Decoupling of the S=1/2 antiferromagnetic zig-zag ladder with anisotropy

The spin-1/2 antiferromagnetic zig-zag ladder is studied by exact diagonalization of small systems in the regime of weak inter-chain coupling. A gapless phase with quasi long-range spiral correlations has been predicted to occur in this regime if easy-plane (XY) anisotropy is present. We find in general that the finite zig-zag ladder shows three phases: a gapless collinear phase, a dimer phase and a spiral phase. We study the level crossings of the spectrum,the dimer correlation function, the structure factor and the spin stiffness within these phases, as well as at the transition points. As the inter-chain coupling decreases we observe a transition in the anisotropic XY case from a phase with a gap to a gapless phase that is best described by two decoupled antiferromagnetic chains. The isotropic and the anisotropic XY cases are found to be qualitatively the same, however, in the regime of weak inter-chain coupling for the small systems studied here. We attribute this to a finite-size effect in the isotropic zig-zag case that results from exponentially diverging antiferromagnetic correlations in the weak-coupling limit.Comment: to appear in Physical Review

Uso da adubação orgânica e cobertura morta na cultura da calêndula (Calendula officinalis L.).

A calêndula representa fonte alternativa econômica principalmente para a agricultura familiar. O objetivo do presente trabalho foi avaliar os efeitos da adubação orgânica e do uso da cobertura morta sobre a produção de biomassa e teor de flavonóides totais em plantas de calêndula. O experimento foi realizado no Campus de Montes Claros da Universidade Federal de Minas Gerais, utilizando-se o delineamento em blocos casualizados em esquema fatorial 2x2x4 com quatro repetições: duas épocas de colheita, presença ou ausência de cobertura morta e quatro doses de composto orgânico (0, 30, 60 e 90 t ha-1). As maiores produções de biomassa e flavonóides totais foram verificadas com o aumento das doses de composto orgânico. Para os flavonóides totais o maior teor foi obtido na segunda colheita na presença de cobertura morta

Observaciones de la Galaxia a bajas latitudes en la línea de 21-cm

Con el objeto de contribuir al estudio de la estructura galáctica, Vieira (1968) había observado la zona comprendida en 302° ≤ l ≤ 310° , 2° ≤ b ≤ 12°, con espaciados Δl y Δb de 0.5°. El rango de velocidades iba desde -100 hasta +100 km/s.Asociación Argentina de Astronomí

Observaciones del cúmulo galáctico NGC 2287 en 21-cm

Observations were made in the direction of the galactic cluster NGC 2287 and its neighbourhood with the radiotelescope at Parque Pereyra Iraola. The results of them were compared with optical data. As the paper will be published elsewhere, we give here only a synthesis.Asociación Argentina de Astronomí

Effects of α-tocopherol and ternatin antioxidants on morphology and activation of goat preantral follicles in vitro cultured

Os efeitos do α-tocoferol e da ternatina sobre morfologia, ativação e crescimento de folículos pré-antrais caprinos cultivados in vitro, por um ou cinco dias, foram avaliados. Os fragmentos ovarianos foram imediatamente fixados (controle não-cultivado) ou cultivados in vitro, por um ou cinco dias, em Meio Essencial Mínimo (MEM) com ou sem suplementação com α-tocoferol ou ternatina nas concentrações de 5, 10 ou 15M, formando os tratamentos MEM, TOC5, TOC10, TOC 15, TER5, TER10, TER15. O percentual de folículos pré-antrais normais no controle não-cultivado foi de 73,2%, depois de cinco dias de cultivo, houve redução desse percentual em todos os tratamentos, quando comparados com o controle não-cultivado (P<0,05). O cultivo por cinco dias aumentou a ativação folicular em todos os tratamentos (P<0,05). A análise ultra-estrutural não mostrou folículos pré-antrais íntegros após cinco dias de cultivo em meio contendo antioxidantes. Concluiu-se que o α -tocoferol e a ternatina podem promover a ativação folicular, no entanto a adição desses antioxidantes nas concentrações testadas reduziu a viabilidade folicular após o cultivo in vitro. ______________________________________________________________________________________________________________ ABSTRACTThe effects of α-tocopherol and ternatin on the morphology, activation, and growth of goat preantral follicles in vitro cultured, for one or five days, were evaluated. Ovarian fragments were immediately fixed (non-cultured control) or in vitro cultured for one or five days in Minimum Essential Medium (MEM) with or without α-tocopherol or ternatin supplementation, both at concentrations of 5, 10, or 15M, corresponding to the following treatments: MEM, TOC5, TOC10, TOC 15, TER5, TER10, and TER15. The percentages of morphologically normal preantral follicles in non-cultured ovarian tissue (control) was 73.2% and after five days of culture, there was a decrease on these percentages in all treatments (P<0.05) when compared with non-cultured control. Culture of ovarian cortex for five days increased the percentages of follicular activation in all treatments (P<0.05). Ultrastructural analysis did not confirm the integrity of caprine preantral follicles cultured for five days in medium containing antioxidants. This study demonstrated that α-tocopherol and ternatin can promote follicular activation; however, addition of these antioxidants in the tested concentrations reduced the follicular viability after in vitro culture

Observaciones de la Galaxia a bajas latitudes en la línea de 21-cm

Con el objeto de contribuir al estudio de la estructura galáctica, Vieira (1968) había observado la zona comprendida en 302° ≤ l ≤ 310° , 2° ≤ b ≤ 12°, con espaciados Δl y Δb de 0.5°. El rango de velocidades iba desde -100 hasta +100 km/s.Asociación Argentina de Astronomí

Observaciones del cúmulo galáctico NGC 2287 en 21-cm

Observations were made in the direction of the galactic cluster NGC 2287 and its neighbourhood with the radiotelescope at Parque Pereyra Iraola. The results of them were compared with optical data. As the paper will be published elsewhere, we give here only a synthesis.Asociación Argentina de Astronomí

Observaciones de la Galaxia a bajas latitudes en la línea de 21-cm

Con el objeto de contribuir al estudio de la estructura galáctica, Vieira (1968) había observado la zona comprendida en 302° ≤ l ≤ 310° , 2° ≤ b ≤ 12°, con espaciados Δl y Δb de 0.5°. El rango de velocidades iba desde -100 hasta +100 km/s.Asociación Argentina de Astronomí

Atlas de hidrógeno galáctico en la región 320° ≤ l ≤ 345°, 18° ≤ b ≤ 26°

Se presenta un atlas constituido por datos observacionales obtenidos en la linea de 21 cm dados en forma de perfiles e isofotas.Asociación Argentina de Astronomí

Dried brewers grains in growing rabbits: nutritional value and effects on performance

[EN] Two assays were carried out to determine i) the nutritional value of dried brewers’ grains and ii) the effects of inclusion of this ingredient in growing rabbit diets on animal performance and economic performance of the breeding unit. In the digestibility assay, a total of 28 male rabbits were distributed in 2 groups differing in the diet offered to animals: a reference diet (35.51% neutral detergent fibre and 16.50% crude protein [CP]) and a test diet (60% of reference diet and 40% of dried brewers grains). The dried brewers’ grain contained 37.9% of CP and 3371 kcal digestible energy/kg dry matter. In the performance study, 80 weaned rabbits (40 males and 40 females) were allotted at 40 d of age to 5 groups differing in the inclusion levels of dried brewers’ grains (0, 7, 14, 21 and 28%) from 40 d to 90 d of age. Inclusion of dried brewers’ grains did not affect the live weight at 90 d, the feed intake between 40 d and 90 d or the dressing percentage of rabbits (on average 223 g, 96 g/d and 51.3%, respectively). There was no effect of diet on the meat quality parameters (69.5% water holding capacity, 25.6% cooking loss, 3.4 kg/cm2 Warner-Bratzler shear force and pH 5.70) and inclusion levels above 14% reduced the feed cost (–18%; P<0.001), while inclusion above 21% improved net income (+32%; P<0.001). In conclusion, these results suggest that the use of dried brewers’ grains in diets for growing rabbits could improve the economic performance of the production system without impairing the animals’ performance.Lima, P.; Watanabe, P.; Cândido, R.; Ferreira, A.; Vieira, A.; Rodrigues, B.; Nascimento, G.... (2017). Dried brewers grains in growing rabbits: nutritional value and effects on performance. World Rabbit Science. 25(3):251-260. doi:10.4995/wrs.2017.6813.SWORD251260253Albuquerque, D. M. N., Lopes, J. B., Klein Junior, M. H., Merval, R. R., Silva, F. E. S., & Teixeira, M. P. F. (2011). Resíduo desidratado de cervejaria para suínos em terminação. Arquivo Brasileiro de Medicina Veterinária e Zootecnia, 63(2), 465-472. doi:10.1590/s0102-09352011000200026AOAC International. 2005. Official methods of analysis of Association Official Analytical Chemists International. AOAC, Arlington VA. USA.Briganó, M. V., Pacheco, G. D., Bridi, A. M., Oba, A., Fonseca, N. A. N., & Silva, C. A. da. (2008). Desempenho e características de carcaça de suínos submetidos a diferentes programas de restrição alimentar na fase dos 30 aos 118 kg. Revista Brasileira de Zootecnia, 37(8), 1398-1404. doi:10.1590/s1516-35982008000800009De Blas, J. C., Rodriguez, C. A., Bacha, F., Fernandez, R., & Abad-Guamán, R. (2015). Nutritive value of co-products derived from olivecake in rabbit feeding. World Rabbit Science, 23(4), 255. doi:10.4995/wrs.2015.4036Etchu K.A., Humbu M.E., Ndamukong K.J.N., Agbor E.B. 2012. Effect of varying levels of brewers' dried grain on the growth performance of weaner rabbits (Oryctolagus Cuniculus). Greener J. Agric. Sci., 2: 237-245.Fazano A.R.T., Zinsly C.F., Mattos W.R.S., Packer I.H. 1986. Digestibilidade e valor biológico da proteína da levedura seca (Saccharomyces spp.) e do farelo de soja para coelhos. Boletim de Indústria Animal, 46: 185-191.Lounaouci-Ouyaed G., Lakabi-ioualitene D., Berchiche M., Lebas F. 2008. Field beans and brewers grain as protein source for growing rabbits in Algeria: first results on growth and carcass quality. Nutrition and Digestive Physiology. In: 9th World Rabbit Congress, June 10-13, Verona, Italy. 723-728.Matterson L.D., Potter L.M., Stutz M.W., Singsen E.P. 1965. The metabolizable energy of feed ingredients for chickens. Storrs: University of Connecticut; Agricultural Experiment Station Research Report, 11: 11.National Research Council. 2007. Nutrient requirements of small ruminants: sheep, goats, cervids, and New World camelids. Washington, D.C.: National Academic Press, 292.Partridge G., Wyatt C. 1995. More flexibility with new generation of enzymes. World Poultry,11: 17-21.SAS 2000. SAS/STAT User's Guide (Release 6.12). SAS Inst. Inc., Cary NC, EUA.Villamide, M. J. (1996). Methods of energy evaluation of feed ingredients for rabbits and their accuracy. Animal Feed Science and Technology, 57(3), 211-223. doi:10.1016/0377-8401(95)00855-