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

Estimation of Dynamic Nonlinear Random Effects Models with Unbalanced Panels

This paper presents and evaluates estimation methods for dynamic non-linear models with correlated random effects (CRE) when we have unbalanced panels. Accounting for the unbalancedness is crucial in dynamic non-linear models and ignoring it produces inconsistent estimates of the parameters even if the process that drives it is completely at random. We show that selecting a balanced panel from the sample can produce efficiency losses or even inconsistent estimates of the average marginal effects. In this paper we allow the sample selection process that determines the unbalancedness structure of the data to be arbitrarily correlated with the permanent unobserved heterogeneity. We discuss how to address the estimation by maximizing the likelihood function for the whole sample and also propose a Minimum Distance approach, which is computationally simpler and asymptotically equivalent to the Maximum Likelihood estimation. Our Monte Carlo experiments and empirical illustration show that our proposed estimation approaches perform better both in terms of bias and RMSE than the approaches that ignore the unbalancedness or that balance the sample.The authors gratefully acknowledge research funding from the Spanish Ministry of Education, Grants ECO2012-31358 and ECO2015-65204-P

Flora, fauna y aventuras : apuntes de un viaje por la India y por la China

Copia digital : Junta de Castilla y León. Conserjería de Cultura y Turismo, 201

Petrolero de crudo de 300.000 TPM

Traballo fin de mestrado (UDC.EPS). Enxeñaría naval e oceánica. Curso 2017/201

El accidente de trabajo "in itinere" = Working in the accident "itinere"

El trabajo aquí presentado aborda el estudio de los accidentes de trabajo, regulado al artículo 115 Ley General de Seguridad Social, y más concretamente el accidente in itinere, claro está, sin olvidar tampoco el accidente en misión. En la primera parte del trabajo, y una vez desarrollado el concepto de accidente de trabajo, el presente trabajo se centra en el estudio pormenorizado del accidente in itinere y sus requisitos (teleológico, topográfico, cronológico y mecánico). Por otro lado, se desarrolla el accidente el misión, enmarcándolo en su contexto y realizando una escueta diferenciación respecto el accidente in itinere. También se desarrolla la presunción de no laboralidad del accidente in itinere. Continuando con el trabajo, en la última parte se desarrollan los supuestos que no tienen la consideración de accidente in itinere pero siempre enmarcándolos dentro de los casos de accidente in itinere aunque en algunos casos exista una visión general

Performance, carcass and ruminal fermentation characteristics of heifers fed concentrates differing in energy level and cereal type (corn vs. wheat)

A total of 144 beef heifers (218 ± 26.4 kg body weight) were housed in 24 pens (6 animals each) and used in a 168-day feedlot study to evaluate the influence of cereal type and energy level on performance, carcass quality and ruminal fermentation. Four concentrates were formulated according to a 2×2 factorial arrangement of treatments, with two energy levels (1,452 vs. 1,700 kcal net energy/kg) and two main cereals (wheat vs. corn). Concentrate and straw were offered ad libitum. Concentrate intake and body weight were recorded on days 42, 84, 126 and 168. Ruminal fluid was obtained by ruminocentesis from 3 heifers per pen on days 1, 84 and 168; and carcass weight, classification and yield, were determined in the same animals. Heifers fed high-energy diets had lower intake (6.97 vs. 7.29 kg fresh matter/d; p=0.011), and lower concentrate to gain ratio (5.15 vs. 5.66 kg/kg; p=0.002) than those fed low energy concentrates, and tended (p=0.069) to be heavier along the time. Neither carcass yield and classification, nor ruminal pH, volatile fatty acids nor NH3-N concentrations were affected (p>0.050) by energy level. Total volatile fatty acids concentration tended (p=0.070) to be greater in heifers fed corn-based than wheat-based concentrates. No energy level x cereal type interactions were observed. These results indicate that high energy concentrates decreased feed intake and feed conversion but had minor effects on carcass performance. Cereal type had no effects on performance and ruminal fermentation and no interactions between cereal type and energy were detected

A review of the concept of resilience in the field of disasters and its evolution = Revisión del concepto de resiliencia en el campo de los desastres y su evolución

Abstract: Introduction: The resilience, as the ability to overcome adverse events and be able to have a successful development despite very adverse circumstances (disasters, wars, emergencies, severe trauma, etc.), has taken a great interest in recent years and has emerged as a key concept in disaster risk management. The purpose of this article is to present an integrated perspective on resilience through an extensive review of its literature over time. Method: Major health electronic databases were searched to retrieve critical relevant publications about the conceptual framework of resilience. Results: A total of 37 publications were included in the final analysis of this document. Definitions have evolved over time, but essentially the term ‘resilience’ is understood as referring to positive adaptation -the ability to maintain or recover mental health-, despite experiencing adversity. The interaction between personal, biological and environmental sources of resilience is also considered. Conclusion: The number of papers published by the term ‘resilience’ in their titles has been growing steadily over recent years. Resilience is a new term that requires greater conceptual clarification, mainly because of its importance as an example of human potential in facing disasters.Keywords: Resilience; disaster; emergency; concept analysis; disaster risk management.Resumen: Introducción: La resiliencia, o capacidad de superar los eventos adversos, y ser capaz de tener un desa­rrollo exitoso a pesar de circunstancias muy adversas (desastres, guerras, graves traumas, etc.), ha desper­tado un gran interés en años recientes y se ha convertido en un concepto clave en la gestión del riesgo de desastres. Este artículo tiene como objetivo presentar una perspectiva íntegra de la resiliencia a través de una extensa revisión a lo largo del tiempo. Método: Se efectuaron búsquedas en bases de datos electrónicas de salud para recuperar publicaciones relevantes que proporcionasen una descripción completa del marco conceptual de la capacidad de resiliencia. Resultados: Un total de 37 publicaciones se incluyeron en el análisis final de este documento. Las definiciones han evolucionado durante mucho tiempo, pero se entiende fundamentalmente que el concepto de resiliencia se refiere a la adaptación positiva (la capacidad de mante­ner o recuperar la salud mental), a pesar de experimentar adversidad. También se considera la interacción entre variables personales, biológicas y ambientales dentro de la resiliencia. Conclusiones: El número de trabajos publicados con el término ‘resiliencia’ en sus títulos ha ido creciendo de forma constante durante los últimos años. La resiliencia es un término nuevo que requiere una mayor clarificación conceptual, principal­mente debido a su importancia como ejemplo del potencial humano ante desastres.Palabras clave: Resiliencia; desastre; emergencia; análisis de conceptos; gestión del riesgo de desastres