Protective effect of phospholipid hydroperoxide glutathione peroxidase (PHGPx) against lipid peroxidation in mussels Perna perna exposed to different metals   总被引：2，自引：0，他引：2  

de Almeida EA  Miyamoto S  Bainy AC  de Medeiros MH  Di Mascio P 《Marine pollution bulletin》2004,49(5-6):386-392

Levels of antioxidant defenses and lipid peroxidation were evaluated in mussels exposed to lead (200 mg/l), iron (500 microg/l), cadmium (200 microg/l) and copper (40 microg/l), for 12, 24, 72 and 120 h. Glutathione S-transferase (GST) activity was unchanged with all treatments. Catalase (CAT) increased after 120 h of exposure to all metals. Mussels exposed to Cd for 12 h, and to Cu and Fe for 120 h had increased lipid peroxidation, which might be associated to decreased levels of reduced glutathione (GSH) and glutathione peroxidase (GPx) activity. Pb exposure caused GSH depletion after 12 h and increased GPx activity after 120 h. Negative correlations were observed between the enzyme phospholipid hydroperoxide glutathione peroxidase (PHGPx) and malonaldehyde (MDA) levels after Fe and Cu exposure, indicating a protective role of PHGPx against lipid peroxidation, and suggesting the use of this enzyme as a new potential biomarker of toxicity associated with contaminant exposure in mussels.  相似文献   

A comparison of direct macrofaunal mortality using three types of clam dredges     

Gaspar  M.B; Leitao  F; Santos  M.N; Chicharo  L; Dias  M.D; Chicharo  A; Monteiro  C.C 《ICES Journal of Marine Science》2003,60(4):733-742

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Z-Less stratification under stable conditions   总被引：2，自引：2，他引：0  

Nelson L. Dias  Wilfried Brutsaert  Marvin L. Wesely 《Boundary-Layer Meteorology》1995,75(1-2):175-187

Turbulent fluctuations were measured at a height of 2.5 m in stable conditions over grass to investigate the variability of the second- and third-order moments involving temperature, humidity and vertical wind velocity. With the exception of the normalized second moment of temperature, very little variation of the normalized moments was found with changes in the dimensionless stability parameter =z/L, whereL is the Obukhov stability length. Such limited variation is expected for stable conditions, and the normalized second moment of temperature might have been affected by nonstationary conditions. In addition, the variability of the normalized moments was lessened by computing the turbulence statistics over 56 min, instead of 26 min. Values of third-order moments involving the vertical velocity were all close to zero.  相似文献   

Comparative study of radiation-induced damage in magnesium aluminate spinel by means of IL,CL and RBS/C techniques     

Iwona Jozwik  Jacek Jagielski  Grzegorz Gawlik  Przemyslaw Jozwik  Renata Ratajczak  Gerard Panczer  Nathalie Moncoffre  Anna Wajler  Agata Sidorowicz  Lionel Thomé 《Physics and Chemistry of Minerals》2016,43(6):439-445

A comparative study of damage accumulation in magnesium aluminate spinel (MgAl₂O₄) has been conducted using ionoluminescence (IL), cathodoluminescence (CL) and Rutherford Backscattering Spectrometry/channeling (RBS/C) techniques. MgAl₂O₄ single crystal and polycrystalline samples were irradiated with 320 keV Ar⁺ ions at fluencies ranging from 1 × 10¹² to 2 × 10¹⁶ cm^?2 in order to create various levels of radiation damage. RBS/C measurements provided quantitative data about damage concentration in the samples. These values were then compared to the luminescence measurements. The results obtained by IL and RBS/C methods demonstrate a two-step character of damage buildup process. The CL data analysis points to the three-step damage accumulation mechanism involving the first defect transformation at fluencies of about 10¹³ cm^?2 and second at about 10¹⁵ cm^?2. The rate of changes resulting from the formation of nonluminescent recombination centers is clearly nonlinear and cannot be described in terms of continuous accumulation of point defects. Both, IL and CL techniques, appear as new, complementary tools bringing new possibilities in the damage accumulation studies in single- and polycrystalline materials.  相似文献   

Evidence of positive tectonic inversion in the north-central sector of the Sicily Channel (Central Mediterranean)     

Cavallaro  Danilo  Monaco  Carmelo  Polonia  Alina  Sulli  Attilio  Di Stefano  Agata 《Natural Hazards》2016,86(2):233-251

In order to unravel the tectonic evolution of the north-central sector of the Sicily Channel (Central Mediterranean), a seismo-stratigraphic analysis of single- and multi-channel seismic reflection profiles has been carried out. This allowed to identify, between 20 and 50 km offshore the central-southern coast of Sicily, a ~80-km-long deformation belt, characterized by a set of WNW–ESE to NW–SE fault segments showing a poly-phasic activity. Within this belt, we observed: i) Miocene normal faults reactivated during Zanclean–Piacenzian time by dextral strike-slip motion, as a consequence of the Africa–Europe convergence; ii) releasing and restraining bend geometries forming well-developed pull-apart basins and compressive structures. In the central and western sectors of the belt, we identified local transpressional reactivations of Piacenzian time, attested by well-defined compressive features like push-up structures and fault-bend anticlines. The reconstruction of timing and style of tectonic deformation suggest a strike-slip reactivation of inherited normal faults and the local subsequent positive tectonic inversion, often documented along oblique thrust ramps. This pattern represents a key for an improved knowledge of the structural style of foreland fold-and-thrust belts propagating in a preexisting extensional domain. With regard to active tectonics and seismic hazards, recent GPS data and local seismicity events suggest that this deformation process could be still active and accomplished through deep-buried structures; moreover, several normal faults showing moderate displacements have been identified on top of the Madrepore Bank and Malta High, offsetting the Late Quaternary deposits. Finally, inside the northern part of the Gela Basin, multiple slope failures, originated during Pleistocene by the further advancing of the Gela Nappe, reveal tectonically induced potential instability processes.

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Fossil Fuel Saving through a Direct Solar Energy Water Heating System     

Ademar Michels  Flávio Dias Mayer  Roger Gallon  Ronaldo Hoffmann  Seimur Tiago Serafini 《洁净——土壤、空气、水》2008,36(9):743-747

The global warming and energy crisis is motivating the search for sustainable power sources. The objective of this work is to analyze the economic return and quantify the reduction in the emission of pollutants, when low‐cost solar collectors are used as a partial substitute for a boiler that uses fuel oil as the energy source, in order to heat water for the swimming pools of the Physical Education Center, Federal University of Santa Maria. The collectors are made from PVC and other easily acquired materials. The estimations for energy saving are based on a collecting area of 182 m². From knowledge of the collectors' efficiency, the mathematical demonstration shows a fuel oil saving of 13,174 kg, representing 24% of the total amount consumed per annum. The investment required for the construction and installation of the collectors is US$ 6,445 and the estimated useful live is five years. The internal rate of return is 30%. The emission of pollutants is reduced by a considerable amount of 41,213 kg CO₂ equivalent/year. The use of direct sun energy as an alternative power source represents a significant economic interest as well as contributing to the mitigation of greenhouse gases.  相似文献   

Assessment of flood hazard during extreme sea levels in a tidally dominated lagoon     

Carina L. Lopes  João M. Dias 《Natural Hazards》2015,77(2):1345-1364

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Impedance Functions of Slab Foundations with Rigid Piles     

U. S. Okyay  D. Dias  P. Billion  D. Vandeputte  A. Courtois 《Geotechnical and Geological Engineering》2012,30(4):1013-1024

The earthquake resistant design of structures depends upon the soil-structure interaction during seismic excitation. The dynamic behavior of surface foundations and deep foundations has been investigated by several authors (Gazetas in Soil Dyn Earthq Eng 2(1):2–42, 1983; Pecker in Dynamique des sols. Presses de l’Ecole Nationale des Ponts et Chaussées, Paris, 1984; Sieffert and Cevaer in Manuel des fonctions d’impédance. Ouest-Editions, Nantes, 1992, etc.) but the dynamic behavior of pile-reinforced soils has not been sufficiently studied yet. The design of pile-reinforced soils comprises the design of the rigid piles and the design of the earth-platform. The foundation system studied in this article consists of an earth-platform over a soft ground reinforced by deep piles. In order to understand the dynamic behavior of a rigid pile, a series of dynamic tests is conducted on an experimental site. The vertical and horizontal impedances of the slab foundation are obtained with and without rigid piles. The numerical models are developed to interpret these dynamic tests. The numerical and experimental impedance functions are compared in both the vertical and the horizontal directions. A sensitivity analysis on the influence of the physical and geometrical properties of rigid piles on the impedance functions is presented.  相似文献   

Three-dimensional numerical simulation for mechanized tunnelling in soft ground: the influence of the joint pattern   总被引：1，自引：1，他引：0  

Ngoc-Anh Do  Daniel Dias  Pierpaolo Oreste  Irini Djeran-Maigre 《Acta Geotechnica》2014,9(4):673-694

The main purpose of this study was to provide a three-dimensional numerical model, which would allow the tunnel lining behaviour and the displacement field surrounding the tunnel to be evaluated. Most of the processes that occur during mechanized excavation have been simulated in this model. The influence of the lining joint pattern, including segmental lining joints and their connections, has in particular been taken into consideration. The impact of the processes during mechanized excavation, such as the grouting pressure and the jacking forces in the structural forces induced in the tunnel lining, has been presented. These values depend on the tunnel advancement. However, a negligible influence of the joint pattern on the ground displacement field surrounding the tunnel has been observed. Generally, a variation in the structural forces in successive rings along the tunnel axis has been found in a staggered segmental lining, indicating the necessity of simulating the joints in the tunnel lining and using a full three-dimensional numerical model to obtain an accurate estimation. In addition, the considerable influence of the coupling effect between successive rings on the lining behaviour has been highlighted.  相似文献   

Overwash vulnerability assessment based on long-term washover evolution   总被引：1，自引：1，他引：0  

Tiago Garcia  Óscar Ferreira  Ana Matias  João Alveirinho Dias 《Natural Hazards》2010,54(2):225-244

An integrated methodology for evaluation of overwash vulnerability is developed with respect to the historical washover evolution of a barrier island system. Three different aspects of overwash are addressed in the vulnerability indices developed: overwashed shoreline ratio, maximum overwash intrusion recurrence, and complete barrier overwash. The indices were applied to the barriers in the Ria Formosa system in Southern Portugal using an aerial photography catalogue covering the period 1947–2001. Historical trends of washover evolution were observed to be different between the barriers analysed, but generally, there was a decrease in washover number and dimensions throughout the analysed period. The final overwash diagnostic obtained allowed an integrated overwash vulnerability rating to be defined for each barrier, with vulnerabilities ranging from low to extreme. The methodology has produced results that may assist coastal managers with information concerning barrier island system overwash hazard, define the temporal and geographical distributions of overwash, and provide indications as to where overwash is most likely to occur in the future.  相似文献