Thin-thick coexistence behavior of 8CB liquid crystalline films on silicon

The wetting behavior of thin films of 4'-n-octyl-4-cyanobiphenyl (8CB) on Si is investigated via optical and x-ray reflectivity measurement. An experimental phase diagram is obtained showing a broad thick-thin coexistence region spanning the bulk isotropic-to-nematic ($T_{IN}$) and the nematic-to-smectic-A ($T_{NA}$) temperatures. For Si surfaces with coverages between 47 and $72\pm3$ nm, reentrant wetting behavior is observed twice as we increase the temperature, with separate coexistence behaviors near $T_{IN}$ and $T_{NA}$. For coverages less than 47 nm, however, the two coexistence behaviors merge into a single coexistence region. The observed thin-thick coexistence near the second-order NA transition is not anticipated by any previous theory or experiment. Nevertheless, the behavior of the thin and thick phases within the coexistence regions is consistent with this being an equilibrium phenomenon.Comment: 4 pages, 3 figure

Análise bibliométrica de revistas veterinárias multilíngues

Indexación: Scopus; Scielo.The purpose of this study was to investigate the association between language and total number of citations found among documents in journals written in English and other languages. We selected all the journals clustered together in the Journal Citation Reports 2014 under the subject category "Veterinary Sciences" and downloaded all the data registered between 1994-2013 by Web of Science for the journals that stated publishing documents in languages other than English. We classified each of these journals by quartile and extracted information regarding their impact factor, language(s) stated, country of origin, total number of documents published, total number of reviews published, percentage of documents published in English and the quartile in which each journal ranked. Of the 48,118 documents published by the 28 journals analyzed, 55.8% were published in English. Interestingly, although most of the journals state being multi-language, most documents published in quartile 1 journals were in English (an average of 99.2%), while the percentage was 93.1% in quartile 2 journals, 62.1% in quartile 3 journals and 27.4% in quartile 4 journals. We also confirmed that citation distribution in these journals was highly skewed. The results of this study suggest that journals should consider adopting English as the main language as this will increase citation counts and the impact factor of the journal.O objetivo deste estudo foi investigar a associação entre a escolha do idioma e o número de citações, a partir da análise de revistas publicadas em inglês e em outras línguas. Foram selecionadas as revistas agrupadas no Journal Citation Reports de 2014 sob a categoria “ciências veterinárias”, bem como os dados registrados na Web of Science entre 1994 e 2013 sobre as revistas que declararam documentos publicados em outro idioma que não o inglês. A seguir, as revistas foram classificadas por quartil, extraindo-se informações acerca de: índice de impacto, idioma(s) declarado(s), país de origem, número total de documentos publicados, número total de revisões publicadas, porcentagem de documentos publicados em inglês e quartil em que cada jornal foi classificado. Dos 48.118 documentos editados por 28 revistas analisadas, 55,8% foram publicados em inglês. Interessantemente, apesar de a maioria dessas revistas se declarar multilíngue, a maior parte dos documentos publicados em revistas quartil 1 empregou o inglês (uma média de 99,2%), enquanto para as revistas quartil 2 esse índice foi de 93,1%, para quartil 3 foi de 62,1%, e para quartil 4 foi de 27,4%. A pesquisa também confirmou que a distribuição das citações nessas revistas foi altamente distorcida. Os resultados do estudo sugerem que as revistas deveriam adotar o inglês como idioma principal, o que faz aumentar o número de citações e o fator de impacto da revista.http://ref.scielo.org/zzbf6

Ion Sizes and Finite-Size Corrections for Ionic-Solvation Free Energies

Free energies of ionic solvation calculated from computer simulations exhibit a strong system size dependence. We perform a finite-size analysis based on a dielectric-continuum model with periodic boundary conditions. That analysis results in an estimate of the Born ion size. Remarkably, the finite-size correction applies to systems with only eight water molecules hydrating a sodium ion and results in an estimate of the Born radius of sodium that agrees with the experimental value.Comment: 2 EPS figure

Ion Pair Potentials-of-Mean-Force in Water

Recent molecular simulation and integral equation results alkali-halide ion pair potentials-of-mean-force in water are discussed. Dielectric model calculations are implemented to check that these models produce that characteristic structure of contact and solvent-separated minima for oppositely charged ions in water under physiological thermodynamic conditions. Comparison of the dielectric model results with the most current molecular level information indicates that the dielectric model does not, however, provide an accurate description of these potentials-of-mean-force. We note that linear dielectric models correspond to modelistic implementations of second-order thermodynamic perturbation theory for the excess chemical potential of a distinguished solute molecule. Therefore, the molecular theory corresponding to the dielectric models is second-order thermodynamic perturbation theory for that excess chemical potential. The second-order, or fluctuation, term raises a technical computational issue of treatment of long-ranged interactions similar to the one which arises in calculation of the dielectric constant of the solvent. It is contended that the most important step for further development of dielectric models would be a separate assessment of the first-order perturbative term (equivalently the {\it potential at zero charge} ) which vanishes in the dielectric models but is generally nonzero. Parameterization of radii and molecular volumes should then be based of the second-order perturbative term alone. Illustrative initial calculations are presented and discussed.Comment: 37 pages and 8 figures. LA-UR-93-420