lasting spatial learning and memory impairments caused by chronic cerebral hypoperfusion associate with a dynamic change of HCN1/HCN2 expression in hippocampal CA1 region.

    PubMed

    Luo, Pan; Lu, Yun; Li, Changjun; Zhou, Mei; Chen, Cheng; Lu, Qing; Xu, Xulin; He, Zhi; Guo, Lianjun

    2015-09-01

    Chronic cerebral hypoperfusion (CCH) causes learning and memory impairments and increases the risk of Alzheimer disease (AD) and vascular dementia (VD) through several biologically plausible pathways, yet the mechanisms underlying the disease process remained unclear particularly in a temporal manner. We performed permanent bilateral occlusion of the common carotid arteries (two-vessel occlusion, 2VO) to induce CCH. To determine whether hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are altered at different stages of cognitive impairment caused by CCH, adult male SD rats were randomly distributed into sham-operated 4, 8 and 12weeks group, 2VO 4, 8 and 12weeks group. Learning and memory performance were evaluated with Morris water maze (MWM) and long-term potentiation (LTP) was used to address the underlying synaptic mechanisms. Expression of NeuN, HCN1 and HCN2 in hippocampal CA1, DG and CA3 areas was quantified by immunohistochemistry and western blotting. Our data showed that CCH induced a remarkable spatial learning and memory deficits in rats of 2VO 4, 8, and 12weeks group although neuronal loss only occurred after 4weeks of 2VO surgery in CA1. In addition, a significant reduction of HCN1 surface expression in CA1 was observed in the group that suffered 4weeks ischemia but neither 8 nor 12weeks. However, HCN2 surface expression in CA1 increased throughout the ischemia time-scales (4, 8 and 12w). Our findings indicate spatial learning and memory deficits in the CCH model are associated with disturbed HCN1 and HCN2 surface expression in hippocampal CA1. The altered patterns of both HCN1 and HCN2 surface expression may be implicated in the early stage (4w) of spatial learning and memory impairments; and the stable and long-lasting impairments of spatial learning and memory may partially attribute to the up-regulated HCN2 surface expression.

  9. HCN1 Channels Constrain Synaptically Evoked Ca2+ Spikes in Distal Dendrites of CA1 Pyramidal Neurons

    PubMed Central

    Tsay, David; Dudman, Joshua T.; Siegelbaum, Steven A.

    2008-01-01

    SUMMARY HCN1 hyperpolarization-activated cation channels act as an inhibitory constraint of both spatial learning and synaptic integration and long-term plasticity in the distal dendrites of hippocampal CA1 pyramidal neurons. However, as HCN1 channels provide an excitatory current, the mechanism of their inhibitory action remains unclear. Here we report that HCN1 channels also constrain CA1 distal dendritic Ca2+ spikes, which have been implicated in the induction of LTP at distal excitatory synapses. Our experimental and computational results indicate that HCN1 channels provide both an active shunt conductance that decreases the temporal integration of distal EPSPs and a tonic depolarizing current that increases resting inactivation of T-type and N-type voltage-gated Ca2+ channels, which contribute to the Ca2+ spikes. This dual mechanism may provide a general means by which HCN channels regulate dendritic excitability. PMID:18093528

  10. Influence of C4 vegetation on 13CO2 discrimination and isoforcing in the upper Midwest, United States

    NASA Astrophysics Data System (ADS)

    Griffis, T. J.; Baker, J. M.; Sargent, S. D.; Erickson, M.; Corcoran, J.; Chen, M.; Billmark, K.

    2010-12-01

    Agricultural crops with a C4 photosynthetic pathway rapidly expanded across North America as early as 800 A.D. Their distribution continues to expand globally as demands for food and biofuel production increase. These systems are highly productive, having a significant impact on carbon and water exchange between the land and atmosphere. Here, we investigate the relative impact of agricultural C4 vegetation on the 13CO2 photosynthetic discrimination and atmospheric isotopic forcing in the upper Midwest, United States. We address three questions: (1) What is the relative importance of C3 and C4 species to the CO2 budget? (2) How do these different photosynthetic pathways influence the photosynthetic discrimination within this heterogeneous landscape? (3) To what extent does land use change (i.e., a change in C4 crops) impact atmospheric isotopic forcing and the isotopic signature of the atmosphere? These questions are addressed using measurements obtained from the University of Minnesota tall tower (244 m) trace gas observatory (TGO) over the growing seasons of 2007 and 2008 and are supported with scaled-up values of discrimination and isotopic forcing based on ecosystem-scale eddy flux observations and high-resolution land use data. Our land use analyses indicate that local and regional C4 production was higher by 10% in 2007 due to increased demand for biofuel. The 2007 growing season was also characterized by moderate drought as a consequence of low antecedent soil water content. Isotopic flux ratio measurements from TGO provide evidence that the increase in C4 land use and drier soil conditions of 2007 had a significant impact on the growing season 13CO2 photosynthetic discrimination, which ranged from 11.5 to 14.8 in 2007 and 12.4‰ to 17.4‰ in 2008. Isotopic partitioning indicated that C4 species accounted for about 20 to 40% of the growing season gross photosynthetic CO2 exchange. The isoforcing analysis revealed that C3 discrimination dominated the

  11. Accurate Quartic Force Fields and Vibrational Frequencies for HCN and HNC

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Dateo, Christopher E.; Gazdy, Bela; Bowman, Joel M.

    1993-01-01

    The quartic force fields of HCN and HNC are determined using atomic natural orbital one-particle basis sets of spdf/spd and spdfg/spdf quality in conjunction with the CCSD(T) electron correlation method (singles and doubles coupled-cluster theory plus a perturbation estimate of the effects of connected triple excitations). The HCN force field is in good agreement with a recent experimentally derived force field and also with the force field recently computed by Wong and Bacskay. On the basis of the good agreement obtained for HCN, it is argued that the ab initio quartic force field for HNC is superior to a prior force field derived from experiment. The harmonic frequencies of HNC are predicted to be 3822 +/- 10, 472 +/- 5, and 2051 +/- 10 cm(exp -1) for omega(sub 1), omega(sub 2), and omega(sub 3), respectively; the experimentally derived values are above these values and fall outside the estimated uncertainties. Using the quartic force field, spectroscopic constants are predicted for HNC based on a vibrational second-order perturbation theory analysis. It is also asserted that the gas-phase fundamental nu(sub 3) for HNC is slightly lower than the matrix isolation value. The range of validity of the quartic force fields is investigated by comparison of variational vibrational energies computed with the quartic force fields to those obtained from our recently reported global HCN/HNC potential energy surface and also to experimental data.

  12. Accurate Quartic Force Fields and Vibrational Frequencies for HCN and HNC

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Dateo, Christopher E.; Gazdy, Bela; Bowman, Joel M.

    1993-01-01

    The quartic force fields of HCN and HNC are determined using atomic natural orbital one-particle basis sets of spdf/spd and spdfg/spdf quality in conjunction with the CCSD(T) electron correlation method (singles and doubles coupled-cluster theory plus a perturbational estimate of the effects of connected triple excitations). The HCN force field is in good agreement with a recent experimentally derived force field and also with the force field recently computed by Wong and Bacskay. On the basis of the good agreement obtained for HCN, it is argued that the ab initio quartic force field for HNC is superior to a prior force field derived from experiment. The harmonic frequencies of HNC are predicted to be 3822 +/- 10,472 +/- 5, and 2051 +/-10/cm for omega1, omega2, and omega3, respectively; the experimentally derived values are above these values and fall outside the estimated uncertainties. Using the quartic force field, spectroscopic constants are predicted for HNC based on a vibrational second-order perturbation theory analysis. It is also asserted that the gas-phase fundamental v(sub 3) for HNC is slightly lower than the matrix isolation value. The range of validity of the quartic force fields is investigated by comparison of variational vibrational energies computed with the quartic force fields to those obtained from our recently reported global HCN/HNC potential energy surface and also to experimental data.

  13. Electron-impact rotational and hyperfine excitation of HCN, HNC, DCN and DNC

    NASA Astrophysics Data System (ADS)

    Faure, Alexandre; Varambhia, Hemal N.; Stoecklin, Thierry; Tennyson, Jonathan

    2007-12-01

    Rotational excitation of isotopologues of HCN and HNC by thermal electron-impact is studied using the molecular R-matrix method combined with the adiabatic-nuclei-rotation approximation. Rate coefficients are obtained for electron temperatures in the range 5-6000 K and for transitions among all levels up to J = 8. Hyperfine rates are also derived using the infinite-order-sudden scaling method. It is shown that the dominant rotational transitions are dipole-allowed, that is, those for which ΔJ = 1. The hyperfine propensity rule ΔJ = ΔF is found to be stronger than that in the case of He-HCN collisions. For dipole-allowed transitions, electron-impact rates are shown to exceed those for excitation of HCN by He atoms by six orders of magnitude. As a result, the present rates should be included in any detailed population model of isotopologues of HCN and HNC in sources where the electron fraction is larger than 10-6, for example, in interstellar shocks and comets.

  14. First-principles insights into interaction of CO, NO, and HCN with Ag{sub 8}

    SciTech Connect

    Torbatian, Zahra; Hashemifar, S. Javad Akbarzadeh, Hadi

    2014-02-28

    We use static as well as time-dependent first-principles computations to study interaction of the CO, NO, and HCN molecules with the Ag{sub 8} nanocluster. The many-body based GW correction is applied for accurate description of the highest occupied (HOMO) and the lowest unoccupied (LUMO) molecular orbital levels. It is argued that the adsorption of these molecules changes the stable structure of Ag{sub 8} from Td to the more chemically active D{sub 2d} symmetry. We discuss that the CO, NO, and HCN molecules prefer to adsorb on the atom of the cluster with significant contribution to both HOMO and LUMO, for the accomplishment of the required charge transfers in the systems. The charge back donation is found to leave an excess energy of about 110 meV on the NO molecular bond, evidencing potential application of silver clusters for NO reduction. It is argued that CO and specially NO exhibit strong physical interaction with the silver cluster and hence significantly modify the electronic and optical properties of the system, while HCN makes very week physical bonds with the cluster. The optical absorption spectra of the Ag{sub 8} cluster before and after molecule adsorption are computed and a nontrivial red shift is observed in the NO and HCN adsorbed clusters.

  15. THE HCN/HNC ABUNDANCE RATIO TOWARD DIFFERENT EVOLUTIONARY PHASES OF MASSIVE STAR FORMATION

    SciTech Connect

    Jin, Mihwa; Lee, Jeong-Eun; Kim, Kee-Tae E-mail: jeongeun.lee@khu.ac.kr

    2015-07-20

    Using the H{sup 13}CN and HN{sup 13}C J = 1–0 line observations, the abundance ratio of HCN/HNC has been estimated for different evolutionary stages of massive star formation: infrared dark clouds (IRDCs), high-mass protostellar objects (HMPOs), and ultracompact H ii regions (UCH iis). IRDCs were divided into “quiescent IRDC cores (qIRDCc)” and “active IRDC cores (aIRDCc),” depending on star formation activity. The HCN/HNC ratio is known to be higher at active and high temperature regions related to ongoing star formation, compared to cold and quiescent regions. Our observations toward 8 qIRDCc, 16 aIRDCc, 23 HMPOs, and 31 UCH iis show consistent results; the ratio is 0.97 (±0.10), 2.65 (±0.88), 4.17 (±1.03), and 8.96 (±3.32) in these respective evolutionary stages, increasing from qIRDCc to UCH iis. The change of the HCN/HNC abundance ratio, therefore, seems directly associated with the evolutionary stages of star formation, which have different temperatures. One suggested explanation for this trend is the conversion of HNC to HCN, which occurs effectively at higher temperatures. To test the explanation, we performed a simple chemical model calculation. In order to fit the observed results, the energy barrier of the conversion must be much lower than the value provided by theoretical calculations.

  16. Photodissociation of HCN and HNC isomers in the 7-10 eV energy range.

    PubMed

    Chenel, Aurelie; Roncero, Octavio; Aguado, Alfredo; Agúndez, Marcelino; Cernicharo, José

    2016-04-14

    The ultraviolet photoabsorption spectra of the HCN and HNC isomers have been simulated in the 7-10 eV photon energy range. For this purpose, the three-dimensional adiabatic potential energy surfaces of the 7 lowest electronic states, and the corresponding transition dipole moments, have been calculated, at multireference configuration interaction level. The spectra are calculated with a quantum wave packet method on these adiabatic potential energy surfaces. The spectra for the 3 lower excited states, the dissociative electronic states, correspond essentially to predissociation peaks, most of them through tunneling on the same adiabatic state. The 3 higher electronic states are bound, hereafter electronic bound states, and their spectra consist of delta lines, in the adiabatic approximation. The radiative lifetime towards the ground electronic states of these bound states has been calculated, being longer than 10 ns in all cases, much longer that the characteristic predissociation lifetimes. The spectra of HCN is compared with the available experimental and previous theoretical simulations, while in the case of HNC there are no previous studies to our knowledge. The spectrum for HNC is considerably more intense than that of HCN in the 7-10 eV photon energy range, which points to a higher photodissociation rate for HNC, compared to HCN, in astrophysical environments illuminated by ultraviolet radiation.

  17. Photodissociation of HCN and HNC isomers in the 7-10 eV energy range

    PubMed Central

    Chenel, Aurelie; Roncero, Octavio; Aguado, Alfredo; Agúndez, Marcelino; Cernicharo, José

    2016-01-01

    The ultraviolet photoabsorption spectra of the HCN and HNC isomers have been simulated in the 7-10 eV photon energy range. For this purpose the three-dimensional adiabatic potential energy surfaces of the 7 lowest electronic states, and the corresponding transition dipole moments, have been calculated, at multi reference configuration interaction level. The spectra are calculated with a quantum wave packet method on these adiabatic potential energy surfaces. The spectra for the 3 lower excited states, the dissociative electronic states, correspond essentially to predissociation peaks, most of them through tunneling on the same adiabatic state. The 3 higher electronic states are bound, hereafter electronic bound states, and their spectra consist of delta lines, in the adiabatic approximation. The radiative lifetime towards the ground electronic states of these bound states have been calculated, being longer than 10 ns in all cases, much longer that the characteristic predissociation lifetimes. The spectra of HCN is compared with the available experimental and previous theoretical simulations while in the case of HNC there are no previous studies to our knowledge. The spectrum for HNC is considerably more intense than that of HCN, which implies a much faster destruction of HNC than HCN in astrophysical environments illuminated by ultraviolet radiation. PMID:27083720

  18. Patch-clamp fluorometry–based channel counting to determine HCN channel conductance

    PubMed Central

    Liu, Chang; Xie, Changan; Grant, Khade; Su, Zhuocheng; Gao, Weihua; Liu, Qinglian

    2016-01-01

    Counting ion channels on cell membranes is of fundamental importance for the study of channel biophysics. Channel counting has thus far been tackled by classical approaches, such as radioactive labeling of ion channels with blockers, gating current measurements, and nonstationary noise analysis. Here, we develop a counting method based on patch-clamp fluorometry (PCF), which enables simultaneous electrical and optical recordings, and apply it to EGFP-tagged, hyperpolarization-activated and cyclic nucleotide–regulated (HCN) channels. We use a well-characterized and homologous cyclic nucleotide–gated (CNG) channel to establish the relationship between macroscopic fluorescence intensity and the total number of channels. Subsequently, based on our estimate of the total number of HCN channels, we determine the single-channel conductance of HCN1 and HCN2 to be 0.46 and 1.71 pS, respectively. Such a small conductance would present a technical challenge for traditional electrophysiology. This PCF-based technique provides an alternative method for counting particles on cell membranes, which could be applied to biophysical studies of other membrane proteins. PMID:27353446

  19. Formation of HCN+ in Heterogeneous Reactions of N2+ and N+ with Surface Hydrocarbons

    PubMed Central

    2013-01-01

    A significant increase of the ion yield at m/z 27 in collisions of low-energy ions of N2+ and N+ with hydrocarbon-covered room-temperature or heated surfaces of tungsten, carbon-fiber composite, and beryllium, not observed in analogous collisions of Ar+, is ascribed to the formation of HCN+ in heterogeneous reactions between N2+ or N+ and surface hydrocarbons. The formation of HCN+ in the reaction with N+ indicated an exothermic reaction with no activation barrier, likely to occur even at very low collision energies. In the reaction with N2+, the formation of HCN+ was observed to a different degree on these room-temperature and heated (150 and 300 °C) surfaces at incident energies above about 50 eV. This finding suggested an activation barrier or reaction endothermicity of the heterogeneous reaction of about 3–3.5 eV. The main process in N2+ or N+ interaction with the surfaces is ion neutralization; the probability of forming the reaction product HCN+ was very roughly estimated for both N2+ and N+ ions to about one in 104 collisions with the surfaces. PMID:23614645

  20. A HCN4+ cardiomyogenic progenitor derived from the first heart field and human pluripotent stem cells.

    PubMed

    Später, Daniela; Abramczuk, Monika K; Buac, Kristina; Zangi, Lior; Stachel, Maxine W; Clarke, Jonathan; Sahara, Makoto; Ludwig, Andreas; Chien, Kenneth R

    2013-09-01

    Most of the mammalian heart is formed from mesodermal progenitors in the first and second heart fields (FHF and SHF), whereby the FHF gives rise to the left ventricle and parts of the atria and the SHF to the right ventricle, outflow tract and parts of the atria. Whereas SHF progenitors have been characterized in detail, using specific molecular markers, comprehensive studies on the FHF have been hampered by the lack of exclusive markers. Here, we present Hcn4 (hyperpolarization-activated cyclic nucleotide-gated channel 4) as an FHF marker. Lineage-traced Hcn4+/FHF cells delineate FHF-derived structures in the heart and primarily contribute to cardiomyogenic cell lineages, thereby identifying an early cardiomyogenic progenitor pool. As a surface marker, HCN4 also allowed the isolation of cardiomyogenic Hcn4+/FHF progenitors from human embryonic stem cells. We conclude that a primary purpose of the FHF is to generate cardiac muscle and support the contractile activity of the primitive heart tube, whereas SHF-derived progenitors contribute to heart cell lineage diversification.

  1. Precipitation Kinetics of M2C Carbide in Severely Ausformed 13Co-8Ni Secondary Hardening Steels

    NASA Astrophysics Data System (ADS)

    Cho, Ki Sub; Park, Sung Soo; Kim, Hong Kyu; Song, Young Beum; Kwon, Hoon

    2015-04-01

    With continuous heating calorimetric data as a basis, the kinetics of M2C formation during isothermal aging was modeled in severely ausformed 13Co-8Ni steels using the Johnson-Mehl-Avrami theory coupled with a variation of effective activation energy with respect to the degree of transformation. These results were compared with small-angle neutron scattering measurements and discussed in terms of variations in the thermodynamic and kinetic behavior of M2C precipitation. In particular, the M2C carbides in the deformed samples contained more Fe content compared with the non-deformed samples. As this can be ascribed to the ausforming effect increasing the driving force for M2C nucleation, it consequently leads to the decrease of the growth/coarsening rate for M2C carbides at over-aged conditions.

  2. Tracking the oxidative kinetics of carbohydrates, amino acids and fatty acids in the house sparrow using exhaled 13CO2.

    PubMed

    McCue, M D; Sivan, O; McWilliams, S R; Pinshow, B

    2010-03-01

    Clinicians commonly measure the (13)CO(2) in exhaled breath samples following administration of a metabolic tracer (breath testing) to diagnose certain infections and metabolic disorders. We believe that breath testing can become a powerful tool to investigate novel questions about the influence of ecological and physiological factors on the oxidative fates of exogenous nutrients. Here we examined several predictions regarding the oxidative kinetics of specific carbohydrates, amino acids and fatty acids in a dietary generalist, the house sparrow (Passer domesticus). After administering postprandial birds with 20 mg of one of seven (13)C-labeled tracers, we measured rates of (13)CO(2) production every 15 min over 2 h. We found that sparrows oxidized exogenous amino acids far more rapidly than carbohydrates or fatty acids, and that different tracers belonging to the same class of physiological fuels had unique oxidative kinetics. Glycine had a mean maximum rate of oxidation (2021 nmol min(-1)) that was significantly higher than that of leucine (351 nmol min(-1)), supporting our prediction that nonessential amino acids are oxidized more rapidly than essential amino acids. Exogenous glucose and fructose were oxidized to a similar extent (5.9% of dose), but the time required to reach maximum rates of oxidation was longer for fructose. The maximum rates of oxidation were significantly higher when exogenous glucose was administered as an aqueous solution (122 nmol min(-1)), rather than as an oil suspension (93 nmol min(-1)), supporting our prediction that exogenous lipids negatively influence rates of exogenous glucose oxidation. Dietary fatty acids had the lowest maximum rates of oxidation (2-6 nmol min(-1)), and differed significantly in the extent to which each was oxidized, with 0.73%, 0.63% and 0.21% of palmitic, oleic and stearic acid tracers oxidized, respectively.

  3. On-line analysis of the (13)CO(2) labeling of leaf isoprene suggests multiple subcellular origins of isoprene precursors.

    PubMed

    Karl, T; Fall, R; Rosenstiel, T N; Prazeller, P; Larsen, B; Seufert, G; Lindinger, W

    2002-10-01

    Isoprene (2-methyl-1,3-butadiene) is the most abundant biogenic hydrocarbon released from vegetation, and there is continuing interest in understanding its biosynthesis from photosynthetic precursors in leaf chloroplasts. We used on-line proton-transfer-reaction mass spectrometry (PTR-MS) to observe the kinetics of (13)C-labeling of isoprene following exposure to (13)CO(2) and then the loss of (13)C after a return to normal (12)CO(2) in oak ( Quercus agrifolia Nee) and cottonwood (Populus deltoides Barr.) leaves. Assignments of labeled isoprene species were verified by gas chromatography-mass spectrometry. For the first time, it was possible to observe the half-lives of individually (13)C-labeled isoprene species during these transitions, and to trace some of the label to a C3 fragment that contained the two isoprene carbons derived from pyruvate via the deoxyxylulose-5-phosphate (DOXP) pathway. At steady state (under (13)CO(2)), approximately 80% of isoprene carbon was labeled, with fully labeled isoprene as the major species (approx. 60%). The source of the unlabeled C is suggested to be extrachloroplastic, but not from photorespiratory carbon. After a transfer to (12)CO(2), (13)C-labeling persisted in one isoprene carbon for several hours; this persistence was much more pronounced in (i) leaves inhibited by fosmidomycin, a specific inhibitor of the DOXP pathway, and (ii) in sun leaves which have higher ratios of soluble sugars to starch. From the mass 41-44 fragment data, and labeling predicted from the DOXP pathway in chloroplasts, precursors may arise from cytosolic pyruvate/phospho enolpyruvate equivalents transported into the chloroplast; this idea was supported by an indirect measure of pyruvate labeling. Other sources of cytosolic isoprene precursors (i.e. dimethylallyl diphosphate or pentose phosphate) could not be excluded. The data obtained shed light on the half-lives of photosynthetic metabolites, exchanges of carbon between cellular pools, and

  4. Synthesis of HCN and HNC in Ion-Irradiated N2-Rich Ices

    NASA Astrophysics Data System (ADS)

    Moore, M. H.; Hudson, R. L.; Ferrante, R. F.

    2002-11-01

    Near-IR observations reveal that nitrogen-rich ice containing small amounts of methane, CH4, and carbon monoxide, CO, is abundant on the surfaces of Triton, a moon of Neptune, and Pluto (Cruikshank et al.. 1993; Owen et al., 1993). N2-rich apolar ices are also possible in some interstellar environments (Ehrenfreund et al., 1998). To investigate the radiation chemical behavior of N2-dominated ices we performed a systematic IR study of ion-irradiated N2-rich ices containing CH4 and CO. Experiments at 18 K, showed that HCN, HNC, and the reactive molecule diazomethane, CH2N2, formed along with several radicals. NH3 was also identified in irradiated N2 + CH4. Comparing results from similarly photolyzed ices (Bohn et al., 1994) shows that the significant difference between radiolysis and photolysis of these N2-dominated ices is that photolyzed ices do not form detectable HCN and HNC. Our experiments examined different N2/CH4 ratios, the half-life of CH4, possible HCN and HNC formation routes, and competing pathways in the presence of CO. Intrinsic band strengths (A(HCN) and A(HNC)) were measured and used to calculate nearly equal values of HCN and HNC yields in N2+CH4 irradiated ices. Low temperature results apply to interstellar ices. Reaction products that appear at 30-35 K are also expected to form and survive on the surfaces of Triton and Pluto and interstellar grains. We examined the evolution of ice features as species undergo acid-base (acids such as HCN, HNC, HNCO and a base NH3) reactions triggered by warming from 18 K to 30-35 K. We identified anions (OCN-, CN- and N3-) attributed to relatively stable salts in ices where NH4+ is the likely cation. These results also have an astrobiology implication since many of these products (HCN, HNC, HNCO, NH3, NH4OCN, and NH4CN) are reactants used in synthesis studies of bio- molecules such as amino acids and peptides.

  5. New Detections of HNC in Planetary Nebulae: Evolution of the [HCN]/[HNC] Ratio

    NASA Astrophysics Data System (ADS)

    Schmidt, D. R.; Ziurys, L. M.

    2017-01-01

    New detections of HNC have been made toward 11 planetary nebulae (PNe), including K4-47, K3-58, K3-17, M3-28, and M4-14. These sources, which represent a wide range of ages and morphologies, had previously been observed in HCN by Schmidt & Ziurys. Measurements of the J=1\\to 0 and J=3\\to 2 transitions of HNC near 90 and 271 GHz were conducted using the new 12 m and the Sub-Millimeter Telescope of the Arizona Radio Observatory. HCN and HNC were also identified via their J=1\\to 0 lines toward eight positions across the Helix Nebula (NGC 7293). Column densities for HNC, determined from radiative transfer modeling, were Ntot(HNC) ∼ (0.06–4.0) × 1013 cm‑2, corresponding to fractional abundances with respect to H2 of f ∼ (0.02–1.4) × 10‑7. The HCN and HNC column densities across the Helix were found to be {N}{tot}({HCN}) ∼ (0.2–2.4) × 1012 cm‑2 and {N}{tot}({HNC}) ∼ (0.07–1.6) × 1012 cm‑2, with fractional abundances of (0.2–3.2) × 10‑7 and (0.09–2.2) × 10‑7. The [HCN]/[HNC] ratio varied between ∼1–8 for all PNe, with [HCN]/[HNC] ∼1–4 across the Helix. These values are greatly reduced from what has been found in asymptotic giant branch stars, where the ratio is typically >100. Both the abundance of HNC and the [HCN]/[HNC] ratio do not appear to vary significantly with nebular age across a time span of ∼10,000 years, in contrast to predictions of chemical models. The increase in HNC appears to arise in the proto-planetary stage, but becomes “frozen” once the PN phase is reached.

  6. Calcium regulation of HCN channels supports persistent activity in a multiscale model of neocortex

    PubMed Central

    McDougal, Robert A.; Bulanova, Anna S.; Zeki, Mustafa; Lakatos, Peter; Terman, David; Hines, Michael L.; Lytton, William W.

    2016-01-01

    Neuronal persistent activity has been primarily assessed in terms of electrical mechanisms, without attention to the complex array of molecular events that also control cell excitability. We developed a multiscale neocortical model proceeding from the molecular to the network level to assess the contributions of calcium regulation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in providing additional and complementary support of continuing activation in the network. The network contained 776 compartmental neurons arranged in the cortical layers, connected using synapses containing AMPA/NMDA/GABAA/GABAB receptors. Metabotropic glutamate receptors (mGluR) produced inositol triphosphate (IP3) which caused release of Ca2+ from endoplasmic reticulum (ER) stores, with reuptake by sarco/ER Ca2+-ATP-ase pumps (SERCA), and influence on HCN channels. Stimulus-induced depolarization led to Ca2+ influx via NMDA and voltage-gated Ca2+ channels (VGCCs). After a delay, mGluR activation led to ER Ca2+ release via IP3 receptors. These factors increased HCN channel conductance and produced firing lasting for ~1 minute. The model displayed inter-scale synergies among synaptic weights, excitation/inhibition balance, firing rates, membrane depolarization, calcium levels, regulation of HCN channels, and induction of persistent activity. The interaction between inhibition and Ca2+ at the HCN channel nexus determined a limited range of inhibition strengths for which intracellular Ca2+ could prepare population-specific persistent activity. Interactions between metabotropic and ionotropic inputs to the neuron demonstrated how multiple pathways could contribute in a complementary manner to persistent activity. Such redundancy and complementarity via multiple pathways is a critical feature of biological systems. Mediation of activation at different time scales, and through different pathways, would be expected to protect against disruption, in this case providing

  7. Structural Insight into the Gene Expression Profiling of the hcn Operon in Pseudomonas aeruginosa.

    PubMed

    Chowdhury, Nilkanta; Bagchi, Angshuman

    2017-01-07

    Pseudomonas aeruginosa is a common opportunistic human pathogen. It generally attacks immunosuppressed patients like AIDS, cancer, cystic fibrosis, etc. The virulence of P. aeruginosa is mediated by various virulence factors. One of such potential virulence factors is HCN synthesized by HCN synthase enzyme, which is encoded by the hcnABC operon. The expressions of the genes of this operon are regulated by three transcriptional regulators, viz., LasR, ANR, and RhlR. In our previous work, we analyzed the molecular details of the functionalities of LasR. In this work, we focused on ANR. ANR is a regulatory protein which belongs to the FNR family and works in anaerobic condition. ANR binds to the promoter DNA, named ANR box, as a dimer. The dimerization of this ANR protein is regulated by Fe4S4, an iron-sulfur cluster. This dimer of ANR (ANR-Fe4S4/ANR-Fe4S4) recognizes and binds the promoter DNA sequence and regulates the transcription of this hcnABC operon. Till date, the biomolecular details of the interactions of ANR dimer with the promoter DNA are not fully understood. Thus, we built the molecular model of ANR-Fe4S4/ANR-Fe4S4. We docked the complex with the corresponding promoter DNA region. We analyzed the mode of interactions with the promoter DNA under different conditions. Thus, we tried to analyze the functionality of the ANR protein during the expressions of the genes of the hcnABC operon. So far, this is the first report to detail the molecular mechanism of the gene expression in P. aeruginosa.

  8. Calcium regulation of HCN channels supports persistent activity in a multiscale model of neocortex.

    PubMed

    Neymotin, S A; McDougal, R A; Bulanova, A S; Zeki, M; Lakatos, P; Terman, D; Hines, M L; Lytton, W W

    2016-03-01

    Neuronal persistent activity has been primarily assessed in terms of electrical mechanisms, without attention to the complex array of molecular events that also control cell excitability. We developed a multiscale neocortical model proceeding from the molecular to the network level to assess the contributions of calcium (Ca(2+)) regulation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in providing additional and complementary support of continuing activation in the network. The network contained 776 compartmental neurons arranged in the cortical layers, connected using synapses containing AMPA/NMDA/GABAA/GABAB receptors. Metabotropic glutamate receptors (mGluR) produced inositol triphosphate (IP3) which caused the release of Ca(2+) from endoplasmic reticulum (ER) stores, with reuptake by sarco/ER Ca(2+)-ATP-ase pumps (SERCA), and influence on HCN channels. Stimulus-induced depolarization led to Ca(2+) influx via NMDA and voltage-gated Ca(2+) channels (VGCCs). After a delay, mGluR activation led to ER Ca(2+) release via IP3 receptors. These factors increased HCN channel conductance and produced firing lasting for ∼1min. The model displayed inter-scale synergies among synaptic weights, excitation/inhibition balance, firing rates, membrane depolarization, Ca(2+) levels, regulation of HCN channels, and induction of persistent activity. The interaction between inhibition and Ca(2+) at the HCN channel nexus determined a limited range of inhibition strengths for which intracellular Ca(2+) could prepare population-specific persistent activity. Interactions between metabotropic and ionotropic inputs to the neuron demonstrated how multiple pathways could contribute in a complementary manner to persistent activity. Such redundancy and complementarity via multiple pathways is a critical feature of biological systems. Mediation of activation at different time scales, and through different pathways, would be expected to protect against disruption, in

  9. HCN channels contribute to serotonergic modulation of ventral surface chemosensitive neurons and respiratory activity

    PubMed Central

    Hawkins, Virginia E.; Hawryluk, Joanna M.; Takakura, Ana C.; Tzingounis, Anastasios V.; Moreira, Thiago S.

    2014-01-01

    Chemosensitive neurons in the retrotrapezoid nucleus (RTN) provide a CO2/H+-dependent drive to breathe and function as an integration center for the respiratory network, including serotonergic raphe neurons. We recently showed that serotonergic modulation of RTN chemoreceptors involved inhibition of KCNQ channels and activation of an unknown inward current. Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels are the molecular correlate of the hyperpolarization-activated inward current (Ih) and have a high propensity for modulation by serotonin. To investigate whether HCN channels contribute to basal activity and serotonergic modulation of RTN chemoreceptors, we characterize resting activity and the effects of serotonin on RTN chemoreceptors in vitro and on respiratory activity of anesthetized rats in the presence or absence of blockers of KCNQ (XE991) and/or HCN (ZD7288, Cs+) channels. We found in vivo that bilateral RTN injections of ZD7288 increased respiratory activity and in vitro HCN channel blockade increased activity of RTN chemoreceptors under control conditions, but this was blunted by KCNQ channel inhibition. Furthermore, in vivo unilateral RTN injection of XE991 plus ZD7288 eliminated the serotonin response, and in vitro serotonin sensitivity was eliminated by application of XE991 and ZD7288 or SQ22536 (adenylate cyclase blocker). Serotonin-mediated activation of RTN chemoreceptors was blocked by a 5-HT7-receptor blocker and mimicked by a 5-HT7-receptor agonist. In addition, serotonin caused a depolarizing shift in the voltage-dependent activation of Ih. These results suggest that HCN channels contribute to resting chemoreceptor activity and that serotonin activates RTN chemoreceptors and breathing in part by a 5-HT7 receptor-dependent mechanism and downstream activation of Ih. PMID:25429115

  10. Unraveling carbohydrate transport mechanisms in young beech trees (Fagus sylvatica f. purpurea) by 13CO2 efflux measurements from stem and soil

    NASA Astrophysics Data System (ADS)

    Thoms, Ronny; Muhr, Jan; Keitel, Claudia; Kayler, Zachary; Gavrichkova, Olga; Köhler, Michael; Gessler, Arthur; Gleixner, Gerd

    2016-04-01

    Transport mechanisms of soluble carbohydrates and diurnal CO2 efflux from tree stems and surrounding soil are well studied. However, the effect of transport carbohydrates on respiration and their interaction with storage processes is largely unknown. Therefore, we performed a set of 13CO2 pulse labeling experiments on young trees of European beech (Fagus sylvatica f. purpurea). We labeled the whole tree crowns in a closed transparent plastic chamber with 99% 13CO2 for 30 min. In one experiment, only a single branch was labeled and removed 36 hours after labeling. In all experiments, we continuously measured the 13CO2 efflux from stem, branch and soil and sampled leaf and stem material every 3 h for 2 days, followed by a daily sampling of leaves in the successive 5 days. The compound specific δ 13C value of extracted soluble carbohydrates from leaf and stem material was measured by high-performance liquid chromatography linked with an isotope ratio mass spectrometer (HPLC-IRMS). The 13CO2 signal from soil respiration occurred only few hours after labeling indicating a very high transport rate of carbohydrates from leaf to roots and to the rhizosphere. The label was continuously depleted within the next 5 days. In contrast, we observed a remarkable oscillating pattern of 13CO2 efflux from the stem with maximum 13CO2 enrichment at noon and minima at night time. This oscillation suggests that enriched carbohydrates are respired during the day, whereas in the night the enriched sugars are not respired. The observed oscillation in stem 13CO2 enrichment remained unchanged even when only single branches were labelled and cut right afterwards. Thus, storage and conversion of carbohydrates only occurred within the stem. The δ13C patterns of extracted soluble carbohydrates showed, that a transformation of transitory starch to carbohydrates and vice versa was no driver of the oscillating 13CO2 efflux from the stem. Carbohydrates might have been transported in the phloem to

  11. Enhancement of dorsal hippocampal activity by knockdown of HCN1 channels leads to anxiolytic- and antidepressant-like behaviors.

    PubMed

    Kim, Chung Sub; Chang, Payne Y; Johnston, Daniel

    2012-08-09

    The hippocampus is an integral brain region for affective disorders. TRIP8b knockout mice lacking functional HCN channels as well as both HCN1 and HCN2 knockout mice have been shown to display antidepressant-like behaviors. The mechanisms or brain regions involved in these alterations in behavior, however, are not clear. We developed a lentiviral shRNA system to examine whether knockdown of HCN1 protein in the dorsal hippocampal CA1 region is sufficient to produce antidepressant-like effects. We found that knockdown of HCN1 channels increased cellular excitability and resulted in physiological changes consistent with a reduction of I(h). Rats infused with lentiviral shRNA-HCN1 in the dorsal hippocampal CA1 region displayed antidepressant- and anxiolytic-like behaviors associated with widespread enhancement of hippocampal activity and upregulation of BDNF-mTOR signaling pathways. Our results suggest that HCN1 protein could be a potential target for treatment of anxiety and depression disorders.

  12. Mechanisms of seizure-induced ‘transcriptional channelopathy’ of hyperpolarization-activated cyclic nucleotide gated (HCN) channels

    PubMed Central

    Richichi, Cristina; Brewster, Amy L.; Bender, Roland A.; Simeone, Timothy A.; Zha, Qinqin; Yin, Hong Z.; Weiss, John H.; Baram, Tallie Z.

    2008-01-01

    Epilepsy may result from abnormal function of ion channels, such as those caused by genetic mutations. Recently, pathological alterations of the expression or localization of normal channels have been implicated in epilepsy generation, and termed ‘acquired channelopathies’. Altered expression levels of the HCN channels--that conduct the hyperpolarization-activated current, Ih--have been demonstrated in hippocampus of patients with severe temporal lobe epilepsy as well as in animal models of temporal lobe and absence epilepsies. Here we probe the mechanisms for the altered expression of HCN channels which is provoked by seizures. In organotypic hippocampal slice cultures, seizure-like events selectively reduced HCN type 1 channel expression and increased HCN2 mRNA levels, as occurs in vivo. The mechanisms for HCN1 reduction involved Ca2+-permeable AMPA receptors-mediated Ca2+ influx, and subsequent activation of Ca2+/calmodulin-dependent protein kinase II. In contrast, upregulation of HCN2 expression was independent of these processes. The data demonstrate an orchestrated program for seizure-evoked transcriptional channelopathy involving the HCN channels, that may contribute to certain epilepsies. PMID:17964174

  13. A new ab initio potential energy surface for the collisional excitation of HCN by para- and ortho-H2.

    PubMed

    Denis-Alpizar, Otoniel; Kalugina, Yulia; Stoecklin, Thierry; Vera, Mario Hernández; Lique, François

    2013-12-14

    We present a new four-dimensional potential energy surface for the collisional excitation of HCN by H2. Ab initio calculations of the HCN-H2 van der Waals complex, considering both molecules as rigid rotors, were carried out at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations [CCSD(T)-F12a] level of theory using an augmented correlation-consistent triple zeta (aVTZ) basis set. The equilibrium structure is linear HCN-H2 with the nitrogen pointing towards H2 at an intermolecular separation of 7.20 a0. The corresponding well depth is -195.20 cm(-1). A secondary minimum of -183.59 cm(-1) was found for a T-shape configuration with the H of HCN pointing to the center of mass of H2. We also determine the rovibrational energy levels of the HCN-para-H2 and HCN-ortho-H2 complexes. The calculated dissociation energies for the para and ortho complexes are 37.79 cm(-1) and 60.26 cm(-1), respectively. The calculated ro-vibrational transitions in the HCN-H2 complex are found to agree by more than 0.5% with the available experimental data, confirming the accuracy of the potential energy surface.

  14. On the HCN and CO 2 abundance and distribution in Jupiter's stratosphere

    NASA Astrophysics Data System (ADS)

    Lellouch, E.; Bézard, B.; Strobel, D. F.; Bjoraker, G. L.; Flasar, F. M.; Romani, P. N.

    2006-10-01

    Observations of Jupiter by Cassini/CIRS, acquired during the December 2000 flyby, provide the latitudinal distribution of HCN and CO 2 in Jupiter's stratosphere with unprecedented spatial resolution and coverage. Following up on a preliminary study by Kunde et al. [Kunde, V.G., and 41 colleagues, 2004. Science 305, 1582-1587], the analysis of these observations leads to two unexpected results (i) the total HCN mass in Jupiter's stratosphere in 2000 was (6.0±1.5)×10 g, i.e., at least three times larger than measured immediately after the Shoemaker-Levy 9 (SL9) impacts in July 1994 and (ii) the latitudinal distributions of HCN and CO 2 are strikingly different: while HCN exhibits a maximum at 45° S and a sharp decrease towards high Southern latitudes, the CO 2 column densities peak over the South Pole. The total CO 2 mass is (2.9±1.2)×10 g. A possible cause for the HCN mass increase is its production from the photolysis of NH 3, although a problem remains because, while millimeter-wave observations clearly indicate that HCN is currently restricted to submillibar ( ˜0.3 mbar) levels, immediate post-impact infrared observations have suggested that most of the ammonia was present in the lower stratosphere near 20 mbar. HCN appears to be a good atmospheric tracer, with negligible chemical losses. Based on 1-dimensional (latitude) transport models, the HCN distribution is best interpreted as resulting from the combination of a sharp decrease (over an order of magnitude in K) of wave-induced eddy mixing poleward of 40° and an equatorward transport with ˜7 cms velocity. The CO 2 distribution was investigated by coupling the transport model with an elementary chemical model, in which CO 2 is produced from the conversion of water originating either from SL9 or from auroral input. The auroral source does not appear adequate to reproduce the CO 2 peak over the South Pole, as required fluxes are unrealistically high and the shape of the CO 2 bulge is not properly matched

  15. Characterization of the hcnABC Gene Cluster Encoding Hydrogen Cyanide Synthase and Anaerobic Regulation by ANR in the Strictly Aerobic Biocontrol Agent Pseudomonas fluorescens CHA0

    PubMed Central

    Laville, Jacques; Blumer, Caroline; Von Schroetter, Christine; Gaia, Valeria; Défago, Geneviève; Keel, Christoph; Haas, Dieter

    1998-01-01

    The secondary metabolite hydrogen cyanide (HCN) is produced by Pseudomonas fluorescens from glycine, essentially under microaerophilic conditions. The genetic basis of HCN synthesis in P. fluorescens CHA0 was investigated. The contiguous structural genes hcnABC encoding HCN synthase were expressed from the T7 promoter in Escherichia coli, resulting in HCN production in this bacterium. Analysis of the nucleotide sequence of the hcnABC genes showed that each HCN synthase subunit was similar to known enzymes involved in hydrogen transfer, i.e., to formate dehydrogenase (for HcnA) or amino acid oxidases (for HcnB and HcnC). These similarities and the presence of flavin adenine dinucleotide- or NAD(P)-binding motifs in HcnB and HcnC suggest that HCN synthase may act as a dehydrogenase in the reaction leading from glycine to HCN and CO2. The hcnA promoter was mapped by primer extension; the −40 sequence (TTGGC … .ATCAA) resembled the consensus FNR (fumarate and nitrate reductase regulator) binding sequence (TTGAT … .ATCAA). The gene encoding the FNR-like protein ANR (anaerobic regulator) was cloned from P. fluorescens CHA0 and sequenced. ANR of strain CHA0 was most similar to ANR of P. aeruginosa and CydR of Azotobacter vinelandii. An anr mutant of P. fluorescens (CHA21) produced little HCN and was unable to express an hcnA-lacZ translational fusion, whereas in wild-type strain CHA0, microaerophilic conditions strongly favored the expression of the hcnA-lacZ fusion. Mutant CHA21 as well as an hcn deletion mutant were impaired in their capacity to suppress black root rot of tobacco, a disease caused by Thielaviopsis basicola, under gnotobiotic conditions. This effect was most pronounced in water-saturated artificial soil, where the anr mutant had lost about 30% of disease suppression ability, compared with wild-type strain CHA0. These results show that the anaerobic regulator ANR is required for cyanide synthesis in the strictly aerobic strain CHA0 and

  16. Characterization of the hcnABC gene cluster encoding hydrogen cyanide synthase and anaerobic regulation by ANR in the strictly aerobic biocontrol agent Pseudomonas fluorescens CHA0.

    PubMed

    Laville, J; Blumer, C; Von Schroetter, C; Gaia, V; Défago, G; Keel, C; Haas, D

    1998-06-01

    The secondary metabolite hydrogen cyanide (HCN) is produced by Pseudomonas fluorescens from glycine, essentially under microaerophilic conditions. The genetic basis of HCN synthesis in P. fluorescens CHA0 was investigated. The contiguous structural genes hcnABC encoding HCN synthase were expressed from the T7 promoter in Escherichia coli, resulting in HCN production in this bacterium. Analysis of the nucleotide sequence of the hcnABC genes showed that each HCN synthase subunit was similar to known enzymes involved in hydrogen transfer, i.e., to formate dehydrogenase (for HcnA) or amino acid oxidases (for HcnB and HcnC). These similarities and the presence of flavin adenine dinucleotide- or NAD(P)-binding motifs in HcnB and HcnC suggest that HCN synthase may act as a dehydrogenase in the reaction leading from glycine to HCN and CO2. The hcnA promoter was mapped by primer extension; the -40 sequence (TTGGC ... ATCAA) resembled the consensus FNR (fumarate and nitrate reductase regulator) binding sequence (TTGAT ... ATCAA). The gene encoding the FNR-like protein ANR (anaerobic regulator) was cloned from P. fluorescens CHA0 and sequenced. ANR of strain CHA0 was most similar to ANR of P. aeruginosa and CydR of Azotobacter vinelandii. An anr mutant of P. fluorescens (CHA21) produced little HCN and was unable to express an hcnA-lacZ translational fusion, whereas in wild-type strain CHA0, microaerophilic conditions strongly favored the expression of the hcnA-lacZ fusion. Mutant CHA21 as well as an hcn deletion mutant were impaired in their capacity to suppress black root rot of tobacco, a disease caused by Thielaviopsis basicola, under gnotobiotic conditions. This effect was most pronounced in water-saturated artificial soil, where the anr mutant had lost about 30% of disease suppression ability, compared with wild-type strain CHA0. These results show that the anaerobic regulator ANR is required for cyanide synthesis in the strictly aerobic strain CHA0 and suggest that ANR

  17. Modelling mechanical heating in star-forming galaxies: CO and 13CO Line ratios as sensitive probes

    NASA Astrophysics Data System (ADS)

    Kazandjian, M. V.; Pelupessy, I.; Meijerink, R.; Israel, F. P.; Spaans, M.

    2016-11-01

    We apply photo-dissociation region (PDR) molecular line emission models, that have varying degrees of enhanced mechanical heating rates, to the gaseous component of simulations of star-forming galaxies taken from the literature. Snapshots of these simulations are used to produce line emission maps for the rotational transitions of the CO molecule and its 13CO isotope up to J = 4-3. We use these maps to investigate the occurrence and effect of mechanical feedback on the physical parameters obtained from molecular line intensity ratios. We consider two galaxy models: a small disk galaxy of solar metallicity and a lighter dwarf galaxy with 0.2 Z⊙ metallicity. Elevated excitation temperatures for CO(1-0) correlate positively with mechanical feedback, that is enhanced towards the central region of both model galaxies. The emission maps of these model galaxies are used to compute line ratios of CO and 13CO transitions. These line ratios are used as diagnostics where we attempt to match them These line ratios are used as diagnostics where we attempt to match them to mechanically heated single component (i.e. uniform density, Far-UV flux, visual extinction and velocity gradient) equilibrium PDR models. We find that PDRs ignoring mechanical feedback in the heating budget over-estimate the gas density by a factor of 100 and the far-UV flux by factors of 10-1000. In contrast, PDRs that take mechanical feedback into account are able to fit all the line ratios for the central <2 kpc of the fiducial disk galaxy quite well. The mean mechanical heating rate per H atom that we recover from the line ratio fits of this region varies between 10-27-10-26 erg s-1. Moreover, the mean gas density, mechanical heating rate, and the AV are recovered to less than half dex. On the other hand, our single component PDR model fit is not suitable for determining the actual gas parameters of the dwarf galaxy, although the quality of the fit line ratios are comparable to that of the disk galaxy.

  18. Evaluating the Community Land Model in a pine stand with shading manipulations and 13CO2 labeling

    DOE PAGES

    Mao, Jiafu; Ricciuto, Daniel M.; Thornton, Peter E.; ...

    2016-02-03

    Carbon partitioning and flow through ecosystems regulates land surface atmosphere CO2 exchange and thus is a key, albeit uncertain component of mechanistic models. The Partitioning in Trees and Soil (PiTS) experiment-model project tracked C partitioning through a young Pinus taeda stand following pulse-labeling with 13CO2 and two levels of shading. The field component of this project provided process-oriented data that was used to evaluate and improve terrestrial biosphere model simulations of rapid shifts in carbon partitioning and hydrological dynamics under varying environmental conditions. Here we tested the performance of the Community Land Model version 4 (CLM4) in capturing short-term carbonmore » and water dynamics in relation to manipulative shading treatments, and the timing and magnitude of carbon fluxes through various compartments of the ecosystem. To constrain CLM4 to closely simulate pretreatment conditions, we calibrated select model parameters with the pretreatment observational data. Compared to CLM4 simulations with default parameters, CLM4 with calibrated model parameters was better able to simulate pretreatment vegetation carbon pools, light response curves, and other initial states and fluxes of carbon and water. Over a 3-week treatment period, the calibrated CLM4 generally reproduced the impacts of shading on average soil moisture at 15-95 cm depth, transpiration, relative change in stem carbon, and soil CO2 efflux rate, although some discrepancies in the estimation of magnitudes and temporal evolutions existed. CLM4, however, was not able to track the progression of the 13CO2 label from the atmosphere through foliage, phloem, roots or surface soil CO2 efflux, even when optimized model parameters were used. This model bias arises, in part, from the lack of a short-term non-structural carbohydrate storage pool and progressive timing of within-plant transport, thus indicating a need for future work to improve the allocation routines in CLM4

  19. Evaluating the Community Land Model in a pine stand with 13CO2 labeling and shading manipulations

    NASA Astrophysics Data System (ADS)

    Mao, J.; Ricciuto, D. M.; Thornton, P. E.; Warren, J. M.; King, A. W.; Shi, X.; Iversen, C. M.; Norby, R. J.

    2015-05-01

    Carbon allocation and flow through ecosystems regulate land surface-atmosphere CO2 exchange and thus is a key, albeit uncertain, component of mechanistic models. The Partitioning in Trees and Soil (PiTS) experiment-model project tracked carbon allocation through a young Pinus taeda stand following pulse-labeling with 13CO2 and two levels of shading. The field component of this project provided process-oriented data that was used to evaluate and improve terrestrial biosphere model simulations of rapid shifts in carbon allocation and hydrological dynamics under varying environmental conditions. Here we tested the performance of the Community Land Model version 4 (CLM4) in capturing short-term carbon and water dynamics in relation to manipulative shading treatments, and the timing and magnitude of carbon fluxes through various compartments of the ecosystem. For CLM4 to closely simulate pretreatment conditions, we calibrated select model parameters with pretreatment observational data. Compared to CLM4 simulations with default parameters, CLM4 with calibrated model parameters was able to better simulate pretreatment vegetation carbon pools, light response curves, and other initial states and fluxes of carbon and water. Over a 3 week treatment period, the calibrated CLM4 generally reproduced the impacts of shading on average soil moisture at 15-95 cm depth, transpiration, relative change in stem carbon, and soil CO2 efflux rate, although some discrepancies in the estimation of magnitudes and temporal evolutions existed. CLM4, however, was not able to track the progression of the 13CO2 label from the atmosphere through foliage, phloem, roots or surface soil CO2 efflux, even when optimized model parameters were used. This model bias arises, in part, from the lack of a short-term non-structural carbohydrate storage pool and progressive timing of within-plant transport, thus indicating a need for future work to improve the allocation routines in CLM4. Overall, these types

  20. VizieR Online Data Catalog: G345.45+1.50 13CO(3-2) clumps (Lopez-Calderon+,

    NASA Astrophysics Data System (ADS)

    Lopez-Calderon, C.; Bronfman, L.; Nyman, L.-A.; Garay, G.; de Gregorio-Monsalvo, I.; Bergman, P.

    2017-02-01

    The 13CO(3-2) line observations were made at 330.588GHz on-the-fly (OTF) observing mode with the APEX-2A heterodyne receiver mounted at the APEX telescope on October 17-19, 2005, May 28, June 24-26, and October 7-10, 2006. To estimate the gas temperature in the region, the 12CO(3-2) line was observed using ASTE toward 29 intensity peaks found in the 13CO(3-2) line map. Observations were made on August 27 2010. (1 data file).

  1. Energy yields for hydrogen cyanide and formaldehyde syntheses - The HCN and amino acid concentrations in the primitive ocean

    NASA Technical Reports Server (NTRS)

    Stribling, Roscoe; Miller, Stanley L.

    1987-01-01

    Simulated prebiotic atmospheres containing either CH4, CO, or CO2, in addition to N2, H2O, and variable amounts of H2, were subjected to the spark from a high-frequency Tesla coil, and the energy yields for the syntheses of HCN and H2CO were estimated from periodic (every two days) measurements of the compound concentrations. The mixtures with CH4 were found to yield the highest amounts of HCN, whereas the CO mixtures produced the highest yields of H2CO. These results model atmospheric corona discharges. From the yearly energy yields calculated and the corona discharge available on the earth, the yearly production rate of HCN was estimated; using data on the HCN production rates and the experimental rates of decomposition of amino acids through the submarine vents, the steady state amino acid production rate in the primitive ocean was calculated to be about 10 nmoles/sq cm per year.

  2. 13C Tracking after 13CO2 Supply Revealed Diurnal Patterns of Wood Formation in Aspen1

    PubMed Central

    Mahboubi, Amir; Linden, Pernilla; Moritz, Thomas

    2015-01-01

    Wood of trees is formed from carbon assimilated in the photosynthetic tissues. Determining the temporal dynamics of carbon assimilation, subsequent transport into developing wood, and incorporation to cell walls would further our understanding of wood formation in particular and tree growth in general. To investigate these questions, we designed a 13CO2 labeling system to study carbon transport and incorporation to developing wood of hybrid aspen (Populus tremula × tremuloides). Tracking of 13C incorporation to wood over a time course using nuclear magnetic resonance spectroscopy revealed diurnal patterns in wood cell wall biosynthesis. The dark period had a differential effect on 13C incorporation to lignin and cell wall carbohydrates. No 13C was incorporated into aromatic amino acids of cell wall proteins in the dark, suggesting that cell wall protein biosynthesis ceased during the night. The results show previously unrecognized temporal patterns in wood cell wall biosynthesis, suggest diurnal cycle as a possible cue in the regulation of carbon incorporation to wood, and establish a unique 13C labeling method for the analysis of wood formation and secondary growth in trees. PMID:25931520

  3. Increased HCN channel driven inward rectification in benign cramp fasciculation syndrome.

    PubMed

    Czesnik, Dirk; Howells, James; Negro, Francesco; Wagenknecht, Melanie; Hanner, Susanne; Farina, Dario; Burke, David; Paulus, Walter

    2015-11-01

    Muscle cramps are a common complaint associated with sudden painful involuntary contractions of a muscle. The mechanisms responsible for muscle cramps are still not clear. Axonal excitability and multi-unit electromyography studies were performed in 20 patients suffering from benign cramp fasciculation syndrome, not currently on medication. The measures of axonal excitability suggested greater inward rectification, indicative of an increase in Ih. Mathematical modelling suggested that the data were best explained by depolarization of the voltage dependence of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. Parameters associated with polarization of resting membrane potential were not changed. These findings suggest that a role for HCN channels may become apparent during the rhythmic discharge associated with a voluntary contraction. Consistent with this view, patients had higher motor unit discharge rates than healthy controls during maximal voluntary effort.

  4. Detection of HCN and C2H2 in ISO Spectra of Oxygen-Rich AGB Stars

    NASA Technical Reports Server (NTRS)

    Carbon, Duane F.; Chiar, Jean; Goorvitch, David; Kwak, Dochan (Technical Monitor)

    2002-01-01

    Cool oxygen-rich AGB stars were not expected to have organic molecules like HCN in either their photospheres or circumstellar envelopes (CSEs). The discovery of HCN and CS microwave emission from the shallowest CSE layers of these stars was a considerable surprise and much theoretical effort has been expended in explaining the presence of such organics. To further explore this problem, we have undertaken a systematic search of oxygen-rich AGB stellar spectra in the Infrared Space Observatory (ISO) data archive. Our purposes are to find evidence regarding critical molecular species that could be of value in choosing among the proposed theoretical models, to locate spectral features which might give clues to conditions deeper in the CSEs, and to lay the groundwork for future SIRTF (Space Infrared Telescope Facility) and SOFIA (Stratospheric Observatory for Infrared Astronomy) observations. Using carefully reduced observations, we have detected weak absorption features arising from HCN and possibly C2H2 in a small number of oxygen-rich AGB stars. The most compelling case is NML Cyg which shows both HCN (14 microns) and CO2 (15 microns). VY CMa, a similar star, shows evidence for HCN, but not CO2. Two S-type stars show evidence for the C-H bending transitions: W Aql at 14 microns (HCN) and both W Aql and S Cas at 13.7 microns (C2H2). Both W Aql and S Cas as well as S Lyr, a SC-type star, show 3 micron absorption which may arise from the C-H stretch of HCN and C2H2. In the case of NML Cyg, we show that the HCN and CO2 spectral features are formed in the CSE at temperatures well above those of the outermost CSE layers and derive approximate column densities. In the case of the S-stars, we discuss the evidence for the organic features and their photospheric origin.

  5. Extended HCN and HCO+ Emission in the Starburst Galaxy M82

    NASA Astrophysics Data System (ADS)

    Salas, P.; Galaz, G.; Salter, D.; Herrera-Camus, R.; Bolatto, A. D.; Kepley, A.

    2014-12-01

    We mapped 3 mm continuum and line emission from the starburst galaxy M82 using the Combined Array for Research in Millimeter-wave Astronomy. We targeted the HCN, HCO+, HNC, CS, and HC3N lines, but here we focus on the HCN and HCO+ emission. The map covers a field of 1.'2 with an ≈5'' resolution. The HCN and HCO+ observations are short spacings corrected. The molecular gas in M82 had been previously found to be distributed in a molecular disk, coincident with the central starburst, and a galactic scale outflow which originates in the central starburst. With the new short spacings-corrected maps we derive some of the properties of the dense molecular gas in the base of the outflow. From the HCN and HCO+ J = (1-0) line emission, and under the assumptions of the gas being optically thin and in local thermodynamic equilibrium, we place lower limits on the amount of dense molecular gas in the base of the outflow. The lower limits are 7 × 106 M ⊙ and 21 × 106 M ⊙, or >~ 2% of the total molecular mass in the outflow. The kinematics and spatial distribution of the dense gas outside the central starburst suggests that it is being expelled through chimneys. Assuming a constant outflow velocity, the derived outflow rate of dense molecular gas is >=0.3 M ⊙ yr-1, which would lower the starburst lifetime by >=5%. The energy required to expel this mass of dense gas is (1-10) × 1052 erg.

  6. Chemical evolution. XXI - The amino acids released on hydrolysis of HCN oligomers

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Wos, J. D.; Nooner, D. W.; Oro, J.

    1974-01-01

    Major amino acids released by hydrolysis of acidic and basic HCN oligomers are identified by chromatography as Gly, Asp, and diaminosuccinic acid. Smaller amounts of Ala, Ile and alpha-aminoisobutyric acid are also detected. The amino acids released did not change appreciably when the hydrolysis medium was changed from neutral to acidic or basic. The presence of both meso and d, l-diaminosuccinic acids was established by paper chromatography and on an amino acid analyzer.

  7. Involvement of HCN Channel in Muscarinic Inhibitory Action on Tonic Firing of Dorsolateral Striatal Cholinergic Interneurons

    PubMed Central

    Zhao, Zhe; Zhang, Kang; Liu, Xiaoyan; Yan, Haitao; Ma, Xiaoyun; Zhang, Shuzhuo; Zheng, Jianquan; Wang, Liyun; Wei, Xiaoli

    2016-01-01

    The striatum is the most prominent nucleus in the basal ganglia and plays an important role in motor movement regulation. The cholinergic interneurons (ChIs) in striatum are involved in the motion regulation by releasing acetylcholine (ACh) and modulating the output of striatal projection neurons. Here, we report that muscarinic ACh receptor (M receptor) agonists, ACh and Oxotremorine (OXO-M), decreased the firing frequency of ChIs by blocking the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. Scopolamine (SCO), a nonselective antagonist of M receptors, abolished the inhibition. OXO-M exerted its function by activating the Gi/o cAMP signaling cascade. The single-cell reverse transcription polymerase chain reaction (scRT-PCR) revealed that all the five subtypes of M receptors and four subtypes of HCN channels were expressed on ChIs. Among them, M2 receptors and HCN2 channels were the most dominant ones and expressed in every single studied cholinergic interneuron (ChI).Our results suggest that ACh regulates not only the output of striatal projection neurons, but also the firing activity of ChIs themselves by activating presynaptic M receptors in the dorsal striatum. The activation of M2 receptors and blockage of HCN2 channels may play an important role in ACh inhibition on the excitability of ChIs. This finding adds a new G-protein coupled receptor mediated regulation on ChIs and provides a cellular mechanism for control of cholinergic activity and ACh release in the dorsal striatum. PMID:27047336

  8. A computational investigation of HCN2+ isomeric structures: implications for the chemistry of Titan's atmosphere.

    PubMed

    Antoniotti, Paola; Borocci, Stefano; Bronzolino, Nicoletta; Grandinetti, Felice

    2004-09-20

    The structure and stability of various HCN2+ isomeric structures have been investigated at the complete active space SCF (CASSCF) and multireference-configuration interaction [MR-Cl-SD(Q)] levels of theory with the 6-31G(d) and 6-311G(d,p) basis sets. The investigated species include the singlet (S) and triplet (T) open-chain H-N-C-N+ ions 1S, 1S', and 1T, the open-chain H-C-N-N+ ions 2S, 2S', and 2T, the HC-N2+ cyclic structures 3S and 3T, and the HN-CN+ cyclic structures 4S and 4T. All these species have been identified as true energy minima on the CASSCF(8,7)/6-31G(d) potential energy surface, and their optimised geometries, refined at the CASSCF(8,8)/6-31G(d) level of theory, have been used to perform single point calculations at the [MR-Cl-SD(Q]/6-311G(d,p) computational level. The most stable structure was the H-N-C-N+ ion 1T, whose absolute enthalpy of formation at 298.15 K has been estimated as 333.9 +/- 2 kcalmol(-1) using the Gaussian-3 (G3) procedure. The two species closest in energy to 1T are the triplet H-C-N-N+ ion 2T and the singlet diazirinyl cation 3S, whose G3 enthalpies of formation at 298.15 K are 343.5 +/- 2 and 340.6 +/- 2 kcalmol(-1), respectively. Finally, we have discussed the implications of our calculations for the detailed structure of the HCN2+ ions formed in the reaction between N3+ and HCN, experimentally observed by flowing after-glow-selected ion flow/drift tube mass spectrometry and possibly occurring in Titan's atmosphere.

  9. Lamellar {gamma}-AlOOH architectures: Synthesis and application for the removal of HCN

    SciTech Connect

    Hou Hongwei; Zhu You; Tang Gangling; Hu Qingyuan

    2012-06-15

    Using hexadecyl trimethyl ammonium bromide (CTAB) as a structure-directing agent and precipitator, the complete synthesis of lamellar {gamma}-AlOOH architectures was successfully accomplished via a hydrothermal route. Different product structures were obtained by varying the molar ratio of aluminum nitrate and CTAB. Several techniques, including X-ray powder diffraction, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and differential scanning calorimetry thermal analysis, were used to characterize the products. The effects of CTAB concentration, reaction temperature and time, and the molar ratio of Al{sup 3+}/CTAB on the product morphologies were investigated. The nitrogen adsorption and desorption measurements indicated that the {gamma}-AlOOH architectures possess a Brunauer-Emmett-Teller surface area of approximately 75.02 m{sup 2}/g. It was also demonstrated that 10 mg {gamma}-AlOOH architectures can remove 45.3% of the HCN (1.68 {mu}g/mL) from model wastewater. When 0.03 mg/cig {gamma}-AlOOH architectures were combined with cigarette paper, 8.12% of the present HCN was adsorbed. These results indicate that lamellar {gamma}-AlOOH architectures may be a potential adsorbent for removing HCN from highly toxic pollutant solutions and harmful cigarette smoke. Highlights: Black-Right-Pointing-Pointer Hexadecyl trimethyl ammonium bromide (CTAB) was used as a structure-directing agent and precipitator. Black-Right-Pointing-Pointer Hydrothermal treatment enables growth of lamellar {gamma}-AlOOH architectures. Black-Right-Pointing-Pointer Lamellar {gamma}-AlOOH architectures were demonstrated to exhibit high BET surface area and excellent adsorptive capacity. Black-Right-Pointing-Pointer HCN in contaminated water and cigarette smoke can be effectively removed by the prepared lamellar {gamma}-AlOOH superstructures.

  10. EXTENDED HCN AND HCO{sup +} EMISSION IN THE STARBURST GALAXY M82

    SciTech Connect

    Salas, P.; Galaz, G.; Salter, D.; Herrera-Camus, R.; Bolatto, A. D.; Kepley, A.

    2014-12-20

    We mapped 3 mm continuum and line emission from the starburst galaxy M82 using the Combined Array for Research in Millimeter-wave Astronomy. We targeted the HCN, HCO{sup +}, HNC, CS, and HC{sub 3}N lines, but here we focus on the HCN and HCO{sup +} emission. The map covers a field of 1.'2 with an ≈5'' resolution. The HCN and HCO{sup +} observations are short spacings corrected. The molecular gas in M82 had been previously found to be distributed in a molecular disk, coincident with the central starburst, and a galactic scale outflow which originates in the central starburst. With the new short spacings-corrected maps we derive some of the properties of the dense molecular gas in the base of the outflow. From the HCN and HCO{sup +} J = (1-0) line emission, and under the assumptions of the gas being optically thin and in local thermodynamic equilibrium, we place lower limits on the amount of dense molecular gas in the base of the outflow. The lower limits are 7 × 10{sup 6} M {sub ☉} and 21 × 10{sup 6} M {sub ☉}, or ≳ 2% of the total molecular mass in the outflow. The kinematics and spatial distribution of the dense gas outside the central starburst suggests that it is being expelled through chimneys. Assuming a constant outflow velocity, the derived outflow rate of dense molecular gas is ≥0.3 M {sub ☉} yr{sup –1}, which would lower the starburst lifetime by ≥5%. The energy required to expel this mass of dense gas is (1-10) × 10{sup 52} erg.

  11. Investigating the Spatial Structure of HCN Emission in Comet C/2012 F6 (Lemmon)

    NASA Astrophysics Data System (ADS)

    Booth, Shawn; Burkhardt, Andrew; Corby, Joanna; Dollhopf, Niklaus; Rawlings, Mark; Remijan, Anthony

    2015-11-01

    Comets are of particular interest in the field of Astrochemistry as they can be used as a direct probe of formation chemistry of the Solar System. Originating in the Oort Cloud reservoir, these long period objects experience relatively limited solar influence. The majority of cometary material (water, methane and ammonia ices) has remained in the same state as when it formed. These ices are precursors to more complex molecules which have been shown to form amino acids that are crucial for the development of life. HCN, or hydrogen cyanide, is of particular interest because it can form the nucleobase adenine (C5H5N5). The goals of this project are to map the HCN distribution of Comet C/2012 F6 (Lemmon) and to show the simultaneous observation capabilities of the Atacama Large Millimeter/Submillimeter Array (ALMA), which allows the extraction of 7-m array, 12-m array and single dish observation data. On UT 2013 May 11, Comet Lemmon was observed using ALMA. The Cycle 1 configuration was used with the Band 6 receivers, with a 1.5 GHz range centered on the HCN transition at 265.86 GHz, which gave a spectral resolution of 0.07 km/s. We show that Comet Lemmon has both a compact HCN region (found with the 12-m array) and also an extended component, forming a tail-like structure in the anti-motion direction (found with the 7-m array). We were also able to extract the autocorrelation data (single dish) and show that it is viable. This project was supported and funded by NRAO in conjunction with the National Science Foundation (NSF), with special thanks to the Astronomy Department at University of Virginia.

  12. Structural basis for the mutual antagonism of cAMP and TRIP8b in regulating HCN channel function.

    PubMed

    Saponaro, Andrea; Pauleta, Sofia R; Cantini, Francesca; Matzapetakis, Manolis; Hammann, Christian; Donadoni, Chiara; Hu, Lei; Thiel, Gerhard; Banci, Lucia; Santoro, Bina; Moroni, Anna

    2014-10-07

    cAMP signaling in the brain mediates several higher order neural processes. Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels directly bind cAMP through their cytoplasmic cyclic nucleotide binding domain (CNBD), thus playing a unique role in brain function. Neuronal HCN channels are also regulated by tetratricopeptide repeat-containing Rab8b interacting protein (TRIP8b), an auxiliary subunit that antagonizes the effects of cAMP by interacting with the channel CNBD. To unravel the molecular mechanisms underlying the dual regulation of HCN channel activity by cAMP/TRIP8b, we determined the NMR solution structure of the HCN2 channel CNBD in the cAMP-free form and mapped on it the TRIP8b interaction site. We reconstruct here the full conformational changes induced by cAMP binding to the HCN channel CNBD. Our results show that TRIP8b does not compete with cAMP for the same binding region; rather, it exerts its inhibitory action through an allosteric mechanism, preventing the cAMP-induced conformational changes in the HCN channel CNBD.

  13. Synchronized network activity in developing rat hippocampus involves regional hyperpolarization-activated cyclic nucleotide-gated (HCN) channel function.

    PubMed

    Bender, Roland A; Galindo, Rafael; Mameli, Manuel; Gonzalez-Vega, Rebeca; Valenzuela, C Fernando; Baram, Tallie Z

    2005-11-01

    The principal form of synchronized network activity in neonatal hippocampus consists of low frequency 'giant depolarizing potentials' (GDPs). Whereas contribution of both GABA and glutamate to their generation has been demonstrated, full understanding of the mechanisms underlying these synchronized activity bursts remains incomplete. A contribution of the h-current, conducted by HCN channels, to GDPs has been a topic of substantial interest. Here we focus on HCN1, the prevalent HCN channel isoform in neonatal hippocampus, and demonstrate an HCN1 spatiotemporal expression pattern in both CA3 principal cells and interneurons that correlates with the developmental profile of GDPs. Abrogation of HCN physiological function in CA3, via the selective I(h)-blocker ZD7288, disrupts GDP generation. Furthermore, ZD7288 specifically abolishes spontaneous bursting of the CA3 pyramidal cells at frequencies typical of GDPs without major influence on interneuronal firing. These findings support a pivotal role for HCN channels expressed by CA3 neurons, and particularly CA3 pyramidal cells, in GDP-related network synchronization.

  14. Synchronized network activity in developing rat hippocampus involves regional hyperpolarization-activated cyclic nucleotide-gated (HCN) channel function

    PubMed Central

    Bender, Roland A.; Galindo, Rafael; Mameli, Manuel; Gonzalez-Vega, Rebeca; Valenzuela, C. Fernando; Baram, Tallie Z.

    2010-01-01

    The principal form of synchronized network activity in neonatal hippocampus consists of low frequency ‘giant depolarizing potentials’ (GDPs). Whereas contribution of both GABA and glutamate to their generation has been demonstrated, full understanding of the mechanisms underlying these synchronized activity bursts remains incomplete. A contribution of the h-current, conducted by HCN channels, to GDPs has been a topic of substantial interest. Here we focus on HCN1, the prevalent HCN channel isoform in neonatal hippocampus, and demonstrate an HCN1 spatiotemporal expression pattern in both CA3 principal cells and interneurons that correlates with the developmental profile of GDPs. Abrogation of HCN physiological function in CA3, via the selective Ih-blocker ZD7288, disrupts GDP generation. Furthermore, ZD7288 specifically abolishes spontaneous bursting of the CA3 pyramidal cells at frequencies typical of GDPs without major influence on interneuronal firing. These findings support a pivotal role for HCN channels expressed by CA3 neurons, and particularly CA3 pyramidal cells, in GDP-related network synchronization. PMID:16307610

  15. Diode laser absorption measurement and analysis of HCN in atmospheric-pressure, fuel-rich premixed methane/air flames

    SciTech Connect

    Gersen, S.; Mokhov, A.V.; Levinsky, H.B.

    2008-10-15

    Measurements of HCN in flat, fuel-rich premixed methane/air flames at atmospheric pressure are reported. Quartz-microprobe sampling followed by wavelength modulation absorption spectroscopy with second harmonic detection was used to obtain an overall measurement uncertainty of better than 20% for mole fractions HCN on the order of 10 ppm. The equivalence ratio, {phi}, was varied between 1.3 and 1.5, while the flame temperature was varied independently by changing the mass flux through the burner surface at constant equivalence ratio. Under the conditions of the experiments, the peak mole fractions vary little, in the range of 10-15 ppm. Increasing the flame temperature by increasing the mass flux had little influence on the peak mole fraction, but accelerated HCN burnout substantially. At high equivalence ratio and low flame temperature, HCN burnout is very slow: at {phi}=1.5, {proportional_to}10ppm HCN is still present 7 mm above the burner surface. Substantial quantitative disagreement is observed between the experimental profiles and those obtained from calculations using GRI-Mech 3.0, with the calculations generally overpredicting the results significantly. Changing the rates of key formation and consumption reactions for HCN can improve the agreement, but only by making unreasonable changes in these rates. Inclusion of reactions describing NCN formation and consumption in the calculations improves the agreement with the measurements considerably. (author)

  16. Increased size and stability of CA1 and CA3 place fields in HCN1 knockout mice

    PubMed Central

    Hussaini, Syed A.; Kempadoo, Kimberly A.; Thuault, Sébastien J.; Siegelbaum, Steven A.; Kandel, Eric R.

    2015-01-01

    Summary Hippocampal CA1 and CA3 pyramidal neuron place cells encode the spatial location of an animal through localized firing patterns called “place fields”. To explore the mechanisms that control place cell firing and their relationship to spatial memory, we studied mice with enhanced spatial memory resulting from forebrain-specific knockout of the HCN1 hyperpolarization-activated cation channel. HCN1 is strongly expressed in CA1 neurons and entorhinal cortex grid cells, which provide spatial information to the hippocampus. Both CA1 and CA3 place fields were larger but more stable in the knockout mice, with the effect greater in CA1 than CA3. As HCN1 is only weakly expressed in CA3 place cells, their altered activity likely reflects loss of HCN1 in grid cells. The more pronounced changes in CA1 likely reflect the intrinsic contribution of HCN1. The enhanced place field stability may underlie the effect of HCN1 deletion to facilitate spatial learning and memory. PMID:22099465

  17. Infrared and microwave study of angular-radial coupling effects in Ar-HCN

    NASA Astrophysics Data System (ADS)

    Fraser, G. T.; Pine, A. S.

    1989-09-01

    Microwave and infrared spectra of Ar-HCN have been obtained using an electric-resonance optothermal spectrometer. The microwave measurements extend to higher J the previous results of Leopold et al. and Klots et al., allowing the determination of higher-order centrifugal distortion constants for this quasilinear, highly nonrigid complex. A Padé approximant fit to the microwave data indicates a significant rotation-induced asymptotic increase in the zero-point center-of-mass separation between the Ar and the HCN, above that expected from pure radial distortion. This results from the large coupling between the angular and radial degrees in the intermolecular potential forcing the centrifugal alignment of the HCN. Infrared spectra are reported for the C-H streching fundamental ν1 and the combination band ν1+ν15, where ν5 is the van der Waals bending vibration. The band-origin difference between these two bands gives ν5=7.8 cm-1, in rough agreement with the 10 cm-1 harmonic value predicted from the microwave-determined nuclear quadrupole coupling constant. The complexation-induced red shift of the C-H stretching vibration is 2.69 cm-1 and the vibrational predissociation linewidths Γ are <10 MHz (FWHM). The vibrationally excited complex predissociates before striking the bolometer detector, implying that the predissociation lifetime τ<1 ms.

  18. United States Historical Climatology Network (US HCN) monthly temperature and precipitation data

    SciTech Connect

    Daniels, R.C.; Boden, T.A.; Easterling, D.R.; Karl, T.R.; Mason, E.H.; Hughes, P.Y.; Bowman, D.P.

    1996-01-11

    This document describes a database containing monthly temperature and precipitation data for 1221 stations in the contiguous United States. This network of stations, known as the United States Historical Climatology Network (US HCN), and the resulting database were compiled by the National Climatic Data Center, Asheville, North Carolina. These data represent the best available data from the United States for analyzing long-term climate trends on a regional scale. The data for most stations extend through December 31, 1994, and a majority of the station records are serially complete for at least 80 years. Unlike many data sets that have been used in past climate studies, these data have been adjusted to remove biases introduced by station moves, instrument changes, time-of-observation differences, and urbanization effects. These monthly data are available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center. The NDP includes this document and 27 machine-readable data files consisting of supporting data files, a descriptive file, and computer access codes. This document describes how the stations in the US HCN were selected and how the data were processed, defines limitations and restrictions of the data, describes the format and contents of the magnetic media, and provides reprints of literature that discuss the editing and adjustment techniques used in the US HCN.

  19. An analysis of HCN observations of the Circumnuclear Disc at the Galactic Centre

    NASA Astrophysics Data System (ADS)

    Smith, I. L.; Wardle, M.

    2014-02-01

    The Circumnuclear Disc (CND) is a torus of dust and molecular gas rotating about the Galactic Centre and extending from approximately 1.6 pc to 7 pc from the central massive black hole, SgrA*. Large Velocity Gradient modelling of the intensities of the HCN 1-0, 3-2 and 4-3 transitions is used to infer hydrogen density and HCN optical depth. From HCN observations we find the molecular hydrogen density ranges from 0.1 to 2 × 106 cm-3, about an order of magnitude less than inferred previously. The 1-0 line is weakly inverted with line-centre optical depth approx -0.1, in stark contrast to earlier estimates of 4. The estimated mass of the ring is approximately 3-4 × 105 M⊙, consistent with estimates based on thermal dust emission. The tidal shear in the disc implies that star formation is not expected to occur without some significant triggering event.

  20. The JCMT dense gas survey in dense molecular clouds: an HCO+/HCN comparison

    NASA Astrophysics Data System (ADS)

    Walker-Smith, Samantha; Richer, John; Buckle, Jane; Salji, Carl; Hatchell, Jennifer; Drabek, Emily

    2013-07-01

    We present the results of a large-scale survey of the very dense molecular gas in Perseus, Orion A and B, Serpens and Ophiuchus using HCO+ and HCN (J = 4 - 3) transitions. We have used this emission to trace the structure and kinematics of gas at the extremely high densities found in pre- and protostellar cores; as well as tracing outflows powered by these early star-forming cores. We present a comparison of the HCO+/HCN data, highlighting regions where there is a marked discrepancy in the spectra of the two emission lines. This is particularly noticeable in some of the more powerful outflows driven by Class 0 sources, where the HCN is greatly enhanced in the linewings in comparison with HCO+. We also use the HCO+ to positively identify protostellar outflows and their driving sources. We present a statistical analysis of the outflow properties that we derive from this tracer. We show that our results are comparable to those obtained from similar outflow analyses using 12CO.

  1. Conformational Flip of Nonactivated HCN2 Channel Subunits Evoked by Cyclic Nucleotides

    PubMed Central

    Thon, Susanne; Schulz, Eckhard; Kusch, Jana; Benndorf, Klaus

    2015-01-01

    Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are tetrameric proteins that evoke electrical rhythmicity in specialized neurons and cardiomyocytes. The channels are activated by hyperpolarizing voltage but are also receptors for the intracellular ligand adenosine-3′,5′-cyclic monophosphate (cAMP) that enhances activation but is unable to activate the channels alone. Using fcAMP, a fluorescent derivative of cAMP, we analyzed the effect of ligand binding on HCN2 channels not preactivated by voltage. We identified a conformational flip of the channel as an intermediate state following the ligand binding and quantified it kinetically. Globally fitting the time courses of ligand binding and unbinding revealed modest cooperativity among the subunits in the conformational flip. The intensity of this cooperativity, however, was only moderate compared to channels preactivated by hyperpolarizing voltage. These data provide kinetic information about conformational changes proceeding in nonactivated HCN2 channels when cAMP binds. Moreover, our approach bears potential for analyzing the function of any other membrane receptor if a potent fluorescent ligand is available. PMID:26636938

  2. Polyatomic Molecules in Planetary Nebulae: A Survey of HCN and HCO+

    NASA Astrophysics Data System (ADS)

    Schmidt, Deborah Rose; Ziurys, Lucy

    2015-08-01

    It has been thought that most of the molecular material from the AGB phase of stellar evolution would be photodissociated by intense ultraviolet radiation from the remnant star as it evolves in the subsequent planetary nebula (PN) stage. However, recent detections of polyatomic species in certain PNe such as the Helix Nebula and M2-48 have indicated that the chemistry of these objects is more complicated than previously anticipated. A more complete evaluation of the molecular content of PNe is vital to our understanding of their environments, as well as their material contribution to the interstellar medium (ISM). In order to address this question, we have conducted a search for HCN and HCO+ in seventeen PNe previously detected in CO. Observations of the J=1→0 and J=3→2 transitions of HCN and HCO+ have been carried out using the 12 m telescope and the Sub-Millimeter Telescope (SMT) of the Arizona Radio Observatory (ARO). Both molecules were detected in eleven sources, or ~65% of the sample. Column densities of HCN and HCO+ were determines in the PNe, and, in those sources where both the J=1→0 and J=3→2 transitions of either molecule were detected, H2 densities. Assuming a kinetic temperature of 20 K, column densities were determined to be ~2.7 x 1012 to 8.0 x 1013 cm-2 for HCN, and between 7.5 x 1010 and 2.1 x 1013 cm-2 for HCO+. Corresponding fractional abundance, with respect to H2, ranged from 2.5 x 10-9 to 9.3 x 10-7 for HCN and 2.2 x 10-9 to 7.5 x 10-7 for HCO+. No apparent decrease in abundance of either molecule with nebular age was found, in contrast to the predictions of chemical models. These molecules are more effectively shielded from incoming radiation than previously thought, and in part reflect survival from the AGB stage. However, there may be an ongoing production mechanism for HCO+ in PNe based on CO+. The abundances are consistent with molecular dispersal into diffuse clouds. Overall, the results of this work suggest that polyatomic

  3. Structural and thermal stabilities of layered Li(Ni 1/3Co 1/3Mn 1/3)O 2 materials in 18650 high power batteries

    NASA Astrophysics Data System (ADS)

    He, Yan-Bing; Ning, Feng; Yang, Quan-Hong; Song, Quan-Sheng; Li, Baohua; Su, Fangyuan; Du, Hongda; Tang, Zhi-Yuan; Kang, Feiyu

    The structural and thermal stabilities of the layered Li(Ni 1/3Co 1/3Mn 1/3)O 2 cathode materials under high rate cycling and abusive conditions are investigated using the commercial 18650 Li(Ni 1/3Co 1/3Mn 1/3)O 2/graphite high power batteries. The Li(Ni 1/3Co 1/3Mn 1/3)O 2 materials maintain their layered structure even when the power batteries are subjected to 200 cycles with 10 C discharge rate at temperatures of 25 and 50 °C, whereas their microstructure undergoes obvious distortion, which leads to the relatively poor cycling performance of power batteries at high charge/discharge rates and working temperature. Under abusive conditions, the increase in the battery temperature during overcharge is attributed to both the reactions of electrolyte solvents with overcharged graphite anode and Li(Ni 1/3Co 1/3Mn 1/3)O 2 cathode and the Joule heat that results from the great increase in the total resistance (R cell) of batteries. The reactions of fully charged Li(Ni 1/3Co 1/3Mn 1/3)O 2 cathodes and graphite anodes with electrolyte cannot be activated during short current test in the fully charged batteries. However, these reactions occur at around 140 °C in the fully charged batteries during oven test, which is much lower than the temperature of about 240 °C required for the reactions outside batteries.

  4. Precise measurements of the total concentration of atmospheric CO2 and 13CO2/12CO2 isotopic ratio using a lead-salt laser diode spectrometer.

    PubMed

    Croizé, Laurence; Mondelain, Didier; Camy-Peyret, Claude; Delmotte, Marc; Schmidt, Martina

    2008-04-01

    We have developed a tunable diode laser spectrometer, called SIMCO (spectrometer for isotopic measurements of CO(2)), for determining the concentrations of (12)CO(2) and (13)CO(2) in atmospheric air, from which the total concentration of CO(2) and the isotopic composition (expressed in delta units) delta(13)CO(2) are calculated. The two concentrations are measured using a pair of lines around 2290.1 cm(-1), by fitting a line profile model, taking into account the confinement narrowing effect to achieve a better accuracy. Using the Allan variance, we have demonstrated (for an integration time of 25 s) a precision of 0.1 ppmv for the total CO(2) concentration and of 0.3[per thousand] for delta(13)CO(2). The performances on atmospheric air have been tested during a 3 days campaign by comparing the SIMCO instrument with a gas chromatograph (GC) for the measurement of the total CO(2) concentration and with an isotopic ratio mass spectrometer (MS) for the isotopic composition. The CO(2) concentration measurements of SIMCO are in very good agreement with the GC data with a mean difference of Delta(CO(2))=0.16+/-1.20 ppmv for a comparison period of 45 h and the linearity of the concentration between the two instruments is also very good (slope of correlation: 0.9996+/-0.0003) over the range between 380 and 415 ppmv. For delta(13)CO(2), the comparison with the MS data shows a larger mean difference of Delta(delta(13)CO(2))=(-1.9+/-1.2)[per thousand], which could be partly related to small residual fluctuations of the overall SIMCO instrument response.

  5. VizieR Online Data Catalog: M 2-9 12CO and 13CO channel maps (Castro-

    NASA Astrophysics Data System (ADS)

    Castro-Carrizo, A.; Bujarrabal, V.; Neri, R.; Alcolea, J.; Sanchez Contreras, C.; Santander-Garcia, M.; Nyman, L.-A.

    2017-02-01

    m2-912co3204kms Cube of channel maps of the 12CO J=3-2 line emission toward M2-9. The center is given by the position of compact continuum emission, here subtracted, at J2000 coordinates RA=17:05:37.966, Dec=-10:08:32.63. The first axis in the cube refers to RA coordinates, second to Declination reference, and third the LSR velocity. The synthesized beam is 0.19x0.16-arcsec with the major axis PA=116-degrees. The spectral spacing of 0.488MHz (0.423km/s). The brightness is presented in Jy/beam units, and the conversion factor into Rayleigh-Jeans-equivalent TMB units is 330K/(Jy/beam). m2-913co3204kms.fits: Cube of channel maps of the 13CO J=3-2 line emission toward M2-9. The center is given by the position of compact continuum emission, here subtracted, at J2000 coordinates RA=17:05:37.966, Dec=-10:08:32.63. The first axis in the cube refers to RA coordinates, second to Declination reference, and third the LSR velocity. The synthesized beam is 0.20x0.17-arcsec with the major axis PA=-79-degrees. The spectral spacing of 0.488MHz (0.442km/s). The brightness is presented in Jy/beam units, and the conversion factor into Rayleigh-Jeans-equivalent TMB units is 326K/(Jy/beam). (2 data files).

  6. Evaluating the Community Land Model in a pine stand with shading manipulations and 13CO2 labeling

    NASA Astrophysics Data System (ADS)

    Mao, J.; Ricciuto, D. M.; Thornton, P. E.; Warren, J. M.; King, A. W.; Shi, X.; Iversen, C. M.; Norby, R. J.

    2016-02-01

    Carbon allocation and flow through ecosystems regulates land surface-atmosphere CO2 exchange and thus is a key, albeit uncertain, component of mechanistic models. The Partitioning in Trees and Soil (PiTS) experiment-model project tracked carbon allocation through a young Pinus taeda stand following pulse labeling with 13CO2 and two levels of shading. The field component of this project provided process-oriented data that were used to evaluate terrestrial biosphere model simulations of rapid shifts in carbon allocation and hydrological dynamics under varying environmental conditions. Here we tested the performance of the Community Land Model version 4 (CLM4) in capturing short-term carbon and water dynamics in relation to manipulative shading treatments and the timing and magnitude of carbon fluxes through various compartments of the ecosystem. When calibrated with pretreatment observations, CLM4 was capable of closely simulating stand-level biomass, transpiration, leaf-level photosynthesis, and pre-labeling 13C values. Over the 3-week treatment period, CLM4 generally reproduced the impacts of shading on soil moisture changes, relative change in stem carbon, and soil CO2 efflux rate. Transpiration under moderate shading was also simulated well by the model, but even with optimization we were not able to simulate the high levels of transpiration observed in the heavy shading treatment, suggesting that the Ball-Berry conductance model is inadequate for these conditions. The calibrated version of CLM4 gave reasonable estimates of label concentration in phloem and in soil surface CO2 after 3 weeks of shade treatment, but it lacks the mechanisms needed to track the labeling pulse through plant tissues on shorter timescales. We developed a conceptual model for photosynthate transport based on the experimental observations, and we discussed conditions under which the hypothesized mechanisms could have an important influence on model behavior in larger-scale applications

  7. Multiscale observations of CO2, 13CO2, and pollutants at Four Corners for emission verification and attribution.

    PubMed

    Lindenmaier, Rodica; Dubey, Manvendra K; Henderson, Bradley G; Butterfield, Zachary T; Herman, Jay R; Rahn, Thom; Lee, Sang-Hyun

    2014-06-10

    There is a pressing need to verify air pollutant and greenhouse gas emissions from anthropogenic fossil energy sources to enforce current and future regulations. We demonstrate the feasibility of using simultaneous remote sensing observations of column abundances of CO2, CO, and NO2 to inform and verify emission inventories. We report, to our knowledge, the first ever simultaneous column enhancements in CO2 (3-10 ppm) and NO2 (1-3 Dobson Units), and evidence of δ(13)CO2 depletion in an urban region with two large coal-fired power plants with distinct scrubbing technologies that have resulted in ∆NOx/∆CO2 emission ratios that differ by a factor of two. Ground-based total atmospheric column trace gas abundances change synchronously and correlate well with simultaneous in situ point measurements during plume interceptions. Emission ratios of ∆NOx/∆CO2 and ∆SO2/∆CO2 derived from in situ atmospheric observations agree with those reported by in-stack monitors. Forward simulations using in-stack emissions agree with remote column CO2 and NO2 plume observations after fine scale adjustments. Both observed and simulated column ∆NO2/∆CO2 ratios indicate that a large fraction (70-75%) of the region is polluted. We demonstrate that the column emission ratios of ∆NO2/∆CO2 can resolve changes from day-to-day variation in sources with distinct emission factors (clean and dirty power plants, urban, and fires). We apportion these sources by using NO2, SO2, and CO as signatures. Our high-frequency remote sensing observations of CO2 and coemitted pollutants offer promise for the verification of power plant emission factors and abatement technologies from ground and space.

  8. Homeostatic regulation of synaptic excitability: tonic GABAA receptor currents replace Ih in cortical pyramidal neurons of HCN1 knockout mice

    PubMed Central

    Chen, Xiangdong; Shu, Shaofang; Schwartz, Lauren C.; Sun, Chengsan; Kapur, Jaideep; Bayliss, Douglas A.

    2010-01-01

    Homeostatic control of synaptic efficacy is often mediated by dynamic regulation of excitatory synaptic receptors. Here, we report a novel form of homeostatic synaptic plasticity based on regulation of shunt currents that control dendritosomatic information transfer. In cortical pyramidal neurons from wild type mice, HCN1 channels underlie a dendritic hyperpolarization-activated cationic current (Ih) that serves to limit temporal summation of synaptic inputs. In HCN1 knockout mice, as expected, Ih is reduced in pyramidal neurons and its effects on synaptic summation are strongly diminished. Unexpectedly, we found a markedly enhanced bicuculline- and L-655,708-sensitive background GABAA current in these cells that could be attributed to selective up-regulation of GABAA α5 subunit expression in the cortex of HCN1 knockout mice. Strikingly, despite diminished Ih, baseline sub-linear summation of evoked EPSPs was unchanged in pyramidal neurons from HCN1 knockout mice; however, blocking tonic GABAA currents with bicuculline enhanced synaptic summation more strongly in pyramidal cells from HCN1 knockout mice than in those cells from wild type mice. Increasing tonic GABAA receptor conductance in the context of reduced Ih, using computational or pharmacological approaches, restored normal baseline synaptic summation, as observed in neurons from HCN1 knockout mice. These data indicate that up-regulation of α5 subunit-mediated GABAA receptor tonic current compensates quantitatively for loss of dendritic Ih in cortical pyramidal neurons from HCN1 knockout mice to maintain normal synaptic summation; they further imply that dendritosomatic synaptic efficacy is a controlled variable for homeostatic regulation of cortical neuron excitability in vivo. PMID:20164346

  9. HCN oxidation in an O{sub 2}/CO{sub 2} atmosphere: An experimental and kinetic modeling study

    SciTech Connect

    Gimenez-Lopez, J.; Millera, A.; Bilbao, R.; Alzueta, M.U.

    2010-02-15

    HCN is one of the most important intermediates in NO{sub x} chemistry including formation and removal processes and the knowledge of HCN oxidation is thus very important to minimize NO{sub x} emissions. The present work aims to evaluate the oxidation behavior of HCN in an O{sub 2}/CO{sub 2} atmosphere, due to the lack of studies at these specific operating conditions and the increasing importance of the oxy-fuel combustion processes, characterized by an O{sub 2}/CO{sub 2} combustion atmosphere instead of air. With this purpose, a flow reactor experimental and kinetic modeling study of the oxidation of HCN under CO{sub 2} diluted conditions, in the 900-1450 K temperature range and for different stoichiometries, ranging from very reducing to oxidizing conditions, has been performed. The large experimental differences observed in the O{sub 2}/CO{sub 2} atmosphere in comparison to traditional air-fired combustion corroborate the importance of the HCN oxidation study in an O{sub 2}/CO{sub 2} environment. The presence of high CO{sub 2} concentration levels clearly inhibits HCN oxidation, since CO{sub 2} competes with O{sub 2} for atomic hydrogen through the CO{sub 2} + H {r_reversible} CO + OH reaction. The experimental results show the oxidation regime of HCN for different stoichiometries, analyzing the formation of the main products of the process: CO, NO, N{sub 2}, N{sub 2}O and HNCO. The higher availability of oxygen increases the HCN conversion, even though the onset temperature for reaction is almost similar at any stoichiometry studied. The mechanism used for calculations was that developed by Dagaut et al. [P. Dagaut, P. Glarborg, M.U. Alzueta, Prog. Energy Combust. Sci. 34 (2008) 1-46] for the oxidation of HCN in air combustion, updated in the present work to take into account the presence of an O{sub 2}/CO{sub 2} combustion atmosphere. In general, the modified model gives a reasonably good description of the experiments performed. (author)

  10. Multifrequency Electron Spin Resonance Detection of Solid-State Organic Free Radicals in HCN Polymer and a Titan Tholin

    NASA Astrophysics Data System (ADS)

    Budil, David E.; Roebber, John L.; Liebman, Shirley A.; Matthews, Clifford N.

    2003-06-01

    Macromolecules derived from hydrogen cyanide (HCN) may be major components of the dark matter observed in bodies in the outer Solar System, which include comets and asteroids. HCN oligomers and polymers are readily formed at room temperature and react with water to produce polypeptides and α-amino acids or undergo pyrolysis to produce nitrogen heterocycles. Electron spin resonance (ESR) spectroscopy shows that HCN polymer mixtures contain a significant amount of long-lived organic free radicals that are primarily carbon-based. For comparison, we have also examined samples of tholins produced from experimental analogs of Titan aerosols, which has been shown by trace organic analysis to consist partly of HCN polymer. The "Titan tholin" exhibits at least two ESR signals that can be assigned to nitrogen- and carbon-centered radicals, although heating the sample eliminates the nitrogen centers and increases the signal from the carbon centers. This result suggests that the nitrogen-centered radicals may be thermodynamically less stable, but are kinetically trapped during the spark-discharge reactions that produce tholins from mixtures of gases such as methane and nitrogen. The results strongly support previous proposals of free radical mechanisms for HCN polymerization.

  11. Dormancy alleviation by NO or HCN leading to decline of protein carbonylation levels in apple (Malus domestica Borkh.) embryos.

    PubMed

    Krasuska, Urszula; Ciacka, Katarzyna; Dębska, Karolina; Bogatek, Renata; Gniazdowska, Agnieszka

    2014-08-15

    Deep dormancy of apple (Malus domestica Borkh.) embryos can be overcome by short-term pre-treatment with nitric oxide (NO) or hydrogen cyanide (HCN). Dormancy alleviation of embryos modulated by NO or HCN and the first step of germination depend on temporary increased production of reactive oxygen species (ROS). Direct oxidative attack on some amino acid residues or secondary reactions via reactive carbohydrates and lipids can lead to the formation of protein carbonyl derivatives. Protein carbonylation is a widely accepted covalent and irreversible modification resulting in inhibition or alteration of enzyme/protein activities. It also increases the susceptibility of proteins to proteolytic degradation. The aim of this work was to investigate protein carbonylation in germinating apple embryos, the dormancy of which was removed by pre-treatment with NO or HCN donors. It was performed using a quantitative spectrophotometric method, while patterns of carbonylated protein in embryo axes were analyzed by immunochemical techniques. The highest concentration of protein carbonyl groups was observed in dormant embryos. It declined in germinating embryos pre-treated with NO or HCN, suggesting elevated degradation of modified proteins during seedling formation. A decrease in the concentration of carbonylated proteins was accompanied by modification in proteolytic activity in germinating apple embryos. A strict correlation between the level of protein carbonyl groups and cotyledon growth and greening was detected. Moreover, direct in vitro carbonylation of BSA treated with NO or HCN donors was analyzed, showing action of both signaling molecules as protein oxidation agents.

  12. The correlation between HCN/H2O flux ratios and disk mass: evidence for protoplanet formation

    NASA Astrophysics Data System (ADS)

    Rose, Caitlin; Salyk, Colette

    2017-01-01

    We analyze hydrogen cyanide (HCN) and water vapor flux ratios in protoplanetary disks as a way to trace planet formation. Analyzing only disks in the Taurus molecular cloud, Najita et al. (2013) found a tentative correlation between protoplanetary disk mass and the HCN/H2O line flux ratio in Spitzer-IRS emission spectra. They interpret this correlation to be a consequence of more massive disks forming planetesimals more efficiently than smaller disks, as the formation of large planetesimals may lock up water ice in the cool outer disk region and prevent it from migrating, drying out the inner disk. The sequestering of water (and therefore oxygen) in the outer disk may also increase the carbon-to- oxygen ratio in the inner disk, leading to enhanced organic molecule (e.g. HCN) emission. To confirm this trend, we expand the Najita et al. sample by calculating HCN/H2O line flux ratios for 8 more sources with known disk masses from clusters besides Taurus. We find agreement with the Najita et al. trend, suggesting that this is a widespread phenomenon. In addition, we find HCN/H2O line flux ratios for 17 more sources that await disk mass measurements, which should become commonplace in the ALMA era. Finally, we investigate linear fits and outliers to this trend, and discuss possible causes.

  13. How are CH3OH, HNC/HCN, and NH3 Formed in the Interstellar Medium?

    NASA Astrophysics Data System (ADS)

    Hiraoka, Kenzo; Mochizuki, Noritaka; Wada, Akira

    2006-09-01

    Simulation experiments for the formation of CH3OH, HNC/HCN, and NH3 in solid-phase reactions were performed. CH3OH and H2CO were formed as major products from the 100 eV electron-irradiated mixed CH4/H2O solid at 10 K. There found to be two pathways for the formation of methanol with about equal importance, i.e., the recombination reaction: CH3 + OH --> CH3OH, and the insertion reaction: CH2+H2O --> CH3OH. One CH3OH molecule was formed per 60 electron irradiation with the electron energy of 100 eV. By using mixed H2O/CD4 ice, it was confirmed that formaldehyde was formed by the insertion reaction, C + H2O -->H2CO. A mixed gas of N2/HCN (50/1) at a few Torr was activated by a dc discharge and was deposited on the gold-plated copper substrate at 10, 15, and 20 K. During the deposition of plasma-activated sample gas, D atoms produced by the dc discharge of D2 were simultaneously sprayed over the solid film. The association reactions of CN with D at 10 K were found to generate DNC and DCN with the intensity ratio DNC/DCN of about 3 in the infrared absorption spectra. This high ratio is in line with the high abundance ratios of HNC/HCN observed in the dark clouds. The formation of DNC and DCN became negligible at 20 K, due to the decrease of the sticking probability of D atoms on the solid surface. Ammonia was not detected as a reaction product from reaction of D with N atoms trapped in the N2 matrix.

  14. Mass Losses Of Co, Cs And Hcn On Jupiter/sl9

    NASA Astrophysics Data System (ADS)

    Moreno, Raphael; Marten, A.

    2006-09-01

    Since comet Shoemaker-Levy 9 (SL9) collided with Jupiter in 1994, the IRAM 30-m Telescope (Pico Veleta, Spain) and the 15-m JCMT (Mauna Kea,Hawaii) have regularly observed Jupiter at millimeter/submillimeter wavelengths. Molecular trace species such as HCN, CO, CS and their isotopomers have been detected in the upper atmosphere since the collision. Because of the high spectral resolution attained, our data allow one to infer both temperature and abundances in Jupiter's stratosphere with a maximum spatial resolution of 10 arcsec. We have used all these data to monitor the latitudinal spreading since the impacts occurred (Marten et al. 1995), to look for changes in their abundances with time (Moreno et al. 2001, 2003) and to determine several isotopic ratios (Matthews et al. 2002). Data taken in 2004 have shown that latitudinal distributions of all these species were almost homogeneous 10 years after impacts, as predicted by Moreno et al. 2003. Moreover, compared to 1998 results, respective mass loss factors as high as 2-7 have been determined for the three molecular main compounds (Moreno et al. 2005). In order to follow-up our monitoring, new disk mapping observations took place in May 2006 using the IRAM-30m Telescope. Here we report the results of the recent measurements of CO, CS and HCN, and also the search for new species: H2CO, H2CS, CH3CN, CH3OH. Such trace compounds could have explained the mass losses observed in 2004, but no clear detections have been obtained after reasonable integration times. Estimates of the new CO, CS and HCN total masses and upper limits for the trace species searched for will be presented. The loss mechanisms will be discussed. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

  15. Observational Evidence of the Formation of Cyanopolyynes in CRL 618 through the Polymerization of HCN

    NASA Astrophysics Data System (ADS)

    Pardo, Juan R.; Cernicharo, José; Goicoechea, Javier R.

    2005-07-01

    The abundance ratio of consecutive members of the cyanopolyyne family has been explored in CRL 618 using data acquired in a complete line survey covering the frequency range 81-356 GHz. The Jup range explored for the different molecules is 1-4 for HCN and HNC, 9-39 for HC3N, 31-133 for HC5N, and 72-85 for HC7N (not detected beyond Jup=85). The lowest vibrationally excited state of HC7N (ν15 at 62 cm-1) has been tentatively detected. Data analysis has been performed by extending our previous geometric and radiative transfer model of the slowly expanding envelope (SEE) surrounding the compact central continuum source of CRL 618, which was established from the study of rotational lines in several vibrationally excited states of HC3N. The new lines analyzed here require modeling of the high-velocity wind (HVW) component and the colder circumstellar gas, a remnant of the AGB phase of CRL 618. The derived HC3N/HC5N and HC5N/HC7N abundance ratios from this set of uniformly calibrated lines are between ~3 and 6 in the different regions, similar to standard values in the circumstellar and interstellar media and consistent with previous estimates obtained from ISO observations and chemical models. However, the abundance ratios of HC3N, HC5N, and HC7N with respect to HCN are at least 2 orders of magnitude larger than those typical for AGB C-rich stars, such as IRC +10216. This fact indicates that in the short transition toward the planetary nebula phase, HCN is quickly reprocessed into longer cyanopolyyne chains. A similar behavior was previously found in this object for the polyacetylenic chains (C2nH2).

  16. 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.

  17. Preparation, characterization of LiNi{sub 1/3}Mn{sub 1/3}Co{sub 1/3}O{sub 2} film cathode.

    SciTech Connect

    Kang, S. H.; Abraham, D. P.; Chemical Engineering

    2006-01-01

    Positive electrodes based on the LiNi{sub 1/3}Mn{sub 1/3}Co{sub 1/3}O{sub 2} material are being evaluated in high-power lithium-ion cells for hybrid-electric vehicle applications. To determine performance degradation mechanisms that are associated with the active material, we prepared carbon- and binder-free LiNi{sub 1/3}Mn{sub 1/3}Co{sub 1/3}O{sub 2} film cathode on a Pt substrate using a sol-gel spin coating technique. The material was characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Initial data from cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy measurements conducted on the electrodes are reported.

  18. Genetically engineered cardiac pacemaker: Stem cells transfected with HCN2 gene and myocytes—A model

    NASA Astrophysics Data System (ADS)

    Kanani, S.; Pumir, A.; Krinsky, V.

    2008-01-01

    One of the successfully tested methods to design genetically engineered cardiac pacemaker cells consists in transfecting a human mesenchymal stem cell (hMSC) with a HCN2 gene and connecting it to a myocyte. We develop and study a mathematical model, describing a myocyte connected to a hMSC transfected with a HCN2 gene. The cardiac action potential is described both with the simple Beeler Reuter model, as well as with the elaborate dynamic Luo Rudy model. The HCN2 channel is described by fitting electrophysiological records, in the spirit of Hodgkin Huxley. The model shows that oscillations can occur in a pair myocyte-stem cell, that was not observed in the experiments yet. The model predicted that: (1) HCN pacemaker channels can induce oscillations only if the number of expressed I channels is low enough. At too high an expression level of I channels, oscillations cannot be induced, no matter how many pacemaker channels are expressed. (2) At low expression levels of I channels, a large domain of values in the parameter space (n, N) exists, where oscillations should be observed. We denote N the number of expressed pacemaker channels in the stem cell, and n the number of gap junction channels coupling the stem cell and the myocyte. (3) The expression levels of I channels observed in ventricular myocytes, both in the Beeler Reuter and in the dynamic Luo Rudy models are too high to allow to observe oscillations. With expression levels below ˜1/4 of the original value, oscillations can be observed. The main consequence of this work is that in order to obtain oscillations in an experiment with a myocyte-stem cell pair, increasing the values of n, N is unlikely to be helpful, unless the expression level of I has been reduced enough. The model also allows us to explore levels of gene expression not yet achieved in experiments, and could be useful to plan new experiments, aimed at improving the robustness of the oscillations.

  19. Recent progress of the HCN interferometer on J-TEXT tokamaka)

    NASA Astrophysics Data System (ADS)

    Gao, L.; Zhuang, G.; Wang, Zhi Jiang; Chen, W.; Chen, J.; Li, Q.; Liu, Y.

    2012-10-01

    A multichannel far-infrared HCN laser interferometer has been developed to measure plasma electron density for the J-TEXT tokamak. Initial operation of a seven chords system with 7 cm spacing and a 0.1 ms temporal resolution is described. Density modulation experiments in J-TEXT show that it is possible to obtain information on particle transport by precise measurement of the density perturbation amplitude and phase spatial variation. An optical configuration upgrade has been implemented in order to improve phase resolution.

  20. Recent progress of the HCN interferometer on J-TEXT tokamak.

    PubMed

    Gao, L; Zhuang, G; Wang, Zhi Jiang; Chen, W; Chen, J; Li, Q; Liu, Y

    2012-10-01

    A multichannel far-infrared HCN laser interferometer has been developed to measure plasma electron density for the J-TEXT tokamak. Initial operation of a seven chords system with 7 cm spacing and a 0.1 ms temporal resolution is described. Density modulation experiments in J-TEXT show that it is possible to obtain information on particle transport by precise measurement of the density perturbation amplitude and phase spatial variation. An optical configuration upgrade has been implemented in order to improve phase resolution.

  1. Probing the Abundance of SiO and HCN throughout the Stellar Wind of R Dor

    NASA Astrophysics Data System (ADS)

    Van de Sande, Marie; Decin, Leen; Lombaert, Robin; Millar, T. J.; Walsh, Catherine; Li, Xiaohu

    2016-07-01

    R Dor is an oxygen-rich AGB star characterised by a low mass-loss rate. Using retrieval methods, we found abundance profiles for SiO and HCN, two chemically important molecules. By comparing these results to those of forward chemistry modelling we will be able to constrain the dominant chemical pathways within the stellar wind. They will also enable us to improve the forward chemistry models, through incorporating dust-gas reactions. The same methodologies will be applied to the abundance profiles retrieved for the O-rich AGB star IK Tau (Decin et al. 2010), which is characterised by a high mass-loss rate.

  2. Competition between abstraction and exchange channels in H + HCN reaction: Full-dimensional quantum dynamics

    SciTech Connect

    Jiang, Bin; Guo, Hua

    2013-12-14

    Dynamics of the title reaction is investigated on an ab initio based potential energy surface using a full-dimensional quantum wave packet method within the centrifugal sudden approximation. It is shown that the reaction between H and HCN leads to both the hydrogen exchange and hydrogen abstraction channels. The exchange channel has a lower threshold and larger cross section than the abstraction channel. It also has more oscillations due apparently to quantum resonances. Both channels are affected by long-lived resonances supported by potential wells. Comparison with experimental cross sections indicates underestimation of the abstraction barrier height.

  3. Recent progress of the HCN interferometer on J-TEXT tokamak

    SciTech Connect

    Gao, L.; Zhuang, G.; Wang Zhijiang; Chen, W.; Chen, J.; Li, Q.; Liu, Y.

    2012-10-15

    A multichannel far-infrared HCN laser interferometer has been developed to measure plasma electron density for the J-TEXT tokamak. Initial operation of a seven chords system with 7 cm spacing and a 0.1 ms temporal resolution is described. Density modulation experiments in J-TEXT show that it is possible to obtain information on particle transport by precise measurement of the density perturbation amplitude and phase spatial variation. An optical configuration upgrade has been implemented in order to improve phase resolution.

  4. High resolution observations of HCN and HCO+J = 3-2 in the disk and outflow of Mrk 231. Detection of vibrationally excited HCN in the warped nucleus

    NASA Astrophysics Data System (ADS)

    Aalto, S.; Garcia-Burillo, S.; Muller, S.; Winters, J. M.; Gonzalez-Alfonso, E.; van der Werf, P.; Henkel, C.; Costagliola, F.; Neri, R.

    2015-02-01

    Aims: Our goal is to study molecular gas properties in nuclei and large scale outflows/winds from active galactic nuclei (AGNs) and starburst galaxies. Methods: We obtained high resolution (0.̋25 to 0.̋90) observations of HCN and HCO+J = 3 → 2 of the ultraluminous QSO galaxy Mrk 231 with the IRAM Plateau de Bure Interferometer (PdBI). Results: We find luminous HCN and HCO+J = 3 → 2 emission in the main disk and we detect compact (r ≲ 0''&dotbelow;1 (90 pc)) vibrationally excited HCN J = 3 → 2ν2 = 1f emission centred on the nucleus. The velocity field of the vibrationally excited HCN is strongly inclined (position angle PA = 155°) compared to the east-west rotation of the main disk. The nuclear (r ≲ 0.̋1) molecular mass is estimated to 8 × 108 M⊙ with an average N(H2) of 1.2 × 1024 cm-2. Prominent, spatially extended (≳350 pc) line wings are found for HCN J = 3 → 2 with velocities up to ± 750 km s-1. Line ratios indicate that the emission is emerging in dense gas n = 104-5 × 105 cm-3 of elevated HCN abundance X(HCN) = 10-8-10-6. The highest X(HCN) also allows for the emission to originate in gas of more moderate density. We tentatively detect nuclear emission from the reactive ion HOC+ with HCO+/HOC+ = 10-20. Conclusions: The HCN ν2 = 1f line emission is consistent with the notion of a hot, dusty, warped inner disk of Mrk 231 where the ν2 = 1f line is excited by bright mid-IR 14 μm continuum. We estimate the vibrational temperature Tvib to 200-400 K. Based on relative source sizes we propose that 50% of the main HCN emission may have its excitation affected by the radiation field through IR pumping of the vibrational ground state. The HCN emission in the line wings, however, is more extended and thus likely not strongly affected by IR pumping. Our results reveal that dense clouds survive (and/or are formed) in the AGN outflow on scales of at least several hundred pc before evaporating or collapsing. The elevated HCN abundance in the

  5. Electrochemical characteristics of layered LiNi 1/3Co 1/3Mn 1/3O 2 and with different synthesis conditions

    NASA Astrophysics Data System (ADS)

    He, Ping; Wang, Haoran; Qi, Lu; Osaka, Tetsuya

    LiNi 1/3Mn 1/3Co 1/3O 2 had been successfully prepared from spherical composite carbonate via a simple uniform-phase precipitation method [P. He, H. Wang, L. Qi, T. Osaka, J. Power Sources, in press] at normal pressure, using nickel, cobalt and manganese sulfate and ammonia bicarbonate as reactants. The preparation of spherical composite carbonate was significantly dependant on synthetic condition, such as the reaction temperature, feed rate, molar ratio of these reactants, etc. The optimized condition resulted in spherical composite carbonate of which the particle size distribution was uniform, as observed by scanning electronic microscopy (SEM). Calcination of the uniform composite carbonate with lithium carbonate at high temperature led to a well-ordered layer structured LiNi 1/3Mn 1/3Co 1/3O 2 as confirmed by X-ray diffraction (XRD), without obvious change in shape. Due to the homogeneity of the composite carbonate, the final product, LiNi 1/3Mn 1/3Co 1/3O 2, was also significantly uniform, i.e., the average particle size was of about 10 μm in diameter and the distribution was relatively narrow. As a result, the corresponding tap density was also high, approximately 2.32 g cm -3, of which the value is very near to that of commercialized LiCoO 2. In the voltage range of 2.8-4.2, 2.8-4.35 and 2.8-4.5 V, the discharge capacities of LiNi 1/3Mn 1/3Co 1/3O 2 electrode were 159, 168 and 179 mAh g -1, respectively, with good cyclability.

  6. THE BOLOCAM GALACTIC PLANE SURVEY. XII. DISTANCE CATALOG EXPANSION USING KINEMATIC ISOLATION OF DENSE MOLECULAR CLOUD STRUCTURES WITH {sup 13}CO(1-0)

    SciTech Connect

    Ellsworth-Bowers, Timothy P.; Glenn, Jason; Rosolowsky, Erik; Ginsburg, Adam; Evans II, Neal J.; Battersby, Cara; Shirley, Yancy L.; Svoboda, Brian

    2015-01-20

    We present an expanded distance catalog for 1710 molecular cloud structures identified in the Bolocam Galactic Plane Survey (BGPS) version 2, representing a nearly threefold increase over the previous BGPS distance catalog. We additionally present a new method for incorporating extant data sets into our Bayesian distance probability density function (DPDF) methodology. To augment the dense-gas tracers (e.g., HCO{sup +}(3-2), NH{sub 3}(1,1)) used to derive line-of-sight velocities for kinematic distances, we utilize the Galactic Ring Survey (GRS) {sup 13}CO(1-0) data to morphologically extract velocities for BGPS sources. The outline of a BGPS source is used to select a region of the GRS {sup 13}CO data, along with a reference region to subtract enveloping diffuse emission, to produce a line profile of {sup 13}CO matched to the BGPS source. For objects with a HCO{sup +}(3-2) velocity, ≈95% of the new {sup 13}CO(1-0) velocities agree with that of the dense gas. A new prior DPDF for kinematic distance ambiguity (KDA) resolution, based on a validated formalism for associating molecular cloud structures with known objects from the literature, is presented. We demonstrate this prior using catalogs of masers with trigonometric parallaxes and H II regions with robust KDA resolutions. The distance catalog presented here contains well-constrained distance estimates for 20% of BGPS V2 sources, with typical distance uncertainties ≲ 0.5 kpc. Approximately 75% of the well-constrained sources lie within 6 kpc of the Sun, concentrated in the Scutum-Centaurus arm. Galactocentric positions of objects additionally trace out portions of the Sagittarius, Perseus, and Outer arms in the first and second Galactic quadrants, and we also find evidence for significant regions of interarm dense gas.

  7. Seasonal and interannual variations in HCN amounts in the upper troposphere and lower stratosphere observed by MIPAS

    NASA Astrophysics Data System (ADS)

    Glatthor, N.; Höpfner, M.; Stiller, G. P.; von Clarmann, T.; Funke, B.; Lossow, S.; Eckert, E.; Grabowski, U.; Kellmann, S.; Linden, A.; Walker, K. A.; Wiegele, A.

    2015-01-01

    We present a HCN climatology of the years 2002-2012, derived from FTIR limb emission spectra measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the ENVISAT satellite, with the main focus on biomass burning signatures in the upper troposphere and lower stratosphere. HCN is an almost unambiguous tracer of biomass burning with a tropospheric lifetime of 5-6 months and a stratospheric lifetime of about 2 years. The MIPAS climatology is in good agreement with the HCN distribution obtained by the spaceborne ACE-FTS experiment and with airborne in situ measurements performed during the INTEX-B campaign. The HCN amounts observed by MIPAS in the southern tropical and subtropical upper troposphere have an annual cycle peaking in October-November, i.e. 1-2 months after the maximum of southern hemispheric fire emissions. The probable reason for the time shift is the delayed onset of deep convection towards austral summer. Because of overlap of varying biomass burning emissions from South America and southern Africa with sporadically strong contributions from Indonesia, the size and strength of the southern hemispheric plume have considerable interannual variations, with monthly mean maxima at, for example, 14 km between 400 and more than 700 pptv. Within 1-2 months after appearance of the plume, a considerable portion of the enhanced HCN is transported southward to as far as Antarctic latitudes. The fundamental period of HCN variability in the northern upper troposphere is also an annual cycle with varying amplitude, which in the tropics peaks in May after and during the biomass burning seasons in northern tropical Africa and southern Asia, and in the subtropics peaks in July due to trapping of pollutants in the Asian monsoon anticyclone (AMA). However, caused by extensive biomass burning in Indonesia and by northward transport of part of the southern hemispheric plume, northern HCN maxima also occur around October/November in several years

  8. A novel high-throughput screening assay for HCN channel blocker using membrane potential-sensitive dye and FLIPR.

    PubMed

    Vasilyev, Dmitry V; Shan, Qin J; Lee, Yan T; Soloveva, Veronica; Nawoschik, Stanley P; Kaftan, Edward J; Dunlop, John; Mayer, Scott C; Bowlby, Mark R

    2009-10-01

    Hyperpolarization-activated cation nonselective (HCN) channels represent an interesting group of targets for drug development. In this study, the authors report the development of a novel membrane potential-sensitive dye (MPSD) assay for HCN channel modulators that has been miniaturized into 384-well fluorescent imaging plate reader (FLIPR) high-throughput screening (HTS) format. When optimized (by cell plating density, plate type, cell recovery from cryopreservation), the well-to-well signal variability was low, with a Z' = 0.73 and coefficient of variation = 6.4%, whereas the MPSD fluorescence signal amplitude was -23,700 +/- 1500 FLIPR(3) relative fluorescence units (a linear relationship was found between HCN1 MPSD fluorescence signal and the cell plating density) and was completely blocked by 30 microM ZD7288. The assay tolerated up to 1% DMSO, inclusion of which did not significantly change the signal kinetics or amplitude. A single-concentration screening of an ion channel-focused library composed of 4855 compounds resulted in 89 HCN1 blocker hits, 51 of which were subsequently analyzed with an 8-point concentration-response analysis on the IonWorks HT electrophysiology platform. The correlation between MPSD and the electrophysiology assay was moderate, as shown by the linear regression analysis (r(2) = 0.56) between the respective IC(50)s obtained using these 2 assays. The reported HTS-compatible HCN channel blocker assay can serve as a tool in drug discovery in the pursuit of HCN channel isoform-selective small molecules that could be used in the development of clinically relevant compounds.

  9. Charge movement in gating-locked HCN channels reveals weak coupling of voltage sensors and gate.

    PubMed

    Ryu, Sujung; Yellen, Gary

    2012-11-01

    HCN (hyperpolarization-activated cyclic nucleotide gated) pacemaker channels have an architecture similar to that of voltage-gated K(+) channels, but they open with the opposite voltage dependence. HCN channels use essentially the same positively charged voltage sensors and intracellular activation gates as K(+) channels, but apparently these two components are coupled differently. In this study, we examine the energetics of coupling between the voltage sensor and the pore by using cysteine mutant channels for which low concentrations of Cd(2+) ions freeze the open-closed gating machinery but still allow the sensors to move. We were able to lock mutant channels either into open or into closed states by the application of Cd(2+) and measure the effect on voltage sensor movement. Cd(2+) did not immobilize the gating charge, as expected for strict coupling, but rather it produced shifts in the voltage dependence of voltage sensor charge movement, consistent with its effect of confining transitions to either closed or open states. From the magnitude of the Cd(2+)-induced shifts, we estimate that each voltage sensor produces a roughly three- to sevenfold effect on the open-closed equilibrium, corresponding to a coupling energy of ∼1.3-2 kT per sensor. Such coupling is not only opposite in sign to the coupling in K(+) channels, but also much weaker.

  10. The 7-channel FIR HCN interferometer on J-TEXT tokamak

    NASA Astrophysics Data System (ADS)

    Chen, W.; Gao, L.; Chen, J.; Li, Q.; Wang, Z. J.; Zhuang, G.

    2012-01-01

    A seven-channel far-infrared hydrogen cyanide (HCN) laser interferometer has been established aiming to provide the line integrated plasma density for the J-TEXT experimental scenarios. A continuous wave glow discharge HCN laser designed with a cavity length 3.4 m is used as the laser source with a wavelength of 337 μm and an output power up to 100 mW. The system is configured as a Mach-Zehnder type interferometer. Phase modulation is achieved by a rotating grating, with a modulation frequency of 10 kHz which corresponds to the temporal resolution of 0.1 ms. The beat signal is detected by TGS detector. The phase shift induced by the plasma is derived by the comparator with a phase sensitivity of 0.06 fringe. The experimental results measured by the J-TEXT interferometer are presented in details. In addition, the inversed electron density profile done by a conventional approach is also given. The kinematic viscosity of dimethyl silicone and vibration control is key issues for the system performance. The laser power stability under different kinematic viscosity of silicone oil is presented. A visible improvement of measured result on vibration reduction is shown in the paper.

  11. THE HCN-WATER RATIO IN THE PLANET FORMATION REGION OF DISKS

    SciTech Connect

    Najita, Joan R.; Salyk, Colette; Carr, John S.; Pontoppidan, Klaus M.; Van Dishoeck, Ewine F.; Blake, Geoffrey A.

    2013-04-01

    We find a trend between the mid-infrared HCN/H{sub 2}O flux ratio and submillimeter disk mass among T Tauri stars in Taurus. While it may seem puzzling that the molecular emission properties of the inner disk (HCN/H{sub 2}O ratio and disk mass is of interest as trends like this among T Tauri disk properties are relatively rare.

  12. Absolute cross sections for dissociative electron attachment to HCN and DCN

    SciTech Connect

    May, O.; Kubala, D.; Allan, M.

    2010-07-15

    Absolute partial cross sections for the formation of CN{sup -} in dissociative electron attachment to HCN and DCN have been measured using a time-of-flight ion spectrometer combined with a trochoidal electron monochromator to be 940pm{sup 2} for CN{sup -}/HCN and 340pm{sup 2} for CN{sup -}/DCN at peaks of the bands due to the {sup 2{Pi}}-shape resonance. The dissociative electron attachment bands were then recorded under higher resolution, 60 meV, with a trochoidal monochromator plus quadrupole mass filter combination and found to have a nearly vertical onset at the threshold energy and to peak at 1.85 eV. Broad structure was observed on the bands, assigned to formation of vibrationally excited CN{sup -}, from which the branching ratios could be determined to be 1,0.49, and 0.22 for the formation of CN{sup -} in the v=0,1, and 2 states, respectively. The results are compared to the recent multidimensional ab initio calculations of Chourou and Orel [Phys. Rev. A 80, 032709 (2009)].

  13. HCO{sup +} AND HCN J = 3-2 ABSORPTION TOWARD THE CENTER OF CENTAURUS A

    SciTech Connect

    Muller, Sebastien; Dinh-V-Trung

    2009-05-01

    We have investigated the presence of dense gas toward the radio source Cen A by looking at the absorption of the HCO{sup +} and HCN (3-2) lines in front of the bright continuum source with the Submillimeter Array. We detect narrow HCO{sup +} (3-2) absorption, and tentatively HCN (3-2), close to the systemic velocity. For both molecules, the J = 3 - 2 absorption is much weaker than for the J = 1 - 0 line. From simple excitation analysis, we conclude that the gas density is of the order of a few 10{sup 4} cm{sup -3} for a column density N(HCO{sup +})/{delta}V of 3 x 10{sup 12} cm{sup -2} km{sup -1} s and a kinetic temperature of 10 K. In particular, we find no evidence for molecular gas density higher than a few 10{sup 4} cm{sup -3} on the line of sight to the continuum source. We discuss the implications of our finding on the nature of the molecular gas responsible for the absorption toward Cen A.

  14. Structure and properties of the radiation-induced intermediates produced from HCN in noble gas matrices

    NASA Astrophysics Data System (ADS)

    Kameneva, Svetlana V.; Tyurin, Daniil A.; Feldman, Vladimir I.

    2016-07-01

    In this work we report the results of systematic studies on the radiation-induced transformations in HCN/Ng systems (Ng=Ne, Ar, Kr or Xe) at 7 K using a combination of FTIR and EPR spectroscopy. It was shown that HCN underwent efficient decomposition producing H atoms, CN radicals and HNC isomer. The thermally induced reactions of H atoms in different matrices result in the formation of two isomeric radicals, H2CN and trans-HCNH, the former being predominated. The temperature dependent dynamics of CN and H2CN radicals in a krypton matrix was observed by EPR spectroscopy in solid krypton. The vibrational frequencies, IR intensities and magnetic resonance parameters of H2CN and trans-HCNH radicals calculated at the CCSD(T) level are in reasonable agreement with the experimental results. It was found that HCNH radical could be effectively bleached with visible light. The comparison of experimental and computational data made it possible to assign a new vibrational band at 918 cm-1 in an Ar matrix (and the corresponding bands in Kr and Xe) to trans-HCNH radical. In addition, HKrCN was found in the case of krypton, whereas HXeCN and HXeNC were produced in solid xenon. The reaction mechanisms and contribution of different channels are discussed.

  15. Millimeter-wave observations of Saturn, Uranus, and Neptune - CO and HCN on Neptune

    NASA Technical Reports Server (NTRS)

    Rosenqvist, Jan; Lellouch, Emmanuel; Romani, Paul N.; Paubert, Gabriel; Encrenaz, Therese

    1992-01-01

    Saturn, Uranus, and Neptune were observed at millimeter wavelengths with the IRAM 30 m telescope. The major result is the detection of CO and HCN in Neptune's stratosphere, with respective mixing ratios of (6.5 +/- 3.5) x 10 exp -7 and (3 +/- 1.5) x 10 exp -10. CO seems to be present in Neptune's troposphere as well and to slowly decrease with altitude (scale height about 200 km). HCN is probably formed from reactions between CH3 and N, which can be supplied in sufficient amounts by escape from Triton's atmosphere. The origin of CO, however, is more problematic, because: (1) thermochemical models fail to reproduce the observed abundance by a factor of about 1000; and (2) an external source would require a very large flux of oxygen. CO appears to be at least 15 times less abundant on Uranus than on Neptune. Finally, an upper limit of 10 exp -7 for CO in Saturn's stratosphere suggests an internal origin for Saturnian CO.

  16. Signal detection circuit design of HCN measurement system based on TDLAS

    NASA Astrophysics Data System (ADS)

    He, Chungui; Zhang, Yujun; Chen, Chen; Lu, Yibing; Liu, Guohua; Gao, Yanwei; You, Kun; He, Ying; Zhang, Kai; Liu, Wenqing

    2016-10-01

    Hydrogen cyanide gas leakage may exist in the petrochemical industry, smelting plant, and other industrial processes, causing serious harm to the environment, and even threatening the safety of personnel. So the continuous detection of HCN gas plays an important role in the prevention of risk in production process and storage environment that existing hydrogen cyanide gas. The Tunable Diode Laser Technology (TDLAS) has advantages of non-contact, high sensitivity, high selectivity, and fast response time, etc., which is one of the ideal method of gas detection technologies and can be used to measure the hydrogen cyanide concentration. This paper studies the HCN detection system based on TDLAS technology, selects the absorption lines of hydrogen cyanide in 6539.12cm-1, and utilizes the center wavelength of 1.529μm distributed feedback (DFB) laser as a light source. It is discussed in detail on technical requirements of a high frequency modulated laser signal detection circuit, including noise level, gain, and bandwidth. Based on the above theory, the high frequency modulation preamplifier circuit and main amplifier circuit are designed for InGaAs photoelectric detector. The designed circuits are calculation analyzed with corresponding formula and simulation analyzed based on the Multisim software.

  17. Vibrationally Excited HCN around AFGL 2591: A Probe of Protostellar Structure

    NASA Astrophysics Data System (ADS)

    Veach, Todd J.; Groppi, Christopher E.; Hedden, Abigail

    2013-03-01

    Vibrationally excited molecules with submillimeter rotational transitions are potentially excellent probes of physical conditions near protostars. This study uses observations of the v = 1 and v = 2 ro-vibrational modes of HCN (4-3) to probe this environment. The presence or absence and relative strengths of these ro-vibrational lines probe the gas excitation mechanism and physical conditions in warm, dense material associated with protostellar disks. We present pilot observations from the Heinrich Hertz Submillimeter Telescope and follow-up observations from the Submillimeter Array. All vibrationally excited HCN (4-3) v = 0, v = 1, and v = 2 lines were observed. The existence of the three v = 2 lines at approximately equal intensity imply collisional excitation with a density of greater than (1010 cm-3) and a temperature of >1000 K for the emitting gas. This warm, high-density material should directly trace structures formed in the protostellar envelope and disk environment. Further, the line shapes of the v = 2 emission may suggest a Keplerian disk. This Letter demonstrates the utility of this technique which is of particular interest due to the recent inauguration of the Atacama Large Millimeter Array.

  18. Global bending quantum number and the absence of monodromy in the HCN{r_reversible}CNH molecule

    SciTech Connect

    Efstathiou, K.; Sadovskii, D.A.; Joyeux, M.

    2004-03-01

    We introduce and analyze a model system based on a deformation of a spherical pendulum that can be used to reproduce large amplitude bending vibrations of flexible triatomic molecules with two stable linear equilibria. On the basis of our model and the recent vibrational potential [ J. Chem. Phys. 115, 3706 (2001) ], we analyze the HCN/CNH isomerizing molecule. We find that HCN/CNH has no monodromy and introduce the second global bending quantum number for this system at all energies where the potential is expected to work. We also show that LiNC/LiCN is a qualitatively different system with monodromy.

  19. Infrared Spectroscopic Study of the Adsorption of HCN by gamma-Al2O3: Competition with Triethylenediamine for Adsorption Sites

    SciTech Connect

    Kim, S.; Sorescu, D.C.; Yates, J.T., Jr.

    2007-04-12

    The adsorption and vibrational properties of chemisorbed HCN on Lewis acid sites, Lewis base sites, and Brønsted Al-OH acid sites on a partially hydroxylated [gamma]-Al2O3 surface have been obtained by a combination of FTIR and density functional theory studies. The vibrational modes from the molecular and dissociative adsorption of HCN were assigned by using deuterium and 13C-labeled D13CN molecules at 170 K. In addition, [eta]2(C, N)-HCN bonding is also found from the [nu](CdN) vibrational spectra. Good correlation of the calculated vibrational frequencies for the adsorbed species with experimental data is found. The effect of triethylenediamine (TEDA) (also called 1, 4-diazabicyclo [2.2.2]octane, DABCO) on the adsorption of hydrogen cyanide (HCN) on the high area [gamma]-Al2O3 surface has been investigated using transmission FTIR spectroscopy. During HCN adsorption on TEDA-functionalized surfaces, there is no spectral change or emerging feature in either the TEDA or HCN spectral regions, indicating that no direct interaction occurs between these two molecules. Instead, we found that TEDA competes with HCN for the active sites on [gamma]-Al2O3. The observed [nu](C [identical with] N) mode on a TEDA-precovered surface is due to the HCN adsorption on Lewis base sites (Al-O-Al) which are less affected by TEDA preadsorption.

  20. Ischemia-induced cell depolarization: does the hyperpolarization-activated cation channel HCN2 affect the outcome after stroke in mice?

    PubMed Central

    2013-01-01

    Background Brain ischemia is known to include neuronal cell death and persisting neurological deficits. A lack of oxygen and glucose are considered to be key mediators of ischemic neurodegeneration while the exact mechanisms are yet unclear. In former studies the expression of two different two-pore domain potassium (K2P) channels (TASK1, TREK1) were shown to ameliorate neuronal damage due to cerebral ischemia. In neurons, TASK channels carrying hyperpolarizing K+ leak currents, and the pacemaker channel HCN2, carrying depolarizing Ih, stabilize the membrane potential by a mutual functional interaction. It is assumed that this ionic interplay between TASK and HCN2 channels enhances the resistance of neurons to insults accompanied by extracellular pH shifts. Methods In C57Bl/6 (wildtype, WT), hcn2+/+ and hcn2-/- mice we used an in vivo model of cerebral ischemia (transient middle cerebral artery occlusion (tMCAO)) to depict a functional impact of HCN2 in stroke formation. Subsequent analyses comprise behavioural tests and hcn2 gene expression assays. Results After 60 min of tMCAO induction in WT mice, we collected tissue samples at 6, 12, and 24 h after reperfusion. In the infarcted neocortex, hcn2 expression analyses revealed a nominal peak of hcn2 expression 6 h after reperfusion with a tendency towards lower expression levels with longer reperfusion times. Hcn2 gene expression levels in infarcted basal ganglia did not change after 6 h and 12 h. Only at 24 h after reperfusion, hcn2 expression significantly decreases by ~55%. However, 30 min of tMCAO in hcn2-/- as well as hcn2+/+ littermates induced similar infarct volumes. Behavioural tests for global neurological function (Bederson score) and motor function/coordination (grip test) were performed at day 1 after surgery. Again, we found no differences between the groups. Conclusions Here, we hypothesized that the absence of HCN2, an important functional counter player of TASK channels, affects neuronal survival

  1. Seasonal and interannual variations of HCN amounts in the upper troposphere and lower stratosphere observed by MIPAS

    NASA Astrophysics Data System (ADS)

    Glatthor, N.; Höpfner, M.; Stiller, G. P.; von Clarmann, T.; Funke, B.; Lossow, S.; Eckert, E.; Grabowski, U.; Kellmann, S.; Linden, A.; Wiegele, A.

    2014-04-01

    A global HCN dataset covering nearly the complete period June 2002 to April 2012 has been derived from FTIR limb emission spectra measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the ENVISAT satellite. HCN is an almost unambiguous tracer of biomass burning with a tropospheric lifetime of 5-6 months and a stratospheric lifetime of about two years. We present a MIPAS HCN climatology with the main focus on biomass burning signatures in the upper troposphere and lower stratosphere. HCN observed by MIPAS in the southern tropical and subtropical upper troposphere has an annual cycle peaking in October-November during or shortly after the maximum of the southern hemispheric biomass burning season. Within 1-2 months after the burning season, a considerable portion of the enhanced HCN is transported southward to Antarctic latitudes. The fundamental period in the northern upper troposphere is also an annual cycle, which in the tropics peaks in May after the biomass burning seasons in northern tropical Africa and South Asia, and in the subtropics in July due to trapping of pollutants in the Asian monsoon anticyclone. However, caused by extensive biomass burning in Indonesia and Northern Africa together with northward transport of parts of the southern hemispheric plume, in several years HCN maxima are also found around October/November, which leads to semi-annual cycles in the northern tropics and subtropics. Because of overlap of interannually varying burning activities in different source regions, both southern and northern low-latitude maxima have considerable interannual variations. There is also a temporal shift between enhanced HCN in northern low and mid-to-high latitudes, indicating northward transport of pollutants. Due to additional biomass burning at mid and high latitudes this meridional transport pattern is not as clear as in the Southern Hemisphere. Presumably caused by ocean uptake, upper tropospheric HCN above the tropical

  2. VOLTAGE-DEPENDENT OPENING OF HCN CHANNELS: FACILITATION OR INHIBITION BY THE PHYTOESTROGEN, GENISTEIN, IS DETERMINED BY THE ACTIVATION STATUS OF THE CYCLIC NUCLEOTIDE GATING RING

    PubMed Central

    Rozario, Anjali. O.; Turbendian, Harma K.; Fogle, Keri J.; Olivier, Nelson B.; Tibbs, Gareth R.

    2009-01-01

    Investigation of the mechanistic bases and physiological importance of cAMP regulation of HCN channels has exploited an arginine to glutamate mutation in the nucleotide-binding fold, an approach critically dependent on the mutation selectively lowering the channel’s nucleotide affinity. In apparent conflict with this, in intact Xenopus oocytes, HCN and HCN-RE channels exhibit qualitatively and quantitatively distinct responses to the tyrosine kinase inhibitor, genistein – the estrogenic isoflavonoid strongly depolarizes the activation midpoint of HCN1-R538E, but not HCN1 channels (+9.8 mV ± 0.9 versus +2.2 mV ± 0.6) and hyperpolarizes gating of HCN2 (−4.8 mV ± 1.0) but depolarizes gating of HCN2-R591E (+13.2 mV ± 2.1). However, excised patch recording, X-ray crystallography and modeling reveal this is not due to either a fundamental effect of the mutation on channel gating per se or of genistein acting as a mutation-sensitive partial agonist at the cAMP site. Rather, we find that genistein equivalently moves both HCN and HCN-RE channels closer to the open state (rendering the channels inherently easier to open but at a cost of decreasing the coupling energy of cAMP) and that the anomaly reflects a balance of these energetic effects with the isoform specific inhibition of activation by the nucleotide gating ring and relief of this by endogenous cAMP. These findings have specific implications with regard to findings based on HCN-RE channels and kinase antagonists and general implications with respect to interpretation of drug effects in mutant channel backgrounds. PMID:19524546

  3. Deletion of the HCN channel auxiliary subunit TRIP8b impairs hippocampal Ih localization and function and promotes antidepressant behavior in mice

    PubMed Central

    Lewis, Alan S.; Vaidya, Sachin P.; Blaiss, Cory A.; Liu, Zhiqiang; Stoub, Travis R.; Brager, Darrin H.; Chen, Xiangdong; Bender, Roland A.; Estep, Chad M.; Popov, Andrey B.; Kang, Catherine E.; Van Veldhoven, Paul P.; Bayliss, Douglas A.; Nicholson, Daniel A.; Powell, Craig M.; Johnston, Daniel; Chetkovich, Dane M.

    2011-01-01

    Output properties of neurons are greatly shaped by voltage-gated ion channels, whose biophysical properties and localization within axodendritic compartments serve to significantly transform the original input. The hyperpolarization-activated current, Ih, is mediated by HCN channels and plays a fundamental role in influencing neuronal excitability by regulating both membrane potential and input resistance. In neurons such as cortical and hippocampal pyramidal neurons, the subcellular localization of HCN channels plays critical functional role, yet mechanisms controlling HCN channel trafficking are not fully understood. Because ion channel function and localization are often influenced by interacting proteins, we generated a knockout mouse lacking the HCN channel auxiliary subunit, TRIP8b. Eliminating expression of TRIP8b dramatically reduced Ih expression in hippocampal pyramidal neurons. Loss of Ih-dependent membrane voltage properties was attributable to reduction of HCN channels on the neuronal surface, and there was a striking disruption of the normal expression pattern of HCN channels in pyramidal neuron dendrites. In heterologous cells and neurons, absence of TRIP8b increased HCN subunit targeting to and degradation by lysosomes. Mice lacking TRIP8b demonstrated motor learning deficits and enhanced resistance to multiple tasks of behavioral despair with high predictive validity for antidepressant efficacy. We observed similar resistance to behavioral despair in distinct mutant mice lacking HCN1 or HCN2. These data demonstrate that interaction with the auxiliary subunit TRIP8b is a major mechanism underlying proper expression of HCN channels and Ih in vivo, and suggest that targeting Ih may provide a novel approach to treatment of depression. PMID:21593326

  4. Synthesis and Electrochemical Properties Characterization of SnO2-coated LiNi1/3Co1/3Mn1/3O2 Cathode Material for Lithium Ion Batteries

    DTIC Science & Technology

    2009-01-01

    Synthesis and electrochemical properties characterization of SnO2 -coated LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries Ping Yang...China Key words: Li-ion battery; cathode materials; LiNi1/3Co1/3Mn1/3O2; heterogeneous nucleation; SnO2 -coated; electrochemical performance...Abstract LiNi1/3Co1/3Mn1/3O2 cathode materials have been coated with SnO2 (3% wt) by heterogeneous nucleation process to improve its electrochemical

  5. Partitioning net ecosystem carbon exchange into net assimilation and respiration using 13CO2 measurements: A cost-effective sampling strategy

    NASA Astrophysics Data System (ADS)

    OgéE, J.; Peylin, P.; Ciais, P.; Bariac, T.; Brunet, Y.; Berbigier, P.; Roche, C.; Richard, P.; Bardoux, G.; Bonnefond, J.-M.

    2003-06-01

    The current emphasis on global climate studies has led the scientific community to set up a number of sites for measuring the long-term biosphere-atmosphere net CO2 exchange (net ecosystem exchange, NEE). Partitioning this flux into its elementary components, net assimilation (FA), and respiration (FR), remains necessary in order to get a better understanding of biosphere functioning and design better surface exchange models. Noting that FR and FA have different isotopic signatures, we evaluate the potential of isotopic 13CO2 measurements in the air (combined with CO2 flux and concentration measurements) to partition NEE into FR and FA on a routine basis. The study is conducted at a temperate coniferous forest where intensive isotopic measurements in air, soil, and biomass were performed in summer 1997. The multilayer soil-vegetation-atmosphere transfer model MuSICA is adapted to compute 13CO2 flux and concentration profiles. Using MuSICA as a "perfect" simulator and taking advantage of the very dense spatiotemporal resolution of the isotopic data set (341 flasks over a 24-hour period) enable us to test each hypothesis and estimate the performance of the method. The partitioning works better in midafternoon when isotopic disequilibrium is strong. With only 15 flasks, i.e., two 13CO2 nighttime profiles (to estimate the isotopic signature of FR) and five daytime measurements (to perform the partitioning) we get mean daily estimates of FR and FA that agree with the model within 15-20%. However, knowledge of the mesophyll conductance seems crucial and may be a limitation to the method.

  6. Mechanism of OH radical reactions with HCN and CH3CN: OH regeneration in the presence of O2.

    PubMed

    Galano, Annia

    2007-06-14

    A theoretical study on the mechanism of the OH reactions with HCN and CH(3)CN, in the presence of O2, is presented. Optimum geometries and frequencies have been computed at BHandHLYP/6-311++G(2d,2p) level of theory for all stationary points. Energy values have been improved by single-point calculations at the above geometries using CCSD(T)/6-311++G(2d,2p). The initial attack of OH to HCN was found to lead only to the formation of the HC(OH)N adduct, while for CH(3)CN similar proportions of CH(2)CN and CH(3)C(OH)N are expected. A four-step mechanism has been proposed to explain the OH regeneration, experimentally observed for OH + CH(3)CN reaction, when carried out in the presence of O2. The mechanism steps are as follows: (1) OH addition to the C atom in the CN group, (2) O2 addition to the N atom, (3) an intramolecular H migration from OH to OO, and (4) OH elimination. This mechanism is in line with the one independently proposed by Wine et al. for HCN. The results obtained here suggest that for the OH + HCN reaction, the OH regeneration might occur even in larger extension than for OH + CH(3)CN reaction. The agreement between the calculated data and the available experimental evidence on the studied reactions seems to validate the mechanism proposed here.

  7. A search for SiO, OH, CO and HCN radio emission from silicate-carbon stars

    NASA Technical Reports Server (NTRS)

    Little-Marenin, I. R.; Sahai, R.; Wannier, P. G.; Benson, P. J.; Gaylard, M.; Omont, A.

    1994-01-01

    We report upper limits for radio emission of SiO at 86 and 43 GHz, of OH at 1612 and 1665/1667 MHz, of CO at 115 GHz and HCN at 88.6 GHz in the silicate-carbon stars. These upper limits of SiO imply that oxygen-rich material has not been detected within 2R(sub star) of a central star even though the detected emission from silicate dust grains, H2O and OH maser establishes the presence of oxygen-rich material from about tens to thousands of AU of a central star. The upper limit of the SiO abundance is consistent with that found in oxygen-rich envelopes. Upper limits of the mass loss rate (based on the CO data) are estimated to be between 10(exp -6) to 10(exp -7) solar mass/yr assuming a distance of 1.5 kpc for these stars. The absence of HCN microwave emission implies that no carbon-rich material can be detected at large distances (thousands of AU) from a central star. The lack of detections of SiO, CO, and HCN emission is most likely due to the large distances of these stars. A number of C stars were detected in CO and HCN, but only the M supergiant VX Sgr was detected in CO.

  8. A new automatic chamber system for measuring soil surface CO2 and its isotopic (13CO2) effluxes in New Jersey Pinelands

    NASA Astrophysics Data System (ADS)

    Xu, M.

    2006-05-01

    A new automatic chamber system was developed to measure soil surface CO2 efflux with 16 pairs of chambers at hourly interval in an oak forest in New Jersey Pinelands. The trench method was applied to separate root respiration from the total soil respiration. I found that soil temperature and moisture alternatively control root and soil heterotrophic respiration in different seasons based on the data collected in about 3 years. The isotopic flux of soil 13CO2 was also measured at hourly interval using the chamber system with a new laser-based stable carbon isotope analyzer.

  9. Biogenic volatile organic compounds (BVOCs) emission of Scots pine under drought stress - a 13CO2 labeling study to determine de novo and pool emissions under different treatments

    NASA Astrophysics Data System (ADS)

    Lüpke, M.

    2015-12-01

    Plants emit biogenic volatile organic compounds (BVOCs) to e.g. communicate and to defend herbivores. Yet BVOCs also impact atmospheric chemistry processes, and lead to e.g. the built up of secondary organic aerosols. Abiotic stresses, such as drought, however highly influence plant physiology and subsequently BVOCs emission rates. In this study, we investigated the effect of drought stress on BVOCs emission rates of Scots pine trees, a de novo and pool emitter, under controlled climate chamber conditions within a dynamic enclosure system consisting of four plant chambers. Isotopic labeling with 13CO2 was used to detect which ratio of emissions of BVOCs derives from actual synthesis and from storage organs under different treatments. Additionally, the synthesis rate of the BVOCs synthesis can be determined. The experiment consisted of two campaigns (July 2015 and August 2015) of two control and two treated trees respectively in four controlled dynamic chambers simultaneously. Each campaign lasted for around 21 days and can be split into five phases: adaptation, control, dry-out, drought- and re-watering phase. The actual drought phase lasted around five days. During the campaigns two samples of BVOCs emissions were sampled per day and night on thermal desorption tubes and analyzed by a gas chromatograph coupled with a mass spectrometer and a flame ionization detector. Additionally, gas exchange of water and CO2, soil moisture, as well as leaf and chamber temperature was monitored continuously. 13CO2 labeling was performed simultaneously in all chambers during the phases control, drought and re-watering for five hours respectively. During the 13CO2 labeling four BVOCs emission samples per chamber were taken to identify the labeling rate on emitted BVOCs. First results show a decrease of BVOCs emissions during the drought phase and a recovery of emission after re-watering, as well as different strength of reduction of single compounds. The degree of labeling with 13

  10. Carbon transfer, partitioning and residence time in the plant-soil system: a comparison of two 13CO2 labelling techniques

    NASA Astrophysics Data System (ADS)

    Studer, M. S.; Siegwolf, R. T. W.; Abiven, S.

    2014-03-01

    Various 13CO2 labelling approaches exist to trace carbon (C) dynamics in plant-soil systems. However, it is not clear if the different approaches yield the same results. Moreover, there is no consistent way of data analysis to date. In this study we compare with the same experimental setup the two main techniques: pulse and continuous labelling. We evaluate how these techniques perform to estimate the C transfer time, the C partitioning along time and the C residence time in different plant-soil compartments. We used identical plant-soil systems (Populus deltoides × nigra, Cambisol soil) to compare the pulse labelling approach (exposure to 99 atom % 13CO2 for three hours, traced for eight days) with a continuous labelling (exposure to 10 atom % 13CO2, traced for 14 days). The experiments were conducted in climate chambers under controlled environmental conditions. Before label addition and at four successive sampling dates, the plant-soil systems were destructively harvested, separated into leaves, petioles, stems, cuttings, roots and soil and soil microbial biomass was extracted. The soil CO2 efflux was sampled throughout the experiment. To model the C dynamics we used an exponential function to describe the 13C signal decline after pulse labelling. For the evaluation of the 13C distribution during the continuous labelling we applied a logistic function. Pulse labelling is best suited to assess the minimum C transfer time from the leaves to other compartments, while continuous labelling can be used to estimate the mean transfer time through a compartment, including short-term storage pools. The C partitioning between the plant-soil compartments obtained was similar for both techniques, but the time of sampling had a large effect: shortly after labelling the allocation into leaves was overestimated and the soil 13CO2 efflux underestimated. The results of belowground C partitioning were consistent for the two techniques only after eight days of labelling, when the

  11. Carbon transfer, partitioning and residence time in the plant-soil system: a comparison of two 13CO2 labelling techniques

    NASA Astrophysics Data System (ADS)

    Studer, M. S.; Siegwolf, R. T. W.; Abiven, S.

    2013-10-01

    Various 13CO2 labelling approaches exist to trace carbon (C) dynamics in plant-soil systems. However, it is not clear if the different approaches yield the same results. Moreover, there is no consistent way of data analysis to date. In this study we compare with the same experimental setup the two main techniques: the pulse and the continuous labelling. We evaluate how these techniques perform to estimate the C transfer velocity, the C partitioning along time and the C residence time in different plant-soil compartments. We used identical plant-soil systems (Populus deltoides x nigra, Cambisol soil) to compare the pulse labelling approach (exposure to 99 atom% 13CO2 for three hours, traced for eight days) with a continuous labelling (exposure to 10 atom% 13CO2, traced for 14 days). The experiments were conducted in climate chambers under controlled environmental conditions. Before label addition and at four successive sampling dates, the plant-soil systems were destructively harvested, separated into leaves, petioles, stems, cuttings, roots and soil and the microbial biomass was extracted from the soil. The soil CO2 efflux was sampled throughout the experiment. To model the C dynamics we used an exponential function to describe the 13C signal decline after pulse labelling. For the evaluation of the 13C distribution during the continuous labelling we suggest to use a logistic function. Pulse labelling is best suited to assess the maximum C transfer velocity from the leaves to other compartments. With continuous labelling, the mean transfer velocity through a compartment, including short-term storage pools, can be observed. The C partitioning between the plant-soil compartments was similar for both techniques, but the time of sampling had a large effect: shortly after labelling the allocation into leaves was overestimated and the soil 13CO2 efflux underestimated. The results of belowground C partitioning were consistent for the two techniques only after eight days of

  12. Theoretical study of HCN-water interaction: five dimensional potential energy surfaces.

    PubMed

    Sánchez, Ernesto Quintas; Dubernet, Marie-Lise

    2017-03-01

    A new five-dimensional potential energy surface is calculated at the coupled-cluster CCSD(T) level of theory for the HCN-water system, treating both monomers as rigid rotors. The associated methodology, which combines extensive ab initio calculations of moderate accuracy (CCSD(T)/AVDZ) and a fitting procedure involving a much lower angular coverage with more accurate ab initio calculations (CCSD(T)/CBS), is described in detail. This methodology provides a time-saving approach to compute quantitatively accurate potential energy surfaces with reasonable computational effort. Our potential reproduces the main features reported in the literature, and will allow us to perform the first quantum and semi-classical simulations of the collisional dynamic on this system.

  13. Electron-impact excitation of the low-lying electronic states of HCN

    NASA Technical Reports Server (NTRS)

    Chutjian, A.; Tanaka, H.; Srivastava, S. K.; Wicke, B. G.

    1977-01-01

    The first study of the low-energy electron-impact excitation of low-lying electronic transitions in the HCN molecule is reported. Measurements were made at incident electron energies of 11.6 and 21.6 eV in the energy-loss range of 3-10 eV, and at scattering angles of 20-130 deg. Inelastic scattering spectra were placed on the absolute cross-section scale by determining first the ratio of inelastic-to-elastic scattering cross sections, and then separately measuring the absolute elastic scattering cross section. Several new electronic transitions are observed which are intrinsically overlapped in the molecule itself. Assignments of these electronic transitions are suggested. These assignments are based on present spectroscopic and cross-sections measurements, high-energy electron scattering spectra, optical absorption spectra, and ab initio molecular orbital calculations.

  14. Observation of the Formation of 0-π Pulses in Rotation Spectra of HCN and HBr

    NASA Astrophysics Data System (ADS)

    Chesnokov, E. N.; Kubarev, V. V.; Koshlyakov, P. V.

    We present the first experimental study of the formation of 0-π pulses in the far infrared region. Experiments were made in rotation spectra of HCN and HBr molecules using a Novosibirsk terahertz free electron laser (NovoFEL) as a source of optical pulses and ultra-fast Schottky diode as detector. Transformation of the shape of 0-π pulses was explored within a wide range of optical density. Throughout the range of experimental conditions, the observed pulse shape is well described by the analytical formula of Grisp (Phys. Rev. A 1 (1970) 1604). The observed effect can be used for time-domain measurements of the oscillator strength of the absorption line.

  15. Theoretical investigation of the mechanism and kinetics for HCO + HCN ⇄ HCHO + CN

    NASA Astrophysics Data System (ADS)

    Wen, Lin Feng; Yan, Wang; Shao, Wen Zhang; Xian, Yong Pang

    1997-02-01

    The mechanism and kinetics for HCO + HCN ⇄ HCNO + CN have been studied theoretically. The potential energy profile along the intrinsic reaction coordinate (IRC) has been obtained at ab initio QCISD/6-31G ∗∗//UHF/6-31G ∗∗ and CCSD/6-31G ∗∗//UHF/6-31G ∗∗ levels. The forward activation barriers are about 136.45 adn 140.94 kJ mol -1 at these levels, respectively, and the reverse barriers are 2.71 and 1.26 kJ mol -1, respectively. The canonical rate constants for the forward and reverse reactions have been calculated by using statistical theory.

  16. A reduced mechanical model for cAMP-modulated gating in HCN channels

    PubMed Central

    Weißgraeber, Stephanie; Saponaro, Andrea; Thiel, Gerhard; Hamacher, Kay

    2017-01-01

    We developed an in silico mechanical model to analyze the process of cAMP-induced conformational modulations in hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which conduct cations across the membrane of mammalian heart and brain cells. The structural analysis reveals a quaternary twist in the cytosolic parts of the four subunits in the channel tetramer. This motion augments the intrinsic dynamics of the very same protein structure. The pronounced differences between the cAMP bound and unbound form include a mutual interaction between the C-linker of the cyclic nucleotide binding domain (CNBD) and the linker between the S4 and S5 transmembrane domain of the channel. This allows a mechanistic annotation of the twisting motion in relation to the allosteric modulation of voltage-dependent gating of this channel by cAMP. PMID:28074902

  17. Low Temperature Measurements of HCN Broadened by N2 in the 14-micron Spectral Region

    SciTech Connect

    Smith, M.A.H.; Rinsland, Curtis P.; Blake, Thomas A.; Sams, Robert L.; Benner, D. C.; Devi, V. M.

    2008-04-01

    N2-broadening and N2-pressure-induced shift coefficients; and the temperature dependence exponent of the N2-broadening and the temperature dependent coefficients of N2-pressure-induced shifts have been measured for transitions in the v2 band of HCN from analysis of high-resolution absorption spectra recorded with two different Fourier transform spectrometers. A total of 34 laboratory spectra recorded at 0.002-0.005 cm-1 resolution and at temperatures ranging from 211 to 300 K were used in the determination of various spectral line parameters. A multispectrum nonlinear least squares curve fitting technique employing a modified Voigt line profile including speed dependence was used in the P- and R-branch measurements. In analyzing the Q branch transitions, the off-diagonal relaxation matrix element coefficients were included in analysis to fit the data. Present results are compared to previous measurements reported in the literature.

  18. A reduced mechanical model for cAMP-modulated gating in HCN channels

    NASA Astrophysics Data System (ADS)

    Weißgraeber, Stephanie; Saponaro, Andrea; Thiel, Gerhard; Hamacher, Kay

    2017-01-01

    We developed an in silico mechanical model to analyze the process of cAMP-induced conformational modulations in hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which conduct cations across the membrane of mammalian heart and brain cells. The structural analysis reveals a quaternary twist in the cytosolic parts of the four subunits in the channel tetramer. This motion augments the intrinsic dynamics of the very same protein structure. The pronounced differences between the cAMP bound and unbound form include a mutual interaction between the C-linker of the cyclic nucleotide binding domain (CNBD) and the linker between the S4 and S5 transmembrane domain of the channel. This allows a mechanistic annotation of the twisting motion in relation to the allosteric modulation of voltage-dependent gating of this channel by cAMP.

  19. Dendritic HCN channels shape excitatory postsynaptic potentials at the inner hair cell afferent synapse in the mammalian cochlea.

    PubMed

    Yi, Eunyoung; Roux, Isabelle; Glowatzki, Elisabeth

    2010-05-01

    Synaptic transmission at the inner hair cell (IHC) afferent synapse, the first synapse in the auditory pathway, is specialized for rapid and reliable signaling. Here we investigated the properties of a hyperpolarization-activated current (I(h)), expressed in the afferent dendrite of auditory nerve fibers, and its role in shaping postsynaptic activity. We used whole cell patch-clamp recordings from afferent dendrites directly where they contact the IHC in excised postnatal rat cochlear turns. Excitatory postsynaptic potentials (EPSPs) of variable amplitude (1-35 mV) were found with 10-90% rise times of about 1 ms and time constants of decay of about 5 ms at room temperature. Current-voltage relations recorded in afferent dendrites revealed I(h). The pharmacological profile and reversal potential (-45 mV) indicated that I(h) is mediated by hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels. The HCN channel subunits HCN1, HCN2, and HCN4 were found to be expressed in afferent dendrites using immunolabeling. Raising intracellular cAMP levels sped up the activation kinetics, increased the magnitude of I(h) and shifted the half activation voltage (V(half)) to more positive values (-104 +/- 3 to -91 +/- 2 mV). Blocking I(h) with 50 microM ZD7288 resulted in hyperpolarization of the resting membrane potential (approximately 4 mV) and slowing the decay of the EPSP by 47%, suggesting that I(h) is active at rest and shortens EPSPs, thereby potentially improving rapid and reliable signaling at this first synapse in the auditory pathway.

  20. D2 dopamine receptors modulate neuronal resonance in subthalamic nucleus and cortical high-voltage spindles through HCN channels.

    PubMed

    Yang, Chen; Yan, Zhiqiang; Zhao, Bo; Wang, Julei; Gao, Guodong; Zhu, Junling; Wang, Wenting

    2016-06-01

    The high-voltage spindles (HVSs), one of the characteristic oscillations that include theta frequencies in the basal ganglia (BG)-cortical system, are involved in immobile behavior and show increasing power in Parkinson's disease (PD). Our previous results suggested that the D2 dopamine receptor might be involved in HVSs modulations in a rat model of PD. Membrane resonance is one of the cellular mechanisms of network oscillation; therefore, we investigated how dopamine modulates the theta frequency membrane resonance of neurons in the subthalamic nucleus (STN), a central pacemaker of BG, and whether such changes in STN neurons subsequently alter HVSs in the BG-cortical system. In particular, we tested whether dopamine modulates HVSs through hyperpolarization-activated cyclic nucleotide-gated (HCN) channels-dependent membrane resonance in STN neurons. We found that an antagonist of D2 receptors, but not of D1 receptors, inhibited membrane resonance and HCN currents of STN neurons through a G-protein activity in acute brain slices. Our further in vivo experiments using local injection of a D2 receptor antagonist or an HCN blocker in STNs of free-moving rats showed an increase in HVSs power and correlation in the BG-cortical system. Local injection of lamotrigine, an HCN agonist, counteracted the effect induced by the D2 antagonist. Taken together, our results revealed a potential cellular mechanism underlying HVSs activity modulation in the BG-cortical system, i.e. tuning HCN activities in STN neurons through dopamine D2 receptors. Our findings might lead to a new direction in PD treatment by providing promising new drug targets for HVSs activity modulation.

  1. ALMA IMAGING OF HCN, CS, AND DUST IN ARP 220 AND NGC 6240

    SciTech Connect

    Scoville, Nick; Manohar, Swarnima; Murchikova, Lena; Sheth, Kartik; Walter, Fabian; Zschaechner, Laura; Yun, Min; Koda, Jin; Sanders, David; Barnes, Joshua; Thompson, Todd; Robertson, Brant; Tacconi, Linda; Narayanan, Desika; Genzel, Reinhard; Davies, Richard; Hernquist, Lars; Brown, Robert; Hayward, Christopher C.; Kartaltepe, Jeyhan; and others

    2015-02-10

    We report ALMA Band 7 (350 GHz) imaging at 0.''4-0.''6 resolution and Band 9 (696 GHz) at ∼0.''25 resolution of the luminous IR galaxies Arp 220 and NGC 6240. The long wavelength dust continuum is used to estimate interstellar medium masses for Arp 220 east and west and NGC 6240 of 1.9, 4.2, and 1.6 × 10{sup 9} M {sub ☉}within radii of 69, 65, and 190 pc. The HCN emission was modeled to derive the emissivity distribution as a function of radius and the kinematics of each nuclear disk, yielding dynamical masses consistent with the masses and sizes derived from the dust emission. In Arp 220, the major dust and gas concentrations are at radii less than 50 pc in both counter-rotating nuclear disks. The thickness of the disks in Arp 220 estimated from the velocity dispersion and rotation velocities are 10-20 pc and the mean gas densities are n{sub H{sub 2}}∼10{sup 5} cm{sup –3} at R <50 pc. We develop an analytic treatment for the molecular excitation (including photon trapping), yielding volume densities for both the HCN and CS emission with n {sub H2} ∼ 2 × 10{sup 5} cm{sup –3}. The agreement of the mean density from the total mass and size with that required for excitation suggests that the volume is essentially filled with dense gas, i.e., it is not cloudy or like swiss cheese.

  2. Double electron–electron resonance reveals cAMP-induced conformational change in HCN channels

    PubMed Central

    Zagotta, William N.; Stoll, Stefan

    2014-01-01

    Binding of 3′,5′-cyclic adenosine monophosphate (cAMP) to hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels regulates their gating. cAMP binds to a conserved intracellular cyclic nucleotide-binding domain (CNBD) in the channel, increasing the rate and extent of activation of the channel and shifting activation to less hyperpolarized voltages. The structural mechanism underlying this regulation, however, is unknown. We used double electron–electron resonance (DEER) spectroscopy to directly map the conformational ensembles of the CNBD in the absence and presence of cAMP. Site-directed, double-cysteine mutants in a soluble CNBD fragment were spin-labeled, and interspin label distance distributions were determined using DEER. We found motions of up to 10 Å induced by the binding of cAMP. In addition, the distributions were narrower in the presence of cAMP. Continuous-wave electron paramagnetic resonance studies revealed changes in mobility associated with cAMP binding, indicating less conformational heterogeneity in the cAMP-bound state. From the measured DEER distributions, we constructed a coarse-grained elastic-network structural model of the cAMP-induced conformational transition. We find that binding of cAMP triggers a reorientation of several helices within the CNBD, including the C-helix closest to the cAMP-binding site. These results provide a basis for understanding how the binding of cAMP is coupled to channel opening in HCN and related channels. PMID:24958877

  3. SUBMILLIMETER-HCN DIAGRAM FOR ENERGY DIAGNOSTICS IN THE CENTERS OF GALAXIES

    SciTech Connect

    Izumi, Takuma; Kohno, Kotaro; Aalto, Susanne; Espada, Daniel; Martín, Sergio; Nakanishi, Kouichiro; Fathi, Kambiz; Harada, Nanase; Hsieh, Pei-Ying; Matsushita, Satoki; Hatsukade, Bunyo; Imanishi, Masatoshi; Krips, Melanie; Meier, David S.; Nakai, Naomasa; Schinnerer, Eva; Sheth, Kartik; Terashima, Yuichi; Turner, Jean L.

    2016-02-10

    Compiling data from literature and the Atacama Large Millimeter/submillimeter Array archive, we show enhanced HCN(4–3)/HCO{sup +}(4–3) and/or HCN(4–3)/CS(7–6) integrated intensity ratios in circumnuclear molecular gas around active galactic nuclei (AGNs) compared to those in starburst (SB) galaxies (submillimeter HCN enhancement). The number of sample galaxies is significantly increased from our previous work. We expect that this feature could potentially be an extinction-free energy diagnostic tool of nuclear regions of galaxies. Non-LTE radiative transfer modelings of the above molecular emission lines involving both collisional and radiative excitation, as well as a photon trapping effect, were conducted to investigate the cause of the high line ratios in AGNs. As a result, we found that enhanced abundance ratios of HCN to HCO{sup +} and HCN to CS in AGNs as compared to SB galaxies by a factor of a few to even ≳10 are a plausible explanation for the submillimeter HCN enhancement. However, a counterargument of a systematically higher gas density in AGNs than in SB galaxies can also be a plausible scenario. Although we cannot fully distinguish these two scenarios at this moment owing to an insufficient amount of multi-transition, multi-species data, the former scenario is indicative of abnormal chemical composition in AGNs. Regarding the actual mechanism to realize the composition, we suggest that it is difficult with conventional gas-phase X-ray-dominated region ionization models to reproduce the observed high line ratios. We might have to take into account other mechanisms such as neutral–neutral reactions that are efficiently activated in high-temperature environments and/or mechanically heated regions to further understand the high line ratios in AGNs.

  4. The catalytic chemistry of HCN + NO2 over Na- and Ba-Y,FAU: an in situ FTIR and TPD/TPR study.

    PubMed

    Szanyi, János; Kwak, Ja Hun; Peden, Charles H F

    2005-02-03

    The adsorption of HCN and the reaction of HCN with NO(2) over Na-, and Ba-Y,FAU zeolite catalysts were investigated using in situ FTIR and TPD/TPR spectroscopies. Both catalysts adsorb HCN molecularly at room temperature, and the strength of adsorption is higher over Ba-Y than Na-Y. Over Na-Y, the reaction between HCN and NO(2) is slow at 473 K. On Ba-Y, HCN reacts readily with NO(2) at 473K, forming N(2), CO, CO(2), HNCO, NO, N(2)O, and C(2)N(2). The results of this investigation suggest that initial step in the HCN + NO(2) reaction over these catalysts is the hydrogen abstraction from HCN, and the formation of ionic CN- and NC- species. The formation of N(2) can proceed directly from these ionic species upon their interaction with NO+. Alternatively, these cyanide species can be oxidized to isocyanates which then can be further transformed to N(2), N(2)O and CO(x) in their subsequent reaction with NO(x).

  5. Pacemaker Activity of the Human Sinoatrial Node: An Update on the Effects of Mutations in HCN4 on the Hyperpolarization-Activated Current

    PubMed Central

    Verkerk, Arie O.; Wilders, Ronald

    2015-01-01

    Since 2003, several loss-of-function mutations in the HCN4 gene, which encodes the HCN4 protein, have been associated with sinus node dysfunction. In human sinoatrial node (SAN), HCN4 is the most abundant of the four isoforms of the HCN family. Tetramers of HCN subunits constitute the ion channels that conduct the hyperpolarization-activated “funny” current (If), which plays an important modulating role in SAN pacemaker activity. Voltage-clamp experiments on HCN4 channels expressed in COS-7, CHO and HEK-293 cells, as well as in Xenopus oocytes have revealed changes in the expression and kinetics of mutant channels, but the extent to which especially the kinetic changes would affect If flowing during a human SAN action potential often remains unresolved. In our contribution to the Topical Collection on Human Single Nucleotide Polymorphisms and Disease Diagnostics, we provide an updated review of the mutation-induced changes in the expression and kinetics of HCN4 channels and provide an overview of their effects on If during the time course of a human SAN action potential, as assessed in simulated action potential clamp experiments. Future research may solve apparent inconsistencies between data from clinical studies and data from in vitro and in silico experiments. PMID:25642760

  6. Effects of waterlogging on carbon assimilate partitioning in the Zoigê alpine wetlands revealed by 13CO2 pulse labeling.

    PubMed

    Gao, Jun-Qin; Gao, Ju-Juan; Zhang, Xue-Wen; Xu, Xing-Liang; Deng, Zhao-Heng; Yu, Fei-Hai

    2015-03-23

    Waterlogging has been suggested to affect carbon (C) turnover in wetlands, but how it affects C allocation and stocks remains unclear in alpine wetlands. Using in situ (13)CO2 pulse labelling, we investigated C allocation in both waterlogged and non-waterlogged sites in the Zoigê wetlands on the Tibetan Plateau in August 2011. More than 50% of total (13)C fixed by photosynthesis was lost via shoot respiration. Shoots recovered about 19% of total (13)C fixed by photosynthesis at both sites. Only about 26% of total fixed (13)C was translocated into the belowground pools. Soil organic C pool accounted for 19% and roots recovered about 5-7% of total fixed (13)C at both sites. Waterlogging significantly reduced soil respiration and very little (13)C was lost via soil respiration in the alpine wetlands compared to that in grasslands. We conclude that waterlogging did not significantly alter C allocations among the C pools except the (13)CO2 efflux derived from soil respiration and that shoots made similar contributions to C sequestration as the belowground parts in the Zoigê alpine wetlands. Therefore, changes in waterlogging due to climate change will not affect C assimilate partitioning but soil C efflux.

  7. PEDOT modified LiNi1/3Co1/3Mn1/3O2 with enhanced electrochemical performance for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Liu, Xizheng; Li, Huiqiao; Li, De; Ishida, Masayoshi; Zhou, Haoshen

    2013-12-01

    Layered LiNi1/3Co1/3Mn1/3O2 was modified by poly(3,4-dioxyethylenethiophene) PEDOT via a facile method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and infrared spectroscopy (IR). PEDOT modified samples exhibited both improved rate and cycle performance compared with the pristine LiNi1/3Co1/3Mn1/3O2. At a charge/discharge current of 1500 mA g-1, the discharge capacity was improved from 44.3 to 73.9 mAh g-1. The sample with 2 wt% and heat treated at 300 °C showed the optimized electrochemical performance. Galvanostatic intermittent titration technique (GITT) and cyclic voltammetry (CV) results indicated that the battery polarization of coated samples have been suppressed obviously because the PEDOT layer facilitated the electron transfer at the interface of electrode and electrolyte.

  8. 13CO2/12CO2 ratio analysis in exhaled air by lead-salt tunable diode lasers for noninvasive diagnostics in gastroenterology

    NASA Astrophysics Data System (ADS)

    Stepanov, Eugene V.; Zyrianov, Pavel V.; Miliaev, Valerii A.; Selivanov, Yurii G.; Chizhevskii, Eugene G.; Os'kina, Svetlana; Ivashkin, Vladimir T.; Nikitina, Elena I.

    1999-07-01

    An analyzer of 13CO2/12CO2 ratio in exhaled air based on lead-salt tunable diode lasers is presented. High accuracy of the carbon isotope ratio detection in exhaled carbon dioxide was achieved with help of very simple optical schematics. It was based on the use of MBE laser diodes operating in pulse mode and on recording the resonance CO2 absorption at 4.2 micrometers . Special fast acquisition electronics and software were applied for spectral data collection and processing. Developed laser system was tested in a clinical train aimed to assessment eradication efficiency in therapy of gastritis associated with Helicobacter pylori infection. Data on the 13C-urea breath test used for P.pylori detection and obtained with tunable diode lasers in the course of the trail was compared with the results of Mass-Spectroscopy analysis and histology observations. The analyzer can be used also for 13CO2/12CO2 ratio detection in exhalation to perform gastroenterology breath test based on using other compounds labeled with stable isotopes.

  9. Calendering effects on the physical and electrochemical properties of Li[Ni1/3Mn1/3Co1/3]O2 cathode

    NASA Astrophysics Data System (ADS)

    Zheng, Honghe; Tan, Li; Liu, Gao; Song, Xiangyun; Battaglia, Vincent S.

    2012-06-01

    Li[Ni1/3Mn1/3Co1/3]O2 cathode laminate containing 8% PVDF and 7% acetylene black is fabricated and calendered to different porosities. Calendering effects on the physical and electrochemical properties of the Li[Ni1/3Mn1/3Co1/3]O2 cathode are investigated. It is found that mechanical properties of the composite laminate strongly depend on the electrode porosity whereas the electronic conductivity is not significantly affected by calendering. Electrochemical performances including the specific capacity, the first coulombic efficiency, cycling performance and rate capability for the cathode at different porosities are compared. An optimized porosity of around 30-40% is identified. Electrochemical impedance spectroscopy (EIS) studies illustrate that calendering improves the electronic conductivity between active particles at relatively high porosities, but increases charge transfer resistance at electrode/electrolyte interface at relatively low porosities. An increase of activation energy of Li interfacial transfer for the electrode at 0% porosity indicates a relatively high barrier of activation at the electrode/electrolyte interface, which accounts for the poor rate capability of the electrode at extremely low porosity.

  10. Capacity improvement by deficit of transition metals in inverse spinel LiNi1/3Co1/3Mn1/3VO4 cathodes

    NASA Astrophysics Data System (ADS)

    Kitajou, Ayuko; Yoshida, Jun; Nakanishi, Shinji; Matsuda, Yasuaki; Kanno, Ryoji; Okajima, Toshihiro; Okada, Shigeto

    2016-01-01

    Although inverse spinel materials have attracted attention because of their unusually high voltage characteristics, their rechargeable capacities are generally less than 50 mAh g-1, as a result of the coexistence of Li and transition metal ions at 16d octahedral sites. This work attempted to improve cathode functioning by optimizing the quantities of Li and transition metal ions residing at the 16d sites of LiNi1/3Co1/3Mn1/3VO4. The rechargeable capacity of the LiNi0.28Co0.28Mn0.26V0.80O4 synthesized in the present study was found to be above 120 mAh g-1, representing the largest capacity reported to date for an inverse spinel material. The results of in-situ XANES analysis demonstrated that the charge-discharge reactions of LiNi1/3Co1/3Mn1/3VO4 corresponds to the Mn2+/Mn4+ and Co2+/Co3+ redox couples, mainly.

  11. Riverine GHG emissions: one year of CO2, 13CO2 and CH4 flux measurements on Vistula river in Krakow, southern Poland

    NASA Astrophysics Data System (ADS)

    Jasek, Alina; Wachniew, Przemyslaw; Zimnoch, Miroslaw

    2013-04-01

    Terrestrial surface waters are generally considered to be sources of carbon dioxide and methane, because respiration of organic matter via aerobic and anaerobic pathways causes supersaturation of surface waters with respect to CO2 and CH4, respectively. In rivers, these processes are influenced by such anthropogenic factors as changes of land-use, wastewater and alteration of river channels. The research object is Vistula, the largest Polish river. It has the length of 1047 km and annual runoff of 6.2x1010m3. The urban section of Vistula in Krakow receives large amounts of organic matter from highly urbanized catchment and point discharges of urban waste waters within the city limits. The river was sampled regularly at three points: the entrance to the city, the center and the point where Vistula leaves the agglomeration. A floating chamber coupled with Picarro G2101-i analyzer was applied to quantify CO2, 13CO2 and CH4 fluxes leaving the surface of the river. A floating chamber was equipped with sensors to measure air pressure, temperature and humidity inside the chamber and the temperature of water. The chamber was equipped with a set of floats and an anchor. The measurements started in October 2011, and were repeated with approximately monthly frequency. Physicochemical properties of water (temperature, conductivity, pH, CO2 partial pressure over the water surface and alkalinity) were also measured during each measurement campaign. In addition, at each site short-term variability of the measured fluxes was also investigated. Additionally, short-term variability of the measured fluxes of CO2, 13CO2 and CH4 were performed in all three sites. The results indicate that fluxes of CO2 released from the river are comparable with the soil emissions of this gas measured in Krakow area. The δ13CO2 signature of riverine CO2 flux allowed to identify decomposition of C3 organic matter as the major source of this gas. No distinct seasonal variability of the CO2 emission and

  12. Airborne measurements of CO2, CH4 and HCN in boreal biomass burning plumes

    NASA Astrophysics Data System (ADS)

    O'Shea, Sebastian J.; Bauguitte, Stephane; Muller, Jennifer B. A.; Le Breton, Michael; Archibald, Alex; Gallagher, Martin W.; Allen, Grant; Percival, Carl J.

    2013-04-01

    Biomass burning plays an important role in the budgets of a variety of atmospheric trace gases and particles. For example, fires in boreal Russia have been linked with large growths in the global concentrations of trace gases such as CO2, CH4 and CO (Langenfelds et al., 2002; Simpson et al., 2006). High resolution airborne measurements of CO2, CH4 and HCN were made over Eastern Canada onboard the UK Atmospheric Research Aircraft FAAM BAe-146 from 12 July to 4 August 2011. These observations were made as part of the BORTAS project (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites). Flights were aimed at transecting and sampling the outflow from the commonly occurring North American boreal forest fires during the summer months and to investigate and identify the chemical composition and evolution of these plumes. CO2 and CH4 dry air mole fractions were determined using an adapted system based on a Fast Greenhouse Gas Analyser (FGGA, Model RMT-200) from Los Gatos Research Inc, which uses the cavity enhanced absorption spectroscopy technique. In-flight calibrations revealed a mean accuracy of 0.57 ppmv and 2.31 ppbv for 1 Hz observations of CO2 and CH4, respectively, during the BORTAS project. During these flights a number of fresh and photochemically-aged plumes were identified using simultaneous HCN measurements. HCN is a distinctive and useful marker for forest fire emissions and it was detected using chemical ionisation mass spectrometry (CIMS). In the freshest plumes, strong relationships were found between CH4, CO2 and other tracers for biomass burning. From this we were able to estimate that 8.5 ± 0.9 g of CH4 and 1512 ± 185 g of CO2 were released into the atmosphere per kg of dry matter burnt. These emission factors are in good agreement with estimates from previous studies and can be used to calculate budgets for the region. However for aged plumes the correlations between CH4 and other

  13. Matrix isolation and ab initio study on HCN/CO2 system and its radiation-induced transformations: Spectroscopic evidence for HCN⋯ CO2 and trans-HCNH⋯ CO2 complexes

    NASA Astrophysics Data System (ADS)

    Kameneva, Svetlana V.; Tyurin, Daniil A.; Nuzhdin, Kirill B.; Feldman, Vladimir I.

    2016-12-01

    Spectroscopic characteristics and X-ray induced transformations of the HCN⋯ CO2 complex in solid Ar and Kr matrices were studied by FTIR spectroscopy and ab initio calculations at the CCSD(T) level. The complex was prepared by deposition of the HCN/CO2/Ng gas mixtures (Ng = Ar or Kr). The comparison of the experiment and calculations prove formation of a linear, H-bonded NCH⋯ OCO complex with a substantial red shift of the C-H stretching band and a blue shift of the H-C-N bending band in respect to the monomer. This result is in contrast with the previous gas-phase observations, where only T-shape complex was found. Irradiation of deposited matrices leads to formation of CN radicals and HNC molecules and subsequent annealing results in appearance of H2CN and trans-HCNH in both matrices plus HKrCN in the case of Kr. In the presence of CO2, the strongest absorption of trans-HCNH radical demonstrates an additional blue-shifted (by 6.4 cm-1) feature, which was assigned to the N-coordinated complex of this radical with CO2 on the basis of comparison with calculations. To our knowledge, it is the first experimentally observed complex of this radical. No evidence was found for HKrCN⋯ CO2 complex, which was explained tentatively by steric hindrance.

  14. Ab initio calculation of a global potential, vibrational energies, and wave functions for HCN/HNC, and a simulation of the (A-tilde)-(X-tilde) emission spectrum

    NASA Technical Reports Server (NTRS)

    Bowman, Joel M.; Gazdy, Bela; Bentley, Joseph A.; Lee, Timothy J.; Dateo, Christopher E.

    1993-01-01

    A potential energy surface for the HCN/HNC system which is a fit to extensive, high-quality ab initio, coupled-cluster calculations is presented. All HCN and HNC states with energies below the energy of the first delocalized state are reported and characterized. Vibrational transition energies are compared with all available experimental data on HCN and HNC, including high CH-overtone states up to 23,063/cm. A simulation of the (A-tilde)-(X-tilde) stimulated emission pumping (SEP) spectrum is also reported, and the results are compared to experiment. Franck-Condon factors are reported for odd bending states of HCN, with one quantum of vibrational angular momentum, in order to compare with the recent assignment by Jonas et al. (1992), on the basis of axis-switching arguments of a number of previously unassigned states in the SEP spectrum.

  15. Increased expression of HCN2 channel protein in L4 dorsal root ganglion neurons following axotomy of L5- and inflammation of L4-spinal nerves in rats.

    PubMed

    Smith, T; Al Otaibi, M; Sathish, J; Djouhri, L

    2015-06-04

    A hallmark of peripheral neuropathic pain (PNP) is chronic spontaneous pain and/or hypersensitivity to normally painful stimuli (hyperalgesia) or normally nonpainful stimuli (allodynia).This pain results partly from abnormal hyperexcitability of dorsal root ganglion (DRG) neurons. We have previously shown, using a modified version of the lumbar 5 (L5)-spinal nerve ligation model of PNP (mSNA model involving L5-spinal nerve axotomy plus loose ligation of the lumbar 4 (L4)-spinal nerve with neuroinflammation-inducing chromic-gut), that L4 DRG neurons exhibit increased spontaneous activity, the key characteristic of neuronal hyperexcitability. The underlying ionic and molecular mechanisms of the hyperexcitability of L4 DRG neurons are incompletely understood, but could result from changes in expression and/or function of ion channels including hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which are active near the neuron's resting membrane potential, and which produce an excitatory inward current that depolarizes the membrane potential toward the threshold of action potential generation. Therefore, in the present study we used the mSNA model to investigate whether: (a) expression of HCN1-HCN3 channels is altered in L4 DRG neurons which, in the mSNA model, are essential for transmission of the evoked pain, and which contribute to chronic spontaneous pain, and (b) local (intraplantar) blockade of these HCN channels, with a specific blocker, ZD7288, attenuates chronic spontaneous pain and/or evoked pain in mSNA rats. We found 7days after mSNA: (1) a significant increase in HCN2-immunoreactivity in small (<30μm) DRG neurons (predominantly IB4-negative neurons), and in the proportion of small neurons expressing HCN2 (putative nociceptors); (2) no significant change in HCN1- or HCN3-immunoreactivity in all cell types; and (3) attenuation, with ZD7288 (100μM intraplantar), of chronic spontaneous pain behavior (spontaneous foot lifting) and mechanical

  16. Rate constant calculations of the C2 + HCN → CCCN+H addition via the Master Equation.

    PubMed

    da Silva, Washington Barbosa; Albernaz, Alessandra F; Barreto, Patricia R P; Correa, Eberth

    2017-04-01

    The addition of C2 to HCN is of relevant interest in astrochemistry. We studied the pathways of this addition to produce CCCN and estimated its reaction rate using the Master Equation in the circumstellar environment. From the results of this study, it was possible to show that a different pathway in the Surface Potential Energy-PES can also be investigated. In a circumstellar envelop environment, with temperatures varying between 1000 K and 2000 K, the abundances of these species are favorable to this kind of addition, and our branching ratio for the rate constant showed that the new pathway is more favorable in comparison with other possibilities for this range of temperatures in this environment, and must be taken into account in any computation of the rate constant. Graphical Abstract Branching ratios of pathways involved in the C2 + HCN → CCCN+H addition, at a temperature range of 1000-2000 K.

  17. High-resolution infrared spectroscopy of HCN-Znn (n = 1-4) clusters: structure determination and comparisons with theory.

    PubMed

    Stiles, Paul L; Miller, Roger E

    2006-05-04

    High-resolution infrared laser spectroscopy has been used to obtain rotationally resolved spectra of HCN-Zn(n) (n = 1-4) complexes formed in helium nanodroplets. In the present study the droplets passed through a metal oven, where the zinc vapor pressure was adjusted until one or more atoms were captured by the droplets. A second pickup cell was then used to dope the droplets with a single HCN molecule. Rotationally resolved infrared spectra are obtained for all of these complexes, providing valuable information concerning their structures. Stark spectra are reported and used to determine the corresponding permanent electric dipole moments. Ab initio calculations are also reported for these complexes for comparison with the experimental results.

  18. Lithium Diffusion & Magnetism in Battery Cathode Material LixNi1/3Co1/3Mn1/3O2

    NASA Astrophysics Data System (ADS)

    Månsson, M.; Nozaki, H.; Wikberg, J. M.; Prša, K.; Sassa, Y.; Dahbi, M.; Kamazawa, K.; Sedlak, K.; Watanabe, I.; Sugiyama, J.

    2014-12-01

    We have studied low-temperature magnetic properties as well as high-temperature lithium ion diffusion in the battery cathode materials LixNi1/3Co1/3Mn1/3O2 by the use of muon spin rotation/relaxation. Our data reveal that the samples enter into a 2D spin-glass state below TSG ≈ 12 K. We further show that lithium diffusion channels become active for T >= Tdiff ~ 125 K where the Li-ion hopping-rate [v(T)] starts to increase exponentially. Further, v(T) is found to fit very well to an Arrhenius type equation and the activation energy for the diffusion process is extracted as Ea ≈ 100 meV.

  19. The photolysis of NH3 in the presence of substituted acetylenes - A possible source of oligomers and HCN on Jupiter

    NASA Technical Reports Server (NTRS)

    Ferris, James P.; Jacobson, Richard R.; Guillemin, Jean C.

    1992-01-01

    An NMR spectral study is presently conducted of NH3 photolysis in the presence of substituted acetylenes with NMR spectra and gas chromatography. Quantum yields and percentage conversions to products are reported. It is shown that acetylenic hydrocarbons generated during methane photolysis in Jupiter's stratosphere can react with radicals formed by NH3 photolysis to yield nonvolatile, yellow-brown polymers, alkylnitriles, and in due course, HCN, as observed on Jupiter.

  20. In-Situ Measurements of HCN and CH3CN In the Pacific Troposphere: Sources, Sinks, and Comparisons with Satellite Observations

    NASA Technical Reports Server (NTRS)

    Singh, Hanwant B.; Salas, L.; Herlth, D.; Viezee, W.; Jacob, D.; Blake, D.; Sachse, G.; Hipskind, R. Stephen (Technical Monitor)

    2002-01-01

    A new capillary gas chromatographic method using a Reduction Gas Detector was developed to measure HCN and CH3CN in the remote troposphere. This instrumental configuration was deployed for the very first time in the Trace-P field mission performed during the spring of 2001. The NASA DC-8 aircraft afforded an opportunity to measure HCN and CH3CN in polluted and pristine environments over the Pacific to a maximum altitude of 12 km. These are some of the first in situ measurements of the distribution of HCN and CH3CN over the Pacific. Large background concentrations of both nitriles were found to be present and significant variability was observed. The abundance of HCN and CH3CN was strongly impacted by outflow of pollution from Asia. In general there appeared to be a direct but nonlinear relationship between the mixing ratios of HCN and CH3CN. The vertical structure of these chemicals shows direct evidence of the presence of a significant oceanic sink. These observations will be compared with the column content HCN data from satellites and other available measurements. A large body of data have been collected and are being analyzed, both statistically and with the help of models, to better understand the sources and sinks of these nitriles. These results will be presented.

  1. ALMA DETECTION OF THE VIBRATIONALLY EXCITED HCN J = 4-3 EMISSION LINE IN THE AGN-HOSTING LUMINOUS INFRARED GALAXY IRAS 20551–4250

    SciTech Connect

    Imanishi, Masatoshi; Nakanishi, Kouichiro

    2013-10-01

    We present results from our ALMA Cycle 0 observations, at the frequencies around the HCN, HCO{sup +}, and HNC J = 4-3 transition lines, of the luminous infrared galaxy IRAS 20551–4250 at z = 0.043, which is known to host an energetically important obscured active galactic nucleus (AGN). In addition to the targeted HCN, HCO{sup +}, and HNC J = 4-3 emission lines, two additional strong emission lines are seen, which we attribute to H{sub 2}S and CH{sub 3}CN(+CCH). The HCN-to-HCO{sup +} J = 4-3 flux ratio (∼0.7) is higher than in the other starburst-dominated galaxy (∼0.2) observed in our ALMA Cycle 0 program. We tentatively (∼5σ) detected the vibrationally excited (v {sub 2} = 1) HCN J = 4-3 (l = 1f) emission line, which is important for testing an infrared radiative pumping scenario for HCN. This is the second detection of this molecular transition in external galaxies. The most likely reason for this detection is not only the high flux of this emission line, but also the small molecular line widths observed in this galaxy, suggesting that vibrational excitation of HCN may be relatively common in AGN-hosting galaxies.

  2. Uncertainty quantification and robust predictive system analysis for high temperature kinetics of HCN/O2/Ar mixture

    NASA Astrophysics Data System (ADS)

    Cheung, Sai Hung; Miki, Kenji; Prudencio, Ernesto; Simmons, Chris

    2016-08-01

    In this paper, a stochastic system based Bayesian approach is applied to quantify the uncertainties involved in the modeling of the HCN/O2/Ar mixture kinetics proposed by Thielen and Roth (1987). This enables more robust predictions of quantities of interest such as rate coefficients of HCN + Ar → H + CN + Ar and O2 + CN → NCO + O by using a stochastic Arrhenius form calibrated against their experimental data. This Bayesian approach requires the evaluation of multidimensional integrals, which cannot be done analytically. Here a recently developed stochastic simulation algorithm, which allows for efficient sampling in the high-dimensional parameter space, is used. We quantify the uncertainties in the modeling of the HCN/O2/Ar mixture kinetics and in turn the two rate coefficients and the other relevant rate coefficients. The uncertainty in the error including both the experimental measurement error and physical modeling error is also quantified. The effect of the number of uncertain parameters on the uncertainties is investigated.

  3. Knock-out of HCN1 subunit flattens dorsal-ventral frequency gradient of medial entorhinal neurons in adult mice.

    PubMed

    Giocomo, Lisa M; Hasselmo, Michael E

    2009-06-10

    Layer II stellate cells at different locations along the dorsal to ventral axis of medial entorhinal cortex show differences in the frequency of intrinsic membrane potential oscillations and resonance (Giocomo et al., 2007). The frequency differences scale with differences in the size and spacing of grid-cell firing fields recorded in layer II of the medial entorhinal cortex in behaving animals. To determine the mechanism for this difference in intrinsic frequency, we analyzed oscillatory properties in adult control mice and adult mice with a global deletion of the HCN1 channel. Data from whole-cell patch recordings show that the oscillation frequency gradient along the dorsal-ventral axis previously shown in juvenile rats also appears in control adult mice, indicating that the dorsal-ventral gradient generalizes across age and species. Knock-out of the HCN1 channel flattens the dorsal-ventral gradient of the membrane potential oscillation frequency, the resonant frequency, the time constant of the "sag" potential and the amplitude of the sag potential. This supports a role of the HCN1 subunit in the mechanism of the frequency gradient in these neurons. These findings have important implications for models of grid cells and generate predictions for future in vivo work on entorhinal grid cells.

  4. CN radical hydrogenation from solid H2 reactions, an alternative way of HCN formation in the interstellar medium

    NASA Astrophysics Data System (ADS)

    Borget, Fabien; Müller, Sandra; Grote, Dirk; Theulé, Patrice; Vinogradoff, Vassilissa; Chiavassa, Thierry; Sander, Wolfram

    2017-01-01

    Context. Molecular hydrogen (H2) is the most abundant molecule of the interstellar medium (ISM) in gas phase and it has been assumed to exist in solid state or as coating on grains. Aims: Our goal is to show that solid H2 can act as a hydrogenation agent, reacting with CN radicals to form HCN. Methods: In a H2 matrix, we studied the hydrogenation of the CN radical generated from the vacuum ultraviolet photolysis (VUV-photolysis) of C2N2 at 3.8 K. We modified the wavelengths and the host gas in order to be sure that CN radicals can abstract H from H2 molecules. Results: HCN monomers, dimers, and oligomers have been characterised by Fourier transform infrared spectroscopy (FTIR). H2CN as well as CN radicals have also been clearly observed during the photolysis performed at 3.8 K. Conclusions: H2 is a hydrogenation reagent towards CN radicals producing HCN. This type of reaction should be taken into account for the reactivity at low temperature in contaminated H2 ice macro-particles (CHIMPs), H2 flakes or in the first sublayers of grains where solid H2 has accumulated.

  5. Benchmark, DFT assessments, cooperativity, and energy decomposition analysis of the hydrogen bonds in HCN/HNC oligomeric complexes.

    PubMed

    de Oliveira, Paulo McMiller C; Silva, Juliana A B; Longo, Ricardo L

    2017-02-01

    Hydrogen cyanide (HCN) and its tautomer hydrogen isocyanide (HNC) are relevant for extraterrestrial chemistry and possible relation to the origin of biomolecules. Several processes and reactions involving these molecules depend on their intermolecular interactions that can lead to aggregates and liquids especially due to the hydrogen bonds. It is thus important to comprehend, to describe, and to quantify their hydrogen bonds, mainly their nature and the cooperativity effects. A systematic study of all linear complexes up to pentamers of HCN and HNC is presented. CCSD(T)/CBS energy calculations, with and without basis set superposition error (BSSE) corrections for energies and geometries, provided a suitable set of benchmarks. Approximated methods based on the density functional theory (DFT) such as BP86, PBE, TPSS, B3LYP, CAM-B3LYP with and without dispersion corrections and long-range corrections, were assessed to describe the interaction energies and cooperativity effects. These assessments are relevant to select DFT functionals for liquid simulations. Energy decomposition analysis was performed at the PBE/STO-TZ2P level and provided insights into the nature of the hydrogen bonds, which are dominated by the electrostatic component. In addition, several linear relationships between the various energy components and the interaction energy were obtained. The cooperativity energy was also found to be practically linear with respect to the interaction energy, which may be relevant for designing and/or correcting empirical force fields. Graphical Abstract Hydrogen bonds in HCN/HNC oligomeric complexesᅟ.

  6. Spatiotemporal Regulation of an Hcn4 Enhancer Defines a Role for Mef2c and HDACs in Cardiac Electrical Patterning

    PubMed Central

    Vedantham, Vasanth; Evangelista, Melissa; Huang, Yu; Srivastava, Deepak

    2012-01-01

    Regional differences in cardiomyocyte automaticity permit the sinoatrial node (SAN) to function as the leading cardiac pacemaker and the atrioventricular (AV) junction as a subsidiary pacemaker. The regulatory mechanisms controlling the distribution of automaticity within the heart are not understood. To understand regional variation in cardiac automaticity, we carried out an in vivo analysis of cis-regulatory elements that control expression of the hyperpolarization-activated cyclic-nucleotide gated ion channel 4 (Hcn4). Using transgenic mice, we found that spatial and temporal patterning of Hcn4 expression in the AV conduction system required cis-regulatory elements with multiple conserved fragments. One highly conserved region, which contained a myocyte enhancer factor 2C (Mef2C) binding site previously described in vitro, induced reporter expression specifically in the embryonic non-chamber myocardium and the postnatal AV bundle in a Mef2c-dependent manner in vivo. Inhibition of histone deacetylase (HDAC) activity in cultured transgenic embryos showed expansion of reporter activity to working myocardium. In adult animals, hypertrophy induced by transverse aortic constriction, which causes translocation of HDACs out of the nucleus, resulted in ectopic activation of the Hcn4 enhancer in working myocardium, recapitulating pathological electrical remodeling. These findings reveal mechanisms that control the distribution of automaticity among cardiomyocytes during development and in response to stress. PMID:23085412

  7. Computational study of the linear proton bound ion-molecule complexes of HCNH+ with HCN and HNC

    NASA Astrophysics Data System (ADS)

    Eric Cotton, C.; Francisco, Joseph S.; Klemperer, William

    2013-07-01

    This work reports the results of a high level ab initio study of the linear proton bound ion-molecule complex of HCNH+ with HCN and its isomer HNC. The energetics, equilibrium geometries, and predicted equilibrium rotational constants of three strongly interacting ion-molecule complexes are reported from calculations performed at the coupled-cluster calculations including singles, doubles, and perturbative triple excitations (CCSD(T))/aug-cc-pVnZ (n = 2-5) level of theory. Harmonic vibrational frequencies from calculations performed at the CCSD(T)/aug-cc-pVnZ (n = 2-4) level of theory are presented. Additional calculations are performed at the CCSD(T)-F12b/VnZ-F12 level of theory, and the associated energetics, equilibrium geometries, and equilibrium spectroscopic properties are reported. Anharmonicity is treated with the vibrational configuration interaction method, and the predicted anharmonic vibrational frequencies are reported. The results of these calculations show that of the four possible linear interactions of HCNH+ with HCN and HNC, there are three strongly interacting proton bound complexes. Further, the study presents results that the fourth possible interaction provides the basis for a novel HNC to HCN isomerization pathway in the interstellar medium.

  8. GATING OF HCN CHANNELS BY CYCLIC NUCLEOTIDES: RESIDUE CONTACTS THAT UNDERLIE LIGAND BINDING, SELECTIVITY AND EFFICACY

    PubMed Central

    Zhou, Lei; Siegelbaum, Steven A.

    2007-01-01

    SUMMARY Cyclic nucleotides regulate the activity of various proteins by interacting with a conserved cyclic nucleotide-binding domain (CNBD). Although X-ray crystallographic studies have revealed the structures of several CNBDs, the residues responsible for generating the high efficacy with which ligand binding leads to protein activation remain unknown. Here we combine molecular dynamics simulations with mutagenesis to identify ligand contacts important for the regulation of the hyperpolarization-activated HCN2 channel by cyclic nucleotides. Surprisingly, out of seven residues that make strong contacts with ligand, only R632 in the C-helix of the CNBD is essential for high ligand efficacy, due to its selective stabilization of cNMP binding to the open state of the channel. Principle component analysis suggests that a local movement of the C-helix upon ligand binding propagates through the CNBD of one subunit to the C-linker of a neighboring subunit to apply force to the gate of the channel. PMID:17562313

  9. Structure and Energetics of Allosteric Regulation of HCN2 Ion Channels by Cyclic Nucleotides*

    PubMed Central

    DeBerg, Hannah A.; Brzovic, Peter S.; Flynn, Galen E.; Zagotta, William N.; Stoll, Stefan

    2016-01-01

    Hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels play an important role in regulating electrical activity in the heart and brain. They are gated by the binding of cyclic nucleotides to a conserved, intracellular cyclic nucleotide-binding domain (CNBD), which is connected to the channel pore by a C-linker region. Binding of cyclic nucleotides increases the rate and extent of channel activation and shifts it to less hyperpolarized voltages. We probed the allosteric mechanism of different cyclic nucleotides on the CNBD and on channel gating. Electrophysiology experiments showed that cAMP, cGMP, and cCMP were effective agonists of the channel and produced similar increases in the extent of channel activation. In contrast, electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) on the isolated CNBD indicated that the induced conformational changes and the degrees of stabilization of the active conformation differed for the three cyclic nucleotides. We explain these results with a model where different allosteric mechanisms in the CNBD all converge to have the same effect on the C-linker and render all three cyclic nucleotides similarly potent activators of the channel. PMID:26559974

  10. Axis-switching transitions and the stimulated emission pumping spectrum of HCN

    NASA Astrophysics Data System (ADS)

    Jonas, David M.; Yang, Xueming; Wodtke, Alec M.

    1992-08-01

    Six of the 14 unidentified bands in the stimulated emission pumping (SEP) spectrum of HCN are shown to be forbidden transitions to l`=1 e parity levels of the ground state. The band origins agree with predictions within the error of the anharmonic expansion; the rotational constants, when corrected for rotational-l doubling, agree within experimental error. Rotational-l resonance between l`=0 and l`=2 is found in highly excited bending levels, confirming the extrapolation of the rotational-l resonance and doubling constant q2 from microwave and infrared measurements to 17 000 cm-1. The rotational intensity of the l`=1 bands due to the axis-switching mechanism of Hougen and Watson [Can. J. Phys. 43, 298 (1965)] is shown to be greater than some of the observed allowed rotational transitions to l`=2 when laser polarization effects are taken into account. A qualitative Franck-Condon analysis of the SEP spectrum provides unusually strong evidence for the axis-switching mechanism. The eight remaining unassigned bands are evidently perturbed and are assigned based on agreement between sums of observed rotational constants and sums of zero-order (unperturbed) rotational constants predicted by the anharmonic expansion, the magnitude of the rotational-l resonance, and the expected Franck-Condon factors.

  11. Millimeter-Wave Spectroscopy of the vdW Bands of He-HCN Near the Dissociation Limit.

    NASA Astrophysics Data System (ADS)

    Harada, Kensuke; Tanaka, Keiichi

    2010-06-01

    The He-HCN complex is a weakly bound complex with binding energy of about 9 cm-1. We have measured the internal rotation bands (to the j = 1 and 2 states) and intermolecular stretching bands of the He-HCN complex by millimeter-wave absorption spectroscopy combined with a pulsed-jet expansion technique, and reported the potential energy surface (PES) to reproduce the observed transition frequencies. The PES obtained has a global minimum in the linear configuration with a depth of 30.3 cm-1 and has a saddle point at the anti-linear configuration with a depth of 20.3 cm-1. The intermolecular stretching level and the second excited (j = 2) level of the internal rotation state are determined to be located 9.1407 and 9.0529 cm-1, respectively, above the ground state, very close to the calculated dissociation limit (D_0) of 9.33 cm-1 . In the present study, we have extended the measurement to the transitions to the bound states above the "dissociation limit" (D_0) and observed several such transitions for the first time in the ground state of the molecular complex. The rovibrational levels of He-HCN with e label dissociate to the HCN molecule with J=0 and the He atom (D_0), while those with f label, due to the parity conservation, to the HCN molecule with J=1 and the He atom which is higher in energy by about 2BHCN ˜ 2.96 cm-1 than D_0, as discussed in the infrared study of He-HF. The PES obtained in the present analysis indicates that four f levels in the j = 1 and 2 excited states are bound above the "dissociation limit" (D_0) due to the parity conservation. In addition five levels (both of e and f labels) are predicted to be bound by centrifugal barrier with finite life times but not yet observed. K. Harada, K. Tanaka, T. Tanaka, S. Nanbu, and M. Aoyagi, J. Chem. Phys. 117, 7041 (2002). C. M. Lovejoy and D. J. Nesbitt, J. Chem. Phys. 93, 5387 (1990).

  12. Electronic properties of hydrogen-bonded complexes of benzene(HCN)(1-4): comparison with benzene(H2O)(1-4).

    PubMed

    Mateus, M P S; Galamba, N; Cabral, B J Costa

    2011-11-24

    The electronic properties, specifically, the dipole and quadrupole moments and the ionization energies of benzene (Bz) and hydrogen cyanide (HCN), and the respective binding energies, of complexes of Bz(HCN)(1-4), have been studied through MP2 and OVGF calculations. The results are compared with the properties of benzene-water complexes, Bz(H(2)O)(1-4), with the purpose of analyzing the electronic properties of microsolvated benzene, with respect to the strength of the CH/π and OH/π hydrogen-bond (H-bond) interactions. The linear HCN chains have the singular ability to interact with the aromatic ring, preserving the symmetry of the latter. A blue shift of the first vertical ionization energies (IEs) of benzene is observed for the linear Bz(HCN)(1-4) clusters, which increases with the length of the chain. NBO analysis indicates that the increase of the IE with the number of HCN molecules is related to a strengthening of the CH/π H-bond, driven by cooperative effects, increasing the acidity of the hydrogen cyanide H atom involved in the π H-bond. The longer HCN chains (n ≥ 3), however, can bend to form CH/N H-bonds with the Bz H atoms. These cyclic structures are found to be slightly more stable than their linear counterparts. For the nonlinear Bz(HCN)(3-4) and Bz(H(2)O)(2-4) complexes, an increase of the binding energy with the number of solvent molecules and a decrease of the IE of benzene, relative to the values for the Bz(HCN) and Bz(H(2)O) complexes, respectively, are observed. Although a strengthening of the CH/π and OH/π H-bonds, with increasing n, also takes place for the Bz(H(2)O)(2-4) and Bz(HCN)(3-4) nonlinear complexes, Bz proton donor, CH/O, and CH/N interactions are at the origin of this decrease. Thus CH/π and OH/π H-bonds lead to higher IEs of Bz, whereas the weaker CH/N and CH/O H-bond interactions have the opposite effect. The present results emphasize the importance of both aromatic XH/π (X = C, O) and CH/X (X = N, O) interactions for

  13. Electric pulse current stimulation increases electrophysiological properties of If current reconstructed in mHCN4-transfected canine mesenchymal stem cells

    PubMed Central

    FENG, YUANYUAN; LUO, SHOUMING; YANG, PAN; SONG, ZHIYUAN

    2016-01-01

    The ‘funny’ current, also known as the If current, play a crucial role in the spontaneous diastolic depolarization of sinoatrial node cells. The If current is primarily induced by the protein encoded by the hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4) gene. The functional If channel can be reconstructed in canine mesenchymal stem cells (cMSCs) transfected with mouse HCN4 (mHCN4). Biomimetic studies have shown that electric pulse current stimulation (EPCS) can promote cardiogenesis in cMSCs. However, whether EPCS is able to influence the properties of the If current reconstructed in mHCN4-transfected cMSCs remains unclear. The present study aimed to investigate the effects of EPCS on the If current reconstructed in mHCN4-transfected cMSCs. The cMSCs were transfected with the lentiviral vector pLentis-mHCN4-GFP. Following transfection, these cells were divided into two groups: mHCN4-transfected cMSCs (group A), and mHCN4-transfected cMSCs induced by EPCS (group B). Using a whole cell patch-clamp technique, the If current was recorded, and group A cMSCs showed significant time and voltage dependencies and sensitivity to extracellular Cs+. The half-maximal activation (V1/2) value was −101.2±4.6 mV and the time constant of activation was 324±41 msec under −160 mV. In the group B cells the If current increased obviously and activation curve moved to right. The absolute value of V1/2 increased significantly to −92.4±4.8 mV (P<0.05), and the time constant of activation diminished under the same command voltage (251±44 vs. 324±41, P<0.05). In addition, the mRNA and protein expression levels of HCN4, connexin 43 (Cx43) and Cx45 were upregulated in group B compared with group A, as determined by reverse transcription-quantitative polymerase chain reaction and western blot analyses. Transmission electron micrographs also confirmed the increased gap junctions in group B. Collectively, these results indicated that reconstructed If channels

  14. Electric pulse current stimulation increases electrophysiological properties of If current reconstructed in mHCN4-transfected canine mesenchymal stem cells.

    PubMed

    Feng, Yuanyuan; Luo, Shouming; Yang, Pan; Song, Zhiyuan

    2016-04-01

    The 'funny' current, also known as the If current, play a crucial role in the spontaneous diastolic depolarization of sinoatrial node cells. The If current is primarily induced by the protein encoded by the hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4) gene. The functional If channel can be reconstructed in canine mesenchymal stem cells (cMSCs) transfected with mouse HCN4 (mHCN4). Biomimetic studies have shown that electric pulse current stimulation (EPCS) can promote cardiogenesis in cMSCs. However, whether EPCS is able to influence the properties of the If current reconstructed in mHCN4-transfected cMSCs remains unclear. The present study aimed to investigate the effects of EPCS on the If current reconstructed in mHCN4-transfected cMSCs. The cMSCs were transfected with the lentiviral vector pLentis-mHCN4-GFP. Following transfection, these cells were divided into two groups: mHCN4-transfected cMSCs (group A), and mHCN4-transfected cMSCs induced by EPCS (group B). Using a whole cell patch-clamp technique, the If current was recorded, and group A cMSCs showed significant time and voltage dependencies and sensitivity to extracellular Cs+. The half-maximal activation (V1/2) value was -101.2±4.6 mV and the time constant of activation was 324±41 msec under -160 mV. In the group B cells the If current increased obviously and activation curve moved to right. The absolute value of V1/2 increased significantly to -92.4±4.8 mV (P<0.05), and the time constant of activation diminished under the same command voltage (251±44 vs. 324±41, P<0.05). In addition, the mRNA and protein expression levels of HCN4, connexin 43 (Cx43) and Cx45 were upregulated in group B compared with group A, as determined by reverse transcription-quantitative polymerase chain reaction and western blot analyses. Transmission electron micrographs also confirmed the increased gap junctions in group B. Collectively, these results indicated that reconstructed If channels may have a

  15. Dense gas in low-metallicity galaxies

    NASA Astrophysics Data System (ADS)

    Braine, J.; Shimajiri, Y.; André, P.; Bontemps, S.; Gao, Yu; Chen, Hao; Kramer, C.

    2017-01-01

    Stars form out of the densest parts of molecular clouds. Far-IR emission can be used to estimate the star formation rate (SFR) and high dipole moment molecules, typically HCN, trace the dense gas. A strong correlation exists between HCN and far-IR emission, with the ratio being nearly constant, over a large range of physical scales. A few recent observations have found HCN to be weak with respect to the far-IR and CO in subsolar metallicity (low-Z) objects. We present observations of the Local Group galaxies M 33, IC 10, and NGC 6822 with the IRAM 30 m and NRO 45 m telescopes, greatly improving the sample of low-Z galaxies observed. HCN, HCO+, CS, C2H, and HNC have been detected. Compared to solar metallicity galaxies, the nitrogen-bearing species are weak (HCN, HNC) or not detected (CN, HNCO, N2H+) relative to far-IR or CO emission. HCO+ and C2H emission is normal with respect to CO and far-IR. While 13CO is the usual factor 10 weaker than 12CO, C18O emission was not detected down to very low levels. Including earlier data, we find that the HCN/HCO+ ratio varies with metallicity (O/H) and attribute this to the sharply decreasing nitrogen abundance. The dense gas fraction, traced by the HCN/CO and HCO+/CO ratios, follows the SFR but in the low-Z objects the HCO+ is much easier to measure. Combined with larger and smaller scale measurements, the HCO+ line appears to be an excellent tracer of dense gas and varies linearly with the SFR for both low and high metallicities.

  16. Distribution of Water Vapor in Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Melnick, Gary J.; Tolls, Volker; Snell, Ronald L.; Bergin, Edwin A.; Hollenbach, David J.; Kaufman, Michael J.; Li, Di; Neufeld, David A.

    2011-01-01

    We report the results of a large-area study of water vapor along the Orion Molecular Cloud ridge, the purpose of which was to determine the depth-dependent distribution of gas-phase water in dense molecular clouds. We find that the water vapor measured toward 77 spatial positions along the face-on Orion ridge, excluding positions surrounding the outflow associated with BN/KL and IRc2, display integrated intensities that correlate strongly with known cloud surface tracers such as CN, C2H, 13CO J = 5-4, and HCN, and less well with the volume tracer N2H+. Moreover, at total column densities corresponding to A V< 15 mag, the ratio of H2O to C18O integrated intensities shows a clear rise approaching the cloud surface. We show that this behavior cannot be accounted for by either optical depth or excitation effects, but suggests that gas-phase water abundances fall at large A V. These results are important as they affect measures of the true water-vapor abundance in molecular clouds by highlighting the limitations of comparing measured water-vapor column densities with such traditional cloud tracers as 13CO or C18O. These results also support cloud models that incorporate freeze out of molecules as a critical component in determining the depth-dependent abundance of water vapor.

  17. Production of hyperpolarized 13CO2 from [1-13C]pyruvate in perfused liver does reflect total anaplerosis but is not a reliable biomarker of glucose production

    PubMed Central

    Moreno, Karlos X.; Moore, Christopher L.; Burgess, Shawn C.; Sherry, A. Dean; Malloy, Craig R.

    2015-01-01

    In liver, 13CO2 can be generated from [1-13C] pyruvate via pyruvate dehydrogenase or anaplerotic entry of pyruvate into the TCA cycle followed by decarboxylation at phosphoenolpyruvate carboxykinase (PEPCK), the malic enzyme, isocitrate dehydrogenase, or α-ketoglutarate dehydrogenase. The purpose of this study was to determine the relative importance of these pathways in production of hyperpolarized (HP) 13CO2 after administration of hyper-polarized pyruvate in livers supplied with a fatty acid plus substrates for gluconeogenesis. Isolated mouse livers were perfused with a mixture of thermally-polarized 13C-enriched pyruvate, lactate and octanoate in various combinations prior to exposure to HP pyruvate. Under all perfusion conditions, HP malate, aspartate and fumarate were detected within ~ 3 s showing that HP [1-13C]pyruvate is rapidly converted to [1-13C]oxaloacetate which can subsequently produce HP 13CO2 via decarboxylation at PEPCK. Measurements using HP [2-13C]pyruvate allowed the exclusion of reactions related to TCA cycle turnover as sources of HP 13CO2. Direct measures of O2 consumption, ketone production, and glucose production by the intact liver combined with 13C isotopomer analyses of tissue extracts yielded a comprehensive profile of metabolic flux in perfused liver. Together, these data show that, even though the majority of HP 13CO2 derived from HP [1-13C]pyruvate in livers exposed to fatty acids reflects decarboxylation of [4-13C]oxaloacetate (PEPCK) or [4-13C]malate (malic enzyme), the intensity of the HP 13CO2 signal is not proportional to glucose production because the amount of pyruvate returned to the TCA cycle via PEPCK and pyruvate kinase is variable, depending upon available substrates. PMID:26543443

  18. Seasonal variations of the amount of carbon allocated to respiration after in situ 13CO2 pulse labelling of trees (Invited)

    NASA Astrophysics Data System (ADS)

    Epron, D.; Dannoura, M.; Ngao, J.; Plain, C.; Berveller, D.; Chipeaux, C.; Gerant, D.; Bosc, A.; Maillard, P.; Loustau, D.; Damesin, C.; Cats Project (Anr-07-Blan-0109)

    2010-12-01

    Soil and trunk respiration are the major sources of carbon from forest ecosystems to the atmosphere and they account for a large fraction of total ecosystem respiration. The amount of photosynthate allocated to respiration affects the growth of the tree and the potential for carbon sequestration of forest ecosystems. This study, aiming at understanding patterns of carbon allocation to respiration among species and seasons, consisted in pure 13CO2 labelling of the entire crown of three different tree species (beech, oak and pine) at distinct phenological stages between Sept 2008 and Feb 2010. 13C was then tracked for several weeks in soil and trunk CO2 efflux at high temporal resolution using tuneable diode laser absorption spectrometry (Plain et al. 2009). Recovery of 13C in trunk and soil CO2 efflux was observed a few couple of hours after the beginning of the labelling in oak and beech. There is a rapid transfer of 13C belowground with a maximum occurring within 2 to 4 days after labelling. Label was recovered at the same time in the respiration and in the biomass of both fine roots and microbes. Maximum recovery occurred earlier in beech and oak, while it happened later in Pine. Indeed, the velocity of phloem transport, calculated as the difference of time lags in 13C recovery in trunk respiration at different height, was around 0.10-0.2m/h in pine and around 0.2-1.2 m/h in oak and beech, reflecting difference in phloem anatomy between angiosperm and gymnosperm. The cumulated amount of label recovered in soil CO2 efflux 20 days after labelling varied among the seasons in all species, from 1 to 16% in beech, 2 to 11% in oak and 1 to 11% in pine. For all species, allocation to soil respiration was greater in early summer compared to spring, late summer and autumn. A compartmental analysis is further conducted to characterise functional pools of labelled substrates and storage compounds that contribute to both trunk and soil respiration. [Plain C, Gérant D

  19. Influence of air-staging on the concentration profiles of NH{sub 3} and HCN in the combustion chamber of a CFB boiler burning coal

    SciTech Connect

    Kassman, H.; Karlsson, M.; Aamand, L.E.

    1999-07-01

    The characterization of the concentration profiles of NH{sub 3} and HCN are of great importance for increasing the knowledge of the formation and destruction pathways of NO and N{sub 2}O in a fluidized bed boiler. Further improvements of the sampling methods for the determination of both NH{sub 3} and HCN in the combustion chamber in full-scale CFB boilers are also needed. A gas-sampling probe connected to a Fourier Transform Infrared (FTIR) instrument and a gas-quenching (GQ) probe in which the sample is quenched directly in the probe tip by a circulating trapper solution were used. The FTIR technique is based on analysis of hot combustion gases, whereas the trapper solutions from the GQ probe were analyzed by means of wet chemistry. The tests were performed during coal combustion in a 12 MW CFB boiler, which was operated at three air-staging cases with the addition of limestone for sulfur capture. The concentration profiles of NH{sub 3} and HCN in the combustion chamber showed a different pattern concerning the influence of air-staging. The highest levels of NH{sub 3} were observed during reducing condition (severe air-staging), and the lowest were found under oxidizing conditions (no air-staging). The levels of HCN were much lower than those measured for NH{sub 3}. The highest levels of HCN were observed for reversed air-staging and severe air-staging showed almost no HCN. The potential reactors involving NH{sub 3} and HCN in the combustion chamber as well as the potential measurement errors in each sampling technique are discussed for the three air-staging cases.

  20. RESOLVING THE BRIGHT HCN(1–0) EMISSION TOWARD THE SEYFERT 2 NUCLEUS OF M51: SHOCK ENHANCEMENT BY RADIO JETS AND WEAK MASING BY INFRARED PUMPING?

    SciTech Connect

    Matsushita, Satoki; Trung, Dinh-V-; Boone, Frédéric; Krips, Melanie; Lim, Jeremy; Muller, Sebastien

    2015-01-20

    We present high angular resolution observations of the HCN(1-0) emission (at ∼1'' or ∼34 pc), together with CO J = 1-0, 2-1, and 3-2 observations, toward the Seyfert 2 nucleus of M51 (NGC 5194). The overall HCN(1-0) distribution and kinematics are very similar to that of the CO lines, which have been indicated as the jet-entrained molecular gas in our past observations. In addition, high HCN(1-0)/CO(1-0) brightness temperature ratio of about unity is observed along the jets, similar to that observed at the shocked molecular gas in our Galaxy. These results strongly indicate that both diffuse and dense gases are entrained by the jets and outflowing from the active galactic nucleus. The channel map of HCN(1-0) at the systemic velocity shows a strong emission right at the nucleus, where no obvious emission has been detected in the CO lines. The HCN(1-0)/CO(1-0) brightness temperature ratio at this region reaches >2, a value that cannot be explained considering standard physical/chemical conditions. Based on our calculations, we suggest infrared pumping and possibly weak HCN masing, but still requiring an enhanced HCN abundance for the cause of this high ratio. This suggests the presence of a compact dense obscuring molecular gas in front of the nucleus of M51, which remains unresolved at our ∼1'' (∼34 pc) resolution, and consistent with the Seyfert 2 classification picture.

  1. State-to-state reaction dynamics of R+HCN (ν1νl22ν3)→RH+CN(v, J) with R=Cl, H

    NASA Astrophysics Data System (ADS)

    Kreher, Christoph; Theinl, Robert; Gericke, Karl-Heinz

    1996-03-01

    Vibrational overtone excitation of HCN in the wavelength region 6 500 cm-1-18 000 cm-1 is used to initiate the endothermic reaction of chlorine and hydrogen atoms with HCN. HCN is excited to the overtone levels (002), (004), (302), (105), and (1115). The labeling of the vibrational levels (ν1ν2l2ν3) corresponds to the normal modes ν1=CN, ν2=bend, ν3=CH, and l2=vibrational angular momentum. The product state distribution of CN(X 2Σ+) is completely analyzed by laser induced fluorescence (LIF). Excitation of the first overtone of CH-stretch leads to vibrationally excited CN in the reaction of Cl+HCN(002), implying the existence of a long living complex. The CN vibrational excitation increases with increasing H-CN stretch excitation. However, a slightly higher CN vibrational excitation is found when at the same internal energy of HCN three quanta of CN-stretch and two quanta of CH-stretch are excited. Therefore, the energy is not completely redistributed in the collision complex. The ratio of rate constants between the reactions of HCN(004) and HCN(302) with Cl is 2.8±0.6. The CN product vibrational excitation decreases again, when HCN is excited to the (105) state. At these high HCN vibrational energies the reaction mechanism seems to change toward a more direct reaction where the time left is not sufficient for energy randomization. The reaction of hydrogen with HCN(004) leads to CN-products with a similar vibrational distribution, as in the case of chlorine, but with a lower rotational excitation. The reaction H+HCN(302) shows no significant generation of CN products and a lower limit of the ratio of rate constants, k(004)/k(302)≳4, is obtained.

  2. Preparation and characterization of 18650 Li(Ni 1/3Co 1/3Mn 1/3)O 2/graphite high power batteries

    NASA Astrophysics Data System (ADS)

    He, Yan-Bing; Tang, Zhi-Yuan; Song, Quan-Sheng; Xie, Hui; Yang, Quan-Hong; Liu, Yuan-Gang; Ling, Guo-Wei

    The commercial 18650 Li(Ni 1/3Co 1/3Mn 1/3)O 2/graphite high power batteries were prepared and their electrochemical performance at temperatures of 25 and 50 °C was extensively investigated. The results showed that the charge-transfer resistance (R ct) and solid electrolyte interface resistance (R sei) of the high power batteries at 25 °C decreased as states of charge (SOC) increased from 0 to 60%, whereas R ct and R sei increased as SOC increased from 60 to 100%. The discharge plateau voltage of batteries reduced greatly with the increase in discharge rate at both 25 and 50 °C. The high power batteries could be discharged at a very wide current range to deliver most of their capacity and also showed excellent power cycling performance with discharge rate of as high as 10 C at 25 °C. The elevated working temperature did not influence the battery discharge capacity and cycling performance at lower discharge rates (e.g. 0.5, 1, and 5 C), while it resulted in lower discharge capacity at higher discharge rates (e.g. 10 and 15 C) and bad cycling performance at discharge rate of 10 C. The batteries also exhibited excellent cycle performance at charge rate of as high as 8 C and discharge rate of 10 C.

  3. Improved electrolyte and its application in LiNi1/3Mn1/3Co1/3O2-Graphite full cells

    NASA Astrophysics Data System (ADS)

    Liu, Minghong; Dai, Fang; Ma, Zhiru; Ruthkosky, Marty; Yang, Li

    2014-12-01

    Lithium oxalatodifluoroborate (LiODFB) has been synthesized and used as a novel electrolyte additive. Standard and modified electrolytes were flame-sealed in NMR tubes and stored at 60 °C for 3 months. Multiple nuclear NMR (1H, 11B, 13C, 19F, 31P) studies confirmed that the modified electrolyte (2% LiODFB added) showed no signs of decomposition as that of regular electrolyte, which is possibly due to the -F of LiPF6 and oxalate of LiODFB ligand exchange effect. The high temperature stabilization mechanism of the added LiODFB was studied using quantum mechanical calculations. Electrochemical tests of LiNi1/3Mn1/3Co1/3O2 (NMC)-Graphite full-cells with and without LiODFB as the electrolyte additive were conducted. When cycling with the NMC-Graphite full-cell at elevated temperature (60 °C), the 100th cycle capacity retention rate of the modified electrolyte was 60%, compared to 27% with the standard electrolyte. The EIS study indicates the full-cells with LiODFB have much lower interfacial impedance than the standard cells. Theoretical calculations reveal that LiODFB generates a layer of thin and resilient SEI on the graphite surface at a higher reduction potential than ethylene carbonate (EC) due to its higher ring strain and protects graphite from the toxic Mn2+ resulting in improved electrochemical performance of NMC-Graphite based cells.

  4. 13CO2/12CO2 isotope ratio analysis in human breath using a 2 μm diode laser

    NASA Astrophysics Data System (ADS)

    Sun, Mingguo; Cao, Zhensong; Liu, Kun; Wang, Guishi; Tan, Tu; Gao, Xiaoming; Chen, Weidong; Yinbo, Huang; Ruizhong, Rao

    2015-04-01

    The bacterium H. pylori is believed to cause peptic ulcer. H. pylori infection in the human stomach can be diagnosed through a CO2 isotope ratio measure in exhaled breath. A laser spectrometer based on a distributed-feedback semiconductor diode laser at 2 μm is developed to measure the changes of 13CO2/12CO2 isotope ratio in exhaled breath sample with the CO2 concentration of ~4%. It is characterized by a simplified optical layout, in which a single detector and associated electronics are used to probe CO2 spectrum. A new type multi-passes cell with 12 cm long base length , 29 m optical path length in total and 280 cm3 volume is used in this work. The temperature and pressure are well controlled at 301.15 K and 6.66 kPa with fluctuation amplitude of 25 mK and 6.7 Pa, respectively. The best 13δ precision of 0.06o was achieved by using wavelet denoising and Kalman filter. The application of denoising and Kalman filter not only improved the signal to noise ratio, but also shorten the system response time.

  5. IRAM 30 m Large Scale Survey of 12CO(2-1) and 13CO(2-1) Emission in the Orion Molecular Cloud

    NASA Astrophysics Data System (ADS)

    Berné, O.; Marcelino, N.; Cernicharo, J.

    2014-11-01

    Using the IRAM 30 m telescope, we have surveyed a 1 × 0.°8 part of the Orion molecular cloud in the 12CO and 13CO (2-1) lines with a maximal spatial resolution of ~11'' and spectral resolution of ~0.4 km s-1. The cloud appears filamentary, clumpy, and with a complex kinematical structure. We derive an estimated mass of the cloud of 7700 M ⊙ (half of which is found in regions with visual extinctions AV below ~10) and a dynamical age for the nebula of the order of 0.2 Myr. The energy balance suggests that magnetic fields play an important role in supporting the cloud, at large and small scales. According to our analysis, the turbulent kinetic energy in the molecular gas due to outflows is comparable to turbulent kinetic energy resulting from the interaction of the cloud with the H II region. This latter feedback appears negative, i.e., the triggering of star formation by the H II region is inefficient in Orion. The reduced data as well as additional products such as the column density map are made available online (http://userpages.irap.omp.eu/~oberne/Olivier_Berne/Data).

  6. CO, NOx and 13CO2 as tracers for fossil fuel CO2: results from a pilot study in Paris during winter 2010

    NASA Astrophysics Data System (ADS)

    Lopez, M.; Schmidt, M.; Delmotte, M.; Colomb, A.; Gros, V.; Janssen, C.; Lehman, S. J.; Mondelain, D.; Perrussel, O.; Ramonet, M.; Xueref-Remy, I.; Bousquet, P.

    2013-08-01

    Measurements of the mole fraction of the CO2 and its isotopes were performed in Paris during the MEGAPOLI winter campaign (January-February 2010). Radiocarbon (14CO2) measurements were used to identify the relative contributions of 77% CO2 from fossil fuel consumption (CO2ff from liquid and gas combustion) and 23% from biospheric CO2 (CO2 from the use of biofuels and from human and plant respiration: CO2bio). These percentages correspond to average mole fractions of 26.4 ppm and 8.2 ppm for CO2ff and CO2bio, respectively. The 13CO2 analysis indicated that gas and liquid fuel contributed 70% and 30%, respectively, of the CO2 emission from fossil fuel use. Continuous measurements of CO and NOx and the ratios CO/CO2ff and NOx/CO2ff derived from radiocarbon measurements during four days make it possible to estimate the fossil fuel CO2 contribution over the entire campaign. The ratios CO/CO2ff and NOx/CO2ff are functions of air mass origin and exhibited daily ranges of 7.9 to 14.5 ppb ppm-1 and 1.1 to 4.3 ppb ppm-1, respectively. These ratios are consistent with different emission inventories given the uncertainties of the different approaches. By using both tracers to derive the fossil fuel CO2, we observed similar diurnal cycles with two maxima during rush hour traffic.

  7. Impact of morphological changes of LiNi1/3Mn1/3Co1/3O2 on lithium-ion cathode performances

    NASA Astrophysics Data System (ADS)

    Cabelguen, Pierre-Etienne; Peralta, David; Cugnet, Mikael; Maillet, Pascal

    2017-04-01

    Major advances in Li-ion battery technology rely on the nanostructuration of active materials to overcome the severe kinetics limitations of new - cheaper and safer - chemistries. However, opening porosities results in the decrease of volumetric performances, closing the door to significant applications such as portable electronics, electromobility, and grid storage. In this study, we analyze the link between morphologies and performances of model LiNi1/3Mn1/3Co1/3O2 materials. By quantifying exhaustively their microstructures using nitrogen adsorption, mercury intrusion porosimetry, and helium pycnometry, we can discuss how porosities and surface areas are linked to the electrochemical behavior. There is no geometrical parameters that can predict the performances of all our materials. The shape of agglomeration dictates the electrochemical behavior. A huge drop in volumetric performances is measured when microstructure is considered. We show that gravimetric and volumetric power performances are contrary to each other. Highly dense materials exhibit, by far, the best power performances in terms of volumetric figures, so that opening porosities might not be the best strategy, even in non-nanosized materials, for Li-ion battery technology.

  8. Effects of experimental conditions on the formation of NH{sub 3}, HCN and H{sub 2}S during the pyrolysis of a brown coal

    SciTech Connect

    Tan, L.L.; Li, C.Z.

    1999-07-01

    A Victorian brown coal was pyrolyzed in a quartz reactor. The reactor has some features of a drop-tube reactor and of a fixed-bed reactor, capable of operating at fast and slow heating rates. Experimental results indicated that thermal cracking of char was an important source of NH{sub 3}, H{sub 2} and HCN (as well as H{sub 2}S) during the pyrolysis of the brown coal. The yield of HCN was found to change with gas flow rate and coal feeding rate, suggesting that HCN (or its precursors) could interact significantly with the nascent char but not to yield NH{sub 3}. The yields of HCN and NH{sub 3} were both sensitive to changes in heating rate. The effects of heating rate could be partly explained by the graphitization/condensation reactions, making the N-containing heteroaromatic ring systems increasingly stable, during the extended holding at high temperatures at the slow heating rate. Experimental results indicated that HCN does not significantly convert to NH{sub 3}, either on the char surface or in the gas phase, at least during the pyrolysis of the brown coal. The changes in heating rate or coal feeding rate did not affect significantly the formation of H{sub 2}S.

  9. Reversal of infall in SgrB2(M) revealed by Herschel/HIFI observations of HCN lines at THz frequencies

    NASA Astrophysics Data System (ADS)

    Rolffs, R.; Schilke, P.; Comito, C.; Bergin, E. A.; van der Tak, F. F. S.; Lis, D. C.; Qin, S.-L.; Menten, K. M.; Güsten, R.; Bell, T. A.; Blake, G. A.; Caux, E.; Ceccarelli, C.; Cernicharo, J.; Crockett, N. R.; Daniel, F.; Dubernet, M.-L.; Emprechtinger, M.; Encrenaz, P.; Gerin, M.; Giesen, T. F.; Goicoechea, J. R.; Goldsmith, P. F.; Gupta, H.; Herbst, E.; Joblin, C.; Johnstone, D.; Langer, W. D.; Latter, W. D.; Lord, S. D.; Maret, S.; Martin, P. G.; Melnick, G. J.; Morris, P.; Müller, H. S. P.; Murphy, J. A.; Ossenkopf, V.; Pearson, J. C.; Pérault, M.; Phillips, T. G.; Plume, R.; Schlemmer, S.; Stutzki, J.; Trappe, N.; Vastel, C.; Wang, S.; Yorke, H. W.; Yu, S.; Zmuidzinas, J.; Diez-Gonzalez, M. C.; Bachiller, R.; Martin-Pintado, J.; Baechtold, W.; Olberg, M.; Nordh, L. H.; Gill, J. J.; Chattopadhyay, G.

    2010-10-01

    Aims: To investigate the accretion and feedback processes in massive star formation, we analyze the shapes of emission lines from hot molecular cores, whose asymmetries trace infall and expansion motions. Methods: The high-mass star forming region SgrB2(M) was observed with Herschel/HIFI (HEXOS key project) in various lines of HCN and its isotopologues, complemented by APEX data. The observations are compared to spherically symmetric, centrally heated models with density power-law gradient and different velocity fields (infall or infall+expansion), using the radiative transfer code RATRAN. Results: The HCN line profiles are asymmetric, with the emission peak shifting from blue to red with increasing J and decreasing line opacity (HCN to H13CN). This is most evident in the HCN 12-11 line at 1062 GHz. These line shapes are reproduced by a model whose velocity field changes from infall in the outer part to expansion in the inner part. Conclusions: The qualitative reproduction of the HCN lines suggests that infall dominates in the colder, outer regions, but expansion dominates in the warmer, inner regions. We are thus witnessing the onset of feedback in massive star formation, starting to reverse the infall and finally disrupting the whole molecular cloud. To obtain our result, the THz lines uniquely covered by HIFI were critically important. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  10. Binding of the auxiliary subunit TRIP8b to HCN channels shifts the mode of action of cAMP.

    PubMed

    Hu, Lei; Santoro, Bina; Saponaro, Andrea; Liu, Haiying; Moroni, Anna; Siegelbaum, Steven

    2013-12-01

    Hyperpolarization-activated cyclic nucleotide-regulated cation (HCN) channels generate the hyperpolarization-activated cation current Ih present in many neurons. These channels are directly regulated by the binding of cAMP, which both shifts the voltage dependence of HCN channel opening to more positive potentials and increases maximal Ih at extreme negative voltages where voltage gating is complete. Here we report that the HCN channel brain-specific auxiliary subunit TRIP8b produces opposing actions on these two effects of cAMP. In the first action, TRIP8b inhibits the effect of cAMP to shift voltage gating, decreasing both the sensitivity of the channel to cAMP (K1/2) and the efficacy of cAMP (maximal voltage shift); conversely, cAMP binding inhibits these actions of TRIP8b. These mutually antagonistic actions are well described by a cyclic allosteric mechanism in which TRIP8b binding reduces the affinity of the channel for cAMP, with the affinity of the open state for cAMP being reduced to a greater extent than the cAMP affinity of the closed state. In a second apparently independent action, TRIP8b enhances the action of cAMP to increase maximal Ih. This latter effect cannot be explained by the cyclic allosteric model but results from a previously uncharacterized action of TRIP8b to reduce maximal current through the channel in the absence of cAMP. Because the binding of cAMP also antagonizes this second effect of TRIP8b, application of cAMP produces a larger increase in maximal Ih in the presence of TRIP8b than in its absence. These findings may provide a mechanistic explanation for the wide variability in the effects of modulatory transmitters on the voltage gating and maximal amplitude of Ih reported for different neurons in the brain.

  11. The Titan 14N/ 15N and 12C/ 13C isotopic ratios in HCN from Cassini/CIRS

    NASA Astrophysics Data System (ADS)

    Vinatier, Sandrine; Bézard, Bruno; Nixon, Conor A.

    2007-11-01

    We report the detection of H 13CN and HC 15N in mid-infrared spectra recorded by the Composite Infrared Spectrometer (CIRS) aboard Cassini, along with the determination of the 12C/ 13C and 14N/ 15N isotopic ratios. We analyzed two sets of limb spectra recorded near 13-15° S (Tb flyby) and 83° N (T4 flyby) at 0.5 cm -1 resolution. The spectral range 1210-1310 cm -1 was used to retrieve the temperature profile in the range 145-490 km at 13° S and 165-300 km at 83° N. These two temperature profiles were then incorporated in the atmospheric model to retrieve the abundance profile of H 12C 14N, H 13CN and HC 15N from their bands at 713, 706 and 711 cm -1, respectively. The HCN abundance profile was retrieved in the range 90-460 km at 15° S and 165-305 km at 83° N. There is no evidence for vertical variations of the isotopic ratios. Constraining the isotopic abundance profiles to be proportional to the HCN one, we find C12/C13=89-18+22 at 15° S, and 68-12+16 at 83° N, two values that are statistically consistent. A combination of these results yields a 12C/ 13C value equal to 75±12. This global result, as well as the 15° S one, envelop the value in Titan's methane ( 82.3±1) [Niemann, H.B., and 17 colleagues, 2005. Nature 438, 779-784] measured at 10° S and is slightly lower than the terrestrial inorganic standard value (89). The 14N/ 15N isotopic ratio is found equal to 56-13+16 at 15° S and 56-9+10 at 83° N. Combining the two values yields 14N/ 15N = 56 ± 8, which corresponds to an enrichment in 15N of about 4.9 compared with the terrestrial ratio. These results agree with the values obtained from previous ground-based millimeter observations [Hidayat, T., Marten, A., Bézard, B., Gautier, D., Owen, T., Matthews, H.E., Paubert, G., 1997. Icarus 126, 170-182; Marten, A., Hidayat, T., Biraud, Y., Moreno, R., 2002. Icarus 158, 532-544]. The 15N/ 14N ratio found in HCN is ˜3 times higher than in N 2 [Niemann, H.B., and 17 colleagues, 2005. Nature 438, 779

  12. Constraints on the Formation of Comets from D/H Ratios Measured in H 2O and HCN

    NASA Astrophysics Data System (ADS)

    Mousis, Olivier; Gautier, Daniel; Bockelée-Morvan, Dominique; Robert, François; Dubrulle, Bérengère; Drouart, Antoine

    2000-12-01

    This report is the follow-up of the paper of A. Drouart et al. (1999, Icarus140, 129) in which it was demonstrated that appropriate models of the solar nebula permit us to interpret the deuterium enrichment in water with respect to the protosolar D/H ratio measured in LL3 meteorites and comets. In the present report, we show that the models selected by Drouart et al. are also able to explain D/H in HCN measured in Comet C/1995 O1 (Hale-Bopp). We find that the D/H ratio in HCN entering the nebula is ˜4×10 -3, which is significantly less than values measured in cold dark clouds, but consistent with values found in hot molecular cores. Both H 2O and HCN ices infalling from the presolar cloud onto the nebula discoid evaporated in the turbulent part of the nebula, isotopically exchanged with hydrogen, and mixed with water vapor coming from the inner part of the nebula. Subsequently, H 2O and HCN ices with D/H ratios measured in Comet Hale-Bopp condensed, agglomerated and were incorporated in cometesimals. In the light of these results, we discuss the story of molecules detected in comets coming from Oort cloud. Most molecules detected in Comet Hale-Bopp originated from ices embedded in the presolar cloud. Ices vaporized prior to entering into the nebula or in the early nebula, and subsequently recondensed, except highly volatile molecules. According to A. Kouchi et al. (1994, Astron. Astrophys.290, 1009), water ice condensed in crystalline form. We discuss the possibility that the most volatile species were then trapped in the form of clathrate hydrates. The oversolar C/N ratio and the strong depletion of Ne/O with respect to the solar abundance observed in comets are in agreement with the theory of clathrate hydrates of J. I. Lunine and D. J. Stevenson (1985, Astrophys. suppl. Ser.58, 493). Comets formed in the Kuiper belt may contain amorphous water ice and have kept the isotopic signature of the presolar cloud. New published models of interiors of Uranus and

  13. Microwave Plasma Chemical Vapor Deposition of Carbon Coatings on LiNi1/3Co1/3Mn1/3O2 for Li-Ion Battery Composite Cathodes

    SciTech Connect

    Doeff, M.M.; Kostecki, R.; Marcinek, M.; Wilcoc, J.D.

    2008-12-10

    In this paper, we report results of a novel synthesis method of thin film conductive carbon coatings on LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} cathode active material powders for lithium-ion batteries. Thin layers of graphitic carbon were produced from a solid organic precursor, anthracene, by a one-step microwave plasma chemical vapor deposition (MPCVD) method. The structure and morphology of the carbon coatings were examined using SEM, TEM, and Raman spectroscopy. The composite LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} electrodes were electrochemically tested in lithium half coin cells. The composite cathodes made of the carbon-coated LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} powder showed superior electrochemical performance and increased capacity compared to standard composite LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} electrodes.

  14. The global carbon cycle over the last millennium: implications of the latest Law Dome and South Pole firn and ice core records of CO2 and δ13CO2

    NASA Astrophysics Data System (ADS)

    Trudinger, C. M.; Rubino, M.; Etheridge, D. M.; Raupach, M. R.; Harman, I. N.

    2012-12-01

    The Law Dome δ 13CO2 ice core record has recently been revised and merged with new firn and ice core measurements. Here we present calculations with a globally-aggregated carbon cycle model looking at both natural variability and the industrial perturbation in CO2 and δ 13CO2. We investigate the use of observations of CO2, {}13CO2 and {}14CO2 to calibrate the Simple Carbon-Climate Model (SCCM), including the implications of the slightly lower preindustrial δ 13C levels in the latest record. We also present a Kalman filter double deconvolution that uses CO2 and δ 13CO2 measurements to infer net fluxes of CO2 between the atmosphere, land and oceans, focussing on decadal variability over the industrial period and century-scale variations back to 1000 AD. We will compare the results of the double deconvolution with calculations of SCCM forced with temperature variations to improve our understanding of the sensitivity of land and ocean carbon fluxes to climate on different timescales.

  15. Wide-field 12CO (J=2-1) and 13CO (J=2-1) Observations toward the Aquila Rift and Serpens Molecular Cloud Complexes. I. Molecular Clouds and Their Physical Properties

    NASA Astrophysics Data System (ADS)

    Nakamura, Fumitaka; Dobashi, Kazuhito; Shimoikura, Tomomi; Tanaka, Tomohiro; Onishi, Toshikazu

    2017-03-01

    We present the results of wide-field 12CO (J=2{--}1) and 13CO (J=2{--}1) observations toward the Aquila Rift and Serpens molecular cloud complexes (25^\\circ < l< 33^\\circ and 1^\\circ < b< 6^\\circ ) at an angular resolution of 3.‧4 (≈ 0.25 pc) and at a velocity resolution of 0.079 km s‑1 with velocity coverage of -5 {km} {{{s}}}-1< {V}{LSR}< 35 {km} {{{s}}}-1. We found that the 13CO emission better traces the structures seen in the extinction map, and derived the {X}{13{CO}}-factor of this region. Applying SCIMES to the 13CO data cube, we identified 61 clouds and derived their mass, radii, and line widths. The line width–radius relation of the identified clouds basically follows those of nearby molecular clouds. The majority of the identified clouds are close to virial equilibrium, although the dispersion is large. By inspecting the 12CO channel maps by eye, we found several arcs that are spatially extended to 0.°2–3° in length. In the longitude–velocity diagrams of 12CO, we also found two spatially extended components that appear to converge toward Serpens South and the W40 region. The existence of two components with different velocities and arcs suggests that large-scale expanding bubbles and/or flows play a role in the formation and evolution of the Serpens South and W40 cloud.

  16. Effects of Microstructure on Electrode Properties of Nanosheet-Derived Hx(Ni1/3Co1/3Mn1/3)O2 for Electrochemical Capacitors

    PubMed Central

    Yano, Masato; Suzuki, Shinya; Miyayama, Masaru; Ohgaki, Masataka

    2013-01-01

    Nanosheet-derived Hx(Ni1/3Co1/3Mn1/3)O2 was prepared by restacking (Ni1/3Co1/3Mn1/3)O2 nanosheets with large or small lateral sizes and their electrochemical properties in a 1 M KOH aqueous solution; microstructural factors were compared with those of bulk Hx(Ni1/3Co1/3Mn1/3)O2 (HNCM). The electrodes composed of small nanosheets exhibited very large capacitances of 1241 F·g−1 (395 mAh·g−1) at a current density of 50 mA·g−1, and 430 F·g−1 (100 mAh·g−1) at a large current density of 1000 mA·g−1. These large capacitances resulted from a heterogeneous layer structure with a large surface area and pore volume. The electrodes of large nanosheets, with a strongly interconnected microstructure and a surface area slightly larger than that of HNCM, exhibited good cycle stability and capacitances larger than that of HNCM. Microstructural control through the restacking of (Ni1/3Co1/3Mn1/3)O2 nanosheets improved the electrochemical properties of Hx(Ni, Co, Mn)O2.

  17. Semi-classical calculations of self-broadening coefficients of OCS and HCN at temperatures between 200 K and 298 K.

    PubMed

    Jellali, C; Galalou, S; Cuisset, A; Dhib, M; Aroui, H

    2016-11-01

    For some temperatures of atmospheric interest from 200 to 298 K, the self-broadening coefficients of OCS-OCS and HCN-HCN collisional systems, at different strengths of electrostatic interactions, were calculated respectively for ν1 and ν2 bands for a wide range of rotational quantum numbers J. In particular, we have considered some lines that were not studied previously. We have employed the approximation of bi-resonance functions (Starikov, 2012) in the frame of the semiclassical model of Robert and Bonamy with exact trajectory (RBE). The calculated results are found to be fully consistent with the available experimental values of self-broadening coefficients of OCS and HCN. A comparative study shows that the RBE calculations reproduce the dependence of broadening coefficients on quantum number J much better than the simpler Robert and Bonamy model with parabolic trajectory (RB) for all considered temperatures.

  18. [Attempt to estimate risks of fatal poisoning on the basis of HCN and HbCO concentrations in blood of fire victims].

    PubMed

    Grabowska, Teresa; Sybirska, Halina; Maliński, Marian

    2003-01-01

    Using the results of HCN and HbCO concentrations in the blood of 174 deceased found in different burning spaces and 35 people with symptoms of poisoning evacuated from the scene of a fire and then admitted to hospital. The correlation between blood concentration of both these xenobiotics and death or chance of survival in a fire was estimated by statistical analysis. An attempt was made to define a value of so-called "cut-off" points for HbCO and HCN by independence test chi 2 with Yates's correction. Point and interval estimations (95% Comfield's confidence interval) were used for the odds ratio (OR). The research showed that there was a strict statistical correlation between the chance of survival and death risks dependent on blood concentrations of HCN and HbCO in all the groups examined.

  19. In-Situ Measurements of HCN and CH3CN in the Pacific Troposphere: Sources, Sinks, and Comparisons with Spectroscopic Observations

    NASA Technical Reports Server (NTRS)

    Singh, Hanwant B.; Salas, L.; Herlth, D.; Czech, E.; Viezee, W.; Li, Q.; Jacob, D. J.; Blake, D.; Sachse, G.; Harward, C. N.; Hipskind, R. Stephen (Technical Monitor)

    2002-01-01

    We report the first in-situ measurements of hydrogen cyanide (HCN) and acetonitrile (CH3CN) from the Pacific troposphere (0-12 km) obtained during the NASA/Trace-P mission (Feb.-April, 2001). Mean HCN and CH3CN mixing ratios of 243 (+/-118) ppt and 149 (+/-56) ppt respectively, were measured. The in-situ observations correspond to a total HCN column of 4.4-4.9 x 10(exp 15) molec. cm(exp -2) and a CH3CN column of 2.8-3.0 x 10(exp 15) molec. cm(exp -2). This HCN column is in good agreement with available spectroscopic observations. The atmospheric concentrations of HCN and CH3CN were greatly influenced by outflow of pollution from Asia. There is a linear relationship between the mixing ratios of HCN and CH3CN, and in turn these are well correlated with tracers of biomass combustion (e.g. CH3Cl, CO). Relative enhancements with respect to known tracers of biomass combustion within selected plumes in the free troposphere, and pollution episodes in the boundary layer allow an estimation of a global biomass burning source of 0.8+/-0.4 Tg (N)/y for HCN and 0.4+/-0.1 Tg (N)/y for CH3CN. In comparison, emissions from automobiles and industry are quite small (<0.05 Tg (N)/y). The vertical structure of HCN and CH3CN indicated reduced mixing ratios in the MBL (Marine Boundary Layer). Using, a simple box model, the observed gradients across the top of the MBL are used to derive an oceanic flux of 6.7 x 10(exp -15) g (N) cm(exp -2)/s for HCN and 4.8 x 10(exp -15) g (N) cm(exp -2)/s for CH3CN. An air-sea exchange model is used to conclude that this flux can be maintained if the oceans are under-saturated in HCN and CH3CN by 23% and 17%, respectively. It is inferred that oceanic loss is a dominant sink for these nitrites, and they deposit some 1.3 Tg (N) of nitrogen annually to the oceans. Assuming reaction with OH radicals and loss to the oceans as the major removal processes, a mean atmospheric residence time of 4.7 months for HCN and 5.1 months for CH3CN is calculated. A global

  20. Semi-classical calculations of self-broadening coefficients of OCS and HCN at temperatures between 200 K and 298 K

    NASA Astrophysics Data System (ADS)

    Jellali, C.; Galalou, S.; Cuisset, A.; Dhib, M.; Aroui, H.

    2016-11-01

    For some temperatures of atmospheric interest from 200 to 298 K, the self-broadening coefficients of OCS-OCS and HCN-HCN collisional systems, at different strengths of electrostatic interactions, were calculated respectively for ν1 and ν2 bands for a wide range of rotational quantum numbers J. In particular, we have considered some lines that were not studied previously. We have employed the approximation of bi-resonance functions (Starikov, 2012) in the frame of the semiclassical model of Robert and Bonamy with exact trajectory (RBE). The calculated results are found to be fully consistent with the available experimental values of self-broadening coefficients of OCS and HCN. A comparative study shows that the RBE calculations reproduce the dependence of broadening coefficients on quantum number J much better than the simpler Robert and Bonamy model with parabolic trajectory (RB) for all considered temperatures.

  1. Carbon Allocation of 13CO2-labeled Photoassimilate in Larix gmelinii Saplings - A Physiological Basis for Isotope Dendroclimatology in Eastern Siberia.

    NASA Astrophysics Data System (ADS)

    Kagawa, A.; Sugimoto, A.; Maximov, T. C.

    2006-12-01

    Tree-ring density and widths have been successfully used to reconstruct summer temperatures in high- northern latitudes, although a discrepancy between tree-growth and temperature has been found for recent decades. The so-called "reduced sensitivity" of tree rings to summer temperatures has been observed especially strongly in northern Siberia (Briffa et al., 1998) and drought stress (increased water use efficiency) arose from global warming and/or increasing CO2 are suggested as causes (Barber et al. 2000, Saurer et al. 2004). By using carbon isotope ratio as an indicator of drought stress and ring-width/density as indicators of growth, we can clarify how drought stress caused by recent global warming affects wood formation of Siberian trees. However, isotope dendroclimatology is still in its infancy and our understanding of basic physiological processes of isotope signal transfer from leaves to tree rings is insufficient. In order to understand translocation, storage, and allocation of photoassimilate to different organs of trees, we pulse- labeled ten L. gmelinii growing in a continuous permafrost zone with stable 13CO2. We studied seasonal course of carbon allocation patterns of photoassimilate among needles, branches, stem and roots and also how spring, summer, and autumn photoassimilate is later used for both earlywood and latewood formation. About half of the carbon in new needles was derived from stored material. The starch pool in non- needle parts, which can be used for xylem formation, drew about 43 percent of its carbon from previous year's photoassimilate, suggesting that carbon storage is the key mechanism behind autocorrelation in (isotope) dendroclimatology. Analysis of intra-annual 13C of the tree rings formed after the labeling revealed that earlywood contained photoassimilate from the previous summer and autumn as well as from the current spring. Latewood was mainly composed of photoassimilate from the current year's summer/autumn, although it

  2. Quantifying protein synthesis and degradation in Arabidopsis by dynamic 13CO2 labeling and analysis of enrichment in individual amino acids in their free pools and in protein.

    PubMed

    Ishihara, Hirofumi; Obata, Toshihiro; Sulpice, Ronan; Fernie, Alisdair R; Stitt, Mark

    2015-05-01

    Protein synthesis and degradation represent substantial costs during plant growth. To obtain a quantitative measure of the rate of protein synthesis and degradation, we supplied (13)CO2 to intact Arabidopsis (Arabidopsis thaliana) Columbia-0 plants and analyzed enrichment in free amino acids and in amino acid residues in protein during a 24-h pulse and 4-d chase. While many free amino acids labeled slowly and incompletely, alanine showed a rapid rise in enrichment in the pulse and a decrease in the chase. Enrichment in free alanine was used to correct enrichment in alanine residues in protein and calculate the rate of protein synthesis. The latter was compared with the relative growth rate to estimate the rate of protein degradation. The relative growth rate was estimated from sequential determination of fresh weight, sequential images of rosette area, and labeling of glucose in the cell wall. In an 8-h photoperiod, protein synthesis and cell wall synthesis were 3-fold faster in the day than at night, protein degradation was slow (3%-4% d(-1)), and flux to growth and degradation resulted in a protein half-life of 3.5 d. In the starchless phosphoglucomutase mutant at night, protein synthesis was further decreased and protein degradation increased, while cell wall synthesis was totally inhibited, quantitatively accounting for the inhibition of growth in this mutant. We also investigated the rates of protein synthesis and degradation during leaf development, during growth at high temperature, and compared synthesis rates of Rubisco large and small subunits of in the light and dark.

  3. Short-term Fate of Carbon in two Woody Species Under Contrasting Resources Availability: Insights From a 13CO2 Pulse Labeling Approach

    NASA Astrophysics Data System (ADS)

    Mambelli, S.; Dawson, T. E.; Bird, J. A.; Torn, M. S.; Gaudinski, J. B.

    2003-12-01

    In response to the environment, plants adjust allocation patterns to maintain a functional balance between the activities of roots and shoots such that belowground resources are acquired in approximate balance with aboveground resources. Changes in allocation driven by changes in environmental conditions may affect the amount of carbon stored in plant tissues, released by the root system, and ultimately sequestered into the soil. The aim of this study was to quantify the allocation belowground of recently fixed carbon in contrasting species and resources availability. We tested the hypothesis that carbon limitation and high nitrogen supply both negatively affect carbon transport to roots, causing a reduction of the carbon flow into the soil rhizosphere. Two woody species, a conifer (Pinus Ponderosa) and a deciduous tree (Acer Rubrum) were grown in a greenhouse under a factorial of light and nitrogen regimes (full light/shade and limited/excess nitrogen). At the stage of full leaf expansion plants were pulse-labeled by addition of 13CO2 and harvested after 0, 7 and 30 days. During the experiment the treatments affected the pattern of plant biomass allocation. Shade negatively influenced belowground growth and Maple showed a more conservative response than Pine. High supply of nitrogen also reduced allocation to roots but only when plants were grown under light. Preliminary results show that the initial amount of recently fixed carbon into the rhizosphere was in general higher under Pine. However, after 7 and 30 days, the new soil carbon pool increased only in the rhizosphere of carbon limited Pine seedlings. These findings suggest that belowground respiration was negatively affected or, alternatively, that the exudates released were less easily decomposable

  4. Measuring and modelling the intra-day variability of the 13CO2 & 12CO2 vertical soil profile production in a Scots pine forest

    NASA Astrophysics Data System (ADS)

    Longdoz, Bernard; Goffin, Stéphanie; Parent, Florian; Plain, Caroline; Epron, Daniel; Wylock, Christophe; Haut, Benoit; Aubinet, Marc; Maier, Martin

    2015-04-01

    Vertical profile of CO2 production (Ps) and transport, as well as their isotopic discrimination (13CO2/12CO2) should be considered to improve the soil CO2 efflux (Fs) mechanistic understanding and especially its short-term temporal variations. In this context, we propose a new methodology able to measure continuously and simultaneously Fs, the vertical soil CO2 concentration ([CO2]) profile and their respective isotopic signature (δFs and δCO2) [1]. The Ps of the different soil layers and their isotopic signature (δPs) can then be determined from these measurements by an approach considering diffusion as the only gas transport. A field campaign was conducted with this device at the Scots Pine Hartheim forest (Germany). The results [2] show (i) a Ps dependence on local temperature specific for each layer, (ii) an enrichment of δPs with soil drought, (iii) Fs and [CO2] large intra-day fluctuations non explained by the soil temperature and moisture. These fluctuations can be generated by other processes creating Ps and/or transport variability. To investigate about the nature of these processes, some sensitivity analyses have been performed with a soil CO2 model simulating both production and transport. The impacts of the introduction of advection, dispersion and phloem pressure concentration wave (through dependence of Ps on vapour pressure deficit) on intra-day Fs and [CO2] variations have been quantified. We conclude that these variations are significantly better represented when the phloem pressure wave expression is included in the simulations. The study of the processes related to CO2 production seems to be a better option than an investigation about transport to explain the intra-day Fs variability.

  5. Effects of season and nitrogen supply on the partitioning of recently fixed carbon in understory vegetation using a 13CO2 pulse labeling technique

    NASA Astrophysics Data System (ADS)

    Hasselquist, Niles; Metcalfe, Daniel; Högberg, Peter

    2013-04-01

    Vegetation research in boreal forests has traditionally been focused on trees, with little attention given to understory vegetation. However, understory vegetation has been identified as a key driver for the functioning of boreal forests and may play an important role in the amount of carbon (C) that is entering and leaving these forested ecosystems. We conducted a large-scale 13C pulse labeling experiment to better understand how recently fixed C is allocated in the understory vegetation characteristic of boreal forests. We used transparent plastic chambers to pulse label the understory vegetation with enriched 13CO2 in the early (June) and late (August) growing seasons. This study was also replicated across a nitrogen (N) fertilization treatment to better understand the effects of N availability on C allocation patterns. We present data on the amount of 13C label found in different components of the understory vegetation (i.e. leaves, stems, lichens, mosses, rhizomes and fine roots) as well as CO2 efflux. Additionally, we provide estimates of C residence time (MRT) among the different components and examine how MRT of C is affected by seasonality and N availability. Seasonality had a large effect on how recently fixed C is allocated in understory vegetation, whereas N fertilization influenced the MRT of C in the different components of ericaceous vegetation. Moreover, there was a general trend that N additions increased the amount of 13C in CO2 efflux compared to the amount of 13C in biomass, suggesting that N fertilization may lead to an increase in the utilization of recently fixed C, whereas N-limitation promotes the storage of recently fixed C.

  6. Glass distilling collector applied for HCN recovery from submerged culture broth and fruiting body of Pleurotus eryngii for identification and quantification.

    PubMed

    Chou, Pei-Yu; Hong, Chian-Huei; Chen, Wenlung; Li, Yu-Jang; Chen, Yen-Shang; Chiou, Robin Y-Y

    2006-03-08

    Detection and surveillance of food commodities containing cyanide is a crucial issue of food safety. In this study, five strains of Pleurotus eryngii (P. eryngii) were grown in submerged culture of yeast malt broth (YMB) with the suspected production of HCN. A safety-warranted U-bent glass distilling collector with three enlarged bulbs on each arm was designed to recover the broth vapor. When AgNO(3) solution was used as an absorbent to interact with the vapor, a white precipitate was formed. The precipitate was isolated and identified as AgCN by FT-Raman spectroscopic analysis. When the absorbent was substituted by KOH, after evaporation to dryness, dissolved in D(2)O, and followed by (13)C-NMR analysis, a KCN spectrum was achieved. Formation of AgCN and KCN confirmed HCN production in the broth by P. eryngii. When a sodium picrate solution (1.4%) was used as an absorbent and various authentic KCN solutions were applied for distillation and followed by absorbance determination at 510 nm, a linear dose-dependent relationship was obtained and the procedure was applied for HCN quantification of the marketed P. eryngii mushrooms (fruiting body). As estimated, 67.3% of the products contained HCN less than 1.0 mg/kg, 17.3% between 1.0 and 2.0 mg/kg, and 15.4% higher than 2.0 mg/kg. When the mushrooms were sliced and cooked in water at 95 degrees C for 6 min, 89.1% of the original HCN was lost. When the P. eryngii strains were respectively grown by submerged cultivation in YMB or YMB supplemented with 2.5% glycine for 16 days, HCN content was slightly higher in the latter than in the former for each strain.

  7. Baclofen ameliorates spatial working memory impairments induced by chronic cerebral hypoperfusion via up-regulation of HCN2 expression in the PFC in rats.

    PubMed

    Luo, Pan; Chen, Cheng; Lu, Yun; Fu, TianLi; Lu, Qing; Xu, Xulin; Li, Changjun; He, Zhi; Guo, Lianjun

    2016-07-15

    Chronic cerebral hypoperfusion (CCH) causes memory deficits and increases the risk of vascular dementia (VD) through several biologically plausible pathways. However, whether CCH causes prefrontal cortex (PFC)-dependent spatial working memory impairments and Baclofen, a GABAB receptor agonist, could ameliorate the impairments is still not clear especially the mechanisms underlying the process. In this study, rats were subjected to permanent bilateral occlusion of the common carotid arteries (two-vessel occlusion, 2VO) to induce CCH. Two weeks later, rats were treated with 25mg/kg Baclofen (intraperitioneal injection, i.p.) for 3 weeks. Spatial working memory was evaluated in a Morris water maze using a modified delayed matching-to-place (DMP) procedure. Western blotting and immunohistochemistry were used to quantify the protein levels and protein localization. Our results showed that 2VO caused striking spatial working memory impairments, accompanied with a decreased HCN2 expression in PFC, but the protein levels of protein gene product 9.5 (PGP9.5, a neuron specific protein), glial fibrillary acidic protein (GFAP), synaptophysin (SYP), brain-derived neurotrophic factor (BDNF), parvalbumin (PV) and HCN1 were not distinguishably changed as compared with sham-operated rats. Baclofen treatment significantly improved the spatial working memory impairments caused by 2VO, accompanied with a reversion of 2VO-induced down-regulation of HCN2. Furthermore, there was a co-localization of HCN2 subunits and parvalbumin-positive neurons in PFC. Therefore, HCN2 may target inhibitory interneurons that is implicated in working memory processes, which may be a possible mechanism of the up-regulation of HCN2 by Baclofen treatment that reliefs spatial working memory deficits in rats with CCH.

  8. Reduction of nitrogen compounds in oceanic basement and its implications for HCN formation and abiotic organic synthesis

    PubMed Central

    2009-01-01

    Hydrogen cyanide is an excellent organic reagent and is central to most of the reaction pathways leading to abiotic formation of simple organic compounds containing nitrogen, such as amino acids, purines and pyrimidines. Reduced carbon and nitrogen precursor compounds for the synthesis of HCN may be formed under off-axis hydrothermal conditions in oceanic lithosphere in the presence of native Fe and Ni and are adsorbed on authigenic layer silicates and zeolites. The native metals as well as the molecular hydrogen reducing CO2 to CO/CH4 and NO3-/NO2- to NH3/NH4+ are a result of serpentinization of mafic rocks. Oceanic plates are conveyor belts of reduced carbon and nitrogen compounds from the off-axis hydrothermal environments to the subduction zones, where compaction, dehydration, desiccation and diagenetic reactions affect the organic precursors. CO/CH4 and NH3/NH4+ in fluids distilled out of layer silicates and zeolites in the subducting plate at an early stage of subduction will react upon heating and form HCN, which is then available for further organic reactions to, for instance, carbohydrates, nucleosides or even nucleotides, under alkaline conditions in hydrated mantle rocks of the overriding plate. Convergent margins in the initial phase of subduction must, therefore, be considered the most potent sites for prebiotic reactions on Earth. This means that origin of life processes are, perhaps, only possible on planets where some kind of plate tectonics occur. PMID:19849830

  9. Noise-induced plasticity of KCNQ2/3 and HCN channels underlies vulnerability and resilience to tinnitus.

    PubMed

    Li, Shuang; Kalappa, Bopanna I; Tzounopoulos, Thanos

    2015-08-27

    Vulnerability to noise-induced tinnitus is associated with increased spontaneous firing rate in dorsal cochlear nucleus principal neurons, fusiform cells. This hyperactivity is caused, at least in part, by decreased Kv7.2/3 (KCNQ2/3) potassium currents. However, the biophysical mechanisms underlying resilience to tinnitus, which is observed in noise-exposed mice that do not develop tinnitus (non-tinnitus mice), remain unknown. Our results show that noise exposure induces, on average, a reduction in KCNQ2/3 channel activity in fusiform cells in noise-exposed mice by 4 days after exposure. Tinnitus is developed in mice that do not compensate for this reduction within the next 3 days. Resilience to tinnitus is developed in mice that show a re-emergence of KCNQ2/3 channel activity and a reduction in HCN channel activity. Our results highlight KCNQ2/3 and HCN channels as potential targets for designing novel therapeutics that may promote resilience to tinnitus.

  10. Statistical-theoretical investigation of the thermal rate coefficient and branching ratio for the reaction O + HCN. -->. products

    SciTech Connect

    Miller, J.A.; Parrish, C.; Brown, N.J.

    1986-07-17

    Using the BAC-MP4 potential surface parameters of Melius and Binkley, we have predicted the thermal rate coefficients for the two reactions: O + HCN ..-->.. NCO + H (a) and O + HCN ..-->.. NH + CO (b). Several levels of approximation are used in the theoretical treatment: a, canonical theory; b, canonical theory with Wigner tunneling correction; c, microcanonical theory (energy conserving); d, microcanonical/J-conservative theory (conserves both energy and angular momentum); e, microcanonical/J-conservative theory with one-dimensional tunneling. At high temperature the available experimental results are predicted accurately by even the crudest theoretical treatment (canonical theory). At lower temperature the theoretical predictions using the basic BAC-MP4 parameters are too low. However, adjustments to the BAC-MP4 energy barriers within their stated error limits lead to satisfactory agreement with experiment over the entire temperature range where experimental results are available (500 to 2500 K). The most important results of the investigation concern the dependence of the predictions on the level of approximation. Each successive refinement in the theory produces larger values of k/sub b/. The details of the theoretical treatment and comparisons with experiment are described in detail.

  11. Probability Fluxes and Transition Paths in a Markovian Model Describing Complex Subunit Cooperativity in HCN2 Channels

    PubMed Central

    Benndorf, Klaus; Kusch, Jana; Schulz, Eckhard

    2012-01-01

    Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are voltage-gated tetrameric cation channels that generate electrical rhythmicity in neurons and cardiomyocytes. Activation can be enhanced by the binding of adenosine-3′,5′-cyclic monophosphate (cAMP) to an intracellular cyclic nucleotide binding domain. Based on previously determined rate constants for a complex Markovian model describing the gating of homotetrameric HCN2 channels, we analyzed probability fluxes within this model, including unidirectional probability fluxes and the probability flux along transition paths. The time-dependent probability fluxes quantify the contributions of all 13 transitions of the model to channel activation. The binding of the first, third and fourth ligand evoked robust channel opening whereas the binding of the second ligand obstructed channel opening similar to the empty channel. Analysis of the net probability fluxes in terms of the transition path theory revealed pronounced hysteresis for channel activation and deactivation. These results provide quantitative insight into the complex interaction of the four structurally equal subunits, leading to non-equality in their function. PMID:23093920

  12. Long-range transport of NH3, CO, HCN, and C2H6 from the 2014 Canadian Wildfires

    NASA Astrophysics Data System (ADS)

    Lutsch, E.; Dammers, E.; Conway, S.; Strong, K.

    2016-08-01

    We report the first long-term measurements of ammonia (NH3) in the high Arctic. Enhancements of the total columns of NH3, carbon monoxide (CO), hydrogen cyanide (HCN), and ethane (C2H6) were detected in July and August 2014 at Eureka, Nunavut, and Toronto, Ontario. Enhancements were attributed to fires in the Northwest Territories using the FLEXPART Lagrangian dispersion model and the Moderate Resolution Imaging Spectroradiometer Fire Hot Spot data set. Emission estimates are reported as average emission factors for HCN (0.62 ± 0.34 g kg-1), C2H6 (1.50 ± 0.75 g kg-1), and NH3 (1.40 ± 0.72 g kg-1). Observations of NH3 at both sites demonstrate long-range transport of NH3, with an estimated NH3 lifetime of 48 h. We also conclude that boreal fires may be an important source of NH3 in the summertime Arctic.

  13. Reduction of nitrogen compounds in oceanic basement and its implications for HCN formation and abiotic organic synthesis.

    PubMed

    Holm, Nils G; Neubeck, Anna

    2009-10-22

    Hydrogen cyanide is an excellent organic reagent and is central to most of the reaction pathways leading to abiotic formation of simple organic compounds containing nitrogen, such as amino acids, purines and pyrimidines. Reduced carbon and nitrogen precursor compounds for the synthesis of HCN may be formed under off-axis hydrothermal conditions in oceanic lithosphere in the presence of native Fe and Ni and are adsorbed on authigenic layer silicates and zeolites. The native metals as well as the molecular hydrogen reducing CO2 to CO/CH4 and NO3-/NO2- to NH3/NH4+ are a result of serpentinization of mafic rocks. Oceanic plates are conveyor belts of reduced carbon and nitrogen compounds from the off-axis hydrothermal environments to the subduction zones, where compaction, dehydration, desiccation and diagenetic reactions affect the organic precursors. CO/CH4 and NH3/NH4+ in fluids distilled out of layer silicates and zeolites in the subducting plate at an early stage of subduction will react upon heating and form HCN, which is then available for further organic reactions to, for instance, carbohydrates, nucleosides or even nucleotides, under alkaline conditions in hydrated mantle rocks of the overriding plate. Convergent margins in the initial phase of subduction must, therefore, be considered the most potent sites for prebiotic reactions on Earth. This means that origin of life processes are, perhaps, only possible on planets where some kind of plate tectonics occur.

  14. The expression of hyperpolarization activated cyclic nucleotide gated (HCN) channels in the rat ovary are dependent on the type of cell and the reproductive age of the animal: a laboratory investigation

    PubMed Central

    Yeh, John; Kim, Beom Su; Gaines, Larry; Peresie, Jennifer; Page, Carly; Arroyo, Armando

    2008-01-01

    Background Aim of this study was to test the hypothesis that levels of hyperpolarization activated cyclic nucleotide gated channels 1 to 4 (HCN1-4) are linked to the reproductive age of the ovary. Methods Young, adult, and reproductively aged ovaries were collected from Sprague-Dawley rats. RT-PCR and western blot analysis of ovaries was performed to investigate the presence of mRNA and total protein for HCN1-4. Immunohistochemistry with semiquantitative H score analysis was performed using whole ovarian histologic sections. Results RT-PCR analysis showed the presence of mRNA for HCN1-4. Western blot analysis revealed HCN1-3 proteins in all ages of ovarian tissues. Immunohistochemistry with H score analysis demonstrated distinct age-related changes in patterns of HCN1-3 in the oocytes, granulosa cells, theca cells, and corpora lutea. HCN4 was present only in the oocytes, with declining levels during the reproduction lifespan. Conclusion The evidence presented here demonstrates cell-type and developmental age patterns of HCN1-4 channel expression in rat ovaries. Based on this, we hypothesize that HCN channels have functional significance in rat ovaries and may have changing roles in reproductive aging. PMID:18710573

  15. Enhanced electrochemical performance of Li-rich cathode Li[Li0.2Mn0.54Ni0.13Co0.13]O2 by surface modification with lithium ion conductor Li3PO4

    NASA Astrophysics Data System (ADS)

    Wang, Zhiyuan; Luo, Shaohua; Ren, Jie; Wang, Dan; Qi, Xiwei

    2016-05-01

    Li-rich layered cathode Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is prepared via a co-precipitation followed with high-temperature calcination, and then successfully modified with nano-Li3PO4 by ball milling and annealing. The TEM and EDS reveal that Li3PO4 is homogeneously coated on the particle surface of Li[Li0.2Mn0.54Ni0.13Co0.13]O2. And the electrochemical performance of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is significantly improved by coating with lithium ion conductor Li3PO4. The Li3PO4-coated sample delivers a high initial discharge capacity of 284.7 mAhg-1 at 0.05 C, and retains 192.6 mAhg-1 after 100 cycles at 0.5 C, which is higher than that of the pristine sample (244 mAhg-1 at 0.05 C and 168.2 mAhg-1 after 100 cycles at 0.5 C). The electrochemical impedance spectroscopy (EIS) demonstrates that the resistance for Li/Li3PO4-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cell was reduced compared to Li/Li[Li0.2Mn0.54Ni0.13Co0.13]O2, which indicates the Li3PO4 coating layer with high ionic conductivity (6.6 × 10-8 S cm-1) facilitates the diffusion of lithium ions through the interface between electrode and electrolyte and accelerates the charge transfer process. What is more, the Li3PO4 coating layer can also act as a protection layer to protect the cathode material from encroachment of electrolyte. The two aspects account for the enhanced electrochemical performance of Li3PO4-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2.

  16. The effect of physical back-diffusion of 13CO2 tracer on the coupling between photosynthesis and soil CO2 efflux in grassland.

    PubMed

    Burri, Susanne; Sturm, Patrick; Baur, Thomas; Barthel, Matti; Knohl, Alexander; Buchmann, Nina

    2014-01-01

    Pulse labelling experiments provide a common tool to study short-term processes in the plant-soil system and investigate below-ground carbon allocation as well as the coupling of soil CO(2) efflux to photosynthesis. During the first hours after pulse labelling, the measured isotopic signal of soil CO(2) efflux is a combination of both physical tracer diffusion into and out of the soil as well as biological tracer release via root and microbial respiration. Neglecting physical back-diffusion can lead to misinterpretation regarding time lags between photosynthesis and soil CO(2) efflux in grassland or any ecosystem type where the above-ground plant parts cannot be labelled in gas-tight chambers separated from the soil. We studied the effects of physical (13)CO(2) tracer back-diffusion in pulse labelling experiments in grassland, focusing on the isotopic signature of soil CO(2) efflux. Having accounted for back-diffusion, the estimated time lag for first tracer appearance in soil CO(2) efflux changed from 0 to 1.81±0.56 h (mean±SD) and the time lag for maximum tracer appearance from 2.67±0.39 to 9.63±3.32 h (mean±SD). Thus, time lags were considerably longer when physical tracer diffusion was considered. Using these time lags after accounting for physical back-diffusion, high nocturnal soil CO(2) efflux rates could be related to daytime rates of gross primary productivity (R(2)=0.84). Moreover, pronounced diurnal patterns in the δ(13)C of soil CO(2) efflux were found during the decline of the tracer over 3 weeks. Possible mechanisms include diurnal changes in the relative contributions of autotrophic and heterotrophic soil respiration as well as their respective δ(13)C values. Thus, after accounting for physical back-diffusion, we were able to quantify biological time lags in the coupling of photosynthesis and soil CO(2) efflux in grassland at the diurnal time scale.

  17. In situ 13CO2 pulse labelling of field-grown eucalypt trees revealed the effects of potassium nutrition and throughfall exclusion on phloem transport of photosynthetic carbon.

    PubMed

    Epron, Daniel; Cabral, Osvaldo Machado Rodrigues; Laclau, Jean-Paul; Dannoura, Masako; Packer, Ana Paula; Plain, Caroline; Battie-Laclau, Patricia; Moreira, Marcelo Zacharias; Trivelin, Paulo Cesar Ocheuze; Bouillet, Jean-Pierre; Gérant, Dominique; Nouvellon, Yann

    2016-01-01

    Potassium (K) is an important limiting factor of tree growth, but little is known of the effects of K supply on the long-distance transport of photosynthetic carbon (C) in the phloem and of the interaction between K fertilization and drought. We pulse-labelled 2-year-old Eucalyptus grandis L. trees grown in a field trial combining K fertilization (+K and -K) and throughfall exclusion (+W and -W), and we estimated the velocity of C transfer by comparing time lags between the uptake of (13)CO2 and its recovery in trunk CO2 efflux recorded at different heights. We also analysed the dynamics of the labelled photosynthates recovered in the foliage and in the phloem sap (inner bark extract). The mean residence time of labelled C in the foliage was short (21-31 h). The time series of (13)C in excess in the foliage was affected by the level of fertilization, whereas the effect of throughfall exclusion was not significant. The velocity of C transfer in the trunk (0.20-0.82 m h(-1)) was twice as high in +K trees than in -K trees, with no significant effect of throughfall exclusion except for one +K -W tree labelled in the middle of the drought season that was exposed to a more pronounced water stress (midday leaf water potential of -2.2 MPa). Our results suggest that besides reductions in photosynthetic C supply and in C demand by sink organs, the lower velocity under K deficiency is due to a lower cross-sectional area of the sieve tubes, whereas an increase in phloem sap viscosity is more likely limiting phloem transport under drought. In all treatments, 10 times less (13)C was recovered in inner bark extracts at the bottom of the trunk when compared with the base of the crown, suggesting that a large part of the labelled assimilates has been exported out of the phloem and replaced by unlabelled C. This supports the 'leakage-retrieval mechanism' that may play a role in maintaining the pressure gradient between source and sink organs required to sustain high

  18. The M12N12 (M  =  Al, Ga) clusters as potential sensors for NO, NO2 and HCN detection

    NASA Astrophysics Data System (ADS)

    Cui, Hongling; Yong, Yongliang; Jiang, Huai; Yang, Liangwei; Wang, Shihao; Zhang, Gaojian; Guo, Menghui; Li, Xiaohong

    2017-01-01

    The geometries, energies and electronic properties of NO, NO2 and HCN molecules adsorption on the M12N12 (M  =Al, Ga) clusters have been studied by using density functional theory in order to find novel sensors for NO, NO2 and HCN detection. We find that the three molecules can be chemisorbed on the M12N12 (M  =  Al, Ga) clusters with reasonable adsorption energies (‑0.503 to  ‑1.377 eV). It is clear that there are optimal charge transfers between the clusters and molecules. The HOMO-LUMO gaps of the M12N12 clusters are very sensitive to the presence of the NO, NO2 and HCN molecules. Due to the reasonable adsorption energies and the changes of electronic properties accompanied with the apparent charge transfer, the M12N12 (M  =  Al, Ga) clusters are potentially good NO, NO2 and HCN sensors.

  19. Constellation of HCN channels and cAMP regulating proteins in dendritic spines of the primate prefrontal cortex: potential substrate for working memory deficits in schizophrenia.

    PubMed

    Paspalas, Constantinos D; Wang, Min; Arnsten, Amy F T

    2013-07-01

    Schizophrenia associates with impaired prefrontal cortical (PFC) function and alterations in cyclic AMP (cAMP) signaling pathways. These include genetic insults to disrupted-in-schizophrenia (DISC1) and phosphodiesterases (PDE4s) regulating cAMP hydrolysis, and increased dopamine D1 receptor (D1R) expression that elevates cAMP. We used immunoelectron microscopy to localize DISC1, PDE4A, PDE4B, and D1R in monkey PFC and to view spatial interactions with hyperpolarization-activated cyclic nucleotide-gated (HCN) channels that gate network inputs when opened by cAMP. Physiological interactions between PDE4s and HCN channels were tested in recordings of PFC neurons in monkeys performing a spatial working memory task. The study reveals a constellation of cAMP-related proteins (DISC1, PDE4A, and D1R) and HCN channels next to excitatory synapses and the spine neck in thin spines of superficial PFC, where working memory microcircuits interconnect and spine loss is most evident in schizophrenia. In contrast, channels in dendrites were distant from synapses and cAMP-related proteins, and were associated with endosomal trafficking. The data suggest that a cAMP signalplex is selectively positioned in the spines to gate PFC pyramidal cell microcircuits. Single-unit recordings confirmed physiological interactions between cAMP and HCN channels, consistent with gating actions. These data may explain why PFC networks are especially vulnerable to genetic insults that dysregulate cAMP signaling.

  20. Computational Studies Of Chemical Reactions: The Hnc-Hcn And Ch[subscript3]Nc-Ch[subscript3]Cn Isomerizations

    ERIC Educational Resources Information Center

    Halpern, Arthur M.

    2006-01-01

    The application of computational methods to the isomerization of hydrogen isocyanide to hydrogen cyanide, HNC-HCN is described. The logical extension to the exercise is presented to the isomerization of the methyl-substituted compounds, methylisocyanide and methylcyanide, Ch[subscript 3]NC-CH[subscript3]CN.

  1. Broadening of the R(0) and P(2) Lines in the 13CO Fundamental by Helium Atoms from 300 K down to 12 K: Measurements and Comparison with Close-Coupling Calculations

    NASA Technical Reports Server (NTRS)

    Thibault, F.; Mantz, A. W.; Claveau, C.; Valentin, A.; Hurtmans, D.

    2007-01-01

    We present measurements of He-broadening parameters for the R(0) and O(2) lines in the fundamental band of 13CO at different temperatures between 12K and room temperature. The broadening parameters are determined, taking into account confinement narrowing, by simultaneous least-squares fitting of spectra recorded using a frequency stabilized diode laser spectrometer. The pressure broadening cross sections are deduced and compared to close-coupling calculations and earlier results obtained for rotational transitions of 12 CO.

  2. REVEALING THE PHYSICAL PROPERTIES OF MOLECULAR GAS IN ORION WITH A LARGE-SCALE SURVEY IN J = 2-1 LINES OF {sup 12}CO, {sup 13}CO, AND C{sup 18}O

    SciTech Connect

    Nishimura, Atsushi; Tokuda, Kazuki; Kimura, Kimihiro; Muraoka, Kazuyuki; Maezawa, Hiroyuki; Ogawa, Hideo; Onishi, Toshikazu; Dobashi, Kazuhito; Shimoikura, Tomomi; Mizuno, Akira; Fukui, Yasuo

    2015-01-01

    We present fully sampled ∼3' resolution images of {sup 12}CO(J = 2-1), {sup 13}CO(J = 2-1), and C{sup 18}O(J = 2-1) emission taken with the newly developed 1.85 m millimeter-submillimeter telescope over the entire area of the Orion A and B giant molecular clouds. The data were compared with J = 1-0 of the {sup 12}CO, {sup 13}CO, and C{sup 18}O data taken with the Nagoya 4 m telescope and the NANTEN telescope at the same angular resolution to derive the spatial distributions of the physical properties of the molecular gas. We explore the large velocity gradient formalism to determine the gas density and temperature using line combinations of {sup 12}CO(J = 2-1), {sup 13}CO(J = 2-1), and {sup 13}CO(J = 1-0) assuming a uniform velocity gradient and abundance ratio of CO. The derived gas density is in the range of 500 to 5000 cm{sup –3}, and the derived gas temperature is mostly in the range of 20 to 50 K along the cloud ridge with a temperature gradient depending on the distance from the star forming region. We found that the high-temperature region at the cloud edge faces the H II region, indicating that the molecular gas is interacting with the stellar wind and radiation from the massive stars. In addition, we compared the derived gas properties with the young stellar objects distribution obtained with the Spitzer telescope to investigate the relationship between the gas properties and the star formation activity therein. We found that the gas density and star formation efficiency are positively well correlated, indicating that stars form effectively in the dense gas region.

  3. A novel process for recycling and resynthesizing LiNi1/3Co1/3Mn1/3O2 from the cathode scraps intended for lithium-ion batteries.

    PubMed

    Zhang, Xihua; Xie, Yongbing; Cao, Hongbin; Nawaz, Faheem; Zhang, Yi

    2014-09-01

    To solve the recycling challenge for aqueous binder based lithium-ion batteries (LIBs), a novel process for recycling and resynthesizing LiNi1/3Co1/3Mn1/3O2 from the cathode scraps generated during manufacturing process is proposed in this study. Trifluoroacetic acid (TFA) is employed to separate the cathode material from the aluminum foil. The effects of TFA concentration, liquid/solid (L/S) ratio, reaction temperature and time on the separation efficiencies of the cathode material and aluminum foil are investigated systematically. The cathode material can be separated completely under the optimal experimental condition of 15vol.% TFA solution, L/S ratio of 8.0 mL g(-1), reacting at 40°C for 180 min along with appropriate agitation. LiNi1/3Co1/3Mn1/3O2 is successfully resynthesized from the separated cathode material by solid state reaction method. Several kinds of characterizations are performed to verify the typical properties of the resynthesized LiNi1/3Co1/3Mn1/3O2 powder. Electrochemical tests show that the initial charge and discharge capacities of the resynthesized LiNi1/3Co1/3Mn1/3O2 are 201 mAh g(-)(1) and 155.4 mAh g(-1) (2.8-4.5 V, 0.1C), respectively. The discharge capacity remains at 129 mAh g(-1) even after 30 cycles with a capacity retention ratio of 83.01%.

  4. High-voltage performance of LiNi1/3Co1/3Mn1/3O2/graphite batteries with di(methylsulfonyl) methane as a new sulfone-based electrolyte additive

    NASA Astrophysics Data System (ADS)

    Zheng, Xiangzhen; Huang, Tao; Pan, Ying; Wang, Wenguo; Fang, Guihuang; Wu, Maoxiang

    2015-10-01

    In order to overcome the capacity fading of LiNi1/3Co1/3Mn1/3O2/graphite lithium-ion batteries (LIBs) cycled in the voltage range of 3.0-4.6 V (vs. Li/Li+), di(methylsulfonyl) methane (DMSM) is evaluated as a new electrolyte additive. This study demonstrated that DMSM additive in the electrolyte can dramatically improve the cycling performance of LiNi1/3Co1/3Mn1/3O2/graphite cell at a higher voltage operation. In addition, the effects of this additive are characterized by linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), as well as transmission electron microscopy (TEM). With the addition of 0.1 wt. % DMSM into the electrolyte, the capacity loss of the LiNi1/3Co1/3Mn1/3O2/graphite cell cycled at the voltage range of 3.0-4.6 V significantly decreased from 39.0 % to 19.9 % after 100 cycles, which shows the promising application of DMSM at higher voltage. The enhanced cycling performance is attributed to the thinner cathode electrolyte interface film originated from DMSM on the LiNi1/3Co1/3Mn1/3O2, which not only resulted in lower interfacial impedance, but also protected the decomposition of electrolyte and prevented the cathode transition metal dissolution at the high voltage.

  5. 3, 3‧-sulfonyldipropionitrile: A novel electrolyte additive that can augment the high-voltage performance of LiNi1/3Co1/3Mn1/3O2/graphite batteries

    NASA Astrophysics Data System (ADS)

    Zheng, Xiangzhen; Huang, Tao; Pan, Ying; Wang, Wenguo; Fang, Guihuang; Ding, Kaining; Wu, Maoxiang

    2016-07-01

    Our study shows that 3, 3‧-sulfonyldipropionitrile (SDPN), as an electrolyte additive, can dramatically enhance the performance of LiNi1/3Co1/3Mn1/3O2/graphite lithium-ion batteries (LIBs) at high voltages (3.0-4.6 V vs. Li/Li+). After adding 0.2 wt% SDPN to the electrolytes; i.-e., 1.0 M LiPF6-EC/DMC/EMC, the capacity for the LiNi1/3Co1/3Mn1/3O2/graphite cell to retain power was significantly increased from 59.5% to 77.3% after only 100 cycles, which shows the promising application of SDPN at higher voltages. Density functional theory calculation results indicate that SDPN had reduced oxidative constancy compared to ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC). The effects of SDPN on cell performance are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The testing results indicate that the improvement in cycling activity could be ascribed to the thinner cathode electrolyte interface film originated from SDPN on the LIB using LiNi1/3Co1/3Mn1/3O2, which reduced the interfacial resistance at a high voltage, but also protected the decomposition of electrolytes and suppressed transition metal dissolution.

  6. 3,3'-(Ethylenedioxy)dipropiononitrile as an Electrolyte Additive for 4.5 V LiNi1/3Co1/3Mn1/3O2/Graphite Cells.

    PubMed

    Wang, Chengyun; Yu, Le; Fan, Weizhen; Liu, Jiangwen; Ouyang, Liuzhang; Yang, Lichun; Zhu, Min

    2017-03-22

    3,3'-(Ethylenedioxy)dipropiononitrile (EDPN) has been introduced as a novel electrolyte additive to improve the oxidation stability of the conventional carbonate-based electrolyte for LiNi1/3Co1/3Mn1/3O2/graphite pouch batteries cycled under high voltage. Mixing 0.5 wt % EDPN into the electrolyte greatly improved the capacity retention, from 32.5% to 83.9%, of cells cycled for 100 times in the range 3.0-4.5 V with a rate of 1C. The high rate performance (3C and 5C) was also improved, while the cycle performance was similar to that of the cell without EDPN when cycled between 3.0 and 4.2 V. Further evidence of a stable protective interphase film can be formed on the LiNi1/3Co1/3Mn1/3O2 electrode surface due to the presence of EDPN in the electrolyte. This process effectively suppresses the oxidative decomposition of electrolyte and the growth in the charge-transfer resistance of the LiNi1/3Co1/3Mn1/3O2 electrode and greatly improves the high-voltage electrochemical properties for the cells. In contrast, EDPN has no positive effect on the cyclic performance of the LiNi0.5Co0.2Mn0.3O2-based cell under high operating voltage.

  7. Niflumic Acid Alters Gating of HCN2 Pacemaker Channels by Interaction with the Outer Region of S4 Voltage Sensing Domains

    PubMed Central

    Cheng, Lan; Sanguinetti, Michael C.

    2009-01-01

    Niflumic acid, 2-{[3-(trifluoromethyl)phenyl]amino}pyridine-3-carboxylic acid (NFA), is a nonsteroidal anti-inflammatory drug that also blocks or modifies the gating of many ion channels. Here, we investigated the effects of NFA on hyperpolarization-activated cyclic nucleotide-gated cation (HCN) pacemaker channels expressed in X. laevis oocytes using site-directed mutagenesis and the two-electrode voltage-clamp technique. Extracellular NFA acted rapidly and caused a slowing of activation and deactivation and a hyperpolarizing shift in the voltage dependence of HCN2 channel activation (-24.5 ± 1.2 mV at 1 mM). Slowed channel gating and reduction of current magnitude was marked in oocytes treated with NFA, while clamped at 0 mV but minimal in oocytes clamped at -100 mV, indicating the drug preferentially interacts with channels in the closed state. NFA at 0.1 to 3 mM shifted the half-point for channel activation in a concentration-dependent manner, with an EC50 of 0.54 ± 0.068 mM and a predicted maximum shift of -38 mV. NFA at 1 mM also reduced maximum HCN2 conductance by ∼20%, presumably by direct block of the pore. The rapid onset and state-dependence of NFA-induced changes in channel gating suggests an interaction with the extracellular region of the S4 transmembrane helix, the primary voltage-sensing domain of HCN2. Neutralization (by mutation to Gln) of any three of the outer four basic charged residues in S4, but not single mutations, abrogated the NFA-induced shift in channel activation. We conclude that NFA alters HCN2 gating by interacting with the extracellular end of the S4 voltage sensor domains. PMID:19218366

  8. Niflumic acid alters gating of HCN2 pacemaker channels by interaction with the outer region of S4 voltage sensing domains.

    PubMed

    Cheng, Lan; Sanguinetti, Michael C

    2009-05-01

    Niflumic acid, 2-[[3-(trifluoromethyl)phenyl]amino]pyridine-3-carboxylic acid (NFA), is a nonsteroidal anti-inflammatory drug that also blocks or modifies the gating of many ion channels. Here, we investigated the effects of NFA on hyperpolarization-activated cyclic nucleotide-gated cation (HCN) pacemaker channels expressed in X. laevis oocytes using site-directed mutagenesis and the two-electrode voltage-clamp technique. Extracellular NFA acted rapidly and caused a slowing of activation and deactivation and a hyperpolarizing shift in the voltage dependence of HCN2 channel activation (-24.5 +/- 1.2 mV at 1 mM). Slowed channel gating and reduction of current magnitude was marked in oocytes treated with NFA, while clamped at 0 mV but minimal in oocytes clamped at -100 mV, indicating the drug preferentially interacts with channels in the closed state. NFA at 0.1 to 3 mM shifted the half-point for channel activation in a concentration-dependent manner, with an EC(50) of 0.54 +/- 0.068 mM and a predicted maximum shift of -38 mV. NFA at 1 mM also reduced maximum HCN2 conductance by approximately 20%, presumably by direct block of the pore. The rapid onset and state-dependence of NFA-induced changes in channel gating suggests an interaction with the extracellular region of the S4 transmembrane helix, the primary voltage-sensing domain of HCN2. Neutralization (by mutation to Gln) of any three of the outer four basic charged residues in S4, but not single mutations, abrogated the NFA-induced shift in channel activation. We conclude that NFA alters HCN2 gating by interacting with the extracellular end of the S4 voltage sensor domains.

  9. Specific inhibition of HCN channels slows rhythm differently in atria, ventricle and outflow tract and stabilizes conduction in the anoxic-reoxygenated embryonic heart model.

    PubMed

    Sarre, Alexandre; Pedretti, Sarah; Gardier, Stephany; Raddatz, Eric

    2010-01-01

    The hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed in pacemaker cells very early during cardiogenesis. This work aimed at determining to what extent these channels are implicated in the electromechanical disturbances induced by a transient oxygen lack which may occur in utero. Spontaneously beating hearts or isolated ventricles and outflow tracts dissected from 4-day-old chick embryos were exposed to a selective inhibitor of HCN channels (ivabradine 0.1-10microM) to establish a dose-response relationship. The effects of ivabradine on electrocardiogram, excitation-contraction coupling and contractility of hearts submitted to anoxia (30min) and reoxygenation (60min) were also determined. The distribution of the predominant channel isoform, HCN4, was established in atria, ventricle and outflow tract by immunoblotting. Intrinsic beating rate of atria, ventricle and outflow tract was 164+/-22 (n=10), 78+/-24 (n=8) and 40+/-12bpm (n=23, mean+/-SD), respectively. In the whole heart, ivabradine (0.3microM) slowed the firing rate of atria by 16% and stabilized PR interval. These effects persisted throughout anoxia-reoxygenation, whereas the variations of QT duration, excitation-contraction coupling and contractility, as well as the types and duration of arrhythmias were not altered. Ivabradine (10microM) reduced the intrinsic rate of atria and isolated ventricle by 27% and 52%, respectively, whereas it abolished activity of the isolated outflow tract. Protein expression of HCN4 channels was higher in atria and ventricle than in the outflow tract. Thus, HCN channels are specifically distributed and control finely atrial, ventricular and outflow tract pacemakers as well as conduction in the embryonic heart under normoxia and throughout anoxia-reoxygenation.

  10. Investigating the impact of light and water status on the exchange of COS, 13CO2, CO18O and H218O from bryophytes

    NASA Astrophysics Data System (ADS)

    Gimeno, Teresa; Royles, Jessica; Ogee, Jerome; Jones, Samuel; Burlett, Regis; West, Jason; Sauze, Joana; Wohl, Steven; Genty, Bernard; Griffiths, Howard; Wingate, Lisa

    2016-04-01

    Terrestrial surfaces are often covered by photoautotrophic communities that play a significant role in the biological fixation of C and N at the global scale. Bryophytes (mosses, liverworts and hornworts) are key members in these communities and are especially adapted to thrive in hostile environments, by growing slowly and surviving repeated dehydration events. Consequently, bryophyte communities can be extremely long-lived (>1500yrs) and can serve as valuable records of historic climate change. In particular the carbon and oxygen isotope compositions of mosses can be used as powerful proxies describing how growing season changes in atmospheric CO2 and rainfall have changed in the distant past over the land surface. Interpreting the climate signals of bryophyte biomass requires a robust understanding of how changes in photosynthetic activity and moisture status regulate the growth and isotopic composition of bryophyte biomass. Thus theoretical models predicting how changes in isotopic enrichment and CO2 discrimination respond to dehydration and rehydration are used to tease apart climatic and isotopic source signals. Testing these models with high resolution datasets obtained from new generation laser spectrometers can provide more information on how these plants that lack stomata cope with water loss. In addition novel tracers such as carbonyl sulfide (COS) can also be measured at high resolution and precision (<5ppt) and used to constrain understanding of diffusional and enzymatic limitations during dehydration and rehydration events in the light and the dark. Here, we will present for the first time simultaneous high-resolution chamber measurements of COS, 13CO2, CO18O and H218O fluxes by a bryophyte species (Marchantia sp.) in the light and during the dark, through complete desiccation cycles. Our measurements consistently reveal a strong enrichment dynamic in the oxygen isotope composition of transpired water over the dessication cycle that caused an increase

  11. Iron regulation of the hcnABC genes encoding hydrogen cyanide synthase depends on the anaerobic regulator ANR rather than on the global activator GacA in Pseudomonas fluorescens CHA0.

    PubMed

    Blumer, C; Haas, D

    2000-10-01

    Pseudomonas fluorescens CHA0 produces hydrogen cyanide (HCN), a secondary metabolite that substantially contributes to this strain's biocontrol ability. Cyanogenesis is induced by oxygen-limiting conditions, but abolished by iron depletion. In P. fluorescens, the anaerobic regulator ANR and the global activator GacA are both required for the maximal expression of the HCN biosynthetic genes hcnABC. The molecular basis of this regulation by ANR and GacA was investigated under conditions of oxygen and iron limitation. A promoter deletion analysis using a translational hcnA'-'lacZ fusion revealed that a conserved FNR/ANR recognition sequence in the -40 promoter region was necessary and sufficient for the regulation by ANR in response to oxygen limitation. Stimulation of hcnA'-'lacZ expression by the addition of iron also depended on the presence of ANR and the FNR/ANR box, but not on GacA, suggesting that in addition to acting as an oxygen-sensitive protein, ANR also responds to iron availability. Expression of the translational hcnA'-'lacZ fusion remained GacA-dependent in hcn promoter mutants that were no longer responsive to ANR, in agreement with earlier evidence for a post-transcriptional regulatory mechanism under GacA control. These data support a model in which cyanogenesis is sequentially activated by ANR at the level of transcription and by components of the GacA network at the level of translation.

  12. A novel process for recycling and resynthesizing LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} from the cathode scraps intended for lithium-ion batteries

    SciTech Connect

    Zhang, Xihua; Xie, Yongbing; Cao, Hongbin; Nawaz, Faheem; Zhang, Yi

    2014-09-15

    Highlights: • A simple process to recycle cathode scraps intended for lithium-ion batteries. • Complete separation of the cathode material from the aluminum foil is achieved. • The recovered aluminum foil is highly pure. • LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} is directly resynthesized from the separated cathode material. - Abstract: To solve the recycling challenge for aqueous binder based lithium-ion batteries (LIBs), a novel process for recycling and resynthesizing LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} from the cathode scraps generated during manufacturing process is proposed in this study. Trifluoroacetic acid (TFA) is employed to separate the cathode material from the aluminum foil. The effects of TFA concentration, liquid/solid (L/S) ratio, reaction temperature and time on the separation efficiencies of the cathode material and aluminum foil are investigated systematically. The cathode material can be separated completely under the optimal experimental condition of 15 vol.% TFA solution, L/S ratio of 8.0 mL g{sup −1}, reacting at 40 °C for 180 min along with appropriate agitation. LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} is successfully resynthesized from the separated cathode material by solid state reaction method. Several kinds of characterizations are performed to verify the typical properties of the resynthesized LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} powder. Electrochemical tests show that the initial charge and discharge capacities of the resynthesized LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} are 201 mAh g{sup −1} and 155.4 mAh g{sup −1} (2.8–4.5 V, 0.1 C), respectively. The discharge capacity remains at 129 mAh g{sup −1} even after 30 cycles with a capacity retention ratio of 83.01%.

  13. HCN and CN in comet 2P/Encke, a three-dimensional view on comet Encke's outgassing

    NASA Astrophysics Data System (ADS)

    Jockers, K.; Szutowicz, S.

    2008-09-01

    Background Simultaneous radio and optical observations of chemically related species in comets promise to supplement each other favorably. High resolution spectra of a submillimeter line provide the distribution of radial velocity. Narrow-band images in the optical region offer the spatial distribution of a species projected into the sky plane perpendicular to the line of sight. Therefore optical and radio observations can in principle be combined into a three-dimensional picture of a comet. A suitable pair of species accessible in the microwave and optical wavelength range is provided by HCN (one of the strongest radio emissions of comets) and CN (strong optical emission). HCN is the most probable parent of CN, but other parents of CN are possible. In this study we use HCN and CN observations of comet it 2P/Encke to address the parental relation of HCN with respect to CN and to investigate the gas outflow from a cometary surface and its dependence on location on the surface (the question of so-called "active vents" or "active areas") and on solar zenith angle. Some known facts about Comet 2P/Encke Comet 2P/Encke is a short period comet. It has the smallest known perihelion distance q = 0.33 AU and a period of 3.28 years. Because of its closeness to the Sun Comet Encke probably is the most evolved comet known. In the optical wavelength range comet Encke does not display a dust tail. Instead a so-called "fan" is observed, a broad feature visible at the solar side of the comet but not directly pointing to the Sun. In the far infrared spectral region Comet Encke displays a huge coma [1] of large dust grains but because of their large size these grains do not contibute significantly to the optical image [2]. In a study based on a large number of historical observations Sekanina [3] has investigated comet Encke's fan-shaped coma. According to this author comet Encke's north rotation pole is located at right ascension 205° and declination 2° (equinox 1950.0). Two vents

  14. Isotope effects in the CO dimer: Millimeter wave spectrum and rovibrational calculations of (12C18O)2

    NASA Astrophysics Data System (ADS)

    Surin, L. A.; Fourzikov, D. N.; Giesen, T. F.; Schlemmer, S.; Winnewisser, G.; Panfilov, V. A.; Dumesh, B. S.; Vissers, G. W. M.; van der Avoird, A.

    2006-09-01

    The millimeter wave spectrum of the isotopically substituted CO dimer, (C12O18)2, was studied with the Orotron jet spectrometer, confirming and extending a previous infrared study [A. R. W. McKellar, J. Mol. Spectrosc. 226, 190 (2004)]. A very dilute gas mixture of CO in Ne was used, which resulted in small consumption of C12O18 sample gas and produced cold and simple spectra. Using the technique of combination differences together with the data from the infrared work, six transitions in the 84-127GHz region have been assigned. They belong to two branches, which connect four low levels of A+ symmetry to three previously unknown levels of A- symmetry. The discovery of the lowest state of A- symmetry, which corresponds to the projection K =0 of the total angular momentum J onto the intermolecular axis, identifies the geared bending mode of the C12O18 dimer at 3.607cm-1. Accompanying rovibrational calculations using a recently developed hybrid potential from ab initio coupled cluster [CCSD(T)] and symmetry-adapted perturbation theory calculations [G. W. M. Vissers et al., J. Chem. Phys. 122, 054306 (2005)] gave very good agreement with experiment. The isotopic dependence of the A+/A- energy splitting, the intermolecular separation R, and the energy difference of two ground state isomers, which change significantly when O18 or C13 are substituted into the normal (C12O16)2 isotopolog [L. A. Surin et al., J. Mol. Spectrosc. 223, 132 (2004)], was explained by these calculations. It turns out that the change in anisotropy of the intermolecular potential with respect to the shifted monomer centers of mass is particularly significant.

  15. A theoretical study of hydrogen complexes of the XH-pi type between propyne and HF, HCL or HCN.

    PubMed

    Tavares, Alessandra M; da Silva, Washington L V; Lopes, Kelson C; Ventura, Elizete; Araújo, Regiane C M U; do Monte, Silmar A; da Silva, João Bosco P; Ramos, Mozart N

    2006-05-15

    The present manuscript reports a systematic investigation of the basis set dependence of some properties of hydrogen-bonded (pi type) complexes formed by propyne and a HX molecule, where X=F, Cl and CN. The calculations have been performed at Hartree-Fock, MP2 and B3LYP levels. Geometries, H-bond energies and vibrational have been considered. The more pronounced effects on the structural parameters of the isolated molecules, as a result of complexation, are verified on RCtriple bondC and HX bond lengths. As compared to double-zeta (6-31G**), triple-zeta (6-311G**) basis set leads to an increase of RCtriple bondC bond distance, at all three computational levels. In the case where diffuse functions are added to both hydrogen and 'heavy' atoms, the effect is more pronounced. The propyne-HX structural parameters are quite similar to the corresponding parameters of acetylene-HX complexes, at all levels. The largest difference is obtained for hydrogen bond distance, RH, with a smaller value for propyne-HX complex, indicating a stronger bond. Concerning the electronic properties, the results yield the following ordering for H-bond energies, DeltaE: propynecdots, three dots, centeredHF>propynecdots, three dots, centeredHCl>propynecdots, three dots, centeredHCN. It is also important to point out that the inclusion of BSSE and zero-point energies (ZPE) corrections cause significant changes on DeltaE. The smaller effect of ZPE is obtained for propynecdots, three dots, centeredHCN at HF/6-311++G** level, while the greatest difference is obtained at MP2/6-31G** level for propynecdots, three dots, centeredHF system. Concerning the IR vibrational it was obtained that larger shift can be associated with stronger hydrogen bonds. The more pronounced effect on the normal modes of the isolated molecule after the complexation is obtained for HX stretching frequency, which is shifted downward.

  16. Stability and breakdown of Ca{sup 13}CO{sub 3} melt associated with formation of {sup 13}C-diamond in static high pressure experiments up to 43 GPa and 3900 K

    SciTech Connect

    Spivak, A.V.; Litvin, Yu.A.; Ovsyannikov, S.V.; Dubrovinskaia, N.A.; Dubrovinsky, L.S.

    2012-07-15

    Melting of calcium carbonate Ca{sup 13}CO{sub 3}, stability of the melt and its decomposition were studied in static high pressure experiments at pressures of 11-43 GPa and temperatures of 1600-3900 K using diamond anvil cell technique with laser heating. We observed formation of {sup 13}C-graphite (below 16 GPa) and {sup 13}C-diamond (between 16 and 43 GPa) on decomposition of the Ca{sup 13}CO{sub 3} melt at temperatures above 3400 K. At temperatures below 3400 K congruent melting of calcium carbonate was confirmed. The experimental results were applied to construction of the phase diagram of CaCO{sub 3} up to 43 GPa and 3900 K focusing at the melting curve of calcium carbonate and the decomposition phase boundary of CaCO{sub 3} melt. - Graphical abstract: Highlights: Black-Right-Pointing-Pointer Phase states of CaCO{sub 3} were studied at P=11-43 GPa and T=1600-3900 K. Black-Right-Pointing-Pointer {sup 13}C-diamond easily crystallizes in carbonate-carbon (Ca{sup 13}CO{sub 3-}{sup 13}C-graphite) melt-solutions. Black-Right-Pointing-Pointer Ca-carbonate melts congruently that was observed in experiments in DAC with laser heating. Black-Right-Pointing-Pointer Decomposition of CaCO{sub 3} melt, indicated by formation of graphite and/or diamond. Black-Right-Pointing-Pointer Decomposition of CaCO{sub 3} was observed at temperatures above 3400 K in the pressure interval studied.

  17. THE ARIZONA RADIO OBSERVATORY CO MAPPING SURVEY OF GALACTIC MOLECULAR CLOUDS. IV. THE NGC 1333 CLOUD IN PERSEUS IN CO J = 2-1 AND {sup 13}CO J = 2-1

    SciTech Connect

    Bieging, John H.; Revelle, Melissa; Peters, William L.

    2014-09-01

    We mapped the NGC 1333 section of the Perseus Molecular Cloud in the J = 2-1 emission lines of {sup 12}CO and {sup 13}CO over a 50' × 60' region (3.4 × 4.1 pc at the cloud distance of 235 pc), using the Arizona Radio Observatory Heinrich Hertz Submillimeter Telescope. The angular resolution is 38'' (0.04 pc) and velocity resolution is 0.3 km s{sup –1}. We compare our velocity moment maps with known positions of young stellar objects (YSOs) and (sub)millimeter dust continuum emission. The CO emission is brightest at the center of the cluster of YSOs, but is detected over the full extent of the mapped region at ≥10 × rms. The morphology of the CO channel maps shows a kinematically complex structure, with many elongated features extending from the YSO cluster outward by ∼1 pc. One notable feature appears as a narrow serpentine structure that curves and doubles back, with a total length of ∼3 pc. The {sup 13}CO velocity channel maps show evidence for many low-density cavities surrounded by partial shell-like structures, consistent with previous studies. Maps of the velocity moments show localized effects of bipolar outflows from embedded YSOs, as well as a large-scale velocity gradient around the central core of YSOs, suggestive of large-scale turbulent cloud motions determining the location of current star formation. The CO/{sup 13}CO intensity ratios show the distribution of the CO opacity, which exhibits a complex kinematic structure. Identified YSOs are located mainly at the positions of greatest CO opacity. The maps are available for download as FITS files.

  18. Hydrogen constituents of the mesosphere inferred from positive ions - H2O, CH4, H2CO, H2O2, and HCN

    NASA Technical Reports Server (NTRS)

    Kopp, E.

    1990-01-01

    The concentrations in the mesosphere of H2O, CH4, H2CO, H2O2, and HCN were inferred from data on positive ion compositions, obtained from one mid-latitude and four high-latitude rocket flights. The inferred concentrations were found to agree only partially with the ground-based microwave measurements and/or model prediction by Garcia and Solomon (1985). The CH4 concentration was found to vary between 70 and 4 ppb in daytime and 900 and 100 ppbv at night, respectively. Unexpectedly high H2CO concentrations were obtained, with H2CO/H2O ratios between 0.0006 and 0.1, and a mean HCN volume mixing ratio of 6 x 10 to the -10th was inferred.

  19. 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

  20. Transcriptional control of the hydrogen cyanide biosynthetic genes hcnABC by the anaerobic regulator ANR and the quorum-sensing regulators LasR and RhlR in Pseudomonas aeruginosa.

    PubMed

    Pessi, G; Haas, D

    2000-12-01

    Virulence factors of Pseudomonas aeruginosa include hydrogen cyanide (HCN). This secondary metabolite is maximally produced at low oxygen tension and high cell densities during the transition from exponential to stationary growth phase. The hcnABC genes encoding HCN synthase were identified on a genomic fragment complementing an HCN-deficient mutant of P. aeruginosa PAO1. The hcnA promoter was found to be controlled by the FNR-like anaerobic regulator ANR and by the quorum-sensing regulators LasR and RhlR. Primer extension analysis revealed two transcription starts, T1 and T2, separated by 29 bp. Their function was confirmed by transcriptional lacZ fusions. The promoter sequence displayed an FNR/ANR box at -42.5 bp upstream of T2 and a lux box centered around -42.5 bp upstream of T1. Expression of the hcn genes was completely abolished when this lux box was deleted or inactivated by two point mutations in conserved nucleotides. The lux box was recognized by both LasR [activated by N-(oxododecanoyl)-homoserine lactone] and RhlR (activated by N-butanoyl-homoserine lactone), as shown by expression experiments performed in quorum-sensing-defective P. aeruginosa mutants and in the N-acyl-homoserine lactone-negative heterologous host P. fluorescens CHA0. A second, less conserved lux box lying 160 bp upstream of T1 seems to account for enhanced quorum-sensing-dependent expression. Without LasR and RhlR, ANR could not activate the hcn promoter. Together, these data indicate that expression of the hcn promoter from T1 can occur under quorum-sensing control alone. Enhanced expression from T2 appears to rely on a synergistic action between LasR, RhlR, and ANR.

  1. Transcriptional Control of the Hydrogen Cyanide Biosynthetic Genes hcnABC by the Anaerobic Regulator ANR and the Quorum-Sensing Regulators LasR and RhlR in Pseudomonas aeruginosa

    PubMed Central

    Pessi, Gabriella; Haas, Dieter

    2000-01-01

    Virulence factors of Pseudomonas aeruginosa include hydrogen cyanide (HCN). This secondary metabolite is maximally produced at low oxygen tension and high cell densities during the transition from exponential to stationary growth phase. The hcnABC genes encoding HCN synthase were identified on a genomic fragment complementing an HCN-deficient mutant of P. aeruginosa PAO1. The hcnA promoter was found to be controlled by the FNR-like anaerobic regulator ANR and by the quorum-sensing regulators LasR and RhlR. Primer extension analysis revealed two transcription starts, T1 and T2, separated by 29 bp. Their function was confirmed by transcriptional lacZ fusions. The promoter sequence displayed an FNR/ANR box at −42.5 bp upstream of T2 and a lux box centered around −42.5 bp upstream of T1. Expression of the hcn genes was completely abolished when this lux box was deleted or inactivated by two point mutations in conserved nucleotides. The lux box was recognized by both LasR [activated by N-(oxododecanoyl)-homoserine lactone] and RhlR (activated by N-butanoyl-homoserine lactone), as shown by expression experiments performed in quorum-sensing-defective P. aeruginosa mutants and in the N-acyl-homoserine lactone-negative heterologous host P. fluorescens CHA0. A second, less conserved lux box lying 160 bp upstream of T1 seems to account for enhanced quorum-sensing-dependent expression. Without LasR and RhlR, ANR could not activate the hcn promoter. Together, these data indicate that expression of the hcn promoter from T1 can occur under quorum-sensing control alone. Enhanced expression from T2 appears to rely on a synergistic action between LasR, RhlR, and ANR. PMID:11092854

  2. Leaching process for recovering valuable metals from the LiNi1/3Co1/3Mn1/3O2 cathode of lithium-ion batteries.

    PubMed

    He, Li-Po; Sun, Shu-Ying; Song, Xing-Fu; Yu, Jian-Guo

    2017-03-18

    In view of the importance of environmental protection and resource recovery, recycling of spent lithium-ion batteries (LIBs) and electrode scraps generated during manufacturing processes is quite necessary. An environmentally sound leaching process for the recovery of Li, Ni, Co, and Mn from spent LiNi1/3Co1/3Mn1/3O2-based LIBs and cathode scraps was investigated in this study. Eh-pH diagrams were used to determine suitable leaching conditions. Operating variables affecting the leaching efficiencies for Li, Ni, Co, and Mn from LiNi1/3Co1/3Mn1/3O2, such as the H2SO4 concentration, temperature, H2O2 concentration, stirring speed, and pulp density, were investigated to determine the most efficient conditions for leaching. The leaching efficiencies for Li, Ni, Co, and Mn reached 99.7% under the optimized conditions of 1M H2SO4, 1vol% H2O2, 400rpm stirring speed, 40g/L pulp density, and 60min leaching time at 40°C. The leaching kinetics of LiNi1/3Co1/3Mn1/3O2 were found to be significantly faster than those of LiCoO2. Based on the variation in the weight fraction of the metal in the residue, the "cubic rate law" was revised as follows: θ(1-f)(1/3)=(1-kt/r0ρ), which could characterize the leaching kinetics optimally. The activation energies were determined to be 64.98, 65.16, 66.12, and 66.04kJ/mol for Li, Ni, Co, and Mn, respectively, indicating that the leaching process was controlled by the rate of surface chemical reactions. Finally, a simple process was proposed for the recovery of valuable metals from spent LiNi1/3Co1/3Mn1/3O2-based LIBs and cathode scraps.

  3. MEG3, HCN3 and linc01105 influence the proliferation and apoptosis of neuroblastoma cells via the HIF-1α and p53 pathways

    PubMed Central

    Tang, Weitao; Dong, Kuiran; Li, Kai; Dong, Rui; Zheng, Shan

    2016-01-01

    The purpose of this study was to investigate the differential expression and functional roles of long non-coding RNAs (lncRNAs) in neuroblastoma tissue. LncRNA microarrays were used to identify differentially expressed lncRNAs between tumor and para-tumor tissues. In total, in tumor tissues, 3,098 and 1,704 lncRNAs were upregulated and downregulated, respectively. HCN3 and linc01105 exhibited the higher expression (P < 0.05; P < 0.01, respectively) in neuroblastoma tissue, whereas MEG3 displayed the lower expression (P < 0.01). HIF-1α expression was negatively correlated with cell proliferation in the linc01105 KD group. In addition, Noxa and Bid expression was positively correlated with cell apoptosis. Moreover, linc01105 knockdown promoted cell proliferation, whereas MEG3 overexpression inhibited proliferation. Finally, linc01105 knockdown, MEG3 overexpression and HCN3 knockdown all increased apoptosis. The correlation coefficients between those three lncRNAs and the International Neuroblastoma Staging System (INSS) stage were −0.48, −0.58 and −0.55, respectively. In conclusion, we have identified lncRNAs that are differentially expressed in neuroblastoma tissues. The lncRNAs HCN3, linc01105, and MEG3 may be important in biological behaviors of neuroblastoma through mechanisms involving p53 pathway members such as HIF-1α, Noxa, and Bid. The expressions of MEG3, HCN3 and linc01105 are all negatively correlated with the INSS stage. PMID:27824082

  4. Inner activation gate in S6 contributes to the state-dependent binding of cAMP in full-length HCN2 channel

    PubMed Central

    Wu, Shengjun; Gao, Weihua; Xie, Changan; Xu, Xinping; Vorvis, Christina; Marni, Farzana; Hackett, Amber R.; Liu, Qinglian

    2012-01-01

    Recently, applications of the patch-clamp fluorometry (PCF) technique in studies of cyclic nucleotide–gated (CNG) and hyperpolarization-activated, cyclic nucleotide–regulated (HCN) channels have provided direct evidence for the long-held notion that ligands preferably bind to and stabilize these channels in an open state. This state-dependent ligand–channel interaction involves contributions from not only the ligand-binding domain but also other discrete structural elements within the channel protein. This insight led us to investigate whether the pore of the HCN channel plays a role in the ligand–whole channel interaction. We used three well-characterized HCN channel blockers to probe the ion-conducting passage. The PCF technique was used to simultaneously monitor channel activity and cAMP binding. Two ionic blockers, Cs+ and Mg2+, effectively block channel conductance but have no obvious effect on cAMP binding. Surprisingly, ZD7288, an open channel blocker specific for HCN channels, significantly reduces the activity-dependent increase in cAMP binding. Independent biochemical assays exclude any nonspecific interaction between ZD7288 and isolated cAMP-binding domain. Because ZD7228 interacts with the inner pore region, where the activation gate is presumably located, we did an alanine scanning of the intracellular end of S6, from T426 to A435. Mutations of three residues, T426, M430, and H434, which are located at regular intervals on the S6 α-helix, enhance cAMP binding. In contrast, mutations of two residues in close proximity, F431A and I432A, dampen the response. Our results demonstrate that movements of the structural elements near the activation gate directly affect ligand binding affinity, which is a simple mechanistic explanation that could be applied to the interpretation of ligand gating in general. PMID:22689828

  5. Histamine Increases Neuronal Excitability and Sensitivity of the Lateral Vestibular Nucleus and Promotes Motor Behaviors via HCN Channel Coupled to H2 Receptor

    PubMed Central

    Li, Bin; Zhang, Xiao-Yang; Yang, Ai-Hong; Peng, Xiao-Chun; Chen, Zhang-Peng; Zhou, Jia-Yuan; Chan, Ying-Shing; Wang, Jian-Jun; Zhu, Jing-Ning

    2017-01-01

    Histamine and histamine receptors in the central nervous system actively participate in the modulation of motor control. In clinic, histamine-related agents have traditionally been used to treat vestibular disorders. Immunohistochemical studies have revealed a distribution of histaminergic afferents in the brainstem vestibular nuclei, including the lateral vestibular nucleus (LVN), which is critical for adjustment of muscle tone and vestibular reflexes. However, the mechanisms underlying the effect of histamine on LVN neurons and the role of histamine and histaminergic afferents in the LVN in motor control are still largely unknown. Here, we show that histamine, in cellular and molecular levels, elicits the LVN neurons of rats an excitatory response, which is co-mediated by the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and K+ channels linked to H2 receptors. Blockage of HCN channels coupled to H2 receptors decreases LVN neuronal sensitivity and changes their dynamic properties. Furthermore, in behavioral level, microinjection of histamine into bilateral LVNs significantly promotes motor performances of rats on both accelerating rota-rod and balance beam. This promotion is mimicked by selective H2 receptor agonist dimaprit, and blocked by selective H2 receptor antagonist ranitidine. More importantly, blockage of HCN channels to suppress endogenous histaminergic inputs in the LVN considerably attenuates motor balance and coordination, indicating a promotion role of hypothalamo-vestibular histaminergic circuit in motor control. All these results demonstrate that histamine H2 receptors and their coupled HCN channels mediate the histamine-induced increase in excitability and sensitivity of LVN neurons and contribute to the histaminergic improvement of the LVN-related motor behaviors. The findings suggest that histamine and the histaminergic afferents may directly modulate LVN neurons and play a critical role in the central vestibular

  6. The nature of interactions between clusters of Mg and Zn with HCN from symmetry-adapted perturbation theory based of DFT

    NASA Astrophysics Data System (ADS)

    Snyder, Desirée N.; Szcześniak, Małgorzata M.; Chałasiński, Grzegorz

    2009-06-01

    The donor-acceptor complexes HCN-Mgn and HCN-Znn (n =1,…,4), which were recently detected in helium nanodroplet infrared spectroscopy experiments by Miller and co-workers [Science 292, 481 (2001); J. Phys. Chem. A 110, 5620 (2006)] are investigated by the symmetry-adapted perturbation theory based on the density functional monomer description [SAPT(DFT)]. The interaction energy components, such as the electrostatic, exchange, induction, and dispersion, are calculated as a function of the metal cluster size. We find that the donor-acceptor interactions manifest themselves by the large induction and dispersion interactions, which counteract the unusually large exchange repulsion. The dependence of the components on the clusters size n follows different patterns in the complexes of magnesium and zinc. In HCN-Mgn the induction effect increases in magnitude much faster than the dispersion effect. In HCN-Znn there is a slight decrease in both dispersion and induction terms between n =2 and n =3. Then dispersion rises faster than induction between n =3 and n =4. The exchange effects are also much different in both types of complexes. The first-order exchange energy rises much faster with n in the magnesium complexes than in the zinc complexes. Furthermore, in the latter there is a significant drop in the exchange energy between n =2 and n =3. The second-order exchange effects tend to quench a larger percentage of the induction and dispersion contributions in the Mgn complexes than in Znn. These different patterns of the interaction energy variations with n are related to the different nature of nonadditive effects in the neat metal clusters.

  7. Histamine Increases Neuronal Excitability and Sensitivity of the Lateral Vestibular Nucleus and Promotes Motor Behaviors via HCN Channel Coupled to H2 Receptor.

    PubMed

    Li, Bin; Zhang, Xiao-Yang; Yang, Ai-Hong; Peng, Xiao-Chun; Chen, Zhang-Peng; Zhou, Jia-Yuan; Chan, Ying-Shing; Wang, Jian-Jun; Zhu, Jing-Ning

    2016-01-01

    Histamine and histamine receptors in the central nervous system actively participate in the modulation of motor control. In clinic, histamine-related agents have traditionally been used to treat vestibular disorders. Immunohistochemical studies have revealed a distribution of histaminergic afferents in the brainstem vestibular nuclei, including the lateral vestibular nucleus (LVN), which is critical for adjustment of muscle tone and vestibular reflexes. However, the mechanisms underlying the effect of histamine on LVN neurons and the role of histamine and histaminergic afferents in the LVN in motor control are still largely unknown. Here, we show that histamine, in cellular and molecular levels, elicits the LVN neurons of rats an excitatory response, which is co-mediated by the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and K(+) channels linked to H2 receptors. Blockage of HCN channels coupled to H2 receptors decreases LVN neuronal sensitivity and changes their dynamic properties. Furthermore, in behavioral level, microinjection of histamine into bilateral LVNs significantly promotes motor performances of rats on both accelerating rota-rod and balance beam. This promotion is mimicked by selective H2 receptor agonist dimaprit, and blocked by selective H2 receptor antagonist ranitidine. More importantly, blockage of HCN channels to suppress endogenous histaminergic inputs in the LVN considerably attenuates motor balance and coordination, indicating a promotion role of hypothalamo-vestibular histaminergic circuit in motor control. All these results demonstrate that histamine H2 receptors and their coupled HCN channels mediate the histamine-induced increase in excitability and sensitivity of LVN neurons and contribute to the histaminergic improvement of the LVN-related motor behaviors. The findings suggest that histamine and the histaminergic afferents may directly modulate LVN neurons and play a critical role in the central vestibular

  8. Rate Coefficients for Reactions of Ethynyl Radical (C2H) With HCN and CH3CN: Implications for the Formation of Comples Nitriles on Titan

    NASA Technical Reports Server (NTRS)

    Hoobler, Ray J.; Leone, Stephen R.

    1997-01-01

    Rate coefficients for the reactions of C2H + HCN yields products and C2H + CH3CN yields products have been measured over the temperature range 262-360 K. These experiments represent an ongoing effort to accurately measure reaction rate coefficients of the ethynyl radical, C2H, relevant to planetary atmospheres such as those of Jupiter and Saturn and its satellite Titan. Laser photolysis of C2H2 is used to produce C2H, and transient infrared laser absorption is employed to measure the decay of C2H to obtain the subsequent reaction rates in a transverse flow cell. Rate constants for the reaction C2H + HCN yields products are found to increase significantly with increasing temperature and are measured to be (3.9-6.2) x 10(exp 13) cm(exp 3) molecules(exp -1) s(exp -1) over the temperature range of 297-360 K. The rate constants for the reaction C2H + CH3CN yields products are also found to increase substantially with increasing temperature and are measured to be (1.0-2.1) x 10(exp -12) cm(exp 3) molecules(exp -1) s(exp -1) over the temperature range of 262-360 K. For the reaction C2H + HCN yields products, ab initio calculations of transition state structures are used to infer that the major products form via an addition/elimination pathway. The measured rate constants for the reaction of C2H + HCN yields products are significantly smaller than values currently employed in photochemical models of Titan, which will affect the HC3N distribution.

  9. THE SOURCES OF HCN AND CH{sub 3}OH AND THE ROTATIONAL TEMPERATURE IN COMET 103P/HARTLEY 2 FROM TIME-RESOLVED MILLIMETER SPECTROSCOPY

    SciTech Connect

    Drahus, Michal; Jewitt, David; Guilbert-Lepoutre, Aurelie; Waniak, Waclaw; Sievers, Albrecht

    2012-09-01

    One of the least understood properties of comets is the compositional structure of their nuclei, which can either be homogeneous or heterogeneous. The nucleus structure can be conveniently studied at millimeter wavelengths, using velocity-resolved spectral time series of the emission lines, obtained simultaneously for multiple molecules as the body rotates. Using this technique, we investigated the sources of CH{sub 3}OH and HCN in comet 103P/Hartley 2, the target of NASA's EPOXI mission, which had an exceptionally favorable apparition in late 2010. Our monitoring with the IRAM 30 m telescope shows short-term variability of the spectral lines caused by nucleus rotation. The varying production rates generate changes in brightness by a factor of four for HCN and by a factor of two for CH{sub 3}OH, and they are remarkably well correlated in time. With the addition of the velocity information from the line profiles, we identify the main sources of outgassing: two jets, oppositely directed in a radial sense, and icy grains, injected into the coma primarily through one of the jets. The mixing ratio of CH{sub 3}OH and HCN is dramatically different in the two jets, which evidently shows large-scale chemical heterogeneity of the nucleus. We propose a network of identities linking the two jets with morphological features reported elsewhere and postulate that the chemical heterogeneity may result from thermal evolution. The model-dependent average production rates are 3.5 Multiplication-Sign 10{sup 26} molecules s{sup -1} for CH{sub 3}OH and 1.25 Multiplication-Sign 10{sup 25} molecules s{sup -1} for HCN, and their ratio of 28 is rather high but not abnormal. The rotational temperature from CH{sub 3}OH varied strongly, presumably due to nucleus rotation, with the average value being 47 K.

  10. cAMP Control of HCN2 Channel Mg2+ Block Reveals Loose Coupling between the Cyclic Nucleotide-Gating Ring and the Pore

    PubMed Central

    Lyashchenko, Alex K.; Redd, Kacy J.; Goldstein, Peter A.; Tibbs, Gareth R.

    2014-01-01

    Hyperpolarization-activated cyclic nucleotide-regulated HCN channels underlie the Na+-K+ permeable IH pacemaker current. As with other voltage-gated members of the 6-transmembrane KV channel superfamily, opening of HCN channels involves dilation of a helical bundle formed by the intracellular ends of S6 albeit this is promoted by inward, not outward, displacement of S4. Direct agonist binding to a ring of cyclic nucleotide-binding sites, one of which lies immediately distal to each S6 helix, imparts cAMP sensitivity to HCN channel opening. At depolarized potentials, HCN channels are further modulated by intracellular Mg2+ which blocks the open channel pore and blunts the inhibitory effect of outward K+ flux. Here, we show that cAMP binding to the gating ring enhances not only channel opening but also the kinetics of Mg2+ block. A combination of experimental and simulation studies demonstrates that agonist acceleration of block is mediated via acceleration of the blocking reaction itself rather than as a secondary consequence of the cAMP enhancement of channel opening. These results suggest that the activation status of the gating ring and the open state of the pore are not coupled in an obligate manner (as required by the often invoked Monod-Wyman-Changeux allosteric model) but couple more loosely (as envisioned in a modular model of protein activation). Importantly, the emergence of second messenger sensitivity of open channel rectification suggests that loose coupling may have an unexpected consequence: it may endow these erstwhile “slow” channels with an ability to exert voltage and ligand-modulated control over cellular excitability on the fastest of physiologically relevant time scales. PMID:24983358

  11. Submillimeter Observations of Titan: Global Measures of Stratospheric Temperature, CO, HCN, HC3N, and the Isotopic Ratios 12C/13C and 14N/15N

    NASA Astrophysics Data System (ADS)

    Gurwell, Mark A.

    2004-11-01

    Interferometric observations of the atmosphere of Titan were performed with the Submillimeter Array on two nights in 2004 February to investigate the global average vertical distributions of several molecular species above the tropopause. Rotational transitions of CO, isomers of HCN, and HC3N were simultaneously recorded. The abundance of CO is determined to be 51+/-4 parts per million (ppm), constant with altitude. The vertical profile of HCN is dependent on the assumed temperature but generally increases from 30 parts per billion at the condensation altitude (~83 km) to 5 ppm at ~300 km. Furthermore, the central core of the HCN emission is strong and can be reproduced only if the upper stratospheric temperature increases with altitude. The isotopic ratios are determined to be 12C/13C=132+/-25 and 14N/15N=94+/-13 assuming the Coustenis & Bézard temperature profile. If the Lellouch temperature profile is assumed, the ratios decrease to 12C/13C=108+/-20 and 14N/15N=72+/-9. The vertical profile of HC3N is consistent with that derived by Marten et al.

  12. Thermal formation of hydroxynitriles, precursors of hydroxyacids in astrophysical ice analogs: Acetone ((CH3)2Cdbnd O) and hydrogen cyanide (HCN) reactivity

    NASA Astrophysics Data System (ADS)

    Fresneau, Aurélien; Danger, Grégoire; Rimola, Albert; Duvernay, Fabrice; Theulé, Patrice; Chiavassa, Thierry

    2015-11-01

    Reactivity in astrophysical environments is still poorly understood. In this contribution, we investigate the thermal reactivity of interstellar ice analogs containing acetone ((CH3)2CO), ammonia (NH3), hydrogen cyanide (HCN) and water (H2O) by means of infrared spectroscopy and mass spectrometry techniques, complemented by quantum chemical calculations. We show that no reaction occurs in H2O:HCN:(CH3)2CO ices. Nevertheless, HCN does indeed react with acetone once activated by NH3 into CN- to form 2-hydroxy-2-methylpropanenitrile (HOsbnd C(CH3)2sbnd CN), with a calculated activation energy associated with the rate determining step of about 51 kJ mol-1. This reaction inhibits the formation of 2-aminopropan-2-ol (HOsbnd C(CH3)2sbnd NH2) from acetone and NH3, even in the presence of water, which is the first step of the Strecker synthesis to form 2-aminoisobutyric acid (NH2C(CH3)2COOH). However, HOsbnd C(CH3)2sbnd CN formation could be part of an alternative chemical pathway leading to 2-hydroxy-2-methyl-propanoic acid (HOC(CH3)2COOH), which could explain the presence of hydroxy acids in some meteorites.

  13. Spatially Resolved HCN J = 4-3 and CS J = 7-6 Emission from the Disk around HD 142527

    NASA Astrophysics Data System (ADS)

    van der Plas, G.; Casassus, S.; Ménard, F.; Perez, S.; Thi, W. F.; Pinte, C.; Christiaens, V.

    2014-09-01

    The disk around HD 142527 attracts a great amount of attention compared to others because of its resolved (sub-)millimeter dust continuum that is concentrated into the shape of a horseshoe toward the north of the star. In this Letter we present spatially resolved ALMA detections of the HCN J = 4-3 and CS J = 7-6 emission lines. These lines give us a deeper view into the disk compared to the (optically thicker) CO isotopes. This is the first detection of CS J = 7-6 coming from a protoplanetary disk. Both emission lines are azimuthally asymmetric and are suppressed under the horseshoe-shaped continuum emission peak. A possible mechanism for explaining the decrease under the horseshoe-shaped continuum is the increased opacity coming from the higher dust concentration at the continuum peak. Lower dust and/or gas temperatures and an optically thick radio-continuum reduce line emission by freezing out and shielding emission from the far side of the disk.

  14. First observations of CO and HCN on Neptune and Uranus at millimeter wavelengths and the implications for atmospheric chemistry

    NASA Technical Reports Server (NTRS)

    Marten, A.; Gautier, D.; Owen, T.; Sanders, D. B.; Matthews, H. E.; Atreya, S. K.; Tilanus, R. P. J.; Deane, J. R.

    1993-01-01

    Observations are presented which show that CO is present in both the troposphere and stratosphere of Neptune, whereas is confined to the Neptune stratosphere with a mean mole fraction in the 0.003-30 mbar pressure level range of 1.0 x 10 exp -9. CO is present in both the stratosphere and in the troposphere with a uniformly mixed model fraction of 1.2 x 10 exp -6. Upper limits of 1.0 x 10 exp -10 and 3.0 x 10 exp -8 mole fractions are derived for HCN and CO respectively on Uranus. The origin of these species in the atmosphere of Neptune and their nondetection in that of Uranus are discussed in detail. It is concluded that the most plausible scenario involves upward convection of CO and N2 from Neptune's deep interior and a failure of chemical equilibrium at deep atmospheric levels, allowing excess CO and presumably N2 to reach the upper atmosphere. Nondetection in Uranus may be explained by the lack of a significant internal heat source in the planet and consequent suppression of vertical convection.

  15. Experimental and theoretical study of electro-optics of molecular dimers OC...HF and HCN...HF

    NASA Astrophysics Data System (ADS)

    Bulanin, Michael O.; Bulychev, V. P.; Tokhadze, K. G.; Uspensky, A. I.

    1997-03-01

    We report an experimental study of the band shapes and relative IR intensities for the stretching v1 and librational vL modes of the HF subunit in complexes with OC and HCN. The ratio of the transition dipole moments for the v1 and vL bands is found to be close to unity. The relative intensities of the stretching and librational modes in typical H-bonded species (CH3)2CO. . .HF and (CH3)2O. . .HF are also measured for comparison. A multidimensional quantum mechanical problem of the relative motion of monomers in complexes is solved using model intermolecular interaction potentials and the wave functions expanded in products of 1D-basis functions. Classification of the states of relative motions of monomers is made by considering various cuts through the wave functions. Motions involving different degrees of freedom are shown to be strongly coupled. The frequencies and transition probabilities of the low-frequency modes are computed. The vibrationally averaged electro-optic parameters of complexes evaluated in the framework of the electrostatic induction model are in satisfactory agreement with the experimental data.

  16. Li1.2Mn0.54Ni0.13Co0.13O2-Encapsulated Carbon Nanofiber Network Cathodes with Improved Stability and Rate Capability for Li-ion Batteries

    PubMed Central

    Ma, Dingtao; Zhang, Peixin; Li, Yongliang; Ren, Xiangzhong

    2015-01-01

    Li1.2Mn0.54Ni0.13Co0.13O2-encapsulated carbon nanofiber network cathode materials were synthesized by a facile electrospinning method. The microstructures, morphologies and electrochemical properties are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), galvonostatic charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy (EIS), etc. The nanofiber decorated Li1.2Mn0.54Ni0.13Co0.13O2 electrode demonstrated higher coulombic efficiency of 83.5%, and discharge capacity of 263.7 mAh g−1 at 1 C as well as higher stability compared to the pristine particle counterpart. The superior electrochemical performance results from the novel network structure which provides fast transport channels for electrons and lithium ions and the outer carbon acts a protection layer which prevents the inner oxides from reacting with HF in the electrolyte during charge-discharge cycling. PMID:26053003

  17. Structure and Electrochemistry of LiNi1/3Co1/3-yMyMn1/3O2 (M=Ti, Al, Fe) Positive Electrode Materials

    SciTech Connect

    Wilcox, James; Patoux, Sebastien; Doeff, Marca

    2009-01-14

    A series of materials based on the LiNi1/3Co1/3-yMyMn1/3O2 (M = Ti,Al,Fe) system has been synthesized and examined structurally and electrochemically. It is found that the changes in electrochemical performance depend highly on the nature of the substituting atom and its effect on the crystal structure. Substitution with small amounts of Ti4+ (y = 1/12) leads to the formation of a high-capacity and high-rate positive electrode material. Iron substituted materials suffer from an increased antisite defect concentration and exhibit lower capacities and poor rate capabilities. Single-phase materials are found for LiNi1/3Co1/3-yAlyMn1/3O2 when y<_ 1/4 and all exhibit decreased capacities when cycled to 4.3 V. However, an increase in rate performance and cycle stability upon aluminum substitution is correlated with an improved lamellar structure.

  18. Microstructural investigation of LixNi1/3Mn1/3Co1/3O2 (x 1) and its aged products via magnetic and diffraction study

    SciTech Connect

    Mohanty, Debasish; Gabrisch, Heike

    2012-01-01

    The thermal stability of the layered oxide LiNi1/3Mn1/3Co1/3O2 and its delithiated product is studied by a combination of x-ray and electron diffraction, TEM imaging and magnetic measurements. Diffraction shows that a small fraction of the layered material converts to spinel phase following delithiation. More spinel phase is observed after thermal annealing. The morphology of the particle changes upon thermal annealing of delithiated materials. The selected area electron diffraction and the magnetic measurement results confirm the presence of Ni+2/Li+ disorder in the delithiated material, which increases upon thermal ageing. The oxidation states of the transition metal ions were determined from magnetic data. It is shown that the charge balance due TO removal of Li+ is maintained through oxidation of Ni+2 and that the oxidation states remain stable during subsequent annealing. No anti-ferromagnetic ordering or crystallographic in plane ordering of transition metal ions is observed. These results clearly describe the thermal degradation of LixNi1/3Mn1/3Co1/3O2 (x 1) occur through the significant microstructural changes.

  19. Structural insights into the functional role of the Hcn sub-domain of the receptor-binding domain of the botulinum neurotoxin mosaic serotype C/D.

    PubMed

    Zhang, Yanfeng; Gardberg, Anna S; Edwards, Thomas E; Sankaran, Banumathi; Robinson, Howard; Varnum, Susan M; Buchko, Garry W

    2013-07-01

    Botulinum neurotoxin (BoNT), the causative agent of the deadly neuroparalytic disease botulism, is the most poisonous protein known for humans. Produced by different strains of the anaerobic bacterium Clostridium botulinum, BoNT effects cellular intoxication via a multistep mechanism executed by the three modules of the activated protein. Endocytosis, the first step of cellular intoxication, is triggered by the ~50 kDa, heavy-chain receptor-binding domain (HCR) that is specific for a ganglioside and a protein receptor on neuronal cell surfaces. This dual receptor recognition mechanism between BoNT and the host cell's membrane is well documented and occurs via specific intermolecular interactions with the C-terminal sub-domain, Hcc, of BoNT-HCR. The N-terminal sub-domain of BoNT-HCR, Hcn, comprises ~50% of BoNT-HCR and adopts a β-sheet jelly roll fold. While suspected in assisting cell surface recognition, no unambiguous function for the Hcn sub-domain in BoNT has been identified. To obtain insights into the potential function of the Hcn sub-domain in BoNT, the first crystal structure of a BoNT with an organic ligand bound to the Hcn sub-domain has been obtained. Here, we describe the crystal structure of BoNT/CD-HCR determined at 1.70 Å resolution with a tetraethylene glycol (PG4) moiety bound in a hydrophobic cleft between β-strands in the β-sheet jelly roll fold of the Hcn sub-domain. The PG4 moiety is completely engulfed in the cleft, making numerous hydrophilic (Y932, S959, W966, and D1042) and hydrophobic (S935, W977, L979, N1013, and I1066) contacts with the protein's side chain and backbone that may mimic in vivo interactions with the phospholipid membranes on neuronal cell surfaces. A sulfate ion was also observed bound to residues T1176, D1177, K1196, and R1243 in the Hcc sub-domain of BoNT/CD-HCR. In the crystal structure of a similar protein, BoNT/D-HCR, a sialic acid molecule was observed bound to the equivalent residues suggesting that residues T

  20. Structural Insights into the Functional Role of the Hcn Sub-domain of the Receptor-Binding Domain of the Botulinum Neurotoxin Mosaic Serotype C/D

    SciTech Connect

    Zhang, Yanfeng; Gardberg, Anna; Edwards, Tom E.; Sankaran, Banumathi; Robinson, Howard; Varnum, Susan M.; Buchko, Garry W.

    2013-07-01

    Botulinum neurotoxin (BoNT), the causative agent of the deadly neuroparalytic disease botulism, is the most poisonous protein known for humans. Produced by different strains of the anaerobic bacterium Clostridium botulinum, BoNT effects cellular intoxication via a multistep mechanism executed by the three modules of the activated protein. Endocytosis, the first step of cellular intoxication, is triggered by the ~50 kDa, heavy-chain receptor-binding module (HCR) that is specific for a ganglioside and a protein receptor on neuronal cell surfaces. This dual receptor recognition mechanism between BoNT and the host cell’s membrane is well documented and occurs via specific intermolecular interactions with the C-terminal sub-domain, Hcc, of BoNT-HCR. The N-terminal sub-domain of BoNT-HCR, Hcn, comprises ~50% of BoNT-HCR and adopts a B-sheet jelly roll fold. While suspected in assisting cell surface recognition, no unambiguous function for the Hcn sub-domain in BoNT has been indentified. To obtain insights into the potential function of the Hcn sub-domain in BoNT, the first crystal structure of a BoNT with an organic ligand bound to the Hcn sub-domain has been obtained. Here, we describe the crystal structure of BoNT/CD-HCR determined at 1.70 Å resolution with a tetraethylene glycol (PG4) molecule bound in an hydrophobic cleft between B-strands in the B-sheet jelly fold roll of the Hcn sub-domain. The molecule is completely engulfed in the cleft, making numerous hydrophobic (Y932, S959, W966, and D1042) and hydrophilic (S935, W977, L979, N1013, and I1066) contacts with the protein’s side chain and backbone that may mimic in vivo interactions with the phospholipid membranes on neuronal cell surfaces. A sulfate ion was also observed bound to residues T1176, D1177, K1196, and R1243 in the Hcc sub-domain of BoNT/CD-HCR. In the crystal structure of a similar protein, BoNT/D-HCR, a sialic acid

  1. Synchrotron radiation-based 61Ni Mössbauer spectroscopic study of Li(Ni1/3Mn1/3Co1/3)O2 cathode materials of lithium ion rechargeable battery

    NASA Astrophysics Data System (ADS)

    Segi, Takashi; Masuda, Ryo; Kobayashi, Yasuhiro; Tsubota, Takayuki; Yoda, Yoshitaka; Seto, Makoto

    2016-12-01

    Layered rocksalt type oxides, such as Li(Ni1/3Mn1/3Co1/3)O2, are widely used as the cathode active materials of lithium-ion rechargeable batteries. Because the nickel ions are associated with the role of the charge compensation at discharge and charge, the 61Ni Mössbauer measurements at 6 K using synchrotron radiation were performed to reveal the role of Ni. The Ni ions of the active materials play two roles for the redox process between the charge and discharge states of lithium-ion batteries. Half of the total Ni ions change to the low-spin Ni3+ with Jahn-Teller distortion from the Ni2+ ions of the discharge state. The remainder exhibit low-spin state divalent Ni ions.

  2. Enhanced oxygen reducibility of 0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2 cathode material with mild acid treatment

    NASA Astrophysics Data System (ADS)

    Xu, Guofeng; Li, Jianling; Xue, Qingrui; Ren, Xianping; Yan, Gang; Wang, Xindong; Kang, Feiyu

    2014-02-01

    Solid solution cathode material 0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2 has been synthesized by a co-precipitation method and a mild acid was adopted to give rise to the H+/Li+ exchange reaction. The inductively coupled plasma-atomic emission spectrometry (ICP-AES) and atomic absorption spectroscopy (AAS) data show that the H+/Li+ exchange reaction actually occurs and the chemical composition is H0.06Li1.15Ni0.13Co0.14Mn0.55O2.03 after the material was treated. The X-ray powder diffraction patterns indicates that the structure doesn't change through the H+/Li+ exchange reaction and remains the hexagonal α-NaFeO2 layered structure with space group of R-3m. The field-emission scanning electron microscope (SEM) and transmission electron microscope (TEM) images show that there are traces of erosion on the surface of the H+/Li+ exchanged sample. The initial charge-discharge curve measured at 0.05C (12.5 mA g-1) demonstrates that the H+/Li+ exchanged electrode delivers a capacity of up to 314.0 mAh g-1 and coulombic increased initial efficiency. Cycle voltammetry (CV) measurement confirms this is attributed to the improvement of the reduction catalytic activity of oxygen released during the initial charging. The processed electrode also displays improved rate performance.

  3. Determination of lithium and transition metals in Li1 Ni1/3 Co1/3 Mn1/3 O2 (NCM) cathode material for lithium-ion batteries by capillary electrophoresis.

    PubMed

    Vortmann-Westhoven, Britta; Lürenbaum, Constantin; Winter, Martin; Nowak, Sascha

    2017-02-01

    In this work, we present a novel electrophoretic method that was developed for the determination of lithium and transition metals in LiNi1/3 Co1/3 Mn1/3 O2 cathode material after microwave digestion. The cations in the digested LiNi1/3 Co1/3 Mn1/3 O2 material were separated by CE and the element content was determined by UV/Vis detection. To characterize the precision of the measurements, the RSDs and concentrations were calculated and compared to those obtained with ICP-optical emission spectrometry (ICP-OES). Furthermore, a certified reference material (BCR 176R-fly ash) was investigated for all techniques. For active material components, the LOD and LOQ were determined. The LODs and LOQs for the metals determined by CE were as follows: lithium (LOD/LOQ): 17.41/62.70 μg/L, cobalt (LOD/LOQ): 348.4/1283 μg/L, manganese (LOD/LOQ): 540.2/2095 μg/L, and nickel (LOD/LOQ): 838.0/2982 μg/L. Recovery rates for lithium were in the range of 95-103%. It could be proven that with the new technique, the results for the determination of the lithium content of active material were comparable with those obtained by ICP-OES and ion chromatography. Furthermore, the recovery rates of the transition metals were determined to be between 96 and 110% by CE and ICP-OES.

  4. Tracing of recently assimilated carbon in respiration at high temporal resolution in the field with a tuneable diode laser absorption spectrometer after in situ 13CO2 pulse labelling of 20-year-old beech trees.

    PubMed

    Plain, Caroline; Gerant, Dominique; Maillard, Pascale; Dannoura, Masako; Dong, Yanwen; Zeller, Bernd; Priault, Pierrick; Parent, Florian; Epron, Daniel

    2009-11-01

    The study of the fate of assimilated carbon in respiratory fluxes in the field is needed to resolve the residence and transfer times of carbon in the atmosphere-plant-soil system in forest ecosystems, but it requires high frequency measurements of the isotopic composition of evolved CO2. We developed a closed transparent chamber to label the whole crown of a tree and a labelling system capable of delivering a 3-h pulse of 99% 13CO2 in the field. The isotopic compositions of trunk and soil CO2 effluxes were recorded continuously on two labelled and one control trees by a tuneable diode laser absorption spectrometer during a 2-month chase period following the late summer labelling. The lag times for trunk CO2 effluxes are consistent with a phloem sap velocity of about 1 m h(-1). The isotopic composition (delta13C) of CO2 efflux from the trunk was maximal 2-3 days after labelling and declined thereafter following two exponential decays with a half-life of 2-8 days for the first and a half-life of 15-16 days for the second. The isotopic composition of the soil CO2 efflux was maximal 3-4 days after labelling and the decline was also well fitted with a sum of two exponential functions with a half-life of 3-5 days for the first exponential and a half-life of 16-18 days for the second. The amount of label recovered in CO2 efflux was around 10-15% of the assimilated 13CO2 for soil and 5-13% for trunks. As labelling occurred late in the growing season, substantial allocation to storage is expected.

  5. Effects of ZD7288, a hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker, on term-pregnant rat uterine contractility in vitro.

    PubMed

    Alotaibi, Mohammed; Kahlat, Karima; Nedjadi, Taoufik; Djouhri, Laiche

    2017-03-01

    The uterus is a myogenic organ that is able to produce discrete spontaneous action potentials and contractions without any stimuli. Myometrial excitability is governed by ion channels including Ca(+2) and K(+) channels, but whether or not other channels such as hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which play an important role in regulating cellular excitability, are also involved has not been reported in uterine smooth muscles. The aim of the present study was to examine whether blocking HCN channels with a specific blocker ZD7288 would modulate the uterine contractility in a rat model. Using longitudinal uterine strips from term-pregnant rats, the effects of varying concentrations of ZD7288 (50 μM, 100 μM, and 200 μM) were examined on uterine contractions generated spontaneously or by oxytocin (5 nmol/L) and on uterine strips depolarized by high-KCl (60 mM/L), or activated by L-type Ca(2+) channels agonist (Bay K8644; 1 μM). Application of ZD7288 at concentrations of 200 μM and 100 μM, but not 50 μM, significantly decreased the amplitude of spontaneous uterine contractions. In addition, 200 μM of ZD7288 significantly reduced the force of contractions induced by oxytocin with a pronounced reduction while the tissues were depolarized by high-KCl solution, or activated by Bay K8644. The present study provides pharmacological evidence suggesting that pregnant uterine contractility is modulated by HCN channels and that these channels might represent a therapeutic target for controlling premature activation of uterine activity associated with preterm labor.

  6. APERTURE SYNTHESIS OBSERVATIONS OF CO, HCN, AND 89 GHz CONTINUUM EMISSION TOWARD NGC 604 IN M33: SEQUENTIAL STAR FORMATION INDUCED BY A SUPERGIANT H II REGION

    SciTech Connect

    Miura, Rie; Okumura, Sachiko K.; Kurono, Yasutaka; Nakanishi, Kouichiro; Tosaki, Tomoka; Tamura, Yoichi; Kuno, Nario; Kawabe, Ryohei; Sakamoto, Seiichi; Hasegawa, Takashi

    2010-12-01

    We present the results from new Nobeyama Millimeter Array observations of CO(1-0), HCN(1-0), and 89 GHz continuum emission toward NGC 604, known as the supergiant H II region in the nearby galaxy M33. Our high spatial resolution images (4.''2 x 2.''6, corresponding to 17 pc x 11 pc physical size) of CO emission allowed us to uncover 10 individual molecular clouds that have masses of (0.8-7.4) x10{sup 5} M{sub sun} and sizes of 5-29 pc, comparable to those of typical Galactic giant molecular clouds. Moreover, we detected for the first time HCN emission in the two most massive clouds and 89 GHz continuum emission at the rims of the 'H{alpha} shells'. The HCN and 89 GHz continuum emission are offset from the CO peak and are distributed in the direction of the central cluster. Three out of ten CO clouds are well correlated with the H{alpha} shells both in spatial and velocity domains, implying an interaction between molecular gas and the expanding H II region. The CO clouds show varieties in star formation efficiencies (SFEs), which are estimated from the 89 GHz emission and combination of H{alpha} and Spitzer 24 {mu}m data. Furthermore, we found that the SFEs decrease with increasing projected distance measured from the heart of the central OB star cluster in NGC 604, suggesting radial changes in the evolutionary stages of the molecular clouds in the course of stellar cluster formation. Our results provide further support to the picture of sequential star formation in NGC 604 initially proposed by Tosaki et al. with the higher spatially resolved molecular clouds, in which an isotropic expansion of the H II region pushes gases outward, which accumulates to form dense molecular clouds, and then induces massive star formations.

  7. Solid-State Nuclear Magnetic Resonance Measurements of HIV Fusion Peptide 13CO to Lipid 31P Proximities Support Similar Partially Inserted Membrane Locations of the α Helical and β Sheet Peptide Structures

    NASA Astrophysics Data System (ADS)

    Gabrys, Charles M.; Qiang, Wei; Sun, Yan; Xie, Li; Schmick, Scott D.; Weliky, David P.

    2013-10-01

    Fusion of the human immunodeficiency virus (HIV) membrane and the host cell membrane is an initial step of infection of the host cell. Fusion is catalyzed by gp41, which is an integral membrane protein of HIV. The fusion peptide (FP) is the -25 N-terminal residues of gp41 and is a domain of gp41 that plays a key role in fusion catalysis likely through interaction with the host cell membrane. Much of our understanding of the FP domain has been accomplished with studies of -HFP-, i.e., a -25-residue peptide composed of the FP sequence but lacking the rest of gp41. HFP catalyzes fusion between membrane vesicles and serves as a model system to understand fusion catalysis. HFP binds to membranes and the membrane location of HFP is likely a significant determinant of fusion catalysis perhaps because the consequent membrane perturbation reduces the fusion activation energy. In the present study, many HFPs were synthesized and differed in the residue position that was 13CO backbone labeled. Samples were then prepared that each contained a singly 13CO labeled HFP incorporated into membranes that lacked cholesterol. HFP had distinct molecular populations with either α helical or oligomeric - sheet structure. Proximity between the HFP 13CO nuclei and 31P nuclei in the membrane headgroups was probed by solid-state NMR (SSNMR) rotational-echo double-resonance (REDOR) measurements. For many samples, there were distinct 13CO shifts for the α helical and - sheet structures so that the proximities to 31P nuclei could be determined for each structure. Data from several differently labeled HFPs were then incorporated into a membrane location model for the particular structure. In addition to the 13CO labeled residue position, the HFPs also differed in sequence and/or chemical structure. -HFPmn- was a linear peptide that contained the 23 N-terminal residues of gp41. -HFPmn_V2E- contained the V2E mutation that for HIV leads to greatly reduced extent of fusion and infection. The

  8. Solid-state nuclear magnetic resonance measurements of HIV fusion peptide 13CO to lipid 31P proximities support similar partially inserted membrane locations of the α helical and β sheet peptide structures.

    PubMed

    Gabrys, Charles M; Qiang, Wei; Sun, Yan; Xie, Li; Schmick, Scott D; Weliky, David P

    2013-10-03

    Fusion of the human immunodeficiency virus (HIV) membrane and the host cell membrane is an initial step of infection of the host cell. Fusion is catalyzed by gp41, which is an integral membrane protein of HIV. The fusion peptide (FP) is the ∼25 N-terminal residues of gp41 and is a domain of gp41 that plays a key role in fusion catalysis likely through interaction with the host cell membrane. Much of our understanding of the FP domain has been accomplished with studies of "HFP", i.e., a ∼25-residue peptide composed of the FP sequence but lacking the rest of gp41. HFP catalyzes fusion between membrane vesicles and serves as a model system to understand fusion catalysis. HFP binds to membranes and the membrane location of HFP is likely a significant determinant of fusion catalysis perhaps because the consequent membrane perturbation reduces the fusion activation energy. In the present study, many HFPs were synthesized and differed in the residue position that was (13)CO backbone labeled. Samples were then prepared that each contained a singly (13)CO labeled HFP incorporated into membranes that lacked cholesterol. HFP had distinct molecular populations with either α helical or oligomeric β sheet structure. Proximity between the HFP (13)CO nuclei and (31)P nuclei in the membrane headgroups was probed by solid-state NMR (SSNMR) rotational-echo double-resonance (REDOR) measurements. For many samples, there were distinct (13)CO shifts for the α helical and β sheet structures so that the proximities to (31)P nuclei could be determined for each structure. Data from several differently labeled HFPs were then incorporated into a membrane location model for the particular structure. In addition to the (13)CO labeled residue position, the HFPs also differed in sequence and/or chemical structure. "HFPmn" was a linear peptide that contained the 23 N-terminal residues of gp41. "HFPmn_V2E" contained the V2E mutation that for HIV leads to greatly reduced extent of fusion and

  9. The probability density function in molecular gas in the G333 and Vela C molecular clouds

    NASA Astrophysics Data System (ADS)

    Cunningham, Maria

    2015-08-01

    The probability density function (PDF) is a simple analytical tool for determining the hierarchical spatial structure of molecular clouds. It has been used frequently in recent years with dust continuum emission, such as that from the Herschel space telescope and ALMA. These dust column density PDFs universally show a log-normal distribution in low column density gas, characteristic of unbound turbulent gas, and a power-law tail at high column densities, indicating the presence of gravitationally bound gas. We have recently conducted a PDF analysis of the molecular gas in the G333 and Vela C giant molecular cloud complexes, using transitions of CO, HCN, HNC, HCO+ and N2H+.The results show that CO and its isotopologues trace mostly the log-normal part of the PDF, while HCN and HCO+ trace both a log-normal part and a power law part to the distribution. On the other hand, HNC and N2H+ mostly trace only the power law tail. The difference between the PDFs of HCN and HNC is surprising, as is the similarity between HNC and the N2H+ PDFs. The most likely explanation for the similar distributions of HNC and N2H+ is that N2H+ is known to be enhanced in cool gas below 20K, where CO is depleted, while the reaction that forms HNC or HCN favours the former at similar low temperatures. The lack of evidence for a power law tail in 13CO and C18O, in conjunction for the results for the N2H+ PDF suggest that depletion of CO in the dense cores of these molecular clouds is significant. In conclusion, the PDF has proved to be a surprisingly useful tool for investigating not only the spatial distribution of molecular gas, but also the wide scale chemistry of molecular clouds.

  10. Quantum reactive scattering studies of the CN + H 2 → HCN + H reaction: the role of the non-reactive CN bond

    NASA Astrophysics Data System (ADS)

    Takayanagi, Toshiyuki; Schatz, George C.

    1997-02-01

    An extended version of the rotating-bond approximation (RBA) has been developed to study the title reaction, in which CN stretching is added to usual CH stretching and bend degrees of freedom in a coupled channel expansion. Calculations have been done on potential energy surfaces developed by Sun and Bowman (SB) and by ter Horst, Schatz, and Harding (TSH). The HCN vibrational product state distribution calculated on TSH surface shows significant population in both CH and CN stretching, indicating that the CN bond is not a spectator.

  11. HCN, A Triple-Resonance NMR Technique for Selective Observation of Histidine and Tryptophan Side Chains in 13C/ 15N-Labeled Proteins

    NASA Astrophysics Data System (ADS)

    Sudmeier, James L.; Ash, Elissa L.; Günther, Ulrich L.; Luo, Xuelian; Bullock, Peter A.; Bachovchin, William W.

    1996-12-01

    HCN, a new 3D NMR technique for stepwise coherence transfer from1H to13C to15N and reverse through direct spin couplings1JCHand1JCN, is presented as a method for detection and assignment of histidine and tryptophan side-chain1H,13C, and15N resonances in uniformly13C/15N-labeled proteins. Product-operator calculations of cross-peak volumes vs adjustable delay τ3were employed for determination of optimal τ3. For the phosphatidylinositol 3-kinase (PI3K SH3 domain, MW = 9.6 kD) at pH 6, H(C)N, the1H/15N projection, produced observable cross peaks within 20 min. and was completely selective for the single tryptophan and single histidine. The 3D HCN experiment yielded well-defined cross peaks in 20 h for the13C/15N-labeled origin-specific DNA binding domain from simian virus 40 T-antigen (T-ag-OBD131-259, MW = 15.4 kD) at pH 5.5. Resonances from all six histidines in T-ag-OBD were observed, and 11 of the 121H and13C chemical shifts and 10 of the 1215N chemical shifts were determined. The13C dimension proved essential in assignment of the multiply overlapping1H and15N resonances. From the spectra recorded at a single pH, three of the imidazoles were essentially neutral and the other three were partially protonated (22-37%). HCN yielded strong cross peaks after 18 h on a 2.0 mMsample of phenylmethanesulfonyl fluoride (PMSF)-inhibited α-lytic protease (MW = 19.8 kD) at pH 4.4. No spectra have been obtained, however, of native or boronic acid-inhibited α-lytic protease after 18 h at various temperatures ranging from 5 to 55°C, probably due to efficient relaxation of active-site imidazole1H and/or15N nuclei.

  12. HCN, a triple-resonance NMR technique for selective observation of histidine and tryptophan side chains in 13C/15N-labeled proteins.

    PubMed

    Sudmeier, J L; Ash, E L; Günther, U L; Luo, X; Bullock, P A; Bachovchin, W W

    1996-12-01

    HCN, a new 3D NMR technique for stepwise coherence transfer from 1H to 13C to 15N and reverse through direct spin couplings 1JCH and 1JCN, is presented as a method for detection and assignment of histidine and tryptophan side-chain 1H, 13C, and 15N resonances in uniformly 13C/15N-labeled proteins. Product-operator calculations of cross-peak volumes vs adjustable delay tau 3 were employed for determination of optimal tau 3. For the phosphatidylinositol 3-kinase (PI3K SH3 domain, MW = 9.6 kD) at pH 6, H(C)N, the 1H/15N projection, produced observable cross peaks within 20 min. and was completely selective for the single tryptophan and single histidine. The 3D HCN experiment yielded well-defined cross peaks in 20 h for the 13C/15N-labeled origin-specific DNA binding domain from simian virus 40 T-antigen (T-ag-OBD131-259, MW = 15.4 kD) at pH 5.5. Resonances from all six histidines in T-ag-OBD were observed, and 11 of the 12 1H and 13C chemical shifts and 10 of the 12 15N chemical shifts were determined. The 13C dimension proved essential in assignment of the multiply overlapping 1H and 15N resonances. From the spectra recorded at a single pH, three of the imidazoles were essentially neutral and the other three were partially protonated (22-37%). HCN yielded strong cross peaks after 18 h on a 2.0 mM sample of phenylmethanesulfonyl fluoride (PMSF)-inhibited alpha-lytic protease (MW = 19.8 kD) at pH 4.4. No spectra have been obtained, however, of native or boronic acid-inhibited alpha-lytic protease after 18 h at various temperatures ranging from 5 to 55 degrees C, probably due to efficient relaxation of active-site imidazole 1H and/or 15N nuclei.

  13. Effect of Hydrogen Bonding on Barrier-Free Proton Transfer in Anionic Complexes of Uracil with Weak Acids: (U...HCN){sup -} versus (U...H{sub 2}S){sup -}

    SciTech Connect

    Haranczyk, Maciej; Rak, Janusz; Gutowski, Maciej S.; Radisic, Dunja; Stokes, Sarah T.; Bowen, Kit H.

    2004-10-26

    A photoelectron spectrum is reported for an anionic complex of uracil (U) with HCN. The effects of electron attachment to a complex of U with HA (A = CN, NC) have been studied at the density functional theory level with 6-31++G** basis sets and the B3LYP and MPW1K exchange correlation functionals. Critical anionic structures have been reexamined at the MP2/6-31++G** level. The B3LYP gas phase deprotonation enthalpies are equal to 14.56, 15.13, and 15.12 eV for HNC, HCN, and H{sub 2}S, respectively. The experimental deprotonation enthalpies are 15.100 {+-} 0.008 and 15.214 {+-}0.125 eV for HCN and H{sub 2}S, respectively. Hence, HCN and H{sub 2}S have very similar deprotonation enthalpies. The photoelectron spectra of anionic complexes of uracil with HCN and H{sub 2}S are, however, very different. The (UHCN){sup -} spectrum reveals a broad feature with a maximum between 1.2-1.4 eV, whereas the main feature of the (UH{sub 2}S){sup -} spectrum has a maximum between 1.7 and 2.1 eV. We suggest that barrier-free proton transfer (BFPT) [Eur. Phys. J. D 2002, 20, 431-439; J. Phys. Chem. B 2003, 107, 7889-7895] occurs in the (UH{sub 2}S){sup -} complex but not in (UHCN){sup -}. Critical factors for the occurrence of BFPT have been analyzed. The difference between the (UHCN){sup -} and (UH{sub 2}S){sup -} complexes is attributed to differences in hydrogen bonds formed by HCN and H{sub 2}S with uracil.

  14. The influence of zinc hydroxystannate on reducing toxic gases (CO, NOx and HCN) generation and fire hazards of thermoplastic polyurethane composites.

    PubMed

    Wang, Bibo; Sheng, Haibo; Shi, Yongqian; Song, Lei; Zhang, Yan; Hu, Yuan; Hu, Weizhao

    2016-08-15

    A uniform zinc hydroxystannate (ZnHS) microcube was synthesized to reduce toxicity and fire hazards of thermoplastic polyurethane (TPU) composites using ammonium polyphosphate as a flame retardant agent. The structure, morphology and thermal properties of ZnHS were characterized by X-ray diffraction, transmission electron microscopy and thermogravimetric analysis, respectively. Smoke suppression properties and synergistic flame retardant effect of ZnHS on flame retardant TPU composites were intensively investigated by smoke density test, cone calorimeter test, and thermalgravimetric analysis. Thermogravimetric analysis/infrared spectrometry and tube furnace were employed to evaluate the toxic gases (CO, NOx and HCN) of TPU composites. The incorporation of ZnHS into TPU matrix effectively improved the fire safety and restrained the smoke density, which is attributed to that the char residue catalyzed by ZnHS enhanced barrier effect that reduced peak heat release rate, total heat release, smoke particles and organic volatiles during combustion. Furthermore, the ZnHS synergist demonstrated high efficiency in catalytic degradation of the toxic gases, which obviously decreased total volatiled product and toxic volatiles evolved, such as the CO, HCN and NOx, indicating suppressed toxicity of the TPU composites.

  15. The reaction of the acrylonitrile ion CH 2dbnd CH-C tbnd N rad + with HCN: Proton-transport catalysis vs formation of ionized pyrimidine

    NASA Astrophysics Data System (ADS)

    Ervasti, Henri K.; Jobst, Karl J.; Gerbaux, Pascal; Burgers, Peter C.; Ruttink, Paul J. A.; Terlouw, Johan K.

    2009-11-01

    The CBS-QB3 model chemistry predicts that the title ion-molecule reaction, of potential interest in astrochemistry, yields a stable head-to-tail dimer, [HC dbnd N-CH 2C(H)C tbnd N] rad + ( D1). Cyclization of D1 into ionized pyrimidine seems possible, but the initiating 1,2-H shift is close in energy to back-dissociation into CH 2dbnd C(H)CN rad + ( AN) + HCN. Less energy demanding is formation of the H-bridged isomers [CH 2dbnd C(CN)H--N tbnd CH] rad + and [HC tbnd N--HC(H) dbnd C(H)CN] rad +, whose HCN component may catalyze isomerization of AN into CH 2dbnd C dbnd C dbnd NH rad + ( AN1) and CH dbnd C(H)C dbnd NH rad + ( AN2) respectively. Tandem mass spectrometry based experiments using 15N/ 13C labelling show that cyclization of D1 does not occur and that AN1 is the predominant reaction product instead.

  16. A new ab initio potential energy surface for the collisional excitation of HCN by para- and ortho-H{sub 2}

    SciTech Connect

    Denis-Alpizar, Otoniel; Kalugina, Yulia; Stoecklin, Thierry; Vera, Mario Hernández; Lique, François

    2013-12-14

    We present a new four-dimensional potential energy surface for the collisional excitation of HCN by H{sub 2}. Ab initio calculations of the HCN–H{sub 2} van der Waals complex, considering both molecules as rigid rotors, were carried out at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations [CCSD(T)-F12a] level of theory using an augmented correlation-consistent triple zeta (aVTZ) basis set. The equilibrium structure is linear HCN–H{sub 2} with the nitrogen pointing towards H{sub 2} at an intermolecular separation of 7.20 a{sub 0}. The corresponding well depth is −195.20 cm{sup −1}. A secondary minimum of −183.59 cm{sup −1} was found for a T-shape configuration with the H of HCN pointing to the center of mass of H{sub 2}. We also determine the rovibrational energy levels of the HCN–para-H{sub 2} and HCN–ortho-H{sub 2} complexes. The calculated dissociation energies for the para and ortho complexes are 37.79 cm{sup −1} and 60.26 cm{sup −1}, respectively. The calculated ro-vibrational transitions in the HCN–H{sub 2} complex are found to agree by more than 0.5% with the available experimental data, confirming the accuracy of the potential energy surface.

  17. Fluoxetine ameliorates cognitive impairments induced by chronic cerebral hypoperfusion via down-regulation of HCN2 surface expression in the hippocampal CA1 area in rats.

    PubMed

    Luo, Pan; Zhang, Xiaoxue; Lu, Yun; Chen, Cheng; Li, Changjun; Zhou, Mei; Lu, Qing; Xu, Xulin; Shen, Guanxin; Guo, Lianjun

    2016-01-01

    Chronic cerebral hypoperfusion (CCH) causes cognitive impairments and increases the risk of Alzheimer's disease (AD) and vascular dementia (VD) through several biologically plausible pathways, yet the underlying neurobiological mechanisms are still poorly understood. In this study, we investigated whether fluoxetine, a selective serotonin reuptake inhibitor (SSRI), could play a neuroprotective role against chronic cerebral hypoperfusion injury and to clarify underlying mechanisms of its efficacy. Rats were subjected to permanent bilateral occlusion of the common carotid arteries (two-vessel occlusion, 2VO). Two weeks later, rats were treated with 30 mg/kg fluoxetine (intragastric injection, i.g.) for 6 weeks. Cognitive function was evaluated by Morris water maze (MWM) and novel objects recognition (NOR) test. Long-term potentiation (LTP) was used to address the underlying synaptic mechanisms. Western blotting was used to quantify the protein levels. Our results showed that fluoxetine treatment significantly improved the cognitive impairments caused by 2VO, accompanied with a reversion of 2VO-induced inhibitory of LTP. Furthermore, 2VO caused an up-regulation of hyperpolarization-activated cyclic nucleotide-gated channel 2 (HCN2) surface expressions in the hippocampal CA1 area and fluoxetine also effectively recovered the disorder of HCN2 surface expressions, which may be a possible mechanism that fluoxetine treatment ameliorates cognitive impairments in rats with CCH.

  18. A Novel Carbamoyloxy Arylalkanoyl Arylpiperazine Compound (SKL-NP) Inhibits Hyperpolarization-Activated Cyclic Nucleotide-Gated (HCN) Channel Currents in Rat Dorsal Root Ganglion Neurons.

    PubMed

    Chung, Gehoon; Kim, Tae-Hyung; Shin, Hyewon; Chae, Eunhee; Yi, Hanju; Moon, Hongsik; Kim, Hyun Jin; Kim, Joong Soo; Jung, Sung Jun; Oh, Seog Bae

    2012-08-01

    In this study, we determined mode of action of a novel carbamoyloxy arylalkanoyl arylpiperazine compound (SKL-NP) on hyperpolarization-activated cyclic nucleotide-gated (HCN) channel currents (I(h)) that plays important roles in neuropathic pain. In small or medium-sized dorsal root ganglion (DRG) neurons (<40 µm in diameter) exhibiting tonic firing and prominent I(h), SKL-NP inhibited I(h) and spike firings in a concentration dependent manner (IC(50)=7.85 µM). SKL-NP-induced inhibition of I(h) was blocked by pretreatment of pertussis toxin (PTX) and N-ethylmaleimide (NEM) as well as 8-Br-cAMP, a membrane permeable cAMP analogue. These results suggest that SKL-NP modulates I(h) in indirect manner by the activation of a Gi-protein coupled receptor that decreases intracellular cAMP concentration. Taken together, SKL-NP has the inhibitory effect on HCN channel currents (I(h)) in DRG neurons of rats.

  19. Effect of long-term vineyard monoculture on rhizosphere populations of pseudomonads carrying the antimicrobial biosynthetic genes phlD and/or hcnAB.

    PubMed

    Svercel, Miroslav; Christen, Danilo; Moënne-Loccoz, Yvan; Duffy, Brion; Défago, Geneviève

    2009-04-01

    The impact of repeated culture of perennial plants (i.e. in long-term monoculture) on the ecology of plant-beneficial bacteria is unknown. Here, the influence of extremely long-term monocultures of grapevine (up to 1603 years) on rhizosphere populations of fluorescent pseudomonads carrying the biosynthetic genes phlD for 2,4-diacetylphloroglucinol and/or hcnAB for hydrogen cyanide was determined. Soils from long-term and adjacent short-term monoculture vineyards (or brushland) in four regions of Switzerland were baited with grapevine or tobacco plantlets, and rhizosphere pseudomonads were studied by most probable number (MPN)-PCR. Higher numbers and percentages of phlD(+) and of hcnAB(+) rhizosphere pseudomonads were detected on using soil from long-term vineyards. On focusing on phlD, restriction fragment length polymorphism profiling of the last phlD-positive MPN wells revealed seven phlD alleles (three exclusively on tobacco, thereof two new ones). Higher numbers of phlD alleles coincided with a lower prevalence of the allele displayed by the well-studied biocontrol strain Pseudomonas fluorescens F113. The prevalence of this allele was 35% for tobacco in long-term monoculture soils vs. >60% in the other three cases. We conclude that soils from long-term grapevine monocultures represent an untapped resource for isolating novel biocontrol Pseudomonas strains when tobacco is used as bait.

  20. IRRADIATION OF ETHYLENE DILUTED IN SOLID NITROGEN WITH VACUUM ULTRAVIOLET LIGHT AND ELECTRONS: ITS IMPLICATIONS FOR THE FORMATION OF HCN AND HNC

    SciTech Connect

    Chen, Hui-Fen; Liu, Meng-Chen; Chen, Sian-Cong; Huang, Tzu-Ping; Wu, Yu-Jong

    2015-05-01

    Chemical reactions of C{sub 2}H{sub 4} dispersed in solid nitrogen at 10 K that occur upon irradiation with Lyα light at a wavelength of 121.6 nm and 500 eV electrons were investigated by measuring the infrared absorption spectra. Photolysis of the matrix samples with 121.6 nm light yielded products, including C{sub 2}H{sub 2}, CN, and isomers of C{sub 2}N{sub 2}, as well as a pair of HCN and HNC. In contrast, electron bombardment of similar matrix samples mainly resulted in the generation of N{sub 3}, C{sub 2}H{sub 2}, C{sub 2}H{sub 3}, C{sub 3}H{sub 2}, and C{sub 3}N{sup −}. Mechanisms of the reactions that occur during the photolysis and electron-radiation of the matrix samples are discussed. The results of the study provide insights into the formation of HNC and HCN, as well as nitriles, in N{sub 2}-rich ice samples containing a small proportion of C{sub 2}H{sub 4}.

  1. The ALMA View of Dense Molecular Gas in 30 Doradus

    NASA Astrophysics Data System (ADS)

    Bittle, Lauren E.; Indebetouw, Remy; Brogan, Crystal L.; Hunter, Todd R.; Leroy, Adam

    2017-01-01

    At a distance of 50 kpc, the 30 Doradus region within the Large Magellanic Cloud (LMC) hosts several sites of star formation including R136, a starburst region home to dozens of evolved O stars. The intense radiation from R136 creates an extreme environment for nearby star formation in such a low-metallicity, low mass galaxy. We have targeted a star-forming region ~15 pc away from R136 within 30 Doradus using the Atacama Large Millimeter/submillimeter Array (ALMA) to map the molecular gas to study the sites of star formation. We are conducting a clump-by-clump analysis of the intensities and line ratios of dense gas (HCO+, HCN, CS, H13CO+, H13CN) and diffuse gas (CO, 13CO, C18O) tracers at sub-parsec resolution. We identify and characterize ~100 molecular clumps within the region. With the observed molecular species, we aim to determine the physical conditions of each clump (e.g. size, internal turbulence, molecular abundance). We compare the intensities and line ratios to non-LTE Radex model grids of the excitation temperature, molecular column density, and volume density of the H2 collider to determine the physical excitation conditions within the clumps. We compare these properties of each clump to both associated and embedded star formation properties to quantify the relative importance of internal feedback from the star formation itself versus external feedback processes from R136 and determine which process dominates in this region.

  2. Warm and Dense Molecular Gas in the N 159 Region: 12CO J = 4-3 and 13CO J = 3-2 Observations with NANTEN2 and ASTE

    NASA Astrophysics Data System (ADS)

    Mizuno, Yoji; Kawamura, Akiko; Onishi, Toshikazu; Minamidani, Tetsuhiro; Muller, Erik; Yamamoto, Hiroaki; Hayakawa, Takahiro; Mizuno, Norikazu; Mizuno, Akira; Stutzki, Jürgen; Pineda, Jorge L.; Klein, Uli; Bertoldi, Frank; Koo, Bon-Chul; Rubio, Monica; Burton, Michael; Benz, Arnold; Ezawa, Hajime; Yamaguchi, Nobuyuki; Kohno, Kotaro; Hasegawa, Tetsuo; Tatematsu, Ken'ichi; Ikeda, Masafumi; Ott, Jürgen; Wong, Tony; Hughes, Annie; Meixner, Margaret; Indebetouw, Remy; Gordon, Karl D.; Whitney, Barbara; Bernard, Jean-Philippe; Fukui, Yasuo

    2010-02-01

    New 12CO J = 4-3 and 13CO J = 3-2 observations of the N 159 region, an active site of massive star formation in the Large Magellanic Cloud, have been made with the NANTEN2 and ASTE submillimeter telescopes, respectively. The 12CO J = 4-3 distribution is separated into three clumps, each associated with N 159 W, N 159 E, and N 159 S. These new measurements toward the three clumps are used in coupled calculations of molecular rotational excitation and line radiation transfer, along with other transitions of the 12CO J = 1-0, J = 2-1, J = 3-2, and J = 7-6 as well as the isotope transitions of 13CO J = 1-0, J = 2-1, J = 3-2, and J = 4-3. The 13CO J = 3-2 data were newly taken for the present work. The temperatures and densities were found to be ˜70-80 K and ˜3 × 10³ cm-3 in N 159 W and N 159 E, and ˜30 K and ˜1.6 × 10³ cm-3 in N 159 S. These results were compared with the star-formation activity based on data of young stellar clusters and HII regions as well as midinfrared emission obtained with the Spitzer MIPS. The N 159 E clump is associated with cluster(s) embedded, as observed at 24μm by the Spitzer MIPS, and the derived high temperature, 80 K, is interpreted as being heated by these sources. The N 159 E clump is likely to be responsible for a dark lane in a large HII region by dust extinction. On the other hand, the N 159 W clump is associated with clusters embedded mainly toward the eastern edge of the clump only. These clusters show offsets of 20''-40'' from the 12CO J = 4-3 peak, and are probably responsible for heating indicated by the derived high temperature, 70 K. The N 159 W clump exhibits no sign of star formation toward the 12CO J = 4-3 peak position and its western region that shows enhanced R4-3/1-0 and R3-2/1-0 ratios. We therefore suggest that the N 159 W peak represents a pre-star-cluster core of ˜105Modot which deserves further detailed studies. The N 159 S clump shows little sign of star formation, as is consistent with the lower

  3. Using eddy covariance of CO2, 13CO2 and CH4, continuous soil respiration measurements, and PhenoCams to constrain a process-based biogeochemical model for carbon market-funded wetland restoration

    NASA Astrophysics Data System (ADS)

    Oikawa, P. Y.; Baldocchi, D. D.; Knox, S. H.; Sturtevant, C. S.; Verfaillie, J. G.; Dronova, I.; Jenerette, D.; Poindexter, C.; Huang, Y. W.

    2015-12-01

    We use multiple data streams in a model-data fusion approach to reduce uncertainty in predicting CO2 and CH4 exchange in drained and flooded peatlands. Drained peatlands in the Sacramento-San Joaquin River Delta, California are a strong source of CO2 to the atmosphere and flooded peatlands or wetlands are a strong CO2 sink. However, wetlands are also large sources of CH4 that can offset the greenhouse gas mitigation potential of wetland restoration. Reducing uncertainty in model predictions of annual CO2 and CH4 budgets is critical for including wetland restoration in Cap-and-Trade programs. We have developed and parameterized the Peatland Ecosystem Photosynthesis, Respiration, and Methane Transport model (PEPRMT) in a drained agricultural peatland and a restored wetland. Both ecosystem respiration (Reco) and CH4 production are a function of 2 soil carbon (C) pools (i.e. recently-fixed C and soil organic C), temperature, and water table height. Photosynthesis is predicted using a light use efficiency model. To estimate parameters we use a Markov Chain Monte Carlo approach with an adaptive Metropolis-Hastings algorithm. Multiple data streams are used to constrain model parameters including eddy covariance of CO2, 13CO2 and CH4, continuous soil respiration measurements and digital photography. Digital photography is used to estimate leaf area index, an important input variable for the photosynthesis model. Soil respiration and 13CO2 fluxes allow partitioning of eddy covariance data between Reco and photosynthesis. Partitioned fluxes of CO2 with associated uncertainty are used to parametrize the Reco and photosynthesis models within PEPRMT. Overall, PEPRMT model performance is high. For example, we observe high data-model agreement between modeled and observed partitioned Reco (r2 = 0.68; slope = 1; RMSE = 0.59 g C-CO2 m-2 d-1). Model validation demonstrated the model's ability to accurately predict annual budgets of CO2 and CH4 in a wetland system (within 14% and 1

  4. The structure and kinematics of dense gas in NGC 2068

    NASA Astrophysics Data System (ADS)

    Walker-Smith, S. L.; Richer, J. S.; Buckle, J. V.; Smith, R. J.; Greaves, J. S.; Bonnell, I. A.

    2013-03-01

    We have carried out a survey of the NGC 2068 region in the Orion B molecular cloud using HARP on the James Clerk Maxwell Telescope, in the 13CO and C18O (J = 3-2) and H13CO+ (J = 4-3) lines. We used 13CO to map the outflows in the region, and matched them with previously defined Submillimetre Common-User Bolometer Array cores. We decomposed the C18O and H13CO+ into Gaussian clumps, finding 26 and eight clumps, respectively. The average deconvolved radii of these clumps are 6200 ± 2000 and 3600 ± 900 au for C18O and H13CO+, respectively. We have also calculated virial and gas masses for these clumps, and hence determined how bound they are. We find that the C18O clumps are more bound than the H13CO+ clumps (average gas mass to virial mass ratio of 4.9 compared to 1.4). We measure clump internal velocity dispersions of 0.28 ± 0.02 and 0.27 ± 0.04 km s-1 for C18O and H13CO+, respectively, although the H13CO+ values are heavily weighted by a majority of the clumps being protostellar, and hence having intrinsically greater linewidths. We suggest that the starless clumps correspond to local turbulence minima, and we find that our clumps are consistent with formation by gravoturbulent fragmentation. We also calculate interclump velocity dispersions of 0.39 ± 0.05 and 0.28 ± 0.08 km s-1 for C18O and H13CO+, respectively. The velocity dispersions (both internal and external) for our clumps match results from numerical simulations of decaying turbulence in a molecular cloud. However, there is still insufficient evidence to conclusively determine the type of turbulence and time-scale of star formation, due to the small size of our sample.

  5. First-cycle defect evolution of Li1-xNi1/3Mn1/3Co1/3O2 lithium ion battery electrodes investigated by positron annihilation spectroscopy

    NASA Astrophysics Data System (ADS)

    Seidlmayer, Stefan; Buchberger, Irmgard; Reiner, Markus; Gigl, Thomas; Gilles, Ralph; Gasteiger, Hubert A.; Hugenschmidt, Christoph

    2016-12-01

    In this study the structure and evolution of vacancy type defects in lithium ion batteries are investigated in respect of crystallographic properties. The relation between positron annihilation and electronic structure is discussed in terms of structural dynamics during the lithiation process. Samples of Li1-xNi1/3Mn1/3Co1/3O2 (NMC-111) electrodes with decreasing lithium content (x = 0-0.7) covering the whole range of state of charge were electrochemically prepared for the non-destructive analysis using positron coincidence Doppler broadening spectroscopy (CDBS). The positron measurements allowed us to observe the evolution of the defect structure caused by the delithiation process in the NMC-111 electrodes. The combination of CDBS with X-ray diffraction for the characterization of the lattice structures enabled the analysis of the well-known kinetic-hindrance-effect in the first charge-discharge cycle and possible implications of vacancy ordering. In particular, CDBS revealed the highest degree of relithiation after discharge to 3.0 V at 55 °C. For the first time, we report on the successful application of CDBS on NMC-111 electrodes yielding new insights in the important role of defects caused by the delithiation process and the kinetic hindrance effect.

  6. Facile Synthesis of Platelike Hierarchical Li1.2Mn0.54Ni0.13Co0.13O2 with Exposed {010} Planes for High-Rate and Long Cycling-Stable Lithium Ion Batteries.

    PubMed

    Zeng, Jiong; Cui, Yanhui; Qu, Deyang; Zhang, Qian; Wu, Junwei; Zhu, Xiaomeng; Li, Zuohua; Zhang, Xinhe

    2016-10-05

    Lithium-rich layered oxides are promising cathode candidates for the production of high-energy and high-power electronic devices with high specific capacity and high discharge voltage. However, unstable cycling performance, especially at high charge-recharge rate, is the most challenge issue which needs to be solved to foster the diffusion of these materials. In this paper, hierarchical platelike Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials were synthesized by a facile solvothermal method followed by calcination. Calcination time was found to be a key parameter to obtain pure layered oxide phase and tailor its hierarchical morphology. The Li-rich material consists of primary nanoparticles with exposed {010} planes assembled to form platelike layers which exhibit low resistance to Li(+) diffusion. In detail, the product by calcination at 900 °C for 12 h exhibits specific capacity of 228, 218, and 204 mA h g(-1) at 200, 400, and 1000 mA g(-1), respectively, whereas after 100 cycles at 1000 mA g(-1) rate of charge and recharge the specific capacity was retained by about 91%.

  7. The impact of calendar aging on the thermal stability of a LiMn2O4-Li(Ni1/3Mn1/3Co1/3)O2/graphite lithium-ion cell

    NASA Astrophysics Data System (ADS)

    Röder, Patrick; Stiaszny, Barbara; Ziegler, Jörg C.; Baba, Nilüfer; Lagaly, Paul; Wiemhöfer, Hans-Dieter

    2014-12-01

    Aging of lithium-ion cells is an inevitable phenomenon limiting the lifetime. Undesirable side reactions during cycle or calendar aging may affect the performance of all components of the lithium-ion cell. This results in a decreased capacity and an increase in the overall cell impedance. Based on electrochemical and physical characterization methods, the aging behavior during calendar aging of a 18650-cell, containing a blend of LiMn2O4 and Li(Ni1/3Mn1/3Co1/3)O2 (NMC) as cathode material and graphite as anode material was systematically investigated. To understand how the safety behavior of a lithium-ion cell changes with aging, accelerating rate calorimetry (ARC) and differential scanning calorimetry (DSC) were applied. With these methods the thermal stability behavior of the complete lithium-ion cell and its respective cathode and anode material were investigated. The focus of this work was it to generate first cause-effect relations between the aging under one exemplary aging condition and the thermal stability of a lithium-ion battery both on cell and material level.

  8. Hydrogen peroxide assisted synthesis of LiNi1/3Co1/3Mn1/3O2 as high-performance cathode for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Lin, Chaohong; Zhang, Yongzhi; Chen, Li; Lei, Ying; Ou, Junke; Guo, Yong; Yuan, Hongyan; Xiao, Dan

    2015-04-01

    LiNi1/3Co1/3Mn1/3O2 (NCM) is a promising cathode material for lithium-ion battery. In this research, a facile co-precipitation process is employed, during which the mixed solution of NH3·H2O, H2O2 (30% aqueous solution) and LiOH·H2O is added into the nitrate solution. Notably, H2O2 is introduced as the oxidant and dispersant during the co-precipitation process to oxidize the metal ions and decrease the agglomeration of the precursor by giving out O2, and then improves the specific capacity, stability and energy density of NCM. Additionally, O3 is employed to further oxidize NCM to enhance the stability during the calcination process. The obtained NCM material with single crystal structure exhibits a high initial discharge specific capacity of 208.9 mAh g-1 at 0.1 C (1 C = 280 mA g-1), an excellent cycle stability with high retained capacity of 176.3 mAh g-1 after 50 cycles, and a high initial discharge specific capacities of 150.6 mAh g-1 at 5 C even at a high cutoff potential (4.6 V).

  9. Unraveling transition metal dissolution of Li1.04Ni1/3Co1/3Mn1/3O2 (NCM 111) in lithium ion full cells by using the total reflection X-ray fluorescence technique

    NASA Astrophysics Data System (ADS)

    Evertz, Marco; Horsthemke, Fabian; Kasnatscheew, Johannes; Börner, Markus; Winter, Martin; Nowak, Sascha

    2016-10-01

    In this work we investigated the transition metal dissolution of the layered cathode material Li1.04Ni1/3Co1/3Mn1/3O2 in dependence on the cycle number and cut-off cell voltage during charge by using the total reflection X-ray fluorescence technique for the elemental analysis of the specific lithium ion battery degradation products. We could show that with ongoing cycling transition metal dissolution from the cathode increased over time. However, it was less pronounced at 4.3 V compared to elevated charge cut-off voltages of 4.6 V. After a maximum of 100 cycles, we detected an overall transition metal loss of 0.2 wt‰ in relation to the whole cathode active material for cells cycled to 4.3 V. At an increased charge cut-off voltage of 4.6 V, 4.5 wt‰ transition metal loss in relation to the whole cathode active material could be detected. The corresponding transition metal dissolution induced capacity loss at the cathode could thus be attributed to 1.2 mAh g-1. Compared to the overall capacity loss of 80 mAh g-1 of the complete cell after 100 galvanostatic charge/discharge cycles the value is quite low. Hence, the overall full cell capacity fade cannot be assigned exclusively to the transition metal dissolution induced cathode fading.

  10. Countering the Segregation of Transition-Metal Ions in LiMn1/3 Co1/3 Ni1/3 O2 Cathode for Ultralong Life and High-Energy Li-Ion Batteries.

    PubMed

    Luo, Dong; Fang, Shaohua; Tamiya, Yu; Yang, Li; Hirano, Shin-Ichi

    2016-08-01

    High-voltage layered lithium transition-metal oxides are very promising cathodes for high-energy Li-ion batteries. However, these materials often suffer from a fast degradation of cycling stability due to structural evolutions. It seriously impedes the large-scale application of layered lithium transition-metal oxides. In this work, an ultralong life LiMn1/3 Co1/3 Ni1/3 O2 microspherical cathode is prepared by constructing an Mn-rich surface. Its capacity retention ratio at 700 mA g(-1) is as large as 92.9% after 600 cycles. The energy dispersive X-ray maps of electrodes after numerous cycles demonstrate that the ultralong life of the as-prepared cathode is attributed to the mitigation of TM-ions segregation. Additionally, it is discovered that layered lithium transition-metal oxide cathodes with an Mn-rich surface can mitigate the segregation of TM ions and the corrosion of active materials. This study provides a new strategy to counter the segregation of TM ions in layered lithium transition-metal oxides and will help to the design and development of high-energy cathodes with ultralong life.

  11. Preparation of thick-film LiNi1/3Co1/3Mn1/3O2 electrodes by aerosol deposition and its application to all-solid-state batteries

    NASA Astrophysics Data System (ADS)

    Iwasaki, Shinya; Hamanaka, Tadashi; Yamakawa, Tomohiro; West, William C.; Yamamoto, Kazuo; Motoyama, Munekazu; Hirayama, Tsukasa; Iriyama, Yasutoshi

    2014-12-01

    We prepared thick and dense-crystalline LiNi1/3Co1/3Mn1/3O2 (NMC) composite films at room temperature that can work well as cathodes in all-solid-state battery cells. The thick films were fabricated by aerosol deposition using NMC powder (D50 = 10.61 μm) as a source material. Commercially-obtained NMC powder did not form films at all on silicon wafer substrates, and cracking of the substrates was observed. However, a few tens of nanometer coating with amorphous niobium oxide resulted in the deposition of 7 μm-thick crystalline dense composite films. The films were successfully fabricated also on Li+-conductive glass-ceramic sheets with 150 μm in thickness, and all-solid-state batteries were fabricated. The solid-state battery provided a cathode-basis discharge capacity of 152 mAh g-1 (3.0-4.2 V, 0.025 C, 333 K) and repeated charge-discharge cycles for 20 cycles.

  12. The effect of composite organic acid (citric acid & tartaric acid) on microstructure and electrochemical properties of Li1.2Mn0.54Ni0.13Co0.13O2 Li-rich layered oxides

    NASA Astrophysics Data System (ADS)

    Zheng, Fenghua; Ou, Xing; Pan, Qichang; Xiong, Xunhui; Yang, Chenghao; Liu, Meilin

    2017-04-01

    The sol-gel method is applied to prepare nano-sized LMNCO lithium-rich layered oxides by adding of composite organic acid (citric acid & tartaric acid). The effect of composite organic acid on the microstructure of Li1.2Mn0.54Ni0.13Co0.13O2 (LMNCO) Li-rich cathode material is explored in this work. The results confirm the existence of interactions between the composite organic acid molecules and the precursors, and formation of stronger space steric effect. The stronger space steric effect can effectively prevent the growth of precursor particles in the presintering process at 550 °C for 5 h, which eventually contributed to the fabrication of nano-sized LMNCO. According to EIS analysis, the synthesized LMNCO has low charge transfer resistance of 135.4 Ω. Furthermore, it shows excellent electrochemical performance with a discharge capacity of 263.1 mAh g-1 at 0.1 C and 187.9 mAh g-1 at 5 C.

  13. Trends, interannual and seasonal variations of tropospheric CO, C2H6 and HCN columns measured from ground-based FTIR at Lauder and Arrival Heights

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    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: CO (-0.90 ± 0.31% yr-1) and C2H6 (-3.10 ± 1.07% yr-1) at Arrival Heights and CO (-0.87 ± 0.30% yr-1), C2H6 (-2.70 ± 0.94% yr-1) and HCN (-0.93 ± 0.32% yr-1) at Lauder. The uncertainties reflect the 95% confidence limits. The dominant seasonal trends of CO and C2H6 at Lauder, and to a lesser degree at Arrival Heights, occur in austral spring when the correlations between CO and C2H6 and between CO and HCN maximize. Tropospheric columns of all three species are characterised by minima in March-June and maxima from August to November; this season is the southern-hemisphere tropical and sub-tropical biomass burning period. A tropospheric chemistry-climate model is used to simulate CO and C2H6 columns for the period of 1997-2009 using interannually varying biomass burning emissions; the model simulated tropospheric columns of CO and C2H6 compare well with the measured partial columns of both species. However, the model does not re-produce the significant negative trends of observed CO and C2H6 partial columns at both locations. Weak negative trends are calculated from model data. The model sensitivity calculations indicate that long-range transport of biomass burning emissions from Southern Africa and South America dominate the seasonal cycles of CO and C2H6 at both Lauder and Arrival Heights. Interannual variability of these compounds at both locations is largely triggered by variations in biomass burning emissions associated with large-scale El Nino Southern Oscillation and prolonged biomass burning events, e.g. the Australian bush fires.

  14. A climatological study of the composition of Titan upper atmosphere from VIMS-IR soundings in limb geometry has been carried out for HCN, C_2H_2 and CH_4

    NASA Astrophysics Data System (ADS)

    Moriconi, M. L.; Adriani, A.; Dinelli, B. M.; Lopez-Puertas, M.; Filacchione, G.; D'Aversa, E.

    A climatological study of the composition of Titan upper atmosphere from VIMS-IR soundings in limb geometry has been carried out for (HCN), (C_2H_2) and (CH_4). The results of this study are here presented for the 2004-2012 period.

  15. HCN and CN in Comet 2P/Encke: Models of the non-isotropic, rotation-modulated coma and CN parent life time

    NASA Astrophysics Data System (ADS)

    Jockers, K.; Szutowicz, S.; Villanueva, G.; Bonev, T.; Hartogh, P.

    2011-09-01

    Axisymmetric models of the outgassing of a cometary nucleus have been constructed. Such models can be used to describe a nucleus with a single active region. The models may include a solar zenith angle dependence of the outgassing. They retrieve the outgassing flux at distances from the nucleus where collisions between molecules are unimportant, as function of the angle with respect to the outgassing axis. The observed emissions must be optically thin. Furthermore the models assume that the outflow speed at large distance from the nucleus does not depend on direction. The value of the outflow speed is retrieved. The models are applied to CN images and HCN spectra of Comet 2P/Encke, obtained nearly simultaneously in November 2003 with the 2 m optical telescope on Mount Rozhen, Bulgaria, and with the 10 m Heinrich Hertz Submillimeter Telescope on Mount Graham, Arizona, USA. According to Sekanina (1988), Astron. J. 95, 911-924, at that time a single outgassing source was active. Input parameters to the models like the rotation period of the nucleus and a small correction to Sekanina's rotation axis are determined from a simpler jet position angle model. The rotation is prograde with a sideric period of 11.056 ± 0.024 h, in agreement with literature values. The best fit model has an outflow speed of 0.95 ± 0.04 km s -1. The same value has been derived from the corkscrew appearing in the CN images. The location of the outgassing axis is at colatitude δa = 7.4° ± 2.9° and longitude λa = 235° ± 17° (a definition of zero longitude is provided). Comet Encke's outgassing corresponds approximately to the longitudinally averaged solar input on a spherical nucleus (i.e. very likely comes from deeper layers) but with some deficiency of outgassing at mid-latitudes and non-zero outgassing from the dark polar cap. The presence of gas flow from the dark polar cap is explained as evidence of gas flow across the terminator. The models rely mostly on the CN images. The HCN

  16. Distribution of voltage-gated potassium (Kv) and hyperpolarization-activated (HCN) channels in sensory afferent fibers in the rat carotid body

    PubMed Central

    Buniel, Maria; Glazebrook, Patricia A.; Ramirez-Navarro, Angelina; Kunze, Diana L.

    2008-01-01

    The chemosensory glomus cells of the carotid body (CB) detect changes in O2-tension. Carotid sinus nerve fibers, which originate from peripheral sensory neurons located within the petrosal ganglion, innervate the CB. Release of transmitter from glomus cells activates the sensory afferent fibers to transmit information to the nucleus of the solitary tract in the brainstem. The ion channels expressed within the sensory nerve terminals play an essential role in the ability of the terminal to initiate action potentials in response to transmitter-evoked depolarization. However, with a few exceptions, the identity of ion channels expressed in these peripheral nerve fibers is unknown. This study addresses the expression of voltage-gated channels in the sensory fibers with a focus on channels that set the resting membrane potential and regulate discharge patterns. Using immunohistochemistry and fluorescence confocal microscopy, potassium channel subunits and HCN (hyperpolarization-activated) family members were localized both in petrosal neurons that expressed tyrosine hydroxylase, and the CSN axons within the carotid body. Channels contributing to resting membrane potential including HCN2, responsible in part for Ih current, and the KCNQ2 and KCNQ5 subunits thought to underlie the neuronal “M current” were identified in the sensory neurons and their axons innervating the carotid body. In addition, the results presented here demonstrate expression of several potassium channels that shape the action potential and the frequency of discharge including Kv1.4, Kv1.5, Kv4.3, KCa (BK). The role of these channels should be considered in interpretation of the fiber discharge in response to perturbation of the carotid body environment. PMID:18668683

  17. Star Formation Laws in Both Galactic Massive Clumps and External Galaxies: Extensive Study with Dust Coninuum, HCN (4-3), and CS (7-6)

    NASA Astrophysics Data System (ADS)

    Liu, Tie; Kim, Kee-Tae; Yoo, Hyunju; Liu, Sheng-yuan; Tatematsu, Ken'ichi; Qin, Sheng-Li; Zhang, Qizhou; Wu, Yuefang; Wang, Ke; Goldsmith, Paul F.; Juvela, Mika; Lee, Jeong-Eun; Tóth, L. Viktor; Mardones, Diego; Garay, Guido; Bronfman, Leonardo; Cunningham, Maria R.; Li, Di; Lo, Nadia; Ristorcelli, Isabelle; Schnee, Scott

    2016-10-01

    We observed 146 Galactic clumps in HCN (4-3) and CS (7-6) with the Atacama Submillimeter Telescope Experiment 10 m telescope. A tight linear relationship between star formation rate and gas mass traced by dust continuum emission was found for both Galactic clumps and the high redshift (z > 1) star forming galaxies (SFGs), indicating a constant gas depletion time of ˜100 Myr for molecular gas in both Galactic clumps and high z SFGs. However, low z galaxies do not follow this relation and seem to have a longer global gas depletion time. The correlations between total infrared luminosities (L TIR) and molecular line luminosities ({L}{mol}\\prime ) of HCN (4-3) and CS (7-6) are tight and sublinear extending down to clumps with L TIR ˜ 103 L ⊙. These correlations become linear when extended to external galaxies. A bimodal behavior in the L TIR-{L}{mol}\\prime correlations was found for clumps with different dust temperature, luminosity-to-mass ratio, and σ line/σ vir. Such bimodal behavior may be due to evolutionary effects. The slopes of L TIR-L‧mol correlations become more shallow as clumps evolve. We compared our results with lower J transition lines in Wu et al. (2010). The correlations between clump masses and line luminosities are close to linear for low effective excitation density tracers but become sublinear for high effective excitation density tracers for clumps with L TIR larger than L TIR ˜ 104.5 L ⊙. High effective excitation density tracers cannot linearly trace the total clump masses, leading to a sublinear correlations for both M clump-L‧mol and L TIR-L‧mol relations.

  18. Molecular ions in the O-rich evolved star OH231.8+4.2: HCO+, H13CO+ and first detection of SO+, N2H+, and H3O+

    NASA Astrophysics Data System (ADS)

    Sánchez Contreras, C.; Velilla Prieto, L.; Agúndez, M.; Cernicharo, J.; Quintana-Lacaci, G.; Bujarrabal, V.; Alcolea, J.; Goicoechea, J. R.; Herpin, F.; Menten, K. M.; Wyrowski, F.

    2015-05-01

    OH 231.8+4.2, a bipolar outflow around a Mira-type variable star, displays a unique molecular richness amongst circumstellar envelopes (CSEs) around O-rich AGB and post-AGB stars. We report line observations of the HCO+ and H13CO+ molecular ions and the first detection of SO+, N2H+, and (tentatively) H3O+ in this source. SO+ and H3O+ have not been detected before in CSEs around evolved stars. These data have been obtained as part of a full mm-wave and far-IR spectral line survey carried out with the IRAM 30 m radio telescope and with Herschel/HIFI. Except for H3O+, all the molecular ions detected in this work display emission lines with broad profiles (FWHM ~ 50-90 km s-1), which indicates that these ions are abundant in the fast bipolar outflow of OH 231.8. The narrow profile (FWHM ~ 14 km s-1) and high critical densities (>106 cm-3) of the H3O+ transitions observed are consistent with this ion arising from denser, inner (and presumably warmer) layers of the fossil remnant of the slow AGB CSE at the core of the nebula. From rotational diagram analysis, we deduce excitation temperatures of Tex~ 10-20 K for all ions except for H3O+, which is most consistent with Tex≈ 100 K. Although uncertain, the higher excitation temperature suspected for H3O+ is similar to that recently found for H2O and a few other molecules, which selectively trace a previously unidentified, warm nebular component. The column densities of the molecular ions reported here are in the range Ntot≈ [1-8] × 1013 cm-2, leading to beam-averaged fractional abundances relative to H2 of X(HCO+) ≈ 10-8, X(H13CO+) ≈2 × 10-9, X(SO+) ≈4 × 10-9, X(N2H+) ≈2 × 10-9, and X(H3O+) ≈7 × 10-9 cm-2. We have performed chemical kinetics models to investigate the formation of these ions in OH 231.8 as the result of standard gas phase reactions initiated by cosmic-ray and UV-photon ionization. The model predicts that HCO+, SO+, and H3O+ can form with abundances comparable to the observed average values

  19. LiNi1/3Co1/3Mn1/3O2 nanoplates with {010} active planes exposing prepared in polyol medium as a high-performance cathode for Li-ion battery.

    PubMed

    Li, Jili; Yao, Ruimin; Cao, Chuanbao

    2014-04-09

    As we know, Li(+)-ion transport in layered LiNi1/3Co1/3Mn1/3O2 (NCM) is through two-dimensional channels parallel to the Li(+)-ion layers that are indexed as {010} active planes. In this paper, NCM nanoplates with exposed {010} active facets are synthesized in a polyol medium (ethylene glycol) and characterized by XRD, XPS, SEM, and HR-TEM. In addition, the effects of reaction conditions on the morphologies, structures and electrochemical performances are also evaluated. The results show that more {010} facets can be exposed with the thickness of NCM nanoplates increasing which can lead to more channels for Li(+)-ion migration. However, when the annealing temperatures exceed 900 °C, many new crystal planes grow along the thickness direction covering the {010} facets. In all of the NCM nanoplates obtained at different conditions, the NCM nanoplates calcined at 850 °C for 12 h (NCM-850-12H) display a high initial discharge capacity of 207.6 mAh g(-1) at 0.1 C (1 C = 200 mA g(-1)) between 2.5 and 4.5 V higher than most of NCM materials as cathodes for lithium ion batteries. The discharge capacities of NCM-850-12H are 169.8, 160.5, and 149.3 mAh g(-1) at 2, 5, and 7 C, respectively, illustrating the excellent rate capability. The superior electrochemical performance of NCM-850-12H cathode can be attributed to more {010} active planes exposure.

  20. Quantifying Protein Synthesis and Degradation in Arabidopsis by Dynamic 13CO2 Labeling and Analysis of Enrichment in Individual Amino Acids in Their Free Pools and in Protein1[OPEN

    PubMed Central

    Fernie, Alisdair R.; Stitt, Mark

    2015-01-01

    Protein synthesis and degradation represent substantial costs during plant growth. To obtain a quantitative measure of the rate of protein synthesis and degradation, we supplied 13CO2 to intact Arabidopsis (Arabidopsis thaliana) Columbia-0 plants and analyzed enrichment in free amino acids and in amino acid residues in protein during a 24-h pulse and 4-d chase. While many free amino acids labeled slowly and incompletely, alanine showed a rapid rise in enrichment in the pulse and a decrease in the chase. Enrichment in free alanine was used to correct enrichment in alanine residues in protein and calculate the rate of protein synthesis. The latter was compared with the relative growth rate to estimate the rate of protein degradation. The relative growth rate was estimated from sequential determination of fresh weight, sequential images of rosette area, and labeling of glucose in the cell wall. In an 8-h photoperiod, protein synthesis and cell wall synthesis were 3-fold faster in the day than at night, protein degradation was slow (3%–4% d−1), and flux to growth and degradation resulted in a protein half-life of 3.5 d. In the starchless phosphoglucomutase mutant at night, protein synthesis was further decreased and protein degradation increased, while cell wall synthesis was totally inhibited, quantitatively accounting for the inhibition of growth in this mutant. We also investigated the rates of protein synthesis and degradation during leaf development, during growth at high temperature, and compared synthesis rates of Rubisco large and small subunits of in the light and dark. PMID:25810096

  1. Hierarchical Porous LiNi1/3Co1/3Mn1/3O2 Nano-/Micro Spherical Cathode Material: Minimized Cation Mixing and Improved Li+ Mobility for Enhanced Electrochemical Performance

    PubMed Central

    Chen, Zhen; Wang, Jin; Chao, Dongliang; Baikie, Tom; Bai, Linyi; Chen, Shi; Zhao, Yanli; Sum, Tze Chien; Lin, Jianyi; Shen, Zexiang

    2016-01-01

    Although being considered as one of the most promising cathode materials for Lithium-ion batteries (LIBs), LiNi1/3Co1/3Mn1/3O2 (NCM) is currently limited by its poor rate performance and cycle stability resulting from the thermodynamically favorable Li+/Ni2+ cation mixing which depresses the Li+ mobility. In this study, we developed a two-step method using fluffy MnO2 as template to prepare hierarchical porous nano-/microsphere NCM (PNM-NCM). Specifically, PNM-NCM microspheres achieves a high reversible specific capacity of 207.7 mAh g−1 at 0.1 C with excellent rate capability (163.6 and 148.9 mAh g−1 at 1 C and 2 C), and the reversible capacity retention can be well-maintained as high as 90.3% after 50 cycles. This excellent electrochemical performance is attributed to unique hierarchical porous nano-/microsphere structure which can increase the contact area with electrolyte, shorten Li+ diffusion path and thus improve the Li+ mobility. Moreover, as revealed by XRD Rietveld refinement analysis, a negligible cation mixing (1.9%) and high crystallinity with a well-formed layered structure also contribute to the enhanced C-rates performance and cycle stability. On the basis of our study, an effective strategy can be established to reveal the fundamental relationship between the structure/chemistry of these materials and their properties. PMID:27185646

  2. Highly stable Na2/3 (Mn0.54 Ni0.13 Co0.13 )O2 cathode modified by atomic layer deposition for sodium-ion batteries.

    PubMed

    Kaliyappan, Karthikeyan; Liu, Jian; Lushington, Andrew; Li, Ruying; Sun, Xueliang

    2015-08-10

    For the first time, atomic layer deposition (ALD) of Al2 O3 was adopted to enhance the cyclic stability of layered P2-type Na2/3 (Mn0.54 Ni0.13 Co0.13 )O2 (MNC) cathodes for use in sodium-ion batteries (SIBs). Discharge capacities of approximately 120, 123, 113, and 105 mA h g(-1) were obtained for the pristine electrode and electrodes coated with 2, 5, and 10 ALD cycles, respectively. All electrodes were cycled at the 1C discharge current rate for voltages between 2 and 4.5 V in 1 M NaClO4 electrolyte. Among the electrodes tested, the Al2 O3 coating from 2 ALD cycles (MNC-2) exhibited the best electrochemical stability and rate capability, whereas the electrode coated by 10 ALD cycles (MNC-10) displayed the highest columbic efficiency (CE), which exceeded 97 % after 100 cycles. The enhanced electrochemical stability observed for ALD-coated electrodes could be a result of the protection effects and high band-gap energy (Eg =9.00 eV) of the Al2 O3 coating layer. Additionally, the metal-oxide coating provides structural stability against mechanical stresses occurring during the cycling process. The capacity, cyclic stability, and rate performance achieved for the MNC electrode coated with 2 ALD cycles of Al2 O3 reveal the best results for SIBs. This study provides a promising route toward increasing the stability and CE of electrode materials for SIB application.

  3. Fatigue in 0.5Li2MnO3:0.5Li(Ni1/3Co1/3Mn1/3)O2 positive electrodes for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Riekehr, Lars; Liu, Jinlong; Schwarz, Björn; Sigel, Florian; Kerkamm, Ingo; Xia, Yongyao; Ehrenberg, Helmut

    2016-09-01

    Two different Li-rich nickel-cobalt-manganese-oxide (Li-rich NCM) active materials with the same nominal composition 0.5Li2MnO3:0.5Li(Ni1/3Co1/3Mn1/3)O2 but different pristine nano structure have been analyzed structurally and electrochemically in different cycling states. For structural characterization, transmission electron microscopy (TEM) and high resolution synchrotron powder diffraction (S-XRD) experiments were conducted. The changes in structure with increasing cycle number are correlated with characteristic features in the corresponding electrochemical dQ/dV-profiles that were obtained by galvanostatically cycling the two different active materials. The presented data demonstrates that structural changes upon cycling, e.g. LiMnO2 and spinel formation, strongly depend on the degree oxygen is involved in the reversible charge compensation for delithiation/lithiation. According to our data, firstly a twin-like environment with nanometer dimensions is formed within the R-3m matrix during the initial cycle, which then gradually transforms into a spinel-like structure with increasing cycle number. As another result, we can show that Li2MnO3 to LiMnO2 transformation is not directly dependent in the irreversible oxygen loss in the first cycle but more importantly on transition metal migration. A model is presented explaining the dependency of LiMnO2 and spinel formation on the ability of Li-rich active materials to include oxygen in the charge compensation process.

  4. DENSE MOLECULAR GAS EXCITATION IN NUCLEAR STARBURSTS AT HIGH REDSHIFT: HCN, HNC, AND HCO{sup +}(J = 6{yields}5) EMISSION IN THE z = 3.91 QUASAR HOST OF APM 08279+5255

    SciTech Connect

    Riechers, Dominik A.; Weiss, Axel; Walter, Fabian; Wagg, Jeff

    2010-12-10

    We report the detection of surprisingly strong HCN(J = 6{yields}5), HNC(J = 6{yields}5), and HCO{sup +}(J = 6{yields}5) emission in the host galaxy of the z = 3.91 quasar APM 08279+5255 through observations with the Combined Array for Research in Millimeter-wave Astronomy. HCN, HNC, and HCO{sup +} are typically used as star formation indicators, tracing dense molecular hydrogen gas [n(H{sub 2}) >10{sup 5} cm{sup -3}] within star-forming molecular clouds. However, the strength of their respective line emission in the J = 6{yields}5 transitions in APM 08279+5255 is extremely high, suggesting that they are excited by another mechanism besides collisions in the dense molecular gas phase alone. We derive J = 6{yields}5 line luminosities of L'{sub HCN} = (4.9 {+-} 0.6), L'{sub HNC} = (2.4 {+-} 0.7), and L{sup '}{sub HCO}{sup +}= (3.0{+-}0.6)x10{sup 10} {mu}{sup -1}{sub L} K km s{sup -1} pc{sup 2} (where {mu}{sub L} is the lensing magnification factor), corresponding to L' ratios of {approx}0.23-0.46 relative to CO(J = 1{yields}0). Such high line ratios would be unusual even in the respective ground-state (J = 1{yields}0) transitions, and indicate exceptional, collisionally and radiatively driven excitation conditions in the dense, star-forming molecular gas in APM 08279+5255. Through an expansion of our previous modeling of the HCN line excitation in this source, we show that the high rotational line fluxes are caused by substantial infrared pumping at moderate opacities in a {approx}220 K warm gas and dust component. This implies that standard M{sub dense}/L' conversion factors would substantially overpredict the dense molecular gas mass M{sub dense}. We also find a HCN(J = 6{yields}5)/HCN(J = 5{yields}4) L' ratio greater than 1 (1.36 {+-} 0.31)-however, our models show that the excitation is likely not 'super-thermal', but that the high line ratio is due to a rising optical depth between both transitions. These findings are consistent with the picture that the bulk of

  5. Short-term carbon dynamics in a temperate heathland upon six years of exposure to elevated CO2 concentration, drought and warming: Evidence from an in-situ 13CO2 pulse-chase experiment

    NASA Astrophysics Data System (ADS)

    Ambus, P.; Reinsch, S.; Sárossy, Z.; Egsgaard, H.; Jakobsen, I.; Michelsen, A.; Schmidt, I.; Nielsen, P.

    2013-12-01

    An in-situ 13CO2 pulse-labeling experiment was carried out in a temperate heathland (8 oC MA