High-depth-resolution SIMS analysis for InGaAs/InP interfaces

The influence of the primary ion impact conditions and of the surface chemical composition on beam-induced effects is investigated in order to achieve a high-depth-resolution analysis for the InGaAs/InP interfaces. The main result is that the oxygen adsorption with an appropriate pressure on the Cs⁺ bombarded surface can suppress the element-dependence of depth resolution which is an artefact in SIMS analysis.     

Stereoselective synthesis of both stereoisomers of β-fluorostyrene derivatives from a common intermediate

The stereoselective synthesis of both cis- and trans-β-fluorostyrene derivatives from a common intermediate, (Z)-1-aryl-2-fluoro-1-(trimethylsilyl)ethenes, is described. The trans isomers are obtained by a stereospecific replacement of the silyl group in the presence of water and a fluoride source, whereas the preparation of the cis isomers is achieved by a bromination/desilicobromination sequence followed by reduction of the newly created C-Br bond. A stereoselective transformation of both stereoisomers of β-fluorostyrene is also presented.     

First efficient uncharged reactivators for the dephosphylation of poisoned human acetylcholinesterase

Nerve agents are highly toxic organophosphorus compounds with strong inhibition potency against acetylcholinesterase (AChE). Herein, we describe two first extremely promising uncharged reactivators for poisoned human AChE with a superior or similar in vitro ability to reactivate the enzyme as compared to that of HI-6, obidoxime, TMB-4 and HL?-7.     

A novel and unusually long-lived chemiluminophore based on the 7-hydroxycoumarin scaffold

Synthesis and chemiluminescent properties of a new 1,2-dioxetane chemiluminophore bearing a 7-hydroxycoumarin moiety are presented. The 1,2-dioxetane decomposition ended up with strong and long-lived emission of light. This new structure opens way to the development of a new generation of bright chemiluminescent bio-probes.     

How Well Do We Handle the Sample Preparation,FT-ICR Mass Spectrometry Analysis,and Data Treatment of Atmospheric Waters?

FT-ICR MS (Fourier-transform ion cyclotron resonance mass spectrometry) analysis has shown great potential to aid in the understanding of the extremely high molecular diversity of cloud water samples. The main goal of this work was to determine the differences in terms of formula assignment for analytical (i.e., measurement replicates) and experimental replicates of a given cloud water sample. The experimental replicates, obtained by solid phase extraction, were also compared to the results obtained for freeze-dried samples to evaluate whether the presence of salts interferes with the analysis. Two S/N ratios, generally adopted for atmospheric samples, were evaluated, and three different algorithms were used for assignment: DataAnalysis 5.3 (Bruker), Composer (Sierra Analytics), and MFAssignR (Chemical Advanced Resolution Methods Lab). In contrast to other works, we wanted to treat this comparison from the point of view of users, who usually must deal with a simple list of m/z ratios and intensity with limited access to the mass spectrum characteristics. The aim of this study was to establish a methodology for the treatment of atmospheric aqueous samples in light of the comparison of three different software programs, to enhance the possibility of data comparison within samples.     

About a possible constancy of the total cross-section of the e+e− annihilation into hadrons

We show how a series of vector mesons can give a constant total cross-section in agreement with the experimental results up to 5 GeV. We discuss also the ratios n_π^°/n_π±,n_K/n_π and the breakdown of scaling in the inclusive spectra.     

Anomalous effects ine + e − annihilation into boson pairs II.e + e −→ZZ, γZ, γγ

In application of the general procedure defined in I, we analyze various kinds of anomalous effects which could appear either in the leptonic or in the bosonic sector of the reactionse ⁺ e ^?→ZZ, γZ and γγ: excited electron, excited vector boson or isoscalar partner, anamalous three-neutral boson couplings, residual contact terms involving transverse or longitudinalZ-components. Results are given in view of SLC, LEP and future linear colliders.     

Possible excitation of new C=+1 states via 2 photons e+e− annihilation

We suggest to look at the reactions e⁺e^?→χ→ hadrons which can occur via 2γ annihilation around 3.4 and 3.5 GeV with a cross-section of the order of a few 10^?34cm² MeV and where the χ could decay mainly into ππη_c and ηη_c.     

1H and 13C NMR study of the effects exerted by an oxirane ring in the epoxybicyclo-[2.2.2]octane series

The ¹H and ¹³C NMR spectra of 2,3-disubstituted exo-5,6- and endo-5,6-bicyclo[2.2.2]octanes, and the corresponding alkanes, have been investigated to determine the effects exerted by an oxirane ring. The ¹H NMR study showed that the anti protons, H-7a and H-8a, are significantly shielded and the syn protons, H-7s and H-8s, are deshielded, although to a smaller extent, by the exo-oxirane. An endo-oxirane has practically no effect on the same protons. The stereochemistry of epoxybicyclo[2.2.2]octanes is, thus, easily deduced from ¹H NMR data. The ¹³C NMR study of the epoxy compounds provided an estimate of the value of α, β, γ syn and γ anti effects (to the epoxide oxygen) of an oxirane ring. In these rigid bicyclic molecules, of known geometry, the γ syn and the γ anti effects are of the same value, even though the dihedral angles are very different (0° and 120°).