D2 Mixtures Research Articles

Elastic electron scattering from methane at high momentum transfer

We describe elastic electron scattering data at high momentum transfer (between ≈20 and ≈40 au) from methane and Xe. Under these conditions there is a significant recoil energy transferred to the target and electrons scattered elastically from methane are separated into two peaks: one due to electrons scattered from carbon, and one due to electrons scattered from hydrogen. The separation of these peaks is within a few per cent identical to what is expected for scattering from isolated C and H atoms. The peak due to electrons scattered from C, is again shifted compared to the peak of electrons scattered from Xe. The Xe, C and H peaks all have clearly different widths. The C and H peak areas are compared. Their relative intensity shows no substantial deviation (<10%) from what is expected based on either simple Rutherford cross sections, or state-of-the-art elastic scattering calculations. The latter observation is in strong contrast to electron scattering results from a gaseous equimolar H2–D2 mixture and from electron and neutron scattering results from polymers at similar momentum transfer.

Anomalous Quasielastic Electron Scattering from SingleH2,D2, and HD Molecules at Large Momentum Transfer: Indications of Nuclear Spin Effects

Quasielectron electron scattering from gaseous H2, D2, a 50:50 mixture of H2 and D2, and HD is investigated with 2.25 keV impact energy and a momentum transfer variant Planck's over 2piq of 19.7 a.u. The energy transfer is less than the dissociation energy. The spectral positions of the H and D recoil peaks agree with Rutherford scattering theory. Surprisingly, in the spectrum of the 50:50 H2-D2 mixture, the integrated intensity of the H peak is 31%+/-4% lower (as compared to that of D) than predicted by Rutherford scattering, despite equal screening of nuclear charges by the electrons. In contrast, the ratio of scattering intensities from H and D in HD agrees with the predictions of Rutherford scattering. Comparison is made with neutron Compton scattering results from the same systems, but at higher energy transfers causing bond breaking. Possible theoretical explanations are outlined.

Ultraviolet emission from OH and ArD in microcavity plasma devices

Intense emission in the ultraviolet (250–400 nm) from OH (A2 Σ+) and the rare gas-deuteride excimer ArD has been observed from mixtures of H2O vapour or D2 in Ar and excited in microcavity plasma devices. Peak wavelength-integrated intensities are measured for H2O and D2 concentrations of ∼0.16% and 0.5–1%, respectively. Spectral simulations indicate the OH (A2 Σ+, v′=0) rotational temperature to be 440±20 K for 600 Torr Ar/0.3 Torr H2O mixtures excited in a 45 nL microcavity.

Tests of the hydrodynamic equivalence of direct-drive implosions with different D2 and He3 mixtures

Direct drive implosions of targets filled with different mixtures of D2 and He3 gas on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] have shown an unexpected scaling of experimental nuclear yields. At temperatures above a few electron volts, D2 and He3 gases are fully ionized, and hydrodynamically equivalent fuels with different ratios of D2 and He3 can be chosen to have the same mass density, total particle density, and equation of state. Implosions with a 50/50 mixture of D:He3 by atom consistently result in measured nuclear yields half of that anticipated by scaling from measured yields of implosions with pure D2 and nearly pure He3. This observation is seen over a wide range of experimental configurations, including targets with a variety of shell thicknesses and fill pressures, simultaneously for two different nuclear yields (DD and DHe3), and for shock and compression yields. A number of possible mechanisms to cause the scaling are considered, but no dominant mechanism has been identified.

Surface mediated isotope exchange reactions between water and gaseous deuterium

Maintaining isotopic purity of hydrogen is one of the major tasks in tritium processing systems. The work with multiple isotopes and isotopomers is accompanied by isotope exchanges which is often accelerated by catalysts e.g. surfaces of various materials. In this work, densities of D2O, HDO produced via isotope exchange reactions in the mixture of D2, H2, D2O, H2O, HD and HDO contained in a stainless steel (type SS304) vessel were measured as a function of time (40–36000s) and pressures near 3.5×102Pa, using mass spectrometry. The derived rates of change of the isotopomers densities are described accurately by a postulated kinetic model.

MASS CULTURE OF MOSQUITOLARVAE (CULEX PIPIENS)AND THEIR NUTRITIVE VALUE AS FOOD FOR THE FREHSWATER PRAWN

arvae of Culex pipiens, mosquito were cultured under controlled laboratory conditions. They were introduced to larvae of the freshwater prawn, Macrobrachium rosenbergii (De Man) in a 7 5-day feeding experiment. Larvae of the prawn with an initial total length of 1.2 cm and initial body weight of 0.02g, received three feeding regimes; (1) live Artemia nauplii alone, Dl (2) live mosquito larvae alone,D2 (3) mixture of Artemia nauplii and mosquito larvae (1:1) (D3). Each treatment was evaluated in duplicate aquaria. The growth rate, survival and amino acids analysis were performed for prawns larvae fed on different diets. No significant difference (P>0.05) was found in growth rates, survival, and amino acid composition of prawns larvae receiving DlandD3. A significantly lower growth and survival rates were observed in prawns larvae fed on mosquito larvae as a sole food and this was due to cannibalism that occurred in this group. The nutritive value and proximate composition of mosquito larvae were measured (crude protein,42.2% and crude lipid,16.1% and high values of most essential amino acids content such as threonine 5.08, valine 5.20, histidine 2.83, isoleucine 6.96, phenylalanine 4.46 and lysine 7.59% ).Also, mosquito larvae contained some major metals such as Ca, Na, K, Mg, Fe, Cu, Zn and Mn. The study revealed that mosquito larvae in their live form failed to improve the growth rate and survival of the freshwater prawn when added to Artemia nauplii. This may be due to their active swimming and breathing behavior.

Multiple Photocycles of Channelrhodopsin

Two rhodopsins with intrinsic ion conductance have been identified recently in Chlamydomonas reinhardtii. They were named “channelrhodopsins” ChR1 and ChR2. Both were expressed in Xenopus laevis oocytes, and their properties were studied qualitatively by two electrode voltage clamp techniques. ChR1 is specific for H +, whereas ChR2 conducts Na +, K +, Ca 2+, and guanidinium. ChR2 responds to the onset of light with a peak conductance, followed by a smaller steady-state conductance. Upon a second stimulation, the peak is smaller and recovers to full size faster at high external pH. ChR1 was reported to respond with a steady-state conductance only but is demonstrated here to have a peak conductance at high light intensities too. We analyzed quantitatively the light-induced conductance of ChR1 and developed a reaction scheme that describes the photocurrent kinetics at various light conditions. ChR1 exists in two dark states, D1 and D2, that photoisomerize to the conducting states M1 and M2, respectively. Dark-adapted ChR1 is completely arrested in D1. M1 converts into D1 within milliseconds but, in addition, equilibrates with the second conducting state M2 that decays to the second dark state D2. Thus, light-adapted ChR1 represents a mixture of D1 and D2. D2 thermally reconverts to D1 in minutes, i.e., much slower than any reaction of the two photocycles.

Entropy-Driven Reentrant Phase Transitions in Even-J/Odd-J Mixtures of Linear Rotors

Depending on the parity of the rotational quantum number J, solid hydrogens exhibit either pressure-driven broken symmetry phase (BSP) transitions (even-J species – para-hydrogen (p-H2), and ortho-deuterium (o-D2)) or usual order-disorder phase transitions (odd-J species – o-H2 and p-D2) with the phase transition temperature increasing monotonically with pressure from the phase transition point at zero pressure. At the same time, for solid HD the BSP phase transition line displays a minimum, indicating that the disordered phase is reentrant. In this work a model of quantum linear rotors is used to study characteristic features of the P–T phase diagrams for ortho–para mixtures in solid H2 and D2. We developed a mean-field theory of even-J – odd-J mixtures of quantum linear rotors on a 3D lattice. Two limiting cases are considered: mixtures at thermodynamic equilibrium, where the conversion time is small or comparable with the thermalization time, and the opposite case, frozen mixtures, when the conversion time is large compared with other relevant times. We found that for all equilibrium linear rotor systems — the even-J – odd-J mixtures — the reentrant behavior of the phase transition lines is an entropy-driven phenomenon, as was previously found for the all-J system. Experimentally, conditions to find the reentrant BSP transition line are most favorable for H2 mixtures, whereas the frozen monotonic phase lines should be the case for D2 even-J – odd-J mixtures. These results may therefore be particularly useful for understanding the anomalous transition region of the BSP transition documented for D2 mixtures.

Transport and relaxation properties of isotopomeric hydrogen–helium binary mixtures. II. HD, D2, T2–He mixtures

The comprehensive comparison between calculated bulk non-equilibrium properties of hydrogen–helium isotopomeric mixtures and experiment that has previously been carried out for H2–helium mixtures [2004, Molec. Phys., submitted] has been extended to mixtures of HD, D2 and T2 with 3He and 4He. For HD–4He mixtures, comparison is also made, where possible, with previous calculations of Köhler and Schaefer [1983, Physica A, 120, 185]. The phenomena examined herein include low temperature interaction second virial coefficients, binary diffusion and thermal conductivity coefficients, rotational relaxation, transport property field effects and flow birefringence. Scattering calculations have been carried out for the HD–He PES of Schaefer and Köhler [1985, Physica A, 129, 469], and for both the Köhler–Schaefer and Tao [1994, J. chem. Phys., 100, 4947] potential surfaces for the D2–He and T2–He interactions. Comparisons between calculated and experimental results for HD, D2, T2–He mixtures confirm the conclusion, reached earlier from the H2–He comparisons, that these potential surfaces are very close to the correct one for the hydrogen–helium interaction, and that the small differences between them cannot be distinguished readily by measurements of bulk gas phenomena unless the attendant experimental uncertainties are better than ±0.3%.

Identification of multiple cell cycle regulatory functions of p57Kip2 in human T lymphocytes.

The specific functions of p57(Kip2) in lymphocytes have not yet been fully elucidated. In this study, it is shown that p57(Kip2), which is a member of the Cip/Kip family of cyclin-dependent kinase inhibitors, is present in the nuclei of normal resting (G(0)) T cells from peripheral blood and in the nuclei of the T cell-derived Jurkat cell line. Activation through the TCR results in rapid transport of cytoplasmic cyclin-dependent kinase 6 (cdk6) to nuclei, where it associates with cyclin D and p57(Kip2) in active enzyme complexes. Using purified recombinant proteins, it was shown in vitro that addition of p57(Kip2) protein to a mixture of cyclin D2 and cdk6 enhanced the association of the latter two proteins and resulted in phosphorylation of p57(Kip2). To probe further the function of p57(Kip2), Jurkat cells stably transfected with a plasmid encoding p57(Kip2) under control of an inducible (tetracycline) promoter were made. Induction of p57(Kip2) resulted in increased association of cdk6 with cyclin D3, without receptor-mediated T cell stimulation. The overall amounts of cdk6 and cyclin D3, and also of cdk4 and cyclin E, remained unchanged. Most notably, increased p57(Kip2) levels resulted in marked inhibition of both cyclin E- and cyclin A-associated cdk2 kinase activities and a decrease in cyclin A amounts. Therefore, although facilitating activation of cdk6, the ultimate outcome of p57(Kip2) induction was a decrease in DNA synthesis and cell proliferation. The results indicate that p57(Kip2) is involved in the regulation of several aspects of the T cell cycle.

Spectral characteristics of nonchain HF and DF electric-discharge lasers in efficient excitation modes

The spectral characteristics of efficient nonchain HF and DF chemical lasers are studied. It is found that the emission spectra of nonchain lasers operating with high efficiency are strongly broadened. Almost 30 emission lines of an HF laser and cascade lasing on the v(3-2) → v(2-1) → v(1-0) vibrational transitions of HF molecules for a number of rotational lines are obtained. It is shown that the development of discharge inhomogeneities significantly reduces the number of lasing lines in the spectra of nonchain chemical lasers. For an SF6 — D2 mixture excited by a generator with an inductive storage, about 40 lasing lines are observed on four vibrational transitions of DF molecules and the v(4-3) → v(3-2) → v(2-1) → v(1-0) cascade lasing is obtained at several rotational lines. Nonchain HF and DF electric-discharge lasers with a total and intrinsic efficiency of up to 6% and 10%, respectively, pumped from capacitive and inductive generators are developed.

Role of μ- and δ-opioid receptors in the nucleus accumbens in turning behaviour of rats

The role of μ-, δ1- and δ2-opioid receptors in the nucleus accumbens in pivoting was investigated in freely moving rats. Unilateral injections of the μ-opioid receptor agonist, [d-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO, 1 and 2 μg) and the δ2-opioid receptor agonist, deltorphin II (1 and 2 μg), but not the δ1-opioid receptor agonist, [d-Pen2,5]-enkephalin (DPDPE, 1–4 μg), into the shell or the core of the nucleus accumbens significantly induced contraversive pivoting. The pivoting induced by DAMGO (2 μg) and deltorphin II (2 μg) was inhibited significantly by the μ-opioid receptor antagonist, d-Phe-Cys-Tyr-d-Trp-Orn-Thr-Phe-Thr-NH2 (CTOP, 0.1 and 1 μg), and the δ2-opioid receptor antagonist, naltriben (NTB, 0.1 and 1 mg/kg, i.p.), respectively. The DAMGO (2 μg)- or deltorphin II (2 μg)-induced pivoting was also inhibited significantly by co-administration of the dopamine D1/D2 receptor antagonist, cis(Z)-flupentixol (1 and 10 μg). The pivoting induced by unilateral injections of a mixture of dopamine D1 (SKF 38393, 5 μg) and D2 (quinpirole, 10 μg) receptor agonists into the shell was significantly inhibited by cis(Z)-flupentixol (1 and 10 μg) or NTB (1 and 3 mg/kg, i.p.), but not CTOP (1 μg) or δ1-opioid receptor antagonist, (E)-7-benzylidenenaltrexone (1 mg/kg, i.p.). The contraversive pivoting elicited by the cholinergic agonist, carbachol (5 μg), into the core was inhibited by co-administration of the muscarinic M1 antagonist, pirenzepine (1 μg), but not cis(Z)-flupentixol (1 μg). The results suggest that unilateral activation of μ- or δ2-opioid, but not δ1-opioid, receptors in the core and/or shell of the nucleus accumbens elicits contraversive pivoting that requires intact dopamine D1/D2 receptors in the shell, but not intact muscarinic M1 mechanism in the core. The study also shows that δ2-opioid, but not μ- and δ1-opioid, receptors in the core and/or shell modulate the shell-specific, dopamine D1/D2 receptor mechanisms involved in the production of pivoting.

Infrared Spectra of Gallium Hydrides in Solid Hydrogen: GaH1,2,3, Ga2H2,4,6, and the GaH2,4- Anions

Reactions of laser-ablated Ga atoms and normal hydrogen during co-deposition at 3.5 K give GaH as the major product and GaH2, GaH3, GaH2-, GaH4-, and Ga2H2 as minor products. Identifications are based on infrared spectra, isotopic substitution (D2, H2 + D2 mixtures, HD), comparisons to earlier work, and frequencies calculated by density functional theory. Mercury arc radiation destroyed the GaH2- and GaH4- anions, decreased GaH and increased GaH3, destroyed Ga2H2, and produced new bands due to Ga2H4, two Ga2H5 radical isomers, and Ga2H6. ArF laser irradiation at 193 nm was particularly effective in converting GaH to GaH3 and to Ga2H6. The GaH4- anion absorptions in solid hydrogen are compatible with solid NaGaH4 bands: Near-ultraviolet excitation of GaD2- with D2 present increases GaD4- absorptions. Warming these samples to remove the H2 matrix replaced sharp gallium hydride molecular absorptions with broad 1800−2000, 1300−1700, and 600−700 cm-1 bands due to higher oligomers containing terminal and bridged Ga−H bonds.

Laboratory Submillimeter-Wave Detection of D 2 H + : A New Probe into Multiple Deuteration?

A pure rotational transition (J = 110-101) of D2H+ is measured in the laboratory with a high-sensitivity submillimeter-wave spectrometer. The D2H+ ions are generated in an extended negative glow discharge in a mixture of H2 and D2 with Ar as buffer gas (H2/D2/Ar = 4/2/17 mTorr) near liquid nitrogen temperature (77 K). The transition frequency is determined to be 691.660440(19) GHz with 1 σ in parentheses. This accurately measured transition frequency should be of great use for astronomical identification of this ion.

Infrared Spectra of Aluminum Hydrides in Solid Hydrogen: Al2H4 and Al2H6.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Influence of the concentration of H2–D2 mixtures on their triple-point dewetting behavior

Triple-point dewetting of pure gases like hydrogen and deuterium on solid substrates is a well-known phenomenon. This property persists even for the mixed system of H2 and D2. There exists an effective triple-point temperature T3(mix), between the T3 of pure H2 and that of pure D2, which depends on the species concentrations. We present new investigations for a wide range of H2–D2 concentrations measured under different thermodynamic conditions. This allows us to map out T3(mix) as function of concentration, which can be different in the melting or solidifying direction. Furthermore, it turns out that the time the system needs to reach an equilibrium state can be very long and depends on concentration. This is not observed for the pure H2 and D2 systems. Sometimes the relaxation times are so extremely long that significant hysteresis occurs during ramping of the temperature, even if this is done very slowly on a scale of hours. This behavior can be understood on the basis of mixing and demixing processes. Possible differences in the species concentrations in the gas, liquid, and especially solid phase of the system are discussed. A preliminary phase diagram of the H2–D2 system is established.

Chromium Hydrides and Dihydrogen Complexes in Solid Neon, Argon, and Hydrogen: Matrix Infrared Spectra and Quantum Chemical Calculations

Reactions of chromium atoms with molecular hydrogen are investigated through matrix-isolation infrared spectroscopy of products and complexes. Laser-ablated chromium atoms react with molecular hydrogen upon condensation in excess neon and argon and in pure hydrogen. The reaction products, CrH, (H2)CrH, CrH2, (H2)CrH2, and (H2)2CrH2 are identified by isotopic substitution (D2, HD, and H2+D2) and comparison with DFT (density functional theory) and MP2 calculations of vibrational fundamentals. The (H2)CrH complex with lower energy than CrH3 is trapped and no band is observed for CrH3. Reactions with H2 and D2 mixtures and with HD give different relative yields of the same mixed isotopic bands, which shows that exchange of dihydride and dihydrogen complex positions occurs in the energized [CrH4]* intermediate in the formation of (H2)CrH2. The major bands at 1529.5 cm-1 for H2 and 1112.2 cm-1 for D2 in neon and at 1521.3 cm-1 in pure hydrogen and 1106.9 cm-1 in pure deuterium are due to (H2)2CrH2 and (D2)2CrD2, respectively, which is the most stable form for chromium hexahydride.

Microcrystalline Silicon Film Growth Using a High-Density Microwave Plasma of SiH4-and-D2 Mixture

The role of hydrogen dilution for fast deposition of microcrystalline silicon (µc-Si) films is demonstrated using a high-density SiH4 and deuterium D2 mixture microwave plasma. Raman crystallinity of µc-Si films is significantly improved by using a D2 dilution rather than H2, although the film microstructure is still random. The degree of preferred (220) orientation, however, is poor in the D2-diluted films compared with H2-diluted films. The plasma potential Vs, corresponding to the degree of ion bombardment impinging on the film surface is lower in the D2 plasma rather than the H2 plasma. The film microstructure is discussed as a function of deposition parameters, along with plasma diagnostics for fast deposition of µc-Si films with preferred (220) orientation while maintaining a high deposition rate.

Homoleptic tetrahydrometalate anions MH(4)(-) (M = Sc, Y, La). Matrix infrared spectra and DFT calculations.

Laser-ablated Sc, Y, and La atoms react with molecular hydrogen upon condensation in excess argon, neon, and deuterium to produce the metal dihydride molecules and dihydrogen complexes MH(2) and (H(2))MH(2). The homoleptic tetrahydrometalate anions ScH(4)(-), YH(4)(-), and LaH(4)(-) are formed by electron capture and identified by isotopic substitution (D(2), HD, and H(2) + D(2) mixtures). Doping with CCl(4) to serve as an electron trap virtually eliminates the anion bands, and further supports the anion identifications. The observed vibrational frequencies are in agreement with the results of density functional theory calculations, which predict electron affinities in the 2.8-2.4 eV range for the (H(2))ScH(2), (H(2))YH(2), and (H(2))LaH(2) complexes, and indicate high stability for the MH(4)(-) (M = Sc, La, Y) anions and suggest the promise of synthesis on a larger scale for use as reducing agents.

State-resolved differential and integral cross sections for the reaction H+D2→HD(v′=3,j′=0–7)+D at 1.64 eV collision energy

A 212.8 nm laser initiates the reaction H+D2→HD+D in a mixture of HBr and D2. A second laser state-selectively ionizes the HD(v′=3,j′) reaction product, allowing a determination of the speed distribution and the relative cross section in a velocity-sensitive time-of-flight mass spectrometer. From these measurements we construct differential and integral cross sections for H+D2→HD(v′=3,j′=0–7)+D at 1.64±0.05 eV collision energy. Although the integral cross sections do not show any unusual features, the differential cross sections reveal forward-scattered features that have not been observed in crossed-beam experiments. An analysis of the scattering features in HD(v′=3,j′=1–4) suggests that these states are dominated by classical hard-sphere scattering. This hard-sphere (direct recoil) mechanism, however, cannot account for the dominant forward scattering observed in HD(v′=3,j′=0).