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   

Phylogeographic patterns in Maguimithrax spinosissimus (Decapoda: Mithracidae) from Colombian Caribbean     

Julio César Hurtado-Alarcón  Néstor Hernando Campos Campos  Adriana Bermúdez Tobón  Edna J. Márquez 《新西兰海洋与淡水研究杂志》2018,52(1):118-137

The Caribbean king crab Maguimithrax spinosissimus is an important artisanal fisheries resource with a distribution range that includes the Florida Keys and Caribbean Sea islands. We carried out a phylogeographic analysis of M. spinosissimus in one oceanic (Old Providence) and two continental islands (Rosario and Tintipán). We analysed 89 and 49 Control Region (CR) and Cytochrome Oxidase I (COI) sequences, respectively. We found genetic differentiation between Old Providence and Rosario?+?Tintipán units (F_ST values of 0.84 for CR and 0.91 for COI gene), and gene flow between Rosario and Tintipán (F_ST values ?0.0085 for CR, P?>?.88; ?0.01 for COI gene, P?>?.99). Our analysis showed two genetic stocks and possibly an isolated biogeographic unit of M. spinosissimus. We suggest managing the species as different populations, and conducting more ecological and biological studies for the determination of possible cryptic species.  相似文献   

Exopolysaccharides produced by bacteria isolated from the pelagic Southern Ocean — Role in Fe binding,chemical reactivity,and bioavailability     

C.S. Hassler  E. Alasonati  C.A. Mancuso Nichols  V.I. Slaveykova 《Marine Chemistry》2011,123(1-4):88-98

As a result of ubiquitous excretion by micro-organisms, extracellular polymeric substances are reported in high concentrations in marine systems. The majority of this material is exopolysaccharide (EPS). Despite previous studies showing that EPS can affect carbon as well as trace metal cycling, little is known about the effect on Fe – a critical nutrient limiting primary productivity in up to 40% of the ocean. Here, we have characterised an EPS purified from bacteria isolated from the pelagic Southern Ocean (Pseudoalteromonas sp.) and investigated its role in Fe chemical speciation, solubility, as well as bioavailability for two keystone Southern Ocean phytoplankton strains. This EPS has an average molecular weight of 4.6 MDa, exhibiting mainly –OH, COO– and –NH₂ functional groups. An asymmetrical flow field-flow fractionation coupled online with UV-spectrophotometer, differential refractive index, and multiangle laser light scattering (aFlFFF-UV-DRI-MALS) demonstrates that this EPS is polydisperse with three, not well resolved, size populations having molar masses in the range from 0.57 to 15.8 MDa. Fe was exclusively associated with the medium size fraction of this EPS and was the most abundant trace metal with 2.2 nM Fe per nM EPS. Only a third of this Fe was chemically labile, and the strength of Fe-EPS complexes increased with equilibration time. 1 nM EPS is efficient to retain Fe in solution, mainly in the colloidal phase (0.02–0.2 μm). Fe bound to the EPS was highly bioavailable (25% as much as for inorganic Fe). Due to combined effect of EPS on Fe solubility and bioavailability, it can increase the residence time of bioavailable Fe in the euphotic zone, therefore possibly sustaining and controlling primary productivity in sensitive oceanic regions, such as the Southern Ocean.  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   

Observed photometric peculiarities of six eclipsing binaries with solar-type activity: I     

L. Milano  S. Mancuso  A. Vittone  A. D'Orsi  S. Marcozzi 《Astrophysics and Space Science》1986,124(1):83-100

From the observed light curves of six eclipsing binaries with solar-type activity and from the analysis of their period variations some problems in the interpretation of the observations came out: Are these binaries similar to classical RS CVn stars? Is the stellar surface spot coverage the unique interpretation of the observed light curves? Are these systems really linked with W UMa's? In a further study some models will be tempted to try to solve these problems.  相似文献   

Three colour photoelectric observations of the symbiotic eclipsing binary CI Cyg     

R. Burchi  D. Chochol  A. Dipaolantonio  S. Mancuso  L. Milano  A. Vittone 《Astrophysics and Space Science》1983,89(2):387-393

We present three colour photoelectric observations of CI Cyg during the 1980 eclipse. Some interesting photometric peculiarities are shown that must be taken into account for a theoretical model of this eclipsing symbiotic star.  相似文献