Coherent waves in a multiply scattering poro-elastic medium obeying Biot's theory

Twersky's theory is generalized to multiple scattering by a uniform random distribution of cylinders in a poro-elastic medium. The high-frequency regime only, where no dispersion effects occur in the absence of scatterers, is investigated in the frame of Biot's theory. The scatterers lie within a slab of the host medium, and an incident wave gives rise to a fast longitudinal coherent wave, a slow longitudinal one, as well as a shear one in the slab. The dispersion equations of those three coherent waves are derived. The shear coherent wave propagates independently of the other two, while the longitudinal coherent waves obey a coupled dispersion equation involving conversion terms. Numerically speaking, coupling effects are significant only when forward scattering by a single cylinder of the fast wave into the slow one (or the slow wave into the fast) is larger than forward scattering with no conversion.     

Valenzisomere aromatischer systeme. Die Synthese des Pyrrolo-3-azabenzvalens

Valence Isomers of Aromatic Systems. The Synthesis of Pyrrolo-3-azabenzvalene 4-Azapentalenyl anion ( 4 ) is shown to react with dichloromethane/butyl lithium in two fundamentally different ways depending on whether diethyl ether or tetrahydrofuran is chosen as solvent. In the first case a tetracyclic valence isomer of indolizine, i.e. pyrrolo-3-azabenzvalene ( 6 ) is formed together with indolizine ( 8 ) itself. In THF however, a pyrrylbutenyne ( 9 ), isomeric with the products mentioned above is obtained in a stereospecific reaction. Once again the appearance of indolizine ( 8 ) accompanies the reaction. Mechanistic implications, based on the finding that the heterovalene 6 is not a precursor of the pyrrylbutenyne 9 , are discussed.     

PHOTOCHEMICAL REACTIONS OF THYMINE WITH CARBOXYLIC ACIDS. A MODEL FOR NUCLEIC ACID-PROTEIN PHOTOCROSSLINKING

When nucleic acid bases are UV-irradiated in the presence of carboxylic acids or carboxylate anions new photoproducts are formed as compared to the bases irradiated in the absence of carboxylic acids. The behavior of thymine and thymidine has been examined in detail. At least four photoproducts are formed in the presence of propionic acid and three in the presence of butyric acid. None of them appears to be a cyclobutyl dimer. From the concentration dependence of the rate of photoproduct formation it is concluded that the reactive excited species is the first excited singlet state of thymine. When ¹⁴C-labelled thymine is irradiated in the presence of polyglutamic acid an important part of the radioactive material is covalently linked to the polymer. Photochemical reaction of thymine with glutamic (or aspartic) acid could thus induce crosslinks between proteins and nucleic acids. It is also shown that these photoproducts are stable under usual conditions of acidic hydrolysis of UV-irradiated DNA.     

Action du N-bromosuccinimide sur les dioxolannes. Intermediaires réactionnels

1,3-Dioxolan-2-ylium ion intermediates formed by reaction of bromine or NBS on 4-syn-aryl-3,5-dioxa-tricyclo [5.2.1.0^2.6] décanes have been isolated. 2-Succinimido-1,3-dioxolanes have been prepared for the first time.     

Identification of diphenhydramine metabolites in human urine by capillary electrophoresis-ion trap-mass spectrometry

The identification of diphenhydramine (DH) metabolites that are frequently observed in the capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) analyses of alkaline liquid/liquid and solid-phase extracts of patient urines is demonstrated. Having standards for DH and diphenhydramine-N-oxide (DHNO), the presence of these two compounds could be confirmed in urines that were collected overnight after administration of 25 mg DH chloride. Using CZE coupled to ion-trap mass spectrometry (CE-MS(n)) with positive electrospray ionization and an acetate buffer at pH 5.6, the [M+H](+) ions of DH (m/z = 256), DHNO (m/z = 272), and nordiphenhydramine (NDH, m/z = 242) and their fragmentation to a common m/z 167 product ion (diphenylcarbinol moiety) was monitored. The data indicate that all three compounds are cations in an acidic environment, the migration order being NDH, DH, and DHNO. Data obtained under negative electrospray ionization conditions suggest the presence of diphenylmethoxyacetic acid-glycine amide ([M-H](-) ion of m/z 298 and fragmentation to m/z 254, loss of CO(2)), a metabolite that could tentatively be assigned to a characteristic peak observed in the MEKC electropherogram at alkaline pH. The data presented in this paper illustrate the value of using CE-MS(n) for identification of urinary drug metabolites for which no standards are available.     

Chiral Ligands Derived from Monoterpenes: Application in the Synthesis of Optically Pure Secondary Alcohols via Asymmetric Catalysis

The preparation of optically pure secondary alcohols in the presence of catalysts based on chiral ligands derived from monoterpenes, such as pinenes, limonenes and carenes, is reviewed. A wide variety of these ligands has been synthesized and used in several catalytic reactions, including hydrogen transfer, C?C bond formation via addition of organozinc compounds to aldehydes, hydrosilylation, and oxazaborolidine reduction, leading to high activities and enantioselectivities.     

PHOTODYNAMIC INHIBITION OF ESCHERICHIA COLI DNA POLYMERASE I BY 8-METHOXYPSORALEN PLUS NEAR ULTRAVIOLET IRRADIATION

Abstract— Morphological abnormality due to the UV irradiation of sperm and its modification by photoreactivation (PR) were studied in the sea urchin, Hemicentrotus pukherrimus. When sperm was UV-irradiated and allowed to fertilize unirradiated eggs, the effect of the UV was manifested as an abnormal morphology of embryos in the gastrula or later stages. The UV-induced morphological abnormality was prevented by photoreactivation when the fertilized eggs were illuminated with visible light. In the experiments on a stage-dependent change of PR effectiveness, it was found that an illumination sufficed to effect a nearly complete PR when applied up to the onset of the first DNA synthetic phase, while the PR effectiveness declined thereafter. Illumination after the completion of DNA synthesis had little effect for PR.     

Inequalities for a simplex and the number e

An n-dimensional form of Winternitz's Theorem for convex sets in Eⁿ can be related to a standard inequality for e. The object of this note is to prove two inequalities for n-dimensional simplexes that can be related to the basic inequalities (1+1/n)ⁿ < e < (1+1/n)ⁿ⁺¹.The author wishes to thank Leon Gerber, St. John's University for his beneficial suggestions.