微生物还原对砷迁移性影响的机理研究

本研究从沈阳冶炼厂旧址采集土壤样品，从中富集厌氧的砷还原菌，并以其为接种微生物，在厌氧条件下考察微生物的作用对砷的还原及迁移的影响，从分子角度探索地下水和土壤体系中砷污染的机理，同时对工业上含砷废渣的长期稳定性进行探讨。 实验在以L-半胱氨酸作为还原剂创造的严格厌氧条件下接种微生物进行培养时，可以观察到As(V)的快速还原并向固体的转移，利用XRD和SEM-EDS技术对固体的分析表明该沉淀为AsS，指出了在周围环境中如果存在足够的含硫化合物时，微生物能够通过形成硫化砷的形式将砷固定下来。 本研究考察了工业上常见的含砷废渣（As:Fe摩尔比为1:8的含砷氢氧化铁）在微生物作用下的长期稳定性，结果表明在厌氧条件下微生物对砷和铁的还原速度都很快，在39天内就将~53%的As(V)还原为As(III)，在一天之内就能将约8.82 mg/L的As(III)释放出来，因此可以得出如果含砷废渣处理不当，就会在长期堆放过程中造成对环境甚至于地下水系统的污染。 本研究进一步采用不同比例（Al:Fe = 1:0, 1:1, 0:1）的铁铝氢氧化物为吸附剂，以As:(Fe+Al)摩尔比为1:100的比例在该介质上吸附砷并进行厌氧培养，考察微生物对吸附于这些载体上的As(V)的还原和迁移作用，结果指出微生物对砷的还原是砷向环境中释放的主要原因，砷的还原发生在铁还原之前，铁的还原和溶解并没有引起砷的迁移量的增加，因此铁的还原性溶解不是砷释放的主要原因；相反，由于氢氧化铝对As(III)几乎不吸附，因此，当铝被引入该体系时，可以观察到As(III)的释放明显增加。该实验结果表明在自然环境中，砷的释放主要是由于微生物对砷的释放以及铝氧化物对As(III)无吸附能力所导致的。

Two-dimensional capillary electrophoresis involving capillary isoelectric focusing and capillary zone electrophoresis

Capillary isoelectric focusing (cIEF) and capillary zone electrophoresis (CZE) was on-line hyphenated by a dialysis interface to achieve a 2D capillary electrophoresis (CE) system. The system was used with just one high-voltage power supply and three electrodes (one cathode shared by the two dimensions). The focused zone in the first dimension (i.e. the cIEF) was driven to the dialysis interface by electroosmotic flow (EOF), besides chemical mobilization from the first anode to the shared cathode. And then in the second dimension (i.e. the CZE), the separated zone was further separated and driven by an inverted EOF, which originated from the charged layer of a cationic surfactant adsorbed onto the inner wall of the capillary. Finally, a solution of ribonuclease was rapidly separated to assess the feasibility of the two-dimensional CE implement. (C) 2003 Elsevier B.V. All rights reserved.

填土边坡水文作用机理与破坏过程研究—以深圳羊宝地填土滑坡为例

A full understanding of failure mechanism, critical hydrological condition, and process of mobilization and deposition of a landslide is essential for optimal design of stabilization measure and forecasting of landslide hazard. This requires a quantitative study of hydrological response of a slope to rainfall through field monitoring, laboratory test and numerical modelling. At 13:40 on September 18, 2002, a fill slope failed following a period of prolonged rain in Shenzhen, resulting in 5 fatalities and 31 injuries. The failed mass with a volume about 2.5×104m3 traveled about 140m on level ground. Field monitoring, laboratory test, theoretical analysis and numerical modelling were carried out to undestand the hydrological response and failure mechanism of this fill slope. This thesis mainly focuses on the following aspects: (1) The hydrological responses and failure processes of slopes under rainfall infiltration were reviewed. Firstly, the factors influencing on the hydrological responses of slopes were analysed. Secondly, the change of stress state of slope soil and modelling methods of slope failure under rainfall infiltration were reviewed. (2) The characteristics of the Yangbaodi landslide and associated rainfall triggering the failure were presented. The failure was characterized by shallow flowslide, due to an increase of ground water table caused by rainfall infiltration. (3) A fully automated instrumentation was carried out to monitor rainfall, and saturated – unsaturated hydrological response of the fill slope, using a raingauge, piezometers, tensiometers and moisture probes. A conceptual hydrogeological model was presented based on field monitoring and borehole data. Analysis of monitoring data showed that the high pore water pressure in fill slope was caused by upward flow of semiconfined groundwater in the moderately decomposed granite. (4) Laboratory and in-situ testing was performed to study the physical and mechanical properties of fills. Isotropically consolidated undrained compression tests and anisotropically consolidated constant shear stress tests were carried out to understand the failure mechanism of the fill slope. It is indicated that loosely compacted soil is of strain-softening behaviour under undrained conditions, accompanied with a rapid increase in excess pore water pressure. In anisotropically consolidated constant shear stress tests, a very small axial strain was required to induce the failure and the excess pore water pressure increased quickly at failure. This indicated that static liquefaction caused by rise in groundwater table due to rainfall infiltration occurred. (5) The hydraulic conductivity of the highly and moderately decomposed granite was estimated using monitering data of pore water pressure. A saturated – unsaturated flow was modeled to study the hydrological response of the fill slope using rainfall records. It was observed that the lagged failure was due to the geological conditions and the discrepancy of hydraulic conductivity of slope soils. The hydraulic conductivity of moderately decomposed granite is relatively higher than the other materials, resulting in a semiconfied groundwater flow in the moderately decomposed granite, and subsequent upward flow into the upper fill layer. When the ground water table in the fill layer was increased to the critical state, the fill slope failed. (6) Numerical exercises were conducted to replay the failure process of the fill slope, based on field monitoring, laboratory and in-situ testing. It was found that the fill slope was mobilized by a rapid transfer of the concentrated shear stress. The movement of failure mass was characterized by viscosity fluid with a gradual increase in velocity. The failure process, including mobilization and subsequent movement and deposition, was studied using numerical methods.

Recovery of linear and nonlinear heart rate dynamics after coronary artery bypass grafting surgery

Background: Conventional coronary artery bypass grafting (C-CABG) and off-pump CABG (OPCAB) surgery may produce different patients' outcomes, including the extent of cardiac autonomic (CA) imbalance. the beneficial effects of an exercise-based inpatient programme on heart rate variability (HRV) for C-CABG patients have already been demonstrated by our group. However, there are no studies about the impact of a cardiac rehabilitation (CR) on HRV behaviour after OPCAB. the aim of this study is to compare the influence of both operative techniques on HRV pattern following CR in the postoperative (PO) period.Methods: Cardiac autonomic function was evaluated by HRV indices pre- and post-CR in patients undergoing C-CABG (n = 15) and OPCAB (n = 13). All patients participated in a short-term(approximately 5 days) supervised CR programme of early mobilization, consisting of progressive exercises, from active-assistive movements at PO day 1 to climbing flights of stairs at PO day 5.Results: Both groups demonstrated a reduction in HRV following surgery. the CR programme promoted improvements in HRV indices at discharge for both groups. the OPCAB group presented with higher HRV values at discharge, compared to the C-CABG group, indicating a better recovery of CA function.Conclusion: Our data suggest that patients submitted to OPCAB and an inpatient CR programme present with greater improvement in CA function compared to C-CABG.

Active paraplegics are protected against exercise-induced oxidative damage through the induction of antioxidant enzymes

Exercise improves functional capacity in spinal cord injury (SCI). However, exhaustive exercise, especially when sporadic, is linked to the production of reactive oxygen species that may have a detrimental effect on SCI. We aimed to study the effect of a single bout of exhaustive exercise on systemic oxidative stress parameters and on the expression of antioxidant enzymes in individuals with paraplegia. The study was conducted in the Physical Therapy department and the Physical Education and Sports department of the University of Valencia. Sixteen paraplegic subjects were submitted to a graded exercise test (GET) until volitional exhaustion. They were divided into active or non-active groups. Blood samples were drawn immediately, 1 and 2 h after the GET. We determined plasma malondialdehyde (MDA) and protein carbonylation as markers of oxidative damage. Antioxidant gene expression (catalase and glutathione peroxidase-GPx) was determined in peripheral blood mononuclear cells. We found a significant increase in plasma MDA and protein carbonyls immediately after the GET (P<0.05). This increment correlated significantly with the lactate levels. Active paraplegics showed lower levels of exercise-induced oxidative damage (P<0.05) and higher exercise-induced catalase (P<0.01) and GPx (P<0.05) gene expression after the GET. These results suggest that exercise training may be useful in SCI patients to develop systemic antioxidant defenses that may protect them against exercise-induced oxidative damage.