This open access edited volume is a comparative effort to discern the short-term educational impact of the covid-19 pandemic on students, teachers and systems in Brazil, Chile, Finland, Japan, ...Mexico, Norway, Portugal, Russia, Singapore, Spain, South Africa, the United Kingdom and the United States. One of the first academic comparative studies of the educational impact of the pandemic, the book explains how the interruption of in person instruction and the variable efficacy of alternative forms of education caused learning loss and disengagement with learning, especially for disadvantaged students. Other direct and indirect impacts of the pandemic diminished the ability of families to support children and youth in their education. For students, as well as for teachers and school staff, these included the economic shocks experienced by families, in some cases leading to food insecurity and in many more causing stress and anxiety and impacting mental health. Opportunity to learn was also diminished by the shocks and trauma experienced by those with a close relative infected by the virus, and by the constrains on learning resulting from students having to learn at home, where the demands of schoolwork had to be negotiated with other family necessities, often sharing limited space. Furthermore, the prolonged stress caused by the uncertainty over the resolution of the pandemic and resulting from the knowledge that anyone could be infected and potentially lose their lives, created a traumatic context for many that undermined the necessary focus and dedication to schoolwork. These individual effects were reinforced by community effects, particularly for students and teachers living in communities where the multifaceted negative impacts resulting from the pandemic were pervasive. This is an open access book.
Abstract Objectives The aim of this study was to provide a quantitative appraisal of the effects on clinical outcomes of radial access for coronary interventions in patients with coronary artery ...disease (CAD). Background Randomized trials investigating radial versus femoral access for percutaneous coronary interventions have provided conflicting evidence. No comprehensive quantitative appraisal of the risks and benefits of each approach is available across the whole spectrum of patients with stable or unstable CAD. Methods The PubMed, Embase, Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov databases were searched for randomized trials comparing radial versus femoral access for coronary interventions. Data were pooled by meta-analysis using a fixed-effects or a random-effects model, as appropriate. Pre-specified subgroup analyses according to clinical presentation, in terms of stable CAD, non–ST-segment elevation acute coronary syndromes, or ST-segment elevation myocardial infarction were performed. Results Twenty-four studies enrolling 22,843 participants were included. Compared with femoral access, radial access was associated with a significantly lower risk for all-cause mortality (odds ratio OR: 0.71; 95% confidence interval CI: 0.59 to 0.87; p = 0.001, number needed to treat to benefit NNTB = 160), major adverse cardiovascular events (OR: 0.84; 95% CI: 0.75 to 0.94; p = 0.002; NNTB = 99), major bleeding (OR: 0.53; 95% CI: 0.42 to 0.65; p < 0.001; NNTB = 103), and major vascular complications (OR: 0.23; 95% CI: 0.16 to 0.35; p < 0.001; NNTB = 117). The rates of myocardial infarction or stroke were similar in the 2 groups. Effects of radial access were consistent across the whole spectrum of patients with CAD for all appraised endpoints. Conclusions Compared with femoral access, radial access reduces mortality and MACE and improves safety, with reductions in major bleeding and vascular complications across the whole spectrum of patients with CAD.
We present the results of analysis of “snapshot” spectra of 253 metal-poor halo stars $-3.8\leq {\rm Fe/H} \leq -1.5$ obtained in the HERES survey. The snapshot spectra have been obtained with ...VLT/UVES and have typically $S/N\sim 54$ per pixel (ranging from 17 to 308), $R\sim20\, 000$, $\lambda = 3760$–4980 Å. This sample represents the major part of the complete HERES sample of 373 stars; however, the CH strong content of the sample is not dealt with here. The spectra are analysed using an automated line profile analysis method based on the Spectroscopy Made Easy (SME) codes of Valenti & Piskunov. Elemental abundances of moderate precision (absolute rms errors of order 0.25 dex, relative rms errors of order 0.15 dex) have been obtained for 22 elements, C, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, and Eu, where detectable. Of these elements, 14 are usually detectable at the 3σ confidence level for our typical spectra. The remainder can be detected in the least metal-poor stars of the sample, spectra with higher than average $S/N$, or when the abundance is enhanced. Among the sample of 253 stars, disregarding four previously known comparison stars, we find 8 r-II stars and 35 r-I stars. The r-II stars, including the two previously known examples CS 22892-052 and CS 31082-001, are centred on a metallicity of ${\rm Fe/H} = -2.81$, with a very small scatter, on the order of 0.16 dex. The r-I stars are found across practically the entire metallicity range of our sample. We also find three stars with strong enhancements of Eu which are s-process rich. A significant number of new very metal-poor stars are confirmed: 49 stars with ${\rm Fe/H}<-3$ and 181 stars with $-3<{\rm Fe/H}<-2$. We find one star with ${\rm Fe/H}<-3.5$. We find the scatter in the abundance ratios of Mg, Ca, Sc, Ti, Cr, Fe, Co, and Ni, with respect to Fe and Mg, to be similar to the estimated relative errors and thus the cosmic scatter to be small, perhaps even non-existent. The elements C, Sr, Y, Ba and Eu, and perhaps Zr, show scatter at ${\rm Fe/H} \la -2.5$ significantly larger than can be explained from the errors in the analysis, implying scatter which is cosmic in origin. Significant scatter is observed in abundance ratios between light and heavy neutron-capture elements at low metallicity and low levels of r-process enrichment.
HD\(\,\)172555 is a young (\(\sim\)20\(\,\)Myr) A7V star surrounded by a 10\(\,\)au wide debris disk suspected to be replenished partly by collisions between large planetesimals. Small evaporating ...transiting bodies, exocomets, have also been detected in this system by spectroscopy. After \(\beta\,\)Pictoris, this is another example of a system possibly witnessing a phase of heavy bombardment of planetesimals. In such system, small bodies trace dynamical evolution processes. We aim at constraining their dust content by using transit photometry. We performed a 2-day-long photometric monitoring of HD\(\,\)172555 with the CHEOPS space telescope in order to detect shallow transits of exocomets with a typical expected duration of a few hours. The large oscillations in the lightcurve indicate that HD\(\,\)172555 is a \(\delta\,\)Scuti pulsating star. Once removing those dominating oscillations, we find a hint for a transient absorption. If fitted with an exocomet transit model, it corresponds to an evaporating body passing near the star at a distance of \(6.8\pm1.4\,\)R\(_\star\) (or \(0.05\pm 0.01\,\)au) with a radius of 2.5 km. These properties are comparable to those of the exocomets already found in this system using spectroscopy, as well as those found in the \(\beta\,\)Pic system. The nuclei of solar system's Jupiter family comets, with radii of 2-6\(\,\)km, are also comparable in size. This is the first evidence for an exocomet photometric transit detection in the young system of HD\(\,\)172555.
Cyanobacteria are an integral part of Earth’s biogeochemical cycles and a promising resource for the synthesis of renewable bioproducts from atmospheric CO₂. Growth and metabolism of cyanobacteria ...are inherently tied to the diurnal rhythm of light availability. As yet, however, insight into the stoichiometric and energetic constraints of cyanobacterial diurnal growth is limited. Here, we develop a computational framework to investigate the optimal allocation of cellular resources during diurnal phototrophic growth using a genome-scale metabolic reconstruction of the cyanobacterium Synechococcus elongatus PCC 7942. We formulate phototrophic growth as an autocatalytic process and solve the resulting time-dependent resource allocation problem using constraint-based analysis. Based on a narrow and well-defined set of parameters, our approach results in an ab initio prediction of growth properties over a full diurnal cycle. The computational model allows us to study the optimality of metabolite partitioning during diurnal growth. The cyclic pattern of glycogen accumulation, an emergent property of the model, has timing characteristics that are in qualitative agreement with experimental findings. The approach presented here provides insight into the time-dependent resource allocation problem of phototrophic diurnal growth and may serve as a general framework to assess the optimality of metabolic strategies that evolved in phototrophic organisms under diurnal conditions.
This open access book provides an analysis of the effects of the COVID-19 Pandemic on diverse education systems, and of the results of the policies adopted to sustain educational opportunities. ...Through a series of diverse national case studies, the book examines the preexisting fragilities and vulnerabilities in educational structures which shaped the nature of the varied responses, around the world, to teaching and learning during the worst crisis in public education in recent history. The chapters in the book take stock of how educational opportunities changed in various education systems around the world as a result of the Covid-19 pandemic, answering the question of what did education systems, and societies, learn about education as a result of the pandemic. The book covers diverse education systems, with varying levels of resources and facing distinct education challenges, including Brazil, Chile, Finland, Japan, Mexico, Norway, Portugal, Russia, Singapore, Spain, South Africa, and the United States.
Context: TOI-2076 is a transiting three-planet system of sub-Neptunes orbiting a bright (G = 8.9 mag), young (\(340\pm80\) Myr) K-type star. Although a validated planetary system, the orbits of the ...two outer planets were unconstrained as only two non-consecutive transits were seen in TESS photometry. This left 11 and 7 possible period aliases for each. Aims: To reveal the true orbits of these two long-period planets, precise photometry targeted on the highest-probability period aliases is required. Long-term monitoring of transits in multi-planet systems can also help constrain planetary masses through TTV measurements. Methods: We used the MonoTools package to determine which aliases to follow, and then performed space-based and ground-based photometric follow-up of TOI-2076 c and d with CHEOPS, SAINT-EX, and LCO telescopes. Results: CHEOPS observations revealed a clear detection for TOI-2076 c at \(P=21.01538^{+0.00084}_{-0.00074}\) d, and allowed us to rule out three of the most likely period aliases for TOI-2076 d. Ground-based photometry further enabled us to rule out remaining aliases and confirm the \(P=35.12537\pm0.00067\) d alias. These observations also improved the radius precision of all three sub-Neptunes to \(2.518\pm0.036\), \(3.497\pm0.043\), and \(3.232\pm0.063\) \(R_\oplus\). Our observations also revealed a clear anti-correlated TTV signal between planets b and c likely caused by their proximity to the 2:1 resonance, while planets c and d appear close to a 5:3 period commensurability, although model degeneracy meant we were unable to retrieve robust TTV masses. Their inflated radii, likely due to extended H-He atmospheres, combined with low insolation makes all three planets excellent candidates for future comparative transmission spectroscopy with JWST.
Parental Involvement, Homework, and TV Time Keith, Timothy Z; Reimers, Thomas M; Fehrmann, Paul G ...
Journal of educational psychology,
10/1986, Letnik:
78, Številka:
5
Journal Article
Recenzirano
The current concern over the state of American education highlights the need to understand the important influences on school learning, especially those influences that are potentially manipulable. ...Parental involvement in students' academic and social lives, time spent doing homework, and leisure TV viewing are three variables generally considered to influence academic achievement, variables that may also be interrelated. In the present study, the direct and indirect effects of TV time, homework, and parental involvement on high school seniors' achievement were investigated by using the massive High School and Beyond data set. As expected, homework had an important, positive effect on student achievement, and TV time had a smaller, negative effect. Parental involvement had no direct effect on seniors' achievement scores but did positively influence the amount of time that seniors spent on homework. Further analysis suggested the possibilities of low homework demands and of excessive weekday TV viewing. Given the time spent on TV and homework and their influence on achievement, we suggest that these variables be considered in the current push for educational improvement.
This paper studies algorithms for decomposition, reconstruction, and approximation based on piecewise linear prewavelets on bounded triangulations of arbitrary topology. Our key mathematical result ...is showing that the Schur complement of the associated two scale matrix is symmetric, positive definite, and well conditioned. Numerical examples suggest that thresholding based on prewavelets yields a smaller approximation error than when based on the simple ‘Faber’ decomposition scheme.
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