Grafted fluoropolymers as supports for solid-phase organic chemistry : preparation and characterization

Solid-phase organic chemistry has rapidly expanded in the last decade, and, as a consequence, so has the need for the development of supports that can withstand the extreme conditions required to facilitate some reactions. The authors here prepare a thermally stable, grafted fluoropolymer support (see Figure for an example) in three solvents, and found that the penetration of the graft was greatest in dichloromethane.

An ESR study of irradiated poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA)

Poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA) with 2 mol% perfluoropropyl vinyl ether (PPVE) was exposed to γ-irradiation in vacuum at both 77 K and room temperature and the ESR spectra recorded. Both the main chain, CF2–C.F–CF2, and end chain, CF2C.F2 radicals were identified at both temperatures and their thermal stabilities measured. No radicals unique to the radiolytic cleavage at the PPVE units were observed at room temperature, either due to the low concentration of the comonomer or β-scission to form a chain end radical and a non-radical species. G-values for radical formation at room temperature and 77 K were found to be 0.93 and 0.16, respectively.

High frequency wave propagation in the earth: theory and observation

The wave-theoretical analysis of acoustic and elastic waves refracted by a spherical boundary across which both velocity and density increase abruptly and thence either increase or decrease continuously with depth is formulated in terms of the general problem of waves generated at a steady point source and scattered by a radially heterogeneous spherical body. A displacement potential representation is used for the elastic problem that results in high frequency decoupling of P-SV motion in a spherically symmetric, radially heterogeneous medium. Through the application of an earth-flattening transformation on the radial solution and the Watson transform on the sum over eigenfunctions, the solution to the spherical problem for high frequencies is expressed as a Weyl integral for the corresponding half-space problem in which the effect of boundary curvature maps into an effective positive velocity gradient. The results of both analytical and numerical evaluation of this integral can be summarized as follows for body waves in the crust and upper mantle:

1) In the special case of a critical velocity gradient (a gradient equal and opposite to the effective curvature gradient), the critically refracted wave reduces to the classical head wave for flat, homogeneous layers.

2) For gradients more negative than critical, the amplitude of the critically refracted wave decays more rapidly with distance than the classical head wave.

3) For positive, null, and gradients less negative than critical, the amplitude of the critically refracted wave decays less rapidly with distance than the classical head wave, and at sufficiently large distances, the refracted wave can be adequately described in terms of ray-theoretical diving waves. At intermediate distances from the critical point, the spectral amplitude of the refracted wave is scalloped due to multiple diving wave interference.

These theoretical results applied to published amplitude data for P-waves refracted by the major crustal and upper mantle horizons (the Pg, P*, and Pn travel-time branches) suggest that the 'granitic' upper crust, the 'basaltic' lower crust, and the mantle lid all have negative or near-critical velocity gradients in the tectonically active western United States. On the other hand, the corresponding horizons in the stable eastern United States appear to have null or slightly positive velocity gradients. The distribution of negative and positive velocity gradients correlates closely with high heat flow in tectonic regions and normal heat flow in stable regions. The velocity gradients inferred from the amplitude data are generally consistent with those inferred from ultrasonic measurements of the effects of temperature and pressure on crustal and mantle rocks and probable geothermal gradients. A notable exception is the strong positive velocity gradient in the mantle lid beneath the eastern United States (2 x 10^-3 sec^-1), which appears to require a compositional gradient to counter the effect of even a small geothermal gradient.

New seismic-refraction data were recorded along a 800 km profile extending due south from the Canadian border across the Columbia Plateau into eastern Oregon. The source for the seismic waves was a series of 20 high-energy chemical explosions detonated by the Canadian government in Greenbush Lake, British Columbia. The first arrivals recorded along this profile are on the Pn travel-time branch. In northern Washington and central Oregon their travel time is described by T = Δ/8.0 + 7.7 sec, but in the Columbia Plateau the Pn arrivals are as much as 0.9 sec early with respect to this line. An interpretation of these Pn arrivals together with later crustal arrivals suggest that the crust under the Columbia Plateau is thinner by about 10 km and has a higher average P-wave velocity than the 35-km-thick, 62-km/sec crust under the granitic-metamorphic terrain of northern Washington. A tentative interpretation of later arrivals recorded beyond 500 km from the shots suggests that a thin 8.4-km/sec horizon may be present in the upper mantle beneath the Columbia Plateau and that this horizon may form the lid to a pronounced low-velocity zone extending to a depth of about 140 km.

墨西哥湾Alaminos Canyon、Bush Hill冷泉碳酸盐岩有机地球化学与沉积环境

本文通过对墨西哥湾Bush Hill 的5个冷泉碳酸盐岩样品和Alaminos Canyon 的1个冷泉碳酸盐岩样品的总有机质含量、可溶有机质含量、饱和烃、芳烃、脂肪酸、δ13C组成分布特征和部分地球化学参数的研究，探讨了冷泉碳酸盐岩中有机质来源、成熟度和沉积环境。 Bush Hill的冷泉碳酸盐岩样品的总有机碳为0.78-9.02%，可溶有机质含量5.77-65.06mg/g。总有机碳达9.02%的GC-B���品高碳数正构烷烃奇偶优势明显，存在荧蒽、芘和苝系列化合物，表明该样品有陆源物质的输入，并明显受深部渗漏原油的影响，其中烷烃的δ13C为-27.64～-32.36‰，正构脂肪酸δ13C为-26.52～-39.99‰，与现代菌藻类及下伏油气藏的δ13C值（-27～-31‰）相似，表明样品中的有机质主体可能来源于深部油气藏。其余4个Bush Hill冷泉碳酸盐岩样品和1个Alaminos Canyon冷泉碳酸盐岩样品正构烷烃的低碳优势明显，而奇偶优势不明显，低碳数分布的环己烷和长链烷基苯，以及三芳甾烷和甲基三芳甾烷的存在，推断这些样品的母质以菌藻类来源为主。 所有分析样品的甾烷成熟度参数C29ββ/(ββ+αα)为0.28-0.40，C2920S/(20S + 20R)为0.42-0.61、及C20-C21三芳孕甾烷TA(Ⅰ)/C26-C28三芳甾烷TA(Ⅱ)为0.49都说明样品的有机质成熟度较低,。 AC深水区AC-E样品UCM隆起不明显，Bush Hill浅水区样品（GC-B���GC-D、GC-F、GC-G，GC-H）UCM隆起均十分明显，这种隆起的形成是因为正烷烃、甚至五环三萜烷遭受生物降解。被微生物降解的正构烷烃与未被降解的环烷烃和支链烷烃等形成不能被溶解的复杂混合物（UCM）。因此，UCM隆起通常被认为是有机质遭受生物降解最直接的证据。深水区AC-E和Bush Hill浅水区GC-F样品中芴、氧芴和硫芴之间的丰度关系为硫芴﹥芴﹥氧芴，表明其为弱氧化-弱还原的沉积环境。具有较负碳同位素组成（-63.95‰ ~ -50.48‰）的异构/反异构脂肪酸是硫酸盐还原细菌的典型生物标志化合物，进一步证实冷泉碳酸盐岩的形成与甲烷缺氧氧化作用有关。 关键词：墨西哥湾 冷泉碳酸盐岩 有机质组成分布 单体烃碳同位素 沉积环境