Charging of highly resistive granular metal films

We have used the Scanning Kelvin probe microscopy technique to monitor the charging process of highly resistive granular thin films. The sample is connected to two leads and is separated by an insulator layer from a gate electrode. When a gate voltage is applied, charges enter from the leads and rearrange across the sample. We find very slow processes with characteristic charging times exponentially distributed over a wide range of values, resulting in a logarithmic relaxation to equilibrium. After the gate voltage has been switched off, the system again relaxes logarithmically slowly to the new equilibrium. The results cannot be explained with diffusion models, but most of them can be understood with a hopping percolation model, in which the localization length is shorter than the typical site separation. The technique is very promising for the study of slow phenomena in highly resistive systems and will be able to estimate the conductance of these systems when direct macroscopic measurement techniques are not sensitive enough.Comment: 8 pages, 7 figure

Efficient photovoltaic and electroluminescent perovskite devices

Planar diode structures employing hybrid organic-inorganic methylammonium lead iodide perovskites lead to multifunctional devices exhibiting both a high photovoltaic efficiency and good electroluminescence. The electroluminescence strongly improves at higher current density applied using a pulsed driving method

Synergetic Exploitation of the Sentinel-2 Missions for Validating the Sentinel-3 Ocean and Land Color Instrument Terrestrial Chlorophyll Index Over a Vineyard Dominated Mediterranean Environment

[EN] Continuity to the Medium Resolution Imaging Spectrometer (MERIS) Terrestrial Chlorophyll Index (MTCI) will be provided by the Ocean and Land Color Instrument (OLCI) on-board the Sentinel-3 missions. To ensure its utility in a wide range of scientific and operational applications, validation efforts are required. In the past, direct validation has been constrained by the need for costly airborne hyperspectral data acquisitions, due to the lack of freely available high spatial resolution imagery incorporating appropriate spectral bands. The Multispectral Instrument (MSI) on-board the Sentinel-2 missions now offers a promising alternative. We explored the synergetic use of MSI data for validation of the OLCI Terrestrial Chlorophyll Index (OTCI) over the Valencia Anchor Station, a large agricultural site in the Valencian Community, Spain. Using empirical and machine learning techniques applied to MSI data, in situ measurements were upscaled to the moderate spatial resolution of the OTCI. An RMSECV of 0.09 g.m(-2) (NRMSECV = 20.93%) was achieved, highlighting the valuable information MSI data can provide when used in synergy with OLCI data for land product validation. Good agreement between the OTCI and upscaled in situ measurements was observed (r = 0.77, p < 0.01), providing increased confidence to users of the product over vineyard dominated Mediterranean environments.This work was supported in part by the European Space Agency and European Commission through the Sentinel-3 Mission Performance Centre.Brown, LA.; Dash, J.; Lidón, A.; Lopez-Baeza, E.; Dransfeld, S. (2019). Synergetic Exploitation of the Sentinel-2 Missions for Validating the Sentinel-3 Ocean and Land Color Instrument Terrestrial Chlorophyll Index Over a Vineyard Dominated Mediterranean Environment. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 12(7):2244-2251. https://doi.org/10.1109/JSTARS.2019.28999982244225112

La selección clonal del limonero en España

La superficie dedicada al cultivo del limonero (Citrus limon (L.) Burm. f.) en España ha experimentado una gran expansión en los últimos veinte años, pasando de 10.000 ha en 1960 a 38.661 ha en 1980. En lo que concierne a las variedades cultivadas en España, la producción se basa en los cultivares autóctonos, siendo muy escasa hasta la fecha la importancia de las variedades extranjeras. Los limoneros "Verna" y "Fino" representan el 95% del total de producción (fig. 1). Otras variedades autóctonas como "Real", "Comunes", "Cuatro Estaciones" etc. están en franca regresión

Technical Note: A new device for cervical insemination of sheep - design and field test1

Deep semen deposition, avoiding retrograde flow, lesions and stress, has proved to be very important in the success of sheep AI. The objective of the present study was to develop a new, suitable antiretrograde flow device for sheep cervical AI (DARIO) that enables deep deposition of semen into the cervix without any modifications to the procedures currently used, and to compare the fertility, fecundity, and prolificacy rates between DARIO and a traditional catheter. Field tests were performed on 16 farms actively participating in the non-profit National Association of Rasa Aragonesa Breeders genetic selection scheme and where sheep management was similar. A total of 242 AI lots were considered, including 1, 299 ewes; 126 lots (662 ewes) were inseminated using DARIO, and 116 lots (637 ewes) using a traditional commercially-available catheter (control group). Several factors affecting AI results were included in the model for mean comparison between DARIO and control groups (farm and ram as random factors; catheter, year and photoperiod as fixed effects; catheter vó photoperiod interaction). The type of catheter had a significant effect on fertility (P &lt; 0.01) and fecundity rates (P &lt; 0.01) but no significant effect was detected on the prolificacy rate (P = 0.45). For fertility rate (percentage of ewes lambing after AI), means ¬± SE for DARIO and control groups were 59.44 ¬± 2.13% and 49.60 ¬± 2.48%, respectively; for fecundity rates, means ¬± SE for DARIO and control groups were 0.99 ¬± 0.04 and 0.82 ¬± 0.05 lambs/inseminated ewe, respectively, and, for prolificacy rates, means ¬± SE for DARIO and control groups were 1.68 ¬± 0.04 and 1.63 ¬± 0.04 lambs/ewe lambing, respectively. Fertility rate was greater in the decreasing photoperiod (P = 0.01). Significant effects were found for both year (P &lt; 0.05) and farm (P &lt; 0.01) on fertility, fecundity, and prolificacy rates. Neither ram nor catheter vó photoperiod showed any significant effects on the variables investigated (P &gt; 0.05). Overall, the use of DARIO instead of the traditional commercially-available catheter increased both fertility and fecundity rates; the marginal mean differences were 9.05 pregnant ewes per 100 inseminated and 0.15 lambs per inseminated ewe, respectively

Economic evaluation of mechanical harvesting of lemons

[EN] Several hypotheses regarding hand and mechanical harvesting have been analysed, in order to estimate the economic possibilities for the mechanical harvesting of lemons taking into account the current availability of technology. We considered several detachment options under experimental conditions; only yellow detachment has been considered for mechanical harvesting, because the sensitivity to the impacts is lower and mechanical detachment was high (80%). Price changes throughout the season were also considered. Total harvest cost is an average of the cost of mechanical harvesting (80%) and the cost of manually harvesting remaining fruit (20%), plus the cost of handling the mechanical harvested fraction. This cost ranges between 0.031 and 0.058 € kg-1 for outputs between 20 and 60 t ha-1, respectively, which is always lower than harvesting by hand (0.065 € kg-1). A Monte Carlo approach was used to study the sensitivity of the results, and Value at Risk (VaR) calculated. The analysis showed that the mechanical harvesting margin is c0.020 € kg-1 higher than the hand harvesting margin, and the output dispersion is higher in March. The VaR analysis showed that at 10% there was no risk that the hand margin is higher than the mechanical margin; at 5% the risk is very low and only for March harvesting. Mechanical harvesting represents a good economic option compared to hand harvesting, since it can increase farmer income by between 400 and 1200 € ha-1.This work was funded by Consejería de Agricultura y Agua de la Región de Murcia and by INIA and FEDER funds (project no. RTA2014-00025-C05-02).Brotons-Martínez, JM.; Martín-Górriz, B.; Torregrosa, A.; Porras, I. (2018). Economic evaluation of mechanical harvesting of lemons. Outlook on Agriculture. 47(1):44-50. https://doi.org/10.1177/0030727018762657S4450471Bordas, M., Torrents, J., Arenas, F. J., & Hervalejo, A. (2012). HIGH DENSITY PLANTATION SYSTEM OF THE SPANISH CITRUS INDUSTRY. Acta Horticulturae, (965), 123-130. doi:10.17660/actahortic.2012.965.15Burns, J. K., Roka, F. M., Li, K.-T., Pozo, L., & Buker, R. S. (2006). Late-season `Valencia’ Orange Mechanical Harvesting with an Abscission Agent and Low-frequency Harvesting. HortScience, 41(3), 660-663. doi:10.21273/hortsci.41.3.660Grafiadellis, I., Mattas, K., Maloupa, E., Tzouramani, I., & Galanopoulos, K. (2000). An Economic Analysis of Soilless Culture in Gerbera Production. HortScience, 35(2), 300-303. doi:10.21273/hortsci.35.2.300Manera, F. J., Brotons, J. M., Conesa, A., & Porras, I. (2012). Influence of temperature on the beginning of degreening in lemon peel. Scientia Horticulturae, 145, 34-38. doi:10.1016/j.scienta.2012.07.021Moreno, R., Torregrosa, A., Moltó, E., & Chueca, P. (2015). Effect of harvesting with a trunk shaker and an abscission chemical on fruit detachment and defoliation of citrus grown under Mediterranean conditions. Spanish Journal of Agricultural Research, 13(1), e0206. doi:10.5424/sjar/2015131-6590Roka, F. M., & Hyman, B. R. (2012). MECHANICAL HARVESTING OF SWEET ORANGES FOR JUICE PROCESSING. Acta Horticulturae, (965), 241-243. doi:10.17660/actahortic.2012.965.32Sanders, K. F. (2005). Orange Harvesting Systems Review. Biosystems Engineering, 90(2), 115-125. doi:10.1016/j.biosystemseng.2004.10.006A. Torregrosa, I. Porras, & B. Martín. (2010). Mechanical Harvesting of Lemons (cv. Fino) in Spain Using Abscission Agents. Transactions of the ASABE, 53(3), 703-708. doi:10.13031/2013.30062Wagner, H. M. (1995). Global Sensitivity Analysis. Operations Research, 43(6), 948-969. doi:10.1287/opre.43.6.948J. D. Whitney. (1999). FIELD TEST RESULTS WITH MECHANICAL HARVESTING EQUIPMENT IN FLORIDA ORANGES. Applied Engineering in Agriculture, 15(3), 205-210. doi:10.13031/2013.576

Using a simple model for water and nitrogentransport in soil in the practical works ofHorticulture

[EN] Simulation models for the transport of water and nitrogen in the soil are useful tools for evaluating the consequen-ces of di erent crop management practices without waiting until the end of the crop cycle. Particularly, simplecompartmental models for the transport of water and nitrogen are based on the solution of mass balance equationsfor the water and a system of ordinary di erential equations for the nitrogen cycle. In this work, these modelsare used to evaluate di erent possible scenarios of irrigation and nitrogen fertilization in a cauli ower crop, as apractical work for the students of Horticulture course. The results show that di erent irrigation and fertilizationstrategies lead to di erent results for the nitrate leaching, water drainage and nitrogen uptake[ES] Los modelos de simulación del transporte de agua y nitrógeno en el suelo son herramientas útiles para evaluar distintas prácticas de cultivo sin necesidad de tener que esperar a que se complete el ciclo de crecimiento. En concreto, los modelos compartimentales sencillos para el agua y el nitrógeno en el suelo se basan en ecuaciones de balance de masa y en la resolución de un sistema de ecuaciones diferenciales ordinarias. Se plantea la posibilidad de utilizar este tipo de modelos en las prácticas de la asignatura Horticultura, evaluando distintos escenarios posibles de riego y abonado en un cultivo de coliflor. Los resultados muestran que distintas prácticas de cultivo producen diferencias en la lixiviación de nitrato y en la extracción de nitrógeno por el cultivo.Lidón, A.; Ginestar, D.; Gómez De Barreda, D. (2017). Utilizacion de un modelo simple de transporte de agua y nitrógeno en el suelo en las practicas de Horticultura. Modelling in Science Education and Learning. 10(2):21-34. doi:10.4995/msel.2017.6600SWORD2134102Contreras, W. A., Lidón, A. L., Ginestar, D., & Bru, R. (2009). Compartmental model for nitrogen dynamics in citrus orchards. Mathematical and Computer Modelling, 50(5-6), 794-805. doi:10.1016/j.mcm.2009.05.008Lidón, A., Ramos, C., Ginestar, D., & Contreras, W. (2013). Assessment of LEACHN and a simple compartmental model to simulate nitrogen dynamics in citrus orchards. Agricultural Water Management, 121, 42-53. doi:10.1016/j.agwat.2013.01.008Cannavo, P., Recous, S., Parnaudeau, V., & Reau, R. (2008). Modeling N Dynamics to Assess Environmental Impacts of Cropped Soils. Advances in Agronomy Volume 97, 131-174. doi:10.1016/s0065-2113(07)00004-1Lidón, A., Ramos, C., & Rodrigo, A. (1999). Comparison of drainage estimation methods in irrigated citrus orchards. Irrigation Science, 19(1), 25-36. doi:10.1007/s002710050068Porporato, A., D’Odorico, P., Laio, F., & Rodriguez-Iturbe, I. (2003). Hydrologic controls on soil carbon and nitrogen cycles. I. Modeling scheme. Advances in Water Resources, 26(1), 45-58. doi:10.1016/s0309-1708(02)00094-5Wang, L., D’Odorico, P., Manzoni, S., Porporato, A., & Macko, S. (2009). Soil carbon and nitrogen dynamics in southern African savannas: the effect of vegetation-induced patch-scale heterogeneities and large scale rainfall gradients. Climatic Change, 94(1-2), 63-76. doi:10.1007/s10584-009-9548-

Utilización de un modelo compartimental de transporte de pesticidas en las prácticas de Química Agrícola y Ambiental

[EN] Computational models are useful tools in most of the knowledge areas and can be easily used to visualize the behaviour of complex systems. In this work, we present a simple com- partmental model to simulate the dynamics of the concentration of a given pesticide in a rice crop. The model considers different compartments such as: air, water, rice plants and sediments, which are coupled with a soil column modelled by means of a convection-advection equation. The model has been implemented in MatlabQc and has a Graphical User Interface (Gui) that allows to change easily the value of different parameters of the model and to obtain graphical representations of the results. Different possible applications of the model for a practical class of the subject Environmental and Agricultural Chemistry are proposed.[ES] Los modelos computacionales son herramientas útiles en la mayoría de las áreas de conocimiento y pueden ser fácilmente utilizados para visualizar el comportamiento de sistemas complejos. En este trabajo se presenta un modelo sencillo de compartimentos para simular la dinámica de la concentración de un plaguicida en un cultivo de arroz. En el modelo se consideran diferentes compartimentos, tales como: aire, agua, plantas de arroz y sedimentos al que se acopla una columna de suelo mediante una ecuación de convección-advección. El modelo ha sido implementado en MatlabQc y tiene una interfaz gráfica de usuario (Gui) que permite cambiar fácilmente el valor de los diferentes parámetros del modelo y obtener representaciones gráficas de los resultados. Se proponen también diferentes posibilidades de aplicación del modelo para una clase práctica de Química Ambiental y Agrícola.Contreras, W.; Bautista-Carrascosa, I.; Lidón, A.; Ginestar, D. (2011). Utilización de un modelo compartimental de transporte de pesticidas en las prácticas de Química Agrícola y Ambiental. Modelling in Science Education and Learning. 4:147-157. doi:10.4995/msel.2011.3068SWORD147157

Rainfall partitioning after thinning in two low-biomass semiarid forests: Impact of meteorological variables and forest structure on the effectiveness of water-oriented treatments

[EN] Water-oriented forest management is an urgent need in semiarid catchments. In the case of low-biomass forests and shrublands, the magnitude, efficiency and temporal duration of thinning effects on rainfall partitioning needs further attention. This work studies the effects of juvenile thinning and shrub clearing on stemflow (Stf), throughfall (Thr) and interception (It) in two low-biomass forests (CAL: post-fire Aleppo pine saplings with 74% of basal area, BA, removed; and HU: evergreen oak coppice with 41% of BA removed), as well as the relative contribution of the event meteorology. The effects are compared with a control plot during the first 3¿4¿years. Stf rate (%) decreased with density and, on a tree scale, it was enhanced by the treatment only in the bigger oaks. Event Thr increased from 55 to 81% and from 68 to 86% of gross rainfall (Pg) for CAL and HU respectively after thinning, resulting in about 15% less intercepted Pg. High evaporative conditions and an open (ventilated) forest structure led to high It rates in the controls when comparing with other studies, thus making the treatments more efficient in net precipitation (Pn) gain (Pg intercepted decreased 17% or 2.3% per unit of LAI or BA removed respectively). In general, depths (mm) were mostly explained (>75%) by the rainfall characteristics of the event (e.g. amount, duration, intensity), with a limited contribution from forest structure (e.g. cover, LAI) and event meteorology (e.g. temperature, wind speed, vapor pressure deficit). On the contrary, when expressed as rates (% of Pg), forest structure and event-meteorology gained importance (explaining 25¿65%), especially in the drier site (CAL). In this site, the low gain in Pn (~25¿mm per year on average) was offset with no temporal dampening during the span of this study, as observed in the wetter site (HU), where plant growth tended to mitigate the effect of the treatment by the end of the study. The results presented here make a contribution to a better understanding of the effects of water-oriented forest management in low-biomass semiarid forests.This study is a component of research projects: HYDROSIL (CGL2011-28776-C02-02), SILWAMED (CGL2014-58127-C3-2) and CEHYRFO-MED (CGL2017-86839-C3-2-R) funded by the Spanish Ministry of Science and Innovation and the FEDER fund of the EU. The authors are grateful to the Valencia Regional Government (CMAAUV, Generalitat Valenciana), Serra municipality, VAERSA and ACCIONA for their support in allowing the use of the experimental forest and for their assistance in carrying out the fieldwork.Campo García, ADD.; González Sanchís, MDC.; Lidón, A.; Ceacero Ruiz, CJ.; Garcia-Prats, A. (2018). Rainfall partitioning after thinning in two low-biomass semiarid forests: Impact of meteorological variables and forest structure on the effectiveness of water-oriented treatments. Journal of Hydrology. 565:74-86. https://doi.org/10.1016/j.jhydrol.2018.08.013S748656

Reactividad del catión 4,6-difenil-2-metiltiopiridinio N-sustituido frente a reactivos nucleófilos

Reactions of the cati&oacute;n 4,6-diphenyl-2-methythiopyridinium with several nucleophilic reagents are reported. Compound (III) reacts with triphenylphosphine to give the corresponding arylmethyl triphenyl phosphonium iodides. Similarly, (III) reacts with triethyl amine, sodium azide and sodium ac&eacute;tate to give the corresponding arylmethyl triethyl ammoniiim iodides, arylmethyl azides and arylmethyl aceta tes. Compound (III) reacts with mercury (II) chloride to give the corresponding pyridinium dichloroiodidemercuriates.Se describen las reacciones del cati&oacute;n 4,6-difenil-2-nietiltiopiridinio (III) frente a diferentes reactivos nucle&oacute;filos. El compuesto (III), reacciona con trifenilfosfina para dar los correspondientes yoduros de arilmetil trifenil fosfonio. Similarmente, (III) reacciona con trietilamina, azida de sodio y acetato de sodio para dar los correspondientes yoduros de arilmetil trietil amonio, arilmetil azidas y acetados de arilmetilo. El compuesto (III) reacciona con cloruro de mercurio (II) para dardos correspondientes dicloroyodomercuriatos de piridinio