THERMAL REGIME AND STABILITY OF JURUMIRIM RESERVOIR (PARANAPANEMA RIVER, SAO-PAULO, BRAZIL)

Thermal regime and stability in Jurumirim Reservoir (São Paulo, Brazil) were studied for a year. Isothermy and thermal stratification were observed from June to September and from October to March, respectively. The annual heat budget was 14.0 Kcal . cm-2 and average heat gain per day was 67.2 cal . cm-2 . day-1. Maximum stability and wind work reached 324.2 and 3,037.5 g . cm . cm-2, respectively. According to thermal structure and heat content, Jurumirim Reservoir was classified as a warm tropical monomictic lake.

THE ENERGY BARRIER FOR ELECTRON TRAPPING IN ALXGA1-XAS

Transient decay of persistent photoconductivity measurements are carried out in samples of different compositions. The capture barrier for electron trapping by DX centers is obtained using a method which employs the Brooks-Herring equation for the electronic mobility. The effect of polarization of the screening cloud is analysed using Takimoto's potential and specifies the limits of applicability of the Brooks-Herring equation in AlxGa1-xAs.

2-DIMENSIONAL QUANTUM GAS

Identical impenetrable particles in a 2-dimensional configuration space obey braid statistics, intermediate between bosons and fermions. This statistics, based on braid groups, is introduced as a generalization of the usual statistics founded on the symmetric groups. The main properties of an ideal gas of such particles are presented. They do interpolate the properties of bosons and fermions but include classical particles as a special case. Restriction to 2 dimensions precludes lambda points but originates a peculiar symmetry, responsible in particular for the identity of boson and fermion specific heats.

MAGNETOOPTICAL PROPERTIES OF F-2(+) CENTER IN KCL-SH-

The magnetic circular dichroism (MCD) of F2+ centers in KCl:SH- has been measured in absorption in the 1ssigma(g) --> 2p(y)pi(u) transitions at 493 and 509 nm, with fields up to 5 T and in the temperature range 1.5 K < T < 77 K. Within the limit of detection, no MCD is observed in the near infrared transition 1ssigma(g) --> 2psigma(u) as well as in both emissions 2ppi(u) --> 1ssigma(g) and 2psigma(u) --> 1ssigma(g). The optical detection of EPR in the F2+ ground state presents an isotropic single band with g = 1.965 +/- 0.007. The spin-lattice relaxation measured at H = 0.32 T is typical of a direct process T-1 = 4.3 x 10(-2_ coth (gmu(B)H/2k(B)T). The spectral variation of the MCD is calculated using perturbation theory to first order. The Hamiltonian includes the spin-orbit interaction in the 2ppi(u) excited state and the orbital molecular wave functions are obtained by a linear combination of 1s and 2p atomic orbitals. The calculated MCD is in good agreement with the observed one, for the spin-orbit interaction strength Pound(z) = 3.6 meV.

Bootstrap confidence regions for canonical variates: Application to studies of evolutionary differentiation

Theory recently developed to construct confidence regions based on the parametric bootstrap is applied to add inferential information to graphical displays of sample centroids in canonical variate analysis. Problems of morphometric differentiation among subspecies and species are addressed using numerical resampling procedures.

Influence of Cu and Cr on the matrix decomposition of quenched Al-Zn-Mg alloy

The Inoue procedure is used to study the influence of Cr and Cu elements, jointly or individually, on the matrix decomposition of quenched Al-Zn-Mg alloys. The addition of copper and copper with chromium does not significantly change the limits of the temperatures of formation of Guinier-Preston zone and the range of the matrix decomposition. The control of the vacancy concentration in the alloys by different heat treatments and the addition of certain elements such as copper and chromium seems to play an important role in the nucleation rate and the kinetics of phase transformations.