川西高原中生代碰撞造山带的大地构造演化

按碰撞造山带模式分析,川西高原基本上属于中生代碰撞造山带。第三纪—至今的构造活动,尤以平移显著,主要受印度板块碰撞及陆内会聚影响所及。基于上述认识,对川西高原造山带提出新的构造单元划分方案,包括3个主要单元和11个次级单元。文中还提出该造山带碰撞前后的大地构造演化阶段,即早二叠世古特提斯洋扩张阶段、晚二叠世—中三叠世陆缘山弧阶段、晚三叠世卡尼期岛弧阶段、诺利—瑞替期碰撞阶段及侏罗—白垩纪陆内会聚阶段。     

Organotin accumulation in an estuarine food chain: comparing field measurements with model estimations

The bioaccumulation model OMEGA (optimal modelling for ecotoxicological applications) is used to explore accumulation of organotins in the Western Scheldt food chain, consisting of herbi-detritivores, primary and secondary carnivorous fish and a piscivorous bird. Organotins studied are tributyltin (TBT) and triphenyltin (TPT) and the respective di- and mono-organotin metabolites. Empirical elimination rate constants are compared to model predictions for organic substances and metals. It is found that field bioaccumulation ratios are higher than predicted based on elimination kinetics relevant for organic compounds. The results indicate that uptake of organotins mainly occurs via hydrophobic mechanisms, whereas elimination may occur via metal-like kinetics. This results in very low elimination rates, which are comparable to model predictions for metals.     

四川西部地质演化、成矿规律与成矿系列

以板块理论为指导，提出本区地质演化阶段四分方案，总结了各阶段相关矿产时空分布特征；阐明成矿地质条件的复杂性、成矿作用的多样性、矿床类型丰富性、成矿元素特征性和矿床规模趋大性等特点；在成矿时代上指出三叠纪、侏罗—白垩纪和第三纪为主要成矿期；在成矿构造环境上，以岛弧、弧后盆地、重熔花岗岩带、走滑剪切带及其拉分盆地为有利成矿场所，并根据成矿系列的定义厘定了成矿系列。     

Developing a Radiative Shock Experiment Relevant to Astrophysics

We assume that internal shocks of gamma-ray bursts (GRBs) consist of multiple sub-jets with a collimation half-angle of about several times gamma-1i, where gammai is the Lorentz factor of each sub-jet. If by chance a sub-jet is first emitted off-axis from the line of sight, the observed peak energy can be in the X-ray region. Next, if by chance a subsequent sub-jet is emitted along the line of sight, then the peak energy will be in the gamma-ray region and the gamma ray may arrive after the X-ray precursor from the former sub-jet depending on parameters. This model predicts a new class of GRBs with extremely weak and short gamma-ray emission but X-ray precursors and/or postcursors as well as an afterglow.     

Initial Time Dependence of Abundances in Solar Energetic Particle Events

We compare the initial behavior of Fe/O and He/H abundance ratios and their relationship to the evolution of the proton energy spectra in "small" and "large" gradual solar energetic particle (SEP) events. The results are qualitatively consistent with the behavior predicted by the theory of Ng et al. published in 1999. He/H ratios that initially rise with time are a signature of scattering by non-Kolmogorov Alfvén wave spectra generated by intense beams of shock-accelerated protons streaming outward in large gradual SEP events.     

How to overcome inter-electrode variability and instability to quantify dissolved oxygen, Fe(II), mn(II), and S(?II) in undisturbed soils and sediments using voltammetry

Background

Although uniquely capable of measuring multiple redox constituents nearly simultaneously with no or minimal sample pretreatment, voltammetry is currently underutilized in characterizing redox conditions in aquatic and terrestrial systems. Investigation of undisturbed media such as pore water requires a solid-state electrode, and such electrodes can be difficult to fabricate reproducibly. An approach to determine the concentrations of electroactive constituents using indirectly calibrated electrodes has been developed, but the protocol for and accuracy of this approach??the pilot ion method??has not been documented in detail.

Results

A detailed procedure for testing electrode quality is provided, and the application and limitations of the pilot ion method have been documented. To quantify Fe(II) and Mn(II), subtraction of non-linear baseline functions from voltammetric signals produced better calibration curves than did linear baselines, enabled lower detection limits and reliable deconvolution of overlapping signals, and was successfully applied to sediment pore water signals. We observed that electrode sensitivities often vary by tens of percent, and that the sensitivity declines over time. The ratio of calibration slopes of Mn(II) to Fe(II) varied by no more than 11% from one Hg/Au electrode to another and Fe(II) concentrations predicted by the Mn(II) pilot ion were, on average, 13% different from their actual values. However, concentration predictions by the pilot ion method were worse for less than 15???M Fe(II) (46% different on average). The ratio of calibration slopes of Mn(II) to S(?II) varied by almost 20% from one Hg/Au electrode to another, and S(?II) predicted concentrations were as much as 58% different from their actual values. These predictions of Fe(II) and S(?II) concentrations indicate that the accuracy of the pilot ion method depends on how independent calibration slope ratios are from the electrode used. At medium-to-high concentration for the ocean, naturally derived dissolved organic carbon did not significantly affect the baseline-corrected electrode response of Mn(II) and Fe(II), but did significantly affect the response of S(?II).

Conclusions

Despite their intrinsic variability, Hg/Au electrodes fabricated by hand can be used to quantify O₂, S(?II), Fe(II), and Mn(II) without calibrating every electrode for every constituent of interest. The pilot ion method can achieve accuracies to within 20% or less, provided that the underlying principle??the independence of slope ratios??is demonstrated for all voltammetric techniques used, and effects of the physicochemical properties of the system on voltammetric signals are addressed through baseline subtraction.