Chlorosulfonation of Some Aldimine-Isocyanate Cycloadducts

Attempts to chlorosulfonate 1,4-diphenyl-1,3-diazetidin-2-one (1) failed, but the 3-methyl derivative (2) reacted with chlorosulfonic acid to give the bis-sulfonyl chloride (3), characterized as the sulfonamides 4 and 5. 2,3,6-Triphenyl-2,3-dihydro-1,3,5-thiadiazin-4-one (6) with chlorosulfonic acid suffered an acid-catalyzed ring-opening reaction forming the sulfonyl derivatives (8, 9) of N-phenyl-N′-thiobenzoylurea (7). Condensation of 8 and 9 with diethylamine afforded the diethyl-sulfonamide (10). Dibenzylideneethylenediamine (11) reacted with thiobenzoyl isocyanate at room temperature to yield the cycloadduct 12; however at 90°C, N,N′-di (thiobenzoylcarbamoyl)ethylenediamine (13) was obtained. The cycloadduct 12 with chlorosulfonic acid gave the ring-opened disulfonyl chloride 14 and the diethylsulfonamide 15. 1,6-Diphenylhexahydro-s-triazine-2,4-dione (17) was converted into the dimethyl derivative (18), which with chlorosulfonic acid afforded the bis-sulfonyl chloride (19), characterized as the sulfonamides 20–22.

     

Reed-Muller codes and Barnes-Wall lattices: Generalized multilevel constructions and representation over GF(2<Superscript><Emphasis Type="Italic">q</Emphasis></Superscript>)

Generalized multilevel constructions for binary RM(r,m) codes using projections onto GF(2 ^q ) are presented. These constructions exploit component codes over GF(2), GF(4),..., GF(2 ^q ) that are based on shorter Reed-Muller codes and set partitioning using partition chains of length-2 ^l codes. Using these constructions we derive multilevel constructions for the Barnes-Wall Λ(r,m) family of lattices which also use component codes over GF(2), GF(4),..., GF(2 ^q ) and set partitioning based on partition chains of length-2 ^l lattices. These constructions of Reed-Muller codes and Barnes-Wall lattices are readily applicable for their efficient decoding.      

A finite element modified method of characteristics for convective heat transport

We propose a finite element modified method of characteristics for numerical solution of convective heat transport. The flow equations are the incompressible Navier‐Stokes equations including density variation through the Boussinesq approximation. The solution procedure consists of combining an essentially non‐oscillatory modified method of characteristics for time discretization with finite element method for space discretization. These numerical techniques associate the geometrical flexibility of the finite elements with the ability offered by modified method of characteristics to solve convection‐dominated flows using time steps larger than its Eulerian counterparts. Numerical results are shown for natural convection in a squared cavity and heat transport in the strait of Gibraltar. Performance and accuracy of the method are compared to other published data. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008     

Numerical simulation of natural and mixed convection flows by Galerkin‐characteristic method

A numerical investigation is performed to study the solution of natural and mixed convection flows by Galerkin‐characteristic method. The method is based on combining the modified method of characteristics with a Galerkin finite element discretization in primitive variables. It can be interpreted as a fractional step technique where convective part and Stokes/Boussinesq part are treated separately. The main feature of the proposed method is that, due to the Lagrangian treatment of convection, the Courant–Friedrichs–Lewy (CFL) restriction is relaxed and the time truncation errors are reduced in the Stokes/Boussinesq part. Numerical simulations are carried out for a natural convection in squared cavity and for a mixed convection flow past a circular cylinder. The computed results are compared with those obtained using other Eulerian‐based Galerkin finite element solvers, which are used for solving many convective flow models. The Galerkin‐characteristic method has been found to be feasible and satisfactory. Copyright © 2006 John Wiley & Sons, Ltd.     

Particle simulation of radio-frequency plasma discharges of methanefor carbon film deposition

Particle-in-cell/Monte Carlo (PIC/MC) simulations of capacitively coupled radio-frequency (RF) glow discharges were carried out for low pressure CH₄ plasmas. The present computational scheme includes the motions and collisions of both neutral and charged particles. The CH₄ plasma is modeled by combining a one-dimensional PIC/MC method with a polyatomic particle collision scheme. The model considers the motions of CH₄, CH₄⁺, CH₃, C₂H₅, H₂, H, and electrons. Space and time dependent results show ionization rate is high at the sheath region. The dissociation rate of CH₄ is found to be high at the sheath as well as in the plasma bulk. Deposition rate of carbon film is calculated by sampling impinging particles at at the powered electrode. The calculations show that neutral radicals are the major depositing species for the cases studied. Ion energy impinging to the electrode was found to be strongly dependent on the “imposed” dc bias (as opposed to self-bias) voltage for a given RF voltage. Deposition rate was found to be almost independent of the “imposed” dc bias voltage as the RF voltage remained constant     

Sulfur stable isotope distribution of polysulfide anions in an (NH4)2Sn aqueous solution

Methylation of polysulfides [(NH4)2Sn)] by reaction with CF3SO3CH3 followed by separation of the produced dimethylpolysulfides by liquid chromatography and subsequent highly accurate stable isotope analysis by a continuous-flow isotope ratio mass spectrometer shows that polysulfide anions in an aqueous solution exchange isotopes with the other sulfur species in the system. It demonstrates for the first time that polysulfide anions are 34S-enriched in equilibrium relative to total sulfur as a function of their sulfur chain length.     

Dissipative solitons compounds in a fiber laser. Analogy with the states of the matter

We investigate experimentally ordered and disordered pattern formation of solitons in a double-clad fiber laser. We point out an analogy between the different states of matter and the states of a set of dissipative solitons. In particular, we have identified a gas, a supersonic gas flow, a liquid, a polycrystal and a crystal of solitons. The different states are obtained only by adjustment of the intracavity phase plates.     

Computational Studies of Atmospheric-Pressure Methane–Hydrogen DC Micro Glow Discharges

Atmospheric-pressure methane–hydrogen micro glow discharges were computationally investigated using a 2-D hybrid model. The plasma model was solved simultaneously with a model for the external circuit. Simulations were conducted for a pin-to-plate electrode configuration with an interelectrode separation of 400 ${rm mu}hbox{m}$. The spatiotemporal evolutions of electrons, species densities, electric field, and electron and gas temperatures were studied. A total of 81 reactions were considered, which included electron–neutral, electron–ion, ion–neutral, and neutral–neutral reactions. An 84-step reaction mechanism consisting of 15 surface species and four deposited bulk species was considered. A time-stepping technique was employed to address the time scales of plasma transport (in microseconds) and neutral and fluid transport (in milliseconds) in 2-D simulations with detailed volume and surface chemistry. The simulations indicated $hbox{H}_{3}^{+}$ and $hbox{CH}_{5}^{+}$ ions to be the most prominent hydrogen and hydrocarbon ions. The gas temperature predictions suggested the discharge to be operating as a nonthermal glow discharge. The effect of discharge current on both plasma and deposition characteristics was studied. The simulations predicted a flat voltage–current characteristic, indicating the discharge to be operating in normal glow mode. The predicted voltage–current characteristic was found to be in favorable agreement with the experimental measurements. With an increase in discharge current, the deposition rate profile expanded in the lateral direction, suggesting that deposition occurred at the cathode spot.      

Low-temperature growth of nanocrystalline silicon films prepared by RF magnetron sputtering: Structural and optical studies

In order to contribute to the understanding of the optoelectronics properties of hydrogenated nanocrystalline silicon films, a detailed study has been conducted. Structural analysis (infrared absorption and Raman scattering spectroscopy), combined with optical measurements spectroscopy (optical transmission, photothermal deflection spectroscopy and photoconductivity) were used to characterize the films. The samples were elaborated by radio-frequency magnetron sputtering of crystalline silicon target, under a hydrogen (70%) and Argon (30%) gas mixture, at three different total pressures (2, 3 and 4 Pa) and varying substrate temperature (100, 150 and 200 °C). The results clearly indicate that the films deposited at 2 Pa are amorphous, while for 3 and 4 Pa nanocrystalline structures are observed. These results are discussed in the framework of the existing models.     

A novel natural source Vicia faba L. membranes as colourant: development and optimisation of the extraction process using response surface methodology (RSM)

In this research paper, an eco-friendly extraction process of dyes from Vicia faba L. membranes was developed. In this regard, the influence of independent process factors like the weight of material, the extraction time, the temperature and the sodium hydroxide concentration on the natural dye extraction from Vicia faba membranes was investigated. The optimisation of the extraction conditions and the effect evaluation of the different operating parameters were carried out using a Box–Behnken design under response surface methodology. The optimum conditions were found to be 66 °C, 90 min, 5 g and 0.1628 mol·L^?1 for extraction temperature, time, mass of the material and sodium hydroxide concentration, respectively. The efficiency of this extraction process under these optimum conditions was evaluated by measuring the total phenolic content (TPC), the total flavonoid content and the relative colour yield (K/S). In these operating conditions, good fastness ratios were observed for the dyed fabrics.