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.     

The interplay of mastery and performance goals in social comparison: A multiple-goal perspective.

Régner, Escribe, and Dupeyrat (2007) recently demonstrated that not only performance-approach and performance-avoidance goals (respectively, the desire to outperform others and not to be outperformed by others) but also mastery goals (the desire to acquire knowledge) were related to social comparison orientation (SCO, the tendency to search for social comparison information). In the present article, the possibility of a link between mastery goals and social comparison that depends on the level of performance-approach goals—a possibility supported by a multiple-goal perspective—was tested by examining the interaction effect between mastery and performance-approach goals. This is an important endeavor, as educational settings are rarely free from performance-approach goals, even when mastery goals are promoted. In Study 1, we tested self-set achievement goals (mastery, performance-approach, and performance-avoidance goals) as predictors of SCO; the interaction between mastery goals and performance-approach goals indicated that the higher the performance-approach goal endorsement, the stronger the link between mastery goals and SCO. In Study 2, we manipulated goal conditions; mastery goals predicted interest in social comparison in the performance-approach goal condition only. Results are discussed in terms of the importance of multiple-goal pursuit in academic settings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

管道流动阻力实验模拟技术研究

针对热工水力学试验研究过程中经常遇到管道的形阻模拟摩阻问题，选择了恰当的形阻单元进行计算分析，获得了形阻单元的特性和局部参数对其特性的影响；利用κ-ε模型中的漩涡耗散ε项给于解释；给出了形阻单元串联模拟直管摩阻的方式，可趋近模拟直管摩阻特性，而使其长度缩短。为热工水力学试验研究过程中的实验模拟和数值模拟提供了有效的技术支持。     

Engineering of Mesoporous Silica Coated Carbon‐Based Materials Optimized for an Ultrahigh Doxorubicin Payload and a Drug Release Activated by pH,T, and NIR‐light

Among the challenges in nanomedicine, engineering nanomaterials able to combine imaging and multitherapies is hugely needed to address issues of a personalized treatment. In that context, a novel class of drug releasing and remotely activated nanocomposites based on carbon‐based materials coated with mesoporous silica (MS) and loaded with an outstanding level of the antitumoral drug doxorubicin (DOX) is designed. First, carbon nanotubes (CNTs) and graphene sheets (called “few‐layer graphene” FLG) are processed to afford a distribution size that is more suitable for nanomedicine applications. Then, the controlled coating of MS shells having a thickness tailored with the sol–gel parameters (amount of precursor, sol–gel time) around the sliced CNTs and exfoliated FLGs is reported. Furthermore, the drug loading in such mesoporous nanocomposites is investigated and the surface modification with an aminopropyltriethoxysilane (APTS) coating leading to a controlled polysiloxane layer provides an ultrahigh payload of DOX (up to several folds the mass of the initial composites). Such new CNT‐based nanocomposites are demonstrated to release DOX at low acidic pH, high temperature (T), and remotely when they are excited by near infrared (NIR) light. Such nanoconstructs may find applications as components of innovative biomedical scaffolds for phototherapy combined with drug delivery.     

Experimental and Thermodynamic Exploration of the High-Temperature Microstructures of Co-30 wt.% Cr- (2.5-5.0 wt.%) C Alloys

Cobalt alloyed with high contents in Cr and C potentially may lead to hard alloys candidate for high temperature applications involving reduced wear degradations. The Co-30wt.%Cr-xC system was explored from x = 2.5 to 5 wt.% by both experiments and thermodynamic calculations. The stable microstructures at 1000, 1100 and 1200 °C and the temperatures of solidus and liquidus were of interest. When the carbon content is between 2.5 and 3.5 the alloys display (hypo-)eutectic microstructures composed of FCC Co-based matrix and M₇C₃ carbides. Between 4 and 5 wt.%C, the microstructures contain coarse pro-eutectic M₇C₃ carbides, leading to a total volume fraction of M₇C₃ close to 50% or higher. The C-richest alloys also contain graphite, instead cementite as predicted by calculations. A better agreement between experiments and calculations about microstructures and solidus temperature can be obtained by forbidding cementite in the calculation conditions. The obtained hardness level is about 650 Hv but decreases when the heat-treatment temperature increases.