Generic properties of a quasi-one dimensional classical Wigner crystal

We studied the structural, dynamical properties and melting of a quasi-one-dimensional system of charged particles, interacting through a screened Coulomb potential. The ground state energy was calculated and, depending on the density and the screening length, the system crystallizes in a number of chains. As a function of the density (or the confining potential), the ground state configurations and the structural transitions between them were analyzed both by analytical and Monte Carlo calculations. The system exhibits a rich phase diagram at zero temperature with continuous and discontinuous structural transitions. We calculated the normal modes of the Wigner crystal and the magneto-phonons when an external constant magnetic field $B$ is applied. At finite temperature the melting of the system was studied via Monte Carlo simulations using the $modified$ $Lindemann$ $criterion$ (MLC). The melting temperature as a function of the density was obtained for different screening parameters. Reentrant melting as a function of the density was found as well as evidence of directional dependent melting. The single chain regime exhibits anomalous melting temperatures according to the MLC and as a check we study the pair correlation function at different densities and different temperatures, formulating a different criterion. Possible connection with recent theoretical and experimental results are discussed and experiments are proposed.Comment: 13 pages text, 21 picture

Candida albicans morphotypes from oral cavity in several families

A total of 108 individuals belonging to 22 families consisting of 3 to 8 members each were studied in order to detect Candida albicans morphotypes. Yeasts were isolated from the oral cavity of at least one individual per family, with or without teeth.Following Phongpaichit et al. technique, identical or different morphotypes were detected in 7 families. In 10 families, C. albicans was isolated both from the saliva and the removable denture of the same individual. A discontinuous fringe, considered to be a probable virulence factor, was observed in 9 (16,7%) of the C.albicans strains, from people having the complete set of theet, in the saliva of the former and of those using denture. A continuous fringe was observed in 5 (83,3%) of the C. albicans strains isolated from a same sites. Mosphotyping, a simple ans easily executed method which is useful to detect cross-infection, may serve as a "risk indicator" for the occurrence of candidosis.C. albicans was the prevalent species (86,4%) detected in at least 2 members from 14 families

Bioactive Chemical Constituents And Comparative Antimicrobial Activity Of Callus Culture And Adult Plant Extracts From Alternanthera Tenella

Crude extracts of a callus culture (two culture media) and adult plants (two collections) from Alternanthera tenella Colla (Amaranthaceae) were evaluated for their antibacterial and antifungal activity, in order to investigate the maintenance of antimicrobial activity of the extracts obtained from plants in vivo and in vitro. The antibacterial and antifungal activity was determined against thirty strains of microorganisms including Gram-positive and Gram-negative bacteria, yeasts and dermatophytes. Ethanolic and hexanic extracts of adult plants collected during the same period of the years 1997 and 2002 [Ribeirão Preto (SP), collections 1 and 2] and obtained from plant cell callus culture in two different hormonal media (AtT43 and AtT11) inhibited the growth of bacteria, yeasts and dermatophytes with inhibition halos between 6 and 20 mm. For the crude extracts of adult plants bioassay-guided fractionation, purification, and isolation were performed by chromatographic methods, and the structures of the isolated compounds were established by analysis of chemical and spectral evidences (UV, IR, NMR and ES-MS). Steroids, saponins and flavonoids (aglycones and C-glycosides) were isolated. The minimum inhibitory concentration (MIC) of the isolated compounds varied from 50 to 500 μg/mL. © 2009 Verlag der Zeitschrift für Naturforschung, Tübingen.645-6373381Agrawal, P.K., (1989) Carbon-13 NMR of Flavonoids, p. 564. , Elsevier, AmsterdamAlfermann, A.W., Petersen, M., Natural product formation by plant cell biotechnology (1995) Plant Cell, Tissue Organ Cult, 43, pp. 199-205Ames, T.T., Worden, R.M., Continuous production of daidzein and genistein from soybean in a magnetofluidized bed bioreactor (1997) Biotechnol. 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