含水砂层对堆积体稳定性的影响研究

受复杂地质环境的影响,我国西南岷江上游沿岸普遍发育一种前缘多分布有一层或多层具一定厚度含水砂层的特殊堆积体。大量工程实践表明,工程开挖的扰动可导致砂层出现明显侧向变形,进而导致整个堆积体的失稳破坏。本文采用数值计算的方法,结合某典型堆积体对开挖条件下砂层影响其整体稳定性的作用机理进行了较为深入的分析和探讨。     

川藏公路培龙沟路段堆积物的分形特征及其地质意义

川藏公路培龙沟路段有多种不同类型的堆积物。本文应用分形理论,探讨了培龙沟路段泥石流堆积物、冰碛堆积物、冲洪积堆积物以及坡积或者残坡积物的分形特征。通过粒度分析法计算出不同类型堆积物的粒度分维,得到泥石流堆积物分维最大,冰碛堆积物分维较大,坡积或者残坡积堆积物较小,冲积物或者洪积物分维最小的规律。最后系统论述了堆积物粒度分维的地质意义,认为堆积物粒度分维是对堆积物物质组成的复杂性和自组织性、堆积物形成过程和形成时间以及泥石流、冰川、河流和洪水等搬运能力和运动过程的反映和度量。该研究为野外不同类型堆积物的区分、成因、形成过程等研究提供了一种新的方法,具有一定参考价值。     

Sedimentary process inferences from Humic substances analysis and deposition rates (Western Ross Sea,Antarctica)

The first 40?cm of sediment of three basins in the Ross Sea were sampled using a box corer. Site Y1 was located close to the coast in Terra Nova Bay; the sediment of site Y3 was collected in a more distal basin in the central sector of the Ross Sea; finally site Y5 was sampled in the deepest zone of the Joides Basin.

Sediment cores were sliced and analysed with a depth resolution of 2–4.5?cm. The distribution of humic substances and their structural features along the cores were determined and related to the pattern of Total Organic Carbon (TOC) and sedimentological data. The grain size distribution and the ²¹⁰Pb inventories allow the sediment of the study sites to be characterised.

The humic substance content in the sediment decreases, with a change in slope between 23 and 26?cm at Y1, between 12 and 15?cm at Y3 and constant values with further depth. At Y5 the depth profile of humic substance content shows constant values in the upper 17?cm and values decrease with further depth. The pattern of humic substance yield is similar to that found for TOC. The analysis of the elemental composition of the humic acids extracted from different sediment depths shows an increasing C/N atomic ratio at sites Y1 and Y3 and constant values along the Y5 core. The depth profile of the C/N atomic ratio is confirmed by the changes observed in the structural characterisation and indicates a shift from the freshly deposited organic matter on the sediment surface to more humified material (humin). The results obtained highlight a different sedimentation rate at the three sites as deduced from sedimentological analysis.     

Detoxification of antimony by selenium and their interaction in paddy rice under hydroponic conditions

Antimony (Sb) contamination has become a growing concern in recent years. Strategies for reducing Sb contamination and its related health risks are urgently desired. This study was conducted to explore the possibility of selenium (Se) detoxification on Sb toxicity in paddy rice in order to find a feasible method to reduce the health risk of Sb pollution. Seedlings of paddy rice were exposed to 5 mg L⁻¹ Sb (KSbC₄H₄ O₇·1/2H₂O), in the presence of Se (Na₂SeO₃) at 0.1, 1, 5 mg L⁻¹ in culture solution, with no Sb and Se addition as the control. Paddy rice took up Sb greatly and the highest Sb contents measured among all treatments in this experiment in the leaves, stems and roots were 65.5, 298.5 and 195.7 mg kg⁻¹, respectively. Without Sb addition in the solution, single exposure to 0.1 mg L⁻¹ Se remarkably reduced the malondialdehyde (MDA) formation in paddy rice,demonstrating the beneficial effect of Se at low dosages. The addition of 5 mg L⁻¹ Sb was found to generate toxicity to paddy rice, showing as decreased biomass and increased leaf MDA content in paddy rice, while addition of 1 mg L⁻¹ Se mitigated the toxicity of Sb, as seen with the decreased leaf MDA content and increased biomass, indicating antidotal role of Se to Sb. In addition, the presence of 0.1, 1, 5 mg L⁻¹ Se generally decreased the accumulation of Sb in the leaves, stems and roots in paddy rice. Toxicity was also seen when paddy rice was exposed to single Se at 1 and 5 mg L⁻¹ levels, however, 5 mg L⁻¹ Sb addition was found to decrease the contents of Se in the leaves/stems whereas increased them in roots, accompanied with decreased MDA contents and increased biomass in paddy rice, indicating a possible detoxification role of Sb to Se too. Therefore, Sb, although toxic, could also be an antitoxin to Se in paddy rice at certain condition. Our results showed that Se could alleviate Sb toxicity efficiently in paddy rice through two effects as antagonism and antioxidation.     

基于结构两相阻力分析的泥石流堆积形态研究

针对泥石流的结构两相阻力特征,采用结构两相阻力对泥石流的堆积形态进行了静力学分析,推导出在一般条件下泥石流堆积形态的公式,并讨论了在不同条件下泥石流堆积形态的特点。分析表明采用结构两相阻力对泥石流堆积形态分析可以较合理的模化阻力项,能够表现泥石流体复杂的成分结构组成,较真实的反映实际泥石流的堆积形态特征。在特定材料条件下,结构两相阻力项转化为单一材料阻力项,所得到的相应结论与已有对单一材料的分析结论一致。     

Classical in-plane negative magnetoresistance and quantum positive magnetoresistance in undoped InSb thin films on GaAs (1 0 0) substrates

Magnetoresistance (MR) effects have been investigated in perpendicular and parallel magnetic fields at 300, 80 K and liquid He temperatures for undoped InSb thin films 0.1–2.3 μm thick grown on GaAs(1 0 0) substrates by MBE. At high temperatures, the intrinsic carriers show the parabolic negative MR observable only in magnetic fields parallel to the film. The skipping-orbit effect due to surface boundary scattering in the classical orbits in the plane vertical to the film has been argued to be responsible for the negative MR. At low temperatures (T=80 K), the transport is dominated by the two-dimensional (2D) electrons in the accumulation layers at the InSb/GaAs(1 0 0) hetero interface; MR is positive and shows a logarithmic increase with anisotropy between parallel and perpendicular field orientation, arising from the 2D weak anti-localization (WAL) that reflects the interplay between the spin-Zeeman effect and strong spin–orbit interaction caused by the asymmetric potential at the interface (Rashba term). The zero-field spin splitting energy of Δ₀13 meV, the electron effective mass of m^*0.10m₀ seven times of the band edge mass in bulk InSb and the effective g-factor of |g^*|15 in the accumulation layer have been inferred from fits of MR for the 0.1 μm thick film to the 2D WL theory.     

Differential pulse voltammetric determination of P(V) following adsorptive accumulation of alpha-[PMo(12)O(40)](3-) on a polypyrrole-modified glassy carbon electrode

On the basis of the formation and pre-concentration of an α-Keggin-type [PMo₁₂O₄₀]³⁻ complex, a novel voltammetric method was developed for the determination of trace levels of P(V). The α-[PMo₁₂O₄₀]³⁻ complex was formed by heating a 5×10⁻⁴ M Mo(VI)-0.2 M HCl-40% (v/v) CH₃CN system containing a trace amount of P(V) at 70 °C for 30 min. During the electrochemical polymerization of pyrrole in the α-[PMo₁₂O₄₀]³⁻ solution, the α-[PMo₁₂O₄₀]³⁻ complex was accumulated into the polypyrrole film on a glassy carbon electrode. The differential pulse voltammetric peak current due to the α-[PMo₁₂O₄₀]³⁻ complex incorporated in the polypyrrole film was linearly dependent on the P(V) concentration in the range of 5×10⁻⁹-5×10⁻⁷ M; a detection limit of 2×10⁻⁹ M was achieved.     

光度法对不同水期黄河甘宁蒙段表层沉积物中磷积累程度和交换能力的比较研究

磷是水体富营养化的主要控制因素，在外源磷输入逐步得到控制后，作为内源磷主要来源的表层沉积物对黄河水体水质的影响作用不容忽视。掌握表层沉积物中磷的积累程度以及沉积物-水界面磷的交换能力，对区域内水环境的治理和磷负荷的调控具有重要的意义。选择黄河甘宁蒙段作为研究区域，分别采集丰水期(2011.07)、枯水期(2014.05)和平水期(2014.10)表层沉积物样品，使用标准测试程序(SMT)和钼锑抗分光光度法测定样品中磷赋存形态，并在实验条件下模拟表层沉积物对磷的等温吸附及吸附动力学过程。研究发现：(1) 相比于国内主要河流表层沉积物中磷的形态特征，黄河甘宁蒙段表层沉积物中有机磷(OP)和铁/铝结合态磷(NaOH-P)含量相对较低，钙结合态磷(HCl-P)含量较高；各形态磷含量的平均值均在丰水期最高，表明丰水期表层沉积物中磷的积累程度最高，黄河甘宁蒙段水环境受到沿程农业发展的冲击较大。因此，合理使用含磷化肥和优化灌渠退水水质是未来降低黄河水体磷污染风险的发展方向。(2) 基于低磷浓度下等温吸附中各采样点表层沉积物吸附-解吸平衡浓度(EPC₀)与判断水体发生富营养化的磷浓度阈值的比较发现，研究区域所有水期大多数采样点表层沉积物发挥着“磷源”的作用，存在向上覆水释放磷的趋势，且枯水期中多数采样点的EPC₀值较高，“磷源”作用更加明显；基于L模型和F模型对高磷浓度下等温吸附的拟合参数，显示丰水期表层沉积物对磷的持留能力最强，枯水期次之，平水期最小，所有采样点表层沉积物对磷的吸附过程均易发生；基于吸附动力学曲线的变化趋势可知，所选择的各采样点磷吸附量在反应开始的12 h内迅速增大，12~48 h内吸附量逐渐增加并趋于稳定；基于伪二级动力学方程对吸附动力学过程的拟合结果，表明表层沉积物对磷吸附过程的反应速率受化学吸附控制为主；从同一水期不同采样点吸附过程中的限速步骤不同及不同水期邻近采样点吸附过程中限速步骤均为微孔扩散的结果发现，表层沉积物组成和理化性质的差异对磷吸附速率的影响大于不同水期条件下上覆水流速和流量的变化。     

薄膜扩散梯度技术——一种原位富集采样技术

本文介绍了薄膜扩散梯度技术的原理、研究现状、应用领域以及发展前景。     

Muller’s ratchet clicks in finite time

We consider the accumulation of deleterious mutations in an asexual population, a phenomenon known as Muller’s ratchet, using the continuous time model proposed by Alison et al. (2009) [4]. We show that for any parameter λ>0$\lambda >0$ (the rate at which mutations occur), for any α>0$\alpha >0$ (the toxicity of the mutations) and for any size N>0$N>0$ of the population, the ratchet clicks a.s. in finite time. That is to say the minimum number of deleterious mutations in the population goes to infinity a.s.