Deviations from Poisson statistics in the spectra of free rectangular thin plates.

The counterintuitive fact that wave chaos appears in the bending spectrum of free rectangular thin plates is presented. After extensive numerical simulations, varying the ratio between the length of its sides, it is shown that (i) frequency levels belonging to different symmetry classes cross each other and (ii) for levels within the same symmetry sector, only avoided crossings appear. The consequence of anticrossings is studied by calculating the distribution of the ratio of consecutive level spacings for each symmetry class. The resulting ratio distributions disagree with the expected Poissonian result. They are then compared with some well-known transition distributions between Poisson and the Gaussian orthogonal random matrix ensemble. It is found that the distribution of the ratio of consecutive level spacings agrees with the prediction of the Rosenzweig-Porter model. Also, the normal-mode vibration amplitudes are found experimentally on aluminum plates, before and after an avoided crossing for symmetrical-symmetrical, symmetrical-antisymmetrical, and antisymmetrical-symmetrical classes. The measured modes show an excellent agreement with our numerical predictions. The expected Poissonian distribution is recovered for the simply supported rectangular plate.

[Microbiology of chronic otitis media in children and comparison of 2 technics for obtaining otic secretions]. / Microbiología de la otitis crónica en niños y comparación de dos técnicas para la obtención de la secreción ótica.

Samples of otic secretion for culture were taken to 50 children with suppurative chronic otitis media; two techniques were followed: with a cotton swab from the external meatus or with a sterile metal aspirator, through the tympanic perforation under microscopic control. To 20 of them with unilateral chronic otitis media, a swab with product from the external meatus of the healthy ear was also taken; in 65% of the latter, the same germs were found in both ears, but when the sample was taken with the aspirator, only in 15% were the germs the same (p less than 0.01). Two or more germs were isolated in 54% of the ears following the technique of the swab and in 32% with the aspiration. The predominant microorganisms with the swab technique were gram-positive cocci (S. epidermidis 48% S. aureus 16%); while the aspiration technique reported gram-negative germs in 96% of cultures (Proteus sp. 42%, Pseudomonas sp. 30% and S. aureus only in 14%). We believe that the sample obtained with a swab has a high degree of contamination with the normal flora of the external meatus; therefore, it should be relinquished.

Hospederos intermediarios de fasciola hepática en el Perú / Intermediate hosts of in Peru fasciola hepatica

Se demostró la infección natural y experimental de los caracoles limneídos peruanos con estadios larvales de Fasciola hepatica. Los índices de infección natural y experimental fueron del 12% y 28% en Lymnaea columella y del 27% y 70% en Lymnaea viatrix, respectivamente. Lymnaea diaphana y Lymnaea cousini no presentaron infección natural y demostraron no ser susceptibles a la infección experimental.

The natural and experimental infection of Peruvian lymnaeid snails with larval stages of Fasciola hepatica was demonstrated. The index of natural and experimental infection was of 12% and 28% in Lymnaea columella and of 27% and 70% in Lymnaea viatrix, respectively. Lymnaea diaphana and Lymnaea cousini did not present natural infection and demonstrated not to be prone to experimental infection.

Microbiologia de la otitis cronica en ninos y comparacion de dos tecnicas para la obtencion de la secrecion otica. / Microbiology of chronic otitis in children and comparison of two technics in obtaining otic secretion

Se estudio la concentracion de las immunoglobulinas G y M mas el perfil electroforetico de las proteinas en 14 sueros de ninos con ascesso hepatico amibiano. Todos tenian diferentes grados de perdida de peso y de necrosis hepatica. La concentracion de las proteinas totales del suero estuvo sujeta a diversos factores y resulto con amplias variaciones individuales. Lo mismo se obtuvo cuando se expresaron, en g/dl, los valores de las fracciones que separo la eletroforesis.En cambio, los valores porcentuales dieron un perfil similar para dos los pacientes. Ademas del aumento significativo de las IgG, se encontro uma inversion de la relacion albumina/ globulinas y un aumento de los porcentajes de las fracciones alfa-l, alfa-2 y gamma. Se especula sobre la importancia que pueden tener los mecanismos antienzimas proteoliticas en la evolucion de la lesion que provocan en el higado, las enzimas liberadas por los protozoarios