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Profile in a nutshell - COVerAGE-DB is an open-access database including cumulative counts of confirmed COVID-19 cases, deaths and tests by age and sex. Original data and sources are provided alongside data and measures in age-harmonized formats. - The database is in continuous development. It includes data since January 2020, and as of 7 January 2021, it includes 108 countries and 371 subnational areas. - The database also documents variations in definitions of all input data and indicators of reporting completeness across sources and over time. - An international team, composed of more than 60 researchers, contributed to the collection of data and metadata in COVerAGE-DB from governmental institutions, as well as to the design and implementation of the data processing and validation pipeline. We encourage researchers interested in supporting this project to send a message to the email: [coverage-db@demogr.mpg.de].

Supplementary materials, including separate sections on Facebook advertising campaigns, response rates, post-stratification approach, respondent selection, and threat perception of influenza. (PDF 3.2 MB)

Concrete structures are increasingly affected by fatigue damage, while new slender building structures with greater mechanical requirements make it necessary to deepen knowledge of their behaviour under fatigue loading. In this research, high-strength plain concrete was studied under two different frequencies of cyclic compressive stress. Wohler curves were obtained in two different ways, on the one hand, applying a uniform frequency of 10 Hz and, on the other hand, applying the specimen resonance frequency. The results show two different types of behaviour. A reduction in fatigue life was observed in those concretes tested at very high frequency. When loads were applied at resonance frequency, they did not seem to modify the breaking mechanisms of the concrete subjected to fatigue.

The English version of the questionnaire used in the study. (PDF 411 kB)

Nowadays, it is necessary to reduce the amount of aggregates extracted from quarries and the valorization of construction and demolition wastes as aggregates for the manufacture of recycled concrete can contribute to that end. One of the possible applications of this recycled concrete is the manufacture of elements for railway superstructure, such as sleepers in case of ballasted tracks or continuous slab in the case of ballastless tracks. For this purpose, it must be checked whether the compressive strength and durability required for conventional concrete can be provided and that the product properly responds to cyclical loads. This chapter begins by highlighting the importance of using recycled concrete for the manufacture of some elements of railway superstructure. Then the influence of fatigue on the behavior of concrete and, specifically, of recycled concrete is analyzed. Next the properties that are required in conventional concrete for the manufacture of railway superstructure elements are described. Finally, case studies are presented on the manufacture of railway superstructure components using recycled concrete.

Due to the large amount of CO2 emissions produced nowadays by the construction sector, the scientific community is looking for measures that will bring constructions to the be as environmental-friendly as possible. One of the most popular lines of research is the use of construction waste as recycled aggregates for the production of recycled aggregates concrete. Regarding the use of coarse recycled aggregates, there are a large number of studies that validate their use at both a mechanical and durability levels. Regarding the use of fine particles, which are inherent to the existence of coarse particles, it is necessary to increase the existing knowledge before they can be widely used. In this paper, the authors have sought to isolate the weakest part of those concrete mixes with exclusively recycled aggregate, i.e. a mortar made exclusively with fine recycled aggregates, in order to analyse the effect of drying-wetting cycles on mixes with recycled aggregates only. Specifically, three types of fine aggregates were used, one natural silica aggregate, one aggregate from crushed ballast and one from crushed sleepers. The mortars made with these aggregates were subjected to 50 durability cycles in distilled water, seawater and water with sulphates. Mechanical, visual and microstructural tests were carried out to analyse the effect of each of these environments on each of the mortars.

Increasing amounts of sustainable concretes are being used as society becomes more aware of the environment. This paper attempts to evaluate the properties of precast concrete elements formed with recycled coarse aggregate and low clinker content cement using recycled additions. To this end, six different mix proportions were characterized: a reference concrete, 2 concretes with 25%wt. and 50%wt. substitution of coarse aggregate made using mixed construction and demolition wastes, and others with recycled cement with low clinker content. The compressive strength, the elastic modulus, and the durability indicator decrease with the proportions of recycled aggregate replacing aggregate, and it is accentuated with the incorporation of recycled cement. However, all the precast elements tested show good performance with slight reduction in the mechanical properties. To confirm the appropriate behaviour of New Jersey precast barriers, a test that simulated the impact of a vehicle was carried out.

COVerAGE-DB is an open access database including cumulative counts of confirmed COVID-19 cases, deaths, and tests by age and sex. Original data and sources are provided alongside data and measures in age-harmonized formats. The database is still in development, and at this writing, it includes 87 countries, and 195 subnational areas. Cumulative counts of COVID-19 cases, deaths, and tests are recorded daily (when possible) since January 2020. Many time series thus fully capture the first pandemic wave and the beginning of later waves. An international team, composed of more than 60 researchers, contributed to the collection of data and metadata in COVerAGE-DB from governmental institutions, as well as to the design and implementation of the data processing and validation pipeline. We encourage researchers interested in supporting this project to send a message to the email: coverage-db@demogr.mpg.de

Surveys of the general population can provide crucial information for designing effective nonpharmaceutical interventions to tackle public health emergencies, such as the COVID-19 pandemic. Yet, conducting such surveys can be difficult, especially when timely data collection is required. In this viewpoint paper, we discuss our experiences with using targeted Facebook advertising campaigns to address these difficulties in relation to the COVID-19 pandemic. We describe central advantages, challenges, and practical considerations. This includes a discussion of potential sources of bias and how they can be addressed.

UNSTRUCTURED Surveys of the general population can provide crucial information for designing effective nonpharmaceutical interventions to tackle public health emergencies, such as the COVID-19 pandemic. Yet, conducting such surveys can be difficult, especially when timely data collection is required. In this viewpoint paper, we discuss our experiences with using targeted Facebook advertising campaigns to address these difficulties in relation to the COVID-19 pandemic. We describe central advantages, challenges, and practical considerations. This includes a discussion of potential sources of bias and how they can be addressed.

Physical distancing measures are intended to mitigate the spread of COVID-19, even though their impact on social contacts and disease transmission remains unclear. Obtaining timely data on social contact patterns can help to assess the impact of such protective measures. We conducted an online opt-in survey based on targeted Facebook advertising campaigns across seven European countries (Belgium, France, Germany, Italy, Netherlands, Spain, United Kingdom (UK)) and the United States (US), achieving a sample of 53,708 questionnaires in the period March 13–April 13, 2020. Post-stratification weights were produced to correct for biases. Data on social contact numbers, as well as on protective behaviour and perceived level of threat were collected and used to the expected net reproduction number by week,Rt, with respect to pre-pandemic data. Compared to social contacts reported prior to COVID-19, in mid-April daily social contact numbers had decreased between 49% in Germany and 83% in Italy, ranging from below three contacts per day in France, Spain, and the UK up to four in Germany and the Netherlands. Such reductions were sufficient to bringRtto one or even below in all countries, except Germany. Evidence from the US and the UK showed that the number of daily social contacts mainly decreased after governments issued the first physical distancing guidelines. Finally, although contact numbers decreased uniformly across age groups, older adults reported the lowest numbers of contacts, indicating higher levels of protection. We provided a comparable set of statistics on social contact patterns during the COVID-19 pandemic for eight high-income countries, disaggregated by week. As these estimates offer a more grounded alternative to the theoretical assumptions often used in epidemiological models, the scientific community could draw on this information for developing more realistic epidemic models of COVID-19.

There is a growing literature and interest on the study of the cognitive achievement gap between the top and bottom SES groups. Amidst public concern for this distancing between social classes, researchers have been unable to find an adequate explanation for the increasing cross-country inequality.In this paper, I argue that we need to refocus our efforts towards understanding better what correlates with the academic performance of both SES groups separately. By shifting attention to the amount of school autonomy that different schools have, I show that school autonomy over academic content, courses and text books is associated with a decrease of test scores of nearly .4 standard deviations for the bottom 10% performers in mathematics and literacy – a whole grade’s worth of knowledge. I show that this relationship holds under several specifications, including fixed effect models. In contrast, the same relationship turns positive when relating to the top 10% of students but it’s much weaker than for the bottom performers. These results point out that perhaps an explanation to the changing gaps is not symmetrical between groups but rather group specific. The importance of understanding what affects separate SES groups is paramount to understanding the achievement gap and these preliminary results can have important implications in policy making as they speak directly to education policy makers trying to fine tune the autonomy measures of their country.

In a future scenario in which all the concrete is recycled concrete, it will be necessary to recycle the recycled concrete. However, it is known that the recycling of concrete implies a loss of properties. This paper shows an innovative technique, the computerized microtomograph, used to evaluate closed porosity, volume of limestone aggregate fraction and volume of mortar of the multi-recycled aggregate concrete, in order to answer the question: how many times it is possible to recycle concrete? First, the source concrete mix using limestone coarse and fine aggregates was characterized. This mix was crushed to obtain a recycled aggregate that was used to manufacture the 1st generation or current recycled aggregate concrete. After the characterization of this 1st generation concrete, and in the same way, a 2nd and a 3rd generation concrete were obtained and characterized, using recycled aggregates from the 1st and 2nd concrete generations respectively. The evaluation by computerized axial tomography allows to know how the successive recycled affect the properties of the concrete. The results show that it is possible to observe the distribution and quantify the aggregate, cement paste and closed porosity contents of the recycled aggregate concrete showing that 3rd generation recycled concrete shows almost twice as much mortar as 1st generation one and demonstrates that it is only possible to recycle the concrete a finite number of times.

In this chapter, the filler or powder materials used in the radiation shielding industry are presented. The current trend is the use of boron-based compounds, abundant materials with relatively accessible costs and with which developers have extensive experience. Today more efficient boron-based compounds are still being developed, although the use of rare earths, the materials with the highest absorption cross section known among all the stable nuclei, represents a great advance in this field. Despite this advantage, these rare earths, based mainly on the use of samarium and gadolinium, have the disadvantage of emitting very high-energy secondary gamma radiation and being very dense, so their use has to be studied. An optimal solution for the development of new neutron shields is the use of boron-based materials that incorporate rare earths, enabling a compromise to be achieved to develop optimal neutron absorption solutions for different energy spectra.

In this chapter, the advancements in shielding materials used in the design of spent fuel containers are presented. Factors such as the target lifetime, the exposure environment, the type of container, and the energy spectrum of the source term are analyzed. The main types of containers and commercial products that incorporate different materials are shown and the main metals or alloys with potential applications for the manufacture of containers are analyzed. The principal specific materials for neutron shielding are described, which include both polymeric materials capable of scattering high-energy neutrons and other materials highly effective in absorbing thermal neutrons. Finally, the breakthrough in numerical simulation, an indispensable tool for model optimization and material selection, is described, with special emphasis on multilayer strategy, a very effective model that is based on the heterogenization of the component for shielding.

Background: Lexis surfaces are widely used to analyze demographic trends across periods, ages, and birth cohorts. When used to visualize rates or trends, these plots usually do not convey information about population size. The failure to communicate population size in Lexis surfaces can lead to misinterpretations of mortality or other conditions that populations face. For example, high mortality rates at very high ages have historically been experienced by only a small proportion of a population or cohort. Objective: We propose enhanced Lexis surfaces that include a visual representation of population size. The examples we present demonstrate how such plots can give readers a more intuitive understanding of the demographic development of a population over time. Methods: Visualizations are implemented using an R-Shiny application, building upon perception theories. Results: We present example plots for enhanced Lexis surfaces that show trends in cohort mortality and first-order differences in cohort mortality developments. These plots illustrate how adding the cohort size dimension allows us to extend the analytical potential of standard Lexis surfaces. Contribution: Our enhanced Lexis surfaces improve conventional depictions of period, age, and cohort trends in demographic developments of populations. An online interactive visualization tool based on Human Mortality Database data allows users to generate and export enhanced Lexis surfaces for their research. The R code to generate the application (and a link to the deployed application) can be accessed at https://github.com/cimentadaj/lexis_plot.

In this chapter, the influence of recycled aggregates (RAs) containing sulphur on recycled concrete (RC) is described. The RAs obtained by crushing clean concrete structures, concrete precast from unused components and clean civil engineering structures present amounts of sulphur and sulphates which are intentionally added to Portland cement, but that can adversely affect the RA and, consequently, the RA concrete. Detection methods are proposed to detect RAs containing excessive amounts of sulphates coming from the exposure of the original concrete structures to specific environments. Sources of sulphur is the RA coming from tested concrete specimens capped using pure sulphur or mortar of sulphur. The presence of sulphur in RAs can have adverse effects on the properties of fresh and hardened concrete. Losses of mechanical properties and durability are detected. The evaluation of the influence of sulphur on RC, according to its origin, and recommendations for their use are made.

By placing particular attention to the socio-economic dimension, this thesis explores the role of three pillars of an educational system: decentralization, early education and curricular tracking. The first article focuses on an experiment in Mexico that aimed to increase parental empowerment in the school's decision-making. Results show that increased participation produced an increase in cognitive abilities, however, this was mediated by the SES of the student. The second article brings an international perspective by comparing the evolution of the achievement gap over time in 32 countries. The findings suggest that tracking and vocational enrollment are important explanatory mechanisms of the cross-country variability in achievement gaps. The third article studies whether early education is associated with adult outcomes but concentrating on a particularly vulnerable population in the United States: GED recipients. Results show that participation in early education is associated with greater odds of graduating high school over attaining a GED. Esta tesis explora el rol de tres pilares de un sistema educativo: descentralización, educación temprana y seguimiento curricular. El primer artículo estudia un experimento en México que tuvo como objetivo aumentar el empoderamiento de padres en la toma de decisiones en la escuela. Los resultados muestran que mayor participación de los padres aumentó las habilidades cognitivas de sus hijos. Sin embargo, esto fue mediado por el SES del estudiante. El segundo artículo compara la evolución de la brecha de logros en 32 países. Los hallazgos sugieren que el seguimiento curricular y los estudios vocacionales pueden ser mecanismos explicativos de la brecha. El tercer artículo estudia si la educación temprana está asociada con resultados positivos en la adultez en Estados Unidos. Los resultados muestran que la participación en educación temprana está asociado con mayores probabilidades de graduarse de la escuela secundaria en comparación con la obtención de un GED.

This paper presents a novel technique used to analyse the volume of adhered mortar to the recycled aggregate. A computerized microtomograph (?CT) device was used to evaluate the volume of the aggregate, the volume of natural aggregate and the volume of adhered mortar. To this end, a natural aggregate has been characterized, using the ?CT, with which a source concrete has been produced. Subsequently, the source concrete has been crushed to obtain a first cycle recycled aggregate. After the characterization of the first-generation of recycled aggregate, a new source concrete has been made with it to be subsequently crushed again obtaining a second-generation recycled aggregates. In the same way a third-generation recycled aggregate has been obtained and has been equally characterized. The results show that the compaction capacity of the aggregate is reduced after successive recycling. It has been possible to quantify how much the closed porosity of the recycled aggregate decreases with the number of times it is recycled. The loss of natural aggregate and increase of the volume of adhered mortar have also been evaluated using this technique. The Erasmus+Program, founded by the Staff Mobility for Teaching Program of the European Council 2016/217, between Instituto Superior Técnico - University of Lisbon and the LADICIM - University of Cantabria. CERIS and the Foundation for Science and Technology (FCT) for funding this research.

The literature on achievement inequality has recently started to focus on the dynamics of the socio-economic achievement gap in cognitive abilities. The main findings come from research in the U.S. revealing that the 90th/10th income achievement gap has widened by about 50% in the last 30 years. This chapter aims to investigate whether there are discernible patterns in the evolution of the achievement gap from a comparative perspective. Using over 15 years of data and 32 countries from the Program for International Student Assessment (PISA), I find that there is considerable variation in the way in which the gap is evolving, with the U.S. and Germany closing at about 50% and 30% in the last 15 years while France is widening at a similar rate. I find that curricular tracking and vocational enrollment explain 40% of the variance in the achievement gap between countries and show that the relationship is conditioned by a strong interaction. Low curricular tracking is associated with a small achievement gap, whereas high levels of curricular tracking is associated with wide achievement gaps. However, once tracking is coupled with high vocational enrollment this can remedy the potential adverse effects and reduce the gap by over 1 standard deviation. I use simulations to show that switching to less curricular tracking can help decrease a country’s SES gap by about 11% while switching to more tracking would increase the achievement gap by about 51% percent.

The recent PIACC data offer us the first ever opportunity to identify the relative salience of abilities versus social origin in comparative social mobility research. Sampling 21 countries, we identify the degree of meritocratic selection by estimating the relative influence of social origin versus individual cognitive and social skills. We pay particular attention to the possibility of skills combinations as regards both upward and downward mobility. Social skills may compensate for weak cognitive abilities, or vice-versa; and what are the added effects of commanding strong skills on both counts? This is, as far as we know, the first time that comparative mobility research has examined such skills-complementarities. As in previous research we, too, uncover a significantly more egalitarian mobility pattern in the Nordic countries. This however obtains also for Canada and the Netherlands. A unique feature of Scandinavia is its asymmetric profile: significant upward mobility for those of low social origin, but surprisingly little downward mobility among those of privileged origins. Contrary to expectations, this cannot be ascribed to skills compensation. We find, however, that social skills play an important role for upward mobility among low-SES sons.