Determination of variability of flow duration curve for non-stationary effects in Colombia

[ES] En el presente trabajo, se analizaron los cambios temporales en las curvas de duración de caudales CDC correspondientes a estaciones de caudales diarios en Colombia mediante la aplicación del test no paramétrico de Mann-Kendall, el Estimador de Pendiente de Sen y la pendiente de la regresión lineal de la serie. Se calculan caudales característicos con el fin de revisar tendencias a largo plazo entre distintas magnitudes o porcentajes de excedencia (percentiles 95, 75, 25 y 1). De forma adicional, se estima la tendencia en la desviación estándar en ventanas móviles de 10 años. Se observan tendencias crecientes significativas en las regiones del occidente (Chocó) y nordeste (Bajo cauca) de Colombia, mientras que para tendencias decrecientes no se observa ningún patrón espacial. Se encontraron tendencias con magnitudes entre –0.0068 m3/s/día y 0.047 m3/s/día.[EN] In this work, long term temporal changes are analyzed in several flow duration curves FDC from Colombian daily gauging stations by the mean of the application of non-parametric Mann-Kendall test, the Sen´s Slope Estimator and the slope of the linear regression of the time series. Characteristic flows were estimated aiming to analyze the existence of long-term trends in different flow magnitudes (percentiles corresponding to 95, 75, 25 and 1 percentage of exceedance). Additionally, standard deviation long term trend is estimated using a 10 years mobile window. Significant increasing trends are observed in the regions of Chocó (east) and Bajo Cauca (north-east) while decreasing trends did not present any particular spatial pattern. Long term trends magnitudes between –0.0068 m3/s/day and 0.047 m3/s/day were found.Los autores agradecen al Instituto de Hidrología Meteorología y Estudios Ambientales de Colombia IDEAM porque cuyos registros fueron parte fundamental de este análisisGaviria, C.; Carvajal-Serna, L. (2020). Determinación de la variabilidad de la curva de duración de caudales por efectos no estacionarios en Colombia. Ingeniería del agua. 24(4):269-283. https://doi.org/10.4995/ia.2020.13556OJS269283244Barriendos, M., Coeur, D., Lang, M., Llast, M.C., Naulet, R., Lemaître, D., Barrera, A. 2003. Stationarity analysis of historical flood series in France and Spain (14th-20th centuries). Natural Hazards and Earth System Sciences, 3, 583-592. https://doi.org/10.5194/nhess-3-583-2003Brown, A.E., Zhang, L., McMahon, T.A., Western, A.W., Vertessy, R.A. 2005. A review of paired catchment studies for determining changes in water yield resulting from alterations in vegetation. Journal of Hydrology, 310(1-4), 28-61. https://doi.org/10.1016/J.JHYDROL.2004.12.010Cantor, D., Ochoa, A. 2011. Señales de cambio climático en series de lluvia en Antioquia. IX Congreso Colombiano de Meteorología y Conferencia Internacional "200 Años de La Meteorología y de La Climatología En América Latina," 11. Bogotá - Colombia.Estupiñán, A. 2016. Estudio de la variabilidad espacio temporal de la precipitación en Colombia. Bdigital.Unal.Edu.Co, 118.Foster, H.A. 1933. Duration Curves. Proceedings of the American Society of Civil Engineers, 59(8), 1223-1246.Gilbert, R.O. 1987. Statistical methods for environmental pollution monitoring. Wiley.Hamed, K.H., Ramachandra, A. 1998. A modified Mann-Kendall trend test for autocorrelated data. Journal of Hydrology, 204(1-4), 182-196. https://doi.org/10.1016/S0022-1694(97)00125-XIDEAM. 2014. Estudio Nacional del Agua 2014.IPCC. 2014. Climate change 2014: synthesis report.Mann, H. 1945. Nonparametric tests against trend. Journal of the Econometric, 13(3), 245-259. https://doi.org/10.2307/1907187Pérez, C., Poveda, G., Mesa, O., Carvajal, L.F. 1998. Evidencias de cambio climático en Colombia: tendencias y cambios de fase y amplitud de los ciclos anual y semianual. Bulletin de l'Institut Français d'études Andines, 27(3), 537-543.Poveda, G., Jaramillo, A., Gil, M.M., Quiceno, N., Mantilla, R.I. 2001. Seasonality in ENSO-related precipitation, river discharges, soil moisture, and vegetation index in Colombia. Water Resources Research, 37(8), 2169-2178. https://doi.org/10.1029/2000WR900395Poveda, G., Álvarez, D.M., Rueda, Ó.A. 2011. Hydro-climatic variability over the Andes of Colombia associated with ENSO: A review of climatic processes and their impact on one of the Earth's most important biodiversity hotspots. Climate Dynamics, 36(11-12), 2233-2249. https://doi.org/10.1007/s00382-010-0931-yProsdocimi, I., Kjeldsen, T.R., Svensson, C. 2013. Non-stationarity in annual and seasonal series of peak flow and precipitation in the UK. Natural Hazards and Earth System Sciences Discussions, 1(5), 5499-5544. https://doi.org/10.5194/nhessd-1-5499-2013Sen, P.K. 1968. Estimates of the Regression Coefficient Based on Kendall's Tau. Journal of the American Statistical Association, 63(324), 1379-1389. https://doi.org/10.1080/01621459.1968.10480934Urán, J.D. 2016. Cambios en los valores extremos de variables climáticas en Colombia asociados a cambio climático. Repositorio Institucional - Universidad Nacional de Colombia, 121.Villarini, G., Serinaldi, F., Smith, J.A., Krajewski, W.F. 2009. On the stationarity of annual flood peaks in the continental United States during the 20th century. Water Resources Research, 45(8). https://doi.org/10.1029/2008WR007645Vogel, R.M., Fennessey, N.M. 1994. Flow-Duration Curves. I: New Interpretation and Confidence Intervals. Journal of Water Resources Planning and Management, 120(4), 485-504. https://doi.org/10.1061/(ASCE)0733-9496(1994)120:4(485)Westra, S., Sisson, S.A. 2011. Detection of non-stationarity in precipitation extremes using a max-stable process model. Journal of Hydrology, 406(1-2), 119-128. https://doi.org/10.1016/J.JHYDROL.2011.06.014WMO. 1995. INFOHYDROManal, Second edition, Operational Hydrology Report. Geneva

Surfactant effects in monodisperse magnetite nanoparticles of controlled size

Monodisperse magnetite Fe3O4 nanoparticles of controlled size within 6 and 20 nm in diameter were synthesized by thermal decomposition of an iron organic precursor in an organic medium. Particles were coated with oleic acid. For all samples studied, saturation magnetization Ms reaches the expected value for bulk magnetite, in contrast to results in small particle systems for which Ms is usually much smaller due to surface spin disorder. The coercive field for the 6 nm particles is also similar to that of bulk magnetite. Both results suggest that the oleic acid molecules covalently bonded to the nanoparticle surface yield a strong reduction in the surface spin disorder. However, although the saturated state may be similar, the approach to saturation is different and, in particular, the high-field differential susceptibility is one order of magnitude larger than in bulk materials. The relevance of these results in biomedical applications is discussed.Comment: 3 pages, 3 figures. Presented at JEMS 2006 (San Sebastian, Spain). Submitted to JMM

Ferrihidrita ferrimagnética: una historia de serendipia y radiación de sincrotón

II Encuentro sobre nanociencia y nanotecnología de investigadores y tecnólogos de la Universidad de Córdoba. NANOUC

Formation Mechanism of Maghemite Nanoflowers Synthesized by a Polyol-Mediated Process

Magnetic nanoparticles are being developed as structural and functional materials for use in diverse areas, including biomedical applications. Here, we report the synthesis of maghemite (¿-Fe2O3) nanoparticles with distinct morphologies: single-core and multicore, including hollow spheres and nanoflowers, prepared by the polyol process. We have used sodium acetate to control the nucleation and assembly process to obtain the different particle morphologies. Moreover, from samples obtained at different time steps during the synthesis, we have elucidated the formation mechanism of the nanoflowers: the initial phases of the reaction present a lepidocrocite (¿-FeOOH) structure, which suffers a fast dehydroxylation, transforming to an intermediate "undescribed" phase, possibly a partly dehydroxylated lepidocrocite, which after some incubation time evolves to maghemite nanoflowers. Once the nanoflowers have been formed, a crystallization process takes place, where the ¿-Fe2O3 crystallites within the nanoflowers grow in size (from ~11 to 23 nm), but the particle size of the flower remains essentially unchanged (~60 nm). Samples with different morphologies were coated with citric acid and their heating capacity in an alternating magnetic field was evaluated. We observe that nanoflowers with large cores (23 nm, controlled by annealing) densely packed (tuned by low NaAc concentration) offer 5 times enhanced heating capacity compared to that of the nanoflowers with smaller core sizes (15 nm), 4 times enhanced heating effect compared to that of the hollow spheres, and 1.5 times enhanced heating effect compared to that of single-core nanoparticles (36 nm) used in this work

Magnetic Nanoparticles for Power Absorption: optimizing size, shape and magnetic properties

We present a study on the magnetic properties of naked and silica-coated Fe3O4 nanoparticles with sizes between 5 and 110 nm. Their efficiency as heating agents was assessed through specific power absorption (SPA) measurements as a function of particle size and shape. The results show a strong dependence of the SPA with the particle size, with a maximum around 30 nm, as expected for a Neel relaxation mechanism in single-domain particles. The SiO2 shell thickness was found to play an important role in the SPA mechanism by hindering the heat outflow, thus decreasing the heating efficiency. It is concluded that a compromise between good heating efficiency and surface functionality for biomedical purposes can be attained by making the SiO2 functional coating as thin as possible.Comment: 15 pages, 7 figures, 2 table

The European Solar Telescope

The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operating in visible and near-infrared wavelengths: the Swedish 1m Solar Telescope, the German Vacuum Tower Telescope and GREGOR, the French Télescope Héliographique pour l'Étude du Magnétisme et des Instabilités Solaires, and the Dutch Open Telescope. With its 4.2 m primary mirror and an open configuration, EST will become the most powerful European ground-based facility to study the Sun in the coming decades in the visible and near-infrared bands. EST uses the most innovative technological advances: the first adaptive secondary mirror ever used in a solar telescope, a complex multi-conjugate adaptive optics with deformable mirrors that form part of the optical design in a natural way, a polarimetrically compensated telescope design that eliminates the complex temporal variation and wavelength dependence of the telescope Mueller matrix, and an instrument suite containing several (etalon-based) tunable imaging spectropolarimeters and several integral field unit spectropolarimeters. This publication summarises some fundamental science questions that can be addressed with the telescope, together with a complete description of its major subsystems

All-sky search for long-duration gravitational wave transients with initial LIGO

We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society

All-sky search for long-duration gravitational wave transients with initial LIGO

We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society

Dendrimers as anti-inflammatory agents

Dendrimers constitute an intriguing class of macromolecules which find applications in a variety of areas including biology. These hyperbranched macromolecules with tailored backbone and surface groups have been extensively investigated as nanocarriers for gene and drug delivery, by molecular encapsulation or covalent conjugation. Dendrimers have provided an excellent platform to develop multivalent and multifunctional nanoconjugates incorporating a variety of functional groups including drugs which are known to be anti-inflammatory agents. Recently, dendrimers have been shown to possess anti-inflammatory properties themselves. This unexpected and intriguing discovery has provided an additional impetus in designing novel active pharmaceutical agents. In this review, we highlight some of the recent developments in the field of dendrimers as nanoscale anti-inflammatory agents

The global burden of cancer attributable to risk factors, 2010–19: a systematic analysis for the Global Burden of Disease Study 2019

BACKGROUND: Understanding the magnitude of cancer burden attributable to potentially modifiable risk factors is crucial for development of effective prevention and mitigation strategies. We analysed results from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 to inform cancer control planning efforts globally. METHODS: The GBD 2019 comparative risk assessment framework was used to estimate cancer burden attributable to behavioural, environmental and occupational, and metabolic risk factors. A total of 82 risk–outcome pairs were included on the basis of the World Cancer Research Fund criteria. Estimated cancer deaths and disability-adjusted life-years (DALYs) in 2019 and change in these measures between 2010 and 2019 are presented. FINDINGS: Globally, in 2019, the risk factors included in this analysis accounted for 4·45 million (95% uncertainty interval 4·01–4·94) deaths and 105 million (95·0–116) DALYs for both sexes combined, representing 44·4% (41·3–48·4) of all cancer deaths and 42·0% (39·1–45·6) of all DALYs. There were 2·88 million (2·60–3·18) risk-attributable cancer deaths in males (50·6% [47·8–54·1] of all male cancer deaths) and 1·58 million (1·36–1·84) risk-attributable cancer deaths in females (36·3% [32·5–41·3] of all female cancer deaths). The leading risk factors at the most detailed level globally for risk-attributable cancer deaths and DALYs in 2019 for both sexes combined were smoking, followed by alcohol use and high BMI. Risk-attributable cancer burden varied by world region and Socio-demographic Index (SDI), with smoking, unsafe sex, and alcohol use being the three leading risk factors for risk-attributable cancer DALYs in low SDI locations in 2019, whereas DALYs in high SDI locations mirrored the top three global risk factor rankings. From 2010 to 2019, global risk-attributable cancer deaths increased by 20·4% (12·6–28·4) and DALYs by 16·8% (8·8–25·0), with the greatest percentage increase in metabolic risks (34·7% [27·9–42·8] and 33·3% [25·8–42·0]). INTERPRETATION: The leading risk factors contributing to global cancer burden in 2019 were behavioural, whereas metabolic risk factors saw the largest increases between 2010 and 2019. Reducing exposure to these modifiable risk factors would decrease cancer mortality and DALY rates worldwide, and policies should be tailored appropriately to local cancer risk factor burden