45 research outputs found

    Hindered rotor tunneling splittings: an application of the two-dimensional non-separable method to benzyl alcohol and two of its fluorine derivatives

    Get PDF
    In this work we present a novel application of the two-dimensional non-separable (2D-NS) method to the calculation of torsional tunneling splittings in systems with two hindered internal rotors. This method could be considered an extension of one-dimensional methods for the case of compounds with two tops. The 2D-NS method includes coupling between torsions in the kinetic and potential energy. Specifically, it has been applied to benzyl alcohol (BA) and two of its fluorine derivatives: 3-fluorobenzyl alcohol (3FBA) and 4-fluorobenzyl alcohol (4FBA). These molecules present two torsions, i.e., about the –CH2OH (ϕ1) and –OH (ϕ2) groups. The electronic structure calculations to build the two-dimensional torsional potential energy surface were performed at the DF-LMP2-F12//DF-LMP2/cc-pVQZ level of theory. For BA and 4FBA the calculated ground-state vibrational level splittings are 429 and 453 MHz, respectively, in good agreement with the experimental values of 337.10 and 492.82 MHz, respectively. In these two cases there are four equivalent wells and the tunneling splitting is the result of transitions between the two closer minima along ϕ1. The analysis of the wavefunctions, as well as the previous experimental work on the system, supports this conclusion. For 3FBA the observed ground-state splitting is 0.82 MHz, whereas in this case the calculated value amounts only to 0.02 MHz. The 2D-NS method, through the analysis of the wavefunctions, shows that this tiny tunneling splitting occurs between the two most stable minima of the potential energy surface. Additionally, we predict that the first vibrationally excited tunneling splitting will also be small and exclusively due to the interconversion between the second lowest minimaS

    Kinetic Isotope Effects in Multipath VTST: Application to a Hydrogen Abstraction Reaction

    Get PDF
    In this work we apply multipath canonical variational transition state theory with small-tunneling corrections (MP-CVT/SCT) to the hydrogen abstraction reaction from ethanol by atomic hydrogen in aqueous solution at room temperature. This reaction presents two transition states which can interconvert by internal rotations about single bonds and another two transition states that are non-interconvertible enantiomers to the former structures. The study also includes another three reactions with isotopically substituted species for which there are experimental values of thermal rate constants and kinetic isotope effects (KIEs). The agreement between the MP-CVT/SCT thermal rate constants and the experimental data is good. The KIEs obtained by the MP-CVT/SCT methodology are factorized in terms of individual transition state contributions to facilitate the analysis. It was found that the percentage contribution of each transition state to the total KIE is independent of the isotopic substitutionT.V.A. thanks Fundação de Amparo à Pesquisa do Estado de São Paulo of Brazil for a postdoctoral fellowship. A.D.-D. acknowledges the SONATA-Bis research grant funded by the National Science Centre, Poland (UMO-2014/14/E/ST4/ 00041). A.F.-R. acknowledges partial funding from Ministerio de Economía y Competitividad of Spain (Research Grant No CTQ2014-58617-R) and from Consellería de Cultura, Educación e Ordenación Universitaria of Xunta de Galicia (Research Grant No R2014/051)S

    Anharmonicity of Coupled Torsions: The Extended Two-Dimensional Torsion Method and Its Use To Assess More Approximate Methods

    Get PDF
    In this work we present the extended two-dimensional torsion (E2DT) method and use it to analyze the performance of several methods that incorporate torsional anharmonicity more approximately for calculating rotational–vibrational partition functions. Twenty molecules having two hindered rotors were studied for temperatures between 100 and 2500 K. These molecules present several kinds of situations; they include molecules with nearly separable rotors, molecules in which the reduced moments of inertia change substantially with the internal rotation, and molecules presenting compound rotation. Partition functions obtained by the rigid-rotor harmonic oscillator approximation, a method involving global separability of torsions and the multistructural methods without explicit potential coupling [MS-T(U)] and with explicit potential coupling [MS-T(C)] of torsions, are compared to those obtained with a quantized version – called the extended two-dimensional torsion (E2DT) method – of the extended hindered rotor approximation of Vansteenkiste et al. (Vansteenkiste et al. J. Chem. Phys. 2006, 124, 044314). In the E2DT method, quantum effects due to the torsional modes were incorporated by the two-dimensional nonseparable method, which is a method that is based on the solution of the torsional Schrödinger equation and that includes full coupling in both the kinetic and potential energy. By comparing other methods to the E2DT method and to experimental thermochemical data, this study concludes that the harmonic approximation yields very poor results at high temperatures; the global separation of torsions from the rest of the degrees of freedom is not justified even when an accurate method to treat the torsions is employed; it is confirmed that methods based on less complete potential energy coupling of torsions, such as MS-T(U), are not accurate when dealing with rotors with different barrier heights, and more complete inclusion of torsional coupling to the method in MS-T(C) improves substantially the results in such a way that it could be used in cases where the E2DT method is unaffordableFinancial support from the Ministerio de Economia y Competitividad of Spain (Research Grant No CTQ2014-58617-R), the Conselleria de Cultura, Educación e Ordenación Universitaria (Centro singular de investigación de Galicia acreditación 2016-2019, ED431G/09), and the European Regional Development Fund (ERDF) is gratefully acknowledgedS

    Substituted diaryl diselenides: Cytotoxic and apoptotic effect in human colon adenocarcinoma cells

    Get PDF
    AbstractAimsTo investigate the effects and study the underlying cell death mechanisms of diaryl diselenides, including: diphenyl diselenide (C6H5Se)2; 4-chlorodiphenyl diselenide (4-ClC6H4Se)2; 3-(trifluoromethyl)-diphenyl diselenide (3-CF3C6H4Se)2 and 4-methoxydiphenyl diselenide (4-MeOC6H4Se)2, on the human colon adenocarcinoma cell line HT-29.Main methodsThe viability of HT-29 cells after exposure to the diaryl diselenides and its substituted structures was based on the MTT assay. To verify if cell death was mediated throughout apoptosis mechanisms, flow cytometry and real-time PCR (qPCR) analyses were conducted.Key findingsThe MTT assay and flow cytometry analyses showed that (3-CF3C6H4Se)2 and (4-MeOC6H4Se)2 induced cytotoxicity through apoptosis mechanisms in HT-29 cells. qPCR revealed there was an up-regulation of pro-apoptotic (Bax, casapase-9, caspase-8, apoptosis-inducing factor (AIF) and Endonuclease G (EndoG)) and cell-cycle arrest genes (p53 and p21) and down-regulation of anti-apoptotic (Bcl-2 and survivin) and Myc genes.SignificanceThese results demonstrate that (3-CF3C6H4Se)₂ and (4-MeOC6H4Se)2 have the potential to induce apoptosis in HT-29 cells through the activation of caspase-dependent and independent pathways and through cell-cycle arrest

    INOVAÇÕES SUSTENTÁVEIS VIA PROJETO ECOCIDADANIA NA UNIVERSIDADE PATATIVA DO ASSARÉ

    Get PDF
    O empreendedorismo social via ações de inovações sustentáveis constitui-se como uma alternativa para solucionar as questões socioambientais, servindo como uma capacitação para o trabalho e para a geração de renda e consequentemente apontando para o desenvolvimento sustentável. Os projetos de responsabilidade socioambiental praticados nas organizações locais  promovem inovações orientadas à sustentabilidade? Nesse contexto, o objeto de estudo dessa pesquisa é o Projeto Ecocidadania ligado à Universidade Patativa do Assaré (UPA). O objetivo geral da pesquisa é analisar as estratégias de responsabilidade socioambiental locais no processo de geração de inovações sustentáveis. Trata-se de uma pesquisa documental. O Ecocidadania engloba pontos importantes como transporte, acondicionamento, e destinação final dos resíduos sólidos urbanos, ligados diretamente ao saneamento ambiental. Conclui-se que o Projeto Ecocidadania é um programa direcionado para uma interação entre organização - comunidade a fim de que o trabalho em conjunto renda frutos de cunho social/sustentável para a comunidade por via da reciclagem de resíduos sólidos

    Fator de reprodução de Meloidogyne javanica, M. incognita e Pratylenchus brachyurus em variedades de sorgo, milheto e girassol

    Get PDF
    The use of agricultural species resistant to root-knotting and root-wounding nematodes, in crop rotation systems, keeps the nematode population at low levels, reducing losses and enabling the planting of more susceptible species. In this study, the resistance of sorghum, millet and sunflower genotypes to root-knot nematodes Meloidogyne javanica, M. incognita and Pratylenchus brachyurus was evaluated. The tests were conducted in a greenhouse and the genotypes sown in plastic pots containing 2 L of sterilized substrate and inoculated with 1,600 nematode eggs and juveniles per pot, arranged in a completely randomized design with nine replications. The evaluation of nematode reproduction was performed by counting the number of juveniles/adults per root system and soil, calculating the Reproduction Factor (FR = Pf/Pi). According to the results, all sorghum, millet and sunflower genotypes behaved as resistant to the reproduction of M. javanica, M. incognita and P. brachyurus. Commercial resistant genotypes are indicated for use in rotation of areas infested by these nematodes.El uso de especies agrícolas resistentes a nematodos formadores de agallas y lesiones radiculares, en sistemas de rotación de cultivos, mantiene la población de nematodos en niveles bajos, reduciendo pérdidas y permitiendo la siembra de especies más susceptibles. En este estudio se evaluó la resistencia de genotipos de sorgo, mijo y girasol a los nematodos agalladores Meloidogyne javanica, M. incognita y Pratylenchus brachyurus. Las pruebas se realizaron en invernadero y los genotipos se sembraron en macetas de plástico con 2 L de sustrato esterilizado, y se inocularon con 1600 huevos y juveniles de nematodos por maceta, dispuestos en un diseño completamente al azar con nueve repeticiones. La evaluación de la reproducción del nematodo se realizó contando el número de juveniles/adultos por sistema radicular y suelo, calculando el Factor de Reproducción (FR = Pf/Pi). De acuerdo con los resultados, todos los genotipos de sorgo, mijo y girasol se comportaron como resistentes a la reproducción de M. javanica, M. incognita y P. brachyurus. Los genotipos comerciales resistentes están indicados para uso en rotación de áreas infestadas por estos nematodos.O uso de espécies agrícolas resistentes aos nematóides formadores de galhas e lesões nas raízes, em sistemas de rotação de culturas, mantém a população dos nematóides em níveis baixos, diminuindo as perdas e possibilitando o plantio de espécies mais susceptíveis. Neste estudo avaliou-se a resistência de genótipos de sorgo, milheto e girassol aos nematóides de galhas Meloidogyne javanica, M. incognita e de lesões Pratylenchus brachyurus. Os ensaios foram conduzidos em casa de vegetação e os genótipos semeados em vasos plásticos contendo 2 L de substrato esterilizado, e inoculados com 1.600 ovos e juvenis de nematóide por vaso, dispostos em delineamento inteiramente casualizado com nove repetições. A avaliação da reprodução dos nematóides foi feita através da contagem do número de juvenis/adultos por sistema radicular e solo, calculando o Fator de Reprodução (FR = Pf/Pi). De acordo com os resultados, todos os genótipos de sorgo, milheto e girassol comportaram-se como resistentes à reprodução de M. javanica, M. incognita e P. brachyurus. Os genótipos resistentes comerciais são indicados para uso em rotação de áreas infestadas por esses nematóides

    REÚSO DE ÁGUA PARA FINS NÃO POTÁVEIS NO IFC CAMPUS BRUSQUE

    Get PDF
    O reaproveitamento da água, seja ele da chuva ou oriundo de outro lugar, é muitoimportante, pois é dada uma nova finalidade para algo que já foi utilizado e quepossui aplicação para outro objetivo prático. Isto ajuda em medidas para diminuir osgastos e na preservação da água. Diante disto, pretendemos fazer a captação deágua da chuva, para utilizar na limpeza e nos canteiros de ervas medicinais do IFCcampus Brusque. Tornando-se um meio de conscientização para a economia deágua, que é algo extremamente importante nos dias atuais, em vista da situação emque nos encontramos

    ATLANTIC EPIPHYTES: a data set of vascular and non-vascular epiphyte plants and lichens from the Atlantic Forest

    Get PDF
    Epiphytes are hyper-diverse and one of the frequently undervalued life forms in plant surveys and biodiversity inventories. Epiphytes of the Atlantic Forest, one of the most endangered ecosystems in the world, have high endemism and radiated recently in the Pliocene. We aimed to (1) compile an extensive Atlantic Forest data set on vascular, non-vascular plants (including hemiepiphytes), and lichen epiphyte species occurrence and abundance; (2) describe the epiphyte distribution in the Atlantic Forest, in order to indicate future sampling efforts. Our work presents the first epiphyte data set with information on abundance and occurrence of epiphyte phorophyte species. All data compiled here come from three main sources provided by the authors: published sources (comprising peer-reviewed articles, books, and theses), unpublished data, and herbarium data. We compiled a data set composed of 2,095 species, from 89,270 holo/hemiepiphyte records, in the Atlantic Forest of Brazil, Argentina, Paraguay, and Uruguay, recorded from 1824 to early 2018. Most of the records were from qualitative data (occurrence only, 88%), well distributed throughout the Atlantic Forest. For quantitative records, the most common sampling method was individual trees (71%), followed by plot sampling (19%), and transect sampling (10%). Angiosperms (81%) were the most frequently registered group, and Bromeliaceae and Orchidaceae were the families with the greatest number of records (27,272 and 21,945, respectively). Ferns and Lycophytes presented fewer records than Angiosperms, and Polypodiaceae were the most recorded family, and more concentrated in the Southern and Southeastern regions. Data on non-vascular plants and lichens were scarce, with a few disjunct records concentrated in the Northeastern region of the Atlantic Forest. For all non-vascular plant records, Lejeuneaceae, a family of liverworts, was the most recorded family. We hope that our effort to organize scattered epiphyte data help advance the knowledge of epiphyte ecology, as well as our understanding of macroecological and biogeographical patterns in the Atlantic Forest. No copyright restrictions are associated with the data set. Please cite this Ecology Data Paper if the data are used in publication and teaching events. © 2019 The Authors. Ecology © 2019 The Ecological Society of Americ
    corecore