Shock and statistical acceleration of energetic particles in the interplanetary medium

Definite evidence for particle acceleration in the solar wind came around a decade ago. Two likely sources are known to exist: particles may be accelerated by the turbulence resulting from the superposition of Alfven and Magnetosonic waves (Statistical Acceleration) or they may be accelerated directly at shock fronts formed by the interaction of fast and slow solar wind (CIR's) or by traveling shocks due to sporadic coronal mass ejections. Naurally both mechanisms may be operative. In this work the acceleration problem was tackled numerically using Helios 1 and 2 data to create a realistic representation of the Heliospheric plasma. Two 24 hour samples were used: one where there are only wave like fluctuations of the field (Day 90 Helios 1) and another with a shock present in it (Day 92 of Helios 2) both in 1976 during the STIP 2 interval. Transport coefficients in energy space have been calculated for particles injected in each sample and the effect of the shock studied in detail

Light Intensity Enhancement Inside the Grooves of Metallic Grating

Light absorption inside the grooves of metallic gratings filled with a semiconductor material can be improved by means of the electric field enhancement. To this end, the influence of grating dimensions in the electric field spectral behavior is theoretically investigated. Two conditions of cavity resonance have been analyzed separately: (1) for TE polarization (electric field parallel to the grooves) and (2) for TM polarization (magnetic field parallel to the grooves). When dimensions are chosen according to the first condition, the enhancement of TE fields is found to increase with the height-to-width ratio, and it is accompanied with a decrease in the bandwidth. The same enhancement levels can be achieved for TM fields if the second condition holds, provided that the period-to-width ratio is large enough. The simultaneous enhancement of TE and TM fields, based on a condition of surface resonance excitation, can also be accomplished. In this case, the TM response is very sensitive to changes in groove depth and width

Light trapping by means of electric field enhancement in metallic grantings

The enhancement of the electromagnetic field within the grooves of a metallic diffraction grating is analyzed. A perfect conductor, rectangular-shaped diffraction grating is assumed, therefore, the field enhancement analyzed in this work is due to resonances caused by the structure itself, and not to the so-called surface-plasmon resonances which are observed to be influenced by metal properties as well. The modal approach has been employed for calculations. Basically, the squared amplitude of the electric field within the grooves is calculated as a function of the wavelength of the incident light. Similarly, the behaviour of the structure when exposed to a conical bundle of light is also analyzed. The present results show that a field intensity enhancement of the order of 100 is achievable. However, the spectral width of the resonances decrease with increasing enhancement as is expecte

Low-injection behaviour of a solar cell with a metallic grating back-reflector

Recent studies have dealt with the possibility of increasing light absorption by using the so-called electric field enhancement taking place within the grooves of metallic gratings. In order to evaluate the potential improvements derived from the absorption increase, we employ a simplified model to analyze the low-injection behaviour of a solar cell with a metallic grating back-reflector

New Records of green (Chlorophyta) and brown algae (Phaeophyta) for Cabezo Reef, National Park Sistema Arrecifal Veracruzano, Gulf of Mexico

Descriptions of 13 green and 12 brown algal species from 20 genera and 15 families collected on Cabezo Reef of the National Park Sistema Arrecifal Veracruzano in the southwestern Gulf of Mexico, which are new records for the reef, are given. The species belong to the chlorophyte genera Caulerpa, Cladophoropsis, Codium, Dictyosphaeria, Ernodesmis, Halimeda, Neomeris, Parvocaulis, Percursaria and Rhipocephalus and the phaeophycean genera Canistrocarpus, Colpomenia, Cladosiphon, Dictyerpa, Dictyota, Ectocarpus, Padina, Rosenvingea, Sargassum and Sphacelaria. The family Dictyotaceae contained the largest number of species (6). The descriptions include morphometric and biological data and are accompanied by photographs and line drawings for each species. Data on the geographic distribution in the State of Veracruz, park and the Gulf of Mexico in general are also given. Percursaria percursa is a new record for the park, while Dictyerpa jamaicensis, Sargassum furcatum, Caulerpa racemosa var. occidentalis and Codium isthmocladum subsp. clavatum are new records for the State of Veracruz. Most of the specimens of Chlorophyta were found in the vegetative stage, whereas all the brown algal species except Dictyerpa jamaicensis and Sphacelaria rigidula possessed gametangia or sporangia.Se presentan las descripciones de 13 especies de algas verdes y 12 de algas pardas de 20 géneros y 15 familias, que son nuevos registros para el arrecife Cabezo ubicado en la parte sureste del Parque Nacional Sistema Arrecifal Veracruzano en el suroeste del Golfo de México. Las especies pertenecen a los géneros de clorofitas Caulerpa, Cladophoropsis, Codium, Dictyosphaeria, Ernodesmis, Halimeda, Neomeris, Parvocaulis, Percursaria y Rhipocephalus, y los géneros de algas pardas Canistrocarpus, Colpomenia, Cladosiphon, Dictyerpa, Dictyota, Ectocarpus, Padina, Rosenvingea, Sargassum y Sphacelaria. La familia Dictyotaceae fue la mejor representada en cuanto al número de especies (6). Las descripciones incluyen datos morfométricos y biológicos y están acompañadas con fotografías y dibujos a línea para cada especie. También se presenta la información sobre la distribución de las especies en el estado de Veracruz, el parque y el Golfo de México en general. Percursaria percursa es un nuevo registro para el parque, mientras Dictyerpa jamaicensis, Sargassum furcatum, Caulerpa racemosa var. occidentalis y Codium isthmocladum subsp. clavatum lo son para el estado de Veracruz. La mayor proporción de ejemplares pertenecientes a Chlorophyta se encontraron en estado vegetativo, mientras que los especímenes de algas pardas excluyendo a las especies Dictyerpa jamaicensis y Sphacelaria rigidula, se encontraron ya sea con gametangios o esporangios

Solar Neutron Events of October-November 2003

During the period when the Sun was intensely active on October-November 2003, two remarkable solar neutron events were observed by the ground-based neutron monitors. On October 28, 2003, in association with an X17.2 large flare, solar neutrons were detected with high statistical significance (6.4 sigma) by the neutron monitor at Tsumeb, Namibia. On November 4, 2003, in association with an X28 class flare, relativistic solar neutrons were observed by the neutron monitors at Haleakala in Hawaii and Mexico City, and by the solar neutron telescope at Mauna Kea in Hawaii simultaneously. Clear excesses were observed at the same time by these detectors, with the significance calculated as 7.5 sigma for Haleakala, and 5.2 sigma for Mexico City. The detector onboard the INTEGRAL satellite observed a high flux of hard X-rays and gamma-rays at the same time in these events. By using the time profiles of the gamma-ray lines, we can explain the time profile of the neutron monitor. It appears that neutrons were produced at the same time as the gamma-ray emission.Comment: 35 pages, 21 figures, accepted for publication in Ap

Impaired autoregulation of renal blood flow in the fawn-hooded rat

The responses to changes in renal perfusion pressure (RPP) were compared in 12-wk-old fawn-hooded hypertensive (FHH), fawn-hooded low blood pressure (FHL), and August Copenhagen Irish (ACI) rats to determine whether autoregulation of renal blood flow (RBF) is altered in the FHH rat. Mean arterial pressure was significantly higher in conscious, chronically instrumented FHH rats than in FHL rats (121 +/- 4 vs. 109 +/- 6 mmHg). Baseline arterial pressures measured in ketamine-Inactin-anesthetized rats averaged 147 +/- 2 mmHg (n = 9) in FHH, 132 +/- 2 mmHg (n = 10) in FHL, and 123 +/- 4 mmHg (n = 9) in ACI rats. Baseline RBF was significantly higher in FHH than in FHL and ACI rats and averaged 9.6 +/- 0.7, 7.4 +/- 0.5, and 7.8 +/- 0.9 ml. min-1. g kidney wt-1, respectively. RBF was autoregulated in ACI and FHL but not in FHH rats. Autoregulatory indexes in the range of RPPs from 100 to 150 mmHg averaged 0.96 +/- 0.12 in FHH vs. 0.42 +/- 0.04 in FHL and 0.30 +/- 0.02 in ACI rats. Glomerular filtration rate was 20-30% higher in FHH than in FHL and ACI rats. Elevations in RPP from 100 to 150 mmHg increased urinary protein excretion in FHH rats from 27 +/- 2 to 87 +/- 3 microg/min, whereas it was not significantly altered in FHL or ACI rats. The percentage of glomeruli exhibiting histological evidence of injury was not significantly different in the three strains of rats. These results indicate that autoregulation of RBF is impaired in FHH rats before the development of glomerulosclerosis and suggest that an abnormality in the control of renal vascular resistance may contribute to the development of proteinuria and renal failure in this strain of rats