Explicit local time-stepping methods for time-dependent wave propagation

Semi-discrete Galerkin formulations of transient wave equations, either with conforming or discontinuous Galerkin finite element discretizations, typically lead to large systems of ordinary differential equations. When explicit time integration is used, the time-step is constrained by the smallest elements in the mesh for numerical stability, possibly a high price to pay. To overcome that overly restrictive stability constraint on the time-step, yet without resorting to implicit methods, explicit local time-stepping schemes (LTS) are presented here for transient wave equations either with or without damping. In the undamped case, leap-frog based LTS methods lead to high-order explicit LTS schemes, which conserve the energy. In the damped case, when energy is no longer conserved, Adams-Bashforth based LTS methods also lead to explicit LTS schemes of arbitrarily high accuracy. When combined with a finite element discretization in space with an essentially diagonal mass matrix, the resulting time-marching schemes are fully explicit and thus inherently parallel. Numerical experiments with continuous and discontinuous Galerkin finite element discretizations validate the theory and illustrate the usefulness of these local time-stepping methods.Comment: overview paper, typos added, references updated. arXiv admin note: substantial text overlap with arXiv:1109.448

Tourism sustainability

The meaning of `sustainable tourism` and `eco-tourism` is presented after a brief review of sustainability concept. The differences of both tourism types are analyzed shortly. Based on that, examples from the practice are presented for sustainable tourism. Some principles related to tourism sustainability are defined as factors for its development

Direct ab initio MD simulation of silver ion diffusion in chalcogenide glasses

In this paper, we present new models of germanium selenide chalcogenide glasses heavily doped with silver. The models were readily obtained with ab initio molecular dynamics and their structure agrees closely with diffraction measurements. Thermal molecular dynamics simulation reveals the dynamics of Ag+ ions and the existence of trapping centers as conjectured in other theory work. We show that first principles simulation is a powerful tool to reveal the motion of ions in glass.Comment: 3 pages, 3 figures, submitted to Phys. Stat. Sol. {b} Rapid Research Letter

Overview of Voluntary Fully Funded Pension Insurance

Voluntary Fully Funded Pension Insurance is part of multi pillar structure of the pension system of Republic of Macedonia. In the Voluntary Fully Funded Pension Insurance the coverage of individuals is more extensive because all persons are included regardless whether or not they are members of the Fully Funded Pension Insurance. Special emphasis is given on the way of gaining membership in Voluntary Pension Fund, the membership agreement for opening an individual account and the agreement for pension schemes used to open a professional account. This paper considers the Voluntary Pension Funds and the management company for the Voluntary Pension Funds. The Directive 2003/41 of the European Parliament and Council has had a big impact on the development of voluntary fully funded pension insurance. The main objective of this article is to present suggestions to overcome existing shortcomings in the functioning of voluntary fully funded pension insurance, the conditions for gaining membership, the manner and contributions for acquiring membership in the Voluntary Fully Funded Pensions Insurance and the payment of retirement benefits to members in the third pillar.Keywords: third pension pillar, individual account, professional account, professional pension schemes, membership contract

Clinical Impact of Insulin Resistance in Women with Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is an endocrine-metabolic disorder characterized by multiple hormonal imbalances, reflecting on the clinical presentation. Among them, the insulin resistance (IR), defined as a metabolic state characterized by a decrease in cellular ability to respond to insulin signaling, is a key feature of PCOS independently of obesity. Thus, IR occurs in more than 70% of obese PCOS women and in 30–50% of lean ones. Compensatory high insulin levels are both a symptom and an underlying physiopathological driver of PCOS. Insulin appears to disrupt all components of the hypothalamic-pituitary-ovarian axis, and ovarian tissue IR results in impaired metabolic signaling but intact mitogenic and steroidogenic activity, favoring hyperandrogenemia. The latter is the main culprit of the clinical picture in PCOS. Testing for IR can be helpful to rule out other conditions that are commonly misdiagnosed as PCOS and to recommend an appropriate treatment for the different PCOS phenotypes

LONG-TERM PROGNOSIS IN CORONARY ARTERY DISEASE PATIENTS WITH HIGH PHYSICAL CAPACITY

No abstrac

Silver Photo-Diffusion and Photo-Induced Macroscopic Surface Deformation of Ge33S67/Ag/Si Substrate

Ge-chalcogenide films show various photo-induced changes, and silver photo-diffusion is one of them which attracts lots of interest. In this paper, we report how silver and Ge-chalcogenide layers in Ge33S67/Ag/Si substrate stacks change under light exposure in the depth by measuring time-resolved neutron reflectivity. It was found from the measurement that Ag ions diffuse all over the matrix Ge33S67layer once Ag dissolves into the layer. We also found that the surface was macroscopically deformed by the extended light exposure. Its structural origin was investigated by a scanning electron microscopy

Risk factors associated with the development of dental caries in Bulgarian children

The purpose of this study was to examine the risk factors associated with the development of dental caries in children in Bulgaria. The research has been carried out at the Faculty of Dental Medicine, in the period 2015-2016, with the permission of the University Scientific Research Committee and informed consent signed by each parent. The subject of observation was parents of children from Varna region in Bulgaria. The results were statistically processed with SPSS v.20.0, using variation and comparison (chi-square) analyzes. For significance level we assume p<0.05. The volume of observation encompasses 100 persons. Units of observation are patients aged three to six years with the need for prevention and treatment of dental caries of the primary dentition. The registration was done in a specially developed questionnaire, including 22 questions, each with the possibility of more than one answer. In processing the obtained data, Student's criterion was used to compare the mean values of two independent samples. In a comparative analysis of the results, we found that 71.01% of children aged three to six years visit a dentist, and patients use fluoride only in the form of toothpaste containing fluoride. When studying the knowledge and behavior of parents in the direction of risk factors for the development of dental caries and oral prophylaxis, need for a new approach of pediatric dentists has been found, focused on programming preventive and non-invasive treatment of children according to their individual needs