Sample records for RADIACION DE FRECUENCIA MUY ALTA (very high frequency radiation)
from WorldWideScience.org

Sample records 1 - 19 shown.



1

Waveform Shaping of Sonar Transducers for Improving the Vertical Resolution in Sub-bottom Sediments Profiling

Cobo, Pedro; Ranz Guerra, Carlos; Fernández, Alejandro; Anthony, David K.; Siguero, Manuel
2005-06-01

Digital.CSIC (Spain)

2

Variaciones espaciales y temporales del fitoplancton en un lago subtropical de Argentina/ Temporal and spatial variations of the phytoplankton in a subtropical lake of Argentina/ Variações espaciais e temporais do fitoplâncton num lago subtropical da Argentina

ZALOCAR DE DOMITROVIC, YOLANDA; ASSELBORN, VIVIANA M.; CASCO, SYLVINA L.
1998-08-01

Resumen en portugués Foi estudada a composição, biomassa e diversidade das espécies de fitoplâncton num lago subtropical (27°29'S; 58°45'O) desde fevereiro de 1995 até março de 1996. Uma ou duas coletas mensais foram feitas em dois locais: uma na área central e outra na região litoral do lago. As contagens foram realizadas segundo o método de Utermöhl (1958). A biomassa do fitoplâncton variou entre 2,38 e 45,59 mm³.m², com valor médio de 12,11 mm³.m-2 (± 10,52 mm³.m-2). A d (mas) ensidade da população oscilou entre 0,3 x 10(6) e 4,7 x 10(6) ind.cm-2. Cyanophyta predominou ao longo de todo o ano, contribuindo com entre 25% e 83% para a biomassa total. Cylindrospermopsis raciborskii, Aphanizomenon sp. e Microcystis aeruginosa foram as espécies melhor representadas . Chlorophyla, segundo grupo em importância, apresentou-se entre 8% a 50%, sendo Botryococcus braunii a espécie dominante. Bacillariophyceae, Xanthophyceae, Euglenophyceae e Cryptophyceae não superaram 20% da biomassa total. O aporte de Chrysophyceae e Dinophyceae à biomasa total não ultrapassou 5%. O conteúdo de clorofila a variou entre 0,7 e 8 µg.L-1, refletindo a variação anual da biomassa do fitoplâncton. A diversidade baseada na densidade do fitoplâncton variou entre 0,34 e 3,69 bits.ind-1 e a diversidade baseada na biomassa oscilou entre 1,04 e 2,92 bits.ind-1, com variação similar nas diferentes profundidades do lago. A mais baixa biomassa e a mais alta diversidade foram sempre registradas na região litoral. Os estrategistas C, com alta relação AS/V, dominaram em densidade (Monoraphidium contortum, M. tortile, Chlorella vulgaris e outros pequenos flagelados de Chlorophyta), enquanto os estrategistas S, com baixa relação AS/V, tais como Microcystis aeruginosa e Botryococcus braunii, predominaram em biovolume durante a maior parte do ano. Cylindrospermopsis raciborskii e Aphanizomenon sp. dominaram em densidade e biomassa quando a temperatura foi superior a 20°C e a radiação solar, a 20 MJ.m-2. Os estrategistas R (Aulacoseira italica e Gymnodinium sp.) dominaram quando a coluna d'água apresentou grande instabilidade. A biomassa do fitoplâncton correlacionouse positivamente com a precipitação ocorrida dez dias antes de cada amostragem (r = 0,772; p Resumen en inglés Species composition, biomass and diversity of the phytoplankton in a subtropical lake (27°29'S; 58°45'W) were studied from February 1995 to March 1996. One or two samples were taken monthly in the limnetic and the littoral area. Cell counts were done by the Utermöhl method (1958). Phytoplankton biomass varied among 2.38 and 45.59 mm³.m-2 with a mean value of 12.11 (±10.52) mm³.m-2. The population density oscillated among 0.3x10(6) and 4.7x10(6) ind.cm-2. Cyanophyta (mas) was the dominant group all the year contributing among 25% and 83% of the total biomass. Cylindrospermopsis raciborskii, Aphanizomenon sp. and Microcystis aeruginosa were the dominant species. The Chlorophyta, second group in importance, contributed among 8% and 50% being Botryococcus braunii the dominant species. Bacillariophyceae, Xanthophyceae, Euglenophyceae and Cryptophyceae they did not surpass 20% of total biomass. Chrysophyceae and Dinophyceae they did not surpass 5% of total biomass. Chlorophyll a content ranged between 0.7 and 8 µg.L-1 reflecting the annual variation of phytoplankton biomass. Phytoplankton density diversity varied among 0.34 and 3.69 bits.ind-1. Biomass diversity varied among 1.04 and 2.92 bits.µm³, with a similar variation in the depths of the lake. The lowest biomass and the highest diversity were always found in the littoral zone. CStrategists, with a high SA/V ratios prevailed in density (Monoraphidium contortum, M. tortile, Chlorella vulgaris and other small flagellates of Chlorophyta) while SStrategists (with a low SA/V ratios) such as Microcystis aeruginosa and Botryococcus braunii prevailed during the greater part of the year. Cylindrospermopsis raciborskii and Aphanizomenon sp. were dominant in density and biomass when the temperatures were superior to 20°C and the solar radiation surpassed 20 MJ.m-2. The RStrategists (Aulacoseira italica and Gymnodinium sp.) prevailed during great unstability of water column. Phytoplankton biomass was positively correlated with rain falls 10 days before each sampling (r = 0.772; p

Scientific Electronic Library Online (Spanish)

3

Transferencia energética en un modelo multicapa de tejido humano sometido a irradiación electromagnética de alta frecuencia

García-Collado, Á.J.; Molina-Cuberos, G. J.; Núñez, M. J.
2009-02-01

Resumen en español La forma en la que la energía es absorbida cuando la superficie de la piel es expuesta a una radiación electromagnética, y las consecuencias físicas implicadas, son esencialmente los propósitos de este trabajo. En particular, se estudia la radiación electromagnética de alta frecuencia. Cuando esta radiación incide directamente sobre la superficie de la piel, la energía es transmitida hacia el interior de los tejidos, incrementando su temperatura. Este proceso ha (mas) sido empleado de forma beneficiosa en muchos casos. Aún hoy día, existe un desconocimiento teórico sobre estos efectos. Este estudio pretende tratar el tema desde su origen, y deja vías de trabajo futuras para abordar a fondo el mismo. La piel es considerada como un sistema de múltiples capas con distintas características cada una de ellas, cada capa es caracterizada por parámetros de permitividad, conductividad, densidad y calor específico. Dos tipos de piel son analizados: un tipo fibroso y un tipo adiposo, cada uno de ellos con diferentes grados de hidratación. En este estudio se muestra la evolución temporal no lineal de la temperatura de los tejidos y es tenida en cuenta la redistribución del calor ejercida por el propio cuerpo humano. Resumen en inglés The way the energy is absorbed when skin surface is being exposed to an electromagnetic radiation, and the physical consequences involved, are essentially the purposes of this study. In particular, we are dealing with High Frequency radiation. When it is directed toward the surface of the skin, energy is transmitted to its inner layers causing an increase of the temperature. This process has experimentally been proved to be beneficial in many cases. Yet theoretically ther (mas) e is still a slightly hollow basis about it. This study pretends to deal with that subject from its origin, and allows future study doors to tap in depth this theme. Skin tissue is actually a multilayer tissue with a different tissue in each layer. Each one of them is characterized by some parameters, such as permittivity, conductivity, density and specific heat. Two kinds of skin tissues will be analysed: a fibrous and a fatty one, each of both with a different skin humidity. In this study some parameters such as the non-linear temporal evolution of tissue temperature and the redistribution of heat them will be take into account.

Scientific Electronic Library Online (Spanish)

4

The abundances of polyacetylenes towards CRL618

Fonfría, José P.; Cernicharo, José; Richter, Matthew J.; Lacy, John H.
2010-12-02

Digital.CSIC (Spain)

5

Síntesis electroquímica y propiedades de Polimetoxibencenos

Márquez, Jairo; Márquez, Olga P
2007-06-01

Resumen en español Los compuestos metoxi-bencénicos son electrooxidados en acetonitrilo/tetrafluoroborato de tetra n-butilamonio, con altos rendimientos orgánicos y en corriente. Si el medio contiene agua, el producto principal de reacción es la alcoxifenil acetamida, formada por ataque nucleofílico del acetonitrilo al anillo aromático y la posterior hidrólisis. En un medio anhidro, el producto principal de reacción es el polímero, formado mediante un mecanismo catiónico, tipo elec (mas) troquímico- químico-electroquímico (EQE). Los polímeros forman, generalmente, una bicapa sobre la superficie del electrodo, la cual es estable, insoluble y conductora. Su coloración varía entre compuestos, presentan propiedades electrocrómicas y algunos son sensibles a cambios en la temperatura, presión, irradiación y frecuencia de sonido. Pueden modificar electrodos y ser modificados con partículas metálicas. Algunos electrodos modificados han sido evaluados en procesos de reducción de dióxido de carbono y de inhibición del desprendimiento de oxígeno. La preparación de estos polímeros, en distintos medios electrolíticos, modifica su morfología y propiedades. Resumen en inglés Methoxybenzenes are electrochemically oxidized at an electrode surface, in acetonitrile/tetrabutylammonium tetrafluoroborate, with high organic and current yields. In the presence of water, the main reaction product is the alkoxy phenylacetamide, due to a nucleophylic attack of acetonitrile to the aromatic ring, followed by hydrolysis. In anhydrous medium, the main reaction product is a polymer, which is formed following an ECE type of mechanism. This polymer forms a bila (mas) yer structure on the electrode surface and is insoluble, stable and good conductor of electricity. It is coloured and shows electrochromic properties, and some of them are sensitive to temperature, pressure, light radiation and sound frequency. They can modify electrodes and can be modified by metallic particles. Some of these modified materials have been used as electrodes for the reduction process of carbon dioxide and electrolytic oxygen evolution. Preparation of these polymers in different media, modified morphology and properties of the material.

Scientific Electronic Library Online (Spanish)

7

Pulsed electroluminescence in silicon nanocrystals-based devices fabricated by PECVD

Barreto, Jorge; Perálvarez, Mariano; Rodríguez, José Antonio; Morales, Alfredo; Riera, Montse; López, Manel; Garrido, Blas; Lechuga, Laura M.; Domínguez, Carlos
2007-04-01

Digital.CSIC (Spain)

8

Macrosonic emiter with vibrating plate comprising internodal zone separators and reflectors which can be used to obtain directional radiation in fluids.

Rodríguez Corral, Germán; Gallego Juárez, Juan Antonio; Vázquez, Fernando; Campos-Pozuelo, Cleofé; Riera, Enrique
2003-05-30

Digital.CSIC (Spain)

10

Estudio de efectos de asimetría en vibradores ultrasónicos axisimétricos

Chacón, David; Rodríguez Corral, Germán; Riera, Enrique; Gallego Juárez, Juan Antonio
2004-09-01

Digital.CSIC (Spain)

11

Efectos de la radiación ultravioleta (UV) en la inducción de mutaciones de p53 en tumores de piel/ Effect of ultraviolet (UV) radiation in the induction of p53 mutations in skin tumors

Cabrera Morales, C. M.; López-Nevot, M. A.
2006-09-01

Resumen en español El cáncer de piel representa el tipo mas frecuente de cáncer humano, con una incidencia que va en aumento en los últimos años. La exposición excesiva a la radiación ultravioleta (UV) de la luz solar se asocia de forma directa con la aparición de tumores no-melanoma; sin embargo esta asociación no es tan aparente en el melanoma. En los tumores de piel no-melanoma, la radiación ultravioleta es la responsable de la producción de mutaciones puntuales en genes releva (mas) ntes como p53, consistentes en transiciones que ocurren en sitios dipirimidina. Encontrándose la acumulación de mutaciones en el gen supresor de tumores p53 inducidas por la radiación UV en el inicio del proceso tumoral de piel. Resumen en inglés Skin cancer is presently the most frequent type of human cancer, showing in addition an increasing incidence in the last years. The excessive exposure to the sunlight ultraviolet (UV) radiation is associated with non-melanoma skin cancers, while such an association is not so apparent in melanoma. The hallmark of UV radiation in non-melanoma skin tumors is the high frequency of transition mutations at dipyrimidine sequences of relevant genes as p53. The accumulation of UV-induced p53 mutations seems to be critical in the development of skin cancer.

Scientific Electronic Library Online (Spanish)

12

Characterization of the time-frequency parameters inherent in the radiation of semiconductor heterolasers using interferometric technique

Shcherbakov, Alexandre S.; Moreno Zarate, Pedro; Campos Acosta, Joaquín; Il'n, Yurij V.; Tarasov, Il'ya
2009-01-01

Digital.CSIC (Spain)

15

Análisis de cadenas de Markov y series de Fourier en una secuencia hemipelágica del Jurásico superior de la Península Antártica

Kietzmann, Diego A.; Cuitiño, José I.; Medina, Rubén A.; Scaso, Roberto A.
2009-07-01

Resumen en español La Formación Ameghino (Kimmeridgiano-Berriasiano), Cuenca Larsen, Península Antártica, está compuesta por una asociación de microfacies de pelitas con radiolarios (P1), pelitas negras (P2), pelitas bioturbadas y peloidales (P3), tobas (T) y areniscas (A) excelentemente preservadas. Este conjunto de microfacies revela sedimentación pelágica/ hemipelágica en un ambiente deficiente en oxígeno, periódicamente interrumpida por caídas de cenizas del arco volcánico a (mas) ntártico. Análisis basados en cadenas de Markov indican la recurrencia de las microfacies y sus relaciones cíclicas. Se interpreta que la alternancia de pelitas con radiolarios y pelitas negras (P1-P2) responde a variaciones en la productividad/dilución, mientras que las microfacies de tobas y areniscas corresponden a depósitos de evento que modificaron las condiciones ambientales y diagenéticas evitando la disolución de los esqueletos de radiolarios en la masa de agua y en el fondo, y generando de este modo una memoria markoviana con ciclos T-P1-P2. Por otra parte, el análisis por transformadas de Fourier indica para los ciclos P1-P2 una duración del orden de 1000 años, en el rango de variaciones sub-Milankovitch. Resumen en inglés The Upper Jurassic strata of the Larsen Basin, in the northeastern tip of the Antarctic Peninsula (Fig. 1), consist of thin, well-bedded, radiolarian-rich shales, fallout tuffs and volcaniclastic sandstones, grouped in a stratigraphic unit known as Ameghino Formation (or Nordenskjöld Formation for British authors - see Whitham and Doyle, 1989). The Ameghino Formation succession records a fine-grained and high-rate continuous suspensive sedimentation in a quiet hemipelagi (mas) c environment, with little reworking at the bottom. A 1.3 m-thick representative section for the Upper Member of the Ameghino Formation was sampled bed by bed and studied under petrographic microscopy for microfacies determination. Cyclicity was defined by means of Markov chain analysis and Fourier series (Blackman- Tukey and wavelet methods). Microfacies: The succession is composed of a microfacies association of radiolarianrich shales (P1), black shales (P2), bioturbated and peloidal shales (P3), tuffs (T) and sandstones (A) superbly preserved (Figs. 2 and 3). Sedimentation took place in an oxygen-depleted environment, periodically interrupted by rapid, event-sedimentation mostly caused by large explosive eruptions at the volcanic arc of the Antarctic Peninsula. The P1 and P2 microfacies are interpreted as the result of the deposition from pelagic suspensions during cycles of varying biological productivity or terrigenous dilution. The microfacies P3 represents similar conditions of sedimentation but higher oxygenation levels at the bottoms. On the other hand, microfacies T and A correspond to fallout deposits and distal turbiditic flows respectively. Microfacies T is associated with siliciclastic explosive volcanic eruptions and microfacies A with reworking of primary pyroclastic deposits. Markov chain and Fourier series analysis: Markov chain analysis reveal cyclic relations between some microfacies with single step transition dependence (Figs. 4 and 5). Transition diagram shows statistically significant transitions from microfacies T and A to P1, between P1 and P2, and also a cycle T-P1-P2 (Fig. 6). Spectra from the Fourier series analysis on 37 pairs P1-P2 (Fig. 7 a) indicate a periodicity of 1140 years (Blackman-Tukey method, 95% confidence, Fig. 7b), and periodicities of 740 and 1160 years (wavelet method, Fig. 7c). Ages were derived from sedimentation rates calculated by Scasso (2001) for the Longing Member due to poor age determinations in the upper Member. A periodicity of about 1000 years may be associated with the Hallstatt cycle of solar activity that influence the intensity of solar radiation reaching the Earth and cause surface temperature variations within the sub-Milankovitch frequency band. A similar frequency was calculated by Scasso (2001) for large volcanic eruptions from the tuff record in the Longing Member. Therefore, P1- P2 transitions are associated to climatic cycles that influence productivity at the surface of the oceans. The accumulation of microfacies T and A are related to events of siliciclastic sedimentation that modified environmental and early-diagenetic conditions avoiding dissolution of radiolarian skeletons in the water body and at the bottom and caused the T and A transitions to P1. P2-T transition might indicate that P2 environmental conditions lasted longer than P1 conditions in spite of the similar thickness observed for both microfacies.

Scientific Electronic Library Online (Spanish)

18

A new gravitational wave background from the Big Bang

García-Bellido, Juan; García Figueroa, Daniel
2008-01-27

Digital.CSIC (Spain)

19

A Gravitational Wave Background from Reheating after Hybrid Inflation

García-Bellido, Juan; García Figueroa, Daniel; Sastre, Alfonso
2007-11-27

Digital.CSIC (Spain)