Buscador

Encontrado(s) 2074711 resultado(s)
Encontrada(s) 207472 página(s)

Biofertilization of Degraded Southern African Soils with Cyanobacteria Affects Organic Matter Content and Quality

  • Pardo Fernández, María Teresa
  • Almendros Martín, Gonzalo
  • Zancada Fernández, M. Cristina
  • López-Fando, Cristina
16 páginas, 2 tablas y 6 figuras, We studied, under laboratory conditions, the effects of Nostoc 9v (cyanobacteria) on the soil organic matter (SOM) content and quality of different soils from Tanzania, Zimbabwe, and South Africa. Soils were inoculated with Nostoc 9v at a rate of 5mg dry biomass g 1 soil and incubated for 3 months at 27 C under 22Wm 2 illumination for 16 h and 8 h under darkness. Moisture content was maintained at 60% of field capacity. The composition of the SOM and the structural features of the humic acid (HA) fraction were studied by visible and infrared (IR) spectroscopies. Nostoc 9v proliferated and colonized the surfaces of all soils very quickly. The results obtained showed significant changes in the quantitative and qualitative characteristics of the SOM due to cyanobacterial growth. Inoculation and further incubation with Nostoc 9v promoted increases in organic carbon (OC) that ranged from 0.4 g C kg-1 soil to 9.0 g C kg-1 soil. Cyanobacterial growth also affected SOM characteristics through the incorporation of free, extractable, or particulate biomass with a predominantly aliphatic character. Important descriptors of the extent to which cyanobacterial metabolism modified the characteristics of the native SOM were the changes in the observed amounts of the two humin types, the increase in lipid concentration, and the changes in the optical density of the HAs., We thank Dr. A Herrero for the inoculum preparation. This work was part of an EU, INCO–DEV funded research program in Southern Africa (Cyanosoils), Project ICA–4–CT– 2001–10058., Peer reviewed
Proyecto:


3D-QSAR as a Tool for Understanding and Improving Single-Site Polymerization Catalysts. A Review

  • Cruz, Víctor L.
  • Martínez, Sonia
  • Ramos, Javier
  • Martínez-Salazar, Javier
16 pags. ; 8 figs. ; 3 schems., This paper reviews the findings of quantitative structure−activity relationship (QSAR) studies focusing on single-site polymerization catalysts, with special attention paid to the use of 3D-QSAR tools. Such tools reveal the fine details of catalyst structure that may be correlated with polymerization activity or the properties of the synthesized polymer. The introduction of effective single-site polymerization catalysts, in addition to allowing scientists to synthesize new tailor-made polymers, has enabled a detailed theoretical analysis of the synthesis process. The benefits of single-site polymerization for theoretical studies include easy elucidation of the catalyst structure, a well-defined mechanism of action, and the fact that experiments can be systematically conducted on catalyst series featuring different substitution patterns. Using QSAR methods, experimental results can be related to theoretical measurements through statistical or chemometric tools. These tools have been extensively and successfully used in the field of drug design. © 2014 American Chemical Society, This study received financial support from the CICYT (project MAT2012-36341)., Peer reviewed
Proyecto:


Initiation signals for the conversion of single-stranded to double-stranded DNA forms in the streptococcal plasmid pLS1

  • Solar, Gloria del
  • Puyet, A.
  • Espinosa, Manuel
20 p.-8 fig.-1 tab., We have characterized a region in the streptococcal plasmid pLSl located between nucleotides 4103 and 4218 which is a signal involved in the conversion of single stranded intermediates of replication to double stranded plasmid forms. This region has a large axis of dyad symmetry resulting in the formation of a secondary structure as revealed by the location of endonuclease S1-cleavage sites in supercoiled covalently closed circular pLS1 DNA. Deletions affecting this region caused a fivefold reduction in plasmid copy number, plasmid instability and the accumulation of single-stranded DNA intermediates. The conversion signal of pLS1 has homologues in other staphylococcal plasmids, sharing a consensus sequence located in the loop of the signal. Computer assisted analysis showed that the signal detected in pLS1 has a high degree of homology with the complementary strand origin of the Escherichia coli single stranded bacteriophages øX174 and M13., Research supported by Grant 618/501 from C.S.I.C.-C.A.I.C.Y.T., Peer reviewed
Proyecto:


Sampling Approaches for Trace Elements Determination in Seawater

  • Tovar-Sánchez, Antonio
Capítulo en: Pawliszyn, Janusz (ed.). Comprehensive Sampling and Sample Preparation : Analytical Techniques for Scientists. [Oxford]: Academic Press, 2012, vol. 1, p.317-334, Peer Reviewed
Proyecto:


Contourite processes associated with the Mediterranean Outflow Water after its exit from the Gibraltar Strait: Global and conceptual implications

  • Hernández-Molina, Francisco J.
  • Ercilla, Gemma
  • García, Marga
  • Arnaiz, Alvaro
2nd Deep-Water Circulation Congress: The Contourite Log-book, 10-12 September 2014, Ghent, Belgium.-- Hernández-Molina, Francisco J. ... et. al., Peer Reviewed
Proyecto:


Surface microlayer

  • Stortini, A.M.
  • Cincinelli, A.
  • Degli Innocenti, N.
  • Tovar-Sánchez, Antonio
  • Knulst, J.
Capítulo en: Pawliszyn, Janusz (ed.). Comprehensive Sampling and Sample Preparation : Analytical Techniques for Scientists. [Oxford]: Academic Press, 2012, vol. 1, p.223-246, Peer Reviewed
Proyecto:


Temporal and spatial variations in the biogeochemical cycling of cobalt in two urban estuaries: Hudson River Estuary and San Francisco Bay

  • Tovar-Sánchez, Antonio
  • Sañudo-Wilhelmy, Sergio A.
  • Flegal, Arthur Russell
Despite the fact that Co is an essential trace element for the growth of marine phytoplankton, there is very limited information on the cycling of this trace metal in the marine environment. We report here the distribution of dissolved (<0.4 μm) and particulate (>0.4 μm) Co in surface waters of the Hudson River Estuary (HRE) and San Francisco Bay (SFB). Samples were collected during several cruises (from 1990 to 1995 in SFB and from 1995 to 1997 in the HRE) along the whole salinity gradient. Dissolved Co concentrations (mean±1 standard deviation) were nearly identical in magnitude in both estuaries despite differences in climate, hydrography, riverine-flow conditions and land-usage (HRE=0.91±0.61 nM; SFB=1.12±0.69 nM). Dissolved Co levels in each system showed non-conservative distributions when plotted as a function of salinity, with increasing concentrations downstream from the riverine end-members. Desorption from suspended particulates and sewage inputs, therefore, seems to be the major processes responsible for the non-conservative behavior of Co observed. Mass balance estimates also indicated that most of the estuarine Co is exported out of both estuaries, indicating that they and other estuarine systems are principal sources of this essential trace element to the open ocean. © 2004 Elsevier Ltd. All rights reserved., This research was partially supported by the Hudson River Foundation, the San Francisco Estuary Institute, San Francisco Regional Water Quality Control Board, Dreyfus Foundation, the University of California Toxic Substances Research & Teaching Program and the Ministry of Education, Culture and Sport of Spain, Peer Reviewed
Proyecto:


Search for heavy narrow dilepton resonances in pp collisions at √s=7 TeV and √s=8 TeV

  • Chatrchyan, S.
  • Brochero Cifuentes, J. A.
  • Cabrillo, I. J.
  • Cabrillo, I. J.
  • Calderon, Alicia
  • Chuang, S. H.
  • Duarte Campderros, J.
  • Felcini, Marta
  • Fernández, M.
  • Gómez, G.
  • González Sánchez, J.
  • Graziano, A.
  • Jorda, C.
  • López Virto, A.
  • Marco, Jesús
  • Marco, Rafael
  • Martínez-Rivero, Celso
  • Matorras, Francisco
  • Muñoz Sánchez, F. J.
  • Rodrigo, Teresa
  • Rodríguez Marrero, Ana Y.
  • Ruiz Jimeno, Alberto
  • Scodellaro, Luca
  • Vila, Iván
  • Vilar, Rocío
  • CMS Collaboration
This article is published Open Access at sciencedirect.com. It is distributed under the terms of the Creative Commons Attribution License 3.0.-- et al., An updated search for heavy narrow resonances decaying to muon or electron pairs using the CMS detector is presented. Data samples from pp collisions at √s = 7 TeV and 8 TeV at the LHC, with integrated luminosities of up to 5.3 and 4.1 fb−1, respectively, are combined. No evidence for a heavy narrow resonance is observed. The analysis of the combined data sets excludes, at 95% confidence level, a Sequential Standard Model Z'SSM resonance lighter than 2590 GeV, a superstring-inspired Z'ψ lighter than 2260 GeV, and Kaluza–Klein gravitons lighter than 2390 (2030) GeV, assuming that the coupling parameter k/MPl is 0.10 (0.05). These are the most stringent limits to date., We acknowledge support from BMWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MEYS (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLPFAI (Mexico); MSI (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine Uzbekistan); MON, RosAtom, RAS and RFBR (Russia); MSTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); ThEP, IPST and NECTEC (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA)., Peer Reviewed
Proyecto:


The impact of surface-adsorbed phosphorus on phytoplankton Redfield stoichiometry

  • Sañudo-Wilhelmy, Sergio A.
  • Tovar-Sánchez, Antonio
  • Fu, Feixue
  • Capone, Douglas G.
  • Carpenter, Edward J.
  • Hutchins, David A.
The Redfield ratio of 106 carbon:16 nitrogen:1 phosphorus in marine phytoplankton1 is one of the foundations of ocean biogeochemistry, with applications in algal physiology2, palaeoclimatology3 and global climate change4. However, this ratio varies substantially in response to changes in algal nutrient status5 and taxonomic affiliation6,7. Here we report that Redfield ratios are also strongly affected by partitioning into surface-adsorbed and intracellular phosphorus pools. The C:N:surface-adsorbed P (80-105 C:15-18 N:1 P) and total (71-80 C:13-14 N:1 P) ratios in natural populations and cultures of Trichodesmium were close to Redfield values and not significantly different from each other. In contrast, intracellular ratios consistently exceeded the Redfield ratio (316-434 C:59-83 N:1 intracellular P). These high intracellular ratios were associated with reduced N2 fixation rates, suggestive of phosphorus deficiency. Other algal species also have substantial surface-adsorbed phosphorus pools, suggesting that our Trichodesmium results are generally applicable to all phytoplankton. Measurements of the distinct phytoplankton phosphorus pools may be required to assess nutrient limitation accurately from elemental composition. Deviations from Redfield stoichiometry may be attributable to surface adsorption of phosphorus rather than to biological processes, and this scavenging could affect the interpretation of marine nutrient inventories and ecosystem models., This work was supported by NSF Chemical and Biological Oceanography and by NOAA Ocean Global Carbon Cycle Program, Peer Reviewed
Proyecto:


Search for narrow resonances using the dijet mass spectrum in pp collisions at √s=8 TeV

  • Chatrchyan, S.
  • Brochero Cifuentes, J. A.
  • Cabrillo, I. J.
  • Calderon, Alicia
  • Chuang, S. H.
  • Duarte Campderros, J.
  • Felcini, Marta
  • Fernández, M.
  • Gómez, G.
  • González Sánchez, J.
  • Graziano, A.
  • Jorda, C.
  • López Virto, A.
  • Marco, Jesús
  • Marco, Rafael
  • Martínez-Rivero, Celso
  • Matorras, Francisco
  • Muñoz Sánchez, F. J.
  • Rodrigo, Teresa
  • Rodríguez Marrero, Ana Y.
  • Ruiz Jimeno, Alberto
  • Scodellaro, Luca
  • Vila, Iván
  • Vilar, Rocío
  • CMS Collaboration
Results are presented of a search for the production of new particles decaying to pairs of partons (quarks, antiquarks, or gluons), in the dijet mass spectrum in proton-proton collisions at √s=8 TeV. The data sample corresponds to an integrated luminosity of 4.0 fb-1, collected with the CMS detector at the LHC in 2012. No significant evidence for narrow resonance production is observed. Upper limits are set at the 95% confidence level on the production cross section of hypothetical new particles decaying to quark-quark, quark-gluon, or gluon-gluon final states. These limits are then translated into lower limits on the masses of new resonances in specific scenarios of physics beyond the standard model. The limits reach up to 4.8 TeV, depending on the model, and extend previous exclusions from similar searches performed at lower collision energies. For the first time mass limits are set for the Randall-Sundrum graviton model in the dijet channel., We acknowledge support from BMWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MEYS (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLPFAI (Mexico); MSI (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine Uzbekistan); MON, RosAtom, RAS and RFBR (Russia); MSTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); ThEP, IPST and NECTEC (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA)., Peer Reviewed
Proyecto:


Buscador avanzado