Reactivite des imines vis a vis d'alcenes gem disubstitues : Synthese d'aza-1 bicyclo (2,1,0) pentanes

Imines undergo 1,3 dipolar cycloadditions reactions as well as 3^- +2 polar cycloadditions reactions with alkenes substituted at the same carbon atom with an electron withdrawing group and a leaving group to give heterocyclic compounds.     

Model, software and database for line-mixing effects in the ν3 and ν4 bands of CH4 and tests using laboratory and planetary measurements—II: H2 (and He) broadening and the atmospheres of Jupiter and Saturn

The absorption shapes of the ν₂, ν₃ and ν₄ infrared bands of CH₄ perturbed by H₂ in large ranges of pressure and temperature have been measured in the laboratory. In order to model these spectra, the theoretical approach accounting for line-mixing effects proposed for CH₄-N₂ and CH₄-air and successfully tested in the companion paper (I), is used. As before, state-to-state rotational rates are used together with some empirical parameters that are deduced from a fit of a single room temperature spectrum of the ν₃ band at about 50 atm. The comparisons between measured and calculated spectra in the ν₃ and ν₄ regions under a vast variety of conditions (9-300 atm, 80-300 K) then demonstrate the quality and consistency of the proposed model. In the case of the ν₂ band, which is of E symmetry, specific parameters, different from those adapted to the ν₃ and ν₄ transitions of F₂ symmetry, are used for proper modeling of the spectral shape. Furthermore, as shown previously, a broad absorption feature grows underneath the ν₂ band with increasing H₂ density. The latter, for which an empirical model is proposed, is attributed to a collision-induced absorption (CIA) process in methane. From the developed models, a database and associated software are built for the updating of planetary atmospheres radiative transfer codes. The quality of these tools is then further demonstrated using emission measurements of the Jovian and Saturnian atmospheres in the ν₄ region (7-10 μm) recorded by the Short Wave Spectrometer of the Infrared Space Observatory and the Composite Infrared Spectrometer on-board Cassini. Comparisons between measured radiances and predictions confirm the failure of the purely Lorentzian approach and the quality of the proposed line-mixing model. Furthermore, it is shown that the methane CIA contribution has a significant influence on the planetary emission beyond 1400 cm⁻¹.     

Growth and characterizations of ZnO and Co-doped ZnO films for their use in spintronic

Diluted Magnetic Semiconductors offer potential applications for spintronics. In this respect, Co-doped ZnO films are particularly interesting due to their Curie temperature. However, the origin of ferromagnetism is controversial. High quality Co-doped ZnO thin films have thusly been grown using the pulsed laser deposition technique on (001) Al₂O₃ substrates. Two series were made. In the first one, the films are grown using metallic targets whereas in the second one, the films are synthesized from ceramic targets. Detailed characterizations have been performed and a comparison have been made, in light of the literature.     

The analysis of alkyl-capped alcohol ethoxylates and alcohol ethoxycarboxylates from alcohol ethoxylates by atmospheric pressure chemical ionization mass spectrometry

Alcohol ethoxylates (AEs) are nonionic surfactants. They are industrially important compounds that have historically been difficult to analyze, with the best results to date achieved through derivatization (e.g., silylation) followed by analysis by gas chromatography/mass spectrometry (GC/MS). Recently, mass spectrometric techniques such as field desorption (FD), time-of-flight secondary ion mass spectrometry (TOF-SIMS), fast atom bombardment (FAB), electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) have been employed to analyze surfynol(R) 4xx. In an effort to produce low-cost alkyl-capped AEs and anionic detergents from AEs, a fast and reliable measure of the product yields and conversions from AEs is required in research. We found that the product yields and conversions from reactions of AEs, obtained by the employment of atmospheric pressure chemical ionization (APCI), were in good agreement with those obtained from proton nuclear magnetic resonance spectroscopy ((1)H-NMR). Therefore, APCI can be used as a validated tool for studying AE reactions. Mixtures that contain either silylated or unsilylated ethoxylates and/or carboxylates yield the same APCI mass spectra. Copyright -Copyright 1999 John Wiley & Sons, Ltd.     

Concept of multipole magnetic field rotation in ECRIS

The conventional type of magnetic well is formed by superposition of two types of magnetic field, axial bumpy field and radial multipole field. It is used to contain plasma that consists of neutrals, ions and electrons. These particles are in constant motion in the well and energetic electrons create plasma by violent collisions with neutrals and ions. The confined electrons are constantly heated by ECR technique in the presence of magnetic field. In this paper it has been shown theoretically that how the electron motion is influenced in terms of heating, containment and azimuthal uniformity of plasma, by the axial rotation of the multipole magnetic field [1,2]. Afterwards, the feasibility of achieving a rotating magnetic multipole field is discussed to some extent. And it is seen that it is not beyond the capability of the scientific community in the present scenario of the advanced technology. Presently, it can be achieved for lesser field and slightly larger size of the multipole electromagnet and can be used for improvement of the ECR ion source (ECRIS).     

Optimizing head/media electrical characterization in the presence of skew at high track density

The skew angle causes a discrepancy in determining the reader-to-writer offset (RWO) when using different periodical patterns in track profile tests. It also separates the peak overwrite (OW) from the peak high frequency amplitude HFA, (1 T periodical pattern) on corresponding track profiles. Furthermore, higher track density and larger skew angle exacerbate the skew effect and induce more RWO error, thus impacting the parametric performance optimization. Simulation studies are used to interpret the skew effect on the RWO determination and OW cross-track characteristics. Based on experimental investigations and simulation analyses, using the HFA, track profile for deriving the optimal RWO is proposed for spin-stand tests. Actual parametric characterization has proven that the optimal RWO minimized the skew effect and the RWO error, thus improving the parametric performance and reducing the test variation. The method is beneficial and necessary for the high track density characterization.     

IR thermometry: a new tool for contactless in situ investigations of metal–insulator transition

In the present work, we focus on an original study of metal–insulator transition in LaNiO₃ (LNO) compound by IR camera mounted on a pulsed laser deposition chamber. IR thermometry is based on the measurement of the radiated energy that is a function of the surface temperature and the emissivity (ε) of a material. Thus, at a fixed high temperature in an oxygen equilibrium state and by fixing arbitrary an emissivity value, we can follow the evolution of the “measured temperature” linked to the change of the real emissivity value during a reduction/reoxygenation treatment. The variation of emissivity is correlated to the change in optical constants, e.g. to the conductivity measured simultaneously by an in situ spectroscopic ellipsometry. The combination of both techniques offers a convenient way to observe in situ and contactless changes from metallic to insulator behavior and vice versa.