Sample bias, weights and efficiency of weights in a continuous web voluntary survey

Using micro data from a continuous voluntary web survey, the Wage Indicator, the paper analyses the type of bias that such a sampling method produces and discusses a methodology to weight the data in order to correct such bias and make it possible to run analyses to obtain results and conclusions applicable to the whole population. In order to evaluate the efficiency of the weighting methodology to solve the potential sample bias of web surveys, the results are confronted with those obtained from an alternative standard labour survey dealing with the same issues. Since the Wage Indicator is a survey oriented to labour market issues, we considered that a labour market case study was most appropriate for the evaluation of the results. The method of evaluation followed is to calculate mean salaries, inequality indexes and salary regressions before and after implementing the weights using the Wage Indicator Survey data for Spain. The results are compared with those reached using the Structure of Earnings Survey, a wage survey run by the Spanish Statistical Institute

Survey vs Scraped Data: Comparing Time Series Properties of Web and Survey Vacancy Data

This paper studies the relationship between a vacancy population obtained from web crawling and vacancies in the economy inferred by a National Statistics Office (NSO) using a traditional method. We compare the time series properties of samples obtained between 2007 and 2014 by Statistics Netherlands and by a web scraping company. We find that the web and NSO vacancy data present similar time series properties, suggesting that both time series are generated by the same underlying phenomenon: the real number of new vacancies in the economy. We conclude that, in our case study, web-sourced data are able to capture aggregate economic activity in the labor market

Cross-Comparison of Climate Change adaptation Strategies Across Large River Basins in Europe, Africa and Asia

A cross-comparison of climate change adaptation strategies across regions was performed, considering six large river basins as case study areas. Three of the basins, namely the Elbe, Guadiana, and Rhine, are located in Europe, the Nile Equatorial Lakes region and the Orange basin are in Africa, and the Amudarya basin is in Central Asia. The evaluation was based mainly on the opinions of policy makers and water management experts in the river basins. The adaptation strategies were evaluated considering the following issues: expected climate change, expected climate change impacts, drivers for development of adaptation strategy, barriers for adaptation, state of the implementation of a range of water management measures, and status of adaptation strategy implementation. The analysis of responses and cross-comparison were performed with rating the responses where possible. According to the expert opinions, there is an understanding in all six regions that climate change is happening. Different climate change impacts are expected in the basins, whereas decreasing annual water availability, and increasing frequency and intensity of droughts (and to a lesser extent floods) are expected in all of them. According to the responses, the two most important drivers for development of adaptation strategy are: climate-related disasters, and national and international policies. The following most important barriers for adaptation to climate change were identified by responders: spatial and temporal uncertainties in climate projections, lack of adequate financial resources, and lack of horizontal cooperation. The evaluated water resources management measures are on a relatively high level in the Elbe and Rhine basins, followed by the Orange and Guadiana. It is lower in the Amudarya basin, and the lowest in the NEL region, where many measures are only at the planning stage. Regarding the level of adaptation strategy implementation, it can be concluded that the adaptation to climate change has started in all basins, but progresses rather slowl

As contradições do processo de desenvolvimento agrícola na Transamazônica.

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Potential-density pairs for axisymmetric galaxies: the influence of scalar fields

We present a formulation for potential-density pairs to describe axisymmetric galaxies in the Newtonian limit of scalar-tensor theories of gravity. The scalar field is described by a modified Helmholtz equation with a source that is coupled to the standard Poisson equation of Newtonian gravity. The net gravitational force is given by two contributions: the standard Newtonian potential plus a term stemming from massive scalar fields. General solutions have been found for axisymmetric systems and the multipole expansion of the Yukawa potential is given. In particular, we have computed potential-density pairs of galactic disks for an exponential profile and their rotation curves.Comment: 8 pages, no figures, corrected version to the one that will appear in Gen. Relativ. Gravit., where a small typo in eq. (13) is presen

Acantoma de células claras. Presentación de un paciente

The clear cell acanthoma is a rare benign epidermal tumor that occurs in adults, and is more common between 50 and 70 years of age. The typical lesion is a well-defined nodule, reddish, with some crusting and peripheral scales, measuring 1-2cm in diameter and usually has a collar. There are pigmented variants. A patient with this condition is reported. The treatment was surgical removal, which in turn is diagnostic and therapeutic.El acantoma de células claras es un raro tumor epidérmico benigno que ocurre en adultos y es más frecuente entre los 50-70 años de edad. La lesión típica es un nódulo bien delimitado, rojizo, con algunas costras y escamas periféricas, que mide de 1-2cm de diámetro y suele tener un collarete; existen variantes pigmentadas. Se presenta un paciente con esta afección donde el tratamiento fue la extirpación quirúrgica, que a su vez es diagnóstica y terapéutica

Quantum Fluctuations and the Unruh Effect in Strongly-Coupled Conformal Field Theories

Through the AdS/CFT correspondence, we study a uniformly accelerated quark in the vacuum of strongly-coupled conformal field theories in various dimensions, and determine the resulting stochastic fluctuations of the quark trajectory. From the perspective of an inertial observer, these are quantum fluctuations induced by the gluonic radiation emitted by the accelerated quark. From the point of view of the quark itself, they originate from the thermal medium predicted by the Unruh effect. We scrutinize the relation between these two descriptions in the gravity side of the correspondence, and show in particular that upon transforming the conformal field theory from Rindler space to the open Einstein universe, the acceleration horizon disappears from the boundary theory but is preserved in the bulk. This transformation allows us to directly connect our calculation of radiation-induced fluctuations in vacuum with the analysis by de Boer et al. of the Brownian motion of a quark that is on average static within a thermal medium. Combining this same bulk transformation with previous results of Emparan, we are also able to compute the stress-energy tensor of the Unruh thermal medium.Comment: 1+31 pages; v2: reference adde