Critical properties and Bose Einstein Condensation in dimer spin systems

We analyze the spin relaxation time $1/T_1$ for a system made of weakly coupled one dimensional ladders.This system allows to probe the dimensional crossover between a Luttinger liquid and a Bose-Einstein condensateof magnons. We obtain the temperature dependence of $1/T_1$ in the various dimensional regimes, and discuss the experimental consequences.Comment: 4 pages, RevTeX 4, 3 EPS figure

Signatures of Planets in Spatially Unresolved Disks

Main sequence stars are commonly surrounded by debris disks, composed of cold dust continuously replenished by a reservoir of undetected dust-producing planetesimals. In a planetary system with a belt of planetesimals (like the Solar System's Kuiper Belt) and one or more interior giant planets, the trapping of dust particles in the mean motion resonances with the planets can create structure in the dust disk, as the particles accumulate at certain semimajor axes. Sufficiently massive planets may also scatter and eject dust particles out of a planetary system, creating a dust depleted region inside the orbit of the planet. In anticipation of future observations of spatially unresolved debris disks with the Spitzer Space Telescope, we are interested in studying how the structure carved by planets affects the shape of the disk's spectral energy distribution (SED), and consequently if the SED can be used to infer the presence of planets. We numerically calculate the equilibrium spatial density distributions and SEDs of dust disks originated by a belt of planetesimals in the presence of interior giant planets in different planetary configurations, and for a representative sample of chemical compositions. The dynamical models are necessary to estimate the enhancement of particles near the mean motion resonances with the planets, and to determine how many particles drift inside the planet's orbit. Based on the SEDs and predicted $\it{Spitzer}$ colors we discuss what types of planetary systems can be distinguishable from one another and the main parameter degeneracies in the model SEDs.Comment: 40 pages (pre-print form), including 16 figures. Published in ApJ 200

Pressure-induced Superconductivity in a Ferromagnet UGe2_2 -- Resistivity Measurements in Magnetic Field --

The electrical resistivity measurements in the magnetic field are carried out on the pressure-induced superconductor UGe$_2$. The superconductivity is observed from 1.06 to 1.44 GPa. The upper critical field of $H_{C2}$ is anisotropic where $H_{C2}(T)$ exhibits positive curvature for $H//b$ and $c$-axis. The characteristic enhancement of $H_{C2}$ is reconfirmed for $H//a$-axis. In the temperature and field dependence of resistivity at $P > P_{C}$ where the ferromagnetic ordering disappears, it is observed that the application of the external field along the {\it a}-axis increases the coefficient of Fermi liquid behavior $AT^{2}$ correspondingly to the metamagnetic transition.Comment: To be published in the proceeding of the International Conference on High Pressure Science and Technology(AIRAPT-18),Beijing,China,23-27 July 200

Multi-Triplet Magnons in SrCu2_2(BO3_3)2_2 Studied by Thermal Conductivity Measurements in Magnetic Fields

We have measured the thermal conductivity parallel to the a-axis of the Zn-free and 1% Zn-substituted SrCu$_{2-x}$Zn$_x$(BO$_3$)$_2$ in magnetic fields up to 14 T, in order to examine the thermal conductivity due to the multi-triplet magnons. It has been found that the thermal conductivity peak observed in the spin gap state is suppressed by the substitution of Zn for Cu in high magnetic fields above 6 T, while it is not changed in low magnetic fields below 6 T. The results suggest that the thermal conductivity peak in the spin-gap state of SrCu$_2$(BO$_3$)$_2$ is composed of not only thermal conductivity due to phonons but also that due to the multi-triplet magnons in high fields above 6 T.Comment: 7 pages, 2 figure

Produção de álcool etílico de colmos de sorgo sacarino em microdestilaria.

A producao de etanol a partir de acucares fermentesciveis de fontes renovaveis de energia, despontou como a mais viavel para substituir os combustiveis derivados de petroleo. As tecnologias para transformar carboidratos em etanol sao bem conhecidos desde longa data, sendo utilizadas como principais fontes de obtencao de acucares fermentesciveis a cana-de-acucar e a beterraba acucareira. Entretanto, nao ha nenhuma limitacao no uso do sorgo sacarino como materia-prima para producao de etanol. Com o aumento do interesse em um melhor uso desta nova fonte de biomassa energetica, informacoes adicionais devem ser obtidas para avaliar o real potencial dessa nova fonte renovavel de energia. Pelo fato de se adaptar as condicoes climaticas diversas, rapido crescimento, moderada exigencia de agua e elevado conteudo de carboidrato, o sorgo sacarino podera vir a se constituir em uma cultura de alto valor para as regioes tropicais e sub-tropicais. Nos experimentos a cultivar de sorgo sacarino BR-505, originaria da cultivar norte-americana Wray, foi plantada nos anos agricolas de 1984/85 e 1985/86, para avaliar o seu comportamento como materia-prima para producao de alcool etilico em microdestilaria. Amostras de colmos foram retiradas por algumas semanas, a partir do aparecimento das paniculas ate que os graos atingissem o estadio firme, que ocorreu 120 dias apos o plantio. Foram determinados nos colmos os teores de acucares redutores, acucares totais e sacarose. O teor em acucares redutores decresceu durante a maturacao do grao, provavelmente pelo fato de ser assimilado na forma de outros metabolicos. O teor em sacarose aumentou significativamente atingindo valores altos quando os graos estavam maduros, bem firmes. Deste modo, e possivel cultivar o sorgo sacarino com dupla finalidade: uso dos colmos para producao de etanol, e uso dos graos para racao animal e/ou consumo humano. Foram obtidos rendimentos de colmos e folhas de 40-50 t.ha no estadio de maturacao completa das paniculas, com uma producao adicional de graos de 2, 5-3, 5 t/ha. Os colmos e folhas foram processadas em uma microdestilaria com sistema de difusao, obtendo-se alta taxa de extracao de acucares fermentesciveis, que permitiu a obtencao de cerca de 50 litros de etanol por tonelada de materia-prima

Physicochemical Characterization And Antioxidant Capacity Of Pitanga Fruits (eugenia Uniflora L.) [caracterização Fisico-química E Capacidade Antioxidante De Pitangas (eugenia Uniflora L.)]

This study was carried out to obtain more information about the physicochemical properties, composition, and antioxidant activity of pitanga fruits (Eugenia uniflora L.), particularly fruits from the State of Rio Grande do Sul, Brazil. Pitanga with different flesh colors (purple, red, and orange) from tree selections cultivated at Embrapa Clima Temperado (RS-Brazil) were analyzed. Only slight differences were observed in the quality parameters and in the proximate and fatty acid compositions among the fruits studied. The extracts from purple-fleshed pitanga had the highest total phenolic and anthocyanin contents along with the highest antioxidant capacity. The antioxidant capacity (DPPH and FRAP assays) of methanolic pitanga extracts was highly correlated with the total phenolic content, but in ethanolic extracts, the anthocyanin content was correlated only with the FRAP antioxidant capacity. Orange fleshed pitanga had higher β-cryptoxanthin and β-carotene levels than those of the red fruit, which had higher lycopene content. The results indicate that the purple-fleshed pitanga, cultivated in Rio Grande do Sul, is a rich source of phenolic compounds and has high antioxidant capacity. The red and orange-fleshed pitanga, on the other hand, are rich sources of carotenoids.311147154Abidille, M.D.H., Antioxidant activity of the extracts from Dillenia indica fruits (2005) Food Chemistry, 90 (4), pp. 891-896Adebajo, A.C., Oloki, K.J., Aladesanmi, A., Antimicrobial activity of the leaf extract of Eugenia uniflora (1989) Journal of Phytotherapy Resource, 3 (6), pp. 258-259Aherne, S.A., O'Brien, N.M., Dietary flavonols: Chemistry, food content, and metabolism (2002) Nutrition, 18 (1), pp. 75-81(1995) Official methods of analysis of the Association of the Official Analytical Chemists, , ASSOCIATION OF OFFICIAL ANALYTICAL CHEMISTS-AOAC, 16th ed. Arlington, Virginia: AOACAzevedo-Meleiro, C.H., Rodriguez-Amaya, D.B., Confirmation of the identity of the carotenoids of tropical fruits by HPLC-DAD and HPLC-MS (2004) Journal of Food Composition and Analysis, 17 (3-4), pp. 385-396Bagetti, M., Antioxidant capacity and composition of pitanga seeds (2009) Ciência Rural, 39 (8), pp. 204-2510Beekwilder, J., Antioxidant in raspberry: On-line analysis links antioxidant activity to a diversity of individual metabolites (2005) Journal of Agricultural and Food Chemistry, 53 (9), pp. 3313-3320Benzie, F.F.I., Strain, J.J., The ferric reducing ability of plasma (FRAP) as a measure of "antioxidant power": The FRAP assay (1996) Analytical Biochemistry, 239 (1), pp. 70-76Bligh, E.G., Dyer, W.J., A rapid method of total lipid extraction and purification (1959) Journal of Biochemistry and Physiology, 37 (8), pp. 911-917Block, G., Patterson, B., Subar, A., Fruits, vegetables and cancer prevention: A review of the epidemiological evidence (1992) Nutrition and Cancer, 18 (1), pp. 1-29Bors, W., Flavonoids as antioxidants: Determination of radical scavenging efficiencies (1990) Methods in Enzymology, 186, pp. 343-355Brand-Williams, W., Cuvelier, M.E., Berset, C., Use of a free radical method to evaluated antioxidant activity (1995) Lebensmittel-Wissenschaft und-Technologie, 28 (1), pp. 25-30Regulamento técnico geral para fixação dos padrões de identidade e qualidade para polpa de fruta (2000) Diário Oficial da República Federativa do Brasil, p. 54. , http://extranet.agricultura.gov.br/sislegisconsulta/consultarLegislacao. do?operacao=visualizar&id=7777, BRASIL. Instrução Normativa, no 1, de 7 de janeiro de 2000, Brasília, DF, 10 jan, Seção 1, Disponível em:, Acesso em: 18 dez. 2008Cavalcante, M.L., Rodriguez-Amaya, D.B., Carotenoid composition of the tropical fruits Eugenia uniflora and Malpighia glabra (1992) Food Science and Human Nutrition, pp. 643-650. , In: CHARALAMBOUS, G. (Ed.), Amsterdam: Elsevier Science PublishersClinton, S.K., Lycopene: Chemistry, biology, and implications for human health and disease (1998) Nutrition Reviews, 56 (2), pp. 35-51Consolini, A.E., Sarubbio, M., Pharmacological effects of Eugenia uniflora L. (Myrtaceae) aqueous extract on rat's heart (2002) Journal of Ethnopharmacology, 81 (1), pp. 57-63di Mascio, P., Kaiser, S., Sies, H., Lycopene as the most efficient biological carotenoid singlet oxygen quencher (1989) Archives of Biochemistry and Biophysics, 274 (2), pp. 532-538Dillard, C.J., German, J.B., Phytochemicals: Neutraceuticals and human health (2000) Journal of the Science of Food and Agriculture, 80 (12), pp. 1744-1756Diplock, A.T., Functional food sciences and defense against reactive oxidative species (1998) British Journal of Nutrition, 80 (1), pp. 77-112Escarpa, A., Gonzalez, M.C., Approach to the content of total extractable phenolic compounds from different food samples by comparison of chromatographic and spectrophotometric methods (2001) Analytica Chimica Acta, 427 (1), pp. 119-127Gemtchüjnicov, I.D., (1976) Manual de taxonomia vegetal: Plantas de interesse econômico, agrícola, ornamentais e medicinais, p. 368. , São Paulo: CeresGenovese, M.I., Bioactive compounds and antioxidant capacity of exotic fruits commercial frozen pulps from Brazil (2008) Food Science and Technology International, 4 (3), pp. 207-214Hartman, L., Lago, B.C., A rapid preparation of fatty methyl esters from lipids (1973) Laboratory Practice, 22 (6), pp. 475-477Hassimotto, N.M.A., Genovese, M.I., Lajolo, F.M., Antioxidant activity of dietary fruits, vegetables, and commercial frozen fruit pulps (2005) Journal of Agricultural and Food Chemistry, 53 (8), pp. 2928-2935Kaur, C., Kapoor, H., Antioxidants in fruits and vegetables-the millennium's health (2001) International Journal of Food Science and Technology, 36 (7), pp. 703-725Kimura, M., Rodriguez-Amaya, D.B., Yokoyama, S.M., Cultivar differences and geographic effects on the carotenoid composition and vitamin A value of papaya (1991) Lebensmittel-Wissenschaft und-Technologie, 24 (5), pp. 415-418Krinsky, N.I., Johnson, E.J., Carotenoid actions and their relation to health and disease (2005) Molecular Aspects of Medicine, 26 (6), pp. 459-516Kris-Etherton, P.M., Bioactive compounds in foods: Their role in the prevention of cardiovascular disease and cancer (2002) American Journal of Medicine, 113 (9), pp. 71-88Kuskoski, M.E., Frutas tropicais silvestres e polpas de frutas congeladas: Atividade antioxidante, polifenóis e antocianinas (2006) Ciência Rural, 36 (4), pp. 1283-1287Lees, D.H., Francis, F.J., Standardization of pigment analyses in cranberries (1972) Hortscience, 7 (1), pp. 83-84Lima, V.L.A.G., Mélo, E.A., Lima, D.E.S., Fenólicos e carotenóides totais em pitanga (2002) Scientia Agricola, 59 (3), pp. 447-450Niizu, P.Y., Rodriguez-Amaya, D.B., A melancia como fonte de licopeno (2003) Revista do Instituto Adolfo Lutz, 62 (3), pp. 195-199Oliveira, A.L., Volatile compounds from pitanga fruit (Eugenia uniflora L.) (2006) Food Chemistry, 99 (1), pp. 1-5Padula, M., Rodriguez-Amaya, D.B., Characterization of the carotenoids and assessment of the vitamin A value of Brazilian guavas (Psidium guajava L.) (1986) Food Chemistry, 20 (1), pp. 11-19Pellegrini, N., Evaluation of antioxidant capacity of some fruit and vegetable foods: Efficiency of extraction of a sequence of solvents (2007) Journal of the Science of Food and Agriculture, 87 (1), pp. 103-111Pietta, P.G., Flavonoids as antioxidants (2000) Journal of Natural Products, 63 (7), pp. 1035-1042Pinto, M.S., Lajolo, F.M., Genovese, M.I., Bioactive compounds and quantification of total ellagic acid in strawberries (Fragaria × ananassa Duch.) (2007) Food Chemistry, 107 (4), pp. 1629-1635Porcu, O.M., Rodriguez-Amaya, D.B., Variation in the carotenoid composition of the lycopene-rich Brazilian fruit Eugenia uniflora L (2008) Plant Foods for Human Nutrition, 63 (4), pp. 195-199Prior, R.L., Cao, G., Antioxidant phytochemicals in fruits and vegetables: Diet and health implications (2000) Horticulture Science, 35 (4), pp. 588-592Rahman, I., Adcock, I.M., Oxidative stress and redox regulation of lung inflammation in COPD (2006) European Respiratory Journal, 28 (1), pp. 219-242Reynerston, K.A., Quantitative analysis of antiradical phenolic constituents from fourteen edible Myrtaceae fruits (2008) Food Chemistry, 109 (4), pp. 883-890Robards, K., Antolovich, M., Analytical chemistry of fruit bioflavonoids (1997) Analyst, 122, pp. 11R-34RRodriguez-Amaya, D.B., (1999) A guide to carotenoid analysis in foods, , Washington, D.C.: ILSI PressSalgado, S.M., Guerra, N.B., Melo Filho, A.B., Frozen fruit pulps: Effects of the processing on dietary fiber contents (1999) Brazilian Journal of Nutrition, 12 (3), pp. 303-308Scalzo, J., Plant genotype affects total antioxidant capacity and phenolic contents in fruit (2005) Nutrition, 21 (2), pp. 207-213Singleton, V.L., Rossi Jr., J.A., Colorimetry of total phenolic with phosphomolybdic-phosphotungstic acid reagents (1965) American Journal of Enology and Viticulture, 16 (3), pp. 144-158Stahl, W., Sies, H., Bioactivity and protective effects of natural carotenoids (2005) Biochimica et Biophysica Acta, 1740 (2), pp. 101-107Tapiero, H., Townsend, D.M., Tew, K.D., The role of carotenoids in the prevention of human pathologies (2004) Biomedicine and Pharmacotherapy, 58 (2), pp. 100-110(2006) Tabela brasileira de composição de alimentos-TACO, p. 113. , UNIVERSIDADE DE CAMPINAS-UNICAMP, 2. ed. Version II. Campinas: NEPA/UNICAMPVison, J.A., Phenol antioxidant quantity and quality in foods: Vegetables (1998) Journal of Agricultural and Food Chemistry, 46 (9), pp. 4113-4117Weyerstahl, P., Volatile constituents of Eugenia uniflora leaf oil (1988) Planta Médica, 54 (6), pp. 546-54

Field- and pressure-induced magnetic quantum phase transitions in TlCuCl_3

Thallium copper chloride is a quantum spin liquid of S = 1/2 Cu^2+ dimers. Interdimer superexchange interactions give a three-dimensional magnon dispersion and a spin gap significantly smaller than the dimer coupling. This gap is closed by an applied hydrostatic pressure of approximately 2kbar or by a magnetic field of 5.6T, offering a unique opportunity to explore the both types of quantum phase transition and their associated critical phenomena. We use a bond-operator formulation to obtain a continuous description of all disordered and ordered phases, and thus of the transitions separating these. Both pressure- and field-induced transitions may be considered as the Bose-Einstein condensation of triplet magnon excitations, and the respective phases of staggered magnetic order as linear combinations of dimer singlet and triplet modes. We focus on the evolution with applied pressure and field of the magnetic excitations in each phase, and in particular on the gapless (Goldstone) modes in the ordered regimes which correspond to phase fluctuations of the ordered moment. The bond-operator description yields a good account of the magnetization curves and of magnon dispersion relations observed by inelastic neutron scattering under applied fields, and a variety of experimental predictions for pressure-dependent measurements.Comment: 20 pages, 17 figure