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Sample records for 6-h study period

  1. An evaluation of the cognitive and mood effects of an energy shot over a 6h period in volunteers: a randomized, double-blind, placebo controlled, cross-over study.

    PubMed

    Wesnes, Keith A; Barrett, Marilyn L; Udani, Jay K

    2013-08-01

    Energy drinks are widely available mostly containing glucose, and several have been demonstrated to improve alertness and cognitive function; these effects generally being identified 30-60min after administration. The present study assessed whether an energy shot without carbohydrates would affect major aspects of cognitive function and also mood in volunteers over a 6h time period. This randomized, double-blind, placebo-controlled,crossover study compared the acute effects of the energy shot with a matching placebo in 94 healthy volunteers. Cognitive function was assessed with a widely used set of automated tests of attention and memory. Mood was assessed with the Bond-Lader, Beck Anxiety Index, Beck Depression Index, Chalder Fatigue Scales (CFS), and the POMS. The volunteers were requested to limit their sleep to between 3 and 6h the night before each testing day. Compared to the placebo, the energy shot significantly improved 6 validated composite cognitive function measures from the CDR System as well as self-rated alertness; the benefits on 4 of the cognitive measures still remaining at 6h. The overall effect sizes of the performance improvements were in the small to medium range and thus notable in this field. In conclusion, an energy shot can significantly improve important aspects of cognitive function for up to 6h compared to placebo in partially sleep-deprived healthy volunteers.

  2. An evaluation of the cognitive and mood effects of an energy shot over a 6h period in volunteers: a randomized, double-blind, placebo controlled, cross-over study.

    PubMed

    Wesnes, Keith A; Barrett, Marilyn L; Udani, Jay K

    2013-08-01

    Energy drinks are widely available mostly containing glucose, and several have been demonstrated to improve alertness and cognitive function; these effects generally being identified 30-60min after administration. The present study assessed whether an energy shot without carbohydrates would affect major aspects of cognitive function and also mood in volunteers over a 6h time period. This randomized, double-blind, placebo-controlled,crossover study compared the acute effects of the energy shot with a matching placebo in 94 healthy volunteers. Cognitive function was assessed with a widely used set of automated tests of attention and memory. Mood was assessed with the Bond-Lader, Beck Anxiety Index, Beck Depression Index, Chalder Fatigue Scales (CFS), and the POMS. The volunteers were requested to limit their sleep to between 3 and 6h the night before each testing day. Compared to the placebo, the energy shot significantly improved 6 validated composite cognitive function measures from the CDR System as well as self-rated alertness; the benefits on 4 of the cognitive measures still remaining at 6h. The overall effect sizes of the performance improvements were in the small to medium range and thus notable in this field. In conclusion, an energy shot can significantly improve important aspects of cognitive function for up to 6h compared to placebo in partially sleep-deprived healthy volunteers. PMID:23587521

  3. Surface birefringence of self-assembly periodic nanostructures induced on 6H-SiC surface by femtosecond laser

    NASA Astrophysics Data System (ADS)

    Song, Juan; Dai, Ye; Tao, Wenjun; Gong, Min; Ma, Guohong; Zhao, Quanzhong; Qiu, Jianrong

    2016-02-01

    In this paper, we report the birefringence effect of surface self-assembly periodic nanostructures induced on 6H-SiC by femtosecond laser irradiation. Birefringence characteristic (e.g. cross-polarized image), measured by cross polarized microscopy, was found to be controlled by both single pulse energy and scanning velocity. Comparing birefringence measurement results of nanostructures and morphology characterization by Scanning electron microscopy, it is shown that ∼200 nm-period deep-subwavelength periodic ripples (DSWR) plays a dominating role in the birefringence effect. Raman spectra show that the change of retardance with pulse energy and scanning velocity is most possibly caused by the thickness variation of DSWR. Finally, a light attenuator based on a single layer of DSWR structure on 6H-SiC surface was constructed and tested by light source of 800 nm to have a tunable attenuating ratio of 69-100%.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  5. Density functional study of adenine tetrads with N6-H6...N3 hydrogen bonds.

    PubMed

    Meyer, Michael; Sühnel, Jürgen

    2008-05-01

    The structure and energy of A-tetrads with N6-H6...N3 H-bonds was studied using B3LYP and BH&H density functional theory. The planar A-tetrad with C(4h) symmetry is more stable than the nonplanar structures at C4 and S4 symmetry. This structure corresponds to a local energy minimum. The energies of the structures with N6-H6...N1 and N6-H6...N7 H-bonds studied previously are of similar magnitude. Structures of A-tetrad complexes with sodium and potassium were most stable at S4 symmetry, and similarly, sandwich complexes consisting of two tetrads and a single cation were most stable at S8 symmetry. Relative energies of sandwich complexes with different symmetries obtained with the B3LYP and BH&H methods were quite different. BH&H overestimates the interaction energies between hydrogen-bonded neighbor bases relative to B3LYP. PMID:18380490

  6. Laser-induced periodic surface structures on 6H-SiC single crystals using temporally delayed femtosecond laser double-pulse trains

    NASA Astrophysics Data System (ADS)

    Song, Juan; Tao, Wenjun; Song, Hui; Gong, Min; Ma, Guohong; Dai, Ye; Zhao, Quanzhong; Qiu, Jianrong

    2016-04-01

    In this paper, a time-delay-adjustable double-pulse train with 800-nm wavelength, 200-fs pulse duration and a repetition rate of 1 kHz, produced by a collinear two-beam optical system like a Mach-Zehnder interferometer, was employed for irradiation of 6H-SiC crystal. The dependence of the induced structures on time delay of double-pulse train for parallel-polarization configuration was studied. The results show that as the time delay of collinear parallel-polarization dual-pulse train increased, the induced near-subwavelength ripples (NSWRs) turn from irregular rippled pattern to regularly periodic pattern and have their grooves much deepened. The characteristics timescale for this transition is about 6.24 ps. Besides, the areas of NSWR were found to decay exponentially for time delay from 0 to 1.24 ps and then slowly increase for time delay from 1.24 to 14.24 ps. Analysis shows that multiphoton ionization effect, grating-assisted surface plasmon coupling effect, and timely intervene of second pulse in a certain physical stage experienced by 6H-SiC excited upon first pulse irradiation may contribute to the transition of morphology details.

  7. A theoretical study of isomeric C 6H 4Br - ions

    NASA Astrophysics Data System (ADS)

    Morgon, Nelson H.; Custodio, Rogério; Riveros, JoséM.

    1995-03-01

    The structural stability of bromide o-benzyne complexes was studied. A new procedure was applied to adapt a basis set to be used with the Hay and Wadt pseudopotential for the Br atom. Calculations at the MP2, MP3 and MP4 levels established two stable structural isomers for the C 6H 4Br - ion: (a) a bromphenide anion and (b) an isomer with a loose hydrogen-bonded bromide-benzyne complex where the Br - ion is straddling the ortho and meta hydrogen of the ring. At the MP4 level the barrier between the two isomers is below the typical energies associated with the loose complexes formed as intermediates in ion/molecule reactions.

  8. Multiphoton ionization studies of clusters of immiscible liquids. II. C6H6- (H2O)n, n=3-8 and (C6H6)2- (H2O)1,2

    NASA Astrophysics Data System (ADS)

    Garrett, Aaron W.; Zwier, Timothy S.

    1992-03-01

    Resonant two-photon ionization (R2PI) time-of-flight mass spectroscopy is used to record S0-S1 spectra of the neutral complexes C6H6-(H2O)n with n=3-8 and (C6H6)2-(H2O)1,2. Due to limitations imposed by the size of these clusters, a number of vibronic level arguments are used to constrain the gross features of the geometries of these clusters. Among the spectral clues provided by the data are the frequency shifts of the transitions, their van der Waals structure, the fragmentation of the photoionized clusters, and the complexation-induced origin intensity and 610 splitting. In the 1:3 cluster, simple arguments are made based on the known structures of the 1:1 and 1:2 clusters which lead to the conclusion that all three water molecules reside on the same side of the benzene ring. Three structures for the 1:3 cluster are proposed which are consistent with the available data. Of these, only one is also consistent with the remarkable similarity of the 1:4 and 1:5 spectra to those of the 1:3 cluster. This structure involves a cyclic water trimer in which one of the water molecules is near the sixfold axis in a π hydrogen-bonded configuration. This structure is then expanded in the 1:4 and 1:5 clusters to incorporate the fourth and fifth water molecules in cyclic structures which place the additional water molecules far from the benzene ring without disturbing the interaction of the other water molecules with the benzene ring. For 1:n clusters with n≥6, subtle and then significant changes are observed in the spectra which indicate changes in the way the water cluster interacts with the benzene ring. This development occurs at precisely the water cluster size which calculations predict that cagelike water cluster structures will begin to compete and eventually be favored over large cyclic structures. Finally, cursory scans of the 2:1 cluster show that this cluster also fragments efficiently upon photoionization by loss of a single water molecule and that it possesses a

  9. Comparative study of 3C-SiC layers sublimation-grown on a 6H-SiC substrate

    SciTech Connect

    Shustov, D. B.; Lebedev, A. A. Lebedev, S. P.; Nelson, D. K.; Sitnikova, A. A.; Zamoryanskaya, M. V.

    2013-09-15

    n-3C-SiC/n-6H-SiC heterostructures grown by vacuum sublimation on CREE commercial 6H-SiC substrates are studied. Transmission electron microscopy (TEM) demonstrated that a transitional layer of varying thickness, composed of a mixture of 3C- and 6H-SiC polytypes, is formed on the substrate. A 3C polytype layer was obtained on the interlayer. Cathodoluminescence study of the surface of the film demonstrated that defects in the form of inclusions of another phase (6H-polytype), stacking faults, and twin boundaries (separating domains of cubic modification, grown in various orientations) are found on the surface and in the surface layer with a thickness on the order of 100 {mu}m. Varying the growth conditions changes the concentration of various types of defects.

  10. Solid state and solution study of some phosphoramidate derivatives containing the P(O)NHC(O) bifunctional group: crystal structures of CCl(2)HC(O)NHP(O)(NCH(3)(CH(2)C(6)H(5)))(2), p-ClC(6)H(4)C(O)NHP(O)(NCH(3)(CH(2)C(6)H(5)))(2), CCl(2)HC(O)NHP(O)(N(CH(2)C(6)H(5))(2))(2) and p-BrC(6)H(4)C(O)NHP(O)(N(CH(2)C(6)H(5))(2))(2).

    PubMed

    Dehghanpour, Saeed; Welter, Richard; Barry, Aliou Hamady; Tabasi, Farzaneh

    2010-04-01

    Synthetic methods for several novel phosphoramidate compounds containing the P(O)NHC(O) bifunctional group were developed. These compounds with the general formula R(1)C(O)NHP(O)(N(R(2))(CH(2)C(6)H(5)))(2), where R(1)=CCl(2)H, p-ClC(6)H(4), p-BrC(6)H(4), o-FC(6)H(4) and R(2)=hydrogen, methyl, benzyl, were characterized by several spectroscopic methods and analytical techniques. The effects of phosphorus substituents on the rotation rate around the P-N(amine) bond were also investigated. (1)H NMR study of the synthesized compounds demonstrated that the presence of bulky groups attached to the phosphorus center and electron withdrawing groups in the amide moiety lead to large chemical-shift non-equivalence (Deltadelta(H)) of diastereotopic methylene protons. The crystal structures of CCl(2)HC(O)NHP(O)(NCH(3)(CH(2)C(6)H(5)))(2), p-ClC(6)H(4)C(O)NHP(O)(NCH(3)(CH(2)C(6)H(5)))(2), CCl(2)HC(O)NHP(O)(N(CH(2)C(6)H(5))(2))(2) and p-BrC(6)H(4)C(O)NHP(O)(N(CH(2)C(6)H(5))(2))(2) were determined by X-ray crystallography using single crystals. The coordination around the phosphorus center in these compounds is best described as distorted tetrahedral and the P(O) and C(O) groups are anti with respect to each other. In the compound Br-C(6)H(4)C(O)NHP(O)(N(CH(2)C(6)H(5))(2))(2) (with two independent molecules in the unit cell), two conformers are connected to each other via two different N-H...O hydrogen bonds forming a non-centrosymmetric dimer. In the crystalline lattice of other compounds, the molecules form centrosymmetric dimers via pairs of same N-H...O hydrogen bonds. The structure of CCl(2)HC(O)NHP(O)(N(CH(2)C(6)H(5))(2))(2) reveals an unusual intramolecular interaction between the oxygen of C=O group and amine nitrogen.

  11. The electron spin resonance study of heavily nitrogen doped 6H SiC crystals

    SciTech Connect

    Savchenko, D. V.

    2015-01-28

    The magnetic and electronic properties of heavily doped n-type 6H SiC samples with a nitrogen concentration of 10{sup 19} and 4 × 10{sup 19 }cm{sup −3} were studied with electron spin resonance (ESR) at 5–150 K. The observed ESR line with a Dysonian lineshape was attributed to the conduction electrons (CE). The CE ESR (CESR) line was fitted by Lorentzian (insulating phase) (T < 40 K) and by Dysonian lineshape (metallic phase) above 40 K, demonstrating that Mott insulator-metal (IM) transition takes place at ∼40 K, accompanied by significant change in the microwave conductivity. The temperature dependence of CESR linewidth follows the linear Korringa law below 40 K, caused by the coupling of the localized electrons (LE) and CE, and is described by the exponential law above 40 K related to the direct relaxation of the LE magnetic moments via excited levels driven by the exchange interaction of LE with CE. The g-factor of the CESR line (g{sub ‖} = 2.0047(3), g{sub ⊥} = 2.0034(3)) is governed by the coupling of the LE of nitrogen donors at hexagonal and quasi-cubic sites with the CE. The sharp drop in CESR line intensity (25–30 K) was explained by the formation of antiferromagnetic ordering in the spin system close to the IM transition. The second broad ESR line overlapped with CESR signal (5–25 K) was attributed to the exchange line caused by the hopping motion of electrons between occupied and non-occupied positions of the nitrogen donors. Two mechanisms of conduction, hopping and band conduction, were distinguished in the range of T = 10–25 K and T > 50 K, respectively.

  12. Electronic transitions of C6H4+ isomers: neon matrix and theoretical studies.

    PubMed

    Fulara, Jan; Nagy, Adam; Filipkowski, Karol; Thimmakondu, Venkatesan S; Stanton, John F; Maier, John P

    2013-12-19

    Three open-chain isomers of C6H4(+) and two cyclic ones were detected following mass-selective trapping in 6 K neon matrixes. The open-chain cations 5-hexene-1,3-diyne (CH2═CH-CC-CC-H)(+) and cis- (cis-HCC-CH═CH-CCH)(+) and trans-3-hexene-1,5-diyne (trans-HCC-CH═CH-CCH)(+), possess two absorption systems commencing at 609 and 373, 622 and 385, and 585 and 373 nm, respectively. They are assigned to the 1 (2)A" and 2 (2)A" ← X (2)A", 1(2)A2 and 2 (2)A2 ← X (2)B1, and 1 (2)Bg and 2 (2)B(g) ← X (2)A(u) electronic transitions of these cations. Two overlapping systems are detected at around 420 nm and tentatively assigned to the 1 (2)A" ← X (2)A" electronic transitions of propargyl cyclopropene and 2 (2)B1 ← X (2)A2 of o-benzyne cation structures. The assignment of the electronic transitions is based on theoretical vertical excitation energies calculated with CASPT2 and EOMEE-CCSDT methods for 12 isomers of C6H4(+). These have been carried out at the geometries optimized using several ab initio methods. Adiabatic excitation energies were calculated for the five identified isomers of C6H4(+).

  13. Study on Λ6H hypernucleus by the (π-, K+) reaction at J-PARC

    NASA Astrophysics Data System (ADS)

    Sugimura, H.; Agnello, M.; Ahn, J. K.; Ajimura, S.; Akazawa, Y.; Amano, N.; Aoki, K.; Bhang, H. C.; Endo, M.; Evtoukhovitch, P.; Feliciello, A.; Fujioka, H.; Fukuda, T.; Hasegawa, S.; Hayakawa, S.; Honda, R.; Hosomi, K.; Hwang, S. H.; Ichikawa, Y.; Igarashi, Y.; Imai, K.; Ishibashi, N.; Iwasaki, R.; Joo, C. W.; Kiuchi, R.; Lee, J. K.; Lee, J. Y.; Matsuda, K.; Matsumoto, Y.; Matsuoka, K.; Miwa, K.; Mizoi, Y.; Moritsu, M.; Nagae, T.; Nagamiya, S.; Nakagawa, M.; Naruki, M.; Noumi, H.; Ota, R.; Roy, B. J.; Saha, P. K.; Sakaguchi, A.; Sako, H.; Samanta, C.; Samoilov, V.; Sasaki, Y.; Sato, S.; Sekimoto, M.; Shimizu, Y.; Shiozaki, T.; Shirotori, K.; Soyama, T.; Takahashi, T.; Takahashi, T. N.; Tamura, H.; Tanabe, K.; Tanaka, T.; Tanida, K.; Tokiyasu, A. O.; Tsamalaidze, Z.; Ukai, M.; Yamamoto, T. O.; Yamamoto, Y.; Yang, S. B.; Yoshida, K.

    2014-03-01

    We carried out an experiment to produce the neutron-rich hypernucleus Λ6H via the (π-, K+) reaction on 6Li target at the pion beam momentum of 1.2 GeV/c (J-PARC E10). In order to calibrate the scale of the missing-mass or of the Λ binding energy of the hypernucleus, we also measured the 12C(π+, K+) Λ12C, p(π-, K+)Σ- and p(π+, K+)Σ+reactions. The experiment was performed at the J-PARC Hadron Hall K1.8 beam line in December 2012 and January 2013. The overall collected data sample corresponds to an integrated beam intensity of 1.65 × 1012 pions.

  14. Study on formation of step bunching on 6H-SiC (0001) surface by kinetic Monte Carlo method

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Chen, Xuejiang; Su, Juan

    2016-05-01

    The formation and evolution of step bunching during step-flow growth of 6H-SiC (0001) surfaces were studied by three-dimensional kinetic Monte Carlo (KMC) method and compared with the analytic model based on the theory of Burton-Cabera-Frank (BCF). In the KMC model the crystal lattice was represented by a structured mesh which fixed the position of atoms and interatomic bonding. The events considered in the model were adatoms adsorption and diffusion on the terrace, and adatoms attachment, detachment and interlayer transport at the step edges. In addition, effects of Ehrlich-Schwoebel (ES) barriers at downward step edges and incorporation barriers at upwards step edges were also considered. In order to obtain more elaborate information for the behavior of atoms in the crystal surface, silicon and carbon atoms were treated as the minimal diffusing species. KMC simulation results showed that multiple-height steps were formed on the vicinal surface oriented toward [ 1 1 bar 00 ] or [ 11 2 bar 0 ] directions. And then the formation mechanism of the step bunching was analyzed. Finally, to further analyze the formation processes of step bunching, a one-dimensional BCF analytic model with ES and incorporation barriers was used, and then it was solved numerically. In the BCF model, the periodic boundary conditions (PBC) were applied, and the parameters were corresponded to those used in the KMC model. The evolution character of step bunching was consistent with the results obtained by KMC simulation.

  15. Infrared Reflectance and Ultrahigh Vacuum Cathodoluminescence of Aluminum Nitride-Gallium Nitride Short Period Superlattice Films and P-Type Porous 6h Silicon Carbide Layers

    NASA Astrophysics Data System (ADS)

    MacMillan, Michael F.

    The room temperature infrared reflectance of AlN -GaN short period superlattice films was measured. These superlattice films were deposited by switched atomic layer metal organic chemical vapor deposition onto GaN or AlN buffer layers deposited on basal plane sapphire substrates. The measured reflectance spectra are compared to calculated spectra generated using an effective medium theory to model the dielectric function of the superlattice. Optical properties of the individual materials comprising the samples are modeled with Lorentz oscillators using bulk input parameters. The effects of film and substrate anisotropy and off normal incidence are included in the calculation. Using this modeling technique, thickness estimates for the total superlattice film and the buffer layer are obtained. Cathodoluminescence of AlN-GaN short period superlattice films was measured at 6K, 77K and room temperature, and at several electron acceleration voltages to allow depth profiling of the samples. An ultraviolet peak located above the band gap energy of GaN is present in all samples and persists from 6K to room temperature. Using the film and buffer thicknesses determined by the reflectance measurement this ultraviolet peak is identified as originating from the superlattice layer. Preliminary results indicate that this peak is due to quantum confinement in the GaN layers. The room temperature infrared reflectance of thick p-type porous 6H SiC layers was measured. Samples were fabricated by anodization of p-type 6H SiC bulk crystals in dilute HF. Striking differences are seen between the reststrahl region reflectance of these porous layers and that of bulk 6H SiC crystals. Several effective medium models, which assume different morphologies of the component materials, 6H SiC and air, were used to model the dielectric function of porous SiC. Calculated reflectance spectra, generated using these dielectric functions, are compared to experimental porous SiC spectra, allowing us to

  16. Study of Electrical Properties in SHI Irradiated 6H-SiC Crystals using Low Temperature Impedance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Viswanathan, E.; Murugaraj, R.; Selvakumar, S.; Kanjilal, D.; Sivaji, K.

    2011-07-01

    In the present work, low temperature impedance measurements were made on the pristine and Ag12+ ions irradiated 6H-SiC samples. The conductivity properties were studied at low temperature. The activation energies were calculated from the Arrhenius plot of d.c conductivity and impedance relaxation time. The activation energy was comparatively higher for the irradiated samples and found to be electronic conduction. From the study we observe the lower conductivity values exhibited for 300 K irradiated sample due to severe damage than the 80 K irradiated sample. The damage production mechanism and the change in electrical properties are discussed.

  17. Rutherford Backscattering Spectrometry Channeling Study of Ion-Irradiated 6H-SiC

    SciTech Connect

    Jiang, Weilin; Weber, William J.; Thevuthasan, Suntharampillai; McCready, David E.

    1999-04-01

    Studies damage accumulation and defect annealing (up to 1170 K) using in-situ 2.0 MeV He Rutherford Backscattering Spectrometry combined with ion channeling methods. Observes that the defect concentration at the damage peak increases sigmoidally with increasing ion fluence during irradiation at low temperatures and that the isochronal recovery of the damage induced at low temperatures follows an exponential dependence on temperature.

  18. Tip induced mechanical deformation of epitaxial graphene grown on reconstructed 6H-SiC(0001) surface during scanning tunneling and atomic force microscopy studies.

    PubMed

    Meza, José Antonio Morán; Lubin, Christophe; Thoyer, François; Cousty, Jacques

    2015-01-26

    The structural and mechanical properties of an epitaxial graphene (EG) monolayer thermally grown on top of a 6H-SiC(0001) surface were studied by combined dynamic scanning tunneling microscopy (STM) and frequency modulation atomic force microscopy (FM-AFM). Experimental STM, dynamic STM and AFM images of EG on 6H-SiC(0001) show a lattice with a 1.9 nm period corresponding to the (6 × 6) quasi-cell of the SiC surface. The corrugation amplitude of this (6 × 6) quasi-cell, measured from AFM topographies, increases with the setpoint value of the frequency shift Δf (15-20 Hz, repulsive interaction). Excitation variations map obtained simultaneously with the AFM topography shows that larger dissipation values are measured in between the topographical bumps of the (6 × 6) quasi-cell. These results demonstrate that the AFM tip deforms the graphene monolayer. During recording in dynamic STM mode, a frequency shift (Δf) map is obtained in which Δf values range from 41 to 47 Hz (repulsive interaction). As a result, we deduced that the STM tip, also, provokes local mechanical distortions of the graphene monolayer. The origin of these tip-induced distortions is discussed in terms of electronic and mechanical properties of EG on 6H-SiC(0001).

  19. Study on the machined depth when nanoscratching on 6H-SiC using Berkovich indenter: Modelling and experimental study

    NASA Astrophysics Data System (ADS)

    Zhang, Feihu; Meng, Binbin; Geng, Yanquan; Zhang, Yong

    2016-04-01

    In order to investigate the deformation characteristics and material removing mechanism of the single crystal silicon carbide at the nanoscale, the nanoscratching tests were conducted on the surface of 6H-SiC (0 0 0 1) by using Berkovich indenter. In this paper, a theoretical model for nanoscratching with Berkovich indenter is proposed to reveal the relationship between the applied normal load and the machined depth. The influences of the elastic recovery and the stress distribution of the material are considered in the developed theoretical model. Experimental and theoretical machined depths are compared when scratching in different directions. Results show that the effects of the elastic recovery of the material, the geometry of the tip and the stress distribution of the interface between the tip and sample have large influences on the machined depth which should be considered for this kind of hard brittle material of 6H-SiC.

  20. DEFECT SELECTIVE ETCHING OF THICK ALN LAYERS GROWN ON 6H-SIC SEEDS - A TRANSMISSION ELECTRON MICROSCOPY STUDY

    SciTech Connect

    Nyakiti, Luke; Chaudhari, Jharna; Kenik, Edward A; Lu, Peng; Edgar, J H

    2008-01-01

    In the present study, the type and densities of defects in AlN crystals grown on 6H-SiC seeds by the sublimation-recombination method were assessed. The positions of the defects in AlN were first identified by defect selective etching (DSE) in molten NaOH-KOH at 400 C for 2 minutes. Etching produced pits of three different sizes: 1.77 m, 2.35 m , and 2.86 m. The etch pits were either aligned together forming a sub-grain boundary or randomly distributed. The smaller etch pits were either isolated or associated with larger etch pits. After preparing crosssections of the pits by the focused ion beam (FIB) technique, transmission electron microscopy (TEM) was performed to determine which dislocation type (edge, mixed or screw) produced a specific etch pit sizes. Preliminary TEM bright field and dark field study using different zone axes and diffraction vectors indicates an edge dislocation with a Burgers vector 1/3[1120] is associated with the smallest etch pit size.

  1. X-Ray Photoelectron Spectroscopy Study of the Heating Effects on Pd/6H-SiC Schottky Structure

    NASA Technical Reports Server (NTRS)

    Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Knight, Dak

    1998-01-01

    X-ray photoelectron spectroscopy is used to study the effects of heat treatment on the Pd/6H-SiC Schottky diode structure. After heating the structure at 425 C for 140 h, a very thin surface layer of PdO mixed with SiO(x) formed on the palladium surface of the Schottky structure. Heat treatment promoted interfacial diffusion and reaction which significantly broadened the interfacial region. In the interfacial region, the palladium concentration decreases with depth, and the interfacial products are Pd(x)Si (x = 1,2,3,4). In the high Pd concentration regions, Pd4Si is the major silicide component while gr and Pd2Si are major components in the low Pd concentration region. At the center of the interface, where the total palladium concentration equals that of silicon, the concentrations of palladium associated with various palladium silicides (Pd(x)Si, x= 1,2,3,4) are approximately equal. The surface passivation layer composed of PdO and SiO, may significantly affect the electronic and catalytic properties of the surface of the Schottky diode which plays a major role in gas detection. The electronic properties of the Schottky structure may be dominated by a (Pd+Pd(x)Si)/SiC interface. In order to stabilize the properties of the Schottky structure the surface and interface diffusion and reactions must be controlled.

  2. Dosimetry and pharmacokinetics of monoclonal antibody A6H with human renal cell carcinoma xenografts: single dose study.

    PubMed

    Palme, D F; Berkopec, J M; Wessels, B W; Elson, M K; Lange, P H; Vessella, R L

    1991-01-01

    Implantable miniature thermoluminescent dosimeters and conventional biodistribution analysis were used to determine the locally absorbed radiation dose delivered to three morphologically distinct human renal cell carcinoma xenografts (TK-39, TK-82 and TK-177C; N = 87) following a 50 microCi infusion of 131iodine-labeled monoclonal antibody A6H. Xenografts were clearly detected by radioimmuno-scintigraphy. Pronounced differences were noted among the three xenografts in MAb pharmacokinetics and in the locally absorbed irradiation doses which ranged from 2 to 5 cGy per injected microCi of 131iodine-labelled A6H. PMID:1917523

  3. Insights into Hydrocarbon Chain and Aromatic Ring Formation in the Interstellar Medium: Computational Study of the Isomers of C4H3+ C6H3+ and C6H5+ and Their Formation Pathways

    NASA Astrophysics Data System (ADS)

    Peverati, Roberto; Bera, Partha P.; Lee, Timothy J.; Head-Gordon, Martin

    2016-10-01

    Small hydrocarbons such as acetylene is present in circumstellar envelopes of carbon-rich stars, but the processes that yield larger molecules, and eventually polycyclic aromatic hydrocarbons (PAHs), remain poorly understood. To gain additional insight into the early steps of such processes, electronic structure calculations were performed on the potential energy surfaces of {{{C}}}4{{{{H}}}3}+, {{{C}}}6{{{{H}}}3}+ and {{{C}}}6{{{{H}}}5}+. The results establish reactive pathways from acetylene and its ion to formation of the first aromatic ring. We characterize the stable isomers, their spectroscopic properties, and many of the transition structures that represent barriers to isomerization. The pathways to stabilized {{{C}}}4{{{{H}}}3}+ and {{{C}}}6{{{{H}}}3}+ are most likely to arise from unimolecular decomposition of hot {{{C}}}4{{{{H}}}4}+ and {{{C}}}6{{{{H}}}4}+ by H atom elimination. By contrast, we found an ion-molecule pathway to {{{C}}}6{{{{H}}}5}+ to be very stable to fragmentation and elimination reactions even without collisional stabilization. This aromatic species is a good nucleation center for the growth of larger PAHs in interstellar conditions.

  4. Electron paramagnetic resonance and theoretical studies of Nb in 4H- and 6H-SiC

    NASA Astrophysics Data System (ADS)

    Tien Son, Nguyen; Thang Trinh, Xuan; Gällström, Andreas; Leone, Stefano; Kordina, Olof; Janzén, Erik; Szász, Krisztián; Ivády, Viktor; Gali, Adam

    2012-10-01

    High purity silicon carbide (SiC) materials are of interest from high-power high temperature applications across recent photo-voltaic cells to hosting solid state quantum bits, where the tight control of electrically, optically, and magnetically active point defects is pivotal in these areas. 4H- and 6H-SiC substrates are grown at high temperatures and the incorporation of transition metal impurities is common. In unintentionally Nb-doped 4H- and 6H-SiC substrates grown by high-temperature chemical vapor deposition, an electron paramagnetic resonance (EPR) spectrum with C1h symmetry and a clear hyperfine (hf) structure consisting of ten equal intensity hf lines was observed. The hf structure can be identified as due to the interaction between the electron spin S = 1/2 and the nuclear spin of 93Nb. Additional hf structures due to the interaction with three Si neighbors were also detected. In 4H-SiC, a considerable spin density of ˜37.4% was found on three Si neighbors, suggesting the defect to be a complex between Nb and a nearby carbon vacancy (VC). Calculations of the 93Nb and 29Si hf constants of the neutral Nb on Si site, NbSi0, and the Nb-vacancy defect, NbSiVC0, support previous reported results that Nb preferentially forms an asymmetric split-vacancy (ASV) defect. In both 4H- and 6H-SiC, only one Nb-related EPR spectrum has been observed, supporting the prediction from calculations that the hexagonal-hexagonal defect configuration of the ASV complex is more stable than others.

  5. Anion Photoelectron Spectroscopic Studies of the NbC4H4-, NbC6H6- and NbC6H4- Products of Flow Tube Reactions of Niobium with Butadiene

    NASA Astrophysics Data System (ADS)

    Baudhuin, Melissa A.; Boopalachandran, Praveenkumar; Schnepper, D. Alex; Leopold, Doreen; Miller, Stephen R.

    2014-06-01

    We report mass spectra, 488 nm anion photoelectron spectra, and density functional theory (DFT) calculations of organometallic complexes produced by flow tube reactions of niobium with butadiene (C4H6), and compare these results with those obtained upon reactions with ethylene (C2H4). In the C4H6 experiments, NbC4H4- is the most abundant product anion, indicating loss of H2 upon reaction with Nb. DFT analysis of the vibrationally-resolved photoelectron spectrum indicates that the 3A^' anion incorporates a five-membered Nb-C4 ring in which the Nb atom lies outside the C4 plane. The electron affinity of the corresponding neutral molecule (2A^') is measured to be 0.997 ± 0.006 eV. Upon reaction with C2H4, at least one additional isomer of NbC4H4- is produced, giving rise to broad spectral features at higher electron binding energies. Reactions with C4H6 also yield relatively small amounts of the NbC6H6- and NbC6H4- product anions, indicating C-C bond activation in addition to dehydrogenation. The former anion displays the 3A1, C6v Nb-benzene π-complex structure previously observed upon reaction with C2H4. The NbC6H4- anion produced upon reaction with C4H6 yields at least two vibrationally-resolved photodetachment transitions. DFT calculations performed to date suggest that the lower electron binding energy transition, which indicates an electron affinity of 1.110 ± 0.008 eV for the corresponding neutral complex, is due to the 4B2 ← 3B2 detachment from a planar, C2v Nb-benzyne anion.

  6. Crystal structure and Mössbauer spectroscopic study of FeSnF6·6H2O

    NASA Astrophysics Data System (ADS)

    Denes, Georges; Mousser, Abdelhamid; Merazig, Hocine

    1994-12-01

    Large single crystals of FeSnF6·6H2O were grown when aqueous hydrofluoric solutions of SnF2 and FeF2 were allowed to evaporate in air. Tin-119 Mössbauer spectroscopy at ambient temperature shows a single line at slightly negative isomer shift relative to CaSnO3 at room temperature (δ=-0.380(6) mm/s, Δ=0). This is characteristic of tetravalent tin octahedrally coordinated by fluorine. The X-ray crystal structure shows that tin(IV) is coordinated by 6 fluorine atoms, and Fe(II) by 6 water molecules. Both sites show a slight distortion from octahedral symmetry: the six distances are equal (Sn-Fe=1.941(3) Å and Fe-O=2.112(3) Å), whereas there are two values of angles (Fe-Sn-F=90.4(1)° and 89.6(1)°; O-Fe-O=91.1(1)° and 88.9(1)°). The material is an ionic compound [SnF6]2-[Fe(H2O)6]2+.

  7. Electronic Spectroscopy of [FePAH](+) Complexes in the Region of the Diffuse Interstellar Bands: Multireference Wave Function Studies on [FeC6H6](+).

    PubMed

    Lanza, Mathieu; Simon, Aude; Ben Amor, Nadia

    2015-06-11

    The low-energy states and electronic spectrum in the near-infrared-visible region of [FeC6H6](+) are studied by theoretical approaches. An exhaustive exploration of the potential energy surface of [FeC6H6](+) is performed using the density functional theory method. The ground state is found to be a (4)A1 state. The structures of the lowest energy states ((4)A2 and (4)A1) are used to perform multireference wave function calculations by means of the multistate complete active space with perturbation at the second order method. Contrary to the density functional theory results ((4)A1 ground state), multireference perturbative calculations show that the (4)A2 state is the ground state. The vertical electronic spectrum is computed and compared with the astronomical diffuse interstellar bands, a set of near-infrared-visible bands detected on the extinction curve in our and other galaxies. Many transitions are found in this domain, corresponding to d → d, d → 4s, or d → π* excitations, but few are allowed and, if they are, their oscillation strengths are small. Even though some band positions could match some of the observed bands, the relative intensities do not fit, making the contribution of the [Fe-C6H6](+) complexes to the diffuse interstellar bands questionable. This work, however, lays the foundation for the studies of polycyclic aromatic hydrocarbons (PAHs) complexed to Fe cations that are more likely to possess d → π* and π → π* transitions in the diffuse interstellar bands domain. PAH ligands indeed possess a larger number of π and π* orbitals, respectively, higher and lower in energy than those of C6H6, which are expected to lead to lower energy d → π* and π → π* transitions in [FePAH](+) than in [FeC6H6](+) complexes.

  8. Electronic Spectroscopy of [FePAH](+) Complexes in the Region of the Diffuse Interstellar Bands: Multireference Wave Function Studies on [FeC6H6](+).

    PubMed

    Lanza, Mathieu; Simon, Aude; Ben Amor, Nadia

    2015-06-11

    The low-energy states and electronic spectrum in the near-infrared-visible region of [FeC6H6](+) are studied by theoretical approaches. An exhaustive exploration of the potential energy surface of [FeC6H6](+) is performed using the density functional theory method. The ground state is found to be a (4)A1 state. The structures of the lowest energy states ((4)A2 and (4)A1) are used to perform multireference wave function calculations by means of the multistate complete active space with perturbation at the second order method. Contrary to the density functional theory results ((4)A1 ground state), multireference perturbative calculations show that the (4)A2 state is the ground state. The vertical electronic spectrum is computed and compared with the astronomical diffuse interstellar bands, a set of near-infrared-visible bands detected on the extinction curve in our and other galaxies. Many transitions are found in this domain, corresponding to d → d, d → 4s, or d → π* excitations, but few are allowed and, if they are, their oscillation strengths are small. Even though some band positions could match some of the observed bands, the relative intensities do not fit, making the contribution of the [Fe-C6H6](+) complexes to the diffuse interstellar bands questionable. This work, however, lays the foundation for the studies of polycyclic aromatic hydrocarbons (PAHs) complexed to Fe cations that are more likely to possess d → π* and π → π* transitions in the diffuse interstellar bands domain. PAH ligands indeed possess a larger number of π and π* orbitals, respectively, higher and lower in energy than those of C6H6, which are expected to lead to lower energy d → π* and π → π* transitions in [FePAH](+) than in [FeC6H6](+) complexes. PMID:25850680

  9. Theoretical and electron paramagnetic resonance studies of hyperfine interaction in nitrogen doped 4H and 6H SiC

    SciTech Connect

    Szász, K.; Gali, A.

    2014-02-21

    Motivated by recent experimental findings on the hyperfine signal of nitrogen donor (N{sub C}) in 4 H and 6 H SiC, we calculate the hyperfine tensors within the framework of density functional theory. We find that there is negligible hyperfine coupling with {sup 29}Si isotopes when N{sub C} resides at h site both in 4 H and 6 H SiC. We observe measurable hyperfine coupling to a single {sup 29}Si at k site in 4 H SiC and k{sub 1} site in 6 H SiC. Our calculations unravel that such {sup 29}Si hyperfine coupling does not occur at k{sub 2} site in 6 H SiC. Our findings are well corroborated by our new electron paramagnetic resonance studies in nitrogen doped 6 H SiC.

  10. Sleep inertia during a simulated 6-h on/6-h off fixed split duty schedule.

    PubMed

    Hilditch, Cassie J; Short, Michelle; Van Dongen, Hans P A; Centofanti, Stephanie A; Dorrian, Jillian; Kohler, Mark; Banks, Siobhan

    2016-01-01

    Sleep inertia is a safety concern for shift workers returning to work soon after waking up. Split duty schedules offer an alternative to longer shift periods, but introduce additional wake-ups and may therefore increase risk of sleep inertia. This study investigated sleep inertia across a split duty schedule. Sixteen participants (age range 21-36 years; 10 females) participated in a 9-day laboratory study with two baseline nights (10 h time in bed, [TIB]), four 24-h periods of a 6-h on/6-h off split duty schedule (5-h TIB in off period; 10-h TIB per 24 h) and two recovery nights. Two complementary rosters were evaluated, with the timing of sleep and wake alternating between the two rosters (2 am/2 pm wake-up roster versus 8 am/8 pm wake-up roster). At 2, 17, 32 and 47 min after scheduled awakening, participants completed an 8-min inertia test bout, which included a 3-min psychomotor vigilance test (PVT-B), a 3-min Digit-Symbol Substitution Task (DSST), the Karolinska Sleepiness Scale (KSS), and the Samn-Perelli Fatigue Scale (SP-Fatigue). Further testing occurred every 2 h during scheduled wakefulness. Performance was consistently degraded and subjective sleepiness/fatigue was consistently increased during the inertia testing period as compared to other testing times. Morning wake-ups (2 am and 8 am) were associated with higher levels of sleep inertia than later wake-ups (2 pm and 8 pm). These results suggest that split duty workers should recognise the potential for sleep inertia after waking, especially during the morning hours.

  11. The effect of split sleep schedules (6h-on/6h-off) on neurobehavioural performance, sleep and sleepiness.

    PubMed

    Short, Michelle A; Centofanti, Stephanie; Hilditch, Cassie; Banks, Siobhan; Lushington, Kurt; Dorrian, Jillian

    2016-05-01

    Shorter, more frequent rosters, such as 6h-on/6h-off split shifts, may offer promise to sleep, subjective sleepiness and performance by limiting shift length and by offering opportunities for all workers to obtain some sleep across the biological night. However, there exists a paucity of studies that have examined these shifts using objective measures of sleep and performance. The present study examined neurobehavioural performance, sleepiness and sleep during 6h-on/6h-off split sleep schedules. Sixteen healthy adults (6 males, 26.13 y ± 4.46) participated in a 9-day laboratory study that included two baseline nights (BL, 10h time in bed (TIB), 2200 h-0800 h), 4 days on one of two types of 6h-on/6h-off split sleep schedules with 5h TIB during each 'off' period (6h early: TIB 0300 h-0800 h and 1500 h-20000 h, or 6-h late: TIB 0900 h-1400 h and 2100 h-0200 h), and two recovery nights (10h TIB per night, 2200 h-0800 h). Participants received 10h TIB per 24h in total across both shift schedules. A neurobehavioural test bout was completed every 2 h during wake, which included the Psychomotor Vigilance Task (PVT) and the Karolinska Sleepiness Scale (KSS). Linear mixed effects models were used to assess the effect of day (BL, shift days 1-4), schedule (6h early, 6h late) and trial (numbers 1-6) on PVT lapses (operationalised as the number of reaction times >500 ms), PVT total lapse time, PVT fastest 10% of reaction times and KSS. Analyses were also conducted examining the effect of day and schedule on sleep variables. Overall, PVT lapses and total lapse time did not differ significantly between baseline and shift days, however, peak response speeds were significantly slower on the first shift day when compared to baseline, but only for those in the 6h-late condition. Circadian variations were apparent in performance outcomes, with individuals in the 6h-late condition demonstrated significantly more and longer lapses and slower peak reaction times at the end of their

  12. Evaluation of pharmacokinetic properties and anaesthetic effects of propofol in a new perfluorohexyloctane (F6H8) emulsion in rats--A comparative study.

    PubMed

    Tsagogiorgas, Charalambos; Theisinger, Sonja; Heesch, Elisabeth; Krebs, Jörg; Holm, René; Beck, Grietje; Yard, Benito

    2015-01-01

    Propofol (2,6-diisopropylphenol) is a safe and widely used anaesthetic, but due to low water solubility and high lipophilicity a difficult compound to formulate. The solubility of propofol in the semifluorinated alkane perfluorohexyloctane (F6H8) is very high (>300 mg/ml). In the present work we investigate if a F6H8-based emulsion could be used as a new intravenous drug delivery system for propofol from a pharmacokinetic, pharmacodynamic and safety point of view. The pharmacokinetic parameters were evaluated after an intravenous bolus injection of either Disoprivan(®) or a F6H8-based propofol emulsion in Wistar rats. The onset and end of sedation after multiple dosings (5, 10 and 15 mg/kg bw) were examined. Clinical chemistry and histology were assessed. No significant difference was found for any of the pharmacokinetic parameters. No differences in the onset nor the end of sedation in the tested dosages could be detected. Histology scores revealed no differences. A slightly increased alanine aminotransferase (ALT) was measured after multiple application of the F6H8-propofol emulsion. In conclusion, the F6H8-propofol emulsion showed no significant different pharmacokinetics and sedation properties, compared to a commercial soy-based propofol emulsion. Further, no toxic effects could be detected on the F6H8 emulsion indicating it was a safe excipient in rats.

  13. On the formation of phenyldiacetylene (C6H5CCCCH) and D5-phenyldiacetylene (C6D5CCCCH) studied under single collision conditions.

    PubMed

    Parker, D S N; Zhang, F; Kim, Y S; Kaiser, R I; Landera, A; Mebel, A M

    2012-03-01

    The crossed molecular beam reactions of the phenyl and D5-phenyl radical with diacetylene (C(4)H(2)) was studied under single collision conditions at a collision energy of 46 kJ mol(-1). The chemical dynamics were found to be indirect and initiated by an addition of the phenyl/D5-phenyl radical with its radical center to the C1-carbon atom of the diacetylene reactant. This process involved an entrance barrier of 4 kJ mol(-1) and lead to a long lived, bound doublet radical intermediate. The latter emitted a hydrogen atom directly or after a few isomerization steps via tight exit transition states placed 20-21 kJ mol(-1) above the separated phenyldiacetylene (C(6)H(5)CCCCH) plus atomic hydrogen products. The overall reaction was determined to be exoergic by about 49 ± 26 kJ mol(-1) and 44 ± 10 kJ mol(-1) as determined experimentally and computationally, thus representing a feasible pathway to the formation of the phenyldiacetylene molecule in combustion flames of hydrocarbon fuel. PMID:22281819

  14. On the structure and reactivity of small iron clusters with benzene, [Fen-C6H6]0,+,-, n ⩽ 7: A theoretical study

    NASA Astrophysics Data System (ADS)

    Valencia, Israel

    2016-09-01

    The structural, energetic, electronic, vibrational, and magnetic properties of iron-benzene clusters, Fen-C6H6, n ⩽ 7, were calculated using an all-electron density functional theory, DFT, with the generalized gradient approximation and the 6-311++G(2d,2p) basis set. A proposal regarding the mechanism of the adsorption of benzene on iron clusters related to the charge transfer model is described. A direct relation between the calculated electron affinity, EA, of the Fen-C6H6 clusters and their reactivity were also determined.

  15. Comparison of the dynamics of the reactions of Ba with aromatic halides and alkyl halides LIF studies of the reactions of Ba with C 6H 5X (X  Cl, Br, I)

    NASA Astrophysics Data System (ADS)

    Han, Ke-Li; He, Guo-Zhong; Lou, Nan-Quan

    1993-03-01

    Nascent internal state energy distributions of BaX have been studied for the reactions Ba + C 6H 5X→BaX+C 6H 5 (X  Cl, Br, 1) using the laser-induced fluorescence method in a beam-gas arrangement. The energy disposal differs markedly from that of the reactions Ba + CH 3X. With the change of X from Cl to I, the vibrational excitations and the reactive cross sections decrease for the reactions Ba + C 6H 5X, whereas those of the reactions Ba + CH 3X increase. The CNDO/2 calculations of C 6H 5X and CH 3X have been used to interpret the experimental results qualitatively.

  16. Molecular dynamics study of congruent melting of the equimolar ionic liquid-benzene inclusion crystal [emim][NTf2]•C6H6

    NASA Astrophysics Data System (ADS)

    Kowsari, M. H.; Alavi, Saman; Ashrafizaadeh, Mahmud; Najafi, Bijan

    2010-01-01

    We use molecular dynamics simulations to study the structure, dynamics, and details of the mechanism of congruent melting of the equimolar mixture of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide with benzene, [emim][NTf2]•C6H6. Changes in the molecular arrangement, radial distribution functions, and the dynamic behavior of species are used to detect the solid to liquid transition, show an indication of the formation of polar islands by aggregating of the ions in the liquid phase, and characterize the melting process. The predicted enthalpy of melting ΔHm=38±2 kJ mol-1 for the equimolar inclusion mixture at 290 K is in good agreement with the differential scanning calorimetry experimental results of 42±2 kJ mol-1. The dynamics of the ions and benzene molecules were studied in the solid and liquid states by calculating the mean-square displacement (MSD) and the orientational autocorrelation function. The MSD plots show strong association between ion pairs of the ionic liquid in the inclusion mixture. Indeed, the presence of a stoichiometric number of benzene molecules does not affect the nearest neighbor ionic association between [emim]+ and [NTf2]-, but increases the MSDs of both cations and anions compared to pure liquid [emim][NTf2], showing that second shell ionic associations are weakened. We monitored the rotational motion of the alkyl chain sides of imidazolium cations and also calculated the activation energy for rotation of benzene molecules about their C6 symmetry axes in their lattice sites prior to melting.

  17. Study of defect structures in 6H-SiC a/m-plane pseudofiber crystals grown by hot-wall CVD epitaxy

    SciTech Connect

    Goue, Ouloide Y.; Raghothamachar, Balaji; Yang, Yu; Guo, Jianqiu; Dudley, Michael; Kisslinger, Kim; Trunek, Andrew J.; Neudeck, Philip G.; Spry, David J.; Woodworth, Andrew A.

    2015-11-25

    Structural perfection of silicon carbide (SiC) single crystals is essential to achieve high-performance power devices. A new bulk growth process for SiC proposed by researchers at NASA Glenn Research Center, called large tapered crystal (LTC) growth, based on axial fiber growth followed by lateral expansion, could produce SiC boules with potentially as few as one threading screw dislocation per wafer. In this study, the lateral expansion aspect of LTC growth is addressed through analysis of lateral growth of 6H-SiC a/m-plane seed crystals by hot-wall chemical vapor deposition. Preliminary synchrotron white-beam x-ray topography (SWBXT) indicates that the as-grown boules match the polytype structure of the underlying seed and have a faceted hexagonal morphology with a strain-free surface marked by steps. SWBXT Laue diffraction patterns of transverse and axial slices of the boules reveal streaks suggesting the existence of stacking faults/polytypes, and this is confirmed by micro-Raman spectroscopy. Transmission x-ray topography of both transverse and axial slices reveals inhomogeneous strains at the seed–epilayer interface and linear features propagating from the seed along the growth direction. Micro-Raman mapping of an axial slice reveals that the seed contains high stacking disorder, while contrast extinction analysis (g·b and g·b×l) of the linear features reveals that these are mostly edge-type basal plane dislocations. Further high-resolution transmission electron microscopy investigation of the seed–homoepilayer interface also reveals nanobands of different SiC polytypes. A model for their formation mechanism is proposed. Lastly, the implication of these results for improving the LTC growth process is addressed.

  18. Study of Defect Structures in 6H-SiC a/ m-Plane Pseudofiber Crystals Grown by Hot-Wall CVD Epitaxy

    NASA Astrophysics Data System (ADS)

    Goue, Ouloide Y.; Raghothamachar, Balaji; Yang, Yu; Guo, Jianqiu; Dudley, Michael; Kisslinger, Kim; Trunek, Andrew J.; Neudeck, Philip G.; Spry, David J.; Woodworth, Andrew A.

    2016-04-01

    Structural perfection of silicon carbide (SiC) single crystals is essential to achieve high-performance power devices. A new bulk growth process for SiC proposed by researchers at NASA Glenn Research Center, called large tapered crystal (LTC) growth, based on axial fiber growth followed by lateral expansion, could produce SiC boules with potentially as few as one threading screw dislocation per wafer. In this study, the lateral expansion aspect of LTC growth is addressed through analysis of lateral growth of 6H-SiC a/ m-plane seed crystals by hot-wall chemical vapor deposition. Preliminary synchrotron white-beam x-ray topography (SWBXT) indicates that the as-grown boules match the polytype structure of the underlying seed and have a faceted hexagonal morphology with a strain-free surface marked by steps. SWBXT Laue diffraction patterns of transverse and axial slices of the boules reveal streaks suggesting the existence of stacking faults/polytypes, and this is confirmed by micro-Raman spectroscopy. Transmission x-ray topography of both transverse and axial slices reveals inhomogeneous strains at the seed-epilayer interface and linear features propagating from the seed along the growth direction. Micro-Raman mapping of an axial slice reveals that the seed contains high stacking disorder, while contrast extinction analysis (g· b and g· b× l) of the linear features reveals that these are mostly edge-type basal plane dislocations. Further high-resolution transmission electron microscopy investigation of the seed-homoepilayer interface also reveals nanobands of different SiC polytypes. A model for their formation mechanism is proposed. Finally, the implication of these results for improving the LTC growth process is addressed.

  19. Study of defect structures in 6H-SiC a/m-plane pseudofiber crystals grown by hot-wall CVD epitaxy

    DOE PAGES

    Goue, Ouloide Y.; Raghothamachar, Balaji; Yang, Yu; Guo, Jianqiu; Dudley, Michael; Kisslinger, Kim; Trunek, Andrew J.; Neudeck, Philip G.; Spry, David J.; Woodworth, Andrew A.

    2015-11-25

    Structural perfection of silicon carbide (SiC) single crystals is essential to achieve high-performance power devices. A new bulk growth process for SiC proposed by researchers at NASA Glenn Research Center, called large tapered crystal (LTC) growth, based on axial fiber growth followed by lateral expansion, could produce SiC boules with potentially as few as one threading screw dislocation per wafer. In this study, the lateral expansion aspect of LTC growth is addressed through analysis of lateral growth of 6H-SiC a/m-plane seed crystals by hot-wall chemical vapor deposition. Preliminary synchrotron white-beam x-ray topography (SWBXT) indicates that the as-grown boules match themore » polytype structure of the underlying seed and have a faceted hexagonal morphology with a strain-free surface marked by steps. SWBXT Laue diffraction patterns of transverse and axial slices of the boules reveal streaks suggesting the existence of stacking faults/polytypes, and this is confirmed by micro-Raman spectroscopy. Transmission x-ray topography of both transverse and axial slices reveals inhomogeneous strains at the seed–epilayer interface and linear features propagating from the seed along the growth direction. Micro-Raman mapping of an axial slice reveals that the seed contains high stacking disorder, while contrast extinction analysis (g·b and g·b×l) of the linear features reveals that these are mostly edge-type basal plane dislocations. Further high-resolution transmission electron microscopy investigation of the seed–homoepilayer interface also reveals nanobands of different SiC polytypes. A model for their formation mechanism is proposed. Lastly, the implication of these results for improving the LTC growth process is addressed.« less

  20. Ab initio molecular orbital/Rice-Ramsperger-Kassel-Marcus theory study of multichannel rate constants for the unimolecular decomposition of benzene and the H+C6H5 reaction over the ground electronic state

    NASA Astrophysics Data System (ADS)

    Mebel, A. M.; Lin, M. C.; Chakraborty, D.; Park, J.; Lin, S. H.; Lee, Y. T.

    2001-05-01

    The potential energy surface for the unimolecular decomposition of benzene and H+C6H5 recombination has been studied by the ab initio G2M(cc, MP2) method. The results show that besides direct emission of a hydrogen atom occurring without an exit channel barrier, the benzene molecule can undergo sequential 1,2-hydrogen shifts to o-, m-, and p-C6H6 and then lose a H atom with exit barriers of about 6 kcal/mol. o-C6H6 can eliminate a hydrogen molecule with a barrier of 121.4 kcal/mol relative to benzene. o- and m-C6H6 can also isomerize to acyclic isomers, ac-C6H6, with barriers of 110.7 and 100.6 kcal/mol, respectively, but in order to form m-C6H6 from benzene the system has to overcome a barrier of 108.6 kcal/mol for the 1,2-H migration from o-C6H6 to m-C6H6. The bimolecular H+C6H5 reaction is shown to be more complicated than the unimolecular fragmentation reaction due to the presence of various metathetical processes, such as H-atom disproportionation or addition to different sites of the ring. The addition to the radical site is barrierless, the additions to the o-, m-, and p-positions have entrance barriers of about 6 kcal/mol and the disproportionation channel leading to o-benzyne+H2 has a barrier of 7.6 kcal/mol. The Rice-Ramsperger-Kassel-Marcus and transition-state theory methods were used to compute the total and individual rate constants for various channels of the two title reactions under different temperature/pressure conditions. A fit of the calculated total rates for unimolecular benzene decomposition gives the expression 2.26×1014exp(-53 300/T)s-1 for T=1000-3000 K and atmospheric pressure. This finding is significantly different from the recommended rate constant, 9.0×1015exp(-54 060/T) s-1, obtained by kinetic modeling assuming only the H+C6H5 product channel. At T=1000 K, the branching ratios for the formation of H+C6H5 and ac-C6H6 are 29% and 71%, respectively. H+C6H5 becomes the major channel at T⩾1200 K. The total rate for the bimolecular H

  1. Longitudinal dielectric properties of molecular liquids: Molecular dynamics simulation studies of CH3CN, C6H6, and CO2

    NASA Astrophysics Data System (ADS)

    Perng, Baw-Ching; Ladanyi, Branka M.

    1999-04-01

    Molecular dynamics (MD) simulations of ɛL(k,ω), the frequency (ω) and wave vector (k) dependent longitudinal component of the dielectric permittivity tensor, a quantity of importance in several theories of solvation dynamics and charge transfer reactions, is reported for three molecular liquids: CH3CN, CO2, and C6H6, represented by nonpolarizable model potentials. In order to study dielectric properties of nondipolar fluids we use, instead of the conventional approach which relates ɛL(k,ω) to longitudinal dipole density fluctuations, a more general approach of Raineri and co-workers which expresses this quantity in terms of charge density fluctuations. The two formulations are compared in the case of acetonitrile to assess the model dependence of ɛL(k,ω). We find that at finite k, 1/ɛL(k), where ɛL(k)=ɛL(k,0) is the static longitudinal permittivity, exhibits several similar features for all three liquids: A partial cancellation between single-molecule and pair charge density fluctuation correlations at small k, their constructive interference at intermediate k and the lack of molecular pair correlation contributions at large k. We also find that the extended reference interaction site model (XRISM) integral equations provide an excellent approximation to ɛL(k) of all three liquids. We use the fact 1/ɛL(k) is a polynomial in k2 at small k to determine the static dielectric constant ɛ0=ɛL(k=0) of acetonitrile and obtain a value in good agreement with ɛ0 evaluated by more conventional methods. We find that intermolecular correlations contribute the most to the dielectric properties of CH3CN and the least to those of CO2. In the range of k most relevant to solvation (k≲1 Å-1), the pair component of the charge-charge time correlation function Φqq(k,t) is negative, partially cancelling the positive single-molecule component. The extent of cancellation varies with k and the strength of intermolecular electrostatic interactions, leading to significant

  2. High pressure structure studies of 6H-SrIrO3 and the octahedral tilting in 3C-SrIrO3 towards a post-perovskite

    NASA Astrophysics Data System (ADS)

    Kronbo, Camilla H.; Nielsen, Morten B.; Kevy, Simone M.; Parisiades, Paraskevas; Bremholm, Martin

    2016-06-01

    The high pressure behaviors of the two perovskite structures (hexagonal 6H-SrIrO3 and orthorhombic 3C-SrIrO3) have been studied in diamond anvil cells to 43 and 60 GPa, respectively, using synchrotron powder X-ray diffraction. 6H-SrIrO3 was first synthesized at ambient pressure and subsequently transformed into 3C-SrIrO3 in a large volume press at 8.8 GPa and 1000 °C. Both polymorphs were found to retain the initial symmetry up to the highest pressures measured, but in the case of 6H-SrIrO3, two anomalies were identified: a change in the axial compressibilities at 24 GPa and a change in both the axial and volume compressibilities at 32 GPa. Fitting a 3rd order Birch-Murnaghan equation of state to the obtained P-V data yielded bulk moduli of K0=151.5(12) GPa (fitted range 06H-SrIrO3 and K0=187.1(9) GPa for 3C-SrIrO3. Analysis of the structural parameters for 6H-SrIrO3 aided by F-f plots suggests the anomalies are caused by changes in the compression mechanism. Comparison of the two polymorphs reveals that 6H-SrIrO3 becomes less compressible than 3C-SrIrO3 above 32 GPa as a result of the mechanistic change, and a crossing of their P-V curves is avoided. For 3C-SrIrO3, analysis of the octahedral tilt angles shows that these increase monotonically from the ambient value of 7.23(6) to 23.0(2)° at 60 GPa suggesting that a transition to a post-perovskite is approached.

  3. Synthesis, thermal, XRD and spectroscopic studies characterization of Tutton salt K2M (SO4)2·6H2O (M = Mg, Ni)

    NASA Astrophysics Data System (ADS)

    Marzougui, H.; Attia-Essaies, S.; Ben Hassen-Chehimi, D.

    2016-09-01

    Tutton's salts K2M(SO4)2·6H2O (M = Mg, Ni) have been synthesized by the slow evaporation method at room temperature. A complete structural characterization has been carried out by means of powder X-ray diffraction (XRD). The results indicate that the structure of these salts is monoclinic system with the space group P21/a (Z = 2). IR and Raman spectra of KMS6 (M = Mg,Ni) have been recorded and analyzed. From the spectra, the vibrations due to SO42- ion, the complex [M(H2O)6]2+ and the water molecules have been identified. Thermogravimetry, differential thermal analysis and XRD at high-temperature investigations show that the dehydration of these salts occurs between 300 and 500 K. This indicates the removal of all water molecules around 426 K.

  4. High density H2 associative absorption on Titanium alpha-borozene (Ti2B6H6): An ab-initio case study

    NASA Astrophysics Data System (ADS)

    Akbarzadeh, Alireza; Tymzcak, C. J.

    2011-03-01

    Hydrogen is considered as a clean energy carrier that could be a future replacement for our addiction to fossil fuels. However, in order to have hydrogen economy at its highest efficiently we need to store hydrogen at high volumetric and gravimetric density. Using the all electron hybrid density functional theory, we have designed a benzene-like-molecule, Ti2B6H6, which has the promise of achieving this goal. Our results show that the molecule can associatively absorb the hydrogen up to ten percent by weight of hydrogen, which exceeds the 2015 US department of energy target. In this presentation we will discuss the mechanisms of H2 absorption and possible applications of this novel molecule. This research is funded by the Welch Foundation under Grant J. 1675 and the Texas Southern University High Performance Computing Center.

  5. A comparative study of pi-arene-bridged lanthanum arylamide and aryloxide dimers. Solution behavior, exchange mechanisms, and X-ray crystal structures of La2(NH-2,6-iPr2C6H3)6, La(NH-2,6-iPr2C6H3)3(THF)3, and La(NH-2,6-iPr2C6H3)3(py)2.

    PubMed

    Giesbrecht, Garth R; Gordon, John C; Clark, David L; Hay, P Jeffrey; Scott, Brian L; Tait, C Drew

    2004-05-26

    Reaction of 3 equiv of 2,6-diisopropylaniline with La[N(SiMe(3))(2)](3) produces the dimeric species La(2)(NHAr)(6) (1). X-ray crystallography reveals a centrosymmetric structure, where the dimeric unit is bridged by intermolecular eta(6)-arene interactions of a unique arylamide ligand attached to an adjacent metal center. Exposure of 1 to THF results in formation of the monomeric tris-THF adduct La(NHAr)(3)(THF)(3) (2), which was shown by X-ray crystallography to maintain a fac-octahedral structure in the solid state. (1)H NMR spectroscopy illustrates that the binding of THF to 1 to form 2 is reversible and removal of THF under vacuum regenerates dimeric 1. Addition of pyridine to 1 yields the monomeric bis-pyridine adduct La(NHAr)(3)(py)(2) (3), which exhibits a distorted trigonal-bipyramidal La metal center. Solution (1)H NMR, IR, and Raman spectroscopy indicate that the pi-arene-bridged dimeric structure of 1 is maintained in solution. Variable-temperature (1)H NMR spectroscopic investigations of 1 are consistent with a monomer-dimer equilibrium at elevated temperature. In contrast, variable-temperature (1)H NMR spectroscopic investigations of the aryloxide analogue La(2)(OAr)(6) (4) show that the bridging and terminal aryloxide groups exchange by a mechanism in which the dimeric nature of the compound is retained. Density functional theory (DFT) calculations were carried out on model compounds La(2)(OC(6)H(5))(6), La(2)(NHC(6)H(5))(6), and (C(6)H(5)R)La(XC(6)H(5))(3), where X = O or NH and R = H, OH, or NH(2). The formation of eta(6)-arene interactions is energetically favored over monomeric LaX(3) (X = OPh or NHPh) with the aryloxide pi-arene interaction being stronger than the arylamide pi-arene interaction. Calculation of vibrational frequencies reveals the origin of the observed IR spectral behavior of both La(2)(OC(6)H(5))(6) and La(2)(NHC(6)H(5))(6), with the higher energy nu(C=C) stretch due to terminal ligands and the lower energy stretch associated

  6. Synthetic, Infrared, 1H and 13C NMR Spectral Studies on N-(2/3/4-Substituted Phenyl)-2,4-Disubstituted Benzenesulphonamides, 2,4-(CH3)2/2-CH3-4-Cl/2,4-Cl2C6H3SO2NH(i-XC6H4) (i-X = H, 2-CH3, 3-CH3, 4-CH3, 2-Cl, 3-Cl, 4-Cl, 4-F, 4-Br)

    NASA Astrophysics Data System (ADS)

    Basappa, Savitha M.; Gowda, Basavalinganadoddy Thimme

    2006-11-01

    Twenty six N-(2/3/4-substituted phenyl)-2,4-disubstituted benzenesulphonamides of the general formulae 2,4-(CH3)2C6H3SO2NH(i-XC6H4), 2-CH3-4-ClC6H3SO2NH(i-XC6H4) and 2,4- Cl2C6H3SO2NH(i-XC6H4), where i-X = H, 2-CH3, 3-CH3, 4-CH3, 2-Cl, 3-Cl, 4-Cl, 4-F or 4-Br, have been prepared, characterized and their infrared spectra in the solid state and 1H and 13C NMR spectra in solution studied. The infrared N-H stretching vibrational frequencies vary in the range 3298 - 3233 cm-1. Asymmetric and symmetric SO stretching vibrations appear in the ranges 1373 - 1311 cm-1 and 1177 - 1140 cm-1, respectively, while C-S, S-N and C-N stretching absorptions vary in the ranges 840 - 812 cm-1, 972 - 908 cm-1 and 1295 - 1209 cm-1, respectively. The various 1H and 13C NMR chemical shifts are assigned to the protons and carbon atoms of the two benzene rings in line with those for similar compounds. The incremental shifts due to the groups in the parent compounds have been computed by comparing the chemical shifts of the protons or carbon atoms in these compounds with those of benzene or aniline, respectively. The computed incremental shifts and other data were used to calculate the 1H and 13C NMR chemical shifts of the substituted compounds in three different ways. The calculated chemical shifts by the three methods compared well with each other and with the observed chemical shifts. It is observed that there are no particular trends in the variation of either the infrared absorption frequencies or the chemical shifts with the nature or site of substitution.

  7. Crystal structure, DSC and Raman studies in CH 3C 6H 4NH(CH 3) 2·SbCl 4

    NASA Astrophysics Data System (ADS)

    Chaabouni, Slaheddine; Hadrich, Ahmed; Romain, François; Ben Salah, Abdelhamid

    2003-07-01

    The salt para methyl phenyl dimethyl ammonium tetrachloroantimonate (III) crystallizes in the monoclinic system with space group Cc. The unit cell dimensions are: a=13.780(1) Å, b=14.943(2) Å, c=8.192(1) Å, β=113.39(1)°, with Z=4. The structure consists of ammonium cations and polynuclear anions in which distorted SbCl 5 square pyramids sharing a common Cl atom are held together in infinite chains parallel to the c axis. These chains are themselves interconnected by means of the NH⋯Cl hydrogen bonds. Differential scanning calorimetry study was carried out. The Raman of polycrystalline samples have been recorded at different temperatures between 77 and 300 K. A low-temperature phase transition at 230 K of order-disorder type was found.

  8. Study of the reversible water vapour sorption process of MgSO4.7H2O and MgCl2.6H2O under the conditions of seasonal solar heat storage

    NASA Astrophysics Data System (ADS)

    Ferchaud, C. J.; Zondag, H. A.; Veldhuis, J. B. J.; de Boer, R.

    2012-11-01

    The characterization of the structural, compositional and thermodynamic properties of MgSO4.7H2O and MgCl2.6H2O has been done using in-situ X-ray Diffraction and thermal analyses (TG/DSC) under practical conditions for seasonal heat storage (Tmax=150°C, p(H2O)=13 mbar). This study showed that these two materials release heat after a dehydration/hydration cycle with energy densities of 0.38 GJ/m3 for MgSO4.7H2O and 0.71 GJ/m3 MgCl2.6H2O. The low heat release found for MgSO4.7H2O is mainly attributed to the amorphization of the material during the dehydration performed at 13 mbar which reduces its sorption capacity during the rehydration. MgCl2.6H2O presents a high energy density which makes this material interesting for seasonal heat storage in domestic applications. This material would be able to fulfil the winter heat demand of a passive house estimated at 6 GJ with a packed bed reactor of 8.5 m3. However, a seasonal heat storage system built with this material should be carefully set with a restricted temperature at 40°C for the hydration reaction to avoid the liquefaction of the material at lower temperature which limits its performances for long term storage.

  9. 1H and 13C NMR Spectral Studies on N-(Aryl)-Substituted Acetamides, C6H5NHCOCH3-iXi and 2/4-XC6H4NHCOCH3-iXi (where X = Cl or CH3 and i = 0, 1, 2 or 3)

    NASA Astrophysics Data System (ADS)

    Gowda, B. Thimme; Usha, K. M.; Jayalakshmi, K. L.

    2003-12-01

    35 N-(Phenyl)-, N-(2/4-chlorophenyl)- and N-(2/4-methylphenyl)-substituted acetamides are prepared, characterised and their NMR spectra studied in solution state. The variation of the chemical shifts of the aromatic protons in these compounds follow more or less the same trend with changes in the side chain. The chemical shifts remain almost the same on introduction of Cl substituent to the benzene ring, while that of methyl group lowers the chemical shifts of the aromatic protons. But only 13C-1 and 13C-4 chemical shifts in these compounds are sensitive to variations of the side chain. The incremental shifts in the chemical shifts of the aromatic protons and carbons due to -COCH3-iXi or NHCOCH3-iXi groups in all the N-(phenyl)-substituted acetamides, C6H5NHCOCH3-iXi (where X = Cl or CH3 and i = 0, 1, 2 or 3) are calculated. These incremental chemical shifts are used to calculate the chemical shifts of the aromatic protons and carbons in all the N-(2/4-chlorophenyl)- and N-(2/4-methylphenyl)-substituted acetamides, in two ways. In the first way, the chemical shifts of aromatic protons or carbons are computed by adding the incremental shifts due to -COCH3-iXi groups and the substituents at the 2nd or 4th position in the benzene ring to the chemical shifts of the corresponding aromatic protons or carbons of the parent aniline. In the second way, the chemical shifts are calculated by adding the incremental shifts due to -NHCOCH3-iXi groups and the substituents at the 2nd or 4th position in the benzene ring to the chemical shift of a benzene proton or carbon, respectively. Comparison of the two sets of calculated chemical shifts of the aromatic protons or carbons of all the compounds revealed that the two procedures of calculation lead to almost the same values in most cases and agree well with the experimental chemical shifts.

  10. A VUV photoionization study of the combustion-relevant reaction of the phenyl radical (C6H5) with propylene (C3H6) in a high temperature chemical reactor.

    PubMed

    Zhang, Fangtong; Kaiser, Ralf I; Golan, Amir; Ahmed, Musahid; Hansen, Nils

    2012-04-12

    We studied the reaction of phenyl radicals (C(6)H(5)) with propylene (C(3)H(6)) exploiting a high temperature chemical reactor under combustion-like conditions (300 Torr, 1200-1500 K). The reaction products were probed in a supersonic beam by utilizing tunable vacuum ultraviolet (VUV) radiation from the Advanced Light Source and recording the photoionization efficiency (PIE) curves at mass-to-charge ratios of m/z = 118 (C(9)H(10)(+)) and m/z = 104 (C(8)H(8)(+)). Our results suggest that the methyl and atomic hydrogen losses are the two major reaction pathways with branching ratios of 86 ± 10% and 14 ± 10%. The isomer distributions were probed by fitting the recorded PIE curves with a linear combination of the PIE curves of the individual C(9)H(10) and C(8)H(8) isomers. Styrene (C(6)H(5)C(2)H(3)) was found to be the exclusive product contributing to m/z = 104 (C(8)H(8)(+)), whereas 3-phenylpropene, cis-1-phenylpropene, and 2-phenylpropene with branching ratios of 96 ± 4%, 3 ± 3%, and 1 ± 1% could account for the signal at m/z = 118 (C(9)H(10)(+)). Although searched for carefully, no evidence of the bicyclic indane molecule could be provided. The reaction mechanisms and branching ratios are explained in terms of electronic structure calculations nicely agreeing with a recent crossed molecular beam study on this system.

  11. A VUV Photoionization Study of the Combustion-Relevant Reaction of the Phenyl Radical (C6H5) with Propylene (C3H6) in a High Temperature Chemical Reactor

    SciTech Connect

    University of Hawaii at Manoa; Sandia National Laboratories; Zhang, Fangtong; Kaiser, Ralf I.; Golan, Amir; Ahmed, Musahid; Hansen, Nils

    2012-02-22

    We studied the reaction of phenyl radicals (C6H5) with propylene (C3H6) exploiting a high temperature chemical reactor under combustion-like conditions (300 Torr, 1,200-1,500 K). The reaction products were probed in a supersonic beam by utilizing tunable vacuum ultraviolet (VUV) radiation from the Advanced Light Source and recording the photoionization efficiency (PIE) curves at mass-to-charge ratios of m/z = 118 (C9H10+) and m/z = 104 (C8H8+). Our results suggest that the methyl and atomic hydrogen losses are the two major reaction pathways with branching ratios of 86 10 percent and 14 10 percent. The isomer distributions were probed by fitting the recorded PIE curves with a linear combination of the PIE curves of the individual C9H10 and C8H8 isomers. Styrene (C6H5C2H3) was found to be the exclusive product contributing to m/z = 104 (C8H8+), whereas 3-phenylpropene, cis-1-phenylpropene, and 2-phenylpropene with branching ratios of 96 4 percent, 3 3 percent, and 1 1 percent could account for signal at m/z = 118 (C9H10+). Although searched for carefully, no evidence of the bicyclic indane molecule could be provided. The reaction mechanisms and branching ratios are explained in terms of electronic structure calculations nicely agreeing with a recent crossed molecular beam study on this system.

  12. DFT(B3LYP/LanL2DZ), non-linear optical and electrical studies of a new hybrid compound: [C6H10(NH3)2]CoCl4·H2O

    NASA Astrophysics Data System (ADS)

    Tounsi, Amal; Hamdi, Besma; Zouari, Ridha; Ben Salah, Abdelhamid

    2016-10-01

    A new organic-inorganic material [C6H10(NH3)2]CoCl4·H2O was reported. The title compound was synthesized at room temperature by slow evaporation and then characterized by a single X-ray diffraction, spectroscopic measurements, thermal analysis and dielectric technique. It crystallizes in the non-centrosymmetric space group Pna21 with the following unit cell parameters: a=12.5328(1) Å, b=9.0908(1) Å, c=11.7440(1) and α=β=γ=90°. The structure can be described by the alternation of two different cationic-anionic layers. It consists of isolated H2O, isolated [CoCl4]2- tetrahedral anions and diammoniumcyclohexane [C6H10(NH3)2]2+ cations, which are connected via N-H…Cl, N-H…O and O-H…N hydrogen bonds. The Hirshfeld surface analysis was conducted to investigate intermolecular interactions and associated 2D fingerprint plots, revealing the relative contribution of these interactions in the crystal structure quantitatively. Theoretical calculations were performed using DFT/B3LYP/LanL2DZ method for studying the molecular structure and vibrational spectra and especially to examine the non-linear optical behavior of the compound. Solid state 13C NMR spectrum shows three signals correspond to three different carbon environments. Thermal analysis discloses a phase transition at the temperature 315 K and the evaporation of water molecule at 327 K. A detailed dielectric study was reported and shows a good agreement with thermal measurements.

  13. Lockheed D-6H: Preliminary report

    SciTech Connect

    1997-07-31

    The assessment of the D-6H conducted at the Lockheed Martin facility was limited in its scope. The scope of the assessment was directed by the type of equipment being used and the amount of accessibility to the equipment. Due to severe time constraints--the assessment was conducted in one day--human factor interface activities were limited. This report covers aspects of the technology that were available to the assessment team. Recommendations for future evaluation of this technology are also included.

  14. Local spin dynamics at low temperature in the slowly relaxing molecular chain [Dy(hfac)3(NIT(C6H4OPh))]: A μ{sup +} spin relaxation study

    SciTech Connect

    Arosio, Paolo Orsini, Francesco; Corti, Maurizio; Mariani, Manuel; Bogani, Lapo; Caneschi, Andrea; Lago, Jorge; Lascialfari, Alessandro

    2015-05-07

    The spin dynamics of the molecular magnetic chain [Dy(hfac){sub 3}(NIT(C{sub 6}H{sub 4}OPh))] were investigated by means of the Muon Spin Relaxation (μ{sup +}SR) technique. This system consists of a magnetic lattice of alternating Dy(III) ions and radical spins, and exhibits single-chain-magnet behavior. The magnetic properties of [Dy(hfac){sub 3}(NIT(C{sub 6}H{sub 4}OPh))] have been studied by measuring the magnetization vs. temperature at different applied magnetic fields (H = 5, 3500, and 16500 Oe) and by performing μ{sup +}SR experiments vs. temperature in zero field and in a longitudinal applied magnetic field H = 3500 Oe. The muon asymmetry P(t) was fitted by the sum of three components, two stretched-exponential decays with fast and intermediate relaxation times, and a third slow exponential decay. The temperature dependence of the spin dynamics has been determined by analyzing the muon longitudinal relaxation rate λ{sub interm}(T), associated with the intermediate relaxing component. The experimental λ{sub interm}(T) data were fitted with a corrected phenomenological Bloembergen-Purcell-Pound law by using a distribution of thermally activated correlation times, which average to τ = τ{sub 0} exp(Δ/k{sub B}T), corresponding to a distribution of energy barriers Δ. The correlation times can be associated with the spin freezing that occurs when the system condenses in the ground state.

  15. VIBRATIONALLY EXCITED C{sub 6}H

    SciTech Connect

    Gottlieb, C. A.; McCarthy, M. C.; Thaddeus, P.

    2010-08-15

    Rotational spectra of the linear carbon chain radical C{sub 6}H in two low-lying excited vibrational states were observed both at millimeter wavelengths in a low-pressure glow discharge and at centimeter wavelengths in a supersonic molecular beam. Two series of harmonically related lines with rotational constants within 0.3% of the {sup 2{Pi}} ground state were assigned to the {sup 2{Sigma}} and {sup 2{Delta}} vibronic components of an excited bending vibrational level. Measurements of the intensities of the lines in the glow discharge indicate that the {sup 2{Sigma}} component lies very close to ground, but the {sup 2{Delta}} component is much higher in energy. The standard Hamiltonian for an isolated {sup 2{Delta}} state with five spectroscopic constants reproduces the observed rotational spectrum, but several high-order distortion terms in the spin-rotation interaction are needed to reproduce the spectrum of the {sup 2{Sigma}} component in C{sub 6}H and C{sub 6}D. The derived spectroscopic constants allow astronomers to calculate the rotational spectra of the {sup 2{Sigma}} and {sup 2{Delta}} states up to 260 GHz to within 0.1 km s{sup -1} or better in equivalent radial velocity.

  16. Theoretical studies of the EPR parameters and local structures for Cu2+ centres in a (CH3)2NH2Al(SO4)2·6H2O crystal

    NASA Astrophysics Data System (ADS)

    Zhang, Hua-Ming; Xiao, Wen-Bo; Wan, Xiong

    2014-10-01

    Local structure and electron paramagnetic resonance (EPR) parameters (the g factors, gi, and the hyperfine structure constants Ai, i = x, y, z) for the impurity Cu2+ centres in a (CH3)2NH2Al(SO4)2·6H2O (DMAAS) crystal are theoretically investigated by using the high-order perturbation formulas of these parameters for a 3d9 ion in an orthorhombically elongated octahedron. The related molecular orbital coefficients are quantitatively determined from the cluster approach in a uniform way. From the studies, the four planar Cu2+-O2- bond lengths are found to experience the relative variation δR ( ≈0.033 and 0.063 Å) along the X- and Y-axes, while the two parallel bond lengths may undergo relative elongation ΔZ (≈0.058 and 0.052 Å) along the C2 axis for the studied Cu2+ centres I and II, respectively, due to the Jahn-Teller effect. The theoretical EPR parameters based on the above local lattice distortions agree well with the experimental data. The results are discussed.

  17. Synthesis, crystal structure, thermal analysis, vibrational study dielectric behaviour and Hirshfeld surface analysis of [C6H10(NH3)2)]2 SnCl6 (Cl)2

    NASA Astrophysics Data System (ADS)

    Mkaouar, Imen; Karâa, Najla; Hamdi, Besma; Zouari, Ridha

    2016-07-01

    A new organotin (IV), bis 1-2 diammonium cyclohexane octachlorotin dichloride, have been synthesized. The molecular structures of the complexes have been determined using single crystal X-ray diffraction analysis reveals that complexes crystallizes in orthorhombic space group P4/n with a = 13.014(3)Å, b = 13.014(3), c = 16.822(4)Å, V = 2849.0(11)Å3. The structure consists of three-dimensional tanks framework. They show further that the tin (IV) ion is octahedral surrounded by six atoms with six chloride ligands, tow [C6H10(NH3)2]2+ cations and tow isolated chloride ion Cl-. The new compound has been characterized by differential scanning calorimetric (DSC) technique, 13C MAS-NMR, FT-IR, RAMAN spectroscopic studies and dielectric properties are detected in the frequency interval of 209 Hz-5 MHz and in the temperature interval of 313-373 K, have been carried out in order to characterize the complexes, the Hirschfeld surface analysis have been performed to gain insight into the behavior of these weak interactions.

  18. Synthesis, structure and optical studies of inorganic–organic hybrid semiconductor, (H{sub 3}NC{sub 6}H{sub 4}CH{sub 2}NH{sub 3}) PbI{sub 4}

    SciTech Connect

    Nageswara Rao, K.; Singh, Amit; Vijaya Prakash, G.

    2014-04-01

    Highlights: • New type of IO hybrid semiconductor has been synthesized and reported. • Inorganic (PbI{sub 4}){sup 2−} nano-ribbons are surrounded by organic entities. • Room-temperature optical exciton and charge-transfer features are reported. • Structural and optical mechanisms are useful in nanoscale electronic devices. - Abstract: Synthesis, structural and optical studies of inorganic–organic (IO) hybrid, 1,2-benzyldiammoniumtetraiodo plumbate (H{sub 3}NC{sub 6}H{sub 4}CH{sub 2}NH{sub 3}) PbI{sub 4} are presented. The titled compound crystallizes into triclinic system of P-1(2) space group with mutually surrounded inorganic (PbI{sub 4}){sup 2−} organic (C{sub 7}H{sub 12}N{sub 2}) entities. These one-dimensional IO hybrids are thermally stable up to 300 °C and show room-temperature exciton along with charge-transfer photoluminescence features. Structural and optical mechanisms are discussed for future applications in nanoscaled optoelectronic devices.

  19. Study of gratings with variable periods

    NASA Astrophysics Data System (ADS)

    Olivares-Pérez, Arturo; Fuentes-Tapia, Israel; Toxqui-López, Santa; Ortiz-Gutiérrez, Mauricio; Ordoñez-Padilla, Manuel Jorge; Mejias-Brizuela, Nildia Y.

    2016-03-01

    A theoretical study with sinusoidal amplitude diffraction gratings, elaborated with variable periods is shown. The diffraction pattern behavior and the symmetry degree of the gratings were observed. The grating period is increased, fringe to fringe, starting with a small period and ending with a big period that is; the grating edge, start with high spatial frequency and finish with low spatial frequency. This gratings modulation causes a widening in the diffracted orders.

  20. F6H8 as an Intraoperative Tool and F6H8/Silicone Oil as a Postoperative Tamponade in Inferior Retinal Detachment with Inferior PVR

    PubMed Central

    Tosi, Gian Marco; Bacci, Tommaso; Romeo, Napoleone; Balestrazzi, Angelo; Martone, Gianluca; Caporossi, Tomaso

    2014-01-01

    Purpose. To evaluate the effectiveness and safety of perfluorohexyloctane (F6H8) for intraoperative flattening of the retina and of F6H8/silicone oil (SO) 1000 cSt as a postoperative tamponade for inferior retinal detachment with inferior proliferative vitreoretinopathy. Methods. This is a retrospective review of 22 patients who underwent pars plana vitrectomy using F6H8 as an intraoperative tool to flatten the retina. At the end of the surgery a direct partial exchange between F6H8 and SO 1000 cSt was performed, tamponing the eye with different ratios of F6H8/SO (70/30, 60/40, 50/50, 40/30, and 30/70). Anatomical and functional results and complications were evaluated over the follow-up period (mean 22.63 months). Results. F6H8 was efficacious for intraoperative flattening of the retina. Twenty-one of the 22 patients achieved a complete retinal reattachment. Postoperative visual acuity (VA) ranged from light perception to 20/70, with 72% of patients obtaining VA better than 20/400. No emulsification/inflammation was observed whatever the ratio of F6H8/SO used. With higher ratios of F6H8/SO (70/30 and 60/40) cloudiness of the tamponade was observed. A transparent mixture was present with all the other ratios. Conclusions. The surgical technique adopted is very simple and safe. The optimal F6H8/SO ratio seems to be between 50/50 and 30/70. PMID:24672710

  1. Charge exchange in C^6+ + H and C^6+ + H2 collisions

    NASA Astrophysics Data System (ADS)

    Guevara-Leon, Nicolais; Saha, Bidhan; Sabin, John R.; Deumens, Erik; Ohrn, N. Y.

    2010-03-01

    In the solar wind, C^6+ ion is one of the most abundant ionic species and its interaction with comets as well as the atmosphere of planets of the solar system produces several interesting phenomena. The charge exchange reaction is one of the most relevant process as it may provide a possible explanation for the X-ray emission from these objects. Electron capture into a highly excited state of C^5+ ion usually generates radiation in the X-ray region of the spectrum. In the present work, charge exchange in C^6+ + H and C^6+ + H2 collisions are investigated theoretically using electron nuclear dynamics (END) [1] at projectile energies below the ionization threshold. For H2 the one- and two- electron charge exchange cross sections are calculated and compared with other theoretical and experimental data. Orientation effects for the collision with the hydrogen molecules will also be discussed at the conference.

  2. Deep ultra violet and visible Raman spectroscopy studies of ion implanted 6H-SiC: Recrytallisation behaviour and thermal decomposition/thermal etching of the near surface region

    NASA Astrophysics Data System (ADS)

    Kuhudzai, R. J.; Malherbe, J. B.; van der Berg, N. G.; Hlatshwayo, T. T.; Odutemowo, O.; Prinsloo, L. C.; Buys, A. V.; Erasmus, R.; Wendler, E.

    2015-12-01

    The recystallisation behaviour and thermal decomposition of the near surface amorphised region of 6H-SiC have been investigated by Raman spectroscopy. 360 keV ions of iodine and silver were implanted at room temperature into wafers of 6H-SiC resulting in the amorphisation of the near surface region. Vacuum annealing of the samples was performed at 1200 °C for 5 h and then sequentially from 1200 to 1600 °C in steps of 100 °C for 30 h at each annealing temperature. Raman spectroscopy was performed using two laser wavelength excitation regimes, the 514 nm laser (visible region) and the 244 nm laser (deep ultraviolet region, DUV). Measurements in the visible region for samples annealed at 1200 °C for 5 h showed that the characteristic 6H-SiC peaks, namely, the Transverse Optical (TO) and Longitudinal Optical (LO) are similar to the virgin samples, albeit with lower intensity due to some retained defects upon recystallisation of the SiC surface region. The similarities between the virgin spectra and the annealed sample were due to the deep penetration of the 514 nm laser into 6H-SiC resulting in the signal from the bulk undamaged 6H-SiC contributing to the overall spectra. However, DUV laser excitation, which only probes the near surface region, shows that after annealing the peaks are broader and asymmetrical compared to the virgin samples. DUV Raman spectra of samples annealed at 1600 °C indicate that SiC has completely decomposed and the top surface layer is now covered by a carbon layer. However the deeper penetrating laser in the visible region showed that the extent of decomposition at 1600 °C was greater for the silver implanted samples than for the iodine implanted samples.

  3. Evidence and detailed study of a second-order phase transition in the (C{sub 6}H{sub 11}NH{sub 3}){sub 2}[PbI{sub 4}] organic-inorganic hybrid material

    SciTech Connect

    Yangui, A.; Pillet, S.; Garrot, D.; Boukheddaden, K.; Triki, S.; Abid, Y.

    2015-03-21

    The thermal properties of the organic-inorganic hybrid material (C{sub 6}H{sub 11}NH{sub 3}){sub 2}[PbI{sub 4}] are investigated using diffuse reflectivity, spectroscopic ellipsometry, differential scanning calorimetry, Raman spectroscopy, and X-ray diffraction. The diffuse reflectivity, performed in heating mode, clearly evidences the presence of a singularity at 336 K. This is confirmed by the temperature dependence of the spectroscopic ellipsometry spectra, which points out a second-order phase transition at 336 K with a critical exponent ∼0.5. Differential scanning calorimetry measurements on a polycrystalline powder of (C{sub 6}H{sub 11}NH{sub 3}){sub 2}[PbI{sub 4}] show a reversible phase transition detected at T{sub C} = 336 K without hysteresis. Raman spectroscopy data suggest that this transition arises from a change in the interactions between inorganic sheets (([PbI{sub 4}]{sup 2−}){sub ∞}) and organic protonated molecules ([C{sub 6}H{sub 11}NH{sub 3}]{sup +}). The structural analysis from power X-ray diffraction reveals an incomplete order-disorder transition of the cyclohexylammonium cation, causing a subtle contraction of the inter-plane distance. The transition results from repulsive close contacts between the organic molecules in the interlayer spacing.

  4. Periodization

    PubMed Central

    Lorenz, Daniel S.; Reiman, Michael P.; Walker, John C.

    2010-01-01

    Background: Clinicians are constantly faced with the challenge of designing training programs for injured and noninjured athletes that maximize healing and optimize performance. Periodization is a concept of systematic progression—that is, resistance training programs that follow predictable patterns of change in training variables. The strength training literature is abundant with studies comparing periodization schemes on uninjured, trained, and untrained athletes. The rehabilitation literature, however, is scarce with information about how to optimally design resistance training programs based on periodization principles for injured athletes. The purpose of this review is to discuss relevant training variables and methods of periodization, as well as periodization program outcomes. A secondary purpose is to provide an anecdotal framework regarding implementation of periodization principles into rehabilitation programs. Evidence Acquisition: A Medline search from 1979 to 2009 was implemented with the keywords periodization, strength training, rehabilitation, endurance, power, hypertrophy, and resistance training with the Boolean term AND in all possible combinations in the English language. Each author also undertook independent hand searching of article references used in this review. Results: Based on the studies researched, periodized strength training regimens demonstrate improved outcomes as compared to nonperiodized programs. Conclusions: Despite the evidence in the strength training literature supporting periodization programs, there is a considerable lack of data in the rehabilitation literature about program design and successful implementation of periodization into rehabilitation programs. PMID:23015982

  5. Synthesis and study of fluorescence properties of novel pyrazolo[4‧,3‧:5,6]pyrido[2,3-d]pyrimidin-5(6H)-one derivatives

    NASA Astrophysics Data System (ADS)

    Quiroga, Jairo; Acosta, Paola; Ortiz, Alejandro; Insuasty, Braulio; Abonia, Rodrigo

    2015-10-01

    New pyrazolo[4‧,3‧:5,6]pyrido[2,3-d]pyrimidin-5(6H)-one derivatives 5 were prepared by cyclocondensation reaction between heterocyclic o-aminonitriles 3 and carboxylic acids 4 in the presence of sulfuric acid as catalyst. This procedure provides the desired compound in good yield with a simple one-step methodology. The obtained products show interesting fluorescence properties in both solution and solid state; in this way several spectra of absorption and emission were measured for selected compounds 5b, 5e, 5g and 5j, showing a broad and intense emission band around of 470 nm. In other to understand the electronic transition processes, theoretical calculations were performed at TD-DFT level, using B3LYP as functional and 6-31(d,p) as basis set, finding a good agreement with experimental measurements.

  6. Static and dynamic interaction between π and d electrons in organic superconductor β″-(BEDT-TTF)4[(H3O ) Fe (C2O4)3] .C6H5Br studied by 13C NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Ihara, Y.; Futami, Y.; Kawamoto, A.; Matsui, K.; Goto, T.; Sasaki, T.; Benmansour, S.; Gómez-García, C. J.

    2016-08-01

    We present the results of 13C NMR experiments in an organic superconductor with localized Fe spins β″-(BEDT-TTF) 4[(H3O ) Fe (C2O4)3] .C6H5Br . We reveal the antiferromagnetic coupling between Fe d spins and π spins, which creates an exchange field antiparallel to the external field direction at the π electrons. In addition to the static effects of Fe spins, we show from the nuclear spin-lattice relaxation rate measurement that the magnetic fluctuations generated by Fe spins are suppressed at low temperatures and high magnetic fields. These conditions are suitable to stabilize the field-induced superconductivity by the field compensation mechanism. After the suppression of Fe-spin dynamics by a magnetic field of 19 T, we observed the underlying π -electron contribution. We discuss a possible anomaly in the π -electron system.

  7. Synthesis of opioidmimetics, 3-[H-Dmt-NH(CH(2))(m)]-6-[H-Dmt-NH(CH(2))(n)]-2(1H)-pyrazinones, and studies on structure-activity relationships.

    PubMed

    Shiotani, Kimitaka; Miyazaki, Anna; Li, Tingyou; Tsuda, Yuko; Yokoi, Toshio; Ambo, Akihiro; Sasaki, Yusuke; Bryant, Sharon D; Jinsmaa, Yunden; Lazarus, Lawrence H; Okada, Yoshio

    2007-11-01

    Opioidmimetics containing 3-[H-Dmt-NH-(CH(2))(m)]-6-[H-Dmt-NH-(CH(2))(n)]-2(1H)-pyrazinone symmetric (m = n, 1-4) (1 - 4) and asymmetric (m, n = 1 - 4) aliphatic chains (5 - 16) were synthesized using dipeptidyl chloromethylketone intermediates. They had high mu-affinity (K(i)mu = 0.021 - 2.94 nM), delta-affinity (K(i)delta = 1.06 - 152.6 nM), and mu selectivity (K(i)delta/K(i)mu = 14 - 3,126). The opioidmimetics (1 - 16) exhibited mu agonism in proportion to their mu-receptor affinity. delta-Agonism was essentially lacking in the compounds except (4) and (16), and (1) and (2) indicated weak delta antagonism (pA(2) = 6.47 and 6.56, respectively). The data verify that a specific length of aliphatic linker is required between the Dmt pharmacophore and the pyrazinone ring to produce unique mu-opioid receptor ligands.

  8. A vibrational spectroscopic study of the silicate mineral harmotome - (Ba,Na,K)1-2(Si,Al)8O16ṡ6H2O - A natural zeolite

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; López, Andrés; Wang, Lina; Romano, Antônio Wilson; Scholz, Ricardo

    2015-02-01

    The mineral harmotome (Ba,Na,K)1-2(Si,Al)8O16ṡ6H2O is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and other industrial applications. It is a natural zeolite with catalytic potential. Raman bands at 1020 and 1102 cm-1 are assigned to the SiO stretching vibrations of three dimensional siloxane units. Raman bands at 428, 470 and 491 cm-1 are assigned to OSiO bending modes. The broad Raman bands at around 699, 728, 768 cm-1 are attributed to water librational modes. Intense Raman bands in the 3100 to 3800 cm-1 spectral range are assigned to OH stretching vibrations of water in harmotome. Infrared spectra are in harmony with the Raman spectra. A sharp infrared band at 3731 cm-1 is assigned to the OH stretching vibration of SiOH units. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral harmotome.

  9. Study on the interaction of 6-(2-morpholin-4-yl-ethyl)-6H-indolo [2,3-b]quinoxaline hydrochloride with human serum albumin by fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Yegorova, A.; Leonenko, I.; Scrypynets, Yu; Maltsev, G.; Antonovich, V.

    2016-09-01

    Under physiological conditions, in vitro interaction between the bio-active substance 6-(2-morpholin-4-yl-ethyl)-6H-indolo[2,3-b]quinoxaline hydrochloride (MIQ) and human serum albumin (HSA) was investigated at an excitation wavelength 260 nm and at different temperatures (298 K, 308 K and 313 K) by fluorescence emission spectroscopy. From spectral analysis, MIQ showed a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The binding constant is estimated asK A   =  2.55  ×  10-4 l · mol-1 at 298 K. Based on the thermodynamic parameters evaluated from the van ’t Hoff equation, the enthalpy change (ΔH°) and entropy change (ΔS°) were derived to be negative values. A value of 2.37 nm for the average distance r between MIQ (acceptor) and tryptophan residues of HSA (donor) was derived from the fluorescence resonance energy transfer. UV/vis absorption spectra were used to confirm the quenching mechanism.

  10. Rhenium Complex with Noninnocent Dioxolene Ligand: Combined Experimental and ab Initio Study of [(3,5-di-tert-Bu2C6H2O2)ReCl3(OPPh3)].

    PubMed

    Abramov, Pavel A; Gritsan, Nina P; Suturina, Elizaveta A; Bogomyakov, Artem S; Sokolov, Maxim N

    2015-07-20

    Reaction of [ReOCl3(PPh3)2] with 3,5-di-tert-butyl-1,2-benzoquinone (3,5-DTBQ) in hot toluene produces a new complex [(3,5-di-tert-Bu2C6H2O2)Re(OPPh3)Cl3] (1), which was isolated and characterized by elemental analysis, IR, UV-vis spectroscopy, and cyclic voltammetry. In order to clarify the charge state of rhenium and the coordinated dioxolene ligand, X-ray experiments at 150 and 290 K were carried out. The C-O, C-C, and Re-O bond distances at both 150 and 290 K fall between those for semiquinolate (3,5-DTBSQ) and catecholate (3,5-DTBCat) forms; an empirical "metrical oxidation state" of the dioxolene ligand was estimated to be -1.5. High-level ab initio calculations (SOC-CASSCF/NEVPT2) revealed a mixed valence nature of the triplet ground state of complex 1 corresponding to a superposition of the Re(IV)-SQ and Re(V)-cat forms. In agreement with the high-level ab initio and DFT calculations, the temperature dependence of the magnetic susceptibility (5-300 K) is well described in the assumption of the triplet ground state, with the anomalously large zero-field splitting (ZFS) arising from the spin-orbit coupling. According to the ab initio calculations, all absorption bands in the visible region of the electronic absorptions spectrum are assigned to the LMCT bands, with significant contribution of the intraligand transition in the most intense band at 555 nm.

  11. Flow over periodic hills: an experimental study

    NASA Astrophysics Data System (ADS)

    Rapp, Ch.; Manhart, M.

    2011-07-01

    Two-dimensional flow over periodically arranged hills was investigated experimentally in a water channel. Two-dimensional particle image velocimetry (PIV) and one-dimensional laser Doppler anemometry (LDA) measurements were undertaken at four Reynolds numbers ({5,600} le Re le {37,000}). Two-dimensional PIV field measurements were thoroughly validated by means of point-by-point 1D LDA measurements at certain positions of the flow. A detailed study of the periodicity and the homogeneity was undertaken, which demonstrates that the flow can be regarded as two-dimensional and periodic for Re ge {10,000}. We found a decreasing reattachment length with increasing Reynolds number. This is connected to a higher momentum in the near-wall zone close to flow separation which comes from the velocity speed up above the obstacle. This leads to a velocity overshoot directly above the hill crest which increases with Reynolds number as the inner layer depth decreases. The flow speed up above that layer is independent of the Reynolds number which supports the assumption of inviscid flow disturbance in the outer layer usually made in asymptotic theory for flow over small hills.

  12. Topological study of the periodic system.

    PubMed

    Restrepo, Guillermo; Mesa, Héber; Llanos, Eugenio J; Villaveces, José L

    2004-01-01

    We carried out a topological study of the Space of Chemical Elements, SCE, based on a clustering analysis of 72 elements, each one defined by a vector of 31 properties. We looked for neighborhoods, boundaries, and other topological properties of the SCE. Among the results one sees the well-known patterns of the Periodic Table and relationships such as the Singularity Principle and the Diagonal Relationship, but there appears also a robustness property of some of the better-known families of elements. Alkaline metals and Noble Gases are sets whose neighborhoods have no other elements besides themselves, whereas the topological boundary of the set of metals is formed by semimetallic elements.

  13. Tuning Chelation by the Surfactant-Like Peptide A6H Using Predetermined pH Values

    PubMed Central

    2013-01-01

    We examine the self-assembly of a peptide A6H comprising a hexa-alanine sequence A6 with a histidine (H) “head group”, which chelates Zn2+ cations. We study the self-assembly of A6H and binding of Zn2+ ions in ZnCl2 solutions, under acidic and neutral conditions. A6H self-assembles into nanotapes held together by a β-sheet structure in acidic aqueous solutions. By dissolving A6H in acidic ZnCl2 solutions, the carbonyl oxygen atoms in A6H chelate the Zn2+ ions and allow for β-sheet formation at lower concentrations, consequently reducing the onset concentration for nanotape formation. A6H mixed with water or ZnCl2 solutions under neutral conditions produces short sheets or pseudocrystalline tapes, respectively. The imidazole ring of A6H chelates Zn2+ ions in neutral solutions. The internal structure of nanosheets and pseudocrystalline sheets in neutral solutions is similar to the internal structure of A6H nanotapes in acidic solutions. Our results show that it is possible to induce dramatic changes in the self-assembly and chelation sites of A6H by changing the pH of the solution. However, it is likely that the amphiphilic nature of A6H determines the internal structure of the self-assembled aggregates independent from changes in chelation. PMID:24369761

  14. A Search for ortho-benzyne (o-C6H4) in CRL 618

    NASA Astrophysics Data System (ADS)

    Weaver, Susanna L. Widicus; Remijan, Anthony J.; McMahon, Robert J.; McCall, Benjamin J.

    2007-12-01

    Polycyclic aromatic hydrocarbons (PAHs) have been proposed as potential carriers of the unidentified infrared bands (UIRs) and the diffuse interstellar bands (DIBs). PAHs are not likely to form by gas-phase or solid-state interstellar chemistry, but rather might be produced in the outflows of carbon-rich evolved stars. PAHs could form from acetylene addition to the phenyl radical (C6H5), which is closely chemically related to benzene (C6H6) and ortho-benzyne (o-C6H4). To date, circumstellar chemical models have been limited to only a partial treatment of benzene-related chemistry, and so the expected abundances of these species are uncertain. A detection of benzene has been reported in the envelope of the proto-planetary nebula (PPN) CRL 618, but no other benzene-related species has been detected in this or any other source. The spectrum of o-C6H4 is significantly simpler and stronger than that of C6H5, and so we conducted deep Ku-, K-, and Q-band searches for o-C6H4 with the Green Bank Telescope. No transitions were detected, but an upper limit on the column density of 8.4 × 1013 cm-2 has been determined. This limit can be used to constrain chemical models of PPNe, and this study illustrates the need for complete revision of these models to include the full set of benzene-related chemistry.

  15. Global reaction route mapping of isomerization pathways of exotic C{sub 6}H molecular species

    SciTech Connect

    Vikas, E-mail: qlabspu@yahoo.com; Kaur, Gurpreet

    2013-12-14

    C{sub 6}H radical is known to exist in the astrophysical environment in linear form; however, it may originate from nonlinear isomeric forms. Potential energy surface of C{sub 6}H is explored to search isomers of C{sub 6}H and transition states connecting them. This work reports first-ever identification of reaction pathways for isomerization of C{sub 6}H. The reaction route search is performed through global reaction route mapping method, which utilizes an uphill walking technique based on an anharmonic downward distortion following approach to search intermediates and transition states. The computations performed at the CASSCF/aug-cc-pVTZ, CCSD(T)/6-311++G(d,p)//DFT/B3LYP/6-311++G(d,p), and DFT/B3LYP/aug-cc-pVTZ levels of the theory identified 14 isomers (including 8 new isomeric forms of C{sub 6}H) and 28 transition states. Most of the identified isomers are found to have significant multireference character. The kinetic stability and natural bond orbital analysis of the identified isomers is also investigated. The isomeric forms are further characterized using spectral analysis involving rotational constants, vibrational frequencies, and Raman scattering activities as well as analyzing the effect of isotopic substitution of hydrogen on the spectral features. This study proposes that the linear-C{sub 6}H can readily isomerize to a six-member ring isomer.

  16. Studying the Nazi Period: Some Considerations.

    ERIC Educational Resources Information Center

    Molnar, Alex; And Others

    1984-01-01

    Students should be taught how to make well-reasoned and analytic judgments about the Nazis. The process of arriving at judgments about the Nazi period should be characterized by a factual knowledge of the Nazi era within a general historical knowledge of the period, sympathy, and an open mind. (RM)

  17. Identification and analysis of the human murine putative chromatin structure regulator SUPT6H and Supt6h

    SciTech Connect

    Chiang, Pei-Wen; Wang, SuQing; Hillman, J.

    1996-06-15

    We have isolated and sequenced SUPT6H and Supt6h, the human and murine homologues of the Saccharomyces cerevisiae and Caenorhabditis elegans genes SPT6 (P using 1603 aa = 6.7 e-{sup 95}) and emb-5 (P using 1603 aa = 7.0 e-{sup 288}), respectively. The human and murine SPT6 homologues are virtually identical, as they share >98% identity and >99% similarity at the protein level. The derived amino acid sequences of these two genes predict a 1603-aa protein (human) and a 1726-bp protein (mouse), respectively. There were several known features, including a highly acidic 5{prime}-region, a degenerate SH2 domain, and a leucine zipper. These features are consistent with a nuclear protein that regulates transcription, whose extreme conservation underscores the likely importance of this gene in mammalian development. Expression of human and murine SPT6 homologues was analyzed by Northern blotting, which revealed a 7.0-kb transcript that was expressed constitutively. The SPT6 homologue was mapped to chromosome 17q11.2 in human by somatic cell hybrid analysis and in situ hybridization. These data indicate that SUPT6H and Supt6h are functionally analogous to SPT6 and emb-5 and may therefore regulate transcription through establishment or maintenance of chromatin structure. 23 refs., 3 figs.

  18. A vibrational spectroscopic study of the phosphate mineral zanazziite - Ca2(MgFe2+)(MgFe2+Al)4Be4(PO4)6ṡ6(H2O)

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; Xi, Yunfei; Scholz, Ricardo; Belotti, Fernanda M.; Dias Menezes Filho, Luiz Alberto

    2013-03-01

    Zanazziite is the magnesium member of a complex beryllium calcium phosphate mineral group named roscherite. The studied samples were collected from the Ponte do Piauí mine, located in Itinga, Minas Gerais. The mineral was studied by electron microprobe, Raman and infrared spectroscopy. The chemical formula can be expressed as Ca2.00(Mg3.15,Fe0.78,Mn0.16,Zn0.01,Al0.26,Ca0.14)Be4.00(PO4)6.09(OH)4.00ṡ5.69(H2O) and shows an intermediate member of the zanazziite-greinfeinstenite series, with predominance of zanazziite member. The molecular structure of the mineral zanazziite has been determined using a combination of Raman and infrared spectroscopy. A very intense Raman band at 970 cm-1 is assigned to the phosphate symmetric stretching mode whilst the Raman bands at 1007, 1047, 1064 and 1096 cm-1 are attributed to the phosphate antisymmetric stretching mode. The infrared spectrum is broad and the antisymmetric stretching bands are prominent. Raman bands at 559, 568, 589 cm-1 are assigned to the ν4 out of plane bending modes of the PO4 and HPO4 units. The observation of multiple bands supports the concept that the symmetry of the phosphate unit in the zanazziite structure is reduced in symmetry. Raman bands at 3437 and 3447 cm-1 are attributed to the OH stretching vibrations; Raman bands at 3098 and 3256 are attributed to water stretching vibrations. The width and complexity of the infrared spectral profile in contrast to the well resolved Raman spectra, proves that the pegmatitic phosphates are better studied with Raman spectroscopy.

  19. Interplay between tetrel and triel bonds in RC6H4CN⋯MF3CN⋯BX3 complexes: A combined symmetry-adapted perturbation theory, Møller-Plesset, and quantum theory of atoms-in-molecules study.

    PubMed

    Yourdkhani, Sirous; Korona, Tatiana; Hadipour, Nasser L

    2015-12-15

    Intermolecular ternary complexes composed of: (1) the centrally placed trifluoroacetonitrile or its higher analogs with central carbon exchanged by silicon or germanium (M = C, Si, Ge), (2) the benzonitrile molecule or its para derivatives on one side, and (3) the boron trifluoride of trichloride molecule (X = F, Cl) on the opposite side as well as the corresponding intermolecular tetrel- and triel-bonded binary complexes, were investigated by symmetry-adapted perturbation theory (SAPT) and the supermolecular Møller-Plesset method (MP2) at the complete basis set limit for optimized geometries. A character of interactions was studied by quantum theory of atoms-in-molecules (QTAIM). A comparison of interaction energies and QTAIM bond descriptors for dimers and trimers reveals that tetrel and triel bonds increase in their strength if present together in the trimer. For the triel-bonded complex, this growth leads to a change of the bond character from closed-shell to partly covalent for Si or Ge tetrel atoms, so the resulting bonding scheme corresponds to a preliminary stage of the SN2 reaction. Limitations of the Lewis theory of acids and bases were shown by its failure in predicting the stability order of the triel complexes. The necessity of including interaction energy terms beyond the electrostatic component for an elucidation of the nature of σ- and π-holes was presented by a SAPT energy decomposition and by a study of differences in monomer electrostatic potentials obtained either from isolated monomer densities, or from densities resulting from a perturbation with the effective field of another monomer.

  20. Synthesis, Characterization and Thermal Studies of Zn(II), Cd(II) and Hg(II) Complexes of N-Methyl-N-Phenyldithiocarbamate: The Single Crystal Structure of [(C6H5)(CH3)NCS2]4Hg2

    PubMed Central

    Onwudiwe, Damian C.; Ajibade, Peter A.

    2011-01-01

    Zn(II), Cd(II) and Hg(II) complexes of N-methyl-N-phenyl dithiocarbamate have been synthesized and characterized by elemental analysis and spectral studies (IR, 1H and 13C-NMR). The single crystal X-ray structure of the mercury complex revealed that the complex contains a Hg centre with a distorted tetrahedral coordination sphere in which the dinuclear Hg complex resides on a crystallographic inversion centre and each Hg atom is coordinated to four S atoms from the dithiocarbamate moiety. One dithiocarbamate ligand acts as chelating ligand while the other acts as chelating bridging ligand between two Hg atoms, resulting in a dinuclear eight-member ring. The course of the thermal degradation of the complexes has been investigated using thermogravimetric and differential thermal analyses techniques. Thermogravimetric analysis of the complexes show a single weight loss to give MS (M = Zn, Cd, Hg) indicating that they might be useful as single source precursors for the synthesis of MS nanoparticles and thin films. PMID:21673933

  1. Kinetic and theoretical studies on the protonation of [Ni(2-SC6H4N){PhP(CH2CH2PPh2)2}]+: nitrogen versus sulfur as the protonation site.

    PubMed

    Petrou, Athinoula L; Koutselos, Andreas D; Wahab, Hilal S; Clegg, William; Harrington, Ross W; Henderson, Richard A

    2011-02-01

    The complexes [Ni(4-Spy)(triphos)]BPh(4) and [Ni(2-Spy)(triphos)]BPh(4) {triphos = PhP(CH(2)CH(2)PPh(2))(2), 4-Spy = 4-pyridinethiolate, 2-Spy = 2-pyridinethiolate} have been prepared and characterized both spectroscopically and using X-ray crystallography. In both complexes the triphos is a tridentate ligand. However, [Ni(4-Spy)(triphos)](+) comprises a 4-coordinate, square-planar nickel with the 4-Spy ligand bound to the nickel through the sulfur while [Ni(2-Spy)(triphos)](+) contains a 5-coordinate, trigonal-bipyramidal nickel with a bidentate 2-Spy ligand bound to the nickel through both sulfur and nitrogen. The kinetics of the reactions of [Ni(4-Spy)(triphos)](+) and [Ni(2-Spy)(triphos)](+) with lutH(+) (lut = 2,6-dimethylpyridine) in MeCN have been studied using stopped-flow spectrophotometry, and the two complexes show very different reactivities. The reaction of [Ni(4-Spy)(triphos)](+) with lutH(+) is complete within the deadtime of the stopped-flow apparatus (2 ms) and corresponds to protonation of the nitrogen. However, upon mixing [Ni(2-Spy)(triphos)](+) and lutH(+) a reaction is observed (on the seconds time scale) to produce an equilibrium mixture. The mechanistic interpretation of the rate law has been aided by the application of MSINDO semiempirical and ADF calculations. The kinetics and calculations are consistent with the reaction between [Ni(2-Spy)(triphos)](+) and lutH(+) involving initial protonation of the sulfur followed by dissociation of the nitrogen and subsequent transfer of the proton from sulfur to nitrogen. The factors affecting the position of protonation and the coupling of the coordination state of the 2-pyridinethiolate ligand to the site of protonation are discussed.

  2. Infrared spectroscopic study of SO42- ions included in M‧2M‧‧(SeO4)2ṡ6H2O (Me‧ = K, NH4+; M‧‧ = Mg, Co, Ni, Cu, Zn) and NH4+ ions included in K2M(XO4)2ṡ6H2O (X = S, Se; M‧‧ = Mg, Co, Ni, Cu, Zn)

    NASA Astrophysics Data System (ADS)

    Marinova, D.; Karadjova, V.; Stoilova, D.

    2015-01-01

    Infrared spectra of Tutton compounds, M‧2M‧‧(XO4)2ṡ6H2O (M‧ = K, NH4+; M‧‧ = Mg, Co, Ni, Cu, Zn; X = S, Se), as well as those of SO42- guest ions included in selenate host lattices and of NH4+ guest ions included in potassium host lattices are presented and discussed in the regions of ν3 and ν1 of SO42- guest ions, ν4 of NH4+ guest ions and water librations. The SO42- guest ions matrix-isolated in selenate matrices (approximately 2 mol%) exhibit three bands corresponding to ν3 and one band corresponding to ν1 in good agreement with the low site symmetry C1 of the host selenate ions. When the larger SeO42- ions are replaced by the smaller SO42- ions the mean values of the asymmetric stretching modes νbar3 of the included SO42- ions are slightly shifted to lower frequencies as compared to those of the same ions in the neat sulfate compounds due to the smaller repulsion potential of the selenate matrices (larger unit-cell volumes of the selenates). It has been established that the extent of energetic distortion of the sulfate ions matrix-isolated in the ammonium selenates as deduced from the values of Δν3 and Δν3/νc is stronger than that of the same ions matrix-isolated in the potassium selenates due to the formation of hydrogen bonds between the SO42- guest ions with both the water molecules in the host compounds and the NH4+ host ions (for example, Δν3 of the sulfate guest ions have values of 30 and 51 cm-1 in the nickel potassium and ammonium compounds, and 33 and 49 cm-1 in the zinc potassium and ammonium compounds, respectively). The infrared spectra of ammonium doped potassium sulfate matrices show three bands corresponding to Δν4 of the included ammonium ions in agreement with the low site symmetry C1 of the host potassium ions. However, the inclusion of ammonium ions in selenate matrices (with exception of the magnesium compound) leads to the appearance of four bands in the region of ν4. At that stage of our knowledge we assume

  3. Studies of Long Period Eclipsing Binaries

    NASA Astrophysics Data System (ADS)

    Ratajczak, M.; Hełminiak, K. G.; Konacki, M.

    2015-07-01

    The survey of long period eclipsing binaries from the All Sky Automated Survey (ASAS) catalog aims at searching for and characterizing subgiants and red giants in double-lined detached binary systems. Absolute physical and orbital parameters are presented based on radial velocities from high-quality optical spectra obtained with the following telescope/instrument combinations: 8.2 m Subaru/HDS, ESO 3.6 m/HARPS, 1.9 m Radcliffe/GIRAFFE, CTIO 1.5 m/CHIRON, and 1.2 m Euler/CORALIE. Photometric data from ASAS, SuperWASP, and the Solaris Project were also used. We discuss the derived uncertainties for the individual masses and radii of the components (better than 3% for several systems), as well as results from the spectral analysis performed for components of systems whose spectra we disentangled.

  4. Microwave annealing of ion implanted 6H-SiC

    SciTech Connect

    Gardner, J.A.; Rao, M.V.; Tian, Y.L.; Holland, O.W.; Kelner, G.; Freitas, J.A. Jr.; Ahmad, I.

    1996-05-01

    Microwave rapid thermal annealing has been utilized to remove the lattice damage caused by nitrogen (N) ion-implantation as well as to activate the dopant in 6H-SiC. Samples were annealed at temperatures as high as 1,400 C, for 10 min. Van der Pauw Hall measurements indicate an implant activation of 36%, which is similar to the value obtained for the conventional furnace annealing at 1,600 C. Good lattice quality restoration was observed in the Rutherford backscattering and photoluminescence spectra.

  5. Serotype-related enterotoxigenicity in Escherichia coli O6.H16 and O148.H28.

    PubMed

    Scotland, S M; Gross, R J; Rowe, B

    1977-12-01

    The ability of certain Escherichia coli strains to produce enterotoxin is determined by transmissible plasmids. It is therefore possible that any E. coli strain might be able to acquire such a plasmid and that the correlation between enterotoxigenicity and serotype might be random. However, recent studies show that the enterotoxigenic strains so far describe belong to a restricted range of serotypes. Enterotoxigenic strains of E. coli O6.H16 and E. coli O148.H28 have been associated with outbreaks of diarrhoea in several countries, therefor strains of E. coli belonging to these serotypes were selected for further study. Twenty-three strains of E. coli O6.H16 and 14 strains of E. coli O148.H28 were examined; 20 strains of E. coli O6.H16 and all 14 strains of E. coli O148.H28 were enterotoxigenic but strains of E. coli O6 wit flagellar antigens other than H16 and strains of E. coli O148 wit flagellar antigens other than H28 were not enterotoxigenic. The examination of single colony subcultures derived from the E. coli O6.H16 strains showed that in some strains loss of enterotoxigenicity had occurred in a proportional of colonies.

  6. Interface-structure of the Si/SiC heterojunction grown on 6H-SiC

    SciTech Connect

    Li, L. B.; Chen, Z. M.; Zang, Y.

    2015-01-07

    The Si/SiC heterojunctions were prepared on 6H-SiC (0001) C-face by low-pressure chemical vapour deposition at 850 ∼ 1050 °C. Transmission electron microscopy and selected area electron diffraction were employed to investigate the interface-structure of Si/SiC heterojunctions. The Si/6H-SiC heterostructure of large lattice-mismatch follows domain matching epitaxy mode, which releases most of the lattice-mismatch strain, and the coherent Si epilayers can be grown on 6H-SiC. Si(1-11)/6H-SiC(0001) heterostructure is obtained at 900 °C, and the in-plane orientation relationship of Si/6H-SiC heterostructure is (1–11)[1-1-2]{sub Si}//(0001)[-2110]{sub 6H-SiC}. The Si(1-11)/6H-SiC(0001) interface has the same 4:5 Si-to-SiC matching mode with a residual lattice-mismatch of 0.26% along both the Si[1-1-2] and Si[110] orientations. When the growth temperature increases up to 1000 °C, the 〈220〉 preferential orientation of the Si film appears. SAED patterns at the Si/6H-SiC interface show that the in-plane orientation relationship is (-220)[001]{sub Si}//(0001)[2-1-10]{sub 6H-SiC}. Along Si[110] orientation, the Si-to-SiC matching mode is still 4:5; along the vertical orientation Si[001], the Si-to-SiC mode change to approximate 1:2 and the residual mismatch is 1.84% correspondingly. The number of the atoms in one matching-period decreases with increasing residual lattice-mismatch in domain matching epitaxy and vice versa. The Si film grows epitaxially but with misfit dislocations at the interface between the Si film and the 6H-SiC substrate. And the misfit dislocation density of the Si(1-11)/6H-SiC(0001) and Si(-220)/6H-SiC(0001) obtained by experimental observations is as low as 0.487 × 10{sup 14 }cm{sup −2} and 1.217 × 10{sup 14 }cm{sup −2}, respectively, which is much smaller than the theoretical calculation results.

  7. Stability and isomerization reactions of phenyl cation C6H5+ isomers

    NASA Astrophysics Data System (ADS)

    Shi, Dandan; Yang, Xue; Zhang, Xiaomei; Shan, Shimin; Xu, Haifeng; Yan, Bing

    2016-03-01

    As a key polyatomic molecular cation that plays a pivotal role in growth of the polycyclic aromatic hydrocarbons, phenyl cation C6H5+ exhibits various isomers and isomerization reactions. Investigation on the structure and stability of the isomers as well as the isomerization is important for better understanding the chemical reactions involving C6H5+ cations. In this work, we have performed a theoretical study on the stability and isomerization reactions of C6H5+ isomers at density functional theory B3LYP/6-311G (d, p) level. We have obtained a total of 60 isomers of C6H5+ cations, most of which are reported for the first time. The geometries, vibrational frequencies, thermodynamic properties and stability of 28 out of 60 isomers have been summarized in detail. Different ring-to-ring and ring-to-chain isomerization pathways, which are connected via 28 transition states, have been investigated using the intrinsic reaction coordinate method. The results show that the isomerization reactions occur via hydrogen migration followed by bond-breaking and reconstruction.

  8. Microstructural and superconducting properties of C6H6 added bulk MgB2 superconductor

    NASA Astrophysics Data System (ADS)

    Babaoğlu, Meral G.; Safran, Serap; Çiçek, Özlem; Ağıl, Hasan; Ertekin, Ercan; Hossain, Md. Shahriar A.; Yanmaz, Ekrem; Gencer, Ali

    2012-10-01

    The effect of aromatic hydrocarbon (benzene, C6H6) addition on lattice parameters, microstructure, critical temperature (Tc), critical current density (Jc) of bulk MgB2 has been studied. In this work only 2 mol% C6H6 addition was found to be very effective in increasing the Jc values, while resulting in slight reduction of the Tc. Jc values of 2 mol% C6H6 added MgB2 bulks reached to 1.83×106 A/cm2 at 15 K and 0 T. Microstructural analyses suggest that Jc enhancement is associated with the substitution of carbon with boron and which also results in the smaller MgB2 grain size. The change in the lattice parameters or the lattice disorder is claimed as a cause of the slight reduction in the Tc by carbon addition. We note that our results show the advantages of C6H6 addition include homogeneous mixing of precursor powders, avoidance of expansive nanoadditives, production of highly reactive C, and significant enhancement in Jc of MgB2, compared to un-doped samples.

  9. Ion implantation induced swelling in 6H-SiC

    SciTech Connect

    Nipoti, R.; Albertazzi, E.; Bianconi, M.; Lotti, R.; Lulli, G.; Cervera, M.; Carnera, A.

    1997-06-01

    Ion implantation induced surface expansion (swelling) of 6H-SiC was investigated through the measurement of the step height between implanted and unimplanted areas. The samples were irradiated at room temperature with 500 keV Al{sup +} ions in the dose range 1.25{times}10{sup 14}{endash}3{times}10{sup 15}ionscm{sup {minus}2}. Swelling was related to dose and the area density of ion-induced damage measured by Rutherford backscattering channeling technique. The observed trend is consistent with the hypothesis that the volume expansion of the ion damaged crystal is proportional to the area density of displaced atoms, plus an additional relaxation occurring at the onset of the crystalline to amorphous transition. {copyright} {ital 1997 American Institute of Physics.}

  10. Trisodium citrate, Na3(C6H5O7)

    PubMed Central

    Rammohan, Alagappa; Kaduk, James A.

    2016-01-01

    The crystal structure of anhydrous tris­odium citrate, Na3(C6H5O7), has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory (DFT). There are two independent five-coordinate Na+ and one six-coordinate Na+ cations in the asymmetric unit. The [NaO5] and [NaO6] polyhedra share edges and corners to form a three-dimensional framework. There are channels parallel to the a and b axes in which the remainder of the citrate anions reside. The only hydrogen bonds are an intra­molecular one between the hy­droxy group and one of the terminal carboxyl­ate O atoms and an intermolecular one between a methylene group and the hydroxyl O atom. PMID:27308044

  11. Frustrated quantum magnetism in the 6H-perovskites

    NASA Astrophysics Data System (ADS)

    Quilliam, Jeffrey

    I will review the recent state of research on the 6H-perovskites, Ba3MA2O9, a large class of materials that can accommodate many different magnetic ions on ostensibly triangular lattices. This class of materials has given rise to several important discoveries in recent years, including quantum spin liquids, a quantum spin-orbital liquid and the first perfectly triangular spin-1/2 antiferromagnet. Many of these materials also provide an interesting interplay of magnetic, orbital and charge degrees of freedom. Others suffer from high levels of site disorder, which leads to interesting physics, at least in the case of the spin-orbital liquid candidate Ba3CuSb2O9. I will primarily discuss our recent work on the materials Ba3MSb2O9, where M = Cu, Ni and Co using the techniques of nuclear magnetic resonance (NMR), muon spin rotation (μSR) and ultrasound velocity measurements.

  12. Theoretical study of isoelectronic molecules: B6H10, 2-CB5H9, 2,3-C2B4H8, 2,3,4-C3B3H7, and 2,3,4,5-C4B2H6.

    PubMed

    Tian, Shan Xi

    2005-07-28

    Isoelectronic molecules regarding B6H10, 2-CB5H9, 2,3-C2B4H8, 2,3,4-C3B3H7, and 2,3,4,5-C4B2H6 are studied by the density functional B3LYP/6-311G(d,p) method and the electron propagator theory in the partial third-order quasiparticale approximation, as well as the extrapolated calculation with the coupled-cluster CCSD(T) theory. The calculated ionization potentials are in good agreement with the experimental data from photoelectron spectroscopy. Valence structures are characterized with natural orbital bond (NBO) theory, exhibiting the multiple three-center two-electron bonds B-H-B, B-B-B, C-B-B, B-C-B, and C-B-C, and chemical bond rearrangements in the cations. PMID:16834005

  13. Deformation behaviour and 6H-LPSO structure formation at nanoindentation in lamellar high Nb containing TiAl alloy

    NASA Astrophysics Data System (ADS)

    Song, L.; Xu, X. J.; Peng, C.; Wang, Y. L.; Liang, Y. F.; Shang, S. L.; Liu, Z. K.; Lin, J. P.

    2015-02-01

    Microstructure and deformation mechanisms at a nanoindentation in the lamellar colony of high Nb containing TiAl alloy have been studied using the focused ion beam and the transmission electron microscopy. Considerable deformation twins are observed around the nanoindentation, and a strain gradient is generated. A continuous change in the bending angle of the lamellar structure can be derived, and a strain-induced grain refinement process is observed as various active deformations split the γ grains into subgrains. In addition to all possible deformation mechanisms (ordinary dislocation, super-dislocation and deformation twining) activated due to the heavy plastic deformation, a 6-layer hexagonal (6H) long-period stacking ordered structure is identified for the first time near the contact zone and is thought to be closely related to the glide of partial dislocations.

  14. Investigation of the transition layer in 3C-SiC/6H-SiC heterostructures

    SciTech Connect

    Lebedev, A. A.; Zamorianskaya, M. V.; Davydov, S. Yu.; Kirilenko, D. A.; Lebedev, S. P. Sorokin, L. M.; Shustov, D. B.; Scheglov, M. P.

    2013-11-15

    Transmission electron microscopy and the cathodoluminescence method are used to study the transition region in 3C-SiC/6H-SiC heterostructures. It is shown that this region is, as a rule, constituted by alternating 3C-SiC and 6H-SiC layers with the possible inclusion of other silicon carbide polytypes. An assumption is made that this structure of the transition region can be explained in terms of the model of spinodal decomposition.

  15. A nonsense mutation in PDE6H causes autosomal-recessive incomplete achromatopsia.

    PubMed

    Kohl, Susanne; Coppieters, Frauke; Meire, Françoise; Schaich, Simone; Roosing, Susanne; Brennenstuhl, Christina; Bolz, Sylvia; van Genderen, Maria M; Riemslag, Frans C C; Lukowski, Robert; den Hollander, Anneke I; Cremers, Frans P M; De Baere, Elfride; Hoyng, Carel B; Wissinger, Bernd

    2012-09-01

    Achromatopsia (ACHM) is an autosomal-recessive retinal dystrophy characterized by color blindness, photophobia, nystagmus, and severely reduced visual acuity. Its prevalence has been estimated to about 1 in 30,000 individuals. Four genes, GNAT2, PDE6C, CNGA3, and CNGB3, have been implicated in ACHM, and all encode functional components of the phototransduction cascade in cone photoreceptors. Applying a functional-candidate-gene approach that focused on screening additional genes involved in this process in a cohort of 611 index cases with ACHM or other cone photoreceptor disorders, we detected a homozygous single base change (c.35C>G) resulting in a nonsense mutation (p.Ser12(∗)) in PDE6H, encoding the inhibitory γ subunit of the cone photoreceptor cyclic guanosine monophosphate phosphodiesterase. The c.35C>G mutation was present in three individuals from two independent families with a clinical diagnosis of incomplete ACHM and preserved short-wavelength-sensitive cone function. Moreover, we show through immunohistochemical colocalization studies in mouse retina that Pde6h is evenly present in all retinal cone photoreceptors, a fact that had been under debate in the past. These findings add PDE6H to the set of genes involved in autosomal-recessive cone disorders and demonstrate the importance of the inhibitory γ subunit in cone phototransduction. PMID:22901948

  16. Synergistic Effects of Iodine and Silver Ions Co-Implanted in 6H-SiC

    SciTech Connect

    Kuhudzai, Remeredzai J.; Malherbe, Johan; Hlatshwayo, T. T.; van der Berg, N. G.; Devaraj, Arun; Zhu, Zihua; Nandasiri, Manjula I.

    2015-10-23

    Motivated by the aim of understanding the release of fission products through the SiC coating of fuel kernels in modern high temperature nuclear reactors, a fundamental investigation is conducted to understand the synergistic effects of implanted silver (Ag) and iodine (I) in 6H-SiC. The implantation of the individual species, as well as the co-implantation of 360 keV ions of I and Ag at room temperature in 6H-SiC and their subsequent annealing behavior has been investigated by Secondary Ion Mass Spectrometry (SIMS), Atom Probe Tomography (APT) and X-ray Photoelectron Spectroscopy (XPS). SIMS and APT measurements indicated the presence of Ag in the co-implanted samples after annealing at 1500 ºC for 30 hours in sharp contrast to the samples implanted with Ag only. In samples implanted with Ag only, complete loss of the implanted Ag was observed. However, for I only implanted samples, some iodine was retained. APT of annealed co-implanted 6H-SiC showed clear spatial association of Ag and I clusters in SiC, which can be attributed to the observed I assisted retention of Ag after annealing. Such detailed studies will be necessary to identify the fundamental mechanism of fission products migration through SiC coatings.

  17. Synergistic effects of iodine and silver ions co-implanted in 6H-SiC

    NASA Astrophysics Data System (ADS)

    Kuhudzai, R. J.; Malherbe, J. B.; Hlatshwayo, T. T.; van der Berg, N. G.; Devaraj, A.; Zhu, Z.; Nandasiri, M.

    2015-12-01

    Motivated by the aim of understanding the release of fission products through the SiC coating of fuel kernels in modern high temperature nuclear reactors, a fundamental investigation is conducted to understand the synergistic effects of implanted silver (Ag) and iodine (I) in 6H-SiC. The implantation of the individual species, as well as the co-implantation of 360 keV ions of I and Ag at room temperature in 6H-SiC and their subsequent annealing behaviour has been investigated by Secondary Ion Mass Spectrometry (SIMS), Atom Probe Tomography (APT) and X-ray Photoelectron Spectroscopy (XPS). SIMS and APT measurements indicated the presence of Ag in the co-implanted samples after annealing at 1500 °C for 30 h in sharp contrast to the samples implanted with Ag only. In samples implanted with Ag only, complete loss of the implanted Ag was observed. However, for I only implanted samples, some iodine was retained. APT of annealed co-implanted 6H-SiC showed clear spatial association of Ag and I clusters in SiC, which can be attributed to the observed I assisted retention of Ag after annealing. Such detailed studies will be necessary to identify the fundamental mechanism of fission products migration through SiC coatings.

  18. Study of possible chaotic, quasi-periodic and periodic structures in quantum dusty plasma

    SciTech Connect

    Ghosh, Uday Narayan; Chatterjee, Prasanta; Roychoudhury, Rajkumar

    2014-11-15

    Existence of chaotic, quasi-periodic, and periodic structures of dust-ion acoustic waves is studied in quantum dusty plasmas through dynamical system approach. A system of coupled differential equations is derived from the fluid model and subsequently, variational matrix is obtained. The characteristic equation is obtained at the equilibrium point, and the behavior of nonlinear waves is studied numerically using Runge-Kutta method. The behavior of the dynamical system changes significantly when any of plasma parameters, such as the dust concentration parameter, temperature ratio, or the quantum diffraction parameter, is varied. The change of the characteristic of solution of the system is extensively studied. It is found that the system changes its behavior from chaotic pattern to limit cycle behavior.

  19. Treatment of uncomplicated gonococcal urethritis by double-dosing of 200 mg cefixime at a 6-h interval.

    PubMed

    Deguchi, Takashi; Yasuda, Mitsuru; Yokoi, Shigeaki; Ishida, Ken-Ichiro; Ito, Masayasu; Ishihara, Satoshi; Minamidate, Ken; Harada, Yoshimasa; Tei, Kanhin; Kojima, Kentaro; Tamaki, Masayoshi; Maeda, Shin-Ichi

    2003-03-01

    The efficacy of antimicrobial regimens for the treatment of uncomplicated gonococcal urethritis depends partially upon the period of time (therapeutic time) during which the drug concentration in the blood after the concentration peak is greater than four times the minimum inhibitory concentration for 90% of clinical isolates of Neisseria gonorrhoeae (MIC(90)). A therapeutic time of at least 10 h is suggested as an important determinant for elimination of 95% or more of the infection. In this study, therapeutic times for a single 400-mg dose of cefixime at various MIC(90)s were calculated, and pharmacokinetic profiles of double-dosing of 200 mg cefixime at various intervals were simulated. Subsequently, a dosing interval of 6 h was tested in 6 healthy Japanese men, and then 93 Japanese men with gonococcal urethritis were treated with a regimen of two 200-mg doses of cefixime given at a 6-h interval. For a single dose of 400 mg cefixime, therapeutic times were calculated to be 12.8, 9.1, 5.4, and 1.7 h for MIC(90)s of 0.06, 0.125, 0.25, and 0.5 microg/ml, respectively. In the simulation study of double-dosing of 200 mg cefixime at a 6-h interval, the therapeutic times for the MIC(90)s of < or =0.125 microg/ml were longer than 10 h. Of the 93 patients, 68 were evaluated for microbiological outcome, and N. gonorrhoeae was eradicated in 60 (88.2%). The MIC(90) of cefixime for the 61 isolates tested was 0.125 microg/ml. All strains with MICs of < or =0.06 microg/ml were eradicated, whereas 8 of 16 strains with MICs of > or =0.125 microg/ml persisted after treatment. This regimen would not be effective against infection by strains exhibiting cefixime MIC(90)s of > or =0.125 microg/ml. For such strains, a different regimen with a higher dose of cefixime would be required.

  20. Comparative study of thyrotoxic periodic paralysis from idiopathic hypokalemic periodic paralysis: An experience from India

    PubMed Central

    Kalita, J.; Goyal, G.; Bhoi, S. K.; Chandra, S.; Misra, U. K.

    2012-01-01

    Objective: There is paucity of reports on thyrotoxic periodic paralysis (TPP) from India. We report the patients with TPP and compare them with idiopathic hypokalemic periodic paralysis (IHPP). Materials and Methods: Patients with hypokalemic periodic paralysis (HPP) treated during the past 11 years were evaluated retrospectively. Their demographic parameters, family history, clinical features, precipitating factors, severity of weakness, laboratory parameters and rapidity of recovery were recorded. The demographic, clinical and laboratory parameters of TPP and IHPP were compared. Results: During the study period, we managed 52 patients with HPP; nine (17.3%) of whom had TPP and 27 (52%) had IHPP. The demographic, precipitating factors, number of attacks and severity of limb weakness were similar between the TPP and IHPP groups, except in the IHPP group, bulbar weakness was present in four and respiratory paralysis in six, needing artificial ventilation in two patients. Serum potassium was significantly lower in TPP (2.21 ± 0.49) compared with IHPP (2.67 ± 0.59, P = 0.04). Four patients with TPP had subclinical thyrotoxicosis and two had subclinical hyperthyroidism. Rebound hyperkalemia occurred in both TPP and IHPP (three versus eight patients). The recovery was faster in IHPP (26.7 ± 15.4 h) compared with TPP (34.0 ± 14.0 h), but was statistically insignificant. Conclusion: TPP constitutes 17.3% of HPP, and absence of clinical features of thyrotoxicosis and subclinical hyperthyroidism in TPP is not uncommon. Clinical features, demographic profile and rebound hyperkalemia are similar in both TPP and IHPP. The serum potassium level is significantly low in the TPP compared with the IHPP group. PMID:22919190

  1. Si growth at graphene surfaces on 6H-SiC(0001) substrates

    NASA Astrophysics Data System (ADS)

    Sone, Junki; Yamagami, Tsuyoshi; Nakatsuji, Kan; Hirayama, Hiroyuki

    2016-03-01

    We studied the growth of Si at the surface of epitaxial graphene on 6H-SiC(0001). Characteristic flower-like islands with a thickness of 2 to 3 nm nucleated during the growth from 290 to 420 K. The islands became featureless in growth at higher temperatures. The growth was predominantly governed by diffusion-limited aggregation. The diffusion energy was evaluated to be 0.21 eV from the temperature-dependent decrease in the density of the islands.

  2. Multihormonal regulation of thyroglobulin production by the OVNIS 6H thyroid cell line.

    PubMed

    Aouani, A; Hovsépian, S; Fayet, G

    1988-02-01

    The hormonal regulation of thyroglobulin production has been studied using a clone of the ovine thyroid cell line: OVNIS 6H. 3 among the 6 hormones proposed for serum replacement are required for an optimal thyroglobulin production; insulin, hydrocortisone and thyrotropin. Insulin alone stimulates thyroglobulin production. The presence of insulin is also required to observe hydrocortisone and TSH stimulations. Newborn calf serum inhibits thyroglobulin production. The best conditions for optimal thyroglobulin expression and TSH responsiveness are obtained in serum-free medium supplemented with 5 micrograms/ml insulin, 100 nM hydrocortisone and 1 mU/ml TSH. PMID:3286455

  3. ACLCP Periodical Storage Center: Feasibility Study, September 1974-April 1975.

    ERIC Educational Resources Information Center

    Cieslicki, Dorothy

    A study of alternative models for establishing a cooperative storage center for little used library materials by the members of the Area College Libraries of Central Pennsylvania (ACLCP) focused on periodicals. Considerations discussed include advantages--lower cost; space for growth and better access to holdings retained in active collections;…

  4. Targeted ablation of the Pde6h gene in mice reveals cross-species differences in cone and rod phototransduction protein isoform inventory.

    PubMed

    Brennenstuhl, Christina; Tanimoto, Naoyuki; Burkard, Markus; Wagner, Rebecca; Bolz, Sylvia; Trifunovic, Dragana; Kabagema-Bilan, Clement; Paquet-Durand, Francois; Beck, Susanne C; Huber, Gesine; Seeliger, Mathias W; Ruth, Peter; Wissinger, Bernd; Lukowski, Robert

    2015-04-17

    Phosphodiesterase-6 (PDE6) is a multisubunit enzyme that plays a key role in the visual transduction cascade in rod and cone photoreceptors. Each type of photoreceptor utilizes discrete catalytic and inhibitory PDE6 subunits to fulfill its physiological tasks, i.e. the degradation of cyclic guanosine-3',5'-monophosphate at specifically tuned rates and kinetics. Recently, the human PDE6H gene was identified as a novel locus for autosomal recessive (incomplete) color blindness. However, the three different classes of cones were not affected to the same extent. Short wave cone function was more preserved than middle and long wave cone function indicating that some basic regulation of the PDE6 multisubunit enzyme was maintained albeit by a unknown mechanism. To study normal and disease-related functions of cone Pde6h in vivo, we generated Pde6h knock-out (Pde6h(-/-)) mice. Expression of PDE6H in murine eyes was restricted to both outer segments and synaptic terminals of short and long/middle cone photoreceptors, whereas Pde6h(-/-) retinae remained PDE6H-negative. Combined in vivo assessment of retinal morphology with histomorphological analyses revealed a normal overall integrity of the retinal organization and an unaltered distribution of the different cone photoreceptor subtypes upon Pde6h ablation. In contrast to human patients, our electroretinographic examinations of Pde6h(-/-) mice suggest no defects in cone/rod-driven retinal signaling and therefore preserved visual functions. To this end, we were able to demonstrate the presence of rod PDE6G in cones indicating functional substitution of PDE6. The disparities between human and murine phenotypes caused by mutant Pde6h/PDE6H suggest species-to-species differences in the vulnerability of biochemical and neurosensory pathways of the visual signal transduction system. PMID:25739440

  5. Long term photometric and period study of AU Serpentis

    NASA Astrophysics Data System (ADS)

    Gürol, Birol

    2005-08-01

    In the present study, the activity of the eclipsing binary AU Ser is examined by analyzing the photometric data covering the period from 1969 till 2003. The orbital-period changes and light-curve variations of the binary system are studied. 4 new times of minima are obtained from our data. A period study covering almost 60,000 cycles based on the visual, photoelectric and CCD times of minima confirms the light-time effect of the system with a period of 94.15 year. With the assumption of a coplanar orbit of the third-body we find a mass of m3 = 0.53 M⊙. Including our data a total of six light curves are formed from the observations published in the literature that are completely covered in B and V. The differences between the two maxima in each light curve appear to be cyclic over a time-scale over 30 years. Based on a spot model, the light curves are analyzed with the Wilson-Devinney code. Using the spectroscopic mass ratio obtained by Hrivnak [Hrivnak, B.J., 1993. in: Leung, K.-C., Nha, I.S., Eds., New Frontiers in Binary Star Research, ASP Conference Series 38, p. 269] the masses and radii for the components are deduced as 0.895 M⊙, 0.635 M⊙, 1.10 R⊙, 0.94 R⊙ for the primary and secondary, respectively.

  6. Monitoring rFVIIa 90 μg kg⁻¹ dosing in haemophiliacs: comparing laboratory response using various whole blood assays over 6 h.

    PubMed

    Brophy, D F; Martin, E J; Christian Barrett, J; Nolte, M E; Kuhn, J G; Gerk, P M; Carr, M E; Pelzer, H; Agersø, H; Ezban, M; Hedner, U

    2011-09-01

    Recombinant FVIIa is a haemostatic agent administered to patients with severe FVIII or FIX deficiency with inhibitors. Although rFVIIa is effective at stopping bleeding, a reliable assay to monitor its effect is lacking. To characterize the pharmacokinetics and global coagulation effects of rFVIIa for 6 h following a IV dose of 90 μg kg⁻¹. Ten non-bleeding subjects with severe FVIII or FIX deficiency were infused with a single-dose of rFVIIa 90 μg k⁻¹ body weight and blood was collected before and at 0.5, 1, 2, 4 and 6 h postdose. Global haemostasis was characterized throughout the study utilizing whole blood analyses (Hemodyne HAS, TEG, ROTEM). The clearance and half-life of factor FVII:C was estimated as 39.0 ± 8.8 mL h⁻¹ kg⁻¹ and 2.1 ± 0.2 h respectively. There was good inter-assay agreement with respect to clot initiation parameters (R, CT and FOT) and these parameters all fell to a mean of approximately 9 min following rFVIIa dosing. The platelet contractile force (PCF) and clot elastic modulus (CEM) were positively correlated to FVII:C (P < 0.0001), and these parameters were dynamic throughout the 6-h period. The MA and MCF did not correlate to FVII:C nor did they significantly change during the study. Prothrombin F1 + 2 significantly increased following rFVIIa dosing (P < 0.001), but remained steady throughout the study. There was no change in D-dimer concentrations over time. The FOT, R and CT characterized clot initiation following rFVIIa dosing. The PCF and CEM were correlated to FVII:C and characterized the dynamics of platelet function and clot strength over the rFVIIa dosing interval. The clinical significance of these findings needs additional study.

  7. Dimensional isotropy of 6H and 3C SiC under neutron irradiation

    NASA Astrophysics Data System (ADS)

    Snead, Lance L.; Katoh, Yutai; Koyanagi, Takaaki; Terrani, Kurt; Specht, Eliot D.

    2016-04-01

    This investigation experimentally determines the as-irradiated crystal axes dimensional change of the common polytypes of SiC considered for nuclear application. Single crystal α-SiC (6H), β-SiC (3C), CVD β-SiC, and single crystal Si have been neutron irradiated near 60 °C from 2 × 1023 to 2 × 1026 n/m2 (E > 0.1 MeV), or about 0.02-20 dpa, in order to study the effect of irradiation on bulk swelling and strain along independent crystalline axes. Single crystal, powder diffractometry and density measurement have been carried out. For all neutron doses where the samples remained crystalline all SiC materials demonstrated equivalent swelling behavior. Moreover the 6H-SiC expanded isotropically. The magnitude of the swelling followed a ∼0.77 power law against dose consistent with a microstructure evolution driven by single interstitial (carbon) mobility. Extraordinarily large ∼7.8% volume expansion in SiC was observed prior to amorphization. Above ∼0.9 × 1025 n/m2 (E > 0.1 MeV) all SiC materials became amorphous with an identical swelling: a 11.7% volume expansion, lowering the density to 2.84 g/cm3. The as-amorphized density was the same at the 2 × 1025 and 2 × 1026 n/m2 (E > 0.1 MeV) dose levels.

  8. Study for elevator cage position during the braking period

    NASA Astrophysics Data System (ADS)

    Ungureanu, M.; Crăciun, I.; Bănică, M.; Dăscălescu, A.

    2016-08-01

    An important problem in order to study an elevator cage position for its braking period is to establish a correlation between the studies in the fields of mechanics and electric. The classical approaches to establish the elevator kinematic parameters are position, velocity and acceleration, but the last studies performed in order to determine the positioning performed by introducing supplementary another parameter - the jerk- which is derived with respect to time of acceleration. Thus we get a precise method for cage motion control for third-order trajectory planning.

  9. The first potential energy surfaces for the C6H--H2 and C6H--He collisional systems and their corresponding inelastic cross sections

    NASA Astrophysics Data System (ADS)

    Walker, Kyle M.; Dumouchel, Fabien; Lique, François; Dawes, Richard

    2016-07-01

    Molecular anions have recently been detected in the interstellar and circumstellar media. Accurate modeling of their abundance requires calculations of collisional data with the most abundant species that are usually He atoms and H2 molecules. In this paper, we focus on the collisional excitation of the first observed molecular anion, C6H-, by He and H2. Theoretical calculations of collisional cross sections rely generally on ab initio interaction potential energy surfaces (PESs). Hence, we present here the first PESs for the C6H--H2 and C6H--He van der Waals systems. The ab initio energy data for the surfaces were computed at the explicitly correlated coupled cluster with single, double, and scaled perturbative triple excitations level of theory. The method of interpolating moving least squares was used to construct 4D and 2D analytical PESs from these data. Both surfaces are characterized by deep wells and large anisotropies. Analytical models of the PESs were used in scattering calculations to obtain cross sections for low-lying rotational transitions. As could have been anticipated, important differences exist between the He and H2 cross sections. Conversely, no significant differences exist between the collisions of C6H- with the two species of H2 (para- and ortho-H2). We expect that these new data will help in accurately determining the abundance of the C6H- anions in space.

  10. Volumetric Properties of the Mixture Benzene C6H6 + C6H10O Cyclohexanone (VMSD1511, LB4829_V)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture Benzene C6H6 + C6H10O Cyclohexanone (VMSD1511, LB4829_V)' providing data from direct measurement of low-pressure thermodynamic speed of sound at variable mole fraction and constant temperature, in the single-phase region(s).

  11. Volumetric Properties of the Mixture Benzene C6H6 + C6H10O Cyclohexanone (VMSD1111, LB4819_V0029

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture Benzene C6H6 + C6H10O Cyclohexanone (VMSD1111, LB4819_V)' providing data from direct low-pressure measurement of mass density at variable mole fraction and constant temperature, in the single-phase region(s).

  12. Vapor-Liquid Equilibrium in the Mixture Cyclohexanone C6H10O + C6H12O Cyclohexanol (EVLM1111, LB5657_E)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume A 'Binary Liquid Systems of Nonelectrolytes I' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Vapor-Liquid Equilibrium in the Mixture Cyclohexanone C6H10O + C6H12O Cyclohexanol (EVLM1111, LB5657_E)' providing data from direct measurement of pressure at variable mole fraction in liquid phase and constant temperature.

  13. Volumetric Properties of the Mixture Benzene C6H6 + C6H10O Cyclohexanone (VMSD1212, LB4824_V)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture Benzene C6H6 + C6H10O Cyclohexanone (VMSD1212, LB4824_V)' providing data by calculation of molar excess volume from low-pressure density measurements at variable mole fraction and constant temperature.

  14. Heat of Mixing and Solution of Cyclohexanone C6H10O + C6H12O Cyclohexanol (HMSD1121, LB4187_H)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume A 'Binary Liquid Systems of Nonelectrolytes I' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Heat of Mixing and Solution of Cyclohexanone C6H10O + C6H12O Cyclohexanol (HMSD1121, LB4187_H)' providing data from direct calorimetric measurement of molar excess enthalpy at variable mole fraction and constant pressure and temperature.

  15. Blue photoluminescence enhancement in laser-irradiated 6H-SiC at room temperature

    SciTech Connect

    Wu, Yan; Ji, Lingfei Lin, Zhenyuan; Jiang, Yijian; Zhai, Tianrui

    2014-01-27

    Blue photoluminescence (PL) of 6H-SiC irradiated by an ultraviolet laser can be observed at room temperature in dark condition. PL spectra with Gaussian fitting curve of the irradiated SiC show that blue luminescence band (∼440 nm) is more pronounced than other bands. The blue PL enhancement is the combined result of the improved shallow N-donor energy level and the unique surface state with Si nanocrystals and graphene/Si composite due to the effect of photon energy input by the short-wavelength laser irradiation. The study can provide a promising route towards the preparation of well-controlled blue photoluminescence material for light-emitting devices.

  16. Experimental study of periodic flow effects on spanwise vortex

    NASA Astrophysics Data System (ADS)

    Garcia Molina, Cruz Daniel; Lopez Sanchez, Erick Javier; Ruiz Chavarria, Gerardo; Medina Ovando, Abraham

    2014-11-01

    We present an experimental study about the spanwise vortex produced in a flow going out of a channel in shallow waters. This vortex travels in front of the dipole. The velocity field measurement was done using the PIV technique, and DPIVsoft (https://www.irphe.fr/ ~meunier/) was used for data processing. In this case the flow has a periodic forcing to simulate ocean tides. The experiment was conducted in a channel with variable width and the measurements were made using three different values of the aspect ratio width-depth. We present results of the position, circulation of this spanwise vortex and the flow inversion effect. The change of flow direction modify the intensity of the vortex, but it does not destroy it. The vertical components of the velocity field contributes particle transport. G. Ruiz Chavarria, E. J. Lopez Sanchez and C. D. Garcia Molina acknowledge DGAPA-UNAM by support under project IN 116312 (Vorticidad y ondas no lineales en fluidos).

  17. Studying Short-Period Comets and Long-Period Comets Detected by WISE/NEOWISE

    NASA Astrophysics Data System (ADS)

    Kramer, Emily A.; Fernández, Yanga R.; Bauer, James M.; Stevenson, Rachel; Mainzer, Amy K.; Grav, Tommy; Masiero, Joseph; Walker, Russell G.; Lisse, Carey M.

    2014-11-01

    The Wide-field Infrared Survey Explorer (WISE) mission surveyed the sky in four infrared wavelength bands (3.4, 4.6, 12 and 22-micron) between January 2010 and February 2011 [1, 2]. During the mission, WISE serendipitously observed 160 comets, including 21 newly discovered objects. About 89 of the comets observed by WISE displayed a significant dust tail in the 12 and 22-micron (thermal emission) bands, showing a wide range of activity levels and dust morphology. Since the observed objects are a mix of both long-period comets (LPCs) and short-period comets (SPCs), differences in their activity can be used to better understand the thermal evolution that each of these populations has undergone. For the comets that displayed a significant dust tail, we have estimated the sizes and ages of the particles using dynamical models based on the Finson-Probstein method [3, 4]. For a selection of 40 comets, we have then compared these models to the data using a novel tail-fitting method that allows the best-fit model to be chosen analytically rather than subjectively. For comets that were observed multiple times by WISE, the dust tail particle properties were estimated separately, and then compared. We find that the dust tails of both LPCs and SPCs are primarily comprised of ~mm to cm sized particles, which were the result of emission that occurred several months to several years prior to the observations. The LPCs nearly all have strong dust emission close to the comet's perihelion distance, and the SPCs mostly have strong dust emission close to perihelion, but some have strong dust emission well before perihelion. Acknowledgments: This publication makes use of data products from (1) WISE, which is a joint project of UCLA and JPL/Caltech, funded by NASA; and (2) NEOWISE, which is a project of JPL/Caltech, funded by the Planetary Science Division of NASA. EK was supported by a NASA Earth and Space Sciences Fellowship. RS gratefully acknowledges support from the NASA

  18. Synthetic and 1H and 13C NMRSpectral Studies on N-(Mono-substitutedphenyl)- acetamides and Substituted Acetamides, 2/3/4-YC6H4NH-COCH3-iXi (Y = CH3, F, Cl, Br, NO2; X = Cl, CH3; i = 0, 1, 2, 3)

    NASA Astrophysics Data System (ADS)

    Gowda, Basavalinganadoddy Thimme; Lakshmipathy, Shilpa; Lakshmipathy, Jayalakshmi K.

    2006-11-01

    Nineteen N-(2/3/4-methyl/halo/nitro-phenyl)-acetamides and substituted acetamides, 2/3/4- YC6H4NH-CO-CH3-iXi (Y = CH3, F, Cl, Br or NO2; X = Cl or CH3 and i = 0, 1, 2 or 3), have been prepared, characterized, and their 1H and 13C NMR spectra in solution measured and correlated. 1H and 13C NMR chemical shifts were assigned to the protons and carbon atoms, respectively, in line with those for similar compounds. Since the chemical shifts are dependent on the electron density around the nucleus or associated with the atom to which it is bound, the incremental shifts of the aromatic protons or carbon atoms due to -NH-CO-CH3-iXi and -CO-CH3-iXi (X = Cl or CH3 and i = 0, 1, 2, 3) in all the N-phenyl-substituted acetamides, C6H5NH-CO-CH3-iXi, are calculated by comparing the proton or carbon chemical shifts of these compounds with those of benzene or aniline. The incremental shifts due to the groups in the parent compounds have also been computed by comparing the chemical shifts of the protons or carbon atoms in these compounds with those of benzene or aniline, respectively. The computed incremental shifts and other data were used to calculate the 1H and 13C NMR chemical shifts of the substituted compounds in three different ways. The calculated chemical shifts by the three methods compared well with each other and with the observed chemical shifts, testing the validity of the principle of additivity of the substituent effects in these compounds. The variation of 1H NMR chemical shifts of either the aromatic or N-H protons, with the substituents in N-(phenyl)- and N-(2/3/4-chloro/methylphenyl)-acetamides and substituted acetamides did not follow the same trend, while the variation of the 13C NMR chemical shifts of C-1 and C=O carbon atoms and those of alkyl carbon atoms of these compounds followed more or less the same trend.

  19. Conductivity compensation in p-6H-SiC in irradiation with 8-MeV protons

    SciTech Connect

    Lebedev, A. A.; Kozlovski, V. V.; Belov, S. V.; Bogdanova, E. V.; Oganesyan, G. A.

    2011-09-15

    Carrier removal rate (V{sub d}) in p-6H-SiC in its irradiation with 8-MeV protons has been studied. The p-6H-SiC samples were produced by sublimation in vacuum. V{sub d} was determined by analysis of capacitance-voltage characteristics and from results of Hall effect measurements. It was found that complete compensation of samples with initial value of N{sub a} - N{sub d} Almost-Equal-To 1.5 Multiplication-Sign 10{sup 18} cm{sup -3} occurs at an irradiation dose of {approx}1.1 Multiplication-Sign 10{sup 16} cm{sup -2}. In this case, the carrier removal rate was {approx}130 cm{sup -1}.

  20. Lateral Growth Expansion of 4H/6H-SiC m-plane Pseudo Fiber Crystals by Hot Wall CVD Epitaxy

    NASA Technical Reports Server (NTRS)

    Trunek, Andrew J.; Neudeck, Philip G.; Woodworth, Andrew A.; Powell, J. A.; Spry, David J.; Raghothamachar, Balaji; Dudley, Michael

    2011-01-01

    Lateral expansion of small mixed polytype 4H/6H-SiC slivers were realized by hot wall chemical vapor deposition (HWCVD). Small slivers cut from m-oriented ..11..00.. SiC boule slices containing regions of 4H and 6H SiC were exposed to HWCVD conditions using standard silane/propane chemistry for a period of up to eight hours. The slivers exhibited approximately 1500 microns (1.5 mm) of total lateral expansion. Initial analysis by synchrotron white beam x-ray topography (SWBXT) confirms, that the lateral growth was homoepitaxial, matching the polytype of the respective underlying region of the seed sliver.

  1. Vibrational properties of the trinuclear spin crossover complex [Fe3(4-(2'-hydroxy-ethyl)-1,2,4-triazole)6(H2O)6](CF3SO3)6: a nuclear inelastic scattering, IR, Raman and DFT study.

    PubMed

    Wolny, Juliusz A; Rackwitz, Sergej; Achterhold, Klaus; Garcia, Yann; Muffler, Kai; Naik, Anil D; Schünemann, Volker

    2010-11-28

    The vibrational properties of the trimeric iron complex [Fe(3)(4-(2'-hydroxy-ethyl)-1,2,4-triazole)(6)(H(2)O)(6)](CF(3)SO(3))(6) which serves as a model of the 1D iron coordination polymers based on 1,2,4-triazoles have been investigated by nuclear inelastic scattering of synchrotron radiation (NIS), as well as by Raman and infrared (IR) spectroscopy. The system reveals a soft spin crossover involving only the central iron atom with its FeN(6) core, while the terminal FeN(3)O(3) units show no spin transition. The NIS spectra of the central low-spin isomer exhibit a number of marker bands in the 350-450 cm(-1) region which have not been detected in the Raman spectra. The density functional theory (DFT) calculations allowed the assignment of these bands to Fe-N bending and stretching modes. A characteristic high-spin marker mode has been identified and discriminated from the iron-ligand modes of the terminal iron atoms. This characteristic central Fe-N mode has been observed experimentally at 245 cm(-1) and theoretically at 255 cm(-1). Contrary to mononuclear centrosymmetric Fe complexes, some of the symmetric vibrations of the trimeric complex involving iron movements are observed by NIS. Furthermore the DFT calculations displayed the importance of the coulombic repulsion between metal ions for the geometry and stability of a given spin isomer. PMID:20931141

  2. Blockage of ROS and NF-κB-mediated inflammation by a new chalcone L6H9 protects cardiomyocytes from hyperglycemia-induced injuries.

    PubMed

    Zhong, Peng; Wu, Lianpin; Qian, Yuanyuan; Fang, Qilu; Liang, Dandan; Wang, Jingying; Zeng, Chunlai; Wang, Yi; Liang, Guang

    2015-07-01

    Increased oxidative stress and cardiac inflammation have been implicated in the pathogenesis of diabetic cardiomyopathy (DCM). We previously found that a novel chalcone derivative, L6H9, was able to reduce LPS-induced inflammatory response in macrophages. This study was designed to investigate its protective effects on DCM and the underlying mechanisms. H9C2 cells were cultured with DMEM containing 33 mmol/L of glucose in the presence or absence of L6H9. Pretreatment with L6H9 significantly reduced high glucose-induced inflammatory cytokine expression, ROS level increase, mitochondrial dysfunction, cell apoptosis, fibrosis, and hypertrophy in H9c2 cells, which may be mediated by NF-κB inhibition and Nrf2 activation. In mice with STZ-induced diabetes, oral administration of L6H9 at 20 mg/kg/day for 8 weeks significantly decreased the cardiac cytokine and ROS level, accompanied by decreasing cardiac apoptosis and hypertrophy, and, finally, improved histological abnormalities and fibrosis, without affecting the hyperglycemia. L6H9 also attenuated the diabetes-induced NF-κB activation and Nrf2 decrease in diabetic hearts. These results strongly suggest that L6H9 may have great therapeutic potential in the treatment of DCM via blockage of inflammation and oxidative stress. This study also provides a deeper understanding of the regulatory role of Nrf2 and NF-κB in DCM, indicating that they may be important therapeutic targets for diabetic complications. PMID:25736300

  3. Atomic probe microscopy of 3C SiC films grown on 6H SiC substrates

    NASA Technical Reports Server (NTRS)

    Steckl, A. J.; Roth, M. D.; Powell, J. A.; Larkin, D. J.

    1993-01-01

    The surface of 3C SiC films grown on 6H SiC substrates has been studied by atomic probe microscopy in air. Atomic-scale images of the 3C SiC surface have been obtained by STM which confirm the 111 line type orientation of the cubic 3C layer grown on the 0001 plane type surface of the hexagonal 6H substrate. The nearest-neighbor atomic spacing for the 3C layer has been measured to be 3.29 +/- 0.2 A, which is within 7 percent of the bulk value. Shallow terraces in the 3C layer have been observed by STM to separate regions of very smooth growth in the vicinity of the 3C nucleation point from considerably rougher 3C surface regions. These terraces are oriented at right angles to the growth direction. Atomic force microscopy has been used to study etch pits present on the 6H substrate due to high temperature HCl cleaning prior to CVD growth of the 3C layer. The etch pits have hexagonal symmetry and vary in depth from 50 nm to 1 micron.

  4. Inelastic X-ray scattering from 6H-SiC

    SciTech Connect

    Macrander, A.T.; Blasdell, B.; Montano, P.A. |; Kao, C.C.

    1995-07-01

    The authors have studied electronic excitations in 6H-SiC using inelastic x-ray scattering. Inelastic scattering spectra were measured at momentum transfers ranging from 0.47 {angstrom}{sup {minus}1} to 2.00 {angstrom}{sup {minus}1} along the c-axis in the hexagonal lattice, i.e. , along [00{center_dot}1], and from 0.67 {angstrom}{sup {minus}1} to 2.00 {angstrom}{sup {minus}1} along the a-axis, i.e., alone, [10{center_dot}0]. Comparison of the two sets of data reveals an orientation dependence of the spectra, except for a characteristic peak at 22--23 eV that occurs for both directions at low Q. This peak has also been observed in electron energy loss spectroscopy studies and is identified as a bulk plasmon. The orientation dependence of the other spectral features is indicative of band structure effects. These data were obtained using a Ge(444) analyzer in a near backscattering geometry.

  5. Targeted Ablation of the Pde6h Gene in Mice Reveals Cross-species Differences in Cone and Rod Phototransduction Protein Isoform Inventory*

    PubMed Central

    Brennenstuhl, Christina; Tanimoto, Naoyuki; Burkard, Markus; Wagner, Rebecca; Bolz, Sylvia; Trifunovic, Dragana; Kabagema-Bilan, Clement; Paquet-Durand, Francois; Beck, Susanne C.; Huber, Gesine; Seeliger, Mathias W.; Ruth, Peter; Wissinger, Bernd; Lukowski, Robert

    2015-01-01

    Phosphodiesterase-6 (PDE6) is a multisubunit enzyme that plays a key role in the visual transduction cascade in rod and cone photoreceptors. Each type of photoreceptor utilizes discrete catalytic and inhibitory PDE6 subunits to fulfill its physiological tasks, i.e. the degradation of cyclic guanosine-3′,5′-monophosphate at specifically tuned rates and kinetics. Recently, the human PDE6H gene was identified as a novel locus for autosomal recessive (incomplete) color blindness. However, the three different classes of cones were not affected to the same extent. Short wave cone function was more preserved than middle and long wave cone function indicating that some basic regulation of the PDE6 multisubunit enzyme was maintained albeit by a unknown mechanism. To study normal and disease-related functions of cone Pde6h in vivo, we generated Pde6h knock-out (Pde6h−/−) mice. Expression of PDE6H in murine eyes was restricted to both outer segments and synaptic terminals of short and long/middle cone photoreceptors, whereas Pde6h−/− retinae remained PDE6H-negative. Combined in vivo assessment of retinal morphology with histomorphological analyses revealed a normal overall integrity of the retinal organization and an unaltered distribution of the different cone photoreceptor subtypes upon Pde6h ablation. In contrast to human patients, our electroretinographic examinations of Pde6h−/− mice suggest no defects in cone/rod-driven retinal signaling and therefore preserved visual functions. To this end, we were able to demonstrate the presence of rod PDE6G in cones indicating functional substitution of PDE6. The disparities between human and murine phenotypes caused by mutant Pde6h/PDE6H suggest species-to-species differences in the vulnerability of biochemical and neurosensory pathways of the visual signal transduction system. PMID:25739440

  6. CCD Photometric Study and Period Investigation of AH Tauri

    NASA Astrophysics Data System (ADS)

    Xiang, Fu-Yuan; Xiao, Ting-Yu; Yu, Yun-Xia

    2015-07-01

    In this paper, we present new CCD photometric observations of AH Tauri in the R band observed in 2006 at the Yunnan Observatory. Two new times of light minima were derived from these observations. We modeled the light curves using the 2003 version of the Wilson-Devinney program. The results show that the variations of the light curves can be expained by a cool spot on the primary star. The fill-out factor is about 6.6%, indicating that AH Tauri is a shallow-contact system. The mass ratio was determined to be about 0.505. In addition, the orbital period variations of AH Tauri were investigated based on all of the photoelectric and CCD light minimum times, including our two new data. It was found that the orbital period exhibits a possible periodic variation with a period of {P}{mod}=54.62\\(+/- 0.20) years and a secular period decrease of {dP}/{dt}=-(1.823+/- 0.215)× {10}-7 {days} {{yr}}-1. Since AH Tauri is an overcontact solar-like system, we discuss three mechanisms of the mass transfer, the light-time effect of the third body, and magnetic activity responsible for the orbital period changes.

  7. Quasi-periodic VLF emissions with short-period modulation and their relationship to whistlers: a case study

    NASA Astrophysics Data System (ADS)

    Titova, Elena; Demekhov, Andrei; Kozlovsky, Alexander; Manninen, Jyrki; Pasmanik, Dmitry

    We study properties of quasiperiodic (QP) VLF emissions recorded on December 24, 2011 during the VLF campaign in Northern Finland. The main attention is paid to interrelationships between different characteristic periods in the QP spectra. In particular, we analyze regular variations in the QP repetition intervals (1 - 10 min) during the event from 15:30 to 22 UT, their changes during substorms, and short periodic (several-second) modulation observed within separate QP elements. We explained the variations of periods of QP emissions in terms of the model of auto-oscillation regime of the cyclotron instability in the magnetosphere. During the considered event lasting about 7 hours we observed a regular increase in the time intervals between the QP elements. We relate this increase with weakening of the magnetospheric source of energetic electrons. Significant variations in the QP period occurred during substorms. These variations can be due to a substorm-related increase in the energetic-electron flux and/or due to the precipitation of these electrons into the ionosphere which changes the reflection coefficient of VLF waves. We analyze the fine structure of QP element spectra and reveal the periods related to the time scales of guided propagation of whistler-mode waves along the magnetic field line, which suggests that ducted propagation regime took place for the QP emissions. The periods were about 6--9 s for frequencies 3.5--1.2 kHz respectively, which was similar to the period of almost simultaneously observed two-hop whistlers In the low-frequency part of QP spectra periodic emissions with меньшими periods of about 3 s were observed. Analysis of fine structure of QP elements shows that their formation is affected by both linear effects (i.e., group-velocity dispersion) and nonlinear effects related

  8. 3d electron transitions in Co- and Ni-doped MgSO3·6H2O

    NASA Astrophysics Data System (ADS)

    Petkova, P.; Bunzarov, Zh; Iliev, I.; Dimov, T.; Tzoukrovsky, Y.

    2012-05-01

    Absorption spectra of magnesium sulfite hexahydrate (MgSO3·6H2O), doped with Co and Ni, have been studied in the spectral region 1.46-3.1 eV. Investigations have been carried out with linear polarized light E||c, E⊥c (c is the optical axis of MgSO3·6H2O) that propagates in the (1210) direction. The Co structure manifests in the spectral region 2.06-3.1 eV and the Ni structures manifest in the spectral region 1.46-2.26 eV. The peculiarities of the Jahn-Teller effect and spin-orbit interaction with respect to the impurity ions in the crystal lattice of MgSO3·6H2O are analyzed and discussed. The electron transitions in Co2+ and Ni2+ ions are determined for E||c, E⊥c. The crystal field parameter Dq and Racah parameters B and C are also calculated.

  9. A first-principles study on the B{sub 5}O{sub 5}{sup +/0} and B{sub 5}O{sub 5}{sup −} clusters: The boron oxide analogs of C{sub 6}H{sub 5}{sup +/0} and CH{sub 3}Cl

    SciTech Connect

    Tian, Wen-Juan; You, Xue-Rui; Ou, Ting; Chen, Qiang; Li, Si-Dian; Li, Da-Zhi; Zhai, Hua-Jin

    2015-08-14

    The concept of boronyl (BO) and the BO/H isolobal analogy build an interesting structural link between boron oxide clusters and hydrocarbons. Based upon global-minimum searches and first-principles electronic structural calculations, we present here the perfectly planar C{sub 2v} B{sub 5}O{sub 5}{sup +} (1, {sup 1}A{sub 1}), C{sub 2v} B{sub 5}O{sub 5} (2, {sup 2}A{sub 1}), and tetrahedral C{sub s} B{sub 5}O{sub 5}{sup −} (3, {sup 1}A′) clusters, which are the global minima of the systems. Structural and molecular orbital analyses indicate that C{sub 2v} B{sub 5}O{sub 5}{sup +} (1) [B{sub 3}O{sub 3}(BO){sub 2}{sup +}] and C{sub 2v} B{sub 5}O{sub 5} (2) [B{sub 3}O{sub 3}(BO){sub 2}] feature an aromatic six-membered boroxol (B{sub 3}O{sub 3}) ring as the core with two equivalent boronyl terminals, similar to the recently reported boronyl boroxine D{sub 3h} B{sub 6}O{sub 6} [B{sub 3}O{sub 3}(BO){sub 3}]; whereas C{sub s} B{sub 5}O{sub 5}{sup −} (3) [B(BO){sub 3}(OBO){sup −}] is characterized with a tetrahedral B{sup −} center, terminated with three BO groups and one OBO unit, similar to the previously predicted boronyl methane T{sub d} B{sub 5}O{sub 4}{sup −} [B(BO){sub 4}{sup −}]. Alternatively, the 1–3 clusters can be viewed as the boron oxide analogs of phenyl cation C{sub 6}H{sub 5}{sup +}, phenyl radical C{sub 6}H{sub 5}, and chloromethane CH{sub 3}Cl, respectively. Chemical bonding analyses also reveal a dual three-center four-electron (3c-4e) π hyperbond in C{sub s} B{sub 5}O{sub 5}{sup −} (3). The infrared absorption spectra of B{sub 5}O{sub 5}{sup +} (1), B{sub 5}O{sub 5} (2), and B{sub 5}O{sub 5}{sup −} (3) and anion photoelectron spectrum of B{sub 5}O{sub 5}{sup −} (3) are predicted to facilitate their forthcoming experimental characterizations. The present work completes the B{sub n}O{sub n}{sup +/0/−} series for n = 1–6 and enriches the analogous relationship between boron oxides and hydrocarbons.

  10. [Study on optimal harvest period of Lonicera Flos (Lonicera macranthoides)].

    PubMed

    Li, Long-Yun; Zhang, Ying; Ma, Peng; Wu, Ye-Kuan

    2014-08-01

    To ascertain the optimal harvest period of Lonicera Flos (Lonicera macranthoides) the configuration yield and quality of L. macranthiodes bloom verity and bud verity flower at different develop periods were Observed. The quality of L. macranthiodes which harvested at different times of the day was Compared. The configuration was significant difference between different develop period of L. macranthiodes flower. As bud growth, yield increased. Bloom verity of L. macranthoides chlorogenic acid content was significantly lower after opening (silver flower stage, golden flower stage), before opening (young bud stage, green-white stage) have no significant difference of the quality. Bud verity of L. macranthoides macranthoidin B is significant lower at yellow-white stage, young bud stage and green-white stage have no significant difference of the quality. The chlorogenic acid and isochlorogenic acid A content is significant difference between L. macranthoides harvested at different time of the day. The optimal harvest period of bloom verity is the white stage, picking time for 10:00 before and after 18:00. The optimal harvest period is the green-white stage, picking time is 8:00 before and after 18:00.

  11. CCD photometric study and period investigation of V508 Oph

    SciTech Connect

    Xiang, Fu-Yuan; Yu, Yun-Xia; Xiao, Ting-Yu

    2015-02-01

    In this paper, new CCD photometric observations of V508 Oph obtained in 2009 and 2010 at the Xinglong Observatory are presented. From the new observations, six new times of minimum light were derived. The light curves were analyzed by using the 2003 version of the Wilson–Devinney program. It is found that the asymmetric light curves can be modeled by a hot spot on the secondary component. The degree of overcontact is 15.4%, implying that the system is a shallow-contact binary. Combining the new times of minimum light with the photoelectric and CCD data compiled from the database, we investigate its orbital period. The results show that the orbital period may be undergoing multiple changes: a long-term decrease at a rate of dP/dt=−(1.502±0.063)×10{sup −7} days year{sup −1}, and a small periodic variation with a period of 24.27(±0.34) years. Since V508 Oph is an overcontact system and both components are late-type stars, we discuss the possible connection between the mass transfer, magnetic activity, the third body, and the orbital period changes.

  12. Damage Accumulation and Annealing in 6H-SiC Irradiated with Si+

    SciTech Connect

    Jiang, Weilin; Weber, William J.; Thevuthasan, Suntharampillai; McCready, David E.

    1998-10-01

    Damage accumulation and annealing in 6H-silicon carbide (alpha-SiC) single crystals have been studied in situ using 2.0 MeV HeRBS in a <0001>-axial channeling geometry (RBS/C). The damage was induced by 550 keV Si ion implantation (30 degrees off normal) at a temperature of -110 degrees C, and the damage recovery was investigated by subsequent isochromal annealing (20 min) over the temperature range from -110 degrees C to 900 degrees C. At ion fluences below 7.5 X 10 13 Si/cm (0.04 dpa in the damage peak), only point defects appear to be created. Furthermore, the defects on the Si sublattice can be completely recovered by thermal annealing at room temperature (RT), and recovery of defects on the C sublattice is suggested. At higher fluences of 6.6 x 10 15 Si/cm (-90 degrees C), an amorphous layer is created from the surface to a depth of 0.6 mu-m. Because of recovery processes at the buried crystalline-amorphous interface, the apparent thickness of this amorphous layer decreases slightly (<10%) with increasing temperature over the range from -90 degrees C to 600 degrees C.

  13. High-voltage 6H-SiC p-n junction diodes

    NASA Technical Reports Server (NTRS)

    Matus, L. G.; Powell, J. A.; Salupo, C. S.

    1991-01-01

    A chemical vapor deposition (CVD) process has been used to produce device structures of n- and p-type 6H-SiC epitaxial layers on commercially produced single-crystal 6H-SiC wafers. Mesa-style p-n junction diodes were successfully fabricated from these device structures using reactive ion etching, oxide passivation, and electrical contact metallization techniques. When tested in air, the 6H-SiC diodes displayed excellent rectification characteristics up to the highest temperature tested, 600 C. To observe avalanche breakdown of the p-n junction diodes, testing under a high-electrical-strength liquid was necessary. The avalanche breakdown voltage was 1000 V representing the highest reverse breakdown voltage to be reported for any CVD-grown SiC diode.

  14. Epitaxial growth of 6H silicon carbide in the temperature range 1320 C to 1390 C

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    High-quality epitaxial layers of 6H SiC have been grown on 6H SiC substrates with the grown direction perpendicular to the crystal c-axis. The growth was by chemical vapor deposition from methyltrichlorosilane (CH3SiCl3) in hydrogen at temperatures in the range of 1320 to 1390 C. Epitaxial layers up to 80 microns thick were grown at rates of 0.4 microns/min. Attempts at growth on the (0001) plane of 6H SiC substrates under similar conditions resulted in polycrystalline cubic SiC layers. Optical and X-ray diffraction techniques were used to characterize the grown layers.

  15. Studies of Long Period Variability in Neutron Star HMXB Systems

    NASA Technical Reports Server (NTRS)

    Heindl, William A.

    1998-01-01

    The purpose of this effort was to investigate the long term, quasi-periodic variability of the X-ray emission from the accreting X-ray pulsars LMC X-4 and SMC X-1. These high mass X-ray binary (HMXB) sources are known to vary in a nearly periodic fashion with cycle lengths of about 30 and 60 days respectively. The prevailing model for such behavior is that it is due to the precession of a tilted accretion disk around the neutron star which is the source of the X-ray emission. As the disk precesses, it periodically obscures the emitting region, resulting in reduced flux as observed at the Earth. The obscuration is not strictly periodic, as the disk precession period changes as the total mass and size of the disk change through variable accretion processes. This model is well established for the long-period variability in the X-ray pulsar Her X-1. With this work, my collaborators and I sought to test whether this model works for LMC X-4 and SMC X-1. Observations with the pointed instruments on the Rossi X-ray Timing Explorer (RXTE) were carried out in order to observe changes in the X-ray spectrum and total flux which were correlated with the long period cycles in these objects. One of the main predictions of the precessing disk model is that the periods of low emission are caused not by changes in the central source, but by increased absorption of that flux as seen at the Earth. Such behavior would be observed in the X-ray spectrum as a relative lack of low energy X-rays (which are more easily absorbed) as compared to high energy X-rays. This is what was observed for SMC X-1, landing strong support to the precessing disk model for this system. For LMC X-1, however, the absorption was consistent with zero at the time of minimum flux. The entire spectrum appeared to be equally reduced. This is not supporting evidence for the model. However, it also does not rule out a precessing disk. If at the time of minimum flux, the intervening disk is so thick that no flux, even

  16. First light curve and period study of LO Andromedae

    NASA Astrophysics Data System (ADS)

    Gürol, B.; Müyesseroğlu, Z.

    2005-01-01

    New BV light curves and times of minimum light for the short period W UMa system LO And were analyzed to derive the preliminary physical parameters of the system. The light curves were obtained at Ankara University Observatory during 5 nights in 2003. A new ephemeris is determined for the times of primary minimum. The analysis of the light curves is made using the Wilson-Devinney 2003 code. The present solution reveals that LO And has a photometric mass ratio q = 0.371 and is an A-type contact binary. The period of the system is still increasing, which can be attributed to light-time effect and mass transfer between the components. With the assumption of coplanar orbit of the third body the revealed mass is M3 = 0.21M. If the period change dP/dt = 0.0212 sec/yr is caused only by the mass transfer between components (from the lighter component to the heavier) the calculated mass transfer rate is dm/dt = 1.682 10-7M/yr. The absolute radii and masses estimated for the components, based on our photometric solution and the absolute parameters of the systems which have nearly same period are R1 = 1.30R, R2 = 0.85R, M1 = 1.31M, M2 = 0.49M respectively for the primary and secondary components.

  17. Numerical modelling and simulation of non-uniformly doped channel 6H-silicon carbide MOSFET

    NASA Astrophysics Data System (ADS)

    Kaushik, Navneet; Haldar, Subhasis; Gupta, Mridula; Gupta, R. S.

    2004-03-01

    An improved model for the non-uniformly doped channel 6H-SiC MOSFET incorporating the incomplete ionization of the dopant impurities using the Fermi-Dirac statistics is developed. The charge-sheet approach is used to evaluate the surface potential, quasi-fermi level, drain current and transconductance for all regions of operation, i.e. subthreshold, linear and saturation. Results so obtained are matched well with the simulated data for two different doping profiles. The improved model will be suitable for CAD (computer aided design) applications to predict the behaviour of the 6H-SiC MOSFET prior to actual device fabrication.

  18. Shubnikov-de Haas oscillations in a new dual-layered quasi-two-dimensional organic metal (BETS)4CoBr4(C6H4Cl2)

    NASA Astrophysics Data System (ADS)

    Lyubovskii, R. B.; Pesotskii, S. I.; Shilov, G. V.; Zhilyaeva, E. I.; Flakina, A. M.; Lyubovskaya, R. N.

    2013-10-01

    The interlayer and intralayer resistances and Shubnikov-de Haas oscillations in a new dual-layered quasi-two-dimensional organic metal (BETS)4CoBr4(C6H4Cl2) with a periodically varying structure of cation layers have been studied. It has been shown that the interlayer resistivity corresponds to an incoherent or weakly incoherent transport regime. The oscillations of the magnetoresistance have been described by a model of a chain of coherent magnetic breakdown orbits taking into account the quantum interference effect. The behavior of the interlayer transport, as well as quantum oscillations, is in good agreement with the theoretical calculations of the band structure.

  19. Hypokalemic periodic paralysis. A single fiber electromyographic study.

    PubMed

    De Grandis, D; Fiaschi, A; Tomelleri, G; Orrico, D

    1978-06-01

    The neurophysiological findings obtained with standard electromyography (EMG) and single fiber EMG (SFEMG) in a case of hypokalemic periodic paralysis (HoPP) are reported. During the period between paralytic attacks the only abnormalities consisted of scanty fibrillation potentials and, with SFEMG, a fiber density increase. In the first stage of an induced paralytic attack the most striking feature was decrease in fiber density, slight increase in jitter with several blocks. These results indicate a failure of the membrane surface to propagate an action potential. In some fibers the block is likely to be permanent, thus explaining the decrease in fiber density. The jitter increase is due to a slight abnormality at the synaptic site or to a variation in the propagation velocity of the muscle fiber. PMID:690662

  20. Silicon vacancy-related centers in non-irradiated 6H-SiC nanostructure

    SciTech Connect

    Bagraev, N. T. Danilovskii, E. Yu.; Gets, D. S.; Kalabukhova, E. N.; Klyachkin, L. E.; Koudryavtsev, A. A.; Malyarenko, A. M.; Mashkov, V. A.; Savchenko, D. V.; Shanina, B. D.

    2015-05-15

    We present the first findings of the silicon vacancy related centers identified in the non-irradiated 6H-SiC nanostructure using the electron spin resonance (ESR) and electrically-detected (ED) ESR technique. This planar 6H-SiC nanostructure represents the ultra-narrow p-type quantum well confined by the δ-barriers heavily doped with boron on the surface of the n-type 6H-SiC(0001) wafer. The new EDESR technique by measuring the only magnetoresistance of the 6H-SiC nanostructure under the high frequency generation from the δ-barriers appears to allow the identification of the isolated silicon vacancy centers as well as the triplet center with spin state S = 1. The same triplet center that is characterized by the large value of the zero-field splitting constant D and anisotropic g-factor is revealed by the ESR (X-band) method. The hyperfine (HF) lines in the ESR and EDESR spectra originating from the HF interaction with the {sup 14}N nucleus seem to attribute this triplet center to the N-V{sub Si} defect.

  1. Light curve and period study of V Trianguli

    NASA Astrophysics Data System (ADS)

    Gürol, B.; Müyesseroğlu, Z.; Özdemir, T.

    2006-08-01

    New BVR light curves and times of minimum light for the short period β Lyrae system V Tri were analyzed to derive the physical parameters of the system. The light curves were obtained at Ankara University Observatory and at the TÜBİTAK National Observatory during 5 nights in 2001 and 2002. A new ephemeris is determined for the times of primary minimum. The analysis of the light curves is made using the Wilson-Devinney 2003 code. The present solution reveals that V Tri is a near-contact system with a mass ratio near 0.5. The absolute radii and masses estimated for the components, based on our photometric solution, are R1=1.94 Rsun, R2=1.44 Rsun, M1=2.68 Msun, M2=1.36 Msun, respectively, for the primary and secondary components. The period variation of the system can be attributed to the light-time effect. With the assumption of a coplanar orbit of the third body its revealed mass is m3=0.17 Msun.

  2. Hidden Superlattice in Tl2(SC6H4S) and Tl2(SeC6H4Se) Solved from Powder X-ray Diffraction

    SciTech Connect

    K Stone; D Turner; M Singh; T Vaid; P Stephens

    2011-12-31

    The crystal structures of the isostructural title compounds poly[({mu}-benzene-1,4-dithiolato)dithallium], Tl{sub 2}(SC{sub 6}H{sub 4}S), and poly[({mu}-benzene-1,4-diselenolato)dithallium], Tl{sub 2}(SeC{sub 6}H{sub 4}Se), were solved by simulated annealing from high-resolution synchrotron X-ray powder diffraction. Rietveld refinements of an initial structure with one formula unit per triclinic cell gave satisfactory agreement with the data, but led to a structure with impossibly close non-bonded contacts. A disordered model was proposed to alleviate this problem, but an alternative supercell structure leads to slightly improved agreement with the data. The isostructural superlattice structures were confirmed for both compounds through additional data collection, with substantially better counting statistics, which revealed the presence of very weak superlattice peaks not previously seen. Overall, each structure contains Tl-S or Tl-Se two-dimensional networks, connected by phenylene bridges. The sulfur (or selenium) coordination sphere around each thallium is a highly distorted square pyramid or a 'see-saw' shape, depending upon how many Tl-S or Tl-Se interactions are considered to be bonds. In addition, the two compounds contain pairs of Tl{sup I} ions that interact through a closed-shell 'thallophilic' interaction: in the sulfur compound there are two inequivalent pairs of Tl atoms with Tl-Tl distances of 3.49 and 3.58 {angstrom}, while in the selenium compound those Tl-Tl interactions are at 3.54 and 3.63 {angstrom}.

  3. Dimensional isotropy of 6H and 3C SiC under neutron irradiation

    DOE PAGES

    Snead, Lance L.; Katoh, Yutai; Koyanagi, Takaaki; Terrani, Kurt A.; Specht, Eliot D.

    2016-01-16

    This investigation experimentally determines the as-irradiated crystal axes dimensional change of the common polytypes of SiC considered for nuclear application. Single crystal α-SiC (6H), β-SiC (3C), CVD β-SiC, and single crystal Si have been neutron irradiated near 60 °C from 2 × 1023 to 2 × 1026 n/m2 (E > 0.1 MeV), or about 0.02–20 dpa, in order to study the effect of irradiation on bulk swelling and strain along independent crystalline axes. Single crystal, powder diffractometry and density measurement have been carried out. For all neutron doses where the samples remained crystalline all SiC materials demonstrated equivalent swelling behavior.more » Moreover the 6H–SiC expanded isotropically. The magnitude of the swelling followed a ~0.77 power law against dose consistent with a microstructure evolution driven by single interstitial (carbon) mobility. Extraordinarily large ~7.8% volume expansion in SiC was observed prior to amorphization. Above ~0.9 × 1025 n/m2 (E > 0.1 MeV) all SiC materials became amorphous with an identical swelling: a 11.7% volume expansion, lowering the density to 2.84 g/cm3. As a result, the as-amorphized density was the same at the 2 × 1025 and 2 × 1026 n/m2 (E > 0.1 MeV) dose levels.« less

  4. Periodic trends in bond dissociation energies. A theoretical study.

    PubMed

    Mó, Otilia; Yáñez, Manuel; Eckert-Maksić, Mirjana; Maksić, Zvonimir B; Alkorta, Ibón; Elguero, José

    2005-05-19

    Bond dissociation energies (BDEs) of all possible A-X single bonds involving the first- and second-row atoms, from Li to Cl, where the free valences are saturated by hydrogens, have been estimated through the use of the G3-theory and at the B3LYP/6-311+G(3df,2pd)//B3LYP/6-31G(2df,p) DFT level of theory. BDEs exhibit a periodical behavior. The A-X (A = Li, Be, B, Na, Mg, Al, and Si) BDEs show a steady increase along the first and the second row of the periodic table as a function of the atomic number Z(X). For A-X bonds involving electronegative atoms (A = C, N, O, F, P, S, and Cl) the bond energies achieve a maximum around Z(X) = 5. The same behavior is observed when BDEs are plotted against the electronegativity chi(X) of the atom X. Thus, for A-X bonds (A = Li, Be, B, Na, Mg, Al, Si), the BDEs for a fixed A increases, grosso modo, as the electronegativity differences between X and A increase, with some exceptions, which reflect the differences in the relaxation energies of the radicals produced upon the bond cleavage. A similar trend, albeit less pronounced, is found for single A-X bonds, where A = C, N, O, F, P, S, and Cl. However, there is an additional feature embodied in the enhancement of the strength of the A-boron bonds due to the ability of boron to act as a strong electron acceptor. The trends in bond lengths and charge densities at the bond critical points are in line with the aforementioned behavior.

  5. Si6H12/Polymer Inks for Electrospinning a-Si Nanowire Lithium Ion Battery Anodes

    SciTech Connect

    Schulz, Douglas L.; Hoey, Justin; Smith, Jeremiah; Elangovan, Arumugasamy; Wu, Xiangfa; Akhatov, Iskander; Payne, Scott; Moore, Jayma; Boudjouk, Philip; Pederson, Larry; Xiao, Jie; Zhang, Jiguang

    2010-08-04

    Amorphous silicon nanowires 'a-SiNWs' have been prepared by electrospinning a liquid silane-based precursor. Cyclohexasilane 'Si6H12' was admixed with poly-methyl methacrylate (PMMA) in toluene giving an ink that was electrospun into the Si6H12/PPMA wires with diameters of 50-2000 nm. Raman spectroscopy revealed that thermal treatment at 350 C transforms this deposit into a-SiNWs. These materials were coated with a thin carbon layer and then tested as half-cells where a reasonable plateau in electrochemical cycling was observed after an initial capacity fade. Additionally, porous a-SiNWs were realized when the thermally decomposable binder polypropylene carbonate/polycyclohexene carbonate was used as the polymer carrier.

  6. The low frequency dynamics of supercooled LiBr, 6H2O

    NASA Astrophysics Data System (ADS)

    Bove, L.; Dreyfus, C.; Polian, A.; Bonello, B.; Malfanti, I.; Taschin, A.; Torre, R.; Pick, R. M.

    2011-01-01

    We present results of a series of experiments performed on LiBr, 6H20 from room temperature down to 172 K ≈ 1.2Tg. These ultrasound, Brillouin and depolarized light scattering, and transient grating experiments show that, above 215 K, this solution behaves like supercooled water: its zero frequency sound velocity C0 continuously decreases with decreasing temperature, and the reorientational dynamics of the water molecules can be directly detected at some temperatures of this domain. Conversely, below 215 K, a new regime sets in, where the apparent C0 is practically temperature independent and where a β, Arrenhius like, relaxation process coexists with the usual, Vogel-Fulcher like, α relaxation process of the supercooled liquid. These results are similar to those recently obtained in LiCl, 6H2O. The onset of the new regime is possibly due to an increase of the interaction of the water molecules with a neighboring Li+ ion when lowering the temperature. We also compare our results with published dielectric data on water solutions of glass forming polyalcohols. Some of them present a low temperature splitting of their relaxation time similar to what is found in LiBr, 6H2O.

  7. 6H-SiC microdisk torsional resonators in a "smart-cut" technology

    NASA Astrophysics Data System (ADS)

    Yang, Rui; Wang, Zenghui; Lee, Jaesung; Ladhane, Kalyan; Young, Darrin J.; Feng, Philip X.-L.

    2014-03-01

    We report on experimental demonstration of high frequency torsional resonators based on microdisk structures enabled by a "smart-cut" 6H-silicon carbide (6H-SiC) technology. Circular microdisks axially supported by pairs of thin tethers, with diameters of ˜5-15 μm, exhibit torsional-mode micromechanical resonances with frequency of ˜1-60 MHz, and quality (Q) factors up to 1280 at room temperature in moderate vacuum (˜10 mTorr). Measured intrinsic thermomechanical vibrations of a microdisk with diameter d ≈ 15.9 μm (and triangular cross-section tethers with width wT ≈ 1.5 μm, length LT ≈ 2 μm, and thickness tT ≈ 0.4 μm) demonstrate a torque resolution of ST1/2 ≈ 3.7 × 10-20 (N m)/√Hz, a force sensitivity of SF1/2 ≈ 5.7fN/√Hz, and an angular displacement sensitivity of Sθ1/2 ≈ 4.0 × 10-8 rad/√Hz. By examining devices with varying disk size, different tether shape, width, and length, and by combining experimental data and theoretical calculations, we depict the scaling pathways for ultrasensitive torsional resonant sensors based on this smart-cut 6H-SiC platform.

  8. Palladium and nickel interactions with stepped 6H-silicon carbide

    NASA Astrophysics Data System (ADS)

    Woodworth, Andrew A.

    Silicon carbide (SiC) has long been recognized as a semiconductor with potential for use in a number of demanding environments. Recent developments in the quality of bulk grown 6H-SiC (and other hexagonal poly-types) have increased interest in issues surrounding the stability of device structures that operate at temperatures in excess of 600°C. It has been observed that the performance of metal-semiconductor devices created on SiC tend to degrade when operating at these temperatures. This change in device performance has been linked to inter-diffusion and reaction at the metal-semiconductor interface. Most of these devices have been fabricated on SiC substrates with surface and sub-surface damage associated with the polishing process (standard surfaces). Recent studies have shown that high temperature hydrogen etching of these substrates removes this damage and produces surfaces with wide atomically flat terraces and nanometer scale steps (stepped surfaces). The basic question this poses is, can such improvements in substrate quality lead to improvements in device performance. The goal of this research is to better understand the interaction of metals on these stepped surfaces. To accomplish this, detailed surface studies of thermally induced Pd-SiC and Ni-SiC surface interactions have been performed on both the standard and stepped surfaces. The metal films range in thickness from the monolayer level (˜0.4 nm) to actual device dimensions (˜50 nm) and are deposited under ultrahigh vacuum conditions at ˜50°C. These films were characterized in-situ using Auger electron spectroscopy both before and after annealing at 670°C for Pd and 700°C for Ni. The Auger lineshapes provide quantitative and qualitative information on the chemistry of the reaction products. Ex-situ atomic force microscopy was used to characterize changes in surface morphology. The results of these experiments yield important insights into the nature of the transport process at the metal

  9. The QTAIM approach to chemical bonding between transition metals and carbocyclic rings: a combined experimental and theoretical study of (eta(5)-C5H5)Mn(CO)3, (eta(6)-C6H6)Cr(CO)3, and (E)-{(eta(5)-C5H4)CF=CF(eta(5)-C5H4)}(eta(5)-C5H5)2Fe2.

    PubMed

    Farrugia, Louis J; Evans, Cameron; Lentz, Dieter; Roemer, Max

    2009-01-28

    Experimental charge densities for (C(5)H(5))Mn(CO)(3) (2), (eta(6)-C(6)H(6))Cr(CO)(3) (3), and (E)-{(eta(5)-C(5)H(4))CF=CF(eta(5)-C(5)H(4))}(eta(5)-C(5)H(5))(2)Fe(2) (4) have been obtained by multipole refinement of high-resolution X-ray diffraction data at 100 K. The resultant densities were analyzed using the quantum theory of atoms in molecules (QTAIM). The electronic structures of these and related pi-hydrocarbyl complexes have also been studied by ab initio density functional theory calculations, and a generally good agreement between theory and experiment with respect to the topological parameters was observed. The topological parameters indicate significant metal-ring covalency. A consistent area of disagreement concerns the topology of the metal-ring interactions. It is shown that because of the shared-shell bonding between the metal and the ring carbons, an annulus of very flat density rho and very small wedge rho is formed, which leads to topologically unstable structures close to catastrophe points. This in turn leads to unpredictable numbers of metal-C bond paths for ring sizes greater than four and fewer M-C bond paths than expected on the basis of the formal hapticity. This topological instability is a general feature of metal-pi-hydrocarbyl interactions and means that a localized approach based on individual M-C(ring) bond paths does not provide a definitive picture of the chemical bonding in these systems. However, other QTAIM indicators, such as the virial paths, the delocalization indices, and the source function, clearly demonstrate that for the n-hapto (eta(n)-C(n)H(n))M unit, there is generally a very similar level of chemical bonding for all M-C(ring) interactions, as expected on the basis of chemical experience.

  10. Iodine assisted retainment of implanted silver in 6H-SiC at high temperatures

    NASA Astrophysics Data System (ADS)

    Hlatshwayo, T. T.; van der Berg, N. G.; Msimanga, M.; Malherbe, J. B.; Kuhudzai, R. J.

    2014-09-01

    The effect of high temperature thermal annealing on the retainment and diffusion behaviour of iodine (I) and silver (Ag) both individually and co-implanted into 6H-SiC has been investigated using RBS, RBS-C and heavy ion ERDA (Elastic Recoil Detection Analysis). Iodine and silver ions at 360 keV were both individually and co-implanted into 6H-SiC at room temperature to fluences of the order of 1 × 1016 cm-2. RBS analyses of the as-implanted samples indicated that implantation of Ag and of I and co-implantation of 131I and 109Ag at room temperature resulted in complete amorphization of 6H-SiC from the surface to a depth of about 290 nm for the co-implanted samples. Annealing at 1500 °C for 30 h (also with samples annealed at 1700 °C for 5 h) caused diffusion accompanied by some loss of both species at the surface with some iodine remaining in the iodine implanted samples. In the Ag implanted samples, the RBS spectra showed that all the Ag disappeared. SEM images showed different recrystallization behaviour for all three sets of samples, with larger faceted crystals appearing in the SiC samples containing iodine. Heavy Ion ERDA analyses showed that both 109Ag and 131I remained in the co-implanted SiC samples after annealing at 1500 °C for 30 h. Therefore, iodine assisted in the retainment of silver in SiC even at high temperature.

  11. On the calculation of the vibrational frequencies of C6H4

    NASA Astrophysics Data System (ADS)

    Bauschlicher, Charles W.; Ricca, Alessandra

    2013-04-01

    DFT and CCSD(T) frequencies are compared with experiment for ortho-benzyne (C6H4). Four bands are found to be in disagreement with experiment at the DFT level. Surprisingly the CCSD(T) method only brings the triple bond stretch into agreement with experiment, but leaves a sizable difference with experiment for the other three bands. The results for three isotopologues suggests that all of the differences cannot be attributed to resonances. Additional experimental work on ortho-benzyne appears warranted.

  12. Experimental charge-density study on the nickel(II) coordination complex [Ni(H3L)][NO3][PF6] [H3L = N,N',N''-tris(2-hydroxy-3-methylbutyl)-1,4,7-triazacyclononane]: a reappraisal.

    PubMed

    Farrugia, L J; Frampton, C S; Howard, J A K; Mallinson, P R; Peacock, R D; Smith, G T; Stewart, B

    2006-04-01

    The experimental charge density in the title complex has been re-examined. The original work, reported some 8 years ago [Smith et al. (1997). J. Am. Chem. Soc. 119, 5028-5034], was undertaken using a very early version of the XD software, which contained serious programming errors. A re-refinement, using the original data and a recent version of the XD software, shows that many of the unusual aspects of this earlier study are artefacts due to these programming errors. The topological properties of the newly obtained experimental density compare well with those calculated from a theoretical DFT (density-functional theory) UHF-SCF (unrestricted Hartree Fock-self-consistent field) density. This report corrects several erroneous conclusions regarding the charge density in the title complex--in particular, the highly unusual diffuse Laplacian distribution about the Ni atom, and the trifurcated bond path from the Ni atom to the alcohol oxygen donor atoms are no longer observed. An examination of a range of topological properties of the metal-ligand bonds leads to the conclusion that the Ni-N and Ni-O bonds have an intermediate character, with a significant shared interaction, but with a substantial ionic component. This new study also reveals a previously unrecognized intramolecular H...H interaction in the macrocyclic ligand. PMID:16552157

  13. Gas-phase synthesis of the benzyl radical (C(6)H(5)CH(2)).

    PubMed

    Dangi, Beni B; Parker, Dorian S N; Yang, Tao; Kaiser, Ralf I; Mebel, Alexander M

    2014-04-25

    Dicarbon (C2 ), the simplest bare carbon molecule, is ubiquitous in the interstellar medium and in combustion flames. A gas-phase synthesis is presented of the benzyl radical (C6 H5 CH2 ) by the crossed molecular beam reaction of dicarbon, C2 (X(1) Σg (+) , a(3) Πu ), with 2-methyl-1,3-butadiene (isoprene; C5 H8 ; X(1) A') accessing the triplet and singlet C7 H8 potential energy surfaces (PESs) under single collision conditions. The experimental data combined with ab initio and statistical calculations reveal the underlying reaction mechanism and chemical dynamics. On the singlet and triplet surfaces, the reactions involve indirect scattering dynamics and are initiated by the barrierless addition of dicarbon to the carbon-carbon double bond of the 2-methyl-1,3-butadiene molecule. These initial addition complexes rearrange via multiple isomerization steps, leading eventually to the formation of C7 H7 radical species through atomic hydrogen elimination. The benzyl radical (C6 H5 CH2 ), the thermodynamically most stable C7 H7 isomer, is determined as the major product.

  14. 6H-SiC Transistor Integrated Circuits Demonstrating Prolonged Operation at 500 C

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Spry, David J.; Chen, Liang-Yu; Chang, Carl W.; Beheim, Glenn M.; Okojie, Robert S.; Evans, Laura J.; Meredith, Roger; Ferrier, Terry; Krasowski, Michael J.; Prokop, Norman F.

    2008-01-01

    The NASA Glenn Research Center is developing very high temperature semiconductor integrated circuits (ICs) for use in the hot sections of aircraft engines and for Venus exploration where ambient temperatures are well above the approximately 300 degrees Centigrade effective limit of silicon-on-insulator IC technology. In order for beneficial technology insertion to occur, such transistor ICs must be capable of prolonged operation in such harsh environments. This paper reports on the fabrication and long-term 500 degrees Centigrade operation of 6H-SiC integrated circuits based on epitaxial 6H-SiC junction field effect transistors (JFETs). Simple analog amplifier and digital logic gate ICs have now demonstrated thousands of hours of continuous 500 degrees Centigrade operation in oxidizing air atmosphere with minimal changes in relevant electrical parameters. Electrical characterization and modeling of transistors and circuits at temperatures from 24 degrees Centigrade to 500 degrees Centigrade is also described. Desired analog and digital IC functionality spanning this temperature range was demonstrated without changing the input signals or power supply voltages.

  15. 40 CFR 721.5560 - Formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz[c...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz oxaphosphorin-6-oxide. 721.5560 Section 721... Formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz oxaphosphorin-6... identified as formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with...

  16. 40 CFR 721.5560 - Formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz[c...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz oxaphosphorin-6-oxide. 721.5560 Section 721... Formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz oxaphosphorin-6... identified as formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with...

  17. 40 CFR 721.5560 - Formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz[c...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz oxaphosphorin-6-oxide. 721.5560 Section 721... Formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz oxaphosphorin-6... identified as formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with...

  18. 40 CFR 721.5560 - Formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz[c...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz oxaphosphorin-6-oxide. 721.5560 Section 721... Formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz oxaphosphorin-6... identified as formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with...

  19. 40 CFR 721.5560 - Formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz[c...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz oxaphosphorin-6-oxide. 721.5560 Section 721... Formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz oxaphosphorin-6... identified as formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with...

  20. Isolation of 1,4-Li(2)-C(6)H(4) and its reaction with [(Ph(3)P)AuCl].

    PubMed

    Flower, Kevin R; McGown, A T; Miles, Philip J; Pritchard, Robin G; Warren, John E

    2010-04-14

    The difficulty in generating 1,4-Li2-C6H4 utilising the lithium halogen exchange reaction on 1,4-Br2-C6H4, 1,4-I2-C6H4 and 1-Br-4-I-C6H4 is revisited and only on treatment of 1,4-I2-C6H4 with 2 molar equivalents of n-BuLi can 1,4-Li2-C6H4 1 be isolated in excellent yield. Treatment of 1 with two equivalents of [ClAu(PPh3)] gives [1,4-(Ph3PAu)2-C6H4] 2a in excellent yield. Subsequent treatment of 2a with 2.5 molar equivalents of PPh2Me, PPhMe2 or PMe3 affords the PPh3 substituted compounds [1,4-(LAu)2-C6H4] (L = PPh2Me 2b, PPhMe2 2c, PMe3 2d) in essentially quantitative yields. On treatment of 1,4-Br2-C6H4 or 1-Br-4-I-C6H4 with 2 molar equivalents of n-BuLi only mono-lithiation takes place to give 1-Br-4-Li-C6H4 3 as shown through the isolation of essentially 1:1 molar equivalents of Ph2PC6H4-4-Br and Ph2PBu on treatment with 2 molar equivalents of ClPPh2. Treatment of 3, prepared by lithium/iodine exchange on 1-Br-4-I-C6H4, with [ClAu(PPh3)] affords [(Ph3P)Au(C6H4-4-Br)] 4 as expected and in addition [(Ph3P)Au(n-Bu)(C6H4-4-Br)2] 5, indicating the straightforward chloride/aryl exchange at gold may proceed in competition with oxidative addition of the n-BuI, generated in the initial lithium/iodine exchange reaction, to some aurate complex Li[Au(C6H4-4-Br)2] 6 formed in situ followed by reductive elimination of Br-C6H4-4-n-Bu in a manner that mimics lithium diorganocuprate chemistry. All of the gold-containing compounds have been spectroscopically characterised by 1H and 31P-{1H} NMR and in addition compounds 2a-d and 5 by single crystal X-ray diffraction studies. The solid state structures observed for 2a-d are dictated by non-conventional hydrogen bonding and the packing requirements of the phosphine ligands. For 2a and 2b there is no close Au...Au approach, however for 2c and 2d the reduction in the number of phenyl rings allows the formation of Au...Au contacts. For 2c and 2d the extended structures appear to be helical chains with Au...Au contact parameters of 3

  1. Isolation of 1,4-Li(2)-C(6)H(4) and its reaction with [(Ph(3)P)AuCl].

    PubMed

    Flower, Kevin R; McGown, A T; Miles, Philip J; Pritchard, Robin G; Warren, John E

    2010-04-14

    The difficulty in generating 1,4-Li2-C6H4 utilising the lithium halogen exchange reaction on 1,4-Br2-C6H4, 1,4-I2-C6H4 and 1-Br-4-I-C6H4 is revisited and only on treatment of 1,4-I2-C6H4 with 2 molar equivalents of n-BuLi can 1,4-Li2-C6H4 1 be isolated in excellent yield. Treatment of 1 with two equivalents of [ClAu(PPh3)] gives [1,4-(Ph3PAu)2-C6H4] 2a in excellent yield. Subsequent treatment of 2a with 2.5 molar equivalents of PPh2Me, PPhMe2 or PMe3 affords the PPh3 substituted compounds [1,4-(LAu)2-C6H4] (L = PPh2Me 2b, PPhMe2 2c, PMe3 2d) in essentially quantitative yields. On treatment of 1,4-Br2-C6H4 or 1-Br-4-I-C6H4 with 2 molar equivalents of n-BuLi only mono-lithiation takes place to give 1-Br-4-Li-C6H4 3 as shown through the isolation of essentially 1:1 molar equivalents of Ph2PC6H4-4-Br and Ph2PBu on treatment with 2 molar equivalents of ClPPh2. Treatment of 3, prepared by lithium/iodine exchange on 1-Br-4-I-C6H4, with [ClAu(PPh3)] affords [(Ph3P)Au(C6H4-4-Br)] 4 as expected and in addition [(Ph3P)Au(n-Bu)(C6H4-4-Br)2] 5, indicating the straightforward chloride/aryl exchange at gold may proceed in competition with oxidative addition of the n-BuI, generated in the initial lithium/iodine exchange reaction, to some aurate complex Li[Au(C6H4-4-Br)2] 6 formed in situ followed by reductive elimination of Br-C6H4-4-n-Bu in a manner that mimics lithium diorganocuprate chemistry. All of the gold-containing compounds have been spectroscopically characterised by 1H and 31P-{1H} NMR and in addition compounds 2a-d and 5 by single crystal X-ray diffraction studies. The solid state structures observed for 2a-d are dictated by non-conventional hydrogen bonding and the packing requirements of the phosphine ligands. For 2a and 2b there is no close Au...Au approach, however for 2c and 2d the reduction in the number of phenyl rings allows the formation of Au...Au contacts. For 2c and 2d the extended structures appear to be helical chains with Au...Au contact parameters of 3

  2. Investigations on the structural and optical properties of the swift heavy ion irradiated 6H sbnd SiC

    NASA Astrophysics Data System (ADS)

    Viswanathan, E.; Katharria, Y. S.; Selvakumar, S.; Arulchakkaravarthi, A.; Kanjilal, D.; Sivaji, K.

    2011-05-01

    Single crystal 6H sbnd SiC wafers have been irradiated with 150 MeV Ag 12+ ions with fluences ranging from 1 × 10 11 to 1 × 10 13 ions/cm 2 at 300 K. The defect accumulation as a function of fluence was studied to determine changes in structural and optical properties. The variation in the fundamental Raman modes of the crystalline 6H sbnd SiC due to irradiation has been correlated with the disorder accumulation. The creation of defect states due to irradiation in the bandgap affects the blue-green photoluminescence emission in the irradiated samples. The UV-Visible absorption studies support the existence of defect states in the bandgap which is observed by the shift in the absorption edge towards the lower energy side with increasing fluence. Time Correlated Single Photon Counting photoluminescence decay results suggest that the existing defect states are radiative, exhibiting three lifetimes when irradiated with a fluence 5 × 10 11 ions/cm 2. The total number of lifetime components was reduced for a fluence 1 × 10 13 ions/cm 2 as the defect states produced increase the non-radiative defect centres. These results suggest that the accumulation of defects due to irradiation at fluences 5 × 10 11 and 1 × 10 13 ions/cm 2 are degenerate configurations which exhibit multiple lifetimes in photoluminescence studies. It is inferred that the optically active defect states influence the transition rate of charge carriers in this device material.

  3. Low-level laser (light) therapy increases mitochondrial membrane potential and ATP synthesis in C2C12 myotubes with a peak response at 3-6 h.

    PubMed

    Ferraresi, Cleber; Kaippert, Beatriz; Avci, Pinar; Huang, Ying-Ying; de Sousa, Marcelo V P; Bagnato, Vanderlei S; Parizotto, Nivaldo A; Hamblin, Michael R

    2015-01-01

    Low-level laser (light) therapy has been used before exercise to increase muscle performance in both experimental animals and in humans. However, uncertainty exists concerning the optimum time to apply the light before exercise. The mechanism of action is thought to be stimulation of mitochondrial respiration in muscles, and to increase adenosine triphosphate (ATP) needed to perform exercise. The goal of this study was to investigate the time course of the increases in mitochondrial membrane potential (MMP) and ATP in myotubes formed from C2C12 mouse muscle cells and exposed to light-emitting diode therapy (LEDT). LEDT employed a cluster of LEDs with 20 red (630 ± 10 nm, 25 mW) and 20 near-infrared (850 ± 10 nm, 50 mW) delivering 28 mW cm(2) for 90 s (2.5 J cm(2)) with analysis at 5 min, 3 h, 6 h and 24 h post-LEDT. LEDT-6 h had the highest MMP, followed by LEDT-3 h, LEDT-24 h, LEDT-5 min and Control with significant differences. The same order (6 h > 3 h > 24 h > 5 min > Control) was found for ATP with significant differences. A good correlation was found (r = 0.89) between MMP and ATP. These data suggest an optimum time window of 3-6 h for LEDT stimulate muscle cells.

  4. Chromium-induced tropane alkaloid production and H6H gene expression in Atropa belladonna L. (Solanaceae) in vitro-propagated plantlets.

    PubMed

    Vakili, Bahareh; Karimi, Farah; Sharifi, Mozafar; Behmanesh, Mehrdad

    2012-03-01

    Hyoscyamine and scopolamine tropane alkaloids found in several solanaceous plants are anticholinergic drugs. Hyoscyamine 6β-hydroxylase (H6H) catalyzes two consecutive oxidation reactions. The first reaction is the hydroxylation of hyoscyamine to 6β-hydroxyhyoscyamine and the second is epoxidation of 6β-hydroxyhyoscyamine yielding scopolamine that is the final metabolite in the tropane alkaloid biosynthetic pathway. The effects of trivalent chromium as KCr (SO4)(2) on the production of tropane alkaloids and the expression of hyoscyamine 6β-hydroxylase gene (h6h) were studied in micro-propagated Atropa belladonna L. plantlets. The results showed that chromium treatment decreased the growth parameters (weights and lengths of the plantlets) and chlorophyll contents and increased proline contents. Moreover, semiquantitave RT-PCR analysis showed that the transcript level of H6H increased under chromium treatment. This treatment also increased hyoscyamine and scopolamine contents as shown by HPLC analysis. Changes of scopolamine contents correlate with the expression levels of h6h gene under different concentrations of chromium. PMID:22305072

  5. Structures and Spectroscopic Properties Calculated for C_6H_7^+ and its Complexes with Ne, Ar, N_2, or CO_2

    NASA Astrophysics Data System (ADS)

    Botschwina, P.; Oswald, R.

    2012-06-01

    Explicitly correlated coupled cluster theory at the CCSD(T)-F12x (x = a, b) level in conjunction with the double-hybrid density functional B2PLYP-D has been employed in a study of the benzenium ion (C_6H_7^+) and its complexes with simple ligands (L = Ne, Ar, N_2, or CO_2). The ground-state rotational constants of C_6H_7^+ are predicted to be A_0 = 5445 MHz, B_0 = 5313 MHz, and C_0 = 2731 MHz. For the complexes with L = Ne, Ar or N_2, the energetically most favourable structure is of π-bonded type, but for the most strongly bound complex C_6H_7^+ ... CO_2 a conformer with the CO_2 ligand lying in the ring-plane of the C_6H_7^+ moiety is slightly lower in energy. T. B. Adler, G. Knizia, and H.-J. Werner, J. Chem. Phys. 127, 221106 (2007) G. Knizia, T. B. Adler, and H.-J. Werner, J. Chem. Phys. 130, 054104 (2009). T. Schwabe and S. Grimme, Phys. Chem. Chem. Phys. 9, 3397 (2007). P. Botschwina and R. Oswald, J. Phys. Chem. A 115, 13664 (2011) P. Botschwina and R. Oswald, J. Chem. Phys. submitted.

  6. Period Studies of 79 Eccentric Eclipsing Binaries in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Hong, K.; Kang, Y. W.; Lee, C.-U.

    2014-08-01

    We present period studies for seventy-nine eclipsing binaries in the Large Magellanic Cloud. New times of minimum light were derived from the data obtained by the EROS, OGLE-II and OGLE-III surveys. Nineteen stars of the seventy-nine stars show period variation were confirmed. All of the systems were studied by means of an O-C diagram analyses. Nine systems show apsidal motion, six systems show parabola, and four systems show sinusoidal period variations, respectively.

  7. Thermochemistry and reaction paths in the oxidation reaction of benzoyl radical: C6H5C•(═O).

    PubMed

    Sebbar, Nadia; Bozzelli, Joseph W; Bockhorn, Henning

    2011-10-27

    Alkyl substituted aromatics are present in fuels and in the environment because they are major intermediates in the oxidation or combustion of gasoline, jet, and other engine fuels. The major reaction pathways for oxidation of this class of molecules is through loss of a benzyl hydrogen atom on the alkyl group via abstraction reactions. One of the major intermediates in the combustion and atmospheric oxidation of the benzyl radicals is benzaldehyde, which rapidly loses the weakly bound aldehydic hydrogen to form a resonance stabilized benzoyl radical (C6H5C(•)═O). A detailed study of the thermochemistry of intermediates and the oxidation reaction paths of the benzoyl radical with dioxygen is presented in this study. Structures and enthalpies of formation for important stable species, intermediate radicals, and transition state structures resulting from the benzoyl radical +O2 association reaction are reported along with reaction paths and barriers. Enthalpies, ΔfH298(0), are calculated using ab initio (G3MP2B3) and density functional (DFT at B3LYP/6-311G(d,p)) calculations, group additivity (GA), and literature data. Bond energies on the benzoyl and benzoyl-peroxy systems are also reported and compared to hydrocarbon systems. The reaction of benzoyl with O2 has a number of low energy reaction channels that are not currently considered in either atmospheric chemistry or combustion models. The reaction paths include exothermic, chain branching reactions to a number of unsaturated oxygenated hydrocarbon intermediates along with formation of CO2. The initial reaction of the C6H5C(•)═O radical with O2 forms a chemically activated benzoyl peroxy radical with 37 kcal mol(-1) internal energy; this is significantly more energy than the 21 kcal mol(-1) involved in the benzyl or allyl + O2 systems. This deeper well results in a number of chemical activation reaction paths, leading to highly exothermic reactions to phenoxy radical + CO2 products.

  8. Utilization of critical periods during development to study the effects of low levels of environmental agents

    SciTech Connect

    Russell, L. B.

    1980-01-01

    Careful definition of critical periods in the development of selected characters can result in experimental systems that may be highly useful in studying risk at low levels of exposure. Three examples are presented. Epidemiological investigations can lose much of their value unless critical periods are known for the end points being studied.

  9. Structural and defects induced phenomena in γ-rays irradiated 6H-SiC

    NASA Astrophysics Data System (ADS)

    Sibuyi, P.; Ngom, B. D.; Kotsedi, L.; Izerrouken, M.; Madjoe, R.; Maaza

    2016-10-01

    Damages and/or defects induced by γ-rays irradiation on 6H-SiC single crystals in channeled configuration towards <006>/<0012> crystallographic directions are reported in the range of 0-1200 kGy. Atomic force microscopy, X-rays diffraction, Raman and photoluminescence investigations were used to obtain a comprehensive set of informations on the nature and population distribution of the induced defects. Primarily, there was no carbon clusterization upon γ-rays irradiation and hence no formation of others SiC polytypes. In contrast, the γ-rays irradiation has induced an increase of the surface roughness at higher doses, which indicates a structural degradation. Larger doses induced an emergence of deeper shallow traps at energies greater than 350 meV below the bandgap.

  10. Band gap states of V and Cr in 6H-silicon carbide

    NASA Astrophysics Data System (ADS)

    Achtziger, N.; Grillenberger, J.; Witthuhn, W.

    Band gap states of Ti, V and Cr in n-type 6H-SiC were investigated by radiotracer deep level transient spectroscopy (DLTS). Doping with the radioactive isotopes 48V and 51Cr was done by recoil implantation followed by annealing (1600 K). Repeated DLTS measurements during the elemental transmutation of these isotopes to 48Ti and 51V respectively revealed the corresponding concentration changes of band gap states. Thus, three levels were identified in the band gap: a Cr level at 0.54 eV and two V levels at 0.71 and 0.75 eV below the conduction band edge. There are no deep levels of Ti in the upper part of the band gap.

  11. [Cp(Ar)Ni{Ga(nacnac)}]: An Open-Shell Nickel(I) Complex Supported by a Gallium(I) Carbenoid (Cp(Ar) = C5(C6H4-4-Et)5, nacnac = HC[C(Me)N-(C6H3)-2,6-iPr2]2).

    PubMed

    Chakraborty, Uttam; Mühldorf, Bernd; van Velzen, Niels J C; de Bruin, Bas; Harder, Sjoerd; Wolf, Robert

    2016-03-21

    The 17 valence electron (VE) open-shell nickel gallanediyl complex [Cp(Ar)Ni{Ga(nacnac)}] (3, Ar = C5(C6H4-4-Et)5, nacnac = HC[C(Me)N(C6H3-2,6-iPr2)]2), having an unsupported Ni-Ga bond, was synthesized from [Cp(Ar)Ni(μ-Br)]2 (1) by reducing the adduct [Cp(Ar)Ni(μ-Br){Ga(nacnac)}] (2) or, alternatively, trapping the "Cp(Ar)Ni(I)" synthon with Ga(nacnac); spectroscopic and DFT studies showed that the single unpaired electron in 3 resides mainly at the Ni center.

  12. Periodic variation in the geomagnetic activity - A study based on the Ap index

    NASA Technical Reports Server (NTRS)

    De Gonzalez, Alicia L. C.; Gonzalez, Walter D.; Dutra, Severino L. G.; Tsurutani, Bruce T.

    1993-01-01

    The monthly and daily samples of the Ap index for the interval from 1932 through 1982 were studied using the power spectrum technique. Results obtained for Bartel's period (about 27 days), the semiannual period, the dual-peak solar cycle distribution of geomagnetic storms, and certain other medium-scale periodicities are examined in detail. In addition, results on the cumulative occurrence number of storms per decade as a function of the Ap and Dst indices for the storm are presented.

  13. Synthetic and structural studies of the cyclopentadienyl-free yttrium alkyl alkoxide and aryloxide complexes [(Me{sub 3}Si){sub 2}CH]{sub 2}Y({mu}-OCMe{sub 3}){sub 2}Li(THF) and [Me{sub 3}SiCH{sub 2}]{sub 2}Y(OC{sub 6}H{sub 3}{sup t}Bu{sub 2}-2,6)(THF){sub 2}

    SciTech Connect

    Evans, W.J.; Broomhall-Dillard, R.N.R.; Ziller, J.W.

    1996-03-05

    YCL{sub 3} reacts with 2 equiv of LiCH(SiMe{sub 3}){sub 2} and 2 equiv of LiOCMe{sub 3} in THF to form the dialkyl dialkoxide complex [(Me{sub 3}Si){sub 2}CH]{sub 2}Y({mu}-OCMe{sub 3}){sub 2}Li(THF), 1. The yttrium in 1 is surrounded by a distorted tetrahedral arrangement of two terminal alkyl groups and two bridging alkoxide groups, and the coordination around lithium is trigonal planar. The reaction of YCl{sub 3} with 2 equiv of LiCH{sub 2}SiMe{sub 3} and 1 equiv of LiOC{sub 6}H{sub 3}{sup t}Bu{sub 2}-2,6 in THF forms the neutral dialkyl aryloxide complex (Me{sub 3}SiCH{sub 2}){sub 2}Y(OC{sub 6}H{sub 3}{sup t}Bu{sub 2}-2,6)(THF){sub 2} 2. The coordination geometry around yttrium in 2 is a distorted trigonal dipyramid with the THF groups in the apical positions. 61 refs., 2 figs., 3 tabs.

  14. A Study of the Orbital Periods of Deeply Eclipsing SW Sextantis Stars

    NASA Astrophysics Data System (ADS)

    Boyd, D.

    2012-06-01

    Results are presented of a five-year project to study the orbital periods of eighteen deeply eclipsing novalike cataclysmic variables, collectively known as SW Sextantis stars, by combining new measurements of eclipse times with published measurements stretching back in some cases over fifty years. While the behavior of many of these binary systems is consistent with a constant orbital period, it is evident that in several cases this is not true. Although the time span of these observations is relatively short, evidence is emerging that the orbital periods of some of these stars show cyclical variation with periods in the range 10-40 years. The two stars with the longest orbital periods, V363 Aur and BT Mon, also show secular period reduction with rates of -6.6 x 10-8 days/year and -3.3 x 10-8 days/year. New ephemerides are provided for all eighteen stars to facilitate observation of future eclipses.

  15. Exposure to p,p′-dichlorodiphenyldichloroethylene (DDE) induces fasting hyperglycemia without insulin resistance in male C57BL/6H mice

    PubMed Central

    Howell, George E.; Meek, Edward; Kilic, Jessica; Mohns, Mariel; Mulligan, Charlee; Chambers, Janice E.

    2014-01-01

    Approximately 8.3% of the United States (U.S.) population have either diagnosed or undiagnosed diabetes mellitus. Out of all the cases of diabetes mellitus, approximately 90–95% of these cases are type 2 diabetes mellitus (T2D). Although the exact cause of T2D remains elusive, predisposing factors include age, weight, poor diet, and a sedentary lifestyle. Until recently the association between exposure to environmental contaminants and the occurrence of diabetes had been unexplored. However, recent epidemiological studies have revealed that elevated serum concentrations of certain persistent organic pollutants (POPs), especially organochlorine pesticides, are positively associated with increased prevalence of T2D and insulin resistance. The current study seeks to investigate if this association is causative or coincidental. Male C57BL/6H mice were exposed to DDE (2.0 mg/kg or 0.4 mg/kg) or vehicle (corn oil; 1 ml/kg) for five days via oral gavage; fasting blood glucose, glucose tolerance, and insulin challenge tests were performed following a seven day resting period. Exposure to DDE caused significant hyperglycemia compared to vehicle and this hyperglycemic effect persisted for up to 21 days following cessation of DDE administration. Intraperitoneal glucose tolerance tests and phosphorylation of Akt in the liver, skeletal muscle, and adipose tissue following insulin challenge were comparable between vehicle and DDE treated animals. To determine the direct effect of exposure to DDE on glucose uptake, in vitro glucose uptake assays following DDE exposure were performed in L6 myotubules and 3T3-L1 adipocytes. In summary, subacute exposure to DDE does produce fasting hyperglycemia, but this fasting hyperglycemia does not appear to be mediated by insulin resistance. Thus, the current study reveals that subacute exposure to DDE does alter systemic glucose homeostasis and may be a contributing factor to the development of hyperglycemia associated with diabetes. PMID

  16. Long-Term Characterization of 6H-SiC Transistor Integrated Circuit Technology Operating at 500 C

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Spry, David J.; Chen, Liang-Yu; Chang, Carl W.; Beheim, Glenn M.; Okojie, Robert S.; Evans, Laura J.; Meredith Roger D.; Ferrier, Terry L.; Krasowski, Michael J.; Prokop, Norman F.

    2008-01-01

    NASA has been developing very high temperature semiconductor integrated circuits for use in the hot sections of aircraft engines and for Venus exploration. This paper reports on long-term 500 C electrical operation of prototype 6H-SiC integrated circuits based on epitaxial 6H-SiC junction field effect transistors (JFETs). As of this writing, some devices have surpassed 4000 hours of continuous 500 C electrical operation in oxidizing air atmosphere with minimal change in relevant electrical parameters.

  17. Periodic travelling waves in cyclic populations: field studies and reaction-diffusion models.

    PubMed

    Sherratt, Jonathan A; Smith, Matthew J

    2008-05-01

    Periodic travelling waves have been reported in a number of recent spatio-temporal field studies of populations undergoing multi-year cycles. Mathematical modelling has a major role to play in understanding these results and informing future empirical studies. We review the relevant field data and summarize the statistical methods used to detect periodic waves. We then discuss the mathematical theory of periodic travelling waves in oscillatory reaction-diffusion equations. We describe the notion of a wave family, and various ecologically relevant scenarios in which periodic travelling waves occur. We also discuss wave stability, including recent computational developments. Although we focus on oscillatory reaction-diffusion equations, a brief discussion of other types of model in which periodic travelling waves have been demonstrated is also included. We end by proposing 10 research challenges in this area, five mathematical and five empirical.

  18. 6H-Indolo[2,3-b]quinoxalines: DNA and protein interacting scaffold for pharmacological activities.

    PubMed

    Moorthy, N S Hari Narayana; Manivannan, E; Karthikeyan, C; Trivedi, Piyush

    2013-08-01

    6H-Indolo[2,3-b]quinoxaline, a planar fused heterocyclic compound exhibits a wide variety of pharmacological activities. The mechanism of pharmacological action exerted by these compounds is predominantly DNA intercalation. The thermal stability of the intercalated complex (DNA and 6H-indolo[2,3-b]quinoxaline derivatives) is an important parameter for the elucidation of anticancer, antiviral and other activities. This thermal stability of the 6H-indolo[2,3- b]quinoxaline-DNA complex depends on the type of substituents and side chains attached to the 6H-indolo[2,3- b]quinoxaline nucleus and also the orientation of the side chain towards the GC rich minor groove of the DNA. Highly active 6H-indolo[2,3-b]quinoxaline derivatives such as NCA0424, B-220 and 9-OH-B-220 have shown good binding affinity to DNA as evident from high thermal stability of compound-DNA complex. Interestingly, these compounds possessed poor inhibitory activity on topoisomerase II enzyme but have significant MDR modulating activity. This review establishes '6H-indolo[2,3-b]quinoxaline' as a valuable template for design and development of novel molecules with different biological activities.

  19. Interfacial reactions and surface analysis of W thin film on 6H-SiC

    NASA Astrophysics Data System (ADS)

    Thabethe, T. T.; Hlatshwayo, T. T.; Njoroge, E. G.; Nyawo, T. G.; Ntsoane, T. P.; Malherbe, J. B.

    2016-03-01

    Tungsten (W) thin film was deposited on bulk single crystalline 6H-SiC substrate and annealed in vacuum at temperatures ranging from 700 to 1000 °C for 1 h. The resulting solid-state reactions, phase composition and surface morphology were investigated by Rutherford backscattering spectroscopy (RBS), grazing incidence X-ray diffraction (GIXRD) and scanning electron microscopy (SEM). XRD was used to identify the phases present and to confirm the RBS results. The RBS spectra were simulated using the RUMP software in order to obtain the deposited layer thickness, composition of reaction zone and detect phase formation at the interface. RBS results showed that interaction between W and SiC started at 850 °C. The XRD analysis showed that WC and CW3 were the initial phases formed at 700 and 800 °C. The concentration of the phases was however, too low to be detected by RBS analysis. At temperatures of 900 and 1000 °C, W reacted with the SiC substrate and formed a mixed layer containing a silicide phase (WSi2) and a carbide phase (W2C). The SEM images of the as-deposited samples showed that the W thin film had a uniform surface with small grains. The W layer became heterogeneous during annealing at higher temperatures as the W granules agglomerated into island clusters at temperatures of 800 °C and higher.

  20. Annealing of silver implanted 6H-SiC and the diffusion of the silver

    NASA Astrophysics Data System (ADS)

    Hlatshwayo, T. T.; Malherbe, J. B.; van der Berg, N. G.; Prinsloo, L. C.; Botha, A. J.; Wendler, E.; Wesch, W.

    2012-03-01

    Annealing and diffusion behavior of implanted silver in 6H-SiC has been investigated using Rutherford backscattering spectroscopy (RBS), channeling, Raman spectroscopy and scanning electron microscopy (SEM) techniques. Silver (109Ag+) ions with an energy of 360 keV were implanted in SiC to a fluence of 2 × 1016 cm-2 at room temperature (23 °C), 350 and 600 °C. After implantation the samples were annealed at temperatures up to 1400 °C. The results revealed that implantation at room temperature created an amorphous layer of about 270 nm from the surface while implantation at 350 and 600 °C retained a crystalline structure with more damage created for 350 °C implantation compared to 600 °C. Diffusion of implanted Ag accompanied by loss from the surface started at 1300 °C in the amorphous SiC with no diffusion observed in the crystalline SiC. A new model explaining this diffusion of silver accompanied silver loss is presented.

  1. Large area graphene growth on 6H-SiC(0001)

    NASA Astrophysics Data System (ADS)

    Johansson, L. I.; Virojanadara, C.; Syväjärvi, M.; Yakimova, R.; Zakharov, A. A.; Balasubramanian, T.

    2009-03-01

    Large area graphene growth on commercial Si-face on-axis 6H-SiC(0001) is demonstrated in this work. Samples were produced in a prototype of an inductively heated furnace. The growth was carried out in strongly isothermal conditions at a temperature of 2000 C and at an ambient argon pressure of 1 atm. The quality and thickness of the graphene layers grown, using this ex situ method, were investigated using PES, ARPES), LEED as well as LEEM, PEEM micro-LEED and micro-PES at specifically defined small areas. Our results show that single layer graphene is formed over quite large areas on the sample but that two different domains can exist on some parts. A comparison with an in situ graphene sample, prepared by resistive heating to 1275 C, was made. The results then obtained were similar to earlier findings [1-2] and showed that the size of the graphene flakes were very small compared to those obtained on the samples prepared with our ex situ method. [3pt] [1]. T. Ohta, F. El Gabaly, A. Bostwick, J.L. McChesney, K.V. Emtsev, A.K. Schmid, Th. Seyller, K. Horn, E. Rotenberg, New. J. Phys. 10 023034 (2008).[0pt] [2]. J.B. Hannon and R. M. Tromp, Phys. Rev. B 77 241404 (2008).

  2. Epitaxial growth of graphene on 6H-silicon carbide substrate by simulated annealing method.

    PubMed

    Yoon, T L; Lim, T L; Min, T K; Hung, S H; Jakse, N; Lai, S K

    2013-11-28

    We grew graphene epitaxially on 6H-SiC(0001) substrate by the simulated annealing method. The mechanisms that govern the growth process were investigated by testing two empirical potentials, namely, the widely used Tersoff potential [J. Tersoff, Phys. Rev. B 39, 5566 (1989)] and its more refined version published years later by Erhart and Albe [Phys. Rev. B 71, 035211 (2005)]. Upon contrasting the results obtained by these two potentials, we found that the potential proposed by Erhart and Albe is generally more physical and realistic, since the annealing temperature at which the graphene structure just coming into view at approximately 1200 K is unambiguously predicted and close to the experimentally observed pit formation at 1298 K within which the graphene nucleates. We evaluated the reasonableness of our layers of graphene by calculating carbon-carbon (i) average bond-length, (ii) binding energy, and (iii) pair correlation function. Also, we compared with related experiments the various distance of separation parameters between the overlaid layers of graphene and substrate surface. PMID:24289364

  3. Methane production in an UASB reactor operated under periodic mesophilic-thermophilic conditions.

    PubMed

    Bourque, J-S; Guiot, S R; Tartakovsky, B

    2008-08-15

    Methane production was studied in a laboratory-scale 10 L anaerobic upflow sludge bed (UASB) reactor with periodic variations of the reactor temperature. On a daily basis the temperature was varied between 35 and 45 degrees C or 35 and 55 degrees C with a heating period of 6 h. Each temperature increase was accompanied by an increase in methane production and a decrease in the concentration of soluble organic matter in the effluent. In comparison to a reactor operated at 35 degrees C, a net increase in methane production of up to 22% was observed. Batch activity tests demonstrated a tolerance of mesophilic methanogenic populations to short-term, 2-6 h, temperature increases, although activity of acetoclastic methanogens decreased after 6 h exposure to a temperature of 55 degrees C. 16S sequencing of DGGE bands revealed proliferation of temperature-tolerant Methanospirillum hungatii sp. in the reactor.

  4. Electrical properties of epitaxial 3C- and 6H-SiC p-n junction diodes produced side-by-side on 6H-SiC substrates

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Larkin, David J.; Starr, Jonathan E.; Powell, J. Anthony; Salupo, Carl S.; Matus, Lawrence G.

    1994-01-01

    3C-SiC (beta-SiC) and 6H-SiC p-n junction diodes have been fabricated in regions of both 3C-SiC and 6H-SiC epitaxial layers which were grown side-by-side on low-tilt-angle 6H-SiC substrates via a chemical vapor deposition (CVD) process. Several runs of diodes exhibiting state-of-the-art electrical characteristics were produced, and performance characteristics were measured and compared as a function of doping, temperature, and polytype. The first 3C-SiC diodes which rectify to reverse voltages in excess of 300 V were characterized, representing a six-fold blocking voltage improvement over experimental 3C-SiC diodes produced by previous techniques. When placed under sufficient forward bias, the 3C-SiC diodes emit significantly bright green-yellow light while the 6H-SiC diodes emit in the blue-violet. The 6H-SiC p-n junction diodes represent the first reported high-quality 6H-SiC devices to be grown by CVD on very low-tilt-angle (less than 0.5 deg off the (0001) silicon face) 6H substrates. The reverse leakage current of a 200 micron diameter circular device at 1100 V reverse bias was less than 20 nA at room temperature, and excellent rectification characteristics were demonstrated at the peak characterization temperature of 400 C.

  5. Are Seminar Periods Supportive of the Professional Development of Social Studies Teachers?

    ERIC Educational Resources Information Center

    Demir, Selçuk Besir; Dogan, Soner; Atasoy, Turgay

    2016-01-01

    The purpose of this study is to determine the efficiency of the seminar periods intended for contributing to the professional development of social studies teachers based on their own perspectives. This study adopts a qualitative approach and is carried out in the form of a case study. Among the purposeful sampling methods, the criteria sample…

  6. Interfacial transformations in the a-SiC/a-Si/6H-SiC structure caused by high-temperature (1500°C) annealing

    NASA Astrophysics Data System (ADS)

    Ivanov, P. A.; Samsonova, T. P.

    2008-07-01

    We have studied the reactions that take place at interfaces in an a-SiC/a-Si/6H-SiC sandwich structure, which was obtained by the sequential deposition of amorphous silicon (a-Si) and amorphous silicon carbide (a-SiC) onto a 6H-SiC substrate by ion sputtering in vacuum and then annealed at 1500°C (i.e., above the melting point of silicon). It is shown that the annealing leads to complete îdissipationî of the silicon film in SiC, probably as a result of the dissolution of carbon in the silicon melt and the diffusion of silicon into SiC.

  7. Thermochemistry and reaction paths in the oxidation reaction of benzoyl radical: C6H5C•(═O).

    PubMed

    Sebbar, Nadia; Bozzelli, Joseph W; Bockhorn, Henning

    2011-10-27

    Alkyl substituted aromatics are present in fuels and in the environment because they are major intermediates in the oxidation or combustion of gasoline, jet, and other engine fuels. The major reaction pathways for oxidation of this class of molecules is through loss of a benzyl hydrogen atom on the alkyl group via abstraction reactions. One of the major intermediates in the combustion and atmospheric oxidation of the benzyl radicals is benzaldehyde, which rapidly loses the weakly bound aldehydic hydrogen to form a resonance stabilized benzoyl radical (C6H5C(•)═O). A detailed study of the thermochemistry of intermediates and the oxidation reaction paths of the benzoyl radical with dioxygen is presented in this study. Structures and enthalpies of formation for important stable species, intermediate radicals, and transition state structures resulting from the benzoyl radical +O2 association reaction are reported along with reaction paths and barriers. Enthalpies, ΔfH298(0), are calculated using ab initio (G3MP2B3) and density functional (DFT at B3LYP/6-311G(d,p)) calculations, group additivity (GA), and literature data. Bond energies on the benzoyl and benzoyl-peroxy systems are also reported and compared to hydrocarbon systems. The reaction of benzoyl with O2 has a number of low energy reaction channels that are not currently considered in either atmospheric chemistry or combustion models. The reaction paths include exothermic, chain branching reactions to a number of unsaturated oxygenated hydrocarbon intermediates along with formation of CO2. The initial reaction of the C6H5C(•)═O radical with O2 forms a chemically activated benzoyl peroxy radical with 37 kcal mol(-1) internal energy; this is significantly more energy than the 21 kcal mol(-1) involved in the benzyl or allyl + O2 systems. This deeper well results in a number of chemical activation reaction paths, leading to highly exothermic reactions to phenoxy radical + CO2 products. PMID:21942384

  8. Unique Properties of Human β-Defensin 6 (hBD6) and Glycosaminoglycan Complex

    PubMed Central

    De Paula, Viviane S.; Pomin, Vitor H.; Valente, Ana Paula

    2014-01-01

    Defensins are components of the innate immune system that promote the directional migration and activation of dendritic cells, thereby modulating the adaptive immune response. Because matrix glycosaminoglycan (GAG) is known to be important for these functions, we characterized the structural features of human β-defensin 6 (hBD6) and GAG interaction using a combination of structural and in silico analyses. Our results showed that GAG model compounds, a pentasaccharide (fondaparinux, FX) and an octasaccharide heparin derivative (dp8) bind to the α-helix and in the loops between the β2 and β3 strands, inducing the formation of a ternary complex with a 2:1 hBD6:FX stoichiometry. Competition experiments indicated an overlap of GAG and chemokine receptor CCR2 binding sites. An NMR-derived model of the ternary complex revealed that FX interacts with hBD6 along the dimerization interface, primarily contacting the α-helices and β2-β3 loops from each monomer. We further demonstrated that high-pressure NMR spectroscopy could capture an intermediate stage of hBD6-FX interaction, exhibiting features of a cooperative binding mechanism. Collectively, these data suggest a “sandwich-like” model in which two hBD6 molecules bind a single FX chain and provide novel structural insights into how defensin orchestrates leukocyte recruitment through GAG binding and G protein-coupled receptor activation. Despite the similarity to chemokines and hBD2, our data indicate different properties for the hBD6-GAG complex. This work adds significant information to the currently limited data available for the molecular structures and dynamics of defensin carbohydrate binding. PMID:24970887

  9. Experimental study of D16AT alloy deformation under periodic loading

    NASA Astrophysics Data System (ADS)

    Kapustin, V. I.; Gileta, V. P.

    2011-09-01

    An experimental procedure and results of an experimental study of the kinetics of the strained state of a material under periodic uniaxial loading are reported. Diagrams of the principal components of the total strain tensor for an asymmetric periodic "soft" regime of tension-compression of the samples are presented. Specific features of deformation revealed under periodic asymmetric loading of the samples can be used to formulate a criterion of fatigue fracture of materials and to identify the mechanism of strain hardening of pre-fracture zones in machine elements.

  10. Pharmacologic Evaluation of Antidepressant Activity and Synthesis of 2-Morpholino-5-phenyl-6H-1,3,4-thiadiazine Hydrobromide.

    PubMed

    Sarapultsev, Alexey P; Chupakhin, Oleg N; Sarapultsev, Petr A; Sidorova, Larisa P; Tseitler, Tatiana A

    2016-01-01

    Substituted thiadiazines exert a reliable therapeutic effect in treating stress, and a schematic description of their ability to influence all aspects of a stress response has been depicted. This study was conducted to pharmacologically evaluate compound L-17, a substituted thiadiazine, (2-morpholino-5-phenyl-6H-1,3,4-thiadiazine, hydrobromide) for possible anti-psychotic/antidepressant activity. Compound L-17 was synthesized by cyclocondensation of α-bromoacetophenone with the original morpholine-4-carbothionic acid hydrazide. Pharmacologic evaluations were conducted using methods described by E.F. Lavretskaya (1985), and in accordance with published guidelines for studying drugs for neuroleptic activity. Compound L-17 was evaluated for various possible mechanisms of action, including its effects on cholinergic system agonists/antagonists, dopaminergic neurotransmission, the adrenergic system, and 5-HT3 serotonin receptors. One or more of these mechanisms may be responsible for the beneficial effects shown by thiadiazine compounds in experiments conducted to evaluate their activity in models of acute stress and acute myocardial infarction. PMID:27213404

  11. Pharmacologic Evaluation of Antidepressant Activity and Synthesis of 2-Morpholino-5-phenyl-6H-1,3,4-thiadiazine Hydrobromide

    PubMed Central

    Sarapultsev, Alexey P.; Chupakhin, Oleg N.; Sarapultsev, Petr A.; Sidorova, Larisa P.; Tseitler, Tatiana A.

    2016-01-01

    Substituted thiadiazines exert a reliable therapeutic effect in treating stress, and a schematic description of their ability to influence all aspects of a stress response has been depicted. This study was conducted to pharmacologically evaluate compound L-17, a substituted thiadiazine, (2-morpholino-5-phenyl-6H-1,3,4-thiadiazine, hydrobromide) for possible anti-psychotic/antidepressant activity. Compound L-17 was synthesized by cyclocondensation of α-bromoacetophenone with the original morpholine-4-carbothionic acid hydrazide. Pharmacologic evaluations were conducted using methods described by E.F. Lavretskaya (1985), and in accordance with published guidelines for studying drugs for neuroleptic activity. Compound L-17 was evaluated for various possible mechanisms of action, including its effects on cholinergic system agonists/antagonists, dopaminergic neurotransmission, the adrenergic system, and 5-HT3 serotonin receptors. One or more of these mechanisms may be responsible for the beneficial effects shown by thiadiazine compounds in experiments conducted to evaluate their activity in models of acute stress and acute myocardial infarction. PMID:27213404

  12. Distinct lymphocyte antigens 6 (Ly6) family members Ly6D, Ly6E, Ly6K and Ly6H drive tumorigenesis and clinical outcome

    PubMed Central

    Luo, Linlin; McGarvey, Peter; Madhavan, Subha; Kumar, Rakesh; Gusev, Yuriy; Upadhyay, Geeta

    2016-01-01

    Stem cell antigen-1 (Sca-1) is used to isolate and characterize tumor initiating cell populations from tumors of various murine models [1]. Sca-1 induced disruption of TGF-β signaling is required in vivo tumorigenesis in breast cancer models [2, 3-5]. The role of human Ly6 gene family is only beginning to be appreciated in recent literature [6-9]. To study the significance of Ly6 gene family members, we have visualized one hundred thirty gene expression omnibus (GEO) dataset using Oncomine (Invitrogen) and Georgetown Database of Cancer (G-DOC). This analysis showed that four different members Ly6D, Ly6E, Ly6H or Ly6K have increased gene expressed in bladder, brain and CNS, breast, colorectal, cervical, ovarian, lung, head and neck, pancreatic and prostate cancer than their normal counter part tissues. Increased expression of Ly6D, Ly6E, Ly6H or Ly6K was observed in sub-set of cancer type. The increased expression of Ly6D, Ly6E, Ly6H and Ly6K was found to be associated with poor outcome in ovarian, colorectal, gastric, breast, lung, bladder or brain and CNS as observed by KM plotter and PROGgeneV2 platform. The remarkable findings of increased expression of Ly6 family members and its positive correlation with poor outcome on patient survival in multiple cancer type indicate that Ly6 family members Ly6D, Ly6E, Ly6K and Ly6H will be an important targets in clinical practice as marker of poor prognosis and for developing novel therapeutics in multiple cancer type. PMID:26862846

  13. Solvation-induced σ-complex structure formation in the gas phase: a revisit to the infrared spectroscopy of [C6H6-(CH3OH)2]+.

    PubMed

    Mizuse, Kenta; Suzuki, Yuta; Mikami, Naohiko; Fujii, Asuka

    2011-10-20

    Structures of the [C(6)H(6)-(CH(3)OH)(2)](+) cluster cation are investigated with infrared (IR) spectroscopy. While the noncovalent type structure has been confirmed for the n = 1 cluster of [C(6)H(6)-(CH(3)OH)(n)](+), only contradictory interpretations have been given for the spectra of n = 2, in which significant changes have been observed with the Ar tagging. In the present study, we revisit IR spectroscopy of the n = 2 cluster from the viewpoint of the σ-complex structure, which includes a covalent bond formation between the benzene and methanol moieties. The observed spectral range is extended to the lower-frequency region, and the spectrum is measured with and without Ar and N(2) tagging. A strongly hydrogen-bonded OH stretch band, which is characteristic to the σ-complex structure, is newly found with the tagging. The remarkable spectral changes with the tagging are interpreted by the competition between the σ-complex and noncovalent complex structures in the [C(6)H(6)-(CH(3)OH)(2)](+) system. This result shows that the microsolvation only with one methanol molecule can induce the σ-complex structure formation.

  14. Suppression of Photoanodic Surface Oxidation of n-Type 6H-SiC Electrodes in Aqueous Electrolytes.

    PubMed

    Sachsenhauser, Matthias; Walczak, Karl; Hampel, Paul A; Stutzmann, Martin; Sharp, Ian D; Garrido, Jose A

    2016-02-16

    The photoelectrochemical characterization of silicon carbide (SiC) electrodes is important for enabling a wide range of potential applications for this semiconductor. However, photocorrosion of the SiC surface remains a key challenge, because this process considerably hinders the deployment of this material into functional devices. In this report, we use cyclic voltammetry to investigate the stability of n-type 6H-SiC photoelectrodes in buffered aqueous electrolytes. For measurements in pure Tris buffer, photogenerated holes accumulate at the interface under anodic polarization, resulting in the formation of a porous surface oxide layer. Two possibilities are presented to significantly enhance the stability of the SiC photoelectrodes. In the first approach, redox molecules are added to the buffer solution to kinetically facilitate hole transfer to these molecules, and in the second approach, water oxidation in the electrolyte is induced by depositing a cobalt phosphate catalyst onto the semiconductor surface. Both methods are found to effectively suppress photocorrosion of the SiC electrodes, as confirmed by atomic force microscopy and X-ray photoelectron spectroscopy measurements. The presented study provides straightforward routes to stabilize n-type SiC photoelectrodes in aqueous electrolytes, which is essential for a possible utilization of this material in the fields of photocatalysis and multimodal biosensing. PMID:26795116

  15. Interaction of Ni90Ti10 alloy thin film with 6H-SiC single crystal

    NASA Astrophysics Data System (ADS)

    Levit, M.; Grimberg, I.; Weiss, B.-Z.

    1996-07-01

    Interfacial reactions, phase formation, microstructure, and composition, as functions of heat treatments (400-800 °C) were investigated in Ni90Ti10 alloy thin film coevaporated on an n-type 6H-SiC (0001) single-crystal substrate. The study was carried out with the aid of Auger electron spectroscopy, x-ray diffraction, and analytical transmission electron microscopy. The interaction was found to begin at 450 °C. Ni and C are the dominant diffusing species. The reaction zone is divided into three layers. In the first layer, adjacent to the SiC substrate, the presence of Ni-rich silicide, Ni2Si, and C precipitates, was observed. The second layer is composed mainly of TiC, while the third consists of Ni2Si. This composite structure, consisting of the silicide as a low resistivity ohmic contact, and of the carbide as a diffusion barrier, promises high-temperature stability crucial to ohmic contact development for SiC technology. Factors controlling phase formation in the Ni-Ti/SiC system are discussed.

  16. Carcass yields and meat quality characteristics of adult emus (Dromaius novaehollandiae) transported for 6h before slaughter.

    PubMed

    Menon, Deepa G; Bennett, Darin C; Uttaro, Bethany; Schaefer, Allan L; Cheng, Kimberly M

    2014-10-01

    The meat quality characteristics of adult emus transported for 6h before slaughter were determined. Forty-two emus were used in two trials, undertaken under warm and cool weather conditions, respectively. Male emus had significantly higher fat yields than females (12.43kg vs 9.5kg, P=0.002). About 38.1% of the emus had no wounds or bruises, 40.5% had bruises, while 21.4% had small wounds after transport. Meat from injured emus had significantly higher pH45. In warm weather, emus experienced significantly higher loss in body weight than that under cool weather. Drip loss in meat after 24h of storage was higher in emus which had greater live weight loss after transport (r=0.66, P<0.0001), confirming the adverse effects of transport stress on meat quality. Nutrient supplementation did not significantly affect processing yield or meat quality characteristics. This study points to the need for optimizing transport conditions of emus to maintain meat quality. PMID:24973774

  17. Effects of 6-h exposure to low relative humidity and low air pressure on body fluid loss and blood viscosity.

    PubMed

    Hashiguchi, N; Takeda, A; Yasuyama, Y; Chishaki, A; Tochihara, Y

    2013-10-01

    The purpose of this study was to investigate the effects of 6-h exposure to low relative humidity (RH) and low air pressure in a simulated air cabin environment on body fluid loss (BFL) and blood viscosity. Fourteen young healthy male subjects were exposed to four conditions, which combined RH (10% RH or 60% RH) and air pressure (NP: sea level or LP: equivalent to an altitude of 2000 m). Subjects remained seated on a chair in the chamber for 6 h. Their diet and water intake were restricted before and during the experiment. Insensible water loss (IWL) in LP10% condition was significantly greater than in NP60% condition; thus, combined 10%RH and LP conditions promoted a greater amount of IWL. The BFL under the LP condition was significantly greater than that under the NP condition. Blood viscosity significantly increased under LP conditions. Increases in red blood cell counts (RBCs) and BFL likely contributed to the increased blood viscosity. These findings suggest that hypobaric-induced hypoxia, similar to the conditions in the air cabin environment, may cause increased blood viscosity and that the combined low humidity and hypobaric hypoxia conditions increase IWL. PMID:23464811

  18. Carcass yields and meat quality characteristics of adult emus (Dromaius novaehollandiae) transported for 6h before slaughter.

    PubMed

    Menon, Deepa G; Bennett, Darin C; Uttaro, Bethany; Schaefer, Allan L; Cheng, Kimberly M

    2014-10-01

    The meat quality characteristics of adult emus transported for 6h before slaughter were determined. Forty-two emus were used in two trials, undertaken under warm and cool weather conditions, respectively. Male emus had significantly higher fat yields than females (12.43kg vs 9.5kg, P=0.002). About 38.1% of the emus had no wounds or bruises, 40.5% had bruises, while 21.4% had small wounds after transport. Meat from injured emus had significantly higher pH45. In warm weather, emus experienced significantly higher loss in body weight than that under cool weather. Drip loss in meat after 24h of storage was higher in emus which had greater live weight loss after transport (r=0.66, P<0.0001), confirming the adverse effects of transport stress on meat quality. Nutrient supplementation did not significantly affect processing yield or meat quality characteristics. This study points to the need for optimizing transport conditions of emus to maintain meat quality.

  19. Study of periodic motions of a satellite with a magnetic damper

    NASA Technical Reports Server (NTRS)

    Sadov, Y. A.; Teterin, A. D.

    1979-01-01

    The motion of a satellite with a magnetic damper in the plane of a circular polar orbit is studied. The asymptotics of periodic solutions are constructed for a satellite close to axisymmetric and the radius of convergence is evaluated for the power series obtained. In a broad range of values of parameters, a periodic solution is obtained by numerical integration of equations of motion of the satellite. The asymptotics of a bifurcated curve obtained (the curve on which origin of a pair of periodic solutions occurs) in the space of the parameters agrees well with the results of numerical computation with all physical values of these parameters. A breakdown is made of the space of the initial data of phase variables in the field of effect of different types of periodic motion.

  20. Incubation period and immune function: A comparative field study among coexisting birds

    USGS Publications Warehouse

    Palacios, M.G.; Martin, T.E.

    2006-01-01

    Developmental periods are integral components of life history strategies that can have important fitness consequences and vary enormously among organisms. However, the selection pressures and mechanisms causing variation in length of developmental periods are poorly understood. Particularly puzzling are prolonged developmental periods, because their selective advantage is unclear. Here we tested the hypotheses that immune function is stronger in species that are attacked at a higher rate by parasites and that prolonged embryonic development allows the development of this stronger immune system. Through a comparative field study among 12 coexisting passerine bird species, we show that species with higher blood parasite prevalence mounted stronger cellular immune responses than species with lower prevalence. These results provide support for the hypothesis that species facing greater selection pressure from parasites invest more in immune function. However, species with longer incubation periods mounted weaker cellular immune responses than species with shorter periods. Therefore, cellular immune responses do not support the hypothesis that longer development time enhances immunocompentence. Future studies should assess other components of the immune system and test alternative causes of variation in incubation periods among bird species. ?? Springer-Verlag 2005.

  1. The Prevalence and Incidence of Glaucoma in Denmark in a Fifteen Year Period: A Nationwide Study

    PubMed Central

    Thygesen, John; Jeppesen, Jørgen; Torp-Pedersen, Christian

    2015-01-01

    Purpose The purpose of the present study was to describe the prevalence, incidence and geographic variation of glaucoma in Denmark in the period from 1996 to 2011. Moreover, the aim was to identify the treatment patterns of glaucoma within the studied period. Methods All Danish citizens were included throughout the study period. The National Prescription Registry was used to identify all claimed prescriptions for glaucoma medication. Results A total of 116,592 incident glaucoma patients were identified. Average age at onset was 66 years (range: 0–105 years), 55% were women. The prevalence of glaucoma increased from 0.79% to 1.72% during the investigated period. In 2011 glaucoma affected 3.76% of the population above 50 years and 10% in patients above 80 years. The age-specific incidence rate of glaucoma seemed to be constant and the increasing prevalence was primarily attributed to an aging population. We found the highest prevalence of glaucoma in the capital region of Denmark. Within the studied period the use of prostaglandin analogs and combination drugs increased, whereas the use of β-blockers, carbon anhydrase inhibitors and parasympathomimetic drugs decreased (p<0.001). Finally, the use of α2-adrenergic agonists remained unchanged. A total of 75% of the patients were treated with two or more glaucoma medications. Conclusions Over all, the present study is the first to assess the frequency and the development of glaucoma in Denmark over a 15-year period. We find that glaucoma affects a little less than 2% of the total population and increases with age to reach a prevalence of more than 10% amongst people above 80 years. Generally, the present study is the largest nation-wide study ever made and must be a close-to-real-life-picture of the utilization of glaucoma medication on a national scale. Our findings confirm other recent estimations on an increasing burden of glaucoma globally. PMID:26182236

  2. Synthesis, structural and magnetic characterisation of the fully fluorinated compound 6H-BaFeO{sub 2}F

    SciTech Connect

    Clemens, Oliver; Wright, Adrian J.; Berry, Frank J.; Smith, Ronald I.; Slater, Peter R.

    2013-02-15

    The compound 6H-BaFeO{sub 2}F (P6{sub 3}/mmc) was synthesised by the low temperature fluorination of 6H-BaFeO{sub 3-d} using polyvinylidenedifluoride (PVDF) as a fluorination agent. Structural characterisation by XRD and NPD suggests that the local positions of the oxygen and fluorine atoms vary with no evidence for ordering on the anion sites. This compound shows antiferromagnetic ordering at room temperature with antiparallel alignment of the magnetic moments along the c-axis. The use of PVDF also allows the possibility of tuning the fluorine content in materials of composition 6H-BaFeO{sub 3-d}F{sub y} to any value of 06H-BaFeO{sub 2}F. Highlights: Black-Right-Pointing-Pointer The crystal structure of the hexagonal perovskite phase 6H-BaFeO{sub 2}F. Black-Right-Pointing-Pointer H-BaFeO{sub 2}F and 6H-BaFeO{sub 3-d}F{sub y} were prepared via low temperature fluorination using PVDF. Black-Right-Pointing-Pointer A structural investigation of the compounds BaFeO{sub 2}F is presented in detail. Black-Right-Pointing-Pointer This analysis suggests differences for the local coordination of O{sup 2-} and F{sup -} anions. Black-Right-Pointing-Pointer H-BaFeO{sub 2}F shows antiferromagnetic ordering at 300 K. Black-Right-Pointing-Pointer The magnetic moments align parallel to the a-axis.

  3. Correlation of EBIC and SWBXT Imaged Defects and Epilayer Growth Pits in 6H-SiC Schottky Diodes

    NASA Technical Reports Server (NTRS)

    Schnable, C. M.; Tabib-Azar, M.; Neudeck, P. G.; Bailey, S. G.; Su, H. B.; Dudley, M.; Raffaelle, R. P.

    2000-01-01

    We show the first direct experimental correlation between the presence of closed core screw dislocations in 6H-SiC epilayers with recombination centers, as well as with some of the small growth pits on the epilayer surface in lightly-doped 6H-SiC Schottky diodes. At every Synchrotron White-Beam X-ray Topography (SWBXT)-identified closed core screw dislocation, an Electron Beam Induced Current (EBIC) image showed a dark spot indicating a recombination center, and Nomarski optical microscope and Atomic Force Microscope (AFM) images showed a corresponding small growth pit with a sharp apex on the surface of the epilayer.

  4. Diffuse soil emission of hydrothermal gases (CO2, CH4 and C6H6) at the Solfatara crater (Phlegraean Fields, southern Italy).

    NASA Astrophysics Data System (ADS)

    Tassi, Franco; Nisi, Barbara; Cardellini, Carlo; Capecchiacci, Francesco; Donnini, Marco; Vaselli, Orlando; Avino, Rosario; Chiodini, Giovanni

    2013-04-01

    The Phlegraean Fields caldera, located in the Plio-Pleistocene tectonic depression of the Campanian Plain (southern Italy) and formed after the Neapolitan Yellow Tuff eruption (12-15 ka), is characterized by numerous (monogenetic) volcanic centers that testify a recurrent unrest. At least 61 eruptions after the Neapolitan Yellow Tuff emplacement occurred. The recent history of the Phlegran Fields is marked by ground surface movements due to volcano-tectonics and cycles of bradyseisms: vertical ground movements up to 12 m were evidenced at the Serapis Temple during the last 2200 years. More recently, ground movements, centered inside the Phlegrean Fields caldera, in 1969-1972 (+1.7 m), 1972-1975 (-0.2 m) and 1982-1984 (+1.8 m), occurred. The bradyseismic activity is likely triggered by periodic gas injection (mainly CO2) at the bottom of the hydrothermal system that feeds the fumarolic field of Solfatara. The present study reports the results of CO2, CH4 and C6H6 soil flux surveys, as well as chemical analyses of mono-aromatic compounds in fumaroles and air, carried out at the Solfatara crater in April 2012. The main aim is to investigate the distribution and behavior of these gases as they migrate from their source to the soil and the atmosphere. Soil flux distribution of the three investigated gas compounds has a good spatial correlation, suggesting that diffuse degassing is mainly controlled by local fractures. The calculated total output of diffuse C6H6 from Solfatara is 0.10 kg day-1, whereas those of CO2 and CH4 are 79×103 and 1.04 kg day-1, respectively. Methane is affected by oxidation processes, which appear to be more efficient for low gas fluxes, i.e. the lower the gas flux the higher the residence time of the uprising hydrothermal gases within the crater soil. Benzene oxidation is independent on gas fluxes, whereas it is strongly controlled by presence of a shallow SO42--rich aquifer located in the central and southwestern sectors of the crater, since

  5. A New Method for Studying the Periodic System Based on a Kohonen Neural Network

    ERIC Educational Resources Information Center

    Chen, David Zhekai

    2010-01-01

    A new method for studying the periodic system is described based on the combination of a Kohonen neural network and a set of chemical and physical properties. The classification results are directly shown in a two-dimensional map and easy to interpret. This is one of the major advantages of this approach over other methods reported in the…

  6. U.S. Virtual School Trial Period and Course Completion Policy Study

    ERIC Educational Resources Information Center

    Hawkins, Abigail; Barbour, Michael K.

    2010-01-01

    Variation in policies virtual schools use to calculate course completion and retention rates impacts the comparability of these quality metrics. This study surveyed 159 U.S. virtual schools examining the variability in trial period and course completion policies--two policies that affect course completion rates. Of the 86 respondents, almost 70%…

  7. Identification and transcriptional profile of multiple genes in the posterior kidney of Nile tilapia at 6h post bacterial infections

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To understand the molecular mechanisms involved in response of Nile tilapia (Oreochromis niloticus) to bacterial infection, suppression subtractive cDNA hybridization technique was used to identify upregulated genes in the posterior kidney of Nile tilapia at 6h post infection with Aeromonas hydrophi...

  8. N-V{sub Si}-related center in non-irradiated 6H SiC nanostructure

    SciTech Connect

    Bagraev, Nikolay; Danilovskii, Eduard; Gets, Dmitrii; Klyachkin, Leonid; Malyarenko, Anna; Kalabukhova, Ekaterina; Shanina, Bella; Savchenko, Dariya

    2014-02-21

    We present the first findings of the vacancy-related centers identified by the electron spin resonance (ESR) and electrically-detected (ED) ESR method in the non-irradiated 6H-SiC nanostructure. This planar 6H-SiC nanostructure represents the ultra-narrow p-type quantum well confined by the δ-barriers heavily doped with boron on the surface of the n-type 6H-SiC (0001) wafer. The EDESR method by measuring the only magnetoresistance of the 6H SiC nanostructure under the high frequency generation from the δ-barriers appears to allow the identification of the silicon vacancy centers as well as the triplet center with spin state S=1. The same triplet center that is characterized by the larger value of the zero-field splitting constant D and anisotropic g-factor is revealed by the ESR (X-band) method. The hyperfine (hf) lines in the ESR and EDESR spectra originating from the hf interaction with the {sup 14}N nucleus allow us to attribute this triplet center to the N-V{sub Si} defect.

  9. ATOMIC AND MOLECULAR PHYSICS: Analysis of femtosecond laser ionization/dissociation of polyatomic molecule C6H10O from one-colour pump-probe measurement

    NASA Astrophysics Data System (ADS)

    Hu, Fei-Fei; Zhou, Sheng-Peng; Hu, Zhan; Jin, Ming-Xing; Zhang, Dong-Dong; Wu, Di; Cheng, Xi-Hui; Jiang, Dian-Wu; Ding, Da-Jun

    2009-04-01

    This paper reports that a one-colour fs pump-probe measurement has been carried out for studying photoionization/photodissociation of cyclohexanone (C6H10O) in intense laser field. Two of the fragments from cyclohexanone, C2H3+ and C3H3+, are studied under 800 nm laser pump-probe and the results obtained show similar time evolutions. It proposes a feasible model for analysing the experimental observations of the one-colour fs pump-probe measurement. The results demonstrate that as an intermediate product, the excited molecular parent ions play a very important role in photionization/photodissociation processes in intense laser field.

  10. Doubly periodic structure for the study of inhomogeneous bulk fermion matter with spatial localizations

    SciTech Connect

    Vantournhout, Klaas; Jachowicz, Natalie; Ryckebusch, Jan

    2011-09-15

    We present a method that offers perspectives to perform fully antisymmetrized simulations for inhomogeneous bulk fermion matter. The technique bears resemblance to classical periodic boundary conditions, using localized single-particle states. Such localized states are an ideal tool to discuss phenomena where spatial localization plays an important role. The antisymmetrization is obtained introducing a doubly periodic structure in the many-body fermion wave functions. This results in circulant matrices for the evaluation of expectation values, leading to a computationally tractable formalism to study fully antisymmetrized bulk fermion matter. We show that the proposed technique is able to reproduce essential fermion features in an elegant and computationally advantageous manner.

  11. Study on the Geomagnetic Short Period Variations of the Northwestern Yunnan

    NASA Astrophysics Data System (ADS)

    Yuan, Y.; Li, Q.; Cai, J.

    2015-12-01

    The Northwestern Yunnan is located in the interaction area between the Eurasian plate and the India plate. This area has been the ideal place for the research of continental dynamics and the prediction for risk region of strong earthquake for its complex tectonic environment and frequent seismic activity. Therefore the study on the geomagnetic short period variations is of great significance in the exploration of deep electrical structure, analysis of the seismic origin and deep geodynamics in the Northwestern Yunnan of China . This paper is based on the geomagnetic data from the magnetometer array with 8 sites built in the northwestern Yunnan to explore the deep electrical structure by the method of geomagnetic depth sounding. Firstly, we selected a total of 183 geomagnetic short period events at the range of 6min to 120min period. And we found a north northwest dividing line, of which two sides has the opposite value in the vertical component variation amplitude, which indicates the obvious conductivity anomaly underground. Secondly, the contour maps of the ratio of vertical component and horizontal component variation amplitude ΔZ/ΔH in different periods reflects the changes of a high conductivity belt's direction and position. In addition, the induction arrows maps within the period of 2 - 256min also shows that on the two sides of the dividing line the induction vectors deviate from each other, and the amplitude and direction of vectors varies with periods regularly. In the light of this, we infer that a high conductivity belt probably exists, which stretches from the deep crust to uppermost mantle and changes with depth constantly with the reference of magnetotelluric sounding. In the end of this paper, the staggered grid finite difference method is used to model the simplified three-dimensional high conductivity anomaly, and the result shows magnetic field distributions are consistent with the observed geomagnetic short period variations characteristics in

  12. Study of the period changes in SW Dor, an RR Lyrae type star with Blazhko effect

    NASA Astrophysics Data System (ADS)

    Berdnikov, L. N.; Kniazev, A. Y.; Dambis, A. K.; Kravtsov, V. V.; Sefako, R.

    2016-09-01

    In 2012-2014 we acquired 1569 CCD BVIc frames for the RR Lyrae type variable SW Dor with the 76-cm telescope of the South African Astronomical Observatory (SAAO) and 1-m telescopes of Las Cumbres Observatory Global Telescope network (LCOGT). Our observations showed a large scatter in the resulting phased light curve, especially near maximum brightness, which allowed us to reveal the Blazhko effect with a period of ˜80.9d. To study the pulsation period changes, we used all the available observations including the 1299 magnitude estimates from the digitized plate library of Harvard University (the DASCH project), which allowed us to construct the O-C diagram spanning a 125-year long time interval and discover for the first time at least three abrupt changes of the pulsation period.

  13. Do periodic arm movements during sleep exist in healthy subjects? A polysomnographic study

    PubMed Central

    Gabelia, David; Mitterling, Thomas; Högl, Birgit; Wenning, Gregor K.; Frauscher, Birgit

    2014-01-01

    Background Despite several polysomnographic studies on periodic leg movements (PLM) in healthy sleep, data on the prevalence and characteristics of periodic arm movements (PAM) in normal subjects are lacking. We aimed to investigate PAM and their association with PLM during wakefulness and sleep in healthy subjects. Methods Ninety-one participants underwent video-polysomnography according to American Academy of Sleep Medicine 2007 criteria. In addition to standard electromyographic registration, data for both flexor digitorum superficialis muscles were recorded. Results Sixty-two subjects (68.1%) had a PAM index during wakefulness >5/h (median PAM index during wakefulness, 8.8/h; range, 0–77). Seven subjects (7.7%) had a PAM index >5/h during sleep (median PAM index during sleep, 0.7/h; range, 0–47.4). In 14% of cases, PAM during wakefulness were coincident with PLM during wakefulness. During sleep, this coincidence was not evident. The correlation between PAM and PLM was weak to moderate (during wakefulness: Spearman's ρ = 0.576, P < 0.001; during sleep: Spearman's ρ = 0.222, P = 0.036). Conclusion In healthy subjects, PAM occur predominantly during wakefulness with no apparent true periodicity. In contrast to classical PLM, some PAM may not present a true periodic phenomenon, but rather random voluntary movements meeting the wide range of periodicity criteria for PLM. PMID:25037838

  14. Defect structures and growth mechanisms of boron arsenide epilayers grown on 6H-silicon carbide and 15R-silicon carbide substrates

    NASA Astrophysics Data System (ADS)

    Chen, Hui

    B12As2 possesses the extraordinary properties, such as wide bandgap of 3.47eV and unique 'self heal' ability from electron irradiation damage, which make it attractive for the applications in space electronics, high temperature semiconductors and in particular, beta cells, devices capable of producing electrical energy by coupling a radioactive beta emitter to a semiconductor junction. Due to the absence of native substrates, B12As2 has been grown on substrates with compatible structural parameters via chemical vapor deposition. To date, growth on Si with (100), (110) and (111) orientation and (0001) 6H-SiC has been attempted. However, structural variants, including rotational and translational variants, have been observed in the epilayers and are expected to have a detrimental effect on device performance which has severely hindered progress of this material to date. In addition, none of the earlier reports provide a detailed atomic level study of defect structures in the films and growth mechanisms remain obscure. The focus of this thesis is to study defect structures in B12As2 films grown on different SiC substrates using synchrotron x-ray topography, high resolution transmission microscopy as well as other characterization techniques. The goals of the studies are to understand the generations of the defects present in B12As 2 films and their growth mechanisms so as to develop strategies to reduce defect densities and obtain better film quality for future device fabrication. The following detailed studies have been carried out: (1) The microstructures in B12As2 epitaxial layers grown on on-axis c-plane (0001) 6H-SiC substrates were analyzed in detail. Synchrotron white beam X-ray topography (SWBXT) and scanning electron microscopy (SEM) revealed a mosaic structure consisting of a solid solution of twin and matrix epilayer domains. The epitaxial relationship was determined to be (0001)B12As2<112¯0> B12As2||(0001)6H-SiC<112¯0>6H-SiC. B 12As2 twinned domains were

  15. Infrared identification of the {sigma}-complex of Cl-C{sub 6}H{sub 6} in the reaction of chlorine atom and benzene in solid para-hydrogen

    SciTech Connect

    Bahou, Mohammed; Witek, Henryk; Lee, Yuan-Pern

    2013-02-21

    The reaction of a chlorine atom with benzene (C{sub 6}H{sub 6}) is important in organic chemistry, especially in site-selective chlorination reactions, but its product has been a subject of debate for five decades. Previous experimental and theoretical studies provide no concrete conclusion on whether the product is a {pi}- or {sigma}-form of the Cl-C{sub 6}H{sub 6} complex. We took advantage of the diminished cage effect of para-hydrogen (p-H{sub 2}) to produce Cl in situ to react with C{sub 6}H{sub 6} (or C{sub 6}D{sub 6}) upon photolysis of a Cl{sub 2}/C{sub 6}H{sub 6} (or C{sub 6}D{sub 6})/p-H{sub 2} matrix at 3.2 K. The infrared spectrum, showing intense lines at 1430.5, 833.6, 719.8, 617.0, and 577.4 cm{sup -1}, and several weaker ones for Cl-C{sub 6}H{sub 6}, and the deuterium shifts of observed new lines unambiguously indicate that the product is a 6-chlorocyclohexadienyl radical, i.e., the {sigma}-complex of Cl-C{sub 6}H{sub 6}. Observation of the {sigma}-complex rather than the {pi}-complex indicates that the {sigma}-complex is more stable in solid p-H{sub 2} at 3.2 K. The spectral information is crucial for further investigations of the Cl + C{sub 6}H{sub 6} reaction either in the gaseous or solution phase.

  16. Nuclear Reaction Analysis of Helium Retention in 6H SiC as a function of irradiation and annealing

    NASA Astrophysics Data System (ADS)

    Bissell, L. J.; Smith, R. J.; Shutthanadan, V.; Adams, E. M.; Thevuthasan, S.; Jiang, W.; Weber, W. J.; Zhang, Y.

    2002-10-01

    Silicon carbide has been proposed as a coating material in nuclear fuel, and silicon carbide composites have been proposed as cladding material in advanced gas-cooled and light water reactors. As such, the effects of irradiation and fission gases on the performance of SiC in the reactor environment are critical in several ways. Since He serves as a fission gas, low-energy He (< 50 keV) will be colliding with coolant gas and outer surface cladding layers. As such, it is important to understand He retention in SiC under advanced reactor operating conditions. We investigated He retention in single crystal 6H SiC as a function of irradiation dose and annealing temperature using nuclear reaction analysis (NRA) via the 3He(D,alpha)1H reaction. Helium ions with 40 keV energy were implanted in the SiC to a depth of ˜360 nm at room temperature under high vacuum conditions. The samples were then transferred to another high vacuum chamber where the NRA was performed using a 1.0 MeV D+ beam. Helium retention was studied as a function of D+ irradiation dose from 5 x 10^(16) to 4 x 10^(18) D+ /cm2, and as a function of annealing temperature ranging from 300 1600 K. No significant helium loss was observed under this dosage range, and only annealing temperatures above 1400 K caused measurable loss of helium. These results will be discussed along with the details associated with the 3He(D,alpha)1H nuclear reaction.

  17. A study on the effect of exclusion period on the suicidal risk among the insured.

    PubMed

    Yip, Paul S F; Chen, Feng

    2014-06-01

    An exclusion period (usually from 12 months to 2 years) is usually found in life insurance policies as a precautionary measure to prohibit people from insuring their lives with the intent to kill themselves shortly thereafter. Several studies have been conducted to investigate the effect of exclusion periods on the risk of suicide among the insured in the US and Australia. However, while Hong Kong has experienced an increase in the number of suicides among the insured, little is known about the dynamic between the exclusion period and suicide in Asia. Here we make use of death claims data from one of the major life insurance companies in Hong Kong to ascertain the impact of a 12-month exclusion period on suicide risk. We also use utility functions derived from economic theory to better understand individual choices regarding suicide among the insured. More specifically, we sought to determine whether there is a greater risk of suicide immediately following the 12-month exclusion period. We also examined whether the risk of suicide claims was higher than that of other non-suicidal claims. The study period for this investigation was from January 1, 1997 to December 31, 2011, during which time there were 1935 claims based on 1243 deaths. Of these, 197 were suicide-related claims for 106 suicide deaths. The mean number of life policies held by suicidal claimants and non-suicidal claimants was 1.6 and 1.4, respectively. The average/median size of the claims (total payment made on all policies held by the insured life) was HK$665,800/426,600 and HK$497,700/276,200 for suicidal and non-suicidal deaths, respectively. The policy lifetime of the claims, or the number of days from policy issuance to suicide occurrence, ranged from 38 to 7561 days, with a mean of 2209 days, a median of 1941 days, and a standard deviation of 1544 days. The peak density of suicide claims occurred on day 1039 of the policy. Our results revealed that suicide claims tend to occur earlier than other

  18. A study on the effect of exclusion period on the suicidal risk among the insured.

    PubMed

    Yip, Paul S F; Chen, Feng

    2014-06-01

    An exclusion period (usually from 12 months to 2 years) is usually found in life insurance policies as a precautionary measure to prohibit people from insuring their lives with the intent to kill themselves shortly thereafter. Several studies have been conducted to investigate the effect of exclusion periods on the risk of suicide among the insured in the US and Australia. However, while Hong Kong has experienced an increase in the number of suicides among the insured, little is known about the dynamic between the exclusion period and suicide in Asia. Here we make use of death claims data from one of the major life insurance companies in Hong Kong to ascertain the impact of a 12-month exclusion period on suicide risk. We also use utility functions derived from economic theory to better understand individual choices regarding suicide among the insured. More specifically, we sought to determine whether there is a greater risk of suicide immediately following the 12-month exclusion period. We also examined whether the risk of suicide claims was higher than that of other non-suicidal claims. The study period for this investigation was from January 1, 1997 to December 31, 2011, during which time there were 1935 claims based on 1243 deaths. Of these, 197 were suicide-related claims for 106 suicide deaths. The mean number of life policies held by suicidal claimants and non-suicidal claimants was 1.6 and 1.4, respectively. The average/median size of the claims (total payment made on all policies held by the insured life) was HK$665,800/426,600 and HK$497,700/276,200 for suicidal and non-suicidal deaths, respectively. The policy lifetime of the claims, or the number of days from policy issuance to suicide occurrence, ranged from 38 to 7561 days, with a mean of 2209 days, a median of 1941 days, and a standard deviation of 1544 days. The peak density of suicide claims occurred on day 1039 of the policy. Our results revealed that suicide claims tend to occur earlier than other

  19. Measuring rotation periods of solar-like stars using TIGRE. A study of periodic CaII H+K S-index variability

    NASA Astrophysics Data System (ADS)

    Hempelmann, A.; Mittag, M.; Gonzalez-Perez, J. N.; Schmitt, J. H. M. M.; Schröder, K. P.; Rauw, G.

    2016-02-01

    Context. The rotation period of a star is a key parameter both for the stellar dynamo that generates magnetic fields as well as for stellar differential rotation. Aims: We present the results from the first year of monitoring a sample of solar-like stars by the TIGRE facility in Guanajuato (Mexico), which will study rotation in solar analogs. Methods: TIGRE is an automatically operating 1.2 m telescope equipped with an Échelle spectrograph with a spectral resolution of 20 000, which covers a spectral range of between 3800 and 8800 Å. A main task is the monitoring the stellar activity of cool stars, mainly in the emission cores of the CaII H and K lines. We observed a number of stars with a sampling between 1-3 days over one year. Results: A total number of 95 stars were observed between August 1 2013 and July 31 2014, the total number of spectra taken for this program was appoximately 2700. For almost a third of the sample stars the number of observations was rather low (less than 20), mainly because of bad weather. Fifty-four stars show a periodic signal but often with low significance. Only 24 stars exhibit a significant period. We interpret these signals as stellar rotation. For about half of them the rotation periods were already previously known, in which case our period measurements are usually in good agreement with the literature values. Besides the periodic signals, trends are frequently observed in the time series. Conclusions: TIGRE is obviously able to detect stellar rotation periods in the CaII H+K emission cores when the time series contains a sufficient number of data points. However, this is frequently not achievable during the wet summer season in Guanajuato. Hence, future estimates of rotation periods will concentrate on stars that are observable during the winter season from October until April.

  20. Heavily doped Au25-xAgx(SC6H11)18(-) nanoclusters: silver goes from the core to the surface.

    PubMed

    Li, Qi; Wang, Shuxin; Kirschbaum, Kristin; Lambright, Kelly J; Das, Anindita; Jin, Rongchao

    2016-04-14

    We report a method for heavy doping of the Au25(SR)18 nanocluster (where R = C6H11) with silver through the Ag(I)-thiolate complex induced size/structure transformation of Au23(SR)16(-) into Au25-xAgx(SR)18(-). X-ray crystallographic analysis revealed that Ag dopants are distributed not only in the icosahedral core but also in the surface staple motifs; the latter was not achieved in earlier studies of alloy Au25-xAgx nanoclusters.

  1. Surface and electronic structure of 6H-SiC(0001)-(3 × 3) surfaces and ultrathin Ag films on Si(111) and Si(001)

    NASA Astrophysics Data System (ADS)

    Gasparov, V. A.

    2011-10-01

    Surface topographic (LEED, STM) and spectroscopic (ARUPS, XPS, STS) studies have been performed on Si-terminated 6H-SiC(0001)-(3 × 3) surfaces and Ag superstructures and ultrathin films on Si(001) and Si(111) surfaces, using a scanning tunneling microscope (STM) in ultrahigh vacuum. Our results confirm that 2D epitaxial metal growth is favored on Si(001) at low temperatures and a solid, two-domain Ag(111) film has been achieved at coverages as low as 10 ML. The films reveal a morphology with 3-dimensional features and with a well defined honeycomb structure in between. An atomically flat Si(111)/Ag -(√3 ×√3 )R30∘ surface has been modified by use of a scanning tunneling microscope (STM) in ultrahigh vacuum (UHV). High quality 6H-SiC(0001)-(3 × 3) and Si(111)/-Ag(√3 ×√3 )R30∘ upper structures have been prepared and studied by means of ARUPS, XPS and LEED. The local density of states proportional to the spectrum of normalized differential conductivity (dI/dV)/(I/V) vs V reveals distinct bands of empty (-0.6 eV) and filled (0.65 eV) sites separated by 1.2 eV, for both areas. The results support the use of a Mott-Hubbard-type model for calculating the density of states of 6H-SiC(0001)-(3 × 3) surfaces with a Hubbard gap of 1 eV.

  2. Quality of Life among Iranian Infertile Women in Postmenopausal Period: A Cross-sectional Study

    PubMed Central

    Direkvand-Moghadam, Ashraf; Montazeri, Ali; Sayehmiri, Kourosh

    2016-01-01

    Objectives Infertility has a significant impact on a women's quality of life (QOL). Infertile women face with physical and mental challenges during their postmenopausal period. Therefore, the present study aimed to evaluate the QOL among Iranian infertile women in the postmenopausal period using a valid and reliable instrument. Methods In this cross-sectional study both snowball and social networking methods were used for sampling. Two demographic and QOL questionnaire were used for data collection. The QOL questionnaire includes 41 items which measure the QOL in five dimensions: socioeconomic, mental health, religiousness, physical health and future imagining. Data analyzed was carried out in IBM SPSS ver. 20.0 using descriptive statistic, χ2 test, and Fisher test. A P value of 0.01 or less was considered significant. Results Overall 211 eligible participants were studied. Some participants obtained full score on socioeconomic, religiousness, physical health and future imagining dimensions of QOL but none on the mental health dimension of the QOL. Only, 6.6% of study participants have a good QOL. There was a significant relationship between age and financial provider whit status of QOL. Conclusion Most Iranian infertile women in the postmenopausal period have poor or moderate QOL. Therefore, improving the QOL among these women should be considered. PMID:27617245

  3. Quality of Life among Iranian Infertile Women in Postmenopausal Period: A Cross-sectional Study

    PubMed Central

    Direkvand-Moghadam, Ashraf; Montazeri, Ali; Sayehmiri, Kourosh

    2016-01-01

    Objectives Infertility has a significant impact on a women's quality of life (QOL). Infertile women face with physical and mental challenges during their postmenopausal period. Therefore, the present study aimed to evaluate the QOL among Iranian infertile women in the postmenopausal period using a valid and reliable instrument. Methods In this cross-sectional study both snowball and social networking methods were used for sampling. Two demographic and QOL questionnaire were used for data collection. The QOL questionnaire includes 41 items which measure the QOL in five dimensions: socioeconomic, mental health, religiousness, physical health and future imagining. Data analyzed was carried out in IBM SPSS ver. 20.0 using descriptive statistic, χ2 test, and Fisher test. A P value of 0.01 or less was considered significant. Results Overall 211 eligible participants were studied. Some participants obtained full score on socioeconomic, religiousness, physical health and future imagining dimensions of QOL but none on the mental health dimension of the QOL. Only, 6.6% of study participants have a good QOL. There was a significant relationship between age and financial provider whit status of QOL. Conclusion Most Iranian infertile women in the postmenopausal period have poor or moderate QOL. Therefore, improving the QOL among these women should be considered.

  4. A Study of the Shortest-period Planets Found with Kepler

    NASA Astrophysics Data System (ADS)

    Sanchis-Ojeda, Roberto; Rappaport, Saul; Winn, Joshua N.; Kotson, Michael C.; Levine, Alan; El Mellah, Ileyk

    2014-05-01

    We present the results of a survey aimed at discovering and studying transiting planets with orbital periods shorter than one day (ultra-short-period, or USP, planets), using data from the Kepler spacecraft. We computed Fourier transforms of the photometric time series for all 200,000 target stars, and detected transit signals based on the presence of regularly spaced sharp peaks in the Fourier spectrum. We present a list of 106 USP candidates, of which 18 have not previously been described in the literature. This list of candidates increases the number of planet candidates with orbital periods shorter than about six hours from two to seven. In addition, among the objects we studied, there are 26 USP candidates that had been previously reported in the literature which do not pass our various tests. All 106 of our candidates have passed several standard tests to rule out false positives due to eclipsing stellar systems. A low false positive rate is also implied by the relatively high fraction of candidates for which more than one transiting planet signal was detected. By assuming these multi-transit candidates represent coplanar multi-planet systems, we are able to infer that the USP planets are typically accompanied by other planets with periods in the range 1-50 days, in contrast with hot Jupiters which very rarely have companions in that same period range. Another clear pattern is that almost all USP planets are smaller than 2 R ⊕, possibly because gas giants in very tight orbits would lose their atmospheres by photoevaporation when subject to extremely strong stellar irradiation. Based on our survey statistics, USP planets exist around approximately (0.51 ± 0.07)% of G-dwarf stars, and (0.83 ± 0.18)% of K-dwarf stars.

  5. Retrospective study of recession of four horizontal rectus muscle in periodic alternating nystagmus

    PubMed Central

    Mimura, Osamu; Ishikawa, Hiroto; Kimura, Naoki; Kimura, Akiko; Borlongan, Cesar V

    2014-01-01

    Purpose Periodic alternating nystagmus (PAN) is a spontaneous horizontal nystagmus observed in disorders of the central nervous system. Patients with congenital PAN complain of oscillating vision at high rates. Medication is the first-choice treatment for PAN; however, clinicians still seek better therapy. The aim of this study was to evaluate outcomes of recession of four horizontal rectus muscle (R-FHR) in patients with congenital PAN. Patients and methods This study reports a retrospective case series of ten patients (seven males and three females; mean age 24.4±10.9) with congenital PAN who underwent R-FHR between 2007 and 2012, which was performed by the same surgeon at the Hyogo College of Medicine. Patients were evaluated for complications, recession amount, deviation angle, eye movements including a nystagmus amplitude, and visual acuity during pre- and post-operative periods. Results Pre-operatively, patients complained of oscillating vision, abnormal head posture, esotropia, and congenital superior oblique palsy. Post-operatively, changes from the previous observations of nystagmus amplitudes and abnormal head posture demonstrated a complete reversal in all patients. In addition, visual acuity determined with a Snellen chart improved in two patients. However, esotropia occurred in three patients who underwent additional strabismus surgery 2 days after R-FHR. R-FHR was particularly effective in eight patients who pre-operatively had periodic oscillating vision with a regular pattern of periodic nystagmus. Conclusion We demonstrated that ten patients with congenital PAN had improved vision following R-FHR, indicating that R-FHR was an effective procedure, especially in patients suffering PAN with periodic oscillating vision. PMID:25525330

  6. A study of the shortest-period planets found with Kepler

    SciTech Connect

    Sanchis-Ojeda, Roberto; Rappaport, Saul; Winn, Joshua N.; Kotson, Michael C.; Levine, Alan; Mellah, Ileyk El E-mail: sar@mit.edu E-mail: ileyk@apc.univ-paris7.fr

    2014-05-20

    We present the results of a survey aimed at discovering and studying transiting planets with orbital periods shorter than one day (ultra-short-period, or USP, planets), using data from the Kepler spacecraft. We computed Fourier transforms of the photometric time series for all 200,000 target stars, and detected transit signals based on the presence of regularly spaced sharp peaks in the Fourier spectrum. We present a list of 106 USP candidates, of which 18 have not previously been described in the literature. This list of candidates increases the number of planet candidates with orbital periods shorter than about six hours from two to seven. In addition, among the objects we studied, there are 26 USP candidates that had been previously reported in the literature which do not pass our various tests. All 106 of our candidates have passed several standard tests to rule out false positives due to eclipsing stellar systems. A low false positive rate is also implied by the relatively high fraction of candidates for which more than one transiting planet signal was detected. By assuming these multi-transit candidates represent coplanar multi-planet systems, we are able to infer that the USP planets are typically accompanied by other planets with periods in the range 1-50 days, in contrast with hot Jupiters which very rarely have companions in that same period range. Another clear pattern is that almost all USP planets are smaller than 2 R {sub ⊕}, possibly because gas giants in very tight orbits would lose their atmospheres by photoevaporation when subject to extremely strong stellar irradiation. Based on our survey statistics, USP planets exist around approximately (0.51 ± 0.07)% of G-dwarf stars, and (0.83 ± 0.18)% of K-dwarf stars.

  7. Age, period, and cohort effects on pulmonary function in a 24-year longitudinal study.

    PubMed

    Xu, X; Laird, N; Dockery, D W; Schouten, J P; Rijcken, B; Weiss, S T

    1995-03-15

    This paper proposes the use of two-factor models (age-period and age-cohort models) to estimate age, period, and cohort effects on pulmonary function by using the data collected in a 24-year longitudinal study in the Netherlands from 1965 to 1990. The analysis included 18,363 pulmonary function measurements on 6,148 subjects aged 20-54 years at the initial visit. The subjects were grouped into four birth cohorts (before 1923, 1923-1934, 1935-1946, and after 1946) and four survey periods (1965-1972, 1973-1978, 1979-1984, and 1985-1990). In the age-cohort model, the decrement in forced expiratory volume in 1 second (FEV1) associated with a yearly increase in age was 28.3 +/- 3.7 ml/year for a man 176 cm tall and 16.0 +/- 1.9 ml/year for a woman 163 cm tall. The estimated acceleration of decline with aging was significant for both men (beta = -0.212; standard error = 0.079 ml) and women (beta = -0.346; standard error = 0.058 ml). Compared with that of the cohort born before 1923, the average level of FEV1 was estimated to increase by 156, 277, and 379 ml, respectively, for the three younger cohorts in men (p = 0.01) and by 133, 213, and 328 ml for the three younger cohorts in women (p < 0.01). In the age-period model, the estimated linear age effect on FEV1 was 36.2 +/- 4.2 ml/year for a man and 30.5 +/- 2.3 ml/year for a woman. The age quadratic term was significant for women, but not for men. Average FEV1 was estimated to be increased by 141, 169, and 250 ml, respectively, for the periods 1973-1978, 1979-1984, and 1985-1990 in men and by 131, 138, and 219 ml in women. These period effects were significant for both men and women. In summary, this study applied the two-factor models to estimate cross-sectional and longitudinal effects of aging on FEV1 and demonstrated significant period and cohort effects, which could be attributed in part to changes in air pollutants, respiratory infections, vaccinations, types of cigarettes, diet, and lifestyles over time.

  8. A study on characteristics of Methane emission from a periodically irrigated paddy field in Japan

    NASA Astrophysics Data System (ADS)

    Wakikuromaru, N.; Iwata, T.; Yagi, K.

    2014-12-01

    Methane (CH4) is generated by organic matter decomposition in the anaerobic soil. Paddy field is one of the most important eco-system in monsoon Asia. It is said that about 10% of CH4sources is paddy fields (IPCC AR4, 2007). In this study, methane emission from a single-rice crop field was estimated by long-term micrometeorological measurements. Methane emission was calculated by the aerodynamic gradient technique from January 2011 to August 2014. Intermittent water management was carried out during cultivation period at the observational site, HCH, located in Okayama, Japan. 3-days flood and 4-days drained condition were regularly repeated from late-June to early October. Seasonal variations of CH4flux for irrigation term from 2011 to 2013 were shown in Fig.1. Remarkably large fluxes were shown at early stage of irrigation term in 2011.It seemed to be caused by the relatively longer flooded condition that the first flooded period was 20 days. Flux in 2012 was smaller than in other year through the entire irrigation period. Rapid rise in flux for early August and gradual decrease between late August and September were shown in 2013. Fluxes under drained condition showed larger emission than under flooded condition. Cumulative CH4 emissions during cultivated period from 2011 to 2013 were estimated 15.7, 8.6, and 12.9 gC/m2, respectively.

  9. The three-level ripples induced by femtosecond laser on a 6H-SiC single crystal and the formation mechanism

    NASA Astrophysics Data System (ADS)

    Song, Juan; Tao, Wenjun; Gong, Min; Ye, Junyi; Dai, Ye; Ma, Guohong; Qiu, Jianrong

    2016-04-01

    In this paper, a line-scanning irradiation of <0001> 6H-SiC single crystal by a femtosecond laser focus was implemented for laser fluence of 2.2 J/cm2 at different scanning velocities from 1000 down to 100 μm/s. The morphology of the obtained ablation lines characterized by a scanning electron microscope shows that there progressively appear three-level ripples with average period of about 222, 600 nm and that between them. Possible formation mechanisms for these three-level ripples were analyzed by numerical simulation employing finite-difference time-domain method (FDTD). Analysis shows that as Obara proposed, the interference of incident wave with the wave scattered by scratches possibly left by fine polishing is the most possible reason for inducing 222 nm-period and 600 nm-period ripples. Main discussions were focused on the orientation characteristics of ripples. Both isolated scratches and crossed scratches with different orientation angles were considered for evaluating their role in field redistribution. The detailed simulations indicate that for scratches oriented 90° with respect to laser polarization generate a pair of strongest ripple-like optical field enhancement compared to scratches with other orientation angles. It is these advantages of 90°-oriented scratch in field enhancement that make the final ripple perpendicular to laser polarization most competitive and finally left on the surface. This complements the physical picture of Obara et al. in terms of their negligence in addressing the orientation characteristics of ripples. Further FDTD simulation of the interaction of incident wave with as-formed 600 nm-period ripples shows that the optical field enhancement located between any two adjacent 600 nm-period ripples is the driving force for splitting 600 nm-period ripples into the third ripples with period between 222 and 600 nm.

  10. A study of admissions and inpatients over the Christmas period using the appropriateness evaluation protocol (AEP).

    PubMed

    Henshaw; Pollock; Rai; Gluck

    2000-08-01

    The aim of the study was to examine appropriateness of admissions and inpatients over Christmas especially in the elderly. The study was a prospective audit of admissions and inpatients to the Whittington Hospital. The main outcome measures were appropriateness of admission or day of hospital residence using the Appropriateness Evaluation Protocol. The protocol was applied to admissions and inpatients over Christmas and control periods. The results showed that there was a significant difference in the number of elderly admissions between the control period and Christmas period, 94 (34%) vs. 104 (43%) (P=0.02). However there was no corresponding change in appropriateness of elderly admissions, ten (10.6%) vs. six (5.8%), (P=0.2). The inappropriateness of day of hospital residence increased from 10% on the control day to 20% on the study day (P=0.02). In conclusion elderly patients are not admitted more inappropriately over Christmas but their discharge at this time appears to be delayed resulting in inappropriate bed use.

  11. The study of periodic changes in altitude of the satellite permanent stations of the world

    NASA Astrophysics Data System (ADS)

    Babiy, Lyubov; Tretyak, Kornyliy; Smirnova, Olha; Kulchyckiy, Andriy

    2013-04-01

    The following investigations were implemented in order to study the period of harmonic oscillations of time series of permanent GNSS stations, which are caused by various geophysical factors. A database of daily time series had been created for 111 permanent stations, there observations were running for at least 3 years. Permanent stations cover the latitudinal zone within +600 to -600. Algorithm and program for processing time series and determination of the optimal harmonic functions were developed. Kinematics model of the satellite station is described by the following equation h = at+b+c*cos(t-t0-n*p)+s*sin(t-t0-n*p), where a,b - coefficients of regression equation of linear displacement of station; c,s - harmonic coefficients, t-t0 - time observations at the station, n - number of periods of oscillation p, which fit in the interval t-t0. Presented equation was calculated at each epoch of observations for each station and coefficients a, b, c, s were determined by the method of least squares. On database 60 stations were selected for the study. The criterion for selection was the availability of clearly specified minimum of function of standard deviation of approximate curve from measurement results depending on the duration of the period of oscillations. From the analysis of created database it can be argued that harmonic oscillations of permanent stations depend on geographic station location and location of satellite receivers. According to results of processing it was defined that amplitude of periodical oscillations is changing in the bounds from 2.0 mm till 10.2 mm; period - from 348.9 days till 392,7 days. The largest amplitudes of function of harmonic oscillations are on the permanent stations that are in the heart of the continent, and the smallest amplitudes are on the stations placed along the coastline and on the islands, which apparently due to the capacity of the Earth's crust. It should be noted that the maximums of oscillation amplitudes of

  12. Electronic spectrum of C 6H: 2Π- X2Π in the gas-phase detected by cavity ringdown

    NASA Astrophysics Data System (ADS)

    Kotterer, Markus; Maier, John P.

    1997-02-01

    The 2Π- X2Π electronic transition of the carbon chain C 6H has been detected in the gas-phase. The radical is generated in a hollow cathode discharge of acetylene in helium, and cavity ringdown spectroscopy is used as a sensitive means to observed the band system in absorption. This is the first result aimed at locating the electronic transitions of the neutral carbon chains, of astrophysical interest, in the gas-phase. The search was based on the measurements made previously on C 6H in neon matrices. The origin band ( Ω = 3/2) in the gas phase at 18996.4 cm -1 is 142 cm -1 to the blue of the matrix value.

  13. Statistical study on magnetotail lobe waves with period 40 - 600 s observed by Cluster

    NASA Astrophysics Data System (ADS)

    Wang, Guoqiang; Zhang, Tielong; Volwerk, Martin

    2016-04-01

    Ultra low frequency (ULF) waves play an important role in energy transport and dissipation in the magnetosphere. In this paper, 263 waves with period 40 - 150 s and 161 waves with period 150 - 600 s in the Earth's magnetotail lobe have been studied by using Cluster data from years 2001 to 2009. Our findings are as follows: (1) 90% of the wave amplitudes with period 40 - 150 s are below ~0.25 nT for transverse components, and ~0.16 nT for compressional component; The amplitudes of longer period waves are somewhat larger; For waves with period 150 - 600 s, 90% of the wave amplitudes are below ~0.36 nT and ~0.39 nT for transverse and compressional components, respectively. (2) Waves within 40 - 150 s prefer to occur in the lobe region close to the plasma sheet, while waves within 150 - 600 s can be observed throughout the lobe region; (3) The amplitudes of lobe waves and AE index are weakly correlated; However, we find that amplitudes tend to be larger when the AE index is larger; (4) Amplitudes also tend to be larger when the solar wind velocity, the solar wind dynamic pressure or its variations (∆PSW) is larger; The correlation coefficient between amplitudes of waves within 150 - 600 s and ∆PSW is up to ~0.58. We suggest that both dynamic pressure in the plasma sheet boundary layer or plasma sheet (inner source) and solar wind conditions (outer source) can contribute to the generation of lobe ULF waves; Waves within 40 - 150 s are effected more by inner source; ∆PSW is more associated with compressional waves within 150 - 600 s than that within 40 - 150 s.

  14. Volumetric Properties of the Mixture Hexane C6H14 + C8H16 Cyclooctane (VMSD1242, LB3843_V)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture Hexane C6H14 + C8H16 Cyclooctane (VMSD1242, LB3843_V)' providing data by calculation of molar excess volume from density measurements at variable pressure and constant temperature and mole fraction.

  15. Volumetric Properties of the Mixture Hexane C6H14 + C8H16 Cyclooctane (VMSD1141, LB3786_V)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture Hexane C6H14 + C8H16 Cyclooctane (VMSD1141, LB3786_V)' providing data from direct measurement of mass density at variable pressure and constant temperature and mole fraction.

  16. Ly6h regulates trafficking of alpha7 nicotinic acetylcholine receptors and nicotine-induced potentiation of glutamatergic signaling.

    PubMed

    Puddifoot, Clare A; Wu, Meilin; Sung, Rou-Jia; Joiner, William J

    2015-02-25

    α7 nAChRs are expressed widely throughout the brain, where they are important for synaptic signaling, gene transcription, and plastic changes that regulate sensory processing, cognition, and neural responses to chronic nicotine exposure. However, the mechanisms by which α7 nAChRs are regulated are poorly understood. Here we show that trafficking of α7-subunits is controlled by endogenous membrane-associated prototoxins in the Ly6 family. In particular, we find that Ly6h reduces cell-surface expression and calcium signaling by α7 nAChRs. We detect Ly6h in several rat brain regions, including the hippocampus, where we find it is both necessary and sufficient to limit the magnitude of α7-mediated currents. Consistent with such a regulatory function, knockdown of Ly6h in rat hippocampal pyramidal neurons enhances nicotine-induced potentiation of glutamatergic mEPSC amplitude, which is known to be mediated by α7 signaling. Collectively our data suggest a novel cellular role for Ly6 proteins in regulating nAChRs, which may be relevant to plastic changes in the nervous system including rewiring of glutamatergic circuitry during nicotine addiction. PMID:25716842

  17. Laser-induced fluorescence of cyclohexadienyl (c-C6H7) radical in the gas phase.

    PubMed

    Imamura, Takashi; Zhang, Weijun; Horiuchi, Hiroaki; Hiratsuka, Hiroshi; Kudo, Takako; Obi, Kinichi

    2004-10-01

    A laser-induced fluorescence spectrum was observed in the 500-560 nm region when a mixture of 1,4-cyclohexadiene and oxalyl chloride was photolyzed at 193 nm. The observed excitation spectrum was assigned to the A (2)A(2)<--X (2)B(1) transition of the cyclohexadienyl radical c-C6H7, produced by abstraction of a hydrogen atom from 1,4-cyclohexadiene by Cl atoms. The origin of the A<--X transition of c-C(6)H(7) was at 18 207 cm(-1). From measurements of the dispersed fluorescence spectra and ab initio calculations, the frequencies of several vibrational modes in both the ground and excited states of c-C(6)H(7) were determined: nu(5)(C-H in-plane bend)=1571, nu(8)(C-H in-plane bend)=1174, nu(10)(C-C-C in-plane bend)=981, nu(12)(C-C-C in-plane bend)=559, nu(16)(C-C-C out-of-plane bend)=375, and nu(33)(C-C-C in-plane bend)=600 cm(-1) for the ground state and nu(8)=1118, nu(10)=967, nu(12)=502, nu(16)=172, and nu(33)=536 cm(-1) for the excited states.

  18. On Flowfield Periodicity in the NASA Transonic Flutter Cascade. Part 1; Experimental Study

    NASA Technical Reports Server (NTRS)

    Lepicovsky, J.; McFarland, E. R.; Chima, R. V.; Wood, J. R.

    2000-01-01

    An extensive study to improve flow uniformity and periodicity in the NASA Transonic Flutter Cascade is presented here. The results are reported in two independent parts dealing with the experimental approach and the analytical approach. The first part, the Experimental Study, focuses first on the data sets acquired in this facility in the past and explains several discrepancies, particularly the questions of actual flow incidence and cascade back pressure levels. Next, available means for control and modifications of the cascade flowfield, boundary layer bleed and tailboard settings are presented in detail. This is followed by experimental data sets acquired in modified test facility configurations that were based on analytical predictions of the cascade flowfield. Finally, several important conclusions about improving the cascade flowfield uniformity and blade load periodicity are summarized. The important conclusions are: (1) boundary layer bleed does not improve the cascade flow periodicity; (2) tunnel wall contours must be carefully matched to the expected shape of cascade streamlines; (3) actual flow incidence for each cascade configuration rather must be measured instead of relying on the tunnel geometry; and (4) the current cascade configuration exhibits a very high blade load uniformity over six blades from blade #2 to blade #7, and the facility is now ready for unsteady pressure data acquisition.

  19. Numerical study of the unsteady flow and heat transfer in channels with periodically mounted square bars

    NASA Astrophysics Data System (ADS)

    Valencia, A.; Martin, J. S.; Gormaz, R.

    Numerical investigations of unsteady laminar flow and heat transfer in a channel of height H with periodically mounted square bars of height d = 0.2H arranged side by side to the approaching flow have been conducted for different transverse separation distances of the bars. Five cases with transverse separation distance of 0, 0.5, 1, 1.5 and 2d for a Reynolds number of 300 in a channel with a periodicity length of 2H were studied. The unsteady Navier-Stokes equations and the energy equation have been solved by a finite volume code with staggered grids combined with the SIMPLEC algorithm and a fine grid resolution. Due to the arrangement of bars detached from the channel walls the flow is unsteady with vortex shedding from the bars. The amplitude and mean values of the drag coefficients, skin friction coefficients, friction factor and Nusselt numbers have a strong dependence of the transverse separation distance of the bars.

  20. Spectroscopic studies of wood fossils from the Crato Formation, Cretaceous Period.

    PubMed

    da Silva, J H; Freire, P T C; Abagaro, B T O; Silva, J A F; Saraiva, G D; de Lima, F J; Barros, O A; Bantim, R A; Saraiva, A A F; Viana, B C

    2013-11-01

    In this work we study two types of wood fossils (Gymnosperms, Araucariaceae) from the Crato Formation of Araripe Basin in Brazil, from the Cretaceous Period. The samples were characterized by Raman and infrared spectroscopies, X-ray diffraction and scanning electron microscopy. The results obtained by different techniques showed that although the rocks surrounding the fossils have predominantly the same constitution - calcite - however, the formation processes of these types of wood fossils are quite different. One of the fossils, denominated as light wood, is predominantly composed of gypsum, while the other fossil, the dark wood, is rich in amorphous carbon, possibly the kerogen type. Implications relative to the environment where the plants lived millions years ago are also given. Finally, the results highlight the constitution of one of the most important paleontological sites of the Cretaceous Period in the South America.

  1. Experimental study of effect of stenosis geometry on pressure loss for periodic flow

    NASA Astrophysics Data System (ADS)

    Veselý, Ondřej; Nováková, Ludmila; Adamec, Josef

    2016-03-01

    A stenosis is a narrowing in a tubular organ. In medicine, vessel stenosis poses health risk for people. In the last work, experimental investigation of pressure loss coefficient for varying stenosis eccentricity and shape for steady flow were performed. In this work, experimental investigation of pressure loss for varying stenosis eccentricity and shape under periodic flow were performed. Four models of different geometry were studied, two models are axisymmetric stenoses and two models are eccentric stenoses. All models were stenosis of 75% area reduction. The periodic flow, generated by a controllable pump, has sinus shape in an inlet. The measuring range of medium Reynolds number was from 500 to 1500, range of ratio between an amplitude and medium flow rate was from 0.2 to 0.6 and range of frequency was from 0.2 to 1 Hz. The pressure loss for each conditions was quantified by mean value, amplitude and phase shift against flow rate.

  2. Spectroscopic studies of wood fossils from the Crato Formation, Cretaceous Period.

    PubMed

    da Silva, J H; Freire, P T C; Abagaro, B T O; Silva, J A F; Saraiva, G D; de Lima, F J; Barros, O A; Bantim, R A; Saraiva, A A F; Viana, B C

    2013-11-01

    In this work we study two types of wood fossils (Gymnosperms, Araucariaceae) from the Crato Formation of Araripe Basin in Brazil, from the Cretaceous Period. The samples were characterized by Raman and infrared spectroscopies, X-ray diffraction and scanning electron microscopy. The results obtained by different techniques showed that although the rocks surrounding the fossils have predominantly the same constitution - calcite - however, the formation processes of these types of wood fossils are quite different. One of the fossils, denominated as light wood, is predominantly composed of gypsum, while the other fossil, the dark wood, is rich in amorphous carbon, possibly the kerogen type. Implications relative to the environment where the plants lived millions years ago are also given. Finally, the results highlight the constitution of one of the most important paleontological sites of the Cretaceous Period in the South America. PMID:23856041

  3. Variational Monte Carlo study of magnetic states in the periodic Anderson model

    NASA Astrophysics Data System (ADS)

    Kubo, Katsunori

    2015-03-01

    We study the magnetic states of the periodic Anderson model with a finite Coulomb interaction between f electrons on a square lattice by applying variational Monte Carlo method. We consider Gutzwiller wavefunctions for the paramagnetic, antiferromagnetic, ferromagnetic, and charge density wave states. We find an antiferromagnetic phase around half-filling. There is a phase transition accompanying change in the Fermi-surface topology in this antiferromagnetic phase. We also study a case away from half-filling, and find a ferromagnetic state as the ground state there.

  4. Studies of short-period comets on the eve of Rosetta

    NASA Astrophysics Data System (ADS)

    Pozuelos, F. J.; Moreno, F.; Aceituno, F.; Casanova, V.; Sota, A.; López-Moreno, J. J.; Cometas-Obs Team

    2015-05-01

    We present an extended study of the dust environment of a sample of short-period comets and their dynamical history. With this aim, we characterized the dust tails when the comets are active, and we make a statistical study to determine their dynamical evolution. The targets selected were 22P/Kopff, 30P/Reinmuth 1, 78P/Gehrels 2, 81P/Wild 2, 103P/Hartley 2, 115P/Maury, 118P/Shoemaker-Levy 4, 123P/West-Hartley, 157P/Tritton, 185P/Petriew, P/2011 W2 (Rinner).

  5. A Case Study of Behaviour and Performance of Confined or Pastured Cows During the Dry Period

    PubMed Central

    Black, Randi A.; Krawczel, Peter D.

    2016-01-01

    Simple Summary Pasture and freestall systems offer benefits and consequences during lactation but have not been investigated during the dry period. The effect of pasture or confined systems during the dry period on behaviour and milk quality was investigated. Freestall housing resulted in more resting behaviour and less locomotor activity during the dry period compared to pastured cows. At calving, freestall housed cows performed fewer lying bouts and less locomotor activity compared to pastured cows. Pasture resulted in less aggression around feeding but high respiration rates during peak heat times. Pasture during the dry period altered lying behavior, reduced feed bunk aggression and increased heat stress behaviors. Abstract The objectives of this study were to determine the effect of the dry cow management system (pasture or confined) on: (1) lying behaviour and activity; (2) feeding and heat stress behaviours; (3) intramammary infections, postpartum. Non-lactating Holstein cows were assigned to either deep-bedded, sand freestalls (n = 14) or pasture (n = 14) using rolling enrollment. At dry-off, cows were equipped with an accelerometer to determine daily lying time (h/d), lying bouts (bouts/d), steps (steps/d) and divided into periods: far-off (60 to 15 d prepartum), close-up (14 to 1 d prepartum), calving (calving date) and postpartum (1 to 14 d postpartum). Respiration rates were recorded once weekly from dry off to calving from 1300 to 1500 h. Feeding displacements were defined as one cow successfully displacing another from the feed bunk and were recorded once per week during the 2 h period, immediately after feeding at 800 h. Pastured cows were fed a commercial dry cow pellet during far-off and total mixed ration during close-up, with free access to hay and grazing. Freestall housed cows were fed a total mixed ration at far-off and close-up. Cows housed in freestalls were moved to a maternity pen with a mattress at commencement of labour. Pastured cows

  6. Critical periods after stroke study: translating animal stroke recovery experiments into a clinical trial

    PubMed Central

    Dromerick, Alexander W.; Edwardson, Matthew A.; Edwards, Dorothy F.; Giannetti, Margot L.; Barth, Jessica; Brady, Kathaleen P.; Chan, Evan; Tan, Ming T.; Tamboli, Irfan; Chia, Ruth; Orquiza, Michael; Padilla, Robert M.; Cheema, Amrita K.; Mapstone, Mark E.; Fiandaca, Massimo S.; Federoff, Howard J.; Newport, Elissa L.

    2015-01-01

    Introduction: Seven hundred ninety-five thousand Americans will have a stroke this year, and half will have a chronic hemiparesis. Substantial animal literature suggests that the mammalian brain has much potential to recover from acute injury using mechanisms of neuroplasticity, and that these mechanisms can be accessed using training paradigms and neurotransmitter manipulation. However, most of these findings have not been tested or confirmed in the rehabilitation setting, in large part because of the challenges in translating a conceptually straightforward laboratory experiment into a meaningful and rigorous clinical trial in humans. Through presentation of methods for a Phase II trial, we discuss these issues and describe our approach. Methods: In rodents there is compelling evidence for timing effects in rehabilitation; motor training delivered at certain times after stroke may be more effective than the same training delivered earlier or later, suggesting that there is a critical or sensitive period for strongest rehabilitation training effects. If analogous critical/sensitive periods can be identified after human stroke, then existing clinical resources can be better utilized to promote recovery. The Critical Periods after Stroke Study (CPASS) is a phase II randomized, controlled trial designed to explore whether such a sensitive period exists. We will randomize 64 persons to receive an additional 20 h of upper extremity therapy either immediately upon rehab admission, 2–3 months after stroke onset, 6 months after onset, or to an observation-only control group. The primary outcome measure will be the Action Research Arm Test (ARAT) at 1 year. Blood will be drawn at up to 3 time points for later biomarker studies. Conclusion: CPASS is an example of the translation of rodent motor recovery experiments into the clinical setting; data obtained from this single site randomized controlled trial will be used to finalize the design of a Phase III trial. PMID

  7. Vickers microhardness of K2Co(SO4)2 · 6H2O single crystals and fracture geometry around impressions of vickers, knoop, and spherical indenters

    NASA Astrophysics Data System (ADS)

    Sizova, N. L.; Novikova, N. E.; Manomenova, V. L.; Rudneva, E. B.; Voloshin, A. E.

    2016-05-01

    The microhardness on the (010) and (001) planes in K2Co(SO4)2 · 6H2O crystal has been measured by the Vickers indentation method. Its values are, respectively, 11500 and 1300 MPa. No microhardness anisotropy of the first kind is revealed on either plane. The fracture geometry under indentation by a spherical indenter and Vickers and Knoop indenters is studied. The crystal has lower brittleness than the isomorphic Cs2Ni(SO4)2 · 6H2O crystal.

  8. Rapid phase adjustment of melatonin and core body temperature rhythms following a 6-h advance of the light/dark cycle in the horse

    PubMed Central

    Murphy, Barbara A; Elliott, Jeffrey A; Sessions, Dawn R; Vick, Mandi M; Kennedy, Erin L; Fitzgerald, Barry P

    2007-01-01

    Background Rapid displacement across multiple time zones results in a conflict between the new cycle of light and dark and the previously entrained program of the internal circadian clock, a phenomenon known as jet lag. In humans, jet lag is often characterized by malaise, appetite loss, fatigue, disturbed sleep and performance deficit, the consequences of which are of particular concern to athletes hoping to perform optimally at an international destination. As a species renowned for its capacity for athletic performance, the consequences of jet lag are also relevant for the horse. However, the duration and severity of jet lag related circadian disruption is presently unknown in this species. We investigated the rates of re-entrainment of serum melatonin and core body temperature (BT) rhythms following an abrupt 6-h phase advance of the LD cycle in the horse. Methods Six healthy, 2 yr old mares entrained to a 12 h light/12 h dark (LD 12:12) natural photoperiod were housed in a light-proofed barn under a lighting schedule that mimicked the external LD cycle. Following baseline sampling on Day 0, an advance shift of the LD cycle was accomplished by ending the subsequent dark period 6 h early. Blood sampling for serum melatonin analysis and BT readings were taken at 3-h intervals for 24 h on alternate days for 11 days. Disturbances to the subsequent melatonin and BT 24-h rhythms were assessed using repeated measures ANOVA and analysis of Cosine curve fitting parameters. Results We demonstrate that the equine melatonin rhythm re-entrains rapidly to a 6-h phase advance of an LD12:12 photocycle. The phase shift in melatonin was fully complete on the first day of the new schedule and rhythm phase and waveform were stable thereafter. In comparison, the advance in the BT rhythm was achieved by the third day, however BT rhythm waveform, especially its mesor, was altered for many days following the LD shift. Conclusion Aside from the temperature rhythm disruption, rapid

  9. Si-adatom kinetics in defect mediated growth of multilayer epitaxial graphene films on 6H-SiC

    NASA Astrophysics Data System (ADS)

    Shetu, Shamaita S.; Omar, S. U.; Daniels, K. M.; Daas, B.; Andrews, J.; Ma, S.; Sudarshan, T. S.; Chandrashekhar, M. V. S.

    2013-10-01

    We present a quantitative study on the growth of multilayer epitaxial graphene (EG) by solid-state decomposition of SiC on polar (c-plane Si and C-face) and non-polar (a and m planes) 6H-SiC faces, with distinctly different defect profiles. The growth rates are slower than expected from a mechanism that involves Si loss from an open and free surface, and much faster than expected for the nucleation of a defect-free EG layer, implying that defects in the EG play a critical role in determining the growth kinetics. We show that a Deal-Grove growth model, which assumes vertical diffusion of Si through these defects as the limiting factor for EG growth, is unsuitable for describing multilayer growth. Instead, we introduce a lateral "adatom" diffusion mechanism for Si out-diffusion, based on a modified Burton, Cabrera, and Frank model. In this model, defects in epitaxial graphene serve as sinks for Si desorption loss, taking the place of reactive sites, such as step edges for nucleation and growth of crystals produced with external precursors. This analysis shows that the surface diffusion of Si atoms to the grain boundaries of EG limits the growth on c-plane C-face and non-polar faces, rather than the purely vertical diffusion of Si through the grain boundaries described in the Deal-Grove model. However, for Si-face c-plane growth, diffusion of Si to the defects, as well as desorption of Si at the grain boundaries are both relevant, leading to a different temperature trend compared with the other faces. This distinct qualitative difference is ascribed to point-defects in Si-face growth, as contrasted with line defects/grain boundaries on the other faces. The size of the EG grains correlates with the surface diffusion length extracted from this model. The longer a Si adatom diffuses, the higher the quality of the grown EG film, an insight that provides valuable information on Si adatom kinetics for optimizing EG growth. We discuss the applicability of this model to

  10. Applying Data-mining techniques to study drought periods in Spain

    NASA Astrophysics Data System (ADS)

    Belda, F.; Penades, M. C.

    2010-09-01

    Data-mining is a technique that it can be used to interact with large databases and to help in the discovery relations between parameters by extracting information from massive and multiple data archives. Drought affects many economic and social sectors, from agricultural to transportation, going through urban water deficit and the development of modern industries. With these problems and drought geographical and temporal distribution it's difficult to find a single definition of drought. Improving the understanding of the knowledge of climatic index is necessary to reduce the impacts of drought and to facilitate quick decisions regarding this problem. The main objective is to analyze drought periods from 1950 to 2009 in Spain. We use several kinds of information, different formats, sources and transmission mode. We use satellite-based Vegetation Index, dryness index for several temporal periods. We use daily and monthly precipitation and temperature data and soil moisture data from numerical weather model. We calculate mainly Standardized Precipitation Index (SPI) that it has been used amply in the bibliography. We use OLAP-Mining techniques to discovery of association rules between remote-sensing, numerical weather model and climatic index. Time series Data- Mining techniques organize data as a sequence of events, with each event having a time of recurrence, to cluster the data into groups of records or cluster with similar characteristics. Prior climatological classification is necessary if we want to study drought periods over all Spain.

  11. On Flowfield Periodicity in the NASA Transonic Flutter Cascade. Part 2; Numerical Study

    NASA Technical Reports Server (NTRS)

    Chima, Rodrick V.; McFarland, Eric R.; Wood, Jerry R.; Lepicovsky, Jan

    2000-01-01

    The transonic flutter cascade facility at NASA Glenn Research Center was redesigned based on a combined program of experimental measurements and numerical analyses. The objectives of the redesign were to improve the periodicity of the cascade in steady operation, and to better quantify the inlet and exit flow conditions needed for CFD predictions. Part I of this paper describes the experimental measurements, which included static pressure measurements on the blade and endwalls made using both static taps and pressure sensitive paints, cobra probe measurements of the endwall boundary layers and blade wakes, and shadowgraphs of the wave structure. Part II of this paper describes three CFD codes used to analyze the facility, including a multibody panel code, a quasi-three-dimensional viscous code, and a fully three-dimensional viscous code. The measurements and analyses both showed that the operation of the cascade was heavily dependent on the configuration of the sidewalls. Four configurations of the sidewalls were studied and the results are described. For the final configuration, the quasi-three-dimensional viscous code was used to predict the location of mid-passage streamlines for a perfectly periodic cascade. By arranging the tunnel sidewalls to approximate these streamlines, sidewall interference was minimized and excellent periodicity was obtained.

  12. Refinement of the charcoal meal study by reduction of the fasting period.

    PubMed

    Prior, Helen; Ewart, Lorna; Bright, Jonathan; Valentin, Jean-Pierre

    2012-05-01

    The aim of this investigation was to determine whether a shorter fasting period than the one historically employed for the charcoal meal test, could be used when measuring gastric emptying and intestinal transit within the same animal, and to ascertain whether the scientific outcome would be affected by this benefit to animal welfare. Rats and mice were fasted for 0, 3, 6 or 18 hours before the oral administration of vehicle or atropine. One hour later, the animals were orally administered a charcoal meal, then 20 minutes later, they were killed and the stomach and small intestine were removed. Intestinal transit time (the position of the charcoal front as a percentage of the total length of the small intestine) and relative gastric emptying (weight of stomach contents) were measured. Rats and mice fasted for six hours showed results for gastric emptying and intestinal transit which were similar to those obtained in animals fasted for 18 hours. Reducing the fasting period reduced the body weight loss in both species, and mice on shorter fasts could be group-housed, as hunger-induced fighting was lessened. Therefore, a fasting period of six hours was subsequently adopted for charcoal meal studies at our institution.

  13. Should Age-Period-Cohort Studies Return to the Methodologies of the 1970s?

    PubMed Central

    Masters, Ryan K.; Yang, Y. Claire; Powers, Daniel A.; Zheng, Hui; Land, Kenneth C.

    2015-01-01

    Social scientists have recognized the importance of age-period-cohort (APC) models for half a century, but have spent much of this time mired in debates about the feasibility of APC methods. Recently, a new class of APC methods based on modern statistical knowledge has emerged, offering potential solutions. In 2009, Reither, Hauser and Yang used one of these new methods – hierarchical APC (HAPC) modeling – to study how birth cohorts may have contributed to the U.S. obesity epidemic. They found that recent birth cohorts experience higher odds of obesity than their predecessors, but that ubiquitous period-based changes are primarily responsible for the rising prevalence of obesity. Although these findings have been replicated elsewhere, recent commentaries by Bell and Jones call them into question – along with the new class of APC methods. Specifically, Bell and Jones claim that new APC methods do not adequately address model identification and suggest that “solid theory” is often sufficient to remove one of the three temporal dimensions from empirical consideration. They also present a series of simulation models that purportedly show how the HAPC models estimated by Reither et al. (2009) could have produced misleading results. However, these simulation models rest on assumptions that there were no period effects, and associations between period and cohort variables and the outcome were perfectly linear. Those are conditions under which APC models should never be used. Under more tenable assumptions, our own simulations show that HAPC methods perform well, both in recovering the main findings presented by Reither et al. (2009) and the results reported by Bell and Jones. We also respond to critiques about model identification and theoretically-imposed constraints, finding little pragmatic support for such arguments. We conclude by encouraging social scientists to move beyond the debates of the 1970s and toward a deeper appreciation for modern APC

  14. A Case Study of Behaviour and Performance of Confined or Pastured Cows During the Dry Period.

    PubMed

    Black, Randi A; Krawczel, Peter D

    2016-01-01

    The objectives of this study were to determine the effect of the dry cow management system (pasture or confined) on: (1) lying behaviour and activity; (2) feeding and heat stress behaviours; (3) intramammary infections, postpartum. Non-lactating Holstein cows were assigned to either deep-bedded, sand freestalls ( n = 14) or pasture ( n = 14) using rolling enrollment. At dry-off, cows were equipped with an accelerometer to determine daily lying time (h/d), lying bouts (bouts/d), steps (steps/d) and divided into periods: far-off (60 to 15 d prepartum), close-up (14 to 1 d prepartum), calving (calving date) and postpartum (1 to 14 d postpartum). Respiration rates were recorded once weekly from dry off to calving from 1300 to 1500 h. Feeding displacements were defined as one cow successfully displacing another from the feed bunk and were recorded once per week during the 2 h period, immediately after feeding at 800 h. Pastured cows were fed a commercial dry cow pellet during far-off and total mixed ration during close-up, with free access to hay and grazing. Freestall housed cows were fed a total mixed ration at far-off and close-up. Cows housed in freestalls were moved to a maternity pen with a mattress at commencement of labour. Pastured cows calved in pasture. After calving, all cows were commingled in a pen identical to the freestall housing treatment. Cows housed in freestalls laid down for longer during far-off and close-up periods, had fewer lying bouts during the calving period and took fewer steps throughout the study period when compared to pastured cows. Freestall housed cows experienced more displacements after feeding than did pastured cows. Respiration rates increased with an increasing temperature humidity index, more in pastured cows than in freestall housed cows. Pastured cows altered their lying behaviour and activity, suggesting a shift in time budget priorities between pastured and confined dry cows. Pastured cows also experienced less aggression

  15. Phyllanthus muellerianus and C6H15NO3 synergistic effects on 0.5 M H2SO4-immersed steel-reinforced concrete: Implication for clean corrosion-protection of wind energy structures in industrial environment

    NASA Astrophysics Data System (ADS)

    Okeniyi, Joshua Olusegun; Omotosho, Olugbenga Adeshola; Popoola, Abimbola Patricia Idowu; Loto, Cleophas Akintoye

    2016-07-01

    This paper investigates Phyllanthus muellerianus leaf-extract and C6H15NO3 (triethanolamine: TEA) synergistic effects on reinforcing-steel corrosion-inhibition and the compressive-strength of steel-reinforced concrete immersed in 0.5 M H2SO4. This is to assess suitability of the synergistic admixture usage for wind-energy steel-reinforced concrete structures designed for industrial environments. Steel-reinforced concrete specimens were admixed with individual and synergistic designs of Phyllanthus muellerianus leaf-extract and C6H15NO3 admixtures and immersed in the 0.5 M H2SO4. Electrochemical monitoring of corrosion potential, as per ASTM C876-91 R99, and corrosion current were obtained and statistically analysed, as per ASTM G16-95 R04, for modelling noise resistance. Post-immersion compressive-strength testing then followed, as per ASTM C39/C39M-03, for detailing the admixture effect on load-bearing strength of the steel-reinforced concrete specimens. Results showed that while individual Phyllanthus muellerianus leaf-extract concentrations exhibited better inhibition-efficiency performance than C6H15NO3, synergistic additions of C6H15NO3 to Phyllanthus muellerianus leaf-extract improved steel-rebar corrosion-inhibition. Thus, 6 g Phyllanthus muellerianus + 2 g C6H15NO3 synergistically improved inhibition-efficiency to η = 84.17%, from η = 55.28% by the optimal chemical or from η = 74.72% by the optimal plant-extract admixtures. The study also established that improved compressive strength of steel-reinforced concrete with acceptable inhibition of the steel-rebar corrosion could be attained through optimal combination of the Phyllanthus muellerianus leaf-extract and C6H15NO3 admixtures.

  16. Forgetting to remember or remembering to forget: a study of the recall period length in health care survey questions.

    PubMed

    Kjellsson, Gustav; Clarke, Philip; Gerdtham, Ulf-G

    2014-05-01

    Self-reported data on health care use is a key input in a range of studies. However, the length of recall period in self-reported health care questions varies between surveys, and this variation may affect the results of the studies. This study uses a large survey experiment to examine the role of the length of recall periods for the quality of self-reported hospitalization data by comparing registered with self-reported hospitalizations of respondents exposed to recall periods of one, three, six, or twelve months. Our findings have conflicting implications for survey design, as the preferred length of recall period depends on the objective of the analysis. For an aggregated measure of hospitalization, longer recall periods are preferred. For analysis oriented more to the micro-level, shorter recall periods may be considered since the association between individual characteristics (e.g., education) and recall error increases with the length of the recall period.

  17. Numerical study of the periodic Anderson model with a quarter-filled conduction band

    NASA Astrophysics Data System (ADS)

    Yang, Shuxiang; Moreno, Juana; Jarrell, Mark

    2015-03-01

    Using the dynamical cluster approximation with continuous-time quantum Monte Carlo as the cluster solver and the recently introduced dual-fermion method, we study the underlying physics of the periodic Anderson model where the conduction band is near quarter-filling while the f-band electron band is half filled. For these parameters, the RKKY coupling changes its nature from ferromagnetic to anti-ferromagnetic, yielding an interesting phase-diagram. Especially, we find the charge ordering of the conduction band is strongly enhanced, which could be due to the proximity to a quantum critical point.

  18. Study on formation mechanism of periodic ripple on finished KDP crystal in cutting process

    NASA Astrophysics Data System (ADS)

    Tie, Guipeng; Guan, Chaoliang

    2015-07-01

    A kind of formation mechanism of periodic ripple on finished KDP (potassium dihydrogen phosphate) crystal in cutting process is studied by analyzing the change of equivalent axial stiffness of aerostatic spindle and consequent motion of spindle shaft caused by fluctuation of supply air pressure. The analysis shows that fluctuation of supply air pressure is one of the reasons to cause surface ripple. Correlative experiments are taken and validate the analysis. By strictly controlling air pressure fluctuation, the Peak-to-Valley (PV) value of surface ripple generated by both spiral turning and face flycutting processes are reduced to less than 5nm.

  19. Gamma-ray spectra of hexane (C6H14) in positron-electron annihilation process

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoguang; Wang, Feng

    2013-08-01

    Theoretical gamma-ray spectra of molecule hexane have been calculated and compared with the experimental results in both gas (Iwata et al., 1997a) and liquid (Kerr et al., 1965) phases. The present study reveals that in gas phase not all valence electrons of hexane contribute the same degree in the electron-positron annihilation of hexane. The electrons which dominate the positron-electron annihilation of molecules are called positrophilic electrons. The positrophilic electrons are predominately found to involve the electrons on the lowest occupied valence orbital (LOVO) of a free molecule in gas phase. When hexane is confined in liquid phase, however, the intermolecular interactions ultimately eliminate the free molecular orientation and selectivity for the positrophilic electrons in the gas phase. As a result, the gamma-ray spectra of hexane become an "averaged" contribution from all valence electrons, which is again in agreement with liquid phase measurement. The roles of valence electrons in annihilation process for gas and liquid phases of hexane have been recognized for the first time in the present study.

  20. Case study: Nutrition and training periodization in three elite marathon runners.

    PubMed

    Stellingwerf, Trent

    2012-10-01

    Laboratory-based studies demonstrate that fueling (carbohydrate; CHO) and fluid strategies can enhance training adaptations and race-day performance in endurance athletes. Thus, the aim of this case study was to characterize several periodized training and nutrition approaches leading to individualized race-day fluid and fueling plans for 3 elite male marathoners. The athletes kept detailed training logs on training volume, pace, and subjective ratings of perceived exertion (RPE) for each training session over 16 wk before race day. Training impulse/load calculations (TRIMP; min × RPE = load [arbitrary units; AU]) and 2 central nutritional techniques were implemented: periodic low-CHO-availability training and individualized CHO- and fluid-intake assessments. Athletes averaged ~13 training sessions per week for a total average training volume of 182 km/wk and peak volume of 231 km/wk. Weekly TRIMP peaked at 4,437 AU (Wk 9), with a low of 1,887 AU (Wk 16) and an average of 3,082 ± 646 AU. Of the 606 total training sessions, ~74%, 11%, and 15% were completed at an intensity in Zone 1 (very easy to somewhat hard), Zone 2 (at lactate threshold) and Zone 3 (very hard to maximal), respectively. There were 2.5 ± 2.3 low-CHO-availability training bouts per week. On race day athletes consumed 61 ± 15 g CHO in 604 ± 156 ml/hr (10.1% ± 0.3% CHO solution) in the following format: ~15 g CHO in ~150 ml every ~15 min of racing. Their resultant marathon times were 2:11:23, 2:12:39 (both personal bests), and 2:16:17 (a marathon debut). Taken together, these periodized training and nutrition approaches were successfully applied to elite marathoners in training and competition. PMID:23011657

  1. Experimental Study of the Effects of Periodic Unsteady Wakes on Flow Separation in Low Pressure Turbines

    NASA Technical Reports Server (NTRS)

    Ozturk, Burak; Schobeiri, Meinhard T.

    2009-01-01

    The present study, which is the first of a series of investigations of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary layer flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed on a large-scale, high-subsonic unsteady turbine cascade research facility with an integrated wake generator and test section unit. Blade Pak B geometry was used in the cascade. The wakes were generated by continuously moving cylindrical bars device. Boundary layer investigations were performed using hot wire anemometry at Reynolds number of 110,000, based on the blade suction surface length and the exit velocity, for one steady and two unsteady inlet flow conditions, with the corresponding passing frequencies, wake velocities, and turbulence intensities. The reduced frequencies cover the entire operation range of LP-turbines. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re = 50,000, 75,000, 100,000, 110,000, and 125,000. For each Reynolds number, surface pressure measurements are carried out at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extension of the separation zone as well as its behavior under unsteady wake flow. The results, presented in ensemble-averaged and contour plot forms, help to understand the physics of the separation phenomenon under periodic unsteady wake flow.

  2. Bulk Micromachined 6H-SiC High-g Piezoresistive Accelerometer Fabricated and Tested

    NASA Technical Reports Server (NTRS)

    Okojie, Robert S.

    2002-01-01

    High-g accelerometers are needed in certain applications, such as in the study and analysis of high-g impact landings and projectiles. Also, these accelerometers must survive the high electromagnetic fields associated with the all-electric vehicle technology needed for aerospace applications. The choice of SiC is largely due to its excellent thermomechanical properties over conventional silicon-based accelerometers, whose material properties inhibit applicability in high electromagnetic radiation and high temperatures (>150 C) unless more complex and sometimes costly packaging schemes are adopted. This work was the outcome of a NASA Glenn Research Center summer internship program, in collaboration with Cornell University and the Munitions Directorate of the U.S. Air Force in Eglin, Florida. It aimed to provide the enabling technology infrastructure (modeling, fabrication, and validation) for the implementation of SiC accelerometers designed specifically for harsh environments.

  3. Growth of Si thin film on 6H-SiC(0001)

    NASA Astrophysics Data System (ADS)

    Wu, Hsin-Ju; Hoang, M. Tien; Li, Yuntao; First, Phillip N.

    2015-03-01

    Graphene is much studied for its unusual electronic properties. Other carbon group elements such as silicon (Si) and germanium (Ge) also are predicted to have stable 2D phases for which the electronic structure and properties could be still more interesting. Silicon carbide, already an excellent insulating substrate for epitaxial graphene, could potentially play a similar role for silicene. Commonalities in the substrate and processing may lead to the integration of carbon and silicon technologies. Here, we use surface analysis techniques (LEED, AES, STM) to investigate the formation of 2D Si on SiC(0001), under low pressures of silane or silicon. Similar methods allow control of surface graphene growth by compensating Si desorption from SiC. Among several Si-rich reconstructions, we find a single stable hexagonal phase, at a coverage close to twice the Si density predicted for silicene, and with a unit cell consistent with a commensurate layer of silicene or silicane. For a graphitized SiC starting surface, silane is shown to etch graphene, reforming SiC. Work supported in part by NSF (DMR-1106131, DMR-0820382 [MRSEC]).

  4. Electronic and Interfacial Properties of PD/6H-SiC Schottky Diode Gas Sensors

    NASA Technical Reports Server (NTRS)

    Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Bansal, Gaurav; Petit, Jeremy B.; Knight, Dak; Liu, Chung-Chiun; Wu, Qinghai

    1996-01-01

    Pd/SiC Schottky diodes detect hydrogen and hydrocarbons with high sensitivity. Variation of the diode temperature from 100 C to 200 C shows that the diode sensitivity to propylene is temperature dependent. Long-term heat treating at 425 C up to 140 hours is carried out to determine the effect of extended heat treating on the diode properties and gas sensitivity. The heat treating significantly affects the diode's capacitive characteristics, but the diode's current carrying characteristics are much more stable with a large response to hydrogen. Scanning Electron Microscopy and X-ray Spectrometry studies of the Pd surface after the heating show cluster formation and background regions with grain structure observed in both regions. The Pd and Si concentrations vary between grains. Auger Electron Spectroscopy depth profiles revealed that the heat treating promoted interdiffusion and reaction between the Pd and SiC dw broadened the interface region. This work shows that Pd/SiC Schottky diodes have significant potential as high temperature gas sensors, but stabilization of the structure is necessary to insure their repeatability in long-term, high temperature applications.

  5. Study of deformed quasi-periodic Fibonacci two dimensional photonic crystals

    NASA Astrophysics Data System (ADS)

    Ben Abdelaziz, K.; Bouazzi, Y.; Kanzari, M.

    2015-09-01

    Quasi-periodic photonic crystals are not periodic structures. These structures are generally obtained by the arrangement of layers according to a recursive rule. Properties of these structures make more attention the researchers especially in the case when applying defects. So, photonic crystals with defects present localized modes in the band gap leading to many potential applications such light localization. The objective of this work is to study by simulation the effect of the global deformation introduced in 2D quasiperiodic photonic crystals. Deformation was introduced by applying a power law, so that the coordinates y of the deformed object were determined through the coordinates x of the non-deformed structure in accordance with the following rule: y = x1+k. Here k is the coefficient defining the deformation. Therefore, the objective is to study the effect of this deformation on the optical properties of 2D quasiperiodic photonic crystals, constructed by Fibonacci generation. An omnidirectional mirror was obtained for optimization Fibonacci iteration in a part of visible spectra.

  6. "Radiative Closure Studies for Clear Skies During the ARM 2003 Aerosol Intensive Observation Period"

    SciTech Connect

    J. J. Michalsky, G. P. Anderson, J. Barnard, J. Delamere, C. Gueymard, S. Kato, P. Kiedron, A. McComiskey, and P. Ricchiazzi

    2006-04-01

    The Department of Energy's Atmospheric Radiation Measurement (ARM) program sponsored a large intensive observation period (IOP) to study aerosol during the month of May 2003 around the Southern Great Plains (SGP) Climate Research Facility (CRF) in north central Oklahoma. Redundant measurements of aerosol optical properties were made using different techniques at the surface as well as in vertical profile with sensors aboard two aircraft. One of the principal motivations for this experiment was to resolve the disagreement between models and measurements of diffuse horizontal broadband shortwave irradiance at the surface, especially for modest aerosol loading. This paper focuses on using the redundant aerosol and radiation measurements during this IOP to compare direct beam and diffuse horizontal broadband shortwave irradiance measurements and models at the surface for a wide range of aerosol cases that occurred during 30 clear-sky periods on 13 days of May 2003. Models and measurements are compared over a large range of solar-zenith angles. Six different models are used to assess the relative agreement among them and the measurements. Better agreement than previously achieved appears to be the result of better specification of input parameters and better measurements of irradiances than in prior studies. Biases between modeled and measured direct irradiances are less than 1%, and biases between modeled and measured diffuse irradiances are less than 2%.

  7. Ft-Ir Measurements of Cold Cross Sections of Benzene (C_6H_6) for Cassini/cirs

    NASA Astrophysics Data System (ADS)

    Sung, Keeyoon; Brown, Linda; Toon, Geoffrey C.

    2014-06-01

    Titan's stratosphere is abundant in hydrocarbons (CxHy) producing highly complicated and crowded features in the spectra of Cassini/CIRS. Among these, benzene (C_6H_6) is the heaviest hydrocarbon ever seen in the Titan and cold planets. For this reason, a series of pure and N_2-broadened C6H6 spectra were recorded in the 640 to 1540 wn region at gas temperatures down to 231 K using a Fourier transform spectrometer (Bruker IFS-125HR) at the Jet Propulsion Laboratory. We report temperature dependent absorption cross sections for three strong fundamental bands (νb{4}, νb{14}, νb{13}). We also derived pseudo-line parameters, which include mean intensities and effective lower state energies on a 0.005 wn frequency grid, obtained by fitting all the laboratory spectra simultaneously. For the pseudoline generation, details can be found in a JPL MK-IV website, http://mark4sun.jpl.nasa.gov/data/spec/Pseudo). The resulting pseudolines of the strong bands reproduce observed cross sections to within ˜3 %. These new results are compared to earlier work, including the C6H6+N2 spectra recorded at PNNL. S. W. Sharpe, et al., Appl Spectrosc 58, 1452-1461 (2004); C. P. Rinsland, et al. JQSRT, 109, 2511-2522 (2008). Research described in this paper was performed at the Jet Propulsion Laboratory and California Institute of Technology, under contracts and cooperative agreements with the National Aeronautics and Space Administration.

  8. Promoting scopolamine biosynthesis in transgenic Atropa belladonna plants with pmt and h6h overexpression under field conditions.

    PubMed

    Xia, Ke; Liu, Xiaoqiang; Zhang, Qiaozhuo; Qiang, Wei; Guo, Jianjun; Lan, Xiaozhong; Chen, Min; Liao, Zhihua

    2016-09-01

    Atropa belladonna is one of the most important plant sources for producing pharmaceutical tropane alkaloids (TAs). T1 progeny of transgenic A. belladonna, in which putrescine N-methyltransferase (EC. 2.1.1.53) from Nicotiana tabacum (NtPMT) and hyoscyamine 6β-hydroxylase (EC. 1.14.11.14) from Hyoscyamus niger (HnH6H) were overexpressed, were established to investigate TA biosynthesis and distribution in ripe fruits, leaves, stems, primary roots and secondary roots under field conditions. Both NtPMT and HnH6H were detected at the transcriptional level in transgenic plants, whereas they were not detected in wild-type plants. The transgenes did not influence the root-specific expression patterns of endogenous TA biosynthetic genes in A. belladonna. All four endogenous TA biosynthetic genes (AbPMT, AbTRI, AbCYP80F1 and AbH6H) had the highest/exclusive expression levels in secondary roots, suggesting that TAs were mainly synthesized in secondary roots. T1 progeny of transgenic A. belladonna showed an impressive scopolamine-rich chemotype that greatly improved the pharmaceutical value of A. belladonna. The higher efficiency of hyoscyamine conversion was found in aerial than in underground parts. In aerial parts of transgenic plants, hyoscyamine was totally converted to downstream alkaloids, especially scopolamine. Hyoscyamine, anisodamine and scopolamine were detected in underground parts, but scopolamine and anisodamine were more abundant than hyoscyamine. The exclusively higher levels of anisodamine in roots suggested that it might be difficult for its translocation from root to aerial organs. T1 progeny of transgenic A. belladonna, which produces scopolamine at very high levels (2.94-5.13 mg g(-1)) in field conditions, can provide more valuable plant materials for scopolamine production. PMID:27135818

  9. Bulk AlN crystal growth: self-seeding and seeding on 6H-SiC substrates

    NASA Astrophysics Data System (ADS)

    Edgar, J. H.; Liu, L.; Liu, B.; Zhuang, D.; Chaudhuri, J.; Kuball, M.; Rajasingam, S.

    2002-12-01

    The properties of bulk AlN crystals grown by sublimation recondensation and either randomly nucleated (i.e. self-seeded) or seeded on 6H-SiC substrates or compared. Self-seeding produces crystals of the highest perfection, lowest stress, and low Si and C impurity content, but the crystals grow in random crystallographic orientations. Crystals grown in boron nitride crucibles typically form thin platelets with the fastest growth occurring in the c-axis direction. Growth striations run the length of the crystals in the c-axis direction. Anisotropic etching in aqueous 45 wt% KOH solutions shows that the growth (0 0 0 1) planes exposed to the AlN source predominately have an aluminum polarity. AlN crystals seeded on 6H-SiC(0 0 0 1) have a single crystallographic orientation and the largest dimensions are perpendicular to the c-axis, determined by the size of the substrate. Cracking and voids in the AlN layer produced by differences in thermal expansion coefficients of AlN and SiC and decomposition of the SiC were ameliorated by depositing an AlN-SiC alloy layer on the SiC before growing the AlN layer. Raman spectroscopy measurements suggest the AlN and AlN-SiC alloy layer are both under tensile stress. The defect density in AlN crystals grown on composite AlN-SiC/6H-SiC substrates was 3.7×10 5 cm -2, as determined by synchrotron white beam X-ray topography.

  10. Synthesis, structural characterization, electrical properties and antioxidant activity of [p-(NH3)C6H4NH3]3P6O18·6H2O

    NASA Astrophysics Data System (ADS)

    Fezai, Ramzi; Mezni, Ali; Kahlaoui, Messaoud; Rzaigui, Mohamed

    2016-09-01

    Single crystals of a novel organic cyclohexaphosphate, [p-(NH3)C6H4NH3]3P6O18.6H2O, have been prepared in aqueous solution. Its crystal structure can be described by a three-dimensional framework where the P6O186- rings are interconnected by hydrogen bonds to form anionic layers between which organic cations are located. Hydrogen bonding network connecting the different components is given. The thermal stability and spectroscopic properties of this material are given too. Its DC and AC electrical conductivities, modulus analysis and dielectric constants have been investigated. The AC conductivity is found to obey the universal power law. The DC electrical conductivity indicates a semiconductor behavior. The kind of the observed conduction is protonic by translocation. X-rays structural and electrical results are correlated. This compound has also been screened for its antioxidant activity, determined in vitro, using 1,1-diphenyl-2-picrylhydrazyl, reducing power, hydroxyl scavenging ability and ferrous ion chelating (FIC) methods and with ascorbic acid as reference.

  11. Volumetric Properties of the Mixture Hexane C6H14 + C8H16 Cyclooctane (VMSD1342, LB3815_V)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture Hexane C6H14 + C8H16 Cyclooctane (VMSD1342, LB3815_V)' providing data by calculation of isothermal compressibility from direct measurements of mass densities at variable pressure and constant temperature and mole fraction.

  12. Volumetric Properties of the Mixture Hexane C6H14 + C14H30 Tetradecane (VMSD1241, LB3873_V)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume A 'Binary Liquid Systems of Nonelectrolytes I' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture Hexane C6H14 + C14H30 Tetradecane (VMSD1241, LB3873_V)' providing data from direct high-pressure dilatometric measurements of molar excess volume at variable pressure and constant temperature and mole fraction.

  13. Comparative calculations of electron transport properties in 6H-SiC using three and five valley models

    NASA Astrophysics Data System (ADS)

    Talha, Nora; Bouazza, Benyounes; Guen Bouazza, Ahlam; Kadoun, Abd-Ed-Daim

    2016-07-01

    Steady-state electron properties are investigated in 6H-SiC at various temperatures, using Monte Carlo simulation where the band structure model is a major part when dealing with high fields. The aim of this work is to optimize the number of valleys involved in the simulation program in order to obtain accurate results while improving the calculation efficiency. For high fields, a five valley model was found to be more accurate than a three valley model and as efficient as the full band method though much less computer time-consuming.

  14. Ultrafast time dynamics studies of periodic lattices with free electron laser radiation

    SciTech Connect

    Quevedo, W.; Busse, G.; Hallmann, J.; More, R.; Petri, M.; Rajkovic, I.; Krasniqi, F.; Rudenko, A.; Tschentscher, T.; Stojanovic, N.; Duesterer, S.; Treusch, R.; Tolkiehn, M.; Techert, S.

    2012-11-01

    It has been proposed that radiation from free electron laser (FEL) at Hamburg (FLASH) can be used for ultrafast time-resolved x-ray diffraction experiments based on the near-infrared (NIR) pump/FEL probe scheme. Here, investigation probing the ultrafast structural dynamics of periodic nano-crystalline organic matter (silver behenate) with such a scheme is reported. Excitation with a femtosecond NIR laser leads to an ultrafast lattice modification which time evolution has been studied through the scattering of vacuum ultraviolet FEL pulses. The found effect last for 6 ps and underpins the possibility for studying nanoperiodic dynamics down to the FEL source time resolution. Furthermore, the possibility of extending the use of silver behenate (AgBh) as a wavelength and temporal calibration tool for experiments with soft x-ray/FEL sources is suggested.

  15. Case-control study of the PERIOD3 clock gene length polymorphism and colorectal adenoma formation.

    PubMed

    Alexander, Melannie; Burch, James B; Steck, Susan E; Chen, Chin-Fu; Hurley, Thomas G; Cavicchia, Philip; Ray, Meredith; Shivappa, Nitin; Guess, Jaclyn; Zhang, Hongmei; Youngstedt, Shawn D; Creek, Kim E; Lloyd, Stephen; Yang, Xiaoming; Hébert, James R

    2015-02-01

    Clock genes are expressed in a self-perpetuating, circadian pattern in virtually every tissue including the human gastrointestinal tract. They coordinate cellular processes critical for tumor development, including cell proliferation, DNA damage response and apoptosis. Circadian rhythm disturbances have been associated with an increased risk for colon cancer and other cancers. This mechanism has not been elucidated, yet may involve dysregulation of the 'period' (PER) clock genes, which have tumor suppressor properties. A variable number tandem repeat (VNTR) in the PERIOD3 (PER3) gene has been associated with sleep disorders, differences in diurnal hormone secretion, and increased premenopausal breast cancer risk. Susceptibility related to PER3 has not been examined in conjunction with adenomatous polyps. This exploratory case-control study was the first to test the hypothesis that the 5-repeat PER3 VNTR sequence is associated with increased odds of adenoma formation. Information on demographics, medical history, occupation and lifestyle was collected prior to colonoscopy. Cases (n=49) were individuals with at least one histopathologically confirmed adenoma. Controls (n=97) included patients with normal findings or hyperplastic polyps not requiring enhanced surveillance. Unconditional multiple logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals (CIs), after adjusting for potential confounding. Adenomas were detected in 34% of participants. Cases were more likely to possess the 5-repeat PER3 genotype relative to controls (4/5 OR, 2.1; 95% CI, 0.9-4.8; 5/5 OR, 5.1; 95% CI, 1.4-18.1; 4/5+5/5 OR, 2.5; 95% CI, 1.7-5.4). Examination of the Oncomine microarray database indicated lower PERIOD gene expression in adenomas relative to adjacent normal tissue. Results suggest a need for follow-up in a larger sample.

  16. A comparative study of four significance measures for periodicity detection in astronomical surveys

    NASA Astrophysics Data System (ADS)

    Süveges, Maria; Guy, Leanne P.; Eyer, Laurent; Cuypers, Jan; Holl, Berry; Lecoeur-Taïbi, Isabelle; Mowlavi, Nami; Nienartowicz, Krzysztof; Blanco, Diego Ordóñez; Rimoldini, Lorenzo; Ruiz, Idoia

    2015-06-01

    We study the problem of periodicity detection in massive data sets of photometric or radial velocity time series, as presented by ESA's Gaia mission. Periodicity detection hinges on the estimation of the false alarm probability of the extremum of the periodogram of the time series. We consider the problem of its estimation with two main issues in mind. First, for a given number of observations and signal-to-noise ratio, the rate of correct periodicity detections should be constant for all realized cadences of observations regardless of the observational time patterns, in order to avoid sky biases that are difficult to assess. Secondly, the computational loads should be kept feasible even for millions of time series. Using the Gaia case, we compare the FM method of Paltani and Schwarzenberg-Czerny, the Baluev method and the GEV method of Süveges, as well as a method for the direct estimation of a threshold. Three methods involve some unknown parameters, which are obtained by fitting a regression-type predictive model using easily obtainable covariates derived from observational time series. We conclude that the GEV and the Baluev methods both provide good solutions to the issues posed by a large-scale processing. The first of these yields the best scientific quality at the price of some moderately costly pre-processing. When this pre-processing is impossible for some reason (e.g. the computational costs are prohibitive or good regression models cannot be constructed), the Baluev method provides a computationally inexpensive alternative with slight biases in regions where time samplings exhibit strong aliases.

  17. [Cloning and expression of the key enzyme hyoscyamine 6 beta-hydroxylase gene (DaH6H) in scopolamine biosynthesis of Datura arborea].

    PubMed

    Qiang, Wei; Hou, Yan-ling; Li, Xiao; Xia, Ke; Liao, Zhi-hua

    2015-10-01

    Hyoscyamine 6 beta-hydroxylase (H6H) is the last rate-limiting enzyme directly catalyzing the formation of scopolamine in tropane alkaloids (TAs) biosynthesis pathway. It is the primary target gene in the genetic modification of TAs metabolic pathway. Full-length cDNA and gDNA sequences of a novel H6H gene were cloned from Datura arborea (DaH6H, GenBank accession numbers for cDNA and gDNA are KR006981 and KR006983, respectively). Nucleotide sequence analysis reveals an open reading frame of 1375 bp encoding 347 amino acids in the cDNA of DaH6H, while the gDNA of DaH6H contains four exons and three introns, with the highest similarity to the gDNA of H6H from D. stramonium. DaH6H also exhibited the most identity of 90.5% with DsH6H in amino acids and harbored conserved 2-oxoglutarate binding motif and two iron binding motifs. The expression level of DaH6H was highest in the mature leaf, followed by the secondary root, and with no expression in the primary root based on qPCR analysis. Its expression was inhibited by MeJA. DaH6H was expressed in E. coli and a 39 kD recombinant protein was detected in SDS-PAGE. Comparison of the contents of scopolamine and hyoscyamine in various TAs-producing plants revealed that D. arborea was one of the rare scopolamine predominant plants. Cloning of DaH6H gene will allow more research in the molecular regulatory mechanism of TAs biosynthesis in distinct plants and provide a new candidate gene for scopolamine metabolic engineering.

  18. [Cloning and expression of the key enzyme hyoscyamine 6 beta-hydroxylase gene (DaH6H) in scopolamine biosynthesis of Datura arborea].

    PubMed

    Qiang, Wei; Hou, Yan-ling; Li, Xiao; Xia, Ke; Liao, Zhi-hua

    2015-10-01

    Hyoscyamine 6 beta-hydroxylase (H6H) is the last rate-limiting enzyme directly catalyzing the formation of scopolamine in tropane alkaloids (TAs) biosynthesis pathway. It is the primary target gene in the genetic modification of TAs metabolic pathway. Full-length cDNA and gDNA sequences of a novel H6H gene were cloned from Datura arborea (DaH6H, GenBank accession numbers for cDNA and gDNA are KR006981 and KR006983, respectively). Nucleotide sequence analysis reveals an open reading frame of 1375 bp encoding 347 amino acids in the cDNA of DaH6H, while the gDNA of DaH6H contains four exons and three introns, with the highest similarity to the gDNA of H6H from D. stramonium. DaH6H also exhibited the most identity of 90.5% with DsH6H in amino acids and harbored conserved 2-oxoglutarate binding motif and two iron binding motifs. The expression level of DaH6H was highest in the mature leaf, followed by the secondary root, and with no expression in the primary root based on qPCR analysis. Its expression was inhibited by MeJA. DaH6H was expressed in E. coli and a 39 kD recombinant protein was detected in SDS-PAGE. Comparison of the contents of scopolamine and hyoscyamine in various TAs-producing plants revealed that D. arborea was one of the rare scopolamine predominant plants. Cloning of DaH6H gene will allow more research in the molecular regulatory mechanism of TAs biosynthesis in distinct plants and provide a new candidate gene for scopolamine metabolic engineering. PMID:26837185

  19. Epidemiology of injuries in elite taekwondo athletes: two Olympic periods cross-sectional retrospective study

    PubMed Central

    Altarriba-Bartes, Albert; Drobnic, Franchek; Til, Lluís; Malliaropoulos, Nikolaos; Montoro, José Bruno; Irurtia, Alfredo

    2014-01-01

    Objective Taekwondo injuries differ according to the characteristics of the athletes and the competition. This analytical cross-sectional retrospective cohort study aimed to describe reported taekwondo injuries and to determine the prevalence, characteristics and possible risk factors for injuries sustained by athletes of the Spanish national team. In addition, we compared each identified risk factor—age, weight category, annual quarter, injury timing and competition difficulty level—with its relation to injury location and type. Settings Injury occurrences in taekwondo athletes of the Spanish national team during two Olympic periods at the High Performance Centre in Barcelona were analysed. Participants 48 taekwondo athletes (22 male, 26 female; age range 15–31 years) were studied; 1678 injury episodes occurred. Inclusion criteria were: (1) having trained with the national taekwondo group for a minimum of one sports season; (2) being a member of the Spanish national team. Results Independently of sex or Olympic period, the anatomical sites with most injury episodes were knee (21.3%), foot (17.0%), ankle (12.2%), thigh (11.4%) and lower leg (8.8%). Contusions (29.3%) and cartilage (17.6%) and joint (15.7%) injuries were the prevalent types of injury. Chronological age, weight category and annual quarter can be considered risk factors for sustaining injuries in male and female elite taekwondists according to their location and type (p≤0.001). Conclusions This study provides epidemiological information that will help to inform future injury surveillance studies and the development of prevention strategies and recommendations to reduce the number of injuries in taekwondo competition. PMID:24531455

  20. Study of electromagnetic wave scattering by periodic density irregularities in plasma

    SciTech Connect

    Lyle, R.; Kuo, S.P.; Huang, J.

    1995-12-31

    A quasi-particle approach is used to formulate wave propagation and scattering in a periodically structured plasma. The theory is then applied to study the effect of bottomside sinusoidal (BSS) irregularities on the propagation of beacon satellites signals through the ionosphere. In this approach, the radio wave is treated as a distribution of quasi-particles described by a Wigner distribution function governed by a transport equation. The irregularities providing the collisional effect are modeled as a two dimensional density modulation on a uniform background plasma. The present work generalizes the previous work by including the spectral bandwidth ({Delta}k/k) effect of the spatially periodic irregularities on the transionospheric signal propagation. The collision of quasi-particles with the irregularities modifies the quasi-particle distribution and give rise to the wave scattering phenomenon. The multiple scattering process is generally considered in this deterministic analysis of radio wave scattering off the ionospheric density irregularities. The analysis shows that this two dimensional density grating effectively modulates the intensity of the beacon satellite signals. This spatial modulation of the wave intensity is converted into time modulation due to the drift of the ionospheric irregularities, which then results in the scintillation of the beacon satellite signals.

  1. Refractory period modulates the spatiotemporal evolution of cortical spreading depression: a computational study.

    PubMed

    Li, Bing; Chen, Shangbin; Li, Pengcheng; Luo, Qingming; Gong, Hui

    2014-01-01

    Cortical spreading depression (CSD) is a pathophysiological phenomenon, which underlies some neurological disorders, such as migraine and stroke, but its mechanisms are still not completely understood. One of the striking facts is that the spatiotemporal evolution of CSD wave is varying. Observations in experiments reveal that a CSD wave may propagate through the entire cortex, or just bypass some areas of the cortex. In this paper, we have applied a 2D reaction-diffusion equation with recovery term to study the spatiotemporal evolution of CSD. By modulating the recovery rate from CSD in the modeled cortex, CSD waves with different spatiotemporal evolutions, either bypassing some areas or propagating slowly in these areas, were present. Moreover, spiral CSD waves could also be induced in case of the transiently altered recovery rate, i.e. block release from the absolute refractory period. These results suggest that the refractory period contributes to the different propagation patterns of CSD, which may help to interpret the mechanisms of CSD propagation. PMID:24400104

  2. Orbital Period Variation and Morphological Light Curve Studies for the W UMa Binary BB Pegasi

    NASA Astrophysics Data System (ADS)

    Hanna, Magdy A.; Awadalla, Nabil S.

    2011-06-01

    The photometric light curves of the W-type W UMa eclipsing contact binary system BB Pegasi have been found to be extremely asymmetric over all the observed 63 years in all wavelengths UBVR. The light curves have been characterized by occultation primary minima. So, the morphology of these light curves has been studied in view of these different asymmetric degrees. The system shows a distinct O'Connell effect as well as depth variation. A 22.96 years cycle, of dark spots group, has been determined for the system combined with about the same cycling for the depth variations (22.78 yr). Also, an analysis of the measurements of mid-eclipse times of BB Peg has been presented. The analysis indicates a period decrease of 5.62× 10-8 d/yr, which can be interpreted in terms of mass transfer of rate -4.38 × 10-8 M_⊙/yr, from the more to the less massive component. The O-C diagram shows a damping sine wave covering two different cycles of 17.0 yr and 12.87 yr with amplitudes equal to 0.0071 and 0.0013 day, respectively. These unequal durations show a non periodicity which may be explained as a result of magnetic activity cycling variations due to star spots. The obtained characteristics are consistent when applying Applegate's (1992) mechanism.

  3. Performance of colloidal silica and ceria based slurries on CMP of Si-face 6H-SiC substrates

    NASA Astrophysics Data System (ADS)

    Chen, Guomei; Ni, Zifeng; Xu, Laijun; Li, Qingzhong; Zhao, Yongwu

    2015-12-01

    Colloidal silica and ceria based slurries, both using KMnO4 as an oxidizer, for chemical mechanical polishing (CMP) of Si-face (0 0 0 1) 6H-SiC substrate, were investigated to obtain higher material removal rate (MRR) and ultra-smooth surface. The results indicate that there was a significant difference in the CMP performance of 6H-SiC between silica and ceria based slurries. For the ceria based slurries, a higher MRR was obtained, especially in strong acid KMnO4 environment, and the maximum MRR (1089 nm/h) and a smoother surface with an average roughness Ra of 0.11 nm was achieved using slurries containing 2 wt% colloidal ceria, 0.05 M KMnO4 at pH 2. In contrast, due to the attraction between negative charged silica particles and positive charged SiC surface below pH 5, the maximum MRR of silica based slurry was only 185 nm/h with surface roughness Ra of 0.254 nm using slurries containing 6 wt% colloidal silica, 0.05 M KMnO4 at pH 6. The polishing mechanism was discussed based on the zeta potential measurements of the abrasives and the X-ray photoelectron spectroscopy (XPS) analysis of the polished SiC surfaces.

  4. Solid State Reaction and Operational Stability of Ruthenium Schottky Contact-on-6H-SiC Under Argon Annealing

    NASA Astrophysics Data System (ADS)

    Munthali, Kinnock V.; Theron, Chris; Auret, F. Danie; Coelho, Sergio M. M.; Njoroge, Eric

    2015-10-01

    Thin films of ruthenium-on-6-hexagonal silicon carbide (6H-SiC) were analysed by Rutherford backscattering spectroscopy (RBS) at various annealing temperatures. Some thin film samples were also analysed by scanning electron microscope (SEM). RBS analysis indicated minimal element diffusion, and formation of ruthenium oxide after annealing at 500°C. Large-scale diffusion of ruthenium (Ru) was observed to commence at 700°C. The SEM images indicated that the as-deposited Ru was disorderly and amorphous. Annealing of the thin film improved the grain quality of Ru. The fabricated Ru-6H-SiC Schottky barrier diodes (SBD) with nickel ohmic contacts showed excellent rectifying behaviour and linear capacitance-voltage characteristics up to an annealing temperature of 900°C. The SBDs degraded after annealing at 1000°C. The degradation of the SBDs is attributed to the inter-diffusion of Ru and Si at the Schottky-substrate interface.

  5. Long-Term Observation of Triplex Surgery for Cataract after Phakic 6H Implantation for Super High Myopia

    PubMed Central

    Liu, Xin; Wang, Xiaoying; Lu, Yi; Zheng, Tianyu; Zhou, Xingtao

    2016-01-01

    Purpose. To analyze the safety, effectiveness, and stability of triplex surgery for phakic 6H anterior chamber phakic intraocular lens explantation and phacoemulsification with in-the-bag IOL implantation for super high myopia in long-term observations. Methods. This retrospective case series evaluated 16 eyes of 10 patients who underwent triplex surgery. Best corrected visual acuity (BCVA), endothelial cell density (ECD), and associated adverse events were evaluated. Results. The mean follow-up time after the triplex surgery was 46 ± 14 months. The mean logMAR BCVA was significantly improved after triplex surgery (P = 0.047). One eye developed endophthalmitis five days postoperatively and underwent pars plana vitrectomy (PPV). Five eyes with preoperative severe endothelial cell loss developed corneal decompensation and underwent keratoplasty at a mean time of 9.4 ± 2.6 months after the triplex surgery. One eye had graft failure and underwent a second keratoplasty. The eye developed rhegmatogenous retinal detachment and underwent PPV with silicone oil 18 months later. ECD before the triplex surgery was not significantly different compared with that at last follow-up (P = 0.495) apart from these five eyes. Three eyes (18.8%) developed posterior capsule opacification. Conclusions. Triplex surgery was safe and effective for phakic 6H related complicated cataracts. Early extraction before severe ECD loss is recommended. PMID:27190642

  6. Isolation of H5N6, H7N9 and H9N2 avian influenza A viruses from air sampled at live poultry markets in China, 2014 and 2015.

    PubMed

    Zhou, Jie; Wu, Jie; Zeng, Xianqiao; Huang, Guofeng; Zou, Lirong; Song, Yingchao; Gopinath, Divya; Zhang, Xin; Kang, Min; Lin, Jinyan; Cowling, Benjamin J; Lindsley, William G; Ke, Changwen; Peiris, Joseph Sriyal Malik; Yen, Hui-Ling

    2016-09-01

    Zoonotic infections by avian influenza viruses occur at the human-poultry interface, but the modes of transmission have not been fully investigated. We assessed the potential for airborne and fomite transmission at live poultry markets in Guangzhou city and in Hong Kong Special Administrative Region (SAR), China, during 2014 and 2015. Viral genome and infectious avian influenza A viruses of H5N6, H7N9, and H9N2 subtypes were detected predominantly from particles larger or equal to 1 μm in diameter in the air sampled with cyclone-based bioaerosol samplers at the live poultry markets in Guangzhou. Influenza A(H9N2) viruses were ubiquitously isolated every month during the study period from air and environmental swabs, and different lineages of H9N2 virus were isolated from markets where chickens and minor land-based poultry were sold. The use of de-feathering devices increased the quantity of virus-laden airborne particles while market closure reduced the amount of such particles. The results highlight the possibility of airborne transmission of avian influenza viruses among poultry or from poultry to humans within such settings. This may explain epidemiological observations in which some patients with H7N9 infection reported being in markets but no direct contact with live poultry or poultry stalls.

  7. Isolation of H5N6, H7N9 and H9N2 avian influenza A viruses from air sampled at live poultry markets in China, 2014 and 2015.

    PubMed

    Zhou, Jie; Wu, Jie; Zeng, Xianqiao; Huang, Guofeng; Zou, Lirong; Song, Yingchao; Gopinath, Divya; Zhang, Xin; Kang, Min; Lin, Jinyan; Cowling, Benjamin J; Lindsley, William G; Ke, Changwen; Peiris, Joseph Sriyal Malik; Yen, Hui-Ling

    2016-09-01

    Zoonotic infections by avian influenza viruses occur at the human-poultry interface, but the modes of transmission have not been fully investigated. We assessed the potential for airborne and fomite transmission at live poultry markets in Guangzhou city and in Hong Kong Special Administrative Region (SAR), China, during 2014 and 2015. Viral genome and infectious avian influenza A viruses of H5N6, H7N9, and H9N2 subtypes were detected predominantly from particles larger or equal to 1 μm in diameter in the air sampled with cyclone-based bioaerosol samplers at the live poultry markets in Guangzhou. Influenza A(H9N2) viruses were ubiquitously isolated every month during the study period from air and environmental swabs, and different lineages of H9N2 virus were isolated from markets where chickens and minor land-based poultry were sold. The use of de-feathering devices increased the quantity of virus-laden airborne particles while market closure reduced the amount of such particles. The results highlight the possibility of airborne transmission of avian influenza viruses among poultry or from poultry to humans within such settings. This may explain epidemiological observations in which some patients with H7N9 infection reported being in markets but no direct contact with live poultry or poultry stalls. PMID:27608369

  8. Isolation of H5N6, H7N9 and H9N2 avian influenza A viruses from air sampled at live poultry markets in China, 2014 and 2015

    PubMed Central

    Zhou, Jie; Wu, Jie; Zeng, Xianqiao; Huang, Guofeng; Zou, Lirong; Song, Yingchao; Gopinath, Divya; Zhang, Xin; Kang, Min; Lin, Jinyan; Cowling, Benjamin J; Lindsley, William G.; Ke, Changwen; Peiris, Joseph Sriyal Malik; Yen, Hui-Ling

    2016-01-01

    Zoonotic infections by avian influenza viruses occur at the human–poultry interface, but the modes of transmission have not been fully investigated. We assessed the potential for airborne and fomite transmission at live poultry markets in Guangzhou city and in Hong Kong Special Administrative Region (SAR), China, during 2014 and 2015. Viral genome and infectious avian influenza A viruses of H5N6, H7N9, and H9N2 subtypes were detected predominantly from particles larger or equal to 1 μm in diameter in the air sampled with cyclone-based bioaerosol samplers at the live poultry markets in Guangzhou. Influenza A(H9N2) viruses were ubiquitously isolated every month during the study period from air and environmental swabs, and different lineages of H9N2 virus were isolated from markets where chickens and minor land-based poultry were sold. The use of de-feathering devices increased the quantity of virus-laden airborne particles while market closure reduced the amount of such particles. The results highlight the possibility of airborne transmission of avian influenza viruses among poultry or from poultry to humans within such settings. This may explain epidemiological observations in which some patients with H7N9 infection reported being in markets but no direct contact with live poultry or poultry stalls. PMID:27608369

  9. Vibrational spectra and dispersion analysis of K2Ni(SeO4)2·6H2O Tutton salt single crystal doped with K2Ni(SO4)2·6H2O

    NASA Astrophysics Data System (ADS)

    Ivanovski, Vladimir; Mayerhöfer, Thomas G.

    2013-10-01

    Dispersion analysis of the polarized IR reflectance spectra of K2Ni(SeO4)2·6H2O doped with K2Ni(SO4)2·6H2O has been performed. Vibrational parameters like oscillator strength, attenuation constant and frequency of the transversal phonons for the modes of Au symmetry type plus the orientation of the transition dipole moments for the modes of Bu symmetry type in the ac crystal plane have been obtained. The spectra-structure correlation of the H2O stretching vibrations show that bands appearing in the spectra for polarization of the external radiation oriented along the b axis are mainly due to the H2O stretching vibrations of one of the three crystallographically distinct sets of water molecules. The orientation of the transition dipoles of stretching vibrations of the selenate ion differ from the characteristic spectra of the sulfate analog in that no mutually perpendicular transition dipoles are found in the ac crystal plane. Water librational bands masked with the bands of the ν4(SO42-) mode in the sulfate analog have now been unveiled and assigned. The ratio between the oscillator strength and the attenuation constant appears to be a helpful tool in the assignment of the sulfate stretching vibrations and water librations. The vibrational and orientational characteristics of the ν4(SeO42-) modes were obtained. Тhe ν3(SO42-) frequency region of the isomorphously isolated SO42- ion in the K2Ni(SeO4)2·6H2O matrix was investigated in some detail. Contrary to the expected three, four bands can be identified. Three of them were assigned to ν3(SO42-) based on the orientation of the transition dipole moments. On the basis of the IR, but also Raman spectra of the pure and mixed crystals, a discussion of the influence of the potential field and the hydrogen bonds with the change in the volume of the unit cell is given.

  10. Density functional periodic study of the dehydrogenation of methane on Pd (1 1 1) surface

    NASA Astrophysics Data System (ADS)

    Jiang, Zhao; Li, Lu; Xu, Jie; Fang, Tao

    2013-12-01

    The adsorption and dehydrogenation mechanism of CH4 on Pd (1 1 1) surface was studied using density functional theory (DFT) together with periodic slab models. According to the optimized structural and energetic properties, it was found that CH3 prefers to adsorb on the top sites of the Pd metal surface. Whereas CH2, CH, and H prefer to adsorb on the fcc sites, and C prefers to adsorb on the hcp sites. In addition, this work identified the optimum configurations for the stable co-adsorption configurations of CHx and H. Finally, four transition states were found for analyzing the mechanism of dehydrogenation of CH4. The results show that the dehydrogenation of CH moiety is relatively difficult and the dehydrogenation of CH3 is the rate-determining step in the overall reaction.

  11. Case studies of multi-day 3He-rich solar energetic particle periods

    NASA Astrophysics Data System (ADS)

    Chen, Nai-hwa; Bučík, Radoslav; Innes, Davina E.; Mason, Glenn M.

    2015-08-01

    Context. Impulsive solar energetic particle events in the inner heliosphere show the long-lasting enrichment of 3He. Aims: We study the source regions of long-lasting 3He-rich solar energetic particle (SEP) events Methods: We located the responsible open magnetic field regions, we combined potential field source surface extrapolations with the Parker spiral, and compared the magnetic field of the identified source regions with in situ magnetic fields. The candidate open field regions are active region plages. The activity was examined by using extreme ultraviolet images from the Solar Dynamics Observatory (SDO) and STEREO together with radio observations from STEREO and WIND. Results: Multi-day periods of 3He-rich SEP events are associated with ion production in single active region. Small flares or coronal jets are their responsible solar sources. We also find that the 3He enrichment may depend on the occurrence rate of coronal jets.

  12. Feasibility study of a periodic arc compressor in the presence of coherent synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Di Mitri, S.

    2016-01-01

    The advent of short electron bunches in high brightness linear accelerators has raised the awareness of the accelerator community to the degradation of the beam transverse emittance by coherent synchrotron radiation (CSR) emitted in magnetic bunch length compressors, transfer lines and turnaround arcs. Beam optics control has been proposed to mitigate that CSR effect. In this article, we enlarge on the existing literature by reviewing the validity of the linear optics approach in a periodic, achromatic arc compressor. We then study the dependence of the CSR-perturbed emittance to beam optics, mean energy, and bunch charge. The analytical findings are compared with particle tracking results. Practical considerations on CSR-induced energy loss and nonlinear particle dynamics are included. As a result, we identify the range of parameters that allows feasibility of an arc compressor for driving, for example, a free electron laser or a linear collider.

  13. Detection specificity studies of bacteriophage adhesin-coated long-period grating-based biosensor

    NASA Astrophysics Data System (ADS)

    Koba, Marcin; Śmietana, Mateusz; Brzozowska, Ewa; Górska, Sabina; Mikulic, Predrag; Cusano, Andrea; Bock, Wojtek J.

    2015-09-01

    In this work, we present a label-free detection specificity study of an optical fiber long-period grating (LPG) biosensor working near the dispersion turning point of higher order cladding modes. The LPG sensor functionalized with bacteriophage adhesin is tested with specific and non-specific bacteria dry weight. We show that such biosensor is able to selectively bind, thus recognize different bacteria. We use bacteria dry weights of E. coli B as positive test and E. coli K12 and Salmonella enterica as negative tests. The resonance wavelength shift induced by E. coli B reaches over 90 nm, while for E. coli K12 and Salmonella enterica approximately 40 and 20 nm, respectively.

  14. Reference datasets for 2-treatment, 2-sequence, 2-period bioequivalence studies.

    PubMed

    Schütz, Helmut; Labes, Detlew; Fuglsang, Anders

    2014-11-01

    It is difficult to validate statistical software used to assess bioequivalence since very few datasets with known results are in the public domain, and the few that are published are of moderate size and balanced. The purpose of this paper is therefore to introduce reference datasets of varying complexity in terms of dataset size and characteristics (balance, range, outlier presence, residual error distribution) for 2-treatment, 2-period, 2-sequence bioequivalence studies and to report their point estimates and 90% confidence intervals which companies can use to validate their installations. The results for these datasets were calculated using the commercial packages EquivTest, Kinetica, SAS and WinNonlin, and the non-commercial package R. The results of three of these packages mostly agree, but imbalance between sequences seems to provoke questionable results with one package, which illustrates well the need for proper software validation.

  15. Ecological periodic tables for benthic macrofaunal usage of estuarine habitats : Insights from a case study in Tillamook bay, Oregon, USA

    EPA Science Inventory

    This study validates the ecological relevance of estuarine habitat types to the benthic macrofaunal community and, together with previous similar studies, suggests they can serve as elements in ecological periodic tables of benthic macrofaunal usage in the bioregion. We compared...

  16. MD-2 as the target of a novel small molecule, L6H21, in the attenuation of LPS-induced inflammatory response and sepsis

    PubMed Central

    Wang, Yi; Shan, Xiaoou; Chen, Gaozhi; Jiang, Lili; Wang, Zhe; Fang, Qilu; Liu, Xing; Wang, Jingying; Zhang, Yali; Wu, Wencan; Liang, Guang

    2015-01-01

    Background and Purpose Myeloid differentiation 2 (MD-2) recognizes LPS, which is required for TLR4 activation, and represents an attractive therapeutic target for severe inflammatory disorders. We previously found that a chalcone derivative, L6H21, could inhibit LPS-induced overexpression of TNF-α and IL-6 in macrophages. Here, we performed a series of biochemical experiments to investigate whether L6H21 specifically targets MD-2 and inhibits the interaction and signalling transduction of LPS-TLR4/MD-2. Experimental Approach The binding affinity of L6H21 to MD-2 protein was analysed using computer docking, surface plasmon resonance analysis, elisa, fluorescence measurements and flow cytometric analysis. The effects of L6H21 on MAPK and NF-κB signalling were determined using EMSA, fluorescence staining, Western blotting and immunoprecipitation. The anti-inflammatory effects of L6H21 were confirmed using elisa and RT-qPCR in vitro. The anti-inflammatory effects of L6H21 were also evaluated in septic C57BL/6 mice. Key Results Compound L6H21 inserted into the hydrophobic region of the MD-2 pocket, forming hydrogen bonds with Arg90 and Tyr102 in the MD-2 pocket. In vitro, L6H21 subsequently suppressed MAPK phosphorylation, NF-κB activation and cytokine expression in macrophages stimulated by LPS. In vivo, L6H21 pretreatment improved survival, prevented lung injury, decreased serum and hepatic cytokine levels in mice subjected to LPS. In addition, mice with MD-2 gene knockout were universally protected from the effects of LPS-induced septic shock. Conclusions and Implications Overall, this work demonstrated that the new chalcone derivative, L6H21, is a potential candidate for the treatment of sepsis. More importantly, the data confirmed that MD-2 is an important therapeutic target for inflammatory disorders. PMID:26076332

  17. Frustrated Quantum Critical Theory of Putative Spin-Liquid Phenomenology in 6H-B-Ba3NiSb2O9

    NASA Astrophysics Data System (ADS)

    Chen, G.; Hermele, M.; Radzihovsky, L.

    2012-07-01

    A recently discovered material, 6H-B-Ba3NiSb2O9 was found to display unusual low-temperature phenomenology, interpreted as a quantum spin liquid with spin S=1 on a triangular lattice. We study a spin S=1 exchange model on an AB stacked triangular lattice near its quantum paramagnet-to-spiral transition, driven by easy-plane single-ion anisotropy. We demonstrate that the frustrated inter- and intralayer exchanges induce contour lines of low-energy excitations that lead to a broad crossover regime of linear-temperature dependence of the specific heat. Based on this and various other predictions, we argue that the observed phenomenology can be understood in terms of a conventional picture of a proximity to this frustrated critical point.

  18. Frustrated quantum critical theory of putative spin-liquid phenomenology in 6H-B-Ba(3)NiSb(2)O(9).

    PubMed

    Chen, G; Hermele, M; Radzihovsky, L

    2012-07-01

    A recently discovered material, 6H-B-Ba(3)NiSb(2)O(9) was found to display unusual low-temperature phenomenology, interpreted as a quantum spin liquid with spin S=1 on a triangular lattice. We study a spin S=1 exchange model on an AB stacked triangular lattice near its quantum paramagnet-to-spiral transition, driven by easy-plane single-ion anisotropy. We demonstrate that the frustrated inter- and intralayer exchanges induce contour lines of low-energy excitations that lead to a broad crossover regime of linear-temperature dependence of the specific heat. Based on this and various other predictions, we argue that the observed phenomenology can be understood in terms of a conventional picture of a proximity to this frustrated critical point. PMID:23031118

  19. An investigation of thin Zr films on 6H-SiC(0001) and GaN(0001) surfaces by XPS, LEED, and STM

    NASA Astrophysics Data System (ADS)

    Idczak, K.; Mazur, P.; Zuber, S.; Markowski, L.

    2016-04-01

    In this work, the results of the growth of zirconium films deposited under the ultrahigh vacuum at room temperature on the 6H-SiC(0001) and GaN(0001) surfaces were studied. Observed changes in the chemical composition, bonding environment, and surface reconstruction, and the effects of high-temperature annealing of the film are presented and discussed as well. In the performed experiment, the X-ray photoelectron spectroscopy, low-energy electron diffraction, and scanning tunneling microscopy were used. The results show that for both investigated substrates, the grown films have eminently rich and varied compositions. Besides the metallic zirconium, there are also zirconium oxides, zirconium carbides, or zirconium nitrides. The growth process proceeds according to the Volmer-Weber mode. Moreover, the zirconium-semiconductor interface does not form typical Schottky contact, but some paths with a quasi-ohmic conduction character can be observed.

  20. Calculation of positron annihilation characteristics of six main defects in 6 H -SiC and the possibility to distinguish them experimentally

    NASA Astrophysics Data System (ADS)

    Linez, F.; Makkonen, I.; Tuomisto, F.

    2016-07-01

    We have determined positron annihilation characteristics (lifetime and Doppler broadening) in six basic vacancy-type defects of 6 H -SiC and two nitrogen-vacancy complexes using ab initio calculations. The positron characteristics obtained allow us to point out which positron technique in the most adapted to identify a particular defect. They show that the coincidence Doppler broadening technique is the most relevant for observing the silicon vacancy-nitrogen complexes, VSiNC , and carbon vacancy-carbon antisite ones, VCCSi . For the other studied defects, the calculated positron characteristics are found to be too close for the defects to be easily distinguished using a single positron annihilation technique. Then it is required to use complementary techniques, positron annihilation based or other.

  1. On the Formation of Ortho-benzyne (o-C6H4) Under Single Collision Conditions and its Role in Interstellar Chemistry

    NASA Astrophysics Data System (ADS)

    Zhang, Fangtong; Parker, Dorian; Kim, Y. Seol; Kaiser, Ralf I.; Mebel, Alexander M.

    2011-02-01

    The elementary reaction of the D1-ethynyl radical (C2D) with vinylacetylene (C4H4) was studied under single collision conditions via crossed molecular beam experiments and electronic structure calculations. The results suggested that besides two acyclic isomers as predicted computationally, the ortho-benzyne (o-C6H4)—in its singly deuterated form—which is considered as an important intermediate in the formation of polycyclic aromatic hydrocarbons, can be formed in this process. This reaction was carried out at a collision energy of 40.9 kJ mol-1, which is roughly equal to about 4000 K as present in photospheres of carbon stars and protoplanetary nebulae close to the central star. As the reaction is exoergic and involves no barriers higher than the separated reactants, our findings suggest that ortho-benzyne can also be formed in molecular clouds like TMC-1.

  2. Synthesis and dynamic behaviour of zwitterionic [M(η(6)-C6H5-BPh3)(coe)2] (M = Rh, Ir) cyclooctene complexes.

    PubMed

    Pérez-Torrente, Jesús J; Angoy, Marta; Gómez-Bautista, Daniel; Palacios, Adrián; Jiménez, M Victoria; Modrego, F Javier; Castarlenas, Ricardo; Lahoz, Fernando J; Oro, Luis A

    2014-10-21

    The synthesis and structural characterization of zwitterionic [(η(6)-C6H5-BPh3)M(coe)2] (M = Rh, Ir) cyclooctene complexes is described. Both complexes exhibit an unusual exo-endo conformation of both cyclooctene ligands in the solid state. However, an equilibrium between the endo-endo and exo-endo rotational isomers arising from the hindered rotation about the metal-cyclooctene bond is observed in solution. Rotational barriers of around 65 kJ mol(-1) (Rh) and 84 kJ mol(-1) (Ir) have been determined by 2D EXSY NMR spectroscopy. The rotation process has also been studied by DFT calculations that showed that the dynamic behaviour is a consequence of the oscillation of the cyclooctene ligands about the metal-olefin bond instead of completing a full rotation.

  3. X-ray structure of beta-cyclodextrin-2,7-dihydroxy-naphthalene.4.6 H(2)O: an unusually distorted macrocycle.

    PubMed

    Añibarro, M; Gessler, K; Usón, I; Sheldrick, G M; Saenger, W

    2001-07-12

    The inclusion complex beta-cyclodextrin.2,7-dihydroxynaphthalene.4.6 H(2)O crystallized in the monoclinic space group P2(1), with a=14.082(3), b=19.079(4), c=12.417(3) A, beta=109.28(3) degrees, V=3149.0(11) A(3), and Z=2. An X-ray study performed at room temperature shows that the crystal packing is of the herringbone type with one 2,7-dihydroxynaphthalene included completely in the beta-CD cavity, its long axis being oriented along the beta-CD molecular axis, and 4.6 water molecules are placed in the interstitial space. The beta-CD macrocycle is elliptically distorted, and the guest molecule is held in the hydrophobic beta-CD cavity by C-H...O and C-H...pi interactions.

  4. Enhanced quality of epitaxial AlN thin films on 6H-SiC by ultra-high-vacuum ion-assisted reactive dc magnetron sputter deposition

    NASA Astrophysics Data System (ADS)

    Tungasmita, S.; Birch, J.; Persson, P. O. A.˚.; Järrendahl, K.; Hultman, L.

    2000-01-01

    Epitaxial AlN thin films have been grown on 6H-SiC substrates by ultra-high-vacuum (UHV) ion-assisted reactive dc magnetron sputtering. The low-energy ion-assisted growth (Ei=17-27 eV) results in an increasing surface mobility, promoting domain-boundary annihilation and epitaxial growth. Domain widths increased from 42 to 135 nm and strained-layer epitaxy was observed in this energy range. For Ei>52 eV, an amorphous interfacial layer of AlN was formed on the SiC, which inhibited epitaxial growth. Using UHV condition and very pure nitrogen sputtering gas yielded reduced impurity levels in the films (O: 3.5×1018cm-3). Analysis techniques used in this study are in situ reflection high-energy electron diffraction, secondary-ion-mass spectroscopy, atomic-force microscopy, x-ray diffraction, and cross-section high-resolution electron microscopy.

  5. Advanced Concept Studies for Supersonic Commercial Transports Entering Service in the 2018 to 2020 Period

    NASA Technical Reports Server (NTRS)

    Morgenstern, John; Norstrud, Nicole; Sokhey, Jack; Martens, Steve; Alonso, Juan J.

    2013-01-01

    Lockheed Martin Aeronautics Company (LM), working in conjunction with General Electric Global Research (GE GR), Rolls-Royce Liberty Works (RRLW), and Stanford University, herein presents results from the "N+2 Supersonic Validations" contract s initial 22 month phase, addressing the NASA solicitation "Advanced Concept Studies for Supersonic Commercial Transports Entering Service in the 2018 to 2020 Period." This report version adds documentation of an additional three month low boom test task. The key technical objective of this effort was to validate integrated airframe and propulsion technologies and design methodologies. These capabilities aspired to produce a viable supersonic vehicle design with environmental and performance characteristics. Supersonic testing of both airframe and propulsion technologies (including LM3: 97-023 low boom testing and April-June nozzle acoustic testing) verified LM s supersonic low-boom design methodologies and both GE and RRLW's nozzle technologies for future implementation. The N+2 program is aligned with NASA s Supersonic Project and is focused on providing system-level solutions capable of overcoming the environmental and performance/efficiency barriers to practical supersonic flight. NASA proposed "Initial Environmental Targets and Performance Goals for Future Supersonic Civil Aircraft". The LM N+2 studies are built upon LM s prior N+3 100 passenger design studies. The LM N+2 program addresses low boom design and methodology validations with wind tunnel testing, performance and efficiency goals with system level analysis, and low noise validations with two nozzle (GE and RRLW) acoustic tests.

  6. Studies of cortical interactions over short periods of time during the search for verbal associations.

    PubMed

    Nikolaev, A R; Ivanitskii, G A; Ivanitskii, A M

    2001-01-01

    Interactions between cortical areas were studied during the search for verbal associations and reading of words. The functional anatomy and the sequence of involvement of cortical areas during the solution of these tasks have been described previously, in studies using positron emission tomography and multichannel recordings of evoked potentials combined with identification of the locations of dipole sources [8, 9, 19, 25]. Cortical interactions reflected in terms of the synchronization of EEG rhythms were studied by developing a method based on correlating curve wavelets, which allows the moments at which this synchronization occurs to be identified over short periods of time comparable with the speeds of individual thought operations (up to 100 msec). Three main stages were identified in the search for associations. During the first 200 msec after stimulus presentation, cortical connections were seen between the right and left frontal areas; at 200-500 msec, there were connections between the frontal and the temporal-parietal areas; finally, at 450-700 sec, there were connections between the left temporal and the right frontal-central-temporal areas. These results are in good agreement with data obtained previously using other methods and supplement them with mapping data on cortical connections. A number of differences in the mechanisms of information processing during the search for associations and reading were also identified.

  7. Near-surface recrystallization of the amorphous implanted layer of ion implanted 6H-SiC

    NASA Astrophysics Data System (ADS)

    Kuhudzai, R. J.; van der Berg, N. G.; Malherbe, J. B.; Hlatshwayo, T. T.; Theron, C. C.; Buys, A. V.; Botha, A. J.; Wendler, E.; Wesch, W.

    2014-08-01

    The recrystallization and subsequent crystal growth during annealing of amorphous surface layers on 6H-SiC produced by ion implantation is investigated. Amorphous surface layers were produced by ion implantation of 360 keV ions of iodine, silver, xenon, cesium and strontium into single crystalline 6H-silicon carbide samples. The ion fluence for all the implantations were in the order of 1016 cm-2. Vacuum annealing of the damaged silicon carbide samples was then performed. The microstructure of SiC surfaces before and after annealing was investigated using a high resolution field emission scanning electron microscope (SEM). SEM analysis was complimented by Atomic Force Microscopy (AFM). SEM images acquired by an in-lens detector using an accelerating voltage of 2 kV show nano-crystallites developed for all implanted samples after annealing. Larger and more faceted crystallites along with elongated thin crystallites were observed for iodine and xenon implanted 6H-SiC. Crystallites formed on surfaces implanted with strontium and cesium were smaller and less faceted. Strontium, silver and cesium implanted samples also exhibited more cavities on the surface. AFM was used to evaluate the effect of annealing on the surface roughness. For all the amorphous surfaces which were essentially featureless, the root mean square (rms) roughness was approximately 1 nm. The roughness increased to approximately 17 nm for the iodine implanted sample after annealing with the surface roughness below this value for all the other samples. AFM also showed that the largest crystals grew to heights of about 17, 20, 45, 50 and 65 nm for Sr, Cs, Ag, Xe and I implanted samples after annealing at 1200 °C for 5 h respectively. SEM images and AFM analysis suggest that iodine is more effective in promoting crystal growth during the annealing of bombardment-induced amorphous SiC layers than the rest of the ions we implanted. In samples of silicon carbide co-implanted with iodine and silver, few

  8. Adsorption and decomposition of cyclohexanone (C6H10O) on Pt(111) and the (2 × 2) and (√3 × √3)r30°-Sn/Pt(111) surface alloys.

    PubMed

    Kim, Jooho; Welch, Lindsey A; Olivas, Amelia; Podkolzin, Simon G; Koel, Bruce E

    2010-11-01

    Adsorption and decomposition of cyclohexanone (C(6)H(10)O) on Pt(111) and on two ordered Pt-Sn surface alloys, (2 × 2)-Sn/Pt(111) and (√3 × √3)R30°-Sn/Pt(111), formed by vapor deposition of Sn on the Pt(111) single crystal surface were studied with TPD, HREELS, AES, LEED, and DFT calculations with vibrational analyses. Saturation coverage of C(6)H(10)O was found to be 0.25 ML, independent of the Sn surface concentration. The Pt(111) surface was reactive toward cyclohexanone, with the adsorption in the monolayer being about 70% irreversible. C(6)H(10)O decomposed to yield CO, H(2)O, H(2), and CH(4). Some C-O bond breaking occurred, yielding H(2)O and leaving some carbon on the surface after TPD. HREELS data showed that cyclohexanone decomposition in the monolayer began by 200 K. Intermediates from cyclohexanone decomposition were also relatively unstable on Pt(111), since coadsorbed CO and H were formed below 250 K. Surface Sn allowed for some cyclohexanone to adsorb reversibly. C(6)H(10)O dissociated on the (2 × 2) surface to form CO and H(2)O at low coverages, and methane and H(2) in smaller amounts than on Pt(111). Adsorption of cyclohexanone on (√3 × √3)R30°-Sn/Pt(111) at 90 K was mostly reversible. DFT calculations suggest that C(6)H(10)O adsorbs on Pt(111) in two configurations: by bonding weakly through oxygen to an atop Pt site and more strongly through simultaneously oxygen and carbon of the carbonyl to a bridged Pt-Pt site. In contrast, on alloy surfaces, C(6)H(10)O bonds preferentially to Sn. The presence of Sn, furthermore, is predicted to make the formation of the strongly bound C(6)H(10)O species bonding through O and C, which is a likely decomposition precursor, thermodynamically unfavorable. Alloying with Sn, thus, is shown to moderate adsorptive and reactive activity of Pt(111).

  9. Admission to psychiatric hospital in the early and late postpartum periods: Scottish national linkage study

    PubMed Central

    Langan Martin, Julie; McLean, Gary; Cantwell, Roch; Smith, Daniel J

    2016-01-01

    Objective To describe weekly admission rates for affective and non-affective psychosis, major depression and other psychiatric disorders in the early and late postpartum periods. To assess the impact of socioeconomic status, age and parity on admission rates. Methods Scottish maternity records were linked to psychiatric hospital admissions. 3290 pregnancy-related psychiatric admissions were assessed. Weekly admission rates were calculated for the pregnancy period, early postpartum period (6 weeks after birth) and late postpartum period (up to 2 years after birth), and compared with pre-pregnancy rates (up to 2 years before pregnancy). Admission rates were generated by calculating the total number of admissions for each time period divided by the number of weeks in the period. Incidence rate ratios (IRRs) were generated for each time period, using deprivation, age, parity and record of previous psychiatric hospital care-adjusted Poisson regression models. Results Women from more deprived social quintiles accounted for the largest proportion of admissions across all time periods. Compared with pre-pregnancy period, admission rates fell during pregnancy, increased markedly during the early postpartum period, and remained elevated for 2 years after childbirth. Within the most affluent quintile, admission IRRs were higher in the early postpartum period (IRR=1.29, 95% CI 1.02 to 1.59) than in the late postpartum period (IRR=0.87, 95% CI 0.74 to 0.98). For the late postpartum period, there was a positive association between higher maternal age and admission IRRs (ages 20–35 years, IRR=1.35, 95% CI 1.16 to 1.54 and age>40 years IRR=1.72, 95% CI 1.41 to 2.09). Conclusions Rates of psychiatric admission fell during pregnancy and increased in the early postpartum period (particularly during the first 2 weeks after birth), and remained elevated above baseline during the 2-year late postpartum period. An understanding of how social deprivation, age and parity

  10. 39 CFR 3050.12 - Obsolescence of special studies relied on to produce the Postal Service's annual periodic reports...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 39 Postal Service 1 2011-07-01 2011-07-01 false Obsolescence of special studies relied on to produce the Postal Service's annual periodic reports to the Commission. 3050.12 Section 3050.12 Postal Service POSTAL REGULATORY COMMISSION PERSONNEL PERIODIC REPORTING § 3050.12 Obsolescence of...

  11. 39 CFR 3050.12 - Obsolescence of special studies relied on to produce the Postal Service's annual periodic reports...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 39 Postal Service 1 2013-07-01 2013-07-01 false Obsolescence of special studies relied on to produce the Postal Service's annual periodic reports to the Commission. 3050.12 Section 3050.12 Postal Service POSTAL REGULATORY COMMISSION PERSONNEL PERIODIC REPORTING § 3050.12 Obsolescence of...

  12. 39 CFR 3050.12 - Obsolescence of special studies relied on to produce the Postal Service's annual periodic reports...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 39 Postal Service 1 2014-07-01 2014-07-01 false Obsolescence of special studies relied on to produce the Postal Service's annual periodic reports to the Commission. 3050.12 Section 3050.12 Postal Service POSTAL REGULATORY COMMISSION PERSONNEL PERIODIC REPORTING § 3050.12 Obsolescence of...

  13. 39 CFR 3050.12 - Obsolescence of special studies relied on to produce the Postal Service's annual periodic reports...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 39 Postal Service 1 2010-07-01 2010-07-01 false Obsolescence of special studies relied on to produce the Postal Service's annual periodic reports to the Commission. 3050.12 Section 3050.12 Postal Service POSTAL REGULATORY COMMISSION PERSONNEL PERIODIC REPORTING § 3050.12 Obsolescence of...

  14. 39 CFR 3050.12 - Obsolescence of special studies relied on to produce the Postal Service's annual periodic reports...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 39 Postal Service 1 2012-07-01 2012-07-01 false Obsolescence of special studies relied on to produce the Postal Service's annual periodic reports to the Commission. 3050.12 Section 3050.12 Postal Service POSTAL REGULATORY COMMISSION PERSONNEL PERIODIC REPORTING § 3050.12 Obsolescence of...

  15. [Preliminary study on the changes of bacterial community structure in Qingcaosha Reservoir during water storage period].

    PubMed

    Peng, Qing; Xie, Bing; Yuan, Qi; Huang, Zhi-Ting; Cui, Lu-Lu; Wang, Wen-Ting

    2012-10-01

    In order to investigate the changes in water quality and the bacterial community structure in Qingcaosha Reservoir during water storage and supply period, the microorganisms in water body were studied by microbial culture counting and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DEEG) technique. Results showed that the water quality had been improved significantly and the nitrogen and phosphorus concentrations significantly reduced after the Yangtze River water flowed into the reservoir. The number of culturable microorganisms in the influent and the reservoir changed with the seasons, and there were more microorganisms in the influent than these in the reservoir during spring and summer, and fewer in autumn and winter, and the precipitation of suspended microorganisms in the water caused the increase of organic matter content in the sediment. PCR-DGGE results showed that bacterial community structure in the reservoir changed with the seasons, and the microbial community diversity was the highest in summer and the lowest in autumn. The cluster analysis showed that the similarity of microbial community structure of water and sediment samples was 62% , which might be due to the contribution of the precipitation of the suspended microorganisms. The dominant microbial species in water had high similarity with alpha, beta-Proteobacteria, Flavobacterium, Rheinheimera, Prochlorococcus, Synechococcus and Marine metagenome, indicating that Qingcaosha Reservoir faced the risk of algae bloom and seawater intrusion. The results provide the fundamental understanding on reservoir operation and can be used as reference for future studies.

  16. High power operation of a nitrogen doped, vanadium compensated, 6H-SiC extrinsic photoconductive switch

    SciTech Connect

    Sullivan, J. S.

    2014-04-28

    We report the high power operation of nitrogen doped, vanadium compensated, 6H-SiC, extrinsic photoconductive switches with improved vanadium and nitrogen dopant density. Photoconductive switching tests are performed on 1 mm thick, m-plane, switch substrates at switch voltage and currents up to 17 kV and 1.5 kA, respectively. Sub-ohm minimum switch on resistance is achieved for peak optical intensities ≥35 MW/cm{sup 2} at 532 nm applied to the switch facet. A reduction of greater than nine orders of magnitude is observed in switch material resistivity between dark and illuminated states.

  17. Stable Electrical Operation of 6H-SiC JFETs and ICs for Thousands of Hours at 500 C

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Spry, David J.; Chen, Liang-Yu; Beheim, Glenn M.; Okojie, Robert S.; Chang, Carl W.; Meredith, Roger D.; Ferrier, Terry L.; Evans, Laura J.; Krasowski, Michael J.; Prokop, Norman F.

    2008-01-01

    The fabrication and testing of the first semiconductor transistors and small-scale integrated circuits (ICs) to achieve up to 3000 h of stable electrical operation at 500 C in air ambient is reported. These devices are based on an epitaxial 6H-SiC junction field-effect transistor process that successfully integrated high temperature ohmic contacts, dielectric passivation, and ceramic packaging. Important device and circuit parameters exhibited less than 10% of change over the course of the 500 C operational testing. These results establish a new technology foundation for realizing durable 500 C ICs for combustion-engine sensing and control, deep-well drilling, and other harsh-environment applications.

  18. Growth of fcc(111) Dy multi-height islands on 6H-SiC(0001) graphene.

    PubMed

    Hershberger, M T; Hupalo, M; Thiel, P A; Tringides, M C

    2013-06-01

    Graphene based spintronic devices require an understanding of the growth of magnetic metals. Rare earth metals have large bulk magnetic moments so they are good candidates for such applications, and it is important to identify their growth mode. Dysprosium was deposited on epitaxial graphene, prepared by thermally annealing 6H-SiC(0001). The majority of the grown islands have triangular instead of hexagonal shapes. This is observed both for single layer islands nucleating at the top of incomplete islands and for fully completed multi-height islands. We analyze the island shape distribution and stacking sequence of successively grown islands to deduce that the Dy islands have fcc(111) structure, and that the triangular shapes result from asymmetric barriers to corner crossing.

  19. AlN bulk single crystal growth on 6H-SiC substrates by sublimation method

    NASA Astrophysics Data System (ADS)

    Nagai, Ichiro; Kato, Tomohisa; Miura, Tomonori; Kamata, Hiroyuki; Naoe, Kunihiro; Sanada, Kazuo; Okumura, Hajime

    2010-09-01

    Large and thick AlN bulk single crystals up to 43 mm in diameter and 10 mm in thickness have been successfully grown on 6H-SiC (0 0 0 1) substrates by the sublimation method using a TaC crucible. Raman spectrum indicates that the polytype of the grown AlN single crystals is a Wurtzite-2H type structure, and the crystals do not include any impurity phases. The quality at the top of the crystal improves as crystal thickness increases along the <0 0 0 1> direction during growth: a low etch pit density (7×10 4 cm -2) and a small full width at half maximum for a 0002 X-ray rocking curve (58 arcsec) have been achieved at a thickness of ˜8 mm. The possible mechanism behind the improvement in the AlN crystal quality is also discussed.

  20. High-Field Fast-Risetime Pulse Failures in 4H- and 6H-SiC pn Junction Diodes

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Fazi, Christian

    1996-01-01

    We report the observation of anomalous reverse breakdown behavior in moderately doped (2-3 x 10(exp 17 cm(exp -3)) small-area micropipe-free 4H- and 6H-SiC pn junction diodes. When measured with a curve tracer, the diodes consistently exhibited very low reverse leakage currents and sharp repeatable breakdown knees in the range of 140-150 V. However, when subjected to single-shot reverse bias pulses (200 ns pulsewidth, 1 ns risetime), the diodes failed catastrophically at pulse voltages of less than 100 V. We propose a possible mechanism for this anomalous reduction in pulsed breakdown voltage relative to dc breakdown voltage. This instability must be removed so that SiC high-field devices can operate with the same high reliability as silicon power devices.

  1. Disodium hydrogen citrate sesquihydrate, Na2HC6H5O7(H2O)1.5.

    PubMed

    Rammohan, Alagappa; Sarjeant, Amy A; Kaduk, James A

    2016-07-01

    The crystal structure of disodium hydrogen citrate sesquihydrate, 2Na2 (+)·C6H6O7 (2-)·1.5H2O, has been solved and refined using laboratory X-ray single-crystal diffraction data, and optimized using density functional techniques. The asymmetric unit contains two independent hydrogen citrate anions, four sodium cations and three water molecules. The coordination polyhedra of the cations (three with a coordination number of six, one with seven) share edges to form isolated 8-rings. The un-ionized terminal carb-oxy-lic acid groups form very strong hydrogen bonds to non-coordinating O atoms, with O⋯O distances of 2.46 Å. PMID:27555936

  2. Surface coating of ZnO nanoparticles onto 6H-SiC(0001): Temperature-dependent rectifying behavior

    NASA Astrophysics Data System (ADS)

    Soylu, Murat

    2016-04-01

    This work reports on the detailed analysis of the temperature-dependent electrical parameters of the ZnO/6H-SiC barrier diodes. The effect of light on the diode current was also examined. It was found that the diode showed low sensitivity to light. No remarkable change in diode characteristics were observed at room temperature. The structure has a high rectification ratio of 1.096×104 at ±2 V with ideality factor of 2.46 at room temperature. The rectification ratio (RR) decreases with increasing temperature, as agree to other heterojunction structures. Some diode parameters such as zero-bias barrier height and ideality factor as temperature-dependent were calculated on the basis of the thermionic emission (TE) theory, by considering a Gaussian distribution (GD).

  3. Disodium hydrogen citrate sesquihydrate, Na2HC6H5O7(H2O)1.5

    PubMed Central

    Rammohan, Alagappa; Sarjeant, Amy A.; Kaduk, James A.

    2016-01-01

    The crystal structure of disodium hydrogen citrate sesquihydrate, 2Na2 +·C6H6O7 2−·1.5H2O, has been solved and refined using laboratory X-ray single-crystal diffraction data, and optimized using density functional techniques. The asymmetric unit contains two independent hydrogen citrate anions, four sodium cations and three water molecules. The coordination polyhedra of the cations (three with a coordination number of six, one with seven) share edges to form isolated 8-rings. The un-ionized terminal carb­oxy­lic acid groups form very strong hydrogen bonds to non-coordinating O atoms, with O⋯O distances of 2.46 Å. PMID:27555936

  4. Depression in Men in the Postnatal Period and Later Child Psychology: A Population Cohort Study

    ERIC Educational Resources Information Center

    Ramchandani, Paul G.; Stein, Alan; O'Connor, Thomas G.; Heron, Jon; Murray, Lynne; Evans, Jonathan

    2008-01-01

    The factors responsible for depression in men following childbirth and the association between their depression in the postnatal period and later psychiatric disorders in their children are assessed. Findings show that depression in fathers in their postnatal period is associated with later psychiatric disorders in their children, independent of…

  5. Adsorption and decomposition of C 6H 5I on the Mo 2C/Mo(1 0 0) surface

    NASA Astrophysics Data System (ADS)

    Bugyi, L.; Oszkó, A.; Solymosi, F.

    2003-08-01

    The adsorption and surface reactions of phenyl iodide on Mo 2C/Mo(1 0 0) surface have been investigated by thermal desorption spectroscopy, X-ray photoelectron spectroscopy (XPS) and high resolution electron energy loss spectroscopy in the 100-1200 K temperature range. Phenyl iodide adsorbed molecularly on the Mo 2C/Mo(1 0 0) surface at 100 K. At submonolayer coverages the molecules adsorbed in a flat-lying, and in the condensed layer in a random position. The desorption of the weakly bonded C 6H 5I occurred in a peak with Tp=200 K. Phenyl iodide bonded in the chemisorbed state underwent dissociation at 160-300 K, as evidenced by XPS data, while photolysis of the monolayer by UV light resulted in a complete dissociation even at 100 K. Iodine atoms formed in the decomposition process were released into the gas phase with Tp=980 and 1080 K. The phenyl groups formed as a result of C-I cleavage reacted in three different ways. A very limited part is coupled into biphenyl ( Tp=510 K). Other part was hydrogenated to benzene which desorbed with a Tp=290-278 K. The third part of C 6H 5(a) decomposed to hydrogen and benzyne groups. This species could be also hydrogenated into benzene, but it mostly decomposed at higher temperature, as shown by H 2 desorption peaks at 600 and 700 K. HREEL spectra suggested that the aromatic ring was preserved on the surface up to ˜430 K. Elevating the adsorption temperature to 400 K enhanced the amount of strongly bonded C 6 species by a factor of ˜3 as evidenced by the increased hydrogen desorption.

  6. Spatiotemporal analysis of precipitation change during the Younger Dryas cold period: a modelling study

    NASA Astrophysics Data System (ADS)

    Renssen, Hans

    2016-04-01

    In Northwest Europe, proxy-based reconstructions have suggested that the Younger Dryas cold period may be sub-divided in a relatively cold and humid first part and a warmer and drier second part. In Scandinavia, the later part of the Younger Dryas climate was characterized by a notable increase in variability. These changes in climatic conditions during the Younger Dryas event have been linked to a northward shift of both the winter sea-ice margin in the North Atlantic Ocean and the main storm track. Recently, we performed transient simulations of the Younger Dryas climate, performed with a global climate model. In this study, we perform a spatiotemporal analysis of these model results to see to what extent our model has been capable to reproduce the reconstructed changes in precipitation. In our Younger Dryas simulation, the main storm track is located at 55°N, resulting in relatively high precipitation rates in mid-latitude Europe. In contrast, our model suggests dry conditions in Northern and Southern Europe.

  7. Periodic Hartree-Fock study of nitric acid monohydrate crystal. Bulk and clean surface

    SciTech Connect

    Poshusta, R.D.; Tseng, D.C. ); Hess, A.C.; McCarthy, M.I. )

    1993-07-15

    This study reports the first quantum mechanical investigation of crystalline nitric acid monohydrate (NAM), HNO[sub 3]-H[sub 2]O. The goal of this work is to characterize the physical properties of NAM in order to better understand its role as a catalyst in the destruction of polar stratospheric ozone in the Antarctic. The computations probed energetic, electronic, and elastic properties of the crystalline material using the Periodic Hartree-Fock (PHF) method (as implemented in the program CRYSTAL92). All calculations were performed by using standard Pople basis sets. A description of the bulk material was obtained from calculations of the estimated cohesive binding energy, optimized lattice constants, band structure, total and projected density of states, Mulliken population analysis, electrostatic potentials, and elastic constants. The computed intracrystal interactions are consistent with the proposed hydronium/nitrate ionic crystal structure inferred from X-ray diffraction data. The calculated elastic constants, interlayer electrostatic potential maps, and characterization of the bonding in the crystal indicate that NAM is composed of weakly bound puckered layers aligned parallel to the (100) plane in the crystal. 55 refs., 6 figs., 3 tabs.

  8. Butanethiol adsorption and dissociation on Ag (111): A periodic DFT study

    NASA Astrophysics Data System (ADS)

    Li, Aixiao; Piquemal, Jean-Philip; Richardi, Johannes; Calatayud, Monica

    2016-04-01

    The molecular and dissociative adsorption of butanethiol (C4H9SH) on regular Ag (111) surfaces has been studied by means of periodic ab initio density functional techniques. In molecular form, butanethiol is bound to the surface only by weak polarization-induced forces with the C-S axis tilted by 38° relative to the normal surface. The S atom occupies a position between a hollow fcc and a bridge site. In the dissociative adsorption process, the S-H bond breaks leading to butanethiolate. The S atom of the thiolate also occupies a threefold position, slightly displaced to a hollow fcc site compared to the thiol adsorption case. The C-S axis of the thiolate is tilted by about 37°. The calculated adsorption energies show that the butanethiol and butanethiolate have similar adsorption ability. The computed reaction pathway for the S-H dissociation gives an activation energy of 0.98 eV indicating that the thiolate formation from thiol, although not spontaneous at room temperature, might be feasible on silver surfaces. The dissociation process induces both adsorbate and surface polarization with a significant charge transfer from the substrate to the adsorbate.

  9. Experimental study of periodic linear internal waves transform at the shelf edge

    NASA Astrophysics Data System (ADS)

    Shishkina, Olga; Litvin, Alexander; Vladimirova, Eleonora; Ivanov, Dmitry; Ivanov, Vladlen

    2010-05-01

    The report contains results of the experimental study of the fine structure of hydrophysical processes of internal waves transform in the shelf zone observed within a thin thermocline. A series of experiments was performed in the stratified tank with its overall dimensions L*B*H = 2.15*0.15*0.35 m where the model of the shelf has been installed. The shadowgraph IAB-455 as well as the multidot spatial system of 40 thermocouples were used for distance and contact measurements. Methods of a digital video fixation of shadow pictures of currents in the thermally stratified liquid, as well as methods of the statistical analysis of non-stationary hydrodynamic processes were applied. As a result of the series of experiments it was revealed that interaction of internal waves in the pycnocline with the shelf model leads to transformation of the internal waves, formation of currents of vortical and turbulent character and water mass mixture. The observations concern a case of creation of a package of five periodic internal waves made in the pycnocline by a submerged wave-maker. Acknowledgement: this work is supported through NWO-RFBR Project (Code: 047.017.2006.003).

  10. Study of EGNOS safety of life service during the period of solar maximum activity

    NASA Astrophysics Data System (ADS)

    Grzegorzewski, Marek; Swiatek, Anna; Oszczak, Stanislaw; Ciecko, Adam; Cwiklak, Janusz

    2012-12-01

    The Satellite Base Augmentation System (SBAS) - EGNOS (European Geostationary Navigation Overlay Service) has been certified for Safety of Life (SoL) service for aircraft navigation since 2nd of March 2011. Unfortunately for the territory of Poland, located at the edge of EGNOS service area, the quality of the service corrections are still not sufficient for aircraft navigation requirements. Years 2012 and 2013 are forecasted as a maximum of solar activity in a 11-year solar cycle. This time period will be the chance to perform the first tests for the EGNOS Safety of Life service quality in disturbed ionospheric conditions. During the previous maximum of solar activity, the storm on 30 October 2003 resulted in the inability to use WAAS corrections for more than 12 hours. This was caused by a very large gradient of disturbances and its' very sharp boundaries - vertical TEC (VTEC) varied from ~ 40 to ~ 120 TECU (TEC units) within an hour (over ~ 150 km distance). These circumstances gave the opportunity to carry out the test flights to examine the navigation parameters obtained for EGNOS SoL service in disturbed ionospheric conditions. The paper presents project proposal of study and analyses of such fundamental navigation parameters as: accuracy of determined position, availability, continuity and integrity, determined for selected disturbances in relation to quiet conditions. It can give a possibility to estimate of the quality of EGNOS SoL service in Polish airspace during the different phases of flight and its resistance to critical ionospheric conditions.

  11. [Hospital outcome in acute coronary syndrome in the period 1987-2001 in West-Herzegovina canton--retrospective study].

    PubMed

    Vasilj, Ivan; Ostojić, Zdenko; Ostojić, Ljerka; Zelenika, D; Misković, J

    2006-01-01

    Objective of the study is to show prevalence of hospital mortality of acute coronary syndrome in pre-war (1987-1991), war (1992-1996) and after war period (1997-2001) among inhabitants of West-Herzegovina canton living in the following municipalities: Siroki Brijeg, Posusje, Grude and Ljubuski (88,992 inhabitants). Collected were data on patients who were admitted in the hospital due to acute coronar syndrome (category I 20, 21, 22- X revision, ICD) in the above period in Mostar. Data were analyzed in regard to sex, age and disease output. Hospital morality in 15 year period for both sex were 15.0 %, men 12.1 %, and women 20.2 %. Statistically it was not found significant differences in the period 1987-2001 in regards to total hospital mortality of men and women and separate hospital mortality of men. Differences were found in women where considerable larger number was in pre-war and post-war period in comparison with war period. The largest hospital mortality was in total and for women in the pre-war period and for men was during the war period. The smallest hospital mortality was in total and for women during the war and for men in pre-war period. We find that lower hospital mortality in women was caused by lower hospital admission because of war time and problems with transport and that larger number of women deceased before admission to the hospital.

  12. Photoelectron spectroscopy study of AlN films grown on n-type 6H-SiC by MOCVD

    NASA Astrophysics Data System (ADS)

    Liang, F.; Chen, P.; Zhao, D. G.; Jiang, D. S.; Zhao, Z. J.; Liu, Z. S.; Zhu, J. J.; Yang, J.; Liu, W.; He, X. G.; Li, X. J.; Li, X.; Liu, S. T.; Yang, H.; Liu, J. P.; Zhang, L. Q.; Zhang, Y. T.; Du, G. T.

    2016-09-01

    Photoelectron spectroscopy has been employed to analyze the content and chemical states of the elements on the surface of AlN films with different thickness, which are synthesized by metalorganic chemical vapor deposition on the n-type SiC substrates under low pressure. It is found that, besides the carbon and gallium on the AlN surface, the atom percentage of surface oxygen increases from 4.9 to 8.4, and the electron affinity also increases from 0.36 to 0.97 eV, when the thickness of AlN films increase from 50 to 400 nm. Furthermore, accompanying with the high-resolution XPS spectra of the O 1s, it is speculated that surface oxygen may be the major influence on the electron affinity, where the surface oxygen changes the surface chemical states through replacing N to form Al-O bond and Ga-O bond, although there are also a few of Ga and C contaminations in the chemical sate of Ga-O and C-C, respectively.

  13. Periodic sound-based 6-minute walk test forpatients with Duchenne muscular dystrophy:a preliminary study

    PubMed Central

    Nishizawa, Hitomi; Genno, Hirokazu; Shiba, Naoko; Nakamura, Akinori

    2015-01-01

    [Purpose] The purpose of this study was to verify if a periodic sound-based 6-minute walk test with the best periodic sound could be used to evaluate physical endurance more precisely than the conventional 6-minute walk test. [Subjects] The subjects were healthy subjects and 6 ambulant patients with Duchenne muscular dystrophy. [Methods] The subjects initially walked for 1 minute to a long-interval metronome sound, and the walking distance was measured. The sound interval was then gradually shortened, and the subjects walked for 1 minute for each of the intervals. The best periodic sound was considered to be the periodic sound used when the subject walked the longest distance in 1 minute, and the process of determining it was referred to as the period shortening walk test. This study administered the 6-minute walk test with the best periodic sound to twenty healthy subjects and 6 ambulant patients with Duchenne muscular dystrophy and compared the walking distance. [Results] The periodic sound-based 6-minute walk test distances in both the healthy subjects and the patients were significantly longer than the conventional 6-minute walk test distances. [Conclusion] The periodic sound-based 6-minute walk test provided a better indication of ambulatory potential in an evaluation of physical endurance than the conventional 6-minute walk test. PMID:26696721

  14. Reactions of (Cp(CO) sub 2 Fe double bond CHAr) sup + (Ar = p-C sub 6 H sub 4 OMe) with O double bond N-Ar prime (Ar prime = C sub 6 H sub 5 , p-C sub 6 H sub 4 NMe sub 2 ) and PhN double bond NPh

    SciTech Connect

    Peng, Wei-Jun; Gamble, A.S.; Templeton, J.L.; Brookhart, M. )

    1990-02-07

    Organometallic products formed from the reaction of an electrophilic iron carbene complex with nitrosoarenes or azobenzene reflect net insertion of the ArN{double bond}X moiety into the Fe{double bond}CHAr bond. Cp(CO){sub 2}Fe-O-N(Ar{prime}){double bond}CHAr{sup +} and Cp(CO){sub 2}FeN(Ph)-N(Ph){double bond}CHAr{sup +} (Ar = p-C{sub 6}H{sub 4}OMe, Ar{prime} = p-C{sub 6}H{sub 4}NMe{sub 2}) have been isolated and spectroscopically characterized; the crystal structure of Cp(CO){sub 2}Fe-O-N(Ph){double bond}CHAr{sup +} is reported. Exposure of acetone solutions of Cp(CO){sub 2}Fe-O-N(Ar{prime}){double bond}CHAr{sup +} or Cp(CO){sub 2}FeN(Ph)-N(Ph){double bond}char{sup +} to light yields imine products Ar{prime}N{double bond}CHAr or PhN{double bond}CHAr, respectively. There is no evidence to support the formation of the simple stoichiometric iron-containing products of these reactions, the oxo and nitrene complexes Cp(CO){sub 2}Fe{double bond}O{sup +} and Cp(CO){sub 2}Fe{double bond}NPh{sup +}. Hydrolysis of the nitrone complexes Cp(CO){sub 2}Fe-O-N(Ar{prime}){double bond}CHAr{sup +} in aqueous acetone yields aldehyde products Ar{prime}CHO. 30 refs., 1 fig., 4 tabs.

  15. Experimental study of flow in a channel with a periodically heated wall

    NASA Astrophysics Data System (ADS)

    Inasawa, Ayumu; Taneda, Keinosuke; Floryan, Jerzy M.

    2015-11-01

    Flows in a channel with spatially periodic wall heating are examined experimentally at the Reynolds numbers below Re = 20 and at the Rayleigh number based on the amplitude of the periodic heating and the channel half width Rap = 3500, to realize the super-thermohydrophobic effect leading to a significant drag reduction (Floryan, 2012). The periodic heating is applied at the lower wall while the temperature of the upper wall is uniform and controlled. The results show that steady separation bubbles are created by periodic heating, which separate the main stream from the wall and, thus, the net friction drag is reduced. It is also found that the separation bubbles are strengthened when the average temperature of the lower wall exceeds that of the upper wall. Comparisons between the experiments and the theoretical results are presented.

  16. Nonlinear thermal lens signal of the (Δυ = 6) C-H vibrational overtone of C6H6 in liquid solutions of n-C6H14 and CCl4

    NASA Astrophysics Data System (ADS)

    Nyaupane, Parashu R.; Diez-y-Riega, Helena; Camejo, David; Manzanares, Carlos E.

    2016-05-01

    The thermal lens technique is applied to vibrational overtone spectroscopy of solutions of benzene. The pump and probe thermal lens technique has been found to be very sensitive for detecting samples of low concentration in transparent solvents. The C-H fifth vibrational (Δ υ = 6) overtone spectrum of benzene is detected at room temperature for compositions per volume in the range (1 to 1 × 10-4) using CCl4 and n-C6H14 as solvents. By detecting the absorption band in a 100-ppm solution, the peak absorption of the signal is approximately (2.2 ± 0.3) × 10-7 cm-1. The parameters that determine the magnitude of the thermal lens signal such as the pump laser power and the thermodynamic properties of the solvent and solute are discussed. A plot of normalized integrated intensity as a function of composition of benzene in solution reveals a nonlinear behavior. The nonlinearity cannot be explained assuming solvent enhancement at low concentrations. A two-color absorption model that includes the simultaneous absorption of the pump and probe lasers explains the enhanced magnitude and the nonlinear behavior of the thermal lens signal for solutions of composition below 0.01.

  17. Treatment with an orthopedic appliance system in relation to treatment intensity and growth periods. A study of initial effects.

    PubMed

    Malmgren, O; Omblus, J; Hägg, U; Pancherz, H

    1987-02-01

    The study comprises an analysis of the effect of treatment with a modified activator combined with a high-pull headgear during a standardized observation period of the initial 6 months of treatment. All patients (24 girls and 32 boys, aged 8.5 to 15 years) had severe skeletal Class II malocclusion. In the first part of the study, the effect of treatment with the appliance both day and night is compared with the effect when it was worn only at night. Only a small and nonsignificant difference was found, but the patients tended to cooperate better if they were instructed to wear the appliance continuously. In the second part of the study, the effect of treatment is related to the somatic maturation of the patients. Longitudinal records of standing height were used to assess whether treatment had been performed before maximal pubertal growth (prepeak period), during maximal pubertal growth (peak period), or after maximal pubertal growth (postpeak period). The skeletal effect was significantly greater in boys treated during the peak period than in those treated during the prepeak period and a similar tendency, although not significant, was found among girls. The number of patients treated during the postpeak period was too small for statistical analysis.

  18. Trends in scientific activity addressing transmissible spongiform encephalopathies: a bibliometric study covering the period 1973–2002

    PubMed Central

    Sanz-Casado, Elías; Ramírez-de Santa Pau, Margarita; Suárez-Balseiro, Carlos A; Iribarren-Maestro, Isabel; de Pedro-Cuesta, Jesús

    2006-01-01

    Background The purpose of this study is to analyse the trends in scientific research on transmissible spongiform encephalopathies by applying bibliometric tools to the scientific literature published between 1973 and 2002. Methods The data for the study were obtained from Medline database, in order to determine the volume of scientific output in the above period, the countries involved, the type of document and the trends in the subject matters addressed. The period 1973–2002 was divided in three sub-periods. Results We observed a significant growth in scientific production. The percentage of increase is 871.7 from 1973 to 2002. This is more evident since 1991 and particularly in the 1996–2001 period. The countries found to have the highest output were the United States, the United Kingdom, Japan, France and Germany. The evolution in the subject matters was almost constant in the three sub-periods in which the study was divided. In the first and second sub-periods, the subject matters of greatest interest were more general, i.e Nervous system or Nervous system diseases, Creutzfeldt-Jakob disease, Scrapie, and Chemicals and Drugs, but in the last sub-period, some changes were observed because the Prion-related matters had the greatest presence. Collaboration among authors is small from 1973 to 1992, but increases notably in the third sub-period, and also the number of authors and clusters formed. Some of the authors, like Gajdusek or Prusiner, appear in the whole period. Conclusion The study reveals a very high increase in scientific production. It is related also with the beginnings of research on bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease, with the establishment of progressive collaboration relationships and a reflection of public health concerns about this problem. PMID:17026743

  19. Predicting the Timeline to the Final Menstrual Period: The Study of Women's Health Across the Nation

    PubMed Central

    Ishii, Shinya; Huang, Mei-Hua; Karlamangla, Arun S.

    2013-01-01

    Context: Predicting the final menstrual period (FMP) would help women know when their menopause transition will be completed. Additionally, biological changes, such as accelerated bone loss, precede the FMP by at least 1 year. Objective: Our objective was to assess whether FSH, estradiol, or urinary N-telopeptide predict where an individual is on her timeline to FMP. Methods: The sample was 554 women from the Study of Women's Health Across the Nation. We modeled the probability of having crossed specified landmarks: 2 years before, 1 year before, and the FMP. We also modeled the probability of being in narrower intervals: 2 to1 year before FMP, 2 years before FMP and FMP, or 1 year before FMP and FMP. We determined the candidate markers that best predicted having crossed each landmark, with the optimum defined as the greatest area under the receiver-operator curve; created formulas for the probability of having crossed each landmark; and calculated sensitivity and specificity. Results: Final models included current estradiol and FSH (each as a fraction of 1 previous reference measure), age, menopause transition stage, race/ethnicity, and whether serum was collected during the early follicular phase. Areas under the receiver-operator curves of final models that predicted the probability of a woman having crossed 2 years before, 1 year before, and the FMP itself were 0.902, 0.926, and 0.945, respectively. If we classified women as having crossed the 2 years before the FMP landmark when predicted probability exceeded 0.3, sensitivity was 85% and specificity 77%. Conclusion: This model could help patients and researchers estimate the time to FMP. PMID:23533245

  20. Dimetallaborane analogues of the octaboranes of the type Cp2M2B6H10: structural variations with changes in the skeletal electron count.

    PubMed

    Brânzanic, Adrian M V; Lupan, Alexandru; King, R Bruce

    2016-05-31

    The structures and energetics of the complete series of hydrogen-rich dimetallaboranes Cp2M2B6H10 and Cp*2M2B6H10 (Cp = η(5)-C5H5; Cp* = η(5)-Me5C5; M = Pd, Pt; Rh, Ir; Ru, Os; Re; Mo, W; Ta), including the experimentally known Cp*2Rh2B6H10 and Cp*2W2B6H10 (Cp* = η(5)-Me5C5), have been investigated by density functional theory. The lowest energy structures of the hyperelectronic Cp2M2B6H10 (M = Pd, Pt; Rh, Ir) systems have central M2B6 frameworks with a hexagonal open face similar to the B8 networks in arachno-B8H14 and nido-B8H12. The two lowest energy structures for Cp2Rh2B6H10 and Cp*2Rh2B6H10, lying within 1 kcal mol(-1) of energy, differ only in the locations of the bridging hydrogen atoms around the hexagonal hole consistent with the experimentally observed fluxionality of the hydrogen atoms in Cp*2Rh2B6H10. Most of the lowest energy Cp2M2B6H10 (M = Ru, Os) structures also have a central M2B6 framework similar to B8H12, typically with such additional features as an additional metal-metal bond or a formal metal-metal double bond. A common motif for the low-energy structures of the hypoelectronic Cp2M2B6H10 (M = Re; Mo, W; Ta) systems, including the experimentally known Cp*2W2B6H10, is a central M2B4 octahedron with its two M2B faces capped by the remaining boron atoms and with four M-B edges bridged by hydrogen atoms. Such structures can also be considered as oblatonido structures derived from the experimentally known 9-vertex oblatocloso Cp*2Re2B7H7 structure by removal of the unique degree 4 vertex atom. PMID:27186632

  1. Vibrational spectra of Cs2Cu(SO4)2·6H2O and Cs2Cu(SeO4)2·nH2O (n = 4, 6) with a crystal structure determination of the Tutton salt Cs2Cu(SeO4)2·6H2O

    NASA Astrophysics Data System (ADS)

    Wildner, M.; Marinova, D.; Stoilova, D.

    2016-02-01

    The solubility in the three-component systems Cs2SO4-CuSO4-H2O and Cs2SeO4-CuSeO4-H2O have been studied at 25 °C. The experimental results show that double salts, Cs2Cu(SO4)2·6H2O and Cs2Cu(SeO4)2·4H2O, crystallize from the ternary solutions within large concentration ranges. Crystals of Cs2Cu(SeO4)2·6H2O were synthesized at somewhat lower temperatures (7-8 °C). The thermal dehydration of the title compounds was studied by TG, DTA and DSC methods and the respective dehydration schemes are proposed. The calculated enthalpies of dehydration (ΔHdeh) have values of: 434.2 kJ mol-1 (Cs2Cu(SeO4)2·6H2O), 280.9 kJ mol-1 (Cs2Cu(SeO4)2·4H2O), and 420.2 kJ mol-1 (the phase transition of Cs2Cu(SO4)2·6H2O into Cs2Cu(SO4)2·H2O). The crystal structure of Cs2Cu(SeO4)2ṡ6H2O was determined from single crystal X-ray diffraction data. It belongs to the group of Tutton salts, crystallizing isotypic to the respective sulfate in a monoclinic structure which is characterized by isolated Cu(H2O)6 octahedra and SeO4 tetrahedra, interlinked by hydrogen bonds and [9]-coordinated Cs+ cations. Infrared spectra of the cesium copper compounds are presented and discussed with respect to both the normal modes of the tetrahedral ions and the water molecules. The analysis of the infrared spectra of the double compounds reveals that the distortion of the selenate tetrahedra in Cs2Cu(SeO4)2·4H2O is stronger than those in Cs2Cu(SeO4)2·6H2O in agreement with the structural data. Matrix-infrared spectroscopy was applied to confirm this claim - Δν3 for SO4 2 - ions matrix-isolated in Cs2Cu(SeO4)2·6H2O has a value of 35 cm-1 and that of the same ions included in Cs2Cu(SeO4)2·4H2O - 84 cm-1. This spectroscopic finding is due to the formation of strong covalent bands Cu-OSO3 on one hand, and on the other to the stronger deformation of the host SeO4 2 - tetrahedra in Cs2Cu(SeO4)2·4H2O as compared to those in Cs2Cu(SeO4)2·6H2O. The strength of the hydrogen bonds as deduced from the

  2. Study of plasmonic crystal to metamaterial transition in dielectric doped two-dimensional periodic structures

    NASA Astrophysics Data System (ADS)

    Gourshetty, Shivkumar; Regan, Charles; Grave de Peralta, Luis; Bernussi, Ayrton

    2012-10-01

    We investigated experimentally the transition from plasmonic crystal to metamaterial in dielectric-loaded plasmonic two-dimensional periodic structures with different lattice periods and lattice symmetries. The transition occurs due to changes in the effective refractive index of the plasmonic crystals when the period and/or the size of the patterned features are varied. The effective refractive index of the plasmonic structure can be further modified when an object (i.e. a virus, a bead, a cell, etc.) is placed on the top of the sample, thus altering the transition. This can be prospectively used for nanosensing applications. The samples investigated here were fabricated using a combination of electron-beam lithography and liftoff techniques and consisted of a glass substrate, a thin film of gold, and periodic arrays of air holes defined on PMMA doped with Rhodamine 6G. The plasmonic crystal to a metamaterial transition region was investigated using the leakage radiation microscopy technique. We determined that the transition occurs for lattice periods 262 nm and 310 nm for samples with square and hexagonal lattice symmetries, respectively.

  3. The occurrence of period IV elements in dinoflagellate chromatin: an X-ray microanalytical study.

    PubMed

    Kearns, L P; Sigee, D C

    1980-12-01

    X-ray microanalysis of unfixed frozen-dried cryosections, and of unfixed cryosections collected by a sucrose drop technique, revealed the presence of Ca, Mn, Fe, Ni, Cu and Zn (Period IV, Periodic Table) in association with the permanently condensed chromosomes of Prorocentrum micans. All of these metals, with the exception of Mn, routinely occurred in the chromatin of cells that had been fixed in glutaraldehyde, ethanol-dehydrated, and resin-embedded. Their detection at high levels in chemically dehydrated chromatin of Prorocentrum micans, and 3 other dinoflagellate species cultured in the laboratory, suggests they are important as bound (insoluble) components of the chromatin. Detailed analysis of the fixed, ethanol-dehydrated material showed that for these particular cultures, each species had its own characteristic mass fraction pattern of chromatin-bound elements which differed markedly from that of the other species. Calculation of relative numbers of atoms from the mass fraction showed that for each species about 40-50 atoms of bound Period IV elements were present per 100 atoms of phosphorus. This is approximately equivalent to one Period IV atom per 2 DNA nucleotides or per base pair. Although considerable variation exists between species in terms of individual element levels, the total number of atoms of Period IV elements relative to phosphorus is remarkably constant. PMID:7194876

  4. Case studies of quasi-periodic VLF emissions and related ULF fluctuations of the magnetic field

    NASA Astrophysics Data System (ADS)

    Hayosh, M.; Santolik, O.; Nemec, F.; Parrot, M.

    2014-12-01

    Quasi-periodic (QP) VLF emissions are observed in the inner magnetosphere mostly on the day-side. These waves exhibit a periodic time modulation of the wave intensity that is possibly a result of the whistler-mode wave growth being periodically modulated by compressional ULF magnetic field pulsations. We have analyzed 50 QP events measured by the DEMETER satellite at altitudes of about 700 km to verify their generation mechanism. The analyzed events have a modulation period between 15 s and 80 s, and they were observed during quiet geomagnetic conditions (Kp<3). Magnetometers of the CARISMA system were used for monitoring the ULF magnetic field pulsations in a wide spatial range. We have found that ULF magnetic field pulsations in the Pc3 - Pc5 range are well correlated with the occurrence of the QP emissions with modulation periods between about 40 and 80 s. At the same time, increased fluxes of high-energy electrons (E > 30 keV) were observed by DEMETER and by the NOAA-17 satellite. We analyze possible links between these electrons, QP emissions, and ULF magnetic field pulsations.

  5. A comparative study of zone axis pattern maps from decagonal phases with varying periodicity

    SciTech Connect

    Ranganathan, S. . Dept of Materials Science and Metallurgy Indian Inst. of Science, Bangalore . Dept. of Metallurgy); Singh, A. . Dept. of Metallurgy); Mukhopadhyay, N.K.; Weatherly, G.C. . Dept. of Metallurgy)

    1994-02-01

    The discovery in 1985 of the decagonal phase with periodicity in one direction and quasiperiodicity in the other two directions has excited considerable interest. This was followed by the observation that the periodicity perpendicular to the quasiperiodicity plane can assume multiple values on n = [1,2,3,4]x0.4 nm. The mapping of reciprocal spaces of these phases, labelled t[sub 2n], by electron diffraction is important in the context of atomic models for the decagonal phase. While partial determinations have been available for T[sub 4] context of atomic models for the decagonal phase. While partial determinations have been available for T[sub 4] [Al-Co], T[sub 6][Al-Mn] and T[sub 8] [Al-Fe], [Al-Pd], the recent complete determination of zone axis pattern maps [ZAPM] and Kikuchi maps of T[sub 6] [Al-Mn] with 1.24 nm periodicity and T[sub 4][Al-Cu-Co-Si] with 0.8 nm periodicity is a tour de force by Kelton and his co-workers. These papers coupled with the complete mapping of the HOLZ line and Kikuchi line patterns of the T[sub 2][Al-Co-Ni] with 0.4 nm periodicity permit the authors to put in perspective the ZAPM of all the four decagonal phases and in addition predict patterns for the T[sub 8] phase for which a complete experimental determination is still lacking.

  6. Study of multi-periodic coronal pulsations during an X-class solar flare

    NASA Astrophysics Data System (ADS)

    Chowdhury, Partha; Srivastava, A. K.; Dwivedi, B. N.; Sych, Robert; Moon, Y.-J.

    2015-12-01

    We investigate quasi-periodic coronal pulsations during the decay phase of an X 3.2 class flare on 14 May 2013, using soft X-ray data from the RHESSI satellite. Periodogram analyses of soft X-ray light curves show that ∼ 53 s and ∼ 72 s periods co-exist in the 3-6 keV, 6-12 keV and 12-25 keV energy bands. Considering the typical length of the flaring loop system and observed periodicities, we find that they are associated with multiple (first two harmonics) of fast magnetoacoustic sausage waves. The phase relationship of soft X-ray emissions in different energy bands using cross-correlation technique show that these modes are standing in nature as we do not find the phase lag. Considering the period ratio, we diagnose the local plasma conditions of the flaring region by invoking MHD seismology. The period ratio P1/2P2 is found to be ∼ 0.65, which indicates that such oscillations are most likely excited in longitudinal density stratified loops.

  7. Fe-implanted 6H-SiC: Direct evidence of Fe{sub 3}Si nanoparticles observed by atom probe tomography and {sup 57}Fe Mössbauer spectroscopy

    SciTech Connect

    Diallo, M. L.; Fnidiki, A. Lardé, R.; Cuvilly, F.; Blum, I.; Lechevallier, L.; Debelle, A.; Thomé, L.; Viret, M.; Marteau, M.; Eyidi, D.; Declémy, A.

    2015-05-14

    In order to understand ferromagnetic ordering in SiC-based diluted magnetic semiconductors, Fe-implanted 6H-SiC subsequently annealed was studied by Atom Probe Tomography, {sup 57}Fe Mössbauer spectroscopy and SQUID magnetometry. Thanks to its 3D imaging capabilities at the atomic scale, Atom Probe Tomography appears as the most suitable technique to investigate the Fe distribution in the 6H-SiC host semiconductor and to evidence secondary phases. This study definitely evidences the formation of Fe{sub 3}Si nano-sized clusters after annealing. These clusters are unambiguously responsible for the main part of the magnetic properties observed in the annealed samples.

  8. Orbital period variation study of massive Beta-Lyrae eclipsing binary IU Auriga

    NASA Astrophysics Data System (ADS)

    Yilan, Erkan; Bulut, İbrahim

    2016-07-01

    The system IU Aur is a semi-detached close binary system with an orbital period of 1.81 days, containing a massive star. The O-C diagram of this binary was analyzed with the least-squares method by using all available times of minima. We have found a periodic change of orbital period of IU Aur. This change has been explained by the gravitational effects of a third companion on the binay star. The orbit Parameters of the third body have been derived from the analysis of the O-C curve. The analysis indicates that the eclipsing binary revolves around a third-body with a mass of about M_{3}>10M_{⊙} in a highly eccentric orbit.

  9. A study on periodic solutions for the circular restricted three-body problem

    SciTech Connect

    Gao, F. B.; Zhang, W. E-mail: gaofabao@gmail.com

    2014-12-01

    For the circular restricted three-body problem (CR3BP) in the inertial frame, we interpret the fact that there is no non-trivial 2π-periodic solution of the problem's homogeneous system. Furthermore, based on Reissig's theory, the existence of periodic solutions for the CR3BP is proved rigorously by using the above fact in conjunction with an a priori estimate. It is significant that the existence of periodic solutions of the CR3BP is mainly influenced by factors such as initial values, primary masses, and selection of the problem's control function. In addition, it is notable that the analytic proof of Poincaré's first class solutions is addressed for all values of the mass parameter in the interval (0, 1), the value of which must be sufficiently small according to previously published literature.

  10. It's T time: A study on the return period of multivariate problems

    NASA Astrophysics Data System (ADS)

    Michailidi, Eleni Maria; Balistrocchi, Matteo; Bacchi, Baldassare

    2016-04-01

    One of the most important tasks a hydrologist must face is the proper estimation of the 'design values' of a natural variable corresponding to a given Return Period, T, of failures of the hydraulic 'structure' to be designed or verified. Sometimes the 'structure' is simply the embankments, the failure of which corresponds to the outflows of flood runoff on the surrounding land. The widely adopted definition of T, in a problem regarding the maxima of hydrological variables, is "the average time elapsing between two successive occurrences of an event exceeding a certain magnitude of the natural variables". If T is referred to the minima, the symmetric definition pertains to the "average time between two periods during which the variable ranges below a given magnitude". Conventional (and the only accepted) approaches for estimation of T involve a single natural variable (i.e. flood-peak of a river at a given cross section, the daily maximum discharge, the maximum daily rainfall depth observed at a given rain-gauge). The method of estimation of T entails a frequency analysis of the variable of interest, where the design value of a given T is needed to design the structure of interest (e.g. dams, sewers). In other words, T is used as the index value to set the assigned risk level for the hydraulic works. However, a univariate approach in complex problems ignores the effect of significant variables interrelation leading to different risk levels for each quantity of interest and resulting in a completely wrong estimate of the risk. For example, if one considers the flood inflow in a lake around which cities and villages are positioned, the variable to be investigated in relation to the risk assessment is the lake water level. It is obvious that the same water level may occur from very different flood hydrographs, even when the same initial water level and the same rate curve of outflows are considered. This is a consequence of the interaction of at least three joint

  11. Experimental Study of Tip Vortex Flow from a Periodically Pitched Airfoil Section

    NASA Technical Reports Server (NTRS)

    Zaman, Khairul; Fagan, Amy; Mankbadi, Mina

    2016-01-01

    An experimental investigation of tip vortex flow from a NACA0012 airfoil, pitched periodically at various frequencies, is conducted in a low-speed wind tunnel. Initially, data for stationary airfoil held fixed at various angles-of-attack are gathered. Flow visualization pictures as well as detailed cross-sectional properties areobtained at various streamwise locations using hot-wire anemometry. Data include mean velocity, streamwise vorticity as well as various turbulent stresses. Preliminary data are also acquired for periodically pitched airfoil. These results are briefly presented in this extended abstract.

  12. Detecting Periodic Genes from Irregularly Sampled Gene Expressions: A Comparison Study

    PubMed Central

    2008-01-01

    Time series microarray measurements of gene expressions have been exploited to discover genes involved in cell cycles. Due to experimental constraints, most microarray observations are obtained through irregular sampling. In this paper three popular spectral analysis schemes, namely, Lomb-Scargle, Capon and missing-data amplitude and phase estimation (MAPES), are compared in terms of their ability and efficiency to recover periodically expressed genes. Based on in silico experiments for microarray measurements of Saccharomyces cerevisiae, Lomb-Scargle is found to be the most efficacious scheme. 149 genes are then identified to be periodically expressed in the Drosophila melanogaster data set. PMID:18584052

  13. Behavioral study of ultradian activity periods of mice enclosed in experimental cages of different dimensions

    NASA Technical Reports Server (NTRS)

    Guillot, A.

    1982-01-01

    Male mice are enclosed in cages of different dimensions (cage A - 23x8x8 cm., cage B - 36x27x17 cm.), in an alternating light/dark regimen, at an ambient temperature of 22 to 23 C. The successions of the behavioral sequences of ultradian activity periods are noticed by direct observation during 11 consecutive hours in light. The experimental situation modifies the mean duration time and the behavioral organization of each activity period. However, the comparison of the overall activity time lengths and the comparison of the overall behavioral frequencies suggest that the energy spent per mouse is constant.

  14. The Abundance of C6H6 and HC3N over Titan's South Pole as winter approaches

    NASA Astrophysics Data System (ADS)

    Bjoraker, Gordon; Cottini, Valeria; Achterberg, Richard; Coustenis, Athena

    2016-06-01

    Benzene and cyanoacetylene have increased dramatically near Titan's South Pole since 2011. First detected near the South Pole in limb measurements, CIRS can now see strong emission lines of these species in nadir observations. This is remarkable because at the same time stratospheric temperatures at the 1-mbar level (185 km) at 70°S have dropped more than 30K in the past 5 years. CIRS obtained measurements of emission from these molecules as a function of latitude during the T104 flyby on 2014 August 20. These data show the strongest emission at 83°S, falling off rapidly towards 70°S. Recently, during T117 on 2016 February 16, CIRS obtained limb spectra at 80°S. These observations show peak emission for C6H6 between 200 and 250 km, while HC3N peaks between 250 and 300 km (0.25 to 0.1 mbars) where the stratospheric temperature is near 160 K. These molecules are tracers of meridional transport in Titan's stratosphere and their confinement near the South Pole is reminiscent of the Antarctic ozone hole on Earth.

  15. SEMICONDUCTOR DEVICES: Simulation and optimization of a 6H-SiC metal-semiconductor-metal ultraviolet photodetector

    NASA Astrophysics Data System (ADS)

    Bin, Chen; Yintang, Yang; Yuejin, Li; Hongxia, Liu

    2010-06-01

    Based on thermionic emission theory, a model of a 6H-SiC metal-semiconductor-metal (MSM) ultraviolet photodetector is established with the simulation package ISE-TCAD. A device with 3 μm electrode width (W) and 3 μm electrode spacing (L) is simulated. The findings show that the MSM photodetector has quite a low dark current of 15 pA at 10 V bias and the photocurrent is two orders of magnitude higher than the dark current. The influences of different structures on dark and illuminated current-voltage characteristics of the MSM photodetector are investigated to optimize the device parameters. Simulation results indicate that the maximum photocurrent and the highest ratio of photocurrent to dark current at 15 V bias are 5.3 nA and 327 with device parameters of W = 6 μm, L = 3 μm and W = 3 μm, L = 6 μm, respectively.

  16. Surface reconstruction and graphene formation on face-to-face 6H-SiC at 2000 ^oC

    NASA Astrophysics Data System (ADS)

    Elmquist, Randolph E.; Real, Mariano; Bush, Brian G.; Shen, Tian; Stiles, Mark D.; Lass, Eric A.

    2012-02-01

    Improved epitaxial graphene films have been widely reported when the sublimation rate of Si is reduced by ambient Ar gas, vapor phase silane, or confined Si vapor. We describe graphene growth on (0001) 6H-SiC samples annealed ``face-to-face'' [1]; in our modified method the separation is limited only by the flatness of the surfaces. After annealing in 100 kPa Ar gas at 2000 ^oC for 300 s, atomic force microscopy (AFM) and electrostatic force microscopy (EFM) show graphene coverage is typically between one and a few layers. Samples without prior hydrogen etching undergo surface reconstruction in the graphitization process, resulting in atomically flat terraces with step bunching. Estimates of the sequestered carbon in the form of graphene are compared to calculated levels due to sublimation and diffusion rates where the sublimated gas is dominated by Si atoms below 2100 ^oC. The 2000 ^oC samples are contrasted against samples processed between 1700 ^oC and 1900 ^oC and transport results on large-scale graphene devices are presented.[4pt] [1] X.Z Yu, C.G. Hwang, C.M. Jozwiak, A. Kohl, A.K. Schmid and A. Lanzara, New synthesis method for the growth of epitaxial graphene, Journal of Electron Spectroscopy and Related Phenomena 184 (2011) 100-106.

  17. Structural and surface topography analysis of AlN single crystals grown on 6H-SiC substrates

    NASA Astrophysics Data System (ADS)

    Sumathi, R. R.; Barz, R. U.; Straubinger, T.; Gille, P.

    2012-12-01

    Bulk AlN single crystals (3 mm thick and 1 in. diameter) were hetero-epitaxially grown on (0001) 6H-SiC substrates by the sublimation method. Double-crystal x-ray diffraction and micro-Raman results confirm the good crystallinity as well as structural homogeneity of the grown crystals. The presence of low-angle grain boundaries was observed by x-ray diffraction rocking curve analysis and also supported by defect-selective etching analysis. The estimated defect density of the 3 mm thick crystals is about (5-8)×105 cm-2. 3D-microstructures with different morphology were observed on the as-grown crystal surfaces and were interpreted to be originated from screw dislocations. These screw dislocations are decorated by carbon impurities as evidenced by micro-Raman spectroscopic measurements. SiC incorporation in the grown crystals was found to be fairly low with 4 mol% at 2 mm distance from the interface and varies slightly between different sub-grains.

  18. Characterization and physical modeling of MOS capacitors in epitaxial graphene monolayers and bilayers on 6H-SiC

    NASA Astrophysics Data System (ADS)

    Winters, M.; Sveinbjörnsson, E. Ö.; Melios, C.; Kazakova, O.; Strupiński, W.; Rorsman, N.

    2016-08-01

    Capacitance voltage (CV) measurements are performed on planar MOS capacitors with an Al2O3 dielectric fabricated in hydrogen intercalated monolayer and bilayer graphene grown on 6H-SiC as a function of frequency and temperature. Quantitative models of the CV data are presented in conjunction with the measurements in order to facilitate a physical understanding of graphene MOS systems. An interface state density of order 2 ṡ 1012 eV-1 cm-2 is found in both material systems. Surface potential fluctuations of order 80-90meV are also assessed in the context of measured data. In bilayer material, a narrow bandgap of 260meV is observed consequent to the spontaneous polarization in the substrate. Supporting measurements of material anisotropy and temperature dependent hysteresis are also presented in the context of the CV data and provide valuable insight into measured and modeled data. The methods outlined in this work should be applicable to most graphene MOS systems.

  19. Coupled antiferromagnetic spin- 12 chains in green dioptase Cu6[Si6O18]·6H2O

    DOE PAGES

    Podlesnyak, Andrey A; Larry M. Anovitz; Kolesnikov, Alexander I; Matsuda, Masaaki; Prisk, Timothy R; Toth, Sandor; Ehlers, Georg

    2016-02-01

    Inmore » this paper, we report inelastic neutron scattering measurements of the magnetic excitations of green dioptase Cu6[Si6O18]∙6H2O. The observed spectrum contains two magnetic modes and a prominent spin gap that is consistent with the ordered ground state of Cu moments coupled antiferromagnetically in spiral chains along the c axis and ferromagnetically in ab planes on the hexagonal cell. The data are in excellent agreement with a spin- 12Hamiltonian that includes antiferromagnetic nearest-neighbor intrachain coupling Jc=10.6(1) meV, ferromagnetic interchain coupling Jab=₋1.2 (1) meV, and exchange anisotropy ΔJc=0.14(1) meV. We calculated the sublattice magnetization to be strongly reduced, ~0.39μB. This appears compatible with a reduced Néel temperature, TN=14.5K

  20. Polarised IR and Raman spectra of non-centrosymmetric Na3Li(SeO4)2.6H2O crystal--a new Raman laser material.

    PubMed

    Hanuza, J; Maczka, M; Lorenc, J; Kaminskii, A A; Bohaty, L; Becker, P

    2008-11-01

    Polarised IR and Raman spectra of Na3Li(SeO4)2.6H2O single crystal have been recorded. Discussion of the results has been based on the factor group approach for the trigonal R3c (C3v6) space group with Z = 2. The obtained results for the spontaneous Raman scattering have been used in the discussion of the stimulated Raman spectra of the material studied--a new Raman laser crystal.

  1. Effect of pressure on the interlayer transport and the electronic structure in the organic quasi-two-dimensional bilayer metal θ-(BETS)4HgBr4(C6H5Cl)

    NASA Astrophysics Data System (ADS)

    Lyubovskii, R. B.; Pesotskii, S. I.; Zhilyaeva, E. I.; Lyubovskaya, R. N.

    2016-01-01

    The behavior of the interlayer resistance and the magnetoresistance in the organic quasi-twodimensional bilayer metal θ-(BETS)4HgBr4(C6H5Cl) is studied at normal pressure and a hydrostatic pressure of 10 kbar. The interlayer transport under atmospheric pressure is found to occur in an incoherent mode. The applied pressure does not change the electronic structure of the conducting layers and causes a transition to a weakly coherent mode at low temperatures.

  2. Connecting modes of linking ligands containing different terminal groups (pyridyl-amine or pyridyl-pyridyl): Preparation and structures of {[Cd( L1) 2(OH 2) 2]·(ClO 4) 2·(C 6H 6)} ∞, {[Cd( L2) 2(ClO 4) 2]·(CH 3OH) 2} ∞, {[Cd( L3) 2(OH 2) 2]·(ClO 4) 2} ∞, and [Cd( L4) 2(CH 3OH) 2(ClO 4) 2] {( m-py)-CH dbnd N-(CH 3)C 6H 3-C 6H 3(CH 3)-NH 2 ( m = 3 ( L1) or 4 ( L2)); ( n-py)-CH dbnd N-(CH 3)C 6H 3-C 6H 3(CH 3)-N dbnd CH-( n-py); ( n = 3 ( L3) or 4 ( L4))}

    NASA Astrophysics Data System (ADS)

    Yun, Sung Yol; Lee, Kyung-Eun; Lee, Soon W.

    2009-10-01

    We prepared four potential linking ligands, [(3-py)-CH dbnd N-(CH 3)C 6H 3-C 6H 3(CH 3)-NH 2, L1], [(4-py)-CH dbnd N-(CH 3)C 6H 3-C 6H 3(CH 3)-NH 2, L2], [(3-py)-CH dbnd N-(CH 3)C 6H 3-C 6H 3(CH 3)-N dbnd CH-(3-py), L3], and [(4-py)-CH dbnd N-(CH 3)C 6H 3-C 6H 3(CH 3)-N dbnd CH-(4-py), L4], all of which contain an intervening biphenyl fragment. Whereas ligands L1 and L2 have two types of terminal groups (pyridyl-amine), ligands L3 and L4 have a single type of terminal groups (pyridyl-pyridyl). Ligands L1- L4 reacted with cadmium nitrate to produce {[Cd( L1) 2(OH 2) 2]·(ClO 4) 2·(C 6H 6)} ∞ ( 1), {[Cd( L2) 2(ClO 4) 2]·(CH 3OH) 2} ∞ ( 2), {[Cd( L3) 2(OH 2) 2]·(ClO 4) 2} ∞ ( 3), and [Cd( L4) 2(CH 3OH) 2(ClO 4) 2] ( 4), respectively. Whereas compounds 1- 3 are 1-dimensional coordination polymers, compound 4 is a discrete molecular species.

  3. Study of Organic Thin Film Transistors on Ultraviolet-Curable Dielectrics with Periodic Patterns Fabricated by Nano Imprint Technology

    NASA Astrophysics Data System (ADS)

    Chen, Henry J. H.; Chen, Jun-Yu

    2013-06-01

    In this work, the organic thin film transistors (OTFTs) on UV-curable dielectrics with periodic patterns fabricated by nano imprint technology were investigated. The surface morphologies of pentacene and device performances with respect to line/space ratio of periodic patterns were studied. The anisotropic electrical characteristics of OTFTs were also investigated. This technique will be suitable for the future low-cost and flexible electronics applications.

  4. Reexamining the Critical Period Hypothesis: A Case Study of Successful Adult SLA in a Naturalistic Environment.

    ERIC Educational Resources Information Center

    Ioup, Elizabeth; And Others

    1994-01-01

    The nativelike linguistic competence of an adult second-language learner of Egyptian Arabic who was first exposed to the target language after the close of the critical period is examined to determine what factors differentiate her from less successful naturalistic adult acquirers. The role of internalized grammar is discussed. (Contains 43…

  5. A Case Study of Periodical Use by Library and Information Science Students

    ERIC Educational Resources Information Center

    Ivins, Tammy

    2013-01-01

    There is a lack of information in the literature about the sources used for research by modern Master of Library and Information Science students in the United States, and so the objective of this project is to understand the use of periodical articles by these students. Specifically: do articles play a major role in student research, how current…

  6. Period studies and photometric models for two EB-type binaries EU Hya and AW Vul

    NASA Astrophysics Data System (ADS)

    Yang, Yuan-Gui; Li, Qun; Li, Hua-Li; Dai, Hai-Feng

    2016-02-01

    New photometry for two Algol-type binaries, EU Hya (P = 0.7782 d) and AW Vul (P = 0.8065 d), was carried out using the 60-cm telescope at Xinglong station of National Astronomical Observatories, Chinese Academy of Sciences. With the updated Wilson-Devinney code, photometric elements were derived from the multi-color light curves. The modeled results indicate that the two systems are near-contact binaries, whose secondary components fill their Roche lobes. The fill-out factors of the primaries are fp = 81.2 (±0.2)% for EU Hya and fp = 82.4 (±0.3)% for AW Vul. Period analysis implies that there exists a downward parabola with a light-time orbit from the (O - C) curve. This kind of periodic oscillation may be attributed to the light-time orbit effect of a third companion. The long-term period decrease may be caused by mass and angular momentum loss. When the orbital period decreases, the fill-out factor of fp will increase. Our results indicate that the primaries will also eventually fill their Roche lobes. EU Hya and AW Vul may possibly evolve from semi-detached binaries into contact ones.

  7. Orbital Period Variation Study of the Algol Eclipsing Binary DI Pegasi

    NASA Astrophysics Data System (ADS)

    Hanna, M. A.; Amin, S. M.

    2013-08-01

    We discuss the orbital period changes of the Algol semi-detached eclipsing binary DI Peg by constructing the (O-C) residual diagram via using all the available precise minima times. We conclude that the period variation can be explained by a sine-like variation due to the presence of a third body orbiting the binary, together with a long-term orbital period increase ( dP/dt=0.17 sec/century) that can be interpreted to be due to mass transfer from the evolved secondary component (of rate 1.52×10^{-8} M_{⊙}/ yr) to the primary one. The detected low-mass third body (M_{3 min.}=0.22±0.0006 M_{⊙}) is responsible for a periodic variation of about 55 years light time effect. We have determined the orbital parameters of the third component which show a considerable eccentricity e_{3}= 0.77±0.07 together with a longitude of periastron ω_{3}=300° ± 10°.

  8. Spectral Methods for Detecting Periodicity in Library Circulation Data: A Case Study.

    ERIC Educational Resources Information Center

    Decroos, Francis; And Others

    1997-01-01

    Describes an investigation that was conducted to show the feasibility of spectral methods in information science, particularly for analyzing academic library circulation data. Signal analysis methods were used to detect periodicity, and spectral methods show promise for analyzing time series and other signals in information science. (Author/LRW)

  9. Period04 FCAPT uvby Photometric Studies of Eight Magnetic CP Stars

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.; Dukes, Robert J.

    2014-06-01

    We present Four College Automated Photometric Telescope (FCAPT) differential Stromgren uvby photometry of 8 magnetic CP (mCP) stars: HD 5797 (V551 Cas), HD 26792 (DH Cam), HD 27309 (56 Tau, V724 Tau), HD 49713 (V740 Mon), HD 74521 (49 Cnc, BI Cnc), HD 120198 (84 UMa, CR UMa), HD 171263 (QU Ser), and HD 215441 (GL Lac, Babcock's star). Our data sets are larger than those of most mCP stars in the literature. These are the first FCAPT observations of HD 5797, HD 26792, HD 49713, and HD 171263. Those for the remaining four stars substantially extend published FCAPT data. The FCAPT observed some stars for a longer time range and with greater accuracy than other optical region automated photometric telescopes.Our goals were to determine very accurate periods, the u, v, b, and y amplitudes, and if there were any long period periods. In addition we wanted to compare our results with those of magnetic field measurements to help interpret the light curves.We used the Period04 computer program to analyze the light curves. This program provides errors for the derived quantities as it fits the light curve. Our derived periods of 68.046 +/- 0.008 days for HD 5797, 3.80205 +/- 0.00006 days for HD 26792, 1.56889 +/- 0.000002 days for HD 27309, 2.13536 +/- 0.00002 days for HD 49713, 7.0505 +/- 0.0001 days for HD 74521, 1.38577 +/- 0.000004 days for HD 120198, 3.9974 +/- 0.0001days for HD 171263, and 9.487792 +/- 0.00005 days for HD 215441 are refinements of the best determinations in the literature.

  10. Human comfort studies in Debrecen regarding the 2006-2008 period

    NASA Astrophysics Data System (ADS)

    Gyarmati, R.; Toth, T.; Szegedi, S.; Kapocska, L.

    2010-09-01

    Human comfort studies in Debrecen regarding the 2006-2008 period Renata Gyarmati, Tamas Toth, Sandor Szegedi and Laszlo Kapocska University of Debrecen Department of Meteorology, 4032 Debrecen Egyetem tér 1. The significance of human meteorological studies, primarily the importance of observing the sensitivity to fronts has been verified by several foreign and native authors. However, this field of research has shown few exact scientific achievements so far, but the understanding of the connection between weather and human comfort could be promotive factor of human health preservation. This project is quite current since a great part of so called ‘healthy people', who are not suffered from constant diseases are sorely tried by the changing weather. Frequent occurrence of extreme meteorological events will increase the number of meteoropathies in the near future. The whole living world is sensitive to changes in temperature, pressure, humidity and wind speed caused by meteorological events. Frequent fluctuations cause a great trial to pregnant women. The presence of the contact between weather and obstetrical events, formerly proved by Raics (1972), Nowinszky-Nowinszky (1996-1997), Puskás (2008) is supported by our examined data from the University of Debrecen Medical School and Health Science Centre Department of Obstetrics and Gynaecology. During our observation we scrutinized the relation between frontal passage macrosynoptic types and birth number. It's evident that higher data of birth number can be observed during on-coming weather fronts. In case of resident warm fronts, contrast with free-from-front days increasing values can't be experienced although an increase can be observed at the other front types. In the mentioned term over the change of pressure a significant change in temperature probably produced an effect on start of labours. This is in harmony with macrosynoptic types applied to the Carpathian basin. According to this, higher birth number was

  11. Design, synthesis and biological evaluation of novel 6H-benzo[c]chromen-6-one, and 7,8,9,10-tetrahydro-benzo[c]chromen-6-one derivatives as potential cholinesterase inhibitors.

    PubMed

    Gulcan, Hayrettin Ozan; Unlu, Serdar; Esiringu, Ilker; Ercetin, Tugba; Sahin, Yasemin; Oz, Demet; Sahin, Mustafa Fethi

    2014-10-01

    Hydroxylated 6H-benzo[c]chromen-6-one derivatives (i.e., urolithins) are the main bioavailable metabolites, and biomarkers of ellagitannins present in various nutrition. Although these dietaries, the sources of urolithins, are employed in folk medicine as cognitive enhancer in the treatment of Alzheimer's Disease, urolithins have negligible potential to inhibit acetylcholinesterase and butyrylcholinesterase enzymes, the validated targets of Alzheimer's Disease. Therefore, within this research, a series of 6H-benzo[c]chromen-6-one, and 7,8,9,10-tetrahydro-benzo[c]chromen-6-one derivatives has been designed, synthesized, and their biological activities were evaluated as potential acetylcholinesterase and butyrylcholinesterase inhibitors. The compounds synthesized exerted comparable activity in comparison to rivastigmine, galantamine, and donepezil both in in vitro and in vivo studies.

  12. Photophysical properties of ESIPT inspired fluorescent 2-(2-hydroxyphenyl)-6-methylimidazo[4,5-f]isoindole-5,7(1H,6H)-dione and its derivative: Experimental and DFT based approach

    NASA Astrophysics Data System (ADS)

    Deshmukh, Mininath S.; Sekar, Nagaiyan

    2015-01-01

    The excited-state intramolecular proton transfer chromophores 2-(2-hydroxyphenyl)-6-methylimidazo[4,5-f]isoindole-5,7(1H,6H)-dione and 2-(4-(diethylamino)-2-hydroxyphenyl)-6-methylimidazo[4,5-f]isoindole-5,7(1H,6H)-dione are synthesized from 4,5-diamino-N-methylphthalimide. The photophysical behavior of the synthesized chromophores was studied using UV-visible and fluorescence spectroscopy in the polar and non-polar solvents. The synthesized o-hydroxyphenyl benzimidazole derivatives are fluorescent and very sensitive to the solvent polarity. These dyes are thermally stable up to 317 °C. Density Functional Theory computations have been used to understand the structural, molecular, electronic and photophysical properties of the chromophores. The experimental absorption and emission wavelengths are in good agreement with the computed vertical excitation and theoretical emission obtained by Density Functional Theory and Time Dependant Density Functional Theory.

  13. Design, synthesis and biological evaluation of novel 6H-benzo[c]chromen-6-one, and 7,8,9,10-tetrahydro-benzo[c]chromen-6-one derivatives as potential cholinesterase inhibitors.

    PubMed

    Gulcan, Hayrettin Ozan; Unlu, Serdar; Esiringu, Ilker; Ercetin, Tugba; Sahin, Yasemin; Oz, Demet; Sahin, Mustafa Fethi

    2014-10-01

    Hydroxylated 6H-benzo[c]chromen-6-one derivatives (i.e., urolithins) are the main bioavailable metabolites, and biomarkers of ellagitannins present in various nutrition. Although these dietaries, the sources of urolithins, are employed in folk medicine as cognitive enhancer in the treatment of Alzheimer's Disease, urolithins have negligible potential to inhibit acetylcholinesterase and butyrylcholinesterase enzymes, the validated targets of Alzheimer's Disease. Therefore, within this research, a series of 6H-benzo[c]chromen-6-one, and 7,8,9,10-tetrahydro-benzo[c]chromen-6-one derivatives has been designed, synthesized, and their biological activities were evaluated as potential acetylcholinesterase and butyrylcholinesterase inhibitors. The compounds synthesized exerted comparable activity in comparison to rivastigmine, galantamine, and donepezil both in in vitro and in vivo studies. PMID:25189690

  14. Pyrolysis of Tropyl Radical (C7H7) and Benzyl Radical (C6H5CH2) in a Heated Micro-Reactor

    NASA Astrophysics Data System (ADS)

    Buckingham, Grant; Ellison, Barney; Porterfield, Jessica P.; Daily, John W.; Ahmed, Musahid; Robichaud, David; Nimlos, Mark R.

    2016-06-01

    Benzyl radical (C6H5CH2) is a crucial intermediate in the combustion and pyrolysis of substituted aromatic species that are common both in modern gasoline and potential future biofuels. The decomposition of benzyl radical is complicated and has been shown by isotopic labeling to require interesting isomerizations pathways. To better understand these pathways, a set of C7H7 radicals has been studied in a heated micro-reactor. Through multiple experiments, it has be shown that benzyl radical and cycloheptatrienyl (tropyl) radical (c-C7H7) do not interconvert, even at temperatures where both have completely thermally decomposed. To confirm this, tropyl radical has been studied directly and its pyrolysis is quite simple, only cyclopentadienyl radical (c-C5H5) and acetylene (HCCH) are formed. Cyclopentadienyl radical then decomposes to acetylene and propargyl radical (HCCCH2). These products have all been identified through use of tunable synchrotron radiation by confirming their respective photoionization spectra. Matrix isolation infrared (IR) spectroscopy has also been used to identity these products. A previously unanswered question in benzyl radical decomposition has been addressed by studying the pyrolysis of 2,5-norbornadiene, which indicates benzyl radical may decompose through a norbornadiene-like bicyclic radical intermediate. This pathways successfully predicts the correct isotopically labeled products observed previously during 13C labeled benzyl pyrolysis.

  15. Variance Function Regression in Hierarchical Age-Period-Cohort Models: Applications to the Study of Self-Reported Health

    PubMed Central

    Zheng, Hui; Yang, Yang; Land, Kenneth C.

    2012-01-01

    Two long-standing research problems of interest to sociologists are sources of variations in social inequalities and differential contributions of the temporal dimensions of age, time period, and cohort to variations in social phenomena. Recently, scholars have introduced a model called Variance Function Regression for the study of the former problem, and a model called Hierarchical Age-Period-Cohort regression has been developed for the study of the latter. This article presents an integration of these two models as a means to study the evolution of social inequalities along distinct temporal dimensions. We apply the integrated model to survey data on subjective health status. We find substantial age, period, and cohort effects, as well as gender differences, not only for the conditional mean of self-rated health (i.e., between-group disparities), but also for the variance in this mean (i.e., within-group disparities)—and it is detection of age, period, and cohort variations in the latter disparities that application of the integrated model permits. Net of effects of age and individual-level covariates, in recent decades, cohort differences in conditional means of self-rated health have been less important than period differences that cut across all cohorts. By contrast, cohort differences of variances in these conditional means have dominated period differences. In particular, post-baby boom birth cohorts show significant and increasing levels of within-group disparities. These findings illustrate how the integrated model provides a powerful framework through which to identify and study the evolution of variations in social inequalities across age, period, and cohort temporal dimensions. Accordingly, this model should be broadly applicable to the study of social inequality in many different substantive contexts. PMID:22904570

  16. Damaging events along roads during bad weather periods: a case study in Calabria (Italy)

    NASA Astrophysics Data System (ADS)

    Petrucci, O.; Pasqua, A. A.

    2012-02-01

    The study focuses on circumstances that affect people during periods of bad weather conditions characterised by winds, rainfall, landslides, flooding, and storm surges. A methodological approach and its application to a study area in southern Italy are presented here. A 10-yr database was generated by mining data from a newspaper. Damaging agents were sorted into five types: flood, urban flooding, landslide, wind, and storm surge. Damage to people occurred in 126 cases, causing 13 victims, 129 injured and about 782 people involved but not injured. For cases of floods, urban flooding and landslides, the analysis does not highlight straightforward relationships between rainfall and damage to people, even if the events showed different features according to the months of occurrence. The events occurring between May and October were characterised by concentrated and intense rainfall, and between May and July, the highest values of hourly (103 mm on the average) and monthly rainfall (114 mm on the average) were recorded. Urban flooding and flash floods were the most common damaging agents: injured, involved people and more rarely, cases with victims were reported. Between November and April, the highest number of events was recorded. Rainfall presented longer durations and hourly and sub-hourly rainfall were lower than those recorded between May and October. Landslides were the most frequent damaging agents but the highest number of cases with victims, which occurred between November and January, were mainly related to floods and urban flooding. Motorists represent the totality of the victims; 84% of the people were injured and the whole of people involved. All victims were men, and the average age was 43 yr. The primary cause of death was drowning caused by floods, and the second was trauma suffered in car accidents caused by urban flooding. The high number of motorists rescued in submerged cars reveals an underestimation of danger in the case of floods, often

  17. Earthquake Early Warning of East China Sea: the study on the experimental relationship between the Predominant Period and the Magnitude

    NASA Astrophysics Data System (ADS)

    Li, Y.; Xue, M.; Ren, Y.; Zhu, A.

    2011-12-01

    Based on seismic hazards analysis in Huadong region (include Shanghai, Zhejiang province, and Jiangsu province), it's necessary to build an earthquake early warning systems in this region. This becomes even more urgent because of the fast developments of High-Speed Trains surrounding the area. In this study, we use the historical earthquake data to build an experimental relationship between the Predominant Period and the Magnitude for Huadong region. We combined ISC earthquake catalogue with the catalogue from Huadong sub-network of Chinese Digital Seismic Network from 1999 to 2008. We manually examined all the local and regional events and selected a total of 117 earthquakes with high signal to noise ratios. Based on the analysis of seismic data from station SSE, we investigate the influence of different parameters such as the eigenfunction, the length of STA/LTA window, and the threshold on P-wave auto triggering and determine the appropriate values of these parameters for Huadong region. By testing different values of the parameters, we obtain different linear relationships between the predominant period and the magnitude; then we determine the optimal set of parameters through error analysis for magnitude estimation. A good linear fitting between the predominant period and magnitudes is obtained. In addition, we use the average predominant period instead of the predominant period of the first few seconds to build the experimental relationship between the average predominant period and the magnitude. Compared with that of using the predominant period directly, the linear fitting using the average predominant period reveals a relatively better relevancy between periods and magnitudes and a better error distribution in magnitude estimating.

  18. Field-induced periodic distortions in a nematic liquid crystal: deuterium NMR study and theoretical analysis.

    PubMed

    Sugimura, A; Zakharov, A V

    2011-08-01

    The peculiarities in the dynamic of the director reorientation in a liquid crystal (LC) film under the influence of the electric E field directed at an angle α to the magnetic B field have been investigated both experimentally and theoretically. Time-resolved deuterium NMR spectroscopy is employed to investigate the field-induced director dynamics. Analysis of the experimental results, based on the predictions of hydrodynamic theory including both the director motion and fluid flow, provides an evidence for the appearance of the spatially periodic patterns in 4-n-pentyl-4'-cyanobiphenyl LC film, at the angles α>60∘, in response to the suddenly applied E. These periodic distortions produce a lower effective rotational viscosity. This gives a faster response of the director rotation than for a uniform mode, as observed in our NMR experiment. PMID:21929001

  19. Indoor radon periodicities and their physical constraints: a study in the Coimbra region (Central Portugal).

    PubMed

    Neves, L J P F; Barbosa, S M; Pereira, A J S C

    2009-10-01

    Indoor radon activities were measured during a period of 6 months, as well as several physical environmental variables (temperature, pressure, humidity and rainfall). The location was a small room at an administrative building of the University of Coimbra, usually undisturbed by human activities and situated over bedrock of low-uranium Triassic red sandstones. A low average activity of radon was observed (36 Bq m(-3)), however showing a very well marked daily periodicity (10+/-5 Bq m(-3)), with maximum values occurring more frequently between 9 and 10 a.m. Daily variations are shown to have no relation with earth tides, and their amplitudes exhibit a significant correlation with outdoor temperature; no dependence on barometric pressure was found. Rainfall disturbs the observed daily radon cycles through a strong reduction of their amplitude, but has no effect on the long-term variability of the gas concentration. PMID:19632749

  20. Indoor radon periodicities and their physical constraints: a study in the Coimbra region (Central Portugal).

    PubMed

    Neves, L J P F; Barbosa, S M; Pereira, A J S C

    2009-10-01

    Indoor radon activities were measured during a period of 6 months, as well as several physical environmental variables (temperature, pressure, humidity and rainfall). The location was a small room at an administrative building of the University of Coimbra, usually undisturbed by human activities and situated over bedrock of low-uranium Triassic red sandstones. A low average activity of radon was observed (36 Bq m(-3)), however showing a very well marked daily periodicity (10+/-5 Bq m(-3)), with maximum values occurring more frequently between 9 and 10 a.m. Daily variations are shown to have no relation with earth tides, and their amplitudes exhibit a significant correlation with outdoor temperature; no dependence on barometric pressure was found. Rainfall disturbs the observed daily radon cycles through a strong reduction of their amplitude, but has no effect on the long-term variability of the gas concentration.

  1. Crystal growth, structure, crystalline perfection and characterization of zinc magnesium ammonium sulfate hexahydrate mixed crystals ZnxMg(1-x)(NH4)2(SO4)2·6H2O

    NASA Astrophysics Data System (ADS)

    Ramasamy, G.; Bhagavannarayana, G.; Madhurambal, G.; Meenakshisundaram, Subbiah

    2012-08-01

    Mixed crystals ZnxMg(1-x)(NH4)2(SO4)2·6H2O of the two well-known Tutton's salts Zn(NH4)2(SO4)2·6H2O and Mg(NH4)2(SO4)2·6H2O were grown with varying molar proportions (x=0.10-0.90) by slow evaporation solution growth technique. The mixed crystal Zn0.54Mg0.46(NH4)2(SO4)2·6H2O is crystallizing in monoclinic system with space group P21/c and cell parameters a=6.2217(4) Å, b=12.5343(7) Å, c=9.2557(6) Å, β=106.912(3)°. The coexistence of zinc and magnesium ions in the mixed crystal was confirmed by inductively coupled plasma (ICP), atomic absorption spectroscopy (AAS) and energy dispersive X-ray spectroscopy (EDS). Compositional dependence of lattice parameters follows Vegard's relations. Slight variations are observed in FT-IR and XRD of pure and mixed crystals. Comparison of crystalline perfection as evaluated by high-resolution X-ray diffraction (HRXRD) for mixed crystals of various proportions reveals a reasonably good crystalline perfection for the mixed crystal with nearly equimolar ratio of Zn and Mg. The surface morphology of the mixed crystals changing with composition was studied by scanning electron microscopy (SEM). UV-vis studies reveal that the transparency of the mixed crystals was not much affected.

  2. Efficient biosynthesis of rare natural product scopolamine using E. coli cells expressing a S14P/K97A mutant of hyoscyamine 6β-hydroxylase AaH6H.

    PubMed

    Cao, Yue-De; He, Yu-Cai; Li, Hao; Kai, Guo-Yin; Xu, Jian-He; Yu, Hui-Lei

    2015-10-10

    Hyoscyamine 6β-hydroxylase (H6H, EC 1.14.11.11), an α-ketoglutarate dependent dioxygenase catalyzes the hydroxylation of (-)-hyoscyamine and the subsequent epoxidation of 6β-hydroxyhyoscyamine to form scopolamine, a valuable natural alkaloid. In this study, random mutagenesis and site-directed saturation mutagenesis were used to enhance the hydroxylation activity of H6H from Anisodus acutangulus (AaH6H). A double mutant, AaH6HM1 (S14P/K97A), showed a 3.4-fold improved hydroxylation activity compared with the wild-type enzyme, and the in vivo epoxidation activity was also improved by 2.3 times. After 34h cultivation of Escherichia coli cells harboring Aah6hm1 in a 5-L bioreactor with a working volume of 3L, scopolamine was produced via a single-enzyme-mediated two-step transformation from 500mgL(-1) (-)-hyoscyamine in 97% conversion, and 1.068g of the product were isolated, corresponding to a space-time yield of 251mgL(-1)d(-1). This study shows that the protein engineering of some key enzymes is a promising and effective way for improving the production of rare natural products such as scopolamine.

  3. Period and light-curve study of the contact eclipsing binary V523 Cas

    NASA Astrophysics Data System (ADS)

    Mohammadi, Mahya; Abedi, Abbas; Riazi, Nematollah

    2016-04-01

    CCD photometry of the eclipsing W Uma binary system V523 Cas in U, B, V and RC filters was carried out during eight nights in 2012. The physical and geometrical parameters of this system are obtained. A possible pulsation period of one of the components is obtained by analyzing the residuals of the ephemeris light curve. Our observations contain 16 times of minimum light. We combined these with all available published times of minimum. By fitting a quadratic curve to the O-C values, a new ephemeris of the system is calculated. By attributing the period change to mass transfer, we find a mass transfer rate of 4 ×10-12 M⊙/yr. Also, Period (80.58 yr) and the minimum mass (0.3 M⊙) of a possible third body is estimated. In addition, the possible existence of a fourth body with a mass of order 0.15 M⊙ is discussed. These third and fourth bodies could be low-mass main-sequence stars (red dwarfs).

  4. Evolution of illustrations in anatomy: a study from the classical period in Europe to modern times.

    PubMed

    Ghosh, Sanjib Kumar

    2015-01-01

    Illustrations constitute an essential element of learning anatomy in modern times. However it required a significant evolutionary process spread over centuries, for illustrations to achieve the present status in the subject of anatomy. This review article attempts to outline the evolutionary process by highlighting on the works of esteemed anatomists in a chronological manner. Available literature suggests that illustrations were not used in anatomy during the classical period when the subject was dominated by the descriptive text of Galen. Guido da Vigevano was first to use illustrations in anatomy during the Late Middle Ages and this concept developed further during the Renaissance period when Andreas Vesalius pioneered in illustrations becoming an indispensable tool in conveying anatomical details. Toward later stages of the Renaissance period, Fabricius ab Aquapendente endeavored to restrict dramatization of anatomical illustrations which was a prevalent trend in early Renaissance. During the 18th century, anatomical artwork was characterized by the individual styles of prominent anatomists leading to suppression of anatomical details. In the 19th century, Henry Gray used illustrations in his anatomical masterpiece that focused on depicting anatomical structures and were free from any artistic style. From early part of the 20th century medical images and photographs started to complement traditional handmade anatomical illustrations. Computer technology and advanced software systems played a key role in the evolution of anatomical illustrations during the late 20th century resulting in new generation 3D image datasets that are being used in the 21st century in innovative formats for teaching and learning anatomy.

  5. A Comparison of Two CD-ROM Periodical Indexes for Use in the Middle School. A Scholarly Study.

    ERIC Educational Resources Information Center

    Thrash, Beverly M.

    This purpose of this study was to determine which periodical index--InfoTrac or EBSCO Magazine Article Summaries--is the most appropriate for use by middle school students preparing required research projects. The study population consisted of randomly selected sixth, seventh, and eighth grade students (N=50) in a Cobb County (Georgia) middle…

  6. Numerical modeling of the large-scale neutral and plasma responses to the body forces created by the dissipation of gravity waves from 6 h of deep convection in Brazil

    NASA Astrophysics Data System (ADS)

    Vadas, S. L.; Liu, H.-L.

    2013-05-01

    We study the response of the thermosphere and ionosphere to gravity waves (GWs) excited by 6 h of deep convection in Brazil on the evening of 01 October 2005 via the use of convective plume, ray trace, and global models. We find that primary GWs excited by convection having horizontal wavelengths of λH˜70-300 km, periods of 10-60 min, and phase speeds of cH˜50-225 m/s propagate well into the thermosphere. Their density perturbations are ρ'/ρ300 km. The dissipation of these GWs creates spatially and temporally localized body forces with amplitudes of 0.2- 1.0 m/s2at z˜120-230 km. These forces generate two counter-rotating circulation cells with horizontal velocities of 50-350 m/s. They also excite secondary GWs; those resolved by our global model have λH˜4000-5000 km and cH˜500-600 m/s. These secondary GWs propagate globally and have ρ'/ρ

  7. Reactions of HC triple bond CCMe sub 2 NHCOR alkynes with M sub 3 (CO) sub 12 carbonyls (M = Ru, R = C sub 6 H sub 9 , Ph; M = Os, R = C sub 6 H sub 9 ). Synthesis and crystal structure of Ru sub 4 (CO) sub 11 (HC triple bond CCMe sub 2 NHCOC sub 6 H sub 9 ), a butterfly cluster showing an interaction between a wingtip metal and the amide CO

    SciTech Connect

    Predieri, G.; Tiripicchio, A.; Camellini, M.T.; Costa, M. ); Sappa, E. )

    1990-06-01

    The alkynes HC{triple bond}CCMe{sub 2}NHCOR react with M{sub 3}(CO){sub 12} (M = Ru or Os) giving, upon oxidative addition, the expected hydrides ({mu}-H)M{sub 3}(CO){sub 9}({mu}{sub 3}-{eta}{sup 2}-C{triple bond}CCMe{sub 2}NHCOR) and the unprecedented butterfly clusters M{sub 4}(CO){sub 11}({mu}{sub 4}-{eta}{sup 2}-HC{triple bond}CCME{sub 2}NHCOR). These complexes have been characterized by spectroscopic studies; the structure of the ruthenium butterfly cluster with R = C{sub 6}H{sub 9} has been determined by X-ray diffraction methods. Crystals, containing CHCl{sub 3} as solvation molecules, are triclinic with Z = 2 in a unit cell of dimensions a = 13.521 (6), b = 14.617 (6), c = 9.049 (5) {angstrom}, {alpha} = 79.28 (2), {beta} = 108.79 (2), {gamma} = 111.85 (2){degree}.

  8. Bioengineering studies of periodic external compression as prophylaxis against deep vein thrombosis-part I: numerical studies.

    PubMed

    Kamm, R D

    1982-05-01

    This paper presents the results of a numerical study of the technique of periodic external compression for the prevention of deep vein thrombosis. In the model the veins of the lower leg are portrayed as a continuous system rather than as discrete elements as in previous models. Consequently, we are able to explore the detailed effects of different modes of compression including (i) uniform compression, the simultaneous application of uniform pressure over the entire lower leg, (ii) graded compression, the application of nonuniform pressure, maximum at the ankle and minimum at the knee, and (iii) wavelike compression, a wave of compression proceeding from the ankle toward the knee. These numerical results indicate that the effectiveness of uniform compression is severely compromised by the formation of a flow-limiting throat at the proximal end of the compression cuff that reduces both the rate at which blood is discharged from the lower leg and the total blood volume removed. Both of these detrimental effects can be avoided by the use of either wavelike of graded compression. Both alternated methods are shown to produce more uniform augmentation of volume flow rate, flow velocity and shear stress, throughout the entire lower leg. In the companion paper, Part II [18] (see following article), these same compression modes are tested using a simple hydraulic model consisting of a single latex tube inside a foam cylinder as a highly simplified representation of a human leg. PMID:7078134

  9. Surgery during holiday periods and prognosis in oesophageal cancer: a population-based nationwide Swedish cohort study

    PubMed Central

    Markar, Sheraz R; Wahlin, Karl; Mattsson, Fredrik; Lagergren, Pernilla; Lagergren, Jesper

    2016-01-01

    Objective Previous studies indicate an increased short-term and long-term mortality from major cancer surgery performed towards the end of the working week or during the weekend. We hypothesised that the prognosis after major cancer surgery is also negatively influenced by surgery conducted during holiday periods. Setting Population-based nationwide Swedish cohort study. Participants Patients undergoing oesophagectomy for oesophageal cancer between 1987 and 2010. Among 1820 included patients, 206 (11.3%) and 373 (20.5%) patients were operated on during narrow and wide holiday periods, respectively. Interventions Narrow (7 weeks) and wide (14 weeks) Swedish holiday periods. Primary and secondary outcome measures 90-day all-cause, 5-year all-cause and 5-year disease-specific mortality. Results Narrow holiday period did not increase all-cause 90-day (HR=0.84, 95% CI 0.53 to 1.33), all-cause 5-year (HR=1.01, 95% CI 0.85 to 1.21) or disease-specific 5-year mortality (HR=1.04, 95% CI 0.87 to 1.26). Similarly, wide holiday period did not increase the risk of 90-day (HR=0.79, 95% CI 0.55 to 1.13), all-cause 5-year (HR=0.96, 95% CI 0.84 to 1.1) or disease-specific 5-year mortality (HR=1.03, 95% CI 0.89 to 1.19). Conclusions No measurable effects of holiday periods on short-term or longer term mortality following surgery for oesophageal cancer were observed in this population-based study, indicating that an adequate surgical experience was maintained during holiday periods. PMID:27601504

  10. Hole injection and dielectric breakdown in 6H-SiC and 4H-SiC metal-oxide-semiconductor structures during substrate electron injection via Fowler-Nordheim tunneling

    NASA Astrophysics Data System (ADS)

    Samanta, Piyas; Mandal, Krishna C.

    2015-12-01

    Hole injection into silicon dioxide (SiO2) films (8-40 nm thick) is investigated for the first time during substrate electron injection via Fowler-Nordheim (FN) tunneling in n-type 4H- and 6H-SiC (silicon carbide) based metal-oxide-semiconductor (MOS) structures at a wide range of temperatures (T) between 298 and 598 K and oxide electric fields Eox from 6 to 10 MV/cm. Holes are generated in heavily doped n-type polycrystalline silicon (n+ -polySi) gate serving as the anode as well as in the bulk silicon dioxide (SiO2) film via hot-electron initiated band-to-band ionization (BTBI). In absence of oxide trapped charges, it is shown that at a given temperature, the hole injection rates from either of the above two mechanisms are higher in n-4H-SiC MOS devices than those in n-6H-SiC MOS structures when compared at a given Eox and SiO2 thickness (tox). On the other hand, relative to n-4H-SiC devices, n-6H-SiC structures exhibit higher hole injection rates for a given tox during substrate electron injection at a given FN current density je,FN throughout the temperature range studied here. These two observations clearly reveal that the substrate material (n-6H-SiC and n-4H-SiC) dependencies on time-to-breakdown (tBD) or injected charge (electron) to breakdown (QBD) of the SiO2 film depend on the mode of FN injections (constant field/voltage and current) from the substrate which is further verified from the rigorous device simulation as well.

  11. Evolution of illustrations in anatomy: a study from the classical period in Europe to modern times.

    PubMed

    Ghosh, Sanjib Kumar

    2015-01-01

    Illustrations constitute an essential element of learning anatomy in modern times. However it required a significant evolutionary process spread over centuries, for illustrations to achieve the present status in the subject of anatomy. This review article attempts to outline the evolutionary process by highlighting on the works of esteemed anatomists in a chronological manner. Available literature suggests that illustrations were not used in anatomy during the classical period when the subject was dominated by the descriptive text of Galen. Guido da Vigevano was first to use illustrations in anatomy during the Late Middle Ages and this concept developed further during the Renaissance period when Andreas Vesalius pioneered in illustrations becoming an indispensable tool in conveying anatomical details. Toward later stages of the Renaissance period, Fabricius ab Aquapendente endeavored to restrict dramatization of anatomical illustrations which was a prevalent trend in early Renaissance. During the 18th century, anatomical artwork was characterized by the individual styles of prominent anatomists leading to suppression of anatomical details. In the 19th century, Henry Gray used illustrations in his anatomical masterpiece that focused on depicting anatomical structures and were free from any artistic style. From early part of the 20th century medical images and photographs started to complement traditional handmade anatomical illustrations. Computer technology and advanced software systems played a key role in the evolution of anatomical illustrations during the late 20th century resulting in new generation 3D image datasets that are being used in the 21st century in innovative formats for teaching and learning anatomy. PMID:25053471

  12. A numerical study of transition control by periodic suction-blowing

    NASA Technical Reports Server (NTRS)

    Biringen, Sedat

    1987-01-01

    The applicability of active control of transition by periodic suction-blowing is investigated via direct numerical simulations of the Navier-Stokes equations. The time-evolution of finite-amplitude disturbances in plane channel flow is compared in detail with and without control. The analysis indicates that, for relatively small three dimensional amplitudes, a two dimensional control effectively reduces disturbance growth rates even for linearly unstable Reynolds numbers. After the flow goes through secondary instability, three dimensional control seems necessary to stabilize the flow. An investigation of the temperature field suggests that passive temperature contamination is operative to reflect the flow dynamics during transition.

  13. Preliminary TES design optimization study for a simple periodic brick plant

    SciTech Connect

    Drake, J.B.; Olszewski, M.; Solomon, A.D.

    1989-03-01

    A general optimization method has been developed for maximizing the return on investment for a brick plant re-using waste heat with the capability of storing energy over periods when a kiln is not operating. The duct connections between devices and storage along with the operating schedule of flow rates in these ducts are the independent variables available for control. A combination of combinatorial search algorithms along with a dynamic programming model and the simplex method are layered to provide the optimization technique.

  14. Breaking inertia: increasing access to journals during a period of declining budgets: a case study.

    PubMed

    Fought, Rick L

    2014-07-01

    Beginning in January 2012, a 1-year pilot pay-per-view (PPV) service was implemented. Twenty-four journal subscriptions were canceled to fund the service, and through the PPV service, the library was able to offer patrons access to over 700 previously unavailable biomedical journals. At the end of the pilot period, the total PPV cost for each journal accessed was compared to the subscription cost to determine if PPV was an effective use of library money. While remaining essentially budget neutral, the number of full-text articles accessed increased over 400%. PPV can be a cost-effective method for expanding access to journals. PMID:25031560

  15. Coding Properties of Three Intrinsically Distinct Retinal Ganglion Cells under Periodic Stimuli: A Computational Study

    PubMed Central

    Wang, Lei; Qiu, Yi-Hong; Zeng, Yanjun

    2016-01-01

    As the sole output neurons in the retina, ganglion cells play significant roles in transforming visual information into spike trains, and then transmitting them to the higher visual centers. However, coding strategies that retinal ganglion cells (RGCs) adopt to accomplish these processes are not completely clear yet. To clarify these issues, we investigate the coding properties of three types of RGCs (repetitive spiking, tonic firing, and phasic firing) by two different measures (spike-rate and spike-latency). Model results show that for periodic stimuli, repetitive spiking RGC and tonic RGC exhibit similar spike-rate patterns. Their spike- rates decrease gradually with increased stimulus frequency, moreover, variation of stimulus amplitude would change the two RGCs' spike-rate patterns. For phasic RGC, it activates strongly at medium levels of frequency when the stimulus amplitude is low. While if high stimulus amplitude is applied, phasic RGC switches to respond strongly at low frequencies. These results suggest that stimulus amplitude is a prominent factor in regulating RGCs in encoding periodic signals. Similar conclusions can be drawn when analyzes spike-latency patterns of the three RGCs. More importantly, the above phenomena can be accurately reproduced by Hodgkin's three classes of neurons, indicating that RGCs can perform the typical three classes of firing dynamics, depending on the distinctions of ion channel densities. Consequently, model results from the three RGCs may be not specific, but can also applicable to neurons in other brain regions which exhibit part(s) or all of the Hodgkin's three excitabilities. PMID:27721751

  16. [Statistical studies on suicides in Shiga Prefecture during the 15-year period, 1974 to 1988].

    PubMed

    Yamamoto, Y; Yamada, M; Fukunaga, T; Tatsuno, Y

    1990-04-01

    The authors examined 3,335 cases of suicides among the unnatural deaths in Shiga Prefecture during the 15-year period, 1974 to 1988. The results obtained were as follows: The number of suicides in a year amounted to 200 during the period from 1974 to 1982, and increased to 280 in 1983 at maximum. The cases of suicide were more in male than in female. The incidence of suicide was higher in March to July and the peak of incidence was observed in April. The highest frequency of suicides was in 40-49 year age group in male, and 70-79 year group in female. Among various procedures of suicide, hanging was most frequent during the past 15 years in both sexes, and the following procedure was carbon monoxide poisoning in male and drowning in female. As to the occupation, housewives and person without a regular occupation constituted 53.1% of the total suicidal cases, and products makers and laborers were found in 11.1%. With regarded to the causative factors, "suffering from illness" was the most frequent factor, and followed by "insanity or mental disorder", "problems of economic distress", "disagreement with family" and others.

  17. Determining polarity and dislocation core structures at atomic level for epitaxial AlN/(0001)6H-SiC from a single image in HRTEM.

    PubMed

    Cui, Y X; Wang, Y M; Wen, C; Ge, B H; Li, F H; Chen, Y; Chen, H

    2013-03-01

    The polarity of epitaxial AlN film grown on (0001)6H-SiC and dislocation core structures in the film have been studied using a 200 kV LaB6 high-resolution transmission electron microscope of point resolution about 0.2 nm. A posterior image processing technique, the image deconvolution, was utilized to transform a single [21¯1¯0] image that does not intuitively represent the structure into the projected structure map. The adjacent Al and N projected atomic columns with the interatomic distance 0.109 nm can be distinguished from each other by analyzing the image contrast change with the sample thickness based on the pseudo-weak phase object approximation. This makes possible to derive the polarity and core structures of partial dislocations in the epitaxial AlN film at atomic level from a single image without relying on any other additional structure information. The atomic configurations for two partial dislocations containing a 10-atom ring and a 12-atom ring, respectively, have been attained. The method is available for II-VI and other III-V compounds. Its principle and procedure are briefly introduced.

  18. cAMP dependent and independent regulation of thyroglobulin synthesis by two clones of the OVNIS 6H thyroid cell line.

    PubMed

    Aouani, A; Hovsépian, S; Fayet, G

    1987-07-01

    The hormonal regulation of thyroglobulin synthesis has been studied using two independent clones of the OVNIS 6H cell line. Insulin, hydrocortisone and TSH were able to stimulate thyroglobulin synthesis, whereas transferrin, somatostatin and glycyl-histidyl-lysine were without effect. Insulin stimulated thyroglobulin synthesis without affecting cAMP production. Hydrocortisone, when combined with insulin was a stimulator too; this stimulation was not accompanied by an increase in cAMP. TSH alone was unable to stimulate either cAMP or thyroglobulin synthesis. The stimulatory effect of TSH on thyroglobulin synthesis took place only when combined with insulin or insulin plus hydrocortisone, and was mediated by cAMP. Consequently, insulin and hydrocortisone stimulated thyroglobulin synthesis by cAMP-independent mechanisms, whereas TSH acted via the cAMP system. Forskolin mimicked TSH effects on cAMP and thyroglobulin synthesis. Calf serum inhibited cAMP and thyroglobulin production. Optimal cAMP and thyroglobulin synthesis as well as TSH responsiveness were obtained in serum-free medium supplemented with 5 micrograms/ml insulin, 100 nM hydrocortisone and 1 mU/ml TSH. PMID:3040495

  19. Abnormal difference between the mobilities of left- and right-twisted conformations of C6H12N2 roto-symmetrical molecules at very low temperatures.

    PubMed

    Gabuda, S P; Kozlova, S G

    2015-06-21

    We report an abnormal difference of low-temperature mobility of left-twisted and right-twisted conformations of roto symmetric molecules C6H12N2 (dabco) located in the same positions in crystal Zn2(C8H4O4)2⋅C6H12N2. The difference between (1)H NMR (Nuclear Magnetic Resonance) spin-relaxation data for left-twisted and right-twisted molecules reaches ∼3 × 10(3) times at 8 K and tends to grow at lower temperatures. We argue that taking into account four-component relativistic Dirac wave functions in the vicinity of the nodal plane of dabco molecules and vacuum fluctuations due to virtual particle-antiparticle pairs can explain the changes which C6H12N2 conformations undergo at low temperatures. PMID:26093554

  20. New metal-organic frameworks of [M(C{sub 6}H{sub 5}O{sub 7})(C{sub 6}H{sub 6}O{sub 7})(C{sub 6}H{sub 7}O{sub 7})(H{sub 2}O)] . H{sub 2}O (M=La, Ce) and [Ce{sub 2}(C{sub 2}O{sub 4})(C{sub 6}H{sub 6}O{sub 7}){sub 2}] . 4H{sub 2}O

    SciTech Connect

    Weng Shengfeng; Wang, Yun-Hsin; Lee, Chi-Shen

    2012-04-15

    Two novel materials, [M(C{sub 6}H{sub 5}O{sub 7})(C{sub 6}H{sub 6}O{sub 7})(C{sub 6}H{sub 7}O{sub 7})(H{sub 2}O)] . H{sub 2}O (M=La(1a), Ce(1b)) and [Ce{sub 2}(C{sub 2}O{sub 4})(C{sub 6}H{sub 6}O{sub 7}){sub 2}] . 4H{sub 2}O (2), with a metal-organic framework (MOF) were prepared with hydrothermal reactions and characterized with photoluminescence, magnetic susceptibility, thermogravimetric analysis and X-ray powder diffraction in situ. The crystal structures were determined by single-crystal X-ray diffraction. Compound 1 crystallized in triclinic space group P1-bar (No. 2); compound 2 crystallized in monoclinic space group P2{sub 1}/c (No. 14). The structure of 1 is built from a 1D MOF, composed of deprotonated citric ligands of three kinds. Compound 2 contains a 2D MOF structure consisting of citrate and oxalate ligands; the oxalate ligand arose from the decomposition in situ of citric acid in the presence of Cu{sup II} ions. Photoluminescence spectra of compounds 1b and 2 revealed transitions between the 5d{sup 1} excited state and two levels of the 4f{sup 1} ground state ({sup 2}F{sub 5/2} and {sup 2}F{sub 7/2}). Compounds 1b and 2 containing Ce{sup III} ion exhibit a paramagnetic property with weak antiferromagnetic interactions between the two adjacent magnetic centers. - Graphical Abstract: [M(C{sub 6}H{sub 5}O{sub 7})(C{sub 6}H{sub 6}O{sub 7})(C{sub 6}H{sub 7}O{sub 7})(H{sub 2}O)] . H{sub 2}O (M=La(1a), Ce(1b)) and [Ce{sub 2}(C{sub 2}O{sub 4})(C{sub 6}H{sub 6}O{sub 7}){sub 2}] . 4H{sub 2}O (2)-with 1D and 2D structures were synthesized and characterized. Highlights: Black-Right-Pointing-Pointer Two MOF - [M(C{sub 6}H{sub 5}O{sub 7})(C{sub 6}H{sub 6}O{sub 7})(C{sub 6}H{sub 7}O{sub 7})(H{sub 2}O)] . H{sub 2}O (M=La(1a), Ce(1b)) and [Ce{sub 2}(C{sub 2}O{sub 4})(C{sub 6}H{sub 6}O{sub 7}){sub 2}] . 4H{sub 2}O (2) - with 1D and 2D structures. Black-Right-Pointing-Pointer The adjacent chains of the 1D framework were correlated with each other through an oxalate

  1. Abnormal difference between the mobilities of left- and right-twisted conformations of C6H12N2 roto-symmetrical molecules at very low temperatures.

    PubMed

    Gabuda, S P; Kozlova, S G

    2015-06-21

    We report an abnormal difference of low-temperature mobility of left-twisted and right-twisted conformations of roto symmetric molecules C6H12N2 (dabco) located in the same positions in crystal Zn2(C8H4O4)2⋅C6H12N2. The difference between (1)H NMR (Nuclear Magnetic Resonance) spin-relaxation data for left-twisted and right-twisted molecules reaches ∼3 × 10(3) times at 8 K and tends to grow at lower temperatures. We argue that taking into account four-component relativistic Dirac wave functions in the vicinity of the nodal plane of dabco molecules and vacuum fluctuations due to virtual particle-antiparticle pairs can explain the changes which C6H12N2 conformations undergo at low temperatures.

  2. IUE observations of long period eclipsing binaries - A study of accretion onto non-degenerate stars

    NASA Technical Reports Server (NTRS)

    Plavec, M. J.

    1980-01-01

    IUE observations made in 1978-1979 recorded a whole class of interacting long-period binaries similar to beta Lyrae, which includes RX Cas, SX Cas, V 367 Cyg, W Cru, beta Lyr, and W Ser, called the W Serpentis stars. These mass-transferring binaries with relatively high mass transfer rate show two prominent features in the far ultraviolet: a continuum with a color temperature higher than the one observed in the optical region (about 12,000 K), and a strong emission line spectrum with the N V doublet at 1240 A, C IV doublet at 1550 A and lines of Si II, Si III, Si IV, C II, Fe III, AI III, etc. These phenomena are discussed on the assumption that they are due to accretion onto non-degenerate stars.

  3. Study of periodic surface profile on improving the window capacity at single and repetitive pulses

    SciTech Connect

    Liu, Y. S.; Zhang, X. W.; Zhang, Z. Q.; Shao, H.; Wang, Y.; Liu, W. Y.; Ke, C. F.; Chen, C. H.; Liang, Y. Q.; Wu, X. L.; Guo, L. T.; Chang, C.

    2015-09-15

    The surface breakdown of dielectric windows seriously limits the transmission of high power microwaves (HPM), and has blocked the development of microwave technology in recent decades. In this paper, X-band HPM experiments of window breakdown at the vacuum/dielectric interface and the atmosphere/dielectric interface at single and repetitive pulses were conducted. The cross-linked polystyrene (CLPS) dielectric window with a periodic surface profile can significantly improve the breakdown threshold at single and repetitive pulses. Furthermore, the flat surface layer of CLPS was discovered to be carbonized to a depth of several millimeters and filled with electrical trees at repetitive pulses. Theoretical models were built to understand the underlying physics behind the phenomena in experiments. With the analysis of the electron resonance process breaking the molecular bond and the temperature rise caused by the traversing current in the dielectric material, a microscopic explanation for the carbonization of the dielectric window was introduced.

  4. Tungsten phosphanylarylthiolato complexes [W{PhP(2-SC6H4)2-kappa3S,S',P} 2] and [W{P(2-SC6H4)3-kappa4S,S',S",P}2]: synthesis, structures and redox chemistry.

    PubMed

    Hildebrand, Alexandra; Lönnecke, Peter; Silaghi-Dumitrescu, Luminita; Hey-Hawkins, Evamarie

    2008-09-14

    PhP(2-SHC6H4)2 (PS2H2) reacts with WCl6 with reduction of tungsten to give the air-sensitive tungsten(IV) complex [W{PhP(2-SC6H4)2-kappa(3)S,S',P}2] (1). 1 is oxidised in air to [WO{PhPO(2-SC6H4)2-kappa(3)S,S',O}{PhP(2-SC6H4)2-kappa(3)S,S',P}] (2). The attempted synthesis of 2 by reaction of 1 with iodosobenzene as oxidising agent was unsuccessful. [W{P(2-SC6H4)3-kappa(4)S,S',S",P}2] (3) was formed in the reaction of P(2-SHC6H4)3 (PS3H3) with WCl6. The W(VI) complex 3 contains two PS3(3-) ligands, each coordinated in a tetradentate fashion resulting in a tungsten coordination number of eight. The reaction of 3 with AgBF4 yields the dinuclear tungsten complex [W2{P(2-SC6H4)3-kappa(4)S,S',S",P}3]BF4 (4). Complexes 1-4 were characterised by spectral methods and X-ray structure determination.

  5. Asthma attack periodicity: A study of hospital emergency visits in Vancouver

    SciTech Connect

    Bates, D.V.; Baker-Anderson, M.; Sizto, R. )

    1990-02-01

    Attendances at the emergency departments of the nine acute care hospitals serving the Vancouver region, with a population of just under a million people, were recorded from July 1, 1984 to October 31, 1986. Of about 25,500 visits a month, 2.7% were for respiratory conditions; and of these, 41.3% were for asthma. Data from 11 air monitoring stations were also tabulated on a daily basis, giving mean maximal hourly values for SO2, NO2, and O3; daily aerosol sulfate measurements from one station were also analyzed, together with daily temperature data and measurements of the coefficient of haze. In 3 consecutive years, a peak in asthma attendances was noted, starting in the last week of September, and continuing for 3 weeks. In these periods, weekly visits for asthma reached 130 patients; during the rest of the year, the weekly visits for asthma varied between 30 and 90. This peak affected children and adults between the ages of 15 and 60, but no increase was seen in those over 60 years. Although pollution levels increased sharply in the fall, a day-by-day analysis showed that the rise in asthma attendances preceded the increase in NO chi and SO2 levels for the region, expressed as the mean of the hourly maxima across all stations. It seems unlikely that a specific pollen is responsible for this, or that house mite replication is the cause. Soya beans are not shipped out of Vancouver. The cause of the peak has not been identified. Variations in emergency visits by day of the week have been recorded; in children and in those aged 15-60, more visits occur on Sundays than on other days, but this does not occur in those over 60. Intercorrelations between environmental variables and emergency visits have been calculated separately for the periods May 1 to October 31, and November 1 to April 30.

  6. Photometric Study and Period Analysis of the Contact Binary XZ Leonis

    NASA Astrophysics Data System (ADS)

    Luo, Chang Qing; Zhang, Xiao Bin; Deng, Licai; Wang, Kun; Luo, Yangping

    2015-09-01

    We present multi-color CCD photometry of the neglected contact binary XZ Leo. Completely covered VRI band light curves and four times of minimum light were obtained. Combining the photometric and previously published radial-velocity data, a revised photometric analysis was carried out for the binary system by applying the Wilson-Devinney code. With a hot spot placed on the massive primary component near the neck region of the common envelope, the light curves were satisfactorily modeled. The photometric solution combined with the radial-velocity solution reveals that XZ Leo is an A-type contact binary with a degree of contact of 24(±1)%. The absolute parameters of the components were determined to be M1 = 1.74(±0.06)M⊙, M2 = 0.61(±0.02)M⊙, R1 = 1.69(±0.01)R⊙, R2 = 1.07(±0.01)R⊙, L1 = 6.73(±0.08) L⊙, and L2 = 2.40(±0.04)L⊙. Based on all the available data, the long-term orbital period behavior of the system was investigated. It indicates that the binary system was undergoing a continuous orbital period increase in the past three decades with a rate of {dP}/{dt} =+6.12× {10}-8 {days} {{yr}}-1, which suggests a probable mass transfer from the secondary to the primary component at a rate of {dM}/{dt}=3.92× {10}-8{M}⊙ {{yr}}-1. The binary system is expected to evolve into the broken-contact stage in 1.56× {10}6 years. This could be evidence supporting the thermal relaxation oscillation theory.

  7. [Experimental study of the root supply system with periodic water return designed for space greenhouses].

    PubMed

    Berkovich, Iu A; Smolianina, S O; Krivobok, N M

    2000-01-01

    To improve reliability of plant's moistening and aeration control in microgravity, an original root supply system with a periodic return water flow has been designed and tested in laboratory. For 30 days crops of Pekinese cabbage (Brassica pekinesis (Lour Rupr), Khibini sort) were raised in the test bench which allowed adjustment of water potential in the root zone within a preset range. A three-step water potential control algorithm included water injection with a pump-dispenser, a pause, and water sucking back to a desired value of water potential. The following parameters of the control cycle were selected in a series of two experiments: time of water injection (2.5 hr) and return (1.5 hr), and a pause of 8 and 20 hr, respectively. Magnitude of water potential about the root module axis was controlled in the range from -1.3 kPa to -3.0 kPa in both experiments and maintained at -1.3 kPa in the control. The root modules consisted of porous metaloceramic tubes wrapped in fibrous ion exchanging cloth and a light-proof film with planting slots on top. In the first experiment, plant characteristics were comparable to the control. The developed procedure and technology can be used to provide favourable moisture-air conditions in the root zone. By and large, the system of root nutrition with a periodic water return has demonstrated high capacity during the ground-based cultivation of plants. To use this system in space greenhouse, it is necessary to specify operational parameters for the microgravity environment. PMID:10826063

  8. Irregular Periods

    MedlinePlus

    ... number of days after the last one. The Menstrual Cycle Most girls get their first period between the ... to skip periods or to have an irregular menstrual cycle. Illness, rapid weight change, or stress can also ...

  9. Three p-tert-butylthiacalix[4]arene-supported cobalt compounds obtained in one pot involving in situ formation of N6H2 ligand.

    PubMed

    Bi, Yanfeng; Liao, Wuping; Xu, Guancheng; Deng, Ruiping; Wang, Meiyan; Wu, Zhijian; Gao, Song; Zhang, Hongjie

    2010-09-01

    Three p-tert-butylthiacalix[4]arene (H(4)TC4A)-supported Co(II) compounds, [Co(4)(TC4A)(N(3))(4)(N(6)H(2))(CH(3)OH)](CH(3)OH)(2) (1), [Co(8)(TC4A)(2)(N(3))(2)(N(6)H(2))(2)(CH(3)COO)(4)(CH(3)OH)(4)](OH)(2)(CH(3)OH)(4) (2), and [Co(10)(TC4A)(4)(N(3))(4)](CH(3)OH)(4) (3), have been solvothermally obtained in one pot and structurally characterized by single-crystal X-ray diffraction analyses, powder XRD, and IR spectroscopy. This work presents the first one-dimensional (1) cobalt cluster for the calixarene complexes and another two octanuclear (2) or decanuclear (3) cobalt clusters. In the structures of compounds 1 and 2, a novel N(6)H(2) ligand formed by the in situ (2 + 3) cycloaddition of two azides was observed. Density functional theory (DFT) calculations give the heat of formation (2N(3)(-) + 2H(+) --> N(6)H(2)) and decomposition energy (N(6)H(2) --> 3N(2) + H(2)) of 677.47 and 124.85 kcal/mol, respectively. Furthermore, an intergradation was determined at the B3LYP/6-311++g(d,p) level for the formation of the N(6)H(2) ligand. In addition, one TC4A ligand of a sandwich unit adopts a cone conformation, while the other adopts a pinched cone conformation in 3. The magnetic properties of these three compounds were influenced mainly by the orbital contributions of the distorted octahedral Co(II) ions.

  10. Measurement of N-Type 6H SiC Minority-Carrier Diffusion Lengths by Electron Bombardment of Schottky Barriers

    NASA Technical Reports Server (NTRS)

    Hubbard, S. M.; Tabib-Azar, M.; Balley, S.; Rybickid, G.; Neudeck, P.; Raffaelle, R.

    2004-01-01

    Minority-Carrier diffusion lengths of n-type 6H-SiC were measured using the electron-beam induced current (EBIC) technique. Experimental values of primary beam current, EBIC, and beam voltage were obtained for a variety of SIC samples. This data was used to calculate experimental diode efficiency vs. beam voltage curves. These curves were fit to theoretically calculated efficiency curves, and the diffusion length and metal layer thickness were extracted. The hole diffusion length in n-6H SiC ranged from 0.93 +/- 0.15 microns.

  11. Reversible addition of water to the high-hydride-content cluster [Rh6(PiPr3)6H12][BArF4]2. Synthesis and Structure of [Rh6PiPr3)6H11(OH)][BArF4]2.

    PubMed

    Douglas, Thomas M; Brayshaw, Simon K; Raithby, Paul R; Weller, Andrew S

    2008-02-01

    The hydroxyhydrido salt [Rh(6)(P(i)Pr(3))(6)H(11)(OH)][BArF(4)](2) results from the addition of water to [Rh(6)(P(i)Pr(3))(6)H(12)][BArF(4)](2). This reaction is reversible, and the addition of dihydrogen to [Rh(6)(P(i)Pr(3))(6)H(11)(OH)][BArF(4)](2) results in the elimination of water and the regeneration of the hydride cluster. PMID:18181618

  12. The reactions of para-halo diaryl diselenides with halogens. A structural investigation of the CT compound (p-FC6H4)2Se2I2, and the first reported “RSeI3” compound, (p-ClC6H4)SeI·I2, which contains a covalent Se-I bond.

    PubMed

    Barnes, Nicholas A; Godfrey, Stephen M; Hughes, Jill; Khan, Rana Z; Mushtaq, Imrana; Ollerenshaw, Ruth T A; Pritchard, Robin G; Sarwar, Shamsa

    2013-02-28

    The reactions of the diaryl-diselenides (p-FC(6)H(4))(2)Se(2) and (p-ClC(6)H(4))(2)Se(2) with diiodine have been investigated. Species of stoichiometry "RSeI" are formed when the ratio employed is 1:1. The solid-state structure of "(p-FC(6)H(4))SeI" has been determined, and shown to be a charge-transfer (CT) adduct, (p-FC(6)H(4))(2)Se(2)I(2), where the Se-Se bond is retained and the diiodine molecule interacts with only one of the selenium atoms. The Se-I bond in (p-FC(6)H(4))(2)Se(2)I(2) is 2.9835(12) Å, which is typical for a (10-I-2) Se-I-I CT system. When diiodine is reacted in a 3:1 ratio with (p-XC(6)H(4))(2)Se(2) (X = F, Cl) species of stoichiometry "RSeI(3)" are formed. The structure of "(p-ClC(6)H(4))SeI(3)" reveals that this is not a selenium(IV) compound, but is better represented as a selenium(II) CT adduct, (p-ClC(6)H(4))SeI·I(2). The Se-I bond to the diiodine molecule is typical in magnitude for a CT adduct, Se-I: 2.8672(5) Å, whereas the other Se-I bond is much shorter, Se-I: 2.5590(6) Å, and is a genuine example of a rarely observed covalent Se-I bond, which appears to be stabilised by a weak Se···I interaction from a neighbouring iodine atom. The reaction of (p-ClC(6)H(4))SeI with Ph(3)P results in the formation of a CT adduct, Ph(3)PSe(p-ClC(6)H(4))I, which has a T-shaped geometry at selenium (10-Se-3). By contrast, the reaction of (p-FC(6)H(4))SeI with Ph(3)P does not form an adduct, but results in the formation of Ph(3)PI(2) and (p-FC(6)H(4))(2)Se(2).

  13. 76 FR 27287 - Port Access Route Study: In the Bering Strait; Extension of Comment Period

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-11

    ... of Study and request for comments for the Port Access Route Study: In the Bering Strait (75 FR 68568..., 2008, issue of the Federal Register (73 FR 3316). This notice is issued under authority of 33 U.S.C... SECURITY Coast Guard 33 CFR Part 167 Port Access Route Study: In the Bering Strait; Extension of...

  14. The study of structural color filter based on periodic nanohole arrays for bio-detection

    NASA Astrophysics Data System (ADS)

    Kim, Seunguk; Shin, Jeonghee; Yoo, Seungjun; Kim, Samhwan; Jeon, Byoungok; Moon, Cheil; Jang, Jae-Eun

    2015-07-01

    A nanostructure which induces localized surface plasmon resonance (LSPR) can be utilized in visible light and near infrared (NIR) regions and it shows promising features as a bio-detector because LSPR state is changed easily by different bio-related materials. Owing to transparent property of many biomolecules as well as diluted states in base solutions, it is hard to distinguish each other by eye or microscope analysis. However, difference in molecular structure and composition makes difference in optical characteristics such as a refractive index or a dielectric constant. Therefore, our LSPR-based nanohole array structure which has high sensitivity to detect small changes in optical characteristics can be a great candidate for a bio detector. Here, we fabricated structural color filters (SCFs) to detect wavelength shifts for several biomolecules and optimized the nanohole array structures for high sensitivity. Periodic nanohole arrays were designed to present resonance peaks in visible light region for optical analysis and fabricated in Au or Al thin film layer. The spectral shifts were detected caused by biomolecules.

  15. ''Inelastic Neutron Scattering and Periodic Density Functional Studies of Hydrogen Bonded Structures''

    SciTech Connect

    Bruce S. Hudson

    2004-10-27

    This project is directed at a fundamental understanding of hydrogen bonding, the primary reversible interaction leading to defined geometries, networks and supramolecular aggregates formed by organic molecules. Hydrogen bonding is still not sufficiently well understood that the geometry of such supramolecular aggregates can be predicted. In the approach taken existing quantum chemical methods capable of treating periodic solids have been applied to hydrogen bonded systems of known structure. The equilibrium geometry for the given space group and packing arrangement were computed and compared to that observed. The second derivatives and normal modes of vibration will then be computed and from this inelastic neutron scattering (INS) spectra were computed using the normal mode eigenvectors to compute spectral intensities. Appropriate inclusion of spectrometer line width and shape was made in the simulation and overtones, combinations and phonon wings were be included. These computed spectra were then compared with experimental results obtained for low-temperature polycrystalline samples at INS spectrometers at several facilities. This procedure validates the computational methodology for describing these systems including both static and dynamic aspects of the material. The resulting description can be used to evaluate the relative free energies of two or more proposed structures and so ultimately to be able to predict which structure will be most stable for a given building block.

  16. Timing Studies of X Persei and the Discovery of Its Transient Quasi-periodic Oscillation Feature

    NASA Technical Reports Server (NTRS)

    Acuner, Z.; Inam,S. C.; Sahiner, S.; Serim, M. M.; Baykal, A.; Swank, J.

    2014-01-01

    We present a timing analysis of X Persei (X Per) using observations made between 1998 and 2010 with the Proportional Counter Array (PCA) onboard the Rossi X-ray Timing Explorer (RXTE) and with the INTEGRAL Soft Gamma-Ray Imager (ISGRI). All pulse arrival times obtained from the RXTE-PCA observations are phase-connected and a timing solution is obtained using these arrival times. We update the long-term pulse frequency history of the source by measuring its pulse frequencies using RXTE-PCA and ISGRI data. From the RXTEPCA data, the relation between the frequency derivative and X-ray flux suggests accretion via the companion's stellar wind. However, the detection of a transient quasi-periodic oscillation feature, peaking at approximately 0.2 Hz, suggests the existence of an accretion disc. We find that doublebreak models fit the average power spectra well, which suggests that the source has at least two different accretion flow components dominating the overall flow. From the power spectrum of frequency derivatives, we measure a power-law index of approximately - 1, which implies that, on short time-scales, disc accretion dominates over noise, while on time-scales longer than the viscous time-scales, the noise dominates. From pulse profiles, we find a correlation between the pulse fraction and the count rate of the source.

  17. Laboratory study of nitrification, denitrification and anammox processes in membrane bioreactors considering periodic aeration.

    PubMed

    Abbassi, Rouzbeh; Yadav, Asheesh Kumar; Huang, Shan; Jaffé, Peter R

    2014-09-01

    The possibility of using membrane bioreactors (MBRs) in simultaneous nitrification-anammox-denitrification (SNAD) by considering periodic aeration cycles was investigated. Two separate reactors were operated to investigate the effect of different anammox biomass in the presence of nitrifying and denitrifying biomass on the final nitrogen removal efficiency. The results illustrated that the reactor with higher anammox biomass was more robust to oxygen cycling. Around 98% Total Nitrogen (TN) and 83% Total Organic Carbon (TOC) removal efficiencies were observed by applying one hour aeration over a four-hour cycle. Decreasing the aeration time to 30, 15, and 2 min during a four-hour cycle affected the final TN removal efficiencies. However, the effect of decreasing aeration on the TN removal efficiencies in the reactor with higher anammox biomass was much lower compared to the regular reactor. The nitrous oxide (N2O) emission was a function of aeration as well, and was lower in the reactor with higher anammox biomass. The results of q-PCR analysis confirmed the simultaneous co-existence of nitrifiers, anammox, and denitrifiers in both of the reactors. To simulate the TN removal in these reactors as a function of the aeration time, a new model, based on first order reaction kinetics for both denitrification and anammox was developed and yielded a good agreement with the experimental observations.

  18. Numerical study on sequential period-doubling bifurcations of graphene wrinkles on a soft substrate

    NASA Astrophysics Data System (ADS)

    Jung, Jong Hyun; Bae, Jaehyun; Moon, Myoung-Woon; Kim, Kyung-Suk; Ihm, Jisoon

    2015-11-01

    A compressed stiff film on a soft substrate may exhibit wrinkles and, under increased compressive strain, post-buckling instabilities as well. We numerically analyze wrinkling behaviors of graphene attached on a polydimethylsiloxane (PDMS) substrate under lateral compression. The finite element method is used to simulate the equilibrium shape of the wrinkles as a function of compressive strain. Two-dimensional stretching and bending properties of graphene are obtained by density functional theory analysis, which are then converted to equivalent elastic properties of a continuum film with finite effective thickness. The PDMS is described using an Ogden or a neo-Hookean material model. Wrinkles first appear at extremely small strain. As the lateral compression increases, due to the nonlinear elasticity of the PDMS, sequential period-doubling bifurcations of the wrinkle mode are activated until the bifurcation stops and the film folds. We show that the bifurcations are consequences of a delicate balance between the deformations of the film and the substrate to minimize the total energy.

  19. Experimental study of outdoor propagation of spherically speading periodic acoustic waves of finite amplitude

    NASA Technical Reports Server (NTRS)

    Theobald, M. A.

    1977-01-01

    The outdoor propagation of spherically spreading sound waves of finite amplitude was investigated. The main purpose of the experiments was to determine the extent to which the outdoor environment, mainly random inhomogeneity of the medium, affects finite amplitude propagation. Periodic sources with fundamental frequencies in the range 6 to 8 kHz and source levels SPLlm from 140 to 149 dB were used. The sources were an array of 7 to 10 horn drivers and a siren. The propagation path was vertical and parallel to an 85 m tower, whose elevator carried the traveling microphone. The general conclusions drawn from the experimental results were as follows. The inhomogeneities caused significant fluctuations in the instantaneous acoustic signal, but with sufficient time averaging of the measured harmonic levels, the results were comparable to results expected for propagation in a quiet medium. Propagation data for the fundamental of the siren approached within 1 dB of the weak shock saturation levels. Extra attenuation on the order of 8 dB was observed. The measurements generally confirmed the predictions of several theoretical models. The maximum propagation distance was 36 m. The narrowbeam arrays were much weaker sources. Nonlinear propagation distortion was produced, but the maximum value of extra attenuation measured was 1.5 dB. The maximum propagation distance was 76 m. The behavior of the asymetric waveforms received in one experiment qualitatively suggested that beam type diffraction effects were present. The role of diffraction of high intensity sound waves in radiation from a single horn was briefly investigated.

  20. Periodic limb movements during sleep and prevalent hypertension in the multi-ethnic study of atherosclerosis.

    PubMed

    Koo, Brian B; Sillau, Stefan; Dean, Dennis A; Lutsey, Pamela L; Redline, Susan

    2015-01-01

    Periodic limb movements during sleep (PLMS) are associated with immediate increases in blood pressure. Both PLMS and hypertension have different distributions across racial/ethnic groups. We sought to determine whether PLMS is associated with hypertension among various racial/ethnic groups. A total of 1740 men and women underwent measurement of blood pressure and polysomnography with quantification of PLMS. Hypertension was defined as systolic blood pressure (SBP) ≥140, diastolic BP ≥90, or taking antihypertensive medication. For those taking antihypertensives, an estimated pretreatment SBP value was derived based on observed SBP and medication type/dose. Measures of PLMS, PLMS index, and PLMS arousal index were the main explanatory variables. Hypertension and SBP were modeled with logistic and multivariable regression adjusted for age, sex, body mass index, cardiovascular risk factors, lifestyle/habitual factors, apnea-hypopnea index, and race/ethnicity. In the overall cohort, prevalent hypertension was modestly associated with PLMS index (10 U; odds ratio, 1.05; 95% confidence interval, 1.00-1.10) and PLMS arousal index (1 U; 1.05; 1.01-1.09) after adjusting for confounders. Association in the overall cohort was influenced by large effect sizes in blacks, in whom the odds of prevalent hypertension increased by 21% (1%-45%) for 10 U PLMS index increase and 20% (2%-42%) for 1-U PLMS arousal index increase. In blacks, every 1-U PLMS arousal index increase was associated with SBP 1.01 mm Hg higher (1.01; 0.04-1.98). Associations between PLMS and blood pressure outcomes were also suggested among Chinese-Americans but not in whites or Hispanics. In a multiethnic cohort of community-dwelling men and women, prevalent hypertension and SBP are associated with PLMS frequency in blacks.

  1. Traditional beliefs and practices in the postpartum period in Fujian Province, China: a qualitative study

    PubMed Central

    Raven, Joanna H; Chen, Qiyan; Tolhurst, Rachel J; Garner, Paul

    2007-01-01

    Background Zuo yuezi is the month postpartum in China associated with a variety of traditional beliefs and practices. We explored the current status of zuo yuezi from social, cultural and western medical perspectives. Methods We interviewed family members (36) and health workers (8) in Fujian Province, selecting one rural and one rapidly developing urban county. We asked about their traditional beliefs and their behaviour postpartum. We used a framework approach to identify main themes. We categorised reported behaviour against their probable effects on health, drawing on Western standards. Results Respondents reported that zuo yuezi was commonly practiced in urban and rural families to help the mother regain her strength and protect her future health. Zuo yuezi included: dietary precautions, such as eating more food and avoiding cold food; behavioural precautions, such as staying inside the home, avoiding housework and limiting visitors; hygiene precautions, such as restricting bathing and dental hygiene; and practices associated with infant feeding, including supplementary feeding and giving honeysuckle herb to the infant. Respondents reported that the main reasons for adhering to these practices were respect for tradition, and following the advice of elders. Categorised against Western medical standards, several zuo yuezi practices are beneficial, including eating more, eating protein rich food, avoiding housework, and daily vulval and perineal hygiene. A few are potentially harmful, including giving honeysuckle herb, and avoiding dental hygiene. Some women reported giving infants supplementary feeds, although zuo yuezi emphasises breast feeding. Conclusion Zuo yuezi is an important ritual in Fujian. In medical terms, most practices are beneficial, and could be used by health staff to promote health in this period. Further research on reported potentially harmful practices, such as supplements to breast feeding, is needed. PMID:17584930

  2. Aerosol Indirect Effect Studies at Southern Great Plains During the May 2003 Intensive Operations Period

    NASA Technical Reports Server (NTRS)

    Feingold, Graham; Furrer, Reinhard; Pilewskie, Peter; Remer, Lorraine A.; Min, Qilong; Jonsson, Haflidi

    2006-01-01

    During May 2003 the Department of Energy's Atmospheric Radiation Measurement Program conducted an Intensive Operations Period (IOP) to measure the radiative effects of aerosol and clouds. A suite of both in situ and remote sensing measurements were available to measure aerosol and cloud parameters. This paper has three main goals: First, it focuses on comparison between in situ retrievals of the radiatively important drop effective radius r(sub e) and various satellite, airborne, and surface remote sensing retrievals of the same parameter. On 17 May 2003, there was a fortuitous, near-simultaneous sampling of a stratus cloud by five different methods. The retrievals of r(sub e) agree with one another to within approx.20%, which is approximately the error estimate for most methods. Second, a methodology for deriving a best estimate of r(sub e) from these different instruments, with their different physical properties and sampling volumes, is proposed and applied to the 17 May event. Third, the paper examines the response of r(sub e) to changes in aerosol on 3 days during the experiment and examines the consistency of remote sensing and in situ measurements of the effect of aerosol on r(sub e). It is shown that in spite of the generally good agreement in derived r(sub e), the magnitude of the response of r(sub e), to changes in aerosol is quite sensitive to the method of retrieving r(sub e) and to the aerosol proxy for cloud condensation nuclei. Nonphysical responses are sometimes noted, and it is suggested that further work needs to be done to refine these techniques.

  3. Work Sampling Study of an Engineering Professor during a Regular Contract Period

    ERIC Educational Resources Information Center

    Brink, Jan; McDonald, Dale B.

    2015-01-01

    Work sampling is a technique that has been employed in industry and fields such as healthcare for some time. It is a powerful technique, and an alternative to conventional stop watch time studies, used by industrial engineers to focus upon random work sampling observations. This study applies work sampling to the duties performed by an individual…

  4. Formation of [Ni(III)(κ(1)-S2CH)(P(o-C6H3-3-SiMe3-2-S)3)]- via CS2 insertion into nickel(III) hydride containing [Ni(III)(H)(P(o-C6H3-3-SiMe3-2-S)3)]-.

    PubMed

    Lai, Kuan-Ting; Ho, Wei-Chieh; Chiou, Tzung-Wen; Liaw, Wen-Feng

    2013-04-15

    Insertion of CS2 into the thermally unstable nickel(III) hydride [PPN][Ni(H)(P(o-C6H3-3-SiMe3-2-S)3)] (1), freshly prepared from the reaction of [PPN][Ni(OC6H5)P(C6H3-3-SiMe3-2-S)3] and 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (HBpin; pin = OCMe2CMe2O) in tetrahydrofuran at -80 °C via a metathesis reaction, readily affords [PPN][Ni(III)(κ(1)-S2CH)(P(o-C6H3-3-SiMe3-2-S)3)] (2) featuring a κ(1)-S2CH moiety. PMID:23541028

  5. Segregation of Incomplete Achromatopsia and Alopecia Due to PDE6H and LPAR6 Variants in a Consanguineous Family from Pakistan.

    PubMed

    Pedurupillay, Christeen Ramane J; Landsend, Erlend Christoffer Sommer; Vigeland, Magnus Dehli; Ansar, Muhammad; Frengen, Eirik; Misceo, Doriana; Strømme, Petter

    2016-01-01

    We report on two brothers with visual impairment, and non-syndromic alopecia in the elder proband. The parents were first-degree Pakistani cousins. Whole exome sequencing of the elder brother and parents, followed by Sanger sequencing of all four family members, led to the identification of the variants responsible for the two phenotypes. One variant was a homozygous nonsense variant in the inhibitory subunit of the cone-specific cGMP phosphodiesterase gene, PDE6H:c.35C>G (p.Ser12*). PDE6H is expressed in the cones of the retina, which are involved in perception of color vision. This is the second report of a homozygous PDE6H:c.35C>G variant causing incomplete achromatopsia (OMIM 610024), thus strongly supporting the hypothesis that loss-of-function variants in PDE6H cause this visual deficiency phenotype. The second variant was a homozygous missense substitution in the lysophosphatidic acid receptor 6, LPAR6:c.188A>T (p.Asp63Val). LPAR6 acts as a G-protein-coupled receptor involved in hair growth. Biallelic loss-of-function variants in LPAR6 cause hypotrichosis type 8 (OMIM 278150), with or without woolly hair, a form of non-syndromic alopecia. Biallelic LPAR6:c.188A>T was previously described in five families from Pakistan. PMID:27472364

  6. Effect of Crystal Defects on Minority Carrier Diffusion Length in 6H SiC Measured Using the Electron Beam Induced Current Method

    NASA Technical Reports Server (NTRS)

    Tabib-Azar, Massood

    1997-01-01

    We report values of minority carrier diffusion length in n-type 6H SiC measured using a planar Electron Beam Induced Current (EBIC) method. Values of hole diffusion length in defect free regions of n-type 6H SiC, with a doping concentration of 1.7El7 1/cu cm, ranged from 1.46 microns to 0.68 microns. We next introduce a novel variation of the planar method used above. This 'planar mapping' technique measured diffusion length along a linescan creating a map of diffusion length versus position. This map is then overlaid onto the EBIC image of the corresponding linescan, allowing direct visualization of the effect of defects on minority carrier diffusion length. Measurements of the above n-type 6H SiC resulted in values of hole diffusion length ranging from 1.2 micron in defect free regions to below 0.1 gm at the center of large defects. In addition, measurements on p-type 6H SiC resulted in electron diffusion lengths ranging from 1.42 micron to 0.8 micron.

  7. Synthesis of furfural from xylose, xylan, and biomass using AlCl3·6H2O in biphasic media via xylose isomerization to xylulose.

    PubMed

    Yang, Yu; Hu, Chang-Wei; Abu-Omar, Mahdi M

    2012-02-13

    Furfural was prepared in high yields (75 %) from the reaction of xylose in a water-tetrahydrofuran biphasic medium containing AlCl(3)·6H2O and NaCl under microwave heating at 140 °C. The reaction profile revealed the formation of xylulose as an intermediate en route to the dehydration product (furfural). The reaction under these conditions reached completion in 45 min. The aqueous phase containing AlCl(3)·6H(2)O and NaCl could be recycled multiple times (>5) without any loss of activity or selectivity for furfural. Extension of this biphasic reaction system to include xylan as the starting material afforded furfural in 64 % yield. The use of corn stover, pinewood, switchgrass, and poplar gave furfural in 55, 38, 56, and 64 % yield, respectively, at 160 °C. Even though AlCl(3)·6H(2)O did not affect the conversion of crystalline cellulose, moderate yields of the by-product 5-hydroxymethylfurfural (HMF) were noted. The highest HMF yield of 42 % was obtained from pinewood. The coproduction of HMF and furfural from biomass was attributed to the weakening of the cellulose network in the biomass, as a result of hemicellulose hydrolysis. The multifunctional capacity of AlCl(3)·6H(2)O (hemicellulose hydrolysis, xylose isomerization, and xylulose dehydration) in combination with its ease of recyclability make it an attractive candidate/catalyst for the selective synthesis of furfural from various biomass feedstocks.

  8. Step Free Surface Heteroepitaxy of 3C-SiC Layers on Patterned 4H/6H-SiC Mesas and Cantilevers

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Powell, J. Anthony; Trunek, Andrew J.; Spry, David J.

    2003-01-01

    Most SiC devices are implemented in homoepitaxial films grown on 4H/6H-SiC wafers with surfaces 3 degrees to 8 degrees off-axis from the (0001) basal plane. This approach has not prevented many substrate crystal defects from propagating into SiC epilayers, and does not permit the realization of SiC heteropolytype devices. This presentation describes recent advances in SiC epitaxial growth that begun to overcome the above shortcomings for arrays of mesas patterned into on-axis 4H/6H-SiC wafers. First, we demonstrated that atomic-scale surface steps can be completely eliminated from 4H/6H-SiC mesas via on-axis homoepitaxial step-flow growth, forming (0001) basal plane surfaces (up to 0.4 mm x 0.4 mm) for larger than previously thought possible. Step-free surface areas were then extended by growth fo thin lateral cantilevers from the mesa tops. These lateral cantilevers enabled substrate defects to be reduced and relocated in homoepitaxial films in a manner not possible with off-axis SiC growth. Finally, growth of vastly improved 3C-SiC heterofilms was achieved on 4H/6H-SiC mesas using the recently develop step-free surface heteroepitaxy process. These epitaxial growth developments should enable improved homojunction and heterojunction silicon carbide prototype devices.

  9. Ring-opening polymerization of epoxidized soybean oil catalyzed by the superacid, Fluroantimonic acid hexahydrate (HSbF6-6H2O)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ring-opening polymerization of epoxidized soybean oil (ESO) catalyzed by the super acid, fluroantimonic acid hexahydrate (HSbF6-6H2O), in ethyl acetate was conducted. The resulting polymers, SA-RPESO, were characterized using infrared spectroscopy, differential scanning calorimetry, thermogravimetri...

  10. Hexagonal phase-pure wide band gap ɛ-Ga2O3 films grown on 6H-SiC substrates by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Xia, Xiaochuan; Chen, Yuanpeng; Feng, Qiuju; Liang, Hongwei; Tao, Pengcheng; Xu, Mengxiang; Du, Guotong

    2016-05-01

    In this paper, hexagonal structure phase-pure wide-band gap ɛ-Ga2O3 films were grown by metal organic chemical vapor deposition on 6H-SiC substrates. The ɛ-Ga2O3 films with good crystal quality were verified by high-resolution X-ray diffraction. The out-of-plane epitaxial relationship between ɛ-Ga2O3 films and 6H-SiC substrates is confirmed to be ɛ-Ga2O3 (0001)//6H-SiC (0001), and the in-plane epitaxial relationship is also confirmed to be ɛ-Ga2O3 ⟨ 11 2 ¯ 0 ⟩//6H-SiC ⟨ 11 2 ¯ 0 ⟩. The SEM and AFM images show that the ɛ-Ga2O3 films are uniform and flat. The ɛ-Ga2O3 films are thermally stable up to approximately 800 °C and begin to transform into β-phase Ga2O3 at 850 °C. Then, they are completely converted to β-Ga2O3 films under 900 °C. The high-quality ɛ-Ga2O3 films with hexagonal structure have potential application in the optoelectronic field.

  11. Segregation of Incomplete Achromatopsia and Alopecia Due to PDE6H and LPAR6 Variants in a Consanguineous Family from Pakistan

    PubMed Central

    Pedurupillay, Christeen Ramane J.; Landsend, Erlend Christoffer Sommer; Vigeland, Magnus Dehli; Ansar, Muhammad; Frengen, Eirik; Misceo, Doriana; Strømme, Petter

    2016-01-01

    We report on two brothers with visual impairment, and non-syndromic alopecia in the elder proband. The parents were first-degree Pakistani cousins. Whole exome sequencing of the elder brother and parents, followed by Sanger sequencing of all four family members, led to the identification of the variants responsible for the two phenotypes. One variant was a homozygous nonsense variant in the inhibitory subunit of the cone-specific cGMP phosphodiesterase gene, PDE6H:c.35C>G (p.Ser12*). PDE6H is expressed in the cones of the retina, which are involved in perception of color vision. This is the second report of a homozygous PDE6H:c.35C>G variant causing incomplete achromatopsia (OMIM 610024), thus strongly supporting the hypothesis that loss-of-function variants in PDE6H cause this visual deficiency phenotype. The second variant was a homozygous missense substitution in the lysophosphatidic acid receptor 6, LPAR6:c.188A>T (p.Asp63Val). LPAR6 acts as a G-protein-coupled receptor involved in hair growth. Biallelic loss-of-function variants in LPAR6 cause hypotrichosis type 8 (OMIM 278150), with or without woolly hair, a form of non-syndromic alopecia. Biallelic LPAR6:c.188A>T was previously described in five families from Pakistan. PMID:27472364

  12. Cryptolepine derivative-6h inhibits liver fibrosis in TGF-β1-induced HSC-T6 cells by targeting the Shh pathway.

    PubMed

    He, Ying-Hua; Li, Zeng; Ni, Ming-Ming; Zhang, Xing-Yan; Li, Ming-Fang; Meng, Xiao-Ming; Huang, Cheng; Li, Jun

    2016-09-01

    Liver fibrosis is a worldwide problem with a significant morbidity and mortality. Cryptolepis sanguinolenta (family Periplocaceae) is widely used in West African countries for the treatment of malaria, as well as for some other diseases. However, the role of C. sanguinolenta in hepatic fibrosis is still unknown. It has been reported that Methyl-CpG binding protein 2 (MeCP2) had a high expression in liver fibrosis and played a central role in its pathobiology. Interestingly, we found that a cryptolepine derivative (HZ-6h) could inhibit liver fibrosis by reducing MeCP2 expression, as evidenced by the dramatic downregulation of α-smooth muscle actin (α-SMA) and type I collagen alpha-1 (Col1α1) in protein levels in vitro. Meanwhile, we also found that HZ-6h could reduce the cell viability and promote apoptosis of hepatic stellate cells (HSCs) treated with transforming growth factor beta 1(TGF-β1). Then, we investigated the potential molecular mechanisms and found that HZ-6h blocked Shh signaling in HSC-T6 cells, resulting in the decreased protein expression of Patched-1 (PTCH-1), Sonic hedgehog (Shh), and glioma-associated oncogene homolog 1 (GLI1). In short, these results indicate that HZ-6h inhibits liver fibrosis by downregulating MeCP2 through the Shh pathway in TGF-β1-induced HSC-T6 cells. PMID:27295431

  13. Structure activity optimization of 6H-pyrrolo[2,3-e][1,2,4]triazolo[4,3-a]pyrazines as Jak1 kinase inhibitors.

    PubMed

    Friedman, Michael; Frank, Kristine E; Aguirre, Ana; Argiriadi, Maria A; Davis, Heather; Edmunds, Jeremy J; George, Dawn M; George, Jonathan S; Goedken, Eric; Fiamengo, Bryan; Hyland, Deborah; Li, Bin; Murtaza, Anwar; Morytko, Michael; Somal, Gagandeep; Stewart, Kent; Tarcsa, Edit; Van Epps, Stacy; Voss, Jeffrey; Wang, Lu; Woller, Kevin; Wishart, Neil

    2015-10-15

    Previous work investigating tricyclic pyrrolopyrazines as kinase cores led to the discovery that 1-cyclohexyl-6H-pyrrolo[2,3-e][1,2,4]triazolo[4,3-a]pyrazine (12) had Jak inhibitory activity. Herein we describe our initial efforts to develop orally bioavailable analogs of 12 with improved selectivity of Jak1 over Jak2. PMID:26372653

  14. Fluoroantimonic acid hexahydrate (HSbF6-6H2O) catalysis: The ring-opening polymerization of epoxidized soybean oil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ring-opening polymerization of epoxidized soybean oil (ESO) catalyzed by a super acid, fluroantimonic acid hexahydrate (HSbF6-6H2O), in ethyl acetate was conducted in an effort to develop useful biodegradable polymers. The resulting polymerized ESO (SA-RPESO) were characterized by using infrared (IR...

  15. Modulation of interhemispheric inhibition by volitional motor activity: an ipsilateral silent period study.

    PubMed

    Giovannelli, Fabio; Borgheresi, Alessandra; Balestrieri, Fabrizio; Zaccara, Gaetano; Viggiano, Maria Pia; Cincotta, Massimo; Ziemann, Ulf

    2009-11-15

    Brief interruption of voluntary EMG in a hand muscle by focal transcranial magnetic stimulation (TMS) of the ipsilateral primary motor cortex (M1), the so-called ipsilateral silent period (ISP), is a measure of interhemispheric motor inhibition. However, little is known about how volitional motor activity would modulate the ISP. Here we tested in 30 healthy adults to what extent and under what conditions voluntary activation of the stimulated right M1 by moving the left hand strengthens interhemispheric inhibition as indexed by an enhancement of the ISP area in the maximally contracting right first dorsal interosseous (FDI). Left index finger abduction, already at low levels of contraction, significantly enhanced the ISP compared to left hand at rest. Even imagination of left index finger movement enhanced the ISP compared to rest or mental calculation. This enhancement occurred in the absence of motor-evoked potential amplitude modulation in the left FDI, thus excluding a non-specific contribution from an increase in right M1 corticospinal excitability. Contraction of the left extensor indicis, but not contraction of more proximal left upper limb or left or right lower limb muscles also enhanced the ISP. A reaction time experiment showed that the ISP enhancement developed at a late stage of movement preparation just before or at movement onset. Interhemispheric inhibition of the motor-evoked potential as tested by a bifocal paired-pulse TMS protocol and thought to be mediated via a neuronal circuit different to the ISP was not enhanced when tested under identical motor task conditions. Finally, ISP enhancement by contraction of the left FDI correlated inversely with EMG mirror activity in the right FDI during phasic abductions of the left index finger. Our findings strongly suggest that voluntary M1 activation by real or imagined movement of the contralateral hand increases interhemispheric motor inhibition of the opposite M1. This phenomenon shows substantial

  16. Paleointensity during periods of rapid reversal: A Case Study from the Middle Jurassic Shamrock Batholith, Nevada

    NASA Astrophysics Data System (ADS)

    Sprain, C. J.; Feinberg, J. M.; Geissman, J. W.; Strauss, B.; Brown, M. C.

    2012-12-01

    Paleointensity is one of the least determined parameters in geomagnetism, yet this information has the potential to address many fundamental geophysical problems that bear on the evolution of the Earth's core and lower mantle. Here we further test the inverse relationship between geomagnetic polarity reversal rate and paleointensity, as proposed by Tauxe and Staudigel (2004) and Tarduno & Cottrell (2005). We report paleointensity results determined using both the modified Coe method (Coe, 1967) and IZZI protocol (Tauxe and Staudigel, 2004) on medium grained, hornblende-biotite granite of the Shamrock batholith in the southern Singatse Range, near Yerington, Nevada. This batholith was emplaced at ca.165.8+/- 0.4 Ma (zircon U-Pb, Dilles & Wright, 1988) during a period of unusually high reversal frequency (~10/Myr) in the Middle Jurassic. Remanence in the Shamrock batholith is held primarily by exsolved submicron magnetite inclusions in plagioclase; the laboratory unblocking temperature range for the very well-defined TRM is narrow, between about 540 and 575°C. Two sets of quality control criteria were used to assess the data. The first set yielded a 87% success rate and required MAD <10°, β <15%, DRATS <22%, MD checks <15% and fvds >30%, while the second set was more stringent (20% success rate) with MAD <5°, β <10%, DRATS <10%, MD checks <10% and fvds >40%. Mean paleointensity values for the Shamrock batholith using the 'loose' and 'strict' quality criteria are 31.4 ± 4.2 μT (N = 13) and 29.7 ± 3.1 μT (N = 3), respectively. After correction for both remanence anisotropy and cooling rate the mean values are15.9 ± 1.7 μT and 14.8 ± 0.3 μT, respectively. The uncorrected and corrected paleointensity values for the 'strict' estimates yield mean virtual dipole moments of 56.1 ± 5.9 ZAm2 and 27.9 ± 0.6 ZAm2, respectively. The uncorrected value is consistent with the VDM results reported by Tarduno & Cottrell (2005) for plagioclase grains isolated from ca

  17. What can we learn about baryon-baryon interaction from hypernuclei {sub {lambda}}{sup 6}H and {sub {lambda}}{sup 8}H?

    SciTech Connect

    Majling, L. Gmuca, S.

    2007-09-15

    At the LHE JINR, an original approach to hypernuclear experiments was elaborated to produce relativistic hypernuclei. The production cross sections and lifetimes, {tau}, of {sub {lambda}}{sup 3}H and {sub {lambda}}{sup 4}H were measured successfully. The results of recent experiments on {sup 5}H and {sup 7}H nuclei suggest that the hypernucleus {sub {lambda}}{sup 6}H might be stable and that this may be the case even for {sub {lambda}}{sup 8}H. The unique quality of the spectrometer SPHERE may be used to identify unambiguously the isotopes of hyperhydrogen-through their pionic decay {sub {lambda}}{sup A}H {sup {yields}} {pi}{sup -} + {sup A}He-including the new hypernuclei {sub {lambda}}{sup 6}H and {sub {lambda}}{sup 8}H with extreme values of N/Z of 4 and 6, respectively. The confirmation of the very existence of these neutron-rich hypernuclei would be a strong motivation to search for their spectra in strangeness and double-charge-exchange reactions (K{sub stop}{sup -}, {pi}{sup +}) at FINUDA or ({pi}{sup -}, K{sup +}) at J-PARC. It is very probable that, similarly as in {sub {lambda}}{sup 4}H, there is a low-lying state 1{sup +} also in {sub {lambda}}{sup 6}H and {sub {lambda}}{sup 8}H. If their electromagnetic width (M1) is small enough, we could see two different values of {tau} for {sub {lambda}}{sup 6}H and/or {sub {lambda}}{sup 8}H. We investigate the spacings of the 1{sup +} and 0{sup +} states of {sub {lambda}}{sup 4}H, {sub {lambda}}{sup 6}H, and {sub {lambda}}{sup 8}H. The understanding of the structure of isospin asymmetric systems plays a key role in the description of systems as diverse as neutron-rich nuclei and neutron matter.

  18. Structural and photophysical properties of HPPCO (4-hydroxy-5-phenyl-6H-pyrido[3,2,1-jk]carbazol-6-one) derivatives

    NASA Astrophysics Data System (ADS)

    Jeong, Yong-Kwang; Kim, Min-Ah; Lee, Hyo-Sung; Kim, Jong-Moon; Lee, Sung Woo; Kang, Jun-Gill

    2015-01-01

    Proton-substitution effects of 4-hydroxy-5-phenyl-6H-pyrido[3,2,1-jk]carbazol-6-one (HPPCO) on structural and photophysical properties were presented. HPPCO crystallized in the orthorhombic space group Pbca with an intermolecular hydrogen bonding between OH and oxygen atom of the carbonyl. The proton-substituted derivatives, 6-oxo-5-phenyl-6H-pyrido[3,2,1-jk]carbazol-4-yl acetate (OPPCA) and 6-oxo-5-phenyl-6H-pyrido[3,2,1-jk]carbazol-4-yl benzoate (OPPCB), crystallized in the monoclinic P21/c space group. For OPPCA and OPPCB, a weak interaction between carbonyl oxygen atom in the substituted group and carbon atom in the fused ring was responsible for three-dimensional arrangements. In addition, 6-oxo-5-phenyl-6H-pyrido[3,2,1-jk]carbazol-4-yl furan-2-carboxylate (OPPCF), and 6-oxo-5-phenyl-6H-pyrido[3,2,1-jk]carbazol-4-yl naphthoate (OPPCN) were also synthesized. HPPCO and the four derivatives excited by ultraviolet (UV) light produced blue emission. Proton substitution of the OH group significantly increased the radiative transitions and moderately decreased the non-radiative transitions. Consequently the luminescence quantum yields of the derivatives enhanced more than 4.6-fold, no matter what the groups were substituted. Structural and optical properties were further determined using density functional theory (DFT) and ZINDO calculations. The planar structure of the pyridocarbazole-fused ring resulted in π → π* electronic transitions within the main frame, with an additional transition from the n(O) of carbonyl to the π* of the main frame. The three excited states that arose from these transitions were responsible for the blue luminescence.

  19. A Center for Environmental Communication and Education Studies. Periodic Report: 1968-1982.

    ERIC Educational Resources Information Center

    Wisconsin Univ., Madison. Center for Environmental Communications and Education Studies.

    This report summarizes the role of the University of Wisconsin-Madison's Center for Environmental Communication and Education Studies (CECES) in helping to foster teaching, research, and public service programs. Included in the first section are program highlights (1968-1982), Center organization, and lists of Center personnel (executive…

  20. Ethical Practices in Journal Publishing: A Study of Library and Information Science Periodicals.

    ERIC Educational Resources Information Center

    Serebnick, Judith; Harter, Stephen P.

    1990-01-01

    Describes a study that examined generally accepted ethical norms in library and information science journals regarding practices such as the multiple publication of the same article, plagiarism, and cronyism. The responses of editors to action scenarios focused on ethical behavior are discussed and conclusions are drawn about the ethical…

  1. Study of the Instructional Effectiveness of Last Period Middle School Classes.

    ERIC Educational Resources Information Center

    Brooks, Jennifer Giddings; Tees, Sandra

    To facilitate cost effective bus schedules, middle school classes begin one hour later than high school classes in the Fort Worth Independent School District, Texas. This study investigated whether middle school students were adversely affected, in terms of grades and classroom performance, by having the class day extended to 4 p.m. High schools…

  2. Evaluation and developmental studies of possible active seismic experiments during the post-Apollo period

    NASA Technical Reports Server (NTRS)

    Kovach, R. L.

    1974-01-01

    Seismic velocity studies pertinent to the lunar crust and mantle are briefly summarized. The compressional and shear wave velocities in loose aggregates are discussed along with the effects of temperature on seismic velocity in compacted powders. Abstracts of papers concerning the lunar structure are included.

  3. An Analytical Study on Periodically Changing Flow Cells in Groundwater Basins

    NASA Astrophysics Data System (ADS)

    Jiang, X.; Zhao, K. Y.; Wang, J. Z.; Wan, L.; Wang, H.

    2014-12-01

    Current understanding on basin-scale groundwater flow is mainly based on Tóth's (1962, 1963) pioneering study, which assumed that water table is a subdued replica of topography and the annual mean water table controls the pattern of groundwater flow. In fact, water table is driven by dynamic forcing and changes with time. This study modifies the conceptual model of basin-scale groundwater flow by taking the fluctuating water-table into account. For both unit basin and complex basin, water table fluctuates throughout the basin cross-section except for at basin valleys. By the method of separation of variables, we derive the analytical solution of hydraulics head and stream function in the unit basin and the complex basin, and discuss the characteristics of the time-dependent flow cells. For the unit basin, the change in amplitude of hydraulic head fluctuation with depth is studied. For the complex basin, the time-dependent distribution of internal stagnation points is discussed. In addition, the relationship between flowing artesian zone and the fluctuating water-table is discussed. The results of the current study enhance our understanding on the transient nature of basin-scale groundwater flow.

  4. From Consciousness to Technology: The Implications of Wave Periodicity Research for Communication Studies.

    ERIC Educational Resources Information Center

    Cooper, Thomas W.

    Attempting to introduce a new viewpoint to communication studies, this speculative and philosophical paper posits technology as an "echo of consciousness." Section one examines technology as a manifestation of attitude, presenting the premise that technologies, consciousness, and systems are not separate components, but products of interacting…

  5. CBVE: A Study to Measure Its Effectiveness in Kentucky. Final Report. Interim Period 1.

    ERIC Educational Resources Information Center

    Vincent, Roger D.; Cobb, Robert A.

    An interim study was conducted in Kentucky to determine the effectiveness of Competency Based Vocational Education (CBVE) and to compare its effectiveness to that of traditional teaching methodologies. Research surveys of those directly involved in the implementation of CBVE were used to ascertain if CBVE is meeting its self-stated goals.…

  6. Studying Changes in Organizational Design and Effectiveness: Retrospective Event Histories and Periodic Assessments.

    ERIC Educational Resources Information Center

    Glick, William H.; And Others

    1990-01-01

    Describes assumptions, rationale, and trade-offs involved in designing the research methodology used in a longitudinal study of organizational change. Data were obtained from over 100 organizations through 4 interviews spaced 6 months apart with top managers. (53 references) (MLF)

  7. Sensitive periods differentiate processing of open- and closed-class words: an ERP study of bilinguals.

    PubMed

    Weber-Fox, C; Neville, H J

    2001-12-01

    The goal of this study was to test the hypothesis that neural processes for language are heterogeneous in their adaptations to maturation and experience. This study examined whether the neural processes for open- and closed-class words are differentially affected by delays in second-language immersion. In English, open-class words primarily convey referential meaning, whereas closed-class words are primarily related to grammatical information in sentence processing. Previous studies indicate that event-related brain potentials (ERPs) elicited by these word classes display nonidentical distributions and latencies, show different developmental time courses, and are differentially affected by early language experience in Deaf individuals. In this study, ERPs were recorded from 10 monolingual English speakers and 53 Chinese-English bilingual speakers who were grouped according to their age of immersion in English: 1-3, 4-6, 7-10, 11-13, and >15 years of age. Closed-class words elicited an N280 that was largest over left anterior electrode sites for all groups. However, the peak latency was later (>35 ms) in bilingual speakers immersed in English after 7 years of age. In contrast, the latencies and distributions of the N350 elicited by open-class words were similar in all groups. In addition, the N400, elicited by semantic anomalies (open-class words that violated semantic expectation), displayed increased peak latencies for only the later-learning bilingual speakers (>11 years). These results are consistent with the hypothesis that language subprocesses are differentially sensitive to the timing of second-language experience. PMID:11776369

  8. Sensitive periods differentiate processing of open- and closed-class words: an ERP study of bilinguals.

    PubMed

    Weber-Fox, C; Neville, H J

    2001-12-01

    The goal of this study was to test the hypothesis that neural processes for language are heterogeneous in their adaptations to maturation and experience. This study examined whether the neural processes for open- and closed-class words are differentially affected by delays in second-language immersion. In English, open-class words primarily convey referential meaning, whereas closed-class words are primarily related to grammatical information in sentence processing. Previous studies indicate that event-related brain potentials (ERPs) elicited by these word classes display nonidentical distributions and latencies, show different developmental time courses, and are differentially affected by early language experience in Deaf individuals. In this study, ERPs were recorded from 10 monolingual English speakers and 53 Chinese-English bilingual speakers who were grouped according to their age of immersion in English: 1-3, 4-6, 7-10, 11-13, and >15 years of age. Closed-class words elicited an N280 that was largest over left anterior electrode sites for all groups. However, the peak latency was later (>35 ms) in bilingual speakers immersed in English after 7 years of age. In contrast, the latencies and distributions of the N350 elicited by open-class words were similar in all groups. In addition, the N400, elicited by semantic anomalies (open-class words that violated semantic expectation), displayed increased peak latencies for only the later-learning bilingual speakers (>11 years). These results are consistent with the hypothesis that language subprocesses are differentially sensitive to the timing of second-language experience.

  9. Scheduled food hastens re-entrainment more than melatonin does after a 6-h phase advance of the light-dark cycle in rats.

    PubMed

    Ángeles-Castellanos, M; Amaya, J M; Salgado-Delgado, R; Buijs, R M; Escobar, C

    2011-08-01

    Circadian desynchrony occurs when individuals are exposed to abrupt phase shifts of the light-dark cycle, as in jet lag. For reducing symptoms and for speeding up resynchronization, several strategies have been suggested, including scheduled exercise, exposure to bright light, drugs, and especially exogenous melatonin administration. Restricted feeding schedules have shown to be powerful entraining signals for metabolic and hormonal daily cycles, as well as for clock genes in tissues and organs of the periphery. This study explored in a rat model of jet lag the contribution of exogenous melatonin or scheduled feeding on the re-entrainment speed of spontaneous general activity and core temperature after a 6-h phase advance of the light-dark cycle. In a first phase, the treatment was scheduled for 5 days prior to the phase shift, while in a second stage, the treatment was simultaneous with the phase advance of the light-dark cycle. Melatonin administration and especially scheduled feeding simultaneous with the phase shift improved significantly the re-entrainment speed. The evaluation of the free-running activity and temperature following the 5-day treatment proved that both exogenous melatonin and specially scheduled feeding accelerated re-entrainment of the SCN-driven general activity and core temperature, respectively, with 7, 5 days (p < 0.01) and 3, 3 days (p < 0.001). The present results show the relevance of feeding schedules as entraining signals for the circadian system and highlight the importance of using them as a strategy for preventing internal desynchrony.

  10. Photometric Studies of Three Neglected Short-period Contact Binaries GN Bootis, BL Leonis, and V1918 Cygni

    NASA Astrophysics Data System (ADS)

    Yang, Y.-G.; Qian, S.-B.; Dai, H.-F.

    2013-03-01

    We present new photometry for three short-period contact binaries, GN Boo, BL Leo, and V1918 Cyg, observed from 2008 December to 2012 April using several small telescopes in China. Photometric models were deduced from new observations using the updated Wilson-Devinney Code. The results show that GN Boo and BL Leo are W-type contact binaries, while V1918 Cyg is an A-type one. The mass ratios and fill-out factors are q = 0.320(± 0.002) and f = 5.8(± 0.1)% for GN Boo, q = 0.476(± 0.005) and f = 21.3(± 1.1)% for BL Leo, q = 0.264(± 0.002), and f = 49.7(± 0.7)% for V1918 Cyg, respectively. From the (O - C) curves, it is discovered that the orbital periods of three binaries have varied in a complicated way, i.e., cyclic oscillation for GN Boo, long-term period decrease for BL Leo, and both for V1918 Cyg. The cyclic variations for GN Boo and V1918 Cyg may probably be attributed to the magnetic activity of the primary component or light-time effect due to the third body. Meanwhile, the secular period decreases for BL Leo and V1918 Cyg may result from mass transfer from the primary to the secondary, accompanying the mass and angular momentum loss from the central system. Finally, GN Boo, BL Leo, and V1918 Cyg will evolve into deep contact binaries. Additionally, a statistical study of 37 contact binaries with decreasing periods is given. We obtained the relations of q - f and q - dln P/dt, and preliminarily determined the mass loss rate of dln M/dt from the binary system.

  11. Energy and water balance studies of a snow cover during snowmelt period at a high arctic site

    NASA Astrophysics Data System (ADS)

    Bruland, O.; Maréchal, D.; Sand, K.; Killingtveit, Å.

    The predicted global warming is supposed to have an enhanced effect on the arctic regions. How this will influence the water, carbon dioxide and methane balances in the European arctic tundra is the objective of the EU-funded project ``Understanding Land Surface Physical Processes in the Arctic'' (LAPP), to which where SINTEF is one of several contributors. The snow cover is one of the limiting factors for these exchange processes and knowledge of how it behaves and will behave under a different climate is important. Data collected for water and energy balance studies in an area close to Ny-Ålesund at 79°N at Svalbard are the basis of this study. Measurements during the ablation periods since 1992 show an average air temperature for the periods of 2.1°C, an average incoming shorwave radiation of 230W/m2 and an average measured runoff intensity of 14mm/day with a maximum of 68mm/day. Three models of different complexity are tested in order to simulate the water and energy balance of a snow cover on the arctic tundra. The three models are: a complex numerical model (CROCUS), a simple energy balance model and a temperature index model. The simulations were carried out for the melt periods in 1992 and 1996 as these two periods represent very different meteorological conditions. The results of these simulations exposed weaknesses in all the models. The energy balance model lacks calculation of cold content in the snowpack. This influences both the outgoing longwave radiation and the timing of the melt. Due to the effect of compensating errors in the simulations, CROCUS performed better than the simple energy balance model but also this model has problems with the simulation of outgoing longwave radiation. The temperature index model does not perform well for snowmelt studies in regions were radiation is the main driving energy source for the melt.

  12. Studies of the Decay of Surface Plasmon Polaritons on Periodic Metallic Nanostructures and Related Applications

    NASA Astrophysics Data System (ADS)

    Cao, Zhaolong

    Surface plasmons (SPs), which generate strong localized electromagnetic fields at metal surface, have been capturing worldwide attention recently because they establish an important link between light and matter. Due to their ability to route and manipulate photon at the nanoscale, SPs have been widely used in nano- and bio-photonics including biosensor, surface enhanced Raman scattering, optical tweezers, light emitting diodes, solar cell, and metamaterials, etc. However, although it is known that system geometry, material, wavelength, excitation condition are important in governing the behaviors of SPs as well as matter/SPPs interactions, how they work together in producing the final outcome is largely unknown. More importantly, there seems to be a "missing link" between these extrinsic parameters and the properties of SPs such that, for example, it is still not quite understood the exact roles of geometry play in controlling the SPs and their related properties. In this thesis, we aim at bridging the link between extrinsic parameters and SPs properties based on temporal coupled-mode theory (CMT). CMT provides the knowledge of intrinsic parameters such as SPs radiative and absorption rates and their relationships with the phase, amplitude, and directionality of SPs. Because decay rates are strong function of system parameters, excitation condition, etc, connection between the extrinsic parameters and the SPs properties can now be established. With the decay rates and other accessories in hand, we study the fundamental of SPs from another perspective. For example, we examine how two degenerate SPs modes couple to yield a pair of dark and bright modes and find not only the radiation damping of SPs but also the absorption are modified. In addition, we study the decay length and the group velocity of SPs in real- and momentum- space to elucidate the interplay between the SPs losses and the wavevector-resolved projected density-of-optical-states (PDOS). We also

  13. Studying X-Ray Binaries with High Energy Frequency Quasi-Periodic Oscillations

    NASA Technical Reports Server (NTRS)

    Oliversen, Ronald J. (Technical Monitor); Kaaret, P.

    2003-01-01

    The goal of this investigation is to further our understanding of the dynamics of accreting neutron stars and black holes in the hope of using these systems as probes of the physics of strong gravitational fields. The main focus of this work has been a multi-year program of simultaneous millisecond x-ray timing and spectral observations carried out with the Rossi X-Ray Timing Explorer (RXTE) to perform the x-ray timing and one of the satellites Asca, BeppoSAX, or Chandra to perform x-ray spectral measurements. With the advent of Chandra, we have extended our work to include imaging of X-ray jets from binaries and the study of extragalactic X-ray binaries. Significant progress was made over the past year.

  14. ARIES-ST STUDIES REPORT FOR THE PERIOD JANUARY 1, 1998 THROUGH DECEMBER 31, 1998

    SciTech Connect

    V.S. CHAN; L.L. LAO; Y.R. LIN-LIU; R.L. MILLER; T.W. PETRIE; P.A. POLITZER; R. PRATER; M.J. SCHAFFER; G.M. STAEBLER; R.D. STAMBAUGH; A.D. TURNBULL; W.P.WEST

    1999-04-01

    During 1998, the General Atomics (GA) ARIES-Spherical Torus (ST) team examined several critical issues related to the physics performance of the ARIES-ST design, and a number of suggestions were made concerning possible improvements in performance. These included specification of a reference plasma equilibrium, optimization about the reference equilibrium to achieve higher beta limits, examination of three possible schemes for plasma initiation, development of a detailed scenario for ramp-up of the plasma current and pressure to its full, final operating values, an assessment of the requirement for electron confinement, and several suggestions for divertor heat flux reduction. The reference equilibrium was generated using the TOQ code, with the specification of a 100%, self-consistent bootstrap current. The equilibrium has {beta} = 51%, 10% below the stability limit (a margin specified by the ARIES-ST study). In addition, a series of intermediate equilibria were defined, corresponding to the ramp-up scenario discussed. A study of the influence of shaping on ARIES-ST performance indicates that significant improvement in both kink and ballooning stability can be obtained by modest changes in the squareness of the plasma. In test equilibria the ballooning beta limit is increased from 58% to 67%. Also the maximum allowable plasma-wall separation for kink stability can be increased by 30%. Three schemes were examined for noninductive plasma initiation. These are helicity injection (HICD), electron cyclotron heating (ECH)-assisted startup, and inductive startup using only the external equilibrium coils. HICD startup experiments have been done on the HIT and CDX devices. ECH-assisted startup has been demonstrated on CDX-U and DIII-D. External coil initiation is based on calculations for a proposed DIII-D experiment. In all cases, plasma initiation and preparation of an approximately 0.3 MA plasma for ARIES-ST appears entirely feasible.

  15. Studying cumulative ozone exposures in Europe during a 7-year period

    NASA Astrophysics Data System (ADS)

    Bastrup-Birk, Annemarie; Brandt, JøRgen; Zlatev, Zahari; Uria, Ignacio

    1997-10-01

    Ozone is one of the most harmful pollutants in the troposphere. High ozone concentrations can damage plants, animals and humans. The damaging effects depend on the magnitude of a critical level of a special parameter, the cumulative ozone exposure. This is why cumulative ozone exposures must be carefully studied. It is important to determine the relationships between relevant emissions (NOx emissions, human-made VOC emissions, and/or a combination of NOx emissions and human-made VOC emissions) and cumulative ozone exposures. All these issues are discussed in this paper. Meteorological data from seven consecutive years, from 1989 to 1995, have been used in the experiments with different scenarios for varying the emissions (the NOx emissions, the human-made VOC emissions, as well as both the NOx emissions and the human-made VOC emissions). The particular air pollution model used in this study is the Danish Eulerian Model. Several hundred runs with different input data (meteorological data and/or emission data) have been performed. Advanced visualization techniques are used to interpret the large amount of digital data collected in these runs and to show clearly different trends and relationships that are normally hidden behind millions and millions of numbers. The model results were compared with measurements taken at more than 80 stations located in different European countries. The experiments indicate that it is sufficient to carry out computations over 5 consecutive years in order to eliminate the influence of extreme meteorological conditions (very warm or very cold summer months) on the cumulative ozone exposures, while this effect is clearly seen if less than 5 years are used in the experiments. It is shown that the relationship between the emissions (NOx and/or human-made VOC emissions) and the cumulative ozone exposures is in general nonlinear. Finally, it is illustrated that the critical values for ozone exposures are exceeded in most of Europe (in many

  16. Maternal recall versus medical records of metabolic conditions from the prenatal period: A validation study

    PubMed Central

    Krakowiak, Paula; Walker, Cheryl K.; Tancredi, Daniel J.; Hertz-Picciotto, Irva

    2015-01-01

    Objectives To assess validity of maternally-reported diabetes and hypertensive disorders, and reliability of BMI measurements during periconception and pregnancy compared with medical records when mothers are interviewed 2-5 years after delivery. To investigate whether reporting accuracy differed by child's case status (autism, delays, typical development). Methods Participants were mothers of 2-5 year old children with and without neurodevelopmental disorders from the CHARGE (CHildhood Autism Risks from Genetics and the Environment) Study who had both prenatal/delivery records and telephone interviews. Sensitivity and specificity of self-report in telephone interview was assessed by comparison with medical records; agreement was evaluated by kappa statistics. Deviations in reported BMI were evaluated with Bland-Altman plots and concordance correlation coefficient (CCC). Results Mothers of children with neurodevelopmental disorders (autism or developmental delay) reported metabolic conditions slightly more accurately than control mothers. For diabetes, sensitivity ranged from 73% to 87% and specificity was ≥98% across groups. For hypertensive disorders, sensitivity ranged from 57% to 77% and specificity from 93% to 98%. Reliability of BMI was high (CCC=0.930); when grouped into BMI categories, a higher proportion of mothers of delayed children were correctly classified (κwt=0.93) compared with the autism group and controls (κwt=0.85 and κwt=0.84, respectively; P=0.05). Multiparity was associated with higher discrepancies in BMI and misreporting of hypertensive disorders. Conclusions For purposes of etiologic studies, self-reported diabetes and hypertensive disorders during periconception and pregnancy show high validity among mothers irrespective of child's case status. Recall of pre-pregnancy BMI is reliable compared with self-reported values in medical records. PMID:25656730

  17. Periodic Peritoneal Dialysis in End Stage Renal Disease: Is it Still Relevant? A Single Center Study from India

    PubMed Central

    Gandhi, K; Prasad, D; Malhotra, V; Agrawal, D; Beniwal, P; Mathur, M

    2015-01-01

    Background: High cost of maintenance hemodialysis (HD) and continuous ambulatory peritoneal dialysis (PD) in India has made renal replacement therapy out of reach of many patients with end stage renal disease (ESRD). Repeated puncture PD although inferior to HD biochemically, is easily and freely available across Rajasthan, India, and is simple to perform, and does not require sophisticated machines, thus making it an attractive option for dialysis for ESRD. Aim: To analyze the outcomes of periodic PD in patients with ESRD requiring dialysis support. Subjects and Methods: A prospective study analyzing the data of patients who underwent PD between August 2010 and January 2013 in Sawai Man Singh Hospital, Jaipur, India was conducted. Patients were divided into three groups based on the time period between first and second session of PD. Detailed demographic and clinical data during the study period were collected along with PD related complications. The main outcome studied was technique survival 1 year post initiation of PD. Results: 234 patients received an initial session of PD, of which 174 had a good response and were included in the study. 19 patients received the second PD within 7 days of first (Group 1), 45 patients within 8–14 days (Group 2) and 110 patients within 15–21 days (Group 3). The overall 1 year technique survival was 68.4% (91/133), with a rate of 50% (5/10), 56.8% (21/37), and 75.6% (65/86) for Group 1, Group 2, and Group 3, respectively. The time duration between first and second PD proved to be reliable indicator of the subsequent response, with a technique survival rate significantly lower in Group 1 patients compared to Groups 2 and 3 (P = 0.04). Median dialysis free days were 11, 16 and 21 days in Group 1, Group 2, and Group 3, respectively. Peritonitis rate observed was 2.1% (49/2261) during the study period. Conclusion: Periodic PD is a simple, safe and cheap procedure, which can be considered as used as a palliative measure in

  18. Studying X-Ray Binaries with High Energy Frequency Quasi-Periodic Oscillations

    NASA Technical Reports Server (NTRS)

    Kaaret, P.; West, Donald K. (Technical Monitor)

    2002-01-01

    The goal of this investigation is to further our understanding of the dynamics of secreting neutron stars and black holes in the hope of using these systems as probes of the physics of strong gravitational fetus. The main focus of this work has been a multi-year program of simultaneous millisecond X-ray timing and spectral observations carried out with the Rossi X-Ray Timing Explorer (RXTE) to perform the X-ray timing and one of the satellites Asca, BeppoSAX, or Chandra to perform X-ray spectral measurements. With the advent of Chandra, we have extended our work to incLude extragalactic X-ray binaries. We conducted a comprehensive study of the X-ray and radio behavior of the Black Hole Candidate (BHC) X-ray transient XTE J1550-564 using RXTE, Chandra, and the Australian Telescope Compact Array (ATCA). We showed that strong radio emission is associated with major X-ray outbursts involving an X-ray state transition, while a compact radio jet is seen in the low/hard X-ray state found in the outburst decay. Interesting, the total energy required to produce the compact jet may be a substantial fraction of the total accretion energy of the system in that state. We also performed a detailed study of the spectral and timing properties of the decay. In joint RXTE/BeppoSAX observations of the neutron-star X-ray binary Cyg X-2, we discovered a correlation between the timing properties (the frequency of the horizontal branch oscillations) and the properties of a soft, thermal component of the X-ray spectrum. d e showed that more det

  19. Spectroscopic studies of the fish fossils (Cladocyclus gardneri and Vinctifer comptoni) from the Ipubi Formation of the Cretaceous Period.

    PubMed

    Sousa Filho, F E; da Silva, J H; Saraiva, G D; Abagaro, B T O; Barros, O A; Saraiva, A A F; Viana, B C; Freire, P T C

    2016-03-15

    Fossils are mineralized remains or traces from animals, plants and other organisms aged to about 10(8)years. The chemical processes of fossilization are dated back from old geological periods on Earth. The understanding of these processes and the structure of the fossils are one of the goals of paleontology and geology in the sedimentary environments. Many researches have tried to unveil details about special kinds of biological samples; however, a lack of data is noticed for various other specimens. This study reports the investigations through infrared spectroscopy, X-ray fluorescence and X-ray diffraction measurements for two types of fish fossils from the Cretaceous Period. The sample of Cladocyclus gardneri and Vinctifer comptoni fossils were collected from the Ipubi Formation, being one of the less studied, among the formations that constitute the important Santana group in the Araripe Basin, Brazil. The results obtained through different techniques, showed that the C. gardneri fish fossil contains hydroxyapatite and calcite as constituents whereas its rock matrix was formed by calcite, quartz and pyrite. Regarding the V. comptoni, the measurements confirmed the presence of hydroxyapatite in the fossil and its rock matrix gypsum, pyrite, quartz and calcite. The above scientific data contributed to the understanding the fossil formation in the Ipubi Formation, an important environment of the Cretaceous Period, which is rich in well-preserved fossils from different species.

  20. Spectroscopic studies of the fish fossils (Cladocyclus gardneri and Vinctifer comptoni) from the Ipubi Formation of the Cretaceous Period

    NASA Astrophysics Data System (ADS)

    Sousa Filho, F. E.; da Silva, J. H.; Saraiva, G. D.; Abagaro, B. T. O.; Barros, O. A.; Saraiva, A. A. F.; Viana, B. C.; Freire, P. T. C.

    2016-03-01

    Fossils are mineralized remains or traces from animals, plants and other organisms aged to about 108 years. The chemical processes of fossilization are dated back from old geological periods on Earth. The understanding of these processes and the structure of the fossils are one of the goals of paleontology and geology in the sedimentary environments. Many researches have tried to unveil details about special kinds of biological samples; however, a lack of data is noticed for various other specimens. This study reports the investigations through infrared spectroscopy, X-ray fluorescence and X-ray diffraction measurements for two types of fish fossils from the Cretaceous Period. The sample of Cladocyclus gardneri and Vinctifer comptoni fossils were collected from the Ipubi Formation, being one of the less studied, among the formations that constitute the important Santana group in the Araripe Basin, Brazil. The results obtained through different techniques, showed that the C. gardneri fish fossil contains hydroxyapatite and calcite as constituents whereas its rock matrix was formed by calcite, quartz and pyrite. Regarding the V. comptoni, the measurements confirmed the presence of hydroxyapatite in the fossil and its rock matrix gypsum, pyrite, quartz and calcite. The above scientific data contributed to the understanding the fossil formation in the Ipubi Formation, an important environment of the Cretaceous Period, which is rich in well-preserved fossils from different species.

  1. Spectroscopic studies of the fish fossils (Cladocyclus gardneri and Vinctifer comptoni) from the Ipubi Formation of the Cretaceous Period.

    PubMed

    Sousa Filho, F E; da Silva, J H; Saraiva, G D; Abagaro, B T O; Barros, O A; Saraiva, A A F; Viana, B C; Freire, P T C

    2016-03-15

    Fossils are mineralized remains or traces from animals, plants and other organisms aged to about 10(8)years. The chemical processes of fossilization are dated back from old geological periods on Earth. The understanding of these processes and the structure of the fossils are one of the goals of paleontology and geology in the sedimentary environments. Many researches have tried to unveil details about special kinds of biological samples; however, a lack of data is noticed for various other specimens. This study reports the investigations through infrared spectroscopy, X-ray fluorescence and X-ray diffraction measurements for two types of fish fossils from the Cretaceous Period. The sample of Cladocyclus gardneri and Vinctifer comptoni fossils were collected from the Ipubi Formation, being one of the less studied, among the formations that constitute the important Santana group in the Araripe Basin, Brazil. The results obtained through different techniques, showed that the C. gardneri fish fossil contains hydroxyapatite and calcite as constituents whereas its rock matrix was formed by calcite, quartz and pyrite. Regarding the V. comptoni, the measurements confirmed the presence of hydroxyapatite in the fossil and its rock matrix gypsum, pyrite, quartz and calcite. The above scientific data contributed to the understanding the fossil formation in the Ipubi Formation, an important environment of the Cretaceous Period, which is rich in well-preserved fossils from different species. PMID:26745511

  2. Low-altitude quasi-periodic echoes studied using a large database of Gadanki radar observations

    NASA Astrophysics Data System (ADS)

    Venkateswara Rao, N.; Patra, A. K.; Rao, S. V. B.

    2009-01-01

    In this paper we present studies on low-altitude quasiperiodic (LQP) echoes based on a large database of Gadanki radar observations. LQP echoes have been observed 33% of the time during daytime and 39% during nighttime. Their occurrence is found to be maximum in the summer (daytime, 58% nighttime, 57%), followed by the September equinox (daytime, 32% nighttime, 48%), the March equinox (daytime, 26% nighttime, 36%), and minimum in the winter (daytime, 25% nighttime, 26%). Height-time occurrence of LQP echoes shows two local time maxima: one in the morning (0700-1100 LT) and another in the evening (1900-0000 LT). The most significant results not reported earlier are the large occurrence rate of LQP echoes and the height-time occurrence maps showing a descending pattern with close resemblance to tidal wind behavior. The Doppler velocities are upward-northward (downward-southward) for positive- (negative-) sloped LQP echoes. Also, we find the Doppler spread as high as 200 m s-1 at times underlining the presence of strong plasma turbulence in the collision-dominated lower E region. These results are discussed in the light of the current understanding of the LQP echoes.

  3. Studying X-Ray Binaries with High Frequency Quasi-Periodic Oscillations

    NASA Technical Reports Server (NTRS)

    Oliversen, Ronald (Technical Monitor); Kaaret, Philip

    2004-01-01

    The goal of this investigation is to further our understanding of the dynamics of accreting neutron stars and black holes in the hope of using these systems as probes of the physics of strong gravitational fields. The main focus of this work has been a multi-year program of millisecond X-ray timing and spectral observations of accreting compact objects. include imaging of X-ray jets from binaries and the study of extragalactic X-ray binaries. past year. Nine papers were accepted and/or published, as listed below. Seven of these are new since our previous annual report. With the advent of Chandra, we have extended our work to Significant progress was made over the The presentation of several talks and posters at astronomical meetings were supported by this grant. The PI was the lead organizer of "X-Ray Timing 2003: Rossi and Beyond", a major conference held in Cambridge, MA, in November, 2003. A t the conference we reviewed the accomplishments of the Rossi X-Ray Timing Explorer and developed the scientific motivation for a future X-ray timing mission. This conference was well attended and generated a significant amount of interest.

  4. [Blood lead levels during pregnancy in th the newborn period. Study of the population of Bari].

    PubMed

    Carbone, R; Laforgia, N; Crollo, E; Mautone, A; Iolascon, A

    1998-01-01

    Blood lead levels during pregnancy and in neonates immediately after birth have been evaluated, showing higher values in mothers compared to neonates (5.81 +/- 3.05 vs 4.87 +/- 3.60 micrograms/100 ml) and a positive correlation between maternal and neonatal levels (r = 0.82). On the basis of the results derived from the population examined, it has been observed that 6% of newborns have blood lead levels higher than 10 micrograms/100 ml a value recently identified by the Centers for Disease Control (CDC, Atlanta, USA) as a limit for toxicity in children. Moreover, neonatal Pb levels were higher than those found in infants from 6 to 12 months (4.87 +/- 3.60 vs 2.24 +/- 0.54 micrograms/100 ml). During the first week of life there is a steady decrease of blood lead levels, together with increasing renal lead excretion. This study was carried out at the "Dipartimento di Biomedicina dell'Età Evolutiva" University of Bari, southern Italy.

  5. Using a pneumatic support to correct sitting posture for prolonged periods: a study using airline seats.

    PubMed

    McGill, Stuart M; Fenwick, Chad M J

    2009-09-01

    Prolonged sitting with spine flexion has been linked to low back disorders. A variety of mechanisms account for this based on biomechanical and neurological variables. Airline seats typically cause pronounced lumbar flexion due to their hollowed seat back design. A pneumatic support, placed between the seat back and the lumbar spine, was tested to see if lumbar flexion was reduced. Results showed that when the seats were positioned in the upright position, 15 of 20 participants experienced reduced lumbar flexion (by 15 degrees on average) with the support. The study was repeated on the five non-responders with the seatback set in the reclined position. This resulted in another four experiencing less lumbar flexion. Since seated flexion is associated with disc stress, reducing flexion with the support reduced lumbar stress. Spine flexion that results from prolonged sitting is associated with disc stress and pain. The pneumatic support tested here reduced spine flexion. While it is not known why airline seats are designed with no lumbar support, which causes excessive lumbar flexion while seated, the pneumatic support corrected this deficit. Reclining the seatback enhanced this effect.

  6. Periodic Density Functional Theory Study of Water Adsorption on the a-Quartz (101) Surface.

    SciTech Connect

    Bandura, Andrei V.; Kubicki, James D.; Sofo, Jorge O.

    2011-01-01

    Plane wave density functional theory (DFT) calculations have been performed to study the atomic structure, preferred H2O adsorption sites, adsorption energies, and vibrational frequencies for water adsorption on the R-quartz (101) surface. Surface energies and atomic displacements on the vacuum-reconstructed, hydrolyzed, and solvated surfaces have been calculated and compared with available experimental and theoretical data. By considering different initial positions of H2O molecules, the most stable structures of water adsorption at different coverages have been determined. Calculated H2O adsorption energies are in the range -55 to -65 kJ/mol, consistent with experimental data. The lowest and the highest O-H stretching vibrational bands may be attributed to different states of silanol groups on the watercovered surface. The dissociation energy of the silanol group on the surface covered by the adsorption monolayer is estimated to be 80 kJ/mol. The metastable states for the protonated surface bridging O atoms (Obr), which may lead to hydrolysis of siloxane bonds, have been investigated. The calculated formation energy of a Q2 center from a Q3 center on the (101) surface with 2/3 dense monolayer coverage is equal to 70 kJ/mol which is in the range of experimental activation energies for quartz dissolution.

  7. First multi-colour photometric study of the short period K-type contact binary NSVS 2701634

    NASA Astrophysics Data System (ADS)

    Martignoni, M.; Acerbi, F.; Barani, C.

    2016-07-01

    We present the first CCD sets of complete light curves for the W Ursae Majoris W-type system NSVS 2701634. The observations were performed in the B, V and Ic bands using the 0.25 m telescope of the "Stazione Astronomica Betelgeuse" Italy, during 8 nights in April 2015. From our observations we were able to confirm and revise the short-period (0.24 days) variation found by Shaw and collaborators in their online list Using our 12 times of minimum light, the orbital period variations of NSVS 2701634 are studied for the first time. The general trend of the (O-C) curve reveals that its period is varying by a downward parabola that means that period is decreasing, this fact could be explained by a mass transfer between the components of the system. The light curves were modelled using the Wilson-Devinney code and the elements obtained from this analysis are used to compute the physical parameters of the system in order to study its evolutionary status. A reasonable fit of the synthetic light curves of the data indicated that NSVS 2701634 is an late-type (K3 -K4+K6) contact binary system of W-Subtype of the W Ursae Majoris systems, with a mass ratio of q = 2.60, a degree of contact factor f = 15.3% and inclination i = 72°. The light curves show asymmetries at the maxima that are fitted adding an hot spot on the surface of the more massive star, known as inverse O'Connell effect. From an estimation of the absolute dimensions of the system and from the logM-logL diagram, it is seen that both components of NSVS 2701634 follow the general pattern of the W subtype W Ursae Majoris systems.

  8. The All Sky Automated Survey. The Catalog of Variable Stars. II. 6^h-12^h Quarter of the Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    Pojmanski, G.

    2003-12-01

    This paper describes the second part of the photometric data from the 9 arcdeg times 9 arcdeg ASAS camera monitoring the whole southern hemisphere in the V-band. Preliminary list of variable stars based on observations obtained since January 2001 is presented. Over 2800000 stars brighter than V=15 mag on 18000 frames were analyzed and 11357 were found to be variable (2685 eclipsing, 907 regularly pulsating, 521 Mira and 7244 other, mostly SR, IRR and LPV stars). Periodic light curves have been classified using the automated algorithm, which now takes into account IRAS infrared fluxes. Basic photometric properties are presented in the tables and some examples of thumbnail light curves are printed for reference. All photometric data are available over the INTERNET at http://www.astrouw.edu.pl/~gp/asas/asas.html or http://archive.princeton.edu/~asas.

  9. Nucleus-specific effects of meal duration on daily profiles of Period1 and Period2 protein expression in rats housed under restricted feeding.

    PubMed

    Verwey, M; Amir, S

    2011-09-29

    Restricted feeding (RF) schedules provide a cycle of fasting and feeding each day and induce circadian rhythms in food-anticipatory activity. In addition, daily rhythms in the expression of circadian clock genes, such as rhythms in Period1 (PER1) or Period2 (PER2), are also shifted in many brain areas that are important for the regulation of motivation and emotion. In order to differentiate brain areas that respond to the time of food presentation from areas that are sensitive to the degree of restriction, the present study compared RF schedules that provided rats with either a 2 h-meal (2hRF) or a 6 h-meal (6hRF) each day. As expected, 2hRF was associated with less food-consumption, more weight-loss, and more food-anticipatory running-wheel activity than 6hRF. In association with these metabolic and behavioral differences, the daily pattern of PER1 and PER2 expression in the dorsomedial hypothalamic nucleus (DMH), which has been proposed to be integral to the generation and/or maintenance of food-anticipatory activities, peaked earlier in the 2hRF group and later in the 6hRF group. Because both RF groups exhibited approximately synchronous food-anticipatory activity, but phase shifted rhythms of PER1 and PER2 expression in the DMH, it suggests that the phase of food-anticipatory activity is not directly regulated by this brain area. Next, daily rhythms of PER2 expression in the limbic forebrain responded to each RF schedule in a nucleus-specific manner. In some brain areas, the amplitude of the PER2 rhythm was differentially adjusted in response to 2hRF and 6hRF, while other areas, responded similarly to both RF schedules. These findings demonstrate that daily rhythms of clock gene expression can be modulated by the motivational state of the animal, as influenced by meal duration, weight loss and food-consumption.

  10. Critical role of the H6-H7 loop in the conformational adaptation of all-trans retinoic acid and synthetic retinoids within the ligand-binding site of RARalpha.

    PubMed

    Mailfait, S; Thoreau, E; Belaiche, D; Formstecher And B Sablonniè, P

    2000-06-01

    The pleiotropic effects of the natural and synthetic retinoids are mediated by the activation of the two subfamilies of nuclear receptors, the retinoic acid receptors (RARs) and the retinoic X receptors (RXRs). At the molecular level, these events begin with the specific ligand recognition by a nuclear receptor subtype. The adaptation of ligands to the receptor binding site leads to an optimal number of interactions for binding and selectivity which justifies elucidation of the structural requirements of the ligand binding pocket. To explore the contribution of H6-H7 loop folding in the ligand-induced conformational changes explained by the mouse-trap model, four RARalpha mutants were constructed. Ligand binding and transactivation studies revealed that three residues from the H6-H7 loop (Gly(301), Phe(302) and Gly(303)) are critical for the conformational adaptation of both synthetic agonists and antagonists. Model building and analysis of both RARalpha-ATRA and RARalpha-CD367 complexes demonstrate that accommodation of CD367 results in a less tight contact of the saturated ring of this ligand with the amino acid side chains of the receptor ligand-binding pocket compared with that of ATRA. According to the flexibility of the agonists tested (ATRA>TTNPB=Am580> CD367), we observed a decrease in binding that was dependent on ligand structure rigidity. In contrast, the binding and transactivating activities of the L266A mutant confirmed the structural constraints imposed by synthetic ligands on binding affinity for the receptor and revealed that subtle local rearrangements induced by specific conformational adaptation changes result in different binding affinities. Our results illustrate the dynamic nature of the interaction between RARalpha and its ligands and demonstrate the critical role of the H6-H7 loop in the binding of both synthetic retinoid agonists and antagonists.

  11. A Study of the X-ray Periodicities in the Remarkable Transient Source Swift J1644+57

    NASA Astrophysics Data System (ADS)

    Griffith, Christopher; Falcone, Abraham

    2016-04-01

    Swift J1644+57 was discovered when it exhibited bright X-ray activity that was believed to be triggered from the infall of a tidally disrupted star near a massive black hole. The observation of a tidal disruption event (TDE) can provide clues to the geometry and physics near the black hole. If a jet forms, as we think happened with Swift J1644+57, it can provide data to study jet creation and the density of matter in a possible accretion disc. We have analyzed Swift X-ray Telescope (XRT) observations of Swift J1644+57 from initial onset to 502 days after TDE onset. We used a Z-transform Discrete Correlation Function (ZDCF) to search for periodicities in the Swift X-ray light curve. We analyzed the X-ray light curve in five time regions, including 0 to 4.5 days after TDE onset, 4.5 to 55 days after TDE onset, 55 to 104 days after TDE onset, 104 to 145 days after TDE onset, and 145 to 502 days after TDE onset. After implementing red and white noise reduction modeling to our ZDCF analysis, we found plausible detections of periodicities. We briefly discuss implications of these periods on the geometry and feeding of the tidal disruption event.

  12. NV centers in 3 C ,4 H , and 6 H silicon carbide: A variable platform for solid-state qubits and nanosensors

    NASA Astrophysics Data System (ADS)

    von Bardeleben, H. J.; Cantin, J. L.; Csóré, A.; Gali, A.; Rauls, E.; Gerstmann, U.

    2016-09-01

    The outstanding magneto-optical properties of the nitrogen-vacancy (NV) center in diamond have stimulated the search for similar systems. We show here that NV triplet centers can also be generated in all the main SiC polytypes. We have identified by electron paramagnetic resonance spectroscopy and first-principles calculations the axial NV- pairs in 3 C ,4 H , and 6 H SiC, showing polytype and lattice site-specific magnetic and optical properties. We demonstrate very efficient room-temperature spin polarization of the ground state upon near infrared optical excitation for the NV center in 3 C SiC and axial NV centers in the hexagonal (4 H ,6 H ) polytypes; the signals of basal pairs are much lower in intensity. Axial NV centers in hexagonal SiC polytypes and thus constitute unidirectional ensembles which may be useful in nanosensing applications.

  13. Synthesis, crystal structure and NLO property of a nonmetal pentaborate [C 6H 13N 2][B 5O 6(OH) 4

    NASA Astrophysics Data System (ADS)

    Liu, Huan-Xin; Liang, Yun-Xiao; Jiang, Xiao

    2008-12-01

    A nonmetal pentaborate [C 6H 13N 2][B 5O 6(OH) 4] ( 1) has been synthesized by 1,4-diazabicyclo[2.2.2] octane (DABCO) and boric acid, and characterized by single-crystal X-ray diffraction, FTIR, elemental analysis, and thermogravimetric analysis. Compound 1 crystallizes in the monoclinic system with space group Cc (no. 9), a=10.205(2) Å, b=14.143(3) Å, c=11.003(2) Å, β=113.97(3)°, V=1451.1(5) Å 3, Z=4. The anionic units, [B 5O 6(OH) 4] -, are interlinked via hydrogen bonding to form a three-dimensional (3D) supramolecular network containing large channels, in which the protonated [C 6H 13N 2] + cations are located. Second-harmonic generation (SHG) measurements on the powder samples reveal that 1 exhibits SHG efficiency approximately 0.9 times that of potassium dihydrogen phosphate (KDP).

  14. Effect of thermal annealing and neutron irradiation in 6H-SiC implanted with silver at 350 °C and 600 °C

    NASA Astrophysics Data System (ADS)

    Hlatshwayo, T. T.; Malherbe, J. B.; van der Berg, N. G.; Botha, A. J.; Chakraborty, P.

    2012-02-01

    The effect of thermal annealing and neutron irradiation in 6H-SiC implanted with silver at 350 °C and 600 °C have been investigated using Rutherford backscattering spectrometry (RBS), Rutherford backscattering spectrometry in channeling mode (RBS-C) and scanning electron spectroscopy (SEM). Implantation at 600 °C and 350 °C caused the 6H-SiC to retain crystallinity. The 600 °C samples had less distortions compared to 350 °C implanted samples. Annealing of the radiation damage created during implantation is also reported. No diffusion of silver was detected after thermal annealing but a shift of the silver peak toward the surface due to thermal etching was observed. The amount of etched SiC has also been estimated by comparing the peak position before and after annealing. Similarly no diffusion was observed after low dose neutron irradiation of the samples.

  15. Nonplanar structure of C6H5SCF3 facilitates πσ∗-mediated photodissociation reaction on the S1 state

    NASA Astrophysics Data System (ADS)

    Kim, So-Yeon; Lee, Jeongmook; Kim, Sang Kyu; Choi, Young S.

    2016-08-01

    Vibrational structure of trifluoromethylthiobenzene (C6H5SCF3) on the S1 state has been investigated by resonance-enhanced two-photon ionization spectroscopy and nature of predissociation dynamics is inferred from homogeneously broadened spectral features. As C6H5SCF3 adopts a nonplanar structure in both the S0 and S1 states, the effective adiabatic barrier generated by avoided crossing of optically-bright bound S1 (ππ∗) and dark-repulsive S2 (πσ∗) surfaces along the reaction coordinate is significantly lowered, giving the S1 lifetime of ∼300 fs. This experiment demonstrates that the molecular structure spanned by the reactive flux near the curve-crossing region dictates reaction rate as well as nonadiabatic transition probability.

  16. Characterization of 6H-SiC JFET Integrated Circuits Over A Broad Temperature Range from -150 C to +500 C

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Krasowski, Michael J.; Chen, Liang-Yu; Prokop, Norman F.

    2009-01-01

    The NASA Glenn Research Center has previously reported prolonged stable operation of simple prototype 6H-SiC JFET integrated circuits (logic gates and amplifier stages) for thousands of hours at +500 C. This paper experimentally investigates the ability of these 6H-SiC JFET devices and integrated circuits to also function at cold temperatures expected to arise in some envisioned applications. Prototype logic gate ICs experimentally demonstrated good functionality down to -125 C without changing circuit input voltages. Cascaded operation of gates at cold temperatures was verified by externally wiring gates together to form a 3-stage ring oscillator. While logic gate output voltages exhibited little change across the broad temperature range from -125 C to +500 C, the change in operating frequency and power consumption of these non-optimized logic gates as a function of temperature was much larger and tracked JFET channel conduction properties.

  17. Measured Attenuation of Coplanar Waveguide on 6H, p-type SiC and High Purity Semi-Insulating 4H SiC through 800 K

    NASA Technical Reports Server (NTRS)

    Ponchak, George E.; Schwartz, Zachary D.; Alterovitz, Samuel A.; Downey, Alan N.

    2004-01-01

    Wireless sensors for high temperature applications such as oil drilling and mining, automobiles, and jet engine performance monitoring require circuits built on wide bandgap semiconductors. In this paper, the characteristics of microwave transmission lines on 4H-High Purity Semi-Insulating SiC and 6H, p-type SiC is presented as a function of temperature and frequency. It is shown that the attenuation of 6H, p-type substrates is too high for microwave circuits, large leakage current will flow through the substrate, and that unusual attenuation characteristics are due to trapping in the SiC. The 4H-HPSI SiC is shown to have low attenuation and leakage currents over the entire temperature range.

  18. Growth of Defect-Free 3C-Sic on 4H- and 6H-SIC Mesas Using Step-Free Surface Heteroepitaxy

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Powell, J. Anthony; Trunek, Andrew J.; Huang, Xianrong R.; Dudley, Michael

    2002-01-01

    A new growth process, herein named step-free surface heteroepitaxy, has achieved 3C-SiC films completely free of double positioning boundaries and stacking faults on 4H-SiC and 6H-SiC substrate mesas. The process is based upon the initial 2-dimensional nucleation and lateral expansion of a single island of 3C-SiC on a 4H- or 6H-SiC mesa surface that is completely free of bilayer surface steps. Our experimental results indicate that substrate-epilayer in-plane lattice mismatch (Delta/a = 0.0854% for 3C/4H) is at least partially relieved parallel to the interface in the initial bilayers of the heterofilm, producing an at least partially relaxed 3C-SiC film without dislocations that undesirably thread through the thickness of the epilayer. This result should enable realization of improved 3C-SiC devices.

  19. BVRI Photometric Study of the Short Period Solar Type Near-Contact W UMa Binary, FF Vulpeculae

    NASA Astrophysics Data System (ADS)

    Caton, Daniel B.; Samec, Ronald G.; Nyaude, Ropafadzo; Van Hamme, Walter V.

    2016-01-01

    High precision BVRcIc light curves of FF Vul were observed during the Fall, 2015 season at the Dark Sky Observatory 0.81-m reflector of Appalachian State University, and the SARA North 0.91-m reflector at KPNO. It is an eclipsing binary with a period of only 0.444983 (2) d. This is the shortest period of our recently studied Pre Contact W UMa Binary (PCWB's), V2421 Cyg, V1043 Cas, ZZ Eri, V500 Peg, and Mis V1287. Our Binary Maker fits and our Wilson-Devinney solution show that the binary is a near-contact, semidetached binary, i.e., a V1010 Oph type configuration (the more massive component has filled its critical lobe while the secondary component is under-filling). Five times of minimum light were calculated, 3 primary and 2 secondary eclipses from our present observations:HJD I = 2457285.7262 ±0.0002, 2457306.6425 ±0.0002, 2457310.6469 ±0.0002HJD II = 2457279.7222 ±0.0006, 2457280.6124 ±0.0017.The following quadratic ephemerides was determined from all available times of minimum light:JDHelMinI=2457310.6473±0.0007d + 0.4449758±0.0000002 X E -0.00000000006± 0.00000000001 X E2The continuous 20 year period study reveals a period decrease in the orbital period at about the 6 sigma level. Our modeling shows a near-equatorial hot spot on the following side of the secondary component. This is probably due to a matter transfer onto the secondary component. The light curve has a large difference in primary and secondary amplitudes and the light curve solution gives a component temperature difference of more than 1500 K. The solution shows a total secondary eclipse of 23 minutes duration. As expected in binaries of this type, it has a cool spot region on its primary component.

  20. Vapor-Liquid Equilibrium in the Mixture Trichloromethane CHCl3 + C6H10O Cyclohexanone (EVLM1111, LB5654_E)

    NASA Astrophysics Data System (ADS)

    Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

    This document is part of Subvolume A 'Binary Liquid Systems of Nonelectrolytes I' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Vapor-Liquid Equilibrium in the Mixture Trichloromethane CHCl3 + C6H10O Cyclohexanone (EVLM1111, LB5654_E)' providing data from direct measurement of pressure at variable mole fraction in liquid phase and constant temperature.

  1. Draft Genome Sequence of Pseudomonas azotifigens Strain DSM 17556T (6H33bT), a Nitrogen Fixer Strain Isolated from a Compost Pile

    PubMed Central

    Busquets, Antonio; Peña, Arantxa; Gomila, Margarita; Mulet, Magdalena; Mayol, Joan; García-Valdés, Elena; Bennasar, Antonio; Huntemann, Marcel; Han, James; Chen, I-Min; Mavromatis, Konstantinos; Markowitz, Victor; Palaniappan, Krishnaveni; Ivanova, Natalia; Schaumberg, Andrew; Pati, Amrita; Reddy, T. B. K.; Nordberg, Henrik; Woyke, Tanja; Klenk, Hans-Peter; Kyrpides, Nikos

    2013-01-01

    Pseudomonas azotifigens strain 6H33bT is a nitrogen fixer isolated from a hyperthermal compost pile in 2005 by Hatayama and collaborators. Here we report the draft genome, which has an estimated size of 5.0 Mb, exhibits an average G+C content of 66.73%, and is predicted to encode 4,536 protein-coding genes and 100 RNA genes. PMID:24179119

  2. Expression of the Ly-6 family proteins Lynx1 and Ly6H in the rat brain is compartmentalized, cell-type specific, and developmentally regulated.

    PubMed

    Thomsen, Morten Skøtt; Cinar, Betül; Jensen, Majbrit Myrup; Lyukmanova, Ekaterina N; Shulepko, Mikhail A; Tsetlin, Victor; Klein, Anders Bue; Mikkelsen, Jens D

    2014-11-01

    The Ly-6 superfamily of proteins, which affects diverse processes in the immune system, has attracted renewed attention due to the ability of some Ly-6 proteins to bind to and modulate the function of neuronal nicotinic acetylcholine receptors (nAChRs). However, there is a scarcity of knowledge regarding the distribution and developmental regulation of these proteins in the brain. We use protein cross-linking and synaptosomal fractions to demonstrate that the Ly-6 proteins Lynx1 and Ly6H are membrane-bound proteins in the brain, which are present on the cell surface and localize to synaptic compartments. We further estimate the amount of Lynx1 in the rat cortex using known amounts of a heterologously expressed soluble Lynx1 variant (ws-Lynx1) to be approximately 8.6 ng/μg total protein, which is in line with the concentrations of ws-Lynx1 required to affect nAChR function. In addition, we demonstrate that Lynx1 and Ly6H are expressed in cultured neurons, but not cultured micro- or astroglial cultures. In addition, Lynx1, but not Ly6H was detected in the CSF. Finally, we show that the Ly-6 proteins Lynx1, Lynx2, Ly6H, and PSCA, display distinct expression patterns during postnatal development in the rat frontal cortex and hippocampus at the mRNA and protein level, and that this is paralleled to some degree by the expression of the nAChR subunits α2, α4, α7 and β2. Our results demonstrate a developmental pattern, localization, and concentration of Ly-6 proteins in the brain, which support a role for these proteins in the modulation of signaling at synaptic membranes.

  3. Face-capping μ3-BO in B6(BO)7-: boron oxide analogue of B6H7- with rhombic 4c-2e bonds.

    PubMed

    Guo, Jin-Chang; Lu, Hai-Gang; Zhai, Hua-Jin; Li, Si-Dian

    2013-11-14

    Using the first-principle approaches, we predict a B6(BO)7(-) cluster with a face-capping μ(3)-BO, which is the boron oxide analogue of closo-B6H7(-) with a face-capping μ(3)-H. Detailed topological analysis of electron density clearly reveals the existence of three rhombic 4c-2e bonds around the B/H apex in both C3v B6(BO)7(-) and C3v B6H7(-), which possesses similar electron densities at their bond and ring critical points. The adaptive natural density partitioning (AdNDP) analysis provides a direct and visual picture of the B-B-B-B/H 4c-2e bonds for the first time. Adiabatic and vertical electron detachment energies of the concerned monoanions are calculated to facilitate their future photoelectron spectroscopy measurements and characterizations. The presence of the B6(BO)7(-) and B6H7(-) clusters extends the BO/H isolobal analogy to the whole μ(n)-BO/H series (n = 1, 2, and 3) and enriches the chemistry of boronyl. PMID:24147988

  4. Structural change induced by thermal annealing of red-light-emitting ZnSnF6 • 6H2O:Mn4+ hexahydrate phosphor

    NASA Astrophysics Data System (ADS)

    Hoshino, Ryosuke; Nakamura, Toshihiro; Adachi, Sadao

    2016-05-01

    Effects of thermal annealing on the red-emitting ZnSnF6 • 6H2O:Mn4+ hexahydrate phosphor properties were investigated using X-ray diffraction measurement (XRD), photoluminescence (PL) analysis, and Raman scattering spectroscopy. Thermal annealing was performed at T a = 50 to 400 °C in air for 1 h. Mn4+-related red emission wavelengths were redshifted about 5 nm after annealing at T a ≥ 200 °C with greatly decreased emission intensities. This change in PL spectral feature was attributed to the dehydration of the hexahydrate phosphor, supported by the XRD and Raman scattering results. The XRD and PL intensity analyses determined thermal decomposition energies of ˜0.3 eV from the ZnSnF6 • 6H2O hexahydrate to anhydrate and of ˜0.9 eV from the ZnSnF6 anhydrate to metallic fluorid/oxide (ZnF2/SnO2). A comparative discussion was given on the PL properties of two different Mn4+-activated phosphors, Ba-IV-F6:Mn4+ anhydrate and Zn-IV-F6 • 6H2O:Mn4+ hexahydrate phosphors with IV = Si, Ge, and Sn.

  5. Carbon p-electron induced magnetic ordering in Zn-implanted 6H-SiC: experimental observation and theoretical calculation

    NASA Astrophysics Data System (ADS)

    Li, Qiang; Xu, Juping; Liu, Jiandang; Ye, Bangjiao

    2016-05-01

    We observed clear ferromagnetic ordering in 6H-SiC crystal bombarded with zinc ions, and presented a detailed investigation of magnetic properties in this sample. The magnetization of Zn-implanted 6H-SiC fell and rose with annealing temperature from 500 °C to 1100 °C. Meanwhile, amount of oxygen penetrated lattices and combined with Si-bonds after 1100 °C annealing. Using ab initio calculations based on density functional theory, we confirm that Zn ions play a role in the origin of ferromagnetism, while the localized moment is mainly comes from C2p electrons surrounding the foreign particle (which is Zn in this work). Silicon vacancies can provide localized moment about 2.0 μB/VSi and form stable ferromagnetic interaction at room temperature. Oxygen may facilitate this coupling and no need of VC-mediation any more. The calculations are consistent with experimental results. We concluded that the dangling C2p bonds are fundamental cause of magnetic ordering in whatever microstructures in 6H-SiC crystal. The type of foreign impurities is not crucial factor for the magnetic origin in such carbon-based materials.

  6. Multidisciplinary experiment on studying short-period variability of the sedimentary process in the northeastern part of the Black Sea

    NASA Astrophysics Data System (ADS)

    Klyuvitkin, A. A.; Ostrovskii, A. G.; Novigatskii, A. N.; Lisitzin, A. P.

    2016-07-01

    The principal aim of this work is to reveal the regularities of short-period synoptic variability of vertical flows and the composition of settling sedimentary material, to obtain information on the quantitative characteristics of the processes that influence sound-scattering layers in the water layer above the continental slope behind the shelf edge in the northeastern part of the Black Sea. The results were obtained due to improvement of the equipment and the procedures for performing sea experiments on studying physicogeological, biological, and hydrophysical processes in the upper illuminated layer of phytoplankton development.

  7. The plasmapause period of magnetic recovery. Combined study of OGO 4, OGO 5 data and of grounded whistler reception

    NASA Technical Reports Server (NTRS)

    Corcuff, P.; Corcuff, Y.; Carpenter, D. L.; Chappell, C. R.; Vigneron, J.; Kleimenova, N.

    1972-01-01

    The equatorial structure and dynamics of the plasmasphere during the period of magnetic recovery, lasting from the 13 to 23 of September 1968, are studied. The H(+) ions density profiles measured in the night and afternoon sectors by the excentered orbital satellite OGO 5 and L sub p positions of the plasmapause deduced from the VLF records of the polar orbital satellite OGO 4, are included. Electron densities are calculated from the whistlers received at Kerguelen (L approximately 3, 7) and Byrd (L approximately 7), ground stations 150 degrees of longitude apart.

  8. Detecting non-uniform period spacings in the Kepler photometry of γ Doradus stars: methodology and case studies

    NASA Astrophysics Data System (ADS)

    Van Reeth, T.; Tkachenko, A.; Aerts, C.; Pápics, P. I.; Degroote, P.; Debosscher, J.; Zwintz, K.; Bloemen, S.; De Smedt, K.; Hrudkova, M.; Raskin, G.; Van Winckel, H.

    2015-02-01

    Context. The analysis of stellar oscillations is one of the most reliable ways to probe stellar interiors. Recent space missions such as Kepler have provided us with an opportunity to study these oscillations with unprecedented detail. For many multi-periodic pulsators such as γ Doradus stars, this led to the detection of dozens to hundreds of oscillation frequencies that could not be found from ground-based observations. Aims: We aim to detect non-uniform period spacings in the Fourier spectra of a sample of γ Doradus stars observed by Kepler. Such detection is complicated by both the large number of significant frequencies in the space photometry and by overlapping non-equidistant rotationally split multiplets. Methods: Guided by theoretical properties of gravity-mode oscillation of γ Doradus stars, we developed a period-spacing detection method and applied it to Kepler observations of a few stars, after having tested the performance from simulations. Results: The application of the technique resulted in the clear detection of non-uniform period spacing series for three out of the five treated Kepler targets. Disadvantages of the technique are also discussed, and include the disability to distinguish between different values of the spherical degree and azimuthal order of the oscillation modes without additional theoretical modelling. Conclusions: Despite the shortcomings, the method is shown to allow solid detections of period spacings for γ Doradus stars, which will allow future asteroseismic analyses of these stars. Based on data gathered with the NASA Discovery mission Kepler and the HERMES spectrograph, which is installed at the Mercator Telescope, operated on the island of La Palma by the Flemish Community at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, and supported by the Fund for Scientific Research of Flanders (FWO), Belgium, the Research Council of KU Leuven, Belgium, the Fonds National de la

  9. Hydrogen-bond-directed assemblies of [La(18-crown-6)(H2O)4](BiCl6)·3H2O and [Nd(18-crown-6)(H2O)4](BiCl6)·3.5H2O regulated by different symmetries

    NASA Astrophysics Data System (ADS)

    Zhang, Shi-Yong; Li, Jian; Zeng, Ying; Wen, He-Rui; Du, Zi-Yi

    2016-12-01

    The reactions of La2O3 or Nd2O3 with BiCl3 and 18-crown-6 in the presence of excessive hydrochloric acid afforded two ion-pair compounds, namely [La(18-crown-6)(H2O)4](BiCl6)·3H2O (1) and [Nd(18-crown-6)(H2O)4](BiCl6)·3.5H2O (2). Although these two compounds contain similar building blocks, they exhibit two distinct hydrogen-bonded networks, which are mainly induced by the slightly different geometries of their large-sized cationic [Ln(18-crown-6)(H2O)4]3+ components.

  10. A Pilot Study to Compare Oxidative Status between Organically and Conventionally Managed Dairy Cattle During the Transition Period.

    PubMed

    Abuelo, A; Hernández, J; Benedito, J L; Castillo, C

    2015-08-01

    The aim of this study was to assess the redox balance of organically managed dairy cattle (OMC; n = 40) during the transition period and to compare this with conventionally managed cattle (CMC; n = 22). Serum samples of dairy cows from two organic and one conventional farm were taken. Markers of oxidants production [reactive oxygen species] and total serum antioxidant capacity were measured in four different production stages: (i) far-off dry (2 to 1 months before calving; 44 samples in CMC and 48 in OMC); (ii) close-up dry (1 month until 3 days before calving; 44 CMC; 54 OMC); (iii) fresh (3 days to +1 month after calving; 44 CMC; 49 OMC); and (iv) peak of lactation (+1 to +3 months; 71 CMC; 78 OMC). Values were compared between production stages and against a metabolic baseline status (4th-5th month of pregnancy; 40 CMC; 30 OMC). Our results indicated that throughout the periparturient period, OMC had lower concentrations of reactive oxygen species, but also a lower antioxidant capacity than CMC. Indeed, when the two components of the redox balance were assessed together through the Oxidative Stress index, the values of this parameter were higher for OMC than for CMC, thereby implying a higher risk of oxidative stress. Therefore, further larger studies are needed to confirm the current observations, as organically reared animals might be exposed to a lack of antioxidants supply.

  11. Solubility of Two Root-End Filling Materials over Different Time Periods in Synthetic Tissue Fluid: a Comparative Study

    PubMed Central

    Shojaee, Nooshin Sadat; Sahebi, Safoora; Karami, Elahe; Sobhnamayan, Fereshte

    2015-01-01

    Statement of the Problem Insolubility is an important criterion for an ideal root-end filling material to both prevent any microleakage between the root canal and the periradicular space and provide sealing ability. Purpose Many recent studies have shown that mineral trioxide aggregate (MTA) and calcium-enriched mixture (CEM) have acceptable sealing ability. The purpose of this in vitro study was to evaluate the solubility of these root-end filling materials. Materials and Method Forty stainless steel ring moulds with an internal diameter of 10±1 mm and a height of 2±0.1 mm were selected. Samples of MTA and CEM were mixed according to the manufacturer’s instructions and inserted into the moulds. The specimens were divided into 4 experimental groups and kept in synthetic tissue fluid (STF) for 2 different time periods (7 and 28 days). The control group contained 8 empty rings. The moulds’ weights were recorded before and after immersion in STF. The changes in the weight of the samples were measured and compared using a two- way ANOVA test at a significance level of 5%. Specimens were evaluated with scanning electron microscopy (SEM) at a magnification of 500×. Results There was no significant difference in weight changes between MTA and CEM samples (p> 0.05). Conclusion MTA and CEM have similar solubility in STF in different time periods. PMID:26331148

  12. Choice of fluid therapy in patients of craniopharyngioma in the perioperative period: A hospital-based preliminary study

    PubMed Central

    Mukherjee, K. K.; Dutta, Pinaki; Singh, Apinderpreet; Gupta, Prakamya; Srinivasan, Anand; Bhagat, Hemant; Mathuriya, S. N.; Shah, Viral N.; Bhansali, Anil

    2014-01-01

    Background: Electrolyte imbalance and acute diabetes insipidus (DI) are the most common complications in patients undergoing craniopharyngioma surgery. Improper management of water and electrolyte imbalance is common cause of morbidity and mortality. Data is sparse and controversial regarding the choice of fluid therapy in this population during perioperative period. Methods: In this retrospective-prospective study involving 73 patients (58 retrospective), the type of fluid therapy was correlated with occurrence of hypernatremia, hyponatremia, DI, morbidity, and mortality. In the retrospective study, 48 patients received normal saline and 10 received mixed fluids as per the prevailing practice. In the prospective group, five patients each received normal saline, half normal saline, and 5% dextrose randomly. Results: The sodium values were significantly higher in first 48 h in the group that received normal saline compared with other groups (P < 0.001). The use of normal saline was associated with higher incidence of hypernatremia, DI, and mortality (P = 0.05), while the group that received 5% dextrose was associated with hyponatremia, hypoglycemia, and seizures. There was no perioperative hypotension with use of any of the fluids. Conclusion: Our results indicate half normal saline was fluid of choice with diminished incidence of water and electrolyte abnormalities without increase in mortality during postoperative period. PMID:25101200

  13. Shortwave Radiative Closure Studies for Clear Skies During the Atmospheric Radiation Measurement 2003 Aerosol Intensive Observation Period

    SciTech Connect

    Michalsky, Joseph J.; Anderson, Gail; Barnard, James C.; Delamere, Jennifer; Gueymard, C.; Kato, Seiji; Kiedron, P.; McComiskey, A.; Ricchiazzi, P.

    2006-07-20

    The Department of Energy's Atmospheric Radiation Measurement (ARM) program sponsored a large aerosol intensive observation period (AIOP) to study aerosol during the month of May 2003 around the Southern Great Plains (SGP) Climate Research Facility (CRF) in north central Oklahoma. Redundant measurements of aerosol optical properties were made using different techniques at the surface as well as in vertical profile with sensors aboard two aircraft. One of the principal motivations for this experiment was to resolve the disagreement between models and measurements of diffuse horizontal broadband shortwave irradiance at the surface, especially for modest aerosol loading. This paper focuses on using the redundant aerosol and radiation measurements during this AIOP to compare direct beam and diffuse horizontal broadband shortwave irradiance measurements and models at the surface for a wide range of aerosol cases that occurred during 30 clear-sky periods on 13 days of May 2003. Models and measurements are compared over a large range of solar-zenith angles. Six different models are used to assess the relative agreement among them and the measurements. Better agreement than previously achieved appears to be the result of better specification of input parameters and better measurements of irradiances than in prior studies. Biases between modeled and measured direct irradiances are in the worst case 1%, and biases between modeled and measured diffuse irradiances are less than 1.9%.

  14. Ecological periodic tables for benthic macrofaunal usage of estuarine habitats: Insights from a case study in Tillamook Bay, Oregon, USA

    NASA Astrophysics Data System (ADS)

    Ferraro, Steven P.; Cole, Faith A.

    2012-05-01

    This study validates the ecological relevance of estuarine habitat types to the benthic macrofaunal community and, together with previous similar studies, suggests they can serve as elements in ecological periodic tables of benthic macrofaunal usage in the bioregion. We compared benthic macrofaunal Bray-Curtis similarity and the means of eight benthic macrofaunal community measures across seven habitat types in Tillamook Bay, Oregon, USA: intertidal eelgrass (Zostera marina), dwarf eelgrass (Zostera japonica), oyster (Crassostrea gigas) ground culture, burrowing mud shrimp (Upogebia pugettensis), burrowing ghost shrimp (Neotrypaea californiensis), sand and subtidal. Benthic macrofaunal Bray-Curtis similarity differed among all the habitats except ghost shrimp and sand. The habitat rank order on mean benthic macrofaunal species richness, abundance and biomass was dwarf eelgrass ≈ oyster ≥ mud shrimp ≈ eelgrass > sand ≈ ghost shrimp ≈ subtidal. The benthic macrofaunal habitat usage pattern in Tillamook Bay was, with a few exceptions, similar to that in two other US Pacific Northwest estuaries. The exceptions indicate variants of eelgrass and ghost shrimp habitat that differ in benthic macrofaunal usage perhaps due to differences in the coarseness of the sand fraction of the sediments in which they live. The similarities indicate periodic benthic macrofaunal usage patterns across the other habitat types extend over a wider geographic scale and range of environmental conditions than previously known.

  15. Numerical study of water flow in a system of two basins connected by a channel with periodic forcing

    NASA Astrophysics Data System (ADS)

    Lopez Sanchez, Erick Javier; Ruiz Chavarria, Gerardo

    2010-11-01

    In oceanography the transport of particles is a frecuent phenomenon, for instance ocean currents carry the plankton from one place to another. In shallow waters drag and depositation of sand can affect positively or negatively certain human activities, such as the navigation near the coast; on the other hand, sand banks can help to mitigate the force with which a tsunami approaches a populated coastline. We study the flow of water in a system of two basins connected by a channel, generated by a periodic forcing that simulates the tidal force. The simulation is done by solving the system of equations in stream function (ψ ) - vorticity (φ ) formulation, obtained from the Navier-Stokes and continuity in two dimensions. A pseudo-spectral method based on polynomials Chebyshev is used. The tidal forcing is reflected in the fact that Reynolds number becomes time dependent. We obtained results that are consistent with previous works (like: Wells, M. G. and Van Heijst, G.J.F., Dynamics of Atmospheres and Oceans, 37 (2003) 223-244). For example the formation and displacement of a dipole at the exit of the channel is observed. The velocity field obtained numerically is used to study the transport of particles by the flow, where the dipole moves away from the channel output or return to it, depending on the geometry of the system and period occurrence of the phenomenon.

  16. HPV clearance in postpartum period of HIV-positive and negative women: a prospective follow-up study

    PubMed Central

    2013-01-01

    Background HPV persistence is a key determinant of cervical carcinogenesis. The influence of postpartum on HPV clearance has been debated. This study aimed to assess HPV clearance in later pregnancy and postpartum among HIV-positive and negative women. Methods We conducted a follow-up study with 151 HPV-positive women coinfected with HIV, in 2007–2010. After baseline assessment, all women were retested for HPV infection using PCR in later pregnancy and after delivery. Multivariable logistic regressions assessed the putative association of covariates with HPV status in between each one of the successive visits. Results Seventy-one women (47%) have eliminated HPV between the baseline visit and their second or third visits. HIV-positive women took a significantly longer time (7.0 ± 3.8 months) to clear HPV, compared to those not infected by HIV (5.9 ± 3.0 months). HPV clearance was significantly more likely to take place after delivery than during pregnancy (84.5% x 15.5%). Conclusions Both HIV-positive and negative women presented a significant reduction in HPV infection during the postpartum period. HIV-positive status was found to be associated with a longer period of time to clear HPV infection in pregnant women. PMID:24289532

  17. Structural phase transition causing anomalous photoluminescence behavior in perovskite (C{sub 6}H{sub 11}NH{sub 3}){sub 2}[PbI{sub 4}

    SciTech Connect

    Yangui, A.; Pillet, S.; Mlayah, A.; Lusson, A.; Bouchez, G.; Boukheddaden, K. E-mail: kbo@physique.uvsq.fr; Triki, S.; Abid, Y. E-mail: kbo@physique.uvsq.fr

    2015-12-14

    Optical and structural properties of the organic-inorganic hybrid perovskite-type (C{sub 6}H{sub 11}NH{sub 3}){sub 2}[PbI{sub 4}] (abbreviated as C{sub 6}PbI{sub 4}) were investigated using optical absorption, photoluminescence (PL), and x-ray diffraction measurements. Room temperature, optical absorption measurements, performed on spin-coated films of C{sub 6}PbI{sub 4}, revealed two absorption bands at 2.44 and 3.21 eV. Upon 325 nm (3.815 eV) laser irradiation, strong green PL emission peaks were observed at 2.41 eV (P1) and 2.24 eV (P2) and assigned to free and localized excitons, respectively. The exciton binding energy was estimated at 356 meV. At low temperature, two additional emission bands were detected at 2.366 eV (P3) and a large band (LB) at 1.97 eV. The former appeared only below 40 K and the latter emerged below 130 K. The thermal dependence of the PL spectra revealed an abnormal behavior accompanied by singularities in the peak positions and intensities at 40 and 130 K. X-ray diffraction studies performed on powder and single crystals as a function of temperature evidenced significant changes of the interlayer spacing at 50 K and ∼138 K. Around 138 K, a commensurate to incommensurate structural phase transition occurred on cooling. It involves a symmetry breaking leading to a distortion of the PbI{sub 6} octahedron. The resulting incommensurate spatial modulation of the Pb–I distances (and Pb–I–Pb angles) causes a spatial modulation of the band gap, which is at the origin of the emergence of the LB below ∼130 K and the anomalous behavior of the position of P1 below 130 K. The change of the interlayer spacing in the 40-50 K range may in turn be related to the significant decrease of the intensity of P2 and the maximum emission of the LB. These results underline the intricate character of the structural and the PL properties of the hybrid perovskites; understanding such properties should benefit to the design of optoelectronic devices with

  18. Structural phase transition causing anomalous photoluminescence behavior in perovskite (C6H11NH3)2[PbI4

    NASA Astrophysics Data System (ADS)

    Yangui, A.; Pillet, S.; Mlayah, A.; Lusson, A.; Bouchez, G.; Triki, S.; Abid, Y.; Boukheddaden, K.

    2015-12-01

    Optical and structural properties of the organic-inorganic hybrid perovskite-type (C6H11NH3)2[PbI4] (abbreviated as C6PbI4) were investigated using optical absorption, photoluminescence (PL), and x-ray diffraction measurements. Room temperature, optical absorption measurements, performed on spin-coated films of C6PbI4, revealed two absorption bands at 2.44 and 3.21 eV. Upon 325 nm (3.815 eV) laser irradiation, strong green PL emission peaks were observed at 2.41 eV (P1) and 2.24 eV (P2) and assigned to free and localized excitons, respectively. The exciton binding energy was estimated at 356 meV. At low temperature, two additional emission bands were detected at 2.366 eV (P3) and a large band (LB) at 1.97 eV. The former appeared only below 40 K and the latter emerged below 130 K. The thermal dependence of the PL spectra revealed an abnormal behavior accompanied by singularities in the peak positions and intensities at 40 and 130 K. X-ray diffraction studies performed on powder and single crystals as a function of temperature evidenced significant changes of the interlayer spacing at 50 K and ˜138 K. Around 138 K, a commensurate to incommensurate structural phase transition occurred on cooling. It involves a symmetry breaking leading to a distortion of the PbI6 octahedron. The resulting incommensurate spatial modulation of the Pb-I distances (and Pb-I-Pb angles) causes a spatial modulation of the band gap, which is at the origin of the emergence of the LB below ˜130 K and the anomalous behavior of the position of P1 below 130 K. The change of the interlayer spacing in the 40-50 K range may in turn be related to the significant decrease of the intensity of P2 and the maximum emission of the LB. These results underline the intricate character of the structural and the PL properties of the hybrid perovskites; understanding such properties should benefit to the design of optoelectronic devices with targeted properties.

  19. Design study of an advanced gas generator. [which can be ignited during start-up period of turbine engines

    NASA Technical Reports Server (NTRS)

    Kim, S.; Trinh, H. P.

    1993-01-01

    A gas generator which can be ignited reliably during the initial start-up period and offers fairly uniform gas temperature at the exit was studied numerically. Various sizes and shapes of the mixing enhancement devices and their positions were examined to evaluate the uniformity of the exit gas temperature and the change of internal pressure drop incurred by introducing the mixing enhancement devices. By introducing a turbulence ring and a splash plate with an appropriate size and position, it was possible to obtain fairly uniform gas temperature distributions and a maximum gas temperature that is within the design limit temperature of 1600 R at the generator exit. However, with the geometry studied, the pressure drop across the generator was great, approximately 1150 psi, to satisfy the assigned design limit temperature. If the design limit temperature is increased to 1650 R, the pressure drop across the generator could be lowered by as much as 350 psi.

  20. Sleep laboratory studies in periodic limb movement disorder (PLMD) patients as compared with normals and acute effects of ropinirole.

    PubMed

    Saletu, M.; Anderer, P.; Saletu, B.; Hauer, C.; Mandl, M.; Semler, B.; Saletu-Zyhlarz, G.

    2001-03-01

    Periodic limb movement disorder (PLMD) occurs in a variety of sleep disorders and can cause insomnia as well as hypersomnia with daytime somnolence. The aim of this study was to investigate 12 untreated PLMD patients as compared with 12 normal controls and to measure the acute effects of 0.5 mg ropinirole (Requip((R))) - a non-ergoline dopamine agonist - as compared with placebo. In three nights (adaptation, placebo, ropinirole night) objective and subjective sleep and awakening quality were evaluated. In the target variable 'periodic leg movements per hour of sleep' (PLM/(hTST)) PLMD patients showed an increased value of 42/h (normal 0-5/h) with a greater number of arousals due to periodic leg movements (PLM) in sleep. They further demonstrated an increased number of awakenings, sleep stage S1, S4, stage shifts and decreased S2, but there were no significant differences concerning total sleep time, sleep efficiency (SE), subjective sleep quality and morning measures of mood, drive and drowsiness. However, measures of attention variability, numerical memory, fine motor activity and reaction time performance were impaired. Ropinirole 0.5 mg was shown to significantly improve the index PLM/(hTST) by 64% and arousals due to PLM, increase spontaneous arousals, REM-latency, stage 2 and stage shifts and decrease SREM. In the morning attention variability was attenuated and numerical memory augmented. Thus, ropinirole improved some sleep architecture and early morning measures of performance but specifically all PLM variables, which suggests a dopaminergic pathogenesis in PLMD. Copyright 2001 John Wiley & Sons, Ltd.