Probability for Primordial Black Holes in Multidimensional Universe with Nonlinear Scalar Curvature Terms

We investigate multi-dimensional universe with nonlinear scalar curvature terms to evaluate the probability of creation of primordial black holes. For this we obtain Euclidean instanton solution in two different topologies: (a) $S^{D-1}$ - topology which does not accommodate primordial black holes and (b) $S^1\times S^{D-2}$-topology which accommodates a pair of black holes. The probability for quantum creation of an inflationary universe with a pair of black holes has been evaluated assuming a gravitational action which is described by a polynomial function of scalar curvature with or without a cosmological constant ($\Lambda$) using the framework of semiclassical approximation of Hartle-Hawking boundary conditions. We discuss here a class of new gravitational instantons solution in the $R^4$-theory which are relevant for cosmological model building.Comment: 18 pages, no figure. accepted in Phys. Rev.

Polyhedral units and network connectivity in calcium aluminosilicate glasses from high-energy x-ray diffraction

Structure factors for Cax/2AlxSi1-xO2 glasses (x=0,0.25,0.5,0.67) extended to a wave vector of magnitude Q= 40 1/A have been obtained by high-energy x-ray diffraction. For the first time, it is possible to resolve the contributions of Si-O, Al-O and Ca-O coordination polyhedra to the experimental atomic pair distribution functions (PDF). It has been found that both Si and Al are four-fold coordinated and so participate in a continuous tetrahedral network at low values of x. The number of network breaking defects in the form of non-bridging oxygens (NBO's) increases slowly with x until x=0.5 (NBO's ~ 10% at x=0.5). By x=0.67 the network breaking defects become significant as evidenced by the significant drop in the average coordination number of Si. By contrast, Al-O tetrahedra remain free of NBO's and fully integrated in the Al/Si-O network for all values of x. Calcium maintains a rather uniform coordination sphere of approximately 5 oxygen atoms for all values of x. The results suggest that not only Si/Al-O tetrahedra but Ca-O polyhedra, too, play a role in determining the glassy structure

Transition rates and nuclear structure changes in mirror nuclei 47Cr and 47V

Lifetime measurements in the mirror nuclei 47Cr and 47V were performed by means of the Doppler-shift attenuation method using the multidetector array EUROBALL, in conjunction with the ancillary detectors ISIS and the Neutron Wall. The determined transition strengths in the yrast cascades are well described by full pf shell model calculations.Comment: Latex2e, 11 pages, 3 figure

Editors' Review and Introduction: Learning Grammatical Structures: Developmental, Cross‐Species, and Computational Approaches

Human languages all have a grammar, that is, rules that determine how symbols in a language can be combined to create complex meaningful expressions. Despite decades of research, the evolutionary, developmental, cognitive, and computational bases of grammatical abilities are still not fully understood. “Artificial Grammar Learning” (AGL) studies provide important insights into how rules and structured sequences are learned, the relevance of these processes to language in humans, and whether the cognitive systems involved are shared with other animals. AGL tasks can be used to study how human adults, infants, animals, or machines learn artificial grammars of various sorts, consisting of rules defined typically over syllables, sounds, or visual items. In this introduction, we distill some lessons from the nine other papers in this special issue, which review the advances made from this growing body of literature. We provide a critical synthesis, identify the questions that remain open, and recognize the challenges that lie ahead. A key observation across the disciplines is that the limits of human, animal, and machine capabilities have yet to be found. Thus, this interdisciplinary area of research firmly rooted in the cognitive sciences has unearthed exciting new questions and venues for research, along the way fostering impactful collaborations between traditionally disconnected disciplines that are breaking scientific ground

The kinetics of surfactant desorption at the air–solution interface

The kinetics of desorption of the anionic surfactant sodium dodecylbenzene sulfonate at the air–solution interface have been studied using neutron reflectivity (NR). The experimental arrangement incorporates a novel flow cell in which the subphase can be exchanged (diluted) using a laminar flow whilst the surface region remains unaltered. The kinetics of the desorption is relatively slow and occurs over many tens of minutes compared with the dilution timescale of approximately 10–30 minutes. A detailed mathematical model, in which the rate of the desorption is determined by transport through a near-surface diffusion layer into a diluted bulk solution below, is developed and provides a good description of the timedependent adsorption data.\ud \ud A key parameter of the model is the ratio of the depth of the diffusion layer, Hc , to the depth of the fluid, Hf, and we find that this is related to the reduced Péclet number, Pe*, for the system, via Hc/Hf, = C/Pe* 1/ 2 . Although from a highly idealised experimental arrangement, the results provide an important insight into the ‘rinse mechanism’, which is applicable to a wide variety of domestic and industrial circumstances

Proposal for an eHealth Based Ecosystem Serving National Healthcare

The European Union (EU)'s keen concern about citizens' health and well-being advancement has been expressed at all levels. It has been understood that at present, these can only be achieved through coordinated actions at the individual member states' level based on EU directives, as well as through promoting and funding R&D and expanding the use of eHealth technologies. Despite the diversities and particularities among member states, common values such as universal access to good quality healthcare, equity, and solidarity have been widely accepted across EU. That demanded the adoption of policies and follow directives, which streamlined actions to bridge healthcare gaps, and facilitate cross-border healthcare. This paper articulates a framework for deriving a national healthcare system, based on interoperable Electronic Health Record (EHR) with safeguarding healthcare quality, enabling quadruple helix (Public, Academia, Industry, NGOs) driven R&D and guided by a patient-centered approach. A methodology to develop an integrated EHR at National level is proposed as a prerequisite for eHealth and put into perspective. Recommendations are given for the steps needed, from the managerial, legal, technical, and financial concerns in developing an open access, patient-centered national healthcare system based on the context and constraints of a country. The example of a small country to apply the proposed methodology is demonstrated. Stakeholders, including citizens, healthcare professionals, academia, and the industry are mobilized, enabled, and incentivized for implementing the methodology. Experiences are aspired to be offered as lessons learned for other countries to adapt on their environment

Evaluation of local stress state due to grain-boundary sliding during creep within a crystal plasticity finite element multi-scale framework

Previous studies demonstrate that grain-boundary sliding could accelerate creep rate and give rise to large internal stresses that can lead to damage development, e.g. formation of wedge cracks. The present study provides more insight into the effects of grain-boundary sliding (GBS) on the deformation behaviour of realistic polycrystalline aggregates during creep, through the development of a computational framework which combines: i) the use of interface elements for sliding at grain boundaries, and ii) special triple point (in 2D) or triple line (in 3D) elements to prevent artificial dilation at these locations in the microstructure with iii) a physically-based crystal plasticity constitutive model for time-dependent inelastic deformation of the individual grains. Experimental data at various scales is used to calibrate the framework and compare with model predictions. We pay particular consideration to effects of grain boundary sliding during creep of Type 316 stainless steel, which is used extensively in structural components of the UK fleet of Advanced Gas Cooled Nuclear Reactors (AGRs). It is found that the anisotropic deformation of the grains and the mismatch in crystallographic orientation between neighbouring grains play a significant role in determining the extent of sliding on a given boundary. Their effect on the development of stress within the grains, particularly at triple grain junctions, and the increase in axial stress along transverse boundaries are quantified. The article demonstrates that the magnitude of the stress along the facets is highly-dependent on the crystallographic orientations of the neighbouring grains and the relative amount of sliding. Boundaries, transverse to the applied load tend to carry higher normal stresses of the order of 100-180 MPa, in cases where the neighbouring grains consist of plastically-harder crystallographic orientations.Comment: Keywords: grain boundary sliding, creep, interface, polycrystalline, triple grain junction, crystal plasticity. 21 Pages, 16 Figures, 2 Table

Thirteen years of integrated precipitable water derived by GPS at Mario Zucchelli Station, Antarctica

Since 1998, the Italian Antarctic Programme is funding space geodetic activities based on the use of episodic and permanent GPS observations. Beside their exploitation in geodynamics, the data can be used to sense the atmosphere and retrieve the water vapour content and variation. The surface pressure and temperature at the GPS tracking sites are necessary to compute the precipitable water; at sites where no information is available, the values can be retrieved from a global grid model. We process the data series of the permanent GPS site TNB1 (Mario Zucchelli Station, Antarctica) from 1998 up to 2010 comparing the use of grid values to the implementation of real surface records. With both approaches, we estimate almost 70000 hourly values of precipitable water over 13 years and we find discrepancies varying between (1.8 ± 0.2) mm in summer and (3.3 ± 0.5) mm in winter. In addition, the discrepancies of the two solutions exhibit a clear seasonal dependency. We validate our results using radio soundings measurements. They agree better with the precipitable water values derived from real surface data. Nevertheless, these latter exhibit dry biases and detect the (77±21) % of the content of moisture measured by the radio soundings. Both GPS and radio sounding observations are processed adopting the most up-to-date strategies to reduce and dominate known systematic errors