102,002 research outputs found
Fluorination And Deoxygenation As Chemical Tools To Study The Conformational Preferences Of Hexopyranoses: A Journey From Gas Phase To Solution
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The 3D-arrangement of carbohydrates and, particularly, the orientation of their hydroxymethyl groups are structural features crucial for their biological activities. In this work, we investigate the influence of water on the conformational preferences of model hexopyranoses by performing a comprehensive analysis in the gas phase via microwave spectroscopy\footnote{C. Calabrese, I. Uriarte, A. Insausti, M. Vallejo-Lopez, F. J. Basterretxea, S. A. Cochrane, B. G. Davis, F. Corzana and E. J. Cocinero \textit{ACS Cent. Sci.}, \textbf{6}, 293-303, 2020.}\footnote{E. J. Cocinero, A. Lesarri, P. Ecija, F. J. Basterretxea, J.-U. Grabow, J. A. Fernandez, F. Castaño \textit{Angew. Chem. Int. Ed.}, \textbf{51}, 3119, 2012.} of different fluorinated and deoxygenated carbohydrate analogues and comparing the results with those obtained in solution using a combination of NMR data and molecular dynamics simulations. The gg conformation is stabilized in the gas phase by intra molecular HBs that lock this conformation when oriented clockwise. However, and contrary to previously reported data, the conformation of the hydroxymethyl group in D-gluco and D-mannopyranose series follows a similar tendency in the gas phase and in solution, indicating the importance of stereo electronic and minimizing the importance of competing water molecules against stabilizing intra molecular HBs
Phytoplankton biomass and production during late austral spring (1991) and summer (1993) in the Bransfield Strait
No full textPhytoplankton biomass and productivity were measured during two cruises in the Bransfield Strait in December 1991 (D91) and January/February 1993 (J93). Strong seasonal variability in productivity values was observed due to differences in the physiological response of phytoplankton. However, although the photosynthetic capacity of phytoplankton was markedly lower in D91 [P m B=0.61 ± 0.25 mg C (mg Chla)−1 h−1] than in J93 [P m B=2.18 ± 0.91 mg C (mg Chla)−1 h−1], average water column chlorophyll values in different areas of the strait were approximately similar in D91 (49–78 mg Chla m−2) and J93 (22–76 mg Chla m−2). The spatial distribution of chlorophyll was patchy and generally associated with the influence of the different water masses that meet together in the Bransfield Strait. No correlation was found between the mixed layer depth and either the integrated chlorophyll or the productivity. Our results suggest that major phytoplankton blooms in the Bransfield Strait are advected from the nearby Gerlache Strait or Bellingshausen Sea following the main eastward surface currents.22110,966Q3SCI
Mesocale variability in phytoplakton biomass distribution and photosynthetic parameters in the Canary-NW African coestal transition zone
No full textPigment distribution and photosynthesis versus irradiance (P-E) responses in the mixed layer (ML) and in the chlorophyll maximum (CM) were examined in the coastal transition zone (CTZ) between the NW African coastal upwelling and the Canary Islands during August 1993. The sampling included 2 island-generated eddies in the lee of the archipelago and an upwelling filament from the African continental shelf, entrained around a cyclonic eddy about 100 km width. Chlorophyll a and P E parameters (α, Pm) showed regional differences reflecting changes in the water column structure and phytoplankton species composition. The deep CM shoaled from ~100 to ~10 m as the African shelf was approached, and there was a clear offshore-onshore transition in the vertically integrated chlorophyll distribution and P-E responses related to the upwelling front. CM oceanic samples presented high α (0.020 to 0.042 mg C mg-1 chl h-1 [µmol m-2 s-1]-1) and photoinhibition, indicating adaptation to low irradiance. Differences between CM and ML in P-E responses decreased in the vicinity of the upwelling until they eventually became indistinguishable in a well-mixed station on the continental shelf. Island-generated eddies affected mainly the productivity and chlorophyll distributions at the deep CM. Nutrient input in the eddy center resulted in an increase of α in the CM to the level of the upwelling samples (~0.053 mg C mg-1 chl h-1 [µmol m-2 s-1]-1). On the basis of the mesoscale variability in the physical structure of the water column and the vertical distribution of chlorophyll, the CTZ was divided into 4 subregions with characteristic photosynthetic parameters. Average integrated production in these areas varied from ~100 mg C m-2 d-1 in the most oligotrophic subregion to more than 5000 mg C m-2 d-1 in the upwelling zone. The range of variation in the photosynthetic parameters in this CTZ was of the same magnitude as ranges observed in basin-scale studies of the Atlantic. Integrated production estimates are also in the lower and higher extremes of the observed values in the ocean. Our results highlight the importance of addressing the variability of the photosynthetic parameters in coastal upwelling-open ocean transition zones in order to model primary production at regional scales.40271,928Q1SCI
Population genetic structure and connectivity of the harmful dinoflagellate Alexandrium minutum in the Mediterranean Sea.
No full textThe toxin-producing microbial species Alexandrium minutum has a wide distribution in the Mediterranean
Sea and causes high biomass blooms with consequences on the environment, human health and
coastal-related economic activities. Comprehension of algal genetic differences and associated connectivity
is fundamental to understand the geographical scale of adaptation and dispersal pathways of
harmful microalgal species. In the present study, we combine A. minutum population genetic analyses
based on microsatellites with indirect connectivity (Ci) estimations derived from a general circulation
model of the Mediterranean sea. Our results show that four major clusters of genetically homogeneous
groups can be identified, loosely corresponding to four regional seas: Adriatic, Ionian, Tyrrhenian and
Catalan. Each of the four clusters included a small fraction of mixed and allochthonous genotypes
from other Mediterranean areas, but the assignment to one of the four clusters was sufficiently robust
as proved by the high ancestry coefficient values displayed by most of the individuals (.84%). The population
structure of A. minutum on this scale can be explained by microalgal dispersion following the main
regional circulation patterns over successive generations. We hypothesize that limited connectivity among
the A. minutum populations results in low gene flow but not in the erosion of variability within the population,
as indicated by the high gene diversity values. This study represents a first and new integrated
approach, combining both genetic and numerical methods, to characterize and interpret the population
structure of a toxic microalgal species. This approach of characterizing genetic population structure and
connectivity at a regional scale holds promise for the control and management of the harmful algal bloom
events in the Mediterranean Sea
Bibliographie Hilarion G. Petzold 1958 – 2009 mit Anhang als Einführung
No full textDieses Archiv enthält die Gesamtbibliographie der Werke des Autors nebst einiger Texte „Über H. G. Petzold“ im Schlussteil der Bibliographie sowie einen Anhang mit einer Einführung in die Architektur des Werkes in seinem wissenslogischen Aufbau als Ausarbeitung seines „Tree of Science Modells“ (2007).This archive contains the complete bibliography of the author and some texts about H. G. Petzold, moreover an epilogue with an introduction to the architecture of the works in its epistemological structure and composition and as an elaborations of Petzold’s „Tree of Science Modell (2007).https://www.fpi-publikation.de/polyloge/01-2009-petzold-h-g-gesamtbibliographie-h-g-petzold-1958-2009-updating-november2009/peerReviewedpublishedVersio
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Population genetic structure and connectivity of the harmful dinoflagellate Alexandrium minutum in the Mediterranean Sea
No full textThe toxin-producing microbial species Alexandrium minutum has a wide distribution in the Mediterranean Sea and causes high biomass blooms with consequences on the environment, human health and coastal-related economic activities. Comprehension of algal genetic differences and associated connectivity is fundamental to understand the geographical scale of adaptation and dispersal pathways of harmful microalgal species. In the present study, we combine A. minutum population genetic analyses based on microsatellites with indirect connectivity (Ci) estimations derived from a general circulation model of the Mediterranean sea. Our results show that four major clusters of genetically homogeneous groups can be identified, loosely corresponding to four regional seas: Adriatic, Ionian, Tyrrhenian and Catalan. Each of the four clusters included a small fraction of mixed and allochthonous genotypes from other Mediterranean areas, but the assignment to one of the four clusters was sufficiently robust as proved by the high ancestry coefficient values displayed by most of the individuals (.84%). The population structure of A. minutum on this scale can be explained by microalgal dispersion following the main regional circulation patterns over successive generations. We hypothesize that limited connectivity among the A. minutum populations results in low gene flow but not in the erosion of variability within the population, as indicated by the high gene diversity values. This study represents a first and new integrated approach, combining both genetic and numerical methods, to characterize and interpret the population structure of a toxic microalgal species. This approach of characterizing genetic population structure and connectivity at a regional scale holds promise for the control and management of the harmful algal bloom events in the Mediterranean Sea. © 2011 The Royal Society.Peer Reviewe
Benthic-pelagic switching in a coastal subtropical lagoon
No full textThe structure of the ecosystem fluxes occurring in the Maspalomas coastal lagoon (Canary Islands) were investigated for three successive stages using estimates of the food webs that typify each interval. The first stage was representative of a benthic producer-dominated system and the third typified a pelagic-dominated system. The second phase was taken as the transient stage between these endpoints. The standing stocks and fluxes pertaining to each compartment and the overall trophic structure of the system were quantified as a network model. This food web budget was subjected to network analysis to assess the status of the system at each stage. The ensuing trophic analysis indicated that detritivory increases in passing from the first to the third stage (ratio of detritivory to herbivory 13·19, 7·57 and 20·32 respectively) and there is a concomitant drop in the average trophic efficiency. Cycle analysis revealed an increase in the amount of matter being cycled during the third stage (percentages of cycled matter 17·7%, 22·6% and 41·8% respectively), mostly via short, fast loops, which suggest that the third stage is representative of an immature ecosystem. Finally, the analysis of topological system-level indices reveals a dramatic increase in organization during the last stage, due primarily to the inflation of the total system throughput (TST). From a global point of view, results show a significant decline in the benthic subsystem, which represents a major perturbation to the ecosystem and renders it vulnerable to the subsequent invasion by pelagic elements. Although conditions in the third stage may seem typical of a eutrophic system, no appreciable resources are being added to the system from the outside. Therefore, the process is more accurately described as a shift in resources from one subsystem (the benthic) to another (the pelagic).3843631,467Q1SCI
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3346: Samuel G. Freedman, author, 2013
No full textPhotograph of author Samuel G. Freedman, at NT Daily Slash meeting in the Mayborn School of Journalism at UNT
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