Acropolis Educational Resources Repository
Not a member yet
31278 research outputs found
Sort by
Prediction of brain age and cognitive age: quantifying brain and cognitive maintenance in aging
No full textThe concept of brain maintenance refers to the preservation of brain integrity in older age, while cognitive reserve refers to the capacity to maintain cognition in the presence of neurodegeneration or aging‐related brain changes. While both mechanisms are thought to contribute to individual differences in cognitive function among older adults, there is currently no “gold standard” for measuring these constructs. Using machine‐learning methods, we estimated brain and cognitive age based on deviations from normative aging patterns in the Whitehall II MRI substudy cohort (N = 537, age range = 60.34–82.76), and tested the degree of correspondence between these constructs, as well as their associations with premorbid IQ, education, and lifestyle trajectories. In line with established literature highlighting IQ as a proxy for cognitive reserve, higher premorbid IQ was linked to lower cognitive age independent of brain age. No strong evidence was found for associations between brain or cognitive age and lifestyle trajectories from midlife to late life based on latent class growth analyses. However, post hoc analyses revealed a relationship between cumulative lifestyle measures and brain age independent of cognitive age. In conclusion, we present a novel approach to characterizing brain and cognitive maintenance in aging, which may be useful for future studies seeking to identify factors that contribute to brain preservation and cognitive reserve mechanisms in older age
Finite temperature and quench dynamics in the Transverse Field Ising Model from form factor expansions
No full textWe consider the problems of calculating the dynamical order parameter two-point function at finite temperatures and the one-point function after a quantum quench in the transverse field Ising chain. Both of these can be expressed in terms of form factor sums in the basis of physical excitations of the model. We develop a general framework for carrying out these sums based on a decomposition of form factors into partial fractions, which leads to a factorization of the multiple sums and permits them to be evaluated asymptotically. This naturally leads to systematic low density expansions. At late times these expansions can be summed to all orders by means of a determinant representation. Our method has a natural generalization to semi-local operators in interacting integrable models
On the application of artificial neural networks for the prediction of NOx emissions from a high-speed direct injection diesel engine
No full textThis article considers the application and refinement of artificial neural network methods for the prediction of NOx emissions from a high-speed direct injection diesel engine over a wide range of engine operating conditions. The relative computational cost and performance of two backpropagation algorithms, Levenberg–Marquardt and Bayesian regularization, for this application are compared, with the Levenberg–Marquardt algorithm demonstrating a significant cost advantage. This work also assesses the performance of two alternative filtering approaches, a p-value test and the Pearson correlation coefficient, for reducing the required number of input variables to the model. The p-value test identified 32 input parameters of significance, whereas the Pearson correlation test highlighted 14 significant parameters while additionally providing a ranking of their relative importance. Finally, the article compares the predictive performance of the models generated by the two filtering methods. Overall, both models show good agreement to the experimental data with the model created using the Pearson correlation test showing improved performance in the low-NOx region
Interferon-stimulated gene products as regulators of central carbon metabolism
No full textIn response to viral infections, the innate immune system rapidly activates expression of several interferon‐stimulated genes (ISGs), whose protein and metabolic products are believed to directly interfere with the viral life cycle. Here, we argue that biochemical reactions performed by two specific protein products of ISGs modulate central carbon metabolism to support a broad‐spectrum antiviral response. We demonstrate that the metabolites generated by metalloenzymes nitric oxide synthase and the radical S‐adenosylmethionine (SAM) enzyme RSAD2 inhibit the activity of the housekeeping and glycolytic enzyme glyceraldehyde 3‐phosphate dehydrogenase (GAPDH). We discuss that this inhibition is likely to stimulate a range of metabolic and signalling processes to support a broad‐spectrum immune response. Based on these analyses, we propose that inhibiting GAPDH in individuals with deteriorated cellular innate immune response like elderly might help in treating viral diseases such as COVID‐19
Thermoelectric behaviour of Bi-Te films on polymer substrates DC-sputtered at room-temperature in moving web deposition
No full textHigh-throughput roll-to-roll processing could be used to scale up the manufacture of flexible thermoelectric generators. Very thin thermoelectric layers can be manufactured at high throughput speed and low cost and, most importantly, are predicted to possess better thermoelectric properties than thicker layers. Here we present a study on a series of bismuth telluride films of different thickness (few nm to 370 nm), deposited on polymer substrates at room temperature using DC magnetron sputtering. Unlike previous studies of deposition of bismuth telluride films onto heated substrates, an island-growth mode, indicated by AFM, was observed for Bi-Te films grown at room temperature. A period of growth in which the layer only partially coats the substrate, with only imperfect connections between islands, was observed. In this partially coated region, the coating exhibited an extremely high Seebeck coefficient. An energy barrier mechanism, similar to the interface effect in nanomaterials, is proposed to explain this phenomenon, along with a possible quantum confinement effect. We found that a thinner Bi-Te film could generate a greater power factor because of a quasi-decoupling of Seebeck coefficient and electrical resistivity. In addition, ensuring that the sample passed directly under the sputtering target, and using a substrate smoothed with an acrylate layer were found to improve film properties, thus enhancing thermoelectric behaviour
The puzzle of falling happiness despite rising income in rural China: ten hypotheses
No full textWith economic development can come social, attitudinal and cultural change, for good or ill or both We pose an unexplored question: why has happiness fallen in rural China whereas rural income has risen rapidly? Two rich data sets are analysed, the rural surveys of the China Household Income Project (CHIP) relating to 2002 and 2013. Our main methods are happiness regressions and decomposition methodology. Several approaches are adopted and no fewer than ten hypotheses are tested. One approach is to examine the variables that are found to be important in happiness functions and to consider their contributions to the fall in the mean happiness score of rural people. Three variables stand out and together can ‘explain’ over twice the fall in happiness: reduced sensitivity of happiness to income, increased sensitivity of happiness to relative income position in the village, and a sharper U-shape of happiness in response to ageing. Another approach is to analyse the effect on rural happiness of the vast rural-urban migration that took place over this period, in particular the effect of temporary migration on information flows to the village, thus broadening reference groups and changing attitudes, and its effect on the lives of those ‘left-behind’ in unbalanced households. This is followed up by introducing tests of the role that changing attitudes – towards sense of community, degree of materialism, and aspirations for income - might have played. The analysis is illuminating both substantively and methodologically, but a puzzle remains. A general conclusion is that the effects of development-driven social change on happiness both directly and also indirectly through changing attitudes are good candidates for further research
A neural network based policy iteration algorithm with global H2-superlinear convergence for stochastic games on domains
No full textIn this work, we propose a class of numerical schemes for solving semilinear Hamilton–Jacobi–Bellman–Isaacs (HJBI) boundary value problems which arise naturally from exit time problems of diffusion processes with controlled drift. We exploit policy iteration to reduce the semilinear problem into a sequence of linear Dirichlet problems, which are subsequently approximated by a multilayer feedforward neural network ansatz. We establish that the numerical solutions converge globally in the 2-norm and further demonstrate that this convergence is superlinear, by interpreting the algorithm as an inexact Newton iteration for the HJBI equation. Moreover, we construct the optimal feedback controls from the numerical value functions and deduce convergence. The numerical schemes and convergence results are then extended to oblique derivative boundary conditions. Numerical experiments on the stochastic Zermelo navigation problem are presented to illustrate the theoretical results and to demonstrate the effectiveness of the method
Short stories of restoration
No full textΗ ταινία «Μικρές ιστορίες αναστήλωσης» δημιουργήθηκε από την Υπηρεσία Συντήρησης Μνημείων Ακρόπολης (ΥΣΜΑ) και προβάλλεται στο πλαίσιο της έκθεσης «Σμίλη και Μνήμη: η συμβολή της μαρμαροτεχνίας στην αναστήλωση των μνημείων της Ακρόπολης», που φιλοξενείται στο Μουσείο της Ακρόπολης από τις 11 Ιουνίου έως τις 31 Οκτωβρίου 2019. Μέσα από κινηματογραφικά αποσπάσματα του αρχείου της ΥΣΜΑ, των εργασιών αποκατάστασης, αλλά και συνεντεύξεις μαρμαροτεχνιτών που συμμετείχαν στις εργασίες, προβάλλονται η καθημερινή ζωή στο εργοτάξιο, η συμβολή των μαρμαροτεχνιτών στα έργα αναστήλωσης, τα συναισθήματα που βιώνουν και οι εμπειρίες που μοιράζονται στη διάρκεια των επεμβάσεων.The film “Short stories of restoration” created by the Acropolis Restoration Service (YSMA) to accompany the photographic exhibition “Chisel and Memory: the contribution of marble craftsmanship to the restoration of the Acropolis monuments” which is hosted at the Acropolis Museum from the 11th of June until the 31st of October 2019. The film uses footages of the audiovisual archive of the YSMA and the personal testimony of marble technicians who took part in the works, to shed light to the everyday life in the worksite, the contribution of marble craftsmen to the restoration works, and the emotions that they experience and share during the interventions
I’ll tell you what I want, what I really, really want: Open Archaeology that is collaborative, participatory, public, and feminist
No full textIn this paper, my aim is to remake a powerful case for an open archaeology that is always collaborative, participatory, and public – but also feminist and activist. Drawing on more than 10 years’ experience as a community archaeologist I discuss some of the reasons why researchers who employ collaborative approaches to the past may be reluctant to publicly acknowledge the frictions which inevitably arise through their work. By unpacking some of the key concepts employed in these approaches, like ‘community’, ‘public’ and ‘collaboration’, I consider how we might define the limits of inclusivity and openness in the name of democracy. Furthermore, I identify some of the strategies and approaches to community archaeology, which I suggest are more likely to lead to beneficial or positive outcomes, proposing that an explicitly feminist lens will achieve the return to politics and provocation for which some scholars have recently called