Pierre Denis, "La valorización del país. La República Argentina". 1920. Buenos Aires, Ediciones Solar, 1987. 333 p.

Fil: Velazco, M. I.

Efecto de la adición de ácido cítrico y la cantidad de yeso sobre las propiedades del cemento de sulfoaluminato de calcio

The influence of citric acid on the hydration and strength development of a calcium sulphoaluminate cement was investigated. Cement pastes were prepared by mixing calcium sulphoaluminate (C4A3Ŝ) with 15, 20 and 25wt% of hemihydrate (CŜH0.5). Citric acid was added as a retarder at 0 and 0.5wt%. The samples were cured at 20 °C for periods of time from 1 to 28 days to evaluate their compressive strength and to characterize the hydration products by scanning electron microscopy and X-ray diffraction. Calorimetric curves showed that the retarding agent considerably decreases the heat release rate and the quantity of total heat released. The main product after the curing was ettringite (C6AŜ3H32). The morphology of this phase consisted of long and thin needles growing radially on the cement grains. Samples with 15wt% of hemihydrate and 0.5wt% of citric acid developed the highest compressive strength (70 MPa) at 28 days of curing.Se investigó el efecto del ácido cítrico sobre la hidratación y propiedades mecánicas de un cemento de sulfoaluminato de calcio. El C4A3Ŝ se mezcló con 15, 20 y 25% e.p. de hemihidrato (CŜH0.5). Se agregó ácido cítrico como retardante en 0 y 0.5% e.p. Las muestras fueron curadas a 20 °C por periodos de 1 a 28 días para realizar mediciones de resistencia a la compresión y caracterizar los productos de hidratación mediante microscopía electrónica de barrido y difracción de rayos X. Las curvas de calorimetría mostraron ue el ácido cítrico disminuye la velocidad de liberación de calor y la cantidad de calor liberado durante la hidratación. La resistencia a la compresión alcanzó un máximo de 70 MPa en muestras con 15% e.p. de hemihidrato y 0,5% e.p de ácido cítrico. Los resultados muestran a la etringita (C6AŜ3H32) como principal producto de hidratación. Se observa a esta fase con morfología acicular creciendo sobre las partículas de cemento

Efecto del contenido de aluminato de estroncio y hemihidrato sobre las propiedades de un cemento de sulfoaluminato de calcio

The effect of strontium aluminate (SrAl2O4) on the hydration process of a calcium sulphoaluminate (C4A3Ŝ) cement was investigated. Cement pastes were prepared by mixing C4A3Ŝ , hemihydrate (CaSO4· ½H2O, CŜH0.5) and 0, 10 or 20wt% of SrAl2O4 (SrA). The amount of CŜH0.5 was 15, 20 or 25wt% based on the C4A3Ŝ quantity. The cement pastes were hydrated using water to cement ratios (w/c) of 0.4 and 0.5. Samples were cured from 1 to 28 d. The compressive strength and setting time were evaluated and the hydration products were characterized. It was found that the setting time was delayed up to 42 min for the samples containing SrAl2O4 compared to samples without addition. The samples with 25wt% hemihydrate containing 20wt% SrAl2O4 developed the highest compressive strength (60 MPa) after 28 d of curing. The main product after hydration was ettringite (C6AŜ3H32). The morphology of this phase consisted of thin needle-shaped crystals.Se investigó el efecto de la adición de aluminato de estroncio (SrAl2O4) sobre las propiedades de un cemento de sulfoaluminato de calcio (C4A3Ŝ). Se prepararon muestras mezclando C4A3Ŝ, hemihidrato (CaSO4· ½H2O, CŜH0.5) y 0, 10 o 20% e.p de SrAl2O4 (SrA). La cantidad de CŜH0.5 fue de 15, 20 o 25% e.p. basado en la cantidad de C4A3Ŝ. Las relaciones agua/cemento utilizadas fueron 0.4 y 0.5. Las muestras fueron curadas hasta 28 d. Se evaluó el tiempo de fraguado y la resistencia a la compresión. Los productos de hidratación se caracterizaron mediante DRX y MEB. El tiempo de fraguado se retardó hasta 42 minutos con la adición del SrAl2O4 comparado con las muestras sin adiciones. Las muestras con 25% e.p. de yeso y 20% e.p. de SrAl2O4 desarrollaron la mayor resistencia a la compresión alcanzando 60 MPa a 28 d de curado. Los análisis por MEB y DRX muestran como principal producto de hidratación a la etringita (C6AŜ3H32), cuya morfología se observa como cristales aciculares

THE EMOTIONAL POWER OF ODORS: IDENTIFYING THE DIMENSIONS REFERRING TO FEELINGS PRODUCED BY ODORS

Abstract There is broad literature on the emotional effect of odors but, so far, little concern with the precise mechanism underlying the elicitation of emotions via olfactory stimuli. One reason for this neglect might be the lack of answers to a major question that underlie any research on odors and emotions: What exactly are the emotions associated to odors and how are they organised? The major issue addressed in the present paper concerns the nature of the verbal labels that refer to the specific states produced by odors. We conducted a series of studies in order to examine which terms are best suited to describe the feelings associated to odors and autobiographical memories. In Study 1, the relevance of a broad list of candidate affect terms to describe odor-related feelings was examined by two groups of participants with different level of knowledge about odors. In study 2, the most relevant terms retained from study 1 were evaluated with actual odorant samples and the data were submitted to a series of exploratory factor analyses to reduce the set of variables to a smaller set of summary-scales and to get a preliminary sense of the differentiation of affects elicited by odors. The Study 3 replicated Study 2 with a larger and more representative sample of odorant samples and participants. Overall, the findings point to a structure of affective responses to odors that differs from the more traditional taxonomies of emotion such as posited by discrete emotion or dimensional theories and suggest that affective states elicited by odors are structured around few dimensions that clearly reflect the role of olfaction in social interactions, danger prevention and arousal/relaxation sensations

Improved Constraints on Northern Extratropical CO₂ Fluxes Obtained by Combining Surface-Based and Space-Based Atmospheric CO₂ Measurements

Top‐down estimates of CO₂ fluxes are typically constrained by either surface‐based or space‐based CO₂ observations. Both of these measurement types have spatial and temporal gaps in observational coverage that can lead to differences in inferred fluxes. Assimilating both surface‐based and space‐based measurements concurrently in a flux inversion framework improves observational coverage and reduces sampling related artifacts. This study examines the consistency of flux constraints provided by these different observations and the potential to combine them by performing a series of 6‐year (2010–2015) CO₂ flux inversions. Flux inversions are performed assimilating surface‐based measurements from the in situ and flask network, measurements from the Total Carbon Column Observing Network (TCCON), and space‐based measurements from the Greenhouse Gases Observing Satellite (GOSAT), or all three data sets combined. Combining the data sets results in more precise flux estimates for subcontinental regions relative to any of the data sets alone. Combining the data sets also improves the accuracy of the posterior fluxes, based on reduced root‐mean‐square differences between posterior flux‐simulated CO₂ and aircraft‐based CO₂ over midlatitude regions (0.33–0.56 ppm) in comparison to GOSAT (0.37–0.61 ppm), TCCON (0.50–0.68 ppm), or in situ and flask measurements (0.46–0.56 ppm) alone. These results suggest that surface‐based and GOSAT measurements give complementary constraints on CO₂ fluxes in the northern extratropics and can be combined in flux inversions to improve constraints on regional fluxes. This stands in contrast with many earlier attempts to combine these data sets and suggests that improvements in the NASA Atmospheric CO₂ Observations from Space (ACOS) retrieval algorithm have significantly improved the consistency of space‐based and surface‐based flux constraints

Improved Constraints on Northern Extratropical CO₂ Fluxes Obtained by Combining Surface-Based and Space-Based Atmospheric CO₂ Measurements

Top‐down estimates of CO₂ fluxes are typically constrained by either surface‐based or space‐based CO₂ observations. Both of these measurement types have spatial and temporal gaps in observational coverage that can lead to differences in inferred fluxes. Assimilating both surface‐based and space‐based measurements concurrently in a flux inversion framework improves observational coverage and reduces sampling related artifacts. This study examines the consistency of flux constraints provided by these different observations and the potential to combine them by performing a series of 6‐year (2010–2015) CO₂ flux inversions. Flux inversions are performed assimilating surface‐based measurements from the in situ and flask network, measurements from the Total Carbon Column Observing Network (TCCON), and space‐based measurements from the Greenhouse Gases Observing Satellite (GOSAT), or all three data sets combined. Combining the data sets results in more precise flux estimates for subcontinental regions relative to any of the data sets alone. Combining the data sets also improves the accuracy of the posterior fluxes, based on reduced root‐mean‐square differences between posterior flux‐simulated CO₂ and aircraft‐based CO₂ over midlatitude regions (0.33–0.56 ppm) in comparison to GOSAT (0.37–0.61 ppm), TCCON (0.50–0.68 ppm), or in situ and flask measurements (0.46–0.56 ppm) alone. These results suggest that surface‐based and GOSAT measurements give complementary constraints on CO₂ fluxes in the northern extratropics and can be combined in flux inversions to improve constraints on regional fluxes. This stands in contrast with many earlier attempts to combine these data sets and suggests that improvements in the NASA Atmospheric CO₂ Observations from Space (ACOS) retrieval algorithm have significantly improved the consistency of space‐based and surface‐based flux constraints

Ground-based FTIR measurements of O3- and climate-related gases in the free troposphere and lower stratosphere

In the frame of the EC project UFTIR (Time series of Upper Free Troposphere observations from a European ground-based FTIR network), a common strategy for an optimal determination of the chemical composition in the free troposphere and lower stratosphere with ground-based Fourier-transform infrared (FTIR) spectrometers is being developed. The project focuses on 6 target species that are O3, CO, CH4, N2O, C2H6 and CHClF2 (HCFC-22). The strategy consists in selecting the most appropriate parameters to retrieve vertical concentration profiles from solar FTIR spectra. Among the important parameters are the spectral microwindows: they have been optimised to maximise the information content and to minimize the influence of poorly known spectroscopic data and interfering species