Surface morphology changes of poly(ethyleneterephthalate) fabrics induced by cold plasma treatments

Some selective cold plasma processing modify specific surface properties of textile polymeric materials such as their dyeability, wettability and hydrorepellence. To correlate the sample surface changes with the acquired surface properties allows one to obtain information on the chemical and physical processing involved in plasma treatment. In this work, atomic force microscopy (AFM) has been applied to investigate the morphological and topographical surface modifications induced by RF cold plasma processing of poly(ethyleneterephthalate) (PET) fabrics. Rms surface roughness and surface area of the samples are measured before and after the treatments. The morphology changes have been analysed as a function of the treatment time and air gas pressure. Measurements have been performed also using plasmas produced by different gases such as He, Ar, SF₆ and CF₄. The PET shows different behaviour with different gas plasmas. In the case of air, He and Ar gases the sample surface modifications seem to be mainly due to etching effects, while the fluorine atoms grafting probably is responsible for surface rearrangement process using SF₆ and CF₄ gases. As a consequence different surface properties are produced in the plasma treated samples. Article presented at the International Conference on the Frontiers of Plasma Physics and Technology, 9–14 December 2002, Bangalore, India.     

High efficiency white luminescence of alumina doped ZnO

The application of alumina-doped ZnO (AZO) films as luminescent material for large area lighting sources has been evaluated. Thin films were grown on quartz using magnetron sputtering and subsequently annealed under argon atmosphere in a rapid thermal annealing experiment. Below 550 °C, red-shift of the optical band gap and increase of the visible emission are observed in agreement with Al diffusion and formation of interstitial oxygen atoms. At temperatures higher than 800 °C, diffusion is activated and Ostwald ripening leads to the formation of larger grains and an increase of the crystalline phase. The photoluminescence (PL) intensity is enhanced, specifically in the UV range. As a result the emission spectrum of AZO thin films can be adjusted by the annealing conditions, with equal contributions from the UV and orange parts of the PL spectrum resulting in an efficient white emission as quantified using the color space map of the Commission Internationale de l'Éclairage.     

Multienzymatic preparation of 3-[(1R)-1-hydroxyethyl]benzoic acid and (2S)-hydroxy(phenyl)ethanoic acid

The use of two oxidoreductases (an aldoketo reductase from Escherichia coli JM109 and an alcohol dehydrogenase from Lactobacillus brevis) has demonstrated that it is possible to prepare enatiomerically pure diols in a one-pot operation. The reactions were applied to the synthesis of (1R)-1-[3-(hydroxymethyl)phenyl]ethanol and (1S)-1-phenylethane-1,2-diol, using a two-step procedure. The yield is nearly quantitative and the enantiomeric purity is greater than 95%. A third step has been introduced by adding a cell biocatalyst showing dihydrodiol dehydrogenase activity from Pseudomonas fluorescens N3. This allows for the preparation of 3-[(1R)-1-hydroxyethyl]benzoic acid and (2S)-hydroxy(phenyl)ethanoic acid.     

Intramolecular [2 + 2]cycloadditions of dialkylketenes with alkenes. Regiochemistry of intramolecular [2+2]cycloadditions of ketenes with alkenes

Unsaturated dialkylketenes 7a, 7b and 7c undergo intramolecular [2 + 2]cycloadditions to give 8a (45%), 9b (23%) and 9c (45%). Intramolecular cycloadditions of dialkylketenes give higher yields than intramolecular cycloadditions of monoalkylketenes, even though dialkylketenes are less reactive than monoalkylketenes. An intramolecular competition experiment with ketene 17 establishes that trans-alkenes are approximately 33 times more reactive than cis-alkenes in intramolecular cycloadditions. Ketene 36 furnishes 22% of the expected bicyclo[3.2.0]heptanone 37 and 28% of bicyclo[3.1.1]heptanone 38.     

A Highly Effective Ruthenium System for the Catalyzed Dehydrogenative Cyclization of Amine–Boranes to Cyclic Boranes under Mild Conditions

We recently disclosed a new ruthenium‐catalyzed dehydrogenative cyclization process (CDC) of diamine–monoboranes leading to cyclic diaminoboranes. In the present study, the CDC reaction has been successfully extended to a larger number of diamine–monoboranes ( 4 – 7 ) and to one amine–borane alcohol precursor ( 8 ). The corresponding NB(H)N‐ and NB(H)O‐containing cyclic diaminoboranes ( 12 – 15 ) and oxazaborolidine ( 16 ) were obtained in good to high yields. Multiple substitution patterns on the starting amine–borane substrates were evaluated and the reaction was also performed with chiral substrates. Efforts have been spent to understand the mechanism of the ruthenium CDC process. In addition to a computational approach, a strategy enabling the kinetic discrimination on successive events of the catalytic process leading to the formation of the NB(H)N linkage was performed on the six‐carbon chain diamine–monoborane 21 and completed with a ¹⁵N NMR study. The long‐life bis‐σ‐borane ruthenium intermediate 23 possessing a reactive NHMe ending was characterized in situ and proved to catalyze the dehydrogenative cyclization of 1 , ascertaining that bis σ‐borane ruthenium complexes are key intermediates in the CDC process.     

Electrochemical reduction of the bis(cyclo-octadiene)rhodium monocation: generation and fate of the 17-electron radical

The electrochemical reduction of the monocation of bis-(cyclo-octadiene)Rh[(COD)₂Rh⁺] has been studied in chlorinated hydrocarbons and d₆-acetone by cyclic voltammetry, chronoamperometry and exhaustive coulometry. Successive one-electron reductions are observed for the couples (COD)₂Rh⁺/(COD)₂Rh and (COD)₂Rh/(COD)₂Rh⁻ at -1.34 V vs. Fc and -1.93 V vs. Fc respectively. The 17-electron Rh(0) radical (COD)₂Rh abstracts a Cl atom from CH₂Cl₂ to give the dinuclear complex [(COD)Rh(μ-Cl)]₂ in high yield at 298 K. At subambient temperatures this reaction is suppressed and the dominant decomposition product is apparently (COD)Rh(C₈H₁₃), formed by H atom abstraction by (COD)₂Rh from solvent and/or adventitious water. Electrolysis products were characterized by electron spin resonance (ESR), nuclear magnetic resonance (NMR) and mass spectrometry. The reactivity of the radical is rationalized by a bonding model in which the lowest unoccupied molecular orbital (LUMO) is d_x²−y² with some diolefin mixing. ESR measurements are consistent with this model and suggest that the COD ligands form a ligand field around Rh which is closer to square planar than to tetrahedral.     

Observations of nonlinear turbulence in the upstream solar wind

Summary Plasma, electric-field and magnetic-field data from several experiments on board the spacecraft ISEE 1 and 2 have been analysed in the interaction region upstream of the Earth's bow shock. Upstream waves which are known to be associated with diffuse distributions of backstreaming protons are shown to correlate also with variability in the distribution of the incoming solar-wind protons. Both phenomena are also clearly connected with the presence of enhanced electric-field turbulence. On the basis of these relations, a preliminary discussion can be given of the complex nonlinear plasma processes occurring in the foreshock region.     

Selective enzymatic reduction of aldehydes

Highly selective enzymatic reductions of aldehydes to the corresponding alcohols was performed using an E. coli JM109 whole cell biocatalyst. A selective enzymatic method for the reduction of aldehydes could provide an eco-compatible alternative to chemical methods. The simplicity, fairly wide scope and the very high observed chemoselectivity of this approach are its most unique features.     

Grade Filtration of Linear Functional Systems

The grade (purity) filtration of a finitely generated left module M over an Auslander regular ring D is a built-in classification of the elements of M in terms of their grades (or their (co)dimensions if D is also a Cohen-Macaulay ring). In this paper, we show how grade filtration can be explicitly characterized by means of elementary methods of homological algebra. Our approach avoids using sophisticated methods such as bidualizing complexes, spectral sequences, associated cohomology, or Spencer cohomology used in the literature of algebraic analysis. Efficient implementations dedicated to the computation of grade filtration can then be easily developed in the standard computer algebra systems. Moreover, this characterization of grade filtration is shown to induce a new presentation of the left D-module M which is defined by a block-triangular matrix formed by equidimensional diagonal blocks. The linear functional system associated with the left D-module M can then be integrated in cascade by successively solving inhomogeneous linear functional systems defined by equidimensional homogeneous linear systems of increasing dimension. This equivalent linear system generally simplifies the computation of closed-form solutions of the original linear system. In particular, many classes of underdetermined/overdetermined linear systems of partial differential equations can be explicitly integrated by the Maple package PurityFiltration and the GAP package homalg, but not by the standard PDE solvers of computer algebra systems such as Maple.