Superfluidity versus localization in bulk 4He at zero temperature

We present a zero-temperature quantum Monte Carlo calculation of liquid $^4$He immersed in an array of confining potentials. These external potentials are centered in the lattice sites of a fcc solid geometry and, by modifying their well depth and range, the system evolves from a liquid phase towards a progressively localized system which mimics a solid phase. The superfluid density decreases with increasing order, reaching a value $\rho_{\rm s}/\rho = 0.079(16)$ when the Lindemann's ratio of the model equals the experimental value for solid $^4$He.Comment: 5 pages,5 figure

The kinetics of homogeneous melting beyond the limit of superheating

Molecular dynamics simulation is used to study the time-scales involved in the homogeneous melting of a superheated crystal. The interaction model used is an embedded-atom model for Fe developed in previous work, and the melting process is simulated in the microcanonical $(N, V, E)$ ensemble. We study periodically repeated systems containing from 96 to 7776 atoms, and the initial system is always the perfect crystal without free surfaces or other defects. For each chosen total energy $E$ and number of atoms $N$, we perform several hundred statistically independent simulations, with each simulation lasting for between 500 ps and 10 ns, in order to gather statistics for the waiting time $\tau_{\rm w}$ before melting occurs. We find that the probability distribution of $\tau_{\rm w}$ is roughly exponential, and that the mean value $<\tau_{\rm w} >$ depends strongly on the excess of the initial steady temperature of the crystal above the superheating limit identified by other researchers. The mean $$ also depends strongly on system size in a way that we have quantified. For very small systems of $\sim 100$ atoms, we observe a persistent alternation between the solid and liquid states, and we explain why this happens. Our results allow us to draw conclusions about the reliability of the recently proposed Z method for determining the melting properties of simulated materials, and to suggest ways of correcting for the errors of the method.Comment: 19 pages, 8 figure

Supersolidity in quantum films adsorbed on graphene and graphite

Using quantum Monte Carlo we have studied the superfluid density of the first layer of $^4$He and H$_2$ adsorbed on graphene and graphite. Our main focus has been on the equilibrium ground state of the system, which corresponds to a registered $\sqrt3 \times \sqrt3$ phase. The perfect solid phase of H$_2$ shows no superfluid signal whereas $^4$He has a finite but small superfluid fraction (0.67%). The introduction of vacancies in the crystal makes the superfluidity increase, showing values as large as 14% in $^4$He without destroying the spatial solid order.Comment: 5 pages, accepted for publication in PR

Data dependent energy modelling for worst case energy consumption analysis

Safely meeting Worst Case Energy Consumption (WCEC) criteria requires accurate energy modeling of software. We investigate the impact of instruction operand values upon energy consumption in cacheless embedded processors. Existing instruction-level energy models typically use measurements from random input data, providing estimates unsuitable for safe WCEC analysis. We examine probabilistic energy distributions of instructions and propose a model for composing instruction sequences using distributions, enabling WCEC analysis on program basic blocks. The worst case is predicted with statistical analysis. Further, we verify that the energy of embedded benchmarks can be characterised as a distribution, and compare our proposed technique with other methods of estimating energy consumption

J002 The cAMP binding protein Epac regulates cardiac myofilament function

In the heart, cAMP is a key regulator of excitation—contraction coupling and its biological effects are mainly associated with the activity of protein kinase A (PKA). The aim of this study was to investigate the contribution of the cAMP-binding protein Epac (Exchange protein directly activated by cAMP) in the regulation of the contractile properties of rat ventricular cardiac myocytes. We report that both PKA and Epac increased cardiac sarcomere contraction but through opposite mechanisms. Differently from PKA, selective Epac activation by the cAMP analog 8-pCPT reduced Ca2+ transient amplitude and increased cell shortening in intact cardiomyocytes as well as myofilament Ca2+ sensitivity in permeabilized cardiomyocytes. Moreover, ventricular myocytes, which were infected in vivo with a constitutively active form of Epac, showed enhanced myofilament Ca2+ sensitivity compared to control cells infected with GFP alone. At the molecular level, Epac increased phosphorylation of two key sarcomeric proteins, cardiac Troponin I (cTnI) and cardiac Myosin Binding Protein-C (cMyBP-C). The effects of Epac activation on myofilament Ca2+ sensitivity and on cTnI and cMyBP-C phosphorylation were independent of PKA, and were blocked by protein kinase C (PKC) and Ca2+ calmodulin kinase II (CaMKII) inhibitors. Altogether these findings identify Epac as a new regulator of myofilament function

A proposal of an evaluation model under the principles of universal design

The aim of this work is to try to set out how the Universal Design (UD) paradigm can influence the process of product design and how the models of evaluation should work for products designed for all users. Firstly, we will give a short introduction of some of the basic models that try to explain the product design and development process emphasizing, especially, the role given to evaluation of the design stage. Secondly, what we would like to do is explain, on one hand, the paradigms of Human Centred Product Planning and Design and, on the other hand, UD/Inclusive Design (ID)/ Design for All (DfA) in order to clarify the bonds and relationships which are established between these in the field of Ergonomics and Human Factors. In this context, we explain how these philosophies have an effect and an influence in the process of design, especially in the interstages of evaluation. Finally, we present a model that proposes the integration of UD principles into the process of design applying it to the case of a wheelchair

Empirical Validation of a Class of Ray-Based Fading Models

As new wireless standards are developed, the use of higher operation frequencies comes in hand with new use cases and propagation effects that differ from the well-established state of the art. Numerous stochastic fading models have recently emerged under the umbrella of generalized fading conditions, to provide a fine-grain characterization of propagation channels in the mmWave and sub-THz bands. For the first time in literature, this work carries out an experimental validation of a class of such ray-based models, in a wide range of propagation conditions (anechoic, reverberation and indoor) at mmWave bands. We show that the independently fluctuating two-ray (IFTR) model has good capabilities to recreate rather dissimilar environments with high accuracy. We also put forth that the key limitations of the IFTR model arise in the presence of reduced diffuse propagation, and also due to a limited phase variability for the dominant specular components.Comment: 9 pages, 13 figure

Solidification of small para-H2 clusters at zero temperature

We have determined the ground-state energies of para-H$_2$ clusters at zero temperature using the diffusion Monte Carlo method. The liquid or solid character of each cluster is investigated by restricting the phase through the use of proper importance sampling. Our results show inhomogeneous crystallization of clusters, with alternating behavior between liquid and solid phases up to N=55. From there on, all clusters are solid. The ground-state energies in the range N=13--75 are established and the stable phase of each cluster is determined. In spite of the small differences observed between the energy of liquid and solid clusters, the corresponding density profiles are significantly different, feature that can help to solve ambiguities in the determination of the specific phase of H$_2$ clusters.Comment: 17 pages, accepted for publication in J. Phys. Chem.

Reading-related Cognitive Deficits in Spanish Developmental Dyslexia

AbstractSpanish-speaking children learn to read words written in a relatively transparent orthography. Variations in orthographic transparency may shape the manifestation of reading difficulties. This study was intended to help clarify the nature of developmental dyslexia in Spanish. Developmentally Dyslexic children (DD) were compared to a chronological age-matched control group (CA). Measures included rapid automated naming, verbal working memory, phonological short-term memory, and phonemic awareness. Results demonstrated that developmental dyslexics show reading-related cognitive deficits in areas such as naming speed, verbal working memory, phonological short-term memory, and phonemic awareness. Our results are consistent with studies conducted in the Spanish language and in other transparent orthographies