Cytotoxicity of CeO2 nanoparticles for Escherichia coli. Physico-chemical insight of the cytotoxicity mechanism

The production of nanoparticles (NPs) is increasing rapidly for applications in electronics, chemistry, and biology. This interest is due to the very small size of NPs which provides them with many interesting properties such as rapid diffusion, high specific surface areas, reactivity in liquid or gas phase, and a size close to biomacromolecules. In turn, these extreme abilities might be a problem when considering a potentially uncontrolled exposure to the environment. For instance, nanoparticles might be highly mobile and rapidly transported in the environment or inside the body through a water or air pathway. Accordingly, the very fast development of these new synthetic nanomaterials raises questions about their impact on the environment and human health. We have studied the impact of a model water dispersion of nanoparticles (7 nm CeO2 oxide) on a Gram-negative bacteria (Escherichia coli). The nanoparticles are positively charged at neutral pH and thus display a strong electrostatic attraction toward bacterial outer membranes. The counting of colony forming units (CFU) after direct contact with CeO2 NPs allows for the defining of the conditions for which the contact is lethal to Escherichia coli. Furthermore, a set of experiments including sorption isotherms, TEM microscopy, and X-ray absorption spectroscopy (XAS) at cerium L3 edge is linked to propose a scenario for the observed toxic contact.     

Thermal and economic evaluation of heat recovery measures for indoor ice rinks

A comparative study of three ventilation systems supplying air to a typical Canadian indoor ice rink illustrates the power, energy and operating cost savings which can be achieved by using the relatively warm air from the air cooled condensers of the refrigeration system. The direct use of this warm air for ventilation results in a reduction of energy consumption during the winter amounting to 24.2% of the yearly consumption of the heating system. On the other hand, the use of a heat exchanger to heat the ventilation air results in energy consumption reductions throughout the year. Depending on the size of the heat exchanger these gains can be as high as 60.8% of the heating energy consumption by the existing system. Based on actual prices of electricity and the heat exchanger it is established that the cost savings over the life of the equipment are at least three times higher than the cost of the heat exchanger.     

Formation of the Perovskite Phase in the PbMg1/3Nb2/3O3─PbTiO3 System

The reaction sequences during calcination of oxide mixtures were studied for the PbMg_1/3Nb_2/3O₃─PbTiO₃ (PMN-PT) system. The effect of reactivity and composition of the starting mixtures was investigated. In the present study, a B-site-deficient, cubic pyrochlore phase in the PbO-Nb₂O₅ system was formed at 500°C. The perovskite phase of PMN was formed at 7007deg;C through the diffusion of MgO into the pyrochlore phase. The lattice parameter of the pyrochlore phase decreased as this transformation to perovskite progressed.     

渤海石油平台的腐蚀与防护

<正> 渤海中使用十几年的石油平台,普遍腐蚀严重,有的已不能继续使用。最严重的是在飞溅区,腐蚀速度甚至超过0.5mm/Yr,低潮位附近和大气区的腐蚀也不容忽视,保护不当的已发生局部腐蚀,有的出现腐蚀洞。 渤海石油平台的保护经历了三个阶段。早期因对腐蚀与防护缺乏认识,措施不力,保护效果很差。1973年后,由于技术力量增加和技术进步,措施得到加强,阴极保护普遍采用,但由于管理等原因,保护效果还不很理想。近几年合资建造的平台,按国际规范引进了技术和材料,使防护工作推进了一大步。 为了确保平台安全,必须十分重视防护工作;平台的设计、建造和维护,应遵循有关规范和标准;防护工作者要不断提高和完善保护技术,同时兼顾保护效果和经济效益。     

Conceptual design study of fusion DEMO plant at SWIP

The basic definition and development strategy of the DEMO plant based on the Chinese fusion power plant (FPP) program are presented briefly. A conceptual design study of fusion HCSB-DEMO reactor with a fusion power of 2550 MW and a neutron wall loading of 2.3 MW/m² is performed recently. Three sets parameters of core plasma for different DEMO design objectives are proposed. A helium-cooled blanket system with ceramic breeder (Li₄SiO₄), the structure material of low-activation ferritic steel (LAF/M) and Be neutron multiplier based on Chinese ITER HCSB-TBM design foundation are considered. The design parameters, preliminary analyses and the basic structure as well as development strategy of HCSB-DEMO reactor are introduced.     

Evolution of number concentration of nano- particles undergoing Brownian coagulation in the transition regime

Evolution of number concentration of nanoparticles undergoing Brownian coagulation in the transition regime is studied theoretically and numerically.The results show that the curves of particle size distribution move toward the area with large particle diameters, the curve peak becomes lower and the range that particle diameters cover becomes wider as time elapses.In the process of coagulation the particles with small diameter disappear gradually and the particle size distribution remains a log-normal distribution.The change rate of the particle size distribution is more appreciable at the initial stage than that at the final stage.The initial Knudsen number has a significant effect on the coagulation rate which increases with decreasing the initial Knudsen number.The larger the initial geometric standard deviation is, the smaller the curve peak is, and the wider the area that curves cover is.The initial geometric standard deviation has a significant effect on the particle size distribution which can remain a self-preserving state when the initial geometric standard deviation is smaller than 2.With the increase of the diversity of initial particle size, the particle size distribution does not obey the log-normal distribution any more as time elapses.     

Role of peroxy chemistry in the high-pressure ignition of n-butanol – Experiments and detailed kinetic modelling

Despite considerable interest in butanol as a potential biofuel candidate, its ignition behaviour at elevated pressures still remains largely unexplored. The present study investigates the oxidation of n-butanol in air at pressures near 80 bar. Ignition delays were determined experimentally in the temperature range of 795–1200 K between 61 and 92 bar. The time of ignition was determined by recording pressure and CH-emission time histories throughout the course of the experiments. The results display the first evidence of the influence of negative temperature coefficient (NTC) behaviour which was not observed in earlier ignition studies. The high-pressure measurements show that NTC behaviour is enhanced as pressures are increased. The experimental results were modelled using an improved chemical kinetic mechanism which includes a simplified sub-mechanism for butyl-peroxy formation and isomerisation reactions currently incompletely accounted for in n-butanol kinetic models. The detailed mechanism validated with the high-pressure ignition results for realistic engine in-cylinder conditions can have significant impact on future advanced low-temperature combustion engines.     

Experimental investigation of the swelling/shrinkage of a hydride bed in a cell during hydrogen absorption/desorption cycles

The storage of hydrogen in hydride materials is currently much researched as a mean of energy storage. This reversible storage is achieved by successive hydriding and dehydriding reactions. During these reactions, the material undergoes structural transformations which result in swelling of the hydride powder grains due to the absorption of hydrogen. This phenomenon can generate major mechanical stresses on the cell containing the hydride. The present experimental study examines the cyclic swelling of a granular bed consisting of hydride Ti–Cr–V + Zr–Ni. Two superimposed phenomena are identified: a cyclic rearrangement causing a reduction and then an increase in porosity coupled with gradual densification of the stack.     

Polymeric solar cells based on P3HT:PCBM: Role of the casting solvent

Polymeric photovoltaic (PV) solar cells have been fabricated using six solvents: chloroform (CHCl₃), toluene (T), chlorobenzene (CB), orthodichlorobenzene (ODCB), 1,2,3,4-tetrahydronaphthalene (THN) and 1,2,4-trichlorobenzene (TCB). The active layers were composed of poly(3-hexyl)thiophene (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM). Special care has been taken to keep all experimental parameters constant (thickness of the active layers, donor/acceptor weight ratio, area of active surface and electrodes) in order to avoid artefacts and truly study the effect of solvents. Studies using atomic force microscopy (AFM) and optical absorption (UV-vis) showed the relationship between the photovoltaic performance and the evaporation rate of solvents. The use of solvents with high boiling point results in a higher degree of organization in the structure of P3HT. A direct comparison with devices processed with thermal treatment has also been performed. As often reported thermal annealing increases photo-conversion efficiency of devices created from common solvents, due to better separation of phase between the two materials of the blend. In the case of solvents with high boiling point such as THN and TCB, neither phase separation nor modification of P3HT crystallization induced by thermal annealing has been observed. However thermal treatment appears to enhance performance, ensuing the evaporation of remaining solvent in the active layers. An overview of the effect of solvent on the electrical properties of films containing pure P3HT and P3HT:PCBM blend reported in the literature has been completed for the discussion.