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  • Elsevier  (305,020)
  • National Academy of Sciences  (11,669)
  • 2005-2009  (316,689)
  • 1990-1994  (2)
  • 2009  (115,443)
  • 2006  (107,085)
  • 2005  (94,165)
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  • 1
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    Changes in biogenic carbon flow in response to sea surface warming (2009)
    National Academy of Sciences
    Details
    Publication Date: 2023-11-08
    Description: The pelagic ocean harbors one of the largest ecosystems on Earth. It is responsible for approximately half of global primary production, sustains worldwide fisheries, and plays an important role in the global carbon cycle. Ocean warming caused by anthropogenic climate change is already starting to impact the marine biota, with possible consequences for ocean productivity and ecosystem services. Because temperature sensitivities of marine autotrophic and heterotrophic processes differ greatly, ocean warming is expected to cause major shifts in the flow of carbon and energy through the pelagic system. Attempts to integrate such biological responses into marine ecosystem and biogeochemical models suffer from a lack of empirical data. Here, we show, using an indoor-mesocosm approach, that rising temperature accelerates respiratory consumption of organic carbon relative to autotrophic production in a natural plankton community. Increasing temperature by 2-6 degrees C hence decreased the biological drawdown of dissolved inorganic carbon in the surface layer by up to 31%. Moreover, warming shifted the partitioning between particulate and dissolved organic carbon toward an enhanced accumulation of dissolved compounds. In line with these findings, the loss of organic carbon through sinking was significantly reduced at elevated temperatures. The observed changes in biogenic carbon flow have the potential to reduce the transfer of primary produced organic matter to higher trophic levels, weaken the ocean's biological carbon pump, and hence provide a positive feedback to rising atmospheric CO2.
    Type: Article , PeerReviewed
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  • 2
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    Application of supercritical CO2 in lipid extraction – A review (2009)
    Elsevier
    Details
    Publication Date: 2023-06-08
    Description: Supercritical fluid extraction (SFE) offers an alternative method to conventional extraction of fatty acids. SFE was developed for analytical application in the mid-1980s in response to the desire to reduce the use of organic solvents in the laboratory environment, and it is now becoming a standard method for the extraction, fractionation, refinement and deodorization of lipids or essential oils containing sample matrices at the industrial scale. This paper reviews applications of supercritical fluid technology in fatty acid/lipid extraction using carbon dioxide. Carbon dioxide is an ideal supercritical fluid because of its environmentally benign, non-toxic, non-flammable, non-polluting, recoverable characteristics and its ability to solubilise lipophilic substances. A summary of commercial applications and examples of recent developments of SFE in the food processing industry are also reviewed.
    Type: Article , PeerReviewed
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  • 3
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    Geotechnical characterization of the upper Pleistocene-Holocene alluvial deposits of Roma (Italy) by means of multivariate geostatistics: Cross-validation results (2009)
    Elsevier
    Details
    Publication Date: 2023-06-05
    Description: We are presenting an attempt to evaluate the spatial variability of geotechnical parameters in the upper Pleistocene–Holocene alluvial deposits of Roma (Italy) by means of multivariate geostatistics. The upper Pleistocene–Holocene alluvial deposits of Roma are sensitive to high levels of geohazard. They occupy a sizable and significant part of the city, being the foundation for many monuments, historical neighborhoods, and archaeological areas, and the main host of the present and future subway lines. We have stored information from more than 2000 geotechnical boreholes crossing the alluvial deposits into a relational database. For the present study, only the boreholes with lithologic/textural interpretation and geotechnical information were selected. The set includes 283 boreholes and 719 samples, which have a set of geotechnical information comprising physical properties and mechanical parameters. Techniques of multivariate statistics and geostatistics were combined and compared to evaluate the estimation methods of the mechanical parameters, with special reference to the drained friction angle from direct shear test (φ′). Principal Component Analysis was applied to the dataset to highlight the relationships between the geotechnical parameters. Through cross-validation analysis, multiple linear regression, kriging, and cokriging were tested as estimators of φ′. Cross-validation demonstrates that the cokriging with granulometries as auxiliary variables is the most suitable method to estimate φ′. In addition to proving that cokriging is a good estimator of φ′, cross-validation demonstrates that input data are coherent and this allows us to use them for estimation of geotechnical parameters, although they come from different laboratories and different vintages. Nevertheless, to get the same good results of cross-validation in estimation, it is necessary for granulometries to be available at grid points. Since this information being not available at all grid points, it is expected that, in the future, textural information can be derived in an indirect way, i.e., from lithologic/textural spatial reconstructions.
    Description: Published
    Description: 251-268
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: open
    Keywords: Alluvial deposits ; Geotechnical properties ; Principal Component Analysis ; Multivariate geostatistics ; Roma ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    Genes, enzymes and regulation of arginine biosynthesis in plants (2005)
    Elsevier
    Details
    Publication Date: 2023-04-25
    Description: Arabidopsis genes encoding enzymes for each of the eight steps in l-arginine (Arg) synthesis were identified, based upon sequence homologies with orthologs from other organisms. Except for N-acetylglutamate synthase (NAGS; EC 2.3.1.1), which is encoded by two genes, all remaining enzymes are encoded by single genes. Targeting predictions for these enzymes, based upon their deduced sequences, and subcellular fractionation studies, suggest that most enzymes of Arg synthesis reside within the plastid. Synthesis of the l-ornthine (Orn) intermediate in this pathway from l-glutamate occurs as a series of acetylated intermediates, as in most other organisms. An N-acetylornithine:glutamate acetyltransferase (NAOGAcT; EC 2.3.1.35) facilitates recycling of the acetyl moiety during Orn formation (cyclic pathway). A putative N-acetylornithine deacetylase (NAOD; EC 3.5.1.16), which participates in the “linear” pathway for Orn synthesis in some organisms, was also identified. Previous biochemical studies have indicated that allosteric regulation of the first and, especially, the second steps in Orn synthesis (NAGS; N-acetylglutamate kinase (NAGK), EC 2.7.2.8) by the Arg end-product are the major sites of metabolic control of the pathway in organisms using the cyclic pathway. Gene expression profiling for pathway enzymes further suggests that NAGS, NAGK, NAOGAcT and NAOD are coordinately regulated in response to changes in Arg demand during plant growth and development. Synthesis of Arg from Orn is further coordinated with pyrimidine nucleotide synthesis, at the level of allocation of the common carbamoyl-P intermediate.
    Type: Article , PeerReviewed
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  • 5
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    An assessment on seasonal analysis of wind energy characteristics and wind turbine characteristics (2005)
    Elsevier
    Details
    Publication Date: 2023-03-30
    Description: This paper presents seasonal variations of the wind characteristics and wind turbine characteristics in the regions around Elazig, namely Maden, Agin and Keban. Mean wind speed data in measured hourly time series format is statistically analyzed for the six year period 1998–2003. The probability density distributions are derived from the time series data and their distributional parameters are identified. Two probability density functions are fitted to the measured probability distributions on a seasonal basis. The wind energy characteristics of all the regions is studied based on the Weibull and Rayleigh distributions. Energy calculations and capacity factors for the wind turbine characteristics were determined for wind machines of different sizes between 300 and 2300 kW. It was found that Maden is the best region, among the regions analyzed, for wind characteristics and wind turbine characteristics.
    Type: Article , PeerReviewed
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  • 6
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    Comparison of entrainment in overflows simulated by z-coordinate, isopycnal and non-hydrostatic models (2006)
    Elsevier
    Details
    Publication Date: 2023-03-10
    Description: A series of idealised numerical simulations of dense water flowing down a broad uniform slope are presented, employing both a z-coordinate model (the MIT general circulation model) and an isopycnal coordinate model (the Hallberg Isopycnal Model). Calculations are carried out at several different horizontal and vertical resolutions, and for a range of physical parameters. A subset of calculations are carried out at very high resolution using the non-hydrostatic variant of the MITgcm. In all calculations dense water descends the slope while entraining and mixing with ambient fluid. The dependence of entrainment, mixing and down-slope descent on resolution and vertical coordinate are assessed. At very coarse resolutions the z-coordinate model generates excessive spurious mixing, and dense water has difficulty descending the slope. However, at intermediate resolutions the mixing in the z-coordinate model is less than found in the high-resolution non-hydrostatic simulations, and dense water descends further down the slope. Isopycnal calculations show less resolution dependence, although entrainment and mixing are both reduced slightly at coarser resolution. At intermediate resolutions the z-coordinate and isopycnal models produce similar levels of mixing and entrainment. These results provide a benchmark against which future developments in overflow entrainment parameterizations in both z-coordinate and isopycnal models may be compared.
    Type: Article , PeerReviewed
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  • 7
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    Effects of different closures for thickness diffusivity (2009)
    Elsevier
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    Publication Date: 2023-03-09
    Description: The effects of spatial variations of the thickness diffusivity (K) appropriate to the parameterisation of [Gent, P.R. and McWilliams, J.C., 1990. Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr., 20, 150–155.] are assessed in a coarse resolution global ocean general circulation model. Simulations using three closures yielding different lateral and/or vertical variations in K are compared with a simulation using a constant value. Although the effects of changing K are in general small and all simulations remain biased compared to observations, we find systematic local sensitivities of the simulated circulation on K. In particular, increasing K near the surface in the tropical ocean lifts the depth of the equatorial thermocline, the strength of the Antarctic Circumpolar Current decreases while the subpolar and subtropical gyre transports in the North Atlantic increase by increasing K locally. We also find that the lateral and vertical structure of K given by a recently proposed closure reduces the negative temperature biases in the western North Atlantic by adjusting the pathways of the Gulf Stream and the North Atlantic Current to a more realistic position.
    Type: Article , PeerReviewed
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  • 8
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    The applicability of accelerated solvent extraction (ASE) to extract lipid biomarkers from soils (2006)
    Elsevier
    Details
    Publication Date: 2023-02-17
    Description: We investigated the ability of accelerated solvent extraction (ASE) to extract selected lipid biomarkers (C19–C34 n-alkanes, n-alcohols and n-fatty acids as well as dehydroabietic acid and β-sitosterol) from a sandy soil profile under Corsican pine. Two organic layers (moss and F1) as well as two mineral soil horizons (EA and C1) were sampled and extracted with DCM/MeOH (93:7 v/v) by ASE at 75 °C and a pressure of 6.9 × 106 Pa or 17 × 106 Pa. Soxhlet extractions were used as the established reference method. After clean-up and derivatization with BSTFA, the extracts were analyzed on GC/MS. Using Soxhlet as a reference, we found ASE to extract all compounds adequately. The n-alkanes, especially, were found to be extracted very efficiently from all horizons studied. Only the n-fatty acids and β-sitosterol from the organic layers seemed to be extracted at a slightly lower efficiency by ASE. In all but two instances the relative abundance of extracted lipids within a component class was the same regardless of the extraction method used. Using a higher pressure in the ASE extractions significantly increased the extraction efficiency for all component classes in the moss layer, except β-sitosterol. The effect was most pronounced for the n-alkanes. In the EA horizon, a higher pressure slightly reduced the extraction efficiency for dehydroabietic acid. The observed differences between ASE and Soxhlet extractions as well as the pressure effect can be explained by a decrease in polarity of the extractant due to the elevated pressure and temperature applied during ASE extractions as compared to Soxhlet extractions. This would mainly increase the extraction efficiency of the least polar biomarkers: the n-alkanes as was observed. In addition, a better penetration of still partially water-filled micro pores under elevated pressure and temperature may have played a role.
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  • 9
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    Overriding plate controls spatial distribution of megathrust earthquakes in the Sunda-Andaman subduction zone (2006)
    Elsevier
    Details
    Publication Date: 2023-01-31
    Description: The historic record of large megathrust earthquakes suggests that the potential for great destructive events is much larger for Sumatra than Java. Bouguer gravity anomalies correlate well with the occurrence of large megathrust earthquakes in the Sunda subduction zone; negative anomalies mark segments characterized by larger earthquakes while positive anomalies indicate lower seismic potential. Thermal models and structural constraints derived from seismic and gravity data are used to explain the seismogenic behaviour in the Sunda subduction zone. With respect to Java, oblique subduction of young oceanic crust shifts the seismogenic coupling zone roughly 40 km trenchward offshore of northern Sumatra and increases the width of the locked megathrust. A prominent positive gravity anomaly offshore of Java is caused by a shallow mantle wedge underlying the forearc basin. A serpentinized mantle wedge would limit the width of the coupling zone off Java to only 30–40 km, compared to 〉 120 km offshore of Sumatra. Sumatra remains therefore the most vulnerable site for future megathrust earthquakes, while the shallow mantle wedge may limit the violence of rupture off Java.
    Type: Article , PeerReviewed
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  • 10
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    Acid-base regulatory capacity and associated proton extrusion mechanisms in marine invertebrates: An overview (2009)
    Elsevier
    Details
    Publication Date: 2023-01-31
    Description: Anthropogenic CO2 emissions will lead to an increased average ocean pCO2 of potentially 1900 ppm (ca. 0.2 kPa) by the year 2300 (Caldeira and Wickett 2003). Associated shifts in carbonate system speciation will cause ocean pH to fall by a maximum of 0.5–0.8 units. Most existing studies suggest that organisms/taxa with high standard metabolic rates, highly sophisticated convection systems and efficient gas exchange organs are coping best with elevated ocean pCO2. Typically, these taxa (decapod crustaceans, and cephalopods) are able to rapidly compensate extracellular pH by accumulating large amounts of bicarbonate. The underlying molecular machinery for this accumulatory response is still largely unknown for most marine invertebrate taxa. Thus, we will briefly review (a) acid-base regulatory responses in a range of marine invertebrates (bivalves, echinoderms, crustacea, and cephalopoda) and then (b) highlight and discuss their main ion-regulatory organs and potential acid-base regulatory proteins. In addition, we will present results from ongoing gene expression studies that specifically target transcripts relevant for ion- and acid-base regulation in the gill of the cephalopod Sepia officinalis, the crustacean Carcinus maenas and pluteus larvae of the sea urchin Strongylocentrotus purpuratus in response to environmental hypercapnia.
    Type: Article , PeerReviewed
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