Effect of the nature of exogenous organic matter on pesticide sorption by the soil

A study was carried out on the sorption of two sparingly water-soluble pesticides (diazinon and linuron) by a sandy loam soil modified with different exogenous organic materials (EOMs) containing humic like substances: city refuse compost (CRC), peat (P), commercial humic acid (HA), liquid humic acid (LHA) extracted from leonardite and two (non humic) model compounds (surfactants): tetradecyltrimethylammonium bromide (TDTMA) and sodium dodecyl sulphate (SDS) before and after 2 and 8 months incubation periods with the soil. In all cases, the isotherms fitted the Freundlich sorption equation (x/m=KCen), generally with r2 values greater than 0.99. The value of the sorption constant K for the natural soil was 8.81 for diazinon and 2.29 for linuron. These values increased significantly for EOM modified soils with respect to natural soil, with the exception of the samples modified with SDS and LHA, in which cases they decreased, possibly due to the micellar properties of these compounds. Incubation of EOMs with soil increased their sorption capacity: the Koc values were increased proportionally to the incubation time for both pesticides and for all treatments carried out. Accordingly, the sorption capacity of hydrophobic pesticides increases with the degree of evolution in the soil of EOMs with humic type compounds, possibly due, among other causes, to the increase in the EOMs colloidal properties and the modifications occurring in the hydrophobic- hydrophilic characteristics of the soil surfaces. The main conclusion is that application to the soil of solid carbon rich wastes, especially those with a high degree of maturity, may offer an important strategy for reducing pesticide leaching, and for eliminating pesticide residues from soil with the use of liquid humic acids.Peer reviewe

Seasonal dynamic factor analysis and bootstrap inference : application to electricity market forecasting

Year-ahead forecasting of electricity prices is an important issue in the current context of electricity markets. Nevertheless, only one-day-ahead forecasting is commonly tackled up in previous published works. Moreover, methodology developed for the short-term does not work properly for long-term forecasting. In this paper we provide a seasonal extension of the Non-Stationary Dynamic Factor Analysis, to deal with the interesting problem (both from the economic and engineering point of view) of long term forecasting of electricity prices. Seasonal Dynamic Factor Analysis (SeaDFA) allows to deal with dimensionality reduction in vectors of time series, in such a way that extracts common and specific components. Furthermore, common factors are able to capture not only regular dynamics (stationary or not) but also seasonal one, by means of common factors following a multiplicative seasonal VARIMA(p,d,q)×(P,D,Q)s model. Besides, a bootstrap procedure is proposed to be able to make inference on all the parameters involved in the model. A bootstrap scheme developed for forecasting includes uncertainty due to parameter estimation, allowing to enhance the coverage of forecast confidence intervals. Concerning the innovative and challenging application provided, bootstrap procedure developed allows to calculate not only point forecasts but also forecasting intervals for electricity prices

Virtual cluster scheduling through the scheduling graph

This paper presents an instruction scheduling and cluster assignment approach for clustered processors. The proposed technique makes use of a novel representation named the scheduling graph which describes all possible schedules. A powerful deduction process is applied to this graph, reducing at each step the set of possible schedules. In contrast to traditional list scheduling techniques, the proposed scheme tries to establish relations among instructions rather than assigning each instruction to a particular cycle. The main advantage is that wrong or poor schedules can be anticipated and discarded earlier. In addition, cluster assignment of instructions is performed using another novel concept called virtual clusters, which define sets of instructions that must execute in the same cluster. These clusters are managed during the deduction process to identify incompatibilities among instructions. The mapping of virtual to physical clusters is postponed until the scheduling of the instructions has finalized. The advantages this novel approach features include: (1) accurate scheduling information when assigning, and, (2) accurate information of the cluster assignment constraints imposed by scheduling decisions. We have implemented and evaluated the proposed scheme with superblocks extracted from Speclnt95 and MediaBench. The results show that this approach produces better schedules than the previous state-of-the-art. Speed-ups are up to 15%, with average speed-ups ranging from 2.5% (2-Clusters) to 9.5% (4-Clusters).Peer ReviewedPostprint (published version

Effect of class size on student achievement in the COVID-19 "new normal"

The COVID-19 pandemic implied measures, such as school closures at the outbreak of the pandemic, that negatively affected children's human capital. However, in some places, the situation later brought a reduction in class sizes, in order to avoid the spread of SARS-Cov-2 at schools. We exploit this unexpected event to evaluate the effect on school performance of a sizable class size reduction implemented in Spain, when schools were reopened. We find a positive and significant effect of the class size reduction of 0.11 standard deviations on overall students performance. Given the situation and nature of our data, we interpret our estimates as a lower bound for the true effect of the reduction in class size. Our conclusion is that the reduction in class size served, on average, to at least compensate the other negative effects for learning. Our findings also point out at the importance of evaluating the quality of the new and unexperienced additional teachers that need to be hired when implementing a general reduction of class size.We are grateful to the Consejeria de Educación y Empleo of the regional Government of Extremadura (Spain) and the employees there that authorized and helped accessing the data. All remaining errors and responsibility for this work are our own. The fi rst author gratefully acknowledge research funding from the Agencia Estatal de Investigación del Gobierno de España, grant RTI2018-095231-B-I00, and Comunidad de Madrid (Spain), grant EPUC3M11 (V PRICIT). There is no other fi nantial sources nor potential con ict of interest to declare

Effect of the nature of exogenous organic matter on pesticide sorption by the soil

A study was carried out on the sorption of two sparingly water-soluble pesticides (diazinon and linuron) by a sandy loam soil modified with different exogenous organic materials (EOMs) containing humic like substances: city refuse compost (CRC), peat (P), commercial humic acid (HA), liquid humic acid (LHA) extracted from leonardite and two (non humic) model compounds (surfactants): tetradecyltrimethylammonium bromide (TDTMA) and sodium dodecyl sulphate (SDS) before and after 2 and 8 months incubation periods with the soil. In all cases, the isotherms fitted the Freundlich sorption equation (x/m=KCen), generally with r2 values greater than 0.99. The value of the sorption constant K for the natural soil was 8.81 for diazinon and 2.29 for linuron. These values increased significantly for EOM modified soils with respect to natural soil, with the exception of the samples modified with SDS and LHA, in which cases they decreased, possibly due to the micellar properties of these compounds. Incubation of EOMs with soil increased their sorption capacity: the Koc values were increased proportionally to the incubation time for both pesticides and for all treatments carried out. Accordingly, the sorption capacity of hydrophobic pesticides increases with the degree of evolution in the soil of EOMs with humic type compounds, possibly due, among other causes, to the increase in the EOMs colloidal properties and the modifications occurring in the hydrophobic- hydrophilic characteristics of the soil surfaces. The main conclusion is that application to the soil of solid carbon rich wastes, especially those with a high degree of maturity, may offer an important strategy for reducing pesticide leaching, and for eliminating pesticide residues from soil with the use of liquid humic acids.Peer reviewe