1,303 research outputs found
Bacterioplankton and Phytoplankton Production in a Large Patagonian Reservoir (Republica-Argentina)
No full textFil: Di Siervi, Migiel Angel. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Mariazzi, Aldo A.. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Donadelli, Jorge L.. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin
Sostenere le comunità nelle pratiche di innovazione place-based. Nuovi paradigmi per le pratiche di homemaking in un Villaggio Urbano Integrato per la cura della demenza.
No full textNell’ambito delle terapie non-farmacologiche per la cura della demenza, e dell’importanza che gli spazi rivestono per la loro efficacia, la ricerca presentata in questo paper descrive e identifica processi e dinamiche di homemaking, che portano alla co-creazione degli spazi interni di un ambiente di cura. Tali pratiche consentono alle persone con demenza e ai loro caregiver di stabilire un senso di appartenenza nei confronti dei nuovi spazi in cui vivono, all’interno di un Villaggio Urbano Integrato per la demenza, dove l’ambiente di cura non è più confinato all’interno di un perimetro sorvegliato, ma si sovrappone e si fonde con l’ambiente urbano esistente, consentendo agli ospiti di vivere una vita quotidiana normale e significativa, insieme alla comunità di cittadini che vive nel quartiere, in un’ottica di inclusività
Limnología en la Argentina: un acontecimiento histórico.
No full textThis short review includes major books, articles and episodes concerned with studies on inland waters that have affected the development of limnology in Argentina.Freshwater Biological AssociationPrograma para el estudio y uso sustentable de la biota austral (ProBiota) - Serie Documentos RelacionadosDebe citarse:
López, H. L. & A. A. Mariazzi. 1994. Limnology in Argentina: an historical account. Freshwater Forum, Ambleside, UK, 4(3): 169-178. ISSN 0961-4664.
Deposited by: Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plat
CO2 Laser irradiation of GeO2 planar waveguide fabricated by rf-sputtering
No full textGeO2 transparent glass ceramic planar waveguides were fabricated by a RF-sputtering technique and then irradiated by a pulsed CO2 laser. The effects of CO2 laser processing on the optical and structural properties of the waveguides were evaluated by different techniques including m-line, micro-Raman spectroscopy, atomic force microscopy, and positron annihilation spectroscopy. After laser annealing, an increase of the refractive index of approximately 0.04 at 1.5 μm and a decrease of the attenuation coefficient from 0.9 to 0.5 db/cm at 1.5 μm was observed. Raman spectroscopy and microscopy results put in evidence that the system embeds GeO2 nanocrystals and their phase varies with the irradiation time. Moreover, positron annihilation spectroscopy was used to study the depth profiling of the as prepared and laser annealed samples. The obtained results yielded information on the structural changes produced after the irradiation process inside the waveguiding films of approximately 1 μm thickness. In addition, a density value of the amorphous GeO2 samples was evaluated.Fil: Chiasera, A.. Consiglio Nazionale delle Ricerche. Istituto di Fotonica e Nanotecnologie; ItaliaFil: Macchi, Carlos Eugenio. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Mariazzi, C.. Università di Trento. Dipartimento di Fisica; ItaliaFil: Valligatla, S.. Consiglio Nazionale delle Ricerche. Istituto di Fotonica e Nanotecnologie; Italia. University of Hyderabad. School of Physics; India. Università di Trento. Dipartimento di Fisica; ItaliaFil: Lunelli, L.. Bruno Kessler Foundation; Italia. National Research Council Institute of Biophysics; ItaliaFil: Pederzolli, C.. Bruno Kessler Foundation; ItaliaFil: Rao, D. N.. University of Hyderabad. School of Physics; IndiaFil: Somoza, Alberto Horacio. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Brusa, R. S.. Università di Trento. Dipartimento di Fisica; ItaliaFil: Ferrari, M.. Consiglio Nazionale delle Ricerche. Istituto di Fotonica e Nanotecnologie; Itali
Biología Acuática | Número 18
No full textMedición de la producción bacteriana en un embalse patagónico. Aspectos metodológicos | Miguel A. Di Siervi. Aldo A. Mariazzi y Jorge L. Donadelli Medición de la producción bacteriana en un embalse patagónico. Importancia de bacterias libres y adheridas | Miguel A. Di Siervi, Aldo A. Mariazzi y Jorge L. Donadelli Medición de la producción bacteriana en un embalse patagónico. Variaciones de cortos períodos de tiempo | Miguel A. Di Siervi, Aldo A. Mariazzi y Jorge L. Donadelli Medición de la producción bacteriana en un embalse patagónico. Variaciones espacio temporales v relaciones con la producción primaria | Miguel A. Di Siervi, Aldo A. Mariazzi y Jorge L. Donadell
Time of Flight system to investigate positronium cooling
No full textA positronium Time of Flight (TOF) apparatus, conceived to work with continuous positron beams of intensity up to ∼10 6 positrons/s, was developed. The geometry of the TOF chamber and the acquisition chain are described in detail. The performances of the set up were preliminary tested with a laboratory positron beam of ∼5 × 10 3 positrons/s by measuring the Time of Flight of Ps emitted from oxidized nanochannels produced in a Si single crystal. A TOF spectrum of ∼10 4 events was collected in 9 days with a time resolution of 8 ns. The analysis of the TOF spectrum is discussed. This apparatus is going to be assembled at the intense positron source NEPOMUC at FRM-II reactor, where the measurement time of each spectrum will be reduced to less than 2 h, making this TOF system appropriate to investigate positronium emission after cooling in porous materials held at cryogenic temperature. © The Author(s) 2012
Production of cold positronium atoms
No full textPositronium will play a primary role in the next generation of antimatter experiments through the following antihydrogen production reaction: (p) over bar + Ps* ->(p) over bare(+) + e(-). In order to study antimatter physical properties (CPT (charge, parity, time) invariance and principle of equivalence test) it is necessary to keep this system at the lowest possible (sub-kelvin) temperatures. This requires the generation of a suitable flux of cold Ps atoms in a vacuum, a non-trivial requirement at the light of the present experimental results. In this paper we discuss the state of the actual knowledge on positronium formation and consequent emission from metallic surfaces and insulators and we show the opportunity to use suitable porous materials to cool positronium through collisions with the inner walls of the pores. We get a rough indication on the geometrical parameters of the pore and we propose a simple experiment to obtain the kinetic energy - and therefore the equivalent temperature - of emitted positronium without using a positron beam
Positronium cooling at cryogenic temperature for advanced experiments
No full textNew Ps spectroscopy measurements, formation of antihydrogen for antimatter-matter comparison experiments, production of Ps beams require the efficient production of cooled positronium in vacuum. At present the most efficient positron-positronium converters are silica based ordered or disordered porous materials, in which formed Ps decreases its kinetic energy by collisional cooling. Recently new positron-positronium converters based on oxidized nanochannels in silicon were found to be very promising because of the tunability of the nanochannel size, which allows to overcome the limits imposed to the Ps cooling by the quantum confinement. With these converters, Ps with temperatures as low as 150 K was detected in vacuum by a TOF apparatus. The Ps formation, quantum confinement, collisional cooling and emission into vacuum from nanochanneled silicon will be discussed in light of recent results. © Published under licence by IOP Publishing Ltd
Depth profiling and morphological characterization of AlN thin films deposited on Si substrates using a reactive sputter magnetron
No full textIt is well-known that the characteristics of aluminum nitride thin films mainly depend on their
morphologies, the quality of the film-substrate interfaces and the open volume defects. A study of the depth
profiling and morphological characterization of AlN thin films deposited on two types of Si substrates is
presented. Thin films of thicknesses between 200 and 400 nm were deposited during two deposition times
using a reactive sputter magnetron. These films were characterized by means of X-ray diffraction and
imaging techniques (SEM and TEM). To analyze the composition of the films, energy dispersive X-ray
spectroscopy was applied. Positron annihilation spectroscopy, specifically Doppler broadening spectroscopy,
was used to gather information on the depth profiling of open volume defects inside the films and the AlN
films-Si substrate interfaces. The results are interpreted in terms of the structural changes induced in the
films as a consequence of changes in the deposition time (i.e., thicknesses) and of the orientation of the
substrates
Structural Evolution and Medium Range Order in Permanently Densified Vitreous SiO2
No full textPositron annihilation lifetime spectroscopy is employed to measure the size of the interstitial void spaces characterizing the structure of a set of permanently densified SiO2 glasses. The average volume of the voids is markedly affected by the densification process and linearly shrinks by almost an order of magnitude after a relative density variation of 22%. In addition, x-ray diffraction shows that this change of density does not modify appreciably the short range order, which remains organized in SiO4 tetrahedra. These results strongly suggest a porous medium description for v-SiO2 glasses where the compressibility and the medium range order are dominated by the density variation of the voids volume up to densities close to that of alpha-quartz
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