Ground-state phase diagram and universality of sequential topological valence-bond-solid quantum transitions in a mixed tetramer chain.

The ground-state ordering of a quantum mixed-spin Heisenberg tetramer chain composed of an alternate sequence ofs = 1 andS=3/2dimers is studied in detail as a function of two considered exchange interactions ascribed to similar and dissimilar spin pairs. At zero magnetic field, the ferrimagnetic mixed spin-(1, 1, 3/2, 3/2) Heisenberg tetramer chain displays, depending on a mutual interplay between two considered exchange interactions, three distinct gapped valence-bond-solid phases separated by gap-closing quantum critical points. Using density-matrix renormalization group calculations we construct the full ground-state phase diagram as a function of the interaction ratio and magnetic field, which exhibits besides three gapped valence-bond-solid phases special Kosterlitz-Thouless and topological quantum critical points. A tangential finite-size scaling analysis is employed to obtain precise estimates of the zero-field valence-bond-solid transitions and unveil their common logarithmic correction to a power-law scaling of the correlation length.

Residual entropy and magnetocaloric effect in a diluted sawtooth spin model of hole-doped CuO chains.

Ground-state and magnetocaloric properties of a site-diluted sawtooth magnetic chain in the presence of an external magnetic field are exactly investigated by using the transfer-matrix method. The model captures the main magnetic interactions along CuO chains present in some hole-doped cuprates. The ground-state diagram is exhibited and analytical expressions for the residual entropy within each ground state and along the transition lines are derived. We explicitly discuss the role of the underlying pairing correlations and the entropy maximization principle. The isothermal entropy change is determined as a function of interaction parameters, doping concentration, and magnetic-field amplitude. Normal and inverse magnetocaloric effects are reported. Adiabatic demagnetization curves are discussed in connection with configurational and spin contributions to the residual entropy.

Surface and finite-size effects on N-Sm-A-Sm-C phase transitions in free-standing films.

The present study is devoted to the investigation of surface anchoring and finite-size effects on nematic-smectic-A-smectic-C (N-Sm-A-Sm-C) phase transitions in free-standing films. Using an extended version of the molecular theory for smectic-C liquid crystals, we analyze how surface anchoring and film thickness affect the thermal behavior of the order parameters in free-standing smectic films. In particular, we determine how the transition temperature depends on the surface ordering and film thickness. We show that the additional orientational order imposed by the surface anchoring may lead to a stabilization of order parameters in central layers, thus modifying the nature of the phase transitions. We compare our results with experimental findings for typical thermotropic compounds presenting a N-Sm-A-Sm-C phase sequence.

Biogeomorphic succession in a fluvial-lacustrine delta of the Middle Paraná River (Argentina): Feedbacks between vegetation and morphodynamics.

The Leyes' Delta lies at the Middle Paraná River, the second-largest fluvial system in South America, and it is being quickly formed into the Setúbal fluvial lake, Argentina. In the context of the Fluvial Biogeomorphic Succession theory, our aim was to better understand interactions between physical and biotic processes contributing to the formation of the Leyes' Delta. We studied the genesis, morphologic development, and vegetation in three groups of its deltaic islands with contrasting formation ages. Different methodologies were applied. Genesis and morphologic development were interpreted from time-series of satellite images and aerial photography obtained from 1974 to 2014. Then landforms and vegetation communities were mapped on the most current images, and they were corroborated and characterized during fieldwork. Our results evidence that the three island groups (Channel crevasse splay islands, Delta bar-plain islands, and Delta front islands) were formed via two different geomorphic processes, determining differences in the initial vegetation colonization. Eight fluvial-lacustrine landforms and eight vegetation communities, both differently represented among the island groups, currently characterize these islands. The species richness accumulation curves and beta diversity showed that the morphodynamic activity can be as important in the floristic composition of the deltaic islands as formation ages. The floristic composition differed statistically among island groups. After identifying three of the four phases of the FBS, we concluded that even though the morphodynamic activity under which islands were formed determined differences in the initial vegetation colonization, under similar subsequent levels of morphodynamics the resulting vegetation heterogeneity tends to be similar even under contrasting genesis. Among the vegetation types, Lotic prairies would play a key role in the morphologic evolution of the deltaic islands, therefore, their distribution and interactions with flow and sediments should be considered during the studies of social ecological systems as the Leyes' Delta, in Santa Fe, Argentina.

Towards conductive textiles: coating polymeric fibres with graphene.

Conducting fibres are essential to the development of e-textiles. We demonstrate a method to make common insulating textile fibres conductive, by coating them with graphene. The resulting fibres display sheet resistance values as low as 600 Ωsq-1, demonstrating that the high conductivity of graphene is not lost when transferred to textile fibres. An extensive microscopic study of the surface of graphene-coated fibres is presented. We show that this method can be employed to textile fibres of different materials, sizes and shapes, and to different types of graphene. These graphene-based conductive fibres can be used as a platform to build integrated electronic devices directly in textiles.

Effects of fullerene addition on the thermo-optical properties of smectic liquid crystals at the vicinity of the nematic-smectic-A phase transition.

The present work is devoted to the study of the thermo-optical properties of liquid crystals doped with traces of fullerene C(60) at the vicinity of the nematic-smectic-A phase transition. By using the time-resolved Z-scan technique, we measure the temperature dependence of the thermo-optical coefficient and the thermal diffusivity. Our results reveal that the critical behavior of the thermal diffusivity is strongly affected by the fullerene addition. We provide a detailed discussion under the light of the distinct mechanisms behind the thermal transport in liquid-crystal samples.

Assessment of mutagenic, antimutagenic and genotoxicity effects of Mimosa tenuiflora

Genotoxic effects of Mimosa tenuiflora (Willd.) Poir, Fabaceae, were investigated by using both micronucleus test and bacterial reverse mutation assay in Salmonella typhimurium TA97, TA98, TA100, TA102 respectively. In respect of Ames test results show that the extract does not induce mutations in any strains of Salmonella typhimurium tested since the mutagenicity index is less than 2. In the antimutagenic effect was observed that the extract at the concentrations tested significantly decreased the mutagenicity index of all strains tested which characterized the extract as antimutagenic in these conditions. In the micronucleus test in vivo, we observed that the concentrations used did not induce an increase in the frequency of micronucleus in normochromatic erythrocytes of mice. Therefore, we concluded that the extract of M. tenuiflora is not mutagenic in the absence of exogenous metabolizing system and does not induce an increase in the frequency of the micronucleus characterized as an agent not mutagenic in these conditions. Further studies of toxicity need to be made to the use of this plant in the treatment of diseases to be stimulated.

Elastic mediated force between nanoparticles adsorbed on smectic films under an external field.

Within the harmonic approximation, we analytically determine the elastic-mediated interaction between colloidal nanoparticles adsorbed on the surface of smectic films under the influence of an external field. Both cases of free-standing films and films deposited over a solid substrate are considered. We show that the asymptotic decay (1/R in free-standing and exponential in deposited films) is not altered by the external field. However, the external field plays distinct roles according to the film configuration, the interparticle distance, the film thickness, and the surface tension at the film-gas interface. We provide a detailed discussion under the light of the distinct mechanisms controlling the undulations of the surface layer.

Crossover from tricritical to critical end point behavior in free-standing smectic films.

We study the smectic to nematic (SmA-N) phase transition taking place at the center of a free-standing film that exhibits enhanced surface order due to the anchoring promoted by a surrounding gas. The usual McMillan mean-field approach predicts that the SmA-N transition in bulk samples can be continuous or discontinuous (first or second order) depending on the molecular geometry, with a tricritical point separating these two regimes. Here we show that the additional orientational order imposed by the surface anchoring stabilizes the surface-induced smectic and nematic phases, leading to the breakdown of the tricritical point and to the emergence of a critical end point. We report the full phase diagram, which depicts four distinct structures as the film thickness is reduced.

Field-induced layer thinning transition on free-standing smectic films.

Strongly anchored free-standing smectic films usually present a stepwise reduction of the number of layers when the temperature is raised above the smectic-isotropic bulk transition temperature. Here, we demonstrate that a field-induced layer thinning transition can take place in smectic films with a negative dielectric anisotropy even below the bulk transition temperature. Using an extended McMillan's model, we provide the phase diagram of this layering transition and show that, when the field is raised above the bulk transition field, the film thickness reduction is well described by a power law with an exponent that depends on the temperature and the aspect ratio of the liquid-crystal molecule.

Antibiotic activity of the extract of Punica granatum Linn. over bovine strains of Staphylococcus aureus / Atividade antimicrobiana do extrato de Punica granatum Linn. em linhagens de Staphylococcus aureus de origem bovina

A medicina humana e veterinária tem falhado no tratamento de infecções em longo prazo causadas por Staphylococcus aureus associadas ao desenvolvimento de resistência a agentes antimicrobianos. A atividade antimicrobiana do extrato da casca do fruto de Punica granatum Linn. foi avaliada sobre 38 linhagens de S. aureus de origem bovina para a determinação da concentração inibitória mínima (CIM). Das 38 linhagens ensaiadas, 22 são resistentes à penicilina.(PRSA). O extrato de P. granatum apresentou potencial ação antimicrobiana sobre todas as linhagens ensaiadas formando halos de inibição variando de 10 a 36 mm de diâmetro. Os resultados deste estudo confirmam a eficácia do extrato de P. granatum como potencial agente antibacteriano sobre S. aureus e demonstram a importância de se avaliar novas substâncias com potencial antimicrobiano, o que pode contribuir para a terapêutica alternativa em Medicina Veterinária.

Human and veterinary medicines have not been so well succeeded in order to achieving their goals concerning the treatment of infections for long term caused by Staphylococcus aureus linked to resistance development against antibiotic agents. The antibiotic activity of the Punica granatum Linn. fresh fruit pericarp extract was evaluated by the agar diffusion method on 38 S. aureus strains, isolated from apparently healthy lactating cows in farms situated in counties of the semi-arid region of the State of Paraíba, Brazil to determine the minimum inhibitory concentration (MIC). Twenty-two of the thirty-eight strains are penicillin-resistant (PRSA). The extract of P. granatum presented potential antibiotic action over all the assayed strains, forming 10 to 36 mm diameter inhibition zones. This paper's results claim the effectiveness of the extract of P. granatum as a potential antibacterial agent on S. aureus, and display the significance of evaluating new substances with antimicrobial potential, which can contribute to alternative therapeutics for veterinary and medicine.

Atividade antimicrobiana e antiaderente in vitro do extrato de Rosmarinus officinalis Linn. sobre bactérias orais planctônicas / In vitro antimicrobial activity and antiadherence of Rosmarinus officinalis Linn. against oral planktonic bacteria

Neste estudo foi investigada a ação antimicrobiana e a inibição de aderência in vitro do extrato hidroalcoólico de Rosmarinus officinalis Linn. (alecrim) sobre cepas padrão de Streptococcus mitis ATCC 98811, Streptococcus sanguinis ATCC 10556, Streptococcus mutans ATCC 25175, Streptococcus sobrinus ATCC 27609 e Lactobacillus casei ATCC 7469. Os ensaios foram realizados pelas técnicas de ágar-difusão em placas de Petri para determinação da Concentração Inibitória Mínima (CIM) e técnica de tubos inclinados para determinação da Concentração Inibitória Mínima de Aderência (CIMA) ao vidro, na presença de 5 por cento de sacarose. Os mesmos procedimentos foram realizados com a clorexidina à 0,12 por cento. As CIMs (mg/mL) do extrato de Rosmarinus officinalis sobre S. sanguinis ATCC 10556, S. mutans ATCC 25175, S. sobrinus ATCC 27609 e L. casei ATCC 7469 foram 1:1, 1:4, 1:1 e 1:4, respectivamente. Não houve inibição de crescimento de S. mitis ATCC 98811. As CIMAs do extrato de Rosmarinus officinalis frente a S. mitis ATCC 98811, S. mutans ATCC 25175 e S. sobrinus ATCC foram 1:8, 1:16 e 1:8, nessa ordem. Os resultados sugerem a possibilidade de uso do extrato de alecrim como antimicrobiano oral. No entanto, modelos de estudo que possam reproduzir situações mais próximas àquelas encontradas na cavidade oral são requeridas para avaliação de agentes antimicrobianos no tratamento e prevenção de infecções orais biofilme-dependentes.

In this study was investigated the antimicrobial activity and in vitro adherence inhibition of a hydro alcoholic Rosmarinus officinalis Linn. (alecrim) on standard strains of Streptococcus mitis ATCC 98811, Streptococcus sanguinis ATCC 10556, Streptococcus mutans ATCC 25175, Streptococcus sobrinus ATCC 27609 and Lactobacillus casei ATCC 7469 extract. The test was carried out by inundation tecniques in Petri dishes to determine the Minimum Inhibitory Concentration (MIC) and inclined tubes techniques the Minimum Inhibitory Concentration of Adherence to glass (MICA) at the presence of 5 percent sucrose. Tests with gluconate of chlorexidine 0.12 percent were performed as controls. MICs of the Rosmarinus officinalis extract dilutions (mg/mL) against S. sanguinis ATCC 10556, S. mutans ATCC 25175, S. sobrinus ATCC 27609 and L. casei ATCC 7469 were 1:1, 1:4, 1:1 e 1:4, respectively. The extract from alecrim inhibited all the standard strains growth tested, except for S. mitis ATCC 98811. MICAs of the Rosmarinus officinalis extract dilutions (mg/mL) against S. mitis ATCC 98811, S. mutans ATCC 25175 e S. sobrinus ATCC were 1:8, 1:16 e 1:8, respectively. The results suggest that there is a possibility of the alecrim use as an oral antimicrobial. Nevertheless, study models which could reproduce situations similar to those seen in bucal caries are necessary for the antimicrobial agents evaluation in the treatment and biofilm dependant oral infections prevention.

Atividade antimicrobiana "in vitro" e determinação da concentração inibitória mínina (CIM) de fitoconstituintes e produtos sintéticos sobre bactérias e fungos leveduriformes / In vitro antimicrobial activity and determination of the minimum inhibitory concentration (MIC) of natural and synthetic compounds against bacteria and leveduriform fungi

Diante da problemática da resistência microbiana as pesquisas apontam para o uso de novos antibióticos que sejam eficazes ante os patógenos emergentes. Este trabalho objetiva testar frente a bactérias gram-positivas (Staphylococcus aureus), bactérias gram-negativas (Escherichia coli e Pseudomonas aeruginosa) e fungos leveduriformes (Candida albicans), a atividade antimicrobiana e a concentração inibitória mínima (CIM) de fitoconstituintes de Ocotea duckei Vattimo, do lapachol, seus derivados semi-sintéticos, alfa-lapachona, beta-nor-lapachona, beta-lapachona, alfa-nor-lapachona, beta-3-iodo-lapachona e alfa-3-iodo-lapachona, assim como 07 derivados nitrogenados obtidos a partir do lapachol por semi-síntese e de imidas cíclicas similares ao alcalóide filantimida. Os resultados obtidos estimulam o aprofundamento dos estudos para algumas dessas substâncias a exemplo do lapachol e seus análogos que demonstraram atividade antimicrobiana, de modo que os produtos que se apresentaram ativos para S. aureus, foram lapachol e o extrato etanólico de Ocotea duckei, para E. coli foi a iangambina e para a Candida albicans foram as imidas. As demais substâncias não apresentaram atividade antimicrobiana para as cepas testadas.

Regarding the problem of microbial resistance, the researches point to the use of new antibiotic which can be active against the emergent pathogens. This work aims to test the activity against Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli e Pseudomonas aeruginosa) and leveduriform fungi (Candida albicans), and also the Minimum Inhibitory Concentration (MIC) of the constituent of Ocotea duckei Vattimo, lapachol and its synthetic derivatives alpha-lapachone, beta-nor-lapachone, beta-lapachone, alpha-nor-lapachone, beta-3-iodin-lapachone and alpha-3-iodin-lapachone, as well as seven nitrogenated derivatives of lapachol obtained through semi synthesis. The achieved results stimulate the deepening of the studies for some of theses substances such as lapachol and its analogous which demonstrated antimicrobial activity. The substances which were active against S. aureus, were lapachol and the ethanolic extract of Ocotea duckei Vattimo, against Escherichia coli iangambin and against C. albicans the imides. The other substances did not show any activity against the tested bacteria.

Preliminary study of the antimicrobial activity of Mentha x villosa Hudson essential oil, rotundifolone and its analogues / Estudo preliminar da atividade antimicrobiana do óleo essencial de Mentha x villosa Hudson, rotundifolona e seus análogos

Essential oils present antimicrobial activity against a variety of bacteria and yeasts, including species resistant to antibiotics and antifungicals. In this context, this work aims at the evaluation of the antimicrobial activity of the essential oil of Mentha x villosa Hudson ("hortelã da folha miúda"), its major component (rotundifolone) and four similar analogues of rotundifolone (limonene oxide, pulegone oxide, carvone epoxide and (+)-pulegone) against strain standards of Staphylococcus aureus ATCC 25923, E. coli ATCC 25922, Pseudomona aeruginosa ATCC 27853, Candida albicans ATCC 76645 and one strain of meticilin - resistant Staphylococcus aureus - MRSA (171c) from human clinic. The method of the diffusion in plates with solid medium was used. The results showed that the oil of Mentha x villosa, rotundifolone, limonene oxide and (+)-pulegone, are similar regarding the antimicrobial activity against the tested strains of S. aureus and C. albicans. All of the products present antimocrobial potential with antibacterial activity for S. aureus ATCC 25923 and antifungal activity for C. albicans ATCC 76645. None of the products presented antimicrobial activity for the strains of E. coli ATCC 25922 and P. aeruginosa ATCC 27853, representatives of the Gram negative bacteria.

Os óleos essenciais apresentam atividade antimicrobiana contra uma variedade de bactérias e fungos, incluindo espécies resistentes a antibióticos e antimicóticos. Neste contexto, este trabalho objetiva a avaliação da atividade de antimicrobiana do óleo essencial de Mentha x villosa Hudson (hortelã-da-folha-miúda) - seu componente majoritário (rotundifolona) e quatro análogos sintéticos da rotundifolona (epóxi-limoneno epóxi-pulegona, epóxi-carvona e (+)-pulegona) frente a cepas padrão de Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922 Pseudomonas aeruginosa ATCC 27853, Candida albicans ATCC 76645 e uma cepa de Staphylococcus aureus meticilina - resistente - MRSA (171c) de clínica humana. Como método, foi utilizada a difusão em placas com médio sólido. Os resultados mostraram que o óleo de Mentha x villosa, rotundifolona, epóxi-limoneno e (+)-pulegona, são semelhante em função da atividade antimicrobiana para as cepas de S. aureus e C.albicans testadas. Todos os produtos apresentaram potencial antimicrobiano com atividade antibacteriana para S. aureus ATCC 25923 e atividade antifúngica para C. albicans ATCC 76645. Nenhum dos produtos apresentou atividade antimicrobiana para as cepas de E. coli ATCC 25922 e P. aeruginosa ATCC 27853, representantes das bactérias Gram negativas.

Atividade antifúngica do extrato de Psidium guajava Linn. (goiabeira) sobre leveduras do gênero Candida da cavidade oral: uma avaliação in vitro / Antifungal activity of the extract of Psidium guajava Linn. (“goiabeira") upon leavens of Candida of the oral cavity: an in vitro evaluation

O presente estudo teve como objetivo avaliar a atividade antifúngica do extrato da folha de Psidium guajava Linn. sobre leveduras do gênero Candida, isoladas da cavidade oral, incluindo Candida albicans, C. tropicalis, C. stelatoidea e C. krusei, em análise comparativa com o gluconato de clorexidina à 0,12 por cento. Os ensaios antifúngicos foram realizados pelas técnicas de difusão em meio sólido para a determinação da Concentração Inibitória Mínima (CIM). A CIM do extrato de Psidium guajava sobre C. albicans e C. tropicalis foi de 1:32, C. stelatoidea e C. krusei de 1:2, formando, em média, halos de inibição entre 11 e 22 mm. Diante dos resultados, concluí-se que o extrato da folha de Psidium guajava (goiabeira) apresenta a capacidade de inibir o crescimento de leveduras do gênero Candida da cavidade oral, o que sugere a possibilidade de utilização deste extrato como meio alternativo no tratamento das candidose orais.

The present study evaluated the antifungal in vitro activity of the extract of the leaf of Psidium guajava Linn. against leavens of Candida of the oral cavity, including Candida albicans, C. tropicalis, C. stelatoidea and C. krusei, in comparative study with chlorhexidine (0,12 percent). The tests were carried out by agar-diffusion technique in dishes to determine the Minimum Inhibitory Concentration (MIC). The MIC of the extract of Psidium guajava upon C. albicans and C .tropicalis was 1:32, C. stelatoidea and C. Krusei was 1:2, making, in average, inhibition halos between 11 and 22 mm. It can be concluded that the extract of Psidium guajava show potential to inhibit the growth of leavens of Candida of the oral cavity, it supports the possibility of the use of this extract as an alternative way in the oral candidosis treatment.

Efeito antibacteriano e antiaderente in vitro do extrato da Punica granatum Linn. sobre microrganismos do biofilme dental / In vitro antibacterial and antiadherence effect of the extract of the Punica granatum Linn. upon dental biofilm microrganisms

Nesta pesquisa foi avaliada a atividade antimicrobiana e a capacidade de inibição da síntese de glucano in vitro do extrato da casca do fruto da romã (Punica granatum Linn.) sobre linhagens bacterianas de Streptococcus mitis, Streptococcus mutans, Streptococcus sanguis, Streptococcus sobrinus e Lactobacillus casei. Os ensaios foram realizados pelas técnicas de ágar-difusão em placas para determinação da Concentração Inibitória Mínima (CIM) e técnica dos tubos inclinados para determinação da Concentração Inibitória Mínima de Aderência (CIMA) ao vidro, na presença de 5 por cento de sacarose. Os mesmos procedimentos foram realizados com a clorexidina à 0,12 por cento. As CIMs (mg/mL) do extrato da P. granatum frente ao S. mitis, S. mutans, S. sanguis, S. sobrinus e L. casei foram 1:32, 1:8, 1:8, 1:512, e 1:128, respectivamente. Para as CIMAs o extrato da P. granatum mostrou resultados melhores que a clorexidina, exceto para o S. mutans com achados semelhantes na diluição de 1:256. Os resultados mostram a potencialidade da P. granatum na inibição do crescimento bacteriano e síntese de glucano representada pela aderência ao vidro, sugerindo o emprego do extrato da romã, como meio alternativo, no controle desses microrganismos na formação do biofilme.

In this study was evaluated the in vitro antibacterial activity and the inhibition of glucan sintesis of the fruit bark of Punica granatum Linn extract upon the following dental biofilm bacteria: Streptococcus mitis, Streptococcus mutans, Streptococcus sanguis, Streptococcus sobrinus and Lactobacillus casei. The tests were carried out by inundation tecniques in Petri dishes to determine the Minimum Inhibitory Concentration (MIC) and inclined tubes techniques to determine the Minimum Inhibitory Concentration of Adherence to glass (MICA) at the presence of 5 percent sucrose. Tests with gluconate of chlorexidine (0.12 percent) were performed as controls. MICs of the P granatum extract dilutions (mg/mL) against S. mitis, S. mutans, S. sanguis, S. sobrinus e L. casei were 1:32, 1:8, 1:8, 1:512, and 1:128 respectively. For MICAs the P. granatum showed better results than chlorexidine, except for S. mutans with both substances showing similar results of 1:256. It can be concluded that the extract of the P. granatum has the potential to inhibit oral bacterial growth and glucan sintesis. The extract of the Punica granatum might be used as an effective antibacterial alternative agent against oral biofilm bacteria.

Eliminação de resistência a drogas por fluorquinolonas em Staphylococcus aureus de origem bovina / Elimination of resistance to drugs by fluoroquinolones in bovine strains of Staphylococcus aureus

Cepas de Staphylococcus aureus de origem bovina foram submetidas ao tratamento com quatro fluoquinolonas na concentração subinibitória (1/2 x CMI), para avaliar a influência desses agentes sobre plasmídios. A ciprofloxacina mostrou ser a fluorquinolona mais eficiente, eliminando marcas de resistência para estreptomicina, tetraciclina, penicilina e cádmio. A norfloxacina e a pefloxacina eliminaram resistência para penicilina e tetraciclina, respectivamente; no entanto, não foi evidenciada a eliminação de plasmídio com ofloxacina. Os resultados confirmam a eficácia das fluor-quinolonas em eliminar plasmídios de resistência mostrando a importância desses estudos como contribuição para o entendimento da prevenção de linhagens multiresistentes, uma vez que as quinolonas em concentrações subinibitórias podem aumentar a sensibilidade das linhagens a outros agentes antimicrobianos.