Characterization of Polypropylene Surface Treated in a CO2 Plasma

The polypropylene modification in CO₂ plasma mainly contributes to degradation, functionalization, and cross-linking. The degradation, whose rate is depending on CO₂ dissociation and oxygen atom formation, is a quite slow reaction and it is associated with surface topography alteration, especially of the amorphous phase of the polypropylene. The surface roughness increases with the treatment duration and the amorphous phase is more degraded than the crystallized part. The functionalization, corresponding to an increase of the surface energy (57.3 mJ m ^{– 2} in 30 s), and to an oxidation (23 oxygen at.%) with the appearance of alcohol, ketone, and acid functions is a much faster phenomenon. Cross-linking takes also place during this type of treatment and will reinforce the stability of the modified surface.     

Analysis of Henrici's Transformation for Singular Problems

Henrici's transformation is the underlying scheme that generates, by cycling, Steffensen's method for the approximation of the solution of a nonlinear equation in several variables. The aim of this paper is to analyze the asymptotic behavior of the obtained sequence (s _n ^* ) by applying Henrici's transformation when the initial sequence (s _n ) behaves sublinearly. We extend the work done in the regular case by Sadok [17] to vector sequences in the singular case. Under suitable conditions, we show that the slowest convergence rate of (s _n ^* ) is to be expected in a certain subspace N of R ^p . More precisely, if we write s _n ^* =s _n ^* ,N+s _n ^* ,N, the orthogonal decomposition into N and N , then the convergence is linear for (s _n ^* ,N) but ( _n ^* ,N) converges to the same limit faster than the initial one. In certain cases, we can have N=R ^p and the convergence is linear everywhere.     

Injection locked multi-section gain-coupled dual mode DFB laser for terahertz generation

A dual mode multi-section gain-coupled distributed feedback laser with tunable mode spacing is subharmonically injection locked at 0.315 THz. The injected signal consists of an optical comb with harmonics 35 GHz apart and a bandwidth of approximately 1.9 THz. The optical comb is a result of strong four-wave mixing in a highly-nonlinear dispersion-shifted fiber. In order to observe locking of the multi-section laser, the output is optically downconverted to RF frequencies using the same optical comb. The locked multi-section DFB laser is a coherent and tunable optical source suitable for continuous-wave terahertz generation systems.     

Open Chain Chiral Macrolide Building Blocks by Opening of Deoxygenated 1,6-Anhydrosugars with 1,3-Propanedithiol

Chiral building blocks for macrolides and related natural products are obtained from 1,6-anhydrosugars by conversion of the bicyclic acetals 2 or 12 into the open chain chiral 1,3-dithianes 6 and 13. Branched precursors can be obtained by opening of the ?erný epoxide 1 with the 1,3-dithiane anion to yield 7, followed by ring opening with 1,3-propanedithiol to the bis-1,3-dithiane 8.     

Synthesis of novel 3-phenyl-2-oxido/sulfido-1,3,4,2-benzoxadiazaphosphepines

An efficient and facile synthetic approach towards a series of novel 3-phenyl-2-oxido/sulfido-2,3-dihydro-1,3,4,2-benzoxadiazaphosphepines 2–7 was described. The method depended on the cyclocondensation of equimolar ratios of salicylaldehyde phenylhydrazone (1) with different examples of phosphorus halides and phosphorus sulfides in toluene containing triethylamine as a catalyst. In the same manner, the fusion of salicylaldehyde phenylhydrazone (1) with triethyl phosphate in the presence of DBU afforded the 2-ethoxy-1,3,4,2-benzoxa-diazaphosphepine 8, while a fusion of compound 1 with diethyl phosphite and tris(2-chloroethyl)phosphite led to the formation of new examples of 1,2-benzoxaphospholes 9 and 10, respectively. Interestingly, the reaction of compound 1 with diethyl ethoxycarbonyl phosphonate in ethanol containing DBU as a catalyst furnished the chromeno[3,4-d][1,2,3]diazaphosphole derivative 12 as a regioselective product.     

An asymptotic preserving scheme for the Kac model of the Boltzmann equation in the diffusion limit

In this article, we propose a numerical scheme to solve the Kac model of the Boltzmann equation for multiscale rarefied gas dynamics. Formally, this scheme is shown to be uniformly stable with respect to the Knudsen number, consistent with the fluid-diffusion limit for small Knudsen numbers, and with the Kac equation in the kinetic regime. Our approach is based on the micro–macro decomposition which leads to an equivalent formulation of the Kac model that couples a kinetic equation with macroscopic ones. This method is validated with various test cases and compared to other standard methods.     

Solid‐State Gas Sensors Developed from Functional Difluoroboradiazaindacene Dyes

This article describes the synthesis and characterization of several new difluoroboradiazaindacene (BODIPY?) dyes functionalized at the central 8‐position by a phenyliodo, phenylheptynoate or phenylheptynoic fragment and at the 3‐ or 3/5‐position(s) by 4‐dimethylaminophenylstyryl residue(s). Single‐crystal structural determinations confirm the planarity of the dyes, while the absorption and fluorescence spectroscopic properties are highly sensitive to the state of protonation (or alkylation) of the terminal anilino donor group(s). Reversible color tuning from green to blue for absorption and from colorless (i.e., near‐IR region) to red for fluorescence is obtained on successive addition of acid and base. The difunctionalized derivative is especially interesting in this respect and shows two well‐resolved pK_a values of 5.10 and 3.04 in acetonitrile. Addition of the first proton causes only small spectral changes and deactivates the molecule towards addition of the second proton. It is this latter step that accommodates the large change in absorption and emission properties, due to the reversible extinction of the intramolecular charge‐transfer character inherent to this type of dye. The main focus of the work is the covalent anchoring of the dyes to inert, porous polyacrylate beads so as to form a solid‐state sensor suitable for analysis of gases or flowing liquids. The final material is highly stable—its performance is undiminished after more than one year—and fully reversible over many cycles. The sensitivity is such that reactions can be followed by the naked eye and the detection limit is about 600 ppb for HCl and about 80 ppb for ammonia. Trace amounts of diphosgene can be detected, as can alkylating agents. The sensing action is indiscriminate and also operates when the beads are dispersed in aqueous media.     

cis,cis,cis‐Tetra­methyl 1,2,4,5‐cyclo­hexane­tetra­carboxyl­ate

The title compound, C₁₄H₂₀O₈, was synthesized from the hydrogenation of tetra­methyl 1,4‐cyclo­hexa­diene‐1,2,4,5‐tetra­carboxyl­ate with a catalytic amount of palladium/carbon. All four carbonyl moieties of the methyl ester groups are on the same face of the chair‐conformed ring. The substantial ring distortion associated with the 1,3‐diaxial methoxycarbonyl substituents is reflected in the large difference between bond angles as well as torsion angles, respectively, that in undistorted cyclo­hexanes would be approximately the same.