Quantum solvation of carbonyl sulfide with helium atoms

High-resolution infrared and microwave spectra of He(N)-carbonyl sulfide (He(N)-OCS) clusters with N ranging from 2 to 8 have been detected and unambiguously assigned. The spectra show the formation of a solvation layer beginning with an equatorial "donut" of five helium atoms around the OCS molecule. The cluster moment of inertia increases as a function of N and overshoots the liquid droplet limit for N > 5, implying that even atoms in the first solvation shell are decoupled from the OCS rotation in helium nanodroplets. To the extent that this is due to superfluidity, the results directly explore the microscopic evolution of a phenomenon that is formally macroscopic in nature.     

Linear alkane polymerization on a gold surface

In contrast to the many methods of selectively coupling olefins, few protocols catenate saturated hydrocarbons in a predictable manner. We report here the highly selective carbon-hydrogen (C-H) activation and subsequent dehydrogenative C-C coupling reaction of long-chain (>C(20)) linear alkanes on an anisotropic gold(110) surface, which undergoes an appropriate reconstruction by adsorption of the molecules and subsequent mild annealing, resulting in nanometer-sized channels (1.22 nanometers in width). Owing to the orientational constraint of the reactant molecules in these one-dimensional channels, the reaction takes place exclusively at specific sites (terminal CH(3) or penultimate CH(2) groups) in the chains at intermediate temperatures (420 to 470 kelvin) and selects for aliphatic over aromatic C-H activation.     

Melting of H2SO4·4H2O Particles upon Cooling: Implications for Polar Stratospheric Clouds

Polar stratospheric clouds (PSCs) are important for the chemical activation of chlorine compounds and subsequent ozone depletion. Solid PSCs can form on sulfuric acid tetrahydrate (SAT) (H2SO4·4H2O) nuclei, but recent laboratory experiments have shown that PSC nucleation on SAT is strongly hindered. A PSC formation mechanism is proposed in which SAT particles melt upon cooling in the presence of HNO3 to form liquid HNO3-H2SO4-H2O droplets 2 to 3 kelvin above the ice frost point. This mechanism offers a PSC formation temperature that is defined by the ambient conditions and sets a temperature limit below which PSCs should form.     

Stable compounds of helium and neon: he@c60 and ne@c60

It is demonstrated that fullerenes, prepared via the standard method (an arc between graphite electrodes in a partial pressure of helium), on heating to high temperatures release (4)He and (3)He. The amount corresponds to one (4)He for every 880,000 fullerene molecules. The (3)He/(4)He isotopic ratio is that of tank helium rather than that of atmospheric helium. These results convincingly show that the helium is inside and that there is no exchange with the atmosphere. The amount found corresponds with a prediction from a simple model based on the expected volume of the cavity. In addition, the temperature dependence for the release of helium implies a barrier about 80 kilocalories per mole. This is much lower than the barrier expected from theory for helium passing through one of the rings in the intact structure. Amechanism involving reversibly breaking one or more bonds to temporarily open a "window" in the cage is proposed. A predicted consequence of this mechanism is the incorporation of other gases while the "window" is open. This was demonstrated through the incorporation of (3)He and neon by heating fullerene in their presence.     

Estimates of mass and angular momentum in the oort cloud

Estimates can be made of unseen mass (in the form of cometary nuclei) at the heliocentric distances between 3 x 10(3) and 2 x 10(4) astronomical units(AU) under the assumptions (i) that the Oort cloud is a rarefied halo surrounding the core (dense, inner cometary cloud) and (ii) that the mass and albedo of comet Halley is typical for comets both in the core and the Oort cloud populations. The mass appears to be approximately 0.03 solar masses, with angular momentum of the order of 10(52) to 10(53) g-cm(2)/s. This mass is of the order of the total mass of the planetary system before the loss of volatiles. This leads to an estimate of a mass M(o) approximately 100 M( plus sign in circle) (where M( plus sign in circle) is the mass of Earth) concentrated in the Oort cloud (r > 2 x 10(4) AU) with an angular momentum that may exceed the present angular momentum of the whole planetary system by one order of magnitude. The present angular momentum of the Oort cloud appears to be of the same order as the total angular momentum of the planetary system before the loss of volatiles.     

Pressure-induced enhancement of tc above 150 k in hg-1223

The recently discovered homologous series HgBa(2)Can-1 Cun O2n+2+delta possesses remarkable properties. A superconducting transition temperature, T(c), as high as 133 kelvin has been measured in a multiphase Hg-Ba-Ca-Cu-O sample and found to be attributable to the Hg-1223 compound. Temperature-dependent electrical resistivity measurements under pressure on a (> 95%) pure Hg-1223 phase are reported. These data show that T(c) increases steadily with pressure at a rate of about 1 kelvin per gigapascal up to 15 gigapascals, then more slowly and reaches a T(c) = 150 kelvin, with the onset of the transition at 157 kelvin, for 23.5 gigapascals. This large pressure variation (as compared to the small effects observed in similar compounds with the optimal T(c)) strongly suggests that higher critical temperatures could be obtained at atmospheric pressure.     

Nonequilibrium self-assembly of long chains of polar molecules in superfluid helium

It is shown that in the low-temperature (0.37 kelvin) environment of superfluid helium droplets, long-range dipole-dipole forces acting between two polar molecules can result in the self-assembly of noncovalently bonded linear chains. At this temperature the effective range of these forces is on the nanometer scale, making them important in the growth of nanoscale structures. In particular, the self-assembly of exclusively linear hydrogen cyanide chains is observed, even when the folded structures are energetically favored. This suggests a design strategy for the growth of new nanoscale oligomers composed of monomers with defined dipole (or higher order) moment directions.     

Nanophase transition metal oxides show large thermodynamically driven shifts in oxidation-reduction equilibria

Knowing the thermodynamic stability of transition metal oxide nanoparticles is important for understanding and controlling their role in a variety of industrial and environmental systems. Using calorimetric data on surface energies for cobalt, iron, manganese, and nickel oxide systems, we show that surface energy strongly influences their redox equilibria and phase stability. Spinels (M(3)O(4)) commonly have lower surface energies than metals (M), rocksalt oxides (MO), and trivalent oxides (M(2)O(3)) of the same metal; thus, the contraction of the stability field of the divalent oxide and expansion of the spinel field appear to be general phenomena. Using tabulated thermodynamic data for bulk phases to calculate redox phase equilibria at the nanoscale can lead to errors of several orders of magnitude in oxygen fugacity and of 100 to 200 kelvin in temperature.     

(Mg,Fe)SiO3-perovskite stability under lower mantle conditions

In three different experiments up to 100 gigapascals and 3000 kelvin, (Mg,Fe)SiO3-perovskite, the major component of the lower mantle, remained stable and did not decompose to its component oxides (Mg, Fe)O and SiO2. Perovskite was formed from these oxides when heated in a diamond anvil cell at pressures up to 100 gigapascals. Both MgSiO3 crystals and glasses heated to 3000 kelvin at 75 gigapascals also formed perovskite as a single phase, as evident from Raman spectra. Moreover, fluorescence measurements on chromium-doped samples synthesized at these conditions gave no indication of the presence of MgO.     

Metastable phases in polar stratospheric aerosols

Phase changes in stratospheric aerosols were studied by cooling a droplet of sulfuric acid (H(2)SO(4)) in the presence of nitric acid (HNO(3)) and water vapor. A sequence of solid phases was observed to form that followed Ostwald's rule for phase nucleation. For stratospheric partial pressures at temperatures between 193 and 195 kelvin, a metastable ternary H(2)SO(4)-HNO(3) hydrate, H(2)SO(4) . HNO(3) . 5H(2)O, formed in coexistence with binary H(2)SO(4) . kH(2)O hydrates (k = 2, 3, and 4) and then transformed to nitric acid dihydrate, HNO(3) . 2H(2)O, within a few hours. Metastable HNO(3) . 2H(2)O always formed before stable nitric acid trihydrate, HNO(3).3H(2)O, under stratospheric conditions and persisted for long periods. The formation of metastable phases provides a mechanism for differential particle growth and sedimentation of HNO(3) from the polar winter stratosphere.     

Energetics of hydrogen bond network rearrangements in liquid water

A strong temperature dependence of oxygen K-edge x-ray absorption fine structure features was observed for supercooled and normal liquid water droplets prepared from the breakup of a liquid microjet. Analysis of the data over the temperature range 251 to 288 kelvin (-22 degrees to +15 degrees C) yields a value of 1.5 +/- 0.5 kilocalories per mole for the average thermal energy required to effect an observable rearrangement between the fully coordinated ("ice-like") and distorted ("broken-donor") local hydrogen-bonding configurations responsible for the pre-edge and post-edge features, respectively. This energy equals the latent heat of melting of ice with hexagonal symmetry (ice Ih) and is consistent with the distribution of hydrogen bond strengths obtained for the "overstructured" ST2 model of water.     

The Reaction of CIONO2 with Submicrometer Sulfuric Acid Aerosol

The measured reaction probability, gamma for the reaction of chlorine nitrate (CIONa(2)) with 60 percent (by weight) sulfuric acid aerosol increases monotonically with particle size at 250 kelvin. The reacto-diffusive length (l, the effective liquid depth over which reaction occurs) derived from these experiments is 0.037 +/- 0.007 micrometer (95 percent confidence level for precision). The reaction probability for the reaction of CIONO(2) with 60 percent sulfuric acid aerosol doped with approximately 7 x 10(-4) M hydrochloric acid at 250 kelvin is larger by about a factor of 4 than in the absence of hydrochloric acid and varies less with particle size (l = 0.009 +/- 0.005 micrometer). These results provide a test of the theory for gas-particle reactions and further insight into the reactivity of atmospheric aerosol.     

Protonated Ozone: Experimental Detection of O3H+ and Evaluation of the Proton Affinity of Ozone

The elusive protonated ozone ion (O(3)H(+)) has been long postulated as a reactive intermediate but never experimentally observed. This ion has been detected here in mass spectrometric experiments with the use of Fourier transform ion cyclotron resonance. In these experiments, ozone (O(3)) was protonated by strong acids-for example, H(3)(+), KrH(+), XeH(+), and CH(5)(+). The hitherto experimentally unknown proton affinity of O(3) was evaluated by a "bracketing" technique and determined to be 148 -/+ 3 kilocalories mole(-1) at 298 kelvin, in excellent agreement with a value determined in a recent theoretical study of the O(3)/O(3)H(+) system, which was 148 kilocalories mole(-1) at zero temperature ( approximately 149.5 kilocalories mole(-1) at 298 kelvin).     

模拟氮沉降对水稻生长、产量及光合特性的影响

田间试验研究4种水平的模拟氮沉降(即N0、N1、N2、N3、N4,施氮量分别为0、3、6、12、24 g/(m2.a)对早稻品种"岳优463"不同生长发育阶段的影响。结果表明,氮沉降对水稻的生长、产量及光合作用有一定的促进作用。经高氮沉降(N4)处理,水稻株高、光合速率在分蘖期分别比对照(N0)增加了45.6%和49.5%,在乳熟期比对照增加了6.4%和28.9%。氮沉降对水稻叶绿素a、叶绿素b和叶绿素(a+b)含量均表现为促进作用。乳熟期N1、N2、N3、N4的叶绿素(a+b)比N0增加了34.9%、51.5%、111.3%和143.6%。中高氮处理(N3,N4)对水稻产量的促进作用较为显著,N1、N2、N3、N4的产量分别比N0增加了1.3%、6.2%、13.0%和42.6%。随施氮水平的增加,秕谷率也增加,而产量指数和籽粒大小呈下降趋势。     

Compression of Ice to 210 Gigapascals: Infrared Evidence for a Symmetric Hydrogen-Bonded Phase

Protonated and deuterated ices (H2O and D2O) compressed to a maximum pressure of 210 gigapascals at 85 to 300 kelvin exhibit a phase transition at 60 gigapascals in H2O ice (70 gigapascals in D2O ice) on the basis of their infrared reflectance spectra determined with synchrotron radiation. The transition is characterized by soft-mode behavior of the nu3 O-H or O-D stretch below the transition, followed by a hardening (positive pressure shift) above it. This behavior is interpreted as the transformation of ice phase VII to a structure with symmetric hydrogen bonds. The spectroscopic features of the phase persisted to the maximum pressures (210 gigapascals) of the measurements, although changes in vibrational mode coupling were observed at 150 to 160 gigapascals.     

Stability and structure of MgSiO3 perovskite to 2300-kilometer depth in Earth's mantle

Unexplained features have been observed seismically near the middle (approximately 1700-kilometer depth) and bottom of the Earth's lower mantle, and these could have important implications for the dynamics and evolution of the planet. (Mg,Fe)SiO3 perovskite is expected to be the dominant mineral in the deep mantle, but experimental results are discrepant regarding its stability and structure. Here we report in situ x-ray diffraction observations of (Mg,Fe)SiO3 perovskite at conditions (50 to 106 gigapascals, 1600 to 2400 kelvin) close to a mantle geotherm from three different starting materials, (Mg0.9Fe0.1)SiO enstatite, MgSiO3 glass, and an MgO+SiO2 mixture. Our results confirm the stability of (Mg,Fe)SiO3 perovskite to at least 2300-kilometer depth in the mantle. However, diffraction patterns above 83 gigapascals and 1700 kelvin (1900-kilometer depth) cannot presently rule out a possible transformation from Pbnm perovskite to one of three other possible perovskite structures with space group P2(1)/m, Pmmn, or P4(2)/nmc.     

Kinetics of the OH Reaction with Methyl Chloroform and Its Atmospheric Implications

The rate coefficients for the reaction of hydroxyl (OH) radicals with methyl chloroform (CH(3)CCI(3)) were measured between 243 and 379 kelvin with the pulsed photolysis-laserinduced fluorescence method. The measured rate coefficients at 298 and 277 kelvin were approximately 20 and approximately 15%, respectively, lower than earlier values. These results will increase the tropospheric OH concentrations derived from the CH(3)CCI(3) budget analysis by approximately 15%. The predicted atmospheric lifetimes of species whose main loss process is the reaction with OH in the troposphere will be lowered by 15% with consequent changes in their budgets, global warming potentials, and ozone depletion potentials.     

水平潜流人工湿地处理北方低浓度生活污水研究

[目的]获得不同条件下水平潜流人工湿地的最佳运行参数。[方法]研究了水平潜流人工湿地在不同工况下处理北方低浓度生活污水的效果,探讨了CODCr、NH4＋-N、TN和TP等指标的去除率与温度、水力负荷等的关系。[结果]在0.04～0.15 m3/（m2.d）的水力负荷区间内,夏季高温采用高水力负荷[0.12～0.15 m3/（m2.d）]、秋季中温采用中水力负荷[0.07～0.10 m3/（m2.d）]、冬季采用低水力负荷[0.04～0.06 m3/（m2.d）]为最佳运行参数。[结论]温度是影响湿地处理效果的关键因素之一。     

Mantle plumes and entrainment: isotopic evidence

Many oceanic island basalts show sublinear subparallel arrays in Sr-Nd-Pb isotopic space. The depleted upper mantle is rarely a mixing end-member of these arrays, as would be expected if mantle plumes originated at a 670-kilometer boundary layer and entrained upper mantle during ascent. Instead, the arrays are fan-shaped and appear to converge on a volume in isotopic space characterized by low (87)Sr/(86)Sr and high (143)Nd/(144)Nd, (206)Pb/(204)Pb, and (3)He/(4)He ratios. This new isotopic component may be the lower mantle, entrained into plumes originating from the core-mantle boundary layer.     

Orientational and Magnetic Ordering of Buckyballs in TDAE-C60

Spin ordering in the low-temperature magnetic phase is directly linked to the orientational ordering of C(60) molecules in organically doped fullerene derivatives. Electron spin resonance and alternating current susceptometry measurements on tetrakis(dimethylamino)ethylene-C(60) (TDAE-C(60)) (Curie temperature T(c) = 16 kelvin) show a direct coupling between spin and merohedral degrees of freedom. This coupling was experimentally demonstrated by showing that ordering the spins in the magnetic phase imprints a merohedral order on the solid or, conversely, that merohedrally ordering the C(60) molecules influences the spin order at low temperature. The merohedral disorder gives rise to a distribution of pi-lectron exchange interactions between spins on neighboring C(60) molecules, suggesting a microscopic origin for the observed spinglass behavior of the magnetic state.