Dependence of the effective rate constants for the hydrogenation of CO on the temperature and composition of the surface

Experiments on the hydrogenation of CO on pure CO and CO-H₂O mixed ice have been performed at temperatures between 8 and 20 K. We obtained temperature and compositional dependence of the effective reaction rate constants. Results indicate that hydrogenation proceeds efficiently on pure solid CO and CO-H₂O mixed ice at temperatures below 10 and 20 K, respectively. Rate constants for pure CO decreased significantly at 12 K compared to those obtained with CO-H₂O mixed ice. Hydrogenation of CO at temperatures greater than 12 K were catalyzed by the H₂O adjacent to the CO. The importance of the experimental results for some relevant astrophysical environments has also been outlined.     

Ice-induced seasonal variability of tidal constants in the Arctic Ocean

The results for three-dimensional (3D) winter and summer tidal flows in the homogeneous Arctic Ocean, obtained with the use of a modified version of the 3D finite-element hydrothermodynamic model QUODDY-4, are presented. It is shown that seasonal variability of the M₂ tidal constants (amplitudes and phases of tidal sea surface level elevations) in the Central and Canadian parts of the Arctic Ocean is less than the error in the predicted tidal sea surface level elevations. This means that the seasonal variability can be neglected at least as a first approximation. A different situation is encountered in the Siberian continental shelf, where seasonal changes of tidal amplitude are ±5 cm, while those of tidal phase vary from 15° to several tens of degrees.     

横向各向同性地层(VTI)井孔声弹效应对弯曲波的影响

本文发展了建立在地层参考状态为各向同性介质假定下的现行井孔声弹性理论,就井外为横向各向同性面与井轴垂直的、具有9个独立三阶弹性模量的横向各向同性介质(VTI井况),水平面内受双轴应力作用下给出了一个简洁的与井内压力、应力差、应力和以及多极源偏振方位角有关的井孔弯曲波声弹公式,并且导出了平面纵、横波速度的声弹公式.数值考察了弯曲波速度之改变量的灵敏系数随频率的变化、受井外水平双轴应力作用时两种偏振的偶极弯曲波频散曲线以及对应不同方位径向偏振的横波速度.研究结果表明弯曲波声弹公式与5个二阶弹性系数以及7个独立的三阶弹性模量有关;而且由内压引起的井孔弯曲波声弹性公式中的三阶弹性模量仅与6个独立的弹性模量有关.横向各向同性介质井孔弯曲波速度的交叉现象仍是判断地应力存在的标志;一个重要的认识是受双轴应力作用的弯曲波速度变化在低频区主要与c₁₄₄和c₁₅₅两个三阶弹性模量有关,而且此认识与径向偏振的平面横波一致.在缺乏足够实验条件情况下,对VTI情况,以c₁₄₄,c₁₅₅和c₁₂₃三个独立的量进行测量,然后可暂不考虑三阶弹性模量的各向异性,建立简化的应力反演公式.反之,如果已知地层的地应力信息,由简化的声弹公式可以反演三阶弹性模量c₁₄₄,c₁₅₅和c₁₂₃.     

High-temperature phase transitions and elasticity of silica polymorphs

The single-crystal acoustic velocities of α- and β-quartz were measured by Brillouin spectroscopy to a maximum temperature >1,500°C at room pressure. From these velocities, the single-crystal elastic moduli were calculated up to 1,050°C, exceeding the temperature range of previous measurements by 350°C for the elastic moduli and by 710°C for acoustic velocities. The ordinary refractive index (n _o) of α- and β-quartz was measured from room temperature to 800°C. In the temperature interval from ∼950 to 1,000°C a subtle change in the temperature derivative of the longitudinal acoustic velocity was observed in platelet geometry for all measured directions. The high-temperature acoustic velocity data may indicate the presence of a second phase, presumably β-cristobalite, that nucleates below 1,000°C.

Characterization of the binding sites for Al(III) and Be(II) in a sample of marine fulvic acids

A sample of coastal marine fulvic acids (mfua) was studied and its binding site structures that form stable complexes with metal ions were identified. A previously developed self-modeling methodology, based on the coupling of synchronous fluorescence (SyF) spectroscopy with evolving factor analysis (EFA), was used for the analysis of the interactions between mfua and two metal ions that act as probes for binding sites, namely Be(II) and Al(III). Two types of binding site structures were detected, probably of the salicylic acid and catechol types. The values of the conditional stability constants between mfua and the two metal ions were: for Be(II), at pH = 6, log K = 5.32(8); for Al(III), at pH = 4, log K = 5.1(2). The concentration of the corresponding binding sites was found to be less than one half of those found for soil fulvic acid samples.     

中国近海潮波图计算与研究

首次给出了解算潮波微分方程较完善的实用公式。采用边界点作为已知点,海上定点验潮站作为控制和检查点,对我国近海30'×30'网格点进行计算,经与实测资料对比,分潮振幅H精度为±15cm,分潮迟角g精度为±20o,完全满足海道测量海上潮汐改正精度要求。给出了潮波图和无潮点位置。最后还分析研究了中国近海潮波传播特征,得出了一些有益的结论。     

The Reaction of Unsaturated Aliphatic Oxygenates with Ozone

The reaction of ozone with unsaturated aliphatic oxygenates has been studied at ambient T (287–297 K) and p = 1 atm. of air (RH = 55 ± 10%) with sufficient cyclohexane added to scavenge the hydroxyl radical. Reaction rate constants, in units of 10-18 cm3 molecule-1 s-1, are 10.7 ± 1.4 for methyl trans-3-methoxy acrylate, 63.7 ± 9.9 for 4-hexen-3-one (predominantly the trans isomer), 125 ± 17 for trans-4-methoxy-3-buten-2-one, 148 ± 13 for cis-4-heptenal, 439 ± 37 for 3- methyl-2-buten-1-ol and 585 ± 132 for (cis + trans)-ethyl 1-propenyl ether. The influence of the oxygen-containing substituents on reactivity toward ozone is examined. Unsaturated ethers react with ozone faster than their alkene structural homologues; the reverse is observed for unsaturated esters and unsaturated carbonyls. Major reaction products have been identified by liquid chromatography with ultraviolet detection (LC-UV), particle beam-mass spectrometry (PB- MS) and gas chromatography-mass spectrometry (GC-MS) and are methyl formate and methyl glyoxylate from methyl trans-3-methoxy acrylate, acetaldehyde and 2-oxobutanal from 4-hexen-3-one, propanal and succinic dialdehyde from cis-4-heptenal, hydroxyacetaldehyde and acetone from 3-methyl-2-buten-1-ol, and ethyl formate and acetaldehyde from (cis + trans)-ethyl 1-propenyl ether. PB-MS and GC- MS were also employed to identify new reaction products and to confirm the structure of products tentatively identified in a previous study of the reaction of ozone with five unsaturated oxygenates (Grosjean and Grosjean, 1997a): formic acid and methyl glyoxylate from methyl acrylate, formic acid and formic acetic anhydride from vinyl acetate, 2-oxoethyl acetate and 3-oxopropyl acetate from cis-3-hexenyl acetate, ethyl formate and formic acid from ethyl vinyl ether, and methyl formate from trans-4-methoxy-3- buten-2-one. The nature and formation yields of the reaction products are consistent with (and supportive of) the reaction mechanism: O3 + R1R2C=CR3X (R1COR2 + R3C(X)OO) + (1 - )(R3COX + R1C(R2)OO), where R1, R2 and R3 = H or alkyl, X is the oxygen-containing substituent, R1COR2 and R3COX are the primary products and R1C(R2)OO and R3C(X)OO are the carbonyl oxide biradicals. The variations of the coefficient , which ranges from 0.25 to 0.61, are discussed in terms of the number and nature of alkyl and oxygen-containing substituents. Subsequent reactions of the alkyl-substituted biradicals R1C(R2)OO and of the biradicals R3C(X)OO that bear the oxygen-containing substituent are discussed. For the biradical CH3CHOO, the ratio ka/kb for the competing pathways of rearrangement to acetic acid (CH3CHOO CH3C(O)OH, reaction (a) and formation of an unsaturated hydroperoxide (CH3CHOO CH2=CH(OOH), reaction (b) is <0.25 for ethyl 1-propenyl ether and <0.27 for 4-hexen-3-one. Concentrations measured in co- located samples, one downstream of a water impinger and the other without water impinger, show the uptake in water impingers to be high (from 83.2 to >99.9%) and comparable to that for formaldehyde (98.4%) for formic acetic anhydride and for difunctional oxygenated compounds. Uptake in water impingers was lower (19–78%) for monofunctional aldehydes and ketones.     

Alkyl nitrates and bifunctional nitrates of atmospheric interest: Henry's law constants and their temperature dependencies

Henry's law coefficients of 15 alkyl nitrates, keto-, hydroxy-, and dinitrates of atmospheric interest have been measured, mostly over the temperature range 1–25°C. The compounds are stable in aqueous solution. Where literature data were available, Henry's law coefficients are in very good agreement. It is concluded that dissolution in cloud and rain water is not an important loss process for alkyl mononitrates in the atmosphere. The residence times of the more soluble bifunctional organic nitrates, however, are significantly affected or even controlled by washout and rainout. Gas chromatographic analysis of bifunctional nitrates in preconcentrated atmospheric samples may be adversely affected by the adsorptive properties of these compounds.     

The Transition Between the Scale Domains of Ray and Effective Medium Theory and Anisotropy: Numerical Models

The anisotropy of a periodically layered isotropic medium is numerically modeled in order to study the effect of the scale of heterogeneity on seismic observations. An important motivation is to delineate the wavelength ranges over which a pulse propagating obliquely through the structure will be described by either ray (short wavelength) or effective medium (long wavelength) theory. The same band-limited pulse is propagated obliquely at a variety of incidence angles through a compositionally uniform layered structure as a function of the layer thicknesses. The resulting seismograms display similar behavior to that encountered for normal incidence including the effects of stop- and pass-bands. Velocities determined from time picks on these seismograms show a large difference in velocities between the long and short wavelength limits as has been previously demonstrated for normal incidence propagation. The bulk of the transition between these two limits is independent of incidence angle and occurs when the ratio between the wavelength and the layering thickness is near a value of 10. Two more geologically reasonable models show that these effects are diminished with smaller contrasts between the layers.