Resonant coupling of Rayleigh waves through a narrow fluid channel causing extraordinary low acoustic transmission.

Coupling of Rayleigh waves propagating along two metal surfaces separated by a narrow fluid channel is predicted and experimentally observed. Although the coupling through a fluid (water) is weak, a strong synchronization in propagation of Rayleigh waves even for the metals with sufficiently high elastic contrast (brass and aluminum) is observed. Dispersion equation for two polarizations of the coupled Rayleigh waves is derived and experimentally confirmed. Excitation of coupled Rayleigh waves in a channel of finite length leads to anomalously low transmission of acoustic energy at discrete set of resonant frequencies. This effect may find useful applications in the design of acoustic metamaterial screens and reflectors.

Microscope spectrometer for light scattering investigations.

We describe a setup including a microscope to study volumes of a few mum(3) by static and dynamic light scattering (DLS) in a backscattering configuration. Light scattered by individual objects of micrometric size can be analyzed in the 400-800?nm spectral range. This setup can also be employed to study both diluted and concentrated colloidal solutions by DLS measurements. For diluted solutions we found evidence of the fluctuations of the number of particles in a confocal volume. We discuss their contribution to the autocorrelation function of the scattered intensity measured as a function of time.

Effects of multiple stressors associated with agriculture on stream macroinvertebrate communities in a tropical catchment.

Tropical forests are declining at unprecedented rates in favour of agriculture, and streams can be severely impacted due to effects of multiple stressors that have rarely been considered together in tropical studies. We studied the effects of multiple stressors associated with agricultural practices (pesticide toxicity, nutrient enrichment and habitat alteration-quantified as TUmax, soluble reactive phosphorus concentration and sedimentation, respectively) on macroinvertebrate communities in a tropical catchment in Panama (13 stream sites sampled in 20 occasions from 2015 to 2017, with 260 samples in total). We examined how macroinvertebrate abundance, taxonomic richness, community composition and biotic indices (SPEAR and BMWP/PAN, which were specifically designed to detect pesticide toxicity and nutrient enrichment, respectively) varied depending on the studied stressors, considering their single and combined effects. Our analyses revealed significant effects of the studied stressors on macroinvertebrate communities, with two particular results that merit further attention: (1) the fact that pesticide toxicity affected BMWP/PAN, but not SPEAR, possibly because the former had been adapted for local fauna; and (2) that most stressors showed antagonistic interactions (i.e., lower combined effects than expected from their individual effects). These results highlight the need for toxicity bioassays with tropical species that allow adaptations of biotic indices, and of observational and manipulative studies exploring the combined effects of multiple stressors on tropical macroinvertebrate communities and ecosystems, in order to predict and manage future anthropogenic impacts on tropical streams.

Aféresis con una máquina de recuperación intraquirúrgica de sangre / Apheresis using a red blood cell saver device

Algunos autores han propuesto que una máquina de recuperación intraoperatoria de sangre, que posea la capacidad de modificar su velocidad de centrifugación a fin de ajustarla a la requisitoria de la separación de componentes sanguíneos, puede ser utilzada con este fin. La Stat-Compact de Dideco cumple con este requisito, por lo que analizamos sus posibilidades como procesador celular. Plasmaféresis terapéutica : dos pacientes con esclerosis en placa fueron tratados con 3 y 5 recambios plasmáticos respectivamente, obteniendo una disminución de la IgG en LCR (de 30,9 a 2,3 Ag por ciento y de 38,9 Ag por ciento a "no dosable") y evolución clínica muy favorable. Una paciente embarazada, portadora de un anticuerpo anti-D con un dosaje ponderal de 40,28 mg/ml, fue sometida a 6 recambios plasmáticos (con disminución de 28,5 mg/ml), interrumpiéndose el tratamiento por muerte fetal intraútero. En este aspecto, consideramos que, a pesar de obtener resultados auspiciosos (de acuerdo con la indicación), el número de casos no es suficiente para obtener conclusiones. (AU)

Aféresis con una máquina de recuperación intraquirúrgica de sangre / Apheresis using a red blood cell saver device

Algunos autores han propuesto que una máquina de recuperación intraoperatoria de sangre, que posea la capacidad de modificar su velocidad de centrifugación a fin de ajustarla a la requisitoria de la separación de componentes sanguíneos, puede ser utilzada con este fin. La Stat-Compact de Dideco cumple con este requisito, por lo que analizamos sus posibilidades como procesador celular. Plasmaféresis terapéutica : dos pacientes con esclerosis en placa fueron tratados con 3 y 5 recambios plasmáticos respectivamente, obteniendo una disminución de la IgG en LCR (de 30,9 a 2,3 µg por ciento y de 38,9 µg por ciento a "no dosable") y evolución clínica muy favorable. Una paciente embarazada, portadora de un anticuerpo anti-D con un dosaje ponderal de 40,28 mg/ml, fue sometida a 6 recambios plasmáticos (con disminución de 28,5 mg/ml), interrumpiéndose el tratamiento por muerte fetal intraútero. En este aspecto, consideramos que, a pesar de obtener resultados auspiciosos (de acuerdo con la indicación), el número de casos no es suficiente para obtener conclusiones.