Spin-phonon coupling in Gd(Co1/2Mn1/2)O3 perovskite

We have investigated the temperature-dependent Raman-active phonons and the magnetic properties of Gd(Co1/2Mn1/2)O3 perovskite ceramics in the temperature range from 40 K to 300 K. The samples crystallized in an orthorhombic distorted simple perovskite, whose symmetry belongs to the Pnma space group. The data reveals spin-phonon coupling near the ferromagnetic transition occurring at around 120 K. The correlation of the Raman and magnetization data suggests that the structural order influences the magnitude of the spin-phonon coupling.Comment: 3 Figures, suplementary materia

Spin–phonon coupling in monoclinic BiCrO3

International audienc

Spin-phonon coupling in the incommensurate magnetic ordered phase of orthorhombic TmMnO₃

International audienceThe search for materials with strong magnetoelectric coupling has been intense since interesting properties were discovered in the perovskite TbMnO 3. Among the manganese-based perovskite family (RMnO 3), magnetic and electric orders coexist in the orthorhombic phase of the distorted perovskite TmMnO 3. The antiferromagnetic phase induces ferroelectricity, leading to type-II multiferroic behavior. Although the temperature-dependent behavior of the Raman-active phonons of other members of the orthorhombic RMnO 3 family was already reported, little information about orthorhombic TmMnO 3 has been published. In this paper, bulk samples of orthorhombic TmMnO 3 were obtained through HPHT treatment. Structural and magnetic properties of the synthesized samples were analyzed for phase con rmation. Temperature-dependent Raman spectra of bulk orthorhombic TmMnO 3 revealed weak spin-phonon coupling in the incommensurate antiferromagnetic ordered phase around 44 K. Raman spectra are also sensitive to the magnetic transition from the incommensurate to Etype antiferromagnetic phase, where the frequency renormalization due to the spin-phonon coupling vanishes. This feature shows the existence of an orbital-spin-phonon coupling based on the magnetic ordering of the lowtemperature phase

Sampling efficiency of different sample units and procedures to sample spittlebug eggs

Foi conduzido um estudo sobre amostragem de ovos de cigarrinhas em pastagens de Brachiaria decumbens Stapf, usando-se as amostras de 25, 50 e 75 cm2 da pastagem. A eficiência de amostragem das três unidades foi comparada calculando-se o número necessário de amostras para um certo nível de precisão (a proporção do erro-padrão, a média, em percentagem). A eficiência de amostragem da unidade de 50 cm2 foi baixa em comparação à de 25 ou 75 cm2. Para se obter um mesmo nível de precisão, por exemplo, de 20% a área total de pasto a ser examinado foi um pouco menor para a unidade de 75 cm2 do que para a de 25 cm2 quando a densidade de ovos era baixa (1/25 cm2), porém essa vantagem desapareceu quando a densidade foi de 4 ovos/25 cm2. Com base nisto, e o fato de que um menor número de amostras seria necessário no caso da unidade de 75 cm2, do que com a de 25 cm2, o uso da anterior foi sugerido. O número de ovos das cigarrinhas por 25 e 50 cm2 de área de pastagem mostrou uma distribuição do tipo binomial negativa. A sampling study of spittlebug eggs in pastures of Brachiaria decumbens Stapf was conducted by using samples of 25, 50 and 75 cm2 of the pasture. The sampling efficiency of three sample units was compared by calculating the number of samples necessary to obtain a certain level of precision (proportion of standard error to mean expressed as a percentage). The sampling efficiency of 50 cm2 sample unit was poor in comparison to 25 and 75 cm2 . To obtain the same level of precision, e.g., 20%, the total pasture area to be examined was slightly smaller for 75 cm2 unit than for 25 cm2 at lower egg density (1/25 cm2);however, such advantage of the 75 cm2 disappeared at egg density of 4/25 cm2 . Based on this finding and the fact that fewer samples would be taken in the case of 75 cm2 than the 25 cm2 unit, the use of former was suggested. The distribution pattern of number of eggs per 25 or 50 cm2 of pasture fitted the negative binomial series

Supersymmetry and Integrability in Planar Mechanical Systems

We present an N=2-supersymmetric mechanical system whose bosonic sector, with two degrees of freedom, stems from the reduction of an SU(2) Yang-Mills theory with the assumption of spatially homogeneous field configurations and a particular ansatz imposed on the gauge potentials in the dimensional reduction procedure. The Painleve test is adopted to discuss integrability and we focus on the role of supersymmetry and parity invariance in two space dimensions for the attainment of integrable or chaotic models. Our conclusion is that the relationships among the parameters imposed by supersymmetry seem to drastically reduce the number of possibilities for integrable interaction potentials of the mechanical system under consideration.Comment: 20 pages, 3 figure

Non-minimal Maxwell-Chern-Simons theory and the composite Fermion model

The magnetic field redefinition in Jain's composite fermion model for the fractional quantum Hall effect is shown to be effectively described by a mean-field approximation of a model containing a Maxwell-Chern-Simons gauge field non-minimally coupled to matter. Also an explicit non-relativistic limit of the non-minimal (2+1)D Dirac equation is derived.Comment: 10 pages, no figure

Bioprospection of Petit Verdot grape pomace as a source of anti-inflammatory compounds

The aim of this study was to evaluate the anti-inflammatory activity of Petit Verdot Extract and hexane, chloroform and ethyl acetate fractions obtained from grape pomace, in addition to identifying active compounds. The PVE and EAF reduced significantly paw edema and neutrophil migration when compared with control groups. The PVE reduced levels of TNF-α and IL1-β in the peritoneal fluid, whereas the EAF did not reduce cytokines significantly. Two hydroxybenzoic acids, two proanthocyanidins, three flavan-3-ol monomers and three anthocyanins were identified in the PVE and EAF by LC-MS/MS. The stilbene transresveratrol was identified only in the EAF. The phenolic compounds were quantified using HPLC-DAD analysis, except for the stilbenes, which were not sensible for the detection by the method. Since PVE and EAF showed significantly anti-inflammatory effects and high concentration of phenolic compounds, we concluded that Petit Verdot pomace could be an interesting source of anti-inflammatory bioactives

Bioprospection of Petit Verdot grape pomace as a source of anti-inflammatory compounds.

The aim of this study was to evaluate the anti-inflammatory activity of Petit Verdot Extract and hexane, chloroform and ethyl acetate fractions obtained from grape pomace, in addition to identifying active compounds. The PVE and EAF reduced significantly paw edema and neutrophil migration when compared with control groups. The PVE reduced levels of TNF-α and IL1-β in the peritoneal fluid, whereas the EAF did not reduce cytokines significantly. Two hydroxybenzoic acids, two proanthocyanidins, three flavan-3-ol monomers and three anthocyanins were identified in the PVE and EAF by LC-MS/MS. The stilbene transresveratrol was identified only in the EAF. The phenolic compounds were quantified using HPLC-DAD analysis, except for the stilbenes, which were not sensible for the detection by the method. Since PVE and EAF showed significantly anti-inflammatory effects and high concentration of phenolic compounds, we concluded that Petit Verdot pomace could be an interesting source of anti-inflammatory bioactives