Main Issues for a Fully Predictive Plasma Spray Torch Model and Numerical Considerations

Plasma spray is one of the most versatile and established techniques for the deposition of thick coatings that provide functional surfaces to protect or improve the performance of the substrate material. However, a greater understanding of plasma spray torch operation will result in improved control of process and coating properties and in the development of novel plasma spray processes and applications. The operation of plasma torches is controlled by coupled dynamic, thermal, chemical, electromagnetic, and acoustic phenomena that take place at different time and space scales. Computational modeling makes it possible to gain important insight into torch characteristics that are not practically accessible to experimental observations, such as the dynamics of the arc inside the plasma torch. This article describes the current main issues in carrying out plasma spray torch numerical simulations at a high level of fidelity. These issues encompass the use of non-chemical and non-thermodynamic equilibrium models, incorporation of electrodes with sheath models in the computational domain, and resolution of rapid transient events, including the so-called arc reattachment process. Practical considerations regarding model implementation are also discussed, particularly the need for the model to naturally reproduce the observed torch operation modes in terms of voltage and pressure fluctuations.     

Synthesis of New Thiosulfonates and Disulfides from Sulfonyl Chlorides and Thiols

Aromatic thiols were converted into thiosulfonates or disulfides, under very mild conditions, with fair to excellent yields, by using sulfonyl chloride as oxydant reagent.     

Screw dislocation-induced influence of transverse modes on Hall conductivity

The Hall conductivity of an electron gas on an interface showing a topological defectcalled screw dislocation is investigated. This kind of defect induces a singular torsionon the medium which in turn induces transverse modes in the quantum Hall effect. It isshown that this topology decreases the plateaus’ widths and shifts the steps in the Hallconductivity to lower magnetic fields. The Hall conductivity is neither enhanced nordiminished by the presence of this kind of defect alone. We also consider the presence oftwo defects on a sample, a screw dislocation together with a disclination. For a specificvalue of deficit angle, there is a reduction in the Hall conductivity. For an excess ofangle, the steps shift to higher magnetic fields and the Hall conductivity is enhanced.Our work could be tested only in common semiconductors but we think it opens a road to theinvestigation on how topological defects can influence other classes of Hall effect.     

Microwave-induced by-products in the synthesis of 2-(4-methyl-2-phenylpiperazinyl)pyridine-3-carbonitrile

The Letter describes the investigation of an industrial reaction of N-methylphenylpiperazine and chloronicotinonitrile, under microwave heating. Besides the formation of the expected 2-(4-methyl-2-phenylpiperazinyl)pyridine-3-carbonitrile (4), extension of the scale leads to unexpected by-products. A specific pathway due to the formation of a reactive ‘ionic alkylating intermediate’ formed in situ under microwave conditions is proposed to explain the results observed.     

Effects of a freezing event during hibernation on further survival,reproduction and growth in the partially freezing tolerant land snail Helix aspersa muller (Gastropoda: helicidae)

Tolerance of ectothermic animals to freezing is often estimated by assessing survival a few days after the treatment. However, in the long term, ice formation in the body tissues can affect survival, as well as reproductive capability and growth. The land snail Helix aspersa survives only short durations with ice in its tissues, to a lethal limit of 40 to 60 % of its body water frozen. Adult and immature snails were treated during their winter dormancy period to a freezing event above this limit; their survival was observed both in the short and long term, as well as their ability to reproduce (adults) and grow (immature snails). Treated snails were compared with a control group, which was not frozen. No difference appeared in the survival, reproduction and growth of control and frozen snails. This study confirms partial freezing tolerance in this population of Helix aspersa.     

Direct and indirect pathways in strong field atomic ionization dynamics

With the help of a suitably chosen momentum-space analysis, we study some of the basic mechanisms governing the physics of the processes occurring when atoms are submitted to intense infrared laser pulses, with peak intensities 10(14) W cm(-2)相似文献   

Influence of σ systems on the ππ* transition energies: A simple application to the series of linear polyenes

One uses a 2nd order perturbation expression of the transition energies for the series of linear polyenes with π delocalized molecular orbitals and σ fully localized bond molecular orbitals. One only keeps the σπ coulombic integrals and the local σσ ^* excitations. Within these assumptions it is possible to demonstrate: the effect of the monoexcitations on CH and CC bonds mainly depends of the pairing or non pairing character of the considered ππ ^* transition. It tends to zero as n ^?1 as the dimension n of the system increases. the rÔle of the \(\begin{array}{*{20}c} \sigma \\ \pi \\ \end{array} \left| {\begin{array}{*{20}c} {\sigma *} \\ {\pi *} \\ \end{array} } \right.\) excitations increases as n increases and tends towards a limit which depends of the considered ππ ^* transition. But the asymptotic final effect of σ system is smaller than for ethylene. the contribution of the σ system to the actual ππ ^* singlet triplet separation decreases towards zero when the dimension of the system increases.     

Evaluation of N‐hydroxymethylphthalimide in alkaline medium: Novel entry to the tricyclic [1,3]oxazepine core via an intramolecular π and O‐cationic cyclization

Fused isoindolo[1,3]benzo(or thieno)oxazepines 8a,b and one of their positional isomers aromatic tricyclic N,O‐acetals 13b are reported to occur efficiently in a three‐step sequence from N‐hydroxy‐methylphthalimide (6) . The key step of this methodology is the intramolecular arylation of an endocyclic and/or exocyclic N‐acyliminium cation. The mechanism leading to these species, in particular to a tricyclic lactam 13b , is discussed.     

Mild and efficient copper-catalyzed cyanation of aryl iodides and bromides

An efficient copper-catalyzed cyanation of aryl iodides and bromides is reported. Our system combines catalytic amounts of both copper salts and chelating ligands. The latter, which have potential nitrogen- and/or oxygen-binding sites, have never previously been used in this type of reaction. A protocol has been developed that enables the cyanation of aryl bromides through the copper-catalyzed in situ production of the corresponding aryl iodides using catalytic amounts of potassium iodide. Aryl nitriles are obtained in good yields and excellent selectivities in relatively mild conditions (110 degrees C) compared with the Rosenmund-von Braun cyanation reaction. Furthermore, the reaction is compatible with a wide range of functional groups including nitro and amino substituents. The protocol reported herein involves two main innovations: the use of catalytic amounts of ligands and the use of acetone cyanohydrin as the cyanating agent in copper-mediated cyanation reactions.     

Reduction electrochimique des derives carbonyles insatures : IX. Indanones et tetralones : electrolyses mixtes en presence d'electrophiles

It is shown that activated cyclic carbonyl compounds, such as tetralones and indanones, can behave in a particular manner when they are reduced in presence of electrophiles. Two classes of electrophiles were chosen : alkyl halides and carbon dioxide. The reactivity (alkylation and carboxylation) often depends on the nature of the activated ketone used as a substrate.