1H NMR study of inclusion compounds of phenylurea derivatives in beta-cyclodextrin

Proton nuclear magnetic resonance spectroscopy ((1)H NMR), which has become an important tool for the study "in situ" of beta-cyclodextrin (beta-CD) complexes, was used to study and structurally characterize the inclusion complexes formed between beta-CD and isoproturon, fenuron, monuron and diuron. The high variation of the chemical shifts from the proton located inside the cavity (H-3, H-5 and H-6) coupled with the non variation of the one located outer sphere of the beta-CD (H-1, H-2 and H-4) provided clear evidence of the inclusion phenomena. Two-dimensional rotating frame Overhauser effect spectroscopy (ROESY) experiments were carried out to further support the proposed inclusion mode.     

Ice nucleation in aqueous electrolytes by light scattering observation

Nucleation of ice is studied in supercooled aqueous electrolytes, after quenching, by light scattering experiments. According to salt concentration heterogeneous nucleation can occur on cracks, decorating and locking most of them. In contrast the homogeneous nucleation results are in agreement with Turnbull's theory if the equilibrium temperature for crystallization is identified with the homogeneous nucleation temperature. The mean field scaling law is obtained for the steady state frequency of the ice nucleation per unit volume which gives some estimate for the quantity β^1/3related to the melting of ice and its interface with the solution near 140–145 K. The scaling law is also obtained for the transient nucleation period.     

Normalité asymptotique des estimateurs semiparamétriques dans le modèle de Cox avec covariable manquante nonignorable

Let T denote a random duration until some event of interest. In the Cox model $\text{λ}{}_{\mathrm{T}}\text{(t)}\text{e}{}^{\mathrm{\beta Z(t)}}$, if the value of Z at event time is unobserved, Dupuy and Mesbah (Lifetime Data Analysis 8 (2002) 99–115) have proposed to estimate the parameters β and $\text{Λ}{}_{\mathrm{T}}\text{(t)=∫}{}_0{}^{\mathrm{t}}\text{λ}{}_{\mathrm{T}}\text{(s)}\text{d}\text{s}$ by maximizing a likelihood obtained from a joint model for survival and the longitudinal covariate data. We show that the estimators derived from this joint likelihood are asymptotically normally distributed. To cite this article: J.-F. Dupuy et al., C. R. Acad. Sci. Paris, Ser. I 336 (2003).     

Direct and delayed emissions from a naphthalene crystal doped with pyrene molecules

Direct and delayed emissions from a naphthalene crystal doped with pyrene molecules are investigated at temperatures between -196 and +70°C. Data are obtained for different optical excitations and for different concentrations of the host molecules. It is shown that these observed emissions are due to the deformation of the crystalline cell by the presence of the guest molecules.     

Characterization of defects in GaP and GaAsP graded heterojunctions by transmission electron microscopy

Misfit dislocations are observed in graded heterojunctions GaAs_1?xP_x by electron microscopy. Results are in agreement with previous work concerning the nature of the dislocations (Lomer and 60° dislocations) and their density dependence on the phosphorus gradient. The discussion concerns the formation of Lomer dislocations and the possibility of reducing the density of inclined dislocations which reach the surface of the epitaxial layer. GaP substrates, S-doped, are examined by transmission electron microscopy. Numerous defects such as Frank loops, perfect loops, helical dislocations and precipitates are observed. A GaP homoepitaxial layer realized on this substrate is free from these defects but exhibits stacking faults. A zinc diffusion does not produce additional defect but a 1000 Å thick amorphous layer is observed a at the surface.     

Raman spectroscopy for identification and quantification analysis of essential oil varieties: a multivariate approach applied to lavender and lavandin essential oils

Lavender (Lavandula angustifolia) is used for cosmetics, perfumes and medicine (antimicrobial activity and relaxant properties) while lavandin (sterile hybrid of L. angustifolia P. Mill. × Lavandula latifolia (L.f.) Medikus) is used for air fresheners, deodorants and soaps. These plants are widely cultivated for essential oil production. In this study, 104 samples were analyzed including 62 lavandin and 42 lavender oil samples from several varieties. The Raman spectra are similar but can be differentiated by chemometrics treatment. Data structure may be studied by PCA. A PLS regression model was used for quantitative analysis of the main compounds such as linalyl acetate, linalool and eucalyptol. The reference data were obtained by gas chromatography. The performance of the method was also tested to discriminate between the two species and the seven varieties (Abrial, Fine, Grosso, Maillette, Matherone, Sumian and Super) by PLS‐DA regression. The examination of PLS and PLS‐DA regression coefficients allowed for the identification of species and of the varieties' metabolomic markers. Copyright © 2015 John Wiley & Sons, Ltd.