Resistive Instabilities In Reversed-field Confinement Configurations Without Shear

A resistive mode with azimuthal mode number m = 1 is shown to exist in reversed-field confinement configurations without shear. The mode has an almost constant radial profile from the magnetic axis to the radius where the magnetic field vanishes; its growth rate scales with the 1/3 power of the plasma resistivity, and the corresponding perturbed displacement parallel to the field lines is much larger than the perpendicular one in the resistive region. This mode may lead to the splitting of the plasma column into many rings, and may also be a triggering mechanism for the rotational m = 1 instability that is observed in θ-pinch discharges. ©1981 American Institute of Physics.24466166

Establishment and development of Tabebuia rosea (Bignoniaceae) seedlings in a semideciduous tropical forest under management, Pacific coast of Mexico [Establecimiento y desarrollo de plántulas de Tabebuia rosea (Bignoniaceae) en una selva subcaducifolia manejada de la costa Pacífica de México]

We evaluated the effect of soil "scarification" and vegetation clearing treatments on the natural regeneration and initial development of Tabebuia rosea (Bertold) DC. seedlings in a moderate sized semideciduous tropical forest subjected to wood harvesting on the coast of Jalisco, Mexico. The treatments were applied under "seed" trees, and the number of germinated seedlings and their development were evaluated for nine months. Soil "scarification" promoted seed germination and initial seedling development, while the control of the competing vegetation increased the seedling growth and reduced their mortality. These results should be taken into account for the natural regeneration of this species, after clearing, to improve wood production, and should be incorporated into the silvicultural techniques currently developed in the region

Establishment and development of Tabebuia rosea (Bignoniaceae) seedlings in a semideciduous tropical forest under management, Pacific coast of Mexico [Establecimiento y desarrollo de plántulas de Tabebuia rosea (Bignoniaceae) en una selva subcaducifolia manejada de la costa Pacáfica de México]

We evaluated the effect of soil "scarification" and vegetation clearing treatments on the natural regeneration and initial development of Tabebuia rosea (Bertold) DC. seedlings in a moderate sized semideciduous tropical forest subjected to wood harvesting on the coast of Jalisco, Mexico. The treatments were applied under "seed" trees, and the number of germinated seedlings and their development were evaluated for nine months. Soil "scarification" promoted seed germination and initial seedling development, while the control of the competing vegetation increased the seedling growth and reduced their mortality. These results should be taken into account for the natural regeneration of this species, after clearing, to improve wood production, and should be incorporated into the silvicultural techniques currently developed in the region

The Viscous Mhd Spectra-application To Coronal Loop Heating And Stability

We have derived the viscous MHD equilibrium and perturbed equations for current carrying cylindrical plasmas. We have considered compressible plasmas and, when the viscosity is introduced in the equation of motion it leads to a linearized vector second order perturbed equation for the fluid displacement, showing the appearance of non Hermitian operators. The Lagrangian representation is used to investigate the stability and we used the normal mode analysis to study the linearized equation. We applied our model for the problem of the coronal loop heating and solved the eigenmode equation, which is nonlinear in the eigenvalue, using a numerical code based on the software "Mathematica", with appropriate boundary conditions. We have confirmed that viscosity is relevant as the dominant mechanism for the coronal loop heating in our self-consistent calculation as indicated by previous non self-consistent work of De Azevedo et al. Solar Phys 136, 295 (1991). In the limit of zero viscosity, we obtain the discrete and the continuous spectra and some unstable points.582173177De Azevedo, C.A., De Assis, A.S., Shigueoka, H., Sakanaka, P.H., (1991) Solar Phys., 136, p. 295Frieman, E., Rotenberg, M., (1960) Rev. Mod. Phys., 32, p. 898Goedbloed, J.P., (1975) Phys. Fluids, 18, p. 1258Harned, D., (1983) Phys. Fluids, 26, p. 1320Hasegawa, A., Uberoi, C., (1982) The Alfvén Wave, , Technical Information Center, U.S. Department of EnergyHoffman, A.L., Slough, J.T., Harding, D.G., (1983) Phys. Fluids, 26, p. 1226Ionson, J.A., (1978) Astrophys. J., 226, p. 650Ishimura, T., (1984) Phys. Fluids, 27, p. 2139Ito, Y., Tanjyo, M., Ohi, S., Goto, S., Ishimura, T., (1987) Phys. Fluids, 30, p. 168Lou, Y., (1990) Astrophys. J., 350, p. 452Kulsrud, R., (1995) Phys. Plasmas, 2, p. 1735Steinolfson, R., Priest, E.R., Poedis, S., Nocera, L., Goosens, M., (1986) Astrophys. J., 304, p. 526Storer, R.G., Schellhase, A.R., (1995) Physica Scripta, T60, p. 5

Efeito do pastejo rotacionado e alternado com bovinos adultos no controle da verminose em ovelhas Effect of rotational and alternate grazing with adult cattle on the control of nematode parasites in sheep

Estudaram-se os efeitos do pastejo alternado de ovinos e bovinos e do pastejo rotacionado sobre o controle da verminose em ovelhas. Utilizou-se uma área experimental composta por três módulos de 1,67ha cada. Os módulos foram subdivididos em oito piquetes. Vinte ovelhas foram colocadas no módulo 1 e quatro bovinos adultos no módulo 2. Os animais permaneceram em cada piquete do módulo por cinco dias, totalizando 40 dias de permanência em cada módulo. Ao final desse período, as ovelhas foram transferidas para o módulo onde estavam os bovinos e estes para o módulo onde estavam os ovinos, mantendo esse esquema até o final do experimento. Um grupo-controle de 20 ovelhas foi mantido, também em sistema rotacionado, em um terceiro módulo, sem compartilhar a pastagem. As ovelhas submetidas ao manejo com bovinos apresentaram o menor grau de infecção por nematódeos gastrintestinais e os maiores valores de volume globular. O pastejo rotacionado de ovinos, sem a utilização de bovinos, não foi eficiente no controle da verminose das ovelhas. A utilização do pastejo rotacionado e alternado de ovinos e bovinos adultos exerceu efeito benéfico significativo no controle da verminose ovina.<br>The effects of rotational and alternate grazing involving cattle and sheep on the control of nematode parasites in sheep were evaluated. Three areas with 1.67ha were subdivided into eight paddocks each. Twenty ewes and four cattle were allotted to areas 1 and 2, respectively. They grazed during five days in each of eight paddocks of each area. The sheep and cattle rotated in each area for 40 days. At the end of this period, ewes were transferred to the area where cattle were previously kept and these animals were transferred to the area where sheep had previously grazed. This arrangement was kept until the end of the experiment. A control group with 20 ewes rotated in the third area, also with eight paddocks. Ewes that alternately grazed with cattle showed the lowest fecal egg counts and the highest values of packed cell volume. The rotational grazing of sheep, without cattle, was not efficient to control gastrointestinal nematodes. The alternate grazing of sheep and cattle resulted in a reduction of parasitic infection in the ewes