998 resultados para 13-129


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This brief chapter describes the occurrence Macrocyclops distinctus in the littoral zone of the Rybinsk Reservoir. Sampling was undertaken in summer and autumn 1961. In order to facilitate distinction of M. distinctus and Macrocyclops fuscus the author presents drawings of the whole species and certain characteristic parts of the body, and also gives a description of M. distinctus, comparing it with M. fuscus.

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The author summarises observations on the behaviour of Polyphemus pediculus and functions of its extremities in the process of feeding. The crustacean Polyphemus pediculus seizes its prey, kills it and pulverises its food with the help of its extremities. Therefore for a study of its feeding method was necessary not only to have been acquainted in detail with the structure of its extremities, but also to have observed their interaction for the accomplishment of the stated functions.

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Eudiaptomus vulgaris Schmeil is the most abundant copepod in Lake Maggiore and forms also, in respect to other entomostraca, the most important element, through its average biomass and because it is fairly numerous throughout the year. Plankton samples collected in a systematic and quantitative way, gave the opportunity to study some aspects of the dynamics of the population of this copepod, in safety in view of the uncertainty which in this kind of study can ensue when samples are taken only at a single station - in consequence of the changes in size of population between different water masses. The results of the biometrical observations are of the population of Eudiaptomus vulgaris is presented.

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Pseudomonas aeruginosa has for some time been known as a denitrifier. Pseudomonas aeruginosa was chosen for further studies, because P. aeruginosa occurs abundantly in Plusssee and moreover there are contradictory assertions on the gas products of denitrification by this bacteria. In experimental research the pattern of growth and gas production of Pseudomonas aeruginosa on nutrient broth was studied.

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Experiments were carried out by the method of direct effect of the tested substance on increase of biomass (1,2). Daphnia magna was cultured under laboratory conditions.The author concludes that concentrations of aniline from 5000 to 0.1 mg/1 appear acutely lethal. The disturbance of feeding, reproduction, the disorganization of the nervous system, speak of the toxicity of the substance.

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The winter eggs of Daphnia pulex, after passing safely through the winter , develop and hatch in the spring, multiplying by themselves, while some males emerging among them with the changes in environment produce fertile eggs, which are universally known as winter eggs . This study researches the factors governing the development of winter eggs through experiments.

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Since 1975 the wildlife interest of the Somerset Levels and Moors have been assessed. Detailed information has been obtained on the conservation interest of meadows, breeding and wintering bird populations and the botany of aquatic habitats (rhynes). Little work to date has been carried out on the terrestrial and aquatic invertebrate fauna. The prime aim of this survey was to sample a wide variety of rhynes in order to obtain information on the nature and distribution of aquatic invertebrates.

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Described in this thesis are measurements made of the thick-target neutron yield from the reaction 13C(α, n)16O. The yield was determined for laboratory bombarding energies between 0.475 and 0.700 MeV, using a stilbene crystal neutron detector and pulse-shape discrimination to eliminate gamma rays. Stellar temperatures between 2.5 and 4.5 x 108 oK are involved in this energy region. From the neutron yield was extracted the astrophysical cross-section factor S(E), which was found to fit a linear function: S(E) = [(5.48 ± 1.77) + (12.05 ± 3.91)E] x 105 MeV-barns, center-of-mass system. The stellar rate of the 13C(α, n)16O reaction if calculated, and discussed with reference to helium burning and neutron production in the core of a giant star.

Results are also presented of measurements carried out on the reaction 9Be(α, n)12C, taken with a thin Be target. The bombarding energy-range covered was from 0.340 to 0.680 MeV, with excitation curves for the ground- and first excited-state neutrons being reported. Some angular distributions were also measured. Resonances were found at bombarding energies of ELAB = 0.520 MeV (ECM = 0.360 MeV, Γ ~ 55 keV CM, ωγ = 3.79 eV CM) and ELAB = 0.600 MeV (ECM = 0.415 MeV, Γ ˂ 4 keV CM, ωγ = 0.88 eV CM). The astrophysical rate of the 9Be(α, n)12C reaction due to these resonances is calculated.

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High-resolution, natural-abundance 13C spectra have been obtained from a wide variety of organic compounds; 13C chemical shifts and coupling constants have been correlated with other molecular properties.

Geminal and vicinal, carbon-proton couplings in benzene and the five- and six-membered aromatic heterocycles have been related to the corresponding proton-proton couplings in substituted ethylenes. The carbon-proton coupling constants in benzene are JCCH = + 1.0, JCCCH = +7.4 and JCCCH = -1.1 Hz. Extended Hückel wavefunctions are uniformly poor in explaining the long-range, carbon-proton couplings in aromatic systems.

Couplings between carbon and elements other than hydrogen have been observed in proton decoupled 13C spectra. All of the carbons in fluorobenzene and 1-fluoronaphthalene, but only six of the carbons in 2-fluoronaphthalene are coupled to the fluorine. One-bond, carbon-phosphorus coupling in trialkylphosphines is negative, while one-bond, carbon-phosphorus coupling in tetra-alkylphosphonium ions is positive. Atoms which do not use hybrid orbitals to form bonds to carbon (F, P(III), Se, Te) may have negative, one-bond coupling constants because of the failure of the average energy approximation. One-bond couplings between carbon and carbon, silicon, tin, lead and mercury appear to be explainable in terms of an effective nuclear charge and the s-bond order of the metal. Couplings between carbon and nitrogen and phosphorus (IV) have significant negative contributions to the Fermi contact coupling expression, though, within one series, correlations with s-bond order may be valid. Carbon-carbon coupling in cyclopropane derivatives (10-15 Hz) is consistent with a high degree of p character in the interior orbitals. Some two- and three-bond carbon-carbon coupling constants have also been observed.

Substituent effects of hydroxyl groups on the 13C chemical shifts of continuous-chain alkanes depend both on steric and electronic factors. The hydroxyl substituent effects in the long-chain, primary alcohols are α = -48.3, β = -10.2, and γ = +6.0 ppm. The upfield γ effect is attributed to steric crowding in the gauche conformations. Additivity of the hydroxyl and carbonyl and alkyl substituent effects in alkyl-substituted cyclohexanols and cyclohexanones has been demonstrated.

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The isotopic and elemental abundances of noble gases in the solar system are investigated, using simple mixing models and mass-spectrometric measurements of the noble gases in meteorites and terrestrial rocks and minerals.

Primordial neon is modeled by two isotopically distinct components from the interstellar gas and dust. Neon from the gas dominates solar neon, which contains about ten times more 20Ne than 22Ne. Neon from the dust is represented in meteorites by neon-E, with 20Ne/22Ne less than 0.6. Isotopic variations in meteorites require neon from both dust and gas to be present. Mixing dust and gas without neon loss generates linear correlation lines on three-isotope and composition-concentration diagrams. A model for solar wind implantation predicts small deviations from linear mixing, due to preferential sputtering of the lighter neon isotopes.

Neon in meteorites consists of galactic cosmic ray spallation neon and at least two primordial components, neon-E and neon-S. Neon was measured in several meteorites to investigate these end- members. Cosmogenic neon produced from sodium is found to be strongly enriched in 22Ne. Neon measurements on sodium-rich samples must be interpreted with care so not to confuse this source of 22Ne with neon-E, which is also rich in 22Ne.

Neon data for the carbonaceous chondrite Mokoia show that the end member composition of neon-Si in meteorites is 20Ne/22Ne = 13.7, the same as the present solar wind. The solar wind composition evidently has remained constant since before the compaction of Mokoia.

Ca, Al-rich inclusions from the Allende meteorite were examined for correlation between neon-E and oxygen or magnesium isotopic anomalies. 22Ne and 36Ar enrichments found in some inclusions are attributed to cosmic- ray-induced reactions on Na and Cl, not to a primordial component. Neon-E is not detectably enriched in Allende.

Measurements were made to determine the noble gas contents of various terrestrial rocks and minerals, and to investigate the cycling of noble gases between different terrestrial reservoirs. Beryl crystals contain a characteristic suite of magmatic gases including nucleogenic 21Ne and 22Ne from (α,n) reactions, radiogenic 40Ar, and fissiogenic 131-136Xe from the decay of K and U in the continental crust. Significant concentrations of atmospheric noble gases are also present in beryl.

Both juvenile and atmospheric noble gases are found in rocks from the Skaergaard intrusion. The ratio 40Ar/36Ar (corrected for in situ decay of 40K) correlates with δ18O in plagioclase. Atmospheric argon has been introduced into samples that have experienced oxygen-isotope exchange with circulating meteoric hydrothermal fluids. Unexchanged samples contain juvenile argon with 40Ar/36Ar greater than 6000 that was trapped from the Skaergaard magma.

Juvenile and atmospheric gases have been measured in the glassy rims of mid-ocean ridge (MOR) pillow basalts. Evidence is presented that three samples contain excess radiogenic 129Xe and fission xenon, in addition to the excess radiogenic 40Ar found in all samples. These juvenile gases are being outgassed from the upper-mantle source region of the MOR magma. No isotopic evidence has been found here for juvenile primordial noble gases accompanying the juvenile radiogenic gases in the MOR glasses. Large argon isotopic variations in a single specimen provide a clear indication of the late-stage addition of atmospheric argon, probably from seawater.

The Skaergaard data demonstrate that atmospheric noble gases dissolved in ground water can be transferred into crustal rocks. Subduction of oceanic crust altered by seawater can transport atmospheric noble gases into the upper mantle. A substantial portion of the noble gases in mantle derived rocks may represent subducted gases, not a primordial component as is often assumed.

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[ES]En la Facultad de Informática de Donostia-San Sebastián siempre se ha podido encontrar interés por la renovación pedagógica. Los desarrollos conceptuales y tecnológicos que hemos experimentado en las últimas décadas en nuestra materia de estudio han llevado a continuos cambios en el diseño de contenidos y formas docentes. En el año 2010, en la Facultad de Informática, comenzábamos a dar forma a una iniciativa que perseguía, principalmente, promover la reflexión individual y grupal sobre nuestra docencia. La iniciativa fue liderada desde el equipo directivo del centro pero en todo momento se ha considerado que debe estar alimentada por la voluntad individual y colectiva de compromiso con un modelo docente compartido, generado desde la integración de propuestas y experiencias del propio profesorado de la facultad. A nuestro entender, la idea clave de este modelo es definir un marco de actuación capaz de integrar las individualidades pero que promueva la concepción de equipo en busca de la mejor formación de nuestros estudiantes. Durante este tiempo hemos organizado seminarios y jornadas en los que ha primado la formación colectiva en nuestro contexto, para promover la coordinación y colaboración. En esta ocasión, entendimos que podía ser el momento de abrir nuestras experiencias a otros centros de la UPV/EHU y, además, animarlos a que nos expusieran las suyas. Así han surgido las Jornadas de Intercambio de Experiencias Docentes, de las que este volumen recoge las ponencias presentadas. Las 21 ponencias presentadas, que provienen de 11 centros distintos de la UPV/EHU, son un reflejo del interés suscitado por la propuesta de estas jornadas. Los temas abordados en las ponencias van desde experiencias y reflexiones docentes en el uso metodologías activas, pasando por análisis de asuntos de organización y gestión, y tocando los trabajos de fin de grado, a experiencias novedosas de formación en alternancia con la empresa o experiencias promovidas por los propios estudiantes.

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A series of zinc tellurite glasses of 75TeO(2)-20ZnO-(5-x)La2O3-xEr(2)O(3) (x=0.02, 0.05, and 0.1 mol%) with the different hydroxl groups were prepared by the conventional melt-quenching method. Infrared spectra were measured in order to estimate the exact content of OH- groups in samples. The observed increase of the fluorescence lifetime with the oxygen bubbling time has been related to the reduction in the OH- content concentration as evidenced by IR transmission spectra. Various nonradiative decay rates from I-4(13/2) of Er3+ with. the change of OH content were determined from the fluorescence lifetime and radiative decay rates were calculated on the basis of Judd-Ofelt theory. (c) 2005 Elsevier B.V. All rights reserved.