Aromatic nitrations by mixed acid. Slow liquid-liquid reaction regime

Aromatic nitrations by mixed acid have been selected as a specific case of a heterogeneous liquid-liquid reaction. An extensive experimental programme has been followed using adiabatic and heat-flow calorimetry and pilot reactor experiments, supported by chemical analysis. A series of nitration experiments has been carried out to study the influences of different initial and operating conditions such as temperature, stirring speed and sulphuric acid concentration. In parallel, a mathematical model to predict the overall conversion rate has been developed. In this paper the mathematical modelling and the implementation and experimental validation for benzene, toluene and chlorobenzene mononitration in the kinetic control regime (slow liquid-liquid reaction) are presented and discussed.     

Solution of temperature fields in hydrodynamics bearings by the numerical network method

Solution to the 2-D steady-state nonlinear heat conduction equation, involving cylindrical coordinates, applied to a plain bearing by a simple and versatile numerical technique based on network method is presented in this work. These advantages of the technique are necessary for the status evaluation of industrial machines during operation because time and computing resources are limited. The pressure field in the fluid is previously solved from the Reynolds equation by finite element method. The main difficulty is associated with the exponential dependency of the viscosity on temperature. The proposed model is very efficient and requires negligible computing times. Solutions are very close to the experimental and numerical results of other researchers.     

Disassembly sequence planning in a disassembly cell context

In this paper a two-phase approach is proposed for determining the optimal disassembly sequence when the disassembly system has a cellular configuration. Operations are first grouped into cells based on the resources they require with the goal of minimizing machine acquisition costs. The aim is to group together those operations that use similar equipment in order to achieve good utilization levels of such equipment. A maximum cell size may be imposed. Once the cells have been formed and the operations have been assigned to them, a metaheuristic algorithm (namely GRASP) is used to search for the disassembly sequence for each product that leads to the minimum number of intercellular movements. To account for uncertainty regarding the condition in which the product may arrive, each disassembly task is assumed to be required with a certain probability, regardless of the other tasks. AND/OR precedence relations among the disassembly tasks are also considered. The proposed approach is illustrated on a randomly generated disassembly problem.     

Contribution a l'etude du polymorphisme de Ga2S3: Structure cristalline de Mn0,23Ga1,85S3

The Mn_0.23Ga_1.85S₃ phase belongs to the solid solution $\text{ф}{}_0$, stable at low temperature in the Ga₂S₃MnS system. It is hexagonal superstructure of the wurtzite, with the Ga₂S₃α′ type ($\text{a}\text{= 6.397}\text{A}\text{?}$; $\text{c}\text{= 18.027}\text{A}\text{?}$Z = 6; space groupe P6₁ or P6₅). Its crystal structure has been refined by the least squares method to a final R = 0.06 with 323 independant reflections. This structure is closely related to Ga₂S₃ α described by Hahn and Frank, and differs only by the partial occupation of the vacant metal site of Ga₂S₃ by Mn atoms in statistical disorder.     

The microscopy cell (MicCell), a versatile modular flowthrough system for cell biology, biomaterial research, and nanotechnology

We describe a novel microfluidic perfusion system for high-resolution microscopes. Its modular design allows pre-coating of the coverslip surface with reagents, biomolecules, or cells. A poly(dimethylsiloxane) (PDMS) layer is cast in a special molding station, using masters made by photolithography and dry etching of silicon or by photoresist patterning on glass or silicon. This channel system can be reused while the coverslip is exchanged between experiments. As normal fluidic connectors are used, the link to external, computer-programmable syringe pumps is standardized and various fluidic channel networks can be used in the same setup. The system can house hydrogel microvalves and microelectrodes close to the imaging area to control the influx of reaction partners. We present a range of applications, including single-molecule analysis by fluorescence correlation spectroscopy (FCS), manipulation of single molecules for nanostructuring by hydrodynamic flow fields or the action of motor proteins, generation of concentration gradients, trapping and stretching of live cells using optical fibers precisely mounted in the PDMS layer, and the integration of microelectrodes for actuation and sensing.     

Cyclamate intake and cyclohexylamine excretion are not related to male fertility in humans

Cyclamate and its metabolite cyclohexylamine affect male fertility in high dose animal studies, but this affect has not been investigated in epidemiological studies. This paper reports the first epidemiological study designed to investigate the possibility of a relationship between cyclamate and cyclohexylamine and male fertility in humans, in which 405 cases of clinically defined infertility in men and 379 controls were surveyed. Semen evaluation, urine analysis for cyclamate and cyclohexylamine and dietary questionnaires were compared between cases and controls. No evidence was found of a significant association between cyclamate intake and male infertility; neither high cyclamate nor high cyclohexylamine excretion were associated with elevated risk. The lack of association remained after adjusting by age, area of residence, education, total energy intake and other variables. No significant correlations were observed between cyclamate intake, metabolism or excretion, and sperm count and motility. The results demonstrate no effect of cyclamate or cyclohexylamine on male fertility at the present levels of cyclamate consumption.     

Glyconanoparticle-DNA interactions: an atomic force microscopy study.

Glyconanoparticles which present carbohydrate and amino groups motifs at their surface were produced. These particles were highly stable and soluble in aqueous solutions. The presence of the carbohydrate groups also allowed the inclusion of more strongly binding groups, without affecting solubility. The binding of a model DNA, plasmid by these nanoparticles was studied by atomic force microscopy, transmission electron microscopy, and gel electrophoresis. Significant differences between the nanoparticles based on their affinities for the DNA were found, with implications for their potential use as nonviral gene delivery agents.     

Hybrid Approach for Addressing Uncertainty in Risk Assessments

Parameter uncertainty is a major aspect of the model-based estimation of the risk of human exposure to pollutants. The Monte Carlo method, which applies probability theory to address model parameter uncertainty, relies on a statistical representation of available information. In recent years, other uncertainty theories have been proposed as alternative approaches to address model parameter uncertainty in situations where available information is insufficient to identify statistically representative probability distributions, due in particular to data scarcity. The simplest such theory is possibility theory, which uses so-called fuzzy numbers to represent model parameter uncertainty. In practice, it may occur that certain model parameters can be reasonably represented by probability distributions, because there are sufficient data available to substantiate such distributions by statistical analysis, while others are better represented by fuzzy numbers (due to data scarcity). The question then arises as to how these two modes of representation of model parameter uncertainty can be combined for the purpose of estimating the risk of exposure. This paper proposes an approach (termed a hybrid approach) which combines Monte Carlo random sampling of probability distribution functions with fuzzy calculus. The approach is applied to a real case of estimation of human exposure, via vegetable consumption, to cadmium present in the surficial soils of an industrial site located in the north of France. The application illustrates the potential of the proposed approach, which allows the uncertainty affecting model parameters to be represented in a way that is consistent with the information at hand. Also, because the hybrid approach takes advantage of the “rich” information provided by probability distributions, while retaining the conservative character of fuzzy calculus, it is believed to hold value in terms of a “reasonable” application of the precautionary principle.     

Formal techniques for performance analysis: blending SAN and PEPA

In this paper we consider two performance modelling techniques from the perspectives of model construction, generation of an underlying continuous time Markov process, and the potential for reduction in the Markov process. Such careful comparison of modelling techniques allows us to appreciate the strengths and weaknesses of different approaches, and facilitates cross-fertilization between them. In the present case we take a characteristic of one formalism, functional rates in Stochastic Automata Networks, and introduce it to the other formalism, Performance Evaluation Process Algebra. We investigate the benefits of this cross-fertilization, particularly from the perspectives of Markov process generation and reduction.