1,510 research outputs found

    Future chlorine-bromine loading and ozone depletion

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    The prediction of future ozone requires three elements: (1) a scenario for the net emissions of chemically and radiatively active trace gases from the land and oceans; (2) a global atmospheric model that projects the accumulation of these gases; and (3) a chemical transport model that describes the distribution of ozone for a prescribed atmospheric composition and climate. This chapter, of necessity, presents models for all three elements and focuses on the following: (1) atmospheric abundance of chlorine and bromine in the form of halocarbons; and (2) the associated perturbations to stratospheric ozone

    Validation and analysis of regional present-day climate and climate change simulations over Europe

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    In the European Commission (EC) project "Regionalization of Anthropogenic Climate Change Simulations, RACCS, recently terminated, 11 European institutions have carried out tests of dynamical and statistical regionalization techniques. The outcome of the "dynamical part" of the project, utilizing a series of high resolution LAMs and a variable resolution global model (all of which we shall refer to as RCMs, Regional Climate Models), is presented here. The per- formance of the dqterent LAMs had first, in a preceding EC project, been tested with "perfect" boundary forcing fields (ECMWF analyses) and also multi-year present-day climate simula- tions with AMIP "perfect ocean " or mixed layer ocean GCM boundary conditions had been validated against available climatological data. The present report involves results of vali- dation and analysis of RCM present-day climate simulations and anthropogenic climate change experiments. Multi-year (5 - 30 years) present-day climate simulations have been per- formed with resolutions between 19 and 70 km (grid lengths) and with boundary conditions from the newest CGCM simulations. The climate change experiments involve various 2xCO2 - ]xCO2 transient greenhouse gas experiments and in one case also changing sulphur aerosols. A common validation and inter-comparison was made at the coordinating institution, MPIfor Meteorology. The validation of the present-day climate simulations shows the importance of systematic errors in the low level general circulation. Such errors seem to induce large errors in precipitation and surface air temperature in the RCMs as well as in the CGCMs providing boundary conditions. Over Europe the field of systematic errors in the mean sea level pressure (MSLP) usually involve an area of too low pressure, often in the form of an east-west trough across Europe with too high pressure to the north and south. New storm-track analyses confirm that the areas of too low pressure are caused by enhanced cyclonic activity and similarly that the areas of too high pressure are caused by reduced such activity. The precise location and strength of the extremes in the MSLP error field seems to be dependent on the physical param- eterization package used. In model pairs sharing the same package the area of too low pressure is deepened further in the RCM compared to the corresponding CGCM, indicating an increase of the excessive cyclonic activity with increasing resolution. From the experiments performed it seems not possible to decide to what extent the systematic errors in the general circulation are the result of local errors in the physical parameterization schemes or remote errors trans- mitted to the European region via the boundary conditions. Additional errors in precipitation and temperature seems to be due to direct local effects of errors in certain parameterization schemes and errors in the SSTs taken from the CGCMs. For all seasons many biases are fOund to be statistically significant compared to estimates of the internal model variability of the time- slice mean values. In the climate change experiments statistically significant European mean temperature changes which are large compared to the corresponding biases are found. How- ever, the changes in the deviations from the European mean temperature as well as the changes in precipitation are only partly sign wcan ce and are of the same order of magnitude or smaller than the corresponding biases found in the present-day climate simulations. Cases of an inter- action between the systematic model errors and the radiative forcing show that generally the errors are not canceling out when the changes are computed. Therefore, reliable regional cli- mate changes can only be achieved after model improvements which reduce their systematic errors sufficiently. Also in future RCM experiments sujiciently long time-slices must be used in order to obtain statistically sign ijicant climate changes on the sub-continental scale aimed at with the present regionalization technique

    Worldwide Research Trends on Transvenous Embolization of Brain Arteriovenous Malformations: A Bibliometric and Visualized Study

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    Background: Transvenous embolization (TVE) of brain arteriovenous malformations (bAVMs) is an emerging endovascular technique that has shown high cure rates in selected cases. The rationale of our study was to determine authorship and worldwide institutional trends and contributions to the knowledge in this topic. Methods: Web of Science database was used. A total of 63 articles were included based on predefined inclusion criteria, which were manually reviewed. The bibliometric analysis involved the use of quantitative bibliometric indicators and network analysis with co-authorship and co-occurrence of terms, which were performed using the bibliometrix package in R and VOSviewer, respectively. Results: The first article was published in 2010, with the largest number of articles published in 2022 (10 articles). The average number of citations per document was 11.38, and the annual growth rate was 14.35%. The top 10 authors with the most scientific production on TVE of bAVMs were from France, and the most cited study was published by Iosif C in 2015, followed by Consoli A in 2013, and Chen CJ in 2018. Journal of Neurointerventional Surgery was the journal with the most articles published. The most commonly used keywords were dural arteriovenous fistula, Onyx, vascular disorders, and neurological surgery around 2016, and intervention around 2021. Conclusions: TVE of bAVMs is an emerging technique. Our search identified some scientific articles, without randomized clinical trials, but many case series from single institutions. French and German institutions are the pioneers in the field, and further research is required in specialized endovascular centers.Revisión por pare

    DSS-Saltirsoil: un sistema de ayuda a la decisión en internet para la obtención de recomendaciones de gestión del riego y el cultivo en tierras amenazadas por salinización

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    En el presente trabajo se presenta un ejemplo de utilización del sistema de ayuda a la decisión DSS-SALTIRSOIL para la recomendación del riego en una plantación de caqui “Rojo Brillante” en la zona de riegos del Magro de la Ribera del Xúquer (Valencia). De acuerdo con la simulación realizada con datos de la zona representativos de su meteorología (año 2010), suelo (franco arcilloso), calidad de agua (2.3 dS/m) y manejo del riego (goteo) y el cultivo, se esperaría una pérdida del 15% de producción como consecuencia de la salinización. Un incremento de la dotación anual de riego de 140 mm, o una disminución de la salinidad hasta 2.0 dS/m reducirían dicha pérdidas a tan solo un 10% en dicho año de meteorología media. No obstante, la simulación del periodo 2000-2015 indica que una disminución de 100 mm en la precipitación anual media supone una amenaza de pérdida de producción de más del 20% en promedio. En consecuencia una solución satisfactoria a los problemas de salinidad en el cultivo del caqui en la zona pasa necesariamente por usar aguas de riego de salinidad más baja (< 2.0 dS/m), o bien por un cambio del patrón del caqui a uno más tolerante a la salinidad como es el D. virginiana.In this article an example of utilization of the decision support system DSSSALTIRSOIL is shown for the recommendation of irrigation in a persimmon "Rojo Brillante" plantation in the Magro irrigation district in the Ribera del Xúquer (Valencia). According to the simulation carried out with data from the area, which is representative of the meteorology (2010), soil (clay loam), water quality (2.3 dS / m) and irrigation (drip) and crop management, 15% yield losses would be expected as a result of salinization. An increase in the annual irrigation dose of 140 mm, or a decrease in salinity down to 2.0 dS / m would reduce such losses to only 10% in such a year of average meteorology. However, the simulation of the span 2000-2015 indicates that an average decrease of 100 mm in the annual rainfall poses a threat of yield losses over 20% on average. Consequently a satisfactory solution for the salinity problems in persimmon cropping in the area necessarily involves using irrigation water of lower salinity (<2.0 dS / m), or replacing the persimmon rootstock by a more salttolerant one such as the D. virginiana.Ministerio de Ciencia e Innovación 14592-C02-01Ministerio de Ciencia e Innovación CGL2009-14592-C02-0

    Mixing and reaction efficiency in closed domains

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    We present a numerical study of mixing and reaction efficiency in closed domains. In particular we focus our attention on laminar flows. In the case of inert transport the mixing properties of the flows strongly depend on the details of the Lagrangian transport. We also study the reaction efficiency. Starting with a little spot of product we compute the time needed to complete the reaction in the container. We found that the reaction efficiency is not strictly related to the mixing properties of the flow. In particular, reaction acts as a "dynamical regulator".Comment: 11 pages, 10 figure

    Effects of muffin processing on fumonisins from 14C-labeled toxins produced in cultured corn kernels.

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    The persistence of fumonisins during cooking is known to be affected by several factors, including thermal degradation and the presence of various ingredients in corn-based food recipes that can react with the toxin. A method for the production of corn kernels containing 14C-fumonisins was developed. The corn kernels were colonized by Fusarium verticillioides MRC 826 and supplemented with 1,2-14C-sodium acetate. The specific activity of 14C-FB1 produced made the study of its fate in cornmeal muffins possible. The double-extraction acetonitrile-water-methanol/immunoaffinity column/o-phthaldialdehyde high-performance liquid chromatography (HPLC) method was used to determine FB1 levels in cornmeal muffins. Reductions in FB1 levels in muffins spiked with 14C-labeled and unlabeled FB1 (43 and 48%, respectively) were similar, indicating that the extraction method was efficient and consistent with previous reports. However, with the labeled corn kernel material, recovery levels based on the 14C counts for the eluate from an immunoaffinity column were much higher (90%). This finding indicates that some fumonisin-related compounds other than FB1 that were present in the cornmeal were recognized by the antibodies but not by the HPLC method
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