Development of multiple drywall with high sound insulation performance

Experimental studies for the development of multiple drywalls with a high sound insulation performance are performed. Firstly, a means of preventing the sound insulation deterioration due to the coincidence effect at high frequencies is investigated by layering two plasterboards with different physical characteristics. Based on the results, a double drywall with a sound insulation performance of R_w = 61 is developed. Further more, a double drywall of R_w = 64 , a triple drywall of R_w = 86 and a quadruple drywall of R_w = 90 are developed.     

Syntheses of polyamides and polybenzodipyrrolediones from pseudo diacetylphthaloyl chlorides and diamines

Novel diacetylphthalic acids, 2,5-diacetylterephthalic and 4,6-diacetylisophthalic acids, were synthesized starting from pyromellitic dianhydride. These diacids were subsequently converted to the corresponding pseudo diacetylphthaloyl chlorides. The ring-opening polyaddition, followed by dehydrochlorination, of the pseudo diacetylphthaloyl chlorides with aliphatic diamines in a polar aprotic solvent afforded almost quantitatively polyamides having inherent viscosities of 0.3–0.7. The solution polymerization was almost completed within 1 hr at room temperature. These polyamides were soluble in acidic solvents like m-cresol. Subsequent cyclodehydration of the polyamides by heating at 200°C gave insoluble polybenzodipyrrolediones, which underwent weight losses of 10% at around 400°C under nitrogen.     

Préparation de la 8,14-diméthyl 18-nor-testostérone

Les sécrétions de 4 espèces de Dipterocarpus Viêt-Namiens ont fourni un triterpène tétracyclique, identifié au diptérocarpol de van Itallie et à l'hydroxy-dammarénone-II (I) de Mills. Le diptérocarpol est dégradé (chaîne latérale) et modifié (cycle A) en un analogue de la testostérone (XXX). Sa stéréochimie est discutée.     

Three Novel Bicyclic Taxoids from the Needles of the Chinensis yew, Taxus chinensis var mairei

PhytochemicalinvestigationontheneedlesofTaxuschinensisvar.mairei.resultedintheisolati=?nofthreenewbicyclictaxoids1--3alongwithtaxachitrieneA4'.Compoundl,lal, 14.5(c0.001,CHCI,),wasisolatedasacolorlessgummysubstance.TheiRspectrumshowedtheacetoxyanda,0-unsaturatedcarbonylsystembandsat1730and1650cm-l.HR-FAB-MSanalysisatm/z847.3152establishedthequasi-molecularforn'ulaasC.,H,=O.,Na([M Na] ,A(B-0.1mmu).ItsIH-NMRspectrum(Tablel)showedthecharacteristicsignalsoffourtertiarymethylgroupsoftaxo…     

Chain‐transfer reaction in the radical polymerization of di‐n‐butyl itaconate at high temperatures

Radical polymerizations of di‐n‐butyl itaconate were investigated. Unexpected resonances (C resonances) were observed in ¹³C NMR spectra of C?O of poly(di‐n‐butyl itaconate)s [poly(DBI)s] obtained at temperatures higher than 60 °C, although two kinds of carbonyl groups showed splittings due to triad tacticities in the spectra of polymers obtained at lower temperatures. The poly(DBI)s formed by the different kinds of initiators or formed in the presence of chain‐transfer agents showed hardly any changes in the intensities of the C resonances; this indicated that the C resonances were not due to the structures formed through initiating and terminating reactions. The poly(DBI)s obtained at different yields showed only a slight increase in the intensities of the C resonances with the yield, which suggested that the C resonances were not attributable to the intermolecular chain‐transfer reaction to the monomer and/or polymer. However, the intensities of the C resonances significantly increased with a decreasing feed monomer concentration; this suggested that intramolecular chain‐transfer reactions took place at high temperatures. Furthermore, a Cu complex‐catalyzed atom transfer radical polymerization mechanism was revealed to be effective for suppressing the intramolecular chain‐transfer reaction at 60 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2415–2426, 2002     

Universal Reaction Mechanism of Boronic Acids with Diols in Aqueous Solution: Kinetics and the Basic Concept of a Conditional Formation Constant

To establish a detailed reaction mechanism for the condensation between a boronic acid, RB(OH)₂, and a diol, H₂L, in aqueous solution, the acid dissociation constants (${K{{{\rm BL}\hfill \atop {\rm a}\hfill}}}$ ) of boronic acid diol esters (HBLs) were determined based on the well‐established concept of conditional formation constants of metal complexes. The pK_a values of HBLs were 2.30, 2.77, and 2.00 for the reaction systems, 2,4‐difluorophenylboronic acid and chromotropic acid, 3‐nitrophenylboronic acid and alizarin red S, and phenylboronic acid and alizarin red S, respectively. A general and precise reaction mechanism of RB(OH)₂ with H₂L in aqueous solution, which can serve as a universal reaction mechanism for RB(OH)₂ and H₂L, was proposed on the basis of (a) the relative kinetic reactivities of the RB(OH)₂ and its conjugate base, that is, the boronate ion, toward H₂L, and (b) the determined pK_a values of HBLs. The use of the conditional formation constant, K′, based on the main reaction: RB(OH)₂+H₂L ${{\mathop \leftrightarrow \limits ^{K{_{1}}}_{}}}$ RB(L)(OH)^?+H₃O⁺ instead of the binding constant has been proposed for the general reaction of uncomplexed boronic acid species (B′) with uncomplexed diol species (L′) to form boronic acid diol complex species (esters, BL′) in aqueous solution at pH 5–11: B′+L′ ${{\mathop \leftrightarrow \limits ^{K{^\prime}}_{}}}$ BL′. The proposed reaction mechanism explains perfectly the formation of boronic acid diol ester in aqueous solution.     

Self-starting mode-locked Cr(4+):YAG laser with a low-loss broadband semiconductor saturable-absorber mirror

We report a self-starting mode-locked Cr(4+):YAG laser with a low-loss broadband metal reflector-based semiconductor saturable-absorber mirror. The minimum pulse width was 44 fs at a wavelength of 1520 nm.     

Synthesis of aromatic polyamide-phthalimidines from chloroformylphthalides and aromatic diamines

New polymer-forming monomers, 3-benzylidene-5-chloroformylphthalide and 3-benzylidene-6-chloroformylphthalide, were synthesized by the Perkin reaction of trimellitic anhydride with phenylacetic acid, followed by chlorination. The polycondensation of these monomers with aromatic diamines in N-methyl-2-pyrrolidone at 200°C afforded aromatic polyamide-phthalimidines having inherent viscosities of 0.2-0.5 dL/g. All the polymers were readily soluble in m-cresol, pyridine, dimethylformamide, and dimethyl sulfoxide. Glass transition temperatures of some of the polymers were in the range of 255–282°C. The polyamide-phthalimidines began to lose weight at around 300°C in both air and nitrogen atmospheres, with 10% weight losses being recorded at 435–475°C in nitrogen by thermogravimetry.     

An EXAFS study of Ag3AsS3 glass

The local structures of Ag₃AsS₃ glass at 80 and 300 K have been investigated by extended X-ray absorption fine structure analysis. By comparing the glass structure with that of Ag₃AsS₃ crystal (proustite), the possibility of ionic conduction by this glass is discussed. The local structure around an As atom in the glass is similar to that in the crystal. This fact suggest that, even in the glass structure, the As atoms from AsS₃ trigonal pyramids of shape similar to that in the crystal. The Ag---S distance (2.449 Å at 300 K) and the large root mean square displacement, σ, for the Ag---S atomic pairs in the glass, groups with a by the parameter fitting method, show that the Ag atoms are quite randomly distributed around the AsS₃ groups with a similar Ag---S distance to that in the crystal. Further, it is possible that the large thermal contribution to σ_Ag---S² for the glass may indicate the involvement of the Ag atoms in ionic conduction.     

The biosynthesis of sorbicillinoids in Trichoderma sp. USF-2690: prospect for the existence of a common precursor to sorbicillinol and 5-epihydroxyvertinolide, a new sorbicillinoid member

Biosynthetic feeding studies of [1-¹³C], [2-¹³C], and [1,2-¹³C₂]-labeled sodium acetates into 5-epihydroxyvertinolide, a new sorbicillinoid, gives an incorporation pattern that proves the γ-lactone ring formation associated with a ring cleavage reaction of the precursor, a potential intermediate of sorbicillinol biosynthesis.