Showing papers by "Federal University of Pernambuco published in 1975"

Biologia do Triatoma brasiliensis: II. Observações sobre a autogenia

Abstract: Femeas virgens de Triatoma brasiliensis produzem ovos mesmo que nao recebam alimento apos a muda imaginal. Em geral, existe uma ampla variacao no peso corporeo das femeas, quando alcancam o estadio adulto. O peso do adulto e proporcional a quantidade de sangue ingerido no 5.o estadio e os animais mais pesados sao aqueles que sobrevivem mais tempo em jejum. A producao total de ovos durante o jejum e proporcional ao peso corporeo, aumentando em relacao ao aumento de peso dos animais. A capacidade de oviposicao, medida atraves de taxa diaria de producao de ovos, e variavel e tambem positivamente correlacionada com o peso dos animais. Variou, em nossa amostra, de 0,01 a 0,2 ovos/femea/dia para femeas cujos pesos variaram entre 150 e 290 mg, respectivamente. A capacidade media de oviposicao foi de 0,14 ± 0,02 ovos/femea/dia. Esta variacao de capacidade de oviposicao em relacao ao peso dos insetos, mostra que a producao de ovos durante o jejum depende do estado nutricional dos animais e, provavelmente, esta correlacionado com o sangue ingerido durante o 5.o estadio.

Gravitational radiation from supernova explosions

Abstract: As a simple model of a supernova explosion we study a point mass exploding into two equal point masses moving back to back at high velocity, or a superposition of such elementary explosions. We employ two calculational methods. In one method we assume an infinite acceleration for zero time and calculate with the gravitational field and the distribution of emitted energy. A cutoff frequency in the power spectrum is necessary to obtain a finite total energy output. The spectrum is constant from zero to this cutoff frequency. For nonrelativistic ejecta velocities the angular distribution is typical of quadrupole radiation, while for ultrarelativistic ejecta it is isotropic. To justify the infinite-acceleration approximation, we also calculate with the quadrupole approximation by using a smooth finite acceleration, and verify the previous qualitative results in the nonrelativistic limit. A brief table of fields, energies, and fluxes is given for some reasonable supernova parameters. (AIP)

Carrier-Assisted Perpendicular Pumping of Spin Waves in Ferromagnetic Semiconductors

Abstract: The carrier contribution to the generation of spin waves in ferromagnetic semiconductors under perpendicular pumping conditions is discussed. It is shown that for degenerate semi­ 'conductors this electronic contribution predicts a threshold pumping power of the same order of magnitude as the one involved in the direct mechanism of spin waves excitation. Also the carrier assisted mechanism excites spin ~aves with k in a broad range of values in· contrast with the direct mechanism.

Effect of the dipolar interaction on the spin wave amplification

Abstract: We have evaluated the effect of the interaction of the carrier spin with the self-consistent magnetic field created by the oscillations of the magnetization in ferromagnetic semiconductors. Under the experimental conditions in CdCr2Se4 the contribution of this interaction to the process of spin wave amplification is negligible compared with the current interaction. It is also shown that it becomes dominant only for large values ofk.

Raciborskieila parva Xavier Filho nova espécie de Strigulaceae (Liquens) do Estado do Amazonas

Abstract: Resumo Descricao de Raciborskiella parva Xavier Filho nova especie da familia Strigulaceae coletada no Estado do Amazonas.

The somersault flap

Abstract: Taking into consideration the disadvantages and inconveniences of the cross-leg flap for the replacement of skin losses of the lower limbs, the author proposes a new type of flap, called the somersault flap. It is a flap created in the vicinity of the injury, with a pedicle that is broader than it is long, which, once raised, curves back over itself, and is sutured to a receiving edge created surgically in the immediate vicinity of the injury. This edge will be as large as the base of the pedicle, and will be the second and definitive pedicle of the flap. The raw area of the flap is exposed and the skin faces inwards, constituting a long tube with two lateral pedicles. An area of 3 to 4 centimeters must exist between the two pedicles, an area from which both pedicles will derive their nourishment, hence it must remain untouched. As the base of the flap is larger than its length there is no need for delay procedures. The donor area is repaired with a split graft. Once good circulatory conditions have been ensured, 3 to 4 weeks later, the first pedicle is severed so that the flap, now attached by the second pedicle, can be sutured to a raw area surgically created including the defect to be repaired, which must have the same shape and size of the flap.

Effect ofs-d hybridization on the spin polarization: doubly degenerated-band in Hartree-Fock approximation

Abstract: The conduction electron spin polarization produced by a magnetic rare-earth impurity placed in a metalic host is calculated within a degenerate-band model, taking into account electron-electron correlations. The degenerated-band is assumed to hybridize to a broads-band, this model attempting to describe the situation encountered in rare-earth metal alloys and intermetallic compounds. One finds that the total magnetization is given by the sum ofs andd contributions, the «bare» impurity exchange couplingsJimp(s) andJimp(d) being replaced by effective exchange parameters which incorporate the effects ofs-d mixing.

Nonlinear effects involving localized magnon modes in impure ferromagnetic insulators

Abstract: A simple theoretical treatment for the study of nonlinear processes involving impurities in ferromagnetic insulators is presented. In particular, the possibility of exciting ferromagnetic magnons with very large wave vectors is analyzed theoretically. The proposed excitation mechanism is analogous to the first-order Suhl instability and takes place via nonlinear processes involving localized modes. A rough estimate of the critical power of a far-infrared laser source necessary to attain the instability threshold is given. It is noted that the threshold value is within the power capabilities of present pulsed far-infrared lasers, suggesting that the process is experimentally feasible.

Analysis of four-body final states: Nonrelativistic

Abstract: The constraints of unitarity and analyticity on four-body final state amplitudes are studied. It is shown that unitarity alone forces the amplitudes to be coherent and have rapid (singular) behavior. The implementation of unitarity yields a set of linear integral equations for the four-body amplitudes that are the minimal set consistent with quantum mechanics, but are also equivalent to the full dynamical equation with separable interactions.