Linear and nonlinear relations between DSC parameters and elastic moduli for chemically and thermally treated human hair

Against the practical context of thermal straightening, hair samples were obtained with a chemical (bleaching) as well as a cumulative thermal history (0–800 s, 200 °C). On these samples, tensile testing and DSC analysis, both in the wet state, were conducted to obtain the elastic moduli E_w as well as denaturation temperatures T_D and enthalpies ΔH_D. 3D plots show overall linearity for the relationships between the parameters for natural hair. For bleached hair, pronounced nonlinearities develop beyond 300 s of thermal treatment. At this stage, T_D as well as E_w approaches limiting values, consistent with the state of a highly cross-linked, thermoset polymer. 2D projections are used to investigate the correlations between pairs of parameters. The results show that bleaching imparts a specific sensitivity for thermal damage, namely, to the matrix proteins, which more readily than the intermediate filaments (IF) turn into a thermoset. Overall, correlations between parameters hold well prior to the thermoset range. It is thus suggested that tensile testing to determine the elastic modulus and DSC come to consistent and equivalent results, at least, for the current experimental context. However, while E_w combines contributions of IFs and matrix, DSC differentiates the specific property changes of these components.

     

Rotational Analysis of the ΔvSiH=3-6 Stretching Vibrational Overtones of HSiD3

The nν₁ SiH stretching overtone transitions of trideuterosilane, HSiD₃, have been recorded by Fourier transform spectroscopy (n=3 and 4) and by intracavity laser absorption spectroscopy (n=5 and 6). The unusually weak 3ν₁ band is affected by considerable intensity and energy perturbations. The 4ν₁ band is also strongly perturbed but the interaction with the dark states is more limited and part of the rotational structure of the v₁=4 upper state could be satisfactorily modeled. Less pronounced perturbations affect the v₁=5 level, newly detected by ICLAS. Its rotational structure is locally perturbed by anharmonic coupling with an unidentified vibrational dark state. The global modeling of the interacting dyad allowed the determination of the perturber parameters and the assignment of extra lines due to an intensity transfer from the v₁=5 bright state to the dark state. In agreement with a previous ICLAS study, the 6ν₁ band near 12 113 cm⁻¹ was found free of perturbation. About six hundred line positions could be reproduced with an rms of 4.6×10⁻³ cm⁻¹, leading to a significantly improved set of rovibrational parameters. The striking evolution of the rotational structure, which exhibits fewer and fewer perturbations when the SiH excitation increases, is discussed.     

Determination of traces of iron in indium phosphide by electrothermal atomic absorption spectrometry combined with solvent extraction

An electrothermal atomic absorption (ETAAS) method for the determination of traces of iron (0.1-1.0 microgram g-1) in Fe-doped indium phosphide (InP) has been developed. In order to overcome the indium matrix-effect and to achieve a useful detection limit, a preliminary solvent-extraction of Fe(III) with acetylacetone (HAA) is necessary. After sample dissolution with hydrochloric acid (1 + 1) the digest is evaporated to dryness, Fe(II) is oxidized to Fe(III) with nitric acid, the residue is dissolved in 0.01 mol L-1 HCl and the iron is extracted at pH 2.0 with 0.5 mol L-1 HAA in toluene. The organic phase is injected into the graphite furnace and the iron is directly evaluated by external organic standard calibration. The limit of detection (3SB) resulting from further in-situ preconcentration is 0.03 microgram g-1. When the method was applied to the analysis of real samples containing 0.2-0.7 microgram g-1 Fe, the RSD was in the range 8-21%. Results were compared with those independently obtained on the decomposed sample solution with inductively coupled atomic emission spectrometry (ICP-AES). The detection limit of the ICP-AES method, that needs matrix-matched standards, is 0.20 microgram g-1.     

Novel and elegant modes of SbF3 coordination in the complexes with azacrown ethers

Synthesis and single-crystal X-ray structures are recorded for three adducts of SbF₃ with different azacrown ethers. [SbF₃·H₂O·L₁], 1, (L₁ = 12,13-benz-1,10-di(azamethyl)-4,7-dioxacyclotetradecane-1,14-dione), triclinic, , a = 11.234(2), b = 11.691(2), c = 8.869(2) Å, = 94.66(3), = 113.12(3), = 67.82(3)°, Z = 2. [SbF₃Cl·H₂O·(HL₂)], 2, (L₂ = monoaza-18-crown-6), orthorhombic, P2₁2₁2₁, a = 8.763(2), b = 13.003(3), a = 16.836(3) Å, Z = 4. [(SbF₃)₂Cl₂·(H₂L₃)], 3, (L₃ = 1,10-diaza-18-crown-6), triclinic, , a = 8.284(2), b = 9.016(2), c = 9.134(2) Å, = 82.92(3), = 65.24(3), = 63.38(3)°, Z = 1. All three structures include SbF₃ neutral molecules in the pyramidal mode and the antimony second coordination sphere is completed up to six in different fashions. In 1 the dimeric (SbF₃)₂ adducts are made up due to the involvement of the symmetry-related fluorine atom in coordination. The distorted octahedron is then completed by water molecule and carbonyl oxygen of L₁. The neutral molecules are joined by coordination and hydrogen bonds in the infinite ribbons. 2 and 3 are both comprised of neutral and charged species also bounded via coordination and hydrogen bonds. L₂ and L₃ in the complexes adopt the form of single and double-charged cations, respectively. The inorganic backbone unites the neutral SbF₃ molecules and chloride anions in the alternative mode. The sixth coordination site in the antimony polyhedron is completed by the water molecule in 2 and the ethereal oxygen atom in 3. Alignment of the inorganic entities within the structures of 2 and 3 is strikingly similar. Hydrogen bonding patterns are discussed.     

Amination of aryl- and vinylacetylenic compounds catalyzed by rhodium(I) complexes

New rhodium-catalyzed amination reactions of arylacetylenes and cyclohexen-1-ylacetylene in the presence of strong bases with the use of carbon dioxide as an auxiliary are described. Secondary amines attack the terminal carbon atom of the triple bond followed by protonation of the adjacent carbon atom. Alternatively, the reaction can proceed further with the addition of the second alkyne molecule. The conditions for the selective synthesis of enamines (up to 87% yield) or α-substituted propynylamines (up to 86% yield) are reported. Dipartimento di Chimica Organica e Industriale dell'Università, Viale delle Scienze, I-43100 Parma, Italia. Dipartimento di Chimica, Università della Calabria, Arcavacata di Rende, I-80036 Cosenza, Italia. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 966–970, May, 1998.     

Una proprietà gruppale delle involuzioni planari che mutano in sé un'ovale di un piano proiettivo finito

Summary The purpose of the present paper is to prove the following theorem: Let Ω be an oval in the projective plane P of odd order n. If P admits a collineation group G wich maps Ω onto itself and is doubly transitive on Ω, then P is desarguesian, Ω is a conic and G contains all collineations in the little projective group PSL(2, n) of P wich leaves Ω invariant.

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Entrata in Redazione il 5 april 1977.     

Bis(triazacyclohexane) sandwich complexes of (Cu(I))(2), Cu(II) and Zn(II): complexes with cuprophilic attraction between two cationic copper(I) leading to unusual reactivity with dioxygen

As the first 1st-row transition metal complexes having six tertiary amine donor groups, bis(triazacyclohexane) sandwich complexes [L2M](BF4)2 (L = benzyl- or p-fluorobenzyl-triazacyclohexane, M = Cu or Zn) have been obtained by the protonolysis of Et2Zn in the presence of L or by reaction of [Cu(MeCN)4](BF4) with L in CH2Cl2 and subsequent air oxidation via an unprecedented Cu(I)(2) sandwich complex containing a short Cu-Cu contact.