[A Cellular Automata Model for a Community Comprising Two Plant Species of Different Growth Forms].

Science.gov (United States)

Frolov, P V; Zubkova, E V; Komarov, A S

2015-01-01

A cellular automata computer model for the interactions between two plant species of different growth forms--the lime hairgrass Deschampsia caespitosa (L.) P. Beauv., a sod cereal, and the moneywort Lysimachia nummularia L., a ground creeping perennial herb--is considered. Computer experiments on the self-maintenance of the populations of each species against the background of a gradual increase in the share of randomly eliminated individuals, coexistence of the populations of two species, and the effect of the phytogenous field have been conducted. As has been shown, all the studied factors determine the number of individuals and self-sustainability of the simulated populations by the degree of their impact. The limits of action have been determined for individual factors; within these limits, the specific features in plant reproduction and dispersal provide sustainable coexistence of the simulated populations. It has been demonstrated that the constructed model allows for studying the long-term developmental dynamics of the plants belonging to the selected growth forms.

Assessment of impact of acoustic and nonacoustic parameters on performance and well-being

Science.gov (United States)

Mellert, Volker; Weber, Reinhard; Nocke, Christian

2004-05-01

It is of interest to estimate the influence of the environment in a specific work place area on the performance and well-being of people. Investigations have been carried out for the cabin environment of an airplane and for class rooms. Acoustics is only one issue of a variety of environmental factors, therefore the combined impact of temperature, humidity, air quality, lighting, vibration, etc. on human perception is the subject of psychophysical research. Methods for the objective assessment of subjective impressions have been developed for applications in acoustics for a long time, e.g., for concert hall acoustics, noise evaluation, and sound design. The methodology relies on questionnaires, measurement of acoustic parameters, ear-related signal processing and analysis, and on correlation of the physical input with subjective output. Methodology and results are presented from measurements of noise and vibration, temperature and humidity in aircraft simulators, and of reverberation, coloring, and lighting in a primary school, and of the environmental perception. [The work includes research with M. Klatte, A. Schick from the Psychology Department of Oldenburg University, and M. Meis from Hoerzentrum Oldenburg GmbH and with the European Project HEACE (for partners see www.heace.org).

Optimization of solid-phase extraction and liquid chromatography-tandem mass spectrometry for simultaneous determination of capilliposide B and its active metabolite in rat urine and feces: Overcoming nonspecific binding.

Science.gov (United States)

Cheng, Zhongzhe; Zhou, Xing; Li, Wenyi; Hu, Bingying; Zhang, Yang; Xu, Yong; Zhang, Lin; Jiang, Hongliang

2016-11-30

Capilliposide B, a novel oleanane triterpenoid saponin isolated from Lysimachia capillipes Hemsl, showed significant anti-tumor activities in recent studies. To characterize the excretion of Capilliposide B, a reliable liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for simultaneous determination of Capilliposide B and its active metabolite, Capilliposide A in rat urine and feces. Sample preparation using a solid-phase extraction procedure was optimized by acidification of samples at various degrees, providing extensive sample clean-up with a high extraction recovery. In addition, rat urinary samples were pretreated with CHAPS, an anti-adsorptive agent, for overcoming nonspecific analytes adsorption during sample storage and process. The method validation was conducted over the curve range of 10.0-5000ng/ml for both analytes. The intra- and inter-day precision and accuracy of the QC samples showed ≤11.0% RSD and -10.4-12.8% relative error. The method was successfully applied to an excretion study of Capilliposide B following intravenous administration. Copyright © 2016 Elsevier B.V. All rights reserved.

Communities of the alliance Bidenti frondosae-Salicion triandrae Golub 2004 on the territory of the Lower Volga Valley

Directory of Open Access Journals (Sweden)

V. B. Golub

2010-01-01

Full Text Available Communities of the alliance Bidenti frondosae-Salicion triandrae Golub 2004 – is a shrub communities with dominant Salix triandra и Amorpha fruticosa along the watercourse banks and lakes in the Lower Volga valley. Diagnostis species of alliance: Fraxinus pennsylvanica, Bidens frondosa, Xanthium strumarium, Thalictrum flavum. The alliance is also diagnosed by the absence or non-significant presence of species number, characteristic of communities with dominant Salix triandra on more northern territories, which are supposed to refer to the alliance Salicion triandrae Th. Muller et Gors 1958. There are Salix fragilis, Salix viminalis, Urtica dioica, Galium palustre, Lythrum salicaria, Lysimachia vulgaris. One more peculiarity of communities of alliance Bidenti frondosae-Salicion triandrae should be noted. It lies in the fact that Salix triamdra in the Lower Volga is represented by lately flowering ecotype. Salix triamdra blooms here after the water abatement in June-Jule. It is 2-3 months later that in other river flood-plains characterized by Salix triamdra earlier flooding. Communities of the alliance including four accociations: Bidenti frondosae-Salicion triandrae, Leersio-Salicetum triandrae, Carici melanostachyаe-Amorphetum fruticosae, Rubo caesii-Amorphetumfruticosae, which have different stage of widespread in the territory of the Lower Volga.

Evaluation of the DNA barcodes in Dendrobium (Orchidaceae) from mainland Asia.

Science.gov (United States)

Xu, Songzhi; Li, Dezhu; Li, Jianwu; Xiang, Xiaoguo; Jin, Weitao; Huang, Weichang; Jin, Xiaohua; Huang, Luqi

2015-01-01

DNA barcoding has been proposed to be one of the most promising tools for accurate and rapid identification of taxa. However, few publications have evaluated the efficiency of DNA barcoding for the large genera of flowering plants. Dendrobium, one of the largest genera of flowering plants, contains many species that are important in horticulture, medicine and biodiversity conservation. Besides, Dendrobium is a notoriously difficult group to identify. DNA barcoding was expected to be a supplementary means for species identification, conservation and future studies in Dendrobium. We assessed the power of 11 candidate barcodes on the basis of 1,698 accessions of 184 Dendrobium species obtained primarily from mainland Asia. Our results indicated that five single barcodes, i.e., ITS, ITS2, matK, rbcL and trnH-psbA, can be easily amplified and sequenced with the currently established primers. Four barcodes, ITS, ITS2, ITS+matK, and ITS2+matK, have distinct barcoding gaps. ITS+matK was the optimal barcode based on all evaluation methods. Furthermore, the efficiency of ITS+matK was verified in four other large genera including Ficus, Lysimachia, Paphiopedilum, and Pedicularis in this study. Therefore, we tentatively recommend the combination of ITS+matK as a core DNA barcode for large flowering plant genera.

Evaluation of the DNA barcodes in Dendrobium (Orchidaceae from mainland Asia.

Directory of Open Access Journals (Sweden)

Songzhi Xu

Full Text Available DNA barcoding has been proposed to be one of the most promising tools for accurate and rapid identification of taxa. However, few publications have evaluated the efficiency of DNA barcoding for the large genera of flowering plants. Dendrobium, one of the largest genera of flowering plants, contains many species that are important in horticulture, medicine and biodiversity conservation. Besides, Dendrobium is a notoriously difficult group to identify. DNA barcoding was expected to be a supplementary means for species identification, conservation and future studies in Dendrobium. We assessed the power of 11 candidate barcodes on the basis of 1,698 accessions of 184 Dendrobium species obtained primarily from mainland Asia. Our results indicated that five single barcodes, i.e., ITS, ITS2, matK, rbcL and trnH-psbA, can be easily amplified and sequenced with the currently established primers. Four barcodes, ITS, ITS2, ITS+matK, and ITS2+matK, have distinct barcoding gaps. ITS+matK was the optimal barcode based on all evaluation methods. Furthermore, the efficiency of ITS+matK was verified in four other large genera including Ficus, Lysimachia, Paphiopedilum, and Pedicularis in this study. Therefore, we tentatively recommend the combination of ITS+matK as a core DNA barcode for large flowering plant genera.

Flowers of Çoruh Valley

Directory of Open Access Journals (Sweden)

Ramazan Çakmakçı

2018-01-01

Full Text Available Coruh valley has an important biological diversity in term of plants, flora-fauna, wildlife and ecosystems. These regions contain the landraces, wild and weedy relatives, other wild, herbaceous and flowering trees, herbaceous flowering plants, medicinal and aromatic and flowering and ornamental shrubs plants species which are especially economically important plant for floriculture, eco-tourism, botanical tourism and nature tourism. Many important medicinal and aromatic and ornamental plants species are found in this region and naturally grow. It is considered that Acantholimon, Achillea, Alkanna, Allium, Amygdalus, Angelica, Anemone, Anthemis, Arabis, Arctium, Artemisia, Asparagus, Asperula, Astragalus, Calamintha, Calendula, Calutea, Campanula, Capparis, Cardamine, Centaurea, Cephalanthera, Cephalaria, Chelidonium, Chenopodium, Chysanthemum, Colchicum, Consolida, Coriandrum, Cornus, Coronilla, Cerasus, Cotoneaster, Crataegus, Crocus, Cyclamen, Dactylorhiza, Digitalis, Dianthus, Draba, Echinops, Equisetum, Ferula, Filipendula, Fritillaria, Fumaria, Gagea, Galanthus, Galium, Genista, Gentiana, Geranium, Geum, Gladiolus, Glychirrza, Helichrysum, Hesperis, Hypericum, İnula, İris, Isatis, Juniperus, Lilium, Linaria, Linum, lysimachia, Malus, Malva, Marrubium, Melissa, Mentha, Micromeria, Morina, Muscari, Mysotis, Narcissus, Neotchichatchewia, Nepeta, Onobrychis, Orchis, Ornithogalum, Origanum, Paeonia, Papaver, Pedicularis, Peganum, Phelypaea, Platanthera, Plantago, Pilosella, Pelargonium, Potentilla, Polygonum, Polygala, Primula, Punica, Prunus, Pyrus, Ranunculus, Rhamnus, Rhododendron, Rhus, Rosa, Rubia, Rubus, Rumex, Salvia, Sambucus, Satureja, Scilla, Scorzonera, Scutellaria, Sedum, Sempervivum, Sideritis, Sophora, Sorbus, Stachys, Tanecetum, Teucrium, Thymus, Trigonella, Tulipa, Tussilago, Uechtriitzia, Vaccinium, Verbascum, Verbena, Veronica, Viburnum and Ziziphora species commonly found in the region may be may be evaluated economically.

Floristic diversity of posavina's floodplain forests in serbia and their wider geographical context

International Nuclear Information System (INIS)

Jurisic, B.; Puvaca, N.

2014-01-01

In order to detect floristic divergence of analysed stands we applied TWINSPAN classification and ordinary Correspondence Analysis. Both analyses have shown an almost identical result of floristic composition, where 114 studied samples were grouped into seven association groups at the third twinspan classification level. These seven groups, successively from the most humid to most dry, comprising two large groups of plant associations, completely corresponding to two alliances: Forest of Pedunculate Oak and Alder and Forest of Pedunculate Oak and Hornbeam. SIMPER procedure have shown tahat within the first 20.51% of cumulative contribution, the floristic divegence among the studied forest stands includes 13 taxa: Carpinus betulus., Fraxinus angustifolia, Quercus cerris, Amorpha fruticosa, Convallaria majalis, Crataegus oxyacantha, Quercus robur, Lysimachia nummularia, Tamus communis, Galium aparine, Rubus caesius, Ulmus carpinifolia and Ajuga reptans. ANOSIM analysis were used to determine the degree of floristic discontinuity. It was largest between forest of Pedunculate Oak, Hornbeam and Turkey Oak and forest of Pedunculate Oak and Ash (statistics R = 0.8824 (p<0.001)). The lowest floristic dissimilarity was between the forest of Pedunculate Oak, Hornbeam and Turkey Oak and forest of Pedunculate Oak, Hornbeam and Turkey Oak with Lindens, where R = 0.2009 (p<0.01). Posavina floodplain forests in Serbia generally show good agreement with analogous communities in neighbouring countries in the Balkan peninsula and Central Europe. (author)

Spatial patterns and links between microbial community composition and function in cyanobacterial mats

KAUST Repository

Alnajjar, Mohammad Ahmad; Ramette, Alban; Kü hl, Michael; Hamza, Waleed; Klatt, Judith M.; Polerecky, Lubos

2014-01-01

We imaged reflectance and variable fluorescence in 25 cyanobacterial mats from four distant sites around the globe to assess, at different scales of resolution, spatial variabilities in the physiological parameters characterizing their photosynthetic capacity, including the absorptivity by chlorophyll a (Achl), maximum quantum yield of photosynthesis (Ymax), and light acclimation irradiance (Ik). Generally, these parameters significantly varied within individual mats on a sub-millimeter scale, with about 2-fold higher variability in the vertical than in the horizontal direction. The average vertical profiles of Ymax and Ik decreased with depth in the mat, while Achl exhibited a sub-surface maximum. The within-mat variability was comparable to, but often larger than, the between-sites variability, whereas the within-site variabilities (i.e., between samples from the same site) were generally lowest. When compared based on averaged values of their photosynthetic parameters, mats clustered according to their site of origin. Similar clustering was found when the community composition of the mats' cyanobacterial layers were compared by automated ribosomal intergenic spacer analysis (ARISA), indicating a significant link between the microbial community composition and function. Although this link is likely the result of community adaptation to the prevailing site-specific environmental conditions, our present data is insufficient to identify the main factors determining these patterns. Nevertheless, this study demonstrates that the spatial variability in the photosynthetic capacity and light acclimation of benthic phototrophic microbial communities is at least as large on a sub-millimeter scale as it is on a global scale, and suggests that this pattern of variability scaling is similar for the microbial community composition. © 2014 Al-Najjar, Ramette, Kühl, Hamza, Klatt and Polerecky.

Floral Visitors of Three Asteraceae Species in a Xeric Environment in Central Mexico.

Science.gov (United States)

Figueroa-Castro, Dulce María; González-Tochihuitl, Guadalupe; Rivas-Arancibia, Sombra Patricia; Castaño-Meneses, Gabriela

2016-12-01

We describe the spatial variation in the structure and composition of the communities of insects visiting the inflorescences of Flaveria ramosissima Klatt, Florestina pedata (Cav.) Cass., and Parthenium bipinnatifidum (Ort.) Rollins (Asteraceae) in a xeric environment in Central Mexico. Inflorescences of the three Asteraceae were visited by a total of 96 species of Hymenoptera, Diptera, Lepidoptera, Coleoptera, and Hemiptera. Total species richness of floral visitors to the three Asteraceae and total abundance of insects of Fl. pedata and P. bipinnatifidum did not differ between low and high vegetation cover sites. Total abundance of insects visiting the inflorescences of F. ramosissima and abundance of Hymenoptera in all three Asteraceae were higher at the low vegetation coverage (LVC) site than at the high vegetation coverage (HVC) one. Diversity of insects of Fl. pedata and P. bipinnatifidum was higher at the HVC site. However, in F. ramosissima diversity was higher at the LVC site. The communities of insects of each Asteraceae were dissimilar between sites. These differences can be attributed to variation in the abundance of Lepidophora (Diptera: Bombyliidae), Miridae (Hemiptera), Melyridae (Coleoptera), Tiphiidae (Hymenoptera), Myrmecocystus mexicanus Wesmael, and Dorymyrmex grandulus (Forel) (Hymenoptera: Formicidae). The first three insect groups were sensitive to LVC, high temperature, and low humidity, whereas the last three tolerated those same environmental conditions. Changes in temperature, humidity, and resources associated with vegetation coverage seem to differentially affect each species of floral visitors of the three Asteraceae species studied. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Spatial patterns and links between microbial community composition and function in cyanobacterial mats

KAUST Repository

Alnajjar, Mohammad Ahmad

2014-08-06

We imaged reflectance and variable fluorescence in 25 cyanobacterial mats from four distant sites around the globe to assess, at different scales of resolution, spatial variabilities in the physiological parameters characterizing their photosynthetic capacity, including the absorptivity by chlorophyll a (Achl), maximum quantum yield of photosynthesis (Ymax), and light acclimation irradiance (Ik). Generally, these parameters significantly varied within individual mats on a sub-millimeter scale, with about 2-fold higher variability in the vertical than in the horizontal direction. The average vertical profiles of Ymax and Ik decreased with depth in the mat, while Achl exhibited a sub-surface maximum. The within-mat variability was comparable to, but often larger than, the between-sites variability, whereas the within-site variabilities (i.e., between samples from the same site) were generally lowest. When compared based on averaged values of their photosynthetic parameters, mats clustered according to their site of origin. Similar clustering was found when the community composition of the mats\\' cyanobacterial layers were compared by automated ribosomal intergenic spacer analysis (ARISA), indicating a significant link between the microbial community composition and function. Although this link is likely the result of community adaptation to the prevailing site-specific environmental conditions, our present data is insufficient to identify the main factors determining these patterns. Nevertheless, this study demonstrates that the spatial variability in the photosynthetic capacity and light acclimation of benthic phototrophic microbial communities is at least as large on a sub-millimeter scale as it is on a global scale, and suggests that this pattern of variability scaling is similar for the microbial community composition. © 2014 Al-Najjar, Ramette, Kühl, Hamza, Klatt and Polerecky.

Floral diversity, composition and distribution in a montane wetland in hogsback, the eastern cape province, south africa

International Nuclear Information System (INIS)

Omar, M.Y.; Tol, J.J.V.; Maroyi, A.

2016-01-01

The objective of this study was to evaluate plant species diversity, composition and distribution in a montane wetland in Hogsback, Eastern Cape province, South Africa. Twenty four circular plots with radius of 2m were established between March and August 2013 within Hogsback montane wetland. Within each sample plot, the habitat information and species present were recorded including Braun-Blanquet cover-abundance values for all species present in the plot. A total of 41 species belonging to 19 families and 36 genera were recorded. Of the documented species, 7.3% were exotic and endemic to South Africa, indicating diversity and dynamic nature of Hogsback montane wetland flora. Plant families with the highest number of species were: Poaceae (11 species), Asteraceae (six species), Onagraceae and Cyperaceae (three species each) and Lamiaceae with two species. The low number of exotic plant species recorded in Hogsback wetland (three species in total) indicates limited anthropogenic influences. Unique species recorded in Hogsback montane wetland were three species that are endemic to South Africa, namely, Alchemilla capensis Thunb., Helichrysum rosum (P.J. Bergius) Lees and Lysimachia nutans Nees. Five main floristic associations were identified from the Hierarchical Cluster Analysis. The Canonical Correspondence Analysis (CCA) indicated that edaphic factors, particularly area covered with water, erosion category, organic matter content and water table depth were the most important environmental variables measured accounting for the vegetation pattern present in the Hogsback montane wetland. Montane wetlands have a relatively low species richness characterised by unique species compositions which are distinctive and habitat specific. (author)

Winery wastewater treatment by heterogeneous Photo-Fenton process and activated sludges; Depuracion de efluentes vinicolas ediante tratamientos Foto-Fenton en fase heterogenea y lodos activos

Energy Technology Data Exchange (ETDEWEB)

Mosteo, R.; Lalinde, N.; Ormad, Maria O. M.; Ovelleiro, J. L.

2007-07-01

The system composed by heterogeneous Photon-Fenton assisted by solar light and biological treatment based on activated sludge process treats adequately real winery wastewaters. the previous stage based on heterogeneous Photo-Fenton process produces a partial degradation of winery wastewaters and achieves a yield of degradation of organic matter (measured as TOC) close to 50%. The activated sludge process in simple stage doesn't present any operation problems (bulking phenomenon) and achieves a yield of degradation of organic matter of 90%. (Author) 16 refs.

Protease-inhibiting, molecular modeling and antimicrobial activities of extracts and constituents from Helichrysum foetidum and Helichrysum mechowianum (compositae).

Science.gov (United States)

Malolo, Fanny-Aimée Essombe; Bissoue Nouga, Achille; Kakam, Antoine; Franke, Katrin; Ngah, Lidwine; Flausino, Otavio; Mpondo Mpondo, Emmanuel; Ntie-Kang, Fidele; Ndom, Jean Claude; Bolzani, Vanderlan da Silva; Wessjohann, Ludger

2015-01-01

Helichrysum species are used extensively for stress-related ailments and as dressings for wounds normally encountered in circumcision rites, bruises, cuts and sores. It has been reported that Helichysum species are used to relief abdominal pain, heart burn, cough, cold, wounds, female sterility, menstrual pain. From the extracts of Helichrysum foetidum (L.) Moench, six known compounds were isolated and identified. They were 7, 4'-dihydroxy-5-methoxy-flavanone (1), 6'-methoxy-2',4, 4'-trihydroxychalcone (2), 6'-methoxy-2',4-dihydroxychalcone -4'-O-β-D-glucoside (3), apigenin (4), apigenin-7-O-β-D-glucoside (5), kaur-16-en-18-oic acid (6) while two known compounds 3,5,7-trihydroxy-8-methoxyflavone (12), 4,5-dicaffeoyl quinic acid (13) together with a mixture of phytosterol were isolated from the methanol extract of Helichrysum mechowianum Klatt. All the compounds were characterized by spectroscopic and mass spectrometric methods, and by comparison with literature data. Both extracts and all the isolates were screened for the protease inhibition, antibacterial and antifungal activities. In addition, the phytochemical profiles of both species were investigated by ESI-MS experiments. These results showed that the protease inhibition assay of H. foetidum could be mainly attributed to the constituents of flavonoids glycosides (3, 5) while the compound (13) from H. mechowianum contributes to the stomach protecting effects. In addition, among the antibacterial and antifungal activities of all the isolates, compound (6) was found to possess a potent inhibitor effect against the tested microorganisms. The heterogeneity of the genus is also reflected in its phytochemical diversity. The differential bioactivities and determined constituents support the traditional use of the species. Molecular modelling was carried out by computing selected descriptors related to drug absorption, distribution, metabolism, excretion and toxicity (ADMET). Graphical abstractCompounds isolated

Three cryptic new species of Aristea (Iridaceae from southern Africa

Directory of Open Access Journals (Sweden)

P. Goldblatt

2005-08-01

Full Text Available Field work in southern Africa over the past several years has resulted in the discovery of three new species of the sub- Saharan African and Madagascan genus Aristea Aiton, which now comprises some 53 species. Aristea has a pronounced centre in southern Africa and a centre of diversity in the winter rainfall zone of the subcontinent, where all three new species occur, one extending eastward into the adjacent southern edge of the summer rainfall zone. All three novelties have been collected in the past but were confused with related species. A elliptica (subgenus Eucapsulares, confused in the past with A. pusilla (Thunb. Ker Gawl., has a more robust habit, usually with 4 or 5 flower clusters per flowering stem, pale blue flowers, smooth ellipsoid seeds with flattened surface cells, and pollen shed as monads, whereas A. pusilla usually has 1-3 flower clusters per flowering stem, dark blue flowers, pollen shed as tetrads, and globose seeds with faint foveate sculpturing and colliculate surface cells. A. nana (also subgenus  Eucapsulares, known from few collections, and also confused with A. pusilla or A. anceps Eckl. ex Klatt. has the unbranched and leafless flowering stem of the latter but has large green floral spathes, flowers borne on long pedicels, and lacks a leaf subtending the single terminal flower cluster in contrast to nearly sessile flowers in A. pusilla and A. anceps, and in the latter, dry, rusty spathes. A. cistiflora (subgenus Pseudaristea closely resembles A. teretifoha Goldblatt & J.C.Manning but has linear to narrowly sword-shaped leaves and ± secund flowers with the outer tepals only slightly smaller than the inner and with small, dark brown markings at the bases of all the tepals. In contrast, A. teretifolia has narrower, sometimes terete leaves and flowers held upright with the outer tepals notice-ably smaller than the inner and bearing dark markings covering the lower half, whereas the inner tepals are unmarked.

Catalysis under Irradiation in the Presence of Non-Metallic Solids; Catalyse sous irradiation en presence de solides non metalliques; Radiatsionnyj kataliz pri nalichii'nemetallicheskikh tverdykh tel; Radiocatalisis en presencia de solidos no metalicos

Energy Technology Data Exchange (ETDEWEB)

Coekelbergs, R.; Crucq, A.; Decot, J.; Degols, L.; Frennet, A.; Lienard, G.; Timmerman, L. [Laboratoire de Chimie Nucleaire, Institut Interuniversitaire des Sciences Nucleaires et Ecole Royale Militaire, Bruxelles (Belgium)

1963-11-15

Catalytic processes induced by radiation in the presence of non-metallic solids are discussed, attention being given exclusively to the effects associated with modification of the steady state concentration of charge carriers. The effect of such modification on the kinetics and equilibrium of heterogeneous reactions is quantitatively estimated within the framework of the electronic theory of catalysis, due regard being paid to the electronic characteristics of the surface of the solid. In conclusion, the relationship between these phenomena, catalyst activation and transfer of energy, as previously described, is discussed. (author) [French] Les auteurs discutent des processus catalytiques induits par les radiations en presence de solides non metalliques. Ils considerent exclusivement les effets lies a la modification de la concentration stationnaire des porteurs de charge.- L'influence de cette modification sur la cinetique et l'equilibre des reactions heterogenes est evaluee quantitativement dans le cadre de la theorie electronique de la catalyse et en tenant compte de caracteristiques electroniques de la surface du solide. Enfin, ils discutent la relation existant entre ces phenomenes, l'activation des catalyseurs et le transfert d'energie decrits anterieurement. (author) [Spanish] Los autores examinan los procesos cataliticos inducidos por las radiaciones en presencia de solidos no metalicos. Consideran exclusivamente los efectos vinculados con la modificacion de la concentracion estacionaria de los portadores de carga. Sobre la base de la teoria electronica de la catalisis y teniendo en cuenta las caracteristicas electronicas de la superficie del solido, determinan cuantitativamente la influencia de aquella modificacion sobre la cinetica y el equilibrio de las reacciones heterogeneas. Por ultimo, analizan la relacion que existe entre estos fenomenos, la activacion de los catalizadores y la transmision de energia descritas anteriormente. (author) [Russian

Experimental numerical study utilizing CFD in a stratified gasifier operating with biomass; Estudio numerico experimental de un gasificador estratificado que opera con biomasa, utilizando CFD

Energy Technology Data Exchange (ETDEWEB)

Rogel Ramirez, Alejandro

2007-07-01

The central idea behind this work is the developing of a numeric-experimental model, useful to optimize the biomass stratified gasifier design. Firstly, model validation will be carried up by comparison with reference experimental data available. This study describes a 1-D + 2-D numerical model used to simulate the gasification of pine wood pellets in a stratified downdraft gasifier whereby Eulerian conservation equations are solved for particle and gas phase components, velocities and specific enthalpies. The model takes into account the biomass particle process such as heating up, drying, primary pyrolysis of biomass, secondary pyrolysis of tar, homogeneous reactions and heterogeneous combustion/gasification reactions, and particle size change. This CFD model can be used to predict temperature profiles, gas composition, producer gas lower heating value, and carbon conversion efficiency, and the reactor performance when operating parameters and feed properties are changed. The standard {kappa}-{epsilon} and RNG {kappa}-{epsilon} models were used to simulate the turbulent flow conditions. [Spanish] La idea central del presente trabajo es el desarrollo de un modelo numerico- experimental, para optimizar el diseno de gasificadores estratificados de biomasa. Primeramente, el modelo sera validado utilizando datos experimentales disponibles en la literatura. Este estudio describe un modelo numerico 1-D+2-D, utilizado para simular la gasificacion de 'pelets' de madera de pino en un gasificador estratificado de flujos paralelos, en el que se resuelven ecuaciones de conservacion Eulerianas para los componentes de la fase gaseosa, la fase solida, velocidades y entalpias especificas. El modelo considera procesos como: calentamiento, secado de la biomasa, pirolisis primaria de la madera, pirolisis secundaria de los alquitranes, reacciones homogeneas, reacciones heterogeneas de combustion/gasificacion y cambio en el tamano de la particula. Este modelo CFD puede ser

Biodiesel production through in situ transesterification of sunflower seeds by homogeneous and heterogeneous catalysis; Producao de biodiesel atraves de transesterificacao in situ de sementes de girassol via catalise homogenea e heterogenea

Energy Technology Data Exchange (ETDEWEB)

Fama, Paola Ervatti; San Gil, Rosane Aguiar da Silva; Lachter, Elizabeth Roditi, E-mail: lachter@iq.ufrj.b [Universidade Federal do Rio de Janeiro (IQ/UFRJ), RJ (Brazil). Inst. de Quimica

2010-07-01

The objective of this work is to show the results of the in situ transesterification of sunflower seed oil with methanol on basic homogeneous and heterogeneous catalysis for the production of biodiesel. In homogeneous catalysis, the activity of K{sub O}H and K{sub 2}CO{sub 3} were evaluated using the same oil:methanol ratio of 1:90. KOH showed to be more active than K2CO{sub 3}, leading to total conversion in biodiesel after 1h reaction time. In the heterogeneous catalysis the activity of K{sub 2}CO{sub 3}/Al{sub 2}O{sub 3} was comparable to the activity of K{sub 2}CO{sub 3} bulk: 53.0 and 66.6% resp. The properties of samples of biodiesel produced by homogeneous and heterogeneous catalysis were evaluated and are in accordance with the recommended fuel properties. (author)

Coordinated Use of Heterogeneous Infrastructures for Scientific Computing at CIEMAT by means of Grid Technologies; Aprovechamiento Coordinado de las Infraestructuras Heterogeneas para Calculo Cientifico Participadas por el CIEMAT por medio de Tecnologias Grid

Energy Technology Data Exchange (ETDEWEB)

Rubio-Montero, A. J.

2008-08-06

Usually, research data centres maintain platforms from a wide range of architectures to cover the computational needs of their scientists. These centres are also frequently involved in diverse national and international Grid projects. Besides, it is very difficult to achieve a complete and efficient utilization of these recourses, due to the heterogeneity in their hardware and software configurations and their unequal use along the time. This report offers a solution to the problem of enabling a simultaneous and coordinated access to the variety of computing infrastructures and platforms available in great Research Organisms such as CIEMAT. For this purpose, new Grid technologies have been deployed in order to facilitate a common interface which enables the final user to access the internal and external resources. The previous computing infrastructure has not been modified and the independence on its administration has been guaranteed. For a sake of comparison, a feasibility study has been performed with the execution of the Drift Kinetic Equation solver (Dikes) tool, a high throughput scientific application used in the TJ-II Flexible Heliac at National Fusion Laboratory. (Author) 35 refs.

Structural and Magnetic Studies on Iron Oxide Nanoparticles in Hybrid Matrices =

Science.gov (United States)

Silva, Nuno Joao de Oliveira

Este trabalho aborda algumas propriedades magneticas e estruturais de nanoparticulas de oxidos e oxidos-hidroxidos de ferro crescidos em matrizes hibridas orgânicas-inorgânicas. As matrizes hibridas, denominadas di-ureasils e obtidas pelo processo sol-gel, sao compostas por uma rede siliciosa ligada covalentemente por pontes ureia a cadeias orgânicas de diferente peso molecular. A estrutura local dos di-ureasils nao dopados esta modelada como grupos de dominios siliciosos com dimensoes nanometricas, estruturalmente correlacionados no seio de uma matriz rica em polimero. Neste trabalho mostra-se que os di-ureasils permitem o crescimento controlado de oxidos e oxidos-hidroxidos de ferro, incluindo a magnetite, maguemite, oxihidroxinitrato de ferro e ferrihidrite. O crescimento das nanoparticulas de ferrihidrite da-se em condicoes acidas a superficie dos dominios siliciosos, junto aos grupos carbonilo, que funcionam como pontos de nucleacao. Desse modo da-se uma nucleacao heterogenea, onde o tamanho das nanoparticulas depende da concentracao de ferro (entre 1 e 6% em massa), sendo a concentracao de particulas constante. As propriedades magneticas das nanoparticulas de ferrihidrite revelam a existencia de interaccoes antiferromagneticas e de momentos descompensados. A contribuicao destas duas componentes nas curvas de magnetizacao em funcao do campo magnetico pode ser separada usando um metodo aqui proposto, o que permite um adequado estudo da evolucao do momento magnetico com a temperatura. O estudo das propriedades magneticas dinâmicas das particulas de ferrihidrite, atraves de susceptibilidade ac, medidas de relaxacao e medidas de efeito Mossbauer, permitiu estudar a evolucao das interaccoes dipolares em funcao da concentracao de ferro, bem como determinar a distribuicao de barreiras de energia de anisotropia no caso em que essas interaccoes sao desprezaveis. E apresentado um novo metodo para comparacao desta distribuicao com a distribuicao de tamanhos, que

Spin-Transfer-Torque Nano-Oscillators: Fabrication, Characterization and Dynamics

Science.gov (United States)

Costa, Jose Diogo Teixeira Barbosa

Este trabalho aborda algumas propriedades magneticas e estruturais de nanoparticulas de oxidos e oxidos-hidroxidos de ferro crescidos em matrizes hibridas orgânicas-inorgânicas. As matrizes hibridas, denominadas di-ureasils e obtidas pelo processo sol-gel, sao compostas por uma rede siliciosa ligada covalentemente por pontes ureia a cadeias orgânicas de diferente peso molecular. A estrutura local dos di-ureasils nao dopados esta modelada como grupos de dominios siliciosos com dimensoes nanometricas, estruturalmente correlacionados no seio de uma matriz rica em polimero. Neste trabalho mostra-se que os di-ureasils permitem o crescimento controlado de oxidos e oxidos-hidroxidos de ferro, incluindo a magnetite, maguemite, oxihidroxinitrato de ferro e ferrihidrite. O crescimento das nanoparticulas de ferrihidrite da-se em condicoes acidas a superficie dos dominios siliciosos, junto aos grupos carbonilo, que funcionam como pontos de nucleacao. Desse modo da-se uma nucleacao heterogenea, onde o tamanho das nanoparticulas depende da concentracao de ferro (entre 1 e 6% em massa), sendo a concentracao de particulas constante. As propriedades magneticas das nanoparticulas de ferrihidrite revelam a existencia de interaccoes antiferromagneticas e de momentos descompensados. A contribuicao destas duas componentes nas curvas de magnetizacao em funcao do campo magnetico pode ser separada usando um metodo aqui proposto, o que permite um adequado estudo da evolucao do momento magnetico com a temperatura. O estudo das propriedades magneticas dinâmicas das particulas de ferrihidrite, atraves de susceptibilidade ac, medidas de relaxacao e medidas de efeito Mossbauer, permitiu estudar a evolucao das interaccoes dipolares em funcao da concentracao de ferro, bem como determinar a distribuicao de barreiras de energia de anisotropia no caso em que essas interaccoes sao desprezaveis. E apresentado um novo metodo para comparacao desta distribuicao com a distribuicao de tamanhos, que

Seismicity, focal mechanisms, and stress distribution in the Tres Virgenes volcanic and geothermal region, Baja California Sur, Mexico

Energy Technology Data Exchange (ETDEWEB)

Wong, Victor; Munguia, Luis [Centro de Investigacion Cientifica y de Educacion Superior de Ensenada (Mexico)

2006-01-15

In October 1993 we carried out a seismic monitoring in the Tres Virgenes volcanic region in order to record the background seismicity associated with the volcanic structures, the geothermal field and the tectonic features of the area. Hypocenters for 257 microearthquakes were located in the volcanic edifices and along the northwest right-lateral, strike-slip La Virgen fault. Focal depths range from close to the Earth surface to about 8 km. Shallow depths occur mainly in the volcanic edifices. Deeper seismic events occurred outside the volcanic area. The duration magnitudes of the located microearthquakes range between 1 and 3. The Vp/Vs ratio and the low-Q values estimated suggest heterogeneous material properties in the volcanic structures mainly toward the El Azufre fault and the El Aguajito Caldera, where hydrothermal activity has been reported. The P- and T-axes of focal mechanisms for 90 microearthquakes suggest that the region is under N-S compression and E-W extension, in agreement with the regional tectonic stress field of the NW-SE right-lateral strike-slip transform fault system of the Gulf of California. [Spanish] En octubre de 1993 se llevo a cabo un monitoreo sismico en la region volcanica Las Tres Virgenes con el proposito de registrar la actividad sismica asociada a las estructuras volcanicas, al campo geotermico y a la tectonica local. Se localizaron 257 microsismos con hipocentros en los edificios volcanicos y a lo largo de la falla de rumbo, lateral derecha conocida como falla La Virgen. La profundidad focal de los sismos varia desde los muy cercanos a la superficie de la Tierra hasta los 8 km. Las profundidades someras ocurren principalmente en los edificios volcanicos. Los sismos mas profundos ocurren fuera del area volcanica. La magnitud de duracion de los microsismos localizados varia entre 1 y 3. La razon Vp/Vs y los valores bajos de Q que se estimaron en la zona sugieren un material con propiedades heterogeneas bajo las estructuras

CFD modelling of an open core downdraft moving bed biomass gasifier; Modelado de un gasificador estratificado de lecho movil de biomasa, utilizando CFD

Energy Technology Data Exchange (ETDEWEB)

Rogel-Ramirez, A [Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)]. E-mail: ARogelR@iingen.unam.mx

2008-10-15

las reacciones heterogeneas entre el carbon activo y O{sub 2}, CO{sub 2} y H{sub 2}O. El efecto de la turbulencia en la fase gaseosa se determina usando el modelo {kappa}-{epsilon}. El modelo proporciona informacion de la composicion del gas, velocidades y temperaturas de salida y el comportamiento del reactor, y permite cambiar los parametros de operacion, y las propiedades de la alimentacion. Finalmente, se comparan los valores predichos por el modelo con datos disponibles en la literatura, mostrando congruencia satisfactoria desde un punto de vista cualitativo.

Romulea pilosa and R. quartzicola (Iridaceae: Crocoideae, two new species from the southern African winter rainfall region, with nomenclatural corrections

Directory of Open Access Journals (Sweden)

J. C. Manning

2011-12-01

known as R. rosea var. muirii (N.E.Br. Goldblatt & J.C.Manning. Finally, the protologue of R. parviflora Eckl., until now treated under the synonomy of R. obscura Klatt var. obscura, is in fact consistent with R. rosea var. australis (Ewart M.P.de Vos, and we therefore include the name in the synonomy of the latter.

Application of heterogeneous photocatalysis solar and artificial for removal of ammonia nitrogen and total phosphorus in sanitary waste water; Aplicacao da fotocatalise heterogenea solar na remocao de nitrogenio amoniacal e fosforo total em esgoto sanitario

Energy Technology Data Exchange (ETDEWEB)

Francisco, Adriana Ribeiro; Paterniani, Jose Euclides Stipp [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Fac. de Engenharia Agricola], E-mail: z_drica@yahoo.com.br; Kuwakino, Adriana Yuri [Universidade Estadual de Campinas (UNICAMP), Limeira, SP (Brazil). Fac. de Tecnologia

2010-07-01

The advanced oxidative processes (AOP) contribute or to polishing a plenty of effluent treatment, or improvement at any stage of treatment, being heterogeneous photocatalysis the most used among AOP. This study aimed to compare the heterogeneous photocatalysis in solar and artificial wastewater treatment according to the removal of ammonia nitrogen and phosphorus. The photocatalytic reactor using titanium dioxide (TiO{sub 2}) as semiconductor photocatalytic process. The heterogeneous photocatalysis using solar UV consisted material of PET bottles and the sample was added TiO{sub 2} in constant aeration for a period of 360 minutes. In the case of reactor artificial UV light protected by a quartz tube, the process was made in a Pyrex glass reactor, where the sample was undergoing 180 minutes of aeration. The photocatalytic tests for removal of ammonia nitrogen showed more favorable in the photocatalysis of artificial UV than the solar, coming achieve average efficiency of 51% and 32%, respectively. In the case of phosphorus, the situation was reversed, the solar UV photocatalytic average efficiency reached 51% and artificial UV 32 %. (author)

Applications of ultrasound in electrochemistry

Energy Technology Data Exchange (ETDEWEB)

Silva Martinez, Susana

1997-10-01

la magnitud de los transitorios de corriente registrados en el micro-electrodo en presencia del ultrasonido. Se presenta una opcion alternativa para caracterizar reacciones heterogeneas rapidas de transferencia del electron que empleando el ultrasonido como herramienta, de realce del transporte de masa. Dos tecnicas innovadoras, la voltametria corriente muestreada y la voltametria corriente-media muestreada, se desarrollaron durante el curso de esta tesis. La tecnica del voltammetria corriente de muestra senalo los valores del regimen estandar constante de la transferencia heterogenea del electron de hasta 1.2 centimetros s-1 en la presencia del ultrasonido. Esta tecnica se centra en los fenomenos electroquimicos bajo investigacion en el punto de impacto del acontecimiento ultrasonico, producido por colapso asimetrico de la burbuja de cavitacion cerca de la superficie del electrodo. Las dinamicas de la burbuja tambien fueron examinadas bajo las condiciones experimentales empleadas en el presente estudio. El comportamiento de la burbuja fue observado desde la solucion numerica de la ecuacion de RPNNP que describe el movimiento de una burbuja llena gas en una fase homogenea. Esta ecuacion fue resuelta numericamente empleando el metodo de cuarto orden de Runge-Kutta. Finalmente se presenta un estudio preliminar del proceso superficial en presencia del ultrasonido. Los eventos de erosion por corriente fueron registrados a una alta resolucion de tiempo. Estos eventos de corriente fueron atribuidos a la re-oxidacion del metal expuesto como resultado de eventos de cavitacion. Este estudio muestra que la erosion superficial puede ser investigada electroquimicamente in situ dentro del medio de cavitacion.

Properties of self-assembled diluted magnetic semiconductor nanostructures =

Science.gov (United States)

Ankiewicz, Amelia Olga Goncalves

Este trabalho centra-se na investigacao da possibilidade de se conseguir um semicondutor magnetico diluido (SMD) baseado em ZnO. Foi levado a cabo um estudo detalhado das propriedades magneticas e estruturais de estruturas de ZnO, nomeadamente nanofios (NFs), nanocristais (NCs) e filmes finos, dopadas com metais de transicao (MTs). Foram usadas varias tecnicas experimentais para caracterizar estas estruturas, designadamente difraccao de raios-X, microscopia electronica de varrimento, ressonancia magnetica, SQUID, e medidas de transporte. Foram incorporados substitucionalmente nos sitios do Zn ioes de Mn2+ e Co2+ em ambos os NFs e NCs de ZnO. Revelou-se para ambos os ioes dopantes, que a incorporacao e heterogenea, uma vez que parte do sinal de ressonancia paramagnetica electronica (RPE) vem de ioes de MTs em ambientes distorcidos ou enriquecidos com MTs. A partir das intensidades relativas dos espectros de RPE e de modificacoes da superficie, demonstra-se ainda que os NCs exibem uma estrutura core-shell. Os resultados, evidenciam que, com o aumento da concentracao de MTs, a dimensao dos NCs diminui e aumentam as distorcoes da rede. Finalmente, no caso dos NCs dopados com Mn, obteve-se o resultado singular de que a espessura da shell e da ordem de 0.3 nm e de que existe uma acumulacao de Mn na mesma. Com o objectivo de esclarecer o papel dos portadores de carga na medicao das interaccoes ferromagneticas, foram co-dopados filmes de ZnO com Mn e Al ou com Co e Al. Os filmes dopados com Mn, revelaram-se simplesmente paramagneticos, com os ioes de Mn substitucionais nos sitios do Zn. Por outro lado, os filmes dopados com Co exibem ferromagnetismo fraco nao intrinseco, provavelmente devido a decomposicao spinodal. Foram ainda efectuados estudos comparativos com filmes de ligas de Zn1-xFexO. Como era de esperar, detectaram-se segundas fases de espinela e de oxido de ferro nestas ligas; todas as amostras exibiam curvas de histerese a 300 K. Estes resultados suportam a

Regional assessment of anthropogenic impacts on air, water and soil, case: Huasteca Hidalguense, Mexico; Evaluacion regional del impacto antropogenico sobre aire, agua y suelo, caso: Huasteca Hidalguense, Mexico

Energy Technology Data Exchange (ETDEWEB)

Gordillo Martinez, Alberto Jose; Cabrera Cruz, Rene Bernardo Elias; Hernandez Mariano, Marisol; Galindo, Erick; Otazo, Elena; Prieto, Francisco [Centro de Investigaciones Quimicas, Universidad Autonoma del Estado de Hidalgo, Pachuca, Hidalgo (Mexico)]. E-mail: gordillo@uaeh.edu.mx; rcabreracruz@yahoo.com.mx

2010-08-15

The state of Hidalgo, Mexico presents an important environmental problem that manifests itself in different ways. To identify the sources, types and the magnitude of pollutants, an inventory of sources of industrial and domestic pollution for air, water and soil in ten municipalities of the Huasteca Region of the state was carried out using the technique of Rapid Assessment of Sources of Environmental Pollution and the results are reported in this paper. A total of combined pollutants emitted was 116 978.95 tons/year. Gasoline vehicles contributed 11 039 tons/year of air pollutants and diesel vehicles 1521 tons/year. For water, industrial sources contributed 22 496 tons/year and domestic effluents 15 776 tons/year. Soil pollution was a result of industrial solid waste, 4025 tons/year, and municipal solid waste, 62 121 tons/year. By municipality, Huejutla de Reyes is the most polluted in air, water and soil, with 53 % of the regional total. These results were evaluated in relation to environmental quality of each medium based on the Mexican regulations; these levels are above permissible limits for water and soil. A database with relevant information was prepared as a support for efficient management of pollutant emissions, provide base mark data for complementary studies, and to promote the future conservation of environmental quality and the biological richness of the area. [Spanish] El estado de Hidalgo, Mexico presenta una importante problematica ambiental que se manifiesta de manera heterogenea a lo largo de su territorio. Existe la necesidad de conocer las fuentes, tipos de agentes contaminantes y su magnitud. En este trabajo se realizo un inventario de la contaminacion emitida por fuentes de origen industrial y domestico en aire, agua y suelo en diez municipios de la region de la Huasteca por medio de la tecnica de Evaluacion Rapida de Fuentes de Contaminacion Ambiental (ERFCA). El total de la contaminacion emitida fue de 116 978.95 ton/ano. Las emisiones al

LandscapeDNDC used to model nitrous oxide emissions from soils under an oak forest in southern England

Science.gov (United States)

Cade, Shirley; Clemitshaw, Kevin; Lowry, David; Yamulki, Sirwan; Casella, Eric; Molina, Saul; Haas, Edwin; Kiese, Ralf

2013-04-01

model and internal parameters of LandscapeDNDC for use with an oak forest in SE England and as a result facilitates the broadening of its application. Modelled N2O soil emissions are compared with measurements from soil chambers in the forest. HAAS, E., KLATT, S., FRÖHLICH, A., KRAFT, P., WERNER, C., KIESE, R., GROTE, R., BREUER, L. and BUTTERBACH-BAHL, K., 2012. LandscapeDNDC: a process model for simulation of biosphere-atmosphere-hydrosphere exchange processes at site and regional scale. Landscape Ecology, , pp. 1-22. LI, C., FROLKING, S. and FROLKING, T.A., 1992. A model of nitrous oxide evolution from soil driven by rainfall events: 1. Model structure and sensitivity. J.Geophys.Res, 97(D9), pp. 9759-9776.

Recent Developments in the Theory of Mechanisms in Radiation Chemical Processes; Developpements recents dans la theorie des mecanismes des reactions radiochimiques; Poslednie dostizheniya v teorii mekhanizmov radiatsionno-khimicheski kh protsessov; Adelantos recientes en la interpretacion teorica del mecanismo de los procesos radioquimicos

Energy Technology Data Exchange (ETDEWEB)

Roberts, R. [U.K.A.E.A., Wantage Research Laboratory, Berks (United Kingdom)

1963-11-15

importancia de los procesos ion-molecula, atendiendo particularmente a la radioquimica del metano. Deduce que se verifican en este sistema reacciones de moleculas excitadas, ademas de los procesos ionicos. Demuestra que los hidrocarburos no saturados desempenan un papel destacado en la radiolisis del metano. Pasa revista a los perfeccionamientos de la polimerizacion ionica, asi como de la polimerizacion en condiciones heterogeneas. Se refiere a la importancia de la pureza de los reactivos y a la limpieza de los recipientes. Examina brevemente el efecto de la aplicacion de un potencial extemo en la polimerizacion en fase solida. Senala la importancia radioquimica de los procesos basados en radicales libres, en relacion con el proceso Dow para la produccion del bromuro de etilo. (author) [Russian] Rassmatrivayutsya poslednie dostizheniya v teorii mekhanizmov khimicheskikh reaktsij, initsiirovannykh oblucheniem. Rassmatrivaetsya rol' iono-yolekulyarnykh protsessov, pri ehtom obrashchaetsya osoboe vnimanie na radiatsionnukh khimiyu metana. Sdelan vyvod, chto v ehtoj sisteme naryadu s ionnymi protsessami proiskhodyat reaktsii vozbuzhdennykh molekul. Pokazano, chto pri radiolize metana nenasyshchennye uglevodorody igravt znachitel'nuyu rol' v mekhanizme reaktsii. Rassmatrivayutsya dostizheniya v oblasti ionnoj polimerizatsii i polimerizatsii pri geterogennykh usloviyakh. Obsuzhdaetsya znachenie stepeni ochistki reagenta i chistoty reaktsionnogo sosuda. Kratko rassmatrivaetsya vozdejstvie prilozhennogo vneshnego potentsiala na polimerizatsiyu tverdykh tel. Znachenie protsessov svobodnykh radikalov v radiatsionnoj khimii rassmatrivaetsya v svete protsessa Dou dlya proizvodstva bromistogo ehtila. (author)

Synthesis of Pure Ca(OH)2 Nanoparticles and Superhydrophobic Suspensions: Consolidation and Waterproofing of Architectural Heritage Materials

Science.gov (United States)

Madrid Mendoza, Juan Antonio

El objetivo de esta tesis es investigar sobre la sintesis, propiedades y aplicaciones de las nanoparticulas de Ca(OH)2 para consolidar materiales patrimoniales arquitectonicos. Las nanoparticulas de Ca(OH)2 se han utilizado recientemente en la conservacion del patrimonio, aunque algunos aspectos de la sintesis no son completamente comprendidos. En el presente estudio, hemos desarrollado metodos optimizados para obtener nanoparticulas de alta pureza mediante sintesis de fase homogenea y heterogenea utilizando diferentes materiales de partida. Se han realizado del orden de cien sintesis en diferentes condiciones para comprobar la validez y fiabilidad del metodo sintetico. Los resultados confirman que la temperatura de reaccion tiene una gran influencia en el tamano y la morfologia de las nanoparticulas de Ca(OH)2. Ademas, se ha investigado la estabilidad de las nanoparticulas a lo largo del tiempo en mezclas de 2-propanol / agua, en las que se encontro que la ausencia de agua era critica para evitar la aglomeracion de Ca(OH)2. Una vez dispersas en 2-propanol, las nanoparticulas se han utilizado para consolidar sustratos reales (piedra, adobe y estuco) confirmando su alto rendimiento en terminos de consolidacion superficial y - cuando se mezcla con ciertos surfactantes - en reduccion de la absorcion de agua. Asimismo, se ha investigado el uso de nanoparticulas modificadas basadas en M(OH)2, donde M=Ca2+, Mg2+, con el objetivo de mejorar tanto la cohesion superficial como la durabilidad de los materiales patrimoniales (p. ej. piedra Tabaire). Finalmente, el tratamiento de consolidacion basado en nanoparticulas puras de Ca(OH)2 se utilizo en emplazamientos con valor patrimonial, como edificios historicos y yacimientos arqueologicos (Teatro Romano de Cartagena) obteniendo resultados satisfactorios. The aim of this thesis is to investigate on the synthesis, properties and applications of Ca(OH)2 nanoparticles to consolidate architectural heritage materials. Ca(OH)2

Effects of Incorporated Radioactivity and External Radiation on Heterogeneous Catalysis; Effets de la radioactivite incorporee et des rayonnements externes sur la catalyse heterogene; Vliyanie vvedennoj radioaktivnosti i vneshnego oblucheniya na geterogennyj kataliz; Efectos de la radiactividad incorporada y de la irradiacion externa sobre la catalisis heterogenea

Energy Technology Data Exchange (ETDEWEB)

Krohn, N. A.; Wymer, R. G. [Oak Ridge National Laboratory, Oak Ridge and University of Tennessee, Knoxville, Tennessee (United States)

1963-11-15

The vapour phase dehydration of cyclohexanol on magnesium sulphate and magnesium sulphatesodium sulphate catalysts and the dehydrogenation of methylcyclohexane to toluene on promoted chromiaalumina catalysts were studied in flow systems. The effects of incorporating radioisotopes into the catalysts and of pre-irradiation with cobalt-60 gamma rays were investigated. Magnesium sulphate and magnesium sulphate-sodium sulphate catalysts containing up to 45.5 mc (S{sup 35})/g were less active than non-radioactive catalysts of similar composition when compared on a unit surface area basis. The reduction in catalytic activity persisted even after the radioactivity had substantially decayed. Further, no change in catalytic activity was observed upon irradiation with X-rays while the reaction was in progress. From these results it is concluded that the emission of beta particles from the catalyst during its use has no effect. Reports of an enhancement of catalytic activity may be attributed to the fact that,for a given set of preparation conditions, the radioactive catalysts have larger surface areas than their non-radioactive counterparts, and that this was not taken into account. Pre-irradiation with cobalt-60 gamma rays to 10{sup 11} erg/g had no effect on the catalysts' activity. In contrast, pre-irradiation of the chromia-alumina catalysts with cobalt-60 gamma rays to a dose of 4.2 x 10{sup 11} erg/g enhanced the catalytic activity by about 34% at 485{sup o}C, but incorporation of up to 148 mc (Pm{sup 147})/g of catalyst had little or no effect. No substantial effect of radiation on surface area or on apparent activation energy was observed in this case. (author) [French] Les auteurs ont etudie dans des circuits la deshydratation du cyclohexanol en phase vapeur en presence de catalyseurs au sulfate de magnesium et au sulfate double de magnesium et de sodium, et la transformation du methylcyclohexane toluene par deshydrogenation en presence de catalyseurs au Cr{sub 2}O{sub 3} - Al{sub 2}O{sub 3} active. Ils ont fait des recherches sur les effets de l'incorporation de radioisotopes dans les catalyseurs et d'une exposition prealable aux rayons gamma du cobalt-60. Les catalyseurs au sulfate de magnesium et au sulfate double de magnesium et de sodium contenant jusqu'a 45,5 mc de {sup 35}S par gramme etaient moins actifs que les catalyseurs non radioactifs de composition analogue si on les comparait par unite de surface. La reduction de l'activite catalytique persistait meme apres qu'une desintegration importante se fut produite. En outre, on n'a pas observe de changements de l'activite catalytique sous exposition a des rayons X au cours de la reaction. On en conclut que l'emission de particules beta par le catalyseur au cours de son emploi est sans effet. Les resultats faisant etat d'une augmentation de l'activite catalytique peuvent etre attribues au fait que pour des conditions donnees de preparation, les catalyseurs radioactifs ont une plus grande surface que leur correspondants non radioactiis et qu'on n'avait pas tenu compte de ce fait. L'exposition prealable de ces catalyseurs aux rayons gamma du cobalt-60 a raison de 10{sup 11} erg/g a ete sans effet sur l'activite du catalyseur. Par contre, la meme exposition prealable des catalyseurs au Cr{sub 2}O{sub 3} - Al{sub 2}O{sub 3} aux rayons gamma du cobalt-60 a raison de 4,2 x 10{sup 11} erg/g a augmente l'activite catalytique d'environ 34% a 485{sup o}C, mais l'incorporation d'une quantite de {sup 147}Pm atteignant 148 mc/g de catalyseur est restee pratiquement sans effet. On n'a pas observe dans ce cas d'effet significatif des rayonnements sur la surface active ou sur l'energie d'activation apparente. (author) [Spanish] Los autores estudian la deshidratacion del ciclohexanol en fase vapor en presencia de catalizadores de sulfato magnesico y d e sulfato magnesico-sulfato sodico, asi como la transformacion del metilciclohexano en tolueno por deshidrogenacion sobre catalizadores de oxido de cromo-alumina activados, en sistemas de circulacion. Examinan tambien los efectos de la incorporacion de radioisotopos en los catalizadores y de su preirradiacion con los rayos gamma emitidos por una fuente de cobalto-60. Los catalizadores de sulfato magnesico y de sulfato magnesico-sulfato sodico, con un contenido de hasta 45, 5 mc de {sup 35}S, se revelaron menos activos por unidad de superficie que los catalizadores no radiactivos de composicion analoga. La merma de actividad catalitica subsistio incluso despues de haber disminuido considerablemente la radiactividad. Ademas, no se observo cambio alguno en l a actividad catalitica despues de una exposicion a rayos X en el curso de la reaccion. Estos resultados sugieren a los autores que la emision de particulas beta por el catalizador durante su empleo no ejerce ningun efecto. Las informaciones relativas a un incremento de esa actividad catalitica podrian atribuirse al hecho de que, para un conjunto dado de condiciones de preparacion, los catalizadores radiactivos ofrecen una superficie mayor que sus equivalentes no radiactivos, circunstancia esta que no fue tenida en cuenta. La preirradiacion con los rayos gamma del cobalto-60 en dosis de hasta 10{sup 11} erg/g no influyo en absoluto sobre la actividad de los catalizadores. Por el contrario, la preirradiacion gamma del cobalto-60 de catalizadores de oxido de cromo-alumina con dosis de 4,2 x 10{sup 11} erg/g incremento esa actividad en un 34% aproximadamente a 485{sup o}C, pero la incorporacion de hasta 148 me de {sup 147}Pm por gramo de catalizador tuvo escaso o ningun efecto. En este caso, las radiaciones no ejercieron un efecto notable sobre el area superficial o sobre la energia de attivacion aparente. (author) [Russian] Na tsirkulyatsionno-staticheskoj ustanovke issledovany parofaehnaya degidratatsiya tsiklogeksanola s primeneniem sul'fatmagnievogo i sul'fatmagnievogo - sul'fatnatrivogo katalizatorov i degidrogenizatsiya metiltsiklogeksana v toluol na aktivirovannykh alyumokhromovykh katalizatorakh. Izucheny ehffekty vvedeniya v katalizator radioaktivnykh izotopov i predvaritel'nogo gamma-oblucheniya ot istochnika Co''6''0. Sud'fatmagnievyj katalizator i katalizator smeshannogo tipa sul'fat magniya + sul'fat natriya, soderzhashchie do 45,5 mkkyuri (S''3''5)/r, pri raschete na edinitsu poverkhnosti menee aktivny, chem katalizatory togo zhe sostava, no ne soderzhashchie radioaktivnykh izotopov. Oslablenie kataliticheskoj aktivnosti sokhranyalos' dazhe posle togo, kak radioaktivnost' sushchestvenno pala, dalee, pri obluchenii rentgenovskimi luchami, kotoroe provodilos' v protsesse reaktsii, nikakikh izmenenij v kataliticheskoj aktivnosti ne nablyudalos'. Na osnovanii ehtikh dannykh sdelan vyvod, chto ehmissiya beta-chastits iz katalizatora v protsesse ego ispol'zovaniya ne okazyvaet nikakogo vliyaniya. Soobshcheniya ob usilenii kataliticheskoj aktivnosti sleduet otnesti za schet togo, chto pri prigotovlenii katalizatorov u tekh iz nikh, kotorye soderzhali radioaktivnye izotopy, vozmozhno poluchalas' bol'shaya ploshchad' poverkh- nosti, chem u tekh, kotorye ne soderzhali radioaktivnykh izotopov. Ehto obstoyatel'stvo ne bylo prinyato vo vnimanie. Predvaritel'noe gamma-obluchenie ot istochnika Co''6''0 dozoj 10''1''1 erg/g ne okazalo vliyaniya na kataliticheskuyu aktivnost'. S drugoj storony, predvaritel'noe obluchenie gamma-luchami ot istochnika Co{sup 60} alyumokhromovykh katalizatorov dozoj 4,2 x 10{sup 11} erg/g usililo kataliticheskuyu aktivnost' pochti na 34%, pri 485{sup o}C. V to zhe vremya vvedenie v katalizator do 148 mkkyuri (Pm{sup 147} )/g katalizatora ne okazyvalo pochti nikakogo vozdejstviya. V ehtom sluchae ne nablyudalos' skol'ko-nibud' zametnogo vliyaniya izlucheniya na ploshchad' poverkhnosti ili na kazhushchuyusya ehnergiyu aktivatsii. (author)

Synthesis and characterization of CeO{sub 2} - TiO{sub 2} system for use in heterogeneous photocatalysis in photodegradation of methylene blue dye; Sintese e caracterizacao do sistema CeO{sub 2} - TiO{sub 2} para aplicacao em fotocatalise heterogenea na fotodegradacao do corante azul de metileno

Energy Technology Data Exchange (ETDEWEB)

Bragatto, Julia

2016-07-01

This study has as its goal the synthesis of a mixed oxide system type CeO{sub 2} - TiO{sub 2}, through the polymeric precursor method, to be used in heterogeneous photocatalysis. The synthesized materials were characterized by Thermogravimetry (TG), Derivative Thermogravimetry (DTG), Differential Thermal Analysis (DTA) and X-Ray Diffraction (XRD). The results of the thermal analysis showed in what temperature ranges certain events occur such as the formation of cerium oxide between 600 and 800 ° C, which refers to the crystallization of the material. Regarding the formation of titanium oxide, events between 600 and 800 ° C are perceived, which suggests the transformation of anatase to rutile phase. The XRD analysis showed no occurrence of the same phase for all materials, meaning that there is a variation in the formation of phases according to concentration of precursor for each sample. Noteworthy are the formation of CeO{sub 2} for Ce75-Ti25 and Ce50-Ti50 concentrations, with cubic crystal structure of the fluorite type. In Ce75-Ti25 and Ce25-Ti75 it is present the TiO{sub 2} in the anatase and rutile phase, with crystal structure of the tetragonal and tetrahedron type, respectively, as well as the formation of CeTi{sub 2}O{sub 6} in Ce50-Ti50 and Ce25-Ti75, with structure monoclinic. From these analyses, it is possible to see which samples, and in which temperatures of calcination the material has increased crystallinity, making the choice for their application in heterogeneous photocatalysis, aiming the degradation of methylene blue dye. Among the tested materials for methylene blue, the sample that stood out was the Ce50-Ti50, with calcination temperature of 800 °C, with values close to 50% degradation, because it was the sample that showed higher dye adsorption capacity, which is the step that precedes photodegradation. (author)

Analysis of X-ray diffraction of the titanium dioxide (TiO{sub 2}) synthesized by the Pechini Method for application in heterogeneous photocatalysis processes; Analise de difracao de raios X do dioxido de titanio (TiO{sub 2}) sintetizado pelo metodo Pechini para aplicacao em processos de fotocatalise heterogenea

Energy Technology Data Exchange (ETDEWEB)

Oliveira, P.L.; Araujo, D.S.; Costa, A.C.F.M.; Oliveira, L.S.C., E-mail: palomalima_eq@yahoo.com [Universidade Federal de Campina Grande (UFCG), PB (Brazil)

2016-07-01

Titanium dioxide (TiO{sub 2}) is a polymorph commonly applied to heterogeneous photocatalysis processes for being relatively inexpensive and photo - stable. It is usually found in three different crystalline phases (anatase, rutile and brookite), which directly interfere in their photocatalytic efficiency. Therefore, this study aimed to investigate the obtainment of TiO{sub 2} by Pechini method in different conditions for application in the heterogeneous photocatalysis process. For this purpose, it was evaluated by analysis of X-ray diffraction (XRD ) the behavior of TiO{sub 2} materials synthesized in proportions of 2:1 and 3:1 (titanium isopropoxide/citric acid), pyrolyzed at 300°C/3h and 400°C /h and calcined at 400°C and 500°C/1h. The results revealed that the TiO{sub 2} samples produced in the ratio of 2:1 and 3:1 isopropoxide/citric acid and calcined at 500°C/h presented the best results. (author)

Sobre a significação da eosinophilia na ancylostomose

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W. O. Cruz

1936-01-01

Full Text Available Procuramos averiguar qual a verdadeira significação da eosinophilia sanguinea na ancylostomose. Ao contrario do que affirmavam autores antigos, tentamos demonstrar que a eosinophilia não tem nenhuma relação com toxinas ou venenos porventura secretados pelos helminthos. Dado o incompleto conhecimento da funcção do leucocyto eosinophilo, a interpretação que damos da eosinophilia na ancylostomose, tem um carater, simplesmente, provisorio. Mostramos que a eosinophilia verificada no inicio da doença é provocada pela migração das larvas no interior do organismo, porém, que a eosinophilia observada posteriormente, não é uma consequencia longiqua desta inicial, pois que ella é devida á acção de albuminas heterologas acantonadas no intestino e provenientes de secreções dos vermes apensos á mucosa deste orgão. Como mechanismo desta eosinophilia, lembramos a possibilidade de que a eosinophilia localisada no intestino possa provocar uma diminuição passageira destas cellulas na circulação, o que determinaria uma excitação da medulla ossea (tal como a excitação trazida oelas perdas sanguineas nas hemorrhagias agudas e a producção de novos leucocytos. Em virtude da constante secreção helminthica, este orgão seria constantemente excitado, por este processo indirecto, o que acarretaria finalmente uma eosinophilia sanguinea persistente. Por alguns estudos que apresentamos e baseados em resultados encontrados na literatura, affirmamos a inexistencia de qualquer relação de causa a effeito entre a eosinophilia e os atores productores da syndrome anemica. Assim dizemos porque verificamos a cura completa da anemia, apezar da persistencia de intensas eosinophilias periphericas, e ainda que a taxa de eosinophilos no sangue é tanto menor quanto mais grave é a anemia. Além disto, chamamos a attenção para que a eosinophilia é um phenomeno sempre presente quando se encontra no interior do organismo albumínas a elle heterogeneas

A study of the mechanism of certain heterogeneous catalytic processes using C{sup 14}-labelled compounds; Utilisation de composes marques au carbone-14 pour l'etude du mecanisme de certains processus catalytiques heterogenes; Issledovanie mekhanizma nekotorykh geterogenno-kataliticheskikh protsessov s primeneniem soedinenij, mechennykh uglerodom-14; Estudio del mecanismo de algunos procesos de catalisis heterogenea con ayuda de compuestos marcados con carbono-14

Energy Technology Data Exchange (ETDEWEB)

Isagulyants, G V; Balandin, A A

1962-03-15

An investigation is made of the method of calculating individual phase velocities for parallel, consecutive and parallel-consecutive reactions from kinetic data obtained by the use of labelled atoms. The method is used for calculating individual phase velocities in the decomposition reaction of isopropyl alcohol into vanadium trioxides, dehydrogenations of butane-butylene mixtures and dehydrations of ethyl alcohol. Compounds containing C{sup 14} were used in this study. (author) [French] Le memoire expose une methode par laquelle on calcule les vitesses a differents stades dans les reactions paralleles, consecutives et paralleles-consecutives en se servant de donnees cinetiques obtenues par l'utilisation d'atomes indicateurs. Cette methode est utilisee pour le calcul des vitesses a differents stades de la decomposition de l'alcool isopropylique par le trioxyde de vanadium, de la deshydrogenation des melanges butane-butylene et de la deshydratation de l'alcool ethylique. Pour ces travaux, on a utilise des composes contenant du carbone-14. (author) [Spanish] Se describe un metodo de calculo de las velocidades correspondientes a las distintas etapas de una serie de reacciones paralelas, consecutivas y paralelo-consecutivas, partiendo de datos cineticos obtenidos mediante atomos marcados. El metodo se aplica a la determinacion de las velocidades de las reacciones de descomposicion del alcohol isopropilico por el trioxido de vanadio, de deshidrogenacion de mezclas de butano y buteno y de deshidratacion del alcohol etilico. El trabajo se llevo a cabo con ayuda de compuestos marcados con carbono-14. (author) [Russian] Rassmotren metod rascheta skorostej otdel'nykh stadij dlya parallel'nykh, konsekutivnykh i parallel'no-konsekutivnykh reaktsij, iskhodya iz kineticheskikh dannykh, poluchennykh s primeneniem mechenykh atomov. Metod primenen k raschetu skorostej otdel'nykh stadij v reaktsii razlozheniya izopropilovogo spirta na trekhokisi vanadiya, degidrogenizatsii butan-butilenovykh smesej, degidratatsii ehtilovogo spirta. V rabote byli ispol'zovany soedineniya, soderzhashchie radiouglerod-14. (author)

Update on the Purdue University 2-second Drop Tower

Science.gov (United States)

Collicott, Steven

," AIAA Journal, 44, 4, pp. 859-867, April 2006. 5. S. L. Fitzpatrick, "A Study of Hydrogen Peroxide Low-Gravity Control for Propellant Management Devices," MS thesis, School of Aeronautics and Astronautics, Purdue Uni-versity. May 2003. 6. M. M. Weislogel, R. Jenson, Y. Chen, S. H. Collicott, J. Klatte, and M. Dreyer. "The capillary flow experiments aboard the International Space Station: Status". Acta Astro-nautica. 65:861-869, 2009

A preliminary interpretation of gas composition in the CP IV sector wells, Cerro Prieto geothermal field, Mexico

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Barragan Reyes, Rosa Maria; Arellano Gomez, Victor M; Portugal Marin, Enrique [Instituto de Investigaciones Electricas, Gerencia de Geotermia, Morelos (Mexico)]. E-mail: rmb@iie.org.mx; Perez Hernandez, Alfredo; Rodriguez Rodriguez, Marco Helio; Leon Vivar, Jesus de [Comision Federal de Electricidad, Residencia General Cerro Prieto, B.C. (Mexico)

2007-07-15

-temperature fluids descending through the H fault to the reservoir was inferred, since results for the wells affected by this process (located at the center of the CP IV area) showed small or negative excess steam values and slightly lower temperatures (265-270 degrees Celsius). [Spanish] A fin de aumentar la capacidad de generacion de 620 a 720 MW, se desarrollo el sector Cerro Prieto IV (CP IV) en la porcion NE del campo geotermico de Cerro Prieto, donde se perforaron catorce pozos nuevos a partir del ano 2000. Los pozos de la zona de CP IV producen fluidos bifasicos con caracteristicas heterogeneas en cuanto a la fraccion de vapor: en la porcion central y hacia el NW los pozos producen liquido dominante mientras que hacia el E y S producen una fraccion de vapor relativamente alta. En este trabajo se estudia la composicion gaseosa de los fluidos producidos para obtener parametros del yacimiento tales como la temperatura y la fraccion de vapor e identificar diferentes aportes de fluidos a los pozos. Se utilizo un metodo basado en la reaccion de Fischer Tropsch y el equilibrio del H{sub 2}S con pirita-pirrotita como amortiguador (FT-HSH3). Los resultados para el estado inicial indican que existen fluidos con temperaturas de yacimiento entre 275 y 310 grados Celsius asi valores de exceso de vapor entre -1 y 50%. Los resultados se alinean en un patron de mezcla FT-HSH3 que sugiere que los pozos descargan una mezcla de los dos miembros finales en diferentes proporciones. Uno de ellos parece ser un liquido con una temperatura superior a los 300 grados Celsius con exceso de vapor negativo o insignificante. El otro parece ser un fluido bifasico con temperatura de unos 275 grados Celsius y un exceso de fraccion de vapor de aproximadamente 0.5. De acuerdo con datos de cada pozo y dependiendo de las condiciones de produccion de cada uno, pueden ocurrir mezclas de fluidos con diferentes proporciones de liquido y vapor en el yacimiento. Datos de 2005 de pozos perforados despues del ano 2000

The effect of physical and chemical parameters on the macroinfaunal community structure of San Vicente bay, Chile Efectos de parámetros físicos y químicos en la estructura comunitaria de la macroinfauna en la bahía de San Vicente, Chile

Directory of Open Access Journals (Sweden)

ROCÍO A. SIEMENS

2001-06-01

(RTR beach morphodynamic parameter. There was also a significant linear relationship between E. analoga and 1/slope parameter. Although there was a significant correlation between the physical parameters of the beach and E. analoga distribution, these results should not be taken as conclusive for we must not exclude other possible factors, including chemical ones, which were not measured in this study. Absence of the amphipod Orchestoidea tuberculata Nicolet at the high water mark in the industrial zone can be explained by destruction of habitat due to direct human disturbanceLa bahía de San Vicente, situada en la zona central de Chile, está altamente industrializada y posee una playa arenosa que se extiende desde un área de uso recreativo a otra de uso industrial, en la que se vierten residuos líquidos. El estudio de la macroinfauna de la zona intermareal mostró una distribución heterogenea de la misma. Un máximo de cinco especies de invertebrados fue hallado en sólo 1 de 6 transectos muestreados a lo largo de la playa. La densidad varió de 0 a 188 individuos m-2, alcanzándose los valores más altos en la zona recreativa y los más bajos en la zona industrializada. La especie más abundante, Emerita analoga (Stimpson, fue elegida para estudiar la posible respuesta de la macrofauna frente a las variables de morfodinámica de la playa, a los parametros fisicoquímicos y a la concentración de metales pesados en el sedimento. E. analoga mostró su más alta densidad en la zona recreativa de la playa, al nivel medio-bajo del intermareal. La densidad de E. analoga a lo largo de la playa estuvo correlacionada significativamente con los valores de pH, temperatura (ºC, salinidad (‰ y concentraciones de oxígeno (ml O2 l -1 en el agua intersticial. Sin embargo, la concentración de oxígeno tuvo un mínimo de 3 ml O2 l -1 en la zona baja intermareal más cercana al area recreativa donde se contó el mayor número de individuos de macroinfauna. El análisis de 12

Construction, Cost and Use of an Enriched Uranium, Light-Water Subcritical Assembly; Assemblage Sous-Critique a Uranium Enrichi et Eau Legere; Realisation, Cout et Application; Realizatsiya i stoimost' podkriticheskoj sborki na obogashchennom urane i legkoj vode; Construccion, Coste y Aplicacion de un Conjunto Subcritico de Uranio Enriquecido

Energy Technology Data Exchange (ETDEWEB)

Vittoz, B.; Berthet, P.; Gavin, P.; Mandrin, C.; Robert, P.; Thurnheer, J. [Ecole Polytechnique de l' Universite de Lausanne (Switzerland)

1964-02-15

flux de neutrons. L'etude est poursuivie en etudiant l'influence de la distance entre les barres d'un meme plan. (author) [Spanish] El conjunto subcritico de la Escuela Politecnica de la Universidad de Lausana esta destinado al estudio experimental de los reticulados multiplicadores, pero se emplea tambien para fines de enseflanza. La instalacion se presta a usos multiples. Los autores exponen los motivos que indujeron al Laboratorio de Ingenieria Nuclear de la citada Escuela Politecnica a construir el conjunto subcritico, por sus propios medios en toda la medida de lo posible, y a elegir un reticulado de uranio poco enriquecido-agua ligera. Describen el principio y la construccion de los dispositivos que permiten variar comoda y rapidamente los parametros relativos al reticulado y a la alimentacion neutronica: 1. Las barras de uranio estan suspendidas verticalmente; cada punto de suspension posee dos grados de libertad sin restriccion de continuidad. Este principio permite, por ejemplo, variar de forma continua el paso del reticulado. 2. La alimentacion neutronica queda asegurada por cinco fuentes de Pu-Be colocadas sobre un pedestal de grafito. La separacion entre estas fuentes tambien se puede regular de forma continua. Los autores examinan los problemas de seguridad que plantea la instalacion, yaque la reactividad puede variar en gran medida de una configuracion a otra. Por ultimo, informan sobre el costo de la construccion y de los gastos de explotacion de este conjunto subcritico. Una de las investigaciones llevadas a cabo en el conjunto es el estudio de un reticulado aperiodico en el que se procura obtener un flujo uniforme. A este efecto se recurre a la teoria heterogenea establecida por Feinberg y Horning, considerando primero un reticulado de barras distribuidas de forma identica en n planos paralelos no equidistantes. Cada plano de barras constituye una fuente de neutrones rapidos y un absorbedor de neutrones termicos. Fuera de estos planos se utilizan las