Textural properties vs. CEC and EGME retention of Na–X zeolite prepared from fly ash at room temperature     

Arkadiusz Derkowski  Wojciech Franus  Halina Waniak-Nowicka  Adriana Czímerová 《International Journal of Mineral Processing》2007

Zeolite Na–X (FAU type) was synthesized from F-class fly ash in simple and economical way. Several months of storage of fly ash in NaOH solution, at room temperature, without any prior treatment, results in the production of material with ca. 50% content of Na–X zeolite. The most efficient reaction takes place at (OH)⁻ activity of 0.1–0.15 mol (OH)⁻/g of ash and at S/L ratio of 33 to 67 g/dm³. Higher S/L value causes an accelerating dissolution–crystallization equilibrium attainment. Cl⁻ ion acts as the inhibitor of this reaction.  相似文献   

Diffuse Component Spectra of Solar Active Regions at Submillimeter Wavelengths     

Adriana?V.?R.?SilvaEmail author  Tatiana?F.?Laganá  C.?Guillermo?Gimenez?De?Castro  Pierre?Kaufmann  Joaquim?E.?R.?Costa  Hugo?Levato  Marta?Rovira 《Solar physics》2005,227(2):265-281

Solar maps at 212 and 405 GHz obtained by the Solar Submillimetric Telescope (SST) show regions of enhanced brightness temperature, which coincide with the location of active regions. A statistical study of the radio emission from these active regions was performed for the first time at such high frequencies during 23 days on June and July 2002, when the atmospheric opacity was low. The brightest regions on the maps were chosen for this study, where the brightness excess observed varies from 3 to 20% above quiet Sun levels (i.e., 200–1000 K) at both wavelengths. Sizes of the regions of enhanced emission calculated at half the maximum value were estimated to be between 2′ and 7′. These sizes agree with observed sizes of active regions at other wavelengths such as Hα and ultraviolet. An important result is that the flux density spectra of all sources increase toward submillimeter frequencies, yielding flux density spectral index with an average value of 2.0. The flux density of the active region sources were complemented with that from maps at 17 and 34 GHz from the Nobeyama Radio Heliograph. The resulting spectra at all four frequencies were fit considering the flux density to be due to thermal bremsstrahlung from the active region. In the calculations, the source radius was assumed to be the mean of the measured values at 212 and 405 K. The effective temperatures of the radio emitting source, assumed homogeneous, obtained from this fit were 0.6–2.9 × 10⁴ K, for source diameters of 2′–7′.  相似文献   

Late Holocene marine terraces of the Cartagena region,southern Caribbean: The product of neotectonism or a former high stand in sea-level?     

J. Ignacio Martínez  Yusuke Yokoyama  Andres Gomez  Adriana Delgado  Hiroyuki Matsuzaki  Esteban Rendon 《Journal of South American Earth Sciences》2010,29(2):214-224

The detailed stratigraphic survey and paleontological study (mollusks, corals, foraminifera and ostracods) of four low-level, ～3 m, marine terrace sections: Punta Canoas, Manzanillo del Mar, Playa de Oro, and Tierra Bomba Island, from the Cartagena region, southern Caribbean, supplemented with 22 radiocarbon dates, reveals that the northern terraces were deposited as parasequences in a clastic depositional system compared to the Tierra Bomba Island succession that was deposited in a carbonate depositional system between ～3600 and ～1700 cal yrs BP. Drier conditions and the southern location of the ITCZ at about 3 ka triggered stronger easterly Trades and more dynamic southwestward sediment drift fed by the Magdalena River mouth, thus promoting the formation of sand spits that ultimately isolated the Cienaga de Tesca coastal lagoon from the Caribbean Sea. Our estimates support the hypothesis that the present position of the terraces is the product of neotectonism rather than a higher 3 ka, sea-level. Upheaval of the terraces varies between ～3.8 mmyr^?1 at Punta Canoas and ～2.2 mmyr^?1 at Tierra Bomba to ～1.5 mmyr^?1 at Manzanillo del Mar and Playa de Oro terraces. Our study corroborates previous contentions on the role of mud diapirism and the dynamics of the Dique Fault as late Holocene upheaval mechanisms.  相似文献   

Chemical and structural defensive external strategies in six sabellid worms (Annelida)     

Adriana Giangrande  Margherita Licciano  Roberto Schirosi  Luigi Musco  Loredana Stabili 《Marine Ecology》2014,35(1):36-45

In the marine environment, sessile invertebrates have developed an impressive array of mechanisms to avoid predation, bacterial exploitation, and epibiotic overgrowth. In the present study we investigated several defensive strategies adopted by six sabellids: the hard bottom species Sabella spallanzanii (Gmelin, 1791), Branchiomma luctuosum Grube, 1869, Branchiomma bairdi (McIntosh, 1885), and Sabellastarte spectabilis (Grube, 1878), and the soft bottom species Myxicola infundibulum (Renier, 1804), and Megalomma lanigera (Grube, 1846), which have different morphological characteristics and geographical distribution. We examined and compared some defensive features such as branchial crown toughness, tube structure and strength, amount of released mucus, and antibacterial lysozyme‐activity in the mucus. The investigated species utilize a combination of defence and deterrence strategies that seems to be related to the colonized habitat. Tube strength was, higher in the hard bottom species compared with the soft bottom ones, where the tubes are generally buried and protected within the sediment. Branchial crown appeared stronger and resistant in hard bottom species, except for S. spallanzanii, which is the species showing the strongest tube. Sabella spallanzanii, M. infundibulum and S. spectabilis secreted high amount of mucus with high lysozyme‐like activity. By contrast, B. luctuosum, B. bairdi, and M. lanigera produced low amounts of mucus exerting lower antibacterial activity.  相似文献   

Transgressive dunefield landforms and vegetation associations,Doña Juana,Veracruz, Mexico     

Patrick Hesp  Marisa Martinez  Graziela Miot da Silva  Natalia Rodríguez‐Revelo  Erika Gutierrez  Adriana Humanes  Daniela Laínez  Irene Montaño  Verónica Palacios  Agustín Quesada  Lorena Storero  Gabriela González Trilla  Carolina Trochine 《地球表面变化过程与地形》2011,36(3):285-295

Transgressive dune fields often comprise a multiplicity of landforms where vegetation processes largely affect landform dynamics, which in turn, also affect vegetation processes. These associations have seldom been studied in detail. This paper examines four separate landform types in a complex coastal transgressive dunefield located in the central Gulf of Mexico, in order to assess the relationships between dunefield habitat, local environmental factors, vegetation associations and landform evolution. Topographic surveys using tape and clinometer were conducted in conjunction with vegetation survey transects at four locations across the Doña Juana dunefield. Vegetation surveys allowed the estimation of relative plant cover of each plant species found along the transects. A large variety of landforms were found at the Doña Juana Dunefield: deflation plains, gegenwalle (counter) ridges, transverse dune trailing ridges, blowouts and parabolic dunes, aklé (fish‐scale shaped) dunefields and precipitation ridges, with plant species associations developing on these different landforms equally variable. Flood tolerant species were located in the lower parts (deflation plain and gegenwalle ridges) whereas the older and dryer parts were covered by coastal matorral shrubs. Burial‐tolerant species were dominant in the most mobile areas (blowouts and aklé dunefield and margin). The dune trailing ridge, with relatively milder conditions, showed the highest richness, with no dominant species. A dual interaction was found such that colonizing species both create and affect topography, and in turn, topography determines vegetation association and succession patterns. In coastal dunes, the vegetation and abiotic environment (namely the different landforms and the inherent micronevironmental variability) interact tightly and generate a complex and highly dynamic biogeomorphic system where substrate mobility and colonization processes reinforce one another in positive feedback. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

A Scincomorpha lizard from the Campanian of Patagonia     

Santiago Brizuela  Adriana Albino 《Cretaceous Research》2011,32(6):781-785

The terrestrial lizard fossil record of Gondwana is very scarce. Few lizards, from mostly fragmentary fossils, have been identified in Madagascar, Tanzania, Morocco, South Africa, India and South America. Among the South American specimens there are basal Squamata forms (Olindalacerta and Tijubina) and a possible iguanid (Pristiguana) form Brazil. In Argentina gondwanian terrestrial lizards are represented by a putative iguanid and a small, poorly preserved dentary. This last specimen, recovered from the Anacleto Formation (Neuquén Group, Río Colorado Subgroup) in vicinity of the locality of Cinco Saltos (Río Negro Province), is here described formally. Comparisons with extant lizards indicate more affinity of the fossil with the Scincomorpha (non Scincophidia) than with any other group of lizards. This finding suggests that lizards were probably better represented and more diverse in the Mesozoic of South America than previously thought, although the fossil record is, at the moment, much poorer than in Laurasia.  相似文献   

Comparison of lacustrine successions and their palaeohydrological implications in two sub‐basins of the Triassic Cuyana rift,Argentina          下载免费PDF全文

Cecilia Benavente  Adriana Mancuso  Nora Cabaleri  Elizabeth Gierlowski‐Kordesch 《Sedimentology》2015,62(7):1771-1813

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POlarization Emission of Millimeter Activity at the Sun (POEMAS): New Circular Polarization Solar Telescopes at Two Millimeter Wavelength Ranges     

Adriana Valio  P. Kaufmann  C. G. Giménez de Castro  J.-P. Raulin  L. O. T. Fernandes  A. Marun 《Solar physics》2013,283(2):651-665

We present a new system of two circular polarization solar radio telescopes, POEMAS, for observations of the Sun at 45 and 90 GHz. The novel characteristic of these instruments is the capability to measure circular right- and left-hand polarizations at these high frequencies. The two frequencies were chosen so as to bridge the gap at radio frequencies between 20 and 200 GHz of solar flare spectra. The telescopes, installed at CASLEO Observatory (Argentina), observe the full disk of the Sun with a half power beam width of 1.4^°, a time resolution of 10 ms at both frequencies, a sensitivity of 2?–?4 K that corresponds to 4 and 20 solar flux unit (=10⁴ Jy), considering aperture efficiencies of 50±5 % and 75±8 % at 45 and 90 GHz, respectively. The telescope system saw first light in November 2011 and is satisfactorily operating daily since then. A few flares were observed and are presented here. The millimeter spectra of some flares are seen to rise toward higher frequencies, indicating the presence of a new spectral component distinct from the microwave one.  相似文献   

Assessment of vulnerability for rockfalls in Cozia Gorge (Southern Carpathians,Romania)     

Ovreiu  Adriana Bianca  Bărsoianu  Iulian Andrei  Nistor  Constantin  Nedelea  Alexandru  Comănescu  Laura 《Natural Hazards》2019,99(1):117-140

Natural Hazards - Rockfalls represents a sudden, extremely important geomorphological hazard and may become a threat for people’s life, as well as goods and transport. The present study aims...  相似文献   

Evaluation of community leaders’ perception regarding Alerta Rio,the warning system for landslides caused by heavy rains in Rio de Janeiro     

Patricia de Oliveira Melo  Renata Marques de Britto  Tharcisio Cotta Fontainha  Adriana Leiras  Renata Albergaria de Mello Bandeira 《Natural Hazards》2017,89(3):1343-1368

Warning systems help reduce damage and save lives in disasters; however, there is a lack of research analyzing the population perception of these systems. In Rio de Janeiro (Brazil), because the city slums face the risk of landslides caused by heavy rains, a siren early warning system named “Alerta Rio” was installed in 102 areas. The purpose of this paper was to understand the perception of community leaders regarding this alert system. To this end, a survey was conducted with community leaders to collect data on whether and why the public do or do not attend to the alert. Results indicated that (1) public adherence to Alerta Rio is low despite the generally positive view of the system, (2) local violence was reported as the reason for staying at home to protect one’s property, and (3) problems with temporary shelters and the routes to them result in lack of people’s involvement in the system. Whereas these factors are similar to population perception regarding other warning systems, the community leaders also raised the public’s lack of trust in the city hall’s adopted concept of risk and in the politicians as a relevant factor in the population perception of Alerta Rio. These factors, together with the lack of prevention policies complementary with the alert system, led to perception of reduced importance of the system. For potential solutions to enhance alarm compliance, this study recommends improvement in communication, educational programs, and public engagement strategies tailored for each target group.  相似文献