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Articles de revues sur le sujet « Biocarbonates »

Auteur : Grafiati
Publié le 8 mars 2025

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1

Sun, Yali, et Min Sun. « Inductively Coupled Plasma Atomic Emission Spectrometry : An Efficient Tool for Precise Determination of Mg/Ca and Sr/Ca Ratios in Biocarbonates ». Applied Spectroscopy 57, no 6 (juin 2003) : 711–14. http://dx.doi.org/10.1366/000370203322005427.

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A method is developed to precisely determine Mg/Ca and Sr/Ca ratios in biocarbonates by inductively coupled plasma atomic emission spectrometry (ICP-AES). This method precision (RSD%) is 0.52% for Mg/Ca and 0.28% for Sr/Ca, respectively. The precision suggests that ICP-AES is satisfactory for supplying good quality Mg/Ca and Sr/Ca data of biocarbonates for paleo-reconstruction. This ICP-AES technique was applied to 51 continuous coral sub-samples, and the results show annually periodical variations in coral Mg/Ca and Sr/Ca ratios, which are consistent with previous findings.
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Peña Carrodeguas, L., À. Cristòfol, J. M. Fraile, J. A. Mayoral, V. Dorado, C. I. Herrerías et A. W. Kleij. « Fatty acid based biocarbonates : Al-mediated stereoselective preparation of mono-, di- and tricarbonates under mild and solvent-less conditions ». Green Chemistry 19, no 15 (2017) : 3535–41. http://dx.doi.org/10.1039/c7gc01206c.

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Kempe, Stephan, et Józef Kaźmierczak. « Satonda Crater Lake, Indonesia : Hydrogeochemistry and biocarbonates ». Facies 28, no 1 (décembre 1993) : 1–31. http://dx.doi.org/10.1007/bf02539726.

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Blanco, A., V. Orofino, M. D’Elia, S. Fonti, A. Mastandrea, A. Guido et F. Russo. « A spectroscopic method for identifying terrestrial biocarbonates and application to Mars ». Icarus 213, no 2 (juin 2011) : 473–79. http://dx.doi.org/10.1016/j.icarus.2011.03.027.

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Forjanes, Pablo, María Simonet Roda, Martina Greiner, Erika Griesshaber, Nelson A. Lagos, Sabino Veintemillas-Verdaguer, José Manuel Astilleros, Lurdes Fernández-Díaz et Wolfgang W. Schmahl. « Experimental burial diagenesis of aragonitic biocarbonates : from organic matter loss to abiogenic calcite formation ». Biogeosciences 19, no 16 (22 août 2022) : 3791–823. http://dx.doi.org/10.5194/bg-19-3791-2022.

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Abstract. Carbonate biological hard tissues are valuable archives of environmental information. However, this information can be blurred or even completely lost as hard tissues undergo diagenetic alteration. This is more likely to occur in aragonitic skeletons because bioaragonite often transforms into calcite during diagenesis. For reliably using aragonitic skeletons as geochemical proxies, it is necessary to understand in depth the diagenetic alteration processes that they undergo. Several works have recently investigated the hydrothermal alteration of aragonitic hard tissues during short-term experiments at high temperatures (T > 160 ∘C). In this study, we conduct long-term (4 and 6 months) hydrothermal alteration experiments at 80 ∘C using burial-like fluids. We document and evaluate the changes undergone by the outer and inner layers of the shell of the bivalve Arctica islandica, the prismatic and nacreous layers of the hard tissue of the gastropod Haliotis ovina, and the skeleton of the coral Porites sp. combining a variety of analytical tools (X-ray diffraction, thermogravimetry analysis, laser confocal microscopy, scanning electron microscopy, electron backscatter diffraction and atomic force microscopy). We demonstrate that this approach is the most adequate to trace subtle, diagenetic-alteration-related changes in aragonitic biocarbonate structural hard materials. Furthermore, we unveil that the diagenetic alteration of aragonitic biological hard tissues is a complex multi-step process where major changes occur even at the low temperature used in this study, well before any aragonite into calcite transformation takes place. Alteration starts with biopolymer decomposition and concomitant generation of secondary porosity. These processes are followed by abiogenic aragonite precipitation that partially or totally obliterates the secondary porosity. Only subsequently does the transformation of the aragonite into calcite occur. The kinetics of the alteration process is highly dependent on primary microstructural features of the aragonitic biomineral. While the skeleton of Porites sp. remains virtually unaltered for the entire duration of the conducted experiments, Haliotis ovina nacre undergoes extensive abiogenic aragonite precipitation. The outer and inner shell layers of Arctica islandica are significantly affected by aragonite transformation into calcite. This transformation is extensive for the prismatic shell layer of Haliotis ovina. Our results suggest that the majority of aragonitic fossil archives are overprinted, even those free of clear diagenetic alteration signs. This finding may have major implications for the use of these archives as geochemical proxies.
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Schramm, D. U., et A. M. Rossi. « Electron spin resonance (ESR), electron nuclear double resonance (ENDOR) and general triple resonance of irradiated biocarbonates ». Applied Radiation and Isotopes 47, no 11-12 (novembre 1996) : 1443–55. http://dx.doi.org/10.1016/s0969-8043(96)00197-2.

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Sun, Yali, et Min Sun. « Simultaneous determination of major, minor and trace elements in biocarbonates by inductively coupled plasma mass spectrometry ». Analytical and Bioanalytical Chemistry 374, no 7-8 (1 décembre 2002) : 1338–40. http://dx.doi.org/10.1007/s00216-002-1633-z.

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Béarez, Philippe, Gabriel Carlier, Jean-Pierre Lorand et Gian-Carlo Parodi. « Destructive and non-destructive microanalysis of biocarbonates applied to anomalous otoliths of archaeological and modern sciaenids (Teleostei) from Peru and Chile ». Comptes Rendus Biologies 328, no 3 (mars 2005) : 243–52. http://dx.doi.org/10.1016/j.crvi.2005.01.003.

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Casella, Laura A., Sixin He, Erika Griesshaber, Lourdes Fernández-Díaz, Martina Greiner, Elizabeth M. Harper, Daniel J. Jackson et al. « Hydrothermal alteration of aragonitic biocarbonates : assessment of micro- and nanostructural dissolution–reprecipitation and constraints of diagenetic overprint from quantitative statistical grain-area analysis ». Biogeosciences 15, no 24 (21 décembre 2018) : 7451–84. http://dx.doi.org/10.5194/bg-15-7451-2018.

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Abstract. The assessment of diagenetic overprint on microstructural and geochemical data gained from fossil archives is of fundamental importance for understanding palaeoenvironments. The correct reconstruction of past environmental dynamics is only possible when pristine skeletons are unequivocally distinguished from altered skeletal elements. Our previous studies show (i) that replacement of biogenic carbonate by inorganic calcite occurs via an interface-coupled dissolution–reprecipitation mechanism. (ii) A comprehensive understanding of alteration of the biogenic skeleton is only given when structural changes are assessed on both, the micrometre as well as on the nanometre scale.In the present contribution we investigate experimental hydrothermal alteration of six different modern biogenic carbonate materials to (i) assess their potential for withstanding diagenetic overprint and to (ii) find characteristics for the preservation of their microstructure in the fossil record. Experiments were performed at 175 °C with a 100 mM NaCl + 10 mM MgCl2 alteration solution and lasted for up to 35 days. For each type of microstructure we (i) examine the evolution of biogenic carbonate replacement by inorganic calcite, (ii) highlight different stages of inorganic carbonate formation, (iii) explore microstructural changes at different degrees of alteration, and (iv) perform a statistical evaluation of microstructural data to highlight changes in crystallite size between the pristine and the altered skeletons.We find that alteration from biogenic aragonite to inorganic calcite proceeds along pathways where the fluid enters the material. It is fastest in hard tissues with an existing primary porosity and a biopolymer fabric within the skeleton that consists of a network of fibrils. The slowest alteration kinetics occurs when biogenic nacreous aragonite is replaced by inorganic calcite, irrespective of the mode of assembly of nacre tablets. For all investigated biogenic carbonates we distinguish the following intermediate stages of alteration: (i) decomposition of biopolymers and the associated formation of secondary porosity, (ii) homoepitactic overgrowth with preservation of the original phase leading to amalgamation of neighbouring mineral units (i.e. recrystallization by grain growth eliminating grain boundaries), (iii) deletion of the original microstructure, however, at first, under retention of the original mineralogical phase, and (iv) replacement of both, the pristine microstructure and original phase with the newly formed abiogenic product.At the alteration front we find between newly formed calcite and reworked biogenic aragonite the formation of metastable Mg-rich carbonates with a calcite-type structure and compositions ranging from dolomitic to about 80 mol % magnesite. This high-Mg calcite seam shifts with the alteration front when the latter is displaced within the unaltered biogenic aragonite. For all investigated biocarbonate hard tissues we observe the destruction of the microstructure first, and, in a second step, the replacement of the original with the newly formed phase.
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Sastry, M. D., Marcelo B. Andrade et Shigueo Watanabe. « Saturation transfer EPR (ST-EPR) for dating biocarbonates containing large amount of Mn2+ : separation of SO3− and CO2− lines and geochronology of Brazilian fish fossil ». Radiation Measurements 37, no 2 (avril 2003) : 191–93. http://dx.doi.org/10.1016/s1350-4487(02)00173-7.

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Schramm, Delson U., Alexandre M. Rossi et George Bemski. « Electron Spin Resonance, Electron-Nuclear Double Resonance and General Triple Resonance Studies on the Contributions to Line Broadening ofCO2-in A-type Carbonated Apatites and Biocarbonates ». Japanese Journal of Applied Physics 37, Part 1, No. 2 (15 février 1998) : 502–8. http://dx.doi.org/10.1143/jjap.37.502.

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Thil, François, Dominique Blamart, Caroline Assailly, Claire E. Lazareth, Thierry Leblanc, John Butsher et Eric Douville. « Development of laser ablation multi-collector inductively coupled plasma mass spectrometry for boron isotopic measurement in marine biocarbonates : new improvements and application to a modern Porites coral ». Rapid Communications in Mass Spectrometry 30, no 3 (28 décembre 2015) : 359–71. http://dx.doi.org/10.1002/rcm.7448.

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Lerouge, C., F. Claret, M. A. Denecke, G. Wille, G. Falkenberg, C. Ramboz, C. Beny et al. « Comparative EPMA and μ-XRF methods for mapping micro-scale distribution of iodine in biocarbonates of the Callovian–Oxfordian clayey formation at Bure, Eastern part of the Paris Basin ». Physics and Chemistry of the Earth, Parts A/B/C 35, no 6-8 (janvier 2010) : 271–77. http://dx.doi.org/10.1016/j.pce.2010.04.003.

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Wirrmann, Denis, et Philippe Mourguiart. « Late Quaternary Spatio-temporal Limnological Variations in the Altiplano of Bolivia and Peru ». Quaternary Research 43, no 3 (mai 1995) : 344–54. http://dx.doi.org/10.1006/qres.1995.1040.

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AbstractBetween the western and eastern Andean cordilleras in Peru and Bolivia, there are three main lacustrine basins: Lake Titicaca, Lake Poopó, and the group of Coipasa-Uyuni. For the past few millennia, highly variable environmental conditions have been recorded in their sediments. Today a latitudinal meteorological gradient influences the lakes' status, leading to specific deposits and ostracod communities. Lake Titicaca in the north is oligohaline, whereas Lake Poopó further south is polyhaline. In the south, the Coipasa-Uyuni depression is characterized by a 12,000-km2 surficial salt crust. During the Late Pleistocene (ca. 40,000 to 25,000 yr B.P.), the water depth and salinity in paleolake Poopó fluctuated widely and paleolake Titicaca was slightly larger than at present. Sedimentation was mostly biocarbonate in the shallower areas and it was detrital-organic in the deepest zones. During the Holocene, a dry period transformed Lake Poopó into a "salar" with evaporite precipitation. Lake Titicaca registered a large decline in water level (8100-3600 yr B.P.) initially inducing gypsum precipitation followed by short influxes of water, with an ostracod faunal composition similar to that of the modern brines of Lake Poopó. Lake Titicacas' present condition only appeared between 2200 and 1500 yr B.P.
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Barton, Hazel. « Safe and effective disinfection of show cave infrastructure in a time of COVID-19 ». International Journal of Speleology 49, no 2 (mai 2020) : 137–47. http://dx.doi.org/10.5038/1827-806x.49.2.2332.

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The COVID-19 pandemic, caused by the novel coronavirus SARS-CoV-2, has been responsible for over 650,000 deaths worldwide. Transmission of SARS-CoV-2 occurs primarily through airborne transmission or direct human contact, demonstrating the importance of social distancing measures and the use of face masks to prevent infection. Nonetheless, the persistence of coronavirus on surfaces means that disinfection is important to limit the possibility of contact transmission. In this paper, the potential for various surfaces in show caves to serve as sources for SARS-CoV-2 infection is examined. Given the isoelectric potential (pI) of SARS and SARS-like coronaviruses, it is likely that they are adsorbed via electrochemical interactions to (limestone) rock surfaces, where the high humidity, pH and presence of biocarbonate ions will quickly lead to inactivation. Nonetheless, show caves contain infrastructure made of other non-porous surfaces that are more permissive for maintaining coronavirus viability. The 423 antiviral products approved by the US Environmental Protection Agency (EPA) were curated into 23 antiviral chemistries, which were further classified based on their potential to be hazardous, impact cave features or ecosystems, and those compounds likely to have the minimum impact on caves. The results suggest that alcohols (70% ethanol), organic acids (citric and lactic acid) and dilute hypochlorite represent the best disinfectants for in-cave use on non-porous surfaces. These disinfectants are able to inactivate coronaviruses inecosystems.
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Ujowundu, Favour N., Nathan N. Oparaeche, Chinyere Henrientta Onuoha, Moshood Abiola Haruna, Chukwudoruo Sunday Chieme et Cosmas O. Ujowundu. « Combretum dolichopentalum extract normalized biochemical and haematological parameters in carbon tetrachloride (CCL4) intoxicated rats ». AROC in Natural Products Research 1, no 2 (9 septembre 2021) : 17–28. http://dx.doi.org/10.53858/arocnpr01021728.

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Background: The ethanol extract of Combretum dolichopentalum (EECD) is employed in Nigeria to stabilize the uterus after parturition. The ability of EECD to confer protection on rats destabilized by moderate concentrations of carbon tetrachloride (CCl4) was evaluated. Methods: Fifty rats were assigned to 5 groups of 10 rats each. The experimental animals after acclimatization were handled accordingly: Groups 1 and 2 respectively were maintained on food and water only throughout the study. Group 3, 4, and group 5 were pre-treated with 250 mg/kg and 500 mg/kg body weight of EECD and 50 mg/kg of silymarin for 28 respectively. All groups except group 1 were intoxicated to 0.2 ml/kg body weight of CCl4, administered via an intraperitoneal route on day 29. Serum pipetted from the blood of the rats after cardiac puncture was assayed for antioxidant enzymes, lipid peroxidation product and serum iron, zinc and biocarbonate. Haematological analysis was also conducted. Results: Administration of CCl4 at 0.2 ml/kg b.w slightly increased the oxidizing species as indicated in the concentration of malondialdehyde in the rats while reducing the antioxidant enzymes; it increased the Iron and zinc concentrations and also the haematological parameters except for the white blood cells. However, this was corrected by pre-treatment with the EECD dosedependently. Conclusion: These characteristics portends that the crude ethanol extract of C. dolichopentalum could be employed to correct minor oxidative perturbation induced by CCl4 intoxication
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Nargis, W., BU Ahamed, Z. Hossain, S. Zabeen et N. Houqe. « Comparison of Conventionally Measured Serum Bicarbonate Values with Bicarbonate Values Obtained in Arterial and Venous Blood Gas Analysis ». Bangladesh Journal of Medical Biochemistry 5, no 1 (20 janvier 2013) : 12–15. http://dx.doi.org/10.3329/bjmb.v5i1.13425.

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Bicarbonate (HCO3-) measurement in serum or plasma from a sample of venous blood is routinely practiced in hospital patient management. HCO3- status can also be assumed from Blood gas analysis requiring arterial blood as sample which is cumbersome for both patients and doctors. This study was undertaken to evaluate the extent of agreement among biocarbonate values obtained during venous, arterial blood gas analysis and conventionally measured serum bicarbonate levels in a group of intensive care unit (ICU) patients to determine whether conventionally measured serum HCO3- (from peripheral venous blood) and calculated HCO3-values (from arterial blood gas [ABG] analyzers) can be used interchangeably. A total of 51 adult patients with diverse medical conditions, presenting at a tertiary health centre ICU were enrolled in this study when deemed by the treating physician to have an ABG analysis. Arterial and venous samples were taken as close in time as possible for blood gas analysis and routine blood tests. Bland-Altman analyses were used to compare the three methods. The HCO3- levels from ABG, Venous Blood gas (VBG) and tconventionally measured serum HCO3- showed acceptably narrow 95% limits of agreement using the Bland-Altman method. VBG reveals higher level of agreement with the ABG bicarbonate values compared to measured serum HCO3-. Thus, venous blood can be an alternate for arterial blood where ABG analyzer is available. conventionaly serum HCO3- measurements can also be useful and used as substitute for an expensive ABG analyzer in resource constrained health care sectors when required. DOI: http://dx.doi.org/10.3329/bjmb.v5i1.13425 Bangladesh J Med Biochem 2012; 5(1): 12-15
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Briguglio, Antonino, Grazia Vannucci, Clarissa Bruzzone et Michele Piazza. « Stratigraphic development of a Late Oligocene Reef Complex under strong fluviatile influence in the Tertiary Piedmont Basin (Liguria, NWItaly) ». Micropaleontology 67, no 4 (2021) : 315–39. http://dx.doi.org/10.47894/mpal.67.4.01.

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The modern-day decline of coral reefs due to bleaching events has been recognized as one of the major consequences of man-driven climate change. However, also eutrophication has been highlighted as an equally great danger for coral reefs and as such for biodiversity hotspots. In the latest years this phenomenon has moved to the forefront in the scientific community. Fossil reefs play a key role in studying the emergence, development and faunal/floral diversity of reef environments under eutrophic conditions. Their importance as valuable data sources for studying long-term changes of coral reef environments and their resilience cannot be disputed, especially since they may record the complete life cycle of a reef complex. In this study, nine sections nearby the town of Dego (Savona Province, NW Italy) are presented and discussed with regards to their lithostratigraphic and paleontological contents. Due to the extensive amount of data, the original morphology of a fringing reef, consisting of core, flank and fore reef, under strong fluviatile influence could be reconstructed. This study emphasizes the importance of the coralline red algae association in such biocarbonatic build-ups as major constituent and as substrate stabilizers. The sections record the original colonization event of the local basement by the builder community, the emergence of the coral reef and finally the suffocation by the fluviatile sediments. The variation of the red algae association reflects a deepening trend and is possibly correlated to enhanced fluvial input, which tends to deteriorate ecological conditions and functions as a major trigger for initial reef suffocation.
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Obiabunmo, Obiora, et Theresa Obiekezie. « Investigating the impact of solid waste dumpsites on groundwater quality : A case study of the Mkpuka Obosi Landfill ». Global Journal of Earth and Environmental Science 9, no 1 (30 juin 2024) : 15–27. https://doi.org/10.31248/gjees2024.146.

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Leachate, which refers to the contaminated fluid that results from water percolating through a landfill or waste disposal site, is a significant concern in sub-Saharan Africa. The uncontrolled release of leachate, particularly from dumpsites, is a primary contributor to groundwater pollution in the region. This research aimed to assess the impact of solid waste dumpsites on groundwater quality, specifically focusing on the landfill at Mkpuka Obosi. The study area was divided into eight concentric cells (C1-C8), each containing water and soil samples for analysis. The parameters examined include Temperature (OoC), pH, Iron (Fe2+), Lead (Pb2+), Copper (Cu), Zinc (Zn2+), Calcium (Ca), Sodium (Na), Magnesium (Mg2+), Suphate (SO2-4), Chloride (Cl-), Nitrate (N03-), Biocarbonate (HCO), Total Dissolved Solid (TDS), Biological Oxygen Demand (BOD), Total Suspended Solid (TSS), Chemical Oxygen Demand (COD), Total Hardness (TH), Electrical conductivity (EC), for the water analyses, while for soil analyses, pH values, Total organic carbon, Iron, Zinc, Temperature, Sand, Slit, Clay, Electric conductivity and copper were analyzed. The results were compared with relevant standards set by organizations like the World Health Organization (WHO). The findings indicated that parameters such as chemical oxygen demand, total suspended solids, chloride, nitrate, sodium, calcium, copper, lead, iron, and electrical conductivity exceeded the recommended standards. This suggests that water contamination from the dumpsite has adversely affected groundwater quality. Analysis of the graphs and tables revealed that the contamination spread decreased proportionally with distance from the dumpsite. As a result, water within approximately 500 m of the centre of the landfill was deemed unsuitable for consumption due to health risks and hazards. The water quality index ranged from 13 to 513, indicating that wells and boreholes located around 500 m from the dumpsite require significant treatment before being considered safe for consumption. The excess presence of sandy soil in the area, attributed to the geological formation, was found to contribute to the rapid flow of contaminants from the dumpsite. Coarse textured soils, being more permeable, have lower sorption potentials, while fine textured soils have slower permeability and higher sorption potentials. Consequently, the high proportion of coarse sandy soil surrounding the landfill favours the accelerated movement of contaminants.
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Zhang, Yi Ge, Mark Pagani, Zhonghui Liu, Steven M. Bohaty et Robert DeConto. « A 40-million-year history of atmospheric CO 2 ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 371, no 2001 (28 octobre 2013) : 20130096. http://dx.doi.org/10.1098/rsta.2013.0096.

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The alkenone– p CO 2 methodology has been used to reconstruct the partial pressure of ancient atmospheric carbon dioxide ( p CO 2 ) for the past 45 million years of Earth's history (Middle Eocene to Pleistocene epochs). The present long-term CO 2 record is a composite of data from multiple ocean localities that express a wide range of oceanographic and algal growth conditions that potentially bias CO 2 results. In this study, we present a p CO 2 record spanning the past 40 million years from a single marine locality, Ocean Drilling Program Site 925 located in the western equatorial Atlantic Ocean. The trends and absolute values of our new CO 2 record site are broadly consistent with previously published multi-site alkenone–CO 2 results. However, new p CO 2 estimates for the Middle Miocene are notably higher than published records, with average p CO 2 concentrations in the range of 400–500 ppm. Our results are generally consistent with recent p CO 2 estimates based on boron isotope-pH data and stomatal index records, and suggest that CO 2 levels were highest during a period of global warmth associated with the Middle Miocene Climatic Optimum (17–14 million years ago, Ma), followed by a decline in CO 2 during the Middle Miocene Climate Transition (approx. 14 Ma). Several relationships remain contrary to expectations. For example, benthic foraminiferal δ 18 O records suggest a period of deglaciation and/or high-latitude warming during the latest Oligocene (27–23 Ma) that, based on our results, occurred concurrently with a long-term decrease in CO 2 levels. Additionally, a large positive δ 18 O excursion near the Oligocene–Miocene boundary (the Mi-1 event, approx. 23 Ma), assumed to represent a period of glacial advance and retreat on Antarctica, is difficult to explain by our CO 2 record alone given what is known of Antarctic ice sheet history and the strong hysteresis of the East Antarctic Ice Sheet once it has grown to continental dimensions. We also demonstrate that in the Neogene with low CO 2 levels, algal carbon concentrating mechanisms and spontaneous biocarbonate–CO 2 conversions are likely to play a more important role in algal carbon fixation, which provides a potential bias to the alkenone– p CO 2 method.
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Bouhachim, Said, Amroumoussa Benmoussa, Amina Wafik, Abdessamad Najine et Raji Abdletife. « Contribution à la Reconnaissance Géologique et Géophysique du Pont Naturel d’Iminifri-Maroc ». European Scientific Journal, ESJ 19, no 40 (31 octobre 2023) : 1. http://dx.doi.org/10.19044/esj.2023.v19n40p1.

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Le pont naturel d’Iminifri l’objet de cette étude est situé dans la commune de Tifni. Administrativement, il relève du cercle de Demnate, la Province d’Azilal-Maroc.L’étude géologique et géophysique des différentes formations pour la vérification de la stabilité du pont . la l’analyse des résultats et leur interprétation montre que l’ossature du pont naturel d’Iminifri est formée principalement de concrétions travertineuses calcaires. Ce sont des formations quaternaire sconstituées par desdépôts bio-carbonatés correspondant à d’anciennes émergences liasiques aujourd’hui disparues ou déplacées. La nature variée des formations travertineuses témoignent de leur formation dans des milieux différents : les ruptures de pente, les chenaux à écoulement pérenne, les berges concaves des méandres soumises à l’action prolongée des embruns dégagés par l’agitation de l’eau. Plusieurs types d’encroûtement travertineux ont été identifiés. Les plus abondants sont les encroûtements plans, les encroûtements de buissons, les encroûtements sur support végétal et les encroûtements sur galets. Toutes les constatations effectuées confirment que les matériaux de la dalle formant l’ossature du pont sont fragilisés et visiblement dégradés. La lente altération et le comportement différé des matériaux soumis à des contraintes agressives sont en général à l’origine de la dégradation des conditions de stabilité. Des facteurs exogènes jouent également un rôle prépondérant comme les infiltrations pluviales et les vibrations engendrées par le trafic routier. Ils peuvent brutalement accélérer un processus de dégradation qui semblait être de plus en plus accentué. Objectif de cette étude à la vérification de la stabilité du pont et à l’analyse des résultats et leur interprétation. La reconnaissance géologique a été complétés par des investigations géophysiques en utilisant des méthodes adaptées aux conditions pétrophysiques des formations géologiques D’après les études effectuées sur le pont, il est raisonnable de dire que la structure d’Iminifri évolue plus ou moins rapidement vers sa ruine. Ce qui nous pousse à trouver des solutions urgentes pour sauver ce patrimoine géologique du danger d’effondrement. The natural bridge of Iminifri, the subject of this study, is located in the commune of Tifni. Administratively, it falls under the Demnate circle, Azilal Province, Morocco. The geological and geophysical study of the various formations is aimed at verifying the stability of the bridge. The analysis of the results and their interpretation shows that the framework of the natural bridge of Iminifri is primarily composed of limestone travertine concretions. These are Quaternary formations consisting of biocarbonate deposits corresponding to ancient Liassic emergencies that have since disappeared or shifted. The diverse nature of the travertine formations reflects their formation in different environments: slope breaks, perennial flow channels, concave banks of meanders subjected to the prolonged action of spray generated by water agitation. Several types of travertine encrustations have been identified, including flat encrustations, bushy encrustations, encrustations on vegetation, and encrustations on pebbles. All observations confirm that the materials forming the bridge's framework are weakened and visibly degraded. Slow deterioration and delayed behavior of materials subjected to aggressive stresses are generally the cause of deteriorating stability conditions. Exogenous factors also play a significant role, such as rainwater infiltration and vibrations generated by road traffic. They can abruptly accelerate a degradation process that appeared to be increasingly pronounced. The objective of this study is to verify the stability of the bridge and analyze the results and their interpretation. Geological reconnaissance was complemented by geophysical investigations using methods adapted to the petrophysical conditions of the geological formations. Based on the studies conducted on the bridge, it is reasonable to conclude that the structure of Iminifri is evolving towards its ruin, more or less rapidly. This pushes us to urgently find solutions to save this geological heritage from the danger of collapse.
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« Evonik develops ‘biocarbonates’ from CO2 and soybeans ; further invests in precipitated silica ». Additives for Polymers 2014, no 7 (juillet 2014) : 2. http://dx.doi.org/10.1016/s0306-3747(14)70098-3.

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Belinchón, Alejandro, Elisa Hernández, Javier Vázquez, Rubén Santiago, Cristian Moya, Marcos Larriba, Pablo Navarro et José Palomar. « Biocarbonates Derived from CO2 and Terpenes : Molecular Design for Aqueous Mixture Treatment Driven by COSMO-RS ». ACS Sustainable Chemistry & ; Engineering, 12 juillet 2022. http://dx.doi.org/10.1021/acssuschemeng.2c02993.

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Adams, Arthur, Damien Daval, Lukas P. Baumgartner, Sylvain Bernard, Torsten Vennemann, Deyanira Cisneros-Lazaro, Jarosław Stolarski et al. « Rapid grain boundary diffusion in foraminifera tests biases paleotemperature records ». Communications Earth & ; Environment 4, no 1 (27 avril 2023). http://dx.doi.org/10.1038/s43247-023-00798-2.

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AbstractThe oxygen isotopic compositions of fossil foraminifera tests constitute a continuous proxy record of deep-ocean and sea-surface temperatures spanning the last 120 million years. Here, by incubating foraminifera tests in 18O-enriched artificial seawater analogues, we demonstrate that the oxygen isotopic composition of optically translucent, i.e., glassy, fossil foraminifera calcite tests can be measurably altered at low temperatures through rapid oxygen grain-boundary diffusion without any visible ultrastructural changes. Oxygen grain boundary diffusion occurs sufficiently fast in foraminifera tests that, under normal upper oceanic sediment conditions, their grain boundaries will be in oxygen isotopic equilibrium with the surrounding pore fluids on a time scale of <100 years, resulting in a notable but correctable bias of the paleotemperature record. When applied to paleotemperatures from 38,400 foraminifera tests used in paleoclimate reconstructions, grain boundary diffusion can be shown to bias prior paleotemperature estimates by as much as +0.86 to −0.46 °C. The process is general and grain boundary diffusion corrections can be applied to other polycrystalline biocarbonates composed of small nanocrystallites (<100 nm), such as those produced by corals, brachiopods, belemnites, and molluscs, the fossils of which are all highly susceptible to the effects of grain boundary diffusion.
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Zhang, Dong, Wengang Zhang, Yang Yang, Hanlong Liu et Liang Cheng. « Enhancing splitting tensile strength of biocarbonated reactive magnesia-based sand using polypropylene fiber reinforcement ». Acta Geotechnica, 16 avril 2022. http://dx.doi.org/10.1007/s11440-022-01562-0.

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